WO2017141088A1

WO2017141088A1 - Processes for separating light components from monochloromethane

Info

Publication number: WO2017141088A1
Application number: PCT/IB2016/057547
Authority: WO
Inventors: Kuang-Yao Brian PENG; Murali Gopalakrishnan; Minghua Ye; Joshua D. Taylor; Mohammad Shafiei; Michael Huckman
Original assignee: Sabic Global Technologies B.V.
Priority date: 2016-02-18
Filing date: 2016-12-12
Publication date: 2017-08-24

Abstract

Processes for separating light hydrocarbons, carbon oxides and inert gases from chlorinated hydrocarbons are described. A method includes obtaining a gaseous feed stream that includes chlorinated hydrocarbons, light hydrocarbons, carbon oxides and inert gases; contacting the gaseous feed stream with an alkyl aromatic solvent at a pressure of 0.82 MPa (120 psi) to 1.6 MPa (230 psi) to produce a stream that includes the light hydrocarbons, the carbon oxides, and the inert gases, and a liquid stream; recovering the light hydrocarbons, carbon oxides, and inert gases; and recovering the monochloromethane from liquid stream.

Description

PROCESSES FOR SEPARATING LIGHT COMPONENTS FROM

MONOCHLOROMETHANE

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 62/296,822, filed February 18, 2016, which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

A. Field of the Invention

[0002] The invention generally concerns the separation of light components from chlorinated hydrocarbons. In particular, the invention concerns separating monochloromethane from a reactant feed that includes chlorinated hydrocarbons, light hydrocarbons, carbon oxides, and inert gases at elevated pressures using effective absorption agents.

B. Description of Related Art [0003] Monochloromethane can be made through a process termed "Oxychlorination". In the oxychlorination processes gaseous hydrogen chloride and an oxygen containing gas such as air and the hydrocarbon to be chlorinated are contacted with a metal halide catalyst. By a series of well-known reactions, the reactive "oxychlorme" intermediate from oxygen and hydrogen chloride (HQ) is generated on the catalytic surface and reacts with a hydrocarbon (e.g., methane) to produce chlorinated hydrocarbons (e.g., monochloromethane) and water. Another process to make monochloromethane uses elemental chlorine (CI₂) as the feed gas. In this process, free chlorine, oxygen containing gas, and the hydrocarbon to be chlorinated are contacted with a metal halide catalyst. The chlorine reacts with the hydrocarbon to produce hydrogen chloride and a chlorinated product of the hydrocarbon. Hy drogen chloride produced in this manner is then converted to elemental chlorine by a well-known series of reactions, thereby providing additional chlorine for the chlorination of more hydrocarbon feed.

[0004] Although oxychlorination processes of this type are well known in the art, there are serious operational difficulties generally associated with. them. For example, the recovery of

27745670.1 the chlorinated hydrocarbon products using conventional absorption techniques is difficult as they require very low temperatures. This is due in part to the fact that the chlorinated hydrocarbon products are diluted in great quantities of inert or non-condensable gases such as methane, elemental nitrogen, carbon monoxide, carbon dioxide, and other like gases. In order to recover the products satisfactorily from such a process it is necessary to process large quantities of gas and efficiently recover the chlorinated hydrocarbon content thereof.

[0005] The recovery process is further complicated by the presence of water and hydrogen chloride in such mixtures which can condense to form an aqueous hydrogen chloride solution. This aqueous hydrogen chloride solution can not only be detrimental to process equipment, but may also have deleterious effects on solvents used in separation processes. There have been many attempts to improve the separation process using liquid absorption processes. By way of example, U.S. Patent No. 3, 148,041 to Dehn et αί,. discloses contacting the gaseous reactant stream from an oxychlorination process with a liquid aromatic halogenated hydrocarbon solvent {e.g., 1, 2,4-trichlorbenzene, or othodichlorbenzene) to produce an aromatic halogenated hydrocarbon/chlorinated hydrocarbon mixture. The chloromethane was separated from the solvent using distillation techniques. In yet another example, U.S. Patent No. 5,954,861 to Crum et a!., discloses a process of employing a liquid hydrocarbon having an average molecular weight within a range of about 142 to 422 to absorb the Ci chiorocarbons from the gaseous mixtures. The chloromethane is recovered from the high molecular weight hydrocarbon using distillation techniques. These and other conventional processes still suffer from inefficiencies and are capital intensive due to the high refrigeration costs for cooling the overhead condenser during the separation process to achieve the desired monochloromethane purity.

SUMMARY OF THE INVENTION [0006] A discovery has been made that improves the efficiency of the separation of monochloromethane from an oxychlorination product stream. The discovery is premised on the idea of a separation column to remove light hydrocarbons from chloromethane produced in the methane oxychlorination process. The new design incorporates an effective absorption agent that allows for a wider range of operation at pressures higher than conventional processes and low reflux temperatures to achieve a high recovery rate of methyl chloride and higher purity of recycled light components without any loss in the absorption liquid in absorption and separation processes. The effective absorption agents have a melting point of

27745670.1 -55 °C or less. As a result, the lighter components (e.g., methane) that are recycled back to the reactor oxychlorination reactor have a higher purity, which can increase the life span of the oxychlorination catalyst and selectivity of the desired methyl chloride product. Furthermore, the separation system of the current invention can reduce the refrigeration cost by shifting the cooling duty from ethylene refrigeration to propylene refrigeration cooling and water or air cooler as supplementary low cost cooling sources.

