HU197524B - Method for producing platinum-tin catalyzers of carrier containing the tin solely in state combined with the acid centres of carrier - Google Patents

Abstract

Catalysts comprise Sn-Pt/Al2O3, Sn-Re-Pt/Al2O3 and Sn-Pd-Pt/ Al2O3. Stable surface tin complexes formed on the aluminium oxide inhibit the absorption of tin chloride and organic tin chloride complexes prevent formation of Pt-Sn films on the aluminium oxide matrix.

Description

The present invention relates to a process for preparing platinum-tin catalysts which contain tin exclusively in the bonded state to the acidic centers of the support.

Single and multi-metal bifunctional catalysts are widely used for the catalytic conversion of hydrocarbons. Such catalysts (e.g., alumina supported Pt and Re-Pt catalysts) have been used in reforming or aromatizing technologies since the early 1970s [Catal. Port. 5, 67 (1971)]. More recently, catalysts of this type are also used in other hydrocarbon conversion technologies, such as hydrodesalkylation of aromatic hydrocarbons (Japanese Patent No. 81,115,728) or isomerization of xylenes or alkyl-aromatic hydrocarbons (French Patent No. 2,477,903). The bifunctional nature of these types of catalysts is due to the fact that they contain different types of catalytically active surface formation: on the one hand, a metallic component which may be one or more metals (e.g. Re-Pt, Ir-Pt or Sn-Pt) and on acidic centers. they may be formed on the support by thermal pretreatment of the support or by the use of suitable additives (e.g., chlorine, fluorine) (Chem. Techn. 31, 473 (1979)). The formation of acidic centers can also be suppressed by introducing into the support metals of columns (la) or (Ha) of the periodic table (French Patent No. 2,031,984).

In bifunctional catalysts, some reactions occur only at the metal centers, while others occur mainly at the acidic centers of the support. Acid centers play an important role in carbon skeleton isomerization reactions. However, adverse side reactions at acidic centers can also occur. The latter include hydrocrack reactions which significantly reduce the selectivity of the formation of target products (isomers, aromatics). Because these reactions consume hydrogen, they are more likely to occur if the amount of hydrogen in the carrier atomic or spill over is increased.

The acidic centers are also partially responsible for the coke formation reactions on the support, which results in reduced catalyst activity and altered catalyst selectivity.

Since the 1970s bifunctional catalysts have been used mainly as bimetallic alumina supported catalysts; of which, in particular, Re-Pt / Al ₂ O ₃ (U.S. Patent 3,415,737), Ir-Pt / Al ₂ O ₃ (U.S. Patent 3,953,368) and Sn- The use of Pt / Al ₂ O ₃ (French Patent No. 2,031,984) is widespread.

Various methods for preparing bimetallic supported catalysts have been described. Recently, several attempts have been made 2 to ensure a direct interaction between the two metals (eg Re-Pt, Sn-Pt, etc.). Significant results have been achieved with the use of suitable organometallic compounds in the preparation of supported metal-metal bonded platinum catalysts (J. Mol. Catal. 35, 1983). The catalysts formed with Pt-M (M = Sn, Re, Mo, W) formed differ significantly in their properties from single metal platinum catalysts (J. Moh Catal. 9, 13/1980 /).

In addition to the Pt-M formation, the bimetallic catalysts prepared using both inorganic salts and organometallic compounds contain separate Pt and M phases of metallic nature, as well as ionic forms of the second metal. In the case of the bimetallic Sn-Pt / Al ₂ O ₃ and Re-Pt / Al ₂ O ₃ catalysts, it has been shown several times that the second metal on the support is only partially reduced (J. Catal. 71, 348 (1981); Preprints, Div. Of Fuel Chemistry, ÁCS, 18, 10 (1973).

