Incorporation of Alkene Hydrogenation in Vinyl Acetate Production Systems and Methods

Abstract

A method for producing vinyl acetate at a higher rate of production can 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 having two or more carbon atoms, also referred to herein as C2+ alkanes) in the diluent in the vinyl acetate reactor can increase the flammability limit. For example, a method for producing vinyl acetate may include the steps of: 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 contains one or more alkanes from the hydrogenation reaction.

Description

Technical Field

[0001] Cross-Reference to Related Applications This application claims the priority benefit of U.S. Provisional Patent Application No. 63 / 580,797, entitled "INCORPORATION OF ALKENE HYDROGENATION IN VINYL ACETATE PRODUCTION SYSTEMS AND METHODS", filed on September 6, 2023, which is incorporated herein by reference in its entirety.

[0002] Statement of Rights to an Invention Made Under Federally Sponsored Research and Development Not applicable

[0003] Reference to a "Sequence Listing" Table or Computer Program Listing Appendix Submitted on a Compact Disc Not applicable

Background Art

[0004] Vinyl acetate is conventionally produced by a gas-phase reaction of ethylene, oxygen, and acetic acid in which ethylene is acetoxylated. As the oxygen concentration in the reactor increases, the rate of acetoxylation increases. However, the amount of oxygen that can be introduced into the reactor is limited by the flammability limit of the reaction mixture. Flammability limit is typically defined as the minimum concentration of oxygen in a mixture that will result in a pressure increase when the mixture is contacted with an ignition source. If the oxygen concentration exceeds this flammability limit, a fire or explosion may occur. It is desirable to make modifications to the reactor and / or gas phase components to increase the flammability limit and consequently increase the production capacity of the reactor.

Summary of the Invention

Means for Solving the Problems

[0005] Non-limiting exemplary methods for producing vinyl acetate include reacting one or more alkenes and 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 contains one or more alkanes from the hydrogenation reaction.

[0006] Another non-limiting exemplary method for producing vinyl acetate involves reacting a feed stream containing acetic acid, ethylene, oxygen, and an alkane diluent in a vinyl acetate reactor to produce a crude vinyl acetate stream containing vinyl acetate, water, and an alkane diluent; cooling the crude vinyl acetate stream in a heat exchanger; and 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 contains ethylene and an alkane diluent; the flash gas stream contains ethylene, carbon dioxide, and an alkane diluent; and the vinyl acetate stream contains acetic acid. This may include separating vinyl acid, adding a second tail gas stream from a natural gas enrichment system to a first tail gas stream, wherein one or more alkanes become part of an alkane diluent, removing at least a portion of carbon dioxide from the flash gas stream to produce one or more recirculating streams containing ethylene and an alkane diluent, mixing vaporized acetic acid with the first tail gas stream and at least one of the one or more recirculating streams in a vaporizer to produce a vaporized stream, and adding oxygen to the vaporized stream to produce a feed stream.

[0007] A further non-limiting exemplary method for producing vinyl acetate involves reacting a feed stream containing acetic acid, ethylene, oxygen, and an alkane diluent in a vinyl acetate reactor to produce a crude vinyl acetate stream containing vinyl acetate, water, and an 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 contains ethylene and an alkane diluent, the flash gas stream contains ethylene, carbon dioxide, and an alkane diluent, and the vinyl acetate stream contains vinyl acetate; reacting one or more alkenes and hydrogen via a hydrogenation reaction in a hydrogenation reactor in the presence of a hydrogenation catalyst to produce a product stream containing one or more alkanes and optionally hydrogen; and adding at least a portion of the product stream to the tail gas stream. This may include adding one or more alkanes to form part of an alkane diluent, monitoring the hydrogen concentration in the alkane feedstream, and if the hydrogen concentration exceeds 1 mol% based on the total number of moles present in the product stream, either or both of the following: (a) reducing the amount of product stream from the hydrogenation reactor added to the tail gas stream, and (b) adding a methane feedstream to the tail gas stream to form part of an alkane diluent, removing at least a portion of carbon dioxide from the flash gas stream to produce one or more recirculating streams containing ethylene and an alkane diluent, mixing vaporized acetic acid with at least one of the tail gas stream and one or more recirculating streams in a vaporizer to produce a vaporized stream, and adding oxygen to the vaporized stream to produce a feedstream.

[0008] Other non-limiting exemplary methods for producing vinyl acetate may include (i) producing one or more alkanes via a hydrogenation reaction and / or (ii) carrying out a natural gas enrichment process to produce enriched natural gas and tail gas, and producing vinyl acetate via the acetoxylation reaction of acetic acid, ethylene and oxygen carried out in the presence of an alkane diluent containing (i) one or more alkanes from the hydrogenation reaction and / or (ii) tail gas. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows a non-limiting example of the scheme of this disclosure for integrating hydrogenation reactions. [Figure 2] This figure shows a process flow diagram of a non-limiting example of the method of this disclosure that implements the scheme of Figure 1. [Figure 3] This figure shows a non-limiting example of the scheme of this disclosure for integrating natural gas enrichment processes. [Figure 4] This figure shows a process flow diagram of a non-limiting exemplary method of implementing the scheme of Figure 3. [Figure 5] This figure shows a process flow diagram of a non-limiting exemplary method of the present disclosure that implements a hybrid of the schemes of Figures 1 and 3. [Figure 6] This figure shows a process flow diagram of a non-limiting, exemplary vinyl acetate manufacturing process. [Modes for carrying out the invention]

[0010] This disclosure relates to a system and method for producing vinyl acetate at a higher production rate by increasing the flammability limit of the mixture in a vinyl acetate reactor. More specifically, the system and method described herein may utilize methane and / or higher carbon alkanes (e.g., alkanes having two or more carbon atoms, also referred to herein as C2+ alkanes) as diluents in the vinyl acetate reactor.

[0011] The gas-phase reaction for producing vinyl acetate is typically carried out in the presence of methane as a diluent. The source of methane is typically natural gas, and may also include small amounts of ethane and propane. Although not limited by theory, increasing the heat of combustion of the alkane diluent is thought to consequently allow for higher concentrations of oxygen that can safely exist 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 having a higher heat of combustion than methane. Methods and systems for determining and monitoring the flammability limit at various points along the vinyl acetate production process and system are described in U.S. Patent Application Publication No. 2022 / 0402852 (incorporated herein by reference).

[0012] The vinyl acetate production system and method of this disclosure may incorporate (a) a hydrogenation reaction to produce one or more C2+ alkanes and / or (b) tail gas from a natural gas enrichment process with an increased concentration of one or more C2+ alkanes. Using higher concentrations of one or more C2+ alkanes can increase the flammability limit of the feed stream to the vinyl acetate reactor and enable operation at higher oxygen concentrations within the vinyl acetate reactor. Advantageously, when incorporating a hydrogenation reaction, a portion of the ethylene designated for use as a reactant can be diverted to the hydrogenation reaction to produce ethane, which minimizes modifications to existing systems.

[0013] Advantageously, the methods and systems of the present disclosure allow for the metering of alkane diluents from hydrogenation reactors and other sources as needed for the effective and safe operation of vinyl acetate production. For example, the cost of producing vinyl acetate may be lower when using conventional methane diluents, but the production capacity may be higher when using alkane diluents with higher concentrations of C2+ alkanes (e.g., ethane, propane, butane, etc.). Therefore, by incorporating tail gas from hydrogenation reactions and / or natural gas enrichment processes into the systems and methods of the present disclosure, operators can easily move between the lowest-cost operation (with respect to alkane diluents) and the highest-capacity operation, including an intermediate position between the above.

