HK1161223A - Integrated process for the production of vinyl acetate from acetic acid via acetaldehyde - Google Patents

Description

Integrated process for the production of vinyl acetate from acetic acid via acetaldehyde

Priority requirement

This application is based on united states provisional application serial No. 12/317,995 filed on 31/12/2009, entitled same, the entire contents of which are hereby incorporated by reference and hereby claiming priority.

Technical Field

The present invention generally relates to an integrated process for the production of Vinyl Acetate Monomer (VAM) from acetic acid via acetaldehyde. More particularly, the present invention relates to an integrated process which first comprises hydrogenating acetic acid to acetaldehyde with high selectivity using a catalyst comprising a supported metal catalyst, e.g., iron, platinum or ruthenium, optionally containing one or more additional hydrogenation metals, supported on a suitable catalyst support. In the next second step, the acetaldehyde thus formed is converted into ethylidene diacetate by a conversion reaction with acetic anhydride. The ethylidene diacetate is then thermally decomposed to VAM and acetic acid. The invention also relates to a process for the direct conversion of acetaldehyde to VAM by reaction with ketene.

Background

There has been a long felt need for an economically viable process for the direct formation of VAM from acetic acid. VAM is an important monomer for the production of polyvinyl acetate and polyvinyl alcohol products, among other important applications. VAM is currently produced from two key feedstocks, ethylene and acetic acid. While acetic acid can be produced to a lesser extent from petroleum-based feedstocks, ethylene is produced primarily from petroleum-based feedstocks. Thus, fluctuations in the prices of natural gas and crude oil affect fluctuations in the cost of VAM derived from oil or natural gas produced according to conventional methods, making the demand for alternative sources of VAM unprecedentedly high as the oil prices rise.

It has now been found that VAM can be produced essentially from a mixture of carbon monoxide and hydrogen (commonly referred to as synthesis gas or syngas) by a number of industrially viable procedures. For example, it is known that synthesis gas can be reduced to methanol, which is a preferred way of industrially producing methanol. The methanol thus formed can then be selectively converted to acetic acid under catalytic carbonylation conditions, which in turn is the preferred method for the commercial production of acetic acid. The acetic acid thus formed can then be selectively converted to acetaldehyde under suitable catalytic conditions. The acetaldehyde thus formed reacts with the acetic anhydride and is converted to ethylidene diacetate, which is subsequently thermally decomposed into VAM and acetic acid. While there are no known preferred processes for such conversion, the prior art provides some means for such conversion of acetic acid to acetaldehyde, but at low conversion and yield, making it unsuitable for industrialization.

For example, catalytic hydrogenation of aromatic carboxylic acids to aromatic aldehydes has been reported in the prior art. For example, U.S. patent 4,613,700 to Maki et al discloses that aromatic aldehydes can be obtained from aromatic carboxylic acids using a catalyst comprising zirconium oxide containing as a major component at least one element selected from the group consisting of chromium, manganese, iron, cobalt, zinc, bismuth, lead, rhenium and group III elements in periods 3 to 6 of the periodic table. However, no examples of catalytic hydrogenation of aliphatic carboxylic acids such as acetic acid are provided in this disclosure.

U.S. Pat. No. 5,306,845 to Yokohama et al discloses a process for producing aldehydes which comprises hydrogenating a carboxylic acid or an alkyl ester thereof with molecular hydrogen in the presence of a catalyst comprising high purity chromium oxide and having a specific surface area of at least 10m²(iv)/g, and the total content of sodium, potassium, magnesium and calcium does not exceed 0.4 wt.%. It is further reported that the hydrogenation reaction is carried out while maintaining the concentration of the carboxylic acid or its alkyl ester at not more than 10% by volume. Furthermore, the only example reported is the hydrogenation of stearic acid to form stearyl aldehyde. Most importantly, even if the total content of sodium, potassium, magnesium and calcium is increased from about 0.3 wt.% to about 0.46 wt.%, the selectivity to aldehydes decreases dramatically, thereby rendering the process unsuitable for commercial operation.

U.S. patent 5,476,827 to Ferero et al describes a process for preparing aldehydes by the catalytic hydrogenation of carboxylic acids, esters or anhydrides using a bimetallic ruthenium/tin catalyst. Preferred carboxylic acids are alpha-beta-unsaturated carboxylic acids or aromatic carboxylic acids having an aromatic hydrocarbon skeleton. No examples of aliphatic carboxylic acids including acetic acid are provided.

U.S. patent 6,121,498 to Tustin et al discloses a process for producing acetaldehyde from acetic acid. In the process, acetic acid is hydrogenated with hydrogen at elevated temperature in the presence of an iron oxide catalyst containing from 2.5 wt.% to 90 wt.% palladium. However, the best conditions reported include an iron oxide catalyst containing at least about 20 wt.% palladium, which provides about 80% selectivity to acetaldehyde and about 50% conversion to acetic acid. In addition, a number of by-products are formed, including methane, ethane, ethylene, ethanol and acetone.

The acetaldehyde thus formed may be selectively reacted with acetic anhydride to first form ethylidene diacetate, which is subsequently thermally decomposed to form VAM and acetic acid.

For example, U.S. patent 2,021,698 to Perkins et al teaches a process for producing vinyl esters, such as vinyl acetate, by reacting acetic anhydride with paraldehyde and sulfuric acid. It does not teach first preparing ethylidene diacetate and then thermally decomposing the diacetate to obtain vinyl acetate and acetic acid. Perkins teaches away from the use of intermediates such as ethylidene diacetate to obtain vinyl acetate.

U.S. patent 4,843,170 to Isshiki et al discloses a process for the production of vinyl acetate from methanol wherein methanol is converted to ethanol, methyl acetate, dimethyl acetal, and acetaldehyde. The methyl acetate is further processed by carbonylation to form acetic anhydride, which is mixed with dimethyl acetal and acetaldehyde from the methanol conversion step. Acetic anhydride, dimethyl acetal and acetaldehyde react to form ethylidene diacetate, which is thermally decomposed to form VAM and acetic acid. The multi-step process comprises a greater number of steps to produce acetaldehyde as compared to the process of the present invention.

U.S. patent 4,978,778 to Isshiki et al also discloses a process for the production of vinyl acetate in which acetic anhydride is reacted with hydrogen instead of acetaldehyde in the presence of a catalyst. Since the process is converted directly from acetic anhydride and hydrogen to vinyl acetate, it is no longer necessary to produce ethylidene diacetate for VAM by thermal decomposition, which is the basis of the present invention.

Alternatively, acetaldehyde may also be reacted with ketene to form VAM. For example, U.S. patents 5,719,315 and 5,531,456 to Tustin et al disclose processes for the production of vinyl acetate in which acetaldehyde is mixed with vinyl ester and the mixture is subsequently contacted with a catalyst in a contacting zone.

It is apparent from the foregoing that in an integrated process in which acetaldehyde is formed directly from acetic acid and the resulting acetaldehyde is then selectively reacted with acetic anhydride to form ethylidene diacetate and further converted to VAM and acetic acid by thermal decomposition, the existing processes do not have the required selectivity, thereby making the production of VAM from primarily syngas and/or syngas-based products commercially viable.

Summary of The Invention

Surprisingly, it has surprisingly been found that VAM can be produced on an industrial scale using an integrated process with which acetaldehyde is first formed directly from acetic acid at very high selectivity and yield, followed by reaction of acetaldehyde with acetic anhydride to form ethylidene diacetate, which is thermally decomposed in the presence of a suitable catalyst to form VAM and acetic acid. More particularly, the present invention provides a process for the selective formation of VAM from acetic acid comprising: (a) hydrogenating acetic acid in the presence of hydrogen over a first hydrogenation catalyst comprising at least one metal selected from the group consisting of iron, copper, gold, platinum, palladium and ruthenium on a suitable catalyst support. Optionally, the catalyst further comprises one or more metal catalysts selected from the group consisting of tin, aluminum, potassium, cobalt, molybdenum, tungsten and vanadium to produce a first gaseous product stream; (b) enriching the first gaseous product stream with acetaldehyde to at least 50 mol%; (c) reacting said enriched first gaseous product stream from step (b) with acetic anhydride in a second reaction zone to form a second gaseous product stream containing primarily ethylidene diacetate; (d) thermally decomposing the second gaseous product stream from step (c) over a suitable catalyst to form a third gaseous product stream comprising predominantly VAM and acetic acid; and (e) separating vinyl acetate from the third gaseous product stream.