A comprehensive overview of the preparation of bimetallic Sn-Pt / Al ₂ O ₃ and Sn-Pt / SiO ₂ catalysts is provided by Yu, I. Yermakov, Β. 351-364 in N. Kuznetsov and VA Zakharov, Catalysis by Supported Complexes (Elsevier Publishing Co., Amsterdam, 1981). side. It is a fundamental feature of all solutions that tin is present in the catalysts in various forms: Sn, Sn ²⁺ and Sn ⁴⁺ . None of the known methods of preparation provides the exclusive formation of a particular tin valence state or form (Sn-Pt alloy, segregated tin crystallite, or ionic form, supported on tin).

Several authors have used various tin-platinum clusters such as H ₄ [Pt ₃ SnCl ₂ O], [Pt (SnCl ₃ )] _{5 for} the preparation of supported Sn-Pt catalysts. [N (C ₂ H ₅ ) ₄ ] ₃ , and [PtCl ₂ (SnCl ₃ ) ₃ ]. [N (C ₂ H ₅ ) ₄ ], -t [Reaction Kin. Cat. Lett. 18 (3-4), 267 (1981); Kinet. i. 22: 1981; Forschungsberichte den Landes Nordheim-Westfalen, BRD, 1, 2838 (1979)]. The primary purpose of these works was to produce catalysts containing a bimetallic (Pt-Sn) surface formation, i.e., to stabilize tin in the form of an alloy. However, this goal was not fully achieved, since in the surface reactions between the various Pt-Sn complexes and the surface OH groups of the alumina support, some of the tin was bonded to the support instead of platinum and the catalysts thus prepared contained ionic tin, the presence of surface complexes chemically strongly bound to the support has also been demonstrated.

The above points clearly indicate that a gap replacement would be so new. the development of a method for the preparation of bimetallic supported catalysts which would ensure that the metal alone and in a particular form and environment would be stabilized.

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SUMMARY OF THE INVENTION It is an object of the present invention to provide a process for preparing a catalyst that binds tin alone to the active acid centers of the support in Pt-Sn supported catalysts to form a highly stable ionic surface complex in the hydrogen atmosphere. It retains.

It has been found that these goals can be fully achieved by thermally pretreating a platinum-containing catalyst, optionally with rhenium or palladium, on an alumina or silica gel support, followed by reaction with an alkyl lithium, followed by reacting the resulting lithium-modified support with chlorine.

In the thermally pretreated platinum-containing support catalyst, the reactive surface hydroxyl groups of the alumina or silica support (i.e., the acid centers of the support) undergoes an exchange reaction with the alkyl lithium, resulting in the formation of -O-Li surface support on the support. The resulting -O-Li surface formations react with lithium chloride on the exit of lithium chloride; reaction on the support surface

- (O) - ", SnCI", Alk ₄ . Formations ^{having the} formula όη ^4τ , chloride and optionally alkyl are formed. This reaction is selective and can safely prevent the ozone compound from reacting with the metal component of the catalyst (platinum). The latter surface formation results in heat treatment (stabilization) in the presence of hydrogen gas to form a surface (-O-) _y Sn type in which the tin is stably bonded to the support in its ionic state and retains its ionic state in a hydrogen atmosphere.

The present invention therefore relates to a process for the production of supported platinum tin catalysts containing tin exclusively in the bonded state to the acidic centers of the support. According to the present invention, the catalysts containing alumina or silica gel containing 0.3 to 10% by weight of platinum and optionally up to 0.5% by weight of rhenium or palladium at atmospheric pressure and in the presence of an inert gas are used ^. Pre-treated at a pressure greater than ⁶ bar at 150-500 ° C, the pre-treated catalyst at a temperature of 15-100 ° C, under an inert gas atmosphere, of 0.06-0.4 g of lithium compound C 'H _2n + | Li per 1 g of supported catalyst wherein n is an integer of from 1 to 4 with a solution of 5 to 10 carbon atoms, the unreacted lithium compound is removed by washing, the resulting lithium-modified supported catalyst is optionally dried, and then in an inert gas in a ketone or hydrocarbon solvent, At 70 ° C for 12-24 hours per 1 g of supported catalyst with 0.0002 to 0.015 g of a tin compound of SnCl ₄ or 5nCl ₂ Alk ₂ , wherein Alk represents a C 1-4 alkyl group, the resulting product is washed, optionally dried, and finally hydrogen in hydrogen or not more than 90% by volume of inert gas. - stabilized in an inert gas mixture for 0.5 to 3 hours at 30 to 600 ° C.

