Method for direct conversion of carbon dioxide to dialkyl carbonates using ethylene oxide as feedstock

A method for co-production of high purity dimethyl carbonate and mono-ethylene glycol by applying a reactor, such as a membrane reactor and/or an adsorbent-catalytic reactor by capturing and reacting carbon dioxide with methanol and ethylene oxide. Carbon dioxide may be recovered from primary sources (utilities and industrial processes) by a membrane or solid adsorbent, and subsequently converted to an intermediate hydroxy-ethyl-methyl carbonate by reacting with ethylene oxide and methanol. For high-purity carbon dioxide (obtained by carbon capture technologies or from an ethanol fermentation process), the membrane reactor is replaced with a catalytic reactor for direct conversion of carbon dioxide to hydroxy-ethyl-methyl carbonate by reacting with ethylene oxide and methanol. The hydro-ethyl-methyl carbonate is further reacted with methanol for conversion to dimethyl carbonate. A combination of heterogeneous and homogeneous catalysts is implemented for an effective conversion of carbon dioxide. An integrated reactive distillation process using side reactors is used for facilitating catalytic reaction for production of high purity dimethyl carbonate.

REFERENCE TO RELATED APPLICATIONS

This Utility Patent Application is based upon Provisional Patent Application No. 62/852,614 filed on 24 May 2019.

INCORPORATION BY REFERENCE

FIELD OF THE INVENTION

The subject invention is directed to a process for synthesis of alkyl carbonates, and particularly, to production of dimethyl carbonate (DMC) from hydroxy-ethyl-methyl-carbonate (HEMC) by a direct reaction of carbon dioxide with ethylene oxide and methanol.

The subject invention is also directed to a process for synthesis of DMC from HEMC by employing either a membrane reactor or a solid adsorbent reactor for recovery and conversion of carbon dioxide from a primary source to HEMC, or, alternatively, using a catalytic reactor for reacting high-purity carbon dioxide (captured in a commercial process, for example, the amine process, or ethanol fermentation process) to high-purity dimethyl carbonate.

The subject invention is further directed to the synthesis of dimethyl carbonate (DMC) which integrates a membrane reactor and/or a solid adsorbent reactor in the synthesis process, where the membrane reactor continuously captures carbon dioxide from primary sources, wherein the captured carbon dioxide diffuses through the membrane surface and reacts with flowing ethylene oxide and methanol to form HEMC. In addition, the adsorbent reactor, which is loaded with a solid adsorbent and conversion catalysts, operates in a cyclic manner by initially capturing carbon dioxide from primary sources by a solid adsorbent until it is nearly saturated. Subsequently, ethylene oxide and methanol reactants are fed to the adsorbent reactor for reacting with adsorbed carbon dioxide to form hydroxyl-ethyl-methyl carbonate. The simultaneous carbon dioxide capture from the primary sources of carbon dioxide (that are preferably the utility plants and industrial processes) for production of value-added dimethyl carbonate (DMC) along with coproduct mono-ethylene glycol (MEG) constitute an essential part of the subject invention.

In addition, the subject invention is directed to an improved process for synthesis of hydroxy-ethyl-methyl carbonate (an intermediate stage for production of dimethyl carbonate) which avoids a conventional process of ethylene carbonate characterized by a high energy consumption and capital costs (CAPEX).

The subject invention also addresses a process for synthesis of dimethyl carbonate which uses three heat-integrated distillation columns for achieving high-concentration of pure dimethyl carbonate with lower energy consumption and low carbon-footprint.

BACKGROUND OF THE INVENTION

Conventionally, amine-process-based recovery of carbon dioxide from a raw natural gas is practiced in a chemical reducing environment. In applications for an oxidizing environment, amine can be used for carbon dioxide recovery from combustion flue gases. In such systems, carbon dioxide is absorbed from the combustion flue gas and subsequently recovered from the rich Amine stream by stream stripping.

Emerging carbon dioxide capture technologies include: a) membrane separation; b) alternate solvents to Amines; c) solid adsorbent; and d) non-aqueous solvents (presented in the DOE/NETL Project Review Proceedings, DOE/NETL Project Review Proceedings http:/www.netl.doe.gov/events/conference-proceedings/2018/2018-netl-co2-capture-technology-project-review-meeting).

Alkyl carbonates cover a group of organic carbonates with a broad supply chain for end-use applications like “green” low-volatile solvents, as electrolytes in lithium-ion batteries, chemical intermediate for production of polyurethanes and in the expanding polycarbonate market.

Commercially, dimethyl carbonate is manufactured by reacting methanol with syngas which is produced from natural gas, petroleum products or coal gasification with high emissions of carbon dioxide. With the expanding global demands of alkyl carbonates the industry is seeking alternate synthesis processes using carbon dioxide.

Unfortunately, the conventional direct conversion of carbon dioxide to DMC using different catalysts has significant limitations, as shown, for example, by Tamboli, et al., (“Catalytic Development in the Direct Dimethyl Carbonate Synthesis from Carbon Dioxide and Methanol,” Chemical Engineering Journal, 33, pp. 530-544, 2017), and Kabra, et al, (“Direct Synthesis of Dimethyl Carbonate from Methanol and Carbon Dioxide: A Thermodynamic and Experimental Study,” J. of Supercritical Fluids, 117, pp. 98-107, 2016).

Thermodynamic limitations of the direct conversion of carbon dioxide to alkyl carbonates require extreme operating conditions, such as high pressure, high temperature, and critical fluid conditions. Even under such reaction conditions, the conversion is relatively low, which requires recycling a large fraction of unreacted reagents.

Unless innovative catalysts are developed for the reaction to occur at moderate conditions with high conversion rate, the direct conversion of CO2to alkyl carbonates is expected to be limited to scientific studies which are prevented from advancing to commercial plants.

Therefore, it would be desirable to develop a process using chemical carriers, such as, for example, ethylene oxide, to form an intermediate stage preceding the stage of synthesis of alkyl carbonates.

PRIOR ART

Described in U.S. Pat. No. 9,518,003, is a process for synthesis of hydroxy-ethyl-methyl carbonate by reacting ethylene carbonate with methanol. Hydroxy-ethyl-methyl carbonate is further reacted with methanol to produce dimethyl carbonate using a heat integrated reactive distillation equipped with side reactors and permeation-vaporization (PerVap) membranes for separation of azeotropic mixture of methanol and dimethyl carbonate. Ethylene carbonate is produced commercially by reacting carbon dioxide with ethylene oxide at high temperature and pressure using homogeneous catalysts (presented in U.S. Pat. No. 4,233,221).