[0007] In a particular aspect of the invention, a process for separating light components from chlorinated hydrocarbons is described. The process can include (a) obtaining a gaseous feed stream that can include chlorinated hydrocarbons, light hydrocarbons, carbon oxides and inert gases, where the chlorinated hydrocarbons can include monochloromethane and heavy chlorinated hydrocarbons; (b) contacting the gaseous feed stream with a liquid stream that includes an alkyl aromatic solvent at a pressure of 0.825 (120 psi) to 1.6 MPa (230 psi) or 1.45 MPa (210 psi) to 1.6 MPa (230 psi) to produce a first gaseous product stream that includes the light hydrocarbons, the carbon oxides, and inert gases, and a liquid stream that includes the chlorinated hydrocarbons and the alkyl aromatic solvent; (c) recovering the light hydrocarbons, carbon oxides, and inert gases from the first gaseous overhead stream; and (d) recovering the monochloromethane from the alkyl aromatic solvent. The mass ratio of liquid to gas in step 1(b) can be in the range of 1 : 1 to 5 : 1, preferably 2: 1. In some instances a flow of the gaseous feed stream is opposite to the flow of the alkyl aromatic solvent. For example, step 1(b) can be performed in an absorption column, preferably a counter-flow absorption column. The gaseous feed stream of 1(a) can include 35 wt.% to 65 wt.% light hydrocarbons (e.g., methane, ethane, or both, preferably methane), 35 wt.% to 65 wt.% of chlorinated hydrocarbons, 0 wt.% to 60 wt.% of carbon oxides, and balance of inert gases and less than 1 wt.%) water, preferably 0 wt.%>. In a particular instance, the gaseous feed stream is a product stream of a methane oxychlorination reaction. The alkyl aromatic solvent (e.g., toluene, ethylbenzene, cumene, or any combination thereof) can have a melting point of -55 °C or less. In a particular embodiment, the alkyl aromatic solvent is toluene. In certain embodiments, the alkyl aromatic solvent does not include a halogenated aromatic compound. The temperature of the gaseous feed stream is 60 °C or less and/or the temperature of the first gaseous overhead stream in step (b) can range from -80 °C to -20 °C, preferably, -50 °C to - 30 °C or more preferably from -40 °C to -30 °C at the pressure of 0.82 MPa (120 psi) to 1.6 MPa (230 psi) or 1.45 MPa (210 psi) to 1.6 MPa (230 psi). The first gaseous product stream can include less than 1 wt.%> of chlorinated hydrocarbons. The light hydrocarbons, carbon

27745670.1 oxides, and inert gases can be recovered from the first gaseous stream by subjecting the stream to conditions suitable to enrich the first gaseous stream in light hydrocarbons. By way of example, the first gaseous product stream can include some alkyl aromatic solvent. The first gaseous stream can be cooled and distilled to lower the concentration of the residual alkyl aromatic solvent in the first gaseous product stream. The residual alkyl aromatic solvent can be collected and/or recycled to the contacting step. Recovering the chlorinated hydrocarbons in step 1(d) can include (i) subjecting the liquid organic stream to conditions sufficient to produce a second gaseous product stream that includes monochloromethane and light hydrocarbons, and a second liquid stream that includes the alkyl aromatic solvent and the heavy chlorinated hydrocarbons; (ii) subjecting the second gaseous product stream to conditions sufficient to produce a third gaseous product stream that includes monochloromethane; and collecting the third gaseous product stream that includes at least 95 wt.%, preferably 99 wt.% of the monochloromethane. The third gaseous product stream can include less than 5 wt.% light hydrocarbons and 90 to 95 wt.% of heavy chlorinated hydrocarbons with the balance being carbon oxides and inert gases. The third gaseous product stream can be recycled to step 1(b). Conditions sufficient to produce the second gaseous product stream from the liquid organic stream include distilling the liquid organic bottoms stream to produce the second gaseous product stream and the second liquid stream. In some instances one or more of the liquid and/or gaseous streams can be subjected to heat exchange with a refrigerated propylene system.

[0008] In another instance of the present invention, a process for separating light components form chlorinated hydrocarbons can include (a) obtaining a gaseous feed stream that includes chlorinated hydrocarbons light hydrocarbons, carbon oxides and inert gases, where the chlorinated hydrocarbons can include monochloromethane and heavy chlorinated hydrocarbons; (b) contacting the gaseous feed stream with a liquid stream that includes an alkyl aromatic solvent to produce a first gaseous product stream that includes the light hydrocarbons, the carbon oxides, and inert gases, and a liquid product stream that includes the chlorinated hydrocarbons and the alkyl aromatic solvent, where the alkyl aromatic solvent has a melting point of -55 °C or less; (c) providing the first gaseous product stream to an oxychlorination reaction; (d) recovering the monochloromethane from the alkyl aromatic solvent.

