KR20030007650A - Integrated process for the production of vinyl acetate - Google Patents

Abstract

(A) contacting a gas feedstock consisting essentially of ethane with a molecular oxygen containing gas in the presence of a catalyst in a first reaction zone to produce a first product stream comprising acetic acid and ethylene,

(B) contacting the first gas product stream in the second reaction zone with a molecular oxygen containing gas in the presence of a catalyst to produce a second product stream comprising vinyl acetate and

And (c) separating the product stream from step (b) and recovering vinyl acetate from the product stream from step (b).

Description

Integrated process for the production of vinyl acetate

The present invention generally relates to an integrated preparing process for vinyl acetate, in which the processes are integrated into one regime, and in particular to a method for producing vinyl acetate from a gas feedstock comprising essentially ethane.

Vinyl acetate is generally prepared by contacting acetic acid and ethylene with molecular oxygen in the presence of a catalyst that is commercially active for vinyl acetate production. Suitably the catalyst may comprise palladium, alkali metal acetate promoters and any co-promoter (eg gold or cadmium) on the catalyst support. Acetic acid produced by carbonylation requires a particularly extensive purification process to remove iodides formed from commonly used catalyst systems, because iodide is considered as a potential vinyl acetate catalytic poison material.

Processes for the production of vinyl acetate, in which the processes are independently combined, are known in the art. Accordingly, WO 98/05620 first discloses contacting ethylene and / or ethane with oxygen to produce a first product stream comprising acetic acid, water and ethylene, further ethylene in the second reaction zone and Contacting the first product stream with oxygen in the presence or absence of acetic acid to produce a second product stream comprising vinyl acetate, water, acetic acid and optionally ethylene, distilling the product stream from the second step to Separating the upper azeotrope fraction comprising acetate and water and the lower fraction comprising acetic acid, recovering acetic acid from the lower fraction and optionally recycling the azeotrope fraction or recovering vinyl acetate from the azeotrope fraction , Methods for preparing vinyl acetate and / or acetic acid are described. There. The catalyst proposed in WO 98/05620 for the oxidation of ethylene to acetic acid or of ethane to acidic acid is a catalyst of the formula Pd _a M _b TiP _c O _x where M is Cd, Au , Zn, Tl, alkali metal and alkaline earth metal), and other catalysts for the oxidation of ethane to acetic acid are catalysts of the formula VP _a M _b O _x , wherein M is Co, Cu, Re, Fe, Ni Nb, Cr, W, U, Ta, Ti, Zr, Zn, Hf, Mn, Pt, Pd, Sn, Sb, Bi, Ce, As, Ag and Au), or ethane and / or ethylene A catalyst that oxidizes to form ethylene and / or acetic acid, which comprises elements A, X and Y, where A is Mo _d Re _e W _f , X is Cr, Mn, Nb, Ta, V or W, Y Is Bi, Ce, Co, Cu, Fe, K, Mg, Ni, P, Pb, Sb, Si, Sn, Tl or U].

Other catalysts for the oxidation of ethane to acetic acid and ethylene proposed in WO 98/05620 are those of the formula Mo _x V _y Z _z , where Z is Li, Na, Be, Mg, Ca, Sr , Ba, Zn, Cd, Hg, Sc, Y, La, Ce, Al, Tl, Ti, Zr, Hf, Pb, Nb, Ta, As, Sb, Bi, Cr, W, U, Te, Fe, Co And Ni).

U.S. Patent No. 5,185,308, cited in WO 98/05620, discloses that a space time yield of 555-993 g of vinyl acetate per hour is achieved for 1 liter of catalyst.

An object of the present invention is an integrated process for preparing vinyl acetate from a gas feedstock which essentially comprises ethane only as an external carbon source of the feedstock, with a space / time yield of 100 to 2000 g of vinyl acetate per hour, preferably 1 liter of catalyst. Is to provide a method representing 500 to 1500 g.

