**The key project “Synthesis of dimethyl carbonate via oxo-carbonyl method” will enter industrial production
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The **key industrial experimental project – ‘Production of 4,000 tons per year of dimethyl carbonate via liquid-phase oxidation of methanol’**, jointly funded by Hubei Xingfa Group Chemical Co., Ltd. and Yankuang Group Lunan Fertilizer Plant, is set to be completed and put into operation by the end of June. Wan Yicheng, general manager of Hubei Xingfa Group Chemical Co., Ltd., said that the total investment in this project is 68 million yuan, of which **10 million yuan has been invested. Upon completion, it will become the largest dimethyl carbonate production base in China, as well as the second-largest dimethyl carbonate production project in Asia. Dimethyl carbonate is a \"green\" organic chemical suitable for the 21st century; it serves as an important raw material in the production of polycarbonates, isocyanates, and urethanes. It can replace highly toxic substances such as dimethyl sulfate, fuel additives, and solvents, and is widely used in industries such as polymer synthesis, organic chemistry, fine chemicals, pharmaceuticals and pesticides, as well as environmental protection. Research and development of dimethyl carbonate in our country began in the 1980s; it was part of the **\"Eighth Five-Year\" and \"Ninth Five-Year\" research projects, and was also included as a key industrial trial project. In September 1999, Hubei Xingfa Group, in partnership with Hubei Qiyue Chemical Co., Ltd. and Huazhong University of Science and Technology, established Hubei Xingshan Xinglihua Chemical Co., Ltd. to undertake the research and development of a key industrial pilot project: \"The production of 4,000 tons per year of dimethyl carbonate through the liquid-phase oxidation carbonylation of methanol.\" In August 2002, the project passed the appraisal and acceptance conducted on behalf of the former **Planning Commission; it was determined that this technology possessed independent intellectual property rights, was the first of its kind in China and at the international forefront, and met the objectives and requirements of **industrial-scale testing. Subsequently, Hubei Xingfa Group, in collaboration with Lunan Fertilizer Plant of Yankuang Group, further industrialized this project; it is now in the preliminary preparation stage for industrial production.
Currently, the main industrial production methods for dimethyl carbonate (DMC) include the phosgene method, transesterification method, and methanol oxidative carbonylation method. (1) Phosgene method: The phosgene method was the first approach to achieve industrial production of DMC. However, due to the high toxicity of phosgene, the complexity of the process, its severe corrosive effect on equipment, and the high chlorine content in the resulting product, this method has been gradually phased out. Currently, there are basically no phosgene-based DMC production facilities either domestically or internationally. (2) Transesterification method: This process consists of two main steps. First, the raw material, either propylene oxide or ethylene oxide, reacts with CO2 under certain pressure and temperature conditions to produce crude propylene carbonate or ethylene carbonate. After removing the light components and catalyst using a distillation tower, high-purity propylene carbonate/ethylene carbonate is obtained ； The second step involves an ester exchange reaction between propylene carbonate or ethylene carbonate and methanol in the presence of a catalyst; the DMC-methanol azeotrope is obtained at the top of the tower. After condensation, it is sent to a pressurized distillation column where DMC is separated from methanol, and the crude DMC is refined to yield a high-purity product. After methanol is removed from the material coming out of the reaction vessel through distillation, propylene glycol or ethylene glycol is recovered. Unreacted substances such as methanol, propylene carbonate, or ethylene carbonate are recovered and reused. This production process is simple, with low emissions of waste materials. All large DMC manufacturers in China use this process; over the years, through continuous development and improvement, the conversion efficiency of this transesterification process has improved significantly. After years of operation, the transesterification process has now become highly mature. (3) Methanol oxidative carbonylation method: DMC is directly synthesized from methanol, carbon monoxide, and oxygen in the presence of a catalyst. This method does not cause any side effects, and it is a key process route that countries are focusing on developing. It can be further divided into two production processes: the liquid-phase method and the gas-phase method. Currently, foreign DMC process technologies are mainly in the hands of a few large companies such as Italy’s ENI, Japan’s Ube Industries, and the United States’ Texaco. The liquid-phase oxidative carbonylation process used by the Italian company ENI employs cuprous chloride as a catalyst, with methanol serving both as a reactant and a solvent. Typical processes include methanol oxidation carbonylation and the separation of DMC from methanol. In 1988, the Japanese company Daeail also utilized this technology to build an industrial plant with a capacity of 6,000 tons per year ； The low-pressure vapor phase process used by Japanese company Ube Industries employs palladium as a catalyst and methyl nitrite as a reaction intermediate, with the reaction taking place in two steps. The process flow includes steps such as synthesis, separation, purification, and the preparation of methyl nitrite. The product purity can reach over 99% ； The transesterification process developed by the American company Texaco involves the combined production of DMC and ethylene glycol from ethylene oxide, CO2, and methanol. The reaction occurs in two steps: CO2 reacts with ethylene oxide to form vinyl carbonate, which then reacts with methanol through an ester transfer reaction to produce DMC and ethylene glycol. Currently, China began research on the ester exchange method for producing DMC in the 1990s; the main research institutions involved include Zhejiang University, East China University of Science and Technology, Huazhong University of Science and Technology, Southwest Institute of Chemical Engineering, and Nanjing Chemical Industry Corporation. In 1995, the transesterification process developed by East China University of Science and Technology was successful, and a pilot plant with a capacity of 300 tons per year was built. Subsequently, a series of commercial production facilities were constructed, with capacities ranging from 500 to 1,000 tons per year. Zhejiang University, the Research Institute of Nanjing Chemical Industry Corporation, and others have also established corresponding industrial-scale facilities. The main plant of Tangshan Chaoyang Chemical Factory was one of the first manufacturers in China to use the transesterification process for the production of DMC, achieving a leap from pilot-scale production to industrial-scale manufacturing. Since then, this process has been used to build several production facilities in China with capacities of 5,000–10,000 tons per year; the process technology is mature and reliable, the facilities operate smoothly, and the product quality is good.
Sure, is there a more detailed version?