ACETATE

Field of the invention

The present invention relates to integrated process and system for the oxidative conversion of ethane to ethylene and vinyl acetate .

Background of the invention

It is known to oxidatively dehydrogenate alkanes, such as ethane, to produce ethylene in an oxidative dehydrogenation (oxydehydrogenation ; ODH) process. Examples of ethane ODH processes, including catalysts and other process conditions, are disclosed in US7091377, WO2003064035, US20040147393, WO2010096909 and US20100256432. Mixed metal oxide catalysts containing molybdenum (Mo) , vanadium (V) , niobium (Nb) and optionally tellurium (Te) can be used as such

oxydehydrogenation catalysts. The dehydrogenated equivalent of ethane may be further oxidized under the same conditions into acetic acid. Presently, the process can achieve over 90% ethylene selectivity to ethylene at over 50% conversion. The process is also typically producing acetic acid (AA, ~5 mol% selectivity) together with carbon dioxide (CO2) .

In the above processes, the carboxylic acids, notably acetic acid, thus produced are generally considered as waste products. Although they could be condensed together with water from the reactor effluent as an aqueous carboxylic acid (ca. 10 wt%) stream, the low relative volatility of carboxylic acids to water renders distillative separation of carboxylic acid and water troublesome, as this would require very large condensate recycle and/or separation trains.

Accordingly, current ODH processes are designed for minimal acetic acid co-production. However, proper

valorization of acetic acid could allow "relaxing" acetic acid specifications, thereby widening the operating window to accommodate e.g. higher pressures, lower temperatures and/or easier management of heat release and explosion risks in the ODH process. For example, relaxing the acetic acid

specification to 10 mol% selectivity could deliver an aqueous side-stream containing 20 wt% acetic acid.

WO1998005620 describes an integrated process for the production of acetic acid and/or vinyl acetate which comprises the steps : (a) contacting in a first reaction zone a gaseous feedstock comprising ethylene and/or ethane and optionally steam with a molecular oxygen-containing gas in the presence of a catalyst active for the oxidation of ethylene to acetic acid and/or ethane to acetic acid and ethylene to produce a first product stream comprising acetic acid, water and ethylene (either as unreacted ethylene and/or as co-produced ethylene) and optionally also ethane, carbon monoxide, carbon dioxide and/or nitrogen; (b) contacting in a second reaction zone in the presence or absence of additional ethylene and/or acetic acid at least a portion of the first gaseous product stream comprising at least acetic acid and ethylene and optionally also one or more of water, ethane, carbon monoxide, carbon dioxide and/or nitrogen with a molecular oxygen- containing gas in the presence of a catalyst active for the production of vinyl acetate to produce a second product stream comprising vinyl acetate, water, acetic acid and optionally ethylene ;

(c) separating the product stream from step (b) by

distillation into an overhead azeotrope fraction comprising vinyl acetate and water and a base fraction comprising acetic acid; (d) either (i) recovering acetic acid from the base fraction separated in step (c) and optionally recycling the azeotrope fraction separated in step (c) after partial or complete separation of the water therefrom to step (c) , or (ii) recovering vinyl acetate from the azeotrope fraction separated in step (c) and optionally recycling the base fraction separated in step (c) to step (b) , or (iii)

recovering acetic acid from the base fraction separated in step (c) and recovering vinyl acetate from the overhead azeotrope fraction recovered in step (c) .

WO2000069802 describes a process for the production of vinyl acetate monomer comprising the steps of: (1) contacting a gaseous feed mixture of ethane or ethylene or

ethane/ethylene, steam and a molecular oxygen containing gas in the presence of a first catalyst active for oxidation of ethane, ethylene or ethane/ethylene to produce a selective stream of acetic acid, ethylene, carbon dioxide and water and (2) converting a second feed mixture comprising ethylene, acetic acid and oxygen to vinyl acetate monomer in the presence of a second catalyst active for the production of vinyl acetate, wherein said process does not include an intermediate separation step to remove the CO between the two reaction steps .

WO2001090042 describes an integrated process for the production of vinyl acetate which comprises the steps of: a) contacting in a first reaction zone a gaseous feedstock comprising essentially ethane 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 in a second reaction zone the first gaseous product stream with a molecular oxygen-containing gas in the presence of a catalyst to produce a second product stream comprising vinyl acetate; c) separating the product stream from step (b) and recovering vinyl acetate from the product stream from step (b) .

These prior art processes generally suffer from poor selectivity to vinyl acetate due to the presence of

considerable amounts of water in the effluent of the oxidative dehydrogenation reaction. It is desirable to provide an ethane oxidative dehydrogenation process, wherein the acetic acid side stream thus produced is valorised by conversion to vinyl acetate in a technically advantageous, efficient and economically

affordable manner.

Summary of the invention

It was surprisingly found that the above-mentioned objective can be attained by means of an ethane oxidative dehydrogenation [oxydehydrogenation; (E)ODH] and VAM process wherein at least part of the ethylene and optionally acetic acid produced in the first ("ODH") step are further converted in a second ("VAM") process to vinyl acetate (also referred to in the art as vinyl acetate monomer or simply "VAM"), and wherein all or at least a portion of the stream comprising acetic acid that has been separated from the ODH effluent is used to recover vinyl acetate from the VAM effluent stream.

Accordingly, in a first aspect the present invention pertains to an integrated process for the production of ethylene and vinyl acetate (VAM) , comprising

contacting in a first reaction zone a gas stream

comprising ethane and optionally ethylene with an oxygen- containing gas stream in the presence of a dehydrogenation catalyst under oxidative dehydrogenation conditions to produce a first product stream comprising ethane, ethylene, acetic acid and water, and optionally other compounds,

separating said first product stream in a first

separation zone into a second stream comprising acetic acid and optionally water and a third stream comprising ethane, ethylene and optionally water,

optionally concentrating the second stream comprising acetic acid, optionally dewatering said third stream in a dewatering zone to produce a dewatered fourth stream comprising ethane and ethylene,

contacting in a second reaction zone said third stream or said dewatered fourth stream comprising ethane and ethylene with a stream comprising concentrated acetic acid and with an oxygen-containing gas stream in the presence of a VAM

catalyst, to produce a fifth product stream comprising vinyl acetate, water, ethane, ethylene, and optionally other compounds, and

recovering vinyl acetate and ethylene from said fifth product stream,

wherein all or at least a portion of the second stream comprising acetic acid is used to recover vinyl acetate from the fifth product stream.

In another aspect, the invention relates to reaction system for the oxidative dehydrogenation of ethane and co- production of vinyl acetate, comprising

a first reaction zone, comprising

an inlet for receiving an ethane-containing feed stream,

an inlet for receiving an oxygen-containing feed stream, and

an outlet for discharging an effluent from the first reaction zone,

a first separation zone, comprising

an inlet for receiving an effluent from the first reaction zone,

optionally an inlet for receiving a washing agent stream,

an outlet for discharging an acetic acid-depleted effluent stream from the first separation zone, and an outlet for discharging an acetic acid-enriched stream from the first separation zone, optionally, an acetic acid recovery unit, comprising an inlet for receiving an acetic acid-enriched stream from the first separation zone, and

an outlet for discharging a concentrated acetic acid stream, and

an outlet for discharging water or recovered selective solvent,

optionally, a dewatering zone, comprising

an inlet for receiving an acetic acid-depleted effluent stream from the first separation zone, and an outlet for discharging a dewatered effluent stream,

a second reaction zone, comprising

an inlet for receiving the acetic acid-depleted effluent stream from the first separation zone or the dewatered effluent stream from the dewatering zone as an ethylene-containing feed stream,

an inlet for receiving an oxygen-containing feed stream,

an inlet for receiving a concentrated acetic acid- containing feed stream, and

an outlet for discharging an effluent from the second reaction zone,

a second separation zone, comprising

an inlet for receiving an effluent from the second reaction zone,

an inlet for receiving an acetic acid-enriched washing agent stream,

an outlet for discharging a vinyl acetate-enriched liquid stream from the second separation zone, and an outlet for discharging a vinyl acetate-depleted gaseous stream from the second separation zone, a purification zone, comprising an inlet for receiving a vinyl acetate-enriched liquid stream from the second separation zone, an outlet for discharging a concentrated acetic acid-containing stream from the purification zone, and,

an outlet for discharging a concentrated vinyl acetate-containing stream from the purification zone, and

one or more outlets for discharging further compounds, and

optionally, a carbon dioxide removal zone, comprising an inlet for receiving a vinyl acetate-depleted gaseous stream from the second washing zone, an outlet for discharging a carbon dioxide-depleted gaseous stream from said carbon dioxide removal zone, and,

optionally, an ethane/ethylene separation unit,

comprising

an inlet for receiving a carbon dioxide-depleted effluent stream from the carbon dioxide removal zone,

an outlet for discharging an ethylene-containing stream from said ethane/ethylene separation unit, and

an outlet for discharging an ethane-containing stream from said ethane/ethylene separation unit.