[0014] Figure 1 shows a non-limiting exemplary reaction scheme of the present disclosure that integrates a hydrogenation reaction 100 and a subsequent acetoxylation reaction 104. In the hydrogenation reaction 100, one or more alkenes (e.g., ethylene, propylene, butylene, or a mixture of two or more of these) are reacted 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 of two or more of the above). 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 will be described in more detail herein, the alkane diluent present in the acetoxylation reaction 104 may include one or more alkanes 102 from the hydrogenation reaction 100, and optionally alkanes 106 from other sources (e.g., from a recirculating stream, a methane-containing stream such as a natural gas stream, a propane-containing stream, a butane-containing stream, etc.). Furthermore, other chemical species (e.g., carbon dioxide and inert gases such as nitrogen and argon) may be present in the acetoxylation reaction 104.

[0015] The reaction conditions, reactant concentrations, and other details for the hydrogenation and acetoxylation reactions are provided in the description of Figure 5. These details are applicable to Figure 1. For example, the hydrogenation reaction 100 may be carried out at a temperature of -50°C to 200°C (or -10°C to 150°C or 0°C to 100°C), a pressure of 0.5 MPa to 4 MPa (or 1 MPa to 3 MPa), using ethylene alone, propylene alone, butylene alone, or a mixture containing two or more of the above in the amounts provided in the description of Figure 5, and the amount of hydrogen provided in the description of Figure 5. Similarly, the description of the conditions for the acetoxylation reaction in Figure 5 is applicable to the acetoxylation reaction 104 in Figure 1.

[0016] Figure 2 shows a flow chart of a non-limiting exemplary vinyl acetate manufacturing process 200 of the present disclosure. The vinyl acetate manufacturing process 200 includes reacting one or more alkenes 202 (e.g., ethylene, propylene, butylene, or a mixture comprising two or more of these) and hydrogen 204 in a hydrogenation reactor 206 in the presence of a hydrogenation catalyst to produce one or more corresponding alkanes 208 (e.g., ethane, propane, butane, or a mixture comprising two or more of the above). The one or more alkanes 208 are then used as at least part of an alkane diluent in a subsequent acetoxylation reaction.

[0017] The reaction feed 218 for the acetoxylation reaction can be prepared by mixing its components. The reaction feed 218 may include ethylene 210, acetic acid 212, oxygen 214, and an alkane diluent (e.g., one or more alkanes 208 from the hydrogenation reactor 206, optionally methane 216 (e.g., a purified methane stream or a natural gas stream), and optionally alkanes from other sources, including steam containing ethane, propane, butane, or mixtures thereof). If present, one or more alkenes 202 and the ethylene in the ethylene 210 may be from the same source or from different sources.

[0018] The reaction feed 218 is introduced into the vinyl acetate reactor 220, where the acetoxylation reaction produces a crude vinyl acetate product 222 containing vinyl acetate, water, and an alkane diluent. The crude vinyl acetate product 222 can then be treated in one or more processes 224 to produce a vinyl acetate product 226. These processes can separate water, the alkane diluent, and other components (e.g., unreacted ethylene) from the crude vinyl acetate product 222. Furthermore, these processes can purify the components after they have been separated from the crude vinyl acetate product 222. Thus, at least a portion of the components separated from the crude vinyl acetate product 222, whether purified or separated, can be recycled into one or more recirculation streams 228 to become part of the reaction feed 218.

[0019] Similar to Figure 1, the reaction conditions, reactant concentrations, and other details for the hydrogenation and acetoxylation reactions provided in the description of Figure 5 are applicable to Figure 2.

[0020] In any embodiment of this disclosure, including a high concentration of C2+ alkanes with an alkane diluent increases the flammability limit for vinyl acetate production. The product stream from the hydrogenation reaction containing C2+ alkanes may also contain unreacted hydrogen and / or unreacted alkenes, which will be incorporated into the reaction feed for the acetoxylation reaction (e.g., reaction feed 218 in Figure 2). Unreacted hydrogen, among other things, can lower the flammability limit. Unreacted alkenes other than ethylene may react in the acetoxylation reaction to produce undesirable products. Therefore, one or more strategies can be implemented in the methods and systems of this disclosure to mitigate or eliminate hydrogen and / or alkene breakthroughs from the hydrogenation reactor.

[0021] In examples where alkene breakthrough is mitigated (e.g., when propylene and / or butylene is used), a stoichiometric excess of hydrogen relative to alkenes may be present in the hydrogenation reactor. For example, the molar ratio of hydrogen to total alkenes can 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.

[0022] In examples for mitigating hydrogen breakthrough, a stoichiometric excess of alkenes relative to hydrogen may be present in the hydrogenation reactor. For example, the molar ratio of hydrogen to total alkenes can 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.

[0023] Stoichiometric excess of unreacted alkene allows breakthrough of unreacted alkene from the hydrogenation reactor, while mitigating hydrogen breakthrough. This strategy can be preferably implemented when ethylene is the alkene, or constitutes at least 50 mol% (or 50 mol% to 99 mol%, or 75 mol% to 99 mol%, or 90 mol% to 99 mol%) of the alkene, because ethylene is a reactant in vinyl acetate synthesis.

[0024] In another example, the amount of hydrogenation catalyst and the residence time in the hydrogenation reactor can be excessive to provide 100 mol% conversion of the limiting reactant, regardless of whether the hydrogenation conditions include excess hydrogen, excess alkenes, or a stoichiometric balance of hydrogen and alkenes. Hydrogenation reaction conditions and hydrogenation catalysts are discussed in more detail herein with reference to FIG. 6.

[0025] In yet another example, the hydrogenation reactor may include a series of multiple hydrogenation catalyst beds or a catalyst bed having a mixture of two or more hydrogenation catalysts to provide 100 mol% conversion of the limiting reactant, regardless of whether the hydrogenation conditions involve excess hydrogen, excess alkenes, or a stoichiometric balance of hydrogen and alkenes. The above configuration may be advantageous when one or more alkenes are a mixture of two or more alkenes, and each hydrogenation catalyst may have a high conversion rate for different alkenes in the mixture of two or more alkenes.

[0026] Another example of mitigating hydrogen and / or alkene breakthroughs is the purification of the product from the hydrogenation reaction to remove unreacted hydrogen and / or unreacted alkenes. For example, a guard bed, membrane, or other extraction technique can be used to remove hydrogen and / or alkenes from the product stream (e.g., one or more alkanes 208 in Figure 2) from the hydrogenation reactor.

[0027] One example of a method to reduce hydrogen buildup is introducing oxygen into the system upstream of the vinyl acetate reactor. Reducing hydrogen buildup may enable higher hydrogen breakthrough concentrations.

[0028] Two or more of the aforementioned strategies may be implemented. For example, hydrogen and / or alkene breakthroughs can be mitigated by using any combination of hydrogenation catalyst selection (including mixed catalysts), molar excess reactants (hydrogen or alkenes), and product flow purification.

[0029] If a breakthrough of reactants occurs from the hydrogenation reaction, an ethylene breakthrough is preferred because ethylene is a reactant in the acetoxylation reaction. While a hydrogen breakthrough may lower the flammability limit in the acetoxylation reactor and produce byproducts in the acetoxylation reaction, a hydrogen breakthrough may be preferred over a propylene or butylene breakthrough because such byproducts may require an additional downstream separate process to remove them from the vinyl acetate product.

[0030] While not limited by theory, the reaction feed for the acetoxylation reaction is considered to be able to contain up to 1 mol% of hydrogen without significantly affecting the flammability limit and the acetoxylation reaction product. Therefore, small amounts of hydrogen breakthrough may be tolerated, but are preferably monitored. For example, the hydrogen concentration in the product stream from the hydrogenation reactor and / or in the reaction feed for the acetoxylation reaction can be monitored. The amount of hydrogen breakthrough that may be tolerated in the methods and systems of this disclosure depends on many factors, including, but not limited to, the conditions of the acetoxylation reaction and the chemical composition of the reaction feed for the acetoxylation reaction. In general, the hydrogenation product preferably has 1 mol% or less, 0.5 mol% or less, or 0.1 mol% or less of hydrogen, or at least is substantially hydrogen-free (e.g., 0 mol% to 0.01 mol%), based on the total number of moles in the product stream from the hydrogenation reaction. However, depending on the factors mentioned above, higher values ​​may be tolerated.

