Research progress on absorption and conversion of ethylene oxide to ethylene carbonate

doi:10.16085/j.issn.1000-6613.2020-0541

Abstract

Abstract:

As an important chemical raw material and intermediate produced from CO₂ utilization, ethylene carbonate has attracted more and more attentions. However, there are common problems in the production process, such as high energy consumption for purification of ethylene oxide, low catalytic efficiency in the reaction, and complex process. In this paper, the absorption and conversion units of ethylene oxide and the production process of ethylene carbonate were reviewed. The types of absorbents, the kinds of catalysts as well as the catalytic mechanism and the production process were summarized emphatically. Finally, based on the production technology of ethylene carbonate, the urgent problems and challenges in this research field were discussed. It was also pointed out that the development of multi-site ionic liquid catalysts and the application of absorption-conversion coupling processes would become the highlights of future research and have good industrialization prospect.

Key words: absorption, recovery, catalysis, ethylene oxide, ethylene carbonate

摘要：

碳酸乙烯酯是重要的化工基础原料和中间体，也是CO₂资源化利用的路径之一，越来越受到人们的关注。然而，在生产过程中广泛存在着环氧乙烷纯化能耗高、反应过程催化效率低和工艺复杂等问题。本文综述了在生产碳酸乙烯酯过程中环氧乙烷的吸收单元、转化单元以及生产工艺，重点总结了吸收剂的类型、催化剂的种类和催化机理以及生产工艺。最后，针对碳酸乙烯酯的生产技术，探讨了该研究领域亟待解决的问题和面临的挑战，并指出多位点离子液体催化剂的开发以及吸收转化耦合工艺的应用将成为未来研究的热点，具有较好的工业化前景。

关键词: 吸收, 回收, 催化, 环氧乙烷, 碳酸乙烯酯

CLC Number:

TQ225.24

Junjie CHU, Jie CHANG, Zhibin LUO, Mingming HOU, Qian LI. Research progress on absorption and conversion of ethylene oxide to ethylene carbonate[J]. Chemical Industry and Engineering Progress, 2021, 40(1): 195-204.

褚俊杰, 常洁, 罗志斌, 侯明明, 李谦. 环氧乙烷吸收和转化合成碳酸酯工艺研究进展[J]. 化工进展, 2021, 40(1): 195-204.

