Note: Descriptions are shown in the official language in which they were submitted.
CA 02314233 2000-06-09
Shaped body comprising an inert support and at least
one porous oxidic material
The present invention relates to a shaped body
comprising an inert support and at least one porous
oxidic material applied thereto, a process for its
production, and its use for the conversion of organic
compounds, in particular for the epoxidation of organic
compounds having at least one C-C double bond. The
shaped body described herein has an excellent abrasion
resistance and excellent mechanical properties and is
cheap compared with catalysts used for these purposes
heretofore.
Abrasion-resistant shaped bodies comprising
catalytically active materials are employed in many
chemical processes, in particular in processes using a
fixed bed.
For the production of solids, a binder, an organic
viscosity-enhancing compound and a liquid for converting
the material into a paste are generally added to the
catalytically active material, ie. the porous oxidic
material, and the mixture is compacted in a mixing or
kneading apparatus or an extruder. The resulting
plastically deformable material is then shaped, in
particular using an extruder, and the resulting shaped
bodies are dried and calcined.
A number of inorganic compounds are used as binders.
For example, according to US-A 5,430,000, titanium
dioxide or titanium dioxide hydrate is used as the
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binder. Examples of further prior-art binders are:
aluminum oxide hydrate or other aluminum-containing
binders (WO 94/29408);
mixtures of silicon and aluminum compounds
(WO 94/13584);
silicon compounds (EP-A 0 592 050);
clay minerals (JP-A 03 037 156);
alkoxysilanes (EP-B 0 102 544).
Further relevant prior art is reviewed in DE 197 23
751.7.
In conversions exhibiting very high intrinsic reaction
rates, the yield that can be achieved technically is
limited by the diffusion of the starting materials or
products in the shaped body. In these cases, only the
surface layer of the shaped body is utilized for
conversion, whereas the rest of the shaped body is only
the support for this surface layer. It will be
appreciated that this is economically prohibitive in the
case of an expensive catalytically active material.
Therefore, a supported or coated catalyst in the form of
a shaped body is rather used in this case. This catalyst
comprises an inert core and a surface layer of
catalytically active material.
Catalysts of this type are also prepared using zeolites
as active components. For instance, JP 07,241,471
describes the application of zeolite powder to a support
by suspending the zeolite in combination with an
inorganic binder in water and organic emulsifiers and
subsequent wash-coating onto the support. These
catalysts are intended for waste gas purification. A
similar procedure is described in JP 07,155,613, where
zeolites and silica sol are suspended in water to form a
wash coat suspension which is applied to a monolithic
cordierite support. Likewise, JP 02,111,438 describes
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the application of zeolites to- monolithic supports
utilizing aluminium sol as a binder. This catalyst is
used for waste gas purification, too. US 4,692,423
describes the application of zeolites to porous supports
by first admixing the zeolite with cyclic oxides which
are,instable with respect to polymerization, coating the
surface of the porous support with this suspension and
subsequently removing the solvent. US 4,283,583
describes catalysts where a zeolite has been supported
on spherical supports of from 0.5 to 10 mm in diameter.
It is true that the adhesion of the active component on
the support is important for gas phase processes such as
waste gas purification, but the forces acting on the
supported layer in a gas phase process are much less
abrasive than in a liquid phase process, for example. In
the latter case, there are much higher requirements on
the adhesion of the supported layer. The anchoring of
active material on the inert carrier may be destabilized
especially by the permanent presence of liquid or
solvent. JP 08,103,659 describes a use for a liquid
phase process. There, titanium silicalite is applied to
spheres of from 0.2 to 20 mm in diameter. To this end,
titanium silicalite is suspended in an aqueous
polyvinylalcohol solution and sprayed onto the sphere.
The sprayed sphere is then calcined to give the ready-
to-use catalyst which is then used in the epoxidation of
propylene with hydrogen peroxide. However, the catalyst
generated in this way still exhibits significant
abrasion of the active component.