Thus, the present invention comprises the steps of (a) contacting a gas feedstock comprising essentially ethane with a molecular oxygen containing gas in the presence of a catalyst in a first reaction zone to produce a first product stream comprising acetic acid and ethylene,

(B) contacting the first gaseous product stream in the second reaction zone with a molecular oxygen containing gas in the presence of a catalyst to produce a second product stream comprising vinyl acetate and

A process for integrating the production of vinyl acetate, comprising the step (c) of separating the product stream from step (b) and recovering the vinyl acetate from the product stream from step (b).

The process according to the invention is based on the discovery that certain classes of catalysts can convert ethane to a mixture of predetermined acetic acid and ethylene with very high selectivity and very high space time yields. This ethylene / acetic acid mixture can be fed directly to the reactor to form vinyl acetate. It is advantageous to use ethane as a feedstock which can be used as natural gas instead of ethylene. In the natural gas aftertreatment process, several ethane containing mixtures are obtained, which are usually simply ejected, but all of them can be used as carbon feedstock for carrying out the process of the invention. Preferably, a mixture with a large amount of ethane (high purity ethane with an ethane content of 90%, see PERP-Report "Natural Gas Liquids Extraction", 94 / 95S4 page 60) can be used in the process described herein.

A particular advantage of the integrated process for the production of vinyl acetate of the invention is that in principle the infrastructure, equipment and other properties can be combined. For example, the present invention requires only one feed gas compressor and one gas discharge scrubbing system, whereas where the acetic acid and vinyl acetate processes are separate, each of these processes has its own feed gas compressor and gas discharge scrubbing. The system is required separately. By combining steps (a) and (b) of the present invention, intermediate storage requirements are reduced when compared to two separate individual processes as described above. All these benefits reduce capital and operating costs.

According to the present invention, a gas feedstock comprising essentially ethane is contacted with a molecular oxygen-containing gas in the first reaction zone in the presence of a catalyst active in the oxidation of ethane to acetic acid and ethylene in a first reaction comprising acetic acid and ethylene Generate a product stream.

Catalysts active for the oxidation of ethane to acetic acid and ethylene can include suitable catalysts described in German Patent Publication No. 197 45 902, incorporated herein by reference.

These catalysts are catalysts of the formula Mo _a Pd _b X _c Y _d where X is selected from one or more elements of the group consisting of Cr, Mn, Nb, Ta, Ti, V, Te and W, and Y is B, Al , Ga, In, Pt, Zn, Cd, Bi, Ce, Co, Rh, Ir, Cu, Ag, Au, Fe, Ru, Os, K, Rb, Cs, Mg, Ca, Sr, Ba, Nb, Zr Is selected from one or more elements of the group consisting of Hf, Ni, P, Pb, Sb, Si, Sn, Tl and U, a, b, c and d are gram atomic ratios, a is 1 and b is 0.0001 To 0.01, preferably 0.0001 to 0.005, c is 0.4 to 1, preferably 0.5 to 0.8, and d is 0.005 to 1, preferably 0.01 to 0.3).

Preferred catalysts are those wherein X is V and Y is Nb, Sb and Ca. Pd ratios above the indicated gram atomic ratio limit are beneficial for the formation of carbon dioxide and Pd ratios below the indicated gram atomic ratio limit are advantageous for the formation of ethylene. Particularly preferred catalysts for the process according to the invention are Mo _1.00 Pd _0.00075 V _0.55 Nb _0.09 Sb _0.01 C _0.01 .

An advantage of the present invention is that within a wide range, the ratio of selectivity to acetic acid to selectivity to ethylene formed in the first reaction zone is varied by varying reaction parameters such as reaction temperature, total pressure, feed composition, residence time, respectively, That is, it can vary from 0 to 95%.

Catalysts active in the oxidation of ethane can be used with or without support. Examples of suitable supports are silica, diatomaceous earth, montmorillonite, alumina, silica alumina, zirconia, titania, silicon carbide, activated carbon and mixtures thereof. Catalysts active in the oxidation of ethane can be used in the form of fixed or fluidized beds.

The molecular oxygen-containing gas used in the reaction zone may be air or a gas rich or lacking molecular oxygen than air. Suitable gases can be, for example, oxygen diluted with a suitable diluent, for example nitrogen or carbon dioxide. Preferably, the molecular oxygen containing gas is supplied to the first reaction zone independently of the ethane feedstock.