Figures/Tables 17

References 70

1	张玉宝. 碳酸乙烯酯的性质与应用[J]. 沈阳师范大学学报(自然科学版), 1997(4): 46-48.
	ZHANG Yubao. The properties and applications of ethylene carbonate[J]. Journal of Shenyang Normal University (Natural Science Edition), 1997(4): 46-48.
2	PAYNE R, THEODOROU I E. Dielectric properties and relaxation in ethylene carbonate and propylene carbonate[J]. The Journal of Physical Chemistry, 1972, 76(20): 2892-2900.
3	程玲, 周建成, 吴东方. 碳酸乙烯酯的合成及应用进展[J]. 精细石油化工进展, 2008, 9(12): 44-52.
	CHENG Ling, ZHOU Jiancheng, WU Dongfang. Progress in the synthesis and application of ethylene carbonate[J]. Progress in Fine Petrochemicals, 2008, 9(12): 44-52.
4	陈向华, 孙凯. EO的生产方法及应用[J]. 化工科技市场, 2008, 31(10): 33-36.
	CHEN Xianghua, SUN Kai. Production method and application of EO[J]. Chemical Technology Market, 2008, 31(10): 33-36.
5	BUKHTIYAROV V I, KNOP-GERICKE A. Ethylene epoxidation over silver catalysts[M]//HESS C, SCHLÖGL R. Nanostructured Catalysts: Selective Oxidations, Knovel, 2011: 214-247.
6	姚小利, 姚虎卿, 堵文斌. 活性炭变压吸附回收环氧乙烷装置排放气中的乙烯[J]. 化工进展, 2003, 22(9): 969-972.
	YAO Xiaoli, YAO Huqing, DU Wenbin. Recovering ethylene from vent gas of ethylene oxide plant by activated carbon with process[J]. Chemical Industry and Engineering Progress, 2003, 22(9): 969-972.
7	GUMEROV F M, SABIRZYANOV A N, GUMEROVA G I, et al. Separation of ethylene oxide from its aqueous solution by supercritical fluid extraction[J]. Theoretical Foundations of Chemical Engineering, 2006, 40(3): 265-269.
8	OZERO B I. Process for the recovery of ethylene oxide: US3964980[P]. 1976-06-22.
9	布莱恩·奥佐罗. 改进的EO回收方法: CN101952268[P]. 2013-10-30.
	OZERO B. Improvement of EO recovery method: CN101952268[P]. 2013-10-30.
10	B·贝斯林, H·哈瑟, J·普吕克汉, 等. 通过蒸馏提纯环氧乙烷的方法: CN1290837C[P]. 2006-12-20.
	BESLIN B, HASSE H, PLUKHAN J, et al. Method of purifying ethylene oxide by distillation: CN1290837C[P]. 2006-12-20.
11	斯特德维泽, 奥斯本, 德弗, 等. 环氧烷纯化方法和系统: CN105148551A[P]. 2015-12-16.
	STADLWIESER K P, OSBORNE B B, DEVER J P, et al. Method and system for purification of alkylene oxide: CN105148551A[P]. 2015-12-16.
12	张军, 刘士达, 潘晓宏, 等. 一种环氧乙烷装置用吸收系统: CN206473984U[P]. 2017-09-08.
	ZHANG Jun, LIU Shida, PAN Xiaohong, et al. An absorption system for ethylene oxide devices: US206473984U[P]. 2017-09-08.
13	耿鹏. 一种环氧乙烷吸收回收装置: CN209060854U[P]. 2019-07-05.
	GENG Peng. Ethylene oxide absorbing and recycling device: CN209060854U[P]. 2019-07-05.
14	LIU Jingru, ZHANG Fan, XU Wei, et al. Thermal reactivity of ethylene oxide in contact with contaminants: a review[J]. Thermochimica Acta, 2017, 652: 85-96.
15	GIOACCHINO C, BENEDETTO C, GIANNI J. Process for the simultaneous separation of ethylene oxide and carbon dioxide from the gaseous mixtures obtained in the direct oxidation of ethylene with oxygen: US3948621[P]. 1976-04-06.
16	DALE A R, OLIVER C A. Ethylene carbonate process: US4233221[P]. 1980-11-11.
17	KAZUKI K, KAZUHIKO M, TOSHIYUKI F. Method of recovery ethylene oxide: US5559255[P]. 1996-09-24.
18	陈玮娜. 以碳酸乙烯酯为吸收剂吸收环氧乙烷的方法[J]. 化工技术与开发, 2013(10): 34-36.
	CHEN Weina. Method of absorbing ethylene oxide with ethylene carbonate as absorbent[J]. Chemical Technology and Development, 2013(10): 34-36.
19	李骏, 杨为民, 何文军. 环氧乙烷纯化方法: CN109422708A[P]. 2019-03-05.
	LI Jun, YANG Weimin, HE Wenjun. Purification method of ethylene oxide: CN109422708A[P]. 2019-03-05.
20	成卫国, 褚俊杰, 董丽, 等. 一种复合吸收剂及其用于环氧乙烷分离纯化的方法: CN110479037A[P]. 2019-11-22.
	CHENG Weiguo, CHU Junjie, DONG Li, et al. A composite absorbent used in the separation and purification of ethylene oxide: CN110479037A[P]. 2019-11-22.