In another embodiment of the invention, the invention provides a process for the selective formation of VAM from acetic acid comprising: (a) hydrogenating acetic acid in the presence of hydrogen over a first hydrogenation catalyst comprising at least one metal selected from the group consisting of iron, copper, gold, platinum, palladium and ruthenium on a suitable catalyst support. Optionally, the catalyst further comprises one or more metal catalysts selected from the group consisting of tin, aluminum, potassium, cobalt, molybdenum, tungsten and vanadium to produce a first gaseous product stream; (b) enriching the first gaseous product stream with acetaldehyde to at least 50 mol%; (c) reacting said enriched first gaseous product stream from step (b) with acetic anhydride in a second reaction zone to form a second gaseous product stream containing primarily ethylidene diacetate; (d) thermally decomposing the second gaseous product stream from step (c) over a suitable cracking catalyst to form a third gaseous product stream comprising predominantly a mixture of VAM and acetic acid; and (e) separating vinyl acetate from the third gaseous product stream.

In another embodiment of the present invention, there is also provided a process for the selective formation of VAM from acetic acid comprising: (a) hydrogenating acetic acid in the presence of hydrogen over a first hydrogenation catalyst comprising at least one metal selected from the group consisting of iron, copper, gold, platinum, palladium and ruthenium on a suitable catalyst support. Optionally, the catalyst further comprises one or more metal catalysts selected from the group consisting of tin, aluminum, potassium, cobalt, molybdenum, tungsten and vanadium to produce a first gaseous product stream; (b) enriching the first gaseous product stream with acetaldehyde to at least 50 mol%; (c) reacting the enriched first gaseous product stream from step (b) with ketene in a second reaction zone to form a second gaseous product stream comprising vinyl acetate; and (c) separating vinyl acetate from the second gaseous product stream.

More specifically, the catalysts used for the selective formation of acetaldehyde in the first step of the process of the present invention generally comprise the following: ruthenium alone or in combination with tin or iron; iron loading alone or in combination with platinum or cobalt; or a combination of platinum and tin. Similarly, other catalysts suitable for use in the process of the invention include palladium alone or a combination of palladium/gold (Pd/Au) or palladium/copper (Pd/Cu) which may further contain potassium acetate. Furthermore, suitable catalysts are combinations of palladium/iron (Pd/Fe), iron/cobalt (Fe/Co), copper/molybdenum (Cu/Mo) or copper/aluminum (Cu/Al). Suitable catalyst supports are not subject to any limitation and include silica, alumina, calcium silicate, carbon, zirconia-silica, titania-silica, iron oxide and zeolite catalysts, such as, for example, H-ZSM-5. Silica and iron oxide are particularly preferred catalyst supports in the process of the present invention.

Detailed Description

The invention is described in detail below with reference to a number of embodiments for the purpose of illustration and description only. Modifications to particular embodiments, as defined in the appended claims, will be readily apparent to those of skill in the art, without departing from the spirit and scope of the invention.

Unless more specific definitions are set forth below, the general meaning of the terms used herein are given. Mole percent (mole% or%) and similar terms refer to mole percent unless otherwise indicated. Mass percent (wt% or%) and similar terms refer to mass percent unless otherwise indicated.

Typically, the metal loading of the catalyst is expressed as a mass percent of the catalyst metal based on the total dry weight of the metal and the catalyst support. Thus, for example, 1(1) mass percent of metal on the support means that 1 gram of pure metal is present in 100 grams of supported metal catalyst (i.e., the total weight of support (99 grams) and metal (1 gram)).

"conversion" means the mole percent based on the acetic acid in the feed. The conversion of acetic acid (AcOH) was calculated from Gas Chromatography (GC) data using the following formula:

"Selectivity" means the mole percentage based on acetic acid converted. For example, if the conversion is 50 mol% and 50 mol% of the converted acetic acid is converted to ethyl acetate (EtOAC), we say that the selectivity to ethyl acetate is 50%. The selectivity was calculated from Gas Chromatography (GC) data using the following formula:

wherein "total mmol C out (GC)" means the total mmol of carbon in all products analyzed by gas chromatography.

The reaction proceeds according to the following formula:

(a) hydrogenation of acetic acid to acetaldehyde

(b) Addition of acetaldehyde to acetic anhydride to form ethylidene diacetate

(c) Thermal decomposition of ethylidene diacetate to form VAM and acetic acid

(d) Pyrolysis of acetic acid to form ketene

(e) Addition of ketene to acetaldehyde to form VAM

Hydrogenation of acetic acid to acetaldehyde:

according to the present invention, the conversion of acetic acid to acetaldehyde can be accomplished in a variety of different designs, such as, for example, in a single reaction zone which can be a layered fixed bed, as it is designed. An adiabatic reactor may be used, or a shell-and-tube reactor with a heat transfer medium may be used. The fixed bed may contain a mixture of different catalyst particles or catalyst particles comprising multiple catalysts, as further described herein. The fixed bed may also include a mixing zone for the particulate matter forming reactants. A reaction mixture comprising acetic acid, hydrogen and optionally an inert carrier gas is fed as a high pressure stream into the bed into the mixing zone. This stream is then fed (via pressure drop) to a reaction zone or zone containing a catalytic composition comprising a suitable hydrogenation catalyst wherein the acetic acid is hydrogenated to acetaldehyde. Any suitable particle size may be used depending on the type of reactor, capacity requirements, and the like.

Although a variety of metal-supported hydrogenation catalysts known to those skilled in the art can be used to hydrogenate acetic acid to acetaldehyde in the process of the present invention, it is preferred to employ a hydrogenation catalyst comprising at least one or more metals selected from the group consisting of iron, copper, gold, platinum, palladium and ruthenium on a suitable catalyst support. Optionally, the second or third metal may be selected from the group consisting of tin, aluminum, potassium, cobalt, molybdenum, tungsten, and vanadium. Preferably, the catalyst suitable for use in the process of the present invention comprises ruthenium alone supported on a suitable support, such as iron oxide or silica, or a combination of ruthenium and tin or ruthenium and iron supported on a suitable catalyst support. Similarly, preferred hydrogenation catalysts are iron alone supported on a suitable support, such as silica, or a combination of iron and platinum or iron and cobalt supported on a suitable catalyst support, such as silica. Similarly, other catalysts suitable for use in the process of the invention include palladium alone or a combination of palladium/gold (Pd/Au) or palladium/copper (Pd/Cu) which may further contain potassium acetate. Furthermore, suitable catalysts are combinations of palladium/iron (Pd/Fe), iron/cobalt (Fe/Co), copper/molybdenum (Cu/Mo) or copper/aluminum (Cu/Al).

Generally, when bimetallic catalysts are employed, a combination of metals, preferably in suitable weight ratios on a suitable support, may be used as the hydrogenation catalyst. Thus, for example, combinations of ruthenium and iron (Ru/Fe), ruthenium and tin (Ru/Sn), palladium/copper (Pd/Cu), palladium/iron (Pd/Fe) in a mass ratio of about 0.1 to 1 are particularly preferred. More preferably, the mass ratio of Ru/Fe or Ru/Sn or Pd/Cu or Pd/Fe is about 0.2-0.5, and most preferably the mass ratio of Ru/Fe or Ru/Sn or Pd/Cu or Pd/Fe is about 0.2. Similar mass ratios can be used for the platinum and iron Pt/Fe catalyst combinations, i.e., mass ratios of 0.1 to 1, preferably 0.2 to 0.5 and most preferably 0.2. When a combination of cobalt and iron (Co/Fe) or copper/molybdenum (Cu/Mo) or copper/aluminum (Cu/Al) supported on a suitable catalyst support is employed, the preferred Co/Fe or Cu/Mo or Cu/Al mass ratio is in the range of 1 to 5. For example, a combination of 17.4 wt.% cobalt and 4.8 wt.% iron supported on silica is commercially available. Similarly, a copper-aluminum catalyst is sold by Sud Chemie under the name T-4489.

When ruthenium alone or palladium alone or iron alone on a suitable support is used as the metal catalyst, any loading level of ruthenium, palladium or iron may be employed to affect the selective hydrogenation of acetic acid to acetaldehyde. Typically, however, the loading level of ruthenium or palladium may be from 0.5 wt.% to about 20 wt.%, preferably 1 wt.% to about 10 wt.% and most preferably 1 wt.% to about 5 wt.%. Generally, in the process of the present invention, 0.5 to 1 wt.% of the metal catalyst is sufficient to obtain optimal catalytic performance when noble metals such as ruthenium or palladium are used alone. Preferred ruthenium or palladium catalyst supports are iron oxide or silica. Similarly, when iron is employed alone as the metal catalyst, the loading level of iron may be from 1 wt.% to about 20 wt.%, preferably 2 wt.% to about 10 wt.% and most preferably 3 wt.% to about 8 wt.%. Iron a preferred catalyst support is silica.

