Title of Invention

A METHOD OF PRODUCING ETHYLENE AND PROPYLENE

Abstract This invention relates to a process for efficiently and stably producing ethylene and propylene which comprises bringing a hydrocarbon feedstock comprising at least one C4-12 olefin into contact with a zeolite-containing catalyst to obtain a reaction mixture containing ethylene and a fraction comprising C4 and higher hydrocarbons, and recycling the C4 and higher hydrocarbon as they are to a reactor.
Full Text TECHNICAL FIELD
The present invention relates to a method of
catalytic conversion of hydrocarbon starting materials.
More particularly, it relates to a method of
efficiently and stably producing ethylene and propylene
useful as petroleum chemistry starting materials from
olefinic hydrocarbon starting materials using specific
zeolites, reaction conditions and specific reaction
processes.
BACKGROUND ART
There are known many methods of catalytically
converting hydrocarbon starting materials containing
olefins using catalysts containing zeolite, and there
are many reports on the method of producing ethylene
and propylene by catalytic conversion.
JP-A-49-41322 discloses a method of
conversion of a paraffin, olefin and/or cycloparaffin
(naphthene) of 5 or more carbon atoms, to an aromatic
hydrocarbon, ethylene and propylene using an H (proton)
type ZSM-5 zeolite. However, according to this method,
aromatic hydrocarbons are obtained in a relatively high
yield, whereas yields of ethylene and propylene are
low.
JP-A-50-49233 discloses a method of
conversion of an olefin or paraffin of 2-4 carbon atoms
to an aromatic hydrocarbon, ethylene and propylene
using a proton type ZSM-5 zeolite. However, according
to this method, the aromatic hydrocarbon is also
obtained in a relatively high yield, but yields of
ethylene and propylene are low.
U.S. patent Nos. 4,527,001 and 4,613,721
disclose methods of conversion of butene to ethylene
and propylene using an aluminophosphate-based molecular
sieve. However, yields of ethylene and propylene are
also low in this method.
EPC Publication 0109060 discloses a method of
conversion of an olefin of 4-12 carbon atoms to
ethylene and propylene using an H type ZSM-5 zeolite
having a molar ratio SiO2/Al203 of 350 or higher under
specific reaction conditions.
WO 2000/010948 discloses a method of
conversion of an olefin of 4-12 carbon atoms to
ethylene and propylene using a non-proton type ZSM-5
zeolite having a molar ratio SiO2/Al2O3 of 200-5000 and
containing a metal of Group IB.
In the method of converting an olefin of 4-12
carbon atoms to ethylene and propylene using a zeolite-
containing catalyst, olefins of about 4-8 carbon atoms
are obtained as reaction products in addition to
ethylene and propylene. This is because the starting
olefin is dimerized and decomposed by the catalyst to
result in conversion to the composition which is close
to the equilibrium composition under the reaction
conditions. Therefore, in order to efficiently convert
the starting olefin to ethylene and propylene, it is
essential to efficiently recycle olefins of 4 or more
carbon atoms in the reaction products to the reaction
vessel by a simple method.
EPC Publication 0109060 describes a method of
recycling to the reaction vessel the olefins of 4-8
carbon atoms obtained by removing aromatic hydrocarbons
from the reaction products. Furthermore, WO
2000/010948 describes a method of recycling to the
reaction vessel the olefins of 4-8 carbon atoms
obtained by removing fractions having a boiling point
higher than those of aromatic hydrocarbons of 8 carbon
atoms from the reaction products. However, these
methods require a plurality of separators for obtaining
the recycling materials, which increases apparatus cost
and operating cost. Thus, a simpler method has been
demanded.
DISCLOSURE OF INVENTION
An object of the present invention is to
provide an improved recycling process for attaining
efficient and stable production of ethylene and
propylene by obtaining recycling materials from
reaction products by a simple process in a method of
producing ethylene and propylene from a hydrocarbon
starting material containing at least one olefin of 4-
12 carbon atoms using a catalyst containing a medium
pore diameter zeolite.
The inventors have conducted intensive
research in an attempt to attain the above object. As
a result, it has been unexpectedly found that in a
method of obtaining a reaction mixture containing
ethylene and propylene by contacting a hydrocarbon
starting material containing an olefin of 4-12 carbon
atoms with a specific zeolite-containing catalyst under
specific conditions, even when the reaction mixture is
separated into a fraction comprising hydrogen and a
hydrocarbons of 3 or less carbon atoms and a
hydrocarbon of 4 or more carbon atoms, and the
hydrocarbon of 4 or more carbon atoms is used, as it
is, as a recycling material (without removing heavy
materials), a stable operation is possible without
adverse effect on deterioration of the catalyst, and
based on this finding, the present invention has been
accomplished.
That is, the present invention relates to the
following production methods.
(1) A method of producing ethylene and
propylene which comprises contacting a hydrocarbon
starting material containing 20% by mass or more of at
least one olefin of 4-12 carbon atoms with a catalyst
containing a medium pore diameter zeolite having a
molar ratio SiO2/Al2C>3 of 200-5000 in a reaction vessel
under the conditions of a reaction temperature of 400-
600°C, a partial pressure of the hydrocarbon starting
material of 0.01-0.5 MPa and a weight hourly space
velocity of 1-100 hr"1 to carry out a catalytic
conversion reaction of said at least one olefin of 4-12
carbon atoms, thereby obtaining a reaction mixture
containing ethylene and propylene, separating the
reaction mixture into a fraction A containing mainly
hydrogen and hydrocarbons of 1-3 carbon atoms and a
fraction B containing mainly at least one hydrocarbon
of 4 or more carbon atoms, and separating ethylene and
propylene from the fraction A, said method meeting the
following requirements (i) and (ii):
(i) to satisfy AAROMA/P AAROMA = AROMAout - AROMAin
(AROMAin: percent by mass of aromatic
hydrocarbon component of 6-8 carbon atoms in the
hydrocarbon starting material at the inlet of the
reaction vessel,
AROMAout: percent by mass of aromatic
hydrocarbon component of 6-8 carbon atoms in the
reaction mixture at the outlet of the reaction vessel,
P: partial pressure of the hydrocarbon
starting material [MPa]); and
(ii) to recycle 10-95% by mass of the
fraction B to the reaction vessel and use it as the
hydrocarbon starting material.
(2) A method described in the above (1),
wherein the fraction A is separated into a fraction Ai
containing mainly hydrogen and a hydrocarbon of 1-2
carbon atoms and a fraction A2 containing mainly
hydrocarbons of 3 carbon atoms, and at least a part of
the fraction Ai is recycled to the reaction vessel and
used as a part of the hydrocarbon starting material.
(3) A method described in the above (1),
wherein 15-90% by mass of the fraction B is recycled to
the reaction vessel and used as a part of the
hydrocarbon starting material.
(4) A method described in the above (1),
wherein the formula in the requirement (i) is AAROMA/P
(5) A method of producing ethylene and
propylene which comprises contacting a hydrocarbon
starting material containing 20% by mass or more of at
least one olefin of 4-12 carbon atoms with a catalyst
containing a medium pore diameter zeolite having a
molar ratio SiO2/Al203 of 200-5000 in a reaction vessel
under the conditions of a reaction temperature of 400-
600°C, a partial pressure of the hydrocarbon starting
material of 0.01-0.5 MPa and a weight hourly space
velocity of 1-100 hr"1 to carry out a catalytic
conversion reaction of said at least one olefin of 4-12
carbon atoms, thereby obtaining a reaction mixture
containing ethylene and propylene, separating the
reaction mixture into a fraction C containing mainly
hydrogen and a hydrocarbon of 1-2 carbon atoms and a
fraction D containing mainly at least one hydrocarbon
of 3 or more carbon atoms, separating the fraction D
into a fraction Di containing mainly hydrocarbons of 3
carbon atoms and a fraction D2 containing mainly at
least one hydrocarbon of 4 or more carbon atoms and
separating ethylene and/or propylene from the fraction
C and/or the fraction Di, said method meeting the
following requirements (i) and (ii):
(i) to satisfy AAROMA/P AAROMA = AROMAout - AROMAin
(AROMAin: percent by mass of aromatic
hydrocarbon component of 6-8 carbon atoms in the
hydrocarbon starting material at the inlet of the
reaction vessel,
AROMAout: percent by mass of aromatic
hydrocarbon component of 6-8 carbon atoms in the
reaction mixture at the outlet of the reaction vessel,
P: partial pressure of the hydrocarbon
starting material [MPa]); and
(ii) to recycle 10-95% by mass of the
fraction B to the reaction vessel and use it as the
hydrocarbon starting material.
(6) A method described in the above (5),
wherein at least a part of the fraction D2 is recycled
to the reaction vessel and used as a part of the
hydrocarbon starting material.
(7) A method described in the above (5),
wherein 15-90% by mass of the fraction D2 is recycled to
the reaction vessel and used as the hydrocarbon
starting material.
(8) A method described in any one of the
above (5), wherein the formula in the requirement (i)
is AAROMA/P (9) A method described in any one of the
above (l)-(8), wherein the zeolite is selected from the
group consisting of ZSM-5 type zeolites.
(10) A method described in any one of the
above (l)-(8), wherein the zeolite in the zeolite-
containing catalyst contains a metal belonging to Group
IB of the periodic table and contains substantially no
protons.
(11) A method described in any one of the
above (l)-(8), wherein the reaction vessel is an
adiabatic fixed bed reaction vessel.
(12) A method described in any one of the
above (l)-(8), wherein the reaction temperature is 500-
580°C, the partial pressure of the hydrocarbon starting
material is 0.05-0.3 MPa and the weight hourly space
velocity is 2-10 hr"1.
(13) A method described in any one of the
above (l)-(4), wherein a part of the fraction B is used
as a part or all of the hydrocarbon starting material
and is contacted with a medium pore diameter zeolite-
containing catalyst containing at least one member
selected from the group consisting of metals belonging
to Group IIB, Group IIIB and Group VIII of the periodic
table and compounds thereof at a temperature of 650°C
or less in a gaseous phase to obtain an aromatic
hydrocarbon.
(14) A method described in the above (13),
wherein in the case of using a part of the fraction B
as a part of the hydrocarbon starting material, the
fraction Ai containing mainly hydrogen and hydrocarbons
of 1-2 carbon atoms which is separated from the
fraction A is further used as a part of the hydrocarbon
starting material.
(15) A method described in any one of the
above (5)-(8), wherein a part of the fraction D2 is used
as a part or all of the hydrocarbon starting material
and is contacted with a medium pore diameter zeolite-
containing catalyst containing at least one selected
from the group consisting of metals belonging to Group
IIB, Group IIIB and Group VIII of the periodic table
and compounds thereof at a temperature of 650°C or less
in a gaseous phase to obtain an aromatic hydrocarbon.
(16) A method described in the above (15),
wherein in the case of using a part of the fraction D2
as a part of the hydrocarbon starting material, the
fraction C is additionally used as a part of the
hydrocarbon starting material.
[Advantages of the Invention]
According to the production method of the
present invention, propylene and ethylene can be
efficiently and stably produced from an olefinic
hydrocarbon starting material.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
[FIG. 1] A flow sheet showing one embodiment
of construction of the system used for producing
ethylene and propylene according to the method of the
present invention.
[FIG. 2] A flow sheet showing another
embodiment of construction of the system used for
producing ethylene and propylene according to the
method of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will be explained in
detail below.
In the method of the present invention, a
hydrocarbon starting material containing 20% by mass or
more of at least one olefin of 4-12 carbon atoms is
used as a starting material for producing ethylene and
propylene.
The term "hydrocarbon starting material" in
the present invention means a starting material
containing mainly at least one material selected from
the group consisting of hydrocarbons of 1-12 carbon
atoms, such as normal paraffins, isoparaffins, olefins,
cycloparaffins (naphthenes) and cycloparaffins having
side chain alkyl groups.
In the method of the present invention, the
hydrocarbon starting material contains at least one
olefin of 4-12 carbon atoms in an amount of 20% by mass
or more based on the mass of the hydrocarbon starting
material.
The term "olefin" includes cycloparaffins in
addition to the straight chain, branched chain and
cyclic olefins.
If the content of the olefin in the
hydrocarbon starting material is less than 20% by mass,
yields of ethylene and propylene are insufficient. In
the method of the present invention, the hydrocarbon
starting material contains at least one olefin of 4-12
carbon atoms in an amount of preferably 30% by mass or
more, more preferably 40% by mass or more and most
preferably 50% by mass or more.
Furthermore, the hydrocarbon starting
material may contain a small amount of an oxygen-
containing compound such as tertiary butanol, methyl
tert-butyl ether or methanol as an impurity. Moreover,
the hydrocarbon starting material may contain a small
amount of a diene or an acetylene such as
methylacetylene, propadiene, butadiene or pentadiene.
Due to their high reactivity, dienes and acetylenes
accelerate deposition of carbonaceous materials
(coking) on the surface of the catalyst. Therefore,
during the conversion reaction continuously, the
catalyst is deteriorated by the coking (deterioration
with coking), resulting in deterioration in catalytic
activity. There is no particular limitation in the
content of dienes and acetylenes in the hydrocarbon
starting material, but for the efficient and stable
production of ethylene and propylene, the total
concentration of dienes and acetylenes in the
hydrocarbon starting material at the inlet of the
reaction vessel is preferably 2% by mass or less, more
preferably 1.5% by mass or less and especially
preferably 1% by mass or less.
As preferred examples of the hydrocarbon
starting material usable in the method of the present
invention, mention may be made of the following
hydrocarbons.
(1) A C4 fraction and a C5 fraction
separated from products obtained by thermal cracking of
petroleum hydrocarbons such as naphtha, and fractions
obtained by partial hydrogenation of diolefins in the
C4 and C5 fractions to olefins.
(2) A fraction obtained by separating and
removing a part or all of butadiene and isobutene from
the above C4 fraction.
(3) A fraction obtained by separating and
removing a part or all of isoprene and cyclopentadiene
from the above C5 fraction.
(4) A C4 fraction and/or gasoline fraction
separated from products obtained by fluid catalytic
cracking (FCC) of petroleum hydrocarbons such as
reduced pressure distillated light oil.
(5) A C4 fraction and/or gasoline fraction
separated from a coker.
(6) A C4 fraction and/or gasoline fraction
separated from hydrocarbons synthesized from carbon
monoxide and hydrogen by Fischer-Tropsch reaction (FT
synthesis).
These may be used each alone or in a mixture
of two or more.
According to the method of the present
invention, the above hydrocarbon starting material is
contacted with a specific zeolite-containing catalyst
in a reaction vessel to carry out a catalytic
conversion reaction of at least one olefin of 4-12
carbon atoms contained in the hydrocarbon starting
material, thereby obtaining a reaction mixture
containing ethylene and propylene, and ethylene and
propylene are separated from the resulting reaction
mixture.
In the method of the present invention, so-
called "medium pore diameter zeolite" having a pore
diameter of 5-6.5 A is used as the zeolite in the above
zeolite-based catalyst.
The term "medium pore diameter zeolite" means
"a zeolite, the pore diameter of which lies between the
pore diameter of small pore diameter zeolites such as A
type zeolites and the pore diameter of large pore
diameter zeolites such as mordenite and X type and Y
type zeolites". The "medium pore diameter zeolites"
have a so-called 10-membered oxygen ring in its crystal
structure.
Examples of the medium pore diameter zeolites
include ZSM-5, ZSM-8, ZSM-11, ZSM-12, ZSM-21, ZSM-23,
ZSM-35, ZSM-38, etc. Of these zeolites, preferred are
ZSM-5 type zeolites such as ZSM-5, ZSM-11 and ZSM-8,
and ZSM-38. Furthermore, there may be used zeolites
analogous to ZSM-5 and ZSM-11 which are disclosed in P.
A. Jacobs and J. A. Martens, "Stud. Surf. Sci. Catal.",
33, P.167-215 (1987, the Netherlands). Among them,
ZSM-5 is especially preferred.
Moreover, in the method of the present
invention, as the above zeolites, there may be used
proton type zeolites or zeolites containing a metal
belonging to Group IB of the periodic table and
containing substantially no protons. Those which
contain a metal belonging to Group IB of the periodic
table and contain substantially no protons are
particularly preferred.
Known methods can be used for obtaining
proton type zeolites. That is, they can be prepared by
a method of subjecting a zeolite obtained by
hydrothermal synthesis, followed by drying and
calcination to ion exchanging in an aqueous solution of
nitric acid, hydrochloric acid or the like; a method of
carrying out ion exchanging in an aqueous solution of
an ammonium salt such as ammonium nitrate, ammonium
chloride or the like to prepare an ammonium type
zeolite, followed by drying and calcination to convert
the zeolite to a proton type; a method of carrying out
ion exchanging with a multivalent metal cation, and
then calcining the zeolite; and the like.
The zeolite containing a metal belonging to
Group IB of the periodic table and containing
substantially no protons can be produced, for example,
by the following methods.
The term "containing substantially no
protons" in the present invention means that the amount
of protons (amount of acid) in the zeolite measured by
liquid phase ion exchanging/filtrate titration method
explained below is 0.02 mmol or less per 1 gram of the
zeolite. In the present invention, the amount of
protons per 1 gram of the zeolite is more preferably
0.01 mmol or less.
The liquid phase ion exchanging/filtrate
titration method is a method disclosed in Intrazeolite
Chemistry, "ACS Symp. Ser.", 218, P369-382 (1983,
U.S.A.), Journal of the Chemical Society of Japan, [3],
P.521-527 (1989), etc. The measurement of the amount
of protons using this method can be carried out in the
following manner.
A zeolite calcined in air is subjected to ion
exchange treatment using an aqueous NaCl solution, and
then the zeolite is recovered by filtration and
simultaneously a filtrate is obtained. The recovered
zeolite is washed with pure water, and the resulting
wash liquid is recovered in total and mixed with the
above filtrate. The amount of protons in the mixed
solution is measured by neutralization titration and
this is referred to as the amount of protons in the
zeolite.
It is known that ammonium ion type zeolites
and multivalent metal cation type zeolites (for
example, rare earth metal cation type zeolites) produce
protons by heat treatment. Therefore, it is necessary
to subject the zeolites to calcination treatment before
the measurement of the amount of protons by the above
method.
In the method of the present invention, a
zeolite containing a metal belonging to Group IB of the
periodic table (hereinafter referred to as "Group IB
metal"), namely, at least one metal selected from the
group consisting of copper, silver and gold, is used.
As the Group IB metal, copper and silver are preferred
and silver is especially preferred.
The "periodic table" in the present invention
is the periodic table described in CRC Handbook of
Chemistry and Physics, 75th edition [(David R. Lide, et
al, published from CRC Press Inc. (1994-1995)), pages
1-15.
The term "containing Group IB metal" means
containing a Group IB metal in the state of the
corresponding cation. However, the Group IB metal may
be contained in the zeolite in the state other than
that of a cation in addition to being present in the
state of cation. For example, it may be contained in
the state of an oxide.
As examples of the method for containing the
Group IB metal in the zeolite, mention may be made of,
for example, a method of treating the zeolite by a
known method such as an ion exchanging method, an
impregnating method or kneading method, but preferably
by the ion exchanging method.
