The present invention concerns a method for the production of a
titanium-containing zeolite, a titanium-containing zeolite obtainable by
this method, a method for the epoxidation of olefins in the presence of
a titanium-containing zeolite produced in this way and also the use of
such a zeolite as a catalyst for the epoxidation of olefins.
A method for the production of titanium silicalite and also the use of
the titanium silicalite as a catalyst in a series of reactions, among
them oxidation reactions, is known from JJS-A 4^410.50^1. It describes two
different procedures. On the one hand the formation of a synthesis gel
starting from a hydrolysable silicon compound such as tetraethyl
orthosilicate, for example, or alternatively the use of a colloidal
silicon dioxide as silicon source. The first version is described in
example 1 of US-A 4,410.501. Here tetraethyl orthosilicate and tetra-n-
propyl ammonium hydroxide (TPAOH) are used in a molar ratio of 0.45.
which also corresponds to the preferred range for the molar ratio of
ammonium compound to silicon compound as stated in the general part of
the description. Common to both versions of the procedure according to
the description in US-A 4.410.501 is a long reaction period for the
hydrothermal stage of at least six days.
EP-A 0 838 431 describes a method for the production of titanium-
containing zeolites starting from tetraalkyl orthosilicate and
t
tetraalkyl orthotitanate. the key feature of which is that the reaction
mixture is reacted in an autoclave under hydrothermal conditions without
distilling off the alcohols formed during hydrolysis.
Many groups of researchers in industry and universities have sought to
optimise the synthesis of titanium silicalite. in terms of both the
activity of the resulting catalyst and the efficiency of the method.

i.e. reducing the length of the hydrothermal stage, improving yields,
etc.. starting from the teaching of US-A 4.410.501.
Thus in "Applied Catalysis A: General. 92 (1992) 93-111" A. J. H. P. van
der Pol and J. H. C. van Hooff examined the influence of Si02 source,
crystallisation time, crystallisation conditions and ratio of ammonium
compound/silicon and silicon/titanium on titanium silicalite synthesis
and on the activity of the resulting catalyst. In these experiments both
the method, starting from tetraethyl orthosilicate. and the variant,
starting from a colloidal silicon dioxide, were investigated. A
comparison of these two methods already shows that a higher ratio of
ammonium compound to Si has to be used for the ester method, i.e. use of
tetraethyl orthosilicate. This corresponds in this respect to.the
teaching of US-A 4.410,501, where a markedly higher ratio of ammonium to
silicon is likewise used for the orthosilicate route. It further emerges
that, irrespective of the method used, crystallisation times of two days
are sufficient for the production of the catalyst. This publication
further teaches that a titanium silicalite produced using orthosilicate
displays a markedly higher catalytic activity than catalysts produced
using colloidal silicon dioxide. A substantial part of the above
publication deals with the question of how the reaction conditions,
particularly the ratios of the starting compounds, should be selected in
order to produce the smallest possible primary crystallites in the
catalyst. The influence on crystallite size of the ratio of ammonium
compound to silicon in the starting compounds was examined in
particular. It was determined that the molar ratio of ammonium compound
to silicon should be at least 0.22 and should preferably be in the range
between 0.3 and 0.35 in order to obtain the desired primary crystallite
size. By contrast, the ratio of Si to Ti has virtually no influence on
the crystallite size of the titanium silicalite.