When the bimetallic catalyst employed is two noble metals, such as palladium and gold, then the metal loading of each noble metal is in the range of from about 0.5 wt.% to about 20 wt.%, preferably 1 wt.% to about 10 wt.% and most preferably 1 wt.% to about 5 wt.%. However, as already indicated above, low loadings of about 0.5 wt.% or 1 wt.% of each noble metal, e.g. palladium or gold, have resulted in the process of the invention having optimal catalytic performance.

Various catalyst supports known in the art may be used to support the catalyst of the present invention. Such a support is not subject to any limitation, and examples thereof include zeolites such as H-ZSM-5, iron oxide, silica, alumina, titania, zirconia, magnesia, calcium silicate, carbon, graphite and a mixture thereof. Preferred supports are silica and iron oxide. More preferably, silica is used as the catalyst support in the process of the present invention. It is important to note that the higher the purity of the silica, the better its function as a support. Various forms of commercially available silica supports may be used in the present invention, including high surface area silica (HS A silica) and low surface area silica (LSA silica).

In another aspect of the process of the present invention, any known zeolite catalyst may be used as the catalyst support. Although any zeolite having a pore size of at least about 0.6nm may be used, it is preferred to employ a catalyst support selected from the group consisting of mordenite, ZSM-5, X zeolite and Y zeolite among these zeolites.

The preparation of large pore mordenite has been described, for example, in U.S. patent 4,018,514 to Plummer and mol.sieves pap.conf., 1967, 78, soc.chem.ind.london to d.domine and j.quabex.

Zeolite X is described, for example, in U.S. patent 2,882,244 to Milton, and zeolite Y is described in U.S. patent 3,130,007 to Breck.

A variety of zeolites and zeolite-like materials are known in the chemical reaction catalysis art. For example, U.S. Pat. No. 3,702,886 to Argauer discloses a class of synthetic zeolites, referred to as "ZSM-5 zeolites," which are effective for catalyzing a variety of hydrocarbon conversion processes.

Zeolites suitable for the process of the invention may be in basic form, partially or fully acidified form, or partially dealuminated form.

Preferably, the zeolite catalyst support in the process of the present invention is in the proton form, referred to as "H-ZSM-5" or "H-mordenite" zeolite, which is prepared by substituting a substantial portion, and usually at least about 80%, of the cations in the corresponding "ZSM-5" or "mordenite" with hydrogen ions by techniques well known in the art. These zeolite catalysts are predominantly crystalline aluminosilicates or a combination of silica and alumina with intact crystalline structure in neutral form. In a particularly preferred class of zeolite catalysts for the purposes of the present invention, the SiO in these zeolites₂And Al₂O₃In a ratio of about 10 to 60.

In another aspect of the invention, the ruthenium is supported on silica or iron oxide. The combination of ruthenium and tin, iron alone or platinum and iron, iron and cobalt, iron and ruthenium, and platinum and tin, are supported on high purity low surface area silica or high purity high surface area silica using procedures known in the art or further described herein. Other preferred catalyst supports for platinum or ruthenium based metal catalysts are titania and zirconia.

As indicated above, the loading level of the two metal bound catalyst is generally referred to the content of the main catalyst metal and the mass ratio of the bound body. For example, the mass ratio of Ru/Sn, Ru/Fe, Pt/Sn or Pt/Fe is in the range of about 0.1 to 2. Thus when the mass ratio of Ru/Sn, Ru/Fe or Pt/Fe is 0.1, the amount of ruthenium or platinum may be 0.1 wt.% or 1 wt.%, and thus 1 wt.% or 10 wt.% tin or iron is present on the catalyst support. Preferably, the mass ratio of Ru/Sn, Ru/Fe, Pt/Sn or Pt/Fe is about 0.5, so the amount of ruthenium or platinum on the catalyst support may be 0.5 wt.% or 1 wt.% and the amount of tin or iron may be 1 wt.% or 2 wt.%. More preferably, the mass ratio of Ru/Sn, Ru/Fe, Pt/Sn or Pt/Fe is 1 or 0.2. Thus, when the mass ratio is 1, the amount of ruthenium or platinum on the support is 0.5 wt.%, 1 wt.% or 2 wt.%, and the amount of tin or iron is also 0.5 wt.%, 1 wt.% or 2 wt.%. Similarly, when the mass ratio of Ru/Sn, Ru/Fe or Pt/Fe is 0.2, the amount of ruthenium or platinum on the support may be 0.5 wt.% or 1 wt.%, and the amount of tin or iron is 2.5 wt.% or 5 wt.%.

If a third metal is present on the support, the amount thereof is not critical in the present invention and may vary from about 0.1 wt.% to about 10 wt.%. Metal loadings of about 1 wt.% to about 6 wt.% based on the mass of the support are particularly preferred.

Impregnation of the metal may be performed by any method known in the art. Typically, the support is dried at 120 ℃ and shaped into particles having a size distribution in the range of about 0.2 to 0.4mm prior to impregnation. Optionally, the carrier may be extruded, crushed and sieved to achieve the desired size distribution. Any known method of shaping the carrier material to the desired size distribution may be used.

For supports with low surface area, such as alpha-alumina, for example, an excess of metal solution is added until fully wetted or an excess of liquid is impregnated to achieve the desired metal loading.

As indicated above, the hydrogenation catalyst used in the process of the present invention is typically a bimetallic comprising platinum/iron, ruthenium/tin, ruthenium/iron, iron/cobalt, and the like. Without intending to be bound by any theory, it is generally believed that one metal acts as the promoting metal and the other metal is the primary metal. For example, in the present process of the invention, platinum, ruthenium, and iron are considered the primary metals for preparing the hydrogenation catalyst of the invention for the combinations mentioned separately above. Other metals, tin along with ruthenium and iron along with cobalt, platinum or ruthenium are considered promoting metals depending on a variety of reaction parameters including, but not limited to, the catalyst support employed, the reaction temperature and pressure, and the like. The catalyst may include other promoting metals such as tungsten, vanadium, molybdenum, chromium or zinc.

Bimetallic catalysts are typically impregnated in two steps. Each impregnation step is followed by drying and calcination. Bimetallic catalysts may also be prepared by co-impregnation. In most cases, the impregnation can be carried out with a metal nitrate solution. However, a variety of other soluble salts that release metal ions upon calcination may also be used. Examples of other suitable metal salts for impregnation include metal oxalates, metal hydroxides, metal oxides, metal acetates, ammonium metal oxides such as ammonium heptamolybdate hexahydrate, metal acids such as perrhenic acid solution, and the like.

Thus in one embodiment of the invention, there is provided a hydrogenation catalyst wherein the catalyst support is silica or iron oxide and ruthenium alone is used as the hydrogenation catalyst. In this aspect of the invention, the metal loading of ruthenium may be from 1(1) to about 20(20) wt.%, preferably from 1 to 10 wt.% and most preferably from 1 to 5 wt.%.

In another embodiment of the present invention, a hydrogenation catalyst is provided wherein the catalyst support is silica and iron alone is used as the hydrogenation catalyst. In this aspect of the invention, the metal loading of iron may be from 1(1) to about 20(20) wt.%, preferably from 2 to 10 wt.% and most preferably from 3 to 8 wt.% iron.

In another embodiment of the present invention, a bimetallic load of ruthenium and tin or platinum and tin is provided. In this aspect of the invention, the loading of ruthenium or platinum is from about 0.5 wt.% to about 2 wt.% and the loading of tin is from about 2.5 wt.% to about 10 wt.%. Specifically, the loading levels of ruthenium/tin or platinum/tin on silica that can be employed are 1/1 wt.%, 1/5 wt.%, 0.5/5 wt.%, and 0.5/2.5 wt.%.

In another embodiment of the present invention, there is further provided a hydrogenation catalyst wherein the catalyst support is a bimetallic supported high purity, low surface area silica with platinum and iron or ruthenium and iron. In this aspect of the invention, the loading of platinum or ruthenium is from about 0.5 wt.% to about 2 wt.%, and the loading of iron is from about 4 wt.% to about 10 wt.%. Specifically, platinum/iron or ruthenium/iron loading levels on high purity low surface area silica that can be employed are 1/1 wt.%, 1/5 wt.%, 0.5/5 wt.%, and 0.5/2.5 wt.%. Other preferred supports in this aspect of the invention include H-ZSM-5, graphitized carbon, zirconia, titania, iron oxide, silica-alumina and calcium silicate.

