Synthesis of sustainable production chains for phosgene-related byproducts

Phosgenation reactions are accompanied by the formation of the byproduct hydrogen chloride, as well as the production of carbon dioxide. Byproduct recovery and valorization may have implications for resource recovery and elimination of pollutive practices. However, phosgene-related byproducts with respect to resource utilization, environmental performance, and techno-economic issues are yet to be investigated using a proactive and integrated approach. This study aims to systematically investigate the comprehensive utilization of phosgenation reaction byproducts. Different detailed utilization routines are proposed. The hydrogen chloride processing methods were evaluated and compared in terms of equipment investment, operation cost, waste discharge, and profit. The results show that, based on the processing of 1 t of hydrogen chloride, polyvinyl chloride, and epichlorohydrin have the best economic benefits, which are CNY 1418.73 and CNY 1463.22, respectively. However, they are wastewater-intensive. The operation cost of preparing hydrochloric acid and the amount of wastewater (CNY 305.72 and 0.028 t, respectively) are both less than that of alkali neutralization (CNY 3903.92 and 3.718 t, respectively). This study establishes an industrial chain scheme for phosgene-related byproducts that meet the requirements of a circular economy to achieve environmental sustainability.