Effect of flue gas impurities in carbon dioxide from power plants in the synthesis of isopropyl N-phenylcarbamate from CO2, aniline, and 2-propanol using CeO2 and 2-cyanopyridine

Current CO2 utilization technologies generally start with purification of CO2, which requires considerable energy input. Using CO2-containing flue gases as a feedstock in chemical conversions of CO2 can help simplify pre-treatment of CO2 and reduce the carbon footprint of the process, however, study of the effects of other components in the flue gases in chemical reactions using CO2 is limited. Our previous study demonstrated that the combination catalyst system of CeO2 and 2-cyanopyridine was effective for the reaction of pure CO2, aniline, and 2-propanol to afford isopropyl N-phenylcarbamate, which is a promising precursor for polyurethane, in over 90% yield. In this study, the addition effect of other components in CO2-containing flue gases namely N2, O2, SO2 (ppm-order) and NO2 (ppm-order) on the reaction was investigated. The addition of N2 and NO2 had almost no influence on the catalytic performance, however, that of O2 and SO2 had some negative effects. The addition of O2 decreased the selectivity and yield to the target carbamate due to the formation of aniline-derived byproducts such as aniline-coupling products and aniline-oligomers. The increase of the amount of 2-cyanopyridine and 2-propanol was effective for the suppression of the aniline-derived byproducts, providing a similar yield of the isopropyl N-phenylcarbamate to the case without any additives. The catalyst system was strongly poisoned by addition of SO2, and the activity of CeO2 was not recovered even by calcination treatment.