[0031] The hydrogen concentration in the product stream from the hydrogenation reactor can be monitored using a hydrogen analyzer.

[0032] If the hydrogen concentration in the product stream from the hydrogenation reactor exceeds a threshold (for example, 1 mol% based on the total number of moles in the product stream), one or more measures may be taken.

[0033] In the first example, the amount of product flow from the hydrogenation reactor used to generate the feed flow for the vinyl acetate reactor can be reduced (or stopped), and the reduction or stoppage can be compensated for by using an amount of alkane diluent from another source (e.g., methane, ethane, propane, butane, or a mixture containing two or more of the aforementioned), in response to a determination that the hydrogen concentration exceeds a threshold. Examples of other sources may include, but are not limited to, natural gas, natural gas liquefied products, petroleum refining by-products, and combinations thereof.

[0034] In another example, the vinyl acetate manufacturing method and system may be stopped in response to a determination that the hydrogen concentration exceeds a threshold.

[0035] Figure 3 shows a non-limiting example of a scheme of this disclosure 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 in a separation system 304 (e.g., a pressure swing absorption system) that produces methane-enriched natural gas 306 and tail gas 308. The separation system 304 is intended to remove at least some of the C2+ alkanes to produce methane-enriched natural gas 306 having a higher methane concentration than natural gas 302. Separation systems 304 are common in chemical processing plants and facilities where one or more processes require high-purity methane. The C2+ alkanes removed from natural gas 302 exit the separation system 304 in tail gas 308. Thus, tail gas 308 has a higher concentration of C2+ alkanes than natural gas 302. Typically, tail gas 308 is used as fuel in other processes or burned as waste.

[0036] The method of this disclosure may utilize tail gas 308 as at least part of the alkane diluent in the subsequent acetoxylation reaction 312. As shown in the figures, tail gas 308 is then used as a diluent (or alkane diluent) in the subsequent acetoxylation reaction 312 between acetic acid, ethylene, and oxygen in the presence of an acetoxylation catalyst to produce vinyl acetate and water. As will be described in more detail herein, the alkane diluent present in the acetoxylation reaction 312 may include one or more alkanes from tail gas 308, and optionally alkane 310 from other sources (e.g., from a recirculated stream, a methane-containing stream such as a natural gas stream, a propane-containing stream, a butane-containing stream, etc.). Furthermore, other chemical species (e.g., carbon dioxide and inert gases such as nitrogen and argon) may be present in the acetoxylation reaction 312.

[0037] Natural gas 302 may contain 96% to 98% by volume (or 97% to 98% by volume) of methane, 1% to 2.5% by volume (or 1% to 2% by volume) of C2+ alkanes, and 0.5% to 1.5% by volume (or 0.5% to 1% by volume) of other chemical species (e.g., carbon dioxide and inert gases such as nitrogen and argon). Methane-enriched natural gas 306 may contain 98% to 99.8% by volume (or 98.5% to 99.5% by volume) of methane, 0.1% to 1.5% by volume (or 0.1% to 1% by volume) of C2+ alkanes, and 0.1% to 1% by volume (or 0.1% to 0.5% by volume) of other chemical species. Tail gas 308 may contain 94% to 97% (or 95% to 96.5% by volume) of methane, 1.5% to 4% (or 1.5% to 3% by volume) of C2+ alkanes, and 1% to 2% (or 1% to 1.5% by volume) of other chemical species.

[0038] The reaction conditions, reactant concentrations, and other details of the acetoxylation reaction are provided in the description of Figure 6. These details are applicable to Figure 3.

[0039] Figure 4 shows a flow diagram of a non-limiting exemplary vinyl acetate manufacturing process 400 of the present disclosure. The vinyl acetate manufacturing process 400 includes enriching natural gas 432 in a separation system 434 (e.g., a pressure swing absorption system) to produce methane enrichment 436 and tail gas 438 (e.g., as shown in Figure 3). The tail gas 438 is then used as at least part of an alkane diluent in a subsequent acetoxylation reaction.

[0040] The reaction feed 218 for the acetoxylation reaction can be prepared by mixing its components. The reaction feed 218 may include ethylene 210, acetic acid 212, oxygen 214, and an alkane diluent (e.g., tail gas 438, optionally methane 216 (e.g., purified methane stream or natural gas stream), and optionally alkanes from other sources including steam containing ethane, propane, butane, or mixtures thereof). The disclosure of the processing of reaction feed 218 in Figure 2 applies to Figure 4, which uses the same reference numerals.

[0041] Similar to Figure 3, the reaction conditions, reactant concentrations, and other details for the hydrogenation and acetoxylation reactions provided in the description of Figure 6 are applicable to Figure 4.

[0042] Hybrids of Figures 1 and 2 and Figures 3 and 4 are also possible. For example, Figure 5 shows a flow chart of a non-limiting exemplary vinyl acetate manufacturing process 500 of the present disclosure. The vinyl acetate manufacturing process 500 includes reacting one or more alkenes 202 (e.g., ethylene, propylene, butylene, or a mixture comprising two or more of these) and hydrogen 204 in a hydrogenation reactor 206 in the presence of a hydrogenation catalyst to produce one or more corresponding alkanes 208 (e.g., ethane, propane, butane, or a mixture comprising two or more of the above). The one or more alkanes 208 are then used as at least part of an alkane diluent in a subsequent acetoxylation reaction.

[0043] The vinyl acetate production process 500 includes enriching natural gas 432 in a separation system 434 (e.g., a pressure swing absorption system) to produce methane enrichment 406 and tail gas 438. The tail gas 438 is then used as at least part of an alkane diluent in a subsequent acetoxylation reaction.

[0044] The reaction feed 218 for the acetoxylation reaction can be prepared by mixing its components. The reaction feed 218 may include ethylene 210, acetic acid 212, oxygen 214, and an alkane diluent (e.g., one or more alkanes 208 from the hydrogenation reactor 206, tail gas 438, optionally methane 216 (e.g., purified methane stream or natural gas stream), and optionally alkanes from other sources including steam containing ethane, propane, butane, or mixtures thereof). If present, one or more alkenes 202 and the ethylene in the ethylene 210 may be from the same source or from different sources. The disclosure of the processing of the reaction feed 218 in Figure 2 applies to Figure 4, which uses the same reference numerals.

[0045] Figure 6 shows a more detailed process flow diagram of a non-limiting, exemplary vinyl acetate manufacturing process 600 of this disclosure. Additional components and modifications can be made to process 600 without altering the scope of this disclosure. Furthermore, as will be recognized by those skilled in the art, the description of process 600 and the associated systems uses flow to describe fluids passing through various lines. For each flow, the associated system has, whether expressly or not, a corresponding line (e.g., a pipe or other path through which the corresponding fluid or other material can easily pass) and, optionally, valves, pumps, compressors, heat exchangers, or other equipment (not shown) to ensure the proper operation of the associated system.

[0046] Furthermore, the descriptors used for individual flows do not limit the composition of the flow to those comprising the descriptors. For example, an ethylene flow does not necessarily consist solely of ethylene. Rather, an ethylene flow may contain ethylene and alkanes, and / or one or more trace amounts of contaminants. Alternatively, an ethylene flow may consist solely of ethylene. Alternatively, an ethylene flow may contain ethylene, another reactant, and optionally alkanes.

[0047] In the illustrated process 600, the acetic acid stream 602 and the ethylene stream 604 are introduced into the vaporizer 606. Furthermore, one or more recirculating streams 630, 658, and 668 (each further described herein) may also be introduced into the vaporizer 606. Optionally, one or more of the recirculating streams 630, 658, and 668 may be combined with each other and / or with the acetic acid stream 602 in any combination before being introduced into the vaporizer 606 (not shown).

