On August 18, the world's first non-phosgene TDI green synthesis process technology pilot test device independently developed by Shaanxi Coal Industry and Chemical Technology Development Center Co., Ltd.(hereinafter referred to as Shaanxi Coal Technology Center) was conducted in Huazhou District, Weinan City, Shaanxi Province Passed the 72-hour assessment and calibration organized by the Shaanxi Petroleum and Chemical Industry Federation.

The main process of this technology includes four sections: synthesis, separation, water washing and pyrolysis. That is, the green chemical dimethyl carbonate is used to replace the highly toxic phosgene, and is reacted with toluene diamine under the action of a self-developed special catalyst to produce the intermediate product toluene methyl dicarbamate (TDC). After separation and washing, it is used under the action of a special catalyst. Pyrolysis to prepare toluene diisocyanate (TDI).

In 2014, Shaanxi Coal Technology Center established a project to carry out the research and development of the non-phosgene TDI green synthesis process. After more than three years of laboratory pilot research, the technical report was completed in August 2017. In August 2020, the pilot test device was built at the Shaanxi Coal Technology Center test base in Huazhou, Weinan, and then three commissioning tests were carried out in December 2020, March and August 2021, which opened the process flow and obtained the target product TDI. After supplementary experiments and technical transformation, the commissioning was successful again in October 2023.

The assessment expert group led by Li Wenhong, a professor at the School of Chemical Engineering of Northwest University, reviewed the original data records on site and conducted a full inspection of DCS control, analysis, on-site sampling and other positions to ensure that the assessment data were true and reliable. The assessment results show that the pilot plant is running smoothly, and all indicators have achieved the expected goals. Compared with the traditional phosgene method route, the reaction process conditions are milder, which improves the intrinsic safety level and reduces the emissions of "three wastes".

It is reported that toluene diisocyanate is an important organic intermediate used to make polyurethane foams. It has the advantages of flame resistance, low temperature resistance, wear resistance and high insulation. It is widely used in aviation, vehicles and ships, refrigeration and coatings, adhesives, sealants and other fields. At present, TDI production at home and abroad is based on the phosgene process, which uses carbon monoxide and chlorine as raw materials to produce phosgene, and then reacts with toluene diamine to produce TDI. Although the production technology is mature, phosgene and chlorine are both highly toxic gases. In particular, phosgene is more dangerous and has problems such as environmental pollution, equipment corrosion, and residual chlorine affecting product quality. The non-phosgene TDI green synthesis process can replace the traditional phosgene process route, which not only achieves low-carbon green but also reduces safety risks, and is in line with the national "double carbon" goal and industrial policies for the transformation and upgrading of the chemical industry. The assessment expert group recommended increasing the industrialization promotion and application of this technology. Source: Shaanxi Petrochemical News