Brief description of the drawings

The drawing figures depict one or more implementations in accord with the present teachings, by way of example only, not by way of limitation. In the figures, like reference numerals refer to the same or similar elements.

Figure 1 shows an embodiment of the present invention. Figure 2 shows an embodiment of the present invention, wherein water is used for washing acetic acid from the effluent of the oxidative dehydrogenation step.

Figure 3 shows an embodiment of the present invention, wherein a selective solvent is used for recovering acetic acid from the effluent of the oxidative dehydrogenation step.

Detailed description of the invention While the process of the present disclosure and the streams used in said process are described in terms of

"comprising", "containing" or "including" one or more various described steps and components, respectively, they can also "consist essentially of" or "consist of" said one or more various described steps and components, respectively.".

The term "at least a portion of", as used herein, may in particular mean at least 1 % thereof, in particular at least 2.5 % thereof, in particular at least 5 % thereof, in

particular at least 10 % thereof, in particular at least 15 % thereof, in particular at least 20 % thereof, in particular at least 25 % thereof, in particular at least 30 % thereof, in particular at least 35 % thereof, in particular at least 40 % thereof, in particular at least 45 % thereof, in particular at least 50 % thereof, in particular at least 55 % thereof, in particular at least 60 % thereof, in particular at least 65 % thereof, in particular at least 70 % thereof, in particular at least 75 % thereof, in particular at least 80 % thereof, in particular at least 85 % thereof, in particular at least 90 % thereof, in particular at least 95 % thereof, in particular at least 98 % thereof, and may also mean at least 99 % thereof.

The present disclosure relates to a process and reaction system for the oxidative dehydrogenation of ethane, and conversion of at least part of the effluent of said

dehydrogenation process to vinyl acetate. The process and the apparatus as described herein allow utilizing the effluent of an ethane oxidative dehydrogenation (ODH) process comprising relatively high concentrations of acetic acid in an efficient manner, thereby producing ethylene and vinyl acetate monomer (VAM) as valuable chemicals, while minimizing losses of ethylene in purge streams. The process and the reaction system as described herein allow significant integration of the ODH and VAM processes, with the possibility of sharing several common process units, such as oxygen supply, carbon dioxide removal and acetic acid drying/recovery, thus further

contributing to the overall cost-effectiveness of the present disclosure. An additional advantage of the process as

disclosed herein is that there is no need to remove remaining oxidizing agent, if any, from the product stream resulting from the oxydehydrogenation step, since oxidizing agent is also required in the subsequent production of vinylacetate .

In the oxidative dehydrogenation part of the present process, a gas stream comprising oxygen (O2) and a gas stream comprising ethylene are contacted with a mixed metal oxide oxydehydrogenation catalyst typically comprising molybdenum, vanadium, niobium and optionally tellurium. The effluent stream of this oxidative dehydrogenation step generally comprises unreacted ethane, ethylene, water of reaction, acetic acid, and optionally also unreacted oxygen, carbon monoxide and carbon dioxide .

The vinylacetate (VAM) part of the process generally involves contacting a gas stream comprising oxygen (O2) , a gas stream comprising ethylene and a (vaporous) stream comprising acetic acid in the presence of a VAM catalyst, typically a palladium-based catalyst, to produce an effluent typically comprising vinylacetate, unreacted ethylene, unreacted acetic acid, unreacted oxygen, water of reaction, carbon dioxide, acetaldehyde and ethyl (di) acetate. The presence of water in the feed is undesirable as it leads to hydrolysis of

vinylacetate to acetaldehyde and acetic acid. Since water is formed during the VAM reaction, acetic acid is typically dried by feeding it in the product work-up (purification) section, and the dried acetic acid may subsequently recirculated

(recycled) to the VAM reactor. The product work-up

(purification) generally comprises absorption of vinylacetate in an acetic acid wash step, azeotropic distillation of vinylacetate and water, followed by decanting and

purification, and removal of the lights (acetaldehyde) and heavies (ethyl (di) acetate) by distillation.

Water is formed in a molar ratio of at least 1:1 to ethylene during the conversion of ethane to ethylene in the ODH step of the present process. In one embodiment of the present invention, a stream comprising unconverted ethane, ethylene and water, suitably the stream comprising unconverted ethane, ethylene, acetic acid and water resulting from said ODH step, is fed to a condensation unit which is typically part of the ODH configuration.

In said condensation step, the ODH effluent stream is cooled down to for example room temperature, after which the condensed water and acetic acid can be separated from the stream comprising unconverted ethane and ethylene. Thus, water and acetic acid in the vaporous effluent of the oxidative dehydrogenation step are condensed to produce an aqueous acetic acid stream and a gaseous stream comprising ethylene and ethane, and optionally other gaseous compounds.

Accordingly, in one embodiment, the first separation zone is a condensation zone and the first product stream comprising ethane, ethylene, acetic acid and water is condensed to produce a second stream comprising acetic acid and water and a third stream comprising ethane and ethylene. In this

embodiment, since water has already been removed by

condensation with water, the condensation zone and the subsequent dewatering zone for the third stream comprising ethane and ethylene may in practice fall together; or, no separate dewatering step and dewatering zone need to be or is present .

In another embodiment, the first separation zone is a first washing zone and the first product stream comprising ethane, ethylene, acetic acid and water is separated by contacting said first stream with a washing stream comprising water, to produce a second stream comprising acetic acid and water and a third stream comprising ethane, ethylene and optionally water. This is illustrated in more detail in FIG. 2.

As used herein, the term "washing" relates to contacting the vaporous stream with a liquid compound, such as water or a liquid solvent, with the purpose of separating acetic acid from said vaporous stream.

Washing of said first stream with water can be performed in a washing column or by absorption in e.g. an absorption column, such that acetic acid and water are retained and a gaseous stream comprising ethylene and ethane, and optional other gaseous compounds such as carbon dioxide, passes through.

In another embodiment of the invention, a selective solvent is used for recovering acetic acid from the effluent of the oxidative dehydrogenation step. The resulting selective solvent-acetic acid solution may then be used to "wash" vinyl acetate from the effluent of the vinyl acetate (VAM) reaction step by means of absorption or extractive distillation, and the selective solvent and acetic acid are recovered separately in the vinyl acetate purification step. Accordingly, in one embodiment, the first separation zone is a first washing zone, wherein the first product stream comprising ethane, ethylene, acetic acid and water is separated by contacting said first stream with a washing stream comprising a selective solvent, to produce a second stream comprising acetic acid and selective solvent and a third stream comprising ethane, ethylene and optionally water.

Said selective solvent can be any solvent that is capable of selectively absorbing or extracting acetic acid from the first (ODH effluent) stream. The selective solvent can be organic or inorganic. In one embodiment, the selective solvent is organic. The selective solvent has an affinity for acetic acid that is higher than that for water, and for any of the other components of the effluent of the ethane oxidative dehydrogenation step of the present disclosure.

