Title of Invention

METHOD FOR RECOVERING MOLYBDENUM AND METHOD FOR PRODUCING CATALYST

Abstract A method for obtaining a material containing recovered molybdenum for use in producing a catalyst from a molybdenum-containing material comprising at least molybdenum, A element (phosphorus and/or arsenic) and X element (at least one selected from the group consisting of potassium, rubidium, cesium and thallium), in particular, from a spent catalyst; and a method for producing a catalyst using said material containing recovered molybdenum, a particularly preferred catalyst is a catalyst for use in producing methacrylic acid through gas- phase catalytic oxidation.
Full Text DESCRIPTION
METHOD FOR RECOVERING MOLYBDENUM AND METHOD FOR
PRODUCING CATALYST
TECHNICAL FIELD
[0001]
The present invention relates to a method for recovering solution containing
at least molybdenum (recovered molybdenum-containing liquid) or precipitate
containing at least molybdenum (recovered molybdenum-containing precipitate)
from a molybdenum-containing material comprising at least molybdenum, A
element (phosphorus and/or arsenic) and X element (at least one selected from
the group consisting of potassium, rubidium, cesium and thallium), and a
method for producing a catalyst using the recovered molybdenum-containing
liquid and/or the recovered molybdenum-containing precipitate.
BACKGROUND ART
[0002]
The molybdenum-containing material comprising at least molybdenum, A
element (phosphorus and/or arsenic) and X element (at least one selected from
the group consisting of potassium, rubidium, cesium and thallium) is widely
known for its effectiveness as a heteropolyacid based catalyst which is used in
producing, for example, methacrylic acid through oxidative dehydrogenases of
isobutyric acid or methacrylic acid through gas-phase oxidation of methacrolein.
It is also used in a process for producing methacrylic acid through direct
gas-phase oxidation of isobutylene.
[0003]
Generally, in an industrial gas-phase oxidation reaction, a catalyst is used for

a certain period of time and after being used for the period of time, the catalyst is
taken out from a reactor and replaced by a new one. The spent catalyst thus
taken out from the reactor contains many useful elements as raw materials for
producing a catalyst, such as molybdenum, potassium, rubidium and cesium.
It is a very important subject from the economical point of view and from the
viewpoint of reducing the load to environment to develop the technology for
recovering and reusing these elements or recycling and reusing the spent
catalyst.
[0004]
As a method for recovering catalyst components from a spent catalyst, a
method is known, which comprises the step of thermally decomposing a
heteropolyacid salt based spent catalyst with sodium hydroxide followed by
contacting the resultant mixture with sodium type strongly acidic resin to
selectively adsorb and separate cesium, rubidium and thallium or potassium,
eluting the adsorbed elements with sulfuric acid and recovering these elements
as sulfates of each element, and the step of recovering a heteropolyacid by
treating the solution of the sodium salt of the heteropolyacid separated in the
foregoing step with proton type strongly acidic ion-exchange resin (refer to, for
example, JPH07-213.922-A1 (Patent document 1)).
[0005]
Further, as a method for regenerating a catalyst, a regenerating method of
treating a spent catalyst used in producing methacrylic acid with hydrochloric
acid (refer to, for example, JPS54-002.293-A1 (Patent document 2)), a
regenerating method of treating the spent catalyst with a nitrogen- containing
heterocyclic compound (refer to, for example, JPS60-232.247-A1 (Patent
document 3)), a regenerating method of adding ammonium species and nitrate
species to a deactivated catalyst (refer to, for example, JPS61 -283.352-A1
(Patent document 4)), a regenerating method of treating the spent catalyst with

inorganic ion exchanger such as crystalline antimonate (refer to, for example,
JPH06-285,373-A1 (Patent document 5)) and the like are known.
[0006]
However, the recovering method disclosed in JPH07-213.922-A1 (Patent
document 1) uses ion-exchange resin in two steps. In a recovering method
using ion-exchange resin, it is necessary to lower the concentration of the
element to be recovered in the solution to be treated for recovering.
Consequently, it causes the problem that using ion-exchange resin in the two
steps as in the above case results in increase in the area of equipment and the
used amount of the ion-exchange resin, and hence, it is not economical.
[0007]
Further, as the regenerating methods disclosed in JPS54-002,293-A1 (Patent
document 2), JPS60-232.247-A1 (Patent document 3), JPS61-283.352-A1
(Patent document 4) and JPH06-285.373-A1 (Patent document 5), there is a
problem that a catalyst can be regenerated to a certain level but its yield of
methacrylic acid using the regenerated catalyst is lower than that using a
catalyst produced in a ordinary method.
[0008]
As a method which has solved these problems, there is a method in which a
recovered spent catalyst is dispersed in water, and to the resultant dispersion,
an alkali metal compound and aqueous ammonia are added, and then pH of the
mixed liquid is adjusted to 6.5 or less to precipitate molybdenum together with
phosphorus and arsenic and to recover them as a molybdenum-containing
precipitate which is usable in producing a catalyst (refer to, for example, USP
6,777,369 (Patent document 6)).
[0009]
However, the molybdenum-containing precipitate obtained by the method
disclosed in USP 6,777,369 (Patent document 6) also contains phosphorus and

arsenic which have been originally included in the raw material for recovering,
and there is a restriction on using this precipitate directly for producing a new
catalyst.
Patent document 1: JPH07-213.922-A1
Patent document 2: JPS54-002.293-A1
Patent document 3: JPS60-232.247-A1
Patent document 4: JPS61 -283.352-A1
Patent document 5: JPH06-285.373-A1
Patent document 6: USP 6,777,369
DISCLOSURE OF INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
[0010]
Therefore, the problems of the present invention are to provide a method for
recovering solution containing at least molybdenum (recovered
molybdenum-containing liquid) or precipitate containing at least molybdenum
(recovered molybdenum-containing precipitate), which can be used in
producing a catalyst as well as fresh molybdenum compounds, from a
molybdenum-containing material comprising at least molybdenum, A element
(phosphorus and/or arsenic) and X element (at least one selected from the
group consisting of potassium, rubidium, cesium and thallium), in particular,
from a recovered spent catalyst, and to provide a method for producing a
catalyst using the recovered molybdenum-containing liquid or the recovered
molybdenum-containing precipitate as a raw material of the catalyst.
MEANS FOR SOLVING PROBLEM
[0011]
To solve the problems described above, the present inventors have

intensively researched and have found that by dispersing a
molybdenum-containing material which is a raw material for recovering
molybdenum in an alkaline solution, and then by making a
magnesium-containing compound act on the dispersion at a specified range of
pH, it is possible to recover molybdenum in a state which can be used in
producing various kinds of catalysts containing molybdenum and thus have
completed the present invention.
[0012]
Namely, the present invention resides in a method for recovering
molybdenum comprising the steps of:
1) dispersing a molybdenum-containing material which contains at least
molybdenum, A element (phosphorus and/or arsenic) and X element (at least
one selected from the group consisting of potassium, rubidium, cesium and
thallium) in water and adding alkali to make pH of the resultant mixed liquid 8 or
more;
2) adjusting pH of the resultant mixed liquid to fall within the range of from 6 to
12 followed by adding a compound containing magnesium and aqueous
ammonia to form a precipitate containing at least magnesium and A element;
and
3) separating the precipitate containing at least magnesium and A element
formed in the step 2) from a solution containing at least molybdenum (recovered
molybdenum-containing liquid).
[0013]
Moreover, the present invention resides in the above-mentioned method for
recovering molybdenum, further comprising the step of:
4) forming a precipitate containing at least molybdenum by adjusting the pH of
the recovered molybdenum-containing liquid to 3 or less with an addition of acid
and separating the precipitate thus formed (recovered molybdenum-containing

precipitate) from the solution.
[0014]
Further, the present invention resides in a method for producing a catalyst by
using a recovered molybdenum-containing liquid a recovered
molybdenum-containing precipitate which has been recovered by the
above-mentioned methods for recovering molybdenum.
EFFECT OF THE INVENTION
[0015]
According to the present invention, useful molybdenum can be recovered in
the form of reusable solution or precipitate by an easy operation from a
molybdenum-containing material which contains at least molybdenum, A
element (phosphorus and/or arsenic) and X element (at least one selected from
the group consisting of potassium, rubidium, cesium and thallium), in particular,
from a molybdenum-containing spent catalyst.
[0016]
Further, when the recovered molybdenum-containing liquid or precipitate
produced in the present invention is used in producing a catalyst, it is possible
not only that a molybdenum-containing spent catalyst can be used effectively,
but also that a catalyst with the same yield of methacrylic acid can be obtained
as in the case where a conventional raw material of molybdenum is used and
the recovered molybdenum-containing material is not used. Moreover, it is
advantageous that there is little limitation on a method for producing a catalyst
because these solutions or precipitates do not practically contain A element
(phosphorus and/or arsenic).
BEST MODE FOR CARRYING OUT THE INVENTION
[0017]