The ethane feedstock of the process of the present invention is substantially diluted with other gases, eg, 90% by weight, such as produced purely or by natural gas separation, or by PERP-Report "Natural Gas Liquids Extraction 94". / 95S4, page 60 "], nitrogen, carbon dioxide, hydrogen and a mixture of one or more of small amounts of C3 / C4 alkenes / alkanes. Catalytic poisons such as sulfur must be removed. Likewise, it is advantageous to minimize the amount of acetylene. The amount of inert components is limited only by economics.

Step (a) of the process of the invention may suitably be carried out by passing ethane, molecular oxygen containing gas, steam and, if necessary, further inerts through the catalyst. The amount of steam may suitably be from 0 to 50% by volume. The molar ratio of ethane: oxygen may suitably be from 1: 1 to 10: 1, preferably from 2: 1 to 8: 1.

Step (a) of the process of the invention may suitably be carried out at a temperature of 200 to 500 ° C, preferably of 200 to 400 ° C.

Step (a) of the process of the invention may suitably be carried out at atmospheric or superatmospheric pressure, for example at 1 to 100 bar, preferably at 1 to 50 bar.

Typically, from 10 to 100%, in particular from 10 to 40% of ethane, in step (a) of the process of the invention according to the reactor design of step (a), which may be a reactor cascade to supply oxygen between the reactors. Conversion rates can be achieved. Typically, an oxygen conversion rate of 90 to 100% can be achieved in step (a) of the process of the invention.

In step (a) of the process of the invention, the catalyst suitably exhibits a productivity in which the space time yield (STY) is from 100 to 2000 g, preferably from 100 to 1500 g of acetic acid / ethylene per hour, per liter of catalyst.

The ratio of ethylene / acetic acid required to feed the vinyl acetate reactor (step (b) of the present invention) depends on the reaction parameters of step (a), e.g. reaction temperature, total pressure, hourly space velocity of gas, It can be suitably adjusted by changing the partial pressure and in particular by changing the steam partial pressure in the feed of step (a).

Step (a) of the present invention can be carried out in a fixed bed reactor as well as a fluidized bed reactor.

The gas product stream from step (a) comprises a predetermined proportion of acetic acid and ethylene and water, and may contain ethane, oxygen, nitrogen and by-products, carbon monoxide and carbon dioxide. Typically, no carbon monoxide is produced or very small (<100 ppm) is produced during step (a). If carbon monoxide is produced in large quantities up to 5%, it can be removed, if necessary, after step (a), for example by adsorption or combustion with carbon dioxide by molecular oxygen containing gas. Ethylene is preferably present in the gas product stream of step (a) in an amount necessary for the direct conversion to vinyl acetate.

The gas product from step (a) is preferably of step (b) together with optionally further molecular oxygen containing gas, optionally further ethylene and optionally further acetic acid, which can be taken from step (c), ie the vinyl acetate separation step. It can be fed directly to the second reaction zone. Catalysts active in the production of vinyl acetate used in step (b) of the process of the present invention are described, for example, in EP 0 330 853, UK 1 559 540, US 5,185,308 and Suitable catalysts known in the art as described in WO 99/08791.

EP 0 330 853 describes a catalyst for the production of fully impregnated vinyl acetate containing Pd, K, Mn and Cd as further promoter instead of Au.

British Patent No. 1 559 540 discloses a catalyst support 1 having a particle diameter of 3 to 7 mm and a pore volume of 0.2 to 1.5 ml / g (10 wt% of a water suspension having a pH of 3.0 to 9.0), the surface layer being 0.5 from the surface of the support. a palladium-gold alloy distributed over the surface layer of the catalyst support, extending less than mm and having palladium in the alloy in an amount of 1.5 to 5.0 g per liter of catalyst and gold in an amount of 0.5 to 2.25 g per liter of catalyst ( 2) and a catalyst active for the production of vinyl acetate by the reaction of ethylene, acetic acid and oxygen, consisting essentially of 5 to 60 g of alkali metal acetate per liter of catalyst.

