DE102004002262A1 - Solid-phase catalysts containing palladium plus antimony, bismuth, tin and/or copper, useful for catalyzing acyloxylation of alkyl-aromatic compounds to give aryl esters, especially benzyl acetate - Google Patents

Abstract

New solid phase catalysts (A) contain (a) palladium (Pd) and (b) one or more of antimony (Sb), bismuth (Bi), tin (Sn) and copper (Cu). An independent claim is included for the preparation of (A), by: (1) impregnating a solid carrier with a salt of Pd and salt(s) of the component(s) (b), sequentially or in single stage; and (2) calcining the (b)-impregnated catalyst (before or after impregnation with Pd) at elevated temperature in presence of oxygen.

Description

The The invention relates to a solid phase catalyst, a process for its preparation and its use for the catalysis of acetoxylation reactions for the preparation of aryl esters.

The chemical industry has an increasing demand for benzyl acetate (C ₆ H ₅ -CH ₂ OCOCH ₃ ) and its derivatives in view of its different industrial application potential. Benzyl acetate is a natural component of plants such as jasmine, hyacinths, gardenias, azaleas and others. It is preferably used in the perfume industry due to its fruity aroma. It is also used in the food industry for the production of chewing gum, gelatin puddings, sweets, ice cream, etc., but also in the chemical industry, especially as a solvent for cellulose acetate. The consumption of benzyl acetate is currently between 5000 and 10 000 t per year. Furthermore, benzyl acetate can be used to prepare benzyl alcohol (by simple hydrolysis), which itself serves as an intermediate for the synthesis of insecticides, such as permethine by esterification of 3-phenoxybenzyl alcohol (chrysanthemum acid derivative). Aromatic esters, for example benzyl esters, are generally used as solvents and as starting materials for the preparation of aromatic intermediates and synthetic resins (eg polyester resins) and others. The ongoing broadening of applications is leading to increasing importance for the chemical industry and increased demand. In this context, a more effective and economical synthesis (eg, by heterogeneously catalyzed oxidation of methyl aromatics with air) of benzyl esters or alcohols is an essential prerequisite for further syntheses of various industrially important chemicals.

The conventional process for the preparation of benzyl acetate is usually carried out in liquid phase in the stirred tank mode. This process means multi-stage operation, tedious process control, separation problems, catalyst deactivation and leaching, as well as other disadvantages such as limited production, and finally environmental problems due to acids and salts. That's how it describes EP 0 965 383 A a process for the preparation of benzyl esters by acetoxylation in liquid phase with a complex multicomponent catalyst with palladium (Pd), gold (Au) and another element. All components are applied as acetates on a support. There is obtained a yield of only 69.3% benzyl acetate. Another liquid phase process according to US 3,547,982 PS uses a catalyst with palladium acetate and another acetate component without carrier. This process is characterized by a rapid deactivation and thus short life of the catalyst and therefore unsuitable for industrial application.

In contrast to the liquid-phase reaction, gas-phase acetoxylation leads to a very advantageous method for the direct synthesis of benzyl esters from their corresponding alkylbenzenes in one step. It therefore represents a significant technology and is therefore currently receiving great interest from industry. Despite this interest, no significant improvements have been achieved to higher yields of benzyl acetate for industrial use. GB 1 017 938 . US 3,275,680 and GB 1,117,595 describe in each case a method for producing organic acetates, such as benzyl acetate in the gas phase by reaction of the corresponding hydrocarbon components with acetic acid and air. A supported palladium catalyst with an alkali or alkaline earth metal acetate is also used. However, the yields achieved per gram of palladium are relatively low. GB 1 328 058 describes a process for the preparation of benzyl acetate by reacting toluene, acetic acid and air in the gas phase over catalysts with palladium metal, bismuth acetate and an alkali acetate supported on silica pills. In the process, however, only low yields of benzyl acetate are achieved.

In summary can be stated that all the above-mentioned methods from an industrial point of view Disadvantages included.

The The aim of the present invention is therefore a newer and more effective Catalyst responsible for the acetoxylation of alkyl-substituted aromatic Compounds with carboxylic acids preferably in the gas phase with high yield and selectivity. The catalyst should continue to have a long lifetime to to be used industrially.

• (a) Palladium (Pd) in Form von Palladiummetall und/oder Palladiumoxid sowie
• (b) mindestens eine weitere Komponente in im Wesentlichen oxidischer Form aus der Gruppe Antimon (Sb), Bismut (Bi) und Zinn (Sn).