US 5,523,426 describes a way to epoxidize propylene over
titanium silicalite catalysts where the titanium
silicalite may be applied onto inert carriers, inter
alia. The application procedure is not described in
detail.
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As can be seen from the prior ar't, there is the problem
that the catalysts used heretofore are not suitable for
use as abrasion-resistant supported catalysts since the
adhesion of the active component is usually insufficient
for this purpose. Furthermore, a limitation to spherical
support bodies is often not sensible for fluid dynamics
reasons.
It is thus an object of the present invention to develop
a process which makes it possible to apply a zeolite and
in particular titanium silicalite to supports of any
shape, preferably non-monolithic supports, in an
abrasion-resistant manner to give catalysts which may be
used in chemical processes, in particular in liquid
phase processes, and to provide such a catalyst per se.
We have now found, surprisingly, that this object is
achieved by applying a mixture comprising at least one
porous oxidic material and at least one metal acid ester
or a hydrolysate thereof or a combinat~.on of metal acid
ester and hydrolysate on an inert support to give a
shaped body which may be used in liquid phase processes
without problems.
Accordingly, the present invention provides a shaped
body comprising an inert support and at least one porous
oxidic material applied thereto and obtainable by
applying a mixture comprising at least one porous oxidic
material and at least one metal acid ester or a
hydrolysate thereof or a combination of metal acid ester
and hydrolysate thereof to the inert support,
and a process for preparing such a shaped body, which
comprises applying a mixture comprising at least one
porous oxidic material and at least one metal acid ester
or a hydrolysate thereof or a combination of metal acid
ester and hydrolysate thereof to an inert support.
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The inert supports which may be' used according to the
invention may consist of oxides, carbides, nitrides or
other inorganic or organic materials, provided that they
do not decompose, melt or become otherwise instable at
the temperatures required in the preparation process.
For the purposes of the present invention, "inert" means
that the materials used as support have negligible
catalytic activity, if any.
Preferred inert supports used are metal oxides or mixed
oxides of metals of transition groups III to VIII and
main groups III to V of the Periodic Table of the
Elements and combinations of two or more thereof, in
particular silicon dioxide, aluminum oxide, titanium
dioxide, zirconium dioxide and mixed oxides thereof.
It is further possible to use metals or metal alloys,
such as steel, Kanthal, aluminum, etc., as materials for
the inert support.
The inert support preferably has an alkali metal or
alkaline earth metal content of < 1,000 ppm, preferably
< 100 ppm, in particular < 10 ppm. The low alkali metal
or alkaline earth metal contents of the support are of
particular importance when the catalyst of the invention
is used for epoxidation, especially with a titanium
silicalite as porous oxidic material.
The external form of the inert support or shaped body is
not critical and can be selected without restriction
depending on the fluid dynamics of the particular
reactor chosen for the reaction. The inert support or
shaped body may be in the form of extrudates, such as
circular extrudates, star-shaped extrudates, hollow
extrudates and cylinders, granules, tablets, annular
tablets, spherical, non-spherical or spherolithic
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granules, as a monolith or in the form of a band-like
structure or a structure having holes, eg. in the form
of a mesh or fabric, in pyramidal form or as a waggon
wheel profile.
The support or shaped body is preferably in the form of
a non-spherical pellet, an extrudate, a granule, a
tablet, a band-like structure or a structure having
holes.
It is also possible to apply the porous oxidic material
directly to the reactor wall. In the case of exothermic
reactions, this is even beneficial for heat removal.
There are no particular restrictions with regard to the
porous oxidic materials which may be used for the
production of the novel shaped body, as long as it is
possible to prepare a shaped body as described herein
starting from these materials and these materials have
the necessary catalytic activity.
The porous oxidic material is preferably a zeolite,
particularly preferably a titanium-, zirconium-,
chromium-, niobium-, iron- or vanadium-containing
zeolite, in particular a titanium silicalite.
Zeolites are known to be crystalline aluminosilicates
having ordered channel and cage structures which have
micropores. The term micropores as used in the present
invention corresponds to the definition given in Pure
Appl. Chem. 45 (1976), p. 7lff., in particular p. 79,
and refers to pores having a diameter of less than 2 nm.
