阅读说明：本技术 甲烷氧化偶联 (Oxidative coupling of methane ) 是由 G·米基迪斯 M·桑·罗曼·马西亚 于 2018-05-15 设计创作，主要内容包括：本发明涉及一种甲烷氧化偶联(OCM)的方法,包含以下步骤：(a)在反应器中使氧气和甲烷与OCM催化剂接触,从而生成包含乙烯、乙烷、甲烷、二氧化碳和水的反应器流出物；(b)冷却步骤(a)中获得的反应器流出物的至少一部分,以获得包含水的液体流和包含乙烯、乙烷、甲烷和二氧化碳的气体流；(c)从步骤(b)中获得的包含乙烯、乙烷、甲烷和二氧化碳的气体流的至少一部分中去除二氧化碳,从而生成包含乙烯、乙烷和甲烷的气体流；(d)从步骤(c)中获得的包含乙烯、乙烷和甲烷的气体流的至少一部分回收包含甲烷的流、包含乙烷的流和包含乙烯的流；(e)将步骤(d)中获得的包含甲烷的流的至少一部分再循环至步骤(a)；(f)通过使乙烷经历氧化脱氢(ODH)条件,将步骤(d)中获得的包含乙烷的流中的乙烷转化为乙烯。(The invention relates to a method for Oxidative Coupling of Methane (OCM), comprising the following steps: (a) contacting oxygen and methane with an OCM catalyst in a reactor, thereby producing a reactor effluent comprising ethylene, ethane, methane, carbon dioxide, and water; (b) cooling at least a portion of the reactor effluent obtained in step (a) to obtain a liquid stream comprising water and a gas stream comprising ethylene, ethane, methane and carbon dioxide; (c) removing carbon dioxide from at least a portion of the gas stream comprising ethylene, ethane, methane and carbon dioxide obtained in step (b), thereby producing a gas stream comprising ethylene, ethane and methane; (d) recovering a stream comprising methane, a stream comprising ethane and a stream comprising ethylene from at least a portion of the gas stream comprising ethylene, ethane and methane obtained in step (c); (e) recycling at least a portion of the methane comprising stream obtained in step (d) to step (a); (f) converting ethane in the ethane-comprising stream obtained in step (d) to ethylene by subjecting the ethane to Oxidative Dehydrogenation (ODH) conditions.)

1. A method of Oxidative Coupling of Methane (OCM) comprising the steps of:

(a) contacting oxygen and methane with an OCM catalyst in a reactor to produce a reactor effluent comprising ethylene, ethane, methane, carbon dioxide, and water;

(b) cooling at least a portion of the reactor effluent obtained in step (a) to obtain a liquid stream comprising water and a gas stream comprising ethylene, ethane, methane and carbon dioxide;

(c) removing carbon dioxide from at least a portion of the gas stream comprising ethylene, ethane, methane and carbon dioxide obtained in step (b), thereby producing a gas stream comprising ethylene, ethane and methane;

(d) recovering from at least a portion of the gas stream comprising ethylene, ethane and methane obtained in step (c) a stream comprising methane, a stream comprising ethane and a stream comprising ethylene;

(e) recycling at least a portion of the methane comprising stream obtained in step (d) to step (a);

(f) converting ethane in the ethane-comprising stream obtained in step (d) to ethylene by subjecting ethane to Oxidative Dehydrogenation (ODH) conditions.

2. The process of claim 1, wherein step (f) comprises contacting oxygen and ethane in the ethane-comprising stream obtained in step (d) with an ODH catalyst in a reactor, thereby producing a reactor effluent comprising ethylene, ethane, carbon dioxide and water, and the process further comprises the steps of:

(g) cooling at least a portion of the reactor effluent obtained in step (f) to obtain a liquid stream comprising water and a gas stream comprising ethylene, ethane and carbon dioxide.

3. The process according to claim 2, wherein at least part of the gas stream comprising ethylene, ethane and carbon dioxide obtained in step (g) is fed to step (c).

4. The method of claim 2, further comprising the steps of:

(h) removing carbon dioxide from at least a portion of the gas stream comprising ethylene, ethane and carbon dioxide obtained in step (g), thereby producing a gas stream comprising ethylene and ethane.

5. The process according to claim 4, wherein at least part of the gas stream comprising ethylene and ethane obtained in step (h) is fed to step (d).

6. The process according to claim 4, wherein step (d) comprises separating at least part of the gas stream comprising ethylene, ethane and methane obtained in step (c) into a stream comprising methane and a stream comprising ethylene and ethane and further separating the stream comprising ethylene and ethane into a stream comprising ethylene and a stream comprising ethane and wherein at least part of the gas stream comprising ethylene and ethane obtained in step (h) is fed to the sub-step of step (d), wherein the separated stream comprising ethylene and ethane is further separated into a stream comprising ethylene and a stream comprising ethane.

7. The process according to claim 4, wherein in a drying step between steps (c) and (d) water is removed from the gas stream comprising ethylene, ethane and methane additionally comprising water obtained in step (c) thereby generating a gas stream comprising ethylene, ethane and methane, and wherein at least a portion of the gas stream comprising ethylene and ethane additionally comprising water obtained in step (h) is fed to the drying step.

8. Process according to claim 4, wherein step (d) comprises separating at least part of the gas stream comprising ethylene, ethane and methane obtained in step (c) into a stream comprising methane and a stream comprising ethylene and ethane, and further separating the stream comprising ethylene and ethane into a stream comprising ethylene and a stream comprising ethane, wherein in a drying step after step (h) water is removed from the gas stream comprising ethylene and ethane additionally comprising water obtained in step (h), thereby generating a gas stream comprising ethylene and ethane, and wherein at least a portion of said gas stream comprising ethylene and ethane obtained in said drying step is fed to said sub-step of step (d), wherein the separated stream comprising ethylene and ethane is further separated into a stream comprising ethylene and a stream comprising ethane.