This object is successfully achieved by a solid phase catalyst according to claim 1. The catalyst according to the invention contains the components

• (a) palladium (Pd) in the form of palladium metal and / or palladium oxide and
• (B) at least one further component in substantially oxidic form from the group antimony (Sb), bismuth (Bi) and tin (Sn).

in view of of the above Prior art allows the catalyst of the invention, numerous the mentioned Overcome problems. Compared to the catalysts described catalyst of the invention shows an excellent performance. If this new palladium-containing Catalyst for the catalytic acetoxylation reaction is used results a yield of benzyl ester, especially benzyl acetate, the one commercial use allowed.

Preferably contains the catalyst of the invention the components palladium and antimony. However, it is still preferred a combination of the three components palladium, antimony and bismuth. The addition of bismuth to the palladium-antimony catalyst increases on the one hand significantly the life of the catalyst and on the other hand its selectivity.

The Palladium in the catalyst is preferably substantially as palladium metal and only to a small extent in the form of palladium oxide. It However, it was observed that the palladium component also alloys with at least one further component, in particular antimony and / or Bismuth, can form. The antimony and / or bismuth component is usually as oxide before. In addition, it was determined by transmission electron microscopy (TEM) in the case of bismuth to a small extent with the alloy formation Palladium observed.

The components are preferably present on a suitable solid support, which may be present both as a compact solid, preferably mesoporous, and in powder form. Various supports can be used, such as titanium oxide (TiO ₂ ), silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), niobium oxide (Nb ₂ O ₅ ), activated carbon (C), zeolites, Diatomaceous earth and mixtures thereof. Preferably, the carrier titanium oxide (TiO ₂ ) is used in the form of anatase.

To a preferred embodiment of the invention is the content on Pd on the carrier 0.5 to 40 wt .-%, preferably 2 to 25 wt .-%. In a preferred Catalyst with the elements Pd and Sb or with the elements Pd, Sb and Bi is the content of Sb on the carrier 2 to 25 wt .-%, preferably 3 to 15 wt .-%. In the further preferred Catalyst system with Pd and Bi or Pd, Sb and Bi is the content to Bi on the carrier 1 to 20 wt .-%, preferably 2 to 15 wt .-%. The content of Sb and also to Bi on the carrier However, it is not critical and can be varied widely.

A particularly preferred catalyst has the empirical formula Pd-Sb _a -Ti _c O _x , wherein a is equal to 0.1 to 14, preferably 0.1 to 4; c is 2 to 150, preferably 2 to 15 and x is determined by the valences of all components.

A likewise preferred catalyst has the empirical formula Pd-Bi _b -Ti _c O _x , wherein b is 0.05 to 20, preferably 0.05 to 7, c is 2 to 150, preferably 2 to 15 and x is determined by the valences of all components.

Another preferred catalyst has the empirical formula Pd-Sb _a -Bi _b -Ti _c O _x , wherein a is equal to 0.1 to 14, preferably 0.1 to 4; b is 0.05 to 20, preferably 0.05 to 7; c is 2 to 150, preferably 2 to 15 and x is determined by the valences of all components.

The catalyst according to the invention shows excellent properties: high catalytic activity and selectivity as well as high mechanical strength and abrasion resistance. It is interesting to note that Pd alone on a titania carrier as well as Sb alone on a titania carrier are both inactive. However, the combination of both components on titanium oxide results in a significantly higher activity corresponding to a synergistic effect of Pd and Sb. However, this catalyst tends to deactivate by coking after several hours of operation. To remedy this deactivation problem and also to increase the selectivity of the desired product (benzyl acetate), the combination of Pd-Sb-titanium oxide was modified by the addition of further promoters / modifiers in suitable amounts. A successful promoter is eg bismuth (Bi). In addition, catalysts were synthesized in which Sb was simply replaced by Bi (Pd-Bi titanium oxide) and their acetoxylation activity tested (Example 11). The catalytic results showed that these Pd-Bi-titania catalysts (without Sb) exhibited extremely high selectivity (> 95%) but slightly lower activity, while solving the deactivation problem. From this can concluded that the presence of Sb is necessary for high activity, and that of Bi is equally essential for higher selectivity in the formation of benzyl acetate, as well as for a longer catalyst life. In view of this, various catalysts with the combination of all three components (ie, Pd, Sb, and Bi) were prepared, supported on titania, and tested for activity and selectivity in benzyl acetate formation in the acetoxylation reaction of toluene (Examples 12 and 13). The development of these catalysts (Pd-Sb-Bi-titanium oxide) with a new composition has, on the one hand, effectively solved the problem of deactivation and, on the other hand, enabled high benzyl acetate selectivities (> 95%). These Pd-Sb-Bi titanium oxide catalysts are very selective but slightly less active than Pd-Sb titanium oxide catalysts.

