Dimethyl ether synthesis and distillation technology

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Dimethyl ether synthesis and distillation technologies. The production methods for dimethyl ether include: liquid-phase methanol dehydration method, gas-phase methanol catalysis method, one-step solid-phase catalysis method, and one-step liquid-phase catalysis method. The first two methods are two-step processes that require the production of methanol first before it is converted into dimethyl ether. In contrast, the one-step method for producing dimethyl ether offers advantages such as lower investment costs, reduced expenses, and better economic returns; it represents the highest level of technology and the prevailing trend in dimethyl ether production worldwide. Status of dimethyl ether production technology in China: The Southwest Research Institute of Chemical Industry conducted research on the production of dimethyl ether via the gas-phase dehydration of methanol, and its scale-up trial was approved in 1992. Guangdong Zhongshan Fine Chemical Industry Co., Ltd. used this technology to build a production facility with a capacity of 2,500 t/a, which came online at the end of 1994 and has been operating properly. Currently, the company is constructing another production facility with a capacity of 5,000 t/a. The Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences, has developed a process and catalyst for producing dimethyl ether through the gas-phase dehydration of methanol, and has built an industrial facility at fuel grade. The Shanghai Research Institute of Petrochemical Technology has also developed a process for producing dimethyl ether via the gas-phase dehydration of methanol. A production facility with a capacity of 2,000 t/a has been built. Many domestic chemical research institutions have also conducted research to varying degrees on the process of producing dimethyl ether from syngas in a one-step manner. According to available information, the Shanxi Institute of Coal Chemistry under the Chinese Academy of Sciences began researching the catalyst activity and reaction conditions for producing dimethyl ether from syngas in 1987, and synthesized dimethyl ether using a self-developed bifunctional catalyst at conditions of 275°C, 2.0 MPa, 1500 ml/(g·h), H2/CO = 2, and CO2 = 1%–2%. Its CO conversion rate can reach 75%, with a dimethyl ether selectivity of >84%. The Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, has conducted extensive research on the process technology for producing dimethyl ether from syngas. Studies have shown that under gas-solid phase conditions, the suitable conditions for dimethyl ether synthesis using the self-prepared copper-based bifunctional catalyst are: a reaction temperature of 270–300°C, a pressure of 4.0 MPa, a space velocity of 1500/h, a H2:CO ratio of (2–2.8):1, and a CO2 concentration of 5% (V). Under these conditions, the conversion rate of CO is >90%, and the selectivity of dimethyl ether among the organic products is >95%. A **patent** has been applied for the preparation of this catalyst (Application No.: 95121619.8). The Dalian Institute of Physical Chemistry, Chinese Academy of Sciences, conducted systematic research on the direct synthesis of dimethyl ether from syngas using a composite catalyst system, and selected the SD219-I, SD219-II, and SD219-III catalysts, all of which exhibited good catalytic performance. Under laboratory pilot-scale conditions of 220°C, 3.0 MPa, and 1000–1500 h-, the CO conversion rate can reach over 90%, while the selectivity for dimethyl ether is around 95%. Intermediate scale-up tests were conducted at 240°C, 3.5 MPa, and for 1000 hours; after 1000 hours of continuous operation, the one-way conversion rate of CO could reach 75–78%, with a selectivity for dimethyl ether of around 95%. This achievement passed the evaluation of scientific and technological achievements organized by the Chinese Academy of Sciences in 1996, winning the Special Prize for Scientific and Technological Progress, and a **patent was applied for (patent number ZL9211187.5). The Catalyst Research Institute at Zhejiang University conducted single-tube experiments using self-developed catalysts to achieve the one-step gas-phase direct synthesis of dimethyl ether from semi-water gas. The one-way conversion rate of CO can reach 60–83%, with a selectivity for dimethyl ether of 95%. After 1000 hours of catalytic operation testing as well as short-term destructive shock tests, the catalyst still maintains good activity and selectivity. This project passed the evaluation organized by the Zhejiang Provincial Science and Technology Commission, and was deemed to be at the leading level in China. Using this technology, a 1,500 t/a dimethyl ether production plant has been built by Hubei Tianli Industrial Co., Ltd. This device can produce both alcohol-ether fuels and dimethyl ether with a purity of over 99.9%; the one-pass conversion rate of CO is 70–80%, and the yield of dimethyl ether reaches 350 kg/t.h. The catalyst maintains good stability even after long-term operation. This facility is China’s first industrial plant to produce high-purity dimethyl ether via the syngas one-step process, and it passed the technical appraisal and acceptance organized by the Hubei Provincial Economic and Trade Commission on March 3, 2000. Based on extensive literature, domestic research in the gas-solid phase synthesis of dimethyl ether using syngas is basically on par with international standards. Status of dimethyl ether production technologies abroad: It is reported that research on the direct gas-phase dehydration of methanol began in 1965. The American company Mobil and the Italian company ESSO have separately studied methods for producing dimethyl ether through the gas-phase dehydration of methanol, using crystalline aluminum silicate as a catalyst. Germany was the first to achieve large-scale industrialization. Japan began using methanol to produce dimethyl ether in 1979. Currently, the total global production capacity of dimethyl ether exceeds 170,000 tons, with the gas-phase catalytic dehydration of methanol being the method primarily used. In the 1970s, Amoco in the United States began researching a process route for producing dimethyl ether from syngas, namely the one-step method. Based on laboratory research findings, the Danish company Hador Topsøe A/S developed a one-step gas-solid process using syngas, and in 1993 established a pilot plant with a capacity of 50 kg/day in Copenhagen, Denmark. This pilot plant has been in operation for 12,000 hours. During this period, the researchers optimized the operational parameters, completed the kinetic studies, and established kinetic equations. The company also plans to build a 7t/d industrial plant after 2000. Abroad, companies that have conducted extensive research on the three-phase bed process include NKK Corporation in Japan (Japan Steel Pipe Company) and Air Products & Chemical Inc. in the United States. With the support of Japan’s Ministry of International Trade and Industry, NKK Corporation (Japan Steel Pipe Company) began laboratory tests on a scale of 1 kg/day in 1989 using the three-phase bed process. Pilot plant tests at a scale of 50 kg/day were carried out in 1994, and an industrial demonstration plant with a capacity of 5 t/day was built in 1999. The company plans to construct the first set of plants with a capacity of 100–500 t/day between 2002 and 2005. In the 1980s, Air Products and Chemicals in the United States also developed and researched a process for synthesizing dimethyl ether from syngas using a three-phase bed method. A laboratory-scale unit was built in 1986, a pilot plant with a capacity of 4 t/day was constructed in 1991, and an industrial demonstration plant with a capacity of 100 t/day was built in 1999. The one-step liquid-phase catalytic process for producing dimethyl ether developed by Air Products and Chemicals Inc. achieves a high yield of dimethyl ether ； High one-way conversion rate of CO, low water content in the product, and low energy consumption for distillation ； The temperature distribution within the reactor is uniform, reducing the formation of side reactions ； The catalyst’s resistance to poisons is significantly improved compared to solid-contact reactions. This post was last edited by chqi527 on 2007-11-27 14:26.]