A method of obtaining a palladium-gold catalyst for production of vinyl acetate and a catalytic composition

 

(57) Abstract:

The invention relates to a deposited palladium-gold catalyst for production of vinyl acetate from ethylene, acetic acid and oxygen. Describes a method of producing the catalyst by impregnating a porous support with an aqueous solution of water-soluble potassium palladium compounds and water-soluble potassium-Golden connection with the subsequent deposition of water-soluble palladium and gold on the surface of the carrier using a basic potassium salt and the recovery of metallic palladium and gold. Describes embodiments of the method and catalyst composition. The reagents used in the preparation of the catalyst are compounds potassium salt which is essentially free of sodium. Presented by the present invention, the catalyst provides exceptional improvement of the selectivity in respect of carbon dioxide in the production of vinyl acetate, at least 9%. 4 C. and 10 C.p. f-crystals, 1 table.

The invention relates to a new method for producing a palladium-gold catalyst with improved selectivity for the production of vinyl acetate and a catalytic composition, polucy reaction of ethylene, acetic acid and oxygen in the presence of deposited palladium catalyst.

The most preferred catalyst for vinyl acetate production is the catalyst containing the metal gold and palladium dispersed on the surface of the carrier, such as silicon dioxide or aluminum oxide.

Famous deposited palladium-gold catalysts for vinyl acetate production are described in U.S. patents 3761513, 3775342, 3822308, 3939199, 4048096, 4087622, 4133962, 4902823, 5179056, 5179057, 5194417, 5314858, 5332710, and also listed in these patent references.

The usual way to obtain a catalyst for production of vinyl acetate, in the future acetate catalyst containing deposited on the carrier of gold and palladium, includes (1) a carrier impregnated with an aqueous solution of water-soluble gold compounds and palladium, (2) the deposition and fixation of water-insoluble compounds of gold and palladium on the catalyst carrier by contacting the impregnated catalyst carrier with an aqueous alkaline solution, capable of reaction with a water-soluble gold compounds and palladium with the formation of water-insoluble compounds of precious metals, (3) washing the treated catalysis is, and (4) the conversion of water-insoluble compounds of gold and palladium in available metals processing regenerating agent. (5) In some cases, the last stage involves the impregnation of the recovered catalyst with an aqueous solution of alkanoate alkali metal and drying.

On the activity and selectivity of the applied gold-palladium catalyst affects the physico-chemical form of the metal gold and palladium contained on the surface of the catalyst carrier.

In U.S. patent 4048096 describes a catalyst comprising an alloy of palladium and gold, distributed in the form of a membrane covering the external surface of the catalyst carrier such as porous silicon dioxide. The distribution of the palladium-gold alloy in the form of a covering sheath improves the product yield in a single pass per unit time per unit volume of the contact space (space-time-yeld) in a vapor-phase reaction of ethylene, acetic acid and oxygen upon receipt of vinyl acetate.

The selectivity of the palladium-gold catalyst in relation to carbon dioxide and make oxygen in the gas-phase reaction of ethylene, acetic acid and oxygen in the synthesis of vinyl acetate affects the degree and Oder alidating media.

Attempts to improve the uniformity of the distribution of gold and palladium on the catalyst carrier include manipulation of stages of preparation of the catalyst and/or the use of media with specific pores of various sizes. Practically useful improvements in the preparation of highly active catalysts for vinyl acetate production are discussed in U.S. patent 5314658 and 5332710. They describe the process of improving the distribution of palladium and gold on the media through manipulation at the stage of deposition, in which a water-soluble compounds of precious metals are fixed on the carrier surface in the form of water-insoluble compounds. In U.S. patent 5314858 fixing the precious metal on the carrier is achieved by using two separate stages of deposition, avoiding the use of a large excess of the fixing agent. In U.S. patent 5332710 describes the fixation of precious metals by immersing physically rotating the impregnated catalyst carrier in the reaction solution, at least in the initial period of deposition. A new process of rotation (rotational) immersion gives you the opportunity to obtain catalysts, in which the precipitated metals are more evenly distributed on the following properties of gold - palladium catalyst for vinyl acetate production.