In a further embodiment of the present invention, there is provided a hydrogenation catalyst wherein the bimetallic catalyst is cobalt and iron supported on silica. In this aspect of the invention, the loading level of cobalt is from about 12 wt.% to about 22 wt.% and the loading level of iron is from about 3 wt.% to 8 wt.%. Specifically, a loading level of 17.4 wt.% cobalt and about 4.8 wt.% iron on silica is commercially available.

Acetic acid can be selectively converted to acetaldehyde at very high rates in general by the practice of this invention. This selectivity to acetaldehyde is generally very high and may be at least 60%. Under preferred reaction conditions, acetic acid is selectively converted to acetaldehyde with a selectivity of at least 70%, or more preferably with a selectivity of more than 80%, e.g., at least 90%.

The conversion of acetic acid with the catalyst of the invention is at least 10% and can reach 40%, when the selectivity to acetaldehyde is at least 60%, preferably 70% and most preferably 80%.

Typically, the active catalyst of the present invention is a mono-or bimetallic catalyst as described herein. More specifically, bimetallic catalysts comprising ruthenium and tin, ruthenium and iron, platinum and tin, platinum and iron, and cobalt and iron supported on silica are preferred, with ruthenium or platinum loading of 0.5 wt.% to 1 wt.% and tin and iron loading of 5 wt.% and cobalt loading of about 18 wt.% being preferred. With this catalyst, acetic acid may be converted at a conversion of about 40% and acetaldehyde selectivity of at least 60%, more preferably at least 80% selectivity to acetaldehyde may be achieved in accordance with the practice of the present invention.

Similar conversions and selectivities can be achieved using zirconia, graphite or titania as the support and similar loadings of ruthenium, platinum, tin, iron and cobalt as described above. Other promoting metals may also be used in combination with ruthenium or platinum as indicated above.

In another aspect of the invention, high levels of conversion on the order of at least 25% and high selectivity to acetaldehyde of at least about 80% can also be obtained using ruthenium or iron supported on silica or iron oxide as the catalyst support at a loading of from 1 wt.% to about 5 wt.%. Other preferred catalyst supports in this aspect of the invention include graphitized carbon, titania, zirconia, silica-alumina and calcium silicate.

In another aspect of the process of the invention, the hydrogenation reaction is carried out at a pressure sufficient only to overcome the pressure drop across the catalytic bed.

The reaction can be carried out under a variety of conditions in the vapor or liquid state. Preferably, the reaction is carried out in the vapor phase. Reaction temperatures which may be employed are, for example, in the range of from about 250 ℃ to about 350 ℃, preferably from about 290 ℃ to about 310 ℃. In general, the pressure is not critical to the reaction and subatmospheric, atmospheric or superatmospheric pressures can be employed. However, in most cases, the pressure of the reaction will be in the range of about 5 to 30 atmospheres absolute, and most preferably the pressure of the reaction zone will be in the range of about 8 to 20 atmospheres absolute.

Although the reaction consumes 1 mole of hydrogen per mole of acetic acid to produce 1 mole of acetaldehyde, the actual molar ratio of acetic acid to hydrogen in the feed stream may vary within wide limits, for example from about 100: 1 to 1: 100. Preferably, however, the ratio is in the range of about 1: 20 to 1: 2. More preferably, the molar ratio of acetic acid to hydrogen is about 1: 5.

The feedstock used in connection with the process of the present invention may be derived from any suitable source, including natural gas, petroleum, coal, biomass, and the like. The production of acetic acid by methanol carbonylation, acetaldehyde oxidation, ethylene oxidation, oxidative fermentation, and anaerobic fermentation, among others, is well known. As petroleum and natural gas become more expensive, processes for producing acetic acid and intermediates such as methanol and carbon monoxide from alternative carbon sources have gained more attention.

Of particular interest is the production of acetic acid from synthesis gas (syngas), which may be derived from any suitable carbon source. For example, U.S. patent 6,232,352 to Vidalin, the disclosure of which is incorporated herein by reference, teaches a method of retrofitting a methanol plant for the production of acetic acid. By retrofitting a methanol plant, the large capital investment involved in CO generation in a new acetic acid plant is greatly reduced or mostly cut down. All or part of the synthesis gas is derived from the methanol synthesis loop and supplied to a separation unit to recover CO and hydrogen, which is then used to produce acetic acid. In addition to acetic acid, the process may also be used to produce hydrogen, which is used in connection with the present invention.

U.S. patent No. re 35,377 to Steinberg et al, which is also incorporated herein by reference, provides a process for the production of methanol by the conversion of carbonaceous materials such as oil, coal, natural gas and biomass materials. The process comprises hydro-gasification of solid and/or liquid carbonaceous material to obtain a process gas, which is pyrolysed with additional natural gas steam to form synthesis gas. The synthesis gas is converted to methanol which can be carbonylated to acetic acid. The process can also produce hydrogen, as indicated above, which is used in connection with the present invention. See also U.S. Pat. No. 5,821,111 to Grady et al, which discloses a process for converting waste biomass to syngas by gasification, and U.S. Pat. No.6,685,754 to Kindig et al, the disclosures of which are incorporated herein by reference.

Acetic acid may be vaporized at the reaction temperature and then may be fed with hydrogen in an undiluted state or diluted with a relatively inert carrier gas such as nitrogen, argon, helium, carbon dioxide, and the like.

Alternatively, acetic acid in vapor form may be withdrawn directly as a crude product from the flash vessel of a methanol carbonylation unit of the type described in U.S. Pat. No.6,657,078 to Scates et al, the disclosure of which is incorporated herein by reference. The crude vapor product can be directly fed into the reaction zone of the present invention without condensing acetic acid and light ends or removing water, thus saving overall process investment.

The contact or residence time may also vary widely depending on such variables as the amount of acetic acid, catalyst, reactor, temperature and pressure. When a non-fixed bed catalyst system is employed, the contact time typically ranges from a fraction of a second to several hours, with preferred contact times, at least for vapor phase reactions, ranging from about 0.5 to 100 seconds.

Typically, the catalyst is used in a fixed bed reactor, for example in the form of an elongated tube or tube, through which the reactants, here usually in vapor form, pass. Other reactors, such as fluidized or ebullating bed reactors, may be employed if desired. In some cases it may be advantageous to use the hydrogenation catalyst in combination with an inert material so that the pressure drop, flow rate, heat balance or other process parameters within the catalyst bed, including the contact time of the reaction compounds and the catalyst particles, can be controlled.

In a preferred embodiment, there is also provided a process for the selective and direct formation of acetaldehyde from acetic acid comprising: the feed stream containing acetic acid and hydrogen is contacted at elevated temperature with a suitable hydrogenation catalyst comprising from about 0.5 wt.% to about 1 wt.% platinum or ruthenium, and from about 2.5 wt.% to about 5 wt.% tin or iron on a suitable catalyst support. The preferred catalyst support in this embodiment of the invention is silica.

In this embodiment of the inventive process, the preferred hydrogenation catalyst contains about 0.5 wt.% or about 1(1) wt.% platinum and about 5(5) wt.% iron or tin; or about 0.5 wt.% or about 1(1) wt.% ruthenium and about 5(5) wt.% tin or iron. Preferably, the hydrogenation catalyst layer is layered in a fixed bed and the reaction is carried out in the vapor phase, the feed stream used contains acetic acid and hydrogen in a molar ratio in the range of about 1: 20 to 1: 5, and the temperature is in the range of about 290 ℃ to 310 ℃, and the pressure in the reaction zone is in the range of about 8 to 20 atmospheres absolute, and the contact time of the reactants is in the range of about 0.5 to 100 seconds.

Enrichment of acetaldehyde in the first gaseous product stream:

in the second step of the process of the present invention, the acetaldehyde produced in the first reaction zone of step (a) of the process of the present invention as described herein is further enriched to obtain a stream containing at least 50 mol% acetaldehyde. Any method known in the art may be used for this purpose. For example, a suitable distillation column may be used to remove volatile gaseous by-products from the top of the column and to separate a high boiling fraction from the bottom of the column. Other cryogenic processes and/or temperature controlled capture devices may also be employed herein, for example a wash column may remove impurities and other by-products, whether low boiling or high boiling, to obtain a stream containing at least 50 mol% acetaldehyde.