9. The process of claim 1, wherein step (f) comprises contacting oxygen and ethane in the ethane-comprising stream obtained in step (d) with an ODH catalyst in a reactor, thereby generating a reactor effluent comprising ethylene, ethane, carbon dioxide and water, and wherein at least a portion of the reactor effluent comprising ethylene, ethane, carbon dioxide and water obtained in step (f) is fed to step (b).

Technical Field

The invention relates to a method for Oxidative Coupling of Methane (OCM).

Background

Methane is a valuable resource not only for use as a fuel, but also for the synthesis of compounds such as higher hydrocarbons.

Methane can be converted to other compounds by indirect conversion, wherein methane is converted to synthesis gas (hydrogen and carbon monoxide) and the reaction of the synthesis gas is then carried out during the fischer-tropsch process. However, such indirect conversions are very expensive and consume a large amount of energy.

Accordingly, it would be desirable in the industry to be able to convert methane directly to other compounds without the need for the formation of intermediates such as syngas. For this reason, the research of Oxidative Coupling of Methane (OCM) method has been receiving more and more attention in recent years.

Oxidative coupling of methane converts methane to saturated and unsaturated non-aromatic hydrocarbons having 2 or more carbon atoms, including ethylene. In this process, a gas stream comprising methane is contacted with an OCM catalyst and an oxidant (e.g., oxygen). In such processes, oxygen is adsorbed on the surface of the catalyst. The methane molecule is then converted to a methyl group. Two methyl groups are first coupled into one ethane molecule, which is then dehydrogenated to ethylene via an ethyl intermediate.

Generally, the conversion achievable in OCM processes is relatively low. In addition, at higher conversions, selectivity decreases, so it is generally desirable to maintain lower conversions. As a result, a significant amount of unconverted methane leaves the OCM reactor. The proportion of unconverted methane in the OCM product gas stream may be as high as 60 to 80 mole percent, based on the total molar amount of the gas stream. Typically, the OCM reactor effluent comprises ethylene, ethane, methane, carbon dioxide and water. Unconverted methane must be recovered from such effluents and subsequently recycled to the OCM process.

Known methods of separating the gas stream leaving the OCM process are as follows. Acid gases (mainly carbon dioxide CO)₂) The removal is divided into two stages, the first stage being a water amine absorption system using, for example, Monoethanolamine (MEA), and the second stage being the final carbon dioxide CO removal by washing with aqueous sodium hydroxide NaOH₂Trace. Will not contain carbon dioxide CO₂Is dried in a desiccant bed and then treated in a similar separation unit as used in conventional ethylene plants. The separation sequence comprises a front-end demethanizer, deethanizer, C2 splitter, depropanizer, C3 splitter, and debutanizer. Methane can be separated off by cryogenic distillation in a so-called "demethanizer". Processes using cryogenic distillation after the OCM process are disclosed, for example, in patents US5113032 and US 5025108.

As mentioned above, the gas stream produced by the OCM process comprises ethylene, ethane and (unconverted) methane. In the case where ethylene is the target product, it may be desirable to recycle ethane to the OCM step in addition to recycling the unconverted methane to the step in which OCM is achieved, in order to maximize the production of ethylene, since ethane is an intermediate in the production of ethylene via OCM. Disadvantageously, however, after recycle to the OCM step in which the OCM catalyst is used, the ethane tends to burn to carbon dioxide rather than dehydrogenate to ethylene.

It is therefore an object of the present invention to provide an improved process for the oxidative coupling of methane, wherein the production of ethylene can be maximized, that is to say wherein an increase in the selectivity and/or yield of ethylene can be achieved, and which does not have the above-mentioned and below-mentioned disadvantages. Another object is to reduce the energy required for such processes, wherein the production of ethylene can be maximized.

Disclosure of Invention

Surprisingly, the above object is achieved by the OCM process of the present invention.

The invention relates to a method for Oxidative Coupling of Methane (OCM), comprising the following steps:

(a) contacting oxygen and methane with an OCM catalyst in a reactor to produce a reactor effluent comprising ethylene, ethane, methane, carbon dioxide, and water;

(b) cooling at least a portion of the reactor effluent obtained in step (a) to obtain a liquid stream comprising water and a gas stream comprising ethylene, ethane, methane and carbon dioxide;

(c) removing carbon dioxide from at least a portion of the gas stream comprising ethylene, ethane, methane and carbon dioxide obtained in step (b), thereby producing a gas stream comprising ethylene, ethane and methane;

(d) recovering from at least a portion of the gas stream comprising ethylene, ethane and methane obtained in step (c) a stream comprising methane, a stream comprising ethane and a stream comprising ethylene;

(e) recycling at least a portion of the stream comprising methane obtained in step (d) to step (a);

(f) converting ethane in the stream comprising ethane obtained in step (d) to ethylene by subjecting the ethane to Oxidative Dehydrogenation (ODH) conditions.

Drawings

Fig. 1 depicts an embodiment of the invention wherein the effluent from the water condensation unit of an Oxidative Dehydrogenation (ODH) configuration, comprising unconverted ethane and ethylene, is fed to an Oxidative Coupling (OCM) configuration.

Fig. 2 depicts an embodiment of the invention wherein the effluent from the carbon dioxide removal unit of the ODH configuration, comprising unconverted ethane and ethylene, is fed to the OCM configuration.

Fig. 3 depicts an embodiment of the invention wherein the effluent from the drying unit of the ODH configuration, comprising unconverted ethane and ethylene, is fed to the OCM configuration.