Such a high-pressure process is not feasible for recovery and conversion of carbon dioxide from low-pressure primary sources. It is highly desirable to provide a low-pressure synthesis of hydroxy-ethyl-methyl carbonate.

Conventional direct conversion of carbon dioxide to dimethyl carbonate using different catalysts has significant limitations, as presented by Tamboli, et al. and Kabra, et al. (referenced in previous paragraphs). Thermodynamic limitations of direct conversion of carbon dioxide to alkyl carbonates require extreme operating conditions such as high pressure, high temperature and critical fluid conditions. Even under such reaction conditions the conversion is relatively low, which requires recycling of large fraction of unreacted reagents. Until novel catalysts are developed for reaction to occur at moderate conditions with high conversion, the direct conversion of carbon dioxide to alkyl carbonate is expected to be limited only to scientific studies without advancing to commercial plants. Therefore, it is essential to develop a process using chemical carrier, such as ammonia, to form an intermediate followed by synthesis of alkyl carbonates.

Significant limitations of conventional process presented in previous paragraphs are partially due to the usage of ethylene oxide or alternate carbonate followed by transesterification reaction for synthesis of alkyl carbonates. The laboratory studies have been focused on evaluating different catalysts by following the reaction path represented by Equation 1:
CH2—O-CH2+CO2→CH2O—CO—OCH2Ethylene Oxide Ethylene Carbonate
CH2O—CO-OCH2+CH3OH⇄CH3O—CO—OCH2CH2OH Ethylene Carbonate Methanol Hydroxy-Ethyl-Methyl Carbonate
CH3O—CO-OCH2CH2OH+CH3OH⇄CH3O—CO-OCH3+HOCH2—CH2OH Hydroxy-Ethyl-Methyl Methanol Dimethyl Carbonate Mono-Ethylene Glycol Carbonate  (Equation 1)

For example, Wang et al., evaluated K2CO3-based binary salt in the presence of water. Dhuri et al., evaluated Amberlyst A-21 catalyst. These laboratory studies however have never transformed into a commercial process or even in pilot-plant demonstration of an integrated process. Numerous processes for synthesis of alkyl carbonates have been developed. Those includes for example: (i) Amoco, U.S. Pat. No. 5,489,703; (ii) Bayer Material Science AG, U.S. Pat. No. 8,338,631; (iii) Asahi Kasei Kogyo Kabushiki Kaisha, U.S. Pat. No. 5,847,189; and (iv) Asahi Kasei Chemicals Corporation, U.S. Pat. No. 7,645,896. Patents (i) and (ii) are not relevant to the proposed process at any level. The Asahi Patents (iii) and (vi) use side reactors. However, the Asahi's '189 Patent which uses a distillation column connected to packed-bed reactors using heterogeneous resin catalysts, have never been advanced to any improved version, nor have been implemented to practice. Asahi-Kasei's system presented '896 Patent moved away from the concept of '189 Patent based on the heterogeneous catalysts to a homogeneous catalyst reactive distillation column. The reason for refusal of further development of the system presented in '198 Patent process is believed to be that the process was not able to achieve high conversion due to slow, reversible and equilibrium-controlled reactions using side reactors.

It would be desirable to provide a process for direct conversion of carbon dioxide to alkyl carbonates using the combination of homogeneous and heterogeneous catalysts and advanced process configuration to overcome shortcomings of the Asahi's system using the heterogeneous catalyst presented in '198 Patent.

DMC and methanol form a homogeneous azeotropic mixture over a wide range of pressures which makes it difficult to separate the two components without the addition of a third component as an entrainer. It would be highly desirable to provide an efficient process that is capable of separation of DMC from other components in the system without the need for an entrainer.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a process for synthesis of concentrated dimethyl carbonate which overcomes limitations of the conventional processes and obviates the need for an entrainer by employing Permeation-Vaporization (PerVap) membrane to partially break the dimethyl carbonate and methanol azeotrope.

It is a further object of the present invention to provide a process for synthesis of concentrated dimethyl carbonate which decouples a reaction distillation column from the product column, which can be operated at a higher pressure for breaking the azeotrope, where PerVap membranes with selective separation of methanol are integrated in the process. By incorporating a PerVap Membrane unit in the separation step, high-concentration DMC is produced.

In the subject process, production of concentrated dimethyl carbonate is accomplished by reacting carbon dioxide directly with ethylene oxide and methanol, thereby eliminating the high temperature commercial process of ethylene carbonate production.

Another object of the present invention is to use alternative embodiments of direct conversion of carbonate dioxide to form high purity dimethyl carbonate and mono-ethylene glycol, which include:(a) A preferred embodiment uses a membrane reactor that captures carbon dioxide from combustion flue gases and other dilute sources. Carbon dioxide diffusing through the membrane reacts with methanol and ethylene oxide flowing on the other side of the membrane surface.(b) A second embodiment employs a catalytic reactor for replacing the membrane reactor for relatively pure carbon dioxide captured from primary sources of combustion flue gases and other primary dilute sources.(c) A third implementation is to capture carbon dioxide from primary sources by selective solid adsorbent, such as a metal-organic framework (MOF), nanowire adsorbent, nano particles or other solid adsorbents. The solid adsorbent chamber is loaded with suitable catalysts, such as Amberlyst A-26 or an alternate catalyst. Once the solid adsorbent is nearly saturated with carbon dioxide, the carbon dioxide source is switched to a parallel unit. Ethylene oxide and methanol reactants are fed to the solid adsorbent-catalytic reactor that was saturated with carbon dioxide facilitating a reaction that forms hydroxy-ethyl-methyl carbonate. These kinds of adsorption/desorption operations are commercially practiced in Pressure Swing Adsorption (PSA).

The resulting product stream from the afore-presented reactors consists of hydroxy-ethyl-methyl carbonate and unreacted methanol, carbon dioxide and ethylene oxide which are subsequently fed into a packed-bed catalytic reactor for further conversion. The product stream is fed into a flash tank for separating vapor and liquid phases. The vapor stream consisting of carbon dioxide and ethylene carbonate is recycled back into the packed-bed catalytic reactor.

Various commercially used and scientifically tested catalysts may be used. They may include, for example, Amberlyst A-21 and A-26, which were tested and proven qualified (Panchal C B, et al., AIChE Spring Meeting, 2018).

These ionic catalysts are soluble in methanol, and hence they may be fed in with the methanol and recovered after passing through individual direct-conversion reactors described in previous paragraphs.