In the present invention, a molybdenum-containing material to be used in
recovering molybdenum comprises at least molybdenum, A element and X
element and, for example, a spent catalyst used in a reaction for producing
methacrylic acid through gas-phase catalytic oxidation of methacrolein or in a
reaction for producing methacrylic acid through oxidative dehydrogenation of
isobutylic acid can be mentioned. In the case of these catalysts for producing
methacrylic acid, those having a composition represented by the following
formula (1) are preferable, and those having a composition represented by the
following formula (2) are particularly preferable.
[0018]
Wherein, Mo and O represent molybdenum and oxygen, respectively; A
represents phosphorus and/or arsenic; Y represents at least one element
selected from the group consisting of iron, cobalt, nickel, copper, zinc,
magnesium, calcium, strontium, barium, titanium, vanadium, chromium,
tungsten, manganese, silver, boron, silicon, aluminum, gallium, germanium, tin,
lead, antimony, bismuth, niobium, tantalum, zirconium, indium, sulfur, selenium,
tellurium, lanthanum and cerium; X represents at least one element selected
from the group consisting of potassium, rubidium, cesium and thallium; and
subscripts a, b, c, d and e represent an atomic ratio of each element,
respectively; when b is 12, a is in the range of from 0.1 to 3, c is in the range of
from 0 to 3 and d is in the range of from 0.01 to 3 and e represents the atomic
ratio of oxygen necessary for fulfilling the requirement of the valence of each
element above.
[0019]
In the formula, Mo, Cu, V and O represent molybdenum, copper, vanadium
and oxygen, respectively; A represents phosphorus and/or arsenic; Y"

represents at least one element selected from the group consisting of iron,
cobalt, nickel, zinc, magnesium, calcium, strontium, barium, titanium, chromium,
tungsten, manganese, silver, boron, silicon, aluminum, gallium, germanium, tin,
lead, antimony, bismuth, niobium, tantalum, zirconium, indium, sulfur, selenium,
tellurium, lanthanum and cerium, preferably selected from iron, zinc, germanium,
antimony, lanthanum and cerium; X represents at least one element selected
from the group consisting of potassium, rubidium, cesium and thallium,
preferably selected from potassium, rubidium and cesium; and subscripts a, b,
c', f, g, d and e represent an atomic ratio of each element, respectively; when b
is 12, a is in the range of from 0.1 to 3, preferably from 0.5 to 3, c' is in the range
of from 0 to 2.98, preferably from 0 to 2.5, f is in the range of from 0.01 to 2.99,
preferably from 0.01 to 2, g is in the range of from 0.01 to 2.99, preferably from
0.01 to 2 and d is in the range of from 0.01 to 3, preferably from 0.1 to 3 and e
represents the atomic ratio of oxygen necessary for fulfilling the requirement of
the valence of each element above, and besides, (c' + f + g) is in the range of
from 0.02 to 3.
[0020]
Further, a catalyst from which molybdenum is recovered is not particularly
limited and a spent catalyst used in a reaction for producing methacrylic acid is
usually used, and a catalyst which has been stopped to use for certain reasons,
a catalyst which has been drawn from a reactor in the middle of its use in a
reaction and the like are also usable.
[0021]
(Step 1)
A molybdenum-containing material which contains at least molybdenum, A
element and X element is dispersed in water first, and then alkali is added to it.
Amount of alkali to be added is such that pH of the resultant dispersion
becomes 8 or more, preferably from 8.5 to 13. A kind of alkali to be used is not

particularly limited and, for example, sodium hydroxide, potassium hydroxide,
cesium hydroxide, sodium carbonate and aqueous ammonia can be mentioned,
and in particular, sodium hydroxide is preferable. Further, when a catalyst is
totally or partially in a reduced state, it is preferable to oxidize it by calcinations
in air, chlorination, hydrogen peroxide treatment or the like before the alkali
addition, or by chlorination, hydrogen peroxide treatment or the like after the
alkali addition.
[0022]
(Step 2)
Then, the resultant liquid of molybdenum-containing material is previously
adjusted for its pH to fall within the range of from 6 to 12, and to the resultant
liquid, a compound containing magnesium and aqueous ammonia are added.
Then, the resultant liquid is adjusted again for its pH to fall within the range of
from 6 to 12 if needed, and a precipitate containing at least magnesium and A
element is formed. It is preferable to remove insoluble materials by filtration or
the like from the solution existing before the compound containing magnesium
and aqueous ammonia are added. Amount of addition of the compound
containing magnesium and ammonia when the precipitate is formed is
preferably one mol or more of each component per one mol of A element.
[0023]
The compound containing magnesium to be used when the precipitate is
formed is not particularly limited and magnesium chloride, magnesium sulfate,
magnesium nitrate or the like can be used.
[0024]
Further, pH of the liquid in the step 2 is from 6 to 12, preferably from 6.5 to 11,
more preferably from 7 to10. When the pH of the liquid is less than 6, a
precipitate is not formed or insufficient if formed so that an uptake of A element
into the precipitate becomes insufficient as well as a rate of recovery of

molybdenum becomes low because ammonium dodecamolybdophosphate is
liable to precipitate, and hence, it is not preferable. On the other hand, when
the pH of the liquid is more than 12, magnesium becomes magnesium
hydroxide, and hence, an uptake of A element becomes insufficient.
[0025]
The compound to be used in adjusting pH of those liquids is not particularly
limited and, for example, hydrochloric acid, sulfuric acid, nitric acid, acetic acid,
ammonia, sodium hydroxide, potassium hydroxide or the like can be mentioned,
and among them, hydrochloric acid and ammonia are preferable.
[0026]
It is preferable to hold the liquid for a certain period of time after adding the
compound containing magnesium and aqueous ammonia to form a precipitate.
At this time, the holding time is preferably around from 0.5 to 24 hours, and
temperature of the liquid is preferably around from room temperature to 90°C.
While holding the liquid, it may be stood still, but preferably it is stirred.
[0027]
(Step 3)
The precipitate containing at least magnesium and A element formed in the
above-mentioned precipitate forming step is separated from a solution
containing at least molybdenum (recovered molybdenum-containing liquid). A
method for separating the precipitate from the solution is not particularly limited
and general methods such as filtration separation method including gravity
filtration, filtration under pressure, filtration under reduced pressure, filter press
and the like or centrifugal separation method can be applied.
[0028]
(Step 4)
The solution containing at least molybdenum (recovered
molybdenum-containing liquid) obtained by separating the precipitate containing

magnesium and A element can be used by itself as a raw material of
molybdenum in the production of a catalyst, however, it is preferable to
subsequently adjust pH of the solution to form a precipitate containing at least
molybdenum (recovered molybdenum-containing precipitate).
[0029]
At the time of forming the recovered molybdenum-containing precipitate, pH
of the solution is preferably 3 or less, particularly preferably 2 or less. A
compound to be used for adjusting pH of the solution is not particularly limited
and, for example, strong acids such as hydrochloric acid, nitric acid and sulfuric
acid can be mentioned, and among them, nitric acid or hydrochloric acid is
preferable. After adjusting pH of the solution, it is preferable to hold the
resultant solution for a certain period of time to form a precipitate. At this time,
the holding time is preferably around from 0.5 to 24 hours, and temperature of
the solution is preferably around from room temperature to 90°C. While
holding the solution, it may be stood still, but preferably it is stirred.
[0030]
A method for separating the recovered molybdenum-containing precipitate
from its bottom is not particularly limited and general methods such as filtration
separation method including gravity filtration, filtration under pressure, filtration
under reduced pressure and filter press or centrifugal separation method can be
used. Further, the recovered molybdenum-containing precipitate may be
washed to remove its impurities if necessary. In this case, the washing liquid is
selected in view of use or solubility of the recovered molybdenum-containing
precipitate and, for example, pure water, dilute aqueous solution of ammonium
nitrate or ammonium chloride can be mentioned. As the recovered
molybdenum-containing precipitate after washed, each amount of sodium and
chlorine contained in the precipitate is preferably 0.1 mole or less per 12 moles
of molybdenum, more preferably 0.05 mole or less.

[0031]
When the recovered molybdenum-containing precipitate is formed from the
recovered molybdenum-containing liquid, the liquid may contain vanadium in
some cases depending on a molybdenum-containing material which is a raw
material for recovering. When the liquid or precipitate is used as a raw material
for producing a catalyst, it is preferable to partially or totally remove vanadium
from the solution depending on a composition of the catalyst to be produced. A
method for removing vanadium from the liquid is not particularly limited and, for
example, a method in which pH of the recovered molybdenum-containing liquid
including vanadium other than molybdenum is adjusted first and vanadium is
removed from the resultant liquid by adsorption with a weak basic
anion-exchange resin or a method of precipitation separation by using
ammonium chloride or ammonium sulfate can be mentioned. Time of
removing vanadium is not particularly limited as long as it is located, after
separating the precipitate containing magnesium and A element and before
forming the recovered molybdenum-containing precipitate.
[0032]
In the present invention, the recovered molybdenum-containing liquid and/or
the recovered molybdenum-containing precipitate thus obtained can be used as
a raw material for producing a catalyst. Hereinafter, the recovered
molybdenum-containing liquid and the recovered molybdenum-containing
precipitate are also expressed altogether as "recovered molybdenum-containing
material". A state of the recovered molybdenum-containing material to be used
in the production of catalyst is not particularly limited and any one of a solution
state, a wet state or a dry state may be chosen. Further, when a state of oxide
is desired to be used as a raw material of a catalyst, an oxide obtained by
calcining these recovered molybdenum-containing materials, in particular, the
recovered molybdenum-containing precipitate can be used. Calcining

condition is preferably from 300 to 600°C under an atmosphere of
oxygen-containing gas such as air, for 0.5 hour or more.
[0033]
(Production of catalyst)
In the present invention, a method for producing a catalyst is not particularly
limited and can be properly chosen from various methods such as
coprecipitation, evaporation to dryness or mixing of oxides in accordance with a
state of the recovered molybdenum-containing material which is used as a raw
material.
[0034]
Further, in the method for producing a catalyst, the recovered
molybdenum-containing material and/or its calcined material may be used alone,
or if necessary, together with the other raw materials of molybdenum such as
those which are recovered by a method other than the above-mentioned
recovering method or produced from molybdenum ore (hereinafter, these are
also expressed as "the other raw materials of molybdenum"). A method for
producing a raw material of molybdenum other than the above-mentioned
recovered molybdenum-containing material is not particularly limited and, for
example, a method in which ammonium paramolybdate is obtained through
calcining molybdenum ore, washing the resultant crude molybdenum trioxide
with nitric acid followed by dissolving it with aqueous ammonia, refining the
resultant solution, adjusting pH of the solution by nitric acid to obtain molybdic
acid, dissolving again the molybdic acid with aqueous ammonia followed by
concentration and crystallization or a method in which molybdenum trioxide is
obtained through calcination of ammonium paramolybdate or molybdic acid can
be mentioned. Moreover, a raw material other than the recovered
molybdenum-containing material to be used in preparing a catalyst is not
particularly limited and nitrates, carbonates, acetates, ammonium salts, oxides,

