Efficient alcoholysis of waste rigid polyurethane foam using MIL-101(Fe) catalyst

Abstract

A considerable quantity of rigid polyurethane foam (RPUF) waste is generated on an annual basis as a consequence of the dismantling of refrigerators across the globe. In this study, waste RPUF from refrigerators was converted into recycled polyols by efficient alcoholysis, catalysed by a metal–organic framework (MOF). The experimental findings indicated that the utilisation of 5 wt% MIL-101(Fe) as a catalyst at 195 °C for a period of four hours resulted in a polyol yield of 78.3 %. Ligand modulation enabled the formation of a spatial structure within MIL-101(Fe), thereby facilitating the intercalation of polymers. This structure provided a supportive framework for domain-specific catalysis within the pores, thereby facilitating targeted catalytic alcoholysis of polyurethane. The viscosity of the polyol catalytically recovered using MIL-101(Fe) was maintained at approximately 670 mPa·s, and the hydroxyl value was maintained at over 270 mgKOH/g, which represent significantly improved values in comparison to those obtained through the traditional chemical alcoholysis method. Furthermore, the yield of recovered polyols over MOF catalysts remained above 65 % after nine cycles. It is a viable proposition to utilise recycled polyols in the synthesis of RPUFs in lieu of virgin polyols. The flexural strengths of the prepared RPUFs ranged from 0.257 to 0.355 MPa, and the water absorption ranged from 0.03 % to 0.08 %. thereby offering a novel approach to the treatment of rigid polyurethane waste.