PET waste as organic linker source for the sustainable preparation of MOF-derived methane dry reforming catalysts

Abstract

A catalyst made of Ni⁰ nanoparticles highly dispersed on a lamellar alumina support was prepared by an environmentally-friendly route. The latter involved the synthesis of an aluminum-containing metal–organic framework (MOF) MIL-53(Al) in which the linkers were derived from the depolymerization of polyethylene terephthalate (PET) originating from plastic wastes. After demonstrating the purity and structure integrity of the PET-derived MIL-53(Al), this MOF was impregnated with nickel nitrate salt and then calcined to form a lamellar Ni–Al₂O₃ mixed metal oxide with a high surface area (S_BET = 1276 m² g⁻¹, N₂ sorption). This mixed oxide consisted of nickel aluminate nanodomains dispersed within amorphous alumina, as revealed by PXRD and TPR analyses. Subsequent reduction under H₂ resulted in the formation of well-dispersed 5 nm Ni⁰ nanoparticles homogeneously occluded within the interlamellar porosity of the γ-alumina matrix, as attested by electron microscopy. This waste-derived catalyst displayed catalytic performances in the reaction of dry reforming of methane (DRM) as good as its counterpart made from a MOF obtained from commercial benzene-1,4-dicarboxylic acid (BDC). Thus, under similar steady state conditions, at 650 °C and 1 bar, the PET-derived catalyst led to CH₄ and CO₂ conversions as high as those on the BDC-derived catalyst, and its catalytic stability and selectivity towards DRM were excellent as well (no loss of activity after 13 h and H₂ : CO products ratio remaining at 1). Moreover, both catalysts were much better than those of a reference nickel alumina catalyst prepared by conventional impregnation route. This work therefore demonstrates the possibility of using plastic wastes instead of commercial chemicals to prepare efficient porous nickel–alumina DRM catalysts from MOFs, fostering the concept of circular economy.