21	YANG Zhenzhen, ZHAO Yanan, He Liangnian. CO₂ chemistry: task-specific ionic liquids for CO₂ capture/activation and subsequent conversion[J]. ChemInform, 2011, 43(4): 545-567.
22	ALVES M, GRIGNARD B, MEREAU R, et al. Organocatalyzed coupling of carbon dioxide with epoxides for the synthesis of cyclic carbonates: catalyst design and mechanistic studies[J]. Catalysis Science & Technology, 2017, 7(13): 2651-2684.
23	YAMAGUCHI K, EBITANI K, YOSHIDA T, et al. ChemInform abstract: Mg-Al mixed oxides as highly active acid-base catalysts for cycloaddition of carbon dioxide to epoxides[J]. Journal of the American Chemical Society, 1999, 121(18): 4526-4527.
24	DAI Weili, YIN Shuangfeng, GUO Rui, et al. Synthesis of propylene carbonate from carbon dioxide and propylene oxide using Zn-Mg-Al composite oxide as high-efficiency catalyst[J]. Catalysis Letters, 2010, 136(1/2): 35-44.
25	WANG Yanyan, LI Shaopeng, YANG Youdi, et al. A fully heterogeneous catalyst Br-LDH for the cycloaddition reactions of CO₂ with epoxides[J]. Chemical Communications, 2019, 55(48): 6942-6945.
26	CALO V, NACCI A, MONOPOLI A, et al. Cyclic carbonate formation from carbon dioxide and oxiranes in tetrabutylammonium halides as solvents and catalysts[J]. Cheminform, 2002, 33(48): 2561-2563.
27	SUN J, WANG L, ZHANG S, et al. ZnCl₂/phosphonium halide: an efficient Lewis acid/base catalyst for the synthesis of cyclic carbonate[J]. Journal of Molecular Catalysis A: Chemical, 2006, 256(1/2): 295-300.
28	KIM H S, BAE J, LEE J S, et al. Phosphine-bound zinc halide complexes for the coupling reaction of ethylene oxide and carbon dioxide[J]. Journal of Catalysis, 2005, 232(1): 80-84.
29	KUMATABARA Y, OKADA M, SHIRAKAWA S. Triethylamine hydroiodide as a simple yet effective bifunctional catalyst for CO₂, fixation reactions with epoxides under mild conditions[J]. ACS Sustainable Chemistry & Engineering, 2017, 5(8): 7295-7301.
30	ZHOU Hui, WANG Guoxu, ZHANG Wenzhen, et al. CO₂ adducts of phosphorus ylides: highly active organocatalysts for carbon dioxide transformation[J]. ACS Catalysis, 2015, 5(11): 6773-6779.
31	SONG J, ZHANG Z, HU S, et al. MOF-5/n-Bu₄NBr: an efficient catalyst system for the synthesis of cyclic carbonates from epoxides and CO₂ under mild conditions[J]. Cheminform, 2009, 11(7):1031-1036.
32	ROKICKI G, KURAN W. Cyclic carbonates from carbon dioxide and oxiranes[J]. Monatshefte fuer Chemie, 1984, 115(2): 205-214.
33	GHOSH A, RAMIDI P, PULLA S, et al. Cycloaddition of CO₂ to epoxides using a highly active Co() complex of tetraamidomacrocyclic ligand[J]. Catalysis Letters, 2010, 137(1/2): 1-7.
34	RAMIDI P, MUNSHI P, GARTIA Y, et al. Synergistic effect of alkali halide and Lewis base on the catalytic synthesis of cyclic carbonate from CO₂ and epoxide[J]. Chemical Physics Letters, 2011, 512(4/5/6): 273-277.
35	PADDOCK R L, NGUYEN S T. Chemical CO₂ fixation: Cr(Ⅲ) salen complexes as highly efficient catalysts for the coupling of CO₂ and epoxides[J]. Journal of the American Chemical Society, 2001, 123(46): 11498-11499.
36	REITER M, ALTENBUCHNER P T, KISSLING S, et al. Amine-bis(phenolato) cobalt(Ⅱ) catalysts for the formation of organic carbonates from carbon dioxide and epoxides[J]. European Journal of Inorganic Chemistry, 2015， 10: 1766-1774.
37	RINTJEMA J, KLEIJ A W. Aluminum-mediated formation of cyclic carbonates: benchmarking catalytic performance metrics[J]. ChemSusChem, 2017, 10(6): 1274-1282.
38	WU Xiao, NORTH M. A bimetallic aluminium (salphen) complex for the synthesis of cyclic carbonates from epoxides and carbon dioxide[J]. ChemSusChem, 2016, 10(1): 74-78.