These results were confirmed by a further investigation by van der Pol.
Verduyn and van Hooff in "Applied Catalysis A: General. 92 (1992) 113-
130". Here the activity of various titanium silicalite catalysts was
examined during the hydroxylation of phenol. It was determined that
activity is a function of crystallite size and increases as the
crystallite size reduces. The crystallite size in turn depends on the
ratio of ammonium to silicon, whereby a ratio of 0.35 will lead to a
crystallite size of 0.2 im and shows the greatest activity. Higher
ratios of ammonium to silicon of 0.53 or 0.78 lead to significantly
larger crystallites and lower activities. A lower ratio of 0.22 likewise
leads to larger crystallites and likewise to a drop in activity.
These studies further show that in the investigated range of ratios of
ammonium compound to silicon, the proportion of incorporated titanium
remains practically constant with a constant ratio of silicon to
titanium compound in the starting composition.
These studies led to the development of a standard synthesis for a
titanium silicalite catalyst that was given the name of EUROTS-1
catalyst and whose synthesis is disclosed in J. A. Martens et al. in
"Applied Catalysis A: General. 99 (1993) 71-84". In the synthesis of
EUROTS-1. tetraethyl orthosilicate, tetraethyl orthotitanate and
tetrapropyl ammonium hydroxide are combined in a molar ratio of Si to Ti
of 35. ammonium to Si of 0.36 and HzO to Si02 of 28.2. hydrolysed and
crystallised for four days at 175°C.
Nevertheless, despite this very extensive and detailed examination of
the parameters that influence the synthesis and activity of titanium
silicalite catalysts and the development of a highly active standard
catalyst as described above, there is still a need within the industry
to synthesise titanium silicalite catalysts efficiently and more cost-

effectively and, if possible, also to increase the activity of the
catalyst, particularly for the epoxidation of olefins.
The object of the present invention is therefore to provide a more
efficient and more cost-effective method for the production of titanium-
containing zeolites, without impairing the catalytic activity of the
resulting zeolite. A further object is to provide a titanium-containing
zeolite with an improved activity for the epoxidation of olefins with
hydrogen peroxide.
This object is achieved by a method for the production of a titanium-
containing zeolite, whereby a synthesis gel is formed by combining and
hydrolysing a hydrolysable silicon compound, a hydrolysable titanium
compound and a basic quaternary ammonium compound in an aqueous medium,
in quantities such that relative to the starting compounds the molar
ratio of Si/Ti is greater than or equal to 30 and that of N/Si is 0.12
to less than 0.20. and the synthesis gel is then crystallised at a
temperature of 150°C to 220°C for a period of less than 3 days, and by a
titanium-containing zeolite obtainable by such a method.
According to the present invention a hydrolysable silicon compound and a
hydrolysable titanium compound are first hydrolysed with a basic
quaternary ammonium compound in the presence of water. The key feature
here is that the starting compounds are reacted in specific molar ratios
to one another. The molar ratio of Si to Ti in the starting compounds
can be varied within broad limits, provided that it is > 30. By
contrast, the molar ratio of N to Si in the starting compound must be
kept within the narrow range of 0.12 to < 0.20.
It was surprisingly established that although in this range of the molar
ratio of N to Si the crystallite size increases markedly in comparison
to the ratio of 0.35 that was regarded as being opt"!** according to the
teaching of A. van der Pol and J. H. C. van Hooff (loc. cit.). the
catalyst activity in a propylene epoxidation reaction with hydrogen
peroxide nevertheless increases in this narrow range in contrast to the
teaching established by van der Pol and van Hooff. Without feeling
committed to a particular theory, it is assumed that this effect is
achieved by proportionately more titanium being incorporated into the
crystal structure of the zeolite in the cited range for the molar ratio
of N to Si with a constant ratio of Si to Ti. The associated increase in
activity overcompensates for the loss in activity due to the increase in
the primary crystallite size. This result is all the more surprising
since van der Pol and van Hooff (loc. cit.) have shown that with an N to
Si ratio of 0.22 and above, if the Si to Ti ratio in the starting
compounds remains constant, the quantity of titanium incorporated into
the zeolite remains constant and is substantially independent of the N
to Si ratio.
Particularly good results in terms of catalyst activity in epoxidation
reactions are achieved with a molar ratio of N to Si in the starting
compounds in the range from 0.12 to 0.17 especially in a range of 0.12
to less than 0.17. preferably from 0.12 to 0.16.
Particularly suitable as hydrolysable silicon or titanium compounds for
the method according to the invention are the tetraalkyl orthosilicates
or tetraalkyl orthotitanates. whereby alky! is preferably selected from
the dfoup consisting of methyl, ethyl, propyl or butyO'The most