The network of such zeolites is composed of Si09 and
A104 tetrahedra which are linked via common oxygen
bridges. An overview of the known structures is given,
for example, by W.M. Meier and D.H. Olson in "Atlas of
Zeolite Structure Types", Elsevier, 4th Edition, London
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1996.
_ _ 7 _
Furthermore, there are zeolites which contain nc
aluminum and in which some of the Si(IV) has been
replaced by titanium as Ti (IV) in the silicate lattice.
Titanium zeolites, in particular those having a crystal
structure of the MFI type, and possibilities for their
preparation are described, for example, in EP-A 0 311
983 or EP-A 0 405 978. Apart from silicon and titanium,
such materials may also contain additional elements,
such as aluminum, zirconium, tin, iron, cobalt, nickel,
gallium, boron or small amounts of fluorine.
Some or all of the titanium in the zeolites described
may be replaced by vanadium, zirconium, chromium,
niobium or iron. The molar ratio of titanium and/or
vanadium, zirconium, chromium, niobium or iron to the
sum of silicon and titanium and/or vanadium, zirconium,
chromium, niobium or iron is usually from 0.001:1 to
0.1:1.
Titanium zeolites having the MFI structure are known to
be identifiable from a particular pattern in their X-ray
diffraction diagrams and, in addition, by a skeletal
vibration band in the infrared (IR) at about 960 cm-1,
and thus differ from alkali metal titanates or
crystalline and amorphous Ti02 phases.
Said titanium, zirconium, chromium, niobium, iron and
vanadium zeolites are usually prepared by reacting an
aqueous mixture of an Si02 source, of a titanium,
zirconium, chromium, niobium, iron or vanadium source,
eg. titanium dioxide or an appropriate vanadium oxide,
zirconium alcoxide, chromium oxide, niobium oxide or
iron oxide, and of a nitrogenous organic base template,
eg. tetrapropylammonium hydroxide, with or without added
basic compounds, in a pressure vessel at elevated
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temperature for several hours or~some days, resulting in
a crystalline product. The crystalline product is
filtered off, washed, dried and baked at high
temperature to remove the organic nitrogen base. In the
resulting powder, the titanium or zirconium, chromium,
niobium, iron and/or vanadium is present at least partly
inside the zeolite framework in varying proportions in
four-, five- or six-fold coordination. To improve the
catalytic characteristics it is also possible to carry
out a subsequent treatment by washing repeatedly with a
solution of hydrogen peroxide containing sulfuric acid,
after which the titanium, zirconium, chromium, niobum,
iron or vanadium zeolite powder must be again dried and
baked; this can be followed by a treatment with alkali
metal compounds in order to convert the zeolite from the
H form into the cation form. The resulting titanium,
zirconium, chromium, niobium, iron or vanadium zeolite
powder is then processed into a shaped body as described
below.
Preferred zeolites are titanium, zirconium, chromium,
niobium or vanadium zeolites, more preferred zeolites
are those having a pentasil zeolite structure,
especially the types with X-ray assignment to a BEA,
MOR, TON, MTW, FER, MFI, MEL, CHA, ERI, RHO, GIS, BOG,
NON, EMT, HEU, KFI, FAU, DDR, MTT, LTL, MAZ, GME, NES,
OFF, SGT, EUO, MFS, MCM-22 or MFI/MEL mixed structure.
Zeolites of this type are described, for example, in the
above Meier and Olson reference. Also possible for the
present invention are titanium-containing zeolites
having the structure of UTD-1, CIT-1 or CIT-5. Such
zeolites are described, inter alia, in US-A-5 430 000
and WO 94/29408, the relevant contents of which are
fully incorporated herein by reference.
Nor are there special restrictions in the pore structure
of the shaped bodies of the invention, ie. the shaped
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_ _ g _
body according to the invention-can have micropores,
mesopores, macropores, micro- and mesopores, micro- and
macropores or micro-, meso- and macropores, the
definition of "mesopores" and "macro ores
P " also
corresponding to the definition given in the Pure Appl.