39	KIM So Han, HAN Sang Yeop, KIM Jeong Hee, et al. Monomeric or dimeric aluminum complexes as catalysts for cycloaddition between CO₂ and epoxides[J]. European Journal of Inorganic Chemistry, 2015, 13: 2323-2329.
40	ZHUO Chunwei, QIN Yusheng, WANG Xianhong, et al. Temperature-responsive catalyst for the coupling reaction of carbon dioxide and propylene oxide[J]. Chinese Journal of Chemistry, 2018, 36(4): 299-305.
41	PEÑA C L, FRAILE C. Fatty acid based biocarbonates: Al-mediated stereoselective preparation of mono-, di- and tricarbonates under mild and solvent-less conditions[J]. Green Chemistry, 2017, 19(15): 3535-3541.
42	MARTÍNEZ J, CASTRO-OSMA J A, ALONSO-MORENO C, et al. One-component aluminium (heteroscorpionate) catalysts for the formation of cyclic carbonates from epoxides and carbon dioxide[J]. ChemSusChem, 2016, 10(6): 1175-1185.
43	CASTRO-OSMA J A, NORTH M, WU Xiao. Development of a halide-free aluminium-based catalyst for the synthesis of cyclic carbonates from epoxides and carbon dioxide[J]. Chemistry: A European Journal, 2014, 20(46): 15005-15008.
44	CASTRO-OSMA J A, ALONSO-MORENO C, LARA-SÁNCHEZ A, et al. Synthesis of cyclic carbonates catalysed by aluminium heteroscorpionate complexes[J]. Catal. Sci. Technol. Chem. Eur. J., 2015, 21(27): 9850-9862
45	RULEV Y A, ZALINA G, MALEEV V I, et al. Robust bifunctional aluminium-salen catalysts for the preparation of cyclic carbonates from carbon dioxide and epoxides[J]. Beilstein Journal of Organic Chemistry, 2015, 11(49): 1614-1623.
46	VERMA S, SI M K, KURESHY R I. Chemical fixation of CO₂ to cyclic carbonates using Al(Ⅲ) β-aminoalcohol based efficient catalysts: an experimental and computational studies[J]. Journal of Molecular Catalysis A: Chemical, 2016, 417(11): 135-144.
47	MELÉNDEZ D O, LARA-SÁNCHEZ A, MARTÍNEZ J. Amidinate aluminium complexes as catalysts for carbon dioxide fixation into cyclic carbonates[J]. ChemCatChem, 2018, 10(10): 2271-2277.
48	TAHERIMEHR M, SERT J P C C, KLEIJ A W, et al. New iron pyridylamino-bis(phenolate) catalyst for converting CO₂ into cyclic carbonates and cross-linked polycarbonates[J]. ChemSusChem, 2015, 8(6): 1034-1042.
49	MONICA F D, VUMMALETI S V C, BUONERBA A, et al. Coupling of carbon dioxide with epoxides efficiently catalyzed by thioether-triphenolate bimetallic iron(Ⅲ) complexes SI[J]. Advanced Synthesis & Catalysis, 2016, 358(20): 3231-3243.
50	GUIDO P, GIULIO B, MARCO B, et al. Iron() N,N-dialkylcarbamates catalyze the formation of cyclic carbonates from carbon dioxide and epoxides at ambient conditions via dynamic CO₂ trapping as carbamato ligand[J]. ChemSusChem, 2018, 11(16): 2737-2743.
51	FRANCESCO D M, BHOLANATH M, THOMAS P. [OSSO]-type iron() complexes for the low-pressure reaction of carbon dioxide with epoxides: catalytic activity, reaction kinetics and computational study[J]. ACS Catalysis, 2018, 8(8): 6882-6893.
52	BUONERBA A, DE NISI A, GRASSI A, et al. Novel iron(Ⅲ) catalyst for the efficient and selective coupling of carbon dioxide and epoxides to cyclic carbonates[J]. Catalysis Science & Technology, 2015, 5(1): 118-123.
53	AL-QAISI, FEDA A, GENJANG N, et al. Synthesis, structure and catalytic activity of bis(phenoxyiminato) iron() complexes in coupling reaction of CO₂ and epoxides[J]. Inorganica Chimica Acta, 2016, 442: 81-85.
54	PENG Jing, YANG Haijian, GENG Yongchao, et al. Novel recyclable supramolecular metal complexes for the synthesis of cyclic carbonates from epoxides and CO₂ under solvent-free conditions[J]. Journal of CO₂ Utilization, 2017, 17: 243-255.