27745670.1 [0009] In some embodiments, a system for separating light components from chlorinated hydrocarbons using any one of the methods described above and throughout the specification is disclosed. The system can include (a) a first inlet configured to receive a gaseous feed stream at a pressure of 1.45 MPa (210 psi) to 1.6 MPa (230 psi); (b) a second inlet configured to receive the liquid alkyl hydrocarbon solvent stream; (c) a first absorbing zone in fluid communication with the first inlet and the second inlet, and configured to remove chlorinated hydrocarbons from the gaseous feed stream to produce an first gaseous product stream that includes the light hydrocarbons and the carbon oxides and a liquid bottoms stream that includes the chlorinated hydrocarbons and the alkyl aromatic solvent; (d) a first outlet in fluid communication with the first absorbing zone and configured to remove the first gaseous product stream; (e) a second outlet in fluid communication with the first absorbing zone and configured to remove the liquid bottoms stream; (f) a first recovery zone in fluid communication with the first outlet and configured to recover the light hydrocarbons and the carbon oxides; (g) a second recovery zone in fluid communication with the second outlet and configured to recover the monochloromethane; (h) a cooling unit coupled to the absorbing zone (c), the first recovery zone (f), the second recovery zone (g), or a combination thereof and configured to perform heat exchange, where the cooling unit that includes a propylene refrigeration system and cooling water. The first gaseous product stream can include less than 1 wt.% chlorinated hydrocarbons and/or the liquid bottoms stream can include the chlorinated hydrocarbons and the alkyl aromatic solvent. The second recovery zone can include a separation zone configured to recover the monochloromethane from the liquid bottoms stream.

[0010] In the context of the present invention 20 embodiments are described. Embodiment 1 can include a process for separating light components from chlorinated hydrocarbons, the process can include: (a) obtaining a gaseous feed stream comprising chlorinated hydrocarbons, light hydrocarbons, carbon oxides and inert gases, wherein the chlorinated hydrocarbons include monochloromethane and heavy chlorinated hydrocarbons; (b) contacting the gaseous feed stream with a liquid stream comprising an alkyl aromatic solvent at a pressure of 0.82 (180 psi) to 1.6 MPa (230 psi) to produce a first gaseous product stream comprising the light hydrocarbons, the carbon oxides, and inert gases, and a liquid stream comprising chlorinated hydrocarbons and the alkyl aromatic solvent; (c) recovering the light hydrocarbons, carbon oxides, and inert gases from the first gaseous overhead stream; and (d) recovering the monochloromethane from the liquid stream. Embodiment 2 is the

27745670.1 process of embodiment 1, wherein a temperature of the first gaseous product stream in step (b) is from -80 °C to -20 °C, preferably, -50 °C to -30 °C or more preferably from -40 °C to - 30 °C, and the pressure is from 0.82 MPa (120 psi) to 1.6 MPa (230 psi) or 1.45 MPa (210 psi) to 1.6 MPa (230 psi). Embodiment 3 is the process of any one of claims 1 to 2, wherein a mass ratio of liquid stream to gaseous feed stream is in a range from 1 : 1 to 5: 1, preferably 2: 1. Embodiment 4 is the process of any one of embodiments 1 to 3, wherein a temperature of the gaseous feed stream is 60 °C or less. Embodiment 5 is the process of any one of embodiments 1 to 4, wherein the alkyl aromatic solvent has a melting point of -55 °C or less. Embodiment 6 is the process of embodiment 5, wherein the alkyl aromatic solvent is toluene, ethylbenzene, cumene, or any combination thereof, preferably toluene. Embodiment 7 is the process of any one of embodiments 1 to 6, wherein the alkyl aromatic solvent does not include a halogenated aromatic compound. Embodiment 8 is the process of any one of embodiments 1 to 7, wherein the first gaseous product stream includes less than 1 wt.% of chlorinated hydrocarbons. Embodiment 9 is the process of any one of embodiments 1 to 8, wherein recovering the chlorinated hydrocarbons in step 1(d) includes: (i) subjecting the liquid organic bottoms stream to conditions sufficient to produce a second gaseous product stream comprising monochloromethane and light hydrocarbons, and a second liquid stream comprising the alkyl aromatic solvent and the heavy chlorinated hydrocarbons; (ii) subjecting the second gaseous product stream to conditions sufficient to produce a third gaseous product stream comprising monochloromethane; and (iii) collecting the third gaseous product stream comprising the monochloromethane. Embodiment 10 is the process of any embodiment 9, wherein the third gaseous product stream includes at least 95 wt.%, preferably 99 wt.%, of monochloromethane and less than 5 wt.% light hydrocarbons. Embodiment 11 is the process of embodiment 10, wherein a gaseous overhead stream is produced in step 9(ii), and the method further includes recycling the gaseous overhead stream to step 1(b). Embodiment 12 is the process of any one of embodiments 1 to 11, wherein the gaseous feed stream of 1(a) includes 35 wt.% to 65 wt.% light hydrocarbons, 35 wt.% to 65 wt.% of chlorinated hydrocarbons, 0 wt.% to 60 wt.% of carbon oxides, and balance of inert gases. Embodiment 13 is the process of any one of embodiments 1 to 12, wherein the gaseous feed stream includes less than 1 wt.% water, preferably 0 wt.%. Embodiment 14 is the process of any one of embodiments 1 to 13, wherein the gaseous feed stream is a product stream of a methane oxychlorination reaction. Embodiment 15 is the process of any one of embodiments 1 to 14, wherein step 1(b) is performed in an absorption column, preferably a counter-flow absorption column. Embodiment 16 is the process of any one of embodiments 1 to 15, further

27745670.1 - 6 - comprising subjecting one or more of the streams to heat exchange with refrigerated propylene.