Chem; reference given above and referring to pores
having a diameter of from > 2 nm to 50 nm or > 50 nm,
respectively.
Furthermore, the shaped body of the invention may be a
material based on a mesoporous silicon-containing oxide
and a silicon-containing xerogel.
Silicon-containing mesoporous oxides which additionally
contain Ti, V, Zr, Sn, Cr, Nb or Fe, in particular Ti,
V, Zr, Cr, Nb or a mixture of two or more thereof, are
particularly preferred.
To obtain a shaped body having the desired abrasion
resistance, the porous oxidic material described in
detail above is always applied to the inert support in
admixture with at least one metal acid ester or a
hydrolysate thereof or a combination of at least one
metal acid ester and a hydrolysate thereof (hereinafter
often referred to as metal acid ester (hydrolysate)).
The metals of the metal acid esters may be selected from
main groups III to IV and transition groups III to VI of
the Periodic Table of the Elements. It is also possible
to use partial hydrolysates thereof.
Particular examples of these are orthosilicates,
alkoxysilanes, tetraalkoxytitanates,
trialkoxyaluminates, trialkoxyniobates,
tetraalkoxyzirconates or a mixture of two or more
thereof. However, particularly preferred metal acid
esters used in the present invention are
tetraalkoxysilanes. Specific examples are
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tetramethoxysilane, '- tetraethoxysilane,
tetrapropoxysilane, tetraisopropoxysilane and
tetrabutoxysilane, the corresponding tetraalkoxytitanium
and tetraalkoxyzirconium compounds and trimethoxy-,
triethoxy-, tripropoxy-, trisisopropoxy-,
tributoxyaluminum or triisobutoxyaluminum, with
tetramethoxysilane and tetraethoxysilane being
especially preferred.
According to the invention, the content of metal oxide
from the metal acid ester or the hydrolysate thereof is
preferably up to about 80% by weight, more preferably
from about 1 to about 50% by weight, in particular from
about 3 to about 30% by weight, based on the amount of
porous oxide.
The content of the mixture applied is generally from
about 1 to about 80% by weight, preferably from about 1
to about 50% by weight, in particular from about 3 to
about 30% by weight, in each case based on the total
amount of mixture and inert support.
As can be seen from the above, mixtures of two or more
of the abovementioned binders may of course also be
employed.
There are no particular restrictions with regard to the
application of the mixture to the inert support. The
application can be effected by impregnating, spraying or
trickling. Some preferred application methods will now
be described in more detail.
To apply the at least one porous oxidic material, the
latter is suspended in a liquid, in the form of a powder
or pellets, and applied. It is also possible to feed the
porous oxidic material in the form of a powder or
pellets and the liquid required for adhesion of the
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porous oxidic material on a he inert support
simultaneously. The oxidic material to be applied is
preferably suspended in the liquid and sprayed onto the
support.
In one embodiment, the metal acid ester (hydrolysate)
used according to the invention is admixed with the
porous oxidic material having the form of a powder or
pellets. The resulting mixture is then trickled onto the
inert support which is simultaneously sprayed with an
adhesion liquid. In this case, preference is given to
using the hydrolysates of the metal acid esters.
In another embodiment of the invention, the metal acid
ester (hydrolysate) is mixed with the adhesion liquid to
give a mixture which is then applied to the inert
support simultaneously with the porous oxidic material
having the form of a powder or pellets. In another,
preferred embodiment, the metal acid ester (hydrolysate)
is suspended in the adhesion-promoting liquid together
with the porous oxidic material to give a suspension
which is sprayed onto the inert support.
The alcohol used in the above mixture preferably
corresponds to the alcohol component of the metal acid
ester used or hydrolysate thereof, but it is also not
critical to use another alcohol.
A particularly quick adhesion of the mixture can be
achieved by impregnating the inert support with acidic
substances, such as organic or inorganic acids, eg.
nitric acid, sulfuric acid, hydrochloric acid, acetic
acid, oxalic acid or phosphoric acid.