The Aim of a high selectivity and the solution of the deactivation problem was successful by inserting Bi dissolved in a suitable amount to the Pd-Sb titanium oxide catalysts. In contrast to most known catalysts contains the catalyst of the invention few components and thus provides a very simple system much better performance.

One Another important aspect of the present invention is that of catalyst according to the invention Synthesis of aryl esters can catalyze by an appropriate substituted aromatic compound reacts with a corresponding carboxylic acid, wherein the alkyl substituent of the aromatic compound is oxidative is acylated. The synthesis according to the invention of esters has many advantages compared to known methods. The benefits include a direct one-step synthesis, a continuous process, higher selectivity at desired Product (ester), high purity and others.

Preferably, the catalytic acetoxylation reaction follows the equation:

Here R _{1 is} a straight or branched, saturated or unsaturated C ₁ - to C ₆ alkyl group, R _{2 is} a straight or branched, saturated or unsaturated C ₁ - to C ₄ alkyl group and the aryl group aryl corresponds to a system having 1 to 5 aromatic rings, which may optionally be further substituted with one or more substituents X.

The C ₁ to C ₆ alkyl groups and / or the substituent X of the alkyl-substituted aromatic compound are, independently of each other, preferably selected from the group comprising methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso Butyl, esc-butyl, pentyl, hexyl and others. The C ₁ to C ₄ alkyl groups of the carboxylic acid are preferably selected from the group comprising methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl and others.

The present invention relates in one essential aspect to the direct synthesis of benzyl acetate from methylbenzene (toluene) and acetic acid over a Pd-containing catalyst according to the invention under suitable reaction conditions according to:

In In this reaction, benzaldehyde is by-produced in minor amounts educated.

Of the needed for the reaction Oxygen can be both pure oxygen and inert gas diluted Shape can also be used as air. The reaction can be at higher or higher lower pressure become. Preferably, the reaction is carried out at atmospheric pressure up to a pressure of 10 atm, preferably at 2 to 8 atm.

The molar ratio of alkyl-substituted aromatic compound to carboxylic acid (eg, toluene to acetic acid) can be varied widely. Preferably, the ratio of alkylsubsti The aromatic compound to the carboxylic acid was 0.5 to 10, preferably 2 to 6. An excess of carboxylic acid is desirable for better catalytic performance. The molar ratio of the alkyl-substituted aromatic compound to oxygen is about 1 to 10, preferably 2 to 6. The amount of oxygen can be varied, but is usually outside the explosive limit, which is an excess of the stoichiometric amount relative to toluene.

Basically the catalytic reaction can be carried out in the gas or liquid phase. Because of the special advantages the gas phase reaction, the reaction is preferably carried out on this Way as one step reaction. The reaction can be chosen arbitrarily, Both fluidized bed and fixed bed processes are possible. Preferably However, the reaction takes place in the fixed bed system in the tubular reactor, if possible made of stainless steel. Here, "gas-phase acetoxylation" is understood as a process in which an alkyl group is converted into an ester group by reaction with a carboxylic acid in one step in the presence of a catalyst in an oxygen-containing one Gas is reacted under suitable conditions. A "fixed bed reactor" is defined as a reactor with a solid catalyst arranged in a fixed bed. The fixed bed reactor can be filled with an oxygen-containing gas and, if necessary, be supplied with argon. The organic starting materials, namely the aromatic compound and the carboxylic acid are by means of a precision pump pumped into the reactor, with a preheating zone ensures that the starting materials are evaporated. Argon as an inert gas added to a constant when varying the process parameters To guarantee space velocity.

Preferably the acetoxylation takes place at a reaction temperature between 100 and 400 ° C, preferably between 150 and 350 ° C, and a pressure of about 2 bar. The optimal temperature depends on various factors, e.g. the concentration of the organic Starting materials, the amount of catalyst, the gas composition, the Contact time etc., from.

The inventive method for the direct synthesis of benzyl acetate shows significant improvements in the reaction parameters compared to the prior art and leads to higher Turnover rates of toluene and higher Yields of benzyl acetate. At the same time, the problem of deactivation solved.

The present invention allows a direct synthesis of aryl esters, especially benzyl acetate, in high yields (e.g., 79%) significantly high sales (e.g., toluene conversion about 93%). Furthermore, the invention allows a One step reaction and a continuous process under gas phase conditions.