Detailed Description

In the process of the present invention, as described above, it has been shown that the total amount of ethylene produced from methane in an Oxidative Coupling of Methane (OCM) process can be maximized by subjecting the ethane in the ethane-containing recovery stream to Oxidative Dehydrogenation (ODH) conditions in step (f) of the process to convert the ethane to ethylene. The combination of said ODH step (f) with step (e) of the process of the invention, wherein unconverted methane is recycled to OCM step (a), enables to maximize the production of ethylene. In such integrated processes comprising an OCM step as the main ethylene production step and an ODH step as an additional ethylene production step, the overall ethylene selectivity and/or yield can advantageously be increased.

Furthermore, converting ethane to ethylene in such an additional ODH step, rather than recycling the ethane to the OCM step where an OCM catalyst is used, can prevent ethane from being burned in the OCM step. As noted above, ethane tends to be burned to carbon dioxide rather than dehydrogenated to ethylene after recycle to the OCM step. Such combustion of recycled ethane in an OCM step using an OCM catalyst occurs more readily than combustion of ethane in an ODH step using an ODH catalyst. This therefore also advantageously contributes to the potential of maximizing the production of ethylene in the present integrated process.

Furthermore, as an alternative to converting ethane to ethylene in the ODH step (f) of the present integrated process, ethane may be converted to ethylene by other means not involving ODH or OCM. For example, ethylene can be produced from ethane by steam cracking (pyrolysis) of an ethane stream under the influence of heat in an oxygen-deficient atmosphere into a product stream comprising ethylene and hydrogen. However, such alternative ethane cracking step has the disadvantages of low ethylene selectivity, high energy consumption, carbon dioxide (CO) for ethane cracking compared to the ODH step (f) of the present integrated process₂) Large footprint, high capital intensity, etc. Thus, in the present process, low CO with high ethylene selectivity and low energy consumption is advantageously used₂Footprint and low capital intensity ethane ODH.

Both OCM and ethane ODH are exothermic chemical processes, while ethane cracking is an endothermic process. This means that the overall energy consumption for producing ethylene and processing the product stream in the present integrated process is relatively low. In fact, in the present integrationThe heat released in the OCM and ODH steps of the process may be advantageously used elsewhere in the process, for example in the processing section. This therefore advantageously improves the energy efficiency of the integrated process. Also, the CO of the integrated process of the invention₂The footprint may be kept relatively small.

In addition, oxygen (O) is required for both OCM step (a) and ODH step (f)₂) And (4) supplying. Thus, advantageously, it is possible to share a common O for the ethylene production steps (a) and (f)₂The source to achieve further synergy.

Furthermore, the product compositions of the OCM and ODH effluents are very similar, both comprising ethylene, ethane, carbon dioxide and water, except for the higher methane content of the OCM effluent. In contrast, ethane cracker effluent comprises ethylene, unconverted ethane, hydrogen and typically a relatively large amount of hydrocarbons having 3 or more carbon atoms. Thus, as described further below, in the present process, the OCM processing portion may also be advantageously used to separate components from the ODH effluent produced by ODH step (f). In addition, the following further integration options may be advantageously implemented in the present integration method, including shared facilities, for example: 1) generating steam from the exotherm generated in the OCM and ODH reactions using the same steam system facilities; 2) similar streams generated in the OCM and ODH configurations are pressurized using the same compressor; 3) the same quencher was used to remove water produced in the OCM and ODH reactions; and 4) use of a common O as described above₂The source is the same oxygen generating unit.

These and other features and synergies of the present integrated process result in that the production of ethylene can be maximized and further that the energy required for such process can be relatively low.

The method of the present invention comprises several steps as further described below. The method may comprise one or more intermediate steps between the above steps. Furthermore, the method may comprise one or more additional steps before the first step and/or after the last step.

Although the methods of the present invention and the one or more streams used in the methods are described in terms of "comprising," "containing," or "including" one or more of the various stated steps or components, they may also "consist essentially of" or "consist of" the one or more of the various stated steps or components.

In the context of the present invention, in case the stream comprises two or more components, the selected total amount of these components does not exceed 100 vol.% or 100 wt.%.

Step (a)

In step (a) of the integrated process, oxygen and methane are contacted with the OCM catalyst in a reactor to produce a reactor effluent comprising ethylene, ethane, methane, carbon dioxide, and water.

In step (a), the reactor may be any reactor suitable for oxidative coupling of methane, for example a fixed bed reactor with axial or radial flow and with interstage cooling or a fluidized bed reactor equipped with internal and external heat exchangers.

In one embodiment of the invention, a catalyst composition comprising an Oxidative Coupling of Methane (OCM) catalyst can be packed in a fixed bed reactor of suitable internal diameter and length along with an inert packing material such as quartz.

Optionally, such catalyst compositions may be pretreated at elevated temperatures to remove moisture and impurities therefrom. The pretreatment may be carried out, for example, in the presence of an inert gas such as helium at a temperature in the range of 100-300 c for about one hour.

Various processes and reactor arrangements are described in the field of OCM, and the process of the present invention is not limited in this respect. Any such method may be conveniently used by those skilled in the art in the reaction step of the method of the present invention.

Suitable methods include those described in EP0206042a1, US4443649, CA2016675, US6596912, US20130023709, WO2008134484 and WO 2013106771.

As used herein, the term "reactor feed" is understood to refer to the total amount of gas flow at the reactor inlet. Thus, as will be understood by those skilled in the art, the reactor feed typically comprises a combination of one or more gas streams, such as a methane stream, an oxygen stream, an air stream, a recycle gas stream, and the like. For example, in one embodiment, a gas stream comprising methane and another gas stream comprising oxygen are fed into the reactor. In another embodiment, a gas stream comprising methane and oxygen is fed to the reactor.

