Benzofuran as deactivation precursor molecule: Improving the stability of acid zeolites in biomass pyrolysis by co-feeding propylene

Abstract

Benzofuran (BZF) is produced during the biomass and waste pyrolysis, playing a key role in the catalytic deactivation in the processing of the resulting fractions, as well as in catalytic pyrolysis reactions. The transformation of this chemical over a typical pyrolysis catalyst (ZSM-5) is studied in this article. When this compound is processed alone, it presents a very high reactivity. At low temperature, the formation of large amount of coke precursors leads to a fast catalyst deactivation. As temperature increases, the weight of cracking reactions (yielding benzenes or naphtalenes) becomes more important, increasing the catalyst’s stability, although new polyaromatic carbon species are detected.A new strategy to minimize the deactivation caused by this compound, consisting of co-feeding propylene, is proposed. The presence of an alkene leads to the formation of alkylated derivatives of Diels-Alder condensation products, hindering their oligomerization capacity and minimizing the formation of polyaromatic coke deposits. Different temperatures and alkene/BZF ratios were tested, concluding that increasing the alkene concentration and the reaction temperature monotonously increase the catalyst’s stability in presence of BZF.