Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
  • B01J37/341—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation
  • B01J37/343—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation of ultrasonic wave energy
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/48—Silver or gold
  • B01J23/52—Gold
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
  • B01J23/8926—Copper and noble metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/0201—Impregnation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/04—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides onto unsaturated carbon-to-carbon bonds
  • C07C67/05—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides onto unsaturated carbon-to-carbon bonds with oxidation
  • C07C67/055—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides onto unsaturated carbon-to-carbon bonds with oxidation in the presence of platinum group metals or their compounds

Definitions

• the invention relates to new and improved catalysts comprising metallic palladium and gold, which are useful for the production of vinyl acetate by reaction of ethylene oxygen and acetic acid.
• U.S. Patent No. 5,322,710 issued July 26, 1994, to Nicolau et al., discloses a method of preparing a catalyst useful for the production of vinyl acetate by reaction of ethylene, oxygen and acetic acid, comprising impregnating a porous support with water soluble salts of palladium and gold, fixing the palladium and gold as insoluble compounds on the support by immersing and tumbling the impregnated support in a reactive solution for at least ! _ hour to precipitate such compounds, and subsequently reducing the compounds to free metallic form.
• U.S. Patent No. 5,347,046, issued September 13, 1994 to White et al. discloses catalysts for the production of vinyl acetate by reaction of ethylene, oxygen, and acetic acid, comprising a palladium group metal and/or a compound thereof, gold and/or a compound thereof, and copper, nickel, cobalt, iron, manganese, lead or silver, or a compound thereof, preferably deposited on a support material.
• a catalyst effective for the production of vinyl acetate by reaction of ethylene, oxygen and acetic acid comprising a porous support on the porous surfaces of which is deposited catalytically effective amounts of metallic palladium and gold, and optionally, one or more additional catalytically active metals such as copper, is prepared by steps comprising impregnating the support with one or more aqueous solutions of water-soluble compounds of the metals, fixing the metals on the support as water-insoluble compounds in one or more fixing steps by reaction with an appropriate alkaline compound, at least one of such fixing steps being carried out in a solution of the alkaline compound in which the impregnated support is immersed, while sonicating, i.e., applying ultrasound waves to, such solution, and reducing the water-insoluble compounds of the catalytically active metals to their free metallic form.
• Catalysts may be prepared by the method of this invention utilizing sonication in the fixing step, which are capable of implementing the production of vinyl acetate by reaction of ethylene, oxygen and acetic acid with relatively low selectivities to C0 2 and/or heavy ends such that the use of such catalysts may result in greater vinyl acetate productivity than when any of various catalysts known in the art is employed.
• the catalyst support material is composed of particles having any of various regular or irregular shapes, such as spheres, tablets, cylinders, rings, stars, or other shapes, and may have dimensions such as diameter, length, or width of about 1 to about 10 mm., preferably about 3 to 9 mm. Spheres having a diameter of about 4 to about 8 mm. are preferred.
• the support material may be composed of any suitable porous substance, e.g., silica, alumina, silica-alumina, titania, zirconia, silicates, aluminosilicates, titanates, spinel, silicon carbide, or carbon and the like.
• the support material may have a surface area within the range, for example, of about 10 to about 350, preferably about 100 to about 200 m 2 /g, an average pore size in the range, for example, of about 50 to about 2000 angstroms, and a pore volume in the range, for example, of about 0.1 to 2, preferably about 0.4 to about 1.2 ml/g.
• the support material may be treated to deposit catalytic amounts of palladium, gold, and any additional catalytically active metal, if any, on the porous surfaces of the support particles. Any of various methods for accomplishing this purpose may be used, all of which involve simultaneous or separate impregnations of the support with one or more aqueous solutions of water-soluble compounds of the catalytically active metals.