This means that under the conditions applied in the first separation zone, including pressure and temperature which are further defined herein below, the selective solvent has an affinity for acetic acid which is higher than that for water and any other components of the effluent stream of the alkane oxidative dehydrogenation step.

It is preferred that the solvent has a higher boiling point than water and does not from an azeotrope with water. It is further preferred that the selective solvent has a relative volatility with respect to water and acetic acid under the absorption, extraction and solvent recovery conditions as defined herein that is substantially below unity. The

selective solvent having a low volatility and low water miscibility offers the advantage of minimizing selective solvent losses as vapor in the effluent stream and subsequent dissolution in water. Additionally, it allows an easy and energy efficient recovery (separation) of absorbed or

extracted acetic acid by, for example, distillation, acetic acid typically being obtained as the top product.

In order to minimize the cost of (distillative ) separation of acetic acid from the selective solvent, an appreciable boiling point difference between these compounds is desirable.

Particularly suitable organic solvents for use as

selective "washing" solvents as described herein are oxygen- containing solvents being characterized by (i) a short Hansen solubility parameter distance R _a with respect to acetic acid, notably an R _a with respect to the acetic acid as determined at 25 °C of 15 MPa ^1/2 or less, (ii) a partition logP ow as

determined at 25 ° C and pH 7 of at least 0 , and (iii) a boiling point at atmospheric pressure that is at least 5 °C higher, preferably at least 1 0 °C higher, more preferably at least 20 °C higher than the boiling point of the acetic acid to be separated, are excellent selective solvents for use in a process for absorbing or extracting acetic acid from the ODH effluent streams comprising acetic acid.

Hansen solubility parameters (HSP) can be used as a means for predicting the likeliness of one compound (solvent) dissolving in another. More specifically, each compound is characterized by three Hansen parameters, each generally expressed in MPa ⁰ - ⁵ : 5d, denoting the energy from dispersion forces between molecules; δ _ρ , denoting the energy from dipolar intermolecular forces between molecules; and 5h , denoting the energy from hydrogen bonds between molecules. The affinity between compounds can be described using a multidimensional vector that quantifies these solvent atomic and molecular interactions, as a Hansen solubility parameters (HSP) distance R _a which is defined in Equation ( 1 ) : ( Ra ) ² = 4 ( 5d2 - 5di ) ² + ( δρ ₂ - δ _Ρ ι ) ² + ( 5 _h2 - 5 _h i ) ² ( D wherein

Ra = distance in HSP space between compound 1 and compound 2 (MPa ⁰ - ⁵ )

5di , δ _ρ ι , 5hi = Hansen (or equivalent) parameter for compound 1 (in MPa ⁰ - ⁵ )

5d2 , δ _Ρ 2 , 5h2 = Hansen (or equivalent) parameter for compound 2 (in MPa ⁰ - ⁵ ) Thus, in the context of the present invention, the smaller the value for R _a for a given solvent calculated with respect to the acetic acid to be recovered (i.e., the acetic acid being compound 1 and the solvent being compound 2, or vice versa) , the higher the affinity of this solvent for the acetic acid to be recovered will be.

Hansen solubility parameters for numerous solvents can be found in, among others, CRC Handbook of Solubility Parameters and Other Cohesion Parameters, Second Edition by Allan F.M. Barton, CRC press 1991; Hansen Solubility Parameters: A User's Handbook by Charles M. Hansen, CRC press 2007. It is also explained in these handbooks how analogous solubility

parameters have been derived by alternative methods to the original Hansen method, resulting in likewise useful

parameters such as Hoy's cohesion parameters for liquids.

It is preferred that the Hansen solubility parameter distance R _a with respect to acetic acid as determined at 25 °C is 12 MPa ^1/2 or less, preferably 10 MPa ^1/2 or less, more

preferably 8 MPa ^1/2 or less, most preferably 5 MPa ^1/2 or less.

It was found by the present inventors that excellent recovery of acetic acid from aqueous solutions is obtained when the 1-octanol/water partition coefficient of the

selective solvent is relatively high. The 1- octanol/water partition coefficient, commonly expressed as its logarithmic value logPow, represents the relative

concentrations of a compound when dissolved in a mixture of 1- octanol and water at equilibrium, according to the following expression : logPow = ¹⁰ log[Coctanol/ Cwater] (2) wherein

Coctanoi = concentration of the compound in 1-octanol

Coctanoi = concentration of the compound in water As such, in the context of the present invention, the partition coefficient is a measure for the hydrophobicity of a solvent. Without wishing to be bound by theory, it is the inventors' belief that solvents having a suitably high partition coefficient are effective in minimizing the

extraction of water from the acetic acid-water mixture .

Suitable selective solvents for use as described herein have a partition coefficient logPow as determined at 25 °C and pH 7 of at least 0. Typically, the selective solvent for use as described herein has a logPow of at least 0.5, preferably at least 1.0, more preferably at least 1.5, even more preferably at least 2.0, yet even more preferably at least 3.0, most preferably at least 4.0.

Experimentally determined 1-octanol/water partition coefficients for several organic solvent classes are listed in, for example, James Sangster, Octanol-Water Partition Coefficients of Simple Organic Compounds, J. Phys . Chem. Ref. Data, Vol.18, No. 3, 1989. Where experimentally determined partition coefficients are not accessible, several established reliable methods for calculating logPow values are available; these include the proprietary methods ClogP (Bio-Loom; BioByte Corp. /Pomona College) and miLogP (Molinspiration

Cheminformatics ) (see also Mannhold, M. et al . Calculation of Molecular Lipophilicity: State-of-the-Art and Comparison of Log P Methods on more than 96,000 compounds. J. Pharm. Sci. 2009, 98, 861-893) .

In order to facilitate effective separation (recovery) of the selective solvent from the acetic acid by e.g.

distillation, it is preferred that the selective solvent has a boiling point at atmospheric pressure that is at least 10 °C higher, preferably at least 20 °C higher, more preferably at least 30 °C higher, even more preferably at least 40 °C higher, most preferably at least 50 °C higher than the boiling point (s) of the acetic acid to be separated.

For example, acetic acid has a boiling point of about 117 °C. Typically, the selective solvent has a boiling point of at least 125 °C. Preferably, it has a boiling point of at least 140 °C, more preferably at least 160 °C, even more preferably at least 170 °C, yet even more preferably at least 180 °C most preferably at least 200 °C.

From an economic perspective, it is preferred that the selective solvent has a boiling point that does not exceed 300 °C, more preferably not exceeds 280 °C, even more preferably not exceeds 250 °C, most preferably not exceeds 225 °C, in order to avoid excessive heating expenditure.

Suitable oxygen-containing compounds having a Hansen solubility parameter distance R _a , partition coefficient and boiling point ranges as defined herein can be found in the classes of carboxylic acids, esters of carboxylic acids, ethers, aldehydes, ketones, alcohols and organic phosphates. These oxygen-containing components may be linear, branched or cyclic, saturated or unsaturated, and may be aliphatic or contain aromatic rings. Examples of such compounds include organic phosphates such as triethyl phosphate and tributyl phosphate, heterocyclic hydrocarbons such as benzofuran, carboxylic esters such as methyl benzoate, n-butyl butyrate, n-butyl acrylate, 2-ethylhexyl acetate, diethyl phthalate, isopropyl acetate, octyl acetate and cyclohexyl acetate, ketones such as acetophenone, dipropyl ketone and 5-ethyl-2- nonanone, high-boiling functionalized ethers such as anisole, diethylene glycol ethyl ether, diethylene glycol monobutyl ether, propylene glycol phenyl ether, 2-butoxy ethanol, 2- phenoxy ethanol and butyl diglycol acetate and carboxylic acids such as pentanoic acid, hexanoic acid, heptanoic acid and octanoic acid. Based on the criteria as provided herein for the Hansen solubility parameter distance R _a , partition coefficient and boiling point, and taking into account the boiling point of the acetic acid to be recovered, the skilled person will be capable of selecting suitable selective solvents from each of these classes of oxygen-containing organic compounds .

