Title : Sustainable advancements in polyurethane monomer synthesis: Green pathways from CO2 to isocyanates
Abstract:
The increasing demand for eco-friendly materials has driven the development of a sustainable process for synthesizing polyurethane monomers directly from CO2, addressing both environmental and industrial challenges. This process incorporates CO2 to avoid the use of toxic phosgene to produce methylene diphenyl diisocyanate (MDI), a critical precursor for polyurethane production. A dual-functional Pd/CeO2 catalyst is employed for the oxidative carbonylation of diamines, achieving high yields of dicarbamates while effectively minimizing urea polymer formation through enhanced methoxylation reactivity. Moreover, a multi-step process utilizing methylene diphenyl diamine (MDA) as a key intermediate has been developed to synthesize CO2-based MDI. The process includes the generation of syngas from CO2 through dry reforming, selective catalytic hydrogenation of nitrobenzene to produce aniline, and the subsequent condensation of aniline with formaldehyde to form MDA. MDA is then converted to dicarbamates via oxidative carbonylation, followed by thermal decomposition to yield MDI. Process modeling and life cycle assessment demonstrate that this approach significantly reduces greenhouse gas emissions and environmental toxicity compared to traditional phosgene-based methods. This study establishes a scalable and eco-friendly pathway for the sustainable production of high-value polyurethane precursors.