• Palladium(II)chloride, sodium palladium(II)chloride, potassium palladium(II)chloride, palladium(II)nitrate or palladium(II)sulfate are examples of suitable water-soluble palladium compounds; an alkali metal, e.g., sodium or potassium salt of auric(III)chloride or tetrachloroauric(III)acid can be used as the water-soluble gold compound; and, if, for example, copper is utilized as an additional catalytically active metal, cupric nitrate trihydrate or hexahydrate, cupric chloride (anliydrous or dihydrate), cupric acetate monohydrate, cupric sulfate (anhydrous or pentahydrate), cupric bromide, or cupric formate (anhydrous or tetrahydrate), can be used as the water-soluble copper compound.
• an alkali metal e.g., sodium or potassium salt of auric(III)chlor
• An alkali metal salt of tetrachloroauric(III)acid, sodium palladium(II)chloride and cupric nitrate trihydrate or cupric chloride are preferred salts for impregnation of gold, palladium and copper respectively because of their good water solubility.
• the impregnations of the support material with solutions of water-soluble salts of the catalytically active metals may be effected by any method known to those skilled in the art. Preferably, however, such impregnations are accomplished by the
• each impregnation may contain water-soluble compound equivalent to all or only a portion of the amount of one or any combination of the catalytically active metals desired in the final catalyst, as long as the amounts of such metals in the total of the impregnating solutions absorbed are equal to the final desired amounts.
• the impregnations are such as to provide, for example, about 1 to about 10 grams of elemental palladium; for example, about 0.5 to about 10 grams of elemental gold; and, for example, if copper is utilized as an additional catalytically active metal, about 0.5 to about 3.0 grams of elemental copper per liter of finished catalyst, with the amount of gold being from about 10 to about 125 weight percent based on the weight of palladium.
• the metal is "fixed," i.e., precipitated, as a water- insoluble compound such as the hydroxide, by reaction with an appropriate alkaline compound, e.g., an alkali metal hydroxide, silicate, borate, carbonate or bicarbonate, in aqueous solution.
• an appropriate alkaline compound e.g., an alkali metal hydroxide, silicate, borate, carbonate or bicarbonate
• Sodium and potassium hydroxides are preferred alkaline fixing compounds.
• the alkaline compound should be in an amount of, for example, about 1 to about 2, preferably about 1.1. to about 1.8 times the amount necessary to completely precipitate the cations of the catalytically active metals present in the water-soluble salts.
• At least one of such fixing steps is accomplished with the aid of sonication, i.e., the application of ultrasound waves to a solution of the alkaline fixing compound in which is immersed the support material impregnated with at least one water- soluble salt of a catalytically active metal.
• sonication i.e., the application of ultrasound waves to a solution of the alkaline fixing compound in which is immersed the support material impregnated with at least one water- soluble salt of a catalytically active metal.
• one or all of the fixing steps may be carried out utilizing sonication.
• the fixing steps other than those employing sonication may be done by the incipient wetness method wherein the impregnated support is dried, e.g., at a temperature of about 150°C for one hour, contacted with an amount of solution of the alkaline material equal to about 95-100% of the pore volume of the support, and allowed to stand for a period of about l A hour to about 16 hours; or the roto-immersion method wherein the impregnated support without drying is immersed in a solution of the alkaline material and is rotated and/or tumbled during at least the initial period of precipitation such that a thin band of the precipitated water-soluble compound is formed at or near the surface of the support particles.
• the rotation and tumbling may be carried out, for example, at about 1 to about 10 rpm for a period of, for example, at least about 0.5 hour, preferably about 0.5 to about 4 hours.
• the contemplated roto-immersion method is disclosed in previously cited U.S.
• Patent No. 5,332,710 the entire disclosure of which is incorporated herein by reference.
• the fixed, i.e. precipitated compounds of palladium, gold, other catalytically active metals, if any, such as copper, may be reduced, for example, in the vapor phase with ethylene, e.g., about 5% in nitrogen at about 150°C for about 5 hours after first washing the catalyst containing the fixed metal compounds, until it is free of anions such as halide, and drying, e.g., at about 150°C for about 1 hour, or such reduction may be accomplished before washing and drying in the liquid phase at room temperature with sonication with an aqueous solution of hydrazine hydrate wherein the excess of hydrazine over that required to reduce all the metal compounds present on the support is in the range, for example, of about 8: 1 to about 15:1, followed by washing drying.