In U.S. patent 5179056 and 5179057 links aimed at improving the palladium-gold catalyst for production of vinyl acetate from ethylene, acetic acid and oxygen. Described in these patents, the catalysts have a high activity due to the reduced content of sodium.

In these two patents, the sodium contained in the deposited gold and palladium, is restored during the preparation of the catalyst by washing palladium - and gold-containing media ion exchange in an aqueous solution of potassium compounds. In the above patents can be used sodium salts of precious metals, such as sodium-palladium tetrachlorid (Na2PdCl4). Added sodium found in processed precious metal carrier is subsequently removed by washing the aqueous ion-exchange solution.

Interest continues to develop catalytic compositions having improved combination of properties for the production of vinyl acetate.

Accordingly, an object of the present invention is to provide a palladium-gold catalyst composition with improved selectivity for carbon dioxide for the production of vinyl acetate from the applied vinyl acetate catalyst, essentially free from sodium and characterized in that it has a thin palladium-gold metal shell covering the surface of the media.

Another object of the present invention is a method of obtaining a deposited palladium-gold catalyst for production of vinyl acetate from ethylene, acetic acid and oxygen, in which all damage done and impregnating reagents are essentially free of sodium compounds potassium salts.

Other objects and advantages of the present invention will become clear from the following description and examples.

Description of the invention

Objects of the present invention is an improved method of producing a catalyst for production of vinyl acetate from ethylene, acetic acid and oxygen, including

(1) impregnating a porous catalyst carrier with an aqueous solution of water-soluble potassium palladium compounds and water-soluble potassium-gold compounds;

(2) the deposition of water-insoluble compounds of gold and palladium on the surface of the catalyst carrier with an aqueous solution of a basic potassium salt as fixing agent, and

(3) the restoration of water with improved selectivity for carbon dioxide.

Catalyst carrier selected from porous substrates, such as silicon dioxide, aluminum oxide, silicon dioxide/aluminum oxide or titanium oxide, in spherical form, in the form of pellets, Raschig rings and the like. To achieve the objective of the present invention it is preferable that the medium did not contain sodium or contained the minimum amount, i.e., the sodium content is less than 0.1 wt.% in relation to the media.

A typical example of the catalyst carrier is spheroidal porous silicon dioxide with a radius of spheres of 1-8 mm, a pore volume of 0.1-2 cm3/g and the area of the inner surface of 10-350 m2/, well-known commercial catalyst carrier under the trade name of KA-160, production Sud-Chemie, representing a spheroidal porous silicon dioxide size 5 mm

In one method of obtaining improved acetate catalyst according to the present invention, the catalyst carrier is first impregnated with an aqueous solution of water-soluble palladium potassium compounds and water-soluble gold-potassium compounds. Examples of suitable water-soluble compounds of gold and palladium are potassium-palladium tetrachlorid (K2PdCl

At stage (2) of the process according to the invention in accordance with the standard method of the impregnated catalyst carrier is treated with an aqueous solution of a basic potassium salt such as potassium silicate, potassium carbonate or potassium hydroxide. Using a processing solution of a basic potassium salt on the media capture compounds of palladium and gold, i.e., palladium hydroxide and the hydroxide of gold is deposited and contact the surface of the catalyst carrier.

The amount of basic potassium salt, is used as a fixing agent in stage (2) of the present invention, such that the ratio of metallic potassium to the anions of water-soluble precipitating compounds of precious metals was from about 1:1 to about 2:1, mainly from about 1.2: 1 to about 1.8:1. When processing the main solution of the potassium salt of water-soluble compounds deposited noble metals are transformed into water-insoluble compounds, which are, in base the response on the impregnated carrier, used in stage (2) of the present invention described in U.S. patent 5332710 (included in this description by reference) and is described as a process of "rotation (rotational) immersion".

Alternatively, the commit process is performed by immersing the impregnated carrier from step (1) in a solution of a basic potassium salt and rotating it in this solution or rotating it with the solution in the drum in an initial stage of deposition of water-insoluble compounds of noble metals. Rotation or tumbling of the media in the alkaline fixing solution are mainly within at least about 0.5 h, preferably for at least about 2.5 hours Processing by rotary dip you can have up to about 4 h, followed by exposure of the treated medium in the fixing solution for complete precipitation of compounds of noble metals.