Preferably, the enriched product stream from the first reaction zone contains at least 60 mol% acetaldehyde. More preferably, the enriched product stream from the first reaction zone contains at least 70 mol% acetaldehyde. Even more preferably, the enriched product stream from the first reaction zone contains at least 80 mol% acetaldehyde.

Reacting acetaldehyde with acetic anhydride to form ethylidene diacetate

In one embodiment of the process of the present invention, the acetaldehyde formed in the first reaction zone is then converted in one or more reaction zones to VAM and acetic acid by first reacting the acetaldehyde with acetic anhydride to form ethylidene diacetate.

Exemplary processes for the production of ethylidene diacetate utilizing acetaldehyde and acetic anhydride can be found in U.S. patents 3,700,722 and 3,383,374 to McTeer which disclose the reaction of acetic anhydride and excess acetaldehyde in the presence of sulfuric acid at 25 deg. -100 deg.C, preferably 40 deg. -60 deg.C, which after neutralization with sodium hydroxide produces ethylidene diacetate and bis (1-acetoxyethyl) ether.

Thermal decomposition of ethylidene diacetate:

subsequent thermal decomposition of the ethylidene diacetate produces VAM and acetic acid, and the product stream containing VAM and acetic acid enters a separation unit. The thermal decomposition of ethylidene diacetate is typically carried out at a temperature between 50 ° and 200 ℃ using a catalyst at a pressure of less than 15 atm.

Examples of suitable acidic catalysts for the thermal decomposition of ethylidene diacetate to VAM and acetic acid are aromatic sulfonic acids, sulfuric acid, and alkanesulfonic acids, see U.S. Pat. No. 2,425,389 to Oxley et al, U.S. Pat. No. 2,859,241 to Schnizer, and 4,843,170 to Isshiki et al. In particular, benzenesulfonic acid, methylbenzenesulfonic acid, ethylbenzenesulfonic acid, dimethylbenzene (zene) sulfonic acid, and naphthalenesulfonic acid are preferred aromatic sulfonic acids.

In another embodiment, the separated acetic acid may be recycled back to the reactor system or vented for purification as a final product.

Addition of ketene to acetaldehyde to form VAM:

in a further embodiment of the present invention, VAM may also be obtained from the reaction of acetaldehyde and ketene obtained in step (b) of the process of the present invention. Ketene is commercially obtained from the pyrolysis of acetic acid. The ketene thus obtained is then contacted with the acetaldehyde formed in step (b) of the process of the present invention.

Generally, the reaction of acetaldehyde and ketene can be carried out in the gas phase with a suitable acid catalyst. Any of the known solid acid catalysts can be used for this purpose. For example, various acid catalysts as described above are suitable for this purpose. Typically, suitable solid acid catalysts include sulfonic acid resins, such as the perfluorosulfonic acid resins disclosed in U.S. patent 4,399,305 to Schreck, as indicated above. Zeolites are also suitable as solid acid catalysts as shown in U.S. Pat. No. 4,620,050 to Cognion et al. Thus, a zeolite catalyst can be simultaneously used with a supported hydrogenation catalyst as described above and the resulting acetaldehyde is then reacted with ketene to form VAM.

Thus, according to one aspect of the process of the present invention, there is also provided an integrated fixed bed reactor, the front end of which is packed with a hydrogenation catalyst as hereinbefore described and the rear end of which is packed with a suitable acid catalyst as hereinbefore described, such that both steps of the process of the present invention can be effectively carried out in a single stage. Any known fixed bed reactor which can achieve this result can be used for this purpose. This task is preferably achieved with a tubular reactor designed to contain two different catalyst layers as described above.

Generally, the reaction of acetaldehyde with ketene in the presence of a solid acid catalyst can be carried out at a temperature in the range of from about 150 ℃ to about 300 ℃, preferably in the range of from about 160 ℃ to about 250 ℃, and more preferably in the range of from about 170 ℃ to 225 ℃. Again, as noted above, any of the zeolite or sulfonic acid resin catalysts may be used as the solid acid catalyst. Preferably, the reaction is carried out in the presence of a zeolite having a pore size greater than about 0.6 nm. Specific examples of such zeolites include, without limitation, mordenite, zeolite X and zeolite Y as described herein.

As mentioned above, another preferred acid catalyst that may be employed in this step of the process of the present invention is a perfluorosulfonic acid resin, such as that described in DuPont de Memours Company of Delaware, WilmingtonTrademarks are sold. Suitable variants of this resin are described in U.S. Pat. No. 4,065,512 to Cares and DuPont "Innovation" Vol.4, No. 3, Spring 1973.

The following examples A-O describe the preparation procedures for preparing the various catalysts employed in examples 1-19, as follows:

example A

Preparation of 1 wt.% ruthenium on iron oxide

Powdered and sieved iron oxide (99g) having a uniform particle size distribution of about 0.2mm was dried in an oven at 120 ℃ under nitrogen atmosphere overnight and then cooled to room temperature. To this was added a solution of ruthenium nitrosylnitrate (Heraeus) (3.14g) in distilled water (32 ml). The resulting slurry was dried in an oven with gradual temperature rise to 110 ℃ (> 2 hours, 10 ℃/min). The impregnated catalyst mixture was then calcined at 500 deg.C (6 hours, 1 deg.C/min).

Example B

Preparation of 3 wt.% ruthenium on iron oxide

The procedure of example A was substantially repeated except for using a solution of ruthenium nitrosyl nitrate (Heraeus) (9.42g) in distilled water (96ml) and 97 g of iron oxide.

Example C

Preparation of 5 wt.% iron on high purity low surface area silica

Powdered and sieved high purity low surface area silica (95g) having a uniform particle size distribution of about 0.2mm was dried in an oven at 120 ℃ under nitrogen atmosphere overnight and then cooled to room temperature. A solution of iron nitrate nonahydrate (Alfa Aesar) (36.2g) in distilled water (36ml) was added thereto. The resulting slurry was dried in an oven with gradual temperature rise to 110 ℃ (> 2 hours, 10 ℃/min). The impregnated catalyst mixture was then calcined at 500 deg.C (6 hours, 1 deg.C/min).

Example D

Preparation of 5 wt.% tin and 0.5 wt.% ruthenium on high purity low surface area silica

Powdered and sieved high purity low surface area silica (94g) having a uniform particle size distribution of about 0.2mm was dried in an oven at 120 ℃ under a nitrogen atmosphere overnight and then cooled to room temperature. To this was added a solution of tin oxalate (Alfa Aesar) (8.7g) in dilute nitric acid (1N 45 ml). The resulting slurry was dried in an oven with gradual temperature rise to 110 ℃ (> 2 hours, 10 ℃/min). The impregnated catalyst mixture was then calcined at 500 deg.C (6 hours, 1 deg.C/min). To the calcined and cooled mass was added a solution of ruthenium nitrosylnitrate (Heraeus) (1.57g) in distilled water (16 ml). The resulting slurry was dried in an oven with gradual temperature rise to 110 ℃ (> 2 hours, 10 ℃/min). The impregnated catalyst mixture was then calcined at 500 deg.C (6 hours, 1 deg.C/min).

Example E

Preparation of 1 wt.% ruthenium and 5 wt.% iron on high purity low surface area silica

Powdered and sieved high purity low surface area silica (94g) having a uniform particle size distribution of about 0.2mm was dried in an oven at 120 ℃ under a nitrogen atmosphere overnight and then cooled to room temperature. To this was added a solution of ruthenium nitrosylnitrate (Heraeus) (3.14g) in distilled water (32 ml). The resulting slurry was dried in an oven with gradual temperature rise to 110 ℃ (> 2 hours, 10 ℃/min). The impregnated catalyst mixture was then calcined at 500 deg.C (6 hours, 1 deg.C/min). To the calcined and cooled mass was added a solution of iron nitrate nonahydrate (Alfa Aesar) (36.2g) in distilled water (36 ml). The resulting slurry was dried in an oven with gradual temperature rise to 110 ℃ (> 2 hours, 10 ℃/min). The impregnated catalyst mixture was then calcined at 500 deg.C (6 hours, 1 deg.C/min).