The product mixture exiting from the direct conversion (catalytic, membrane or adsorbent) reactor system is fed to a catalyst recovery process which uses a heat exchanger to cool the product mixture and a flash tank for separation of vapor and liquid phases. The liquid from the flash tank is fed to a distillation column to concentrate the catalyst fraction for recycling back to the direct conversion reactor. The product stream from the catalyst recovery distillation column is fed to the first of the three columns for conversion of hydroxy-ethyl-methyl carbonate to dimethyl carbonate.

A mixture of dimethyl carbonate, hydroxy-ethyl-methyl carbonate and unreacted methanol is drawn from one of the stages of the first distillation column and passed through a side reactor thereby producing a more concentrated dimethyl carbonate composition. The product stream from the side reactor is fed to a side separation unit for separating concentrated dimethyl carbonate vapor stream and unreacted liquid stream.

The vapor streams from each of the side reactors are fed to the second column for further concentrating dimethyl carbonate. The liquid stream is then returned to the distillation column. This step is repeated for plurality of side reactor for further concentrated dimethyl carbonate.

A concentrated vapor stream of dimethyl carbonate and methanol is drawn from the top section of the first column, while the condensed stream is fed to a Permeation-Vaporization (PerVap) membrane for selective separation of methanol as the permeate stream. The retentate stream from the PerVap membrane is fed to the second column for recovery of unreacted hydroxy-ethyl-methyl carbonate for recycling to one or more of side reactors for further reaction.

The second recycling column concentrates unreacted hydroxy-ethyl-methyl carbonate as a bottom product which returns to the middle section of the first reaction column. The vapor stream from the second column is condensed and the condensed liquid stream is fed to PerVap membrane for selective separation of methanol.

The retentate from the PerVap membrane is fed to the third column, namely a product recovery column for recovery of high-concentration dimethyl carbonate as bottom product. The product recovery column is efficiently integrated with heat transfer devices to provide internal reflux in the upper section of the column and internal heating in the lower section of the column. The heat recovered from the internal reflux devices is utilized by the PerVap membrane, where such heat is required for selective vaporization of methanol. Methanol recovered from all of PerVap and the top section of the product recovery column is collected in a vessel and pumped back to side reactor as a recycle stream.

The subject invention relates to the first step of catalytic conversion of carbon dioxide to hydroxy-ethyl-methyl carbonate by reacting methanol and ethylene oxide as depicted below by chemical reaction (Equation 2).
CH2—O-CH2+CO2⇄CH3OH CH3O—CO—OCH2CH2OH Ethylene Oxide Methanol Hydroxy-Ethyl-Methyl Carbonate  (Equation 2)

Hydroxy-ethyl-methyl carbonate can be further reacted with methanol to synthesize dimethyl carbonate (DMC) and mono-ethylene glycol (MEG) as coproduct as illustrated by the second chemical reaction (Equation 3).
CH3O—CO-OCH2CH2OH⇄CH3OH CH3O—CO-OCH3+HOCH2—CH2OH Hydroxy-Ethyl-Methyl Methanol Dimethyl Carbonate Mono-Ethylene Glycol   (Equation 3)

This following chemical reaction (Equation 4) is presented in U.S. Pat. No. 9,518,003, where hydroxy-ethyl-methyl carbonate is the product of reacting methanol with ethylene carbonate, where the ethylene carbonate is commercially produced by reacting ethylene oxide with carbon dioxide. The present invention combines the first two steps of chemical reaction depicted by (Equation 4), and hence bypasses the cost and energy intensive commercial process of ethylene carbonate.
CH2—O-CH2+CO2→CH2O—CO—OCH2Ethylene Oxide Ethylene Carbonate
CH2O—CO-OCH2+CH3OH⇄CH3O—CO—OCH2CH2OH Ethylene Carbonate Methanol Hydroxy-Ethyl-Methyl Carbonate
CH3O—CO-OCH2CH2OH+CH3OH⇄CH3O—CO-OCH3+HOCH2—CH2OH Hydroxy-Ethyl-Methyl Methanol Dimethyl Carbonate Mono-Ethylene Glycol Carbonate  (Equation 4)

DMC is further reacted to form methyl-ethyl carbonate by partial transesterification with ethanol (Equation 5) releasing one molecule of methanol that can be recycled. Complete transesterification with ethanol yields diethyl carbonate (Equation 6) releasing two molecules of methanol that can be recycled. These two forms of dialkyl carbonates have broad applications, including as electrolyte in lithium-ion batteries.
CH3O—CO-OCH3+CH3CH2OH⇄CH3O—CO-OCH2CH3+CH3OH Dimethyl Carbonate Ethanol Methyl-Ethyl Carbonate Methanol  (Equation 5)
CH3O—CO-OCH3+2CH3CH2OH⇄CH3CH2O—CO—OCH2CH3+2CH3OH Dimethyl Carbonate Ethanol Diethyl Carbonate Methanol  (Equation 6)

These and other objects and advantages of the present invention will be fully understood when taken in view of the Patent Drawings and Detailed Description of the Preferred Embodiment(s).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIGS. 1-4, a process and system for producing purified concentrated dimethyl carbonate uses carbon dioxide as a feedstock, where the carbon dioxide is either captured from primary sources using a reactor, which may be a membrane reactor, a catalytic reactor, or an integrated adsorbent-catalytic reactor. The catalytic reactor may be employed which uses the concentrated carbon dioxide captured from primary sources by one of the commercial processes, such as, for example, the Amine absorption process.

As shown inFIGS. 1-4, the subject system10includes a distillation sub-system which is built with a Reaction Distillation Column100, a Recycle column200, and a Product Recovery column300interconnected one with another in a specific order. The Reaction Distillation Column (also referred to herein as a Reaction column or a Distillation column)100operates in conjunction with one or numerous side reactor(s)42,72,114and one or numerous separation units, such as for example, Permeation-Vaporization (PerVap) membrane(s). One or several PerVap membrane(s) may be integrated with either a membrane reactor16or a catalytic reactor, or, alternatively, with an integrated adsorbent-catalytic reactor, for selective separation of methanol as the permeate stream and the direct conversion by reaction of carbon dioxide with ethylene oxide and methanol in the presence of combined heterogeneous and homogeneous catalysts.

Interfacing the side reactors42,72,114with the reaction distillation column100without adverse impacts on the column performance requires careful design. The care is taken in the subject system on several criteria in the design interface which may include: 1) vapor flow should not be disturbed; 2) total or partial liquid flow to the side reactor using flow control valves should be employed; 3) liquid should returned to the next stage, preferably to a tray or packed column embedded therein; 4) heat is preferably recovered using a feed/effluent heat exchanger for the side reactor, and the columns100,200,300should operate at different temperatures and pressures; and 5) interfacing design is based on commercially available hardware devices for minimizing operational risks.