The gas stream or streams that may be fed to the OCM reactor may also contain inert gases. Inert gas refers to a gas that does not participate in the oxidative coupling of methane. The inert gas can be selected from the group consisting of noble gases and nitrogen (N)₂). Preferably, the inert gas is nitrogen or argon, more preferably nitrogen. In case air is fed to the reactor, the one or more gas streams comprise oxygen as well as nitrogen.

In the oxidative coupling of methane of step (a), a reactor feed comprising methane and oxygen may be introduced into the reactor such that the methane and oxygen contact the methane oxidative coupling catalyst within the reactor.

The oxygen-containing gas stream (combined with methane in step (a)) may be a high purity oxygen stream. Such high purity oxygen may have a purity of greater than 90%, preferably greater than 95%, more preferably greater than 99%, and most preferably greater than 99.4%.

In step (a) of the process of the present invention, methane and oxygen may be added to the reactor as a mixed feed at the same reactor inlet, optionally containing additional components therein. Alternatively, methane and oxygen may be fed separately, optionally with additional components included therein, to the reactor at the same reactor inlet or at separate reactor inlets. In another alternative, the oxygen may be provided by a metal oxide (preferably, mixed metal oxide) catalyst which is both a source of oxygen and a catalyst for the oxidative coupling of methane. Introduction of metal oxide catalysts into an OCM reactor with methane under conditions that allow easy migration of oxygen atoms to the catalyst surface and activation of methane while limiting the availability of fuel for the desired products to CO and CO₂Amount of free oxygen (c). Metal oxide catalyst in situOne or more oxygen atoms may be released prior to harvest and regenerated with air in a separate reactor vessel prior to reintroduction into the OCM reactor. The above-described process of providing oxygen for the oxidative coupling of methane, also referred to as chemical looping, can improve the production and selectivity of C2+ hydrocarbons.

In step (a) of the process of the present invention, the methane in the reactor feed: the oxygen molar ratio can be between 2: 1 to 10: 1, more preferably 3: 1 to 6: 1. In the present invention, in the case where air is used as the oxidant in step (a), such methane: the molar ratio of oxygen corresponds to methane: the air molar ratio is 2: 4.8 to 10: 4.8 and 3: 4.8 to 6: 4.8.

methane may be present in the reactor feed in a concentration of at least 35 mole%, more preferably at least 40 mole%, relative to the reactor feed. Furthermore, methane may be present in the reactor feed in a concentration of at most 90 mol%, more preferably at most 85 mol%, most preferably at most 80 mol% relative to the reactor feed. Thus, in the present invention, methane may be present in the reactor feed, for example, in a concentration of 35-90 mole-%, more preferably 40-85 mole-%, and most preferably 40-80 mole-%, relative to the reactor feed. In the context of the present invention, the selected total amount of components of the reactor feed does not exceed 100 vol.%.

Generally, the oxygen concentration in the reactor feed should be less than the oxygen concentration at the reactor inlet or reactor outlet at the current operating conditions to form a combustible mixture.

The ratio of methane to oxygen in the reactor feed and the volume percentages of the various components are the ratio and volume percentage at the inlet of the catalyst bed, respectively. Obviously, at least a portion of the oxygen and methane from the gas stream is consumed after entering the catalyst bed.

In step (a), a reactor feed comprising methane and oxygen may be contacted with an Oxidative Coupling of Methane (OCM) catalyst such that the methane is converted to one or more C2+ hydrocarbons, including ethylene. Suitably, the reactor temperature in the reaction step is in the range of 500-. Preferably, the conversion is carried out at a reactor temperature in the range of 700-1100 deg.C, more preferably 700-1000 deg.C, even more preferably 750-950 deg.C.

In a preferred embodiment, the conversion of methane to one or more C2+ hydrocarbons is carried out at a reactor pressure in the range of from 0.1 to 20bar, more preferably from 0.5 to 20bar, more preferably from 1 to 15bar, more preferably from 2 to 10 bar.

According to the present invention, the above-mentioned methane oxidative coupling catalyst may be any methane oxidative coupling catalyst. Typically, the catalyst may contain one or more of manganese, one or more alkali metals (e.g. sodium) and tungsten. Preferably, the catalyst contains manganese, one or more alkali metals (e.g., sodium) and tungsten. The carrier may be unsupported or supported. In particular, the catalyst may be a mixed metal oxide catalyst containing manganese, one or more alkali metals (e.g., sodium) and tungsten. Further, the catalyst may be a supported catalyst, such as a catalyst comprising manganese, one or more alkali metals (e.g., sodium), and tungsten on a support. The support may be any support, such as silica or a metal-containing support. Particularly suitable catalysts comprise manganese, tungsten and sodium (Mn-Na) on a silica support₂WO₄/SiO₂)。

Suitable methane oxidative coupling catalysts are described in the following publications.

Chua et al, in applied catalysis A: general A343 (2008)142-₂) The oxidative coupling of methyl to ethylene was studied.

Arndt et al in applied catalysis a: general A425-426 (2012)53-61 and Lee et al in Fuel (Fuel) 106(2013)851-857 for Mn-Na₂WO₄/SiO₂The performance of the catalysts was further reviewed.

US20130023709 describes high throughput screening of catalyst libraries for oxidative coupling of methane and tests various catalysts, including catalysts comprising sodium, manganese and tungsten on silica and zirconia supports.

US20140080699 describes the preparation of a catalyst such as Mn-Na₂WO₄/SiO₂A specific method of catalyst is said to provide an improved catalyst material.

