Heterogeneous bimetallic palladium-gold catalyst to obtain vinyl acetate and method thereof

 

(57) Abstract:

The invention relates to a method for heterogeneous bimetallic palladium-gold catalyst to obtain a vinyl acetate from ethylene, acetic acid and oxygen. The method includes obtaining a catalyst precursor by impregnation of a porous catalyst carrier with a solution of palladium compounds and recovering the obtained compound of palladium with the formation of the first "korechkovogo" dispersed coating of colloidal palladium metal on the surface of the catalyst carrier, the impregnated catalyst precursor ORGANOMETALLIC compound of gold in an organic solvent and recovering the obtained compound of gold before formation of the second "korechkovogo" dispersed coating of colloidal metallic gold on the surface of the catalyst carrier, obtaining bimetallic palladium-gold catalyst. The resulting catalyst has a high degree of retention of metallic gold and possesses durability and selectivity over a long period of synthesis of vinyl acetate. 12 C.p. f-crystals, 5 PL.

The invention relates to the production of vinyl acetate by vzaimozachetnomu Pd-Au catalyst on the media to produce vinyl acetate.

Known industrial method of producing vinyl acetate by reaction of ethylene, acetic acid and oxygen in the presence of a catalyst on a carrier containing palladium.

The preferred type of catalyst receipt of vinyl acetate is a catalyst containing metallic palladium and metallic gold distributed on the surface of carrier substances, such as silicon dioxide or aluminum oxide.

References to the prior art, which are described palladium-gold catalysts on the media to produce vinyl acetate, include the following U.S. patents: 3761513; 3775342; 3822308; 3939199; 4048096; 4087622; 4133962; 4902823; 5194417; 5314858, and cited in these references are included in the present description.

The activity and selectivity of palladium-gold catalyst on the carrier depend on the physico-chemical form of metallic palladium and gold contained in the substance of the catalyst carrier.

In U.S. patent 4048096 described catalyst, which contains alloy of palladium and gold, distributed in the form of a "crust" that covers the external surface area of the catalyst carrier such as porous silicon dioxide. "Korotkova distribution of the alloy of palladium and gold obespechivayuschie ethylene, oxygen and acetic acid.

The selectivity of the palladium-gold catalyst obtain vinyl acetate also depends on the degree and uniformity of distribution of metallic palladium and gold on the outer and/or inner surface of the porous material of the catalyst carrier, as, for example, the selectivity for carbon dioxide and the conversion of oxygen by the interaction of ethylene, oxygen and acetic acid in the vapor phase.

The objective of this invention is to provide a catalytic composition of palladium and gold on the media with improved activity and selectivity for receipt of vinyl acetate from ethylene, oxygen and acetic acid.

Another objective of this invention is to provide a catalyst on the carrier to obtain vinyl acetate, which is applied separately layered coating dispersed colloidal metallic palladium and metallic gold.

Another objective of this invention is to provide a palladium-gold catalyst on the carrier to obtain vinyl acetate, which has high fixation of gold and which has durability and selectivity for a long time to get the blame who is creating a method of producing catalyst on the carrier to obtain vinyl acetate, which has a separately applied "crackovia coatings dispersed colloidal metallic palladium and metallic gold on the surface of the media.

Other objectives and advantages of the present invention will become apparent from the description and examples.

The task of the present invention are achieved by a method of producing a catalyst for the synthesis of vinyl acetate from ethylene, acetic acid and oxygen, which includes:

1) formation of the catalyst precursor by impregnation of the porous catalyst carrier with a solution of palladium compounds and recovery of the palladium compounds with the formation of the first "korechkovogo" dispersed coating of colloidal palladium metal on the surface of the catalyst carrier, and

2) the impregnation of the catalyst precursor with a solution of ORGANOMETALLIC compound of gold in an organic solvent, and recovering the compound of gold before the second "korechkovogo" dispersed coating of colloidal metallic gold on the surface of the catalyst carrier with the formation of bimetallic palladium-gold catalyst, which has an improved selectivity for the dioxide of plastics technology: turning & the LASS="ptx2">

Catalyst carrier selected from porous substrates, such as silicon dioxide, aluminium oxide, aluminium silicate, titanium dioxide and zirconium dioxide in the form of spheres, pellets, Raschig rings, etc.

Typical catalyst carrier is a porous spheres of silicon dioxide, which have a radius of 1.8 mm, a pore volume of 0.1-2 ml/g and the area of the inner surface of 10-350 m2/2. Media industrial catalyst is in the public domain, as, for example, 5 mm spheres of silicon dioxide, having a trademark KA-160 and sold by the company süd-Chemie.

