HK1072914B - A catalyst - Google Patents

Description

Catalyst

Technical Field

The present invention relates generally to catalysis, and more particularly to a catalyst comprising titanium in bonded form, amorphous silica and at least one crystalline silicate phase having a zeolite structure, wherein the amorphous silica is added to the at least one crystalline silicate phase having a zeolite structure, and wherein the at least one crystalline silicate phase having a zeolite structure comprises silicon-carbon bonds by which non-hydrolytically separable organic groups R are bonded to silicon atoms.

Background

It is known from EP-A0100119, EP-A1221442, DE-A19954322 and EP-A0904151 that olefins can be reacted with hydrogen peroxide to form epoxides when zeolites containing only inorganic titanium are used as catalysts.

However, all these catalysts which have been disclosed have the disadvantage that the oxidizing agent used (hydrogen peroxide, ethyl-or cumene hydroperoxide) decomposes to some extent on the catalyst. As a result, yields of epoxide of < 100% relative to the oxidant and in some cases molecular oxygen formed as a decomposition product of the oxidant pose a safety handling problem.

Furthermore, all the catalysts disclosed have the disadvantage of gradually losing the catalytic activity during the reaction.

WO99/01445 discloses that the minimum olefin conversion desired is kept constant for a limited time by increasing the reaction temperature and/or pressure. However, this method is limited from a technical point of view due to high epoxidation reaction activity. Even a slight temperature increase can significantly reduce epoxide selectivity. In industrial plant operations at the thousands ton scale, a slight reduction in product selectivity compromises economic viability.

Thermal regeneration, preferably with molecular oxygen, is described in EP-A0743094 and EP-A0790075. In order to reach the specified temperature of 200, even 550 ℃, the catalyst must in some cases be removed from the reactor. At the very least, it is a common factor in the disclosed regeneration process that the epoxidation reaction must be interrupted during the regeneration stage.

The short catalyst life results in reduced yields during the regeneration phase or requires lengthy, expensive production means. Thus, it is desirable to develop a novel catalyst which can achieve high reactivity while having an industrially satisfactory service life and high selectivity.

EP-A1221442 describes the regeneration of titanium zeolite catalyst TS1 with aqueous hydrogen peroxide. The disclosed features are particularly characterized when the epoxidation reaction occurs in a continuous flow system with olefin, methanol, and aqueous hydrogen peroxide.

The mechanism of passivation is not fully understood. It is possible that the coverage of the surface of the catalytically active solid by organic molecules is to such an extent that no active epoxidised species is available for the intended reaction.

DE-A19954322 describes TS1 molded catalysts which are distinguished by extrudates composed of TS1 powder and other SiO-based catalysts for shaping purposes₂The composition of the material (c). These extrudates, which contain crystalline and amorphous silica phases, have incorporated therein aminopropyltrialkoxysilanes and a matrix, together with a reagent to modify the surface of the extrudates, and are then calcined at 550 ℃ under an air stream until no further analysis of the silicon-carbon bonds can be detected. Although the pure inorganic molded catalysts obtained in this way have the same catalytic activity as similar systems without silane surface treatment in the reaction step after synthesis of TS1, these catalysts have a tendency to produce fewer by-products. In addition, the resistance of the extrudate bundle is about 50% higher than the lateral pressure. The ensuing reaction of PO and water or methanol to propylene glycol and methoxypropanol, respectively, is significantly inhibited somewhat compared to the disclosed catalysts.

This is demonstrated by the data given in the table below:

	without modification	Modification of
			Methoxypropanol [ ppm]：	3100-3800	1700-3200
Propylene glycol [ ppm ]]：	400-600	300-500

In industrial processes, it is desirable to develop catalysts that achieve both longer catalyst life and even higher epoxidation selectivity and epoxy productivity. Also, less loss is desirable due to the expensive oxidant consumed by decomposition on the catalyst and used for catalyst regeneration.

In order to be able to prepare the catalyst on an industrial scale (ton scale), the process steps for the preparation of the catalyst should be as reproducible and simple as possible. In order to obtain an economically viable preparation, the catalyst should be prepared at a low cost.

Disclosure of Invention

The present invention provides new catalysts for industrial processes which have a high reactivity and are not deactivated and at the same time have an excellent selectivity and lead to the loss of oxidizing agent due to decomposition on the catalyst being as low as possible.

The invention also provides a process for preparing these catalysts.

The invention further provides a technically simple liquid-phase process for the selective oxidation of hydrocarbons by means of hydrogen peroxide on a catalyst, which leads to high yields and low costs due to high reactivity, high selectivity and industrially interesting catalytic service lives.

The present invention provides an alternative catalyst for the direct oxidation of hydrocarbons which eliminates, at least to some extent, the disadvantages of known catalysts.