In the process according to the invention, butyllithium is preferably used as the lithium compound of the formula C "H ₂ " _{+ 1} Li.

Preferably, the lithium compound is reacted in solution in hexane or heptane with the supported catalyst, and the unreacted lithium compound is also preferably washed with hexane or heptane in the supported catalyst. If desired, the resulting lithium-modified catalyst! dried; drying is preferably carried out under reduced pressure at 20-80 ° C.

In the next step, the reaction between the lithium-modified supported catalyst and the tin compound, the ketone solvent is preferably acetone or methyl ethyl ketone, while the hydrocarbon solvent is preferably benzene. The SnCl ₂ Alk ₂ tin compound is preferably diethyl 1-tin dichloride. The lithium chloride formed in the reaction and the unreacted tin compound are preferably washed out of the product with an alcohol (such as methanol), a ketone solvent (such as acetone) or a hydrocarbon solvent (such as hexane or benzene).

As used herein, the term "inert gas" refers to anhydrous gases other than hydrogen and oxygen. The inert gas is preferably nitrogen or argon.

The process of the present invention not only provides a rigid tin-supported catalyst containing the support in its ionic state, but also blocks the acidic centers of the catalyst support. In our studies with platinum catalysts with a reforming support, we have found that blocking the acidic centers of the support promotes single dehydrogenation reactions, i.e. olefin formation, while suppressing both hydrocrack and skeletal isomerization reactions. In parallel, the rate of coke formation reactions at the acidic centers of the support is reduced, thereby increasing catalyst stability and reducing catalyst aging.

The major advantages of the catalysts of the present invention over the known supported Pt-Sn catalysts include:

- more stable operation;

- reduced formation of coke;

- suppression of crack reactions;

- Enhanced, targeted selectivity.

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The invention is illustrated in detail by the following non-limiting Examples.

Example 1 g Al ₂ O ₃ support, 0.5 wt% platinum catalyst (specific surface area: 240 m ^{2 * *} / g, particle size: 0.31-0.63 mm) for 6 hours at 150 ° C. pre-treated with 10 ~ ⁵ bar pressure, then cooled under an atmosphere of argon, oxygen and moisture free catalyst. The catalyst was charged to a stirred reactor under argon, 50 mL of hexane was added, the slurry was heated to 50 ° C and 6 mL of a 15% w / w solution of butyl lithium in hexane was added slowly. After 1 h, the reaction was quenched, the liquid phase removed and the catalyst washed with hexane (4 x 10 mL) to remove unreacted butyllithium. Traces of solvent were removed by drying at 10 ⁵ bar at 20 ° C.

To the resulting lithium modified support catalyst was added a solution of 0.011 g of tin tetrachloride in 1 ml of acetone and the reaction was continued for 24 hours at 20 ° C. The solid was filtered off, washed with acetone (4 x 10 mL) and dried at 50 ° C under argon. The supported catalyst is then heated to 450 ° C in a stream of hydrogen at 5 ° C / min for 1 hour. Sn-Pt / Al ₂ O ₃ catalyst containing 0.11 wt% tin was digested.