The reaction occurs at space velocities (GHSV) and residence times which allow industrial production. The GHSV is preferably 1000 to 5000 h ^-1 and the residence time is between 1 and 6 seconds. The major product is the desired aryl ester (eg benzyl acetate) in high selectivity. Small scale byproducts are total oxidation products and aldehydes, eg benzaldehyde. The method allows the synthesis of aryl esters in high space-time yield, so in the case of Benzylacetatsynthese up to 694 g / kg cat / h. "Space-time yield" is defined herein as the amount of product in grams obtained per kg of catalyst in one hour.

• (a) Imprägnierung eines festen Trägers mit einem geeigneten Palladiumsalz und einem geeigneten Salz von mindestens einer weiteren Komponente aus der Gruppe Antimon(Sb), Bismut (Bi) und Zinn (Sn), wobei die Imprägnierung sowohl sequentiell als auch in einem Schritt erfolgen kann, und
• (b) vor oder nach der Imprägnierung Kalzinierung des Trägers mit Palladium bei erhöhter Temperatur in Gegenwart von Sauerstoff.

The catalyst of the invention can be prepared in a simple manner, by

• (A) impregnation of a solid support with a suitable palladium salt and a suitable salt of at least one further component from the group antimony (Sb), bismuth (Bi) and tin (Sn), wherein the impregnation can be carried out both sequentially and in one step , and
• (b) before or after impregnation calcination of the support with palladium at elevated temperature in the presence of oxygen.

These simple method allows on the one hand, a highly active and selective To obtain catalyst and on the other hand, a high dispersion of active phase on the catalyst, resulting in an improved catalytic power leads.

• (a) zunächst Imprägnierung des Trägers mit einem geeigneten Salz von mindestens einer zusätzlichen Komponente aus der Gruppe Sb, Bi und Sn,
• (b) dann Kalzinierung des Trägers und
• (c) anschließend Imprägnierung des Trägers mit einem geeigneten Pd-Salz.

Preferably, the catalyst is prepared in the following manner

• (a) first impregnating the support with a suitable salt of at least one additional component from the group Sb, Bi and Sn,
• (b) then calcination of the carrier and
• (c) then impregnating the support with a suitable Pd salt.

• (a) Imprägnierung des Titanoxid-Trägers nur mit der Sb-Verbindung oder danach auch mit der Bi-Verbindung,
• (b) Trocknung im Ofen bei 120°C (16 h) und Kalzinierung bei 400°C in Luft (3 h),
• (c) Imprägnierung der erhaltenen festen Masse mit der Pd-Verbindung, gefolgt von einer Trocknung im Ofen bei 120°C (16 h) und
• (d) Pelletierung, Verformung und Aktivierung unter den gewünschten Bedingungen.

In a particularly preferred manner, the preparation is carried out as follows

• (A) Impregnation of the titanium oxide carrier only with the Sb compound or thereafter with the Bi-verbin dung,
• (b) oven drying at 120 ° C (16 h) and calcining at 400 ° C in air (3 h),
• (c) impregnation of the resulting solid with the Pd compound, followed by oven drying at 120 ° C (16 h) and
• (d) pelleting, deformation and activation under the desired conditions.

The Palladium may be on the support also by immersing in an aqueous solution a suitable palladium compound are applied. suitable Palladium compounds are e.g. Palladium halides, nitrates, acetates or sodium palladium chloride, Palladium-amine complexes, palladium acetylacetonate and others.

Of the Catalyst is preferably activated prior to the catalytic reaction.

The second component antimony exists essentially on the catalyst oxidic. Suitable antimony compounds for impregnation are: halides, e.g. Antimony chloride, antimony oxide, antimony sulfate or the like Links. It is possible, a uniform solution produce if slightly soluble Antimony compound with the aid of an inorganic acid (such as hydrochloric acid or nitric acid) or an organic acid (like tartaric acid, oxalic or glycolic acid) or a corresponding salt is dissolved. Made by impregnation a uniform distribution on the carrier.

The third component bismuth is mostly oxidic on the catalyst in front. Suitable bismuth compounds for catalyst preparation are bismuth halides, e.g. Chloride, bromide, bismuth oxide, bismuth nitrate, Bismuth acetate, bismuth hydroxide, bismuth oxychloride and the like. In the case of one slightly soluble in water Bismuth compound can be used as for Antimony described procedure. By impregnation is a uniform distribution on the carrier. As already mentioned, elevated the Bismutzugabe to the supported Pd-Sb catalyst the life of the catalyst and its selectivity.