The mixture to be applied to the inert support may
contain further additives, such as organic viscosity-
enhancing substances and others as defined below.
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Adhesion-promoting liquids include water, various
organic liquid classes, such as alcohols, diols,
polyols, ketones, acids, amines, hydrocarbons and
mixtures of two or more thereof. If these liquids are
used to suspend the porous oxidic material, preference
is given to using liquids volatilizable at the spraying
temperatures of from about 30 to about 200EC, preferably
from about 50 to about 150EC, in particular from about
60 to about 120EC. If these liquids are added, as
adhesion promoters, separately from the porous oxidic
material, but simultaneously, a liquid having a boiling
point which is considerably higher than the
abovementioned temperatures will be chosen.
In a preferred embodiment, the porous oxidic material is
suspended in alcohols, such as methanol, ethanol,
propanol, isopropanol, n-butanol, isobutanol, tert-
butanol and mixtures of two or more thereof. Particular
preference is given to using a mixture of an alcohol,
preferably one of the alcohols mentioned above, with
water. Such a mixture generally comprises from about 1
to about 80% by weight, preferably from about 5 to about
70°s by weight, in particular from about 10 to about 600
by weight, in each case based on the total weight of the
mixture of alcohol and water.
High-boiling liquids are those having a boiling point at
atmospheric pressure of more than 150gC. Preferred high-
boiling liquids are propanediol, glycerol, ethanediol,
polyether, polyester, dipropylene glycol or mixtures of
two or more thereof.
The organic viscosity-enhancing substance used may
likewise be any prior art substances suitable for this
purpose. Those preferred are organic, in particular
hydrophilic, polymers, eg. cellulose, starch,
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polyacrylates, polymethacrylates,, polyvinyl alcohol,
polyvinylpyrrolidone, polyisobutene and
polytetrahydrofuran. These substances primarily promote
the adhesion of the porous oxidic material on the
support in the uncalcined state.
Amines or amine-like compounds, for example
tetraalkylammonium compounds or aminoalcohols, and
carbonate-containing substances, such as calcium
carbonate, may be used as further additives. Such
further additives are described in EP-A 0 389 041, EP-A
0 200 260 and WO 95/19222, the relevant contents of
which are fully incorporated herein by reference.
The shaped body obtained by applying the mixture
comprising the porous oxidic material to the inert
support may be subjected to a calcination step. This
calcination step may be superfluous when using the
shaped body as a catalyst in a reaction which is carried
out at high temperatures and in the presence of oxygen.
In this case, the calcination is effected in situ in the
reactor.
This applies in particular when the novel mixture of
porous oxidic material and metal acid ester
(hydrolysate) is applied directly to the reactor wall
and a reaction is then carried out at high temperature.
Otherwise, the shaped bodies are calcined. By this
treatment, the shaped bodies are provided with the
desired hardness and abrasion resistence. The
calcination is generally carried out at from about 200EC
to 1,OOOgC, preferably from 250gC to 900EC, particularly
preferably from about 300gC to about 800gC, preferably
in the presence of an oxygen-containing gas.
The shaped bodies are preferably dried at from about 50
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to about 200EC, preferably from about 80 to about 150EC,
prior to calcination.
The shaped bodies according to the invention or produced
S by a process according to the invention have very good
catalytic activity and excellent mechanical abrasion
resistance and are thus suitable for use in liquid phase
reactions.
The novel shaped bodies contain virtually no particles
finer than those with a minimum particle diameter of
about 0.1 mm.
The shaped bodies according to the invention or produced
according to the invention and comprising a porous
oxidic material have improved mechanical stability while
at the same time retaining their activity and
selectivity in comparison with corresponding prior art
shaped bodies.