Specifically, the present invention relates to the following aspects:

1. a catalyst for partial oxidation of hydrocarbons with hydrogen peroxide, comprising:

a) titanium in bonded form;

b) amorphous silicon dioxide; and

c) at least one crystalline silicate phase having a zeolite structure,

wherein amorphous silica is added to at least one crystalline silicate phase having a zeolite structure, with at least titanium atoms being tetrahedrally bonded in one crystalline silicate phase, and wherein the at least one crystalline silicate phase having a zeolite structure comprises silicon-carbon bonds which bond non-hydrolytically separable organic groups R to the silicon atoms.

2. The catalyst of item 1, further comprising:

d) additional silicon in bonded form, which is present neither in the form of amorphous silicon dioxide nor in the form of crystalline silicate phases having a zeolite structure.

3. The catalyst of claim 1, wherein the at least one crystalline silicate phase having a zeolite structure has a zeolite structure selected from the group consisting of MFI, MEL, BEA, MOR, and mixtures thereof.

4. The catalyst of item 1, wherein the crystalline silicate phase comprising silicon-carbon bonds is organically modified glass and comprises organic end groups and/or organic bridge groups in the crystalline network.

5. The catalyst according to item 1, wherein the organic group R is present in an amount of 0.01 to 5 wt% relative to the amount of a crystalline silicate phase having a zeolite structure, which crystalline silicate phase comprises silicon-carbon bonds by means of which non-hydrolytically separable organic groups R are bonded to silicon atoms.

6. In a process for producing an epoxide from a compound containing a carbon-carbon double bond, the improvement which comprises reacting a compound containing a carbon-carbon double bond with hydrogen peroxide in the presence of the catalyst of item 1.

7. The method according to item 6, wherein the compound containing a carbon-carbon double bond is propylene.

These and other advantages and benefits of the present invention are apparent from the detailed description of the invention below.

Detailed Description

The present invention will now be described for purposes of illustration and not limitation. Except in the examples, or where otherwise indicated, all numbers expressing quantities, percentages, and so forth, used in the specification are to be understood as being modified in all instances by the term "about".

The invention provides a catalyst comprising titanium, amorphous silica and at least one crystalline silicate phase having a zeolite structure, in elemental or bound form, wherein the amorphous silica is added to the at least one crystalline silicate phase having a zeolite structure, and wherein the at least one crystalline silicate phase having a zeolite structure comprises silicon-carbon bonds by means of which non-hydrolytically separable organic groups R are bound to silicon atoms. Furthermore, the present invention provides a process for preparing the catalyst and a process for preparing an epoxide from a compound containing a carbon-carbon double bond, preferably propene, comprising reacting the compound containing a carbon-carbon double bond with hydrogen peroxide in the presence of the catalyst of the present invention.

The crystalline silicate phase having a zeolite structure and containing silicon-carbon bonds by means of which non-hydrolytically separated organic groups R are bound to the silicon atoms is referred to as hybrid organic-inorganic zeolite.

The organic groups R are preferably present in an amount of from 0.01 to 5% by weight, more preferably from 0.1 to 4% by weight, most preferably from 0.3 to 2% by weight, relative to the amount of crystalline silicate phase which has a zeolite structure and contains silicon-carbon bonds by means of which non-hydrolytically separable organic groups R are bonded to silicon atoms.

In preparing the catalyst of the present invention, the calcination temperature is 100-550 ℃, more preferably 200-450 ℃.

The invention therefore provides, in particular, compositions which comprise predominantly silicon, titanium, oxygen and carbon elements, where these compositions comprise, in addition to the pure inorganic constituents, organic silicon-carbon bonds and the compositions comprise at least one crystalline phase in a silica oxide having a zeolite structure. The crystalline phase system in the present invention, comprising uniformly distributed inorganic and organic components, is referred to in this document as a hybrid system. The synthesis of these hybrid compositions and the use of these hybrid compositions as catalysts are disclosed in detail.

Zeolites are crystalline, porous aluminosilicates whose crystal lattice consists of SiO₄And AlO₄And (4) tetrahedron composition. This structure results in the formation of very regularly shaped cavities or channels, the size of which is the same order of magnitude as most molecules (0.3-1.5 nm).

The use of aluminum-rich zeolites (A, X or Y) as hydrophilic adsorbents is based on the strong polarity brought about by the presence of aluminum atoms in the crystal lattice. Lowering the aluminum content by dealumination or, if possible, by appropriate synthetic methods results in a decrease in the polarity of the lattice and an increase in the hydrophobic character of the adsorbent. If zeolite ZSM-5 is synthesized in the absence of aluminum, Silicalite-1, a modified silica and typical hydrophobic adsorbent, is obtained.

