Polyurethane Recycling: Thermal Decomposition of 1,3-Diphenyl Urea to Isocyanates

Substituted urea linkages are formed during the production of polyurethane foam. To chemically recycle polyurethane toward its key monomers via depolymerization (i.e., isocyanate), it is essential to break the urea linkages to form the corresponding monomers, namely, an isocyanate and an amine. This work reports the thermal cracking of a model urea compound (1,3-diphenyl urea, DPU) into phenyl isocyanate and aniline in a flow reactor at different temperatures. Experiments were performed at 350–450 °C, with a continuous feed of a solution of 1 wt.% DPU in GVL. In the temperature range studied, high conversion levels of DPU are achieved (70–90 mol%), with high selectivity towards the desired products (close to 100 mol%) and high average mole balance (∼95 mol%) in all cases.