The catalyst prepared was tested in the reaction of n-hexane at 500 ° C in a continuous flow reactor at a pressure of 1 bar at ₁₅ ° C, with a Pkexa: P _H2 = 1: 5 ratio. The reactor load was 5.7 kg / kg X hr. Prior to the reaction, the catalyst was pretreated with hydrogen at 550 ° C for 1.5 hours. The results determined after the 4 hour reaction time are shown in Table I; Pt-Sn / Al ₂ O results in Pt / Al ₂ O ₃ catalyst for comparison containing no tin and tin tetrachloride by impregnation (i.e. non-directed reaction surface) ₃ catalyst achieved is given, Table

Catalyst Catalytic Con- Selectivity, «Old Catalyst Pre- ---------------------------------

, -1 '' statement FBAR cracked C6-1Z0 Hexen Benzene factor ** Pt / Al ₂ 0 3 55.4 27.8 29.5 12.4 6.9 1.15 Sn-Pt / Al ₂ O ₃ Present -J ¹ description 20.0 4.0 9.7 62.4 16.8 1, 06 Sn ~ Pt / Al ₂ O ₃ impregnated amination * 48.2 40.9 20.6 10.9 11.4 1.15 X /. - See e.g. R. Burch: J. Catal. 71 348 (1981)

** Response times of 1 and 4 hours, respectively

The data in Table I illustrate that the cracking and isomerizing activity of the catalyst prepared according to the invention is greatly reduced, while the dehydrogenation activity resulting in the formation of olefins is greatly increased, that is, the reactions at the acidic centers of the catalyst are greatly suppressed.

Example 2 G Al ₂ O ₃ supported catalyst containing 0.35 wt% platinum and 0.35 wt% rhenium (support specific surface area: 180 m ² / g, particle size: 0.31-0.63 mm) for 6 hours The reaction mixture is pre-treated at 150 DEG C. with a pressure of 10 ⁵ bar and cooled under a stream of nitrogen.

The supported catalyst is suspended in 25 ml of hexane and then 8 ml of a 15% w / w solution of butyl lithium in hexane are added at 50 ° C with slow stirring.

After hours, the liquid phase is removed, and conversion value measured after the catalyst is four times with 10 ml of hexane mos4 suk ratio and dried at 50 ° C ΙΟ ⁵ bar pressure for 1 hour. The resulting lithium-modified supported catalyst was reacted with 0.0135 g of tin tetrachloride in 25 ml of acetone for 24 hours at 50 ° C. Aj: acetone solution was removed, and the supported catalyst was washed four times with 10 ml acetone and dried at 50 ° C, a pressure of 10 ⁵ bar for 1 hour. The resulting catalyst was heated to 500 ° C in a stream of hydrogen at ₅₅ ° C / min for ₅₅ minutes and maintained at this temperature for 1 hour. A catalyst containing 0.10 wt% tin was obtained.

The catalyst thus obtained was tested as described in Example 1, except that the catalyst was kept at 400 ° C for 1 hour before the reaction and in a stream of hydrogen for 1.5 hours. The results after 4 hours of reaction with the known Pt-Re / Al ₂ O ₃ catalyst are shown in Table II. in Table.

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II. spreadsheet

Catalyst converter version Selectivity, / aging factor Krakk ίζο-Οθ hexenes Benzene· Pt-Re / Al ₂ O ₃ 41.6 34.1 17.2 23.4 13.7 1J5 Sn-Pt-Re / Al ₂ O ₃ 22.74 9.5 3.4 52.3 22.3 1, 05

The cracking and isomerizing activity of the catalyst produced by the process of the invention is significantly reduced due to blocking of acidic centers; however, aging of the catalyst is also reduced. The selectivity of hexenes and benzene formation more than doubles.

Example 3 G catalyst containing Al ₂ O _3, containing 0.50 wt% platinum and 0.22 wt% palladium (specific surface area: 240 m ² / g, particle size 0.31-0.63 mm) under nitrogen It was pretreated at 150 ° C for 6 hours and then cooled under nitrogen. The pretreated supported catalyst was suspended in 25 mL of hexane under nitrogen and the suspension was heated to 50 ° C and 8 mL of a 15% w / w solution of butyl lithium in hexane was added slowly. After 3 hours reaction time, foIII.

The liquid phase was removed, the supported catalyst was washed with hexane (4 x 10 mL) and dried at 50 ° C for 1 hour at ^10-5 bar. The resulting lithium-modified supported catalyst was maintained for 24 hours

At 50 ° C, a solution of 0.013 g of tin tetrachloride in ml of acetone was reacted. The acetone solution was removed, and the supported catalyst was washed with acetone (4 x 10 mL) and methanol (2 x 10 mL).