Referring toFIG. 1, the Reaction Distillation Column100includes a plurality of recycling components and stages which produce a purified and concentrated dimethyl carbonate which exits as a product from a the final column i.e., the Product Recovery Column (also referred to herein as a Product Column or product Distillation Column)300on a dimethyl carbonate product line212.

The system10, as shown inFIG. 1, is designed for synthesis of alkyl carbonates using carbon dioxide recovered from primary source stream12gases using a membrane reactor system16and reacting with methanol26and ethylene oxide20to form hydroxy-ethyl-methyl carbonate22, which is an intermediate substance for synthesis of dimethyl carbonate. The carbon dioxide lean treated flue-gas stream14exits from the Membrane Reactor16.

As shown inFIG. 1, the recycled methanol (MeOH) is fed to the Membrane Reactor16on the recycled methanol stream18.

Fresh ethylene oxide is fed to the Membrane Reactor16on the feed line20. Recycled methanol from the line204is fed on the recycled methanol line18mixed with ethylene oxide line20along with the recycled unreacted ethylene oxide line26. The mixed stream of stream18stream20and stream26can be in liquid or vapor phase before inserting into the Membrane Reactor16.

Carbon dioxide12permeating though the membrane reacts with methanol and ethylene oxide inserted by streams18and20which are in liquid or vapor phases. Homogeneous catalyst recovered from catalyst recovery unit30is fed into the Membrane Reactor16on the line32along with make-up catalyst on the line34. The resulting hydroxy-ethyl-methyl carbonate, as well dimethyl carbonate and unreacted ethylene oxide and methanol along with homogeneous catalyst, exit the Membrane Reactor16on the stream line22feeding into a flash tank24for separation of vapor and liquid phases. The recovered unreacted ethylene oxide is recycled into the Membrane Reactor16via the stream line26.

The liquid stream28from the flash tank24is fed into the Catalyst Recovery unit30. Recovered homogeneous catalyst dissolved in methanol is fed back to the Membrane Reactor16on the line32. The product stream from the catalyst recovery unit30is fed to the first side reactor unit A42on the line36by the pump38feeding the side reactor unit A42via line40.

The side reactor unit A42shown inFIGS. 1-4, is packed with a heterogeneous catalyst in order to facilitate the reaction of hydroxy-ethyl-methyl carbonate with methanol for synthesis of dimethyl carbonate and mono ethylene glycol.

The product stream exiting the side reactor unit A42on line44is reduced in pressure by a valve on line46to produce a vapor, a liquid or a vapor/liquid mixture. The product stream on the line46is fed into the flash column unit A48. The unit48includes a structured packing on the top and an internal heat exchanger for vaporization. The vapor product on the line50consists of the high concentration dimethyl carbonate or azeotropic mixture of dimethyl carbonate and methanol.

The product stream on the line50is fed into the Recycle Column200for further concentration of dimethyl carbonate and recovery and recycling of unreacted hydroxy-ethyl-methyl carbonate.

The liquid product stream52from the Flash Column unit48consisting of the unreacted hydroxy-ethyl-methyl carbonate and methanol along with dimethyl carbonate and mono ethylene glycol is fed to the first distillation column100. The hydroxy-ethyl-methyl carbonate is converted to dimethyl carbonate and mono ethylene glycol by way of the multiple side reactors72and114.

It is to be understood that a number of the side reactors may vary and more or less of the side reactors than that shown in the present embodiment may be used, including the side reactor72connected to the bottom of the Reaction Distillation Column100. As an example only and for the simplicity and in sake of brevity and clarification of the description, a flow process for one of the many of the contemplated side reactors will be presented in the following paragraphs.

With respect to the process associated with the side reactor Unit B72, a product stream is side drawn from one of the stages of the Reaction Distillation Column100which flows through the product line62to a pump64which inserts the product stream into the side reactor Unit B72along with the recycle methanol stream68and the recycle stream122from the bottom of the Column100.

The hydroxy-ethyl-methyl carbonate is subsequently converted to dimethyl carbonate and mono ethylene glycol which exit the side reactor unit B72on the product line74and is fed into the flash column unit B78after reducing the pressure on line76. The vapor product stream80consisting of concentrated dimethyl carbonate or azeotropic mixture of dimethyl carbonate and methanol is fed from the Flush Column Unit B78to the Recycle Volumn200for further concentration of dimethyl carbonate and recycling of the unreacted hydroxy-ethyl-methyl carbonate into the Reaction Distillation Column100.

The liquid product stream consisting of the unreacted hydroxy-ethyl-methyl carbonate, mono-ethylene glycol, low-concentration dimethyl carbonate and unreacted methanol is fed back into the Reaction Distillation Column100on the line82on a stage lower than the side draw stage. It is to be understood that multiple side reactors may be used for achieving desired conversion of hydroxy-ethyl-methyl carbonate to dimethyl carbonate and mono ethylene glycol.

As depicted inFIG. 1, the product stream returning on the re-entry product lines82is inserted into the Reaction Distillation Column100one stage lower than the withdrawal stage represented by the product line62. The distillation stages where the product streams are introduced into the Reaction Distillation Column100are equipped with thermal devices58to selectively vaporize dimethyl carbonate and mono ethylene glycol. The thermal devices58may be incorporated on distillation trays or within packed columns. Thermal devices58are thermally coupled with thermal devices168incorporated in the Product Distillation Column300or the overhead condenser186for recovering heat energy from the Product Distillation Column300operating at a higher temperature than the Reaction Distillation Column100. Well-known heat transfer fluids or systems, such as, for example, a heat pipe, may be used to transfer the heat energy from Product Distillation Column300to the Reaction Distillation Column100.

A product mixture consisting of the unreacted hydroxy-ethyl-methyl carbonate and methanol along with low concentration of dimethyl carbonate and mono ethylene glycol accumulates in the bottom portion60of the distillation column100and is fed to the side reactor unit C114via the stream line104and the pump106on line108along with fresh methanol feed on line110for further conversion of residual hydroxy-ethyl-methyl carbonate and the liquid product stream118from the flash column unit C126is returned to the heat exchanger120, also referred to herein as a reboiler. Dimethyl carbonate, along with the unreacted methanol and mono ethylene glycol, is vaporized in through the reboiler120. Vapor phase dimethyl carbonate, along with methanol and mono ethylene glycol in vapor phase, is re-introduced into the Reaction Distillation Column100via the streamline124. The liquid product stream122containing a higher concentration of the unreacted hydroxy-ethyl-methyl carbonate from the reboiler120is fed to the side reactors for further conversion to dimethyl carbonate and mono ethylene glycol.