Various catalysts comprising manganese and titanium for oxidative coupling of methane have been studied in the literature and disclosed in various patent publications, including Gong et al, Catalysis Today 24(1995),259-261, Gong et al, Catalysis Today 24(1995),263-264, Jeon et al, applied Catalysis A: general A: General 464-465(2013)68-77, US4769508 and US 20130178680.

The amount of catalyst in the process is not essential. Preferably, a catalytically effective amount of catalyst is used, i.e. an amount sufficient to promote the oxidative coupling of methane reaction in step (a).

In step (a) of the process of the invention, the gas hourly space velocity (GHSV; in m)³Gas/m³Catalyst/hr) generally in the range of from 100 to 50,000hr^-1In the meantime. The GHSV was measured at standard temperature and pressure, i.e., 32 ℃ F. (0 ℃) and 1bara (100 kPa). In a preferred embodiment of the invention, the GHSV is 2,500 to 25,000hr^-1More preferably 5,000 to 20,000hr^-1And most preferably 7,500 to 15,000hr^-1In the meantime.

The catalyst used in step (a) may be a particulate catalyst, preferably a heterogeneous catalyst in particulate form. The particles may be of any size suitable for use in a reactor. The particles may be small enough to be used in a fluidized bed reactor. Alternatively, the particles may be arranged in a catalyst bed in the reactor. In this case, the reactor may be a (multi) tubular fixed bed reactor. Such catalyst beds may comprise pellets, extrudates or catalyst on a metal support such as a metal wire or foil. In addition to the catalyst particles, the catalyst bed may also contain inert particles, i.e. particles which are catalytically inactive.

In step (a), ethane, ethylene and water are formed by oxidative coupling of methane. Furthermore, carbon dioxide is formed as a by-product. In step (a), gas is fed into the reactor and effluent is withdrawn from the reactor. The reactor effluent comprises ethylene, ethane, methane, carbon dioxide and water. The methane comprises unconverted methane.

Step (b)

In step (b) of the present integrated process, at least a portion of the reactor effluent obtained in step (a) is cooled to obtain a liquid stream comprising water and a gas stream comprising ethylene, ethane, methane and carbon dioxide. This may also be referred to as quenching, which may be performed in a quencher.

In step (b), the reactor effluent may be cooled from the reaction temperature to a lower temperature, for example room temperature, such that water condenses, and then water may be removed from the gas stream (reactor effluent).

In step (b), a liquid stream comprising water and a gas stream comprising ethylene, ethane, methane and carbon dioxide are obtained by cooling the reactor effluent.

Step (c)

In step (c) of the integrated process, carbon dioxide is removed from at least a portion of the gas stream comprising ethylene, ethane, methane and carbon dioxide obtained in step (b), thereby generating a gas stream comprising ethylene, ethane and methane.

Step (c) is preferably carried out using one or more amines and/or by caustic treatment. The caustic treatment may be performed, for example, using a sodium hydroxide solution. Suitable carbon dioxide scavengers may be aqueous solutions of bases such as sodium hydroxide or amines.

Step (d)

In step (d) of the integrated process a stream comprising methane, a stream comprising ethane and a stream comprising ethylene are recovered from at least a portion of the gas stream comprising ethylene, ethane and methane obtained in step (c).

These 3 streams may be recovered in step (d) by any separation method known to the skilled person, for example by distillation, absorption or adsorption or any combination thereof.

In one embodiment of step (d) (hereinafter referred to as "first embodiment"), at least part of the gas stream comprising ethylene, ethane and methane obtained in step (c) is separated into a stream comprising methane and a stream comprising ethylene and ethane. The stream comprising ethylene and ethane is then further separated into a stream comprising ethylene and a stream comprising ethane. This embodiment of step (e) is shown in fig. 1-3, as will be discussed further below.

In another embodiment of step (d) (hereinafter referred to as "second embodiment"), at least a portion of the gas stream comprising ethylene, ethane and methane obtained in step (c) is separated into a stream comprising methane and ethylene and a stream comprising ethane. The stream comprising methane and ethylene is then further separated into a stream comprising methane and a stream comprising ethylene.

Generally, the first embodiment described above is preferred. However, the second embodiment described above may be applicable where the amount of methane and/or the amount of ethane is relatively low and/or high in the stream or combination of streams fed to step (d). In case the conversion of methane in step (a) is relatively high, the amount of methane in the stream may be relatively low. In the case where fresh ethane is fed to step (f) in addition to the ethane of the ethane-comprising stream obtained in step (d), and at least a portion of the stream resulting from step (f) is treated in one of the steps of treating the reactor effluent produced in step (a), for example in step (b), (c) or (d), the amount of ethane in said stream may be relatively high.

Step (e)

In step (e) of the present integrated process, at least a portion of the methane comprising stream obtained in step (d) is recycled to step (a). As noted above, such recycle helps to maximize ethylene production in the present integrated process.

Step (f)

In step (f) of the integrated process, ethane in the ethane-comprising stream obtained in step (d) is converted to ethylene by subjecting the ethane to Oxidative Dehydrogenation (ODH) conditions. As noted above, such conversion also helps to maximize ethylene production in the present integrated process.

The product of ODH step (f) comprises the dehydrogenated equivalent of ethane, i.e. ethylene. Such dehydrogenation equivalents were originally formed in the ethane ODH process. However, in the same process, the dehydrogenation equivalent can be further oxidized to the corresponding carboxylic acid under the same conditions. In the case of ethane, the product of the ODH process comprises ethylene and optionally acetic acid.