halides or oxyacids of each element can be used in combination. For example,
as a raw material of molybdenum, ammonium paramolybdate, molybdenum
trioxide, molybdic acid, molybdenum chloride and the like can be used and as a
raw material of phosphorus, phosphoric acid, phosphorus pentoxide,
ammonium phosphate and the like can be used.
[0035]
As a practical method for preparing a catalyst, for example, a method in which
a dried material of a slurry containing at least A element and X element together
with the recovered molybdenum-containing material and the other raw materials
of molybdenum mentioned above which is used if necessary are calcined or a
method in which a dried mixture containing at least A element and X element
together with the recovered molybdenum-containing material and the other raw
materials of molybdenum mentioned above which is used if necessary are
calcined can be mentioned. Further, in a method for producing a catalyst,
when amounts of addition of raw materials containing elements of the catalyst
components are adjusted in view of the amount of the impurities originating from
the elements which are included in the recovered molybdenum-containing
material to be used as a raw material, a supplemental amount of raw materials
equivalent to shortage of counter ions contained in the raw materials may be
added. For example, when an amount of addition of vanadium is adjusted by
reducing the amount of addition of ammonium metavanadate, shortage of
ammonium ion can be adjusted by supplemental addition of aqueous ammonia
or when an amount of addition of potassium or cesium is adjusted by reducing
the amount of addition of potassium nitrate or cesium nitrate, shortage of nitrate
ion can be adjusted by supplemental addition of nitric acid.
[0036]
In the present invention, it is preferable that ammonia is mixed when a
catalyst is produced. A source of ammonia is not particularly limited and

ammonia itself or its aqueous solution or ammonium salts of various acids may
be used. Further, ammonia may be mixed as ammonium salts of molybdic acid
or phosphoric acid. Amount of ammonia to be used is preferably 1 to 17 moles
per 12 moles of molybdenum, particularly preferably 2 to 13 moles. As an
ammonium salt, ammonium carbonate, ammonium hydrogencarbonate or
ammonium nitrate can be mentioned. These salts may be used alone or in
combination of two or more kinds and not particularly limited.
[0037]
In the present invention, a method for mixing ammonia is not particularly
limited and, for example, a method in which aqueous ammonia is added after
dispersing the recovered molybdenum-containing material in water or a method
in which aqueous ammonia or ammonium nitrate is added after heating and
stirring a liquid containing at least the recovered molybdenum-containing
material, A element and X element under refluxing and cooling to a fixed
temperature can be mentioned. Further, ammonia to be mixed may be the one
contained in the recovered molybdenum-containing material. Using various
raw materials containing ammonia component to be normally used in producing
a catalyst can serve as an ammonia addition.
[0038]
Further, in the production of a catalyst of the present invention, when a step in
the production proceeds via a state of solution or slurry, temperature of the
solution or slurry may be the same as that in a normal method for producing a
catalyst, in which the recovered molybdenum-containing material of the present
invention is not used, but can be lower than that in the normal method in a part
of the steps or in the entire steps. In that case, it is preferable to properly
determine the temperature of the solution or slurry in view of a particle size
distribution of the precipitated particles in the slurry, moldability of the obtained
powder, pore size distribution of the catalyst or reaction performance of the

catalyst, and the temperature is preferably 0 to 40°C, more preferably 0 to 30°C
lower than that in the normal method.
[0039]
Further, a method for drying slurry is not particularly limited and a method
using a box type dryer, a spray dryer, a drum dryer or the like is usable. In this
case, the resultant dried material (catalyst precursor) is preferably powder in
view of the subsequent molding. The dried material may be molded directly or
after calcined. A method for molding is not particularly limited either and, for
example, tablet molding, extrusion molding, granulation, supporting on carrier or
the like can be mentioned. As a carrier of supported catalyst, for example,
inert carriers such as silica, alumina, silica-alumina and silicon carbide can be
mentioned. When molding is carried out, additives, for example, inorganic
salts such as barium sulfate and ammonium nitrate, lubricants such as graphite,
organic materials such as cellulose, starch, polyvinyl alcohol and stearic acid,
hydroxide sols such as silica sol and alumina sol, inorganic fibers such as
whisker, glass fiber and carbon fiber, or the like may be properly added with a
view to controlling specific surface area, pore volume and pore-size distribution
and improving mechanical strength of the molded articles.
[0040]
When a molded article is calcined, calcinations may be carried out either
before the molded article being packed in a reactor or in the reactor in which the
molded article has been packed. Calcining conditions can not be exactly said
because they are variant depending on raw materials of a catalyst to be used, a
catalyst composition, a preparing condition and the like. However, they are
preferably from 300 to 500°C, more preferably from 300 to 450°C, under a flow
of oxygen-containing gas such as air and/or inert gas, for 0.5 hour or more,
more preferably from 1 to 40 hours.
[0041]

(Production of methacrylic acid)
Hereinafter, a reaction condition in the case of producing methacrylic acid
through gas-phase catalytic oxidation of methacrolein is explained.
[0042]
A reaction condition in the case that a reaction is carried out by using a
catalyst produced by the method of the present invention is not particularly
limited and a publicly known reaction condition can be applied.
[0043]
In the gas-phase catalytic oxidation reaction, feed gas containing at least
methacrolein and molecular oxygen is contacted with a catalyst. Normally, a
tubular reactor packed with a catalyst is used for reaction. Industrially, a
multitubular reactor equipped with a lot of reaction tubes is used.
[0044]
Concentration of methacrolein in the feed gas can be changed in a wide
range; however, it is preferably from 1 to 20% by volume, particularly preferably
from 3 to 10% by volume. In raw methacrolein, impurities such as water and
lower saturated aldehyde, which do not substantially exert influence on the
reaction, are included in some cases, but those impurities originating from
methacrolein are allowable.
[0045]
Molecular oxygen needs to be contained in the feed gas and the amount of
molecular oxygen in the feed gas is preferably 0.4 to 4 times in moles as much
as the amountof methacrolein, particularly preferably 0.5 to 3 times in moles.
As a source of molecular oxygen in the feed gas, it is industrially profitable to
use air, but oxygen-enriched air by pure oxygen can also be used, if necessary.
Further, it is preferable that the feed gas is diluted with inert gas such as
nitrogen and carbon dioxide or water vapor.
[0046]

Reaction pressure of the gas-phase catalytic oxidation is from normal
pressure to several atmospheric pressure. Reaction temperature is preferably
200 to 450°C, more preferably 250 to 400°C. Contact time of the feed gas with
the catalyst is preferably 1.5 to 15 seconds, more preferably 2 to 7 seconds.
EXAMPLES
[0047]
Next, the present invention is explained by using examples. In these
examples, "part(s)" means part(s) by mass. Further, quantitative analysis of
elements (or molecules) contained in a material was carried out by ICP emission
analysis or atomic absorption analysis. The analysis of the feed gas and
products in the production of methacrylic acid was carried out by gas
chromatography.
[0048]
A ratio of recovery of each element, conversion of methacrolein which is a raw
material, selectivity to methacrylic acid produced and yield of methacrylic acid
are defined as follows:
[0049]
a) Ratio of recovery of each element:
Ratio of recovery (% by mass) = (Wr / Ws) x 100
Wherein Wr represents the amount by mass of an element contained in an
obtained composition and Ws represents the amount by mass of an element
contained in a composition used for recovery.
[0050]
b) Conversion of methacrolein which is a raw material, selectivity to
methacrylic acid produced and per pass yield of methacrylic acid:
Conversion of methacrolein (mol%) = (B /A) x 100
Selectivity to methacrylic acid (mol%) = (C / B) x 100

Per pass yield of methacrylic acid (mol%) = (C / A) x 100
Wherein A represents mole number of methacrolein supplied; B represents
mole number of methacrolein reacted; and C represents mole number of
methacrylic acid produced.
[0051]
Reference Example 1
(Production of catalyst A for use in producing methacrylic acid)
In 300 parts of pure water, 100 parts of ammonium paramolybdate, 4.4 parts
of ammonium metavandate and 9.2 parts of cesium nitrate were dissolved at
70°C. To the resultant solution, a solution obtained by dissolving 8.7 parts of
85 mass% phosphoric acid in 10 parts of pure water was added and then 5.5
parts of antimony trioxide was added and heated to 95°C with stirring, and a
solution obtained by dissolving 1.1 parts of copper nitrate in 10 parts of pure
water was added. Further, the resultant mixed liquid was stirred for 15 minutes
at 95°C and evaporated to dryness with stirring under heating. The solid
material thus obtained was dried for 16 hours at 130°C, and then pressure
molded, and further, crushed, and particles which were passed through a 1.70
mm-mesh opening sieve and kept on a 0.85 mm-mesh opening sieve were
fractionated, and the resultant particles were heat treated at 380°C for 5 hours
under a flow of air to obtain catalyst A (the composition exclusive of oxygen: PL6
Moi2 Sb0.8 Cu0.i V0.8 CSi).
[0052]
(Test A of the production of methacrylic acid)
The catalyst A was packed in a reactor and a mixed gas containing 5% by
volume of methacrolein, 10% by volume of oxygen, 30% by volume of water
vapor and 55% by volume of nitrogen was passed through it at a reaction
temperature of 290°C and contact time of 3.6 seconds. As a result, conversion
of methacrolein was 82.9 mol%, selectivity to methacrylic acid was 83.7 mol%

and per pass yield of methacrylic acid was 69.3 mol%.
[0053]
Example 1
(Recovery of molybdenum 1)
A catalyst was produced in the same manner as in the production of catalyst A
for use in producing methacrylic acid of Reference Example 1 (the composition
exclusive of oxygen of the catalyst: P1.6 Mo12 Cs1) and by using this catalyst, the
test A of the production of methacrylic acid was carried out for 2,000 hours and
the spent catalyst was recovered. In 100 parts of the recovered catalyst, 56.3
parts of molybdenum, 2.4 parts of phosphorus and 6.5 parts of cesium were
contained. To 400 parts of pure water, 100 parts of the recovered catalyst was
dispersed. To the resultant dispersion, 130 parts of 45 mass% sodium
hydroxide aqueous solution was added and stirred for 3 hours at 60°C. The
pH of the resultant solution was 12.3. The solution was neutralized to pH 7 by
36 mass% hydrochloric acid, and a solution obtained by dissolving 20.5 parts of
magnesium chloride hexahydrate in 50 parts of pure water and 4.5 parts of 29
mass% aqueous ammonia were added, and further, the pH of the resultant
solution was adjusted to 9 by adding 29 mass% aqueous ammonia, and kept at
30°C for 3 hours with stirring, and precipitates were thus formed and the bottom
liquid (recovered molybdenum-containing liquid) were separated by filtration.
The pH of the recovered molybdenum-containing liquid thus obtained was
adjusted to 1.0 by adding 36 mass% hydrochloric acid and the resultant solution
was kept at 30°C for 3 hourawith stirring. The precipitate thus obtained was
filtrated and washed by 2 mass% ammonium nitrate solution to obtain
"recovered molybdenum-containing material 1". The recovered
molybdenum-containing material 1 contained 55.5 parts of molybdenum and 2.9
parts of cesium. And, at this time, ratio of recovery of molybdenum was 98.6%
by mass. Furthermore, phosphorus was not detected in the recovered