It is dried at 50 ° C and ^10-5 bar for 1 hour. The supported catalyst was then heated to 500 ° C in a hydrogen stream at 5 ° C / min and maintained at this temperature for 1 hour. 0.08% by weight of tin catalyst was obtained.

The catalyst thus obtained was tested as described in Example 2. The results after 4 hours of reaction time compared to the known Pt-Pd / Al ₂ O ₃ catalyst are shown in Table III. in table

Catalyst Reaction temperature, ° C con- blood- ziód % Selectivity aging: factor cracked ίζο-Οθ hexenes Benzene Pt-Pd / Al ₂ O ₃ 500 60.0 26.0 21.5 10.0 28.0 1.2 450 32.5 25.0 30.0 8.0 26.0 - Sn-Pt-Pd / 500 31, 9 8.0 H, 9 33.0 33.1 1.06 Al ₂ 0 ₃ 450 13.3 5.5 3.7 64.1 8.8 -

The cracking and isomerizing activity of the catalyst prepared by the process of the invention is significantly reduced by blocking acidic centers; however, the selectivity of hexenes and benzene formation and catalyst stability are greatly increased.

Example 4 G Al ₂ O ₃ supported catalyst containing 0.50 wt.% Platinum (specific surface area: 240 m ² / g, particle size: 0.31-0.63 mm) under argon at 150 ° C for 6 hours. The catalyst was suspended in 40 ml of hexane under argon and 10 ml of a 15% w / w solution of butyl lithium in hexane was added at 50 ° C with constant stirring. After a reaction time of 2 hours, the liquid phase is removed, the lithium-modified support catalyst is washed four times with 15 ml of hexane, and then dried for one hour at 50 DEG C. (10 ^{4 5} bar). dichloride in benzene (30 ml) at 65 ° C for 12 hours

-5197524. The liquid phase is removed and the catalyst is washed four times with 10 ml of benzene and 15 ml of hexane twice, and dried for 1 hour at 50 ° C and a pressure of 10 ^-5 bar. The resulting supported catalyst was heated to 500 ° C in a hydrogen stream at 5 ° C / min for 1 hour. A catalyst containing 0.25 wt / tin was obtained.

EXAMPLE 5 G catalyst containing 0.35% by weight platinum (specific surface area: 180 m ² / g, particle size: 0.31-0.63 mm) with Al ₂ O _{3 for} 6 hours at 150 ° C, ICL ^{It was} pretreated at ⁵ bar and cooled under nitrogen. The supported catalyst was suspended in 25 ml of hexane under nitrogen and 3 ml of 15% w / w solution of butyl lithium in hexane was added at 20 ° C with slow stirring. After a reaction time of 8 hours, the liquid phase is removed, the catalyst is washed four times with 10 ml of hexane and then dried at 50 ° C and 10 ⁵ bar for 1 hour. The resulting lithium-modified supported catalyst was reacted with 0.05 g of tin tetrachloride in 30 ml of methyl ethyl ketone at 70 ° C for 24 hours. The liquid phase was removed, and the supported catalyst was washed at 50 ° C four times with 10 ml acetone and twice with 10 ml of methanol and then dried for 1 hour at 50 ° C and a pressure of 10 ^-5 bar. The resulting material was heated to 500 ° C in a hydrogen stream at 2 ° C / min for 1 hour. A catalyst containing 0.15 wt% tin was obtained.

