Note: Descriptions are shown in the official language in which they were submitted.
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Zeolites are crystalline al~minosilicates, in which due to
a three-dimensional linkage of SiOI~ and Al04 tetrahedra
regular structures with cavities and pores are formed. In
hydrated state, these pores and cavities are filled with
water, which, on the other hand, can be easily removed
without influencing the crystalline structure, or replaced
by other molecules. The negative charges of the AlOL~
tetrahedra are balanced by cations, which can be replaced by
other ions of positive charge. These properties allow the
use of the zeolites as ion exchangers, adsorbents and
catalysts (D.W. Breck: Zeolite Molecular Sieves, 1974).
Zeolites of the X, Y, mordenite, erionite or of~re-
tite type, ~or example, are o~ considerable interest in the
industrial practice as catalysts for hydrocarbon conversion
reactions such as cracking, hydrocracking or lsomerization.
Zeolites of the pentasil type (for example Zeolite ~SM-5)
become increasingly important as catalysts ~or the conver-
sion of methanol to hydrocarbons.
Because of the numerous application possibilities as
20 catalysts, there is great interest in novel zeolites having
specific catalytical properties.
Very interesting zeolites are for example obtained by
incorporating other elements in~tead of aluminum and/or
silicon into the zeolite frame. Thus, zeolites of the
25 pentasil series are known which contain boron (German
Offenlegungsschrift No. 2,746,790), iron (German Offenle- j
gungsschriPt No. 2,831,611), arsenic (German Auslegeschrift
No. 2,830,830), antimony (German Offenle~ungsschrift No.
2,830,787), vanadium (German Offenlegungsschrift No.
30 2,831,631) chromium (German Offenlegungsschrift No. 2,831,630)
or gallium ~Belgian Patent No. 842,484) in tetrahedral
posi~ion.
Furthermore, titanosilicates (U.S. Patent No. 3,329,481
and zirconosilicates (U.S. Patent No. 3,329,480) have been
35 described.
Sub~ect of the invention are titano-aluminosilicates
having a pentasil structure.
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By pentasils, there are to be understood those defined by Ko-
kotailo and Meier t~'Pentasil family of high silica crystal~
line materials" in: Special Publication No. 33 of the Chemi-
cal Society, London 1980). The pentasil family comprises for
example the synthetic zeolites ZSM-5 (US Patent No. 3,702,886),
ZSM-8 (British Patent No. 1,334,243), ZSM-11 (US Patent No.
3,709,979~ and ZSM-23 (US Patent No. 4,076,842).
The titano-aluminosilicate of the invention differs from
the titanosilicate according to U.S. PLatent No. 3,329,481
with respect to the structure and the aluminum content.
Subject of the invention are especially titano-alu-
minosilicates having a ZSM-5 structure, preferably those
having the following composition, expressed as molar ratio
of oxides:
SiO2 : (0.001 - 0.15) Al2O3 : (0.002 - 1.0) TiO2
especially
SiO2 : (0.005 - 0.1) Al2O3 : (0.01 - 0.4) TiO2.
The titano~aluminosilicates can be prepared according to the
same methods and with the use o~ the same organic compounds
as described for the synthesis of the titanium-~ree zeolite
~SM-5, for example with the use o~
alkylammonium compounds (U.S. Patent No. 3,702,886)
alkylamines (U.g. Patent No. 4,151,189)
alkyldiamines (German Offenlegungsschriften Nos. 2,817,576
and 2,831,334)
alkylamines in the presence of alkylation agents (Published
European Patent Application No. 11362, German Auslegeschrift
No. 2,212,810)
aminoalcohols (British Patent No. 2,023,562)
alcohols (German Offenlegungsschri~ten Nos. 2,935,123,
2,643,929, U.S. Patents No3. 4,199,556, 4,175,114, Pub-
lished European Patent Application No. 42225)
ethers (European Patent Application No. 51741).
Preferably, alkylammonium compounds, alkyl diamines or
alkylamines are used in the presence of alkylation agentq.
Especially preferred alkylammonium compounds are tetrapro-
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pylammonium compounds, for example the hydroxide or one of
the halides. A particularly suitable alkyldiarnine is hexa-
methylene diamine.