In one method of obtaining an improved catalyst of the present invention for the synthesis of vinyl acetate catalyst carrier is first impregnated with an aqueous solution of palladium compounds, soluble in water. Suitable compounds of divalent palladium include palladium chloride, palladium nitrate, palladium sulfate, sodium palladium tetrachloride, etc.

The volume of the aqueous impregnating solution is preferably about 95-100% of the absorptive capacity of the catalyst carrier.

The impregnated catalyst carrier treated with an aqueous solution of a basic salt of an alkali metal, such as silicate of AutoRAE enough to secure the connection of palladium on the catalyst carrier, that is, the palladium hydroxide precipitates and is introduced to the surface of the catalyst carrier.

In another method of preparation of the catalyst the catalyst carrier is first impregnated with a solution of at least one ORGANOMETALLIC palladium compounds in an organic solvent. Suitable ORGANOMETALLIC compounds include palladium acetylacetonate, palladium acetate, bis (3-allyl) -palladium (O),3-allyl (3-cyclopentadienyl) palladium(O),3-allyl (1, 5cyclooctadiene) palladium (o) tetrafluoroborate etc.

Organic solvents that can be used for dissolving the ORGANOMETALLIC palladium compounds include pentane, hexane, cyclohexane, heptane, octane, isooctane, naphtha, naphthenic hydrocarbons, benzene, chlorobenzene, nitrobenzene, dichloromethane, etc.

In the patent EP 0089252 disclosed a method of producing a catalyst, which consists in the impregnation of the carrier compound of palladium, the firing in the presence of oxygen, the processing of reducing agent and subsequent introduction of a halogenated compound of gold and restoring it. Halogenated compound of gold is an inorganic water-soluble gold. This from the investments and washing, required when using solutions of inorganic gold (such as soloconsolidation acid used in the above method).

Using a solution of ORGANOMETALLIC palladium compounds in an organic solvent instead of the aqueous solution of palladium compounds, soluble in water, have a significant advantage. After impregnation of the catalyst carrier with a solution of ORGANOMETALLIC compound of palladium is not required fixing processing basic salt of an alkali metal. The exception being committed noble metal prevents metal loss which usually occur during the fixing process and stages of leaching. For optimum activity and selectivity in the synthesis of vinyl acetate need a high content of noble metals in the catalyst.

After a stage of impregnation of the catalyst carrier connection palladium catalyst carrier handle regenerating agent to make the connection palladium "Korotkova" coating of colloidal particles of metallic palladium on the surface of the catalyst carrier. Examples of reducing agents are hydrazine, what about the recovered metal palladium, impregnated with a solution of at least one ORGANOMETALLIC compound of gold in an organic solvent. Suitable ORGANOMETALLIC compounds include gold trimethylsilylimidazole, trimethylsilylamodimethicone, dimethylacetal gold, triacetate gold, etc.

For impregnation with a solution of ORGANOMETALLIC compound of gold you can use any suitable organic solvent of the above for ORGANOMETALLIC palladium compounds.

After impregnation stage ORGANOMETALLIC compound of gold to restore the second "korechkovogo" coating of colloidal particles of metallic gold on the surface of the catalyst carrier. The exception being committed to recovery is especially important with the introduction of colloidal metallic gold in the catalyst synthesis of vinyl acetate. Gold is more difficult to fix a basic salt of an alkali metal, so that the method of fixation is a weak and inconsistent holding gold during the preparation of the catalyst. The method of preparation of the catalyst of the present invention for the synthesis of vinyl acetate provides a strong and appropriate holding of gold in CA is lazette use the original reagents palladium and gold in such quantities, which provide content about 1-10 g of metallic palladium and about 1-10 g of metallic gold in 1 liter of the finished catalyst.

The catalyst according to the invention may contain palladium metal of about 0.2 to 2.5 wt.% and metallic gold approximately 0.2 to 2.5 wt.%. The weight ratio of palladium: gold may vary between about 0.5 and 10:1.

The method of preparation of the catalyst of the present invention optionally may include an additional procedure in order to increase the selectivity of the catalyst to obtain vinyl acetate. Palladium-gold catalyst obtained as described above, treated with an aqueous solution of acetate of an alkali metal, such as palladium acetate, and then dried. The content of alkali metal acetate may be in the range of about 2-10 wt.% based on the weight of the finished catalyst.