To the impregnation with the antimony and / or bismuth component, the catalyst must for transfer to the corresponding oxides are calcined. This calcination takes place preferably in an oxygen-containing gas, e.g. Air at a temperature of 300 to 900 ° C, preferably at 350 to 700 ° C. If the temperature is too low, the decomposition of the Sb and Bi compounds will occur and the removal of inorganic acids incomplete. at too high a temperature deteriorates the mechanical properties of the catalyst and the surface of the carrier decreases to the detriment of the catalytic activity. Calcination in air takes place in 2 to 10 hours, preferably in 3 to 6 hours Reaching the required temperature.

The Addition of palladium and at least one of the other components, Sb or Bi, may be simultaneous or sequential. It is useful at sequential addition immediately after addition of Sb and / or Bi component to calcine. So it is e.g. also possible, first the Sb and Bi connections to impregnate, then in the presence of an oxygen-containing gas at a suitable Calcine the temperature and finally the Pd component afterwards to impregnate. The order of impregnation of all Three components can each be changed.

To the general description of the present invention is intended to be be explained in more detail by a number of specific examples. These examples however, are not intended to limit the present invention.

embodiments

The Examples 1 to 6 below describe the preparation methods the differently supported and promoted Pd catalysts according to the present invention. Example 7 explained the experimental procedure for performing the catalytic tests in a fixed bed reactor. Examples 8 to 14 show results of catalytic Tests with the catalysts prepared according to Examples 1 to 6.

example 1

example 1 describes the preparation of Pd-Sb titanium oxide catalysts with different Pd proportions.

The catalyst preparation takes place mainly in two stages. In the first step, 4.575 g of titanium oxide (Anatas from Kronos, Dtschld., BET 315 m ² / g) with an aqueous solution of 0.7503 g of SbCl ₃ in 2 ml of conc. HCl and 5 ml of dist. Impregnated with water and allowed to stand with occasional stirring for 1 h at room temperature (RT). Then an aqueous solution of 2.4 g of ammonium sulfate in 6.6 ml of dist. Water was added to this mixture and then heated on the water bath at 70 ° C for 1 h. After cooling, the suspension is neutralized with 25% ammonia to pH 7 and heated again for one hour. Thereafter, the solid portion is filtered off and dried first in a rotary dryer under vacuum and then in the oven at 120 ° C for 16 h and then calcined at 400 ° C for 3 h in air (50 ml / min).

In a second step, an aqueous solution of palladium chloride by dissolving 0.0417 g of PdCl ₂ in 5 ml dest. Water, adding a few drops of conc. HCl and heating to about 60 ° C for about 20 min prepares. Then, a pH of 4 is adjusted by dropwise addition of sodium carbonate. With this solution, the calcined mass obtained in the first step is impregnated, stirred for 1 h with a magnetic stirrer and then dried as described above in vacuo and in the oven at 120 ° C for 16 h. The catalyst corresponds to a composition of 0.5 wt .-% Pd, 8 wt .-% Sb and titanium oxide ad 100%.

In Similarly, various Pd-Sb titanium oxide catalysts with different Pd contents (0.5 to 20 wt .-%) at constant Sb content (8 wt .-%) produced. The influence of Pd content on the catalytic performance was tested in a fixed bed reactor (see Table 1).

Example 2

In Example 2 will describe the preparation of Pd-Sb catalysts at various support materials described.

The supported Pd-Sb catalysts were prepared as described in Example 1, wherein the titanium oxide is replaced in each case by a different oxide (SiO ₂ , ZrO ₂ and γ-Al ₂ O ₃ ) in an appropriate amount. Here, the antimony source was SbCl ₃ and the palladium source PdCl ₂ . The oxidic supports were used in each case without pretreatment. The composition of the catalysts corresponded to 10 wt .-% Pd, 8 wt .-% Sb and titanium oxide ad 100 wt .-%. The corresponding catalytic results are shown in Table 2.

Example 3

In Example 3 is the preparation of titanium oxide supported catalysts described with different promoters.

The catalysts were prepared as described in Example 1, wherein in addition to the antimony by an appropriate amount of bismuth or tin was added (BiCl ₃ or SnCl ₂ · H ₂ O). The weight fractions of SbCl _3, BiCl ₃ and SnCl ₂ · H ₂ O were 0.7503 g, 0.5189 g and 0.7606 g, respectively. The catalysts contained in each case 10 wt .-% Pd and 8 wt .-% Sb and 7 wt .-% Bi or 8 wt .-% Sn. The promoter influence is shown in Table 3.