• reducing agents and means for reducing the fixed metal compounds present on the support may be employed as conventional in the art.
• the reduction may be carried out after each fixing step or after the total of the metallic elements have been fixed on the support.
• sonication may also be utilized in one or more reduction steps, e.g., by applying the sonication to water containing immersed therein the catalyst support containing the fixed (water-insoluble) metal compounds and through which is bubbled 5% ethylene in nitrogen, or the sonication may be applied to an aqueous solution of hydrazine hydrate containing immersed therein the catalyst support containing the fixed metal compounds.
• a simple example of carrying out the foregoing catalyst preparation includes a single impregnation of the support with water soluble salts such that the impregnated support contains the palladium and gold desired in the final catalyst, a single fixing step by immersing the impregnated support in a solution of the alkaline compound while applying sonication to the solution, and a single reducing step whereby the fixed palladium and gold are reduced to their free metallic form.
• a "separate fix” method may be used to fix the catalytically active metallic elements on the support and reduce the water-insoluble metal compounds to the desirable free metallic form.
• the support is first impregnated with an aqueous solution of a water-soluble compound of palladium and of any additional catalytically active metal, if any, other than gold, e.g. copper, by incipient wetness, and the palladium, and additional metal, if present, are then fixed by treatment with an alkaline fixing solution utilizing sonication.
• the catalyst is then dried and separately impregnated with a solution of a soluble gold compound having the amount of elemental gold desired in the catalyst, and the gold is fixed by treatment with an alkaline fixing solution by sonication. If a hydrocarbon such as ethylene, or hydrogen is to be used in the vapor phase as reducing agent, the catalyst containing the fixed metal compounds is washed until it is free of dissolved anions, dried , and reduced with ethylene or other hydrocarbon, or hydrogen, as previously described.
• a hydrocarbon such as ethylene, or hydrogen
• the catalyst containing the fixed metal compounds is treated with an aqueous solution of excess hydrazine hydrate with sonication before washing and drying to reduce the metal compounds to the free metals, and the catalyst is then washed and dried as described. Sonication may be utilized in the reduction step as described previously.
• the catalyst containing palladium, gold and any additional catalytically active metal, if any, e.g., copper, in a free metallic form, deposited on a support material is prepared by any of the foregoing methods, it is advantageously further impregnated with a solution of an alkali metal acetate, preferably potassium or sodium acetate, and most preferably potassium acetate.
• the catalyst is then dried such that the finished catalyst contains, for example, about 10 to about 70, preferably about 20 to about 60 grams of alkali metal per liter of finished catalyst.
• a stream of gas which contains ethylene, oxygen or air, acetic acid, and desirably an alkali metal acetate, is passed over the catalyst.
• the composition of the gas stream can be varied within wide limits, taking into account explosive limits.
• the molar ratio of ethylene to oxygen can be about 80:20 to about 98:2
• the molar ratio of acetic acid to ethylene can be about 2:1 to about 1 :10, preferably about 1 : 1 to about 1 :5
• the content of gaseous alkali metal acetate can be about 1-100 ppm, relative to the acetic acid employed.
• the alkali metal acetate may be conveniently added to the feed stream as a spray of an aqueous solution of such acetate.
• the gas stream also can contain other inert gases, such as nitrogen, carbon dioxide and/or saturated hydrocarbons.
• Reaction temperatures which can be used are elevated temperatures, preferably those in the range of about 150-220°C.
• the pressure employed can be a somewhat reduced pressure, normal pressure or elevated pressure, preferably a pressure of up to about 20 atmospheres gauge.
• the sonication was carried out in a 250-ml round bottom sonication flask (Misonix) with three 24/40 side necks using an XL2020 Sonicator Programmable Ultrasonic Processor (Misonix) fitted with a flat-tipped tapped disrupter horn (titanium alloy, 3/4" diameter).
