On August 18, the first world’s pilot plant for non-phosgene synthesis of green TDI, independently developed by Shaanxi Coal Chemical Industry Technology and Development Center Co., Ltd., passed the 72-hour operation trials, which organized by Shaanxi Petroleum and Chemical Industry Association in Shaanxi,China.
This technology comprises 4 main processes: synthesis, separation, water washing and pyrolysis. It involves using the green chemical dimethyl carbonate (DMC) to replace the highly toxic phosgene and reacting with toluenediamine (TDA) to produce the intermediate Dimethyl toluene-2,4-dicarbamate (TDC) with a self-developed catalyst. After separation and water washing, toluene diisocyanate (TDI) is produced through pyrolysis with the help of catalysts.
Shaanxi Coal Chemical Industry Technology and Development Center initiated the research on the manufacture of TDI by non-phosgene method in 2014. After over three years of laboratory-scale study, the technical report was completed in August 2017. A pilot plant was inaugurated at the Center in August 2020. Subsequently, three trials were conducted in December 2020, March 2021 and August 2021 to validate the process, resulting in the successful production of TDI. Following supplementary trials and technical improvements, a successful trial was achieved in October 2023.
An expert group led by Professor Li Wenhong from the School of Chemical Engineering at Northwest University reviewed original records on site and carried out a full inspection of DCS control, analysis, field sampling, and other positions to ensure the authenticity and reliability of the test data. The test results indicated that the pilot plant operated smoothly, meeting the expected targets across all indicators. Compared to the conventional phosgene method, the process is milder, enabling higher intrinsic safety and less pollutant emissions.
TDI is an important organic intermediate used in the manufacture of polyurethane foams, which possess advantages such as flame resistance, low temperature resistance, wear resistance, and excellent insulation. TDI is widely employed in various industries including aviation, automobile, refrigeration, coatings, adhesives, sealants, and more. Currently, the phosgenation method is widely used for industrial TDI production, where phosgene is produced from carbon monoxide and chlorine, which is then reacted with TDA to produce TDI. Despite the maturity of this production technology, both phosgene and chlorine are highly toxic gases, and phosgene is particularly hazardous. This process results in environmental pollution, equipment corrosion, lower product quality arising from residual chlorine. Non-phosgene method can replace the traditional route to achieving low-carbon and eco-friendly production while reducing safety risks. This approach aligns with China’s dual carbon goals and industrial upgrading policies. The expert group recommends increasing efforts to strengthen the industrial application of this technology.
Translated by PUdaily