Particularly preferred oxygen-containing compounds having a Hansen solubility parameter distance R _a , partition

coefficient and boiling point as defined herein are selected from the class of protic oxygenates, i.e. containing -OH group such as acids and alcohols and more preferably organic alcohols. Herein, organic alcohols are understood to organic compounds wherein one or more hydroxyl functional groups (-OH) are bound to a carbon atom. This includes linear, branched and cyclic alcohols, saturated and unsaturated alcohols, primary, secondary or tertiary alcohols, and aromatic as well as aliphatic alcohols. The alcohol may contain one hydroxyl group, or may contain two (diol) or more (triol, etc.) hydroxyl groups, provided that any surplus of hydroxyl groups does not result in an undesirably high affinity for water. The alcohols for use according to the invention may further contain other functional groups, such as oxygen-containing groups such as carbonyl, acid-, ether- or ester functional groups .

Preferred alcohols for use according to the invention are cyclic or aromatic alcohols having 6 to 20 carbon atoms, linear aliphatic alcohols having 6 to 14 carbon atoms and branched aliphatic alcohols having 5 to 14 carbon atoms.

Examples of cyclic alcohols include unsubstituted and alkyl- substituted cyclohexanols and cyclopentanols , such as

cyclohexanol, methyl cyclohexanol, methyl cyclopentanol, trimethyl cyclohexanols and ( 4-methylcyclohexyl ) methanol ;

examples of aromatic alcohols include phenol, benzyl alcohols,

1- phenyl ethanol, 2-phenyl ethanol, cumyl alcohol (2-phenyl-

2-propanol) , xylenols (such as 2 , 6-xylen-l-ol ) , guaiacol (2- methoxyphenol ) , creosol, cresols such as m-cresol, phenoxy ethanol and naphthol; examples of suitable linear alcohols include those having the general formula C _n H _n +iOH, wherein n is in the range of 6 to 14, preferably in the range of from 8 to 12, such as 1-hexanol, 2-hexanol, 3-hexanol, 1-octanol and 2- octanol, 1-decanol, 2-decanol, 1-dodecanol and 2-dodecanol; examples of suitable branched alcohols include those having in the range of 5 to 14, preferably in the range of 6 to 12 carbon atoms, such as 2-methyl-2-pentanol, 2-methyl-3- pentanol, 3-methyl-3-pentanol , 2-methyl-l-pentanol, 2,3- dimethyl-l-butanol, 2, 2-dimethyl-l-butanol, 2 , 3-dimethyl-2- butanol, 3, 3-dimethyl-2-butanol, 4 -methyl-l-pentanol (iso- hexanol) , 4-methyl-2-pentanol, 2-ethyl-l-butanol, 5-methyl-2- hexanol, 3-methyl-2-hexanol, 2 , 2-dimethyl-l-pentanol , 4,4- dimethyl-l-pentanol , 2-ethyl-l-hexanol (iso-octanol) , di- isobutyl carbinol (2, 6-dimetyl-4-heptanol) , 2-propyl heptanol, 3-methyl-l-butanol (isopentyl alcohol) , 2-methyl-l-butanol, 2- benzyloxy-ethanol, 2-phenoxy ethanol and 2-butoxy-ethanol .

Examples of alcohols containing other functional groups, such as oxygen-containing groups like aldehyde, ether- or ester groups, are diacetone alcohol and methyl salicylate. Other suitable alcohols include terpene-based alcohols such as pinacol, citronellol, menthol, and isoborneol.

Particularly preferred selective solvents for use

according to the invention are 1-hexanol, 1-octanol, 1- decanol, 1-dodecanol, 2-ethyl-hexanol, diisobutyl carbinol, cresols, xylenols, anisole, butyl butyrate and 2-ethyl-hexyl- acetate .

Thus, in one embodiment of the present disclosure, the first separation zone is an absorption column or washing column, wherein the first product stream comprising ethane, ethylene, acetic acid and water is separated by contacting said first stream with a washing stream comprising a selective solvent, to produce a second stream comprising acetic acid and selective solvent and a third stream comprising ethane, ethylene and optionally water. This is typically achieved in a column having inlets for receiving an ODH effluent stream and for selective solvent, wherein the effluent stream comprising acetic acid is fed into the lower zone of a packed or tray absorption column and the liquid selective solvent is fed into the upper zone of the column, and wherein the acetic acid is absorbed by the selective solvent via direct contact of the rising vapour stream and the falling selective solvent.

In another embodiment, the acetic acid separation step in the first separation zone is performed by means of extractive distillation (ED) from the ODH effluent stream using a selective solvent as described herein. Extractive distillation is a distillation process wherein a selective ("extractive") solvent is added in order to modify the relative volatility of the components that need to be separated, thus enabling a larger degree of separation or requiring less effort to effect the same separation. The extractive solvent is typically a high-boiling, relatively non-volatile compound. The extractive solvent typically boils at a higher temperature than any of the close-boiling components being separated. In this way the lower-boiling component of the resulting mixture is obtained at the top of the extractive distillation column and the other component along with the extractive solvent is obtained from the bottom section. Owing to the high boiling point of the extractive solvent, this bottom stream can then be separated in a secondary distillation (or rectification) column in order to provide a concentrated product and recover the extractive solvent. Extractive distillation should be distinguished from the best-known form of azeotropic distillation, i.e. wherein the solvent (or entrainer) forms a low-boiling azeotrope with the compound to be separated, and is thus vaporized into the top rather than collected at the bottom of the distillation column . It is preferred that in the embodiment using selective solvent absorption or extractive distillation, the first separation zone is operated at such pressure and temperature conditions that water does not condensate.

In some cases, it may be desirable to recover acetic acid from the second stream separated from the ODH effluent, comprising acetic acid and water and/or selective solvent, in order to obtain purified (concentrated) acetic acid for washing vinylacetate from the VAM effluent, and optionally recovered solvent. Accordingly, in one embodiment, the second stream comprising acetic acid and water or acetic acid and selective solvent is at least partially fed to an acetic acid recovery unit to produce a sixth stream comprising

concentrated acetic acid. In said acetic acid recovery unit, acetic acid is separated from water or selective solvent by a separation technique or a combination of techniques including (azeotropic) distillation, extraction, extractive

distillation, etc. If the second stream mainly comprises acetic acid and water, acetic acid recovery (and regeneration of the selective solvent) may be accomplished by a combination of extraction and regeneration such that acetic acid is selectively extracted (using a suitable solvent) from the water phase and subsequently acetic acid is selectively separated from this solvent e.g. by distillation.

Alternatively, recovery of acetic acid is achieved by

adsorption onto an adsorbent having affinity for acetic acid, and subsequent release (desorption) of the acetic acid (and regeneration of adsorbent) by temperature swing or pressure swing .

If the second stream comprising acetic acid also comprises a selective solvent, this acetic acid recovery step further produces a recovered (concentrated) selective solvent stream, which may at least partially be recirculated to the first separation zone. If the selective solvent contains entrained water, it may be desirable to provide the recovered selective solvent stream to a dewatering zone as described herein prior to recycling it to the first separation zone.

Accordingly, in one embodiment, the second stream

comprises acetic acid and selective solvent, and the acetic acid recovery unit further produces a stream comprising concentrated selective solvent, wherein all or at least a portion of said concentrated selective solvent, optionally after dehydration, is recirculated to the first separation zone .

As mentioned above, all or at least a portion of the acetic acid in the second (ODH effluent after first

separation) stream is used to recover vinyl acetate from the fifth (VAM effluent) product stream. This may be (a portion of) the second stream as such, or (a portion of) the sixth stream comprising concentrated acetic acid resulting from recovery of acetic acid from said second stream. Typically, the recovery of vinylacetate from the VAM effluent involves a vinylacetate wash step to absorb VAM from the vaporous VAM effluent followed by purification of the resulting mixture, to produce concentrated vinylacetate product and acetic acid, the latter of which may be used as acetic acid feed for the VAM reaction step.