Incorporation of titanium into the Silicalite-1 lattice also increases polarity. This results in an increased absorption of water and a decreased absorption of non-polar materials (S. Mirajkar et al, J. Phys. chem.96, 3073/3079 (1992)). The hydrophobicity decreases with increasing titanium content. Furthermore, it is to be distinguished whether the titanium is incorporated in the crystal lattice or in amorphous TiO₂This is present because the latter does not have any effect on the polarity of the lattice.

Titanium atoms, incorporated into TS1 on the four-sided surface (preferably 1.3 mol%), are the so-called active lattice sites. From a catalytic point of view, it is desirable on the one hand to incorporate more titanium species in the Silicalite lattice without forming amorphous TiO₂(as a precipitate), but on the other hand a catalytic system which is as hydrophobic as possible (obtained by using as little titanium as possible) greatly increases the absorption of propylene and, above all, the desorption of PO, thus reducing the side reactions of PO and water to form ethylene glycol at the active lattice sites.

Surprisingly, the present invention has been successful in the synthesis of titanium Silicalite, which is characterized by the presence of xTiO₂(1-x)SiO₂The non-hydrolyzed organic complexes in the network are homogeneously bonded, so that the stable crystal structure and its regular shaped cavities or channels can be largely retained. Homogeneous incorporation of the non-hydrolyzable organic ligand is preferably accomplished by incorporating a co-condensing agent with a non-polar hydrocarbon in the polymer.

In this document, the catalyst of the invention is referred to as hybrid titanium Silicalite or hybrid TS 1. The catalysts of the invention are preferably crystalline, since the titanium tetrahedral centres remain stable and catalytically active under the conditions of epoxidation, especially while maintaining a stable crystal lattice.

Furthermore, surprisingly, the organic ligand only slightly hinders the amorphous arrangement to form the crystalline ZSM-5 structure.

A significant feature of the catalysts of the invention is that the decomposition of hydrogen peroxide on these systems is greatly reduced. In many cases, H in the presence of the hybrid TS1, as compared to conventional purely organic TS1₂O₂The stability improvement rate of (2) is more than 1.5-2.

The hybrid system of the present invention having high hydrophobicity is particularly useful for the epoxidation of hydrogen peroxide because the hybrid TS1 of the present invention has reduced polarity, which can significantly meet and accurately accommodate the catalytic reaction requirements. It is clearly demonstrated experimentally that the problem of diffusion of non-polar reactants (e.g. olefins such as propylene) and polar products (e.g. PO) is significantly minimized. The hydrophobic properties also give the material additional stability to water vapor, which can further extend the catalytic life.

The synthesis of TS1 was first published by Clerioco (ENICHEM) in 1983, and is well known to those skilled in the art.

The synthesis of the hybrid TS1 according to the invention is based on a one-step synthesis according to EP-B0904151 and a two-step synthesis according to p.serrano/m.a.ugauina/r.von Grieken/m.camacho, appl.catal, a1995, 124(2), 391408.

In a conventional one-step synthesis, a template molecule (modeled as tetrapropylammonium hydroxide) is used for hydrolysis/condensation of the silicon and titanium precursors and formation of the ZSM-5 zeolite structure.

The two-step synthesis is known as the impregnation method for synthesizing pure inorganic TS1, and the two-step synthesis comprises the following two steps:

step 1: preparation of amorphous SiO of the silicon and titanium alkoxide (stably bonded Ti (IV) -O-Si type) prior to the actual zeolite synthesis (heterocondensation)₂-TiO₂Sol-gel intermediate (cogel).

Step 2: the amorphous cogel was converted to a zeolite structure by hydrothermal synthesis (autoclave reaction) after impregnation with template (tetrapropylammonium hydroxide).

The hybrid TS1 catalyst is described below.

Within the scope of the present invention, the organic-inorganic hybrid material preferably comprises at least one hybrid SiO based on hybrid₂/RSiO_xThe crystalline phase of (1).

The hybrid system preferably comprises from 0.1 to 4 mol% of titanium, more preferably from 0.5 to 2 mol%, most preferably from 0.8 to 1.6 mol%, relative to the main constituent crystalline silica of the starting material of the invention.

The titanium is preferably present in the form of an oxide and is preferably chemically bound or linked in the hybrid organic-inorganic material by Si-O-Ti bonds. This type of active catalyst has only a minor Ti-O-Ti crystalline region.

In the active catalyst, it is preferred that titanium be bonded to silicon through a hetero siloxane bond.

The hybrid system preferably comprises 0.01 to 5 mol% of non-hydrolysed organic complex, more preferably 0.05 to 4 mol%, most preferably 0.2 to 1.5 mol% with respect to the crystalline silica which is the base of the active substance. The non-hydrolyzable organic complexes are preferably homogeneously bonded or linked in the organic-inorganic hybrid material.