The shaped bodies according to the invention or produced
according to the invention can be employed for the
catalytic conversion of organic molecules. Reactions of
this type are, for example, oxidations, the epoxidation
of olefins, for example the preparation of propylene
oxide from propylene and H202, the hydroxylation of
aromatics, for example phenol from benzene and H202 and
hydroquinone from phenol and H202, the conversion of
alkanes into alcohols, aldehydes and acids,
isomerization reactions, for example the conversion of
epoxides into aldehydes, and further reactions described
in the literature utilizing such shaped bodies, in
particular zeolite catalysts, as described, for example,
in W. Holderich, Zeolites: Catalysts for the Synthesis
of Organic Compounds, Elsevier, Stud. Surf. Sci. Catal.,
49, Amsterdam (1989), 69-93, and, in particular for
possible oxidation reactions, by B. Notari in Stud.
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Surf. Sci. Catal., 37 (1987) 413-X25.
The shaped bodies discussed in detail above are
particularly suitable for the epoxidation of olefins,
preferably those of 2 to 8 carbon atoms, particularly
preferably ethylene, propylene or butene, in particular
propene, to give the corresponding olefin oxides.
Accordingly, the present invention relates in particular
to the use of the shaped body described herein for the
preparation of propylene oxide starting from propylene
and hydrogen peroxide as described, for example, in EP-A
0 100 119.
EXAMPLES
Preparation Example 1
910 g of tetraethyl orthosilicate were initially taken
in a 4 1 four-necked flask and 15 g of tetraisopropyl
orthotitanate were added from a dropping funnel in the
course of 30 minutes while stirring (250 rpm, paddle
stirrer). A colorless, clear mixture formed. 1600 g of
a 20o strength by weight tetrapropylammonium hydroxide
solution (alkali metal content < 10 ppm) were then added
and stirring was continued for a further hour. The
alcohol mixture (about 900 g) formed from the hydrolysis
was distilled off at from 90 to 100gC. The mixture was
made up with 3 1 of water and the meanwhile slightly
opaque sol was transferred to a 5 1 stainless steel
stirred autoclave.
The closed autoclave (anchor stirrer, 200 rpm) was
brought to a reaction temperature of 175gC at a heating
rate of 3EC/min. The reaction was complete after 92
hours. The cooled reaction mixture (white suspension)
was centrifuged and the sediment was washed several
times with water until it was neutral. The solid
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obtained was dried at 110EC in the course of 24 hours
(weight obtained 298 g).
The template remaining in the zeolite was then burnt off
under air at 550EC in 5 hours (calcination loss: 14% by
weight).
According to wet chemical analysis, the pure white
product had a Ti content of 1.3~ by weight and a
residual alkali content of less than 100 ppm. The yield
was 97%, based on Si02 used. The crystallites had a
size of from 0.05 to 0.25 um and the product showed a
typical band at about 960 cm-1 in the IR spectrum.
Comparative Example 1
120 g of titanium silicalite powder, synthesized
according to Preparation Example 1, were mixed with 48 g
of tetramethoxysilane for 2 h in a kneader. 6 g of
Walocel (methylcellulose) were then added. For
conversion into a paste, 77 ml of a water/methanol
mixture containing 25o by weight of methanol were then
added. The material obtained was compacted for a
further 2 h in the kneader and then shaped in an
extruder to give 1 mm extrudates. The extrudates thus
obtained were dried at 120gC for 16 h and then calcined
at 500gC for 5 h. The epoxidation characteristics of the
catalyst V1 thus obtained were evaluated in epoxidation
experiments.
Comparative Example 2
120 g of titanium silicalite powder, synthesized
according to Preparation Example 1, were mixed with 48 g
of tetramethoxysilane for 2 h in a kneader. 6 g of
Walocel (methylcellulose) were then added. For
conversion into a paste, 77 ml of a water/methanol
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mixture containing 25$ by weight-_of methanol were then
added. The material obtained was compacted for a
further 2 h in the kneader and then shaped in an
extruder to give 3 mm extrudates. The extrudates thus
obtained were dried at 120EC for 16 h and then calcined
at SOOEC for 5 h. The epoxidation characteristics of the
catalyst V2 thus obtained were evaluated in epoxidation
experiments.