Thus, in one embodiment, the fifth product stream

comprising vinyl acetate, water, ethane, ethylene, and optionally other compounds is contacted in a second washing zone with

the second stream comprising acetic acid and water or acetic acid and selective solvent, and/or

the sixth stream comprising concentrated acetic acid, to produce a seventh stream comprising vinyl acetate, acetic acid and water and/or selective solvent and an eighth gaseous stream comprising ethane, ethylene, carbon dioxide and optionally other gaseous compounds . This means that in the above-mentioned embodiment, the fifth product stream comprising vinyl acetate, water, ethane, ethylene, and optionally other compounds may be contacted in the second washing zone with all or at least a portion of the second stream comprising acetic acid and water or acetic acid and selective solvent, and/or all or at least a portion of the sixth stream comprising concentrated acetic acid.

As for the first stream in the first washing zone as described above, washing of the VAM effluent in order to separate vinyl acetate can be performed in a washing column or by absorption in e.g. an absorption column, such that vinyl acetate, water and acetic acid are retained and a gaseous stream comprising ethylene and ethane, and optional other gaseous compounds such as carbon dioxide, passes through.

Furthermore, in one embodiment the seventh stream comprising vinyl acetate, acetic acid and water and/or selective solvent is fed to a purification zone to produce an ninth stream comprising concentrated acetic acid, a tenth stream comprising vinyl acetate, and one or more streams comprising water and/or selective solvent.

In one embodiment, all or at least a portion of the sixth stream comprising concentrated acetic acid, and/or

all or at least a portion of the ninth stream comprising concentrated acetic acid, is used as the feed stream

comprising concentrated acetic acid supplied to the second (VAM) reaction zone.

In one embodiment, the fifth product stream comprising vinyl acetate, water, and optionally other compounds is contacted in a second washing zone with all or at least a portion of the ninth stream comprising concentrated acetic acid to produce a seventh stream comprising vinyl acetate, acetic acid and water and/or selective solvent and an eighth gaseous stream comprising ethane, ethylene, carbon dioxide and optionally other gaseous compounds . The vaporous effluent from the VAM wash step generally comprises unreacted ethylene, unreacted ethane and carbon dioxide. Typically, this stream is first subjected to a carbon dioxide removal step to produce a stream comprising ethylene and ethane, which may subsequently be split in a stream enriched in ethylene and a stream enriched in ethane. The stream enriched in ethylene may be withdrawn as product, and after optional further purification, be stored for sale or use in another conversion process. Alternatively or additionally, all or at least a portion of the stream enriched in ethylene may be recirculated to the VAM reaction step. Alternatively or additionally, all or at least a portion of the stream enriched in ethane may be recirculated to the ODH reaction step. Thus, in one embodiment the eighth gaseous stream is fed to a carbon dioxide removal zone to remove carbon dioxide and optionally light condensable compounds to produce an eleventh stream enriched in ethane and ethylene. In one embodiment, all or at least a portion of said eleventh stream enriched in ethane and ethylene is recirculated as feed to the first (ODH) reaction zone. In one embodiment, said eleventh stream enriched in ethane and ethylene is further separated in an ethane/ethylene separation unit to produce a twelfth stream enriched in ethane and a thirteenth stream enriched in ethylene. In one

embodiment, all or at least a portion of the twelfth stream enriched in ethane is recirculated to the first reaction zone. In one embodiment, all or at least a portion of the thirteenth stream enriched in ethylene is recirculated to the second reaction zone. Any combination of the above recirculation steps of streams enriched in ethane, ethylene or both is also possible.

In a preferred embodiment, the first stream leaving the oxydehydrogenation (ODH) unit comprising ethylene, unconverted ethane, acetic acid and water is supplied to a first

separation zone to which a stream comprising or consisting of a selective solvent as described herein is provided, to produce a second stream comprising acetic acid and selective solvent and a third stream comprising ethylene, ethane and water. In this embodiment, substantially all or all of the second stream comprising acetic acid and selective solvent is provided to an acetic acid recovery unit to produce a sixth stream comprising concentrated acetic acid and a stream comprising concentrated selective solvent. The latter

selective solvent stream is at least partially, and preferably entirely, recirculated to the first separation zone, thus obviating the need to recover selective solvent from the VAM purification zone. The sixth stream comprising concentrated acetic acid may be supplied to the second reaction ("VAM") unit as reagent, to the vinylacetate wash zone as washing agent, or a combination of both options. In this embodiment, preferably, more ethylene is produced in the

oxydehydrogenation (ODH) step of the process than required by the vinyl acetate (VAM) reaction step of the process, such that recycling of the (thirteenth) ethylene-enriched stream, obtained after carbon dioxide removal and ethane/ethane separation of the washed vaporous effluent of the VAM reaction step, to the VAM reaction zone is not required.

In the ODH step of the process of the present invention, oxygen and ethane may be fed to the reactor together or separately. That is to say, one or more feed streams, suitably gas streams, comprising one or more of said 2 components may be fed to the reactor. For example, one feed stream comprising oxygen and ethane may be fed to the reactor. Alternatively, two or more feed streams, suitably gas streams, may be fed to the reactor, which feed streams may form a combined stream inside the reactor. For example, one feed stream comprising oxygen and another feed stream comprising ethane may be fed to the reactor separately. Further, in the ODH step of the process of the present invention, suitably during contacting oxygen and ethane with an ODH catalyst, the temperature is of from 300 to 500 °C. More preferably, said temperature is of from 310 to 450 °C, more preferably of from 320 to 420 °C, most preferably of from 330 to 420 °C.

Still further, in the above-mentioned ODH step, suitably during contacting the oxygen and ethane with an ODH catalyst, typical pressures are 0.1-30 or 0.1-20 bara (i.e. "bar absolute") . Further, preferably, said pressure is of from 0.1 to 15 bara, more preferably of from 1 to 8 bara, most

preferably of from 3 to 8 bara. The product of the above- mentioned ODH step comprises the dehydrogenated equivalent of ethane, that is to say ethylene. Ethylene is initially formed in said step. However, in said same step, ethylene may be further oxidized under the same conditions into the

corresponding carboxylic acid, that is to say acetic acid. In addition to oxygen and ethane, an inert gas may also be fed to the ODH reactor. Said inert gas may be selected from the group consisting of the noble gases and nitrogen (N2) . Preferably, the inert gas is nitrogen or argon, more preferably nitrogen. Said oxygen is an oxidizing agent, thereby resulting in oxidative dehydrogenation of ethane. Said oxygen may originate from any source, such as for example air. Ranges for the molar ratio of oxygen to ethane which are suitable, are of from 0.01 to 1, more suitably 0.05 to 0.5. Said ratio of oxygen to ethane is the ratio before oxygen and ethane are contacted with the catalyst. In other words, said ratio of oxygen to ethane is the ratio of oxygen as fed to ethane as fed.

Obviously, after contact with the catalyst, at least part of the oxygen and ethane gets consumed.

Oxidative dehydrogenation catalysts suitable for use in the present disclosure are not particularly limited and may include any ethane oxidative dehydrogenation catalyst. The amount of such catalyst is not essential. Preferably, a catalytically effective amount of the catalyst is used, that is to say an amount sufficient to promote the ethane

oxydehydrogenation reaction.

Examples of suitable oxidative dehydrogenation catalyst include, but are not necessarily limited to, one or more mixed metal oxide catalyst comprising molybdenum, vanadium, niobium and optionally tellurium as the metals and may have the following formula:

MOlVaTe _b NbcOn

wherein :

a, b, c and n represent the ratio of the molar amount of the element in question to the molar amount of molybdenum (Mo) ;

a (for V) is from 0.01 to 1, preferably 0.05 to 0.60, more preferably 0.10 to 0.40, more preferably 0.20 to 0.35, most preferably 0.25 to 0.30;

b (for Te) is 0 or from >0 to 1, preferably 0.01 to 0.40, more preferably 0.05 to 0.30, more preferably 0.05 to 0.20, most preferably 0.09 to 0.15;

c (for Nb) is from >0 to 1, preferably 0.01 to 0.40, more preferably 0.05 to 0.30, more preferably 0.10 to 0.25, most preferably 0.14 to 0.20; and

n (for 0) is a number which is determined by the valency and frequency of elements other than oxygen.