For the synthe3is of the titano-aluminosilicates of
the invention, one or more compounds from the cited classes
are mixed with titanium, silicon, ~odium and aluminum com-
pounds and water, and the mixture is heated in a closed ves-
sel. Before heating the mixture, preferably, seed crystals
of a pentasil are furthermore added. In the case where
tetrapropylammonium compounds are used, the starting
compounds are generally used in the following ratio, ex~
pressed as molar ratio of oxides:
SiO2 : (0.01 - 0.2) Al203 : (0.01 - 1.0) TiO2 :
(0.01 - 0.5) Na20 : (0~02 ~ 1~0) R20 : (5 ~ 100) H2O,
preferably in a ratio of:
SiO2 : (0.01 - 0.1) Al203 : (0.01 - 0.4) TiO2 :
(0~02 ~ 0~3) Na2O : (0~03 ~ 0~6) R20 (10 ~ 40) H2O,
R being tetrapropylammonium.
A~s silicon, aluminum, titanium and sodium compounds, there
are used for example silica gel, sodium silicate, aluminum
hydroxide, aluminum sulfate, sodium aluminate, aluminum ha~
lides, aluminum metahydroxide, titanium halides, titanium
sulfate, sodium hydroxide, sodium sulfate, sodium halides.
Other compounds of the four cited elements are also suit-
able for the manufacture of the zeolites according to the
invention.
The mixture of the compounds chosen and water is ge-
nerally heated for 18 to 360, preferably 24 to 240~ hoursat a temperature of from 100 to 200 C~ peferably 130 to 170 C,
in a closed vessel.
The crystalline zeolites which are formed are isola-
ted :in usual manner, for example by filtration, washed and
dried. They can be converted according to known methods to
catalytically active forms, for example by calcination and/or
ion exchange (D.W. Breck, ~eolite Molecular Sieves, 1974)o
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After conversion to the catalytically active ~orm,
the zeolites of the invention display high selectivity and a
considerably reduced deposition of coke in the con~ersion of
methanol to lower olefins. This reaction is carried out, for
example, at temperatures between 350 and 430C using
methanol with a water contant of O to 80 ~7 by weight or
raw methanol.
The following Examples illustrate the invention with-
out limiting it in its scope. All X-ray dif~raction data as
indicated were obtained by means of a computer oontrolled
powder diffractometer D-500 of the Siemens company. The
radiation was the K- ~ doublet of copper.
Example 1
1.66 g of sodium aluminate (54 weight ~7 Al203,
41 weight % Na20) and 2.74 g o~ sodium hydroxide are dis-
solved in 20 g oP 20 weight % aqueous tetrapropylammonium
hydroxide solution (solution A). A further solution (solu-
tion B) is obtained by dissolving 62 g of 40 weight % col-
loidal silica gel in 230 g of 20 weight % aqueous tetrapro-
pylammonium hydroxide solution and concentrating this solu-
tion to a total 230 g in a rotation evaporator. The solu-
tions A and B are mixed, and 2.2 g of titanium tetrachloride
are added to this mixture with thorough stirring. The sus
pension obtaiend is homogenized and heated for 120 hours at
160C in a closed vessel. The product formed is filtered
oPf7 washed with water and dried at 120C. 29.7 g o~ ti-
tano-aluminosilicate according to the invention is obtained.
An X-ray diffraction analysis shows a well crystal-
li~ed product having a ZSM-5 structure. According to a
chemical analysis of the product calcined for 16 hours at
540C, it has the following composition, expressed as molar
ratio of oxides:
SiO2 : 0.047 TiO2 : 0.023 Al203 : 0.051 Na20.
~1
~ ~ . . . _
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Example 2
The titano-aluminosilicate having a ZSM-5 structura
prepared according to Example 1 (calcined form) is exchan-
ged with ammonium nitrate solution, and to~ether with a
binder (Boehmit) extruded (zeolite content 65 weight %),
and calcined again as indicated in Example 1.
520 ml/h of 33 weight % aqueous methanol are dosed at
a temperature of 350C under normal pressure to a verti-
cally positioned, electrically heated tube reactor having a
length of l m and packed with 250 ml of this catalyst. The
reaction mixture which forms is cooled, and after separa-
tion of the condensable portions the gaseous phase is ana-
ly~ed. The C2-C4 olefin selectivity is 64 %, and the se-
lectivlty to hydrocarbons having more than 4 carbon atoms
is 13 %.
Comparative Example
Operations are as in Example 2; however, instead of
the titano-aluminosilicate a commercial aluminosilicate
catalyst having a ZSM-5 structure is used.
The C2-C4 olefin selectivit~ is 56 %, and the se-
lectivity to hydrocarbons having more than 4 carbon atoms is
23 %.