When a Group IB metal is contained in the
zeolite by the ion exchanging method, it is necessary
to use a salt of the Group IB metal. Examples of the
salt of the Group IB metal include silver nitrate,
silver acetate, silver sulfate, copper chloride, copper
sulfate, copper nitrate and gold chloride.
There is no severe limitation in the content
of the Group IB metal, but the content is preferably
0.01-5% by mass, more preferably 0.02-3% by mass based
on the mass of the zeolite. If the content of the
Group IB metal is less than 0.01% by mass, catalytic
activity of the zeolite-containing catalyst is
insufficient, and even if it is added in an amount of
more than 5% by mass, the performance of the zeolite-
containing catalyst is usually not improved. The
content of Group IB metal in the zeolite can be
determined by known methods such as X-ray fluorescent
analysis.
In the method of the present invention, it is
essential that the molar ratio SiO2/Al203 of the zeolite
is 200 or more and 5,000 or less. If the molar ratio
SiO2/Al2O3 is less than 200, the zeolite-containing
catalyst is apt to be deteriorated owing to coking
caused by the conversion reaction. If the molar ratio
SiO2/Al203 exceeds 5000, the catalytic activity of the
zeolite-containing catalyst is insufficient. The molar
ratio SiO2/Al203 of the zeolite is preferably 220 or
more and 4,000 or less, more preferably 250 or more and
3,500 or less, most preferably 500 or more and 3,000 or
less. The molar ratio SiO2/Al203 of the zeolite can be
determined by a known method, for example, by
completely dissolving zeolite in an aqueous alkali
solution and analyzing the resulting solution by plasma
emission spectrochemical analysis or the like.
In the method of the present invention, it is
also possible to use a metalloaluminosilicate in which
a part of aluminum atoms constituting the zeolite
skeleton are replaced with metals such as Ga, Fe, B and
Cr or a metallosilicate in which all of the aluminum
atoms constituting the zeolite skeleton are replaced
with the metals mentioned above. In this case, the
content of the above metals in the
metalloaluminosilicate or metallosilicate is converted
into the mol number of A1203 and then the molar ratio
SiO2/Al203 is calculated.
Furthermore, it is preferred that the zeolite
additionally contains at least one metal selected from
alkali metals and alkaline earth metals, more
preferably at least one metal selected from alkali
metals, further preferably at least one metal selected
from the group consisting of sodium and potassium. In
this case, the zeolite contains both the Group IB metal
and at least one metal selected from alkali metals and
alkaline earth metals.
As examples of the method for containing at
least one metal selected from alkali metals and
alkaline earth metals in the zeolite, mention may be
made of the same methods as those for incorporating the
Group IB metal in the zeolite.
The content of at least one metal selected
from alkali metals and alkaline earth metals varies
depending on the kind of the metals, and, for example,
in the case of sodium, it is preferably 0.01-0.4% by
mass based on the mass of the zeolite and in the case
of potassium, it is preferably 0.01-0.8% by mass based
on the mass of the zeolite. It is preferred that at
least one metal selected from alkali metals and
alkaline earth metals is contained in the state of the
corresponding cation.
In preparing such zeolite, there are no
particular limitations in the order and the number of
times of the method of containing at least one metal
selected from alkali metals and alkaline earth metals
in the zeolite and the method of containing the Group
IB metal. For example, the Group IB metal may be
contained in the zeolite after at least one metal
selected from alkali metals and alkaline earth metals
is contained in the zeolite or at least one metal
selected from alkali metals and alkaline earth metals
may be contained in the zeolite after the Group IB
metal is contained. In either case, however, it is
preferred that the zeolite, in which the metals have
been contained, contains substantially no protons as
mentioned above.
If necessary, at least one metal selected
from the group consisting of metals belonging to Groups
lib, III, Vb, VIb, Vllb and VIII, such as V, Cr, Mo, W,
Mn, Pt, Pd, Fe, Ni, Zn and Ga, may be further contained
in the zeolite-containing catalyst for purposes of
inhibition of deterioration due to coking and
improvement of the yield of ethylene and propylene.
The method for containing these metals is the
same as the method for containing the Group IB metal,
except that the kind of the metals used is different.
The content of these metals is preferably 0.1-2% by
mass based on the mass of the zeolite.
Furthermore, for the purpose of further
improvement of resistance to deterioration due to
coking, the zeolite-containing catalyst can be heat
treated at a temperature of 500°C or more in the
presence of water vapor before contacting with the
hydrocarbon starting material. The above heat
treatment is preferably carried out under the
conditions of a temperature of 500°C or more and 900°C
or less and a partial pressure of water vapor of 0.01
atm or more.
When the zeolite-containing catalyst
containing Group IB metal and containing substantially
no proton is subjected to the above heat treatment, the
heat treatment can also be carried out before the Group
IB metal is contained in the zeolite. It is more
preferred to carry out the heat treatment after the
Group IB metal is contained in the zeolite.
In a case where the zeolite-containing
catalyst is used for conversion reaction for a long
period of time, deterioration due to coking may occur.
In this case, the catalyst suffering from the coking
deterioration can be regenerated by burning and
removing the coke on the catalyst at a temperature of
400-700°C usually in air or a mixed gas comprising
oxygen and an inert gas. In this specification, such a
treatment is called "regeneration treatment".
Because water vapor is produced in the
regeneration treatment, the above heat treatment in the
presence of water vapor can be carried out utilizing
the produced water vapor. That is, by repeating the
regeneration treatment of the zeolite-containing
catalyst suffering from the coking deterioration caused
by long-term use in conversion reactions, the same
effect as that of the heat treatment can be attained.
Furthermore, if necessary, the zeolite used
in the present invention can be used as a catalyst
after subjected it to calcination. In this case, the
calcination temperature is usually 500-900°C.
In using the zeolite-containing catalyst, it
is preferred to make the zeolite-containing catalyst
into a molded body to provide particles of proper
shapes. In this case, only the zeolite is molded and
the resulting molded body can be used as the zeolite-
containing catalyst. However, ordinarily, the zeolite
is mixed with a porous refractory inorganic oxide such
as alumina, silica, silica/alumina, zirconia, titania,
diatomaceous earth, or clay as a binder or molding
diluent (matrix), the resulting mixture is molded and
the resulting molded body is used as the zeolite-
containing catalyst.
When the matrix or binder is used, the
content thereof is preferably 10-90% by mass, more
preferably 20-50% by mass based on the total mass of
the zeolite and the matrix or binder.
According to the method of the present
invention, by using the zeolite-containing catalyst
mentioned above, in spite of using a hydrocarbon
starting material containing an olefin in a high
concentration of 20% by mass or more, coking
deterioration of the zeolite-containing catalyst hardly
occurs as compared with conventional methods.
Therefore, it is not necessary to frequently repeat the
regeneration operation. As a result, it becomes
23
possible to stably and efficiently produce ethylene and
propylene over a long period of time.
In the method of the present invention, a
catalytic conversion reaction of at least one olefin of
4-12 carbon atoms is carried out in a reaction vessel
by contacting the olefin with the above zeolite-
containing catalyst. It is preferred to carry out the
catalytic conversion reaction of the olefin of 4-12
carbon atoms under the following conditions where the
olefin of 4-12 carbon atoms in the starting hydrocarbon
is converted to ethylene and propylene at a high
selectivity and paraffin coexisting in the starting
hydrocarbon does not substantially react. That is, the
reaction temperature is preferably 400-600°C, more
preferably 500-580°C. The partial pressure of the
hydrocarbon starting material is desirably lower, and
is usually 0.01-0.5 MPa, preferably 0.05-0.3 MPa. The
weight hourly space velocity WHSV of the hydrocarbon
starting material with respect to the weight of the
zeolite in the zeolite-containing catalyst is
preferably 1-100 hr-1, more preferably 2-10 hr"1. The
contact time of the hydrocarbon starting material with
the zeolite-containing catalyst is preferably 5 seconds
or less, more preferably 1 second or less.
Furthermore, the hydrocarbon starting
material may be a mixture with a diluent gas. As the
diluent gas, there may be used an inert gas such as
hydrogen, methane, water vapor or nitrogen, but
dilution with hydrogen is preferably not carried out.
That is, hydrogen is used for inhibiting the
deterioration of the catalyst due to coking. However,
simultaneously, a hydrogenation reaction of the
produced propylene or the like takes place, resulting
in the adverse effect of reduction in propylene purity
(propylene/(propylene + propane)). In the method of
the present invention, coking deterioration of the
catalyst is slight even without carrying out dilution
with hydrogen, and stable operation can be performed.
Thus, the dilution with hydrogen is preferably not
carried out. (A small amount of hydrogen supplied to
the reaction vessel by recycling of C2- fraction
mentioned hereinafter, or the like, does not affect
adversely as in the above-mentioned hydrogen for
dilution.)
When the conversion reaction is carried out
under the conditions where paraffin does not
substantially react, the conversion reaction of olefin
in the hydrocarbon starting material is selectively
accelerated, and the conversion reaction of paraffin is
suppressed. As a result, production of methane,
ethane, propane, etc. by the conversion reaction of
paraffin as by-products is inhibited, and separation
and purification of ethylene and propylene from the
reaction mixture can be easily performed.
The reaction vessel utilized in the method of