The homogeneous hybrid composition of the present invention, which comprises silicon, titanium and carbon atoms, in particular embodiments in dry form, can be described approximately by the following formula (I) (without taking into account the residues and optional non-fully reacted groups formed on the surface after modification):

(TiO₂)_x(SiO₂)_(1-x)/(TiO₂)_y(RSiO_1.5)_(1-y)/M (I)

in the formula (I), (TiO)₂)_x(SiO₂)_(1-x)Represents the pure inorganic crystalline state TS1 (MF)I crystal structure) or TS2(MEL crystal structure), (TiO crystal structure)₂)_y(RSiO_1.5)_(1-y)Represents organically modified TS1 (hybrid TS 1; as a result of the hybrid TS1 moiety, the entire molecular unit, including xTiO₂(1-x)SiO₂/xTiO₂(1-x)RySiO_4-yPromiscuous TS1, referred to in this document).

M in formula (I) is a heteroatom other than titanium, which may be incorporated in the molecular unit, and is preferably Sn, Fe, Al, Ge or a combination thereof.

X and y in formula (I) represent the number of available oxygen atoms required to saturate the valences of Si and Ti.

The above-mentioned compositions (I) can vary within wide limits.

The specific surface area of the organic-inorganic hybrid material is not at all limited. The specific surface area of the catalyst in the attached examples is in the range of 0.5 to 100m²(ii) in terms of/g. However, systems with smaller or larger surface areas are also catalytically active.

Suitable precursor compounds for the silicon, titanium and promoter centers are desirably low molecular weight organic-inorganic hybrid compounds which are suitable for sol-gel processes or combinations of corresponding inorganic and organic-inorganic hybrid compounds. In the context of the present invention, low molecular weight means monomers or oligomers. Silicon, titanium and the polymer matrix compound of the accelerator are also suitable if they have sufficient solubility.

Preferred solvents for the sol-gel process are alcohols such as isopropanol, butanol, ethanol, methanol, or ketones such as acetone, and ethers such as THF or tert-butyl methyl ether.

Suitable starting materials are, for the person skilled in the art, in particular all soluble silicon and titanium compounds of the general formula (□), which can be used as starting materials for the corresponding oxides or hydroxides,

[R_xM′(OR′)_4-x] (II)

wherein M' is selected from the group consisting of silicon and titanium,

r and R' may be the same or different and are independently selected from C₁-C₁₂-alkyl and C₆-C₁₂-an aryl group,

wherein

x is 0, 1, 2, 3 and

r' may also be H.

In certain organomodified silane embodiments, one or more hydrolyzable groups are saturated with a terminal and/or bridging group (e.g., CH)₃、C₂H₅、C₃H₇Etc.) or unsaturated (e.g. C)₂H₃、C₆H₅) R groups are substituted. Polyfunctional organosilicon compounds, such as silanols and alkoxides, may also be used. The organically modified or unmodified silanes may also be reacted in the presence of diols or polyols, such as 1, 4-butanediol, to give organically modified polysiloxanes. In the context of the present invention, the bridge group R (alkylene group) is of a bridge structure, for example a chain, star (dendritic), cage or cyclic structural unit.

For the synthesis of the catalysts of the invention, preference is given to organically modified silicon precursors in which the steric requirements of the organic ligand are relatively low, such as methyltrimethoxysilane, methyltriethoxysilane, methyltriacetoxysilane (methyltriacetoxysilane), ethyltrimethoxysilane, ethyl-triethoxysilane or similar precursors.

Instead of these, the present invention may also use condensation products of monomeric alkoxides. The composition of the invention can be used in any physical form for the oxidation reaction, for example milled powders, spherical particles, pellets, extrudates, granules.

In a preferred embodiment, the crystalline hybrid TS1 system in powder form is converted into mechanically stable moldings. Moldings are preferred modifications for use in packed fixed bed reactors, for example tubular reactors. It is known to produce moldings by curing molding processes, such as linear pultrusion (for example extrudates in accordance with EP-B0904151 or DE-A19954322, having a diameter of from 1 to 12 mm).

Up to 15 wt% of binder (relative to the total weight of the calcined or conditioned catalyst) is advantageously mixed with the hybrid TS1 system of the present invention for linear pultrusion purposes. The non-polar binder is preferably amorphous or crystalline silica, like fine powder or a silicon precursor compound (e.g. tetraethoxysilane). Other binders, such as those described in EP-B0904151, are also suitable if the Lewis acidity of the moldings is not increased to a large extent (Lewis centers can react with organic functional groups, such as epoxy functional groups, in this way generating by-products).

In the production of dough mixtures from the starting materials of the invention, small amounts of binders and solvents, such as water, alcohols or mixtures thereof, auxiliary materials, for example methylcellulose, can be used from the well-known literature.

The proportion of auxiliary materials, with respect to the total weight, of the feed according to the invention should preferably be less than 5% by weight, more preferably less than 2.5% by weight.