Example F

Preparation of 5 wt.% iron and 1 wt.% platinum on high purity low surface area silica

Powdered and sieved high purity low surface area silica (94g) having a uniform particle size distribution of about 0.2mm was dried in an oven at 120 ℃ under a nitrogen atmosphere overnight and then cooled to room temperature. A solution of iron nitrate nonahydrate (Alfa Aesar) (36.2g) in distilled water (36ml) was added thereto. The resulting slurry was dried in an oven with gradual temperature rise to 110 ℃ (> 2 hours, 10 ℃/min). The impregnated catalyst mixture was then calcined at 500 deg.C (6 hours, 1 deg.C/min). To the calcined and cooled mass was added a solution of platinum nitrate (Chempur) (1.64g) in distilled water (16 ml). The resulting slurry was dried in an oven with gradual temperature rise to 110 ℃ (> 2 hours, 10 ℃/min). The impregnated catalyst mixture was then calcined at 500 deg.C (6 hours, 1 deg.C/min).

Example G

Preparation of 1 wt.% platinum and 5 wt.% tin on high purity low surface area silica

Powdered and sieved high purity low surface area silica (94g) having a uniform particle size distribution of about 0.2mm was dried in an oven at 120 ℃ under a nitrogen atmosphere overnight and then cooled to room temperature. To this was added a solution of platinum nitrate (Chempur) (1.64g) in distilled water (16ml) and a solution of tin oxalate (Alfa Aesar) (8.7g) in dilute nitric acid (1N 43.5 ml). The resulting slurry was dried in an oven with gradual temperature rise to 110 ℃ (> 2 hours, 10 ℃/min). The impregnated catalyst mixture was then calcined at 500 deg.C (6 hours, 1 deg.C/min).

Example H

Preparation of 1 wt.% palladium, 1 wt.% gold and 5 wt.% potassium acetate on high purity low surface area silica

The procedure of example D was substantially repeated except for using a solution of palladium nitrate (Heraeus) (2.17g) in distilled water (22ml), a solution of gold (III) hydroxide (Alfa Aesar) (1.26g) and potassium hydroxide (0.28g) in distilled water (10ml) and a solution of potassium acetate (Sigma) (5g) in distilled water (10ml) and 93g of silica. The catalyst was impregnated sequentially first with palladium and then with gold and finally with potassium acetate.

Example I

Preparation of 1 wt.% palladium, 5 wt.% copper and 5 wt.% potassium acetate on high purity low surface area silica

The procedure of example D was substantially repeated except for using a solution of palladium nitrate (Heraeus) (2.17g) in distilled water (22ml), a solution of copper nitrate trihydrate (Alfa Aesar) (19g) in distilled water (20ml) and a solution of potassium acetate (Sigma) (5g) in distilled water (10ml) and 89g of silica. The catalyst was impregnated sequentially first with copper and then palladium and finally with potassium acetate.

Example J

Preparation of 1 wt.% palladium and 5 wt.% copper on carbon

The procedure of example D was substantially repeated except for using a solution of palladium nitrate (Heraeus) (2.17g) in distilled water (22ml), a solution of copper nitrate trihydrate (Alfa Aesar) (19g) in distilled water (20ml) and 94g of carbon. The catalyst is impregnated sequentially first with copper and then with palladium.

Example K

Preparation of 1 wt.% palladium and 5 wt.% iron on high purity low surface area silica

The procedure of example D was substantially repeated except for using a solution of palladium nitrate (Heraeus) (2.17g) in distilled water (22ml), a solution of iron nitrate nonahydrate (Alfa Aesar) (36.2g) in distilled water (30ml) and 94g of silica. The catalyst was sequentially impregnated first with iron and then with palladium.

Example L

Preparation of 5 wt.% iron and 5 wt.% cobalt on high purity low surface area silica

The procedure of example D was substantially repeated except for using a solution of iron nitrate nonahydrate (Alfa Aesar) (36.2g) in distilled water (30ml), a solution of cobalt nitrate hexahydrate (24.7g) in distilled water (25ml) and 90g of silica. The catalyst was impregnated first with iron and then with cobalt in sequence.

Example M

Preparation of 5 wt.% copper and 5 wt.% molybdenum on high purity low surface area silica

The procedure of example D was substantially repeated except for using a solution of copper nitrate trihydrate (Alfa Aesar) (19g) in distilled water (20ml), a solution of ammonium heptamolybdate hexahydrate (Sigma) (9.5g) in distilled water (65ml) and 90g of silica. The catalyst was impregnated sequentially first with copper and then with molybdenum.

Example N

Preparation of 5 wt.% tin and 1 wt.% ruthenium on high purity low surface area silica

The procedure of example D was substantially repeated except for using a solution of tin oxalate (Alfa Aesar) (8.7g) in dilute nitric acid (1N 43.5ml), a solution of ruthenium nitrosyl nitrate (Heraeus) (3.14g) in distilled water (32ml) and 94g of silica. The catalyst was co-impregnated with tin and ruthenium.

Example O

Preparation of 1 wt.% palladium on iron oxide

The procedure of example D was substantially repeated except for using a solution of palladium nitrate (Heraeus) (2.17g) in distilled water (22ml) and 99g of iron oxide.

Gas Chromatography (GC) analysis of the product

Product analysis was performed by online GC. The reactants and products were analyzed using a three-channel integrated GC equipped with 1 Flame Ionization Detector (FID) and 2 Thermal Conductivity Detectors (TCD). The front channel was equipped with FID and CP-Sil 5(20m) + WaxFFap (5m) columns and used for quantitation:

acetaldehyde

Ethanol

Acetone (II)

Acetic acid methyl ester

Vinyl acetate (VAA)

Ethyl acetate

Acetic acid

Ethylene diacetate

Ethylene glycol

Ethylidene diacetate

Paraldehyde

The intermediate channel was fitted with a TCD and Porabond Q column and used to meter:

CO₂

ethylene

Ethane (III)

The rear channel was fitted with a TCD and Molsieve 5A column and used to meter:

helium gas

Hydrogen gas

Nitrogen gas

Methane

Carbon monoxide

Prior to the reaction, the retention times of the different components were determined by spiking with the respective compositions and GC was calibrated with a calibration gas of known composition or a liquid solution of known composition. This enables the determination of the response coefficients of the different components.

Examples 1-17 describe the hydrogenation of acetic acid to acetaldehyde as described in the first step of the process of the present invention.

Example 1

The catalyst used was 1 wt.% ruthenium on iron oxide prepared according to the procedure of example a.

In a tubular reactor made of stainless steel with an internal diameter of 30mm and capable of being warmed up to a controlled temperature, 50ml of 1 wt.% ruthenium supported on iron oxide were arranged. The length of the catalyst bed after loading was approximately about 70 mm. Prior to the reaction, the catalyst was reduced in situ by heating at a rate of 2 deg.C/min to a final temperature of 400 deg.C, followed by a nitrogen atmosphere containing 5 mol% hydrogen for 7500hr^-1Is introduced into the catalyst chamber. After reduction, the catalyst was cooled to a reaction temperature of 350 ℃ by continuously passing a stream of nitrogen containing 5 mol% of hydrogen. Once the reaction temperature stabilized at 350 ℃, the hydrogenation of acetic acid was started as follows:

the liquid feed consists essentially of acetic acid. Reacting the starting materials at a temperature of about 350 ℃The liquid is evaporated and mixed with hydrogen and helium as carrier gas for about 2500hr^-1Is injected into the reactor at a mean total Gas Hourly Space Velocity (GHSV). The resulting feed stream contains a mole percent of acetic acid from about 4.4% to about 13.8% and a mole percent of hydrogen from about 14% to about 77%. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The selectivity to acetaldehyde was 60% at 50% acetic acid conversion.

Example 2

The catalyst used was 5 wt.% iron on silica prepared according to the procedure of example C.

At a temperature of 350 ℃, contains evaporated acetic acid and hydrogen (H)₂And acetic acid at a molar ratio of 5) has a mean total Gas Hourly Space Velocity (GHSV) of 2,500hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was 75% and the acetaldehyde selectivity was 70%.

Example 3

The catalyst used was 0.5 wt.% ruthenium and 5 wt.% tin on silica prepared according to the procedure of example D.

At a temperature of 250 ℃ and a pressure of 1bar, evaporated acetic acid and hydrogen (H) are contained₂And acetic acid at a molar ratio of 5) has a mean total Gas Hourly Space Velocity (GHSV) of 10,000hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was 4% and the acetaldehyde selectivity was 91%. Other products formed were ethane (1%) and ethanol (8%).

Example 4

The catalyst used was 1 wt.% ruthenium and 5 wt.% iron on silica prepared according to the procedure of example E.