the present invention for contacting the hydrocarbon
starting material with the zeolite-containing catalyst
may be any of fixed bed type, moving bed type,
fluidized bed type and gas stream carrying type. The
zeolite-containing catalyst used in the method of the
present invention is hardly deteriorated by coking.
Therefore, even when the fixed bed type reaction vessel
is used, ethylene and propylene can be stably produced
over a long period of time.
Furthermore, the conversion reaction of
paraffin is a highly endothermic reaction, while the
conversion reaction of olefin is a slightly endothermic
reaction or an exothermic reaction though it depends on
the reaction conditions. Therefore, when the olefin in
the hydrocarbon starting material is selectively
reacted under conditions where paraffin does not
substantially react, it is not necessary to supply heat
of reaction, and hence it is also possible to use a
one-stage adiabatic fixed bed type reaction vessel
having a simple structure.
Ethylene and propylene are separated from the
reaction mixture containing ethylene and propylene
which is obtained as above. Specifically, the first
process comprises preferably separating the reaction
mixture into a fraction A containing mainly hydrogen
and hydrocarbons of 1-3 carbon atoms and a fraction B
containing mainly at least one hydrocarbon of 4 or more
carbon atoms, and separating ethylene and propylene
from the fraction A. The second process comprises
preferably separating the reaction mixture into a
fraction C containing mainly hydrogen and hydrocarbons
of 1-2 carbon atoms and a fraction D containing mainly
at least one hydrocarbon of 3 or more carbon atoms,
separating the fraction D into a fraction Di containing
mainly a hydrocarbon of 3 carbon atoms and a fraction D2
containing mainly at least one hydrocarbon of 4 or more
carbon atoms, and separating ethylene and propylene
from the fraction C and the fraction Di. These
separation steps can be carried out by combining
various known processes such as fractional distillation
and extraction.
As aforementioned, in the reaction mixture,
olefins of 4 or more carbon atoms, aromatic
hydrocarbons, etc. are present in addition to ethylene
and propylene. Therefore, the effective utilization of
the hydrocarbon starting material can be attained by
using a so-called recycling reaction system which
comprises separating all or a part of the olefins of 4
or more carbon atoms from the reaction mixture,
recycling them to the reaction vessel and again
reacting them.
In the method of the present invention, at
least a part of the above fraction B or D2 is recycled
to the reaction vessel and is used as a part of the
hydrocarbon starting material. That is, since the
fraction B or D2 is utilized, as it is, as a recycling
material without carrying out purification, the
simplest recycling process can be constructed.
In the method of the present invention, in
order to efficiently obtain ethylene and propylene from
the above-mentioned recycling process, it is preferred
that AAROMA/P preferred that AAROMA/P AAROMA = AROMAout - AROMAin. AROMAout indicates the
percent by mass of aromatic hydrocarbon component of 6-
8 carbon atoms in the hydrocarbon stating material at
the inlet of the reaction vessel, and AROMAout
indicates the percent by mass of aromatic hydrocarbon
component of 6-8 carbon atoms in the reaction mixture
at the outlet of the reaction vessel. P means the
partial pressure of the hydrocarbon starting material
[MPa].
AAROMA is a yield [% by mass] of the aromatic
hydrocarbon component of 6-8 carbon atoms produced in
the reaction vessel. Therefore, the above formula
shows that in order to efficiently obtain ethylene and
propylene, it is desirable to inhibit the production of
the aromatic hydrocarbon component of 6-8 carbon atoms
as much as possible. Under the reaction conditions
where the above formula is AAROMA/P > 13, namely,
aromatic hydrocarbons are readily produced, reduction
of catalytic activity is apt to be caused by coking.
Furthermore, due to the increase of the aromatic
hydrocarbon component of 6-8 carbon atoms produced in
the reaction vessel, the yields of ethylene and
propylene decrease, and moreover, the proportions of
the aromatic hydrocarbon component of 6-8 carbon atoms
and a hydrocarbon component of 9 or more carbon atoms
in the recycling material increase. As a result, there
occur problems of accumulation in the reaction system
and acceleration of coking.
The method for controlling the production of
the aromatic hydrocarbon component of 6-8 carbon atoms
in the present invention is not limited, and a method
of reducing the conversion of olefin in the hydrocarbon
starting material is generally employed. Here, the
conversion of olefin means the olefin conversion on the
basis of butene represented by the following formula.
Olefin conversion (%) = {(concentration of
olefin of 4 or more carbon atoms in hydrocarbon
starting material at inlet of reaction vessel -
concentration of butene in hydrocarbon component at
outlet of reaction vessel)/concentration of olefin of 4
or more carbon atoms in hydrocarbon starting material
at inlet of reaction vessel} * 100.
The conversion of olefin is preferably 40-75%
by mass.
The means for reducing the olefin conversion
is also not limited, and includes, for example,
increasing the weight hourly space velocity of the
hydrocarbon starting material; lowering the reaction
temperature; increasing the molar ratio SiO2/Al203 of
medium pore diameter zeolite in medium pore diameter
zeolite-containing catalyst; and other methods.
Moreover, in changing the zeolite, it is further
preferred to use a zeolite containing a metal belonging
to Group IB of the periodic table mentioned before and
containing substantially no proton. This is because
the zeolite inhibits production of the aromatic
hydrocarbon of 6-8 carbon atoms more effectively than
the conventional H type zeolite to make it possible to
further increase the olefin conversion, and hence there
is obtained the effect to increase yields of ethylene
and propylene.
In the method of the present invention, the
recycling ratio of the fraction B or D2 is preferably
10-95% by mass, more preferably 15-90% by mass. If the
recycling ratio is less than 10% by mass, the yields of
ethylene and propylene are not sufficient. If the
recycling ratio is more than 95% by mass, accumulation
of the paraffin component contained in the starting
hydrocarbon or the aromatic hydrocarbon component of 6-
8 carbon atoms produced in the reaction vessel becomes
conspicuous to excessively increase load on the
reaction apparatus.
In the method of the present invention, the
percent by mass of the hydrocarbon component of 9 or
more carbon atoms in the fraction B or D2 is preferably
20% by mass or less, more preferably 15% by mass or
less. This is because ethylene and propylene cannot
efficiently be obtained under the conditions where the
percent by mass of the hydrocarbon component of 9 or
more carbon atoms exceeds 20% by mass.
The method of the present invention will be
explained in more detail taking the case of using as
the hydrocarbon starting material a C4 fraction
(fraction containing mainly hydrocarbons of 4 carbon
atoms, such as butane, isobutane, butene and isobutene)
obtained from a product of steam cracking of a
petroleum hydrocarbon.
FIG. 1 shows one preferred embodiment of the
recycle reaction system when the C4 fraction is used as
the hydrocarbon starting material. A reaction mixture
(a mixture of hydrogen and a hydrocarbon of 1 or more
carbon atoms) is separated into a fraction containing
mainly hydrogen and a hydrocarbon of 1-3 carbon atoms
(hereinafter referred to as "H2-C3 fraction") and a
fraction containing mainly at least one hydrocarbon of
4 or more carbon atoms (hereinafter referred to as "C4+
fraction"). As the apparatus used for the separation
(C3 separator), there may be used, for example, a
distillation column, a flash drum (vapor-liquid
separator), etc., and the distillation column is
preferred. Ethylene and propylene are recovered from
the resulting H2-C3 fraction. On the other hand, at
least a part of the C4+ fraction is recycled to the
reaction vessel and utilized as a part of the starting
material. By recycling the C4+ fraction, butane
contained in the starting hydrocarbon is concentrated
in the C4+ fraction. Therefore, when the total amount
of the C4+ fraction is recycled, butane is accumulated,
and hence accumulation of butane is controlled by
recycling only a part of the resulting C4 + fraction to
the reaction vessel.
Furthermore, the H2-C3 fraction may be
separated into a fraction containing mainly hydrogen
and a hydrocarbon of 1-2 carbon atoms (hereinafter
referred to as "C2- fraction") and a fraction
containing mainly a hydrocarbon of 3 carbon atoms
(hereinafter referred to as "C3 fraction"). As the
apparatus used for separation (C2 separator), there may
be used, for example, a distillation column, a flash
drum (vapor-liquid separator), etc., and the
distillation column is preferred. When propylene is
selectively produced, at least a part of the C2-
fraction is'recycled to the reaction vessel and
ethylene in the C2- fraction can be utilized as a part
of the starting material. Since the C2- fraction
contains hydrogen, methane and ethane in addition to
ethylene, hydrogen, methane and ethane are accumulated
if the total amount of the C2- fraction is recycled.
Therefore, accumulation of hydrogen, methane and ethane
is controlled by recycling only a part of the resulting
C2- fraction to the reaction vessel. On the other
hand, propylene is recovered from the C3 fraction, and
this propylene can be utilized, as it is, as propylene
of chemical grade in case the reaction conditions and
separation conditions are properly set.
If necessary, the C4+ fraction can be
separated into a fraction containing mainly a
hydrocarbon of 4 carbon atoms (hereinafter referred to
as "C4 fraction") and a fraction containing mainly at
least one hydrocarbon of 5 or more carbon atoms
(hereinafter referred to as "C5+ fraction"). The
position of separation of the C4 fraction from the C4+
fraction may be either before or after recycling of the
C4+ fraction. As the apparatus used for separation (C4
separator), there may be used, for example, a
distillation column, a flash drum (vapor-liquid
separator), etc., and the distillation column is
preferred. At least a part of the resulting C4
fraction and/or C5+ fraction is recycled to the
reaction vessel and can be used as a part of the
starting hydrocarbon.
FIG. 2 shows another preferred embodiment of
the recycle reaction system when the C4 fraction is
used as the hydrocarbon starting material. A reaction
mixture (a mixture of hydrogen and a hydrocarbon of 1
or more carbon atoms) is separated into a fraction
containing mainly hydrogen and a hydrocarbon of 1-2
carbon atoms (hereinafter referred to as "C2-
fraction") and a fraction containing mainly at least
one hydrocarbon of 3 or more carbon atoms (hereinafter
referred to as "C3+ fraction"). As apparatus used for
separation (C2 separator), there may be used, for
example, a distillation column, a flash drum (vapor-
liquid separator), etc., and the distillation column is
preferred. Ethylene is recovered from the resulting
C2- fraction. When propylene is selectively produced,
at least a part of the C2- fraction is recycled to the
reaction vessel and ethylene in the C2- fraction is
utilized as a part of the starting material as
aforementioned.
On the other hand, the C3+ fraction is
separated into a fraction containing mainly a
hydrocarbon of 3 carbon atoms (hereinafter referred to
as "C3 fraction") and a fraction containing mainly at
least one hydrocarbon of 4 or more carbon atoms
(hereinafter referred to as "C4 + fraction"). As the
apparatus used for separation (C3 separator), there may
be used, for example, a distillation column, a flash
drum (vapor-liquid separator), etc., and the
distillation column is preferred. Propylene is
recovered from the C3 fraction, and this propylene can
be utilized, as it is, as propylene of chemical grade
in case the reaction conditions and separation
conditions are properly set.
On the other hand, at least a part of the C4+
fraction is recycled to the reaction vessel and
utilized as a part of the starting material. By
recycling the C4+ fraction, butane contained in the
starting hydrocarbon is concentrated in the C4+
fraction. Therefore, when the total amount of the C4+
fraction is recycled, butane is accumulated, and hence
accumulation of butane is controlled by recycling only
a part of the resulting C4+ fraction to the reaction
vessel. As explained above on FIG. 1, if necessary,
the C4+ fraction can be separated into a fraction
containing mainly a hydrocarbon of 4 carbon atoms
(hereinafter referred to as "C4 fraction") and a
fraction containing mainly at least one hydrocarbon of
5 or more carbon atoms (hereinafter referred to as "C5+
fraction"). The position of separation of the C4
fraction from the C4+ fraction may be either before or
after recycling of the C4+ fraction. As the apparatus
used for separation (C4 separator), there may be used,
for example, a distillation column, a flash drum
(vapor-liquid separator), etc., and a distillation
column which is preferred. At least a part of the
resulting C4 fraction and/or C5+ fraction is recycled
to the reaction vessel and can be used as a part of the
starting hydrocarbon.
In the method of the present invention,
yields of ethylene and propylene per the hydrocarbon
starting material can be improved by carrying out in
parallel the production of ethylene and propylene by
the catalytic conversion mentioned above and the
production of ethylene and propylene by steam cracking
method (tube type thermal cracking method). In this
case, since production of by-products such as methane
can be inhibited, purification of ethylene and
propylene can be efficiently performed. As an example
of such method, mention may be made of a method which
comprises feeding the fraction B or D2 to a tube type
cracking furnace to carry out steam cracking to obtain
a steam cracking product containing ethylene and
propylene and separating ethylene and propylene from
the resulting steam cracking product. This steam
cracking is carried out preferably under the conditions
of 750-850°C in temperature of the tube type cracking
furnace, 0-15 kg/cm2G in pressure, 0.1-0.8 second in
residence time and 0.1-1 in weight ratio of
steam/hydrocarbon.
[Catalytic cyclization reaction]
In another embodiment of the method of the
present invention, a part of the fraction B or the
fraction D2 is used as a part or all of the hydrocarbon
starting material and is contacted with the medium pore
diameter zeolite-containing catalyst, whereby an
aromatic hydrocarbon of 6-9 carbon atoms can be
obtained. In this specification, this reaction is
referred to as "catalytic cyclization reaction". In
the catalytic cyclization reaction, as the hydrocarbon
starting material capable of being added to the
fraction B or D2, mention may be made of, for example,
a starting material containing mainly at least one
material selected from the group consisting of
hydrocarbons of 1-12 carbon atoms, such as normal
paraffins, isoparaffins, olefins, cycloparaffins
(naphthenes) and cycloparaffins having side chain alkyl
group.
Furthermore, the hydrocarbon starting
material used for the catalytic cyclization reaction
may contain as impurities a small amount of oxygen-
containing compounds such as tertiary butanol, methyl
tertiary butyl ether, methanol, etc. Moreover, it may
contain a small amount of a diene or acetylene such as
methylacetylene, propadiene, butadiene, pentadiene,
etc.
Examples of preferred hydrocarbon starting
materials which can be added to the fraction B or D2 in
the catalytic cyclization reaction are the following
materials as aforementioned.
(1) A C4 fraction and C5 fraction separated
from products obtained by thermal cracking of petroleum
hydrocarbons such as naphtha and fractions obtained by
partial hydrogenation of diolefins in the C4 fraction
and the C5 fraction to olefins.
(2) A fraction obtained by separating and
removing a part or all of butadiene and isobutene from
the above C4 fraction.
(3) A fraction obtained by separating and
removing a part or all of isoprene and cyclopentadiene
from the above C5 fraction.
(4) A C4 fraction and/or gasoline fraction
separated from products obtained by fluid catalytic
cracking (FCC) of petroleum hydrocarbons such as
reduced pressure distillated light oil.
(5) A C4 fraction and/or gasoline fraction
separated from a coker.
(6) A C4 fraction and/or gasoline fraction
separated from hydrocarbons synthesized from carbon
monoxide and hydrogen by Fischer-Tropsch reaction (FT
synthesis).
These may be used each alone or in a mixture
of two or more.
The zeolites used in the catalytic
cyclization reaction are so-called "medium pore
diameter zeolites" having a pore diameter of 5-6.5 A.
The meaning and examples of the term "medium pore
diameter zeolites" are the same as aforementioned.
Furthermore, the medium pore diameter
zeolite-containing catalyst used for the catalytic
cyclization reaction can be made more suitable by
adding thereto a hydrogenation/dehydrogenation metal
component. Particularly, when at least one material
selected from metals belonging to Group IIB, Group IIIB
and Group VIII of the periodic table and compounds
thereof, the zeolite-containing catalyst is improved in
dehydrogenation cyclization ability and can be a
suitable catalyst for producing aromatic hydrocarbons.
The metals belonging to Group IIB, Group IIIB and Group
VIII of the periodic table and compounds thereof are
preferably zinc, gallium, indium, nickel, palladium,
and platinum, and oxides and composite oxides thereof,
and more preferably zinc, zinc oxide and composite
oxides of zinc such as zinc aluminate. The amount of
the metals belonging to Group IIB, Group IIIB and Group
VIII of the periodic table and compounds thereof with
respect to the zeolite-containing catalyst is
preferably 0.1-20% by mass in terms of metal.
As the zeolite contained in the medium pore
diameter zeolite-containing catalyst, there can be used
proton type zeolite or a zeolite containing a Group IB
metal, namely, at least one metal selected from the
group consisting of copper, silver and gold. As the
Group IB metal, copper and silver are preferred and
silver is especially preferred. The method for
obtaining the proton type zeolite and the method for
containing the Group IB metal in the zeolite are the
same as mentioned hereinbefore.
There is no severe limitation on the content
of the Group IB metal, but the content is preferably
0.1-10% by mass, more preferably 0.2-5% by mass based
on the mass of the zeolite. If the content of the
Group IB metal is less than 0.1% by mass, the activity
for the catalytic cyclization reaction is insufficient,
and even if it is added in an amount exceeding 10% by
mass, the performance is no longer improved.
The molar ratio SiO2/Al203 of the zeolite in
the catalytic cyclization reaction must be 20 or more
from the point of view of stability as a catalyst. The
upper limit of the molar ratio SiO2/Al203 is not
particularly restricted, and a zeolite of about 20-500,
preferably about 28-300 in molar ratio SiO2/Al203 is
generally used.
In the catalytic cyclization reaction, it is
also possible to use a metalloaluminosilicate in which
a part of aluminum atoms constituting the zeolite
skeleton are replaced with metals such as Ga, Fe, B and
Cr or a metallosilicate in which all of the aluminum
atoms constituting the zeolite skeleton are replaced
with the above metals. In this case, the content of
the above metals in the metalloaluminosilicate or
metallosilicate is converted into terms of the mol
number of A1203 and then the molar ratio SiO2/Al203 is
calculated.
Containing of alkali metal and alkaline earth
metal in the zeolite and heat treatment of the zeolite
in the presence of water vapor in the catalytic
cyclization reaction are the same as aforementioned.
In a case where the zeolite-containing
catalyst is used for the catalytic cyclization reaction
for a long period of time, deterioration due to coking
may sometimes occur. In this case, the catalyst
deteriorated by coking can be regenerated by burning
and removing the coke on the catalyst at a temperature
of 400-700°C usually in air or a mixed gas comprising
oxygen and an inert gas. Because water vapor is
produced in the regeneration treatment, the above heat
treatment in the presence of water vapor can also be
carried out utilizing the produced water vapor. That
is, by repeating the regeneration treatment of the
zeolite-containing catalyst used for the catalytic
cyclization reaction for a long time and deteriorated
by coking, the same effect as of the heat treatment can
be attained.
Furthermore, if necessary, the zeolite used
in the catalytic cyclization reaction can be used as a
catalyst after being subjected to calcination. In this
case, the calcination temperature is usually 500-900°C.
In using the zeolite-containing catalyst in