The titanium centers are described below.

The parent of the titanium center is not fixed. For example, a titanium alkoxide, a titanium salt, or an organic titanium compound may be used.

Although many titanium salts, such as halides, nitrates and hydroxides, may be used, it is preferred to use titanium alkoxides, such as butoxide, isopropoxide, propoxide or ethoxide.

The invention preferably uses titanium derivatives, e.g. having C₁-C₁₀Tetraalkoxytitanates of alkyl radicals such as isobutyl, tert-butyl, n-butyl, isopropyl, n-propylethyl and the like, or alkoxy complexes of titanium as described in U.S. Pat. No. 5, 6090961, for example (. eta.5-tetramethyl-cyclopentadienyl) -3-tert-butyl-5-methyl-2-phenoxy) -dimethylsilyl-titanium-dimethanolate, or other organotitanium species, for example titanium acetylacetonate, Ti (OSIPh)₃)₄Dicyclopentadienyl titanium halides, titanium dihalide dialkoxides, titanium trihalide salts, titanium siloxanes such as diethoxysilane-ethyl titanate copolymers (commercially available from Gelest). The halogen component is preferably chlorine. Mixtures of titanium alkoxides and other components, such as titanium triisopropoxide-tri-n-butyl tin alkoxide (Stannoxide), may also be used. The titanium precursor compound may also be used in the presence of a complex-forming component such as acetylacetone or ethyl acetoacetate.

For the synthesis of the compositions according to the invention, preference is given to using tetraalkoxy titanates as titanium precursors, preferably having C₂-C₆Alkyl radicals, such as the precursors of isobutyl, tert-butyl, n-butyl, isopropyl, n-propyl, ethyl.

Thermal activation is described below.

After hydrothermal synthesis, the composition of the invention is preferably further activated by heat treatment at 100-500 ℃ under various ambient atmosphere conditions such as air, nitrogen, hydrogen. The crystalline material of the present invention is preferably dried at 80-120 ℃ and then heated to 300-500 ℃ under an inert gas. In some cases, it is advantageous to accomplish the thermal activation at the specified temperature, 300-. The calcination temperature and time depend on the targeted content of organic complex in the system of the invention. From above 450 c, the combustion of organic matter, especially in oxygen-containing atmospheres, can reach much higher levels.

The thermally activated (conditioned) hybrid compositions of the present invention often exhibit significantly higher catalytic activity and longer catalytic service life in hydrogen peroxide epoxidation than known pure inorganic TS1 catalysts.

The compositions of the present invention slowly deactivate over time.

It is known that regeneration can be obtained for pure inorganic TS1 systems by washing with hydrogen peroxide solution (known from the examples of EP-A1221442).

Surprisingly, it has been found that the hybrid system of the invention, despite the presence of homojunctionsWith or in addition to organic components, can also be prepared by using hydrogen peroxide solutions (e.g. H with a strength of 3-40%)₂O₂Methanol solution) washing to obtain complete regeneration. This finding is all the more surprising, since in theory the organic ligand is also capable of being oxidized by the oxidizing agent hydrogen peroxide. The regeneration experiments of the epoxidation/hybrid TS1 of the kilogram scale hybrid TS1 for 500 hours in succession showed no loss of organic ligand at all (by IR analysis of the hybrid TS1 composition, powder and molded articles).

Thus, the composition of the present invention can be used with all hydrocarbons. The term hydrocarbon is understood to include unsaturated or saturated hydrocarbons, such as alkenes or alkanes, which may also contain heteroatoms such as N, O, P, S or halogens. The organic component to be oxidized can be acyclic, monocyclic, bicyclic or polycyclic, and can also be a monoolefin, diolefin or polyene. In the case of organic components having two or more double bonds, the double bonds may be in conjugated or non-conjugated positions.

The unsaturated hydrocarbon is preferably one having 2 to 15 carbon atoms, more preferably 2 to 10 carbon atoms, and particularly ethylene, propylene, isobutylene, 1-butene, 2-butene, cis-2-butene, trans-2-butene, 1, 3-butadiene, pentene, 1-hexene, other hexenes, hexadienes, cyclohexene, benzene.

The process parameters are described below.

The hybrid TS1 catalyst is preferably used in a liquid phase reaction for the partial oxidation of hydrocarbons in the presence of hydrogen peroxide. The hybrid TS1 catalyst is also active in the gas phase.

The process parameters of the hydrogen-oxidation reaction in the liquid phase can be varied within wide limits.

The HO catalysts of the invention are preferably used at temperatures of from 30 to 200 ℃, more preferably from 40 to 80 ℃ and in particular from 40 to 70 ℃.