U. S. Patent No. 5,185, 308 discloses a catalyst support 1 having a particle diameter of about 3 to about 7 mm and a pore volume of 0.2 to 1.5 ml / g, palladium and gold distributed in the outermost layer having a thickness of 1.0 mm of catalyst support particles (2). ) And shell impregnated active for the production of vinyl acetate from ethylene, acetic acid and oxygen containing gases consisting essentially of about 3.5 to about 9.5 weight percent potassium acetate (3) having a weight ratio of gold to palladium in the catalyst of 0.6 to 1.25. Catalysts are described.

WO 99/08791 describes a process for preparing a catalyst containing metal nanoparticles on a porous support, in particular a catalyst for gas phase oxidation of ethylene and acetic acid to form vinyl acetate. The present invention provides a process for the preparation of a catalyst containing one or several metals from a metal group comprising subgroups Ib and VIIIb of the Periodic Table of Elements on a porous support particle, the method comprising: from subgroups Ib and VIIIb of the Periodic Table of Elements A first step of applying one or several precursors from a group of metal compounds to a porous support and a porous, preferably nanoporous support to which one or more precursors have been applied, are treated with one or more reducing agents to generate themselves in the pores of the support. And a second step of obtaining the metal nanoparticles.

Typically, step (b) of the process of the invention is carried out heterogeneously and the reactants are in the gas phase.

The ethylene reactant used in step (b) of the process of the invention is produced in step (a) of the process of the invention.

The molecular oxygen containing gas used in step (b) of the process of the invention may comprise an unreacted molecular oxygen containing gas from step (a) and / or an additional molecular oxygen containing gas. Preferably, at least a portion of the molecular oxygen containing gas is fed independently from the acetic acid and ethylene reactants to the second reaction zone.

Step (b) of the process of the invention may suitably be carried out at a temperature of 140 to 220 ° C.

Step (b) of the process of the invention may suitably be carried out at a pressure of 1 to 100 bar.

Step (b) can be carried out in a suitable reactor configuration which can remove the heat of reaction in a suitable manner, with a preferred technical solution being a fixed bed reactor or a fluidized bed reactor.

An acetic acid conversion of 5 to 50% can be achieved in step (b) of the process of the invention.

Oxygen conversion of 20 to 100% can be achieved in step (b) of the present invention.

In step (b) of the process of the invention, it is suitable that the catalyst has a productivity of 100 to 2000 g of vinyl acetate per hour for 1 liter of catalyst, but a productivity of 10000 g or more is also suitable.

The second product stream from step (b) of the process of the invention comprises vinyl acetate and water and optionally also contains unreacted acetic acid, ethylene, ethane, nitrogen, carbon monoxide, carbon dioxide and traces of other by-products. If ethylene, ethane, carbon monoxide and carbon dioxide are present between steps (b) and (c) of the process of the invention, they are suitably scrubbed from the second product stream, where vinyl acetate, water and acetic acid are It is preferred that the liquid fraction comprising is removed from the bottom as a top gas fraction.

The second product stream from step (b) comprising vinyl acetate, water and acetic acid is distilled in step (c) with or without an intermediate scrubbing step to obtain acetic acid and the top azeotrope fraction comprising vinyl acetate and water. Separate into the bottom fraction containing.

The vinyl acetate is suitably recovered, for example, by pouring over, from the azeotrope fraction separated in step (c). The vinyl acetate recovered can be further purified, if necessary, by known methods. The bottom fraction comprising acetic acid separated in step (c) is recycled to step (b) of the process of the invention without further purification or preferably without further purification.

The total space time yield (STY) of vinyl acetate (relative to ethane) produced in the process of the invention is 100 to 5000 g, preferably 500 to 1500 g, of vinyl acetate per hour for 1 liter of catalyst.

The total yield is a number of methods, including oxygen concentration and / or reaction temperature, including independently adjusting the reactant ratios and / or reaction conditions of steps (a) and / or (b) of the process of the invention. And by adjusting the pressure independently.