molybdenum-containing material 1.
[0054]
(Production of catalyst 1)
The total amount of the recovered molybdenum-containing material 1
obtained above (55.5 parts as molybdenum) was dispersed in 280 parts of pure
water and 29.1 parts of 29 mass% aqueous ammonia was added to it and the
material was dissolved at 60°C. In the resultant solution, 4.5 parts of
ammonium metavanadate and 5.2 parts of cesium nitrate were dissolved.
Then, a solution obtained by dissolving 8.9 parts of 85 mass% phosphoric acid
in 10 parts of pure water was added, and further, 5.6 parts of antimony trioxide
was added and the resultant solution was heated to 95°C with stirring, and a
solution obtained by dissolving 1.2 parts of copper nitrate in 10 parts of pure
water was added. The amount of ammonia in the resultant solution was 11.1
moles per 12 moles of molybdenum. Further, the mixed liquid was stirred for
15 minutes at 95°C, and then, evaporated to dryness with stirring under heating.
The solid material thus obtained was dried, molded, crushed, fractionated by
sieves and calcined in the same manner as in the production of catalyst A for
use in producing methacrylic acid of Reference Example 1 to obtain catalyst 1.
The composition exclusive of oxygen of the catalyst 1 was P1.6 MO12 Sb0.8 Cu0.1
V0.8 Cs1 which was the same as the catalyst A produced in Reference Example
1.
[0055]
(Test 1 of the production of methacrylic acid)
By using this catalyst 1, reaction was carried out in the same reaction
condition as that in the test A of the production of methacrylic acid and obtained
the following results. Conversion of methacrolein was 83.0 mol%, selectivity to
methacrylic acid was 83.5 mol% and per pass yield of methacrylic acid was 69.3
mol%, and the catalyst 1 had the same performance as the catalyst A.

[0056]
Example 2
(Recovery of molybdenum 2)
In 100 parts of the spent catalyst which had been used in the reaction for
2,000 hours in the test 1 of the production of methacrylic acid of Example 1,
55.1 parts of molybdenum, 2.4 parts of phosphorus, 4.5 parts of antimony, 0.3
part of copper, 2.0 parts of vanadium and 6.4 parts of cesium were contained.
The elemental composition exclusive of oxygen of the recovered catalyst was
P1.6 M012 Sb0.8 Cu0.1 V0.8 CS1. In 400 parts of pure water, 100 parts of the spent
catalyst was dispersed. To the resultant dispersion, 130 parts of 45 mass%
sodium hydroxide aqueous solution was added and stirred for 3 hours at 60°C
and its residue was removed by filtration. The pH of the resultant solution was
12.1. This solution was treated in the same manner as in the recovery of
molybdenum 1 of Example 1 and recovered molybdenum-containing liquid was
obtained. Further, recovered molybdenum-containing precipitate (recovered
molybdenum-containing material 2) was obtained in the same manner as in the
recovery of molybdenum 1 of Example 1. The recovered
molybdenum-containing material 2 contained 53.5 parts of molybdenum, 1.8
parts of vanadium and 2.6 parts of cesium. And, at this time, rate of recovery
of molybdenum was 97.1 % by mass. Furthermore, phosphorus, antimony and
copper were not detected in the recovered molybdenum-containing material 2.
[0057]
(Production of catalyst 2)
The total amount of the recovered molybdenum-containing material 2
obtained above (53.5 parts as molybdenum) was dispersed in 270 parts of pure
water and 28.1 parts of 29 mass% aqueous ammonia was added to it and the
material was dissolved at 60°C. In the resultant solution, 0.2 part of
ammonium metavanadate and 5.2 parts of cesium nitrate were dissolved.

Then, a solution obtained by dissolving 8.6 parts of 85 mass% phosphoric acid
in 10 parts of pure water was added, and further, 5.4 parts of antimony trioxide
was added and the resultant solution was heated to 95°C with stirring, and a
solution obtained by dissolving 1.1 parts of copper nitrate in 10 parts of pure
water was added. The amount of ammonia in the resultant solution was 11.1
moles per 12 moles of molybdenum. Further, the mixed liquid thus obtained
was stirred for 15 minutes at 95°C, and then, evaporated to dryness with stirring
under heating. The solid material thus obtained was dried, molded, crushed,
fractionated by sieves and calcined in the same manner as in the production of
catalyst A for use in producing methacrylic acid of Reference Example 1 to
obtain catalyst 2. The composition exclusive of oxygen of the catalyst 2 was
P1.6 MO12 Sb0.8 CU0.1 V0.8 CS1.
[0058]
(Test 2 of the production of methacrylic acid)
By using this catalyst 2, reaction was carried out in the same reaction
condition as that in the test A of the production of methacrylic acid and obtained
the following results. Conversion of methacrolein was 83.1 mol%, selectivity to
methacrylic acid was 83.5 mol% and per pass yield of methacrylic acid was 69.4
mol%, and the catalyst 2 had the same performance as the catalyst A.
[0059]
Reference Example 2
(Production of catalyst B for use in producing methacrylic acid)
In 200 parts of pure water, 100 parts of ammonium paramolybdate was
dissolved at 70CC. To the resultant solution, a solution obtained by dissolving
2.8 parts of ammonium metavanadate and 8.2 parts of 85 mass% phosphoric
acid in 30 parts of pure water, a solution obtained by dissolving 1.1 parts of
copper nitrate in 30 parts of pure water and a solution obtained by dissolving 3.8
parts of iron nitrate in 10 pars of pure water were added in this order, and the

resultant solution was heated to 90°C with stirring and kept at 90°C for 5 hours
with stirring, and a solution obtained by dissolving 9.2 parts of cesium nitrate in
100 parts of pure water was further added and the resultant liquid was
evaporated to dryness with stirring under heating. The solid material thus
obtained was dried, molded, crushed, fractionated by sieves and calcined in the
same manner as in the production of catalyst A of Reference Example 1 to
obtain catalyst B (the composition exclusive of oxygen of the catalyst B: PL5
MO12Fe0.2Cu0.1V0.5Cs1).
[0060]
(Test B of the production of methacrylic acid)
By using this catalyst B, reaction was carried out in the same reaction
condition as that in the test A of the production of methacrylic acid and obtained
the following results. Conversion of methacrolein was 82.4 mol%, selectivity to
methacrylic acid was 81.3 mol% and per pass yield of methacrylic acid was 67.0
mol%.
[0061]
Example 3
(Recovery of molybdenum 3)
In 100 parts of the spent catalyst which had been used in the reaction for
2,000 hours in the test B of the production of methacrylic acid of Reference
Example 2, 54.6 parts of molybdenum, 2.2 parts of phosphorus, 1.2 parts of
vanadium, 0.3 part of copper, 0.5 part of iron and 6.3 parts of cesium were
contained. The elemental composition exclusive of oxygen of the recovered
catalyst was P1.5 Mo12 Fe02 Cu0.1 V0.5 Cs1. In 400 parts of pure water, 100
parts of the spent catalyst was dispersed. To the resultant dispersion, 130
parts of 45 mass% sodium hydroxide aqueous solution was added and stirred
for 3 hours at 60°C and its residue was removed by filtration. The pH of the
resultant solution was 12.3. This solution was treated in the same manner as

in the recovery of molybdenum 1 of Example 1 and recovered
molybdenum-containing liquid was obtained. Further, recovered
molybdenum-containing precipitate (recovered molybdenum-containing material
3) was obtained in the same manner as in the recovery of molybdenum 1 of
Example 1. The recovered molybdenum-containing material 3 contained 53.1
parts of molybdenum, 1.1 parts of vanadium and 2.6 parts of cesium. And, at
this time, ratio of recovery of molybdenum was 97.3 % by mass. Furthermore,
phosphorus, iron and copper were not detected in the recovered
molybdenum-containing material 3.
[0062]
(Production of catalyst 3)
The total amount of the recovered molybdenum-containing material 3
obtained above (53.1 parts as molybdenum) was dispersed in 180 parts of pure
water and 27.8 parts of 29 mass% aqueous ammonia was added to it and the
material was dissolved at 60CC. To the resultant solution, a solution obtained
by dissolving 0.2 part of ammonium metavanadate and 8.0 parts of 85 mass%
phosphoric acid in 30 parts of pure water, a solution obtained by dissolving 1.1
parts of copper nitrate in 30 parts of pure water and a solution obtained by
dissolving 3.7 parts of iron nitrate in 10 pars of pure water were added in this
order, and the resultant solution was heated to 90°C with stirring and kept at
90°C for 5 hours with stirring, and a solution obtained by dissolving 5.1 parts of
cesium nitrate in 57 parts of pure water was further added. The amount of
ammonia in the resultant solution was 10.8 moles per 12 moles of molybdenum.
Further, the mixed liquid was evaporated to dryness with stirring under heating.
The solid material thus obtained was dried, molded, crushed, fractionated by
sieves and calcined in the same manner as in the production of catalyst B of
Reference Example 2 to obtain catalyst 3. The composition exclusive of
oxygen of the catalyst 3 was P1.5 Mo12 Fe0.2 CU0.1 V0.5 CS1

[0063]
(Test 3 of the production of methacrylic acid)
By using this catalyst 3, reaction was carried out in the same reaction
condition as that in the test B of the production of methacrylic acid of Reference
Example 2 and obtained the following results. Conversion of methacrolein was
82.6 mol%, selectivity to methacrylic acid was 81.2 mol% and per pass yield of
methacrylic acid was 67.1 mol%, and the catalyst 3 had the same performance
as the catalyst B.
[0064]
Reference Example 3
(Production of catalyst C for use in producing methacrylic acid)
To 400 parts of pure water, 100 parts of molybdenum trioxide, 7.3 parts of 85
mass% phosphoric acid, 4.7 parts of vanadium pentoxide, 0.9 part of copper
oxide and 0.2 part of iron oxide were added and stirred for 5 hours under
refluxing. The resultant mixed liquid was cooled to 50°C and 37.4 parts of 29
mass% aqueous ammonia was added to it by dropping and the resultant
solution was stirred for 15 minutes. Then, a solution obtained by dissolving 9.0
parts of cesium nitrate in 30 parts of pure water was added to it by dropping and
the resultant liquid was stirred for 15 minutes and evaporated to dryness with
stirring under heating. The solid material thus obtained was dried, molded,
crushed, fractionated by sieves and calcined in the same manner as in the
production of catalyst A of Reference Example 1 to obtain catalyst C (the
composition exclusive of oxygen of the catalyst C: P^ MO12 Fe0.05 Cu0.2 V0.g
CSo.8)-
[0065]
(Test C of the production of methacrylic acid)
By using this catalyst C, reaction was carried out in the same reaction
condition as that in the test A of the production of methacrylic acid of Reference