It is advantageous to operate at elevated reaction pressures for liquid phase reactions from an economic and structural device point of view. The heterogeneous catalysts of the present invention show particularly high catalytic activity in the pressure range from atmospheric pressure to 70 bar. The pressure range is more preferably from 2 to 35 bar, most preferably from 5 to 30 bar.

The residence time can also vary within wide limits. The residence time is preferably < 70 seconds. The hybrid TS1 molded catalyst showed particularly high catalytic activity and excellent selectivity at residence times < 90 seconds. The invention also provides shorter residence times, i.e., in the shorter seconds range (< 40 seconds).

The feed composition is described below.

The hybrid TS1 catalyst is preferably used in a liquid phase reaction for the partial oxidation of hydrocarbons in the presence of hydrogen peroxide.

Thus, preference is given to obtaining epoxides selectively from olefins, ketones from saturated secondary hydrocarbons and alcohols from saturated tertiary hydrocarbons.

The molar amount of hydrocarbon used, relative to the total amount of hydrocarbon, diluent gas, hydrogen peroxide and solvent moles, and the relative molar ratios of the components may vary within wide ranges. Preferably, the hydrocarbon is used in excess (on a molar basis) relative to the oxygen used. The content of hydrocarbon is more than 1 mol% and less than 80 mol%. The content of hydrocarbon used more preferably varies in the range of 4 to 90 mol%, most preferably in the range of 8 to 70 mol%. The hydrocarbon content can range between any combination of these values, including the recited values.

The form of oxygen used is varied, for example molecular oxygen, air, nitrogen oxides, hydrogen peroxide. Molecular oxygen is preferred.

The molar proportion of oxygen relative to the total molar amount of hydrocarbon, oxygen, hydrogen and diluent gas may vary within wide ranges. The molar amount of oxygen used is preferably less than the amount of hydrocarbon. Preferably, 1-30 vol.% oxygen is used, more preferably 5-25 vol.%.

The moldings of the invention exhibit only low activity and selectivity in the absence of hydrogen. The yields up to 180 ℃ under hydrogen-free conditions are generally low; at temperatures above 200 c, a significant amount of carbon dioxide is formed in addition to the partial oxidation products.

Any known source of hydrogen may be used, such as pure hydrogen, cracked hydrogen, synthesis gas produced by dehydrogenation of hydrocarbons and alcohols, or hydrogen. In embodiments of the invention, hydrogen may also be generated in situ in downstream reactors, for example by dehydrogenation of an alcohol such as propane or isobutane, or methanol or isobutanol. Hydrogen can also be introduced into the reaction system as a complex bound species, such as a catalyst-hydrogen complex.

The volume ratio of hydrogen peroxide with respect to the total volume, which is mainly composed of methanol/water/hydrogen peroxide/hydrocarbon components, can vary within wide limits. Typically the hydrogen peroxide is present in an amount of from 10 to 40 vol.%, more preferably from 15 to 40 vol.%, most preferably from 17 to 30 vol.%.

A diluent gas, such as nitrogen, helium, argon, methane, carbon dioxide, carbon monoxide or similar inert gases, may optionally be added to the essentially necessary reactant gases described above. Mixtures of the inert ingredients may also be used. Other inert hydrocarbons, e.g. fluorinated hydrocarbons (hexafluoroethane, CF)₄Etc.) may also be used as a component of the dilution feed gas or recycle gas. The added inert components facilitate the transport of the heat generated by the exothermic oxidation reaction and often facilitate safe handling.

The HO catalyst of the invention has great economic advantages over the prior art. In addition, the systems of the present invention exhibit longer catalytic life than conventional pure inorganic titanium Silicalite catalysts.

From the viewpoint of chemical engineering on an industrial scale, the catalyst of the present invention is simple to prepare and cost-effective.

The present invention is illustrated in more detail by the following examples. The present invention is not limited to these examples.

Examples

Instructions for testing HO Molding catalysts (test instructions)

A250 ml Buchi glass autoclave conditioned with a thermostat (oil) was used in the semi-batch mode of operation. The feed gas to the reactor of the present invention is continuously supplied by a set of two-stream regulators (propylene, nitrogen). During the reaction, 0.2g of the hybrid TS1 powder catalyst was initially introduced at 50 ℃ and 3 bar, the catalyst being suspended in a methanol/water mixture (15g of methanol, 5g of aqueous 30% strength hydrogen peroxide). A swaglelok pressure maintenance valve was used to ensure that the pressure remained constant. The suspension was stirred with a magnetic stirring core at 800 rpm. The reaction gas was added directly to the suspension through a 1mm0.2mm capillary (immersion). The standard active mass loading was 21l of gas/(g TS1 × h). To complete the oxidation reaction with 0.2g of TS1, the following gas streams were selected, namely the standard gas compositions mentioned below:

0.252l/h of C₃H₆3.96l/h of N₂(corresponding to N)₂Containing 6% of propylene).

