Hierarchical LTL Zeolite as an Efficient and Sustainable Solid Acid Catalyst for Replacing HCl in the Production of Polyurethane Intermediates

Abstract

In many industrially important reactions, caustic mineral acid catalysts have been successfully replaced with green solid acids such as zeolites. In this context, extensive efforts have been devoted to replacing HCl to produce methylenedianiline (MDA), a key intermediate in polyurethane production. Unfortunately, limited success has been achieved thus far due to low activity, selectivity towards the desired 4,4′‐MDA, and rapid catalyst deactivation. Here we report that meso‐/microporous hierarchical LTL zeolite exhibits unprecedentedly high activity, selectivity, and stability. The one‐dimensional cage‐like micropores of LTL promote the bimolecular reaction between two para‐aminobenzylaniline intermediates to selectively produce 4,4′‐MDA and inhibit the formation of undesired isomers and heavy oligomers. Meanwhile, the secondary mesopores alleviate mass transfer limitations, resulting in a 7.8‐fold higher MDA formation rate compared to solely microporous LTL zeolite. Due to suppressed oligomer formation and fast mass transfer, the catalyst exhibits inappreciable deactivation in an industrially relevant continuous flow reactor.

Self-evolutionary recycling of flame-retardant polyurethane foam enabled by controllable catalytic cleavage

“…Polyurethane (PU) foam is widely used in home building materials, vehicle seat cushions, and other fields due to its high open porosity, good resilience, chemical stability, etc. 1–3 In 2021, China consumed a staggering 6.69 million tons of polyurethane foam, attesting to its popularity. Despite its many benefits, however, the safe use and waste disposal of PU present significant challenges that must be tackled.…”