preferred starting compounds are tetraethyl orthosi1icate and tetraethyl
orthotitanate.
The quaternary ammonium compound is a template compound that determines
the crystal structure by absorption in the crystal lattice of the
product during crystallisation. Tetraalkyl ammonium compounds such as
tetraalkyl amorriuw hydroxide, particularly tetra-n-propyl ammonium

hydroxide, are preferably used to prpriuce titanium silica!ite-1 (HFI
structure), tetra-n-butyl ammonium hydroxide to produce titanium
silicalite-2 (MEL structure) and tetraethyl ammonium hydroxide to
produce titaniurn-p-zeolite (BEA crystal structure). The quaternary
ammonium compound is preferably used as an aqueous solution.
The pH value for the synthesis sol of > 9, preferably > 11. that is
necessary for synthesis is adjusted by the basic-reacting quaternary
ammonium compound.
The temperature at which the synthesis sol is produced can be selected
between broad limits, but the mixture of hydrolysable silicon compound
and hydrolysable titanium compound is preferably cooled to a temperature
in the range from 0°C to 10°C. preferably 0°C to 5°C. and the basic
quaternary ammonium compound in an aqueous solution cooled to the same
temperature is then added dropwise. According to an alternative
embodiment, tetraethyl orthosilicate and tetraethyl orthotitanate are
heated to 35°C before hydrolysis and stirred at this temperature for 30
minutes in order to achieve complexation between the two products
(precondensation). This precondensation has no noticeable influence on
the catalytic properties of the end product, however.
In a further embodiment of the present invention, where tetraalkyl
orthosilicates and tetraalkyl orthotitanates are used as silicon or
titanium source respectively, the alcohol produced during hydrolysis is •
distilled off as a water azeotrope. In some cases it can then be
advisable to replace the volume of alcohol/water azeotrope removed from
the reaction mixture by distillation at least in part by water in order
to avoid the formation of a solid gel or of wall deposits during
crystallisation.

The synthesis sol. optionally after an additional maturing period, is
then crystallised under autogenous pressure at a temperature of 150°C to
220°C. preferably 170°C to 190°C (hydrothernial synthesis). Under the
specified conditions of the method according to the invention the
crystallisation time is less than 3 days, preferably less than 24 hours,
particularly preferably a maximum of 12 hours.
According to a preferred embodiment of the method according to the
invention, the quantities of the starting compounds are selected such
that relative to the starting compounds a molar ratio for H20 to Si is
established in the range from 10 to 20. preferably 12 to 17. It is
particularly advantageous if the molar ratio of H20 to Si in the
synthesis gel before hydrothermal synthesis, i.e. after the possible at
least partial replacement by water of the water-alcohol azeotrope
optionally distilled off after hydrolysis, is adjusted in the range from
15 to 42. preferably 15 to 35. It was surprisingly established that
despite this very small quantity of water the procedure and the
catalytic activity of the resulting product are not impaired. By
contrast, it was found that a molar ratio of water to Si in the above
range combined with the molar ratio according to the invention of
ammonium compound to Si in the starting composition leads to an active
catalyst. One reason for this could be the high concentration of
quaternary ammonium compound in the synthesis gel despite markedly
reduced quantities of ammonium compound in the starting compound due to
the similarly small quantities of water.
A further advantage of the small quantity of water lies in the markedly
increased yield of titanium-containing zeolite per kg of synthesis gel
as compared with the prior art. making the overall method more efficient
and cost-effective.