[0048] The temperature and pressure of the vaporizer 606 can vary over a wide range. The vaporizer 606 preferably operates at temperatures of 100°C to 250°C, or 100°C to 200°C, or 120°C to 150°C. The operating pressure of the vaporizer 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. The vaporizer 606 generates a vaporized feed stream 608. The vaporized feed stream 608 exits the vaporizer 606 and combines with the oxygen stream 610 to generate a combined feed stream 612. The combined feed stream 612 is supplied to the vinyl acetate reactor 616.

[0049] 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 limits of the combined feed stream 612. An exemplary range of operating conditions in the vinyl acetate reactor 616 is given below.

[0050] The combined feed stream 612 may contain one or more of ethylene, acetic acid, oxygen, methane, ethane, propane, butane, water, nitrogen, argon, and carbon dioxide. If a breakthrough occurs from the hydrogenation portion of process 100, the combined feed stream 612 may also contain propylene, butylene, and / or hydrogen. The composition of the combined feed stream 612 is considered at the inlet of the vinyl acetate reactor.

[0051] The concentrations of various components in a flow described herein can be measured directly or calculated based on measurements of different components. For example, the acetic acid content in the flow (considering dimerization) can be calculated based on measured values. The acetic acid content can then be derived from the water content. Furthermore, measured values ​​or values ​​derived from measured values ​​do not need to be at the location of interest. For example, the water content at the reactor inlet may be derived from the water content of the recirculated flow coming from purification process 648. Thus, where conditional values ​​(e.g., temperature, pressure, or concentration of components in a flow) are described herein, the conditional values ​​are not limited to direct measurements at the location but include derived values ​​at that location based on measurements at that location or other locations in process 600.

[0052] The ethylene concentration in the combined feed stream 612 may be 30 mol% to 80 mol%, or 35 mol% to 75 mol%, or 40 mol% to 70 mol%, where the mol% is based on the total moles of the combined feed stream with no contributions from oxygen and water (or the total moles of a dry combined feed stream without oxygen).

[0053] The concentration of acetic acid in the combined feed stream 612 may be 10 mol% to 40 mol%, or 15 mol% to 35 mol%, or 20 mol% to 30 mol%, where the mol% is based on the total moles of the combined feed stream without oxygen contribution (or the total moles of the combined feed stream without oxygen).

[0054] In the combined feed stream 612, the molar ratio of ethylene to oxygen is preferably less than 20:1, or 1:1 to 20:1, or 1:1 to 10:1, or 1.5:1 to 5:1, or 2:1 to 4:1. In the combined feed stream 612, the molar ratio of acetic acid to oxygen is preferably less than 10:1, or 0.5:1 to 10:1, 0.5:1 to 5:1, or 0.5:1 to 3:1. In the combined feed stream 612, the molar ratio of ethylene to acetic acid is preferably less than 10:1, or 1:1 to 10:1, or 1:1 to 5:1, or 2:1 to 3:1.

[0055] The water concentration in the combined feed stream 612 may be 0 mol% to 10 mol%, or 0 mol% to 5 mol%, or 1 mol% to 4 mol%, where the mol% is based on the total moles of the combined feed stream that does not contain oxygen.

[0056] The combined concentration of the alkane diluent in the combined feed stream 612 (i.e., the total concentration of the alkanes present, which may include, for example, methane, ethane, propane, butane, or any combination thereof) may be 10 mol% to 50 mol%, or 20 mol% to 50 mol%, or 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 alkane present in the alkane diluent may 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%, where the mol% is based on the total moles of the alkanes in the alkane diluent. For example, the combined feed stream 612 may contain an alkane diluent composed of methane and ethane (i.e., without propane), and 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 the above example, methane may constitute 0.1 mol% to 10 mol% of the alkane diluent, with the remainder being ethane. In another example, the combined feed stream 612 may contain ethane, propane, and optionally methane, and the alkane diluent concentration (or the total concentration of alkanes) may be 10 mol% to 50 mol% based on the total moles of the oxygen-free, dry combined feed stream. In the above example, the concentration of ethane may be 0.1 mol% to 99.9 mol% based on the total moles of the alkane diluent, the concentration of propane may be 0.1 mol% to 99.9 mol% based on the total moles of the alkane diluent, and the concentration of methane may be 0 mol% to 5 mol% based on the total moles of the alkane diluent. In yet another example, the combined feed stream 612 may contain ethane, propane, butane and optionally methane, and the alkane diluent concentration (or total alkane concentration) may be 10 mol% to 50 mol% based on the total moles of the oxygen-free, dry combined feed stream.In the above example, the concentration of ethane may be 0.1 mol% to 99.8 mol% based on the total moles of the alkane diluent, the concentration of propane may be 0.1 mol% to 99.8 mol% based on the total moles of the alkane diluent, the concentration of butane may be 0.1 mol% to 99.8 mol% based on the total moles of the alkane diluent, and the concentration of methane may be 0 mol% to 10 mol% based on the total moles of the alkane diluent.

[0057] The concentration of carbon dioxide in the combined feed stream 612 may be 0 mol% to 30 mol%, or 0 mol% to 25 mol%, or 5 mol% to 20 mol%, where the mol% is based on the total moles of the oxygen-free, dry combined feed stream.

[0058] The concentration of inert gas (e.g., nitrogen and / or argon) in the combined feed stream 612 can be 0 mol% to 20 mol%, or 1 mol% to 20 mol%, or 2 mol% to 15 mol%, where the mol% is based on the total moles of the oxygen-free, dry combined feed stream. Typically, the concentration of inert gas increases over time from the inert gas present in the stream supplied to the system.

[0059] The vinyl acetate reactor 616 may be a shell-and-tube reactor configured to absorb heat generated by the exothermic reaction via a heat exchange medium and control the temperature inside within a range of 100°C to 250°C, 110°C to 200°C, or 120°C to 180°C. The pressure inside the vinyl acetate reactor 616 may be maintained at 0.5 MPa to 2.5 MPa, or 0.5 MPa to 2 MPa.

[0060] Furthermore, the vinyl acetate reactor 616 may be a fixed-bed reactor or a fluidized-bed reactor, preferably a fixed-bed reactor containing a catalyst suitable for the acetoxylation of ethylene. Suitable acetoxylation catalysts for the production of vinyl acetate are described, for example, 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 incorporated herein by reference. Suitable acetoxylation catalysts may include palladium, gold, vanadium, and mixtures thereof. The following acetoxylation catalysts are particularly preferred: palladium acetate / potassium acetate / cadmium acetate and palladium acetate / barium acetlaurate / potassium acetate. Generally, the palladium content of the acetoxylation catalyst can be 0.5% to 5% by weight, or 0.5% to 3% by weight, or 0.6% to 2% by weight. If gold or one of its compounds is used, it is added in a proportion of 0.01% to 4% by weight, or 0.2% to 2% by weight, or 0.3% to 1.5% by weight. The acetoxylation catalyst also preferably contains a refractory support, preferably a metal oxide such as silica, silica-alumina, titania, or zirconia, more preferably silica.

[0061] The acetoxylation reaction in the vinyl acetate reactor 616 produces a crude vinyl acetate stream 618. Depending on the conversion and reaction conditions, the crude vinyl acetate stream 618 may contain 15% to 45% by weight of vinyl acetate, 20% to 70% by weight of acetic acid, 0.1% to 10% by weight of water, 10% to 80% by weight of ethylene, 1% to 40% by weight of carbon dioxide, 0.1% to 50% by weight of alkanes (e.g., methane, ethane, propane, butane, or mixtures thereof), and 0.1% to 15% by weight of oxygen. Optionally, the crude vinyl acetate stream 618 may also contain 0.01% to 10% by weight of ethyl acetate. The crude vinyl acetate stream 618 may also contain other compounds such as methyl acetate, acetaldehyde, acrolein, propane, and inert gases such as nitrogen or argon. Generally, these other compounds, with the exception of the inert gas, are present in very small amounts (e.g., less than 2% by weight).