Significant advantages of the present invention are achieved by a composition of heterogeneous bimetallic palladium-gold catalyst for the synthesis of vinyl acetate from ethylene, oxygen and acetic acid, which comprises a porous catalyst carrier, which contains the first "Korotkova" dispersed coating their colloidal metallic gold in the form of a layer on the surface of the catalyst carrier.

Typically, the catalyst of the present invention is used in the synthesis of vinyl acetate by contacting ethylene, acetic acid and oxygen or air with the catalyst at temperatures of about 100-200oC and a pressure of about 0.1-1 MPa. Usually the process is carried out in an excess of ethylene.

The preferred catalyst of the present invention is characterized by a high level of retention of the metals palladium and gold, it has the durability and high selectivity to vinyl acetate for a long period upon receipt of vinyl acetate from ethylene, oxygen and acetic acid.

The catalyst of the present invention may provide efficient production of vinyl acetate with a lower output of carbon dioxide than traditional Bayer catalysts for the synthesis of vinyl acetate, of the type described in UK patent 1246015, which is included as reference material.

The following additional examples illustrate the present invention. Components and special reagents are presented as typical, and can be implemented in various modifications with regard to the preceding disclosure within the scope of the invention.

In these Examples, the s palladium and gold, and they were compared with palladium-gold catalysts Bayer type for the synthesis of vinyl acetate from ethylene, oxygen and acetic acid.

Palladium-gold catalysts designated in the Examples as catalysts a-E were prepared from a mixture of Na2dl4/ triacetate gold on silica gel.

Palladium-gold catalysts designated in the Examples as catalysts F and G were prepared from a mixture of Na2dl4/PH3Rain2Si3on silica gel.

Palladium-gold catalysts designated in the Examples as catalysts H and I were prepared from a mixture of Na2PdCl4/Me2AuOSiMe3on silica gel.

In these Examples, the reactor for the synthesis of vinyl acetate (RSV) tank mixing is a reactor Bertie or reactor with the capacity of continuous mixing of the recirculating type, which operates at a constant conversion of oxygen (about 45%). The catalyst (62 ml) are loaded onto the grid of the reactor, add a measured quantity of acetic acid, ethylene and oxygen in the atmosphere of nitrogen, and the reactor is brought to a temperature of experience with heating jacket, and the temperature measured above and below the layer katalia oxygen 45%. The products analyzed by the method of gas-phase chromatography. Selectivity for carbon dioxide when testing the same catalyst has a tendency to a slight increase in unit RSV compared to the microreactor synthesis of vinyl acetate, because the product is the vinyl acetate is recycled to the catalyst during the reaction.

The microreactor synthesis of vinyl acetate (MSA) in the Examples is a reactor with a stream of the piston type which operates at a constant temperature. The reactor MSA is a tube of stainless steel length of 914 mm and an inner diameter of 16 mm and located concentrically pocket for thermocouples with a diameter of 3 mm Reactor equipped with a heating jacket through which circulates hot water and steam. A sample of catalyst (30 ml), dilute with medium to volume of 150 ml and loaded into the reactor. On top of the mixture, the catalyst/carrier placed 30 ml of media. After a single pass of a mixture of ethylene, oxygen and acetic acid in a nitrogen atmosphere or at a constant temperature, or at a constant conversion of oxygen products analyzed by the method of gas-phase chromatography.

EXAMPLES

Example 1

This example illustrates the obtaining of the triacetate is by heating HAuCl4in an aqueous solution of sodium carbonate at pH 8 for 3 hours. The obtained red solution is filtered, the precipitate of hydroxide gold washed with water and dried in air. The hydroxide of gold dissolved in glacial acetic acid when heated, obtaining a solution of the triacetate of gold.

Example 2

This Example illustrates a composition previously restored palladium on silicon dioxide of Na2PdCl4used as an intermediate substance in the synthesis of palladium-gold catalysts of the present invention. Spheres of silicon dioxide with a diameter of 5 mm in 250 ml (KA-160, the company süd-Chemie) impregnated with an 82.5 ml of an aqueous solution of Na2PdCl4(7 g of palladium per 1 liter of the carrier) in accordance with plaguemaster media. Impregnated carrier handle 283 ml of an aqueous solution (50 wt.% NaOH/H2About; 120% of the amount required for the conversion of the metal salt in the form of hydroxide). Fixed carrier rotate in a rotary evaporator for 2.5 h at a speed of about 5 rpm

After fixing the processed media continuously washed with distilled water to remove chloride ions to the negative reaction of water leaching on the silver nitrate.main stream of nitrogen at a temperature of approximately 150oC. the Dried media restore a mixture of 5% ethylene in nitrogen at 150oC for 5 h

Example 3

This example illustrates the receipt of palladium-gold catalysts of the present invention and the properties of these catalysts in the synthesis of vinyl acetate from ethylene, oxygen and acetic acid in systems RSV, MSV compared with palladium-gold catalysts firm Bayer.