Preparation Exam le 2
2500 g of Aerosil 200 obtained from Degussa were
compacted together with 150 g of ammonia solution (300),
100 g of potato starch and 3000 g of water in a kneader
and then shaped in an extruder to give 2 mm extrudates.
The extrudates thus obtained were dried at 110EC and
then calcined at 500gC for 16 h. The extrudates thus
obtained had an alkali metal content of 40 ppm. Half of
the extrudates.were processed into 1-1.6 mm granules for
the following examples.
Example 1
10 g of titanium silicalite powder obtained in
Preparation Example 1 (particle sizes < 0.1 mm) were
suspended in 100 g of methanol and 4 g of
tetramethoxysilane. 100 g of Aerosil granules obtained
in Preparation Example 2 were initially taken in a
heated splash plate. The suspension of the titanium
silicalite in methanol/tetramethoxysilane was sprayed on
slowly while steadily rotating the splash plate. The
granules thus obtained were dried at 120EC, screened and
calcined at 500EC for 5 h. About 7 g of TS-1 powder were
recovered by the screening procedure after drying.
Calcination gave abrasion-resistant shaped bodies
suitable for liquid phase reactions. The shaped body
contained 2$ by weight Ti silicalite, as determined by
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atomic emission spectroscopy. The epoxidation
characteristics of the catalyst A thus obtained were
evaluated in epoxidation experiments.
Example 2
. g of titanium silicalite powder obtained in
Preparation Example 1 (particle sizes < 0.1 mm) were
suspended in 100 g of methanol and 4 g of
10 tetramethoxysilane. 100 g of Aerosil granules obtained
in Preparation Example 2 were impregnated with acetic
acid and initially taken in a heated splash plate. The
suspension of the titanium silicalite in
methanol/tetramethoxysilane was sprayed on slowly while
steadily rotating the splash plate. The granules thus
obtained were dried at 120gC, briefly screened and
calcined at 500EC for 5 h. About 2 g of TS-1 powder were
recovered by the screening procedure after drying.
Calcination gave abrasion-resistant shaped bodies
suitable for liquid phase reactions. The shaped body
contained 5°s by weight Ti silicalite, as determined by
atomic emission spectroscopy. The impregnation of the
shaped bodies with acetic acid provided better adhesion
of the TS-1 during spraying. The epoxidation
characteristics of the catalyst B thus obtained were
evaluated in epoxidation experiments.
Example 3
20 g of titanium silicalite powder obtained in
Preparation Example 1 (particle sizes < 0.1 mm) were
suspended in 300 g of methanol and 8 g of
tetramethoxysilane. 100 g of Aerosil extrudates obtained
in Preparation Example 2 were impregnated with acetic
acid and initially taken in a heated splash plate. The
suspension of the titanium silicalite in
methanol/tetramethoxysilane was sprayed on slowly while
CA 02314233 2000-06-09
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steadily rotating the splash plate. The extrudates thus
obtained were dried at 120EC, briefly screened and
calcined at 500EC for 5 h. About 3 g of TS-1 powder were
recovered by the screening procedure after drying.
Calcination gave abrasion-resistant shaped bodies
suitable for liquid phase reactions. The shaped body
contained 8.5o by weight Ti silicalite, as determined by
atomic emission spectroscopy. The epoxidation
characteristics of the catalyst C thus obtained were
evaluated in epoxidation experiments.
Comparative Example 3
10 g of titanium silicalite powder obtained in
Preparation Example 1 (particle sizes < 0.1 mm) were
suspended in 100 g of methanol and 4 g of
tetramethoxysilane. 100 g of silicon dioxide spheres
(Siliperl AF-125 obtained from Engelhardt) were
initially taken in a heated splash plate. The suspension
of the titanium silicalite in
methanol/tetramethoxysilane was sprayed on slowly while
steadily rotating the splash plate. The spheres thus
obtained were dried at 120EC, briefly screened and
calcined at 500EC for 5 h. About 7 g of TS-1 powder were
recovered by the screening procedure after drying. The
shaped body contained 2% by weight Ti silicalite, as
determined by atomic emission spectroscopy, and the
alkali metal content was 400 ppm. The epoxidation
characteristics of the catalyst V3 thus obtained were
evaluated in epoxidation experiments.