[0011] Embodiment 17 is a process for separating light components from chlorinated hydrocarbons, the process can include: (a) obtaining a gaseous feed stream comprising chlorinated hydrocarbons light hydrocarbons, carbon oxides and inert gases, wherein the chlorinated hydrocarbons includes monochloromethane and heavy chlorinated hydrocarbons; (b) contacting the gaseous feed stream with a liquid stream comprising an alkyl aromatic solvent to produce a first gaseous overhead stream comprising the light hydrocarbons, the carbon oxides, and inert gases, and a liquid bottoms stream comprising the chlorinated hydrocarbons and the alkyl aromatic solvent, wherein the alkyl aromatic solvent has a melting point of -55 °C or less; (c) providing the first gaseous overhead stream to an oxychlorination reaction; and (d) recovering the monochloromethane from the alkyl aromatic solvent.

[0012] Embodiment 18 is a system for separating light components from chlorinated hydrocarbons using any one of the processes of embodiments 1 to 17, the system can include: (a) a first inlet configured to receive a gaseous feed stream at a pressure of 0.82 MPa (120 psi) to 1.6 MPa (230 psi); (b) a second inlet configured to receive the liquid alkyl hydrocarbon solvent stream; (c) a first absorbing zone in fluid communication with the first inlet and the second inlet, and configured to remove chlorinated hydrocarbons from the gaseous feed stream to produce an first gaseous overhead stream comprising the light hydrocarbons and the carbon oxides and a liquid bottoms stream comprising the chlorinated hydrocarbons and the alkyl aromatic solvent; (d) a first outlet in fluid communication with the first absorbing zone and configured to remove the first gaseous overhead stream; (e) a second outlet in fluid communication with the first absorbing zone and configured to remove the liquid bottoms stream; (f) a first recovery zone in fluid communication with the first outlet and configured to recover the light hydrocarbons and the carbon oxides; (g) a second recovery zone in fluid communication with the second outlet and configured to recover the monochloromethane; and (h) a cooling unit coupled to the absorbing zone (c), the first recovery zone (f), the second recovery zone (g), or a combination thereof, and configured to perform heat exchange, wherein the cooling unit includes a propylene refrigeration system and cooling water. Embodiment 19 is the system of embodiment 18, wherein first gaseous overhead stream includes less than 1 wt.% chlorinated hydrocarbons. Embodiment 20 is the

27745670.1 - 7 - system of any one of embodiments 18 to 19, wherein liquid bottoms stream includes the chlorinated hydrocarbons and the alkyl aromatic solvent, and wherein the second recovery zone includes a separation zone configured to recover the monochloromethane from the liquid bottoms stream. [0013] The following includes definitions of various terms and phrases used throughout this specification.

[0014] The phrase "chlorinated hydrocarbons" refers to chlorinated hydrocarbons having a general formula of CH_4-XC1_X, where x is 1 to 4. Non-limiting examples of chlorinated hydrocarbons include monochloromethane, dichloromethane, chloroform, and carbon tetrachloride. "Heavy chlorinated hydrocarbons" are defined as CH_4-XC1_X, where x is 2 to 4.

[0015] The phrase "light components" or "light hydrocarbons" refer to compounds or hydrocarbons that are not condensable at standard temperature and pressure (25 °C and 1 atm).

[0016] The term "inert" is defined as chemically inactive or substantially inactive under the reaction conditions. Non-limiting examples of inert chemical compounds in the context of this invention include helium, nitrogen, and argon.

[0017] The terms "about" or "approximately" are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment the terms are defined to be within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0018] The term "substantially" and its variations are defined as includes ranges within 10%, within 5%, within 1%, or within 0.5%.

[0019] The terms "inhibiting" or "reducing" or "preventing" or "avoiding" or any variation of these terms, when used in the claims and/or the specification includes any measurable decrease or complete inhibition to achieve a desired result.

[0020] The term "effective," as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.

27745670.1 [0021] The use of the words "a" or "an" when used in conjunction with any of the terms "comprising," "including," "containing," or "having" in the claims, or the specification, may mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more than one." [0022] The terms "wt.%", "vol.%", or "mol.%" refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume of material, or total moles, that includes the component. In a non-limiting example, 10 grams of component in 100 grams of the material is 10 wt.% of component.

[0023] The words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "includes" and "include") or "containing" (and any form of containing, such as "contains" and "contain") are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0024] The methods of the present invention can "comprise," "consist essentially of," or "consist of particular ingredients, components, compositions, etc. disclosed throughout the specification. With respect to the transitional phase "consisting essentially of," in one non- limiting aspect, a basic and novel characteristic of the methods of the present invention are their abilities to separate monochloromethane from light hydrocarbons in an efficient and cost effective manner. [0025] Other objects, features and advantages of the present invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.

27745670.1 - 9 - BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Advantages of the present invention may become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings.

[0027] FIG. 1 is a schematic of an embodiment to separate light components from monochloromethane.

[0028] FIG. 2 is a schematic of a system to separate light components from monochloromethane.

[0029] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and may herein be described in detail. The drawings may not be to scale.