Example 1 and obtained the following results. Conversion of methacrolein was
87.4 mol%, selectivity to methacrylic acid was 85.8 mol% and per pass yield of
methacrylic acid was 75.0 mol%.
[0066]
Example 4
(Recovery of molybdenum 4)
In 100 parts of the spent catalyst which had been used in the reaction for
2,000 hours in the test C of the production of methacrylic acid of Reference
Example 3, 55.2 parts of molybdenum, 1.6 parts of phosphorus, 2.2 parts of
vanadium, 0.6 part of copper, 0.1 part of iron and 5.1 parts of cesium were
contained. The elemental composition exclusive of oxygen of the recovered
spent catalyst was P1.1 M012 Feo.05 CU0.2 V0.9 CSOO.B- In 400 parts of pure water,
100 parts of the spent catalyst was dispersed. To the resultant dispersion, 130
parts of 45 mass% sodium hydroxide aqueous solution was added and stirred
for 3 hours at 60°C and its residue was removed by filtration. The pH of the
resultant solution was 12.4. This solution was treated in the same manner as
in the recovery of molybdenum 1 of Example 1 and recovered
molybdenum-containing liquid was obtained. Further, recovered
molybdenum-containing precipitate was isolated in the same manner as in the
recovery of molybdenum 1 of Example 1 and dried at 110°C for 16 hours. The
dried material thus obtained was calcined at 550CC for 3 hours and "recovered
molybdenum-containing material 4" was obtained. The recovered
molybdenum-containing material 4 contained 53.9 parts of molybdenum, 2.0
parts of vanadium and 2.5 parts of cesium. And, at this time, ratio of recovery
of molybdenum was 97.7 % by mass. Furthermore, phosphorus, iron and
copper were not detected in the recovered molybdenum-containing material 4.
[0067]
(Production of catalyst 4)

To 320 parts of pure water, the total amount of the recovered
molybdenum-containing material 4 obtained above (53.9 parts as molybdenum),
5.9 parts of 85 mass% phosphoric acid, 0.3 part of vanadium pentoxide, 0.7 part
of copper oxide and 0.2 part of iron oxide were added and stirred for 5 hours
under refluxing. The resultant mixed liquid was cooled to 50°C and 30.2 parts
of 29 mass% aqueous ammonia was added to it by dropping and the resultant
solution was stirred for 15 minutes. Then, a solution obtained by dissolving 3.7
parts of cesium nitrate in 13 parts of pure water was added to it by dropping.
The amount of ammonia in the resultant solution was 11.0 moles per 12 moles
of molybdenum. Further, the resultant liquid was stirred for 15 minutes and
evaporated to dryness with stirring under heating. The solid material thus
obtained was dried, molded, crushed, fractionated by sieves and calcined in the
same manner as in the production of catalyst C of Reference Example 3 to
obtain catalyst 4. The composition exclusive of oxygen of the catalyst 4 was

[0068]
(Test 4 of the production of methacrylic acid)
By using the catalyst 4, reaction was carried out in the same reaction
condition as that in the test C of the production of methacrylic acid of Reference
Example 3 and obtained the following results. Conversion of methacrolein was
87.6 mol%, selectivity to methacrylic acid was 85.5 mol% and per pass yield of
methacrylic acid was 74.9 mol%, and the catalyst 4 had the same performance
as the catalyst C.
[0069]
Reference Example 4
(Production of catalyst D for use in producing methacrylic acid)
To 800 parts of pure water, 100 parts of molybdenum trioxide, 2.6 parts of
vanadium pentoxide and 6.7 parts of 85 mass% phosphoric acid were added

and the resultant solution was heated and stirred for 3 hours under refluxing.
To the resultant solution, 1.4 parts of copper oxide was added and further
heated and stirred for 2 hours under refluxing. The resultant mixed liquid after
refluxing was cooled to 50°C and a solution obtained by dissolving 7.1 parts of
potassium nitrate in 40 parts of pure water was added and a solution obtained
by dissolving 9.8 parts of ammonium nitrate in 40 parts of pure water was further
added, and the resultant liquid was evaporated to dryness with stirring under
heating. The solid material thus obtained was dried, molded, crushed,
fractionated by sieves and calcined in the same manner as in the production of
catalyst A of Reference Example 1 to obtain catalyst D (the composition
exclusive of oxygen of the catalyst D: Pi Mo12 Cu0.3 V0.5 K1.2).
[0070]
(Test D of the production of methacrylic acid)
By using this catalyst D, reaction was carried out in the same reaction
condition as that in the test A of the production of methacrylic acid of Reference
Example 1 except that the reaction temperature was 285°C, and obtained the
following results. Conversion of methacrolein was 85.0 mol%, selectivity to
methacrylic acid was 84.2 mol% and per pass yield of methacrylic acid was 71.6
mol%.
[0071]
Example 5
(Recovery of molybdenum 5)
In 100 parts of the spent catalyst which had been used in the reaction for
2,000 hours in the test D of the production of methacrylic acid of Reference
Example 4, 57.6 parts of molybdenum, 1.6 parts of phosphorus, 1.3 parts of
vanadium, 1.0 part of copper and 2.4 parts of potassium were contained. The
elemental composition exclusive of oxygen of the recovered spent catalyst was
Pi Mo12 Cuo.3 Vo.5 KL2. In 400 parts of pure water, 100 parts of the spent

catalyst was dispersed. To the resultant dispersion, 130 parts of 45 mass%
sodium hydroxide aqueous solution was added and stirred for 3 hours at 60°C
and its residue was removed by filtration. The pH of the resultant solution was
12.4. This solution was treated in the same manner as in the recovery of
molybdenum 1 of Example 1 and recovered molybdenum-containing liquid was
obtained. Further, recovered molybdenum-containing precipitate was isolated
in the same manner as in the recovery of molybdenum 1 of Example 1 and dried
at 110°C for 16 hours. The dried material thus obtained was calcined at 550°C
for 3 hours and "recovered molybdenum-containing material 5" was obtained.
The recovered molybdenum-containing material 5 contained 55.9 parts of
molybdenum, 1.1 parts of vanadium and 0.6 part of potassium. And, at this
time, ratio of recovery of molybdenum was 97.1 % by mass. Furthermore,
phosphorus and copper were not detected in the recovered
molybdenum-containing material 5.
[0072]
(Production of catalyst 5)
To 660 parts of pure water, the total amount of the recovered
molybdenum-containing material 5 obtained above (55.9 parts as molybdenum),
0.2 part of vanadium pentoxide and 5.6 parts of 85 mass% phosphoric acid
were added and the resultant solution was heated and stirred for 3 hours under
refluxing. To the resultant solution, 1.2 parts of copper oxide was added and
the resultant mixed liquid was further heated and stirred for 2 hours under
refluxing. The resultant mixed liquid after refluxing was cooled to 50°C and a
solution obtained by dissolving 4.4 parts of potassium nitrate in 26 parts of pure
water was added and a solution obtained by dissolving 8.1 parts of ammonium
nitrate in 35 parts of pure water was further added. The amount of ammonia in
the resultant solution was 2.1 moles per 12 moles of molybdenum. Further, the
resultant mixed liquid was evaporated to dryness with stirring under heating.

The solid material thus obtained was dried, molded, crushed, fractionated by
sieves and calcined in the same manner as in the production of catalyst D of
Reference Example 4 to obtain catalyst 5. The composition exclusive of
oxygen of the catalyst 5 was Pi M012 Cu0.3 V0.5 K1.2.
[0073]
(Test 5 of the production of methacrylic acid)
By using this catalyst 5, reaction was carried out in the same reaction
condition as that in the test D of the production of methacrylic acid of Reference
Example 4 and obtained the following results. Conversion of methacrolein was
85.3 mol%, selectivity to methacrylic acid was 84.1 mol% and per pass yield of
methacrylic acid was 71.7 mol%, and the catalyst 5 had the same performance
as the catalyst D.
[0074]
Reference Example 5
(Production of catalyst E for use in producing methacrylic acid)
In 400 parts of pure water, 100 parts of ammonium paramolybdate, 4.4 parts
of ammonium metavanadate and 4.8 parts of potassium nitrate were dissolved
at 70°C. To the resultant solution under stirring, a solution obtained by
dissolving 8.2 parts of 85 mass% phosphorus acid in 10 parts of pure water was
added and a solution obtained by dissolving 1.1 parts of copper nitrate in 10
parts of pure water was further added. Then, to the resultant mixed liquid
mentioned above, a homogeneous solution of bismuth nitrate obtained by
adding 7.0 parts of 60 mass% nitric acid and 40 parts of pure water to 6.9 parts -
of bismuth nitrate was added and heated to 95°C. To the resultant liquid, a
solution obtained by dissolving 2.2 parts of 60 mass% arsenic acid in 10 parts of
pure water was added and 2.1 parts of antimony trioxide and 1.6 parts of cerium
dioxide were subsequently added. The aqueous slurry thus obtained was
evaporated to dryness with stirring under heating. The solid material thus

obtained was dried, molded, crushed, fractionated by sieves and calcined in the
same manner as in the production of catalyst A of Reference Example 1 to
obtain catalyst E (the composition exclusive of oxygen of the catalyst E: P1i5
Aso.2 M012 Sbo.3 Bio.3 Ceo.2 Cuo.i V0.8 K1).
[0075]
(Test E of the production of methacrylic acid)
By using this catalyst E, reaction was carried out in the same reaction
condition as that in the test A of the production of methacrylic acid of Reference
Example 1 and obtained the following results. Conversion of methacrolein was
90.0 mol%, selectivity to methacrylic acid was 88.2 mol% and per pass yield of
methacrylic acid was 79.4 mol%.
[0076]
Example 6
(Recovery of molybdenum 6)
In 100 parts of the spent catalyst which had been used in the reaction for
2,000 hours in the test E of the production of methacrylic acid of Reference
Example 5, 55.7 parts of molybdenum, 2.3 parts of phosphorus, 0.7 part of
arsenic, 1.8 parts of antimony, 3.0 parts of bismuth, 1.4 parts of cerium, 0.3 part
of copper, 2.0 parts of vanadium and 1.9 parts of potassium were contained.
The elemental composition exclusive of oxygen of the recovered spent catalyst
was PLS AS0.2 M012 Sbo.3 Bi0.3 Ce0.2 Cu0.i V0.8 K1. In 400 parts of pure water,
100 parts of the spent catalyst was dispersed. To the resultant dispersion, 130
parts of 45 mass% sodium hydroxide aqueous solution was added and stirred
and kept for 3 hours at 60°C. The pH of the resultant solution was 12.2. This
solution was treated in the same manner as in the recovery of molybdenum 1 of
Example 1 and recovered molybdenum-containing liquid was obtained. To the
recovered molybdenum-containing liquid thus obtained, 36 mass% hydrochloric
acid was added and pH of the resultant solution was adjusted to 6.0, and the

resultant solution was passed through a column of weak basic ion-exchange
resin (trade name "XE-583" manufactured by ORGANO CORPORATION).
The solution after treatment by the ion-exchange resin was treated in the same
manner as in the recovery of molybdenum 1 of Example 1 and recovered
molybdenum-containing precipitate (recovered molybdenum-containing material
6) was obtained. The recovered molybdenum-containing material 6 contained
53.6 parts of molybdenum and 0.5 part of potassium. And, at this time, ratio of
recovery of molybdenum was 96.2 % by mass. Furthermore, phosphorus,
arsenic, antimony, bismuth, cerium, copper and vanadium were not detected in
the recovered molybdenum-containing material 6.
[0077]
(Production of catalyst 6)
To 650 parts of pure water, the total amount of the recovered
molybdenum-containing material 6 obtained above (53.6 parts as molybdenum),
2.1 parts of vanadium pentoxide and 5.5 parts of 85 mass% phosphoric acid
were added, and heated and stirred for 3 hours under refluxing. To the
resultant solution, 1.1 parts of copper oxide was added and the resultant mixed
liquid was further heated and stirred for 2 hours under refluxing. The mixed
liquid after refluxing was cooled to 50°C and a solution obtained by dissolving
4.6 parts of potassium nitrate in 26 parts of pure water was added and a solution
obtained by dissolving 8.0 parts of ammonium nitrate in 35 parts of pure water
was further added. The amount of ammonia in the resultant solution was 2.1
moles per 12 moles of molybdenum. Further, the resultant mixed liquid was
evaporated to dryness with stirring under heating. The solid material thus
obtained was dried, molded, crushed, fractionated by sieves and calcined in the
same manner as in the production of catalyst D of Reference Example 4 to
obtain catalyst 6. The composition exclusive of oxygen of the catalyst 6 was Pi
M012 CUo.3 VQ.5 K1.2.

[0078]
(Test 6 of the production of methacrylic acid)
By using this catalyst 6, reaction was carried out in the same reaction
condition as that in the test D of the production of methacrylic acid of Reference
Example 4 and obtained the following results. Conversion of methacrolein was
85.2 mol%, selectivity to methacrylic acid was 84.0 mol% and per pass yield of
methacrylic acid was 71.6 mol%, and the catalyst 6 had the same performance
as the catalyst D.
[0079]
Reference Example 6
(Production of catalyst F for use in producing methacrylic acid)
To 800 parts of pure water, 100 parts of molybdenum trioxide, 3.2 parts of
vanadium pentoxide and 8.7 parts of 85 mass% phosphoric acid were added
and the resultant solution was heated and stirred for 3 hours under refluxing.
To the resultant solution, 1.4 parts of copper nitrate was added and the resultant
solution was further heated and stirred for 2 hours under refluxing. The mixed
liquid after refluxing was cooled to 60°C and a solution obtained by dissolving
12.3 parts of cesium bicarbonate in 30 parts of pure water was added and
stirred for 15 minutes. Then, to the resultant solution, a solution obtained by
dissolving 10 parts of ammonium nitrate in 30 parts of pure water was added
and further stirred for 15 minutes, and the resultant solution was evaporated to
dryness with stirring under heating. The solid material thus obtained was dried,
molded, crushed, fractionated by sieves in the same manner as in the
production of catalyst A of Reference Example 1 and calcined for 5 hours at
400°C under a flow of nitrogen to obtain catalyst F (the composition exclusive of
oxygen of the catalyst F: P13 Mo12 Cu01 V06 Csi.i).
[0080]
(Test F of the production of methacrylic acid)

By using this catalyst F, reaction was carried out in the same reaction
condition as that in the test A of the production of methacrylic acid of Reference
Example 1 and obtained the following results. Conversion of methacrolein was
83.4 mol%, selectivity to methacrylic acid was 84.9 mol% and per pass yield of
methacrylic acid was 70.8 mol%.
[0081]
Example 7
(Recovery of molybdenum 7)
In 100 parts of the spent catalyst which had been used in the reaction for
2,000 hours in the test F of the production of methacrylic acid of Reference
Example 6, 55.9 parts of molybdenum, 2.0 parts of phosphorus, 1.5 parts of
vanadium, 0.3 part of copper and 7.1 parts of cesium were contained. The
elemental composition exclusive of oxygen of the recovered catalyst was PL3
M012 Cu0.i Vo.6 CSM . In 400 parts of pure water, 100 parts of the spent catalyst
was dispersed. To the resultant dispersion, 25.7 parts of sodium hypochlorite
(effective chlorine: 12 mass%) was added and stirred for 3 hours at 60°C, and
130 parts of 45 mass% sodium hydroxide aqueous solution was added and
further stirred for 3 hours at 60°C and its residue was removed by filtration.
The pH of the resultant solution was 12.4. This solution was treated in the
same manner as in the recovery of molybdenum 1 of Example 1 and recovered
molybdenum-containing liquid was obtained. Further, recovered
molybdenum-containing precipitate was isolated in the same manner as in the
recovery of molybdenum 1 of Example 1 and dried at 110°C for 16 hours. The
dried material thus obtained was calcined at 550°C for 3 hours and "recovered
molybdenum-containing material 7" was obtained. The recovered
molybdenum-containing material 7 contained 54.1 parts of molybdenum, 1.2
parts of vanadium and 2.9 parts of cesium. And, at this time, ratio of recovery
of molybdenum was 96.8 % by mass. Furthermore, phosphorus and copper

were not detected in the recovered molybdenum-containing material 7.
[0082]
(Production of catalyst 7)
To 650 parts of pure water, the total amount of the recovered
molybdenum-containing material 7 obtained above (54.1 parts as molybdenum),
0.9 part of vanadium pentoxide and 7.0 parts of 85 mass% phosphoric acid
were added and the resultant solution was heated and stirred for 3 hours under
refiuxing. To the resultant solution, 0.9 part of copper nitrate was added and
the resultant solution was further heated and stirred for 2 hours under refiuxing.
The mixed liquid after refiuxing was cooled to 60°C and a solution obtained by
dissolving 5.7 parts of cesium bicarbonate in 14 parts of pure water was added
and stirred for 15 minutes. Then, to the resultant solution, a solution obtained
by dissolving 8.1 parts of ammonium nitrate in 24.4 parts of pure water was
added. The amount of ammonia in the resultant solution was 2.2 moles per 12
moles of molybdenum. Further, the resultant mixed liquid was stirred for 15
minutes and evaporated to dryness with stirring under heating. The solid
material thus obtained was dried, molded, crushed, fractionated by sieves and
calcined in the same manner as in the production of catalyst F of Reference
Example 6 to obtain catalyst 7. The composition exclusive of oxygen of the
catalyst 7 was P1.3 Moi2 Cu0.i V06 Csu.
[0083]
(Test 7 of the production of methacrylic acid)
By using this catalyst 7, reaction was carried out in the same reaction
condition as that in the test F of the production of methacrylic acid of Reference
Example 6 and obtained the following results. Conversion of methacrolein was
83.6 mol%, selectivity to methacrylic acid was 84.5 mol% and per pass yield of
methacrylic acid was 70.6 mol%, and the catalyst 7 had the same performance
as the catalyst F.

[0084]
Reference Example 7
(Production of catalyst G for use in producing methacrylic acid)
In 300 parts of pure water, 100 parts of ammonium paramolybdate, 1.7 parts
of ammonium metavanadate and 4.8 parts of potassium nitrate were dissolved
at 70°C. To the resultant solution, a solution obtained by dissolving 8.2 parts of
85 mass% phosphorus acid in 10 parts of pure water was added and 4.1 parts
of antimony trioxide was added and the resultant liquid was heated to 95°C with
stirring, and a solution obtained by dissolving 1.1 parts of copper nitrate in 30
parts of pure water was further added. Subsequently, to the resultant liquid,
4.5 parts of 20 mass% nitric acid was added. The resultant mixed liquid was
evaporated to dryness with stirring under heating. The solid material thus
obtained was dried, molded, crushed, fractionated by sieves and calcined in the
same manner as in the production of catalyst A of Reference Example 1 to
obtain catalyst G (the composition exclusive of oxygen of the catalyst G: P1]5
Mo12 Sb0.6 Cuo.i V0.3 K,).
[0085]
(Test G of the production of methacrylic acid)
By using this catalyst G, reaction was carried out in the same reaction
condition as that in the test A of the production of methacrylic acid of Reference
Example 1 except that the reaction temperature was 280°C, and obtained the
following results. Conversion of methacrolein was 80.2 mol%, selectivity to
methacrylic acid was 82.3 mol% and per pass yield of methacrylic acid was 66.0
mol%.
[0086]
(Recovery of molybdenum 8)
In 100 parts of the spent catalyst which had been used in the reaction for
2,000 hours in the test G of the production of methacrylic acid of Reference