• the ultrasound waves emitted by the sonicator had a frequency of about 20 kHz. Sonication was carried out for about 1 hour to about 20 hours.
• the sonication may be effected by any of the various types of sonicators known in the art, several of which are commercially available.
• the support material for the catalyst consisted of Sud Chemie KA-160 silica spheres having a nominal diameter of 5 mm., a surface area of about 160 to 175 m 2 /g, and a pore volume of about 0.68 ml/g.
• 100 cc of the 5 mm silica support material for the catalyst was measured into a 500-ml round bottom flask.
• aqueous NaAuCl 4 (4 g Au/1 support) were added to produce a total solution volume equal to the total volume the support could absorb.
• the Pd/Au-containing solution was poured into the silica support to impregnate the support to incipient wetness, and the support was shaken for approximately 5 minutes to ensure complete absorption of the solution.
• the treated support was then poured into a 250-ml sonication flask containing 1 14 cc of aqueous NaOH (from 50% w/w NaOH/H 2 O, 120% of the amount of NaOH needed to convert the metal salts to their hydroxides).
• the flask was immediately placed on the sonicator to sonicate for 1 hour at level 2.
• the solution was drained from the treated support, and the treated support was poured in a 500-ml graduated cylinder with dip tube to wash with a continuous flow of deionized water for 5 hours.
• the effluent was tested with AgNO 3 to detect the presence of chlorides via formation of insoluble AgCl.
• the effluent was drained from the treated support, and the treated support was transferred to a 500-ml round bottom flask. The flask was placed in an oven, and the treated support was dried overnight at 150° C under constant N 2 purge. The metal hydroxides were reduced with 5% C 2 H 4 in N 2 at a flow rate of 0.5 SCFH at 150°C for 5 hours. KOAc (40 g/1 support) and deionized water were added to a 100-ml graduated cylinder to produce a solution volume equal to the amount of solution the support would absorb. The treated support was impregnated by incipient wetness with the aqueous KOAc and let stand for 15 minutes. The catalyst was transferred to a fluid-bed dryer to dry for 1 hour at 100°C.
• Example 1 The procedure of Example 1 was followed through sonication at level 2 for 1 hour. 3.0 ml of hydrazine hydrate, N 2 H 4 »H 2 O was added to the NaOH solution (large excess of the amount necessary to reduce the metal hydroxides to the metals), and the sonication was continued at level 2 for 1 hour. After sonication, the washing, drying, reduction, and impregnation with KOAc were carried out following the procedure of Example 1.
• Example 3 100 cc of the 5 mm silica catalyst support material was measured into a 500-ml bottom flask.
• aqueous Na 2 PdCl 4 7 g Pd/1 support
• aqueous NaAuCL 4 g Au/1 support
• CuCl 2 0.264 g/1 support
• deionized water was added to produce a total solution volume equal to the total volume the support could absorb.
• the Pd/Au/Cu- containing solution was poured into the silica support to impregnate the support by incipient wetness, and the support was shaken for approximately 5 minutes to ensure complete absorption of the solution.
• Example 4 The treated support was then poured into a 250-ml sonication flask containing 114 cc of aqueous NaOH (from 50% w/w NaOH/H 2 O, 120% of the amount needed to convert the metal salts to their hydroxides). The flask was immediately placed on the sonicator for 1 hour at level 2. After sonication, the washing, drying, reduction, and impregnation with KOA c were carried out following the procedure of Example 1.
• Example 4 Example 4
• 100 cc of the 5 mm silica catalyst support material was measured into a 500-ml round bottom flask.
• aqueous Na 2 PdCl 4 (7 g Pd/1 support), CuCl 2 (0.9264 g Cu/1 support), and deionized water were added to produce a total solution volume equal to the total volume the support could absorb.
• the Pd/Cu-containing solution was poured into the silica support to impregnate the support by incipient wetness, and the support was shaken for approximately 5 minutes to ensure complete absorption of the solution.
• the treated support was then poured into a 250-ml sonication flask containing 114 cc of aqueous NaOH (from 50%) w/w NaOH/H 2 O, 120% of the amount needed to convert the metal salts to their hydroxides).