A product mixture consisting primarily of methanol, dimethyl carbonate and mono ethylene glycol flows upward in the Reaction Distillation Column100. On stage158of the Reaction Distillation Column100, the bottom product stream consisting of the unreacted hydroxy-ethyl-methyl carbonate156fed from the Recycle Column200is mixed with the product stream rising from the lower section of the Reaction Distillation Column100. Thermal devices56, such as internal cooler/reflux condenser, preferably condenses the unreacted hydroxy-ethyl-methyl carbonate, thus increasing the concentration of other products rising into the upper section54of the Reaction Distillation Column100.

A high-purity mono ethylene glycol (MEG) is side drawn on the line86from the upper stage84of the Reaction Distillation Column100. A product mixture stream88consisting primarily of methanol and dimethyl carbonate formed at the top portion54of the Distillation Column100is fed to the heat exchanger90, also referred to herein as an overhead total condenser. The overhead product stream94is fed into the PerVap96for selective separation of fraction of methanol from product stream94. A fraction of the condensate is returned, as a reflux, from the overhead total condenser90to the first stage of the Reaction Distillation Column100via the stream92.

The permeate vapor stream102with nearly pure methanol from the PerVap membrane96is fed into heat exchanger192, also referred to herein as a PerVap condenser. The retentate liquid stream98from the PerVap membrane96consisting of a higher concentrated dimethyl carbonate is fed into the Recycle Column200at its stage location132.

The product streams50,80and128in the vapor phase exiting from the flash columns48,78and126, respectively, that are attached to the side reactors42,72and114, respectively, are fed to the Recycle Column200at the stage130located above the stage132.

As shown inFIG. 1, the product stream (containing the unreacted hydroxy-ethyl-methyl carbonate along with methanol) flows down to the bottom section136of the Recycle Column200. The bottom product is fed via the line150from the bottom section136into a heat exchanger, also referred to herein as a reboiler,152. The vapor product from the reboiler152is fed back into the Recycle Column200via the line154. The liquid product from the reboiler152consisting of a higher concentration of unreacted hydro-ethyl-methyl carbonate is fed back into the Reaction Distillation Column100, at the stage158, via the line156. The volatile product stream exits from the top section134of the Recycle Column200via the line138and flows into a heat exchanger140, also referred to herein as an overhead condenser. Fraction of the condensate from the overhead condenser140is returned, as the reflux stream142, to the first stage of the Recycle Column200.

As shown inFIG. 1the major fraction of the condensate from the overhead condenser140is pumped via the line144to a higher pressure by a pump146and is fed into the PerVap membrane Unit B160for selective separation of methanol to increase the concentration of dimethyl carbonate. The permeate vapor stream164is fed into the PerVap condenser192. The liquid retentate stream162is fed into the stage170of the Product Column300.

The Product Column300operates at a higher pressure for effective separation of azeotropic mixture of dimethyl carbonate and methanol into pure overhead and bottom products. In order to enhance the separation, a single PerVap membrane unit C178, or multiple side PerVap units, are interlinked with the Product Column300. A side draw stream176is fed into the PerVap membrane unit C178. A nearly pure permeate vapor stream180is fed into the PerVap condenser192.

The dimethyl carbonate concentrated retentate stream182is returned to the Product Column300at a stage located lower than the side drawn stage. An internal heat transfer device172is incorporated in the Production Column300to further enhance the separation by vaporizing methanol that flows upward to the top section166of the Production Column300. The methanol-rich stream flows to the top section166of the Production Column300and encounters heat transfer devices168, also referred to herein as internal coolers or reflux condensers, to condense out dimethyl carbonate, thus increasing methanol concentration in the vapor phase.

The heat extracted by the internal coolers or reflux condensers168is utilized by one or more PerVap membrane units160. The heat extracted by the internal coolers or reflux condensers168is also utilized within the Reaction Distillation Column100. Incorporating the side connect PerVap membrane(s) and the internal heat transfer devices in the subject system10enhances the energy efficiency of the Product Column300and the product recovery.

The methanol rich product stream exiting the top section166of the Product Column300is fed into the heat exchanger186, also referred to herein as an overhead condenser. A fraction of the condensate from the heat exchanger186is returned, as a reflux, on the line188to the first stage of the Production Column300.

The major fraction of the condensate stream190is fed into the methanol storage tank198. The permeate vapor streams102,164, and180from all PerVap membranes units A, B and C96,160and178, respectively, are condensed by the heat exchanger192, also referred to herein as a PerVap condenser, and the condensate of fed into the methanol storage tank198by the pump194via the line196. The methanol from the storage tank198is pumped by the pump202via the line204to the side reactors and the membrane reactor.

As shown inFIG. 1, the product stream206with high-concentration of dimethyl carbonate is withdrawn from the bottom portion174of the Product Distillation Column300and is fed into the heat exchanger208, also referred to herein as a reboiler, for vaporizing a small fraction of methanol that may have been carried down the Product Distillation column300and fed back on line210into the Product Distillation Column300. The purified high-concentration dimethyl carbonate is withdrawn via the line212as a final product.

Referring toFIG. 2, in an alternative implementation10A of the subject system, the membrane reactor16and associated components (shown inFIG. 1) are replaced by a Catalytic Reactor716and corresponding components for conversion of high-purity carbon dioxide captured by one of the commercial or emerging carbon capture technologies.

Specifically, in the embodiment of the subject system10A depicted inFIG. 2, high-purity carbon dioxide712is fed at the top of the Catalytic Reactor716. A combined stream of the high-purity carbon dioxide stream712, recycled methanol stream720, ethylene oxide stream718, recycled unreacted vapor phase carbon dioxide and ethylene oxide from the flash tank724, recycled catalyst stream732and the makeup catalyst dissolved in methanol stream734are also fed at the top of the Catalytic Reactor716for a down-flow catalytic reactor in a trickle-bed reactor mode. The combined feed stream entering the Catalytic Reactor716consists of a vapor phase and a liquid phase.

The product stream722containing hydroxy-ethyl-methyl carbonate along with the unreacted methanol, ethylene oxide, carbon dioxide, and homogeneous catalyst is fed to the flash tank724The vapor stream726from the flash tank724consisting of the unreacted ethylene oxide and carbon dioxide is recycled back into the Catalytic Reactor716. The liquid stream728is fed to the Catalyst Recovery unit30. The subsequent process is identical to that shown inFIG. 1.

Referring toFIG. 3, in another alternative embodiment10B of the subject system, the membrane reactor16and associated components shown inFIG. 1are replaced by adsorbent-catalytic reactors816and816′ for capture and conversion of carbon dioxide from primary sources. Two or more adsorbent-catalytic reactors may be used for alternate processes of capturing carbon dioxide from a primary source and converting to hydroxy-ethyl-methyl carbonate. A primary source of carbon dioxide on the line812is fed into the adsorbent-catalytic reactor816to adsorb carbon dioxide using commercial adsorbents or new solid adsorbents.