You can use any rotary or drum equipment to ensure effective contact of the entire surface of the carrier with a solution of a basic potassium salt. The rotation should be easy enough to avoid losses of water-insoluble compounds of gold and palladium from powerscene thin layer of metallic gold and palladium, covering the surface of the catalyst carrier, with adjustable thickness, for example with a thickness of about 0.1-0.5 mm In accordance with the present invention thin gold-palladium layer covering the surface of the catalyst carrier, improves the selectivity in respect of carbon dioxide in the production of vinyl acetate from ethylene, acetic acid and oxygen.

Another process of fixation at the stage (2) in the present invention is a method of impregnation by capacity" ("incipient wetness"). According to this process, for processing media using an aqueous solution of a basic potassium salt in an amount equal absorption air-dried catalyst carrier from step (1). The reaction mixture was kept until the end of the deposition of insoluble compounds of gold and palladium.

Another method of fixation used in stage (2) of the present invention described in U.S. patent 5314858 included in this description by reference. In this method, stage (2) commit process is divided at least into two separate stages of processing of the carrier in an aqueous solution of a basic potassium salt.

After carrying out stage (2) fixation lubiaz deionized water to remove anions (e.g., chlorine ions), introduced by impregnation stage (1) of the present invention. After the catalyst carrier to be completely washed from the anions, the catalyst is dried at a temperature of approximately 150oWith in an inert atmosphere.

After stage (3) is completed, carry out stage (4), on which the catalyst carrier is in contact with a regenerating agent for the conversion of the fixed connections of gold and palladium in the shell of the particles of metallic gold and palladium covering the surface of the catalyst carrier. Examples of reducing agents are hydrazine, formaldehyde, ethylene, hydrogen and the like.

If the recovery of lead with a solution of hydrazine hydrate is added, the reaction is usually carried out at ambient temperature. When the recovery of lead in the gas phase ethylene or hydrogen, it is preferable to carry out the reaction at elevated temperature of about 100-200oC. To complete the conversion of water-insoluble compounds of gold and palladium in the free metal reducing agent is preferably used in excess. In the case of hydrazine, the weight ratio of hydrazine to the noble metal ranges from about 10:1 to conerto atmosphere at a temperature of approximately 150oC.

In the present invention, in some cases, the method of preparation of the catalyst may include additional procedure (stage (5)) to increase the selectivity of the catalyst for production of vinyl acetate. Gold-palladium catalyst obtained above, treated with an aqueous solution of alkanoate potassium and dried. The content of alkanoate potassium may be about 2-10 wt. % by weight of all of the obtained catalyst. Suitable alkanoate potassium include potassium salts of formic acid, acetic acid, propionic acid, butyric acid and the like.

The catalyst obtained in the present invention, mainly used in the method of producing vinyl acetate by contacting ethylene, acetic acid and oxygen or air with the catalyst at a temperature of about 100-200oC and a pressure of about 1-10 ATM. Usually the process is conducted with an excess of ethylene.

The catalyst obtained in the present invention, is characterized by high holding ability of metallic Pd and AU and has an improved selectivity in the production of vinyl acetate from ethylene, acetic acid and oxygen.

The catalyst of the present invention ocname commercial vinyl acetate catalysts. Distinctive, unique features of the process of preparation of the catalyst according to the invention are useful selective properties and use exclusively free from sodium potassium salts of derivatives at all stages of impregnation of the catalyst carrier.

The following examples illustrate the present invention. They represented the most common components and specific ingredients, it is possible that various modifications within the above description.

Used in the examples of the stirring tank reactor for the synthesis of vinyl acetate (VAST) is a Berty reactor or a continuously operating mixing tank reactor recirculation type with a constant conversion of oxygen (about 45%). The catalyst (62 cm3) load in the basket reactor, serves a certain measured amount of acetic acid, ethylene and oxygen in the diluent nitrogen, raise the temperature in the reactor with a heating jacket and measure the temperature above and below the catalyst. The reaction is complete after about 18 hours at a temperature at which is stored the conversion of oxygen to 45%. The reaction products determine gasochromic is but the invention of the standard method using potassium Pd-Au salts and potassium hydroxide as the fixing agent and the properties of this catalyst in the production of vinyl acetate from ethylene, acetic acid and oxygen in the reactor system is VAST.