At a temperature of 300 ℃, contains acetic acid and hydrogen gas which are vaporizedH₂And acetic acid at a molar ratio of 5) has a mean total Gas Hourly Space Velocity (GHSV) of 2,500hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was 35% and the acetaldehyde selectivity was about 70%.

Example 5

The catalyst used was 1 wt.% platinum and 5 wt.% iron on high purity low surface area silica prepared according to the procedure of example F.

At a temperature of 350 ℃ and a pressure of 1bar, evaporated acetic acid and hydrogen (H) are contained₂And acetic acid at a molar ratio of 5) has a mean total Gas Hourly Space Velocity (GHSV) of 2,500hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was 65% and the acetaldehyde selectivity was 60%. Other products formed were titanium dioxide (6%) and ethyl acetate (9%).

Example 6

The catalyst used was 0.5 wt.% platinum and 5 wt.% tin on silica prepared according to the procedure of example G.

At a temperature of 350 ℃ and a pressure of 1bar, evaporated acetic acid and hydrogen (H) are contained₂And acetic acid at a molar ratio of 5) has a mean total Gas Hourly Space Velocity (GHSV) of 2,500hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was 85% and the acetaldehyde selectivity was 65%. Other products formed were methane (4%) and ethyl acetate (9%).

Example 7

The catalyst used was a commercial Co/Fe catalyst containing 17.4 wt.% cobalt and 4.8 wt.% iron on silica.

At a temperature of 350 ℃, comprising evaporationThe average total Gas Hourly Space Velocity (GHSV) of the acetic acid and hydrogen feed stream of (A) is 2,500hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was about 65% and the acetaldehyde selectivity was 75%.

Example 8

The catalyst used was 1 wt.% palladium, 1 wt.% gold and 5 wt.% potassium acetate on silica prepared according to the procedure of example H.

At a temperature of 250 ℃ and a pressure of 1bar, evaporated acetic acid and hydrogen (H) are contained₂And acetic acid at a molar ratio of 5) has a mean total Gas Hourly Space Velocity (GHSV) of 10,000hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was 5% and the acetaldehyde selectivity was 98.5%. Other products formed were ethane (1%) and ethanol (0.5%).

Example 9

The catalyst used was 1 wt.% palladium, 5 wt.% copper and 5 wt.% potassium acetate on silica prepared according to the procedure of example I.

At a temperature of 250 ℃ and a pressure of 1bar, evaporated acetic acid and hydrogen (H) are contained₂And acetic acid at a molar ratio of 5) has a mean total Gas Hourly Space Velocity (GHSV) of 10,000hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was 2% and the acetaldehyde selectivity was 97.5%. The other product formed was ethane (2.5%).

Example 10

The catalyst used was 1 wt.% palladium and 5 wt.% copper on carbon prepared according to the procedure of example J.

Containing evaporated material at a temperature of 250 ℃ and a pressure of 1barAcetic acid and hydrogen (H)₂And acetic acid at a molar ratio of 5) has a mean total Gas Hourly Space Velocity (GHSV) of 10,000hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was 1% and the acetaldehyde selectivity was 97%. The other product formed was ethane (3%).

Example 11

The catalyst used was 1 wt.% palladium and 5 wt.% iron on silica prepared according to the procedure of example K.

At a temperature of 250 ℃ and a pressure of 1bar, evaporated acetic acid and hydrogen (H) are contained₂And acetic acid at a molar ratio of 5) has a mean total Gas Hourly Space Velocity (GHSV) of 10,000hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was 9% and the acetaldehyde selectivity was 96%. Other products formed were ethane (0.6%) and ethanol (3.6%).

Example 12

The catalyst used was 5 wt.% iron and 5 wt.% cobalt on silica prepared according to the procedure of example L.

At a temperature of 250 ℃ and a pressure of 1bar, evaporated acetic acid and hydrogen (H) are contained₂And acetic acid at a molar ratio of 5) has a mean total Gas Hourly Space Velocity (GHSV) of 10,000hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was 11% and the acetaldehyde selectivity was 95%. Other products formed were ethane (1%) and ethanol (4%).

Example 13

The catalyst used was 5 wt.% iron and 5 wt.% cobalt on silica prepared according to the procedure of example L.

At a temperature of 350 ℃ andat a pressure of 1bar, with evaporated acetic acid and hydrogen (H)₂And acetic acid at a molar ratio of 5) has a mean total Gas Hourly Space Velocity (GHSV) of 2,500hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was 75% and the acetaldehyde selectivity was 70%. Other products formed were methane (4%) and carbon dioxide (3%).

Example 14

The catalyst used was 5 wt.% copper and 5 wt.% molybdenum on silica prepared according to the procedure of example M.

At a temperature of 350 ℃ and a pressure of 1bar, evaporated acetic acid and hydrogen (H) are contained₂And acetic acid at a molar ratio of 5) has a mean total Gas Hourly Space Velocity (GHSV) of 2,500hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was 10% and the acetaldehyde selectivity was 90%. Other products formed were ethane (1.5%) and acetone (6.6%).

Example 15

The catalyst used was 5 wt.% ruthenium and 1 wt.% tin on silica prepared according to the procedure of example N.

At a temperature of 350 ℃ and a pressure of 1bar, evaporated acetic acid and hydrogen (H) are contained₂And acetic acid at a molar ratio of 5) has a mean total Gas Hourly Space Velocity (GHSV) of 2,500hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was 60% and the acetaldehyde selectivity was 78%. Other products formed were methane (6%) and ethanol (12%).

Example 16

The catalyst used was 1 wt.% palladium on iron oxide prepared according to the procedure of example O.

At a temperature of 350 ℃ and a pressure of 15bar, evaporated acetic acid and hydrogen (H) are contained₂And acetic acid at a molar ratio of 5) has a mean total Gas Hourly Space Velocity (GHSV) of 10,000hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was 66% and the acetaldehyde selectivity was 59%. Other products formed were carbon dioxide (4%) and ethanol (18%).

Example 17

The catalyst used was a copper-aluminum catalyst available from Sud Chemie under the trade name T-4489.

At a temperature of 350 ℃ and a pressure of 1bar, evaporated acetic acid and hydrogen (H) are contained₂And acetic acid at a molar ratio of 5) has a mean total Gas Hourly Space Velocity (GHSV) of 2,500hr^-1The procedure set forth in example 1 was essentially repeated. A portion of the vapor effluent was passed through a gas chromatograph for effluent content analysis. The acetic acid conversion was 88% and the acetaldehyde selectivity was 51%. Other products formed were carbon dioxide (5%) and ethanol (16%).

Comparative examples 1A to 4A

These examples show the reaction of acetic acid and hydrogen over a series of catalysts in which no acetaldehyde is formed and/or the selectivity to acetaldehyde is very low at very low acetic acid conversions.

In all of these examples, the procedure set forth in example 1 was substantially repeated, except that a different catalyst was used as listed in table 1. The reaction temperature and selectivity to acetaldehyde and other products are also listed in table 1.

Table 1 acetic acid conversion and selectivity in comparative examples

Example 18

To produce ethylidene diacetate in step (c), the enriched product feed stream containing primarily acetaldehyde from step (b) is passed into a reactor with acetic anhydride to form a second product stream containing primarily ethylidene diacetate, according to either of U.S. patents 3,700,722 and 3,383,374, both issued to McTeer, which disclose the reaction of acetic anhydride and excess acetaldehyde in the presence of sulfuric acid at 25 deg. -100 deg.C, (preferably 40 deg. -60 deg.C).

Example 19 describes the thermal decomposition of ethylidene diacetate to form VAM and acetic acid as described in step (d) of the present invention. The procedure set forth in U.S. patent 4,843,170 to Isshiki et al was used to thermally decompose the ethylidene diacetate formed in step (c) of the present invention using any of examples 1-17 to produce acetaldehyde which was reacted with acetic anhydride in step (c) of the present invention. The thermal decomposition of ethylene diacetate typically occurs at a temperature in the range of 50 ° to 200 ℃ and a pressure of less than 15 atm.

Example 19

Any of the catalysts prepared according to examples A-O can be used in the procedure set forth in U.S. Pat. No. 5,719,315 to Tustin et al to perform the final step of producing VAM from the reaction of acetaldehyde and ketene formed from step (b) using an acid catalyst.

While the invention has been illustrated by specific examples, it will be apparent to those skilled in the art that modifications can be made to these examples without departing from the spirit and scope of the invention. In view of the foregoing discussion, relevant knowledge in the art and the documents identified above, together with background and detailed description of the invention, the disclosure of which is incorporated herein by reference in its entirety, further description is not necessary.