When the adsorbent—catalytic reactor816is nearly saturated with carbon dioxide, the primary source stream812is switched to another reactor unit816′ that has been cleared of carbon dioxide by reaction with ethylene oxide and methanol. The reactor816is thus switched to the alternating reaction mode as depicted by816′.

The carbon dioxide lean treated flue-gas stream814exits from the reactor816.

The combined stream of a recycled ethylene oxide stream826, recycled methanol stream820, fresh feed ethylene oxide stream818, recycled catalyst stream832, and the make-up catalyst dissolved in methanol stream834are also fed at the top for a down-flow catalytic reactor, also referred to herein as a trickle-bed reactor. The combined feed stream entering the Catalytic Reactor816can be liquid, vapor, or vapor and liquid mixed.

The product stream822containing hydroxy-ethyl-methyl carbonate along with unreacted methanol, ethylene oxide, and homogeneous catalyst is fed to the flash tank824. The vapor stream826from the flash tank824consisting of unreacted ethylene oxide is recycled back into the adsorbent-catalytic reactor816. The liquid stream828is fed to the catalyst recovery unit30. The subsequent process is identical to that shown inFIG. 1.

FIG. 4depicts another alternative embodiment10C of the subject system, where the ethylene carbonate process presented in U.S. Pat. No. 9,518,003 is replaced by the adsorbent-catalytic reactors916,916′ for a direct conversion of carbon dioxide from primary sources. The adsorbent-catalytic reactor916and916′ are identical to the reactors816and816′ presented inFIG. 3.

Two or more adsorbent-catalytic reactors916,916′ may be used for alternate processes of capturing carbon dioxide from a primary source and converting to hydroxy-ethyl-methyl carbonate. A primary source of carbon dioxide on the line912is fed into the adsorbent-catalytic reactor916to adsorb carbon dioxide using commercial adsorbents or new solid adsorbents.

When the adsorbent-catalytic reactor916is nearly saturated with carbon dioxide, the primary source stream912is switched to another reactor unit916′ that has been cleared of carbon dioxide by reaction with ethylene oxide and methanol. The reactor916is thus switched to the alternating reaction mode as depicted by916′.

The carbon dioxide lean treated flue-gas stream914exits from the reactor916.

The combined stream of a recycled ethylene oxide stream926, recycled methanol stream920, fresh feed ethylene oxide stream918, recycled catalyst stream932, and the make-up catalyst dissolved in methanol stream934are also fed at the top for a down-flow catalytic reactor, also referred to herein as a trickle-bed reactor. The combined feed stream entering the Catalytic Reactor916can be liquid, vapor, or vapor and liquid mixed.

The product stream922containing hydroxy-ethyl-methyl carbonate along with unreacted methanol, ethylene oxide, and homogeneous catalyst is fed to the flash tank924. The vapor stream926from the flash tank924consisting of unreacted ethylene oxide is recycled back into the adsorbent-catalytic reactor916. The liquid stream928is fed to the catalyst recovery unit30.

The membrane reactor16depicted inFIG. 1or the catalytic reactor716depicted inFIG. 2can also be used in the embodiment ofFIG. 4.

The remaining part of the process is identical to that presented in U.S. Pat. No. 9,518,003 with the stream and components numbers identified by pre-text of 1, such as, for example, the column534(in '003 Patent) is identified as1534(inFIG. 4herein).

FIG. 5depicts a schematic flow diagram of the catalyst recovery unit30referenced inFIGS. 1, 2, 3 and 4. As an example, the catalyst recovery unit30is connected to a direct-conversion catalyst reactor1016.

The recycled methanol1034is fed into the catalyst chamber1000, and the makeup ionic catalyst1034is fed into the catalyst chamber1000to be dissolved in methanol. In addition, the ionic catalysts1032dissolved in methanol are fed in the catalyst chamber1000from the fractionation column400. Thus prepared catalysts are fed form the catalyst chamber1000into the catalyst reactor1016.

Ethelene oxide1018and high purity captured CO21012are fed into the catalytic reactor1016.

The product stream1022exiting the catalytic reactor1016is cooled down by the heat exchanger402to enhance the effective separation of vapor phase1024containing unreacted ethylene oxide and carbon dioxide that are recycled via the stream1026. The liquid stream1036consisting of hydroxy-ethyl-methyl carbonate, unreacted methanol, homogeneous catalyst and traces of dimethyl carbonate and mono-ethylene glycol is fed into the heat exchanger410, also referred to herein as a side reboiler, for generating vapor-liquid stream412.

The stream412is introduced into the fractionation column400, also referred to herein as a divided-wall column equipped with the partition422to divide the column into two sections416and418. A lighter fraction, mainly methanol with traces of dimethyl carbonate and mono-ethylene glycol, flows upward to upper section414, while the heavier fraction, mainly, hydroxy-ethyl-methyl carbonate and homogeneous catalyst, flow downward towards the lower section442.

The vapor stream424exiting from the upper section414is condensed by the heat exchanger426, also referred to herein as an overhead condenser. A fraction of the condensate is returned to the first stage of the fractionation column400. The overhead product stream430is combined with hydroxy-ethyl-methyl stream drawn via the line432from the middle section418of the fractionation column400and is fed to the Side Reactor Unit A42depicted inFIG. 2.

A homogeneous stream434consisting of hydroxy-ethyl-methyl carbonate is withdrawn from the bottom section442and fed into heat exchanger436, also referred to herein as a reboiler. The vapor stream438from the reboiler436is retuned below the last stage of the fractionation column400.

The liquid stream440with a concentrated homogeneous catalyst is recycled to the catalyst reactor1016via the stream1032. The vapor with a higher concentration of hydroxy-ethyl-methyl carbonate from the lower section442of the fractionation Column400is divided by the dynamic divider at the bottom of the dividing wall422. The rising vapor stream with a higher concentration combined with a reflux returning from the upper section414of the section418effectively concentrate hydro-ethyl-methyl carbonate and is withdrawn at an appropriate state via the stream432. The divided-wall fraction column400is ideally suited for concentrating three products with varying volatility, such a volatile methanol, intermediate hydroxy-ethyl-methyl carbonate, and homogeneous catalyst with low volatility. The catalyst recovery unit30presented inFIG. 5may be employed with any of the direction conversion reactors presented inFIGS. 1, 2 and 3.