the catalytic cyclization reaction, it is preferred to
make the zeolite-containing catalyst into a molded body
for giving particles of proper shapes. In this case,
only the zeolite is molded and the resulting molded
body can be used as the zeolite-containing catalyst.
However, ordinarily, the zeolite is mixed with a porous
refractory inorganic oxide such as alumina, silica,
silica/alumina, zirconia, titania, diatomaceous earth,
clay or the like as a binder or molding diluent
(matrix), the resulting mixture is molded and the
resulting molded body is used as the zeolite-containing
catalyst.
When the matrix or binder is used, the
content thereof is preferably 5-90% by mass, more
preferably 10-50% by mass based on the total mass of
the zeolite and the matrix or binder.
The conditions of the catalytic cyclization
reaction in the present invention varies depending on
the hydrocarbon starting material, particularly, the
ratio of amount of olefin and paraffin in the starting
material, and preferably the temperature is 300-650°C,
the partial pressure of the hydrocarbon starting
material is 0.01-3 MPa, and the weight hourly space
velocity is 0.1-50 hr"1, and more preferably the
temperature is 400-600°C.
The reaction vessel utilized in the catalytic
cyclization reaction of the present invention may be
any of fixed bed type, moving bed type and fluidized
bed type and the reaction manner is not particularly
limited. Preferred is an adiabatic fixed bed type
reaction vessel which is simple in structure.
(Examples)
The present invention will be explained more
specifically by the following examples and comparative
examples, which should not be construed as limiting the
invention in any manner.
Measurements conducted in the examples and
comparative examples are as follows.
(1) Measurement of amount of proton in the
zeolite by liquid phase ion exchanging/filtrate
titration method.
1.5 g of zeolite was calcined in air at a
temperature of 400-600°C, and thereafter subjected to
ion exchanging in 25 ml of an aqueous NaCl solution of
3.4 mols/liter while ice cooling for 10 minutes. After
the resulting mixture was filtered, the zeolite was
washed with 50 ml of pure water, and total amount of
the filtrate containing the water used for washing was
recovered. This filtrate (containing water used for
washing) was subjected to neutralization titration with
0.IN aqueous NaOH solution, and the amount of protons
in the zeolite was obtained from the point of
neutralization.
(2) Calculation of reaction rate constant K.
The reaction rate constant K (hr-1) which is
an indication of catalytic activity was obtained by the
following formula.
K = WHSV x ln[l/(l-X)]
[In the above formula, WHSV (hr"1) is the
weight hourly space velocity of the fed starting
material with respect to the weight of the zeolite, and
X (with no unit) is an olefin conversion on the basis
of butene {(concentration of olefin of 4-8 carbon atoms
in starting material (% by mass) - concentration of
butene in product (% by mass)/ concentration of olefin
of 4-8 carbon atoms in starting material (% by mass)}.
[Example 1]
An extrusion molded article of H type ZSM-5
having a molar ratio SiO2/Al2C>3 of 1000 (containing 30%
by mass of SiO2 binder and having 1.6 ramij), and bought
from Nikki Universal Co., Ltd.) was dispersed in a IN
aqueous sodium nitrate solution (10 cc/g-zeolite molded
body), and ion exchanging treatment was carried out at
room temperature for 1 hour repeatedly three times,
followed by carrying out filtration, washing with water
and drying to prepare an Na type ZSM-5/SiO2. This was
dispersed in a 0.01N aqueous silver nitrate solution
(10 cc/g-zeolite molded body), and ion exchanging was
carried out at room temperature for 2 hours, followed
by filtration, washing with water and drying to prepare
a catalyst A. The amount of Ag in the catalyst A
measured by fluorescent X-ray analysis was 0.15% by
mass. The catalyst A was packed in a quartz glass
reaction vessel of 16 mm(j) in inner diameter and
subjected to steaming for 5 hours under the conditions
of a temperature of 650°C, a steam flow rate of 27.6
g/hr and a nitrogen flow rate of 140 Ncc/min. The
amount of protons in the catalyst A after subjected it
to the steaming treatment was measured by liquid phase
ion exchanging/filtrate titration method to obtain
0.002 mmol/g. 10 g of the catalyst A after the
steaming treatment was packed in a reaction vessel made
of HASTELLOY C having an inner diameter of 17 mm.
Using C4 raffinate-2 shown in Table 1
(obtained by extracting butadiene and isobutene from a
C4 fraction obtained by steam cracking naphtha) as a
starting material, a reaction was carried out under the
conditions of a reaction temperature of 580°C, a feed
amount of the C4 raffinate-2 of 60 g/hr (WHSV = 6 hr"1)
and a pressure of 0.1 MPaG, the resulting reaction
product was cooled to about 30°C at the outlet of the
reaction vessel using a heat exchanger and then
introduced into a gas-liquid separation drum to
separate and recover a liquid (C4+ fraction). The
composition of the recovered C4+ fraction is shown in
Table 1. Then, using the recovered C4+ fraction and C4
raffinate-2 as starting materials, an experiment of C4+
recycling was carried out for 24 hours under the
following experimental conditions.
Experimental conditions:
Reaction temperature: 580°C; feed rate of C4
raffinate-2: 30 g/hr; feed rate of C4 + fraction: 31.2
g/hr (WHSV =6.1 hr"1) ; reaction pressure: 0.1 MPaG
The reaction product obtained after a given
time from starting of feeding of starting material was
directly introduced into a gas chromatography (TCD, FID
detectors) to analyze the composition.
The analysis by gas chromatograph was carried
out under the following conditions.
Device: GC-17A manufactured by Shimadzu Corp.
Column: Custom capillary column SPB-1 (0.25
mm in inner diameter, 60 m in length, 3.0 \xm in film
thickness) manufactured by SUPELCO, Inc.
Amount of sample gas: 1 ml (the sampling line
was kept at 200-300°C to prevent liquefaction).
Heating program: Keeping at 40°C for 12
minutes, then heating to 200°C at 5°C/min, and keeping
at 200°C for 22 minutes.
Split ratio: 200 : 1
Flow rate of carrier gas (nitrogen): 120
ml/min.
FID detector: Air supplying pressure 50 kPa
(about 500 ml/min), hydrogen supplying pressure 60 kPa
(about 50 ml/min).
Measuring method: TCD detector and FID
detector were connected in series, and hydrogen and
hydrocarbons of 1 carbon atom and 2 carbon atoms were
detected by the TCD detector and hydrocarbons of 3 or
more carbon atoms were detected by the FID detector.
After 10 minutes from starting of analysis, the
detecting output was switched from TCD to FID.
The results of analysis of the reaction
product after 12 hours from starting of the reaction
were that yields of propylene and ethylene (% by mass)
with respect to the olefin of 4-8 carbon atoms in the
feed starting material were 32.1% and 8.7%,
respectively. However, the components of 6-8 carbon
atoms in the recovered C4+ fraction were all olefins
except for aromatic hydrocarbons. Moreover, the ratio
of the reaction rate constant K after 4 hours and 24
hours from starting of the reaction [K(24 hours)/K(4
hours)], was 0.90.
[Comparative Example 1]
The reaction of C4 raffinate-2 was carried
out under the same conditions as in Example 1, except
that only the C4 raffinate-2 in a feed amount of 60
g/hr (WHSV = 6 hr"1) was used as a starting material fed
to the reaction vessel. The results of analysis of the
reaction product after 12 hours from starting of the
reaction were that yields of propylene and ethylene (%
by mass) with respect to the olefin of 4-8 carbon atoms
in the feed starting material were 31.1% and 8.9%,
respectively. Moreover, the ratio of the reaction rate
constant K after 4 hours and 24 hours from starting of
the reaction [K(24 hours)/K(4 hours)], was 0.87.
From the comparison of Example 1 with
Comparative Example 1, it can be seen that use of the
C4+ fraction, as it is, as a recycling material without
removing heavy materials had no adverse effect on
deterioration of the catalyst. Furthermore, it can be
seen that the non-aromatic components of 6-8 carbon
atoms in the C4+ fraction can be effectively utilized
for production of propylene and ethylene.
[Example 2]
An experiment corresponding to recycling of
ethylene was conducted under the same conditions as in
Example 1, except that the C4 raffinate-2 in an amount
of 26.8 g/hr, the C4+ fraction in an amount of 27.2
g/hr, and ethylene in an amount of 6 g/hr (WHSV = 6
hr-1) were used as the starting materials fed to the
reaction vessel.
The results of analysis of the reaction
product after 4 hours from starting of the reaction
were that yields of propylene and ethylene (% by mass)
with respect to the olefin of 4-8 carbon atoms in the
feed starting material were 34.8% and 0.5%,
respectively. A comparison with Example 1 shows that
production of ethylene was suppressed by recycling
ethylene and that the yield of propylene was improved.
[Example 3]
An extrusion molded article of Na type ZSM-5
having a molar ratio SiO2/Al203 of 1200 (containing 30%
by mass of SiO2 binder and having 1.6 mmcj), and bought
from Nikki Universal Co., Ltd.) was dispersed in 0.02N
aqueous silver nitrate solution (10 cc/g-zeolite molded
body), and ion exchange treatment was carried out at
60°C for 1 hour which was repeated two times, followed
by carrying out filtration, washing with water and
drying to prepare a catalyst B. The amount of Ag in
the catalyst B measured by fluorescent X-ray analysis
was 0.22% by mass. The catalyst B was packed in a
reaction vessel made of HASTELLOY C having an inner
diameter of 27 mrruj) and subjected to steaming for 5 hours
under the conditions of a temperature of 650°C, a steam
flow rate of 214 g/hr, a nitrogen flow rate of 400
NL/hr, and a pressure of 0.1 MPaG. The amount of
protons in the catalyst B, after the steaming
treatment, was measured by liquid phase ion
exchanging/filtrate titration method and determined to
be 0.002 mmol/g. 60 g of the catalyst B, after the
steaming treatment, was packed in a reaction vessel
made of HASTELLOY C having an inner diameter of 27 mm(|).
Using C4 raffinate-2 shown in Table 2 as a
starting material, a reaction was carried out under the
conditions of a reaction temperature of 550°C, a feed
amount of the C4 raffinate-2 of 220.2 g/hr, a feed
amount of the recycling C4 + fraction of 139.8 g/hr
(WHSV = 6 hr_1) , a feed amount of steam of 108 g/hr, and
a reaction pressure of 0.1 MPaG, and the resulting
reaction product was fed to a distillation column and