For simplicity, the vol.% concentration of PO in the vent gas stream was quantitatively detected with GC analysis alone in the following directional experiments; in the qualitative evaluation, the amount of PO dissolved in the liquid phase was taken into account. (PO is an abbreviation for propylene oxide).

The reaction gas was quantitatively analyzed by gas chromatography. Gas chromatographic separation of the individual reaction products is accomplished using an integrated FID/WLD process involving passage through three capillary columns.

FID: HP-INNOW, internal diameter 0.32mm, length 60m, layer thickness 0.25 μm.

WLD: ax arranged in series

HP-Plot Q, internal diameter 0.32mm, length 30m, layer thickness 20 μm

HP-Plot molecular sieveInner diameter 0.32mm, length 30m, layer thickness 12 μm.

Abbreviations are defined as follows:

FID: flame ionization detector

WLD: thermal conductivity detector

HP-Plot Q: Hewlett-Packard gas chromatography column (fused silica; PLOT ═ porous layer open tube)

HP-Plot molecular sieve: Hewlett-Packard gas chromatography column (molecular sieve, 5 angstrom; PLOT ═ porous layer open tube)

Two-step synthesis of hybrid TS 1:

the concentration of the non-hydrolyzable organic complex was 0.5 mol% with respect to silica.

The following substances were used as starting materials:

silicon source: tetraethyl orthosilicate (TEOS, from Merck)

Methyltrimethoxysilane (MTMS from Merck)

A titanium source: tetrabutyl orthotitanate (TBOT from Aldrich)

Template: tetrapropylammonium hydroxide (TPAOH from SACHEW, HH)

Water: water without cations (cations < 10ppm)

Reactants	Dosage of
		TEOS	137.78g
MTMS	0.46g
		HCl，0.05mol/l	47.8g
TBOT	5.72g
		Isopropanol (I-propanol)	33.3g
TPAOH (matrix)	10-12ml
		TPAOH (template)	32g

Hydrolysis of silicon component

TEOS and MTMS were initially charged to a 250ml round-bottom flask and stirred well, then an aqueous HCl solution was metered in over a period of 5 minutes and the mixture was stirred for approximately 1 hour. The maximum temperature of 69 ℃ was reached after 39 minutes. After complete hydrolysis of TEOS, the mixture was cooled to 1-2 ℃ in an ice bath; this process takes about 40 minutes.

Incorporating titanium species in a network

A solution of 5.72g of TBOT in 33.3g of isopropanol is now metered slowly into the mixture by means of a syringe pump. The metering rate was 11ml/h and the process took 4.5 hours. Care must be taken to ensure that the temperature of the mixture does not rise above 3 c and that the mixture is stirred at maximum intensity because anatase precipitation is otherwise promoted. After the addition of the titanium component is complete, the clear solution must be stirred for a further hour under the same conditions to ensure complete condensation of the titanium species in the mixed network. After this, the free TiOH groups are completely saturated with silicate, so that the reaction can be accelerated without the risk of anatase precipitation. The clear solution was then heated to Room Temperature (RT) over a period of 30 minutes.

Basic gelling process

Approximately 10ml of a 20% strength TPAOH solution were metered into the stirred mixture by means of a syringe pump at a rate of 10 ml/h. After 32 minutes, the gel point was reached. Within 10 minutes, the clear gel changed from a flexible structure to a brittle structure. After a further 60 minutes, the gel material was crushed in a mixer and then dried in a drying cabinet at 110 ℃ and a pressure of 300 mbar for 12 hours. The dried gel was crushed to 100-160 μm with a mortar.

Formation of zeolites

20g of the dried and crushed powder are placed in an autoclave lined with polytetrafluoroethylene, thoroughly mixed (weight ratio 1.6) with 32g of a 20% strength TPAOH solution (the powder must be uniformly wetted with liquid) and dried in a drying oven under natural pressure at 170 ℃ for 12 hours (hydrothermal synthesis). After cooling to room temperature, the reactor contents were rinsed out of the reactor with fully deionized water and the solid and liquid phases were separated in a centrifuge (5 minutes, 3000 rpm). The resulting solid was then washed three times with 30ml of alkali-free, fully deionized water. After washing, the resulting product was dried at 110 ℃ for 4 hours, then conditioned and calcined to form two variants:

promiscuous TS 1550: the dried amorphous hybrid gel was heated to 550 ℃ in one hour under a muffle furnace and nitrogen flow (250 l/h). The product was then held at 550 ℃ for a further hour under a stream of nitrogen, and was subsequently calcined at 550 ℃ for 15 hours with air (100 l/h).

Promiscuous TS 1400 short: the dried amorphous hybrid gel was heated to 400 ℃ in one hour under a muffle furnace and a nitrogen flow (250 l/h). The product was then held at 400 ℃ for a further hour under a nitrogen stream, and then calcined at 400 ℃ for 15 hours with air supply (100 l/h).