Examples 4 to 9
Catalysts A to C and V1 to V3 were installed in a steel
autoclave with basket insert and gassing stirrer in the
amounts shown in Table 1. The autoclave was filled with
100 g of methanol, closed and tested for leakage. It
CA 02314233 2000-06-09
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was then heated to 40EC, and 11 g_of liquid propene were
metered into the autoclave. 9.0 g of an aqueous hydrogen
peroxide solution (hydrogen peroxide content of the
solution 30°s by weight) were then pumped into the
autoclave by means of an HPLC pump, and the hydrogen
peroxide residues in the feed lines were then flushed
into the autoclave by means of 16 ml of methanol. The
initial hydrogen peroxide content of the reaction
solution was 2.5o by weight. After a reaction time of 2
h, the autoclave was cooled and depressurized. The
liquid effluent was investigated cerimetrically for
hydrogen peroxide. The analysis and the determination of
the propylene oxide (PO) content were carried out by gas
chromatography.
The PO and and hydrogen peroxide contents are shown in
Table 1.
Catalyst V1 (TS-1, 1 mm extrudates) is significantly
more active than Catalyst V2 (TS-l, 3 mm extrudates).
This indicates a poor utilization of the TS-1 extrudate
having a diameter of 3 mm (V2). The supported catalysts
A to C gave a higher PO yield although a lower amount of
TS-1 was used. Owing to its high alkali metal content of
400 ppm, Catalyst V3 shows virtually no epoxidation
activity.
Despite the high mechanical stress in the stirred steel
autoclave, the supported catalysts showed no abrasion
(no TS-1 in the effluent).
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- Table 1
Batchwise autoclave epoxidation of, propene to give
propene oxide
Catalyst Amount TS-1 Amount of pp g2~2
. used content TS-1 used content content
(g) (~ by (g) ($ by ($ by
weight) weight) weight)
Vl 0.55 90 0.5 1.71 1.0
V2 0.55 90 0.5 1.29 1.25
V3 5.5 2 0.11 0.05 2.30
A 15.5 2 0.31 2.45 0.49
B 5.5 5 0.275 1.86 0.94
C 5.3 8.5 0.45 1.56 1.29
Examples 10 to 13
Flows of 27. 5 g/h of hydrogen peroxide (20% by weight) ,
65 g/h of methanol and 14 g/h of propene were passed
through a reactor battery consisting of two reactors
which had a reaction volume of 98 ml each and a
downstream tube reactor having a volume of 13 ml, filled
with the amount of the catalysts V1, V2, A and B shown
in Table 2 at a reaction temperature of 40EC and a
reaction pressure of 20 bar. The reaction mixture exited
from the tube reactor and was depressurized to
atmospheric pressure in a Sambay evaporator. The removed
low boilers were analyzed on-line by gas chromatography.
The liquid reaction effluent was collected, weighed and
also analyzed by gas chromatography.
The hydrogen peroxide conversion decreased over the
running time of 30 h from initially 96$ and reached the
value given in Table 2. The PO selectivity, based on
hydrogen peroxide, was always more than 95~.
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Table 2 -
Continuous epoxidation of propene with hydrogen peroxide
to give propylene oxide
Catalyst Amount TS-1 TS-1 amount H2p2
used (g) content used (g) conversion
($ by after 30 h
weight)
Vl 0.55 90 0.5 1.0
V2 0.55 90 0.5 1.25
15.5 2 0.31 0.49
5.5 I5 10.27510.94
In the procedure, the supported TS-1 catalysts are also
significantly more active than the catalysts used in the
form of an unsupported catalyst (extrudate), based cn
the amount of TS-1 used.
Despite the high mechanical stress in the stirred
reactors, the catalysts showed no abrasion (no TS-1 in
the effluent) in the experiments.