In the ethane ODH step (f), oxygen and ethane may be contacted with the ODH catalyst to produce a reactor effluent comprising ethylene, ethane, carbon dioxide and water, the ethane being from the stream comprising ethane obtained in step (d). Methane and oxygen (O)₂) May be fed to the reactor together or separately. That is, one or more feed streams (suitably gas streams) comprising one or more of the two components may be fed to the reactor. For example, one feed stream comprising oxygen and ethane may be fed to the reactor. Alternatively, two or more feed streams (suitably gas streams) may be fed into the reactor, which feed streams may form a combined stream within the reactor. For example, one feed stream comprising oxygen and another feed stream comprising ethane may be fed to the reactor separately.

In the ethane ODH step (f), ethane and oxygen are suitably fed to the reactor in the vapour phase.

Preferably, in the ethane ODH step (f), that is, during contacting ethane with oxygen in the presence of the ODH catalyst, the temperature is between 300 and 500 ℃. More preferably, the temperature is between 310 and 450 ℃, more preferably between 320 and 420 ℃, most preferably between 330 and 420 ℃.

Furthermore, typical pressures in the ethane ODH step (f), i.e. during contacting of ethane with oxygen in the presence of the ODH catalyst, range from 0.1 to 30 or from 0.1 to 20bara (i.e. "absolute pressure"). Further, preferably, the pressure is in the range of from 0.1 to 15bara, more preferably from 1 to 8bara, most preferably from 3 to 8 bara.

Inert gas may be fed to step (f) in addition to oxygen and ethane. The inert gas may be selected from the group consisting of noble gases and nitrogen (N)₂). Preferably, the inert gas is nitrogen or argon, more preferably nitrogen.

The above-mentionedOxygen is the oxidant, resulting in the oxidative dehydrogenation of ethane. The oxygen may originate from any source, such as air. Alternatively, oxygen may be provided over a metal oxide (preferably, mixed metal oxide) catalyst, which is both a source of oxygen and a catalyst for the oxidative dehydrogenation of ethane. Introduction of metal oxide catalysts into ODH reactors with ethane under conditions that allow easy migration of oxygen atoms to the catalyst surface and activation of the ethane while limiting the availability for combustion of the desired product to CO and CO₂Amount of free oxygen (c). The metal oxide catalyst may release one or more oxygen atoms prior to recovery and regeneration with air in a separate reactor vessel prior to reintroduction into the ODH reactor. The above-described process of providing oxygen for the oxidative dehydrogenation of ethane, also referred to as chemical looping, can improve ethylene yield and selectivity.

Suitably the molar ratio of oxygen to ethane is in the range 0.01 to 1, more suitably 0.05 to 0.5. The oxygen to ethane ratio is the ratio of oxygen and ethane prior to contact with the ODH catalyst. In other words, the ratio of oxygen to ethane is the ratio of oxygen at the time of feed to ethane at the time of feed. Obviously, at least a portion of the oxygen and ethane is consumed after contact with the catalyst.

In step (f), the ODH catalyst may be a catalyst comprising a mixed metal oxide. Preferably, the ODH catalyst is a heterogeneous catalyst. Further, preferably, the ODH catalyst is a mixed metal oxide catalyst containing molybdenum, vanadium, niobium and optionally tellurium as metals, which catalyst may have the formula:

Mo₁V_aTe_bNb_cO_n

wherein:

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

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

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

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

n (for O) is a number determined by the valence and frequency of the elements other than oxygen.

The amount of catalyst in the ethane ODH step (f) is not essential. Preferably, a catalytically effective amount of the catalyst is used, i.e., an amount sufficient to promote the oxidative dehydrogenation of ethane.

The ODH reactor useful in the ethane ODH step (f) may be any reactor, including fixed bed and fluidized bed reactors. Suitably, the reactor is a fixed bed reactor.

Examples of oxidative dehydrogenation processes, including catalysts and process conditions, are disclosed, for example, in the above-mentioned US7091377, WO2003064035, US20040147393, WO2010096909 and US20100256432, the disclosures of which are incorporated herein by reference.

In the ethane ODH step (f), water is formed in the product stream in addition to the desired ethylene product. Furthermore, the product stream comprises unconverted ethane and carbon dioxide. That is, the ethane ODH step (f) may produce a reactor effluent comprising ethylene, ethane, carbon dioxide and water.

At least a portion of the reactor effluent comprising ethylene, ethane, carbon dioxide and water obtained in step (f) may be fed to step (b) above where water is removed. Furthermore, in the latter case, at least a portion of the reactor effluent obtained in step (a) may be fed to step (f). In such cases, both the OCM effluent and ODH effluent are treated by the same water removal step (b).

Step (g)

In an optional step (g) of the present integrated process, at least a portion of the reactor effluent obtainable in step (f) is cooled to obtain a liquid stream comprising water and a gas stream comprising ethylene, ethane and carbon dioxide. Step (b) is different from step (g). This may also be referred to as quenching, which may be performed in a quencher.

In step (g), the reactor effluent may be cooled from the reaction temperature to a lower temperature, e.g. room temperature, such that water condenses, and may then be removed from the gas stream (reactor effluent).

In step (g), a liquid stream comprising water and a gas stream comprising ethylene, ethane and carbon dioxide are obtained by cooling the reactor effluent. In the case where the stream fed to step (g) also comprises acetic acid, the acetic acid may be removed in step (g) together with water from the stream, suitably together with water condensed from the stream. During or after step (g), additional water may be added to facilitate the removal of any acetic acid.

At least a portion of the gas stream comprising ethylene, ethane and carbon dioxide obtained in step (g) may be fed to the above-mentioned step (c) wherein carbon dioxide is removed. As shown in fig. 1, discussed further below.

Step (h)

In an optional step (h) of the integrated process, carbon dioxide is removed from at least a portion of the gas stream comprising ethylene, ethane and carbon dioxide obtained in step (g), thereby generating a gas stream comprising ethylene and ethane. The step (c) is different from the step (h).