250 cm3silicon dioxide in the form of spheroidal particles with a size of 5 mm (KA-160, Sud Chemie) impregnate 87,29 ml of an aqueous solution (5,13 g K2PdCl4and of 1.46 g KAuCl4) prior to treatment on capacity. The impregnated carrier is dried and then treated 87,29 ml of an aqueous solution of potassium hydroxide (2,62 g KOH), treated silicon carrier left for about 16 hours a Silicon carrier is washed to negative reactions to silver nitrate.

The silicon carrier is dried at 150oWith about 16 hours in a stream of nitrogen. Dry media restore 5% ethylene in nitrogen at 150o5 o'clock the Recovered carrier impregnated with 10 g COAs in 87,29 ml of water and the resulting catalyst is dried in a fluidized bed under 100oWith 1 h

Pd-Au catalyst contains 0.9 wt.% Pd, 0.32 wt.% Au, 8.2 wt.% COAs and 945 ppm Cl.

Pd-Au catalyst for production of vinyl acetate was tested in a VAST reactor and the results are presented in table a (catalyst I).

Example II.

This example illustrates the preparation of Pd-Au catalyst according to the invention by a standard method using potassium Pd-Au salts and potassium hydroxide as physicality in the reactor system is VAST.

Following the standard procedure of example I, use (K2PdCl4(5,13 g), KAuCl4(1.45 g), KOH (2.86 g) and Kaas (10 g).

After recovering ethylene Pd-Au catalyst contains 1.0 wt.% Pd, 0,41 wt.% Au, 7.5 wt.% COAs and 1000 ppm Cl.

Pd-Au catalyst for production of vinyl acetate was tested in a VAST reactor and the results are presented in table a (catalyst II).

In the long-term experience of aging (23 months) fully potassium catalyst maintains high activity and shows low selectivity for carbon dioxide in the production of vinyl acetate, in comparison with a commercial Pd-Au catalysts.

Example III.

This example illustrates the preparation of Pd-Au catalyst according to the invention by a standard method using potassium Pd-Au salts and potassium hydroxide as the fixing agent, and demonstrates the properties of the obtained catalyst proizvodstve of vinyl acetate from ethylene, acetic acid and oxygen in the reactor system is VAST.

Following the standard procedure of example I, use (K2PdCl4(5,13 g), KAuCl4(1.45 g), NaOH (2,04 g), COAs (10 g).

After recovery of ethylene, Pd-Au catalyst contains 1.1 the l tested in a VAST reactor and the results are presented in table a (catalyst III).

Example IV.

This example illustrates the preparation of Pd-Au catalyst according to the invention the standard method, using sodium Pd-Au salts and sodium hydroxide as the fixing agent, and demonstrates the properties of the resulting catalyst in the production of vinyl acetate from ethylene, acetic acid and oxygen in the reactor system is VAST.

Following the standard procedure of example I, using Na2PdCl4(1,65 g Pd), NaAuCl4(0.75 g Au), NaOH (up 1.766 g), COAs (10 g).

After recovery of ethylene, Pd-Au catalyst contains 0,92 wt.% Pd, of 0.38 wt.% Au, 7,98 wt.% COAs and 750 ppm Cl.

Pd-Au catalyst for production of vinyl acetate was tested in a VAST reactor and the results are presented in table a (the catalyst (IV).

Example V.

This example illustrates the preparation of Pd-Au catalyst according to the invention the standard method, using sodium Pd-Au salts and sodium hydroxide as the fixing agent, and demonstrates the properties of the resulting catalyst in the production of vinyl acetate from ethylene, acetic acid and oxygen in the reactor system is VAST.

Following the standard procedure of example I, using Na2PdCl4(1,65 g Pd), NaAuCl4(0.75 g Au), NaOH (wt.% Au, 7.5 wt.% COAs and 770 ppm Cl.

Pd-Au catalyst for production of vinyl acetate was tested in a VAST reactor and the results are presented in table a (catalyst V).

Example VI.