Example 6 G Al ₂ O ₃ supported catalyst containing 0.50 wt.% Platinum (specific surface area: 240 m ² / g, particle size 0.31-0.63 mm) at 500 ° C for 6 hours under nitrogen. pre-treat and then cool. The supported catalyst was suspended in 25 ml of heptane under nitrogen and 6 ml of a 15% w / w solution of butyl lithium in hexane was added at 80 ° C with constant stirring. After a reaction time of 3 hours, the liquid phase is removed, the supported catalyst is washed four times with 10 ml of hexane and then dried at 50 ° C and 10 ' ³ bar for 1 hour. The resulting lithium-modified supported catalyst was reacted with 0.018 g of tin tetrachloride in 30 ml of acetone at 50 ° C for 24 hours. The liquid phase is removed by decantation, the solid is washed four times with 10 ml of acetone and dried at 50 ° C and 10 DEG C. for 1 hour. Subsequently, the supported catalyst was heated to 500 ° C under a stream of hydrogen at 20 ° C / min for 1 hour. A catalyst containing 0.12 wt% tin was obtained.

Example 7 A catalyst containing 0.48% by weight of platinum on silica gel (specific surface area: 250 m ² / g, particle size: 0.25-0.50 mm) was pre-treated at 150 ° C under nitrogen for 6 hours. then cool. The supported catalyst was suspended in 25 ml of hexane under nitrogen and 6 ml of a 15% w / w solution of butyllithium in hexane was added at 50 ° C with constant stirring. After a reaction time of 2 hours, the liquid phase was removed by decantation, the solid was washed with hexane (4 x 10 mL) and dried at 50 ° C under 10 ⁶ bar for 1 hour. The resulting lithium-modified supported catalyst was reacted with 0.02 g of tin tetrachloride in 30 ml of acetone at 50 ° C for 24 hours. The liquid phase was removed and the solid was washed with acetone (4 x 10 mL) and methanol (2 x 10 mL) and dried at 50 ° C (10 x ⁵ bar) for 1 h. The supported catalyst thus obtained was heated to 600 ° C in a hydrogen / nitrogen gas mixture (1: 9) at 5 ° C / min and maintained at this temperature for 1 hour. 0.07% by weight of tin catalyst was obtained.

Claims (7)

PATENT CLAIMS A process for the production of supported platinum tin catalysts containing only tin in the state bonded to the acidic centers of the support, characterized in that the aluminum oxide contains 0.3 to 10% by weight of platinum and optionally up to 0.5% by weight of rhenium or palladium. silica gel supported catalyst at atmospheric pressure and inert gas, or reduced, but 10 ^-6 browns higher pressure pretreated at 150-500 ° C, C and under inert atmosphere, based on 1 g of supported catalyst is from 0.06 to 0.4 g of C _n H ₂ n + lithium compound of formula III to the pretreated catalyst is 15 to 100 ° - wherein n is an integer from 1 to 4 by reaction with a solution of 5 to 10 hydrocarbons, the unreacted lithium compound is washed off, the resulting lithium modified support catalyst is optionally dried and then in an inert gas, ketone or hydrocarbon solvent, At a temperature of 15-70 ° C for 12-24 hours, 0.0002-0.115 g of a tin compound of SnCl ₄ or SnCl ₂ Alk ₂ , wherein Alk represents a C 1-4 alkyl group, are added to 1 g of supported catalyst, and the resulting product is washed, drying, if desired, and finally hydrogen or containing up to 90% by volume of inert gas stabilize in a gas-in gas mixture at 300-600 ° C for 0.5 to 3 hours. A process according to claim 1, wherein the lithium compound of the formula C _n H _{2n +} , Li is butyl lithium. -6197524 Process according to claim 1 or 2, characterized in that the reaction of the pretreated catalyst with the lithium compound is carried out in hexane or heptane. 4. A process according to any one of claims 1 to 4, characterized in that the supported catalyst reacted with the lithium compound is washed with a hydrocarbon having from 5 to 10 carbon atoms, preferably hexane or heptane. 5. A process according to any one of claims 1 to 4, wherein the modified lithium catalyst is reacted with a tin compound in aether, methyl ethyl ketone or benzene. 6. Process according to any one of claims 1 to 3, characterized in that the tin compound SnCl ₂ Alk ₂ is diethyl tin dichloride. 7. A process according to any one of claims 1 to 3, wherein the inert gas is nitrogen or argon.