Title of Invention

PROCESS FOR PRODUCING TERTIARY OLEFINS BY DECOMPOSITION OF THE CORRESPONDING ALKYL-TERT-ALKYLETHERS

Abstract A catalyst for producing tertiary olefins from alkyl-tert- alkylethers is described, consisting of silica modified by adding alumina in a quantity of between 0.3 and 1% by weight with respect to the silica, and is prepared by a method consisting essentially 5 of impregnating a silica with a solution of aluminium salts, followed by drying and calcining, the material then being subjected to purification treatment with aqueOUS acid solutions or with aqueous solutions which release acidity by thermal decomposition, followed by washing, a second drying and a. second
Full Text

This invention relates to a catalyst prepared by a particular
method and its use in a process for producing tertiary olefins by
decomposition of the corresponding alkyl-tert-alkylethers.
Various methods for producing tertiary olefins are known.
For example, some are based on the use of H2SO4, which however in
addition to corrosion and pollution problems has various
drawbacks, including the need to concentrate the acid before its
recycling. Others are based on decomposition of the corresponding
methyl ethers in the presence of suitable catalyst systems.
However the use of known catalysts for this reaction leads in most
cases to the formation of dialkylether following the dehydration
of the corresponding primary alcohols.
This reaction proceeds more easily the higher the reaction
temperature. Some of the known catalysts require the use of
relatively high temperatures, resulting in a loss of alcohol with
the consequent need to feed new alcohol to the initial
etherification reaction.
In addition, this formation of dialkylether requires more complex

plant because of the need to separate the dialkylether from the tertiary olefin. Again, the formation of a considerable quantity of dialkylether makes it necessary to dehydrate the primary alcohol before it is recycled, otherwise there would be phase separation during the etherification reaction, with the possible formation of tertiary alcohols.
A further drawback when the reaction is conducted beyond a certain temperature is the appearance of dimerization and trimerization of the tertiary olefin recovered from the ether decomposition. Some problems disappear if the tert-alkylether decomposition is conducted in the presence of a catalyst system consisting of activated alumina modified by partial substitution of the surface -OH groups by silanol groups as described in Italian patents Nos. 1001614 and 1017878 in the name of the present applicant. However the activated alumina modified as described in the aforesaid patents gives rise, even for a modest raising of the reaction temperature, to the formation of alkylether with consequent reduction in the recovery of primary alcohol for recycling.
In contrast, US Patent No. 4,254,296 of the present
applicant uses a catalyst chosen from a crystalline silica modified with oxides of metal cations such as aluminium and boron, which gives much better performance than activated alumina modified with silanol groups.
However, this material has a very high production cost and is difficult to prepare. In addition the siliconized alumina catalyst does not have a long

low economically quantitative recovery of the products obtained. Higher dimethylether quantities correspond to higher methanol quantities and higher quantities of isobutene, which is lost during the distillation or separation stage*
European patent application EP-50992 of SUMITOMO Chem. Ind. claims a tertiary olefin production process using a catalyst prepared by high-temperature calcining of silica and an aluminium compound (particularly aluminium sulphate), in which the weight percentage of the aluminium compound is between 1 and 50% and preferably between 5 and 30%.
The present applicant has shown in European Patent No. 0 261 129 that using a catalyst consisting of silica modified by adding alumina in a quantity of between 0.1 and 1.5% by weight with respect to the silica, high conversion can be obtained provided that the silica used is of high purity.
The present applicant has now found that the conversion obtained with this type of catalyst can be substantially increased by a preparation method comprising purification treatment. This substantial increase applies particularly to commercial silica, but even with high-purity silica the percentage conversion is a few points higher.
As demonstrated by the examples, it is important to effect the purification treatment downstream of the step involving silica impregnation with alumina if substantially higher results are to be obtained. The catalyst according to the present invention for producing