DETAILED DESCRIPTION OF THE INVENTION [0030] A discovery has been made that provides a more cost effective and efficient manner to separate light components from monochloromethane. The present process is useful for separating chlorinated hydrocarbons from gaseous mixtures that include one or more chlorinated hydrocarbons (e.g., monochloromethane, dichloromethane, chloroform and carbon tetrachloride) and light components. The present process is especially useful for recovering monochloromethane formed from the oxychlorination reaction of methane and hydrogen chloride (HC1). A typical oxychlorination process consists of feeding methane or natural gas, an oxygen source, and a chlorine source such as hydrogen chloride or chlorine gas to a reactor containing a catalyst. The product stream from this process can include monochloromethane, heavy chlorinated hydrocarbons, and light components (e.g., methane, carbon oxides and inert gases) as shown in the general reaction scheme below. The present invention provides an economical solution to the isolation of the unreacted methane and other light components (carbon oxides (CO and C0₂ and inert gases) from the chlorinated hydrocarbons. catalyst

CH₄ + HC1 + 0₂ CH₄._XC1_X + H₂0 + CO + C0₂, where x is 1 to 4.

inert gas

27745670.1 - 10 - [0031] The discovery is premised on the ability to separate the light components from the chloromethane at high pressures. The use of high pressures reduces the need for low temperatures for the overhead condenser, and that can be cooled with propylene and water cooling systems, thereby reducing the need for expensive refrigeration constituents (e.g., ethylene propylene refrigeration systems). High pressures separation can be achieved by contacting, in an absorbent column reactor, a gaseous feed stream that includes chlorinated hydrocarbons and light components (e.g., light hydrocarbons, carbon oxides, and inert gases) with an alkyl aromatic solvent that has a melting point of about -55 °C or less at a pressure from about 0.82 MPa to about 1.6 MPa. The alkyl aromatic solvent absorbs the chlorinated hydrocarbons while the non-condensed gaseous light components flow through the solvent. The monochloromethane can be removed from the alkyl aromatic solvent using known separation methods to produce monochloromethane having a purity of 95 mol% and an alkyl aromatic stream that includes heavy chlorinated hydrocarbons (e.g., methylene chloride, chloroform and carbon tetrachloride). [0032] These and other non-limiting aspects of the present invention are discussed in further detail in the following sections with reference to the Figures.

[0033] FIG. 1 depicts a schematic of a system that can be used to perform the methods of the current invention to separate light components from monochloromethane. In system 100, a gaseous feed stream 102 and the alkyl aromatic solvent 104 can enter extraction column 106 (absorbing zone). Gaseous feed stream 102 can include chlorinated hydrocarbons and light components (e.g., light hydrocarbons, carbon oxides and inert gases). The gaseous feed stream 102 can include 35 wt.% to 65 wt.% or 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%), 60 wt.%), 65 wt.%) or any value or range there between of light hydrocarbons (e.g., methane, ethane, or both, preferably methane), 35 wt.%> to 65 wt.%> or 35 wt.%, 40 wt.%, 45 wt.%), 50 wt.%), 55 wt.%), 60 wt.%, 65 wt.%> or any value or range there between of chlorinated hydrocarbons, 0 wt.% to 60 wt.% or 0 wt.%, 1 wt.%, 5 wt.% 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, 60 wt.%, or any value or range there between of carbon oxides, and balance of inert gases, based on the total weight of the stream. The water content of the gaseous feed stream 102 can be less than that required to form methane hydrate when the gaseous feed stream is subjected to high pressures and/or cold temperatures. For example, a water content of the gaseous feed stream can be less than 1 wt.%, and less than 1 wt.%, less than 0.1 wt.%, less than 0.0001 wt.% or 0 wt.%.

27745670.1 - 1 1 - In some instances, the gaseous feed stream is dried using known gas drying methods to remove any condensable water generated in an oxychlorination reaction. The temperature of gaseous feed stream 102 can be 60 °C or less, or 55 °C or less, or 40 °C or less, or 30 °C or less or 25 °C at operating pressures (e.g., a pressure of 0.82 MPa (120 psi) to 1.6 MPa (230 psi)). The alkyl aromatic solvent can be any alkyl aromatic solvent having a melting point of -55 °C or less. In a particular embodiment, the alkyl aromatic solvent has a molar mass of 92 to 140, 100 to 120, or 92, 94, 96, 98, 100, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132, 140 or any range or value there between. Non-limiting examples of suitable alkyl aromatic solvents are listed in Table 1. In a particular instance, toluene is used. The alkyl aromatic solvent can be cooled to -30 °C, -40 °C, -45 °C or -50 °C prior to providing the solvent to column 106. For example, the alkyl aromatic solvent can be cooled by circulation of the fluid through a propylene and water heat exchanger.

Table 1

Contact of the gaseous feed stream 102 with the liquid alkyl aromatic solvent 104 in extraction column 106 can be by standard methods for effecting contact of gases and liquids. The contact can be performed, for example, in packed, unpacked, bubble cap, perforated plate, and other similar type columns used to effect contact of a gas with a liquid. In particular, a packed column can be used. The column can be packed with for example, glass or polytetrafluoroethylene (TEFLON™, Chemours, USA) Beryl saddles, or ceramic or metal Raschig (Raschig USA, Inc.) rings. The gaseous feed stream 102 and liquid alkyl aromatic

27745670.1 - 12 - solvent 104 can be fed to the absorption column 106 as co-current feeds or as countercurrent feeds, preferably a countercurrent manner (e.g., the gaseous feed stream flows in a direction opposite to the liquid alkyl bottoms stream). As shown in FIG. 1, the flow of the feed streams is in a countercurrent manner. A mass ratio of liquid stream to gaseous feed stream is about 5 : 1, 4: 1, 3 : 1, and 2: 1, with 2: 1 being preferred.

