Carbon2Polymer-Chemical Utilization of CO2 in the Production of Isocyanates

CO2 was investigated as carbon source for the synthesis of the polymer precursor toluene-2,4-diisocyanate (TDI). A four-step synthesis was envisaged. The first step, i.e., the Ru-catalyzed CO2 hydrogenation to [HCOOHamine] adducts, was carried out under biphasic conditions allowing for straightforward reutilization of the catalyst phase. The investigation of the second step, the esterification of formic acid with methanol to yield methyl formate (MF), is ongoing with a strong focus on the integration with the hydrogenation step. The potential hazards of the third step, the Pd-catalyzed oxidative carbonylation of toluene-2,4-diamine with MF, have been addressed developing a sophisticated protocol for a safe operation with organics/CO/O-2 mixtures. For the final step, the carbamate cleavage of toluene-2,4-dicarbamate (TDC) towards TDI, monofunctional model substrates and TDC were cleaved in the presence of bifunctional catalysts. The obtained kinetic data allowed to implement the reaction in a continuous stirred-tank reactor and will serve as starting point for further process optimization.