Step (h) is preferably carried out using one or more amines and/or by means of caustic treatment. The caustic treatment may be performed, for example, using a sodium hydroxide solution. Suitable carbon dioxide scavengers may be aqueous solutions of bases such as sodium hydroxide or amines.

At least part of the gas stream comprising ethylene and ethane obtained in step (h) may be fed to step (d) above, wherein a stream comprising methane, a stream comprising ethane and a stream comprising ethylene are recovered. As shown in fig. 2 and 3, discussed further below.

In the above-described first embodiment of step (d), at least a portion of the gas stream comprising ethylene, ethane and methane obtained in step (c) is separated into a stream comprising methane and a stream comprising ethylene and ethane, which stream is then further separated into a stream comprising ethylene and a stream comprising ethyleneAn ethane-containing stream. In said first embodiment of step (d), preferably at least a portion of the gas stream comprising ethylene and ethane obtained in step (h) is fed into said sub-step of step (d), wherein the separated stream comprising ethylene and ethane is further separated into a stream comprising ethylene and a stream comprising ethane. As shown in fig. 3, discussed further below. Furthermore, in said first embodiment of step (d), at least a portion of the gas stream comprising ethylene and ethane obtained in step (h) may be fed into said sub-step of step (d), wherein at least a portion of the gas stream comprising ethylene, ethane and methane obtained in step (c) is separated into a stream comprising methane and a stream comprising ethylene and ethane. This is also shown in fig. 3, discussed further below. An example where this applies is where the gas stream comprising ethylene and ethane obtained in step (H) further comprises carbon monoxide and/or methane and/or H₂And/or inert gases such as N₂The case (1).

In the above-mentioned second embodiment of step (d), at least a portion of the gas stream comprising ethylene, ethane and methane obtained in step (c) is separated into a stream comprising ethane and a stream comprising methane and ethylene, and said stream comprising methane and ethylene is then further separated into a stream comprising methane and a stream comprising ethylene. In said second embodiment of step (d), preferably at least a portion of the gas stream comprising ethylene and ethane obtained in step (h) is fed to said sub-step of step (d), wherein at least a portion of the gas stream comprising ethylene, ethane and methane obtained in step (c) is separated into a stream comprising ethane and a stream comprising methane and ethylene.

An optional drying step after step (c)

In an optional drying step between steps (c) and (d), water may be removed from the gas stream comprising ethylene, ethane and methane, possibly additionally comprising water, obtained in step (c), thereby generating a gas stream comprising ethylene, ethane and methane. The water may be from the carbon dioxide remover used in step (c).

In the case of such an optional drying step between steps (c) and (d), at least a portion of the gas stream comprising ethylene and ethane obtained in step (h) may be fed to said drying step. As shown in fig. 2, discussed further below. The gas stream comprising ethylene and ethane obtained in step (h) may also comprise water. The water may be derived from the carbon dioxide remover used in step (h).

An optional drying step after step (h)

In an optional drying step after step (h), water may be removed from the gas stream comprising ethylene and ethane obtained in step (h), possibly additionally comprising water, thereby generating a gas stream comprising ethylene and ethane. The water may be derived from the carbon dioxide remover used in step (h). Said optional drying step after step (h) is not the same as the optional drying step described above between steps (c) and (d).

In case of such an optional drying step after step (h) and the above-described first embodiment of step (d), preferably at least a portion of the gas stream comprising ethylene and ethane obtained in said drying step is fed into the sub-step of step (d), wherein the separated stream comprising ethylene and ethane is further separated into a stream comprising ethylene and a stream comprising ethane. As shown in fig. 3, discussed further below. Furthermore, in the case of such an optional drying step after step (h) and the above-described first embodiment of step (d), at least a portion of the gas stream comprising ethylene and ethane obtained in said drying step may be fed into said sub-step of step (d), wherein a stream comprising methane and a stream comprising ethylene and ethane are produced. This is also shown in fig. 3, discussed further below. An example where this applies is where the gas stream comprising ethylene and ethane obtained in step (H) further comprises carbon monoxide and/or methane and/or H₂And/or inert gases such as N₂The case (1).

Furthermore, in the case of step (h) and such an optional drying step after the second embodiment of step (d) described above, preferably at least a portion of the gas stream comprising ethylene and ethane obtained in said drying step is fed to said sub-step of step (d), wherein a stream comprising ethane and a stream comprising methane and ethylene are produced.

Drawings

The process of the present invention is further illustrated in FIGS. 1-3.

In fig. 1, a methane Oxidative Coupling (OCM) configuration is shown. The OCM configuration includes an OCM unit 3, a water condensation unit 5, a carbon dioxide removal unit 8, a drying unit 12, and separation units 15 and 18. The separation units 15 and 18 are distillation columns. Further, in fig. 1, an Oxidative Dehydrogenation (ODH) configuration integrated with the OCM configuration is also shown. The ODH configuration includes an ODH unit 22 and a water condensation unit 24.

In said figure 1, a stream 1 comprising methane and a stream 2 comprising oxidant are fed to an OCM unit 3 operating under OCM conditions. Product stream 4 from OCM unit 3 comprises ethane, ethylene, methane, carbon dioxide, and water. Said stream 4 is fed to a water condensation unit 5. In water condensing unit 5, water is removed via condensation of stream 6. In fig. 1, stream 7 from water condensation unit 5 (which comprises ethane, ethylene, methane and carbon dioxide) is fed to carbon dioxide removal unit 8.