[0062] The crude vinyl acetate stream 618 passes through the heat exchanger 620 to lower its temperature, and then proceeds to the separator 622 (e.g., a distillation column). Preferably, the 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 the separator 622. Preferably, condensation of liquefiable components does not occur, and the cooled crude vinyl acetate stream 618 is introduced into the separator 622 as a gas.

[0063] The energy for separating the components of the crude vinyl acetate flow 618 may be supplied by the reaction heat in reactor 616. In some embodiments, there may be an optional reboiler to increase the separation energy in separator 622.

[0064] The separator 622 separates the crude vinyl acetate stream 618 into at least two streams: an overhead stream 624 and a bottom stream 626. The overhead stream 624 may contain ethylene, carbon dioxide, water, alkanes (e.g., methane, ethane, propane, butane, or mixtures thereof), oxygen, and vinyl acetate. The bottom stream may contain vinyl acetate, acetic acid, water, and potentially ethylene, carbon dioxide, and alkanes.

[0065] The overhead flow 624 is transported to the scrubber 628 to remove vinyl acetate from the overhead flow 624. As a result, the scrubber 628 has a tail gas flow 630 and a bottom flow 632. Vinyl acetate scrubbing can be achieved by passing the overhead flow 624 through a mixture of water and acetic acid.

[0066] The tail gas stream 630 contains ethylene, carbon dioxide, alkanes, and oxygen. The tail gas stream 630 (also called the recirculation stream) is returned to the vaporizer 606 through the heat exchanger 620, where the crude vinyl acetate stream 618 heats the tail gas stream 630. Optionally, the tail gas stream 630 may be expanded or otherwise added by other streams, including other recirculation streams (not shown) in the process stream and feed stream. As shown, the alkane feed stream 634 from the hydrogenation reactor 670, the ethylene feed steam 636, the tail gas stream 640 from the natural gas enrichment process (not shown) (e.g., as described in Figures 3-5), and the methane feed stream 638 are combined with the tail gas stream 630 from the scrubber 628 (e.g., mixed or encompassed). Although the methane feed stream 638 is shown, the use of methane in the systems and methods described herein is optional. Furthermore, the methane feed stream 638 may more generally be the alkane feed stream, which contains one or more alkanes from the other feed sources mentioned above rather than from the hydrogenation reactor. The alkane feed stream may actually be multiple streams combined with the tail gas stream 630.

[0067] Furthermore, Figure 6 shows the use of both the alkane feed stream 634 from the hydrogenation reactor 670 and the tail gas stream 640 from the natural gas enrichment process. The methods and systems of this disclosure may include only one of the aforementioned, rather than both as shown in the figures.

[0068] Furthermore, Figure 6 shows the use of both the methane feed stream 638 and the tail gas stream 640 from the natural gas enrichment process. The methods and systems of this disclosure may include only one of the aforementioned, rather than both as shown in the illustration. Advantageously, the methane feed stream 638 may be completely replaced by the tail gas stream 640, which contains methane as described above, but also contains higher concentrations of C2+ alkanes. Moreover, the hydrogen and / or alkene breakthrough concerns relating to the hydrogenation process do not exist with the tail gas stream 640 from the natural gas enrichment process. Therefore, if a hydrogen and / or alkene breakthrough is observed, the tail gas stream 640 from the natural gas enrichment process can be a primary source and / or secondary source of alkane diluents.

[0069] For the hydrogenation process, the first alkene feed stream 636a (shown as an ethylene slip stream from the ethylene feed stream 636), the hydrogen feed stream 672, and the second alkene feed stream 674 are delivered to the hydrogenation reactor 670. As a slip stream for the ethylene feed stream 636, the first alkene feed stream 636a can be used in a maximum of 5 volume% of the ethylene feed stream 636, or 0.1 to 5 volume%, or 0.5 to 2 volume%, with the remainder directed to the tail gas stream 630 and combined with it.

[0070] The second alkene feed stream 674 may contain ethylene, propylene, butylene, or any mixture thereof.

[0071] Figure 6 shows the use of two sources (or feeds) of alkenes, but process 600 can be modified to use one or more sources of alkenes introduced into the hydrogenation reactor 670.

[0072] When two or more alkenes are used as reactants in the hydrogenation reactor 670, each alkene may be present in amounts of 1 mol% to 99 mol%, or 1 mol% to 50 mol%, 25 mol%, to 75 mol%, or 50 mol% to 99 mol%, based on the total moles of the alkenes. For example, when both ethylene and propylene are used as reactants in the hydrogenation reactor 670, ethylene and propylene may be present individually in amounts of 0.1 mol% to 99.9 mol%, or 1 mol% to 50 mol%, 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 butylene are all used as reactants in hydrogenation reactor 670, each alkene may be present individually in amounts of 0.1 mol% to 99.9 mol%, or 1 mol% to 50 mol%, 25 mol%, to 75 mol%, or 50 mol% to 99 mol%, based on the total moles of the alkenes. In yet another example, the alkene reactants in hydrogenation reactor 670 may contain 30 mol% to 99.9 mol% of ethylene, 0.1 mol% to 50 mol% of propylene, and optionally 0.1 mol% to 50 mol% of butylene, based on the total moles of the alkenes. In yet another example, the alkene reactants in hydrogenation reactor 670 may contain 90 mol% to 99.9 mol% of ethylene, 0.1 mol% to 10 mol% of propylene, and optionally 0.1 mol% to 5 mol% of butylene, based on the total moles of the alkenes. In another example, the alkene reaction product of hydrogenation reactor 670 may contain 0.1 mol% to 70 mol% ethylene, 30 mol% to 99.9 mol% propylene, and optionally 0.1 mol% to 50 mol% butylene, based on the total moles of alkenes.

[0073] Hydrogen may be present at any appropriate level, depending on the composition of the alkene used. As described above, hydrogen is present to accommodate 100 mol% of the conversion of all alkenes to alkanes, including any excess hydrogen present, especially when the alkene contains propylene and / or butylene. Furthermore, to mitigate the hydrogen breakthrough from hydrogenation reactor 670, particularly when ethylene is used, hydrogen may be present at lower concentrations to accommodate, for example, 99 mol%, or 98 mol%, or 95 mol%, or 90 mol% of the conversion of all alkenes to alkanes.

[0074] The molar ratio of hydrogen to total alkenes as reactants for 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.

[0075] The alkane feed stream 634 may contain 1 mol% or less, 0.5 mol% or less, or 0.1 mol% or less of hydrogen, or at least substantially free of hydrogen (e.g., 0 mol% to 0.01 mol%). Furthermore, the alkane feed stream 634 may contain 1 mol% or less, 0.5 mol% or less, or 0.1 mol% or less of unreacted alkenes, or at least substantially free of unreacted alkenes (e.g., 0 mol% to 0.01 mol%).

[0076] The hydrogenation reactor 670 can be operated in a temperature range of -50°C to 200°C, -10°C to 150°C, or 0°C to 100°C. The pressure in the vinyl acetate reactor 616 can be maintained at 0.5 MPa to 4 MPa, or 1 MPa to 3 MPa.

[0077] The hydrogenation reactor 670 may 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% to 5% by weight, or 0.5% to 3% by weight, or 0.6% to 2% by weight. If gold or one of its compounds is used, it is added in a proportion of 0.01% to 4% by weight, or 0.2% to 2% by weight, or 0.3% to 1.5% by weight. The hydrogenation catalyst also preferably contains a refractory support, preferably a metal oxide such as silica, silica-alumina, titania, or zirconia, more preferably silica.

[0078] Contaminants in the hydrogen feed, such as carbon monoxide, may reduce the activity of the hydrogenation catalyst. Therefore, the hydrogen feed stream 672 can be treated before introducing hydrogen into the hydrogenation reactor 670 to reduce the concentration of contaminants such as carbon monoxide in the hydrogen feed using a carbon monoxide scrubber or other suitable equipment. The hydrogen feed may contain carbon monoxide at concentrations 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 0 ppm to 500 ppm, or 0 ppm to 250 ppm, or 0 ppm to 200 ppm, or 0 ppm to 150 ppm, or 0 ppm to 100 ppm, or 0 ppm to 50 ppm, or 0 ppm to 25 ppm.