Example 4

In Example 4 is the preparation of a titanium oxide supported catalyst described with a bi-promoter.

Various Pd-Bi titanium oxide catalysts were prepared as described in Example 1, with the antimony replaced by various amounts of bismuth. The bismuth source was BiCl ₃ . Three catalysts with a Pd / Bi ratio of 0.1 to 0.7 were prepared. The influence of the Pd / Bi ratio on the catalytic performance is shown in Table 4.

Example 5

In Example 5 is the preparation of Pd-Sb-Bi titanium oxide catalysts described with different Pd proportions.

The Pd-Sb-Bi-titanium oxide catalysts were prepared as described in Example 1, wherein initially the impregnation of the carrier with antimony and then with bismuth takes place. The content of Sb and Bi was 8 wt% and 7 wt%, respectively, while the Pd content was varied between 0.5 and 20 wt%. The corresponding catalytic results are shown in Tables 5 and 6.

Example 6

In Example 6 is the preparation of Pd-Sb titanium oxide catalysts described using different Pd sources.

These catalysts were prepared as described in Example 1, using various Pd compounds for preparation, namely PdCl ₂ , Pd (NO ₃ ) ₂ and Pd (CH ₃ COO) ₂ . In this case, the proportion of Pd and Sb was kept constant at 10% by weight and 8% by weight, respectively. The influence of the various Pd compounds on the catalytic performance is shown in Table 7.

Example 7

In Example 7 becomes the method for carrying out the acetoxylation reaction and the determination of the activity and selectivity behavior the catalysts described.

The Reaction was in a stainless steel fixed bed tubular reactor Steel, which allows a reaction at 2 bar, carried out. in the The reactor was charged with about 1 ml of catalyst (particle size 0.425 to 0.6 mm). air and argon (commercially available) were over Measure flow controller. The organic starting materials were dosed with an HPLC pump and in the upper preheating zone in the reactor vaporized and with the gaseous Starting materials mixed and over passed the catalyst layer. The temperature of the catalyst bed was measured continuously with a thermocouple. The catalyst was then activated in air (27 ml / min) at 300 ° C for 2 h before the reaction was started.

The product stream was on line by GC (HP-5890) provided with a FID and HP-5 capillaries (50 m x 0.32 mm). The capillary was connected to a methanizer (30% Ni / silica cat.) To convert all C-containing products, including CO and CO ₂ , to methane, providing an elegant and simple method of analyzing the products. It should be noted that all catalysts in their catalytic reaction were evaluated only after reaching steady state conditions (about 10 h, or as in the case of bi-promoted catalysts longer) in their performance.

The reaction was examined under the following reaction conditions: reaction temperature 150 to 350 ° C, GHSV 1000 to 5000 h ^-1 , contact time 1 to 6 s, molar ratio toluene: acetic acid: oxygen: inert gas = 1: 4: 2-5: 14-20.

Example 8

In Example 8 illustrates the influence of Pd content on the activity and selectivity of Pd-Sb titanium oxide catalysts investigated in the acetoxylation reaction.

Of the catalysts described in Example 1, 1 ml each were added to the reactor and treated according to the method described in Example 7. The reaction conditions were as follows: reaction temperature 210 ° C., GHSV 2688 h ^-1 , contact time 1.34 s, molar ratio of toluene: acetic acid: oxygen: inert gas = 1: 4: 3: 16. The molar concentration of toluene was 4.2%. ; 16.75% acetic acid, 12.5% oxygen and 66.6% inert gas.

The Results of the influence of the Pd content (each with a constant 8 Wt% Sb on titania) on catalytic performance are in Table 1 shown.

Table 1

Example 9

In Example 9 illustrates the influence of the carrier on the catalytic performance of supported ones Pd-Sb catalysts shown.

In each case 1 ml of the catalysts prepared in Example 7 was added to the reactor and tested under the following conditions: reaction temperature 210 ° C., pressure 2 bar, GHSV 2688 h ^-1 , contact time 1.34 s, molar ratio toluene: acetic acid oxygen: inert gas 1: 4: 3: 16, molar concentration of toluene was 4.2%, 16.7% of acetic acid, 12.5% of oxygen and 66.6% of inert gas. The results on the influence of the carrier on the catalytic performance are shown in Table 2.

Table 2

Example 10

In Example 10 becomes the promoter effect on the catalytic property of Pd titanium oxide catalysts.