The catalyst is a Hydroxide of gold AU(OH)3(0.88 g) in 35 ml of acetic acid are heated in a flask for 2 h at 60oWith getting clear red-brown solution of the triacetate of gold. This solution of 35 ml added to 100 ml of previously restored palladium on silica (from Example 2) at 60oSince in the reaction flask and spend soaking for about 30 minutes. The solvent medium is removed at 60oWith the vacuum. The treated media (silicon dioxide) restore a mixture of 5% ethylene in nitrogen at 150oC for 5 hours the catalyst is impregnated with a solution of 4 g of potassium acetate in 33 ml of water and then dried in the dryer fluidized bed under 100oC for 1 h to obtain a palladium-gold catalyst A.

The catalyst Century, Followed by the methods of the notes, receiving a palladium-gold catalyst Century

Catalyst C. Followed by the method of preparation of the catalyst A, except that using 0.5 g of a hydroxide of gold in 35 ml of acetic acid, getting a palladium-gold catalyst C.

Catalyst D. Follow the method of preparation of the catalyst A, except that using 0.25 g of hydroxide of gold in 35 ml of acetic acid, getting a palladium-gold catalyst D.

The catalyst that is Followed by the method of preparation of the catalyst A, except that the use of 0.88 g of hydroxide of gold in 17 ml of acetic acid and 45 ml of pre-restored palladium on silica (from Example 2), receiving the palladium-gold catalyst E.

Catalysts A-D experience in the system RSV in comparison with palladium-gold catalysts firm buyer upon receipt of vinyl acetate from ethylene, oxygen and acetic acid.

Comparative data are summarized in table 1. In the catalysts A-D activity increases as you increase the ratio of gold to palladium. For catalysts A-D has a tendency to generate less carbon dioxide than for catalysts of the firm Bayer. The catalyst And has an improved selektivnoi 0,06), than industrial Bayer catalyst.

Catalysts a-E have in the system MSA in comparison with palladium-gold catalyst of the firm Bayer upon receipt of vinyl acetate.

In order to evaluate the catalyst activity, record the temperature at the midpoint of the shell installation at a fixed conversion rate of oxygen (about 45%). The lowered temperature of the shell indicates increased activity of the catalyst at a constant oxygen consumption.

These comparative data are summarized in table 2. For catalysts D and E, there is high selectivity for carbon dioxide and reduced catalytic activity than the catalysts A-C. the Catalysts a-C have improved selectivity for carbon dioxide and increased catalytic activity compared with palladium-gold Bayer catalyst.

Using the display method of x-ray radiation SEM-EDX shows that the catalysts a-E metal palladium dispersed on the outer surface kremmidiotis media in the form of "korechkovogo" coverage.

Metallic gold is dispersed mainly on the outer surface kremmidiotis noticeany surface kremmidiotis media.

Example 4

This example illustrates the receipt of palladium-gold catalysts of the present invention and the properties of these catalysts in the synthesis of vinyl acetate from ethylene, oxygen and acetic acid in systems RSV, MSV compared with palladium-gold catalysts firm Bayer.

Catalyst F catalyst G. a Solution of 1 g Ph3PAuCH2SiMe3in 34 ml of methylene chloride is added to 90 ml of pre-restored palladium on silica (from Example 2) in a reaction flask and spend soaking for about 30 minutes. Dissolving medium (solvent) is removed in vacuum. The treated media (silicon dioxide) restore a mixture of 5% ethylene in nitrogen at 120oC for 5 hours the catalyst was washed with toluene and dried at 120oC in vacuum for approximately 16 hours, the Catalyst was impregnated with a solution of 3.8 g of potassium acetate in 30 ml of water and then dried in the dryer fluidized bed under 100oC for 1 h to obtain a palladium-gold catalyst F. the Catalyst G was prepared in the same way.