Optionally, a catalyst bed may comprise more than one oxidative dehydrogenation catalyst. For example, in one embodiment, a catalyst bed may comprise a plurality of oxidative dehydrogenation catalysts having varied activity levels (e.g. so as to vary the activity level along the length of the reactor tube) . Further, if desired, the catalyst bed may further comprise inert material (e.g. to dilute and/or reduce the activity of the catalyst bed) .

Preferably, the oxidative dehydrogenation catalyst is heterogeneous and in the form of particles. Further, preferably, said heterogeneous catalyst is porous, specifically a porous, particulate catalyst.

The ODH reactor that may be used in the above-mentioned ODH step may be any reactor, including fixed-bed and

fluidized-bed reactors. Suitably, the reactor is a fixed-bed reactor. Examples of oxydehydrogenation processes, including catalysts and process conditions, are for example disclosed in above-mentioned US7091377, WO2003064035, US20040147393,

WO2010096909 and US20100256432.

The VAM process as disclosed herein typically proceeds by co-feeding the stream comprising a vaporous acetic acid and ethylene in an preferred ethylene : acetic acid molar ratio in the range of 2:1 to 4:1, together with oxygen in a

concentration of preferably at most 9 vol%, based on total volume of the VAM process gas feed, in the presence of a catalyst active for the production of vinyl acetate. Suitable catalysts for the oxidative conversion of ethylene and acetic acid to vinyl acetate are known in the art, and typically comprise unsupported or supported (e.g., on silica or alumina) palladium. Typically, suitable VAM catalysts further comprise one or more alkali metal promoters, for example sodium or potassium acetate, and an optional co-promoter such gold and/or cadmium. The pressure is typically in the range of 5 to 8 bara and the temperature is typically in the range of 100- 250 °C, preferably in the range of 160 to 180 °C. Generally, acetate salt is co-fed with the acetic acid/ethylene feed in order to compensate for losses of the VAM catalyst alkali promoter. The VAM reactor that may be used in the above- mentioned ODH step may be any reactor, including fixed-bed and fluidized-bed reactors. Suitably, the reactor is a fixed-bed reactor .

The present disclosure further relates to an integrated reaction system which is suitable for performing the oxidative dehydrogenation (ODH) and vinylacetate (VAM) production process as disclosed herein, more in particular a reaction system for the oxidative dehydrogenation of ethane and co- production of vinyl acetate, comprising

a first reaction zone, comprising

an inlet for receiving an ethane-containing feed stream,

an inlet for receiving an oxygen-containing feed stream, and

an outlet for discharging an effluent from the first reaction zone,

a first separation zone, comprising

an inlet for receiving an effluent from the first reaction zone,

optionally an inlet for receiving a washing agent stream,

an outlet for discharging an acetic acid-depleted effluent stream from the first separation zone, and an outlet for discharging an acetic acid-enriched stream from the first separation zone,

optionally, an acetic acid recovery unit, comprising

an inlet for receiving an acetic acid-enriched stream from the first separation zone, and an outlet for discharging a concentrated acetic acid stream, and

an outlet for discharging water or recovered selective solvent,

optionally, a dewatering zone, comprising

an inlet for receiving an acetic acid-depleted effluent stream from the first separation zone, and an outlet for discharging a dewatered effluent stream,

a second reaction zone, comprising

an inlet for receiving the acetic acid-depleted effluent stream from the first separation zone or the dewatered effluent stream from the dewatering zone as an ethylene-containing feed stream, an inlet for receiving an oxygen-containing feed stream,

an inlet for receiving a concentrated acetic acid- containing feed stream, and

an outlet for discharging an effluent from the second reaction zone,

a second separation zone, comprising

an inlet for receiving an effluent from the second reaction zone,

an inlet for receiving an acetic acid-enriched washing agent stream,

an outlet for discharging a vinyl acetate-enriched liquid stream from the second separation zone, and an outlet for discharging a vinyl acetate-depleted gaseous stream from the second separation zone, a purification zone, comprising

an inlet for receiving a vinyl acetate-enriched liquid stream from the second separation zone, an outlet for discharging a concentrated acetic acid-containing stream from the purification zone, and,

an outlet for discharging a concentrated vinyl acetate-containing stream from the purification zone, and

one or more outlets for discharging further compounds, and

optionally, a carbon dioxide removal zone, comprising an inlet for receiving a vinyl acetate-depleted gaseous stream from the second washing zone, an outlet for discharging a carbon dioxide-depleted gaseous stream from said carbon dioxide removal zone, and, optionally, an ethane/ethylene separation unit,

comprising

an inlet for receiving a carbon dioxide-depleted effluent stream from the carbon dioxide removal zone,

an outlet for discharging an ethylene-containing stream from said ethane/ethylene separation unit, and

an outlet for discharging an ethane-containing stream from said ethane/ethylene separation unit.

As shown in Figures 2 and 3, the vinylacetate section comprising vinylacetate reaction unit (13), second washing zone (17) and purification zone (19) may be inserted between the dewatering zone (9) and CO2 removal unit (21) of an existing apparatus (plant) for oxidative dehydrogenation of alkanes. Typically, such integration design involves means, such as by-pass line (30) for by-passing the "VAM section", allowing production, by means of oxidative dehydrogenation (only) under suitable conditions, of ethylene and acetic acid at market specification when the VAM process is down.

Accordingly, in one embodiment the apparatus as disclosed herein comprises means for by-passing the second reaction zone and second washing zone, said means comprising means for directly feeding the acetic acid-depleted effluent stream from the first separation zone or the dewatered effluent stream from the dewatering zone to the carbon dioxide removal zone (and subsequent ethane/ethylene separation unit) . As used herein, such "means" typically comprise a conduit for fluidly connecting an outlet with an inlet of the referenced

apparatuses and/or units, and may further comprise equipment for, e.g., compressing streams in such conduits, if necessary. As used herein, "feeding directly to the carbon dioxide removal zone" should be understood to imply that no or substantially no effluent from the dewatering zone is supplied to and reacted in the vinyl acetate reaction unit; it may still be possible though to have process units other than the VAM section units present between the ODH effluent dewatering zone and the carbon dioxide removal and ethane/ethylene separation units.

Additionally or alternatively, in one embodiment, the apparatus as disclosed herein comprises means for directly feeding the acetic acid-enriched stream from the first separation zone to the first purification zone.

In the present disclosure, any carbon dioxide may be removed from streams containing carbon dioxide by any one of well-known methods in a carbon dioxide removal zone comprising one or more carbon dioxide removal units. A suitable carbon dioxide removal agent that may be fed to a carbon dioxide removal unit may be an aqueous solution of a base, for example sodium hydroxide or an amine. After such carbon dioxide removal, the stream should be dried in a drying unit to remove residual water from the stream. Contacting an aqueous solution of an amine with a carbon dioxide containing stream is preferred in a case where the carbon dioxide amount is relatively high. Contacting an aqueous solution of sodium hydroxide with a carbon dioxide containing stream is preferred in a case where the carbon dioxide concentration is relatively low, or as second carbon dioxide removal step in the case of an ethane ODH effluent that was first treated with an aqueous solution of an amine and which still contains some residual carbon dioxide .