It In each case 1 ml of a catalyst prepared according to Example 1 and 3 tested according to Example 7, with the same reaction conditions as in Example 8 or 9 were met.

The Results of the catalytic tests are shown in Table 3.

Table 3

Example 11

In Example 11 becomes the influence of the Pd / Bi atomic ratio shown the catalytic performance of supported titanium oxide catalysts.

For this 1 ml (0.85 g) of each of Examples 1 and 4 was prepared Catalyst tested according to the procedure of Example 7. The reaction conditions and the molar concentrations of the reaction components corresponded to the details of Examples 8 to 10.

The Results for Pd / Bi influence on the catalytic performance are in Table 4.

Table 4

Example 12

In Example 12 demonstrates the long-term performance of 10% Pd-8% Sb-7% Bi-titania catalysts over a period of time represented by 160 h.

1 ml (0.85 g) each of a prepared according to Examples 1 and 5 Catalyst was prepared by the method described in Example 7 tested. The reaction conditions and the molar concentrations Each reaction component corresponded to the information in the examples 8 to 11. The results are for the 10% Pd-8% Sb-7% Bi-titania catalysts in Table 5.

Table 5

Example 13

In Example 13, the influence of Pd content in the Pd (8%) Sb (7%) Bi-titanium oxide catalysts on the represented catalytic performance.

1 ml (0.85 g) each one of Examples 1 and 5 shown Catalyst was prepared according to that described in Example 7 Method tested. The conditions of the reaction and the molar concentrations the reactants corresponded to those of Examples 8 to 12. The catalytic results on the influence of Pd content in Pd (8%) Sb (7%) Bi-titanium oxide catalyst are given in Table 6.

Table 6

Example 14

In Example 14 shows the influence of the Pd source on the catalytic Performance of 10% Pd-8% Sb titanium oxide catalysts described.

1 ml (0.85 g) each of a prepared according to Examples 1 and 6 Catalyst was prepared by the method described in Example 7 tested. The reaction conditions and the molar concentrations the reactants corresponded to the details of Examples 8 to 13. The results of the influence of the Pd source on the catalytic Performance of 10% Pd-8% Sb titanium oxide catalysts are shown in Table 7 is shown.

Table 7

Claims (31)