[0034] Contact of the gaseous feed stream with the liquid alkyl aromatic solvent stream effects the absorption of the chlorinated hydrocarbons into the liquid stream and produces gaseous product stream 108 that is depleted in chlorinated hydrocarbons (e.g., enriched in light components) and liquid stream 1 10. Gaseous product stream 108 can include less than 1 wt.%, 0.5 wt.%, 0.1 wt.% or less of chlorinated hydrocarbons. The temperature of the exiting first gaseous product stream 108 can range from -80 °C to -5 °C, preferably, -50 °C to -30 °C or more preferably from -40 °C to -30 °C, or -80 °C, -75 °C, -70 °C, -65 °C, -60 °C, -55 °C, - 50 °C, -45 °C, -40 °C, -35 °C, -30 °C, -25 °C, -20 °C, -15 °C, -10 °C, -5 °C or any value or range there between at operating pressures (e.g., 0.82 MPa (120 psi), or 1.24 MPa (180 psi) to 1.6 MPa (230 psi)). The gaseous product stream 108 can exit the absorption column 106 and enter condenser 1 12. Condenser 1 12 can cool the first gaseous product stream 108 to about - 85 °C to -15 °C, preferably, -50 °C to -30 °C or more preferably from -40 °C to -35 °C, or - 85 °C, -80 °C, -75 °C, -70 °C, -65 °C, -60 °C, -55 °C, -50 °C, -45 °C, -40 °C, -35 °C, -30 °C, -25 °C, -20 °C, -15 °C, or any range or value there between at operating pressures. The use of an alkyl aromatic solvent having a melting point of -55 °C or less allows the absorption column 106 to be operated at pressures higher than conventional gas/liquid chloromethane absorption separators, thereby, producing a gaseous product stream at, or near, the temperature suitable to effect condensing of the liquid phase from the gaseous phase. Thus, the amount of energy required for separation of the gaseous product stream 108 flows from the liquid phase in condenser 1 12 and/or separator 1 14 is reduced as compared to conventional systems using ethylene refrigeration systems. In some embodiments, the desired temperature for the first and second gaseous streams are 10 °C to 5 °C above the minimum temperature of propylene refrigeration system. Due to the temperature difference of the two gaseous streams, the cooling fluid provided to the condenser can be propylene refrigeration system or a two-stage propylene and water system instead of a more energy intensive refrigeration system (e.g., an ethylene refrigeration system) normally required for lower temperatures (e.g., temperatures below -55 °C). The use of propylene can minimize the work consumed in the refrigeration cycle, thereby reducing the overall cost in the

27745670.1 - 13 - production of chloromethane. In some embodiments, the propylene system can include some ethylene refrigerant.

[0035] The cooled gaseous product stream 108 can enter gas-liquid separation unit 1 14. In separation unit 1 14, any residual alkyl aromatic solvent and/or chlorinated hydrocarbons in the gaseous product stream 108 can be separated from the gaseous product stream to produce a reflux stream 1 16 and second gaseous product stream 1 18. Separation unit 1 14 can be any type of unit (e.g., flash drum, settling unit, depressurizing vessel, etc.) capable of separating liquids from a gaseous mixture. Reflux stream 1 16 can be provided via pump 120 to the absorption column 106. Reflux stream 1 16 can include the alkyl aromatic solvent and chlorinated hydrocarbons. The amounts of alkyl aromatic solvent and chlorinated hydrocarbons can vary and are dependent on the initial starting amount of components in the gaseous feed stream. Second gaseous product stream 1 18 can include less than 1 wt.%, 0.5 wt.%, 0.1 wt.% or less of chlorinated hydrocarbons with the balance being light hydrocarbons, carbon oxides and inert gases. In some embodiments, the second gaseous product stream 1 18 can be provided to an oxychlorination unit (not shown). Since the second gaseous product stream 1 18 contains none or substantially no chlorinated hydrocarbons or alkyl aromatic solvent, the catalyst life in the oxychlorination unit can be extended and selectivity to the desired monochloromethane product can be increased as compared to conventional methods. [0036] The liquid stream 1 10 can be removed from absorption column 106 and be provided to separation unit 122 using fluid mover (e.g., pump) 124. Liquid stream 1 10 can include chlorinated hydrocarbons and the alkyl aromatic solvent. The temperature of liquid stream 1 10 can range from 45 °C to 60 °C, 50 °C to 55 °C, or 45 °C, 50 °C, 55 °C, 60 °C, or any value or range there between, at operating pressures (e.g., 0.82 MPa to 1.64 MPa). In some embodiments, the liquid stream includes less than 1 wt.% of light components (e.g., methane and/or ethane). A molar ratio of monochloromethane to aromatic alkyl solvent can range from 4: 1, 3 : 1, or 2: 1. In some embodiments, the molar ratio is 3.75 : 1. Separation unit 122 can be any unit capable of separating two compounds having different boiling points. Non-limiting examples of separation units include a thin film distillation unit, a flash distillation unit, a liquid-liquid extraction unit, and the like. The separation unit 122 can include one or more heating systems (for example, a reboiler system, heat exchangers and the like) to heat the liquid stream to a temperature sufficient to remove any monochloromethane