tertiary olefins from the corresponding alkyl-tert-alkylethers and
consisting of silica modified by adding alumina in a quantity of
between 0.3 and 1% by weight with respect to the silica is
characterised by being prepared by a method consisting essentially
of impregnating a silica with a solution of aluminium salts,
followed by drying and calcining, the material then being
subjected to purification treatment with aqueous acid solutions
(such as HCl, H2SO4 etc.) or with aqueous solutions which release
acidity by thermal decomposition, followed by washing, a second
drying and a second calcining.
The preferred aqueous solutions which release acidity by
decomposition are aqueous solutions of ammonium salts, in
particular ammonium acetate, ammonium propionate and ammonium
chloride.
The purification treatment is preferably conducted at a
temperature of between 20 and 100oC for a time of between 0.5 and
24 hours.
The aqueous solutions are preferably used at a molar concentration
of between 0.05 and 0.5 in a quantity of between 1 and 20 times
the volume of the material to be purified.
The present invention further provides a process for producing
tertiary olefins consisting essentially of reacting the
corresponding alkyl-tert-alkylethers in the presence of a catalyst
obtained by the aforedescribed preparation method and consisting
of silica modified by adding alumina in a quantity of between 0.3
and 1% by weight with respect to the silica.
In particular, said process can be used to obtain isobutene by

decomposing methyl-tert-butyl-ether (MTBE).
The alkyl-tert-alkylether decomposition is conducted at a
temperature equal to or lower than 500oC, and preferably between
130 and 350oC.
The operating pressure is generally between 1 and 10 kg/cm2, and
preferably at least equal to the vapour pressure of the recovered
olefin at the condensation temperature used.
The space velocity expressed as liquid volume per volume of
catalyst per hour (LHSV) at which the reaction is conducted is
between 0.5 and 200 h-1 and preferably between 1 and 50 h-1
The primary alcohols recoverable for the purpose of the
decomposition process of the invention preferably contain from 1
to 6 carbon atoms.
The process of the present invention can be used to recover
tertiary olefins from mixtures of C4-C7 olefins such as those
originating from thermal cracking, steam cracking or catalytic
cracking.
The various tertiary olefins obtainable in the pure state include
isobutylene, isoamylenes such as 2-methyl-2-butene and 2-methyl-l-
butene, isohexanes such as 2,3-dimethyl-l-butene, 2,3-dimethyl~2-
butene, 2-methyl-l-pentene, 2-methyl-2-pentene, 3-methyl-2-pentene
(cis and trans), 2-ethyl-l-butene, 1-methyl-cyclopentene, and
tertiary isoheptenes.
The transformation of the tert-alkylether into primary alcohol and
tertiary olefin is practically quantitative in accordance with the
relative thermodynamic data.
The formation of very small quantities of dimers and triraers of

the recovered tertiary olefin is noted, whereas there is no
formation of tertiary alcohol.
The operation and the advantages of the process according to the
present invention will be more apparent from an examination of the
following illustrative examples, which are in no way to be
considered as limitative of the invention.
Examples of catalyst preparation
EXAMPLE 1
The catalyst in the form of silica modified with alumina is
prepared in the following manner:
10 g of commercial silica (980B of Shell), of composition:
Na2O 0.08 wt%
SO4 0.10 wt%
Al2O3 0.10 wt%
Si02 remainder to 100% are impregnated with 8.5 cc of an aqueous solution containing 0.368 g of aluminium nitrate enneahydrate (Al2O3 added = 0.5% by weight with respect to the silica); slow drying then follows at 120oC for 3 hours, plus calcining at 500oC for 4 hours. The material obtained is treated with 100 cc of an ammonium acetate solution (0.17 molar) at 50oC for 2 hours. The material is then separated from the solution and washed with deionized water (3 times with 100 cc), dried in an oven at 120oC for 3 hours and calcined at 450oC for 4 hours. EXAMPLE 2
A catalyst is prepared in the manner of Example 1 starting from Shell 980B commercial silica.

Compared with Example 1, the 10 g of silica are impregnated with
8.5 cc of an aqueous solution containing 0.515 g of aluminium
nitrate enneahydrate {Al2O3 added = 0.7% by weight with respect to
the silica).
EXAMPLE 3
A catalyst is prepared in the manner of Example 1 starting from
Shell 980B commercial silica.
Compared with Example 1, the 10 g of silica are impregnated with
8.5 cc of an aqueous solution containing 0.736 g of aluminium
nitrate enneahydrate (Al2O3 added = 1% by weight with respect to
the silica).
EXAMPLE 4 (comparative)
A catalyst is prepared starting from 10 g of Shell 980B commercial
silica.
The 10 g of silica are treated with 100 cc of an ammonium acetate
solution (0.17 molar) at 50'C for 2 hours.
The material is then separated from the solution and washed with
ieionized water (3 times with 100 cc), dried in an oven at 120oC
for 3 hours and calcined at 450oC for 4 hours.
The material obtained is impregnated with 8.5 cc of an aqueous
solution containing 0.736 g of aluminium nitrate enneahydrate
[Al2O3 added = 1% by weight with respect to the silica), slow
trying then following at 120oC for 3 hours, plus calcining at
100oC for 4 hours.
compared with Example 3, the purification treatment is conducted
upstream of the impregnation with Al2O3.
EXAMPLES 5-7 (comparative)