Example 7, 55.9 parts of molybdenum, 2.3 parts of phosphorus, 0.7 part of
vanadium, 0.3 part of copper, 3.5 parts of antimony and 1.9 parts of potassium
were contained. The elemental composition exclusive of oxygen of the
recovered catalyst was P1.5 Mo12 Sb06 Cu0.i V0.3 Ki. In 400 parts of pure water,
100 parts of the spent catalyst was dispersed. To the resultant dispersion, 130
parts of 45 mass% sodium hydroxide aqueous solution was added and stirred
for 3 hours at 60°C and its residue was removed by filtration. The pH of the
resultant solution was 12.1. This solution was treated in the same manner as
in the recovery of molybdenum 1 of Example 1 and recovered
molybdenum-containing liquid was obtained. Further, recovered
molybdenum-containing precipitate (recovered molybdenum-containing material
8) was obtained in the same manner as in the recovery of molybdenum 1 of
Example 1. The recovered molybdenum-containing material 8 contained 54.5
parts of molybdenum, 0.6 part of vanadium and 0.5 part of potassium. And, at
this time, ratio of recovery of molybdenum was 97.5 % by mass. Furthermore,
phosphorus, antimony and copper were not detected in the recovered
molybdenum-containing material 8.
[0087]
(Production of catalyst 8)
The total amount of the recovered molybdenum-containing material 8
obtained above (54.5 parts as molybdenum) was dispersed in 270 parts of pure
water and 28.6 parts of 29 mass% aqueous ammonia was added to it and the
material was dissolved at 60°C. In the resultant solution, 0.3 part of
ammonium metavanadate and 3.6 parts of potassium nitrate were dissolved.
Then, a solution obtained by dissolving 8.2 parts of 85 mass% phosphoric acid
in 10 parts of pure water was added, and further, 4.1 parts of antimony trioxide
was added and the resultant solution was heated to 95°C with stirring, and a
solution obtained by dissolving 1.1 parts of copper nitrate in 30 parts of pure

water was added, and then 4.5 parts of 20 mass% nitric acid was added. The
amount of ammonia in the resultant solution was 10.6 moles per 12 moles of
molybdenum. Further, the mixed liquid thus obtained was evaporated to
dryness with stirring under heating. The solid material thus obtained was dried,
molded, crushed, fractionated by sieves and calcined in the same manner as in
the production of catalyst A of Reference Example 1 to obtain catalyst %. The
composition exclusive of oxygen of the catalyst 8 was P1.5 Mo12 Sb0.6 Cu0.i V0.3
K,.
[0088]
(Test 8 of the production of methacrylic acid)
By using this catalyst 8, reaction was carried out in the same reaction
condition as that in the test G of the production of methacrylic acid of Reference
Example 7 and obtained the following results. Conversion of methacrolein was
80.1 mol%, selectivity to methacrylic acid was 82.5 mol% and per pass yield of
methacrylic acid was 66.1 mol%, and the catalyst 8 had the same performance
as the catalyst G
[0089]
Reference Example 8
(Production of catalyst H for use in producing methacrylic acid)
To 200 parts of pure water, 100 parts of molybdenum trioxide, 2.6 parts of
vanadium pentoxide, 6.7 parts of 85 mass% phosphoric acid and 2.7 parts of 60
mass% arsenic acid were added and the resulting solution was heated and
stirred for 5 hours under refluxing. The resultant solution was cooled to 50°C
and a solution obtained by dissolving 13.5 parts of cesium nitrate in 30 parts of
pure water was added, and the mixed liquid thus obtained was heated to 70°C
with stirring. Then, 34.0 parts of 29 mass% aqueous ammonia was added and
the resultant mixed liquid was stirred for 90 minutes at 70°C and a solution
obtained by dissolving 2.8 parts of copper nitrate in 10 parts of pure water and a

solution obtained by dissolving 1.2 parts of iron nitrate in 10 parts of pure water
were further added, and the resultant liquid was evaporated to dryness with
stirring under heating. The solid material thus obtained was dried, molded,
crushed, fractionated by sieves and calcined in the same manner as in the
production of catalyst A of Reference Example 1 to obtain catalyst H (the
composition exclusive of oxygen of the catalyst H: Pi AS0.2M012 Feo.osCu0.2 V0.5
CS1.2).
[0090]
(Test H of the production of methacrylic acid)
By using this catalyst H, reaction was carried out in the same reaction
condition as that in the test A of the production of methacrylic acid of Reference
Example 1 and obtained the following results. Conversion of methacrolein was
82.5 mol%, selectivity to methacrylic acid was 87.6 mol% and per pass yield of
methacrylic acid was 72.3 mol%.
[0091]
Example 9
(Recovery of molybdenum 9)
In 100 parts of the spent catalyst which had been used in the reaction for
2,000 hours in the test H of the production of methacrylic acid of Reference
Example 8, 55.8 parts of molybdenum, 1.5 parts of phosphorus, 1.2 parts of
vanadium, 0.6 part of copper, 0.1 part of iron, 0.7 part of arsenic and 7.7 parts of
cesium were contained. The elemental composition exclusive of oxygen of the
recovered spent catalyst was Pi Aso.2Mo12 Fe0.o5 Cu0.2 V0.5 Csi.2. In 400 parts
of pure water, 100 parts of the spent catalyst was dispersed. To the resultant
dispersion, 130 parts of 45 mass% sodium hydroxide aqueous solution was
added and stirred for 3 hours at 60°C and its residue was removed by filtration.
The pH of the resultant solution was 12.2. This solution was treated in the
same manner as in the recovery of molybdenum 1 of Example 1 and recovered

molybdenum-containing liquid was obtained. Further, recovered
molybdenum-containing precipitate was isolated in the same manner as in the
recovery of molybdenum 1 of Example 1 and dried at 110°C for 16 hours. The
dried material thus obtained was calcined at 550°C for 3 hours and "recovered
molybdenum-containing material 9" was obtained. The recovered
molybdenum-containing material 9 contained 54.3 parts of molybdenum, 1.0
part of vanadium and 2.9 parts of cesium. And, at this time, ratio of recovery of
molybdenum was 97.4 % by mass. Furthermore, phosphorus, arsenic, iron
and copper were not detected in the recovered molybdenum-containing material
9.
[0092]
(Production of catalyst 9)
To 160 parts of pure water, the total amount of the recovered
molybdenum-containing material 9 obtained above (54.3 parts as molybdenum),
0.4 part of vanadium pentoxide, 5.4 parts of 85 mass% phosphoric acid and 2.2
parts of 60 mass% arsenic acid were added and the resultant solution was
heated and stirred for 5 hours under refluxing. The resultant solution was
cooled to 50°C and a solution obtained by dissolving 6.7 parts of cesium nitrate
in 15 parts of pure water was added, and the mixed liquid thus obtained was
heated to 70°C. Then, 27.4 parts of 29 mass% aqueous ammonia was added
and the resultant mixed liquid was stirred for 90 minutes at 70°C and a solution
obtained by dissolving 2.3 parts of copper nitrate in 8 parts of pure water and a
solution obtained by dissolving 1.0 part of iron nitrate in 8 parts of pure water
were further added. The amount of ammonia in the resultant solution was 9.9
moles per 12 moles of molybdenum. Further, the resultant mixed liquid was
evaporated to dryness with stirring under heating. The solid material thus
obtained was dried, molded, crushed, fractionated by sieves and calcined in the
same manner as in the production of catalyst H of Reference Example 8 to

obtain catalyst 9. The composition exclusive of oxygen of the catalyst 9 was P1
AS0.2M012 Fe0.05Cu0.2 V0.5 Cs1.2.
[0093]
(Test 9 of the production of methacrylic acid)
By using this catalyst 9, reaction was carried out in the same reaction
condition as that in the test H of the production of methacrylic acid of Reference
Example 8 and obtained the following results. Conversion of methacrolein was
82.7 mol%, selectivity to methacrylic acid was 87.4 mol% and per pass yield of
methacrylic acid was 72.3 mol%, and the catalyst 9 had the same performance
as the catalyst H.
[0094]
Example 10
(Production of catalyst 10)
To 260 parts of pure water, the total amount of the recovered
molybdenum-containing material obtained in the same manner as in recovery of
molybdenum 9 of Example 9 (54.3 parts as molybdenum), 50 parts of
molybdenum trioxide obtained by calcining ammonium paramolybdate at 550°C
for 3 hours, 1.7 part of vanadium pentoxide, 8.8 parts of 85 mass% phosphoric
acid and 3.6 parts of 60 mass% arsenic acid were added and the resultant
solution was heated and stirred for 5 hours under refluxing. The resultant
solution was cooled to 50oC and a solution obtained by dissolving 13.5 parts of
cesium nitrate in 30 parts of pure water was added, and the mixed liquid thus
obtained was heated to 70°C. Then, 44 parts of 29 mass% aqueous ammonia
was added. The amount of ammonia in the resultant solution was 9.9 moles
per 12 moles of molybdenum. The resultant mixed liquid was stirred at 70°C
for 90 minutes and a solution obtained by dissolving 3.7 parts of copper nitrate
in 13 parts of pure water and a solution obtained by dissolving 1.6 parts of iron
nitrate in 13 parts of pure water were added and the resultant mixed liquid was

evaporated to dryness with stirring under heating. The solid material thus
obtained was dried, molded, crushed, fractionated by sieves and calcined in the
same manner as in the production of catalyst H of Reference Example 8 to
obtain catalyst 10. The composition exclusive of oxygen of the catalyst 10 was
P1 AS0.2M012 Fe0.05Cu0.2 V0.5 Cs1.2.
[0095]
(Test 10 of the production of methacrylic acid)
By using this catalyst 10, reaction was carried out in the same reaction
condition as that in the test H of the production of methacrylic acid of Reference
Example 8 and obtained the following results. Conversion of methacrolein was
82.9 mol%, selectivity to methacrylic acid was 87.3 mol% and per pass yield of
methacrylic acid was 72.4 mol%, and the catalyst 10 had the same performance
as the catalyst H.
[0096]
Comparative Example 1
(Recovery of molybdenum 10)
The same manner as in the recovery of molybdenum 1 of Example 1 was
carried out except that pH of the liquid after adding 45 mass% sodium hydroxide
aqueous solution and stirring was adjusted to 4 by 36 mass% hydrochloric acid
and pH of the liquid after adding magnesium chloride hexahydrate solution and
29 mass% aqueous ammonia was adjusted to 5 by 29 mass% aqueous
ammonia, and thus "recovered molybdenum-containing material 10" was
obtained. The recovered molybdenum-containing material 10 contained 21.4
parts of molybdenum, and 0.6 part of phosphorus. At this time, ratio of
recovery of molybdenum was 38.2 % by mass and the ratio of recovery was
drastically lowered. Removal of phosphorus was insufficient in this method.
Nevertheless, cesium was not detected in the recovered
molybdenum-containing material 10.