Promiscuous TS 1400 long: the dried amorphous hybrid gel was heated to 400 ℃ in one hour under a muffle furnace and a nitrogen flow (250 l/h). The product was then held at 400 ℃ for a further hour under a nitrogen stream and subsequently calcined at 400 ℃ for 30 hours with air supply (100 l/h).

Example 1

During the reaction, 0.2g of a mixed TS 1550 powder catalyst suspended in a methanol/water mixture (15g of methanol, 5g of 30% strength aqueous hydrogen peroxide) was initially introduced at 50 ℃ and 3 bar. The suspension was stirred with a magnetic stirring core at 800 rpm. The reaction gas was added directly to the suspension through a 1mm0.2mm capillary (immersion). To complete the oxidation reaction with 0.2g of catalyst, 0.252l/h of C were bubbled through the liquid phase₃H₆And 3.96l/h of nitrogen (corresponding to N)₂Containing 6% of propylene).

A constant PO selectivity of 95% was achieved in tests performed according to the test instructions. The PO solubility in the off-gas phase was 5%. Up to H in the liquid phase₂O₂Until the concentration of (c) is reduced to less than 4%, the PO yield remains the same.

Example 2

During the reaction, 0.2g of a hybrid TS 1400 short powder catalyst suspended in a methanol/water mixture (15g of methanol, 5g of 30% strength aqueous hydrogen peroxide) was initially introduced at 50 ℃ and 3 bar. The experiment was completed in the same manner as in example 1.

On the basis ofExperiments show that a constant PO selectivity of 95% can be achieved in the tests performed. The PO concentration in the effluent gas phase was 6.1%. Up to H in the liquid phase₂O₂Until the solubility of (c) is reduced to less than 4%, the yield of PO remains the same.

Example 3

During the reaction, 0.2g of a mixed TS 1400 long powder catalyst suspended in a methanol/water mixture (15g of methanol, 5g of 30% strength aqueous hydrogen peroxide) was initially introduced at 50 ℃ and 3 bar. The experiment was completed in the same manner as in example 1.

A constant PO selectivity of 95% was achieved in tests performed according to the test instructions. The PO concentration in the effluent gas phase was 6.5%. Up to H in the liquid phase₂O₂Until the solubility of (c) is reduced to less than 4%, the yield of PO remains the same.

Example 4

The unsaturated hydrocarbon is selected to be cyclohexene instead of propylene. A similar catalyst as in example 3 was used for the partial oxidation of cyclohexene. Cyclohexene was continuously added to the liquid phase by means of an evaporator.

In tests performed according to the test specifications, a constant epoxide selectivity of 93% was achieved. The solubility of the epoxide in the vent gas phase was 4%. Up to H in the liquid phase₂O₂The yield of cyclohexane oxide remains the same until the solubility of cyclohexane is reduced to less than 5%.

Although the foregoing has described the invention in detail, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

Claims (7)

1. A catalyst for partial oxidation of hydrocarbons with hydrogen peroxide, comprising:

a) titanium in bonded form;

b) amorphous silicon dioxide; and

c) at least one crystalline silicate phase having a zeolite structure,

wherein amorphous silica is added to at least one crystalline silicate phase having a zeolite structure, with at least titanium atoms being tetrahedrally bonded in one crystalline silicate phase, and wherein the at least one crystalline silicate phase having a zeolite structure comprises silicon-carbon bonds which bond non-hydrolytically separable organic groups R to the silicon atoms.

2. The catalyst of claim 1, further comprising:

d) additional silicon in bonded form, which is present neither in the form of amorphous silicon dioxide nor in the form of crystalline silicate phases having a zeolite structure.

3. The catalyst of claim 1, wherein said at least one crystalline silicate phase having a zeolite structure has a zeolite structure selected from the group consisting of MFI, MEL, BEA, MOR, and mixtures thereof.

4. The catalyst of claim 1, wherein the crystalline silicate phase comprising silicon-carbon bonds is organically modified glass and comprises organic end groups and/or organic bridge groups in a crystalline network structure.

5. The catalyst as claimed in claim 1, wherein the organic group R is present in an amount of 0.01 to 5% by weight relative to the amount of a crystalline silicate phase having a zeolite structure, which crystalline silicate phase comprises silicon-carbon bonds by means of which non-hydrolytically separable organic groups R are bonded to silicon atoms.

6. In a process for producing an epoxide from a compound containing a carbon-carbon double bond, the improvement comprising reacting a compound containing a carbon-carbon double bond with hydrogen peroxide in the presence of the catalyst of claim 1.

7. The method of claim 6, wherein the compound containing a carbon-carbon double bond is propylene.