This example illustrates the preparation of Pd-Au catalyst according to the invention by a standard method using potassium Pd-Au salts and potassium silicate as a fixing agent, and demonstrates the properties of the resulting catalyst in the production of vinyl acetate from ethylene, acetic acid and oxygen in the reactor system is VAST.

Following the standard procedure of example I, use (K2PdCl4(1,65 g Pd), KAuCl4(0.75 g Au), K2SIO, SIS3(2.0 g), COAs (10 g).

After recovery of ethylene, Pd-Au catalyst contains 1.0 wt.% Pd, of 0.44 wt.% Au and 7.6 wt.% COAs and 665 ppm Cl.

Pd-Au catalyst for production of vinyl acetate was tested in a VAST reactor and the results are presented in table a (the catalyst (VI).

Example VII.

This example illustrates the preparation of Pd-Au catalyst according to the invention the standard method, using sodium Pd-Au salts and potassium silicate as a fixing agent, and demonstrates the properties of the resulting catalyst in the production of VI is the procedure of example I, use Na2PdCl4(1,65 g Pd), NaAuCl4(0.75 g Au), K2SiO3(2.0 g), COAs (10 g).

After recovery of ethylene, Pd-Au catalyst contains 0,98 wt.% Pd, of 0.42 wt.% Au, 7.2 wt.% COAs and 910 ppm Cl.

Pd-Au catalyst for production of vinyl acetate was tested in a VAST reactor and the results are presented in table a (catalyst VII).

Example VIII.

This example illustrates the preparation of Pd-Au catalyst according to the invention the standard method, using sodium Pd-Au salts and sodium silicate as the fixing agent, and demonstrates the properties of the resulting catalyst in the production of vinyl acetate from ethylene, acetic acid and oxygen in the reactor system is VAST.

Following the standard procedure of example I, using Na2PdCl4(1,65 g Pd), NaAuCl4(0.75 g Au), PA2SiO3(of 7.23 g), COAs (10 g).

After recovery of ethylene, Pd-Au catalyst contains 1.0 wt.% Pd, of 0.44 wt.% Au, 7.4 wt.% COAs and 765 ppm Cl.

Pd-Au catalyst for production of vinyl acetate was tested in a VAST reactor and the results are presented in table a (catalyst VIII).

Example IX.

This example illustrates the preparation of sodium silicate, as the fixing agent, and the properties of this catalyst in the production of vinyl acetate from ethylene, acetic acid and oxygen in the reactor system is VAST.

Following the example I, the silicon dioxide in the form of spheroidal particles with a size of 5 mm impregnate 87,29 ml of an aqueous solution (5,13 g K2PdCl4and of 1.46 g KAuCl4) before beginning humidity.

The impregnated carrier is treated with 300 ml of an aqueous solution of potassium silicate (2.0 g). Following the procedure described in U.S. patent 5332710 processed silicon carrier is placed in a rotary dip the bulb and rotate it to 2.5 hours a Silicon carrier is washed to negative reactions to silver nitrate.

The silicon carrier is dried and then restore 5% ethylene in nitrogen at 150o5 o'clock the Recovered carrier impregnated with 10 g COAs in 87,29 ml of water and the resulting catalyst is dried in a fluidized bed under 100oWith 1 h

Pd-Au catalyst contains 0,83 wt.% Pd, to 0.34 wt.% Au, 7.8 wt.% COAs and 430 ppm Cl.

Pd-Au catalyst for production of vinyl acetate was tested in a VAST reactor and the results are presented in table a (catalyst IX).

Example X.

This example illustrates the preparation of Pd-Au catalysis is potassium, as the fixing agent, and the properties of this catalyst in the production of vinyl acetate from ethylene, acetic acid and oxygen in the reactor system is VAST.

Following the procedure of rotary dip of example IX, using Na2PdCl4(1,65 g Pd), NaAuCl4(0.75 g Au), K2SIO, SIS3(2,09 g), COAs (10 g).

After recovery of ethylene, Pd-Au catalyst contains 0,94 wt.% Pd, to 0.19 wt.% Au, 7.5 wt.% COAs and 1165 ppm Cl.

Pd-Au catalyst for production of vinyl acetate was tested in a VAST reactor and the results are presented in table a (catalyst X).