Claims (24)

1. A process for the production of vinyl acetate from acetic acid comprising:

a. contacting a feed stream comprising acetic acid and hydrogen at an elevated temperature in a first reaction zone with a suitable hydrogenation catalyst comprising at least one metal selected from the group consisting of iron, copper, gold, platinum, palladium and ruthenium on a suitable catalyst support, optionally in combination with one or more metal catalysts selected from the group consisting of tin, aluminum, potassium, cobalt, molybdenum, tungsten and vanadium, to form a first gaseous product stream comprising acetaldehyde;

b. enriching the first gaseous product stream with acetaldehyde to at least 50 mol%;

c. contacting said enriched first gaseous product stream obtained in step (b) with acetic anhydride at elevated temperature in a second reaction zone to form a second gaseous product stream of ethylidene diacetate;

d. thermally decomposing said second gaseous product from step (c) in a third reaction zone using a suitable acid catalyst to form a third gaseous product stream comprising predominantly vinyl acetate and acetic acid;

e. vinyl acetate is separated from the third gaseous product stream.

2. The process according to claim 1, wherein the hydrogenation catalyst in step (a) is selected from the group consisting of ruthenium supported on silica or iron oxide; iron supported on silica; ruthenium and tin or a combination of ruthenium and iron in a Ru/Sn or Ru/Fe mass ratio in the range of about 0.1 to 1; a combination of platinum and iron or platinum and tin having an Rt/Sn or Rt/Fe mass ratio in the range of about 0.1 to 1; and combinations of iron and cobalt.

3. The process according to claim 1, wherein the second hydrogenation catalyst in step (c) is selected from the group consisting of platinum supported on alumina or silica and ruthenium supported on alumina or silica; and wherein the acid catalyst in step (d) is selected from the group consisting of aromatic sulfonic acids, sulfuric acids, and alkane sulfonic acids.

4. The process according to claim 1, wherein acetaldehyde in the first gaseous product stream is enriched in step (b) to at least 80 mol%.

5. The process according to claim 1 wherein the reactants in step (a) are comprised of acetic acid and hydrogen in a molar ratio in the range of about 100: 1 to 1: 100, the temperature of the reaction zone is in the range of about 250 ℃ to 350 ℃, and the pressure of the reaction zone is in the range of about 5 to 25 atmospheres absolute.

6. The process according to claim 1 wherein the reactants in step (a) are comprised of acetic acid and hydrogen in a molar ratio in the range of about 1: 20 to 1: 2, the temperature of the reaction zone is in the range of about 270 ℃ to 210 ℃, and the pressure of the reaction zone is in the range of about 8 to 20 atmospheres absolute.

7. The process according to claim 1, wherein the hydrogenation catalyst in step (a) is platinum at a loading level of about 0.5 wt.% or about 1(1) wt.% and tin or iron at a loading level of about 5(5) wt.%, and the catalyst support is silica.

8. The process according to claim 1, wherein the hydrogenation catalyst in step (a) is ruthenium at a loading level of about 0.5 wt.% or about 1(1) wt.% and tin or iron at a loading level of about 5(5) wt.%, and the catalyst support is silica.

9. A process for the production of vinyl acetate from acetic acid comprising:

a. contacting a feed stream comprising acetic acid and hydrogen at an elevated temperature in a first reaction zone with a suitable hydrogenation catalyst comprising at least one metal selected from the group consisting of iron, copper, gold, platinum, palladium and ruthenium on a suitable catalyst support, optionally in combination with one or more metal catalysts selected from the group consisting of tin, aluminum, potassium, cobalt, molybdenum, tungsten and vanadium, to form a first gaseous product stream comprising acetaldehyde;

b. enriching the first gaseous product stream with acetaldehyde to at least 50 mol%;

c. contacting said enriched first gaseous product stream obtained in step (b) with acetic anhydride at elevated temperature in a second reaction zone to form a second gaseous product stream of ethylidene diacetate;

d. contacting said second gaseous product from step (c) with an acid catalyst selected from the group consisting of aromatic sulfonic acids, sulfuric acid, and alkanesulfonic acids at elevated temperature in a third reaction zone to form a mixture third gaseous product comprising vinyl acetate and acetic acid; and

e. vinyl acetate is separated from the third gaseous product stream.

10. The process according to claim 9, wherein the hydrogenation reaction in step (a) is carried out over a hydrogenation catalyst supported on a carrier, wherein the catalyst is selected from the group consisting of platinum supported on silica at a loading level of about 0.5 wt.% or about 1(1) wt.%, and tin or iron supported on silica at a loading level of about 5(5) wt.%; and a loading level of about 0.5 wt.% or about 1(1) wt.% ruthenium on silica.

11. The process according to claim 9, wherein the acid catalyst in step (d) is selected from the group consisting of aromatic sulfonic acids, sulfuric acids, and alkanesulfonic acids.

12. The process of claim 9 wherein the hydrogenation reaction in step (a) is carried out at a pressure sufficient only to overcome the pressure drop across the catalytic bed.

13. The process according to claim 9 wherein the reactants in step (a) are comprised of acetic acid and hydrogen in a molar ratio in the range of about 100: 1 to 1: 100, the temperature of the reaction zone is in the range of about 250 ℃ to 350 ℃, and the pressure of the reaction zone is in the range of about 5 to 25 atmospheres absolute and the contact time of the reactants and catalyst is in the range of about 0.5 to 100 seconds.

14. The process according to claim 9 wherein the reactants in step (a) are comprised of acetic acid and hydrogen in a molar ratio in the range of about 1: 20 to 1: 2, the temperature of the reaction zone is in the range of about 270 ℃ to 310 ℃, and the pressure of the reaction zone is in the range of about 8 to 20 atmospheres absolute and the contact time of the reactants and catalyst is in the range of about 0.5 to 100 seconds.

15. The process according to claim 9, wherein the acid catalyst in step (d) is an aromatic sulfonic acid.

16. A process for the production of vinyl acetate from acetic acid comprising:

a. contacting a feed stream comprising acetic acid and hydrogen at an elevated temperature in a first reaction zone with a suitable hydrogenation catalyst comprising at least one metal selected from the group consisting of iron, copper, gold, platinum, palladium and ruthenium on a suitable catalyst support, optionally in combination with one or more metal catalysts selected from the group consisting of tin, aluminum, potassium, cobalt, molybdenum, tungsten and vanadium, to form a first gaseous product stream comprising acetaldehyde;

b. enriching the first gaseous product stream with acetaldehyde to at least 50 mol%;

c. contacting said enriched first gaseous product obtained in step (b) with ketene and a suitable catalyst in a second reaction zone at elevated temperature to form a second gaseous product comprising vinyl acetate; and

e. vinyl acetate is separated from the second gaseous product stream.

17. The process according to claim 16, wherein the hydrogenation reaction in step (a) is carried out on a hydrogenation catalyst supported on a carrier selected from the group consisting of platinum at a loading level of about 0.5 wt.% or about 1(1) wt.% on silica, tin or iron at a loading level of about 5(5) wt.%; and a loading level of about 0.5 wt.% or about 1(1) wt.% ruthenium on silica.

18. The process according to claim 16, wherein the first and second reaction zones comprise a first layer of the first catalytic composition and a second layer of the second catalytic composition, respectively, in a fixed bed.

19. The process according to claim 16, wherein the first and second reaction zones are located in separate vessels.

20. The process according to claim 16, wherein the selectivity to acetaldehyde in step (a) based on acetic acid consumed is at least about 80%.

21. The process according to claim 16 wherein the reactants in step (a) are comprised of acetic acid and hydrogen in a molar ratio in the range of about 100: 1 to 1: 100, the temperature of the reaction zone is in the range of about 250 ℃ to 350 ℃, and the pressure of the reaction zone is in the range of about 5 to 25 atmospheres absolute.

22. The process according to claim 16 wherein the reactants in step (a) are comprised of acetic acid and hydrogen in a molar ratio in the range of about 1: 20 to 1: 2, the temperature of the reaction zone is in the range of about 270 ℃ to 310 ℃, and the pressure of the reaction zone is in the range of about 8 to 20 atmospheres absolute.

23. The process according to claim 16, wherein the catalyst in step (c) is selected from the group consisting of perfluorosulfonic acid resin, H-mordenite, H-ZSM-5, zeolite X and zeolite Y.

24. The process according to claim 16, wherein in step (c), the catalyst is a perfluorosulfonic acid resin.