The crystals produced after the hydrothermal stage have a primary
crystal size in the range from 0.2 to 2.0 fm. preferably from 0.3 to 1.5
im, and are separated from the parent liquor by filtration,
centrifugation or decantation and washed with a suitable washing liquid,
preferably water. The crystals are then optionally dried and calcined at
a temperature of between 400°C and 1000°C. preferably between 500°C and
750°C. to remove the template.
According to a preferred embodiment of the present invention the crystal
suspension is neutralised after the hydrothermal stage and before
separation of the crystals. The crystal suspension as formed after
completion of crystallisation in the method according to the invention
is alkaline because of the excess of basic quaternary ammonium salt and
generally displays a pH greater than 12. If the pH value of the
suspension is reduced to a value from 7 to 10. preferably from 7 to 8.5,
a greater agglomeration of primary crystallites is observed. This
greatly improves the filterability of the suspension, such that
separation can be performed with standard membrane filters without
breaking through of the product and with conventional filtration times.
This preferred embodiment can thus further increase the efficiency of
the method according to the invention.
The pH value of the crystal suspension can be reduced either by the
addition of acid, such as e.g. mineral acids or organic acids, after
completion of the hydrothermal stage or by crystallisation at elevated •
temperatures, e.g. at 200°C to 220°C. In the latter case the quaternary
ammonium compound, e.g. tetra-n-propyl ammonium hydroxide, is thermally
decomposed with consumption of hydroxide ions. Preferred acids are
hydrochloric acid and acetic acid.
The lower pH value of the crystal suspension causes the silicates and
titanates dissolved within it to be at least partially precipitated.

such that the separated titanium-containing zeolite contains a small
quantity of titanium compounds that are not incorporated into the
lattice. No negative influence on the activity of the resulting catalyst
has been observed, however.
The crystalline titanium-containing zeolites according to the invention
are obtained in powder form. For their use as oxidation catalysts they
can optionally be converted into a suitable shape for use. such as. for
example, micro-pellets, balls, tablets, solid cylinders, hollow
cylinders or honeycomb shapes, by known methods for shaping powdered
catalysts such as. for example, pelletisation. spray drying, spray
pelletisation or extrusion.
The titanium-containing zeolite produced according to the invention can
be used as a catalyst in oxidation reactions with H202. In particular the
titanium-containing zeolite according to the invention can be used as a
catalyst in the epoxidation of olefins by means of aqueous hydrogen
peroxide in a solvent miscible with water.
The method according to the invention has the advantage that because of
the low ratio of ammonium to silicon relative to the amount of zeolite
produced, in comparison to the prior art, a significantly smaller
quantity of quaternary ammonium compound, the most expensive of the
starting materials used, is required. This has markedly improved the
cost-efficiency of the manufacturing process. Furthermore, the yield of,
product relative to the mass of synthesis gel can be increased if the
molar ratio of Hz0 to Si relative to the starting compounds can be kept
within the stated range. Surprisingly it has been established that, in
contrast to the teaching of the prior art. the catalyst activity is not
impaired by these measures to optimise the economy of the method but on
the contrary a new product is ootained that is characterised by an

improved activity in spite of a larger primary crystallite size in
comparison to the prior art.
The primary crystallite size of the titanium-containing zeolite produced
by the method according to the invention lies in the range between 0.2
and 2.0 im. preferably between 0.3 and 1.5 /vm. whereas according to the
prior art a crystallite size in the range between 0.1 and 0.2 tm is
described as being the optimum size for catalyst activity.
The present invention is illustrated in greater detail by means of the
examples:
Comparative example 1
Production of EUROTS-1
EUROTS-1 was produced by reference to the instructions in Martens et
al.. "Applied Catalysis A: General. 99 (1993) 71-84". Tetraethyl
orthosilicate was placed in a 10 1 autoclave rendered inert with
nitrogen, tetraethyl orthotitanate was added with stirring and on
completion of the addition the resulting mixture was cooled to approx.
1.0°C. A 40 wt.l solution of tetra-n-propyl ammonium hydroxide and
deionised water was then added with stirring at this temperature over
around five hours by means of a hose pump. The quantities were selected
such that the molar ratio of Si02 to TiOz is 35, the molar ratio of N to.
Si is 0.36 and the molar ratio of HjO to Si02 is 28.2. Although the
reaction solution initially became milky-opaque, the solids formed
dissolved again completely as further tetra-n-propyl ammonium hydroxide
was added.
In order to complete the hydrolysis and to distil off the etnanol
formed, the reaction mixture was heated first to approx. 8Q°C and then