[0079] The first alkene feed stream 636a, the hydrogen feed stream 672, and the second alkene feed stream 674 are shown as being introduced into the hydrogenation reactor 670 separately, but any combination of the streams may be pre-mixed before being introduced into the hydrogenation reactor 670.

[0080] The product of the hydrogenation reaction is the alkane feed stream 634. Along the alkane feed stream 634, one or more analyzers 678 may be present to measure the concentration of hydrogen and / or alkenes in the alkane feed stream 634. As discussed herein, hydrogen may lower the flammability limit of the downstream vinyl acetate reactor 616, and unreacted propylene and / or butylene may produce undesirable byproducts. Methods described herein for reducing and / or reacting reactant breakthroughs are applicable to the vinyl acetate production process 600. Examples of reactant (e.g., hydrogen and / or alkene) breakthrough mitigation are discussed above.

[0081] In an example of a reaction for reactant breakthrough in the alkane feed stream 634 from the hydrogenation reactor 670, the vinyl acetate production process 600 may be operated so that the methane feed stream 638 (or, more generally, the alkane feed stream from a source other than the hydrogenation reactor 670) is used, optionally, with little or no additional alkanes added to the tail gas stream 630. Then, if the hydrogen breakthrough threshold concentration and / or alkene breakthrough threshold concentration are exceeded, the amount from the alkane feed stream 634 added to the tail gas stream 630 can be reduced or stopped, and the amount from the methane feed stream 638 added to the tail gas stream 630 can be increased to compensate for the reduction or stoppage of the flow from the alkane feed stream 634.

[0082] The alkane feed stream 634 from the hydrogenation reactor 670, the ethylene feed steam 636, and the methane feed stream 638 (or, more generally, the alkane feed stream from a source other than the hydrogenation reactor 670) are shown to be introduced separately into the tail gas stream 630, however, any combination of these streams may be pre-mixed before being introduced into the tail gas stream 630.

[0083] Furthermore, other processes (not shown) may be performed on the tail gas flow 630 between the scrubber 628 and the heat exchanger 620. For example, at least some of the carbon dioxide may be removed from the tail gas flow 630.

[0084] Referring again to separator 622, the bottom flow 626 from separator 622 and the bottom flow 632 from scrubber 628 can be combined and supplied to crude tank 642. Generally, the flow entering crude tank 642 is reduced to a pressure of 0.1 MPa to 0.15 MPa. When the incoming flow is reduced in pressure, ethylene, carbon dioxide, inert gas (e.g., nitrogen and / or argon), and acetic acid flash to produce a flash gas flow 644. The bottom of crude tank 642 mainly contains vinyl acetate, water, and acetic acid and some ethyl acetate by-products. The bottom is transported as a vinyl acetate flow 646, which is purified by various processes 648 to produce a purified vinyl acetate product flow 650. Examples of purification processes 648 include, but are not limited to, azeotropic distillation, water stripping, distillation, phase separation, and any combination thereof. Examples of different 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 Publication No. 2014 / 0066649.

[0085] Furthermore, the purification process 648 can generate additional flows that can be reused individually or in any combination in the vaporizer 606, tail gas flow 630, flash gas flow 644, and / or other flows within the process 600.

[0086] In some cases (not shown), a portion of the tail gas slip flow 630 may be combined with (for example, mixed with or encompassed with) the flash gas flow 644.

[0087] At least a portion of the carbon dioxide in the flash gas flow 644 (and possibly combined with a portion of the tail gas slip flow 630) may be removed before being recirculated to the vaporizer 606. As shown in the figure, the flash gas flow 644 first passes through the CO2 scrubber 652 and then through the CO2 absorber 656 to generate a CO2 depletion overhead flow 658. Between the CO2 scrubber 652 and the CO2 absorber 656, ethylene may be added to the flash gas flow 644 from the ethylene flow 654 (or as shown in its slip flow 662).

[0088] Next, the CO2-depleting overhead flow 658 can pass through the heat exchanger 660 and be supplied to the vaporizer 606. Furthermore, nitrogen and argon can be purged from the system using the flash gas flow 644 and / or the slip flow 662 from the CO2-depleting overhead flow 658. This slip flow 662 can be sent through the ethylene recovery process 664. The ethylene recovery process 660 generates an ethylene vent flow 666 and a recirculation flow 668.

[0089] Examples of ethylene recovery processes 664 may include, but are not limited to, scrubbing systems, membrane recovery processes, and any combination thereof.

[0090] The ethylene recovery process 664 can generate a vent flow 666 and an additional flow 668 for recirculating the recovered ethylene to other processes or to the vinyl acetate vaporizer 606.

[0091] Figure 6 illustrates a vinyl acetate manufacturing process 600 in general terms, but those skilled in the art will recognize how the teachings of this disclosure can be adapted to other vinyl acetate manufacturing processes that may differ from the illustrated process 600. Examples of different vinyl acetate manufacturing processes and systems are disclosed in U.S. Patent Nos. 6,410,817; 8,993,796; and 9,045,413, and U.S. Patent Application Publication No. 2014 / 0066649.

[0092] Unless otherwise specified, all numbers used in this disclosure and related claims to represent quantities of components, properties (e.g., molecular weight), reaction conditions, etc., should be understood in all cases to be modified by the term “approximately.” At the very least, the term “approximately” for each numerical parameter should be interpreted by applying ordinary rounding techniques in light of the number of significant figures reported, not as an attempt to limit the application of the doctrine of equivalents to the claims.

[0093] Concentration ranges listed or described as useful, appropriate, etc., are intended to be considered to describe all concentrations within the range, including the endpoint. For example, the range "1 to 10" or "of 1 to 10" should be read as indicating all possible numbers along the continuum between approximately 1 and approximately 10. Therefore, even if specific data points within the range are explicitly identified or only a few specific data points are referred to, the inventors should be considered to have specified all data points within the range, and should understand that the inventors recognize and understand that they have knowledge of the entire range and all points within the range.

[0094] The term "and / or" is used herein for brevity and refers to both the inclusive "and" case and the exclusive "or" case. For example, a mixture containing acetic acid and / or methyl acetate may contain acetic acid alone, methyl acetate alone, or both acetic acid and methyl acetate.

[0095] Enumerations following "one or more of ~" or "at least one of ~" use "and" to link the enumerations and are intended to be alternative or conjunctive, not disjunctive. For example, "at least one of A, B, and C" and "one or more of A, B, and C" are thought to disclose embodiments of A alone, B alone, C alone, a combination of A and B, a combination of A and C, a combination of B and C, and a combination of all three of A, B, and C, respectively.

[0096] Unless otherwise specified, room temperature is 25°C and atmospheric pressure is 101.325 kPa.

[0097] While compositions, systems, and methods are described herein in terms of "comprising" various components or processes, compositions, systems, and methods may also "consist essentially of" or "consist of" various components and processes.

[0098] Exemplary embodiments of the present invention are described herein. For clarity, not all features of actual embodiments are described herein. Naturally, in developing such actual embodiments, many embodiment-specific decisions will have to be made, which will differ from embodiment to embodiment, in order to achieve the developer's specific goals, such as complying with system-related and business-related constraints. Furthermore, although such development efforts may be complex and time-consuming, it will be understood that they are routine work for those skilled in the art who are interested in this disclosure.

[0099] Exemplary Embodiments Embodiment 1. A method for producing vinyl acetate, comprising: reacting one or more alkenes and 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 contains one or more alkanes from the hydrogenation reaction.

[0100] Embodiment 2. The method according to Embodiment 1, wherein the alkane diluent further comprises methane.

[0101] Embodiment 3. The method according to Embodiment 2, wherein methane is present in the alkane diluent at a concentration of 0.1 mol% to 5 mol% based on the total moles of the alkane diluent.