• the flask was immediately placed on the sonicator to sonicate for 1 hour at level 2.
• the solution was drained from the treated support, and the support was dried on a fluid-bed dryer at 100° C for 1 hour.
• aqueous NaAuCl 4 (4 g Au/1 support), NaOH (as 50% w/w NaOH/H 2 O, 180% of the amount needed to convert the Au salt to its hydroxide), and deionized water were added to produce a total solution volume equal to the amount of solution the support could absorb.
• the solution was allowed to stand for up to one hour before being added to the treated support to avoid precipitation of the Au hydroxide.
• the treated support was impregnated by incipient wetness with the Au/NaOH-containing solution, and it was shaken for approximately 5 minutes to ensure complete absorption of the solution.
• the treated support was allowed to stand for 16 hours, then it was poured in a 500-ml graduated cylinder with a dip tube. The washing, drying, reduction, and impregnation with
• Example 1 The procedure of Example 1 was followed up through washing of the catalyst for 5 hours in a 500-ml graduated cylinder with a dip tube. After washing, the effluent was drained from the treated support, and the support was transferred to a sonication flask, and approximately 114 cc of deionized H 2 0 was added with 4.71 ml of N 2 H 4 H 2 O (1200% of the amount necessary to reduce the metal hydroxides to the metals). The solution was sonicated for 1 hour at level 2. The flask was removed from the sonicator, and the excess solution was drained from the treated support. After 30 minutes, the treated support was rinsed with deionized H 2 O several times to remove excess hydrazine.
• the treated support was poured into a 500-ml graduated cylinder with a dip tube and washed continuously with deionized H 2 O for 35 minutes.
• the treated support was transferred to a round bottom flask and dried overnight under constant N 2 purge.
• the reduction and impregnation with KOAc were carried out following the procedure of Example 1.
• Example 2 The procedure of Example 1 was followed except that the sonication was carried out for 3.5 hours at level 2.
• Example 7 o The procedure of Example 1 was followed up through washing the catalyst for 5 hours in a 500-ml graduated cylinder with a dip tube. After washing, the effluent was drained from the treated support, and the support was placed in a round bottom flask to dry overnight at 150°C. The treated support was transferred to a sonication flask, and approximately 114 cc of deionized H 2 O was added with 4.71 ml of N 2 H 4 H 2 O (approximately 1200% of the amount necessary to 5 reduce the metal hydroxides to the metals). The solution was sonicated at level 2 for 3 hours.
• the flask was removed from the sonicator, and the excess solution was drained from the treated support.
• the treated support was rinsed with deionized H 2 O several times to remove excess N 2 H 4 .
• the treated support was poured into a 500-ml graduated cylinder with a dip tube and washed continuously with deionized H 2 O for 3 hours and 15 minutes.
• the treated support was 0 transferred to a fluid bed dryer and dried for 1 hour at 100°C.
• the reduction and impregnation with KOAc were carried out following the procedure of Example 1.
• Example 2 The procedure of Example 1 was followed, except that the sonication was carried out for 5 16 hours at level 2.
• Example 10 The procedure of Example 1 was followed, except that the sonication was carried out for 1 hour at level 2, and the support was impregnated to 95% by incipient wetness. 0
• Example 10 The procedure of Example 1 was followed, except that the sonication was carried out for 1 hour at level 2, and the support was impregnated to 95% by incipient wetness. 0
• Example 10 The procedure of Example 1 was followed, except that the sonication was carried out for 1 hour at level 2, and the support was impregnated to 95% by incipient wetness. 0
• Example 10 The procedure of Example 1 was followed, except that the sonication was carried out for 1 hour at level 2, and the support was impregnated to 95% by incipient wetness. 0
• Example 10 The procedure of Example 1 was followed, except that the sonication was carried out for 1 hour at level 2, and the support was impregnated to 95% by incipient wetness. 0
• Example 10 The procedure of Example 1 was followed
• Example 1 The procedure of Example 1 was followed, except that the sonication was carried out for 1 hour at level 4 and the support was impregnated to 95% by incipient wetness.