to max. 95°C over around 3 hours. The ethanol-water azeotrope distilled
off in this way was replaced by the same volume of double-deionised
water. The synthesis sol was then heated to 175°C and kept at this
temperature for 12 hours. After cooling of the resulting titanium
silicalite suspension, the solid formed was separated by centrifugation
from the strongly basic parent liquor still containing tetra-n-propyl
ammonium hydroxide, washed and dried overnight at 120°C and then finally
calcined in air at 550°C for five hours in a muffle furnace.
This results in a consumption of 2.9 kg 40 wt.* tetra-n-propyl ammonium
hydroxide solution per kg TS-1 and a yield of 50 g TS-1 per kg synthesis
gel with an activity coefficient of 22 min 1.
The activity coefficient was determined as follows:
1.0 g of the titanium silicalite catalyst produced in comparative
example 1 in 300 ml methanol was then placed in a thermostatically
controlled laboratory autoclave with aeration stirrer at 40°C under a
propylene atmosphere and the solvent saturated with propylene at 3 bar
overpressure. 13.1 g of 30 wt.* aqueous hydrogen peroxide solution are
then added in one portion and the reaction mixture kept at 40°C and 3
bar. with propylene being made up via a pressure regulator to compensate
for consumption by the reaction. Samples were taken at regular intervals
via a filter and the hydrogen peroxide content of the reaction mixture
determined by redox titration with cerium(IV) sulfate solution. Plotting
ln(c/c„) against time t. where c is the Hz02 concentration measured at
time t and c0 is the Hj.02 concentration calculated at the start of the
reaction, produces a straight line. The activity coefficient was
determined from the gradient of the straight line using the equation
30
dc v
--- — K • C • Ccit
dt

where ccit stands for the catalyst concentration in kg catalyst per kg
reaction mixture.
Example 1
Production of a titanium silicalite 1 according to the present
invention.
The procedure described for comparative example 1 was repeated with the
exception that quantities of starting compounds were used such that
relative to the starting compounds the molar ratio of N to Si was 0.17
and that of HjO to Si was 13.3. The molar ratio of Si to Ti of 35 was
maintained.
This synthesis method resulted in a consumption of tetra-n-propyl
ammonium hydroxide (40* solution) of 1.6 kg per kg TS-1, a yield of 110
g TS-1 per kg synthesis gel and as activity coefficient of the resulting
catalyst of 31.6 min1 after crystallisation for 12 hours.
This comparison already shows that with a method that uses 50* less of
the costly tetra-n-propyl auHioniun hydroxide, the yield of catalyst per
kg of synthesis gel can be more than doubled and yet. contrary to the
expectations of the prior art. a considerable increase in the catalytic
activity of the resulting catalyst can be achieved.
Examples 2 and 3
Example 1 was repeated with the ratios of feedstocks as set out in Table
1. The resulting product properties are likewise set out in Table 1.

Comparative examples 2 to 4
Comparative experiment 1 was repeated with the ratios of feedstocks as
stated in Table 1. The product properties of the resulting titanium
silicalite-1 samples are likewise summarised in Table 1.
The molar ratio of Si to Ti relative to the starting compounds was kept
constant at 35 in all of the experiments.
The comparison between the examples according to the present invention
and the comparative examples shows that the correlation between the
ratio of nitrogen to silicon in the starting compounds and the primary
crystallite size reflects the progression described in the prior art.
The experiments show that an optimum primary crystallite size of between
0.1 and 0.2 /« is achieved witft a ratio of N to Si of 28 or higher.

However, in contrast to the predictions from the prior art. a lower
molar ratio of N to Si does not lead to a reduction in catalytic
activity; on the contrary, the increased incorporation of titanium in
the crystal lattice in the examples according to the present invention
overcompensates for the negative influence of the increasing primary
crystallite sizes on catalyst activity.
The comparison with the synthesis of the EUROTS-1 catalyst (comparative
example 1) shows that a catalyst with increased activity can be produced
by the method according to the invention, whereby in comparison to the
prior art the method leads to a markedly reduced consumption of
expensive starting materials such as tetra-n-propyl ammonium hydroxide
and to a markedly increased yield of titanium silicate per kg of
synthesis gel and hence the cost-efficiency of the synthesis method has
also been able to be improved.
Example 4
Example 1 was repeated, whereby the titanium silicate crystals were
separated not by centrifugation but by filtration, however. The basic
(pH - 12.5) crystal suspension was passed through a nutsch filter with a
blue belt filter. No solid remained on the nutsch.
Examples 5 and 6
Example 4 was repeated, whereby the pH value of the crystal suspension
was reduced to the value stated in Table 2 by addition of hydrochloric
acid before filtration. In both cases the titanium silicalite was able
to be separated off by means of a nutsch filter with a blue belt filter
without breaking through of the product.