The carbon dioxide removal agent is fed to carbon dioxide removal unit 8 via stream 9. The carbon dioxide remover may be an aqueous solution of a base such as sodium hydroxide or an amine. The carbon dioxide removal unit 8 may comprise a sub-unit for removing carbon dioxide by means of an aqueous amine solution and a downstream sub-unit for removing carbon dioxide by means of an aqueous sodium hydroxide solution. Carbon dioxide is removed by water stream 10. Stream 11 comprising ethane, ethylene, methane and water from carbon dioxide removal unit 8 is fed to drying unit 12. In drying unit 12, water is removed via stream 13. The stream 14 comprising ethane, ethylene and methane from the drying unit 12 is fed to a separation unit 15.

In the separation unit 15, the stream 14 comprising ethane, ethylene and methane is separated into an overhead stream 16 comprising methane and a bottom stream 17 comprising ethane and ethylene. Stream 17 is fed to separation unit 18. In separation unit 18, stream 17 is separated into an overhead stream 19 comprising ethylene and a bottom stream 20 comprising ethane.

Stream 16 comprising methane is recycled to OCM unit 3.

Further, in said figure 1, a stream 20 comprising ethane and a stream 21 comprising an oxidant are fed to an ODH unit 22 containing an ODH catalyst and operating under ODH conditions. The oxygen source fed to the OCM unit 3 and the ODH unit 22 may be the same. For example, the same oxygen generation unit (not shown in fig. 1) may be used to generate streams 2 and 21. The product stream 23 from the ODH unit 22 comprises water, ethane, ethylene, carbon dioxide and any acetic acid. Said stream 23 is fed to a water condensation unit 24. In water condensation unit 24, water and any acetic acid are removed via condensation of stream 25.

In fig. 1, stream 26 from water condensation unit 24 (which comprises ethane, ethylene, and carbon dioxide) is fed to carbon dioxide removal unit 8, which is part of an OCM configuration.

In fig. 2, an OCM configuration and an ODH configuration integrated with the OCM configuration are shown. The OCM configuration is the same as that of fig. 1. In fig. 2, the ODH configuration includes an ODH unit 22, a water condensation unit 24, and a carbon dioxide removal unit 28.

The process of figure 2 is the same as that of figure 1 except that stream 26 from the water condensation unit 24 as part of the ODH configuration (this stream 35 comprises ethane, ethylene and carbon dioxide) is not fed to the carbon dioxide removal unit 8 as part of the OCM configuration but is fed via stream 27 to the carbon dioxide removal unit 28 as part of the ODH configuration. The carbon dioxide removal agent is fed to carbon dioxide removal unit 28 via stream 29. The carbon dioxide remover may be an aqueous solution of a base such as sodium hydroxide or an amine. Carbon dioxide removal unit 28 may comprise a sub-unit for removing carbon dioxide by an aqueous amine solution and a downstream sub-unit for removing carbon dioxide by an aqueous sodium hydroxide solution. Carbon dioxide is removed by water stream 30. In fig. 2, stream 31 comprising ethane, ethylene and water from carbon dioxide removal unit 28 is fed to drying unit 12 as part of an OCM configuration.

In fig. 3, an OCM configuration and an ODH configuration integrated with the OCM configuration are shown. The OCM configuration is the same as that of fig. 1 and 2. In fig. 3, the ODH configuration includes an ODH unit 22, a water condensation unit 24, a carbon dioxide removal unit 28, and a drying unit 33.

The process of fig. 3 is the same as the process of fig. 2, except that stream 31 from carbon dioxide removal unit 28 as part of the ODH configuration (which stream 31 comprises ethane, ethylene and water) is not fed to drying unit 12 as part of the OCM configuration, but is fed via stream 32 to drying unit 33 as part of the ODH configuration. In drying unit 33, water is removed via stream 34. Stream 35 from drying unit 33 comprises ethane and ethylene. The stream 35 is fed to a separation unit 18 which is part of the OCM configuration. Optionally, for example, wherein the stream 35 further comprises carbon monoxide and/or methane and/or H₂And/or inert gases (e.g. N)₂) In this case, the stream 35 may be fed to the separation unit 15 via stream 37, which is part of the OCM configuration.

In fig. 1-3, the integration of the OCM with the ODH configuration may include one or more compressors (not shown in fig. 1-3), as illustrated below.

In fig. 1, the integration of the OCM with the ODH configuration may contain 1 compressor. The compressor may be positioned between the point where carbon dioxide removal unit 8 merges with streams 7 and 26.

Furthermore, in fig. 1, the integration of the OCM with the ODH configuration may contain 2 compressors. A first compressor may be provided between the point where carbon dioxide removal unit 8 is combined with streams 7 and 26; and a second compressor may be disposed between the carbon dioxide removal unit 8 and the drying unit 12. Alternatively, a first compressor may be provided between the point at which water condensation unit 5 merges with streams 7 and 26; and a second compressor may be provided between the point at which water condensation unit 24 combines with streams 7 and 26.

Furthermore, in fig. 1, the integration of the OCM with the ODH configuration may contain 3 compressors. A first compressor may be disposed between the carbon dioxide removal unit 8 and the drying unit 12; a second compressor may be provided between the point at which water condensation unit 5 is combined with streams 7 and 26; and a third compressor may be provided between the point at which water condensation unit 24 combines with streams 7 and 26.

In fig. 2 and 3, the integration of the OCM with the ODH configuration may contain 2 compressors. The first compressor may be disposed between the water condensing unit 5 and the carbon dioxide removing unit 8; a second compressor may be disposed between the water condensation unit 24 and the carbon dioxide removal unit 28.

Furthermore, in fig. 2, the integration of the OCM with the ODH configuration may contain 3 compressors. The first compressor may be disposed between the water condensing unit 5 and the carbon dioxide removing unit 8; a second compressor may be disposed between the water condensation unit 24 and the carbon dioxide removal unit 28; and a third compressor may be provided between the point where the drying unit 12 merges with streams 11 and 31.