The dewatering zone may comprise any apparatus or combination of apparatuses known in the art that is capable of removing water from a process stream, including a condensation unit, an absorption unit (e.g., an absorption column) or an adsorption unit, a distillation unit or membrane-based units such as a pervaporation unit or a vapor permeation unit . If the first separation zone is utilized to separate an aqueous acetic acid stream from the ODH effluent stream, the first separation zone can comprise a condensation unit, an absorption unit (e.g., an absorption column) or a washing unit (e.g., a washing column using water as washing agent), a distillation or a membrane-based (such as pervaporation or vapour permeation) unit. Generally, the unit will be designed to retain acetic acid and optionally water and let a gaseous stream comprising ethylene and ethane, and optional other gaseous compounds such as carbon dioxide, pass through.

If, in another embodiment of the present disclosure, the first separation zone is utilized to extract or absorb

("wash") acetic acid from the ODH effluent stream with a suitable selective solvent, said first separation zone may be any absorption or extraction system available in the art that is suitable for contacting a gaseous or vaporous stream comprising acetic acid with a selective solvent to result in absorption or extraction of acetic acid by the selective solvent. Accordingly, in one embodiment, the first separation zone comprises an extractive distillation unit or an

absorption unit configured to extract or absorb or extract acetic acid from the effluent of the first reaction zone with a selective solvent .

In one embodiment, the first separation zone comprises an absorption unit. Typically, this is an absorption or washing column having inlets for receiving an ODH effluent stream and for selective solvent, wherein the effluent stream comprising acetic acid is fed into the lower zone of a packed or tray column and the liquid selective solvent is fed into the upper zone of the column, and wherein the acetic acid is absorbed by the selective solvent via direct contact of the rising vapor stream and the falling selective solvent.

In one embodiment the first separation zone comprises an extractive distillation unit, such as an extractive distillation column. Herein, the lower-boiling and gaseous components (e.g., ethylene, ethane, carbon dioxide) of the ODH effluent/selective solvent mixture are obtained at the top of the extractive distillation column and the acetic acid along with the selective (extractive) solvent and other components are obtained from the bottom section.

As described above, recovery of acetic acid and, if present, concomitant recovery of the selective solvent takes place in a suitable acetic acid recovery unit. Depending on the presence and nature of selective solvent, the acetic acid recovery unit may be a (vacuum or atmospheric) distillation unit. If the first separation step in the first separation zone involves washing with a selective solvent acetic acid is typically obtained in the top stream and the selective solvent in the top stream. If the first separation step in the first separation zone involves condensation or a water wash, or washing with a light selective solvent, acetic acid is typically obtained in the bottom stream and water and/or solvent in the top stream.

The acetic acid recovery unit may also be an extraction and regeneration unit that selectively extracts, using a selective solvent, acetic acid from the water phase and then separate acetic acid from the solvent e.g. by distillation.

The acetic acid recovery unit can also be an adsorption unit that retains acetic acid, and wherein the adsorbent is regenerated by thermal (temperature) or pressuring swing.

The vinyl acetate purification zone will generally a combination of apparatuses configured for (azeotropic) distillation of vinylacetate and water, followed by decanting and purification, and removal of the lights (acetaldehyde ) and heavies (ethyl (di) acetate) by distillation.

Separation of ethane from ethylene in the carbon dioxide- depleted ("eleventh") gaseous stream produced in the VAM reaction step is typically performed using cryogenic distillation, wherein said stream is cooled until it liquefies and subsequently distilled at the various boiling

temperatures of the components. Other suitable, non-cryogenic, ethane/ethylene separation methods include pressure-swing and temperature-swing absorption, wherein components of the gaseous stream are selectively adsorbed on or absorbed by an absorbent or adsorbent material depending on their affinity for said material at the prevailing pressure or temperature, respectively, and selectively desorbed by changing said pressure or temperature; membrane permeation, which is based on the difference in rate of permeation through a membrane; and combinations of such methods, such as pressure swing permeation .

The reaction system as disclosed herein may further comprise means for recirculating the concentrated acetic acid- containing stream from the purification zone to the second reaction zone or to the second separation zone.

The reaction system as disclosed herein may further comprise means for recirculating recovered selective solvent from the acetic acid recovery unit to the first separation zone .

The reaction system as disclosed herein may further comprise means for recirculating recovered selective solvent from the purification zone to the first separation zone.

The reaction system as disclosed herein may further comprise means for recirculating an ethylene-containing stream from the ethane/ethylene separation unit to the second reaction zone.

The reaction system as disclosed herein may further comprise means for recirculating an ethane-containing stream from the ethane/ethylene separation unit to the first reaction zone .

The reaction system as disclosed herein may further comprise means for recirculating the carbon dioxide-depleted gaseous stream from the carbon dioxide removal zone to the first reaction zone .

Combinations of two or more of the above embodiments also fall within the scope of the present disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a flow scheme for the oxidative hydrogenation of ethylene and production of vinyl acetate, according to an embodiment of the present disclosure. In the flow scheme of FIG. 1, a stream (1) comprising ethane and an oxygen-comprising stream (2) are fed to the first reaction (oxydehydrogenation) unit (3) . A stream (4)

comprising ethylene, unconverted ethane, acetic acid and water leaves the oxydehydrogenation unit (3), and is supplied to a first separation zone (5) to produce a stream (7) comprising acetic acid and a stream (8) comprising ethylene, ethane and water. If first separation zone (5) is a condensation unit, or if first separation zone (5) is a wash zone to which water is supplied as washing agent stream (6), stream (7) comprising acetic acid will further comprise water. If first separation zone (5) is a wash zone to which a selective solvent is supplied as washing agent stream (6), stream (7) comprising acetic acid will further comprise selective solvent. Stream (8) comprising ethylene, ethane and water may be supplied to a dewatering zone (9) to produce a dewatered stream (10) comprising ethylene and ethane and a stream (9a) mainly comprising water. In the embodiment wherein first separation zone (5) is a condensation unit, dewatering zone (9) and first separation zone (5) may in fact be integrated. Dewatered stream (10) comprising ethylene and ethane is supplied to second reaction (vinylacetate ; "VAM") unit (13), as well as oxygen-containing stream (14) . A stream (15) comprising concentrated acetic acid is also supplied to vinylacetate reaction unit (13) . This stream (15) comprising concentrated acetic acid may comprise concentrated acetic acid obtained as stream (27) from the vinyl acetate purification section (19) .

The effluent stream (16) of the vinylacetate reaction unit (13) is supplied to a second (vinylacetate) wash zone (17), to which all or at least a portion of stream (7) comprising acetic acid is supplied. A stream (18) comprising

vinylacetate, acetic acid and optional other components leaves vinylacetate wash zone (17), which is subsequently supplied to purification zone (19) . Another stream (20) comprising ethane, ethylene and carbon dioxide also leaves vinylacetate wash zone (17) . In purification zone (19), stream (18) is separated into a concentrated vinylacetate stream (26) , a concentrated acetic acid stream (27) and one or more streams (28) comprising water, acetaldehyde , ethyl acetate and/or other by-products. As mentioned above, all or at least a portion of concentrated acetic acid stream (27) may be used as feed stream (15) for the second (vinylacetate) reaction unit (13) . Concentrated acetic acid stream (27) may further be used as washing agent in vinylacetate wash zone (17) (not shown) .

FIG. 2 is a schematic view of a flow scheme for the oxidative hydrogenation of ethylene and production of vinyl acetate, according to an embodiment of the present disclosure. In the flow scheme of FIG. 2, a stream (1) comprising ethane and a stream (2) comprising oxygen, are fed to the first reaction (oxydehydrogenation) unit (3) . A stream (4)

comprising ethylene, unconverted ethane, acetic acid and water leaves the oxydehydrogenation unit (3), and is supplied to a first separation zone (5), with optional addition of water as stream (6), to produce a stream (7) comprising aqueous acetic acid and a stream (8) comprising ethylene, ethane and water. Stream (8) comprising ethylene, ethane and water is supplied to a dewatering zone (9) to produce a dewatered stream (10) comprising ethylene and ethane and a stream (9a) mainly comprising water. Stream (7) comprising aqueous acetic acid may be supplied to an acetic acid recovery unit (11) to produce concentrated acetic acid stream (12), and a watery stream (11a) . Dewatered stream (10) comprising ethylene and ethane is supplied to second reaction (vinylacetate; "VAM") unit (13), as well as oxygen-containing stream (14) . A stream (15) comprising concentrated acetic acid is also supplied to vinylacetate reaction unit (13) . This stream (15) comprising concentrated acetic acid may comprise concentrated acetic acid obtained as stream (27) from the vinyl acetate purification section (19) . Alternatively or additionally, concentrated acetic acid may be supplied to vinylacetate reaction unit (13) through concentrated acetic acid stream (12) from acetic acid recovery unit (11) .

The effluent stream (16) of the vinylacetate reaction unit (13) is supplied to a second (vinylacetate) wash zone (17), to which all or at least a portion of stream (7) comprising aqueous acetic acid and/or all or at least a portion of concentrated acetic acid stream (12), and/or all or at least a portion of concentrated acetic acid stream (27) is supplied. A liquid stream (18) comprising vinylacetate, acetic acid and optional other components (typically heavy components such as acetaldehyde and ethyl acetate) leaves vinylacetate wash zone (17) , which is subsequently supplied to purification zone (19) . Another stream (20) comprising ethane, ethylene and carbon dioxide leaving wash zone (17) is supplied to carbon dioxide removal zone (21) to produce a carbon dioxide stream (21a) and a stream (22) comprising ethane and ethylene depleted of carbon dioxide, which is subsequently supplied to ethane/ethylene separation unit (23) to produce an ethylene- enriched stream (24) . The ethane-enriched stream (25) leaving the ethane/ethylene separation unit may at least partially be recirculated to the first (oxidative dehydrogenation) reaction unit (3) . The ethylene-enriched stream (24) may be withdrawn as product or at least partially be recirculated to the second (VAM) reaction unit (13) . In purification zone (19), stream (18) is separated into a concentrated vinylacetate stream (26), a concentrated acetic acid stream (27) and one or more streams (28) comprising water, acetaldehyde, ethyl acetate and/or other by-products. As mentioned above, all or at least a portion of concentrated acetic acid stream (27) may be used as feed stream (15) for the second (vinylacetate) reaction unit (13) . Concentrated acetic acid stream (27) may

additionally or alternatively be recycled as washing agent to vinylacetate wash zone (17) (not shown) .

In this design, it is possible to (partially) by-pass the second (VAM) reaction unit (13) and second separation zone (17) , by directly feeding a part or all of the dewatered effluent stream (10) from the dewatering zone (9) to the carbon dioxide removal zone (21) through line (30) . Typically, in such case, the acetic acid-enriched stream (7) from the first separation zone (5) is directly fed (not shown) to the VAM purification zone (19) in order to provide concentrated acetic acid. Alternatively or additionally, this acetic acid- enriched stream (7) is supplied to acetic acid recovery unit (11) to produce concentrated acetic acid. This allows the integrated ODH-VAM system as disclosed herein to (further) produce acetic acid at market specification when the VAM production is not in operation.

FIG. 3 is another schematic view of a flow scheme for the oxidative hydrogenation of ethylene and production of vinyl acetate, according to the present disclosure.

In the flow scheme of FIG. 3, a stream (1) comprising ethane and a stream (2) comprising oxygen, for example air, are fed to the first reaction (oxydehydrogenation ) unit (3) . A stream (4) comprising ethylene, unconverted ethane, acetic acid and water leaves the oxydehydrogenation unit (3), and is supplied to a first separation zone (5), with addition of a selective solvent as stream (6), to produce a stream (7) comprising acetic acid and selective solvent and a stream (8) comprising ethylene, ethane and water. Stream (8) comprising ethylene, ethane and water is supplied to a dewatering zone

(9) to produce a dewatered stream (10) comprising ethylene and ethane and a stream (9a) mainly comprising water. Stream (7) comprising acetic acid and selective solvent may be supplied to an acetic acid recovery unit (11) to produce concentrated acetic acid stream (12), and a selective solvent stream (11a) . Selective solvent stream (11a) may, after optional

dehydration, at least partially be recirculated to separation unit (5) as selective solvent stream (6) . Dewatered stream

(10) comprising ethylene and ethane is supplied to second reaction (vinylacetate ; "VAM" ) unit (13), as well as oxygen- containing stream (14) . A stream (15) comprising concentrated acetic acid is also supplied to vinylacetate reaction unit

(13) . This stream (15) comprising concentrated acetic acid may comprise concentrated acetic acid obtained as stream (27) from the vinyl acetate purification section (19) .

The effluent stream (16) of the vinylacetate reaction unit (13) is supplied to a second (vinylacetate) wash zone (17), to which all or at least a portion of stream (7) comprising acetic acid and selective solvent and/or all or at least a portion of concentrated acetic acid stream (12), and/or all or at least a portion of concentrated acetic acid stream (27) are supplied. A stream (18) comprising vinylacetate, acetic acid and optional other components leaves vinylacetate wash zone (17) , which is subsequently supplied to purification zone (19) . Another stream (20) comprising ethane, ethylene and carbon dioxide leaving wash zone (17) is supplied to carbon dioxide removal zone (21) to produce a carbon dioxide stream (21a) and a stream (22) comprising ethane and ethylene depleted of carbon dioxide, which is subsequently supplied to ethane/ethylene separation unit (23) to produce an ethylene- enriched stream (24) . The ethane-enriched stream (25) leaving the ethane/ethylene separation unit may at least partially be recirculated to the first (oxidative dehydrogenation) reaction unit (3) . The ethylene enriched stream (24) may be withdrawn as product or at least partially be recirculated to the second (VAM) reaction unit (13) . In purification zone (19), stream (18) is separated into a concentrated vinylacetate stream (26), a concentrated acetic acid stream (27), one or more streams (28) comprising water, acetaldehyde, ethyl acetate and/or other by-products, and a stream (29) of recovered selective solvent, which may at least partially be

recirculated to first separation zone (5) as selective solvent stream (6) . As mentioned above, all or at least a portion of concentrated acetic acid stream (27) may be used as feed stream (15) for the second (vinylacetate) reaction unit (13) . Concentrated acetic acid stream (27) may further be used as washing agent in vinylacetate wash zone (17) (not shown) .

As for the design schematically represented in Fig. 2, in this design it is possible to by-pass the second (VAM) reaction unit (13) and second separation zone (17), by directly feeding the dewatered effluent stream (10) from the dewatering zone (9) to the carbon dioxide removal zone (21) through line (30) . Typically, in such case, the acetic acid- enriched stream (7) from the first separation zone (5) is directly fed (not shown) to the VAM purification zone (19) in order to provide concentrated acetic acid.

Alternatively or additionally, this acetic acid-enriched stream (7) is supplied to acetic acid recovery unit (11) to produce concentrated acetic acid. This allows the integrated ODH-VAM system as disclosed herein to (further) produce acetic acid at market specification when the VAM production is not in operation .

It will be clear to the skilled person, that as a schematic diagrams these figures do not show all necessary inputs, outputs, recycle streams, etc. that may be present in the reaction system. Furthermore, in the figures, as will be appreciated, elements can be added, exchanged, and/or

eliminated so as to provide any number of additional

embodiments. In addition, as will be appreciated, the

proportion and the relative scale of the elements provided in the figures are intended to illustrate the embodiments of the present disclosure, and should not be taken in a limiting sense. It should additionally be appreciated that the

orientation and configuration shown in FIGS. 1-3 are not intended to be limiting or exhaustive of all possible

orientations or configurations, but rather are intended to be merely examples provided to illustrate the spirit of the present disclosure.

In the table below, it is indicated how the "first", "second" etc., streams mentioned in the claims and description correspond to the Arabic numerals in Figures 1-3.

"first" 4

"second" 7

"third" 8

"fourth" 10

"fifth" 16

"sixth" 12

"seventh" 18

"eighth" 20

"ninth" 27

"tenth" 26

"eleventh" 22

"twelfth" 25

"thirteenth" 24