55	张锁江. 离子液体: 从基础研究到工业应用[M]. 北京: 化学工业出版社, 2006.
	ZHANG Suojiang. Ionic liquids: from basic research to industrial applications[M]. Beijing: Chemical Industry Press, 2006.
56	费腾, 张延强, 杜耀, 等. 自燃离子液体的研究进展[J]. 含能材料, 2016, 10(24): 1017-1028.
	FEI Teng, ZHANG Yanqiang, DU Yao, et al. Review on hypergolic ionic liquids[J]. Chinese Journal of Energetic Materials, 2016, 10(24): 1017-1028.
57	SONG Jinliang, ZHANG Binbin, ZHANG Peng, et al. Highly efficient synthesis of cyclic carbonates from CO₂ and epoxides catalyzed by KI/lecithin[J]. Catalysis Today, 2012, 183(1): 130-135.
58	PENG Jiajian, DENG Youquan. Cycloaddition of carbon dioxide to propylene oxide catalyzed by ionic liquids[J]. New Journal of Chemistry, 2001, 25(4): 639-641.
59	SUN Jian, ZHANG Suojiang, CHENG Weiguo, et al. Hydroxyl-functionalized ionic liquid: a novel efficient catalyst for chemical fixation of CO₂ to cyclic carbonate[J]. Tetrahedron Letters, 2008, 49(22): 3588-3591.
60	SUN Jian, CHENG Weiguo, ZHANG Suojiang, et al. Reusable and efficient polymer-supported task-specific ionic liquid catalyst for cycloaddition of epoxide with CO₂[J]. Catalysis Today, 2009, 148: 361-367.
61	ZHOU Yinxi, HU Suqin, MA Xiumin, et al. Synthesis of cyclic carbonates from carbon dioxide and epoxides over betaine-based catalysts[J]. Journal of Molecular Catalysis A: Chemical, 2008, 284(1/2): 52-57.
62	ZHANG Yuanyuan, YIN Shuangfeng, LUO Shenglian, et al. Cycloaddition of CO₂ to epoxides catalyzed by carboxyl-functionalized imidazoliumbased ionic liquid grafted onto cross-linked polymer[J]. Industrial & Engineering Chemistry Research, 2012, 51: 3951-3957.
63	HAN Lina, CHOI Hye-Ji, CHOI Soo-Jin, et al. Ionic liquids containing carboxyl acid moieties grafted onto silica: synthesis and application as heterogeneous catalysts for cycloaddition reactions of epoxide and carbon dioxide[J]. Green Chemistry, 2011, 13(4): 1023-1028.
64	RAJENDRA B. Synergistic effect of a binary ionic liquid/base catalytic system for efficient conversion of epoxide and carbon dioxide into cyclic carbonates[J]. Journal of CO₂ Utilization, 2019, 33: 284-291.
65	LIU Ning, XIE Yafei, WANG Chuan, et al. Cooperative multi-functional organocatalysts for ambient conversion of carbon dioxide into cyclic carbonates[J]. ACS Catalysis, 2018, 8: 9945-9957.
66	HU Jiayin, MA Jun, LIU Huizhen, et al. Dual-ionic liquid system: an efficient catalyst for chemical fixation of CO₂ to cyclic carbonates under mild conditions[J]. Green Chemistry, 2018, 20(13): 2990-2994.
67	LIU Fusheng, GU Yongqiang, ZHAO Penghui. Cooperative conversion of CO₂ to cyclic carbonates in dual-ionic ammonium salts catalytic medium at ambient temperature[J]. ACS Sustainable Chemistry & Engineering, 2019, 7(6): 5940-5945.
68	SHI Lijuan, XU Shaobo, ZHANG Qiri, et al. Ionic liquid/quaternary ammonium salt integrated heterogeneous catalytic system for the efficient coupling of carbon dioxide with epoxides[J]. Industrial & Engineering Chemistry Research, 2018, 57(45): 15319-15328.
69	刘雪静, 吕庆霖, 别福生. 一种环氧乙烷装置联产碳酸乙烯酯的方法: CN 108467383A[P]. 2018-08-31.
	LIU Xuejing, Qinglin LYU, BIE Fusheng. A method for producing ethylene carbonate by coupling of ethylene oxide absorption device: CN 108467383A[P]. 2018-08-31.
70	成卫国, 董丽, 褚俊杰, 等. 一种复合吸收剂及其用于环氧乙烷吸收转化耦合联产碳酸乙烯酯的方法: CN 201910785196.2[P]. 2019-11-12.
	CHENG Weiguo, DONG Li, CHU Junjie, et al. Absorbents for ethylene oxide absorption and conversion coupling production of ethylene carbonate: CN 201910785196.2[P]. 2019-11-12.

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