As in comparative example 1. the titanium silicate was washed, dried
overnight at 120°C and calcined in air at 550°C for five hours in a
muffle furnace. The product was then analysed for titanium content,
qualitatively for non-lattice titanium compounds and for activity as
described above. The results are likewise set out in Table 2.
The content of non-lattice titanium compounds was estimated
qualitatively from the intensity of the DR-UV-Vis bands between 250 and
300 nm. The product from example 6 had a higher content of non-lattice
titanium compounds than the product from example 5. As the comparison of
the activity coefficients of example 5 and 6 with example 1 shows, the
reduction in the pH value of the crystal suspension has a negligible
influence on the activity of the catalyst.
WE CLAIM
1. Method for the production of a titanium-containing zeolite.
- forming a synthesis gel by combining and hydrolysing a hydrolysable
silicon compound a hydrolysable titanium compound and a basic
quaternary ammonium in an aqueous medium in quantities such that
relative to the starting compounds the molar ratio of Si/Ti is greater than
or equal to 30 and that of N/Si is 0.12 to less 0.20;
- crystallizing the synthesis gel at a temperature of 150°C to 220°C for a
period of iess than 3 days, wherein the molar ratio H20/Si relative to the
starting compounds is 10 to 20.
2. Method as claimed in claim 1, wherein the molar ratio of N/Si is 0.12 to
less than 0.17.
3. Method as claimed in claim 1, wherein the molar ratio of H2O/Si is 12 to
17.
4. Method as claimed in any of the preceding claims, wherein the
hydrolysable silicon compound is a tetraalkyl orthosilicate, preferably
tetraethyl orthosilicate, and wherein the hydrolysable titanium compound
is a tetraalkyl orthotitanate, preferably tetraethyl orthotitanate.

5. Method as claimed in claims 4, wherein the hydrolysis of the hydrolysable
titanium and silicon compounds is supported by distilling off the resulting
alcohols and optionally the volume of alcohol removed by distillation is
replaced at least in part by the addition of water to the reaction mixture.
6. Method as claimed in any of the preceding claims wherein the quaternary
ammonium compound is a tetraalkyl ammonium hydroxide, preferably
tetra-n-propyl ammonium hydroxide.
7. Method as claimed in any of the preceding claims, wherein whereby the
pH value of the crystal suspension from the crystallisation stage is
adjusted to a value of 7 to 10, preferably 7 to 8.5.
8. Method as claimed in any of the preceding claims wherein the titanium-
containing zeolite is separated off, dried and calcined.
9. Titanium-containing zeolite obtainable by a method as claimed in any of
the preceding claims with a primary crystallite size of 0.2 to 2.0 urn.
10. Method for the epoxidation of olefins by reacting olefins with aqueous
hydrogen peroxide in a solvent miscible with water in the presence of a
titanium-containing zeolite as catalyst as claimed in claim 9 or that is
obtainable by the method as claimed in claim 8.

The present invention concerns a method for the production of a titanium-
containing zeolite whereby a synthesis gel is formed by combining and
hydrolysing a hydrolysable silicon compound, a hydrolysable titanium compound
and a basic quaternary ammonium compound in an aqueous medium, in
quantities such that relative to the starting compounds the molar ratio of Si/Ti is
greater than or equal to 30 and that of N/Si is 0.12 to less than 0.20, and the
synthesis gel is then crystallised at a temperature of 150 degree. C. to 220
degree. C. for a period of less than 3 days, and a titanium-containing zeolite
obtainable by this method.