• 100 cc of the 5 mm silica catalyst support material was measured into a 500-ml round bottom flask.
• aqueous Na 2 PdCl 4 (7 g Pd/1 support) and deionized water were added to produce a total solution volume equal to the total volume the support could absorb.
• the Pd-containing solution was poured into the silica support to impregnate the support by incipient wetness, and the support was shaken for approximately
• the treated support was then poured into a 250-ml sonication flask containing 114 cc of aqueous NaOH (from 50% w/w NaOH/H 2 O, 120% of the amount needed to convert the metal salts to their hydroxides).
• the flask was immediately placed on the sonicator to sonicate for 1 hour at level 4.
• the solution was drained from the treated support, and the treated support was poured in a 500-ml graduated cylinder with a dip tube to wash with a continuous flow of deionized water for 1 hour.
• the catalyst was left overnight, and the washing was continued for 3 hours and 45 minutes.
• the effluent was tested with AgNO 3 to detect the presence of chlorides via formation of insoluble AgCl.
• the effluent was drained from the treated support, and the treated support was transferred to a fluid bed dryer to dry at 100°C for 1 hour.
• aqueous NaAuCl 4 (7 g Au/1 support) and deionized water were added to produce a total solution volume equal to the total volume the support could absorb.
• the Au-containing solution was poured into the Pd-containing silica support to impregnate the support by incipient wetness, and the support was shaken for approximately 5 minutes to ensure complete absorption of the solution.
• the treated support was then poured into a 250-ml sonication flask containing 114 cc of aqueous NaOH (from 50% w/w
• Example 12 The procedure of Example 4 was followed, except that the sonication was carried out for
• Example 4 The procedure of Example 4 was followed , except that the amount of Cu from CuCl 2 was 2.084 g/1 support, and the sonication was carried out for 1 hour at level 4.
• Example 1 The procedure of Example 1 was followed, except that the sonication was carried out for 1 hour at level 3 and the catalyst was dried (after washing) on a fluid-bed dryer at 100°C for 1 hour instead of in an oven at 150°C under constant N 2 purge.
• Example 1 The procedure of Example 1 was followed, except that the amount of Pd from Na 2 PdCl 4 was 9.844 g/1 and the amount of the Au from NaAuCl 4 was 5.625 g/1; the sonication was carried out for 1 hour at level 2; and the catalyst was dried (after washing) on a fluid-bed dryer at 100 °C for 1 hour instead of in an oven at 150°C under constant N 2 purge.
• Example 11 The procedure of Example 11 was followed, except that the amount of Au from NaAuCL, was 4 g/1 and the sonications were carried out for 1 hour at level 2.
• the catalysts of the examples were tested for their selectivity to various byproducts in the production of vinyl acetate by reaction of ethylene, oxygen and acetic. This was accomplished using the Vinyl Acetate Micro Unit (VAMU) which is a plug flow reactor run at a temperature sufficient to effect an oxygen conversion of 45%.
• VAMU Vinyl Acetate Micro Unit
• the VAMU reactor is a 3 ft-long. 16 mm i.d. stainless steel tube with a 3 mm concentric thermocouple well.
• the reactor is equipped with a heating jacket or "shell" through which hot water and steam are circulated.
• a 30 cc sample of catalyst is diluted with support up to 150 cc and loaded to the reactor.
• the catalyst/support mixture is topped with 30 cc of support.
• Table I shows for each example details of the method of making the catalyst and its make-up, in terms of the nominal amounts, i.e. total of the catalytically active metals Pd, Au, and optionally Cu, impregnated onto the support (Metal Content of Catalyst, Nominal Amount), the percentage of the amount of each metal initially impregnated onto the support and retained in the final catalyst (Metal Content of Catalyst, % Retention), the intensity level of sonication applied to each fixing of the metals on the catalyst (Sonication, Level), the period of time of such fixing (Sonication, t., hr.), and the reducing agent (Red.

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