FIG. 6depicts a schematic flow diagram representing catalytic reactor716used inFIG. 2. Transesterification heterogeneous catalyst, such as Amberlyst A-26, is packed within the reactor716and is supported by a sieve tray1120. The combined gaseous phase stream consisting of high-purity carbon dioxide stream1112, ethylene oxide stream1118and are recycled unreacted ethylene oxide and carbon dioxide stream1126are mixed in manifold.

The mixed vapor stream is fed from the top of the reactor716. The liquid streams which consist of the recycled methanol stream1120and a combined stream of1126and1128(consisting of homogeneous catalysts1132recovered from the catalyst recovery unit30and a fresh makeup homogeneous catalyst1134dissolved in methanol) are fed at the top section of the reactor716.

The liquid is uniformly distributed across the top of the packed-bed catalyst using a commercial liquid distributor1119. The vapor and liquid flow down in a trickle-bed reactor mode of operation. The product stream exits the reactor716via the stream1122and is fed into the flash tank1124as depicted inFIG. 2. The subsequent process is identical to that presented inFIG. 2.

FIG. 7is illustrative of a schematic flow diagram representing adsorbent-catalytic reactor816depicted inFIG. 3. Transesterification heterogeneous catalyst821, such as Amberlyst A-26, is packed within the reactor816and816′ along with a commercial or one of the new solid adsorbents, such as metal-organic framework (MOF) or nanowire or nanoparticle or an alternate solid adsorbent818and supported by the sieve tray823and the support plate825. Two or multiple adsorbent-catalytic reactors816,816′ may be used for the alternate processes of capturing carbon dioxide from a primary source and converting to hydroxy-ethyl-methyl carbonate. Primary source of carbon dioxide on line812is fed into the reactor816for adsorption using commercial or new solid adsorbents. The saturation of the reactor816with the adsorbed carbon dioxide is continuously monitored by detecting carbon dioxide in the stream814. When the reactor816is nearly saturated with the carbon dioxide primary source, the stream812is switched to another reactor unit816′ that has been cleared of carbon dioxide by reaction with ethylene oxide and methanol. The reactor816thus is switched to reaction mode as depicted by816′.

The combined stream of recycled ethylene oxide stream826, recycled methanol stream820, fresh feed ethylene oxide stream818, recycled catalyst stream832and make-up catalyst dissolved in methanol stream834are also fed from at top for a down flow catalytic reactor in a trickle-bed reactor mode of operation by the uniform distribution of the vapor and liquid phase by the distribution tray823.

The reaction mode of operation of816′ is continued until adsorbed carbon dioxide is consumed as indicated by sensor located on the outlet stream822or inside the reactor. The product stream822containing hydroxy-ethyl-methyl carbonate along with the unreacted methanol, ethylene oxide, and homogeneous catalyst is fed to the flash tank824. The subsequent process is identical toFIG. 3.

FIGS. 8 and 9depict two alternative design concepts of the membrane reactor16presented inFIG. 1. Specifically,FIGS. 8 and 9represent an element section500of the membrane reactor16where the membrane501includes a membrane support and carbon dioxide transport membrane film. InFIG. 8, catalysts502are packed on the other side of the membrane in the form of a packed-bed catalyst, while inFIG. 9, the catalyst502′ is embedded on the membrane surface. InFIG. 8, the reactants (ammonia and methanol) flow505passes through the catalysts.

The carbon dioxide stream503from primary sources flows through one side of the membrane501and, as the carbon dioxide diffuses through the membrane, the carbon dioxide reacts with methanol and ethylene oxide in the presence of heterogeneous and homogeneous catalysts in the bulk flow region as depicted by the reaction equation507. The resulting product exits via the streamline506. The carbon dioxide lean treated flue-gas504exits form the membrane reactor16.

InFIG. 9, the carbon dioxide diffuses through the membrane and reacts with methanol and ethylene oxide at the membrane surface on which catalysts502′ are embedded. The product methyl carbamate is then carried away by flowing methanol and exit via the streamline506.

FIGS. 10, 11 and 12depict three alternative configurations of the membrane modules.FIG. 10represents a shell-and-tube module700with tubular membranes701providing a cross-flow of the carbon dioxide stream703. The tubular membrane701may have carbon dioxide transport membrane film either inside or outside of the tube. Membrane tubes701are either packed with catalyst as shown inFIG. 8, or are embedded on the membrane surface as shown inFIG. 9.

Methanol, ethylene oxide and homogeneous catalyst are fed as a stream702in the module700. Some fraction of the carbon dioxide is converted to products, and the flow stream704exits as a treated flue gas. The product stream (consisting of hydroxy-ethyl-methyl carbonate, some fraction of dimethyl carbonate and mono ethylene glycol and unreacted ethylene oxide, methanol and carbon dioxide) exits via the flow stream705for further conversion.

FIG. 11is representative of an innovative concept of parallel-plate membrane module620. Parallel plates621are assembled with alternate plate flow channels623and are packed with catalysts622as shown inFIG. 8. Alternatively, the catalysts622are embedded on the surface as shown inFIG. 9.

The carbon dioxide stream624enters from the side of the parallel-plate membrane module620, as shown byFIG. 11, and exists from the other side as a flow stream626. Flow stream628consisting of ethylene oxide, methanol and homogenous catalyst is introduced from the top of the module620and flows down through the channels623that hold catalysts622. Carbon dioxide diffusing through the membrane reacts with ethylene oxide and methanol in the presence of heterogeneous catalyst622packed in the flow channels623and the homogeneous catalyst flowing with the reactants to produce hydroxy-ethyl-methyl carbonate.

The products stream630is withdrawn from the bottom of the membrane module620. The elemental section of plate-and-frame membrane module620can be assembled in a commercial-scale unit based on the well-known technology “know how” of plate heat exchangers as exemplified inFIG. 12.

Alternatively to the design presented inFIGS. 10-12, commercial membrane modules including spiral-wound membrane modules or hollow-fiber membrane modules can also be employed. However, loading these types of commercial membranes with catalysts is difficult and such membrane modules cannot be built on a large scale required for capture and conversion of carbon dioxide from large-scale primary sources from utilities and industrial processes to alkyl carbonates.

For the process streams illustrated inFIGS. 1, 2 and 3, the methanol/dimethyl carbonate azeotrope is shown to be broken at the PerVap membrane unit in a distillate between the two distillation columns, and the recovered methanol is recycled and fed to either singular or multiple side reactors. PerVap membrane units used in the subject system may be commercially available and may include zeolite, cross-linked chitosan and highly fluorinated polymer membranes.