The Catalyst N. A solution of 0.38 g IU2uOSi3in 16 ml of hexane is added to 45 ml of pre-restored palladium on di the environment is removed in vacuum. The treated media (silicon dioxide) restore a mixture of 5% ethylene in nitrogen at 120oC for 5 hours the catalyst is impregnated with a solution of 1.8 g of potassium acetate in 15 ml of water and then dried in the dryer fluidized bed under 100oC for 1 h to obtain a palladium-gold catalyst N.

Catalyst I. Follow the method of preparation of the catalyst N, except that use 32 ml hexane solution Me2AuOSiMe3(0,85 g) and 90 ml of pre-restored palladium on silica (from Example 2) to obtain a palladium-gold catalyst I.

Catalysts F-I feel in MSA in comparison with palladium-gold catalyst of the firm Bayer upon receipt of vinyl acetate.

These comparative data are summarized in table 3. For catalysts F-I observed improved selectivity for carbon dioxide in comparison with the catalyst of the firm Bayer. Catalyst I worked at a much lower temperature shell (higher catalytic activity than the catalyst of the firm Bayer. Catalysts H and I have a high degree of retention of metallic gold, respectively, 86 and 98%. Catalysts F and G have a degree of retention of Zolotoye company Bayer upon receipt of vinyl acetate.

These comparative data are summarized in table 4. Catalysts F and I have improved selectivity for carbon dioxide and increased catalytic activity compared to Bayer catalyst.

Using the display method of x-ray radiation SEM-EDX shows that the catalyst I have "Korotkova" distribution of metallic palladium and gold on the outer surface of the silicon dioxide. The catalyst F palladium metal dispersed in the form of "korechkovogo" coating on the outer surface of the silicon dioxide. Metallic gold is dispersed mainly on the outer surface kremmidiotis media in the form of the second "korechkovogo" cover, and the lower part of the metallic gold dispersed on the inner surface kremmidiotis media.

Catalyst G experience in MSV continuously within 7 days upon receipt of vinyl acetate. The purpose of this long period of testing was to determine the durability of the catalyst and selectivity of the catalyst according to the invention over a long period of time.

These comparative data are summarized in table 5. From these data it is seen that the catalyst nastojasih the s in tables 1-5, expressed in percent.

1. The method of producing catalyst to obtain a vinyl acetate from ethylene, acetic acid and oxygen, including 1) the formation of the catalyst precursor by impregnation of the porous catalyst carrier with a solution of palladium compounds and restore it, 2) the impregnation of the catalyst precursor solution of the compound of gold and restoration, characterized in that after impregnation of the carrier in stage 1) carry out the restoration of the compounds of palladium with the formation of the first "korechkovogo" dispersed coating of colloidal palladium metal on the surface of the catalyst carrier, and in stage 2) as a solvent for impregnation of the catalyst precursor using a solution of ORGANOMETALLIC compound of gold in an organic solvent and carry out the restoration of the compounds obtained gold to the formation of the second "korechkovogo" dispersed coating of colloidal metallic gold on the surface of the catalyst carrier, obtaining bimetallic palladium-gold catalyst.

2. The method according to p. 1, characterized in that the impregnation of the catalyst carrier at the stage (1) conduct Westboro to recovery.

3. The method according to p. 1, characterized in that the impregnation of the catalyst carrier at the stage (1) is conducted with a solution of ORGANOMETALLIC palladium compounds in an organic solvent.

4. The method according to p. 1, characterized in that the ORGANOMETALLIC compound of gold at the stage (2) is the triacetate of gold.

5. The method according to p. 1, characterized in that the ORGANOMETALLIC compound of gold at the stage (2) is dimethylacetal gold.

6. The method according to p. 1, characterized in that the ORGANOMETALLIC compound of gold at the stage (2) is trimethylsilylimidazole.

7. The method according to p. 1, characterized in that the ORGANOMETALLIC compound of gold at the stage (2) is trimethylsilylamodimethicone.

8. The method according to p. 1, characterized in that in a finished catalyst containing metallic palladium is about 0.2 to 2.5 weight. % and the content of metallic gold is 0.2 to 2.5 weight. % by weight of the catalyst.

9. The method according to p. 1, characterized in that the catalyst carrier is a substrate of silicon dioxide.

10. The method according to p. 1, characterized in that the catalyst carrier is a substrate of aluminum oxide.

12. The method according to p. 1, characterized in that the finished catalyst for improving the selectivity in the production of vinyl acetate is additionally impregnated with an aqueous solution of alkali metal acetate and then dried.

13. The method according to p. 12, characterized in that the alkali metal acetate using potassium acetate.

 

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