The method of the invention is now described by way of example with reference to FIG. 1, which schematically shows an apparatus for use in the method of the invention.

The apparatus comprises a first reaction zone 1, a second reaction zone 2 and a scrubber column 3.

In use, a gas feedstock 4 comprising molecular oxygen containing gas, optionally steam, and essentially ethane, is fed to the first reaction zone 1 containing an active catalyst which oxidizes ethane to form acetic acid and ethylene. Depending on the scale of the process, the first reaction zone 1 may comprise a single reactor or may comprise several reactors in parallel or in series. The first reaction zone can also include a reactor cascade through which additional molecular oxygen containing gas can be supplied between the individual reactors. A first gas product stream comprising acetic acid, ethylene, unreacted feedstock, optionally unconsumed molecular oxygen containing gas and water together with carbon monoxide, carbon dioxide and inerts is recovered from the first reaction zone 1 and the second reaction zone Supply to (2). Additional molecular oxygen containing gas 5 and / or ethylene 6 may be mixed with the product stream recovered from the first reaction zone 1. In the second reaction zone 2 acetic acid and ethylene are contacted with a molecular oxygen containing gas in the presence of a catalyst active for the production of vinyl acetate. Depending on the scale of the process, the second reaction zone 2 may comprise a single reactor or may comprise several reactors in parallel or in series. A product stream comprising vinyl acetate, water, optionally ethane, gas by-products and unreacted acetic acid and ethylene is recovered from the second reaction zone (2) and fed to the scrubber column (3), wherein ethylene and optionally ethane are inerts, Carbon monoxide and carbon dioxide by-products are recovered at the top and recycled to the first reaction zone (1). A liquid stream comprising vinyl acetate, water, unreacted acetic acid and capable of presenting the high boiling point product of the process of the present invention is recovered from the bottom of the scrubber column (3), wherein vinyl acetate is not shown Is separated from. For example, it is fed to a distillation column such that vinyl acetate and water are removed as an azeotrope and the high boiling products that may be present with acetic acid are removed as bleed from the bottom of the distillation column. Water in the top stream of the distillation column can be separated from vinyl acetate in a decanter, and the vinyl acetate product stream removed from the decanter is purified by conventional methods known in the art.

Carbon dioxide by-products can be removed by viable technical methods known in the art, for example by reversible absorption in aqueous K ₂ CO ₃ aqueous solution and regenerated in a desorbent column (not shown). .

The invention is illustrated by the following examples.

Example

Preparation of the catalyst

Example (1)

Preparation of Catalyst (Mo _1.00 Pd _0.00075 V _0.55 Nb _0.09 Sb _0.01 Ca _0.01 O _x )

Solution 1: 80 g of ammonium molybdate in 400 ml of water (Riedel-de Haen)

Solution 2: Ammonium metavanadate in 400 ml of water from Riedel-De Jaen] 29.4 g

Solution 3: niobium ammonium oxalate in 200 ml of water. Seed. Stark [H. C. Starck]] 19.01 g, antimony oxalate (manufactured by Pfaltz & Bauer) and calcium nitrate [man: Riedel-de Jaen] 1.34 g

Solution 4: 0.078 g of palladium (II) acetate in 200 ml of ethanol (Aldrich)

Solution 1, solution 2 and solution 3 are separately stirred at 70 ° C. for 15 minutes. Then solution 3 is poured into solution 2 and stirred together at 70 ° C. for an additional 15 minutes, after which it is added to solution 1. Then, solution 4 is added.

The resulting mixture is evaporated to yield 800 ml of total remaining capacity. After the mixture is spray dried at 180 ° C., the powder is dried in 120 ° C. static air for 2 hours and calcined at 300 ° C. for 5 hours. The resulting catalyst I is compressed, milled and sieved to a granular fraction of 0.35 to 0.70 mm.