Catalysts are prepared (Examples 5, b and in a manner anatogous
to Examples 1, 2 and 3 respectively, but without conducting the
purification treatment downstream of the first drying and first
calcining steps.
EXAMPLES 8-10 (comparative)
Catalysts are prepared (Examples 8, 9 and 10) in a manner
analogous to Examples 5, 6 and 7 respectively but, instead of
using the Shell 980B commercial silica, using a high purity AKZO
silica of the following composition:
Na2O 0.02 wt%
SO4 0.15 wt%
Al2O3 0.15 wt%
SiO2 remainder to 100% Examples of their use in the tertiary olefin production process EXAMPLES 11-20
The catalysts prepared as described in Examples 1-10 are used in a process for producing tertiary olefins by methyl-tert-butylether (MTBE) decoraposition. The reaction conditions are as follows:
Catalyst bed temperature 130'C
LHSV 4 h-i
Inlet pressure 1.4 ata
The results obtained are given in Table 1, from which the beneficial effect of the catalyst purification treatment can be seen. The conversion is much higher than that obtained using catalysts prepared from commercial silica by known methods, and is also clearly higher than that obtained using catalysts prepared

from high purity silica by known methods.
It can also be seen that when the purification treatment is conducted before the impregnation with Al2O3 the advantages are very modest (in terms not of conversion increase but rather of the conversion value obtained).



WE CLAIM :
1, A process for producing tertiary olefins by decomposition of corresponding alkyl-tert-alkylethers, characterised in that the alkyl-tert-alkylethers are reacted in presence of a catalyst consisting of modified silica by adding alumina in a quantity comprised of from 0.3 to 1 % by weight with respect to silica
at a pressure comprised between 1 and 10 kg-cm2 , at a temperature
lower than or equal to 500oC and at a spatial velocity comprised
between 0.5 and 200 h-1.
2. The process as claimed in claim 1, wherein the alkyl-tert-alkylethers are reacted at a pressure of between 1 and
10 kg-cm , at a temperature of less than or equal to 500 C
-1 and at a space velocity of between 0.5 and 200 h •
3. The process as claimed in claim 2, wherein the temperature is between 130 and 350oC and the space velocity is between 1 and 50 h-1.
4. -the process as claimed in claim 1, wherein the alkyl-tert-alkylether is methyl-tert-butylether.
5. A process for producing tertiary olefins by decomposition
of the corresponding alkyl-tert-alkylethers, substantially as hereinbefore described and illustrated with reference to the


Documents:

859-mas-1996 others.pdf

859-mas-1996 abstract duplicate.pdf

859-mas-1996 form-4.pdf

859-mas-1996 petition.pdf

859-mas-1996-abstract.pdf

859-mas-1996-claims duplicate.pdf

859-mas-1996-claims original.pdf

859-mas-1996-correspondance others.pdf

859-mas-1996-correspondance po.pdf

859-mas-1996-description complete duplicate.pdf

859-mas-1996-description complete original.pdf

859-mas-1996-form 1.pdf

859-mas-1996-form 26.pdf

859-mas-1996-other documents.pdf


Patent Number 207292
Indian Patent Application Number 859/MAS/1996
PG Journal Number 26/2007
Publication Date 29-Jun-2007
Grant Date 04-Jun-2007
Date of Filing 22-May-1996
Name of Patentee M/S. SNAMPROGETTI S.P.A
Applicant Address CORSO VENEZIA 16, MILAN ITALY.
Inventors:
# Inventor's Name Inventor's Address
1 FORLANT ORFEO VIA AGADIR2/A SAN DONATO,MILANESE, MILAN.
PCT International Classification Number C07C11/12
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA