TW202528276A - Incorporation of alkene hydrogenation in vinyl acetate production systems and methods - Google Patents

Abstract

Methods for producing vinyl acetate at higher production rates may be achieved by increasing the flammability limit of the mixture in the vinyl acetate reactor. For example, methane and/or higher carbon alkanes (e.g., alkanes with two or more carbons, also referred to herein as C2+ alkanes) in a diluent in the vinyl acetate reactor may increase the flammability limit. For example, a method of producing vinyl acetate may include the following steps: reacting via a hydrogenation reaction one or more alkenes and hydrogen in the presence of a hydrogenation catalyst to produce one or more alkanes; and reacting via an acetoxylation reaction acetic acid, ethylene, and oxygen in the presence of an acetoxylation catalyst and an alkane diluent to produce vinyl acetate and water, wherein the alkane diluent comprises the one or more alkanes from the hydrogenation reaction.

Description

Vinyl acetate production system and method with olefin hydrogenation

Vinyl acetate is typically produced via a vapor phase reaction of ethylene, oxygen, and acetic acid, wherein the ethylene is acetoxylated. The rate of acetoxylation increases with increasing oxygen concentration in the reactor. However, the amount of oxygen that can be introduced into the reactor is limited by the flammability limit of the reaction mixture. The flammability limit is generally defined as the lowest concentration of oxygen in the mixture that will cause a pressure increase upon contact with an ignition source. If the oxygen concentration exceeds this flammability limit, combustion or explosion may result. It is desirable to modify the reactor and/or vapor phase composition to increase the flammability limit and, therefore, the production capacity of the reactor.

A non-limiting example method for producing vinyl acetate may include reacting one or more alkenes with hydrogen in the presence of a hydrogenation catalyst to produce one or more alkanes via a hydrogenation reaction; and reacting acetic acid, ethylene, and oxygen in the presence of an acetoxylation catalyst and an alkane diluent via an acetylation reaction to produce vinyl acetate and water, wherein the alkane diluent includes the one or more alkanes from the hydrogenation reaction.

Another non-limiting example process for producing vinyl acetate may include: reacting a feed stream comprising acetic acid, ethylene, oxygen, and an alkane diluent in a vinyl acetate reactor to produce a crude vinyl acetate stream comprising vinyl acetate, water, and the alkane diluent; cooling the crude vinyl acetate stream in a heat exchanger; separating the crude vinyl acetate stream into a first tail gas stream, a flash gas stream, and a vinyl acetate stream, wherein the first tail gas stream comprises ethylene and the alkane diluent, and wherein the flash gas stream comprises ethylene, carbon dioxide, and the vinyl acetate stream. and an alkane diluent, and wherein the vinyl acetate stream comprises vinyl acetate; adding a second tail gas stream from a natural gas enrichment system to the first tail gas stream, wherein the one or more alkanes become part of the alkane diluent; removing at least a portion of the carbon dioxide from the flash gas stream to produce one or more recovery streams comprising ethylene and the alkane diluent; mixing vaporized acetic acid with the first tail gas stream and at least one of the one or more recovery streams in a gasifier to produce a gasification stream; and adding oxygen to the gasification stream to produce a feed stream.

Another non-limiting example process for producing vinyl acetate may include: reacting a feed stream comprising acetic acid, ethylene, oxygen, and an alkane diluent in a vinyl acetate reactor to produce a crude vinyl acetate stream comprising vinyl acetate, water, and the alkane diluent; cooling the crude vinyl acetate stream in a heat exchanger; separating the crude vinyl acetate stream into a tail gas stream, a flash gas stream, and a vinyl acetate stream, wherein the tail gas stream comprises ethylene and the alkane diluent, and wherein the flash gas stream comprises Ethylene, carbon dioxide, and an alkane diluent, and wherein the vinyl acetate stream comprises vinyl acetate; reacting one or more olefins with hydrogen in the presence of a hydrogenation catalyst in a hydrogenation reactor to produce a product stream comprising one or more alkanes and, optionally, hydrogen; adding at least a portion of the product stream to a tail gas stream, wherein the one or more alkanes become part of the alkane diluent; monitoring the hydrogen concentration in the alkane feed stream, wherein the hydrogen concentration is greater than 1 based on the total number of moles of hydrogen present in the product stream. % mol%, one or both of the following are performed: (a) reducing the amount of a product stream from the hydrogenation reactor added to the tail gas stream; and (b) adding a methane feed stream to the tail gas stream to become part of the alkane diluent; removing at least a portion of the carbon dioxide from the flash gas stream to produce one or more recovery streams including ethylene and the alkane diluent; mixing vaporized acetic acid with the tail gas stream and at least one of the one or more recovery streams in a gasifier to produce a gasification stream; and adding oxygen to the gasification stream to produce a feed stream.

Another non-limiting example method for producing vinyl acetate may include: (i) producing one or more alkanes through a hydrogenation reaction and/or (ii) performing a natural gas enrichment process to produce enriched natural gas and tail gas; and producing vinyl acetate through an acetoxylation reaction of acetic acid, ethylene, and oxygen performed in the presence of an alkane diluent comprising (i) one or more alkanes from the hydrogenation reaction and/or (ii) the tail gas.

This application claims priority to U.S. Provisional Patent Application No. 63/580,797, filed on September 6, 2023, entitled “INCORPORATION OF ALKENE HYDROGENATION IN VINYL ACETATE PRODUCTION SYSTEMS AND METHODS,” the entire contents of which are incorporated herein by reference.

The present invention relates to systems and methods for producing vinyl acetate at higher production rates by increasing the flammability limit of the mixture in a vinyl acetate reactor. More specifically, the systems and methods described herein can utilize methane and/or higher carbon number alkanes (e.g., alkanes with two or more carbon atoms, also referred to herein as C2+ alkanes) in the diluent in a vinyl acetate reactor.

Vinyl acetate is typically produced by conducting a steam phase reaction in the presence of methane as a diluent. The source of the methane is typically natural gas, which also contains small amounts of ethane and propane. Without being limited by theory, it is believed that increasing the heat of combustion of the alkane diluent will thereby achieve a higher concentration of oxygen that can be safely present in the vinyl acetate reactor. Therefore, the flammability limit can be increased by increasing the concentration of C2+ alkanes in the vinyl acetate reactor, each of which has a higher heat of combustion than methane. Methods and systems for determining and monitoring the flammability limit at various points in a vinyl acetate manufacturing process and system are described in U.S. Patent Application Publication No. 2022/0402852, which is incorporated herein by reference.

The vinyl acetate production system and method of the present invention can be fed into (a) a hydrogenation reaction to produce one or more C2+ alkanes and/or (b) tail gas from a natural gas enrichment process having an elevated concentration of one or more C2+ alkanes. The use of higher concentrations of one or more C2+ alkanes can increase the flammability limit of the feed stream to the vinyl acetate reactor and allow operation at higher oxygen concentrations in the vinyl acetate reactor. Advantageously, when fed into the hydrogenation reaction, a portion of the ethylene designated as a reactant can be diverted to the hydrogenation reaction to produce ethane, providing minimal modification to existing systems.

Advantageously, the methods and systems of the present invention allow for metering of alkane diluents from the hydrogenation reactor and from other sources as needed for efficient and safe operation of vinyl acetate production. For example, using a conventional methane diluent can reduce the cost of vinyl acetate production, while using an alkane diluent with a higher concentration of C2+ alkanes (e.g., ethane, propane, butane, and the like) can increase production capacity. Thus, the systems and methods of the present invention, including the use of hydrogenation and/or tail gas from a natural gas enrichment process, allow the operator to easily switch between the lowest cost operation (relative to alkane diluent) and the highest capacity operation (including intermediate positions between the aforementioned operations).

FIG1 schematically illustrates a non-limiting example scheme of the present invention, which integrates a hydrogenation reaction 100 and a subsequent acetoxylation reaction 104. In the hydrogenation reaction 100, one or more alkenes (e.g., ethylene, propylene, butene, or a mixture comprising two or more of the foregoing alkenes) react with hydrogen in the presence of a hydrogenation catalyst to produce one or more corresponding alkanes 102 (e.g., ethane, propane, butane, or a mixture comprising two or more of the foregoing alkenes). The one or more alkanes 102 are then used as diluents (or alkane diluents) in the subsequent acetoxylation reaction 104 between acetic acid, ethylene, and oxygen in the presence of an acetoxylation catalyst to produce vinyl acetate and water. As described in more detail herein, the alkane diluent present during the acetoxylation reaction 104 can include one or more alkanes 102 from the hydrogenation reaction 100 and, optionally, alkanes 106 from other sources (e.g., from a recycle stream, a methane-containing stream (such as a natural gas stream), a propane-containing stream, a butane-containing stream, and the like). Additionally, other chemicals can be present during the acetoxylation reaction 104, such as carbon dioxide and inert gases (such as nitrogen and hydrogen).

The description of FIG5 provides reaction conditions, reactant concentrations, and other details for the hydrogenation and acetoxylation reactions. These details apply to FIG1 . For example, hydrogenation reaction 100 can be carried out under the following conditions: at a temperature of -50°C to 200°C (or -10°C to 150°C, or 0°C to 100°C); at a pressure of 0.5 MPa to 4 MPa (or 1 MPa to 3 MPa); using ethylene alone, propylene alone, butene alone, or a mixture of two or more of the foregoing alkenes in the amounts provided in the description of FIG5 ; and using the amounts of hydrogen provided in the description of FIG5 . Similarly, the description of the conditions for the acetoxylation reaction in FIG5 applies to the acetoxylation reaction 104 in FIG1 .

FIG2 illustrates a flow diagram of a non-limiting example vinyl acetate production process 200 according to the present invention. Vinyl acetate production process 200 comprises reacting one or more olefins 202 (e.g., ethylene, propylene, butene, or a mixture comprising two or more of the foregoing olefins) with hydrogen 204 in the presence of a hydrogenation catalyst in a hydrogenation reactor 206 to produce one or more corresponding alkanes 208 (e.g., ethane, propane, butane, or a mixture comprising two or more of the foregoing olefins). The one or more alkanes 208 are then used as at least a portion of the alkane diluent in a subsequent acetoxylation reaction.

The reaction feed 218 for the acetoxylation reaction can be produced by mixing its components. The reaction feed 218 can include ethylene 210, acetic acid 212, oxygen 214, and an alkane diluent (e.g., one or more alkanes 208 from hydrogenation reactor 206, optionally methane 216 (e.g., a purified methane stream or a natural gas stream), and optionally alkanes from other sources including streams including ethane, propane, butane, or mixtures thereof). The ethylene (if present) in the one or more olefins 202 and the ethylene 210 can come from the same source or from different sources.

Reaction feed 218 is introduced into vinyl acetate reactor 220, where an acetoxylation reaction produces a crude vinyl acetate product 222 comprising vinyl acetate, water, and an alkane diluent. Crude vinyl acetate product 222 may then be processed in one or more processes 224 to produce vinyl acetate product 226. The processes may separate water, alkane diluent, and other components (e.g., unreacted ethylene) from crude vinyl acetate product 222. Additionally, the processes may purify these components after separation from crude vinyl acetate product 222. Thus, at least some of the components separated from crude vinyl acetate product 222 (either purified or as separated) may be recycled into one or more recycle streams 228 to form part of reaction feed 218.

As with Figure 1 , the reaction conditions, reactant concentrations, and other details for the hydrogenation and acetoxylation reactions provided in the description of Figure 5 apply to Figure 2 .

In any embodiment of the present invention, incorporating a higher concentration of C2+ alkanes into the alkane diluent can increase the flammability limit of vinyl acetate production. The product stream from the hydrogenation reaction that includes C2+ alkanes can also include unreacted hydrogen and/or unreacted olefins in the reaction feed (e.g., reaction feed 218 of Figure 2) that is introduced into the acetoxylation reaction. Unreacted hydrogen can, in particular, reduce the flammability limit. Unreacted olefins, ethylene, can react in the acetoxylation reaction to produce undesirable products. Therefore, one or more strategies can be implemented in the methods and systems of the present invention to reduce or eliminate hydrogen and/or olefin leakage from the hydrogenation reactor.

In examples where olefin breakthrough is to be mitigated (e.g., when using propylene and/or butene), a stoichiometric excess of hydrogen relative to the olefins may be present in the hydrogenation reactor. For example, the molar ratio of hydrogen to total olefins may be from 1.01:1 to 3:1, or from 1.1:1 to 2:1, or from 1.01:1 to 1.5:1, or from 1.01:1 to 1.1:1.

In examples of reducing hydrogen slip, a stoichiometric excess of olefins relative to hydrogen may be present in the hydrogenation reactor. For example, the molar ratio of hydrogen to total olefins may be from 1:3 to 1:1.01, or from 1:2 to 1:1.1, or from 1:1.5 to 1:1.01, or from 1:1.1 to 1:1.01.

A stoichiometric excess of unreacted olefin allows for the release of unreacted olefin from the hydrogenation reactor while mitigating hydrogen release. This strategy is preferably implemented when ethylene is the olefin, or at least 50 mol% (or 50 mol% to 99 mol%, or 75 mol% to 99 mol%, or 90 mol% to 99 mol%) of the olefin, as ethylene is a reactant in vinyl acetate synthesis.

In another example, the amount of hydrogenation catalyst and the residence time in the hydrogenation reactor can be in excess to provide 100 mol% conversion of the limiting reactant, regardless of whether the hydrogenation conditions include excess hydrogen, excess olefin, or stoichiometric equilibrium hydrogen and olefin. The hydrogenation reaction conditions and hydrogenation catalyst are discussed in more detail herein in FIG6 .

In another example, the hydrogenation reactor may comprise one or more hydrogenation catalyst beds connected in series or a catalyst bed comprising a mixture of two or more hydrogenation catalysts to provide 100 mol% conversion of the limiting reactant, regardless of whether the hydrogenation conditions include excess hydrogen, excess olefin, or stoichiometric equilibrium of hydrogen and olefin. Such configurations may be advantageous when one or more olefins are a mixture of two or more olefins, wherein each hydrogenation catalyst may have a high conversion rate for a different olefin in the mixture of two or more olefins.

In another example of reducing hydrogen and/or olefin breakthrough, the products from the hydrogenation reaction can be purified to remove unreacted hydrogen and/or unreacted olefin. For example, guard beds, membranes, or other extraction techniques can be used to remove hydrogen and/or olefin from the product stream from the hydrogenation reactor (e.g., one or more alkanes 208 in FIG. 2 ).

In an example of reducing hydrogen buildup, oxygen can be introduced into the system upstream of the vinyl acetate reactor. Reducing hydrogen buildup can allow for higher hydrogen break-through concentrations.

More than one of the aforementioned strategies may be implemented. For example, any combination of hydrogenation catalyst selection (including mixed catalysts), molar excess of reactant (hydrogen or olefin), and product stream purification to mitigate hydrogen and/or olefin breakthrough may be used.

If a reactant blow-through occurs from the hydrogenation reaction, ethylene blow-through is preferred because ethylene is a reactant in the acetylation reaction. Although hydrogen blow-through can lower the flammability limit in the acetylation reactor and produces by-products in the acetylation reaction, hydrogen blow-through is preferred over propylene or butylene blow-through because these by-products require separate downstream processing to remove from the vinyl acetate product.

Without being bound by theory, it is believed that the reaction feed to the acetylation reaction can include up to 1 mol% hydrogen without significantly affecting the flammability limit and the acetylation reaction products. Therefore, a small amount of hydrogen slip can be tolerated but is preferably monitored. For example, the hydrogen concentration in the product stream from the hydrogenation reactor and/or in the reaction feed used in the acetylation reaction can be monitored. The amount of hydrogen slip that can be tolerated in the present methods and systems will depend on many factors, including, but not limited to, the conditions of the acetylation reaction and the chemical composition of the reaction feed to the acetylation reaction. In general, the hydrogenated product preferably has 1 mol% or less, 0.5 mol% or less, or 0.1 mol% or less of hydrogen, based on the total moles of the product stream from the hydrogenation reaction, or is at least substantially free of hydrogen (e.g., 0 mol% to 0.01 mol%). However, higher values may be tolerated depending on the aforementioned factors.

A hydrogen analyzer can be used to monitor the hydrogen concentration of the product stream from the hydrogenation reactor.

If the hydrogen concentration of the product stream from the hydrogenation reactor is above a threshold value (e.g., 1 mol % based on the total moles of the product stream), one or more actions may be taken.

In a first example, the amount of the product stream from the hydrogenation reactor used to produce the feed stream to the vinyl acetate reactor can be reduced (or even stopped), and a fixed amount of an alkane diluent (e.g., methane, ethane, propane, butane, or a mixture comprising two or more of the foregoing alkenes) from another source can be used to compensate for the reduction or stoppage, each in response to a determination that the hydrogen concentration is above a critical value. Examples of other sources can include, but are not limited to, natural gas, natural gas liquids, petroleum refining byproducts, the like, and combinations thereof.

In another example, in response to determining that the hydrogen concentration is above a threshold value, the vinyl acetate manufacturing process and system may be shut down.

FIG3 illustrates a non-limiting example of a method of the present invention that integrates a natural gas enrichment process 300 with a subsequent acetoxylation reaction 312. In the natural gas enrichment process 300, natural gas 302 is treated with a separation system 304 (e.g., a pressure swing adsorption system) to produce a methane-enriched natural gas 306 and a tail gas 308. The separation system 304 is designed to remove at least a portion of the C2+ alkanes to produce the methane-enriched natural gas 306 having a higher concentration of methane than the natural gas 302. The separation system 304 is commonly used in chemical processing plants and facilities where one or more processes require high-purity methane. The C2+ alkanes removed from the natural gas 302 leave the separation system 304 in the tail gas 308. Therefore, the tail gas 308 has a higher concentration of C2+ alkanes than the natural gas 302. Typically, the tail gas 308 is used as fuel in other processes or burned as waste.

The present process can utilize tail gas 308 as at least a portion of an alkane diluent in a subsequent acetoxylation reaction 312. As illustrated, tail gas 308 is then used as a diluent (or alkane diluent) in a subsequent acetoxylation reaction 312 between acetic acid, ethylene, and oxygen in the presence of an acetoxylation catalyst to produce vinyl acetate and water. As described in more detail herein, the alkane diluent present during acetoxylation reaction 312 can include one or more alkanes from tail gas 308 and, optionally, alkanes 310 from other sources (e.g., from a recycle stream, a methane-containing stream (e.g., a natural gas stream), a propane-containing stream, a butane-containing stream, and the like). Additionally, other chemicals may be present during the acetoxylation reaction 312 (e.g., carbon dioxide and inert gases such as nitrogen and hydrogen).

Natural gas 302 may include 96 vol% to 98 vol% (or 97 vol% to 98 vol%) methane, 1 vol% to 2.5 vol% (or 1 vol% to 2 vol%) C2+ alkanes, and 0.5 vol% to 1.5 vol% (or 0.5 vol% to 1 vol%) other chemicals, such as carbon dioxide and inert gases such as nitrogen and hydrogen. Methane-enriched natural gas 306 may include 98 vol% to 99.8 vol% (or 98.5 vol% to 99.5 vol%) methane, 0.1 vol% to 1.5 vol% (or 0.1 vol% to 1 vol%) C2+ alkanes, and 0.1 vol% to 1 vol% (or 0.1 vol% to 0.5 vol%) other chemicals. The tail gas 308 may include 94 vol% to 97 vol% (or 95 vol% to 96.5 vol%) methane, 1.5 vol% to 4 vol% (or 1.5 vol% to 3 vol%) C2+ alkanes, and 1 vol% to 2 vol% (or 1 vol% to 1.5 vol%) other chemicals.

The description of Figure 6 provides reaction conditions, reactant concentrations, and other details for the acetoxylation reaction. These details apply to Figure 3.

FIG4 illustrates a flow diagram of a non-limiting example vinyl acetate production process 400 according to the present invention. Vinyl acetate production process 400 includes enriching natural gas 432 in a separation system 434 (e.g., a pressure swing adsorption system) to produce methane-enriched natural gas 436 and tail gas 438 (e.g., as described in FIG3 ). Tail gas 438 is then used as at least a portion of the alkane diluent in a subsequent acetoxylation reaction.

The reaction feed 218 for the acetoxylation reaction can be produced by mixing its components. The reaction feed 218 can include ethylene 210, acetic acid 212, oxygen 214, and an alkane diluent (e.g., tail gas 438, optionally methane 216 (e.g., a purified methane stream or a natural gas stream), and optionally alkanes from other sources including streams including ethane, propane, butane, or mixtures thereof). The disclosure regarding the processing of the reaction feed 218 in FIG. 2 applies to FIG. 4 using the same reference numbers.

As with FIG3 , the reaction conditions, reactant concentrations, and other details for the hydrogenation and acetoxylation reactions provided in the description of FIG6 apply to FIG4 .

Consider also a mixture of Figures 1 and 2 and Figures 3 and 4. For example, Figure 5 illustrates a flow diagram of a non-limiting example vinyl acetate production process 500 according to the present invention. Vinyl acetate production process 500 comprises reacting one or more olefins 202 (e.g., ethylene, propylene, butene, or a mixture comprising two or more of the foregoing olefins) with hydrogen 204 in the presence of a hydrogenation catalyst in a hydrogenation reactor 206 to produce one or more corresponding alkanes 208 (e.g., ethane, propane, butane, or a mixture comprising two or more of the foregoing olefins). The one or more alkanes 208 are then used as at least a portion of the alkane diluent in a subsequent acetoxylation reaction.

Vinyl acetate production process 500 includes enriching natural gas 432 in a separation system 434 (e.g., a pressure swing adsorption system) to produce methane-rich 406 and tail gas 438. Tail gas 438 is then used as at least a portion of the alkane diluent in a subsequent acetoxylation reaction.

The reaction feed 218 for the acetoxylation reaction can be produced by mixing its components. The reaction feed 218 can include ethylene 210, acetic acid 212, oxygen 214, and an alkane diluent (e.g., one or more alkanes 208 from hydrogenation reactor 206, tail gas 438, optionally methane 216 (e.g., a purified methane stream or a natural gas stream), and optionally alkanes from other sources including streams including ethane, propane, butane, or mixtures thereof). The ethylene in the one or more olefins 202 (if present) and the ethylene 210 can come from the same source or from different sources. The disclosure regarding the processing of the reaction feed 218 in FIG. 2 applies to FIG. 4 using the same reference numbers.

FIG6 illustrates a more detailed process flow diagram of a non-limiting example vinyl acetate manufacturing process 600 of the present invention. Additional components and modifications may be made to process 600 without altering the scope of the present invention. Furthermore, as will be appreciated by those skilled in the art, the description of process 600 and associated systems uses flows to describe the fluids passing through various circuits. For each flow, the associated system has corresponding circuits (e.g., pipes or other paths through which the corresponding fluid or other material can readily pass) and, as appropriate, valves, pumps, compressors, heat exchangers, or other equipment (not shown) to ensure proper operation of the associated system, whether or not explicitly described.

Furthermore, the use of a descriptor for an individual stream does not limit the composition of that stream to that descriptor. For example, an ethylene stream need not consist solely of ethylene. Rather, an ethylene stream may include ethylene and alkanes and/or contain one or more secondary contaminants. Alternatively, an ethylene stream may consist solely of ethylene. Alternatively, an ethylene stream may include ethylene, another reactant, and, optionally, alkanes.

In the illustrated process 600, an acetic acid stream 602 and an ethylene stream 604 are introduced into a vaporizer 606. Additionally, one or more recovery streams 630, 658, 668 (each described separately herein) may also be introduced into the vaporizer 606. Optionally, one or more of the recovery streams 630, 658, 668 may be combined with one another (not shown) and/or with the acetic acid stream 602 in any combination prior to introduction into the vaporizer 606.

The temperature and pressure of gasifier 606 can vary over a wide range. Gasifier 606 is preferably operated at a temperature of 100° C. to 250° C., or 100° C. to 200° C., or 120° C. to 150° C. The operating pressure of gasifier 606 is preferably 0.1 MPa to 2 MPa, or 0.25 MPa to 1.75 MPa, or 0.5 MPa to 1.5 MPa. Gasifier 606 produces a gasification feed stream 608. Gasification feed stream 608 exits gasifier 606 and is combined with oxygen stream 610 to produce a combined feed stream 612. Combined feed stream 612 is fed to vinyl acetate reactor 616.

The operating conditions in the vinyl acetate reactor 616 can be adjusted based on the composition of the combined feed stream 612, which can be used to determine the flammability limit of the combined feed stream 612. Example ranges for operating conditions in the vinyl acetate reactor 616 are provided below.

Combined feed stream 612 may include one or more of the following: ethylene, acetic acid, oxygen, methane, ethane, propane, butane, water, nitrogen, hydrogen, and carbon dioxide. Combined feed stream 612 may also contain propylene, butenes, and/or hydrogen (if a blow-through from the hydrogenation portion of process 100 occurs). The composition of combined feed stream 612 is considered at the inlet of the vinyl acetate reactor.

The concentrations of components in the various streams described herein may be measured directly or calculated based on measurements of different components. For example, the acetic acid content of a stream (taking dimerization into account) may be calculated based on a measurement. The acetic acid content may then be derived from the water content. Additionally, the values measured or derived from measurements need not be located at the location of interest. For example, the water content at the reactor inlet may be derived from the water content of a recycle stream from the purification process 648. Thus, when a condition value is described herein (e.g., a temperature value, a pressure value, or a concentration of a component in a stream), the condition value is not limited to direct measurements at that location, but encompasses derived values for that location based on measurements at that location or other locations in the process 600.

The concentration of ethylene in combined feed stream 612 may be from 30 mol% to 80 mol%, or from 35 mol% to 75 mol%, or from 40 mol% to 70 mol%, where these mol% are based on the total moles of the combined feed stream in the absence of oxygen and water contributions (or the total moles of an oxygen-free, dry combined feed stream).

The concentration of acetic acid in combined feed stream 612 can be from 10 mol% to 40 mol%, or from 15 mol% to 35 mol%, or from 20 mol% to 30 mol%, where these mol% are based on the total moles of the combined feed stream in the absence of oxygen contribution (or the total moles of the oxygen-free combined feed stream).

In combined feed stream 612, the molar ratio of ethylene to oxygen is preferably less than 20:1, or from 1:1 to 20:1, or from 1:1 to 10:1, or from 1.5:1 to 5:1, or from 2:1 to 4:1. In combined feed stream 612, the molar ratio of acetic acid to oxygen is preferably less than 10:1, or from 0.5:1 to 10:1, from 0.5:1 to 5:1, or from 0.5:1 to 3:1. In combined feed stream 612, the molar ratio of ethylene to acetic acid is preferably less than 10:1, or from 1:1 to 10:1, or from 1:1 to 5:1, or from 2:1 to 3:1.

The concentration of water in the combined feed stream 612 can be from 0 mol% to 10 mol%, or from 0 mol% to 5 mol%, or from 1 mol% to 4 mol%, where the mol% are based on the total moles of the oxygen-free combined feed stream.

The combined concentration of the alkane diluent in 612 in the combined feed stream (i.e., the total concentration of alkanes present, which may, for example, include methane, ethane, propane, butane, or any combination thereof) may be from 10 mol% to 50 mol%, or from 20 mol% to 50 mol%, or from 30 mol% to 50 mol%, where the mol% is based on the total moles of the oxygen-free, dry combined feed stream. Individually, the concentration of each of the alkanes present in the alkane diluent can be 0.1 mol% to 100 mol%, 0.1 mol% to 99.9 mol%, 0.1 mol% to 5 mol%, or 1 mol% to 10 mol%, or 5 mol% to 25 mol%, or 20 mol% to 60 mol%, or 50 mol% to 80 mol%, or 70 mol% to 100 mol%, wherein the mol% are based on the total moles of alkanes in the alkane diluent. For example, the combined feed stream 612 may include an alkane diluent comprised of methane and ethane (i.e., no propane), wherein the alkane diluent concentration (or the total concentration of methane and ethane) is 20 mol% to 50 mol%, based on the total moles of the oxygen-free, dry combined feed stream. In this example, methane may comprise 0.1 mol% to 10 mol% of the alkane diluent, with the remainder being ethane. In another example, the combined feed stream 612 may include ethane, propane, and optionally methane, wherein the alkane diluent concentration (or the total concentration of alkanes) is 10 mol% to 50 mol%, based on the total moles of the oxygen-free, dry combined feed stream. In this example, the concentration of ethane can be from 0.1 mol% to 99.9 mol%, the concentration of propane can be from 0.1 mol% to 99.9 mol%, and the concentration of methane can be from 0 mol% to 5 mol%, based on the total moles of the alkane diluent. In another example, the combined feed stream 612 can include ethane, propane, butane, and optionally methane, where the alkane diluent concentration (or total concentration of alkanes) can be from 10 mol% to 50 mol%, based on the total moles of the oxygen-free, dry combined feed stream. In this example, the concentration of ethane may be 0.1 mol% to 99.8 mol%, the concentration of propane may be 0.1 mol% to 99.8 mol%, the concentration of butane may be 0.1 mol% to 99.8 mol%, and the concentration of methane may be 0 mol% to 10 mol%, based on the total moles of the alkane diluent.

The concentration of carbon dioxide in the combined feed stream 612 may be from 0 mol% to 30 mol%, or from 0 mol% to 25 mol%, or from 5 mol% to 20 mol%, where the mol% are based on the total moles of the oxygen-free, dry combined feed stream.

The concentration of the inert gas (e.g., nitrogen and/or hydrogen) in the combined feed stream 612 can be from 0 mol% to 20 mol%, or from 1 mol% to 20 mol%, or from 2 mol% to 15 mol%, where these mol% are based on the total moles of the oxygen-free, dry combined feed stream. Typically, the concentration of the inert gas accumulates over time from the inert gas present in the stream supplied to the system.

Vinyl acetate reactor 616 may be a shell-and-tube reactor configured to absorb heat generated by the exothermic reaction through a heat exchange medium and to control the temperature therein within a range of 100° C. to 250° C., or 110° C. to 200° C., or 120° C. to 180° C. The pressure within vinyl acetate reactor 616 may be maintained at 0.5 MPa to 2.5 MPa or 0.5 MPa to 2 MPa.

Alternatively, vinyl acetate reactor 616 can be a fixed bed reactor or a fluidized bed reactor, preferably a fixed bed reactor containing a catalyst suitable for the acetylation of ethylene. For example, acetylation catalysts suitable for the production of vinyl acetate are described in U.S. Patent Nos. 3,743,607, 3,775,342, 5,557,014, 5,990,344, 5,998,659, 6,022,823, 6,057,260, and 6,472,556, each of which is incorporated herein by reference. Suitable acetylation catalysts may include palladium, gold, vanadium, and mixtures thereof. Particularly preferred are the following acetylation catalysts: palladium acetate/potassium acetate/cadmium acetate and palladium acetate/barium acetylaurate/potassium acetate. Generally, the palladium content of the acetylation catalyst may be 0.5 wt % to 5 wt %, or 0.5 wt % to 3 wt %, or 0.6 wt % to 2 wt %. When gold or one of its compounds is used, it is added in a ratio of 0.01 wt % to 4 wt %, or 0.2 wt % to 2 wt %, or 0.3 wt % to 1.5 wt %. The acetylation catalyst also preferably contains a refractory carrier, preferably a metal oxide (e.g., silica, silica-alumina, titanium oxide, or zirconium oxide), more preferably silica.

The acetoxylation reaction in vinyl acetate reactor 616 produces a crude vinyl acetate stream 618. Depending on the conversion and reaction conditions, crude vinyl acetate stream 618 may include 15 to 45 wt% vinyl acetate, 20 to 70 wt% acetic acid, 0.1 to 10 wt% water, 10 to 80 wt% ethylene, 1 to 40 wt% carbon dioxide, 0.1 to 50 wt% alkanes (e.g., methane, ethane, propane, butane, or mixtures thereof), and 0.1 to 15 wt% oxygen. Optionally, crude vinyl acetate stream 618 may also include 0.01 to 10 wt% ethyl acetate. Crude vinyl acetate stream 618 may include other compounds such as methyl acetate, acetaldehyde, acrolein, propane, and inert gases (e.g., nitrogen or hydrogen). Typically, these other compounds, other than the inert gases, are present in very low amounts (e.g., 2 wt% or less).

Crude vinyl acetate stream 618 passes through heat exchanger 620 to reduce the temperature of crude vinyl acetate stream 618 and then reaches separator 622 (e.g., a distillation column). Preferably, crude vinyl acetate stream 618 is cooled to a temperature of 80°C to 145°C or 90°C to 135°C before being introduced into separator 622. Preferably, no condensation of the liquefiable components occurs, and cooled crude vinyl acetate stream 618 is introduced into separator 622 in gaseous form.

The energy to separate the components of crude vinyl acetate stream 618 may be provided by the heat of reaction in reactor 616. In some embodiments, there may be an optional reboiler dedicated to increasing the separation energy within separator 622.

Separator 622 separates crude vinyl acetate stream 618 into at least two streams: an overhead stream 624 and a bottoms stream 626. Overhead stream 624 may include ethylene, carbon dioxide, water, alkanes (e.g., methane, ethane, propane, butane, or mixtures thereof), oxygen, and vinyl acetate. The bottoms stream may include vinyl acetate, acetic acid, water, and potentially ethylene, carbon dioxide, and alkanes.

Overhead distillate stream 624 is fed to degasser 628 to remove vinyl acetate from overhead distillate stream 624. Degasser 628 thus has tail gas stream 630 and bottoms stream 632. Vinyl acetate scrubbing is achieved by passing overhead distillate stream 624 through a mixture of water and acetic acid.

Tail gas stream 630 includes ethylene, carbon dioxide, alkanes, and oxygen. Tail gas stream 630 (also referred to as a recycle stream) is fed back to gasifier 606 via heat exchanger 620, where it is heated by crude vinyl acetate stream 618. Optionally, tail gas stream 630 may be augmented or supplemented with other streams, including other recycle streams (not shown) and feed streams from the process. As illustrated, an alkane feed stream 634, an ethylene feed stream 636, a tail gas stream 640 from a natural gas enrichment process (not shown) (e.g., as described in Figures 3-5), and a methane feed stream 638 from a hydrogenation reactor 670 are combined with (e.g., mixed with or carried away from) the tail gas stream 630 from the degasser 628. Although a methane feed stream 638 is illustrated, the use of methane in the systems and methods described herein is optional. Alternatively, the methane feed stream 638 may (more generally) be an alkane feed stream, wherein the alkane feed stream includes one or more alkanes not from the hydrogenation reactor but from other sources as discussed above. The alkane feed stream may actually be multiple streams that are combined with the tail gas stream 630.

6 illustrates the use of an alkane feed stream 634 from a hydrogenation reactor 670 and a tail gas stream 640 from a natural gas enrichment process, the present methods and systems may include only one of the illustrated foregoing, but not both.

Additionally, although FIG. 6 illustrates the use of a methane feed stream 638 and a tail gas stream 640 from a natural gas enrichment process, the present methods and systems may include only one of the illustrated foregoing, but not both. Advantageously, the use of a tail gas stream 640, which comprises methane but contains a higher concentration of C2+ alkanes as discussed above, may completely replace the methane feed stream 638. Additionally, the tail gas stream 640 from the natural gas enrichment process is free of hydrogen and/or olefin blow-by associated with the hydrogenation process. Thus, the tail gas stream 640 from the natural gas enrichment process may be a primary source of alkane diluent and/or a backup source of alkane diluent if hydrogen and/or olefin blow-by is observed.

Regarding the hydrogenation process, a first olefin feed stream 636a (illustrated as an ethylene side stream from the ethylene feed stream 636), a hydrogen feed stream 672, and a second olefin feed stream 674 are fed to a hydrogenation reactor 670. As a side stream of the ethylene feed stream 636, the first olefin feed stream 636a may use up to 5 vol%, or 0.1 vol% to 5 vol%, or 0.5 vol% to 2 vol% of the ethylene feed stream 636, with the remainder being introduced and combined with the tail gas stream 630.

The second olefin feed stream 674 may include ethylene, propylene, butene, or any mixture thereof.

Although FIG. 6 illustrates the use of two sources (or feeds) of olefins, the process 600 can be modified to use olefins from one or more sources introduced into the hydrogenation reactor 670 .

When more than one olefin is used as a reactant in hydrogenation reactor 670, the individual olefins may be present at 1 mol% to 99 mol%, or 1 mol% to 50 mol% to 25 mol% to 75 mol%, or 50 mol% to 99 mol%, based on the total moles of olefins. For example, when ethylene and propylene are used as reactants in hydrogenation reactor 670, the ethylene and propylene may each be present at 0.1 mol% to 99.9 mol%, or 1 mol% to 50 mol% to 25 mol% to 75 mol%, or 50 mol% to 99 mol%, based on the total moles of ethylene and propylene. In another example, when ethylene, propylene, and butene are used as reactants in hydrogenation reactor 670, each olefin may be present in an amount of 0.1 mol% to 99.9 mol%, or 1 mol% to 50 mol% to 25 mol% to 75 mol%, or 50 mol% to 99 mol%, based on the total moles of olefins. In yet another example, the olefin reactants used in hydrogenation reactor 670 may include 30 mol% to 99.9 mol% ethylene, 0.1 mol% to 50 mol% propylene, and optionally 0.1 mol% to 50 mol% butene, based on the total moles of olefins. In another example, the olefin reactant used in hydrogenation reactor 670 may include 90 mol% to 99.9 mol% ethylene, 0.1 mol% to 10 mol% propylene, and optionally 0.1 mol% to 5 mol% butene, based on the total molar amount of the olefin. In another example, the olefin reactant used in hydrogenation reactor 670 may include 0.1 mol% to 70 mol% ethylene, 30 mol% to 99.9 mol% propylene, and optionally 0.1 mol% to 50 mol% butene, based on the total molar amount of the olefin. In another example, the olefin reactant for hydrogenation reactor 670 may include 0.1 mol% to 10 mol% ethylene, 90 mol% to 99.9 mol% propylene, and optionally 0.1 mol% to 5 mol% butene, based on the total moles of olefins.

Hydrogen may be present in any suitable amount based on the composition of the olefins used. As discussed above, hydrogen is present to achieve 100 mol% conversion of all olefins to alkanes (including excess hydrogen), particularly when the olefins comprise propylene and/or butene. Additionally, to mitigate hydrogen blow-through from hydrogenation reactor 670, particularly when ethylene is used, hydrogen may be present at a lower concentration (for example) to achieve 99 mol%, 98 mol%, 95 mol%, or 90 mol% conversion of all olefins to alkanes.

The molar ratio of hydrogen to total olefins as reactants in the hydrogenation reaction may be 1:3 to 3:1, or 1:1.5 to 1.5:1, or 1:1, 1.01:1 to 3:1, or 1.1:1 to 2:1, or 1.01:1 to 1.5:1, or 1.01:1 to 1.1:1, or 1:3 to 1:1.01, or 1:2 to 1:1.1, or 1:1.5 to 1:1.01, or 1:1.1 to 1:1.01.

The alkane feed stream 634 may include 1 mol% or less, 0.5 mol% or less, or 0.1 mol% or less of hydrogen, or at least be substantially free (e.g., 0 mol% to 0.01 mol%) of hydrogen. Additionally, the alkane feed stream 634 may include 1 mol% or less, 0.5 mol% or less, or 0.1 mol% or less of unreacted alkanes, or at least be substantially free (e.g., 0 mol% to 0.01 mol%) of unreacted alkanes.

Hydrogenation reactor 670 may be operated at a temperature range of -50°C to 200°C, or -10°C to 150°C, or 0°C to 100°C. The pressure in vinyl acetate reactor 616 may be maintained at 0.5 MPa to 4 MPa, or 1 MPa to 3 MPa.

Hydrogenation reactor 670 can be a fixed bed reactor or a fluidized bed reactor, preferably a fixed bed reactor containing a hydrogenation catalyst suitable for the hydrogenation of ethylene and/or propylene. Suitable hydrogenation catalysts may include iridium, nickel, palladium, platinum, rhodium, ruthenium, and mixtures thereof. Generally, the metal content of the hydrogenation catalyst may be 0.5 wt % to 5 wt %, or 0.5 wt % to 3 wt %, or 0.6 wt % to 2 wt %. When gold or one of its compounds is used, it is added in a ratio of 0.01 wt % to 4 wt %, or 0.2 wt % to 2 wt %, or 0.3 wt % to 1.5 wt %. The hydrogenation catalyst also preferably contains a refractory carrier, preferably a metal oxide (such as silicon dioxide, silicon dioxide-alumina, titanium oxide, or zirconium oxide), more preferably silicon dioxide.

Contaminants in the hydrogen feed, such as carbon monoxide, can reduce the activity of the hydrogenation catalyst. Therefore, a carbon monoxide degasser or other suitable equipment can be used to treat the hydrogen feed stream 672 before introducing the hydrogen into the hydrogenation reactor 670 to reduce the concentration of contaminants, such as carbon monoxide in the hydrogen feed. The hydrogen feed can contain carbon monoxide at a concentration of up to 500 ppm, or up to 250 ppm, or up to 200 ppm, or up to 150 ppm, or up to 100 ppm, or up to 50 ppm, or from 0 ppm to 500 ppm, or from 0 ppm to 250 ppm, or from 0 ppm to 200 ppm, or from 0 ppm to 150 ppm, or from 0 ppm to 100 ppm, or from 0 ppm to 50 ppm, or from 0 ppm to 25 ppm.

Although the first olefin feed stream 636a, hydrogen feed stream 672, and second olefin feed stream 674 are illustrated as being introduced separately into the hydrogenation reactor 670, any combination of these streams may be premixed prior to introduction into the hydrogenation reactor 670.

The product of the hydrogenation reaction is an alkane feed stream 634. Along with the alkane feed stream 634 can be one or more analyzers 678 for measuring the concentration of hydrogen and/or olefins in the alkane feed stream 634. As discussed herein, hydrogen lowers the flammability limit of the downstream vinyl acetate reactor 616 and unreacted propylene and/or butenes can produce undesirable by-products. The methods of reducing and/or addressing reactant breakthrough described herein are applicable to the vinyl acetate manufacturing process 600. Examples of reducing reactant (e.g., hydrogen and/or olefin) breakthrough are discussed above.

As an example of responding to reactant blowthrough in alkane feed stream 634 from hydrogenation reactor 670, vinyl acetate production process 600 can be operated so that methane feed stream 638 (or more generally, an alkane feed stream from a source other than hydrogenation reactor 670) is used as appropriate with minimal addition of other alkanes to tail gas stream 630. Then, if a hydrogen blowthrough threshold concentration and/or an olefin blowthrough threshold concentration is exceeded, the amount of alkane feed stream 634 added to tail gas stream 630 can be reduced or stopped, and the amount of methane feed stream 638 added to tail gas stream 630 can be increased to compensate for the reduction or stoppage of flow from alkane feed stream 634.

Although alkane feed stream 634 is from hydrogenation reactor 670, ethylene feed stream 636 and methane feed stream 638 (or more generally, alkane feed streams from sources other than hydrogenation reactor 670) are illustrated as being introduced separately into tail gas stream 630, any combination of these streams may be premixed prior to introduction into tail gas stream 630.

Additionally, other processes (not illustrated) may be performed on the tail gas stream 630 between the degasser 628 and the heat exchanger 620. For example, at least a portion of the carbon dioxide in the tail gas stream 630 may be removed.

Referring again to separator 622, bottoms stream 626 from separator 622 and bottoms stream 632 from degasser 628 can be combined and fed to crude tank 642. Typically, the stream entering crude tank 642 is depressurized to a pressure of 0.1 MPa to 0.15 MPa. Upon depressurizing the incoming stream, ethylene, carbon dioxide, an inert gas (e.g., nitrogen and/or hydrogen), and acetic acid flash to produce a flash gas stream 644. The bottom portion of crude tank 642 primarily comprises vinyl acetate, water, and acetic acid, as well as some ethyl acetate byproduct. The bottom portion is conveyed as vinyl acetate stream 646, which is purified by various processes 648 to produce a purified vinyl acetate product stream 650. Examples of purification process 648 include, but are not limited to, azeotropic distillation, water stripping, distillation, phase separation, and the like, and any combination thereof. Examples of various processing methods and systems are described in U.S. Patent Nos. 6,410,817, 8,993,796, and 9,045,413, and U.S. Patent Application No. 2014/0066649, each of which is incorporated herein by reference.

Additionally, the purification process 648 may produce other streams that may be recycled back to the gasifier 606, the tail gas stream 630, the flash gas stream 644, and/or other streams within the process 600, individually or in any combination.

Optionally (not shown), a portion of the tail gas stream 630 may be combined with (eg, mixed with or entrained from) the flash gas stream 644 .

At least a portion of the carbon dioxide in the flash gas stream 644 (optionally combined with a portion of the tail gas side stream 630) may be removed prior to recirculation to the gasifier 606. As illustrated, the flash gas stream 644 is first passed through a _CO2 degasser 652 and then a _CO2 absorber 656 to produce a _CO2 -depleted overhead stream 658. Between the _CO2 degasser 652 and the _CO2 absorber 656, ethylene may be added to the flash gas stream 644 (or, as illustrated, to a side stream 662 thereof) from the ethylene stream 654.

The _CO2 -depleted overhead purge stream 658 can then be passed through a heat exchanger 660 and fed to the gasifier 606. Additionally, a side stream 662 from the flash gas stream 644 and/or the _CO2 -depleted overhead purge stream 658 can be used to purge nitrogen and argon from the system. Side stream 662 can be sent through an ethylene recovery process 664. The ethylene recovery process 660 produces an ethylene vent stream 666 and a recovery stream 668.

Examples of ethylene recovery processes 664 may include, but are not limited to, scrubbing systems, membrane recovery processes, and the like, and any combination thereof.

The ethylene recovery process 664 may produce an offgas stream 666 and another stream 668 for ethylene recovery to other processes or for recycling to the vinyl acetate gasifier 606.

Although FIG6 illustrates a general vinyl acetate manufacturing process 600, those skilled in the art will recognize how to apply the teachings of the present invention to other vinyl acetate manufacturing processes that may differ from the illustrated process 600. Examples of different vinyl acetate manufacturing processes and systems are described in U.S. Patent Nos. 6,410,817, 8,993,796, and 9,045,413, and U.S. Patent Application No. 2014/0066649, each of which is incorporated herein by reference.

Unless otherwise indicated, all numbers expressing ingredient quantities, properties (e.g., molecular weight), reaction conditions, and the like used in this invention and the related claims are to be understood as being modified in all instances by the term "about." At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the claims, the term "about" relative to each numerical parameter should at least be interpreted in light of the number of reported significant digits and by applying ordinary rounding techniques.

Where a concentration range is listed or recited as useful, appropriate, or the like, it is intended that any and every concentration within that range, inclusive, should be considered recited. For example, the range "from 1 to 10" or "1 to 10 of 1 to 10" should be understood to indicate each and every possible value along the continuum between about 1 and about 10. Thus, even if a data point within a range is specifically identified, or even if no data points are within a range or only a few specific data points are referenced, it should be understood that the inventor understands and appreciates that any and all data points within the range are considered to be specified, and that the entire range and all points within the range are known to the inventor.

The term "and/or" refers to an inclusive "and" and an exclusive "or" and is used herein for convenience. For example, a mixture comprising acetic acid and/or methyl acetate may include acetic acid alone, methyl acetate alone, or both acetic acid and methyl acetate.

In a list following "one or more of" or "at least one of," the use of "and" to connect the list is intended to be alternative or conjunctive rather than disjunctive. For example, "at least one of the following: A, B, and C" and "one or more of the following: A, B, and C" are each considered to disclose embodiments of A alone, B alone, C alone, A and B combined, A and C combined, B and C combined, and all three of A, B, and C combined.

Unless otherwise indicated, room temperature is 25°C and atmospheric pressure is 101.325 kPa.

Although compositions, systems, and methods are described herein as “comprising” various components or steps, such compositions, systems, and methods may also “consist essentially of” or “consist of” the various components and steps.

Illustrative embodiments of the present invention are described herein. For the sake of clarity, not all features of an actual embodiment are described in this specification. Of course, it will be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from implementation to implementation. Moreover, it will be appreciated that such a development effort may be complex and time-consuming, but will nevertheless be a routine undertaking for those skilled in the art who benefit from this disclosure.

Example embodiments

Example 1. A method for producing vinyl acetate, comprising: reacting one or more alkenes with hydrogen in the presence of a hydrogenation catalyst to produce one or more alkanes via a hydrogenation reaction; and reacting acetic acid, ethylene, and oxygen in the presence of an acetylation catalyst and an alkane diluent via an acetylation reaction to produce vinyl acetate and water, wherein the alkane diluent comprises one or more alkanes from the hydrogenation reaction.

Example 2. The method of Example 1, wherein the alkane diluent further comprises methane.

Example 3. The method of Example 2, wherein the methane group is present in the alkane diluent in an amount of 0.1 mol% to 5 mol% based on the total molar amount of the alkane diluent.

Example 4. The method of any one of Examples 1 to 3, wherein the one or more olefins include one or more of ethylene, propylene and butene.

Example 5.   The method of Example 4, wherein the alkane diluent includes ethane, propane and, if appropriate, methane, wherein at least a portion of the ethane and propane are derived from a hydrogenation reaction, and wherein the ethane group is present in the alkane diluent at 0.1 mol% to 99.9 mol% of the total molar amount of the alkane diluent, the propane group is present in the alkane diluent at 0.1 mol% to 99.9 mol% of the total molar amount of the alkane diluent, and the methane group is present in the alkane diluent at 0 mol% to 5 mol% of the total molar amount of the alkane diluent.

Example 6.   The method of Example 4 or 5, wherein the alkane diluent includes ethane, propane and, if appropriate, methane, wherein at least a portion of the ethane and propane are derived from a hydrogenation reaction, and wherein the ethane group is present in the alkane diluent at 0.1 mol% to 50 mol% of the total molar number of the alkane diluent, the propane group is present in the alkane diluent at 50 mol% to 99.9 mol% of the total molar number of the alkane diluent, and the methane group is present in the alkane diluent at 0 mol% to 5 mol% of the total molar number of the alkane diluent.

Example 7. The method of any one of Examples 1 to 6, wherein the alkane diluent comprises tail gas from a natural gas enrichment process.

Example 8. The method of any one of Examples 1 to 7, further comprising: conducting a hydrogenation reaction in a hydrogenation reactor; introducing a hydrogen stream into the hydrogenation reactor; and treating the hydrogen stream to reduce the concentration of carbon monoxide from the hydrogen stream before introducing the hydrogenation reactor.

Example 9. The method of any one of Examples 1 to 8, wherein the acetoxylation reaction produces a crude vinyl acetate stream; wherein the crude vinyl acetate stream further comprises unreacted ethylene; and wherein the method further comprises: treating the crude vinyl acetate stream to recover at least a portion of the unreacted ethylene and at least a portion of the alkane diluent in an ethylene recovery stream; and recycling the ethylene recovery stream to the acetoxylation reaction.

Embodiment 10. The method of any one of Embodiments 1 to 9, wherein the hydrogenation reaction produces a product stream comprising one or more alkanes and, optionally, hydrogen, and wherein the method further comprises: monitoring the concentration of hydrogen in the product stream from the hydrogenation reactor; and reducing the amount of the one or more alkanes from the hydrogenation reactor in the alkane diluent and adding methane to the alkane diluent when the concentration of hydrogen in the product stream from the hydrogenation reactor is greater than 1 mol % based on the total moles present in the product stream.

Example 11. A method for producing vinyl acetate, comprising: reacting a feed stream comprising acetic acid, ethylene, oxygen, and an alkane diluent in a vinyl acetate reactor to produce a crude vinyl acetate stream comprising vinyl acetate, water, and the alkane diluent; cooling the crude vinyl acetate stream in a heated exchange medium; separating the crude vinyl acetate stream into a first tail gas stream, a flash gas stream, and a vinyl acetate stream, wherein the first tail gas stream comprises ethylene and the alkane diluent, and the flash gas stream comprises ethylene, carbon dioxide, and the alkane diluent; a first tail gas stream and a second tail gas stream from a natural gas enrichment system to produce a first tail gas stream containing ethylene and an alkane diluent, wherein the vinyl acetate stream comprises vinyl acetate; adding a second tail gas stream from a natural gas enrichment system to the first tail gas stream, wherein one or more alkanes become part of the alkane diluent; removing at least a portion of the carbon dioxide from the flash gas stream to produce one or more recovery streams comprising ethylene and the alkane diluent; mixing vaporized acetic acid with the first tail gas stream and at least one of the one or more recovery streams in a gasifier to produce a gasification stream; and adding oxygen to the gasification stream to produce a feed stream.

Example 12. A method for producing vinyl acetate, the method comprising: reacting a feed stream comprising acetic acid, ethylene, oxygen, and an alkane diluent in a vinyl acetate reactor to produce a crude vinyl acetate stream comprising vinyl acetate, water, and the alkane diluent; cooling the crude vinyl acetate stream in a heated exchange medium; separating the crude vinyl acetate stream into a tail gas stream, a flash gas stream, and a vinyl acetate stream, wherein the tail gas stream comprises ethylene and the alkane diluent, and the flash gas stream comprises acetic acid, water, and the alkane diluent; olefins, carbon dioxide, and an alkane diluent, and wherein the vinyl acetate stream comprises vinyl acetate; reacting one or more olefins with hydrogen in the presence of a hydrogenation catalyst in a hydrogenation reactor to produce a product stream comprising one or more alkanes and, optionally, hydrogen; adding at least a portion of the product stream to a tail gas stream, wherein the one or more alkanes become part of the alkane diluent; monitoring the hydrogen concentration in the alkane feed stream, wherein the hydrogen concentration is greater than 1% based on the total molar hydrogen present in the product stream. mol %, one or both of the following are performed: (a) reducing the amount of a product stream from the hydrogenation reactor added to the tail gas stream; and (b) adding a methane feed stream to the tail gas stream to become a portion of the alkane diluent; removing at least a portion of the carbon dioxide from the flash gas stream to produce one or more recovery streams including ethylene and the alkane diluent; mixing vaporized acetic acid with the tail gas stream and at least one of the one or more recovery streams in a gasifier to produce a gasification stream; and adding oxygen to the gasification stream to produce a feed stream.

Embodiment 13. The method of embodiment 12, wherein the tail gas stream is a first tail gas stream, and the method further comprises: adding a second tail gas stream from a natural gas enrichment system to the first tail gas stream, wherein the one or more alkanes become part of the alkane diluent.

Embodiment 14. The method of any one of embodiments 12 to 13, wherein the alkane diluent of the feed stream comprises 0.1 mol% to 5 mol% methane based on the total moles of the alkane diluent.

Embodiment 15. The method of any one of embodiments 12 to 14, wherein the alkane diluent of the feed stream comprises 0 mol% to 0.1 mol% methane based on the total moles of the alkane diluent.

Embodiment 16. The method of any one of Embodiments 12 to 15, wherein the one or more olefins include one or more of ethylene, propylene, and butene.

Example 17. The method of Example 16, wherein the alkane diluent of the feed stream comprises ethane, propane, and optionally methane, wherein at least a portion of the ethane and propane is derived from a hydrogenation reaction, and wherein ethane groups are present in the alkane diluent of the feed stream at 0.1 mol% to 99.9 mol% of the total moles of the alkane diluent, propane groups are present in the alkane diluent of the feed stream at 0.1 mol% to 99.9 mol% of the total moles of the alkane diluent, and methane groups are present in the alkane diluent of the feed stream at 0 mol% to 5 mol% of the total moles of the alkane diluent.

Embodiment 18. The method of embodiment 16 or 17, wherein the alkane diluent of the feed stream comprises ethane, propane, and optionally methane, wherein at least a portion of the ethane and propane is derived from a hydrogenation reaction, and wherein ethane groups are present in the alkane diluent of the feed stream at 0.1 mol% to 50 mol%, propane groups are present in the alkane diluent of the feed stream at 50 mol% to 99.9 mol%, and methane groups are present in the alkane diluent of the feed stream at 0 mol% to 5 mol%, based on the total moles of the alkane diluent.

Example 19. A method for producing vinyl acetate, comprising: (i) producing one or more alkanes through a hydrogenation reaction and/or (ii) performing a natural gas enrichment process to produce enriched natural gas and tail gas; and producing vinyl acetate through an acetoxylation reaction of acetic acid, ethylene, and oxygen in the presence of an alkane diluent comprising (i) one or more alkanes from the hydrogenation reaction and/or (ii) the tail gas.

Embodiment 20. The method of Embodiment 19, wherein the alkane diluent comprises ethane, propane, and optionally methane, wherein at least a portion of the ethane and propane is derived from the hydrogenation reaction and/or tail gas, and wherein the ethane group is present in the alkane diluent at 0.1 mol% to 99.9 mol% of the total molar amount of the alkane diluent, the propane group is present in the alkane diluent at 0.1 mol% to 99.9 mol% of the total molar amount of the alkane diluent, and the methane group is present in the alkane diluent at 0 mol% to 5 mol% of the total molar amount of the alkane diluent.

Hereinafter, the present invention will be better understood based on the following non-limiting examples.

Example

_The hydrogenation reactions were carried out in a laboratory-scale reactor using a hydrogenation catalyst from the ACTISORB® O series available from Clariant with a feed of approximately 1 mol% _H₂ and the balance _C₂H₄ at various temperatures ranging from below 0°C to approximately 80°C and a pressure of approximately 2.8 MPa. 100% hydrogen consumption was observed at all temperatures tested.

The hydrogenation reaction was conducted in a pilot plant-scale reactor using a hydrogenation catalyst from the ACTISORB® O series available from Clariant, with a feed of up to about ₄ mol% _H₂ and the balance _C₂H₄ at a temperature of about 250°C and a pressure of about 2.8 MPa. 100% hydrogen consumption was observed. The hydrogenated product was then used as at least a portion of the alkane diluent in the vinyl acetate production process, with up to about 10 mol% oxygen in the reaction feed to the vinyl acetate reactor.

100: Hydrogenation 102: Alkanes 104: Acetoxylation 106: Alkanes 200: Vinyl Acetate Manufacturing Process 202: Olefins 204: Hydrogenation 206: Hydrogenation Reactor 208: Alkanes 210: Ethylene 212: Acetic Acid 214: Oxygen 216: Methane 218: Reaction Feed 220: Vinyl Acetate Reactor 222: Crude Vinyl Acetate Product 2 24: Process 226: Vinyl Acetate Product 228: Recycle Stream 300: Natural Gas Enrichment Process 302: Natural Gas 304: Separation System 306: Methane-Enriched Natural Gas 308: Tail Gas 310: Alkanes 312: Acetoxylation 400: Vinyl Acetate Manufacturing Process 432: Natural Gas 434: Separation System 436: Methane-Enriched Natural Gas 438: Tail Gas 500: Vinyl Acetate Manufacturing Process 600: Vinyl Acetate Manufacturing Process 602: Acetic Acid Stream 604: Ethylene Stream 606: Vaporizer 608: Vaporization Feed Stream 610: Oxygen Stream 612: Combined Feed Stream 616: Vinyl Acetate Reactor 618: Crude Vinyl Acetate Stream 620: Heat Exchanger 622: Separator 624: Top Distillate Stream 626: Bottom Stream 628: Degasser 630: Recovery Stream/Tail Gas Stream 632: Bottoms Stream 634: Alkane Feed Stream 636: Ethylene Feed Stream 636a: First Ethylene Feed Stream 638: Methane Feed Stream 640: Tail Gas Stream 642: Crude Drum 644: Flash Gas Stream 646: Vinyl Acetate Stream 648: Purification Process 650: Vinyl Acetate Product Stream 652: _CO2 Degasser 654: Ethylene Stream 656: _CO2 Absorber 658: Recovery Stream/ _CO2 -Depleted Top Distillate Stream 660: Ethylene Recovery Process 662: Side Stream 664: Ethylene Recovery Process 666: Exhaust Stream 668: Recovery Stream 670: Hydrogenation Reactor 672: Hydrogen Feed Stream 674: Second Olefin Feed Stream 678: Analyzer

FIG1 schematically illustrates a non-limiting example of the present invention scheme for integrating a hydrogenation reaction.

FIG. 2 illustrates a process flow diagram of a non-limiting example of the method of the present invention for implementing the scheme of FIG. 1 .