27745670.1 - 14 - and, if present, light hydrocarbons. In separation unit 1 12, liquid stream 1 10 can be separated into an overhead gaseous stream 126 and a liquid bottoms stream 128. Overhead gaseous stream 126 can include about 90 wt.%, 95 wt.% or 99 wt.% chlorinated hydrocarbons with the balance being light hydrocarbons, carbon oxides and inert gases. In a particular embodiment overhead gaseous stream 126 can include 98 wt.% or more of monochlorom ethane. The overhead gaseous stream 126 can undergo heat exchange in condenser 130 and enter gas/gas separation unit 132. In gas/gas separation unit 132, the overhead gaseous stream 126 can be separated in to an overhead recycle stream 134 and a gaseous monochloromethane product stream 136. Overhead recycle stream can include light hydrocarbons, carbon oxides, inert gases and monochloromethane. Overhead recycle stream 134 can be provided to absorption column 106. The gaseous monochloromethane product stream 136 can include at least 95 wt.%, 96 wt.%, 97 wt.%, 98 wt.%, 99 wt.% or more of monochloromethane (CH₃C1) based on the total weight of the stream. A portion of the gaseous monochloromethane stream 136 can be used as a reflux stream for gas/liquid separation unit 122. Liquid bottoms stream 128 can include the alkyl aromatic solvent and heavy chlorinated hydrocarbons (e.g., methylene chloride, chloroform and carbon tetrachloride). The liquid bottoms stream 128 can be provided to other units to recover the alkyl aromatic solvent and the heavy hydrocarbons.

[0037] FIG. 2 depicts a schematic of system 200 that can be used for the separation of light components from monochloromethane. System 200 can include a first absorbing zone 202, a first recovery zone 204, and a second recovery zone 206, and a cooling unit 208 operatively coupled to the first absorbing zone, the first recovery zone, the second recovery zone, or a combination thereof. Cooling unit 208 can include one or more refrigeration units that use propylene as refrigerant cooling, and water or an air cooler as the supplementary low cost cooling sources. In some embodiments, ethylene can be added to the propylene. Cooling unit 208 can provide cooling to one or more units in the absorption zone 202, first recovery zone 204 and second recovery zone 206.

[0038] The gaseous feed stream 102 can enter the first absorbing zone 202 via absorbing zone inlet 102 and cold liquid alkyl aromatic solvent stream 102 can enter the first absorbing zone 202 via second absorbing inlet 214. In absorbing zone 202, light components in gaseous stream 102 can be separated as described above to produce the first gaseous product stream 108 and the liquid stream 1 10. First gaseous product stream 108 can enter first

27745670.1 - 15 - recovery zone 204 and undergo further purification to produce the reflux steam 1 16 and second gaseous product stream 1 18 as described above. Liquid stream 1 10 can enter second recovery zone 206. In second recovery zone 206, the liquid stream 1 10 can be separated into a monochloromethane product stream 128 and gaseous overhead stream 134 as described above. Gaseous overhead stream 134 can be recycled to absorption zone 202 as described above.

EXAMPLES

[0039] The present invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes only, and are not intended to limit the invention in any manner. Those of skill in the art will readily recognize a variety of noncritical parameters which can be changed or modified to yield essentially the same results.

EXAMPLE 1

[0040] Table 2 lists the liquid to gas ratios (L/G) of the absorption solvent to feed gas and wt.% of monochloromethane recovered for given amounts of monochloromethane, pressures, and overhead temperatures for the present invention and a conventional process (e.g., U.S. Patent No. 5,954,861 to Crum et al.).

Table 2

27745670.1 - 16 - Mole% of L/G Pressure (psig) Overhead Temp Wt.% of MeCl

MeCl (° F) Recovery

Conventional 30 20 40 NA 96.7

Process

Conventional 30 20 30 NA 98.5

Process

Conventional 30 30 30 NA 99.8

Process

Present 30 1.65 211.3 5 98.8 invention

Present 40 1.56 211.3 20 98.4

Invention

Present 46.5 1.51 211.3 30 98.1

Invention

[0041] As shown from the values in Table 2, it was determined that the lower L/G ratio of the present invention provided more efficiency and advantages in sizing requirement as compared to conventional processing.

27745670.1 - 17 -

Claims

1. A process for separating light components from chlorinated hydrocarbons, the process comprising:

(a) obtaining a gaseous feed stream comprising chlorinated hydrocarbons, light hydrocarbons, carbon oxides and inert gases, wherein the chlorinated hydrocarbons comprises monochloromethane and heavy chlorinated hydrocarbons;

(b) contacting the gaseous feed stream with a liquid stream comprising an alkyl aromatic solvent at a pressure of 0.82 (180 psi) to 1.6 MPa (230 psi) to produce a first gaseous product stream comprising the light hydrocarbons, the carbon oxides, and inert gases, and a liquid stream comprising chlorinated hydrocarbons and the alkyl aromatic solvent;

(c) recovering the light hydrocarbons, carbon oxides, and inert gases from the first gaseous overhead stream; and

(d) recovering the monochloromethane from the liquid stream.