From the comparative data of table a shows that Pd-Au catalyst prepared using only potassium reagents, has low selectivity for carbon dioxide in the production of vinyl acetate, compared with the corresponding Pd-Au catalyst prepared using one or more sodium compounds.

The comparative data in table a show that Pd-Au catalyst prepared using potassium chemicals, including potassium silicate as a fixing agent, such as a catalyst IX, detects exclusive, improved selectivity against the torus, improving its selectivity for carbon dioxide, compared with Pd-Au catalyst with thickened Pd-Au shell on the catalyst surface. Using the method rotary dip get thin Pd-Au shell, which helps to improve the selectivity in respect to carbon dioxide.

Another important advantage of using potassium silicate, as a fixing agent, in comparison with the potassium hydroxide is that the potassium silicate is an alkaline compound and does not damage the silicon carrier, as it makes a strong Foundation.

1. The way to obtain a catalyst for production of vinyl acetate from ethylene, acetic acid and oxygen, comprising impregnating a porous catalyst carrier with an aqueous solution of water-soluble palladium compounds and water-soluble gold compounds, deposition of water-insoluble compounds of palladium and gold on the surface of the catalyst carrier with an aqueous solution of a basic potassium salt, the recovery of water-insoluble compounds of palladium and gold to metallic palladium and gold, characterized in that at the stage of impregnation using an aqueous solution of water-soluble potassium palladium with listinin carrier is silica or alumina.

3. The method according to p. 1, characterized in that the catalyst carrier used in the form of spherical structures, tablets or Raschig rings.

4. The method according to p. 1, characterized in that the potassium palladium compound and potassium-gold connection at the stage of impregnation used in the same aqueous solution or, respectively, in separate aqueous solutions.

5. The method according to p. 1, characterized in that at the stage of impregnation of potassium palladium compound is potassium palladium tetrachlorid, potassium-gold compound is potassium tetrachloroaurate.

6. The method according to p. 1, characterized in that the basic potassium salt at the stage of precipitation of the salt is selected from the group consisting of potassium hydroxide, potassium carbonate, metasilicate potassium or the like.

7. The method according to p. 1, characterized in that the deposition and fixation of water-insoluble compounds of palladium and gold includes the process rotary dip.

8. The method according to p. 1, characterized in that the recovery of the compounds of palladium and gold carry ethylene or hydrazine as a reducing agent.

9. The method according to p. 1, characterized in that the catalyst is additionally impregnated with an aqueous solution of al zitat potassium.

11. The way to obtain a catalyst for production of vinyl acetate from ethylene, acetic acid and oxygen, comprising impregnating a porous catalyst carrier with an aqueous solution of water-soluble palladium compounds and water-soluble gold compounds, deposition of water-insoluble compounds of palladium and gold on the surface of the catalyst carrier with an aqueous solution of a basic potassium salt, the recovery of water-insoluble compounds of palladium and gold to metallic palladium and gold, characterized in that at the stage of impregnation using an aqueous solution of water-soluble potassium palladium compounds and water-soluble potassium gold compounds, the deposition is carried out by rotating immersion and restoration is carried out to obtain a palladium-gold metal shell thickness of about 0.1-0.5 mm on the surface of the media.

12. The way to obtain a catalyst for production of vinyl acetate from ethylene, acetic acid and oxygen, comprising impregnating a porous catalyst carrier with an aqueous solution of water-soluble palladium compounds and water-soluble gold compounds, deposition of water-insoluble compounds of palladium and gold on powiatowego compounds of palladium and gold to metallic palladium and gold, characterized in that at the stage of impregnation using an aqueous solution of water-soluble potassium palladium compounds and water-soluble potassium-gold compounds and recovery of lead to obtain a catalyst containing metallic palladium in the amount of about 0.4-2.5 wt. % and metallic gold in an amount of about 0.1 to 1.0 wt. % relative to the weight of the entire catalyst.

13. The method according to p. 12, characterized in that the impregnation is used compounds essentially free of sodium.

14. Catalytic composition for the production of vinyl acetate from ethylene, acetic acid and oxygen, obtained by the method according to any of paragraphs. 1-13, characterized in that it has a shell thickness of 0.1-0.5 mm, and the selectivity for CO2at least 9%.

 

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