FIG3 schematically illustrates a non-limiting example of an embodiment of the present invention for integrating a natural gas enrichment process.

FIG4 illustrates a process flow diagram of a non-limiting example method of the present invention for implementing the scheme of FIG3 .

FIG. 5 illustrates a process flow diagram of a non-limiting example method of the present invention for implementing the hybrid scheme of FIG. 1 and FIG. 3 .

FIG6 illustrates a process flow diagram of a non-limiting example vinyl acetate production process of the present invention.

100: Hydrogenation reaction

102: Alkanes

104: Acetylation reaction

106: Alkanes

Claims (20)

A method for producing vinyl acetate, comprising: Reacting one or more alkenes with hydrogen in the presence of a hydrogenation catalyst via a hydrogenation reaction to produce one or more alkanes; and Reacting acetic acid, ethylene, and oxygen in the presence of an acetoxylation catalyst and an alkane diluent via an acetoxylation reaction to produce vinyl acetate and water, wherein the alkane diluent comprises the one or more alkanes from the hydrogenation reaction. The method of claim 1, wherein the alkane diluent further comprises methane. The method of claim 2, wherein the methane group is present in the alkane diluent at 0.1 mol% to 5 mol% of the total molar amount of the alkane diluent. The method of claim 1, wherein the one or more olefins include one or more of ethylene, propylene and butene. The method of claim 4, wherein the alkane diluent comprises ethane, propane, and optionally methane, wherein at least a portion of the ethane and propane are derived from the hydrogenation reaction, and wherein the ethane group is present in the alkane diluent at 0.1 mol% to 99.9 mol% of the total moles of the alkane diluent, the propane group is present in the alkane diluent at 0.1 mol% to 99.9 mol% of the total moles of the alkane diluent, and the methane group is present in the alkane diluent at 0 mol% to 5 mol% of the total moles of the alkane diluent. The method of claim 4, wherein the alkane diluent comprises ethane, propane, and optionally methane, wherein at least a portion of the ethane and propane are derived from the hydrogenation reaction, and wherein the ethane group is present in the alkane diluent at 0.1 mol% to 50 mol% of the total moles of the alkane diluent, the propane group is present in the alkane diluent at 50 mol% to 99.9 mol% of the total moles of the alkane diluent, and the methane group is present in the alkane diluent at 0 mol% to 5 mol% of the total moles of the alkane diluent. The method of claim 1, wherein the alkane diluent comprises tail gas from a natural gas enrichment process. The method of claim 1, further comprising: performing the hydrogenation reaction in a hydrogenation reactor; introducing a hydrogen stream into the hydrogenation reactor; and treating the hydrogen stream to reduce the concentration of carbon monoxide in the hydrogen stream prior to introduction into the hydrogenation reactor. The method of claim 1, wherein the acetoxylation reaction produces a crude vinyl acetate stream; wherein the crude vinyl acetate stream further comprises unreacted ethylene, and wherein the method further comprises: treating the crude vinyl acetate stream to recover at least a portion of the unreacted ethylene and at least a portion of the alkane diluent in an ethylene recovery stream; and recycling the ethylene recovery stream for use in the acetoxylation reaction. The method of claim 1, wherein the hydrogenation reaction produces a product stream comprising the one or more alkanes and, optionally, hydrogen, and wherein the method further comprises: monitoring the concentration of hydrogen in the product stream from the hydrogenation reaction; and reducing the amount of the one or more alkanes from the hydrogenation reaction in the alkane diluent and, when the concentration of hydrogen in the product stream from the hydrogenation reactor is greater than 1 mol % based on the total moles present in the product stream, adding methane to the alkane diluent. A method for producing vinyl acetate, the method comprising: reacting a feed stream comprising acetic acid, ethylene, oxygen, and an alkane diluent in a vinyl acetate reactor to produce a crude vinyl acetate stream comprising vinyl acetate, water, and the alkane diluent; cooling the crude vinyl acetate stream in a heat exchanger; separating the crude vinyl acetate stream into a first tail gas stream, a flash gas stream, and a vinyl acetate stream, wherein the first tail gas stream comprises ethylene and the alkane diluent, wherein the flash gas stream comprises ethylene, carbon dioxide, and the alkane diluent, and wherein the vinyl acetate stream comprises vinyl acetate; adding a second tail gas stream from a natural gas enrichment system to the first tail gas stream, wherein the one or more alkanes become part of the alkane diluent; Removing at least a portion of the carbon dioxide from the flash gas stream to produce one or more recovery streams including ethylene and the alkane diluent; Combining vaporized acetic acid with the first tail gas stream and at least one of the one or more recovery streams in a vaporizer to produce a vaporized stream; and Adding oxygen to the vaporized stream to produce the feed stream. A method for producing vinyl acetate, the method comprising: Reacting a feed stream comprising acetic acid, ethylene, oxygen, and an alkane diluent in a vinyl acetate reactor to produce a crude vinyl acetate stream comprising vinyl acetate, water, and the alkane diluent; Cooling the crude vinyl acetate stream in a heat exchanger; Separating the crude vinyl acetate stream into a tail gas stream, a flash gas stream, and a vinyl acetate stream, wherein the tail gas stream comprises ethylene and the alkane diluent, wherein the flash gas stream comprises ethylene, carbon dioxide, and the alkane diluent, and wherein the vinyl acetate stream comprises vinyl acetate; Reacting one or more olefins with hydrogen in the presence of a hydrogenation catalyst in a hydrogenation reactor via a hydrogenation reaction to produce a product stream comprising one or more alkanes and, optionally, hydrogen; adding at least a portion of the product stream to the tail gas stream, wherein the one or more alkanes become part of the alkane diluent; monitoring the hydrogen concentration in the product stream, wherein when the hydrogen concentration is greater than 1 mol % based on the total moles of hydrogen present in the product stream, performing one or both of the following: (a) reducing the amount of the product stream from the hydrogenation reactor added to the tail gas stream; and (b) adding a methane feed stream to the tail gas stream to become part of the alkane diluent; Removing at least a portion of the carbon dioxide from the flash gas stream to produce one or more recovery streams including ethylene and the alkane diluent; Combining vaporized acetic acid with the tail gas stream and at least one of the one or more recovery streams in a vaporizer to produce a vaporized stream; and Adding oxygen to the vaporized stream to produce the feed stream. The method of claim 12, wherein the tail gas stream is a first tail gas stream, and the method further comprises: adding a second tail gas stream from a natural gas enrichment system to the first tail gas stream, wherein the one or more alkanes become part of the alkane diluent. The method of claim 12, wherein the alkane diluent of the feed stream comprises 0.1 mol% to 5 mol% methane based on the total moles of the alkane diluent. The method of claim 12, wherein the alkane diluent of the feed stream comprises 0 mol% to 0.1 mol% methane based on the total moles of the alkane diluent. The method of claim 12, wherein the one or more olefins include one or more of ethylene, propylene, and butene. The method of claim 16, wherein the alkane diluent of the feed stream comprises ethane, propane, and optionally methane, wherein at least a portion of the ethane and the propane are derived from the hydrogenation reaction, and wherein the ethane groups are present in the alkane diluent of the feed stream at 0.1 mol% to 99.9 mol%, the propane groups are present in the alkane diluent of the feed stream at 0.1 mol% to 99.9 mol%, and the methane groups are present in the alkane diluent of the feed stream at 0 mol% to 5 mol%, based on the total moles of the alkane diluent. The method of claim 16, wherein the alkane diluent of the feed stream comprises ethane, propane, and optionally methane, wherein at least a portion of the ethane and the propane are derived from the hydrogenation reaction, and wherein the ethane groups are present in the alkane diluent of the feed stream at 0.1 mol% to 50 mol%, the propane groups are present in the alkane diluent of the feed stream at 50 mol% to 99.9 mol%, and the methane groups are present in the alkane diluent of the feed stream at 0 mol% to 5 mol%, based on the total moles of the alkane diluent. A method for producing vinyl acetate, comprising: (i) producing one or more alkanes via a hydrogenation reaction and/or (ii) performing a natural gas enrichment process to produce enriched natural gas and tail gas; and producing vinyl acetate via an acetoxylation reaction of acetic acid, ethylene, and oxygen in the presence of an alkane diluent comprising (i) the one or more alkanes from the hydrogenation reaction and/or (ii) the tail gas. The method of claim 19, wherein the alkane diluent comprises ethane, propane and, optionally, methane, wherein at least a portion of the ethane and the propane are derived from the hydrogenation reaction and/or the tail gas, and wherein the ethane group is present in the alkane diluent at 0.1 mol% to 99.9 mol% of the total molar number of the alkane diluent, the propane group is present in the alkane diluent at 0.1 mol% to 99.9 mol% of the total molar number of the alkane diluent, and the methane group is present in the alkane diluent at 0 mol% to 5 mol% of the total molar number of the alkane diluent.