2. The process of claim 1, wherein a temperature of the first gaseous product stream in step (b) is from -80 °C to -20 °C, preferably, -50 °C to -30 °C or more preferably from -40 °C to -30 °C, and the pressure is from 0.82 MPa (120 psi) to 1.6 MPa (230 psi) or 1.45 MPa (210 psi) to 1.6 MPa (230 psi).

3. The process of claim 1, wherein a mass ratio of liquid stream to gaseous feed stream is in a range from 1 : 1 to 5: 1, preferably 2: 1.

4. The process of claim 1, wherein a temperature of the gaseous feed stream is 60 °C or less.

5. The process of claim 1, wherein the alkyl aromatic solvent has a melting point of about -55 °C or less.

6. The process of claim 5, wherein the alkyl aromatic solvent is toluene, ethylbenzene, cumene, or any combination thereof, preferably toluene.

27745670.1 - 18 -

7. The process of claim 1, wherein the alkyl aromatic solvent does not include a halogenated aromatic compound.

8 The process of claim 1, wherein the first gaseous product stream comprises less than 1 wt.% of chlorinated hydrocarbons.

9. The process of claim 1, wherein recovering the chlorinated hydrocarbons in step 1(d) comprises:

(i) subjecting the liquid organic bottoms stream to conditions sufficient to produce a second gaseous product stream comprising monochloromethane and light hydrocarbons, and a second liquid stream comprising the alkyl aromatic solvent and the heavy chlorinated hydrocarbons;

(ii) subjecting the second gaseous product stream to conditions sufficient to produce a third gaseous product stream comprising monochloromethane; and

(iii) collecting the third gaseous product stream comprising the monochloromethane.

10. The process of any claim 9, wherein the third gaseous product stream comprises at least 95 wt.%, preferably 99 wt.%, of monochloromethane and less than 5 wt.% light hydrocarbons.

11. The process of claim 10, wherein a gaseous overhead stream is produced in step 9(ii), and the method further comprises recycling the gaseous overhead stream to step 1(b).

12. The process of claim 1, wherein the gaseous feed stream of 1(a) comprises 35 wt.% to 65 wt.%) light hydrocarbons, 35 wt.%> to 65 wt.%> of chlorinated hydrocarbons, 0 wt.%> to 60 wt.%) of carbon oxides, and balance of inert gases.

13. The process of claim 1, wherein the gaseous feed stream comprises less than 1 wt.%> water, preferably 0 wt.%>.

The process of claim 1, wherein the gaseous feed stream is a product stream of methane oxychlorination reaction.

27745670.1 - 19 -

15. The process of claim 1, wherein step 1(b) is performed in an absorption column, preferably a counter-flow absorption column.

16. The process of claim 1, further comprising subjecting one or more of the streams to heat exchange with refrigerated propylene.

17. A process for separating light components from chlorinated hydrocarbons, the process comprising:

(a) obtaining a gaseous feed stream comprising chlorinated hydrocarbons light hydrocarbons, carbon oxides and inert gases, wherein the chlorinated hydrocarbons comprises monochloromethane and heavy chlorinated hydrocarbons;

(b) contacting the gaseous feed stream with a liquid stream comprising an alkyl aromatic solvent to produce a first gaseous overhead stream comprising the light hydrocarbons, the carbon oxides, and inert gases, and a liquid bottoms stream comprising the chlorinated hydrocarbons and the alkyl aromatic solvent, wherein the alkyl aromatic solvent has a melting point of -55 °C or less;

(c) providing the first gaseous overhead stream to an oxychlorination reaction; and

(d) recovering the monochloromethane from the alkyl aromatic solvent.

18. A system for separating light components from chlorinated hydrocarbons using any one of the processes of claim 1 or 17, the system comprising:

(a) a first inlet configured to receive a gaseous feed stream at a pressure of 0.82 MPa (120 psi) to 1.6 MPa (230 psi);

(b) a second inlet configured to receive the liquid alkyl hydrocarbon solvent stream;

(c) a first absorbing zone in fluid communication with the first inlet and the second inlet, and configured to remove chlorinated hydrocarbons from the gaseous feed stream to produce an first gaseous overhead stream comprising

27745670.1 - 20 - the light hydrocarbons and the carbon oxides and a liquid bottoms stream comprising the chlorinated hydrocarbons and the alkyl aromatic solvent;

(d) a first outlet in fluid communication with the first absorbing zone and configured to remove the first gaseous overhead stream;

(e) a second outlet in fluid communication with the first absorbing zone and configured to remove the liquid bottoms stream;

(f) a first recovery zone in fluid communication with the first outlet and configured to recover the light hydrocarbons and the carbon oxides;

(g) a second recovery zone in fluid communication with the second outlet and configured to recover the monochloromethane; and

(h) a cooling unit coupled to the absorbing zone (c), the first recovery zone (f), the second recovery zone (g), or a combination thereof, and configured to perform heat exchange, wherein the cooling unit comprises a propylene refrigeration system and cooling water.

19. The system of claim 18, wherein first gaseous overhead stream comprises less than 1 wt.% chlorinated hydrocarbons.

20. The system of claim 18, wherein liquid bottoms stream comprises the chlorinated hydrocarbons and the alkyl aromatic solvent, and wherein the second recovery zone comprises a separation zone configured to recover the monochloromethane from the liquid bottoms stream.

27745670.1 - 21 -