The PerVap membrane units presented in previous paragraphs are representative of an exemplary concept of the separation technique, and other separation techniques for separating and recycling the excess reactant methanol from the product stream may be used as well in the subject system. Such separation methods applicable in the subject system may include, for example, molecular-sieve separation, pressure-swing adsorption (PSA), temperature-swing adsorption (TSA), liquid-liquid separation of immiscible liquid mixtures, liquid entrainment and heat integrated distillation.

The side reactors, main catalytic reactor, adsorbent-catalytic reactor and membrane reactors illustrated inFIGS. 1-3may be packed with commercial heterogeneous catalysts for either process illustrated. Alternatively, homogeneous catalysts that are soluble in methanol and referenced here may be used along with heterogeneous catalyst. Such catalysts may be used in a form of Amberlyst A21, or A26, or an alternate catalyst.

Homogeneous ionic catalysts may be Tri-methyl-butyl ammonium chloride (TMBAC), or Tri-methyl-butyl ammonium bromide (TMBAB), or Tri-ethyl-butyl ammonium bromide (TEBAB), or Tetra-butyl ammonium chloride (TBAC), or Tetra-butyl ammonium bromide (TBAB). Alkyl may be any saturated carbon chain having less than 10 carbons. Different catalysts may be also used on an individual membrane reactor, primary catalytic reactor, or an adsorbent-catalytic reactor for direct conversion, as well as the individual side reactor.

Table 1 represents process parameters for a typical commercial plant depicted inFIG. 1with production capacity of 51,700 metric tons per year and product purity of 99 wt %. It co-produces 35,700 metric tons/year of high-value mono ethylene glycol with purity of 98 wt %. The process consumes 0.49 kg of carbon dioxide per kg of dimethyl carbonate with net emissions of 0.19 kg carbon dioxide, as shown in table below, by accounting credit for coproduction of mono ethylene glycol. If the feed stock methanol is produced by renewable hydrogen and carbon dioxide, then there would be net permanent sequestration of carbon dioxide in the form of consumer products. This is compared to emissions of 1.76 kg carbon dioxide per kg of dimethyl carbonate produced by syngas-based commercial process.

Table 2 represents the estimated global demands of dimethyl carbonate and corresponding potential abatement of carbon dioxide emissions in 2018 and 2030. With full implementation of the subject process by 2050, there would be significant global abatement of carbon dioxide.

TABLE 2Dimethyl carbonate market and CO2abatement potentialDMC MarketCO2Abatementpotentials, kTA*Potentials, kTA*Applications2018203020182030Polycarbonate production2,4404,9103,8317,708Lithium-ion batteries4535071550Solvent (replacing ketones)1,4301,4302,2452,857Polyurethane production11,35011,35017,82028,998Diesel-engine additive**1,580,0002,480,000*Thousand metric tons per year**Based on government approval for pollution control
Validation of ASPEN Plus® Design Model

The subject system and method enabled development of an ASPEN Plus® model for design and simulation of the dimethyl carbonate process depicted inFIGS. 1-3. The model was validated with performance data acquired using a prototype test unit shown by process diagram presented inFIG. 13. Ethylene carbonate was used as a feed for a laboratory testing since ethylene oxide is hazardous and was not to be used for laboratory tests. This prototype test unit transpires as the first column equipped with side reactors. Table 3 represents the test matrix covering process parameters typical of commercial process.

The overall process parameters including experimental overhead distillate flow, bottom product flow and ethylene glycol flow, as side product, are presented in the Table 4. The measured experimental values are compared with ASPEN Plus® model predictions. Table 4 also shows experimental and predicted purity of mono ethylene glycol under different test conditions.

TABLE 4Performance parameters of the reaction columnMain ColumnFlow g/minDistillateBottomsMEG Flow g/minMEG Purity wt %Test RunEXPASPENEXPASPENEXPASPENEXPASPENDMCD014.15.32.16.011.211.287%76%DMCD025.75.013.617.98.88.8492%77%DMCD036.05.24.37.19.39.387%74%DMCD047.48.29.610.75.15.192%94%DMCD058.84.76.310.48.68.691%74%DMCD064.24.87.09.26.86.891%92%DMCD074.17.13.91.810.710.792%87%DMCD082.94.91.75.07.17.191%94%DMCD093.06.91.40.68.48.489%88%DMCD103.33.57.59.47.77.790%84%DMCD113.74.09.011.57.0790%92%DMCD124.04.28.314.77.87.892%77%DMCD133.04.65.88.57.97.791%88%
Validation of Side Reactors

ASPEN Plus® process analysis is validated with the experimental test data obtained for individual three side reactors shown inFIG. 13. A flow redirecting device is installed in a packed column for directing a liquid flowing down the packed column to the side reactor. The vapor rising from the bottom part of the column is bypassed as the side draw line of the liquid.

The product stream from the side reactor is returned to the next stage of the packing below the point of side draw. An integrated pump and a surge tank system are used for controlling the liquid flow to the side reactor. As presented in Table 5, the ASPEN Plus® model was validated with the measured conversion of ethylene carbonate (EC) and yield of dimethyl carbonate (DMC).

TABLE 5Conversion of ethylene carbonate (EC)and yield of dimethyl carbonate (DMC) inside reactorsSide Reactor ConversionSR-1SR-2SR-3EXPASPENEXPASPENEXPASPENECDMCECDMCECDMCECDMCECDMCECDMCTest RunConvYieldConvYieldConvYieldConvYieldConvYieldConvYieldDMCD0159%28%50%24%46%16%36%10%33%17%38%12%DMCD0254%22%49%18%36%9%31%5%36%7%30%4%DMCD0356%26%52%24%41%12%33%6%42%8%36%6%DMCD0458%27%51%23%40%11%33%5%36%6%37%7%DMCD0556%23%49%19%38%8%35%6%47%10%42%8%DMCD0654%24%54%24%42%7%33%6%36%4%35%6%DMCD0755%35%59%38%40%12%34%11%45%13%38%11%DMCD0856%27%53%28%40%9%36%9%44%12%43%10%DMCD0959%36%55%34%44%17%36%15%55%NA46%13%DMCD1054%25%51%23%33%8%31%7%36%5%38%8%DMCD1151%21%47%19%35%8%33%7%38%5%40%8%DMCD1247%16%41%16%39%10%31%5%38%7%33%5%DMCD1354%22%52%24%37%8%34%7%38%6%39%7%
Performance of PerVap Membrane

Table 6 represents a summary of the performance parameters. Two series of tests were performed with liquid phase and vapor phase feed as shown in Table 6. In general high-purity methanol was separated as permeate with high-degree of selectivity. The PerVap membrane performance parameters were incorporated into the ASPEN Plus® process model.