separated into an H2-C3 fraction and a C4 + fraction.
About 56% by mass of the C4+ fraction was recycled to
the reaction vessel. After continuing the reaction for
2 days, the catalyst was subjected to regeneration
treatment under the following conditions.
Conditions of the regeneration treatment:
Regeneration temperature: 500-550°C;
regeneration pressure: 0.5 MPaG; flow rate of nitrogen
+ air: 1008 NL/hr; oxygen concentration: 1-5% by
volume; regeneration time: 10 hours.
The yields (% by mass) based on the C4
raffinate-2 are shown in Table 2. The AAROMA/P was
3.5. The regeneration gas at the outlet of the
reaction vessel in the regeneration treatment was
periodically sampled and the regeneration gas was
analyzed using a gas chromatograph to measure
concentrations of CO2 and CO, from which the amount of
coke was determined. The amount of coke was divided by
the total amount of the starting materials fed during
the reaction to obtain a yield of the coke, which was
72 ppm by mass.
[Comparative Example 2]
The reaction of C4 raffinate-2 was carried
out under the same conditions as in Example 3, except
that only the C4 raffinate-2 in a feed amount of 360
g/hr (WHSV = 6 hr_1) was used as a starting material fed
to the reaction vessel. The yields (% by mass) based
on the C4 raffinate-2 are shown in Table 2. The yield
of coke was 77 ppm by mass.
In comparison with Example 3, it can be seen
that the yields of ethylene and propylene were improved
by recycling the C4+ fraction. Furthermore, it can be
seen that the yield of coke did not increase even when
the C4+ fraction was recycled as it was.
[Example 4]
72 parts by mass of H type ZSM-5 (having a
molar ratio SiO2/Al203 = 80), zinc nitrate (10 parts by
mass in terms of zinc metal) and alumina sol (18 parts
by mass in terms of AI2O3) were kneaded and extruded to
prepare a molded product of 1.6 mm in diameter and 4-6
mm in length. This was dried at 120°C for 4 hours and
then calcined at 500°C for 3 hours to obtain a ZSM-5
zeolite molded catalyst. This catalyst was dispersed
in IN aqueous sodium nitrate solution (10 cc/g-zeolite
molded body), and ion exchange treatment was carried
out at room temperature for 1 hour and was repeated
three times, followed by filtration, washing with water
and drying to prepare an Na-containing ZSM-5/SiO2. This
was dispersed in 0.IN aqueous silver nitrate solution
(10 cc/g-zeolite molded body), and ion exchange
treatment was carried out at room temperature for 2
hours, followed by filtration, washing with water and
drying to prepare a catalyst C. The amount of Ag in
the catalyst C measured by fluorescent X-ray analysis
was 1.8% by weight. The catalyst C was packed in a
reaction vessel made of HASTELLOY C having an inner
diameter of 27 mm and subjected to steaming for 3 hours
under the conditions of a temperature of 650°C, a steam
flow rate of 214 g/hr, a nitrogen flow rate of 400
NL/hr, and a pressure of 0.1 MPaG. 39.6 g of the
catalyst C after the steaming treatment was packed in a
reaction vessel made of HASTELLOY C having an inner
diameter of 27 mm A reaction was carried out under the
conditions of a feed amount of the C4+ fraction
obtained in Example 3 of 110.9 g/hr, a reaction
temperature of 515°C and a pressure of 0.5 MPa. The
yield of aromatic hydrocarbon of 6-9 carbon atoms after
2 hours from starting of the reaction was 45.32% by
mass. From the results of Example 3 and Example 4, the
yields based on the C4 raffinate-2 were 9.08% by mass
for ethylene, 38.05% by mass for propylene and 22.82%
by mass for aromatic hydrocarbon of 6-9 carbon atoms.
Thus, it can be seen that ethylene, propylene and
aromatic hydrocarbon of 6-9 carbon atoms are
selectively obtained by subjecting the by-product C4+
fraction to a catalytic cyclization reaction.
INDUSTRIAL APPLICABILITY
According to the production method of the
present invention, in the method for producing ethylene
and propylene from hydrocarbon starting materials
containing olefins, recycling of starting materials is
obtained from the reaction product by a simple method.
An efficient and stable recycle process can be
achieved. Therefore, the method is industrially useful
for producing ethylene and propylene.
WE CLAIM
1. A method of producing ethylene and propylene which comprises
contacting a hydrocarbon starting material containing 20% by mass or
more of at least one olefin of 4-12 carbon atoms with a catalyst containing
a medium pore diameter zeolite, the zeolite containing silver and
substantially no protons, having a molar ratio SiO2/AI2O3 of 200-5000 and
selected from the group consisting of ZSM-5 type zeolites, in a reaction
vessel under conditions of a reaction temperature of 400-600°C, a partial
pressure of the hydrocarbon starting material of 0.01-0.5 MPa and a
weight hourly space velocity of 1-100 hr"1 to carry out a catalytic
conversion reaction of said at least one olefin of 4-12 carbon atoms,
thereby obtaining a reaction mixture containing ethylene and propylene,
separating the reaction mixture into a fraction A containing mainly
hydrogen and at least one hydrocarbon of 1-3 carbon atoms and a
fraction B mainly containing at least one hydrocarbon of 3-12 carbon
atoms, and separating ethylene and propylene from the fraction A, said
method meeting the following requirements (i) and (ii):
(i) to satisfy AAROMA/P AAROMA = AROMAout - AROMAin
(AROMAin: percent by mass of aromatic hydrogen component
of 6-8 carbon atoms in the hydrocarbon starting material at the inlet of
the reaction vessel,
AROMAout : percent by mass of aromatic hydrocarbon
component of 6-8 carbon atoms in the reaction mixture at the outlet of
the reaction vessel,
P: partial pressure of the hydrocarbon starting material [MPa]);
and
(ii) to recycle 10-95% by mass of the fraction B to the reaction
vessel and use it as the hydrocarbon starting material.
2. A method as claimed in claim 1, wherein the fraction A is separated into a
fraction A1 containing mainly hydrogen and hydrocarbons of 1-2 carbon
atoms and a fraction A2 containing mainly hydrocarbons of a 3 carbon
atoms, and at least a part of the fraction Ai is recycled to the reaction
vessel and used as a part of the hydrocarbon starting material.
3. A method as claimed in claim 1, wherein 15-90% by mass of the fraction
B is recycled to the reaction vessel and used as a part of the hydrocarbon
starting material.
4. A method as claimed in claim 1, wherein the formula in the requirement
(i) is AAROMA/P 5. A method of producing ethylene and propylene which comprises
contacting a hydrocarbon starting material containing 20% by mass or
more of at least one olefin of 4-12 carbon atoms with a catalyst containing
a medium pore diameter zeolite, the zeolite containing silver and
substantially no protons, having a molar ration SiO2/Al203 of 200-5000 and
selected from the group consisting of ZSM-5 type zeolites, in a reaction
vessel under the conditions of a reaction temperature of 400-600°C, a
partial pressure of the hydrocarbon starting material of 0.01-05 MPa and a
weight hourly space velocity of 1-100 hr"1 to carry out a catalytic
conversion reaction of said at least one olefin of 4-12 carbon atoms,
thereby obtaining a reaction mixture containing ethylene and propylene,
separating the reaction mixture into a fraction C containing mainly
hydrogen and hydrocarbons of 1-2 carbon atoms and a fraction D
containing mainly at least one hydrocarbon of 3 to 6 carbon atoms,
separating the fraction D into a fraction Di containing mainly a
hydrocarbon of 3-9 carbon atoms and a fraction D2 containing mainly at
least one hydrocarbon of 3-12 carbon atoms, and separating ethylene
and/or propylene from the fraction C and/or the fraction Di, said method
meeting the following requirements (i) and (ii):
(i) to satisfy AAROMA/P AAROMA = AROMAout - AROMAin
(AROMAin : percent by mass of aromatic hydrocarbon
component of 6-8 carbon atoms in the hydrocarbon starting material
at the inlet of the reaction vessel,
AROMAout : percent by mass of aromatic hydrocarbon
component of 6-8 carbon atoms in the reaction mixture at the outlet of
the reaction vessel,
P: partial pressure of the hydrocarbon starting material [MPa]);
and
(ii) to recycle 1 - 95% by mass of the fraction D2 to the reaction
vessel and use it as the hydrocarbon starting material.
6. A method as claimed in claim 5, wherein at least a part of the fraction C is
recycled to the reaction vessel and used as a part of the hydrocarbon
starting material.
7. A method as claimed in claim 5, wherein 15-90% by mass of the fraction
D2 is recycled to the reaction vessel and used as the hydrocarbon starting
material.
8. A method as claimed in claim 5, wherein the formula in the requirement
(i) is AAROMA/P 9. A method as claimed in any one of claim 1-8, wherein the reaction vessel
is an adiabatic fixed bed reaction vessel.
10. A method as claimed in any one of claims 1-8, wherein the reaction
temperature is 500-580°C, the partial pressure of the hydrocarbon starting
material is 0.05-0.3 MPa and the weight hourly space velocity is 2-10 hr"1.
11. A method as claimed in any one of claims 1-4, wherein a part of the
fraction B is used as a part or all of the hydrocarbon starting material and
is contacted with a medium pore diameter zeolite - containing catalyst
containing at least one member selected from the group consisting of
metals belonging to Group IIB, Group III B and Group VIII of the periodic
table and compounds thereof at a temperature of 650°C or less in a
gaseous phase to obtain an aromatic hydrocarbon.
12.A method as claimed in claim 11, wherein in the case of using a part of
the fraction B as a part of the hydrocarbon starting material, the fraction
Ai containing mainly hydrogen and hydro carbons of 1-2 carbon atoms
which is separated from the fraction A is additionally used as a part of the
hydrocarbon starting material.
13. A method as claimed in any one of claims 5-8, wherein a part of the
fraction D2 is used as a part or all of the hydrocarbon starting material and
is contacted with a medium pore diameter zeolite - containing catalyst
containing at least one selected from the group consisting of metals
belonging to Group IIB, Group IIIB and Group VIII of the periodic table
and compounds thereof at a temperature of 650°C or less in a gaseous
phase to obtain an aromatic hydrocarbon.
14. A method as claimed in claim 13, wherein in the case of using a part of
the fraction D2 as a part of the hydrocarbon starting material, the fraction
C is additionally used as a part of the hydrocarbon starting material.