Solid phase catalyst comprising the components (A) Palladium (Pd) in the form of palladium metal and / or palladium oxide and (B) at least one further, essentially in oxidic Form present component consisting of the group consisting of antimony (Sb), bismuth (Bi) and tin (Zn). Catalyst according to claim 1, characterized in that that the catalyst comprises the components Pd and Sb. Catalyst according to claim 1, characterized in that the catalyst comprises the components Pd, Sb and Bi. Catalyst according to one of the preceding claims, characterized characterized in that palladium is substantially in the form of palladium metal and / or in the form of an alloy with the at least one other Component is present. Catalyst according to one of the preceding claims, characterized characterized in that the components are molded on a solid support an integral body or a powder. Catalyst according to claim 5, characterized in that the solid support is selected from the group consisting of titanium dioxide (TiO ₂ ), silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), zirconium dioxide (ZrO ₂ ), niobium oxide (Nb ₂ O ₅ ), activated carbon (C), zeolites, diatomaceous earth (diatomaceous earth) and mixtures of these, especially in mesoporous structure. Catalyst according to claim 6, characterized in that the support is TiO ₂ , in particular anatase. Catalyst according to one of claims 5 to 7, characterized that a mass fraction of Pd on the support in the range of 0.5 to 40%, in particular from 2 to 25%. Catalyst according to one of Claims 5 to 8, characterized a mass fraction of Sb on the carrier in the range of 2 to 25%, especially from 3 to 15%. Catalyst according to one of Claims 5 to 9, characterized that a mass fraction of Bi on the support in the range of 1 to 20%, especially from 2 to 15%. Catalyst according to one of the preceding claims, characterized in that the catalyst corresponds to the empirical formula Pd-Sb _a -Ti _c O _x , wherein a is 0.1 to 14, in particular 0.1 to 4; c is 2 to 150, in particular 2 to 15 and x is determined by the valences of all components. Catalyst according to one of claims 1 to 10, characterized in that the catalyst corresponds to the empirical formula Pd-Bi _b -Ti _c O _x , wherein b is 0.05 to 20, in particular 0.05 to 7; c is 2 to 150, in particular 2 to 15 and x is determined by the valences of all components. Catalyst according to one of Claims 1 to 10, characterized in that the catalyst corresponds to the empirical formula Pd-Sb _a -Bi _b -Ti _c O _x , where a is from 0.1 to 14, in particular from 0.1 to 4; b is 0.05 to 20, in particular 0.05 to 7; c is 2 to 150, in particular 2 to 15 and x is determined by the valences of all components. Process for the preparation of a catalyst according to one of the claims 1 to 13 with the steps (a) impregnating a solid support with a suitable salt of palladium (Pd) and a suitable salt of at least one other component selected from the group consisting of antimony (Sb), bismuth (Bi) and tin (Sn), wherein the impregnation either sequentially or in one step, and (B) before or after impregnation of the carrier with Pd calcination of the at least one other component impregnated carrier at a raised temperature in the presence of oxygen. Method according to claim 14, characterized in that that (a) first the carrier with a suitable salt of the at least one further component is impregnated from the group consisting of Sb, Bi and Sn, (b) then the carrier is calcined and (c) then the carrier with a suitable salt impregnated with Pd becomes. Method according to claim 14 or 15, characterized that the impregnation either by sequentially dipping the support in separate solutions suitable salts of the components is carried out or by dipping of the carrier into a solution, contains the appropriate salts of two or more of the components. Method according to one of claims 14 to 16, characterized that the calcination at a temperature between 300 and 900 ° C, in particular between 350 and 700 ° C, carried out becomes. Method according to one of claims 14 to 17, characterized that the appropriate salt of Pd is selected from the group the at least palladium halides, in particular chloride, palladium nitrate, palladium acetate, sodium palladium chloride, Palladium amine complex and palladium acetylacetonate contains. Method according to one of claims 14 to 18, characterized that the appropriate salt of Sb is selected from the group the at least antimony halides, in particular chloride, antimony nitrate, Antimony oxide and antimony sulfate. Method according to one of claims 14 to 19, characterized in that the suitable salt of Bi is selected from the group comprising at least bismuth halides, in particular chloride and bromide, bismuth nitrate, bismuth oxide, bismuth acetate, bismuth hydroxide and bismuth oxychloride. Method according to one of claims 14 to 20, characterized in that for the impregnation aqueous solutions of the components are used which may optionally contain an inorganic acid such as HCl or HNO ₃ , or organic acids such as tartaric acid, oxalic acid or glycolic acid, or a suitable Salt from these. Use of a catalyst according to any one of claims 1 to 13 for the catalysis of the synthesis of aryl esters by reaction of a corresponding alkyl-substituted aromatic compound with a corresponding carboxylic acid, wherein the alkyl group the aromatic compound is acetoxylated. Use according to claim 22, characterized that the acetoxylation in the gas phase or in the liquid phase carried out is, preferably in the gas phase. Use according to claim 22 or 23, characterized that the acetoxylation in a fixed-bed reactor, in particular in the form of a tubular reactor. Use according to any one of claims 22 to 24, characterized in that the catalyzed acetoxylation follows the following equation,

wherein R _{1 is} an unbranched or branched, saturated or unsaturated C _{1 to} C ₆ alkyl group, R _{2 is} a straight or branched, saturated or unsaturated C ₁ - to C ₄ alkyl group and the aryl group is a system having 1 to 5 aromatic Rings, which may optionally additionally carry one or more substituents X. Use according to claim 25, characterized in that C ₁ - to C ₆ alkyl group of the alkyl-substituted aromatic component and the one or more substituents X are independently selected from the group comprising methyl, ethyl, n-propyl, isopropyl, n- Butyl, isobutyl, sec-butyl, tert-butyl, pentyl and hexyl. Use according to claim 25 or 26, characterized in that the C ₁ - to C ₄ -alkyl group of the carboxylic acid is selected from the group comprising methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl and tert-butyl. Use according to any one of claims 22 to 27, characterized in that the alkyl-substituted aromatic component is toluene (C ₆ H ₅ -CH ₃ ) and the carboxylic acid is acetic acid (CH ₃ COOH). Use according to one of Claims 22 to 28, characterized that a molar ratio the alkyl-substituted aromatic component and the carboxylic acid in the range from 0.5 and 10, in particular from 2 to 6, is located. Use according to one of claims 22 to 29, characterized that a molar ratio the alkyl-substituted aromatic component and oxygen in the range of 1 and 10, in particular from 2 to 6, is located. Use according to one of claims 22 to 30, characterized a reaction temperature of the acetoxylation in the range of 100 to 400 ° C, in particular from 150 to 350 ° C, lies.