Enhanced production of aromatic hydrocarbons and phenols by catalytic co-pyrolysis of fruit and garden pruning wastes

Abstract

Nowadays, urban bio-wastes (food, park and garden residues) are mainly processed into compost and biogas for energy recovery, or even directly landfilled without exploiting their potential as feedstock for valuable products. As an alternative, this work reports a comprehensive experimental study for their potential valorization via catalytic co-pyrolysis. For that, different mixtures of fruit wastes (FW), a representative component of food refuse, and garden pruning residues (GP) were co-pyrolyzed in presence of a nano-ZSM-5 zeolite (and in absence of catalyst for comparison purposes) in an ex-situ fixed-bed reactor to evaluate the occurrence of different interactions that may affect the yield and properties of the pyrolysis bio-oil* (water-free basis). All pyrolysis fractions were characterized and the composition of bio-oil* was exhaustively identified and quantified, going further than the previous works devoted to the co-pyrolysis of feedstock comprising lignocellulose and fruit wastes usually performed at microgram scale (using micropyrolysis), with intrinsic limitations in terms of the product yields and properties determination. Thus, we found that the incorporation of higher FW amounts in the feed mixture led to lower oxygen contents in the bio-oil*, improving its quality and its potential use as bio-fuel. Moreover, the bio-oil* composition was notably narrowed to marketable chemicals, both phenolic derivatives (cresols and phenol) and especially monoaromatics (mainly xylenes and trimethylbenzenes).