This invention relates to a process for efficiently and stably producing ethylene
and propylene which comprises bringing a hydrocarbon feedstock comprising at
least one C4-12 olefin into contact with a zeolite-containing catalyst to obtain a
reaction mixture containing ethylene and a fraction comprising C4 and higher
hydrocarbons, and recycling the C4 and higher hydrocarbon as they are to a
reactor.

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00035-kolnp-2007-correspondence-1.3.pdf

00035-kolnp-2007-correspondence-1.4.pdf

00035-kolnp-2007-form-18.pdf

00035-kolnp-2007-others document.pdf

00035-kolnp-2007-pct request.pdf

00035-kolnp-2007-priority document.pdf

0035-kolnp-2007-abstract.pdf

0035-kolnp-2007-assignment.pdf

0035-kolnp-2007-claims.pdf

0035-kolnp-2007-correspondence others.pdf

0035-kolnp-2007-description (complete).pdf

0035-kolnp-2007-drawings.pdf

0035-kolnp-2007-form1.pdf

0035-kolnp-2007-form2.pdf

0035-kolnp-2007-form3.pdf

0035-kolnp-2007-form5.pdf

0035-kolnp-2007-international publication.pdf

0035-kolnp-2007-international search authority report.pdf

0035-kolnp-2007-pct form.pdf

35-KOLNP-2007-ABSTRACT.pdf

35-kolnp-2007-abstract1.1.pdf

35-KOLNP-2007-CLAIMS.pdf

35-kolnp-2007-claims1.1.pdf

35-kolnp-2007-correspondence.pdf

35-kolnp-2007-description (complete).pdf

35-KOLNP-2007-DESCRIPTION COMPLETE.pdf

35-kolnp-2007-drawings.pdf

35-kolnp-2007-examination report.pdf

35-kolnp-2007-form 1.1.pdf

35-KOLNP-2007-FORM 1.pdf

35-kolnp-2007-form 18.pdf

35-kolnp-2007-form 2.1.pdf

35-KOLNP-2007-FORM 2.pdf

35-kolnp-2007-form 3.pdf

35-kolnp-2007-form 5.pdf

35-KOLNP-2007-FORM-27.pdf

35-kolnp-2007-gpa.pdf

35-KOLNP-2007-OTHERS.pdf

35-KOLNP-2007-PETITION UNDER RULE 137.pdf

35-KOLNP-2007-REPLY TO EXAMINATION REPORT.pdf

35-kolnp-2007-specification.pdf

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Patent Number 244693
Indian Patent Application Number 35/KOLNP/2007
PG Journal Number 52/2010
Publication Date 24-Dec-2010
Grant Date 15-Dec-2010
Date of Filing 03-Jan-2007
Name of Patentee ASAHI KASEI CHEMICALS CORPORATION
Applicant Address 1-2, YURAKU-CHO, 1-CHOME, CHIYODA-KU, TOKYO
Inventors:
# Inventor's Name Inventor's Address
1 TAKASHI TSUNODA C/O ASAHI KASEI KABUSHIKI KAISHA, 1-2, YURAKUCHO, 1-CHOME, CHIYODA-KU, TOKYO
2 MITSUHIRO SEKIGUCHI 1-2, YURAKUCHO 1-CHOME, CHIYODA-KU, TOKYO
PCT International Classification Number C07C 11/06
PCT International Application Number PCT/JP2005/013128
PCT International Filing date 2005-07-15
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2004-209654 2004-07-16 Japan