[0102] Embodiment 4. The method according to any one of Embodiments 1 to 3, wherein one or more alkenes include one or more of ethylene, propylene, and butylene.

[0103] Embodiment 5. The method according to Embodiment 4, wherein the alkane diluent comprises ethane, propane, and optionally methane, and at least a portion of the ethane and propane is from a hydrogenation reaction, the ethane is present in the alkane diluent at a concentration of 0.1 mol% to 99.9 mol% based on the total moles of the alkane diluent, the propane is present in the alkane diluent at a concentration of 0.1 mol% to 99.9 mol% based on the total moles of the alkane diluent, and the methane is present in the alkane diluent at a concentration of 0 mol% to 5 mol% based on the total moles of the alkane diluent.

[0104] Embodiment 6. The method according to Embodiment 4 or 5, wherein the alkane diluent comprises ethane, propane, and optionally methane, and at least a portion of the ethane and propane is from a hydrogenation reaction, the ethane is present in the alkane diluent at a concentration of 0.1 mol% to 50 mol% based on the total moles of the alkane diluent, the propane is present in the alkane diluent at a concentration of 50 mol% to 99.9 mol% based on the total moles of the alkane diluent, and the methane is present in the alkane diluent at a concentration of 0 mol% to 5 mol% based on the total moles of the alkane diluent.

[0105] Embodiment 7. The method according to any one of Embodiments 1 to 6, wherein the alkane diluent includes tail gas from a natural gas enrichment process.

[0106] Embodiment 8. The method according to any one of Embodiments 1 to 7, further comprising: carrying out a hydrogenation reaction in a hydrogenation reactor; introducing a hydrogen stream into the hydrogenation reactor; and treating the hydrogen stream before it is introduced into the hydrogenation reactor to reduce the concentration of carbon monoxide from the hydrogen stream.

[0107] Embodiment 9. The method according to any one of Embodiments 1 to 8, wherein the acetoxylation reaction generates a crude vinyl acetate stream, the crude vinyl acetate stream further containing unreacted ethylene, and 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 recirculating the ethylene recovery stream to the acetoxylation reaction.

[0108] Embodiment 10. The method according to any one of Embodiments 1 to 9, wherein the hydrogenation reaction produces a product stream containing one or more alkanes and optionally hydrogen, and the method comprises monitoring the hydrogen concentration in the product stream from the hydrogenation reactor, and if the hydrogen concentration in the product stream from the hydrogenation reactor exceeds 1 mol% based on the total number of moles present in the product stream, reducing the amount of one or more alkanes from the hydrogenation reaction in the alkane diluent and adding methane to the alkane diluent.

[0109] Embodiment 11. A method for producing vinyl acetate, comprising: reacting a feed stream containing acetic acid, ethylene, oxygen, and an alkane diluent in a vinyl acetate reactor to produce a crude vinyl acetate stream containing vinyl acetate, water, and an alkane diluent; cooling the crude vinyl acetate stream in a heat exchanger; and 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 contains ethylene and an alkane diluent, the flash gas stream contains ethylene, carbon dioxide, and an alkane diluent, and the vinyl acetate stream contains vinyl acetate. A method for producing vinyl acetate, comprising: separating; adding a second tail gas stream from a natural gas enrichment system to a first tail gas stream, wherein one or more alkanes become part of an alkane diluent; removing at least a portion of carbon dioxide from a flash gas stream to produce one or more recirculating streams containing ethylene and an alkane diluent; mixing vaporized acetic acid with the first tail gas stream and at least one of the one or more recirculating streams in a vaporizer to produce a vaporized stream; and adding oxygen to the vaporized stream to produce a feed stream.

[0110] Embodiment 12. A method for producing vinyl acetate, comprising: reacting a feed stream containing acetic acid, ethylene, oxygen, and an alkane diluent in a vinyl acetate reactor to produce a crude vinyl acetate stream containing vinyl acetate, water, and an 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 contains ethylene and an alkane diluent, the flash gas stream contains ethylene, carbon dioxide, and an alkane diluent, and the vinyl acetate stream contains vinyl acetate; reacting one or more alkenes and hydrogen via a hydrogenation reaction in a hydrogenation reactor in the presence of a hydrogenation catalyst to produce a product stream containing one or more alkanes and optionally hydrogen; and adding at least a portion of the product stream to the tail gas stream. A method for producing vinyl acetate, comprising: adding one or more alkanes so that they become part of an alkane diluent; monitoring the hydrogen concentration in the alkane feed stream, and if the hydrogen concentration exceeds 1 mol% based on the total number of moles present in the product stream, (a) reducing the amount of 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 make it part of an alkane diluent, or both; removing at least a portion of carbon dioxide from the flash gas stream to produce one or more recirculating streams containing ethylene and an alkane diluent; mixing vaporized acetic acid with at least one of the tail gas stream and one or more recirculating streams in a vaporizer to produce a vaporized stream; and adding oxygen to the vaporized stream to produce a feed stream.

[0111] Embodiment 13. The method according to Embodiment 12, wherein the tail gas flow is a first tail gas flow, and the method further comprises adding a second tail gas flow from a natural gas enrichment system to the first tail gas flow, wherein one or more alkanes are part of an alkane diluent.

[0112] Embodiment 14. The method according to any one of Embodiments 12 to 13, wherein the alkane diluent in the feed stream contains 0.1 mol% to 5 mol% methane based on the total moles of the alkane diluent.

[0113] Embodiment 15. The method according to any one of Embodiments 12 to 14, wherein the alkane diluent in the feed stream contains 0 mol% to 0.1 mol% methane based on the total moles of the alkane diluent.

[0114] Embodiment 16. The method according to any one of Embodiments 12 to 15, wherein one or more alkenes include one or more of ethylene, propylene, and butylene.

[0115] Embodiment 17. The method according to Embodiment 16, wherein the feedstream alkane diluent comprises ethane, propane, and optionally methane, and at least a portion of the ethane and propane is from a hydrogenation reaction, the ethane is present in the feedstream alkane diluent at a concentration of 0.1 mol% to 99.9 mol% based on the total moles of the alkane diluent, the propane is present in the feedstream alkane diluent at a concentration of 0.1 mol% to 99.9 mol% based on the total moles of the alkane diluent, and the methane is present in the feedstream alkane diluent at a concentration of 0 mol% to 5 mol% based on the total moles of the alkane diluent.

[0116] Embodiment 18. The method according to Embodiment 16 or 17, wherein the feedstream alkane diluent comprises ethane, propane, and optionally methane, and at least a portion of the ethane and propane is from a hydrogenation reaction, with ethane present in the feedstream alkane diluent at a concentration of 0.1 mol% to 50 mol% based on the total moles of the alkane diluent, propane present in the feedstream alkane diluent at a concentration of 50 mol% to 99.9 mol% based on the total moles of the alkane diluent, and methane present in the feedstream alkane diluent at a concentration of 0 mol% to 5 mol% based on the total moles of the alkane diluent.

[0117] Embodiment 19. A method for producing vinyl acetate, comprising: (i) producing one or more alkanes via a hydrogenation reaction and / or (ii) carrying out 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 carried out in the presence of an alkane diluent containing one or more alkanes from the hydrogenation reaction and / or (ii) tail gas.

[0118] Embodiment 20. The method according to Embodiment 19, wherein the alkane diluent comprises ethane, propane, and optionally methane, and at least a portion of the ethane and propane is from hydrogenation reactions and / or tail gases, the ethane is present in the alkane diluent at a concentration of 0.1 mol% to 99.9 mol% based on the total moles of the alkane diluent, the propane is present in the alkane diluent at a concentration of 0.1 mol% to 99.9 mol% based on the total moles of the alkane diluent, and the methane is present in the alkane diluent at a concentration of 0 mol% to 5 mol% based on the total moles of the alkane diluent.

[0119] The present invention will be better understood by considering the following non-limiting examples. [Examples]

[0120] Using the ACTISORB® O series hydrogenation catalyst available from Clariant, hydrogenation reactions were carried out in a laboratory-scale reactor at various temperatures ranging from below 0°C to approximately 80°C and at a pressure of approximately 2.8 MPa, with a supply of approximately 1 mol% H2-balanced C2H4. 100% hydrogen consumption was observed across the tested temperatures.

[0121] Using a hydrogenation catalyst from the ACTISORB® O series available from Clariant, a hydrogenation reaction was carried out in a pilot plant reactor at a temperature of approximately 250°C and a pressure of approximately 2.8 MPa, with a supply of C2H4 with an H2 balance of up to approximately 4 mol%. 100% hydrogen consumption was observed. The hydrogenation product was then used as at least part of an alkane diluent in a vinyl acetate production process, with a reaction feed containing up to approximately 10 mol% oxygen to a vinyl acetate reactor.

Claims

1. A method for producing vinyl acetate, The process involves reacting one or more alkenes with hydrogen in the presence of a hydrogenation catalyst via a hydrogenation reaction to produce one or more alkanes. The process involves reacting acetic acid, ethylene, and oxygen via an acetoxylation reaction in the presence of an acetoxylation catalyst and an alkane diluent to produce vinyl acetate and water, wherein the alkane diluent contains one or more alkanes from the hydrogenation reaction. A method for producing vinyl acetate, including [the specified component].

2. The method according to claim 1, wherein the alkane diluent further comprises methane.

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

4. The method according to claim 1, wherein the one or more alkenes comprises one or more of ethylene, propylene, and butylene.

5. The method according to claim 4, wherein the alkane diluent comprises ethane, propane, and optionally methane, and at least a portion of the ethane and propane is from the hydrogenation reaction, the ethane is present in the alkane diluent in an amount of 0.1 mol% to 99.9 mol% based on the total moles of the alkane diluent, the propane is present in the alkane diluent in an amount of 0.1 mol% to 99.9 mol% based on the total moles of the alkane diluent, and the methane is present in the alkane diluent in an amount of 0 mol% to 5 mol% based on the total moles of the alkane diluent.

6. The method according to claim 4, wherein the alkane diluent comprises ethane, propane, and optionally methane, and at least a portion of the ethane and propane is from the hydrogenation reaction, the ethane is present in the alkane diluent in an amount of 0.1 mol% to 50 mol% based on the total moles of the alkane diluent, the propane is present in the alkane diluent in an amount of 50 mol% to 99.9 mol% based on the total moles of the alkane diluent, and the methane is present in the alkane diluent in an amount of 0 mol% to 5 mol% based on the total moles of the alkane diluent.

7. The method according to claim 1, wherein the alkane diluent comprises tail gas from a natural gas enrichment process.

8. The hydrogenation reaction is carried out in a hydrogenation reactor, Introducing a hydrogen stream into the hydrogenation reactor, The hydrogen stream is treated before being introduced into the hydrogenation reactor to reduce the concentration of carbon monoxide from the hydrogen stream. The method according to claim 1, further comprising:

9. The acetoxylation reaction generates a crude vinyl acetate stream, and the crude vinyl acetate stream further contains unreacted ethylene, and the method is The crude vinyl acetate stream is treated to recover at least a portion of the unreacted ethylene and at least a portion of the alkane diluent in the ethylene recovery stream. The ethylene recovery stream is to be recycled to the acetoxylation reaction. The method according to claim 1, further comprising:

10. The hydrogenation reaction generates a product stream containing one or more alkanes and optionally hydrogen, and the method To monitor the hydrogen concentration in the product stream from the hydrogenation reaction, If the hydrogen concentration in the product stream from the hydrogenation reactor exceeds 1 mol% based on the total number of moles present in the product stream, the amount of one or more alkanes in the alkane diluent is reduced from the hydrogenation reaction, and methane is added to the alkane diluent. The method according to claim 1, further comprising:

11. A method for producing vinyl acetate, A feed stream containing acetic acid, ethylene, oxygen, and an alkane diluent is reacted in a vinyl acetate reactor to produce a crude vinyl acetate stream containing vinyl acetate, water, and the alkane diluent. Cooling the crude vinyl acetate flow in the heat exchanger, The crude vinyl acetate stream is separated into a first tail gas stream, a flash gas stream, and a vinyl acetate stream, wherein the first tail gas stream contains ethylene and the alkane diluent, the flash gas stream contains ethylene, carbon dioxide, and the alkane diluent, and the vinyl acetate stream contains 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; To remove at least a portion of the carbon dioxide from the flash gas flow to generate one or more recirculated flows containing ethylene and the alkane diluent, The vaporized acetic acid is mixed with the first tail gas flow and at least one of the one or more recirculation flows in the vaporizer to generate a vaporized flow. To generate the supply flow by adding oxygen to the vaporization flow. A method for producing vinyl acetate, including [the specified component].

12. A method for producing vinyl acetate, A feed stream containing acetic acid, ethylene, oxygen, and an alkane diluent is reacted in a vinyl acetate reactor to produce a crude vinyl acetate stream containing vinyl acetate, water, and the alkane diluent. Cooling the crude vinyl acetate flow in the heat exchanger, The separation of the crude vinyl acetate stream into a tail gas stream, a flash gas stream, and a vinyl acetate stream, wherein the tail gas stream contains ethylene and the alkane diluent, the flash gas stream contains ethylene, carbon dioxide and the alkane diluent, and the vinyl acetate stream contains vinyl acetate. In a hydrogenation reactor, in the presence of a hydrogenation catalyst, one or more alkenes and hydrogen are reacted via a hydrogenation reaction to produce a product stream containing one or more alkanes and, optionally, hydrogen. Adding at least a portion of the product stream to the tail gas stream, wherein one or more alkanes become part of the alkane diluent; Monitoring the hydrogen concentration in the product stream, wherein if the hydrogen concentration exceeds 1 mol% based on the total number of moles present in the product stream, (a) reducing the amount of the product stream from the hydrogenation reactor added to the tail gas stream, and (b) Adding the methane supply stream to the tail gas stream to make it part of the alkane diluent, To perform one or both of the following, To remove at least a portion of the carbon dioxide from the flash gas flow to generate one or more recirculated flows containing ethylene and the alkane diluent, The vaporized acetic acid is mixed with at least one of the tail gas flow and one or more recirculation flows in the vaporizer to generate a vaporized flow. To generate the supply flow by adding oxygen to the vaporization flow. A method for producing vinyl acetate, including [the specified component].

13. The tail gas flow is a first tail gas flow, and the method is 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; The method according to claim 12, further comprising:

14. The method according to claim 12, wherein the alkane diluent in the supply stream contains 0.1 mol% to 5 mol% methane based on the total moles of the alkane diluent.

15. The method according to claim 12, wherein the alkane diluent in the supply stream contains 0 mol% to 0.1 mol% of methane based on the total moles of the alkane diluent.

16. The method according to claim 12, wherein the one or more alkenes comprises one or more of ethylene, propylene, and butylene.

17. The method according to claim 16, wherein the alkane diluent in the feed stream comprises ethane, propane, and optionally methane, and at least a portion of the ethane and propane is from the hydrogenation reaction, the ethane is present in the alkane diluent in the feed stream in an amount of 0.1 mol% to 99.9 mol% based on the total moles of the alkane diluent, the propane is present in the alkane diluent in the feed stream in an amount of 0.1 mol% to 99.9 mol% based on the total moles of the alkane diluent, and the methane is present in the alkane diluent in the feed stream in an amount of 0 mol% to 5 mol% based on the total moles of the alkane diluent.

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

19. A method for producing vinyl acetate, (i) producing one or more alkanes via a hydrogenation reaction, and / or (ii) carrying out a natural gas enrichment process to produce enriched natural gas and tail gas, (i) producing vinyl acetate via the acetoxylation reaction of acetic acid, ethylene, and oxygen, carried out in the presence of one or more alkanes from the hydrogenation reaction and / or (ii) an alkane diluent containing the tail gas. A method for producing vinyl acetate, including [the specified component].

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

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