Example (2)

Catalyst II: Preparation of K, Pd, Au / TiO ₂

2.11 g of palladium acetate (Aldrich) and 1.32 g of gold acetate are dissolved in 30 ml of acetic acid. The process for preparing gold acetate used is described in US Pat. No. 4,933,204. 100 ml of TiO ₂ support (P25 pellet, Degussa, Hanau, Germany) is added to a palladium and gold acetate solution. Subsequently, most of the acetic acid is evaporated using a rotary evaporator at 70 ° C., followed by evaporation of the remaining liquid using an oil pump at 60 ° C. and finally 14 hours in a 60 ° C. vacuum drying cabinet.

In order to reduce the resulting pellets to a 10 vol% hydrogen gas mixture in nitrogen, the gas (40 L / h) is passed directly through the pellets at 500 ° C. and 1 bar for 1 hour. To load the potassium ions, the reduced pellet is added to a solution containing 4 g of potassium acetate in 30 ml of water in a mixing apparatus for 15 minutes.

The solvent is then evaporated using a rotary evaporator. The pellet is dried at 100 ° C. for 14 hours.

Catalyst II is prepared in three batches using the same method and these are referred to as IIa, IIb and IIc, respectively.

Catalyst test

In order to carry out the catalytic reaction described in steps (a) and (b) of the present invention, a double-wall fixed bed reactor having an internal diameter of 14 mm and 20 mm and a length of 350 mm is used, respectively. The reactor is heated through an outer tube with an oil bath. Typically, 5 ml of catalyst and 15 ml of catalyst are each combined with a specific inert material, for example, typically glass, quartz or alumina granules or beads, and a catalyst to inert material volume ratio such as 2: 1, 1: 1. Partially mix 1: 2, 1: 5. In order to reduce the dead volume of the reactor, the inert material (mentioned above) is charged before and after the catalyst bed. Volumetric flow rates are typically controlled by mass and liquid flow regulators, respectively.

Analysis of the reaction product is carried out by on-line gas chromatography.

Table 1 shows the results of catalyst measurements for Catalyst I (Example (1)) for carrying out step (a) of the present invention using a single reactor. For easy comparison of results, the measurements taken at the same total pressure (15 bar) are listed.

The data in Table 1 are defined as follows:

Conversion of ethane [%] = (0.5 × [CO] + 0.5 × [CO ₂ ] + [C ₂ H ₄ ] + [CH ₃ COOH]) / (0.5 × [CO] + 0.5 × [CO ₂ ] + [ C ₂ H ₄ ] + [C ₂ H ₆ ] + [CH ₃ COOH]) × 100

Selectivity of ethylene [%] = ([C ₂ H ₄ ]) / (0.5 × [CO] + 0.5 × [CO ₂ ] + [C ₂ H ₄ ] + [CH ₃ COOH]) × 100

Selectivity of acetic acid [%] = ([CH ₃ COOH]) / (0.5 × [CO] + 0.5 × [CO ₂ ] + [C ₂ H ₄ ] + [CH ₃ COOH]) × 100

From above,

[] Is the concentration (mol%),

[C ₂ H ₆ ] is the concentration of ethane not converted.

τ [s] is the volume of catalyst (ml) / volume flow rate of gas (ml / s) at reaction conditions.

STY is product g / (l catalyst × h).

Catalytic Results for Catalyst I for Oxidizing Ethane with Ethylene and Acetic Acid Reaction conditions result Feed composition Conversion rate Selectivity Space time yield number T [℃] τ [s] V (C ₂ H ₆ ) [ml / s] V (O ₂ ) [ml / s] V (N ₂ ) [ml / s] V (H ₂ O) [ml / h] X (C ₂ H ₅ ) [%] S (HOAc) [%] S (C ₂ H ₄ ) [%] S (CO + CO ₂ ) [%] STY (HOAc) [g / (hl)] STY (C ₂ H ₄ ) [g / (hl)] One 280 14.8 1.0 0.2 0.8 1.4 13.3 91.5 0.7 7.8 235 One 2 280 7.4 2.0 0.4 1.6 2.9 10.5 90.4 3.5 6.0 362 7 3 300 7.1 2.0 0.4 1.6 2.9 13.2 89.0 2.0 9.0 447 5 4 300 4.8 3.0 0.6 2.4 4.3 11.3 87.2 5.5 7.3 564 17 5 300 4.1 3.5 0.7 2.8 5.0 10.2 86.2 7.4 6.4 584 24 6 300 3.7 4.0 0.8 3.2 5.0 9.9 84.1 9.2 6.6 630 33 7 300 2.6 6.0 1.2 4.8 5.0 7.7 60.4 35.4 4.3 532 147 8 320 3.5 4.0 0.8 3.2 5.0 13.5 65.2 28.0 6.8 672 136 9 320 2.5 6.0 1.2 4.8 5.0 14.4 38.7 57.1 4.1 638 447 10 340 3.4 4.0 0.8 3.2 5.0 17.9 44.3 49.8 5.9 604 322 11 340 2.4 6.0 1.2 4.8 5.0 18.2 36.2 59.0 4.8 754 582