[0097]
Comparative Example 2
(Recovery of molybdenum 11)
The same manner as in the recovery of molybdenum 1 of Example 1 was
carried out except that 36 mass% hydrochloric acid was not added after adding
45 mass% sodium hydroxide aqueous solution and stirring and 29 mass%
aqueous ammonia was not added after adding magnesium chloride
hexahydrate solution and 29 mass% aqueous ammonia, and thus "recovered
molybdenum-containing material 11" was obtained. The recovered
molybdenum-containing material 11 contained 54.3 parts of molybdenum, 1.5
parts of phosphorus and 5.9 parts of cesium. At this time, ratio of recovery of
molybdenum was 96.4 % by mass, however, removal of phosphorus was
insufficient in this method.
INDUSTRIALAPPLICABILITY
By the method for recovering molybdenum of the present invention,
molybdenum can be recovered in high yield from a molybdenum-containing
material comprising at least molybdenum, A element (phosphorus and/or
arsenic) and X element (at least one selected from the group consisting of
potassium, rubidium, cesium and thallium), and hence, a spent
molybdenum-containing material, in particular, a spent catalyst can be used
effectively. Further, by using the present invention, it is possible to produce a
catalyst by using a recovered molybdenum-containing material which has been
recovered from the molybdenum-containing material comprising at least
molybdenum, A element and X element as a raw material for the catalyst, and
hence, the molybdenum-containing material comprising at least molybdenum, A
element and X element, in particular, a catalyst for use in producing methacrylic
acid can be used effectively even after it has been spent.

WE CLAIM:
1. A method for recovering molybdenum comprising the steps of:
1) dispersing a molybdenum-containing material which contains at
least molybdenum, A element (phosphorus and/or arsenic) and X element
(at least one element selected from the group consisting of potassium,
rubidium, cesium and thallium) in water and adding alkali to make pH of
the resultant mixed liquid 8 or more;
2) adjusting pH of the resultant mixed liquid to fall within the range of
from 6 to 12 followed by adding a compound containing magnesium and
aqueous ammonia to form a precipitate containing at least magnesium
and A element; and
3) separating the precipitate containing at least magnesium and A
element formed in the step 2) from a solution containing at least
molybdenum (recovered molybdenum-containing liquid);
wherein the molybdenum-containing material which contains at least
molybdenum, A element (phosphorus and/or arsenic) and X element (at
least one element selected from the group consisting of potassium,
rubidium, cesium and thallium) is a catalyst for use in producing
methacrylic acid through gas-phase catalytic oxidation of methacrolein
having a composition represented by the following formula (1):


wherein Mo and O represent molybdenum and oxygen, respectively; A
represents phosphorus and/or arsenic; Y represents at least one element
selected from the group consisting of iron, cobalt, nickel, copper, zinc,
magnesium, calcium, strontium, barium, titanium, vanadium, chromium,
tungsten, manganese, silver, boron, silicon, aluminum, gallium,
germanium, tin, lead, antimony, bismuth, niobium, tantalum, zirconium,
indium, sulfur, selenium, tellurium, lanthanum and cerium; X represents at
least one element selected from the group consisting of potassium,
rubidium, cesium and thallium; and subscripts a, b, c, d, and e represent
an atomic ratio of each element, respectively; when b is 12, a is in the
range of from 0.1 to 3, c is in the range of from 0 to 3 and d is in the range
of from 0.01 to 3 and e represents the atomic ratio of oxygen necessary
for fulfilling the requirement of the valence of each element above.
2. The method for recovering molybdenum as claimed in claim 1, further
comprising the step of
4) forming a precipitate containing at least molybdenum by adjusting
the pH of the recovered molybdenum-containing liquid to 3 or less and
separating the precipitate thus formed (recovered molybdenum-containing
precipitate) from the solution.

3. A method for producing a catalyst by using a recovered molybdenum-
containing liquid and/or a recovered molybdenum-containing precipitate
(expressed altogether as "recovered molybdenum-containing material")
which has been recovered by using the method as claimed in claim 1 or 2.
4. The method for producing a catalyst as claimed in claim 3, wherein the
catalyst is produced by using a raw material of molybdenum other than the
recovered molybdenum-containing material together with the recovered
molybdenum-containing material.
5. The method for producing a catalyst as claimed in claim 3 or 4, wherein 1
to 17 moles of ammonia per 12 atoms of molybdenum is included when
the catalyst is produced.
6. The method for producing a catalyst as claimed in any one of claims 3 to
5, wherein the temperature of solution or slurry in the entire steps or a part
of the steps in the production of catalyst is 0 to 40°C lower than that in the
case where a raw material of molybdenum other than the recovered
molybdenum-containing material which has been recovered by using the
method as claimed in claim 1 or 2 is used.

7. The method for producing a catalyst as claimed in any one of claims 3 to
6, wherein the catalyst has a composition represented by the following
formula (1):

wherein Mo and O represent molybdenum and oxygen, respectively; A
represents phosphorus and/or arsenic; Y represents at least one element
selected from the group consisting of iron, cobalt, nickel, copper, zinc,
magnesium, calcium, strontium, barium, titanium, vanadium, chromium, tungsten,
manganese, silver, boron, silicon, aluminum, gallium, germanium, tin, lead,
antimony, bismuth, niobium, tantalum, zirconium, indium, sulfur, selenium,
tellurium, lanthanum and cerium; X represents at least one element selected
from the group consisting of potassium, rubidium, cesium and thallium; and
subscripts a, b, c, d, and e represent an atomic ratio of each element,
respectively; when b is 12, a is in the range of from 0.1 to 3, c is in the range of
from 0 to 3 and d is in the range of from 0.01 to 3 and e represents the atomic
ratio of oxygen necessary for fulfilling the requirement of the valence of each
element above.


A method for obtaining a material containing recovered molybdenum for use in
producing a catalyst from a molybdenum-containing material comprising at least
molybdenum, A element (phosphorus and/or arsenic) and X element (at least
one selected from the group consisting of potassium, rubidium, cesium and
thallium), in particular, from a spent catalyst; and a method for producing a
catalyst using said material containing recovered molybdenum, a particularly
preferred catalyst is a catalyst for use in producing methacrylic acid through gas-
phase catalytic oxidation.

Documents:

02542-kolnp-2006 abstract.pdf

02542-kolnp-2006 claims.pdf

02542-kolnp-2006 correspondence others.pdf

02542-kolnp-2006 description (complete).pdf

02542-kolnp-2006 form-1.pdf

02542-kolnp-2006 form-2.pdf

02542-kolnp-2006 form-3.pdf

02542-kolnp-2006 form-5.pdf

02542-kolnp-2006 international publication.pdf

02542-kolnp-2006 international search report.pdf

02542-kolnp-2006 pct form.pdf

02542-kolnp-2006 priority document.pdf

02542-kolnp-2006-correspondence others-1.1.pdf

02542-kolnp-2006-correspondence-1.2.pdf

02542-kolnp-2006-form-26.pdf

02542-kolnp-2006-international search authority report-1.1.pdf

02542-kolnp-2006-pct others.pdf

2542-KOLNP-2006-(12-09-2012)-FORM-27.pdf

2542-KOLNP-2006-ABSTRACT.pdf

2542-KOLNP-2006-AMANDED CLAIMS.pdf

2542-KOLNP-2006-CORRESPONDENCE 1.1.pdf

2542-KOLNP-2006-CORRESPONDENCE.1.2.pdf

2542-KOLNP-2006-CORRESPONDENCE.pdf

2542-KOLNP-2006-EXAMINATION REPORT REPLY RECIEVED.pdf

2542-KOLNP-2006-EXAMINATION REPORT.1.2.pdf

2542-KOLNP-2006-FORM 1.pdf

2542-KOLNP-2006-FORM 18.1.2.pdf

2542-kolnp-2006-form 18.pdf

2542-KOLNP-2006-FORM 2.pdf

2542-KOLNP-2006-FORM 26.1.2.pdf

2542-KOLNP-2006-FORM 3.1.2.pdf

2542-KOLNP-2006-FORM 3.pdf

2542-KOLNP-2006-FORM 5.1.2.pdf

2542-KOLNP-2006-FORM-27.pdf

2542-KOLNP-2006-GRANTED-ABSTRACT.pdf

2542-KOLNP-2006-GRANTED-CLAIMS.pdf

2542-KOLNP-2006-GRANTED-DESCRIPTION (COMPLETE).pdf

2542-KOLNP-2006-GRANTED-FORM 1.pdf

2542-KOLNP-2006-GRANTED-FORM 2.pdf

2542-KOLNP-2006-GRANTED-SPECIFICATION.pdf

2542-KOLNP-2006-OTHERS.pdf

2542-KOLNP-2006-REPLY TO EXAMINATION REPORT.1.2.pdf

2542-KOLNP-2006-TRANSLATED COPY OF PRIORITY DOCUMENT.1.2.pdf

2542-KOLNP-2006-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf


Patent Number 250571
Indian Patent Application Number 2542/KOLNP/2006
PG Journal Number 02/2012
Publication Date 13-Jan-2012
Grant Date 10-Jan-2012
Date of Filing 05-Sep-2006
Name of Patentee MITSUBISHI RAYON CO., LTD.
Applicant Address 6-41, KONAN 1-CHOME, MINATO-KU TOKYO 108-8506
Inventors:
# Inventor's Name Inventor's Address
1 TOMOMASA TATSUMI C/O CORPORATE RESEARCH LABORATORIES, MITSUBISHI RAYON CO., LTD., 20-1, MIYUKICHO, OTAKE-SHI, HIROSHIMA 739-0693 JAPAN
2 TORU KURODA C/O OTAKE PLANTS, MITSUBISHI RAYON CO., LTD., 20-1, MIYUKICHO, OTAKE-SHI, HIROSHIMA 739-0693 JAPAN
3 HIROYUKI NAITOU C/O CORPORATE RESEARCH LABORATORIES, MITSUBISHI RAYON CO., LTD., 20-1, MIYUKICHO, OTAKE-SHI, HIROSHIMA 739-0693 JAPAN
PCT International Classification Number B01J 38/00
PCT International Application Number PCT/JP2005/002593
PCT International Filing date 2005-02-18
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2004-047935 2004-02-24 Japan
2 2004-234723 2004-08-11 Japan