Table 1 clearly shows that the desired ethylene / acetic acid ratio in the product mixture of step (a) of the present invention can be easily adjusted by changing different reaction parameters.

Catalyst II (Example (2)) is used in step (b) of the present invention for producing vinyl acetate. The catalyst test is carried out at a reaction temperature of 150 to 170 ° C. and a reaction pressure of 8 to 9 bar.

The results of the catalyst measurements for Catalyst II (Example 2) for carrying out step (b) of the present invention are shown in Table 2.

The data in Table 2 is defined as follows:

Selectivity to vinyl acetate (VAM) [%] = ([VAM]) / ([VAM]) + 0.5 × [CO] + 0.5 × [CO ₂ ]) × 100

From above,

[] Is the concentration (mol%).

STY is product g / (l catalyst × h).

Catalyst Results for Catalyst II Performing Vinyl Acetate Synthesis Reaction conditions result Selectivity Space time yield number T [℃] p [bar] S (VAM) [%] STY [g / (hl)] A 155 9 98 1000 A 160 9 98 1050 A 170 9 96 1000 B 160 9 98 1150 B 170 9 97 700 C 170 9 98 1300

Claims (7)

Contacting a gas feedstock comprising essentially ethane in a first reaction zone with a molecular oxygen containing gas in the presence of a catalyst to produce a first product stream comprising acetic acid and ethylene, (B) contacting the first gas product stream in the second reaction zone with a molecular oxygen containing gas in the presence of a catalyst to produce a second product stream comprising vinyl acetate and Separating (c) the product stream from step (b) and recovering vinyl acetate from the product stream from step (b). The method of claim 1, wherein the gas feedstock for step (a) comprises ethane and molecular oxygen containing gas in an ethane to oxygen ratio of 1: 1 to 10: 1, and steam is based on the total gas feedstock capacity, A method comprising 0 to 50% by volume. The process according to claim 1 or 2, wherein the ratio of selectivity to ethylene to acetic acid in the first product stream is from 0:95 to 95: 0. The catalyst of any one of claims 1 to 3, wherein the catalyst in the first reaction zone is a catalyst of the formula Mo _a Pd _b X _c Y _d , wherein X is Cr, Mn, Nb, Ta, Ti, V, Te And one or more elements of the group consisting of W, Y is B, Al, Ga, In, Pt, Zn, Cd, Bi, Ce, Co, Rh, Ir, Cu, Ag, Au, Fe, Ru, Os, K, Rb, Cs, Mg, Ca, Sr, Ba, Nb, Zr, Hf, Ni, P, Pb, Sb, Si, Sn, Tl and U are selected from one or more elements of the group , b, c and d are the gram atomic ratio, a is 1, b is 0.0001 to 0.01, preferably 0.0001 to 0.005, c is 0.4 to 1, preferably 0.5 to 0.8, d is 0.005 to 1 , Preferably 0.01 to 0.3). 5. The process according to claim 1, wherein further ethylene and / or acetic acid is fed to the second reaction zone. 6. The process according to claim 1, wherein the molecular oxygen containing gas is fed to the first reaction zone independently of the ethane feed stock. The process of claim 1, wherein the molecular oxygen containing gas is fed to the second reaction zone independently of the acetic acid and ethylene reactants.