Co-pirólise catalítica de resíduo de polietileno e biomassa de eucalipto para obtenção de bio-óleo

Abstract

Research on sustainable energy sources has encouraged alternative conversion processes. Based on this context, the present work evaluates the co-pyrolysis of the lignocellulosic biomass mixture of eucalyptus (Eucalyptus) and low density polyethylene (LDPE) wood chips using Beta zeolite as a catalyst. The Beta samples employed have different Si / Al ratios (18 and 80) and are formed by aggregates of nanocrystals, which gives them significant mesopore / outer surface area and, therefore, with appropriate accessibility for the conversion of voluminous molecules. The reactions were performed in a two-stage system (thermal / catalytic), operating at 550 and 500 ° C, respectively. All the fractions produced (coal, coke, wax, bio-oil, water and gases) were quantified and characterized using standard analytical techniques for solid products (coal and coke). Thermogravimetric Analysis and Element Analysis (CHNS-O) , while the liquid product (bio-oil) analyzed by Karl Fischer, CHNS-O and Gas Chromatography / Mass Spectrum and, finally, the gaseous product monitored by the Gas Chromatograph. The evolution of the product distribution with the variation of the ratio catalyst / blend of biomass and polyethylene (C / M) was investigated. A maximum organic fraction yield (bio-oil) was observed for both samples at intermediate C / M ratios, ie with 40 and 50% catalyst, consisting mainly of linear hydrocarbons produced by cracking of LDPE, on the sites zeolite acid. The yield corresponding to this maximum was higher for the Beta sample with higher acidity (Si / Al = 18). The cracking of the wax fraction was accompanied by a significant reduction of the oxygen content of the bio-oil, which remarkably improved its fuel properties, indicating that positive synergistic effects occur during the copyrolysis of the mixture of lignocellulosic biomass and polyolefin plastics. Finally, it was observed that for the high C / M ratios, relative to 75% catalyst, the main components of the bio-oil fraction consisted of aliphatic and aromatic hydrocarbons from wax cracking, oligomerization / cyclization / aromatization of light olefins and Diels-Alder condensation between furans and light olefins. These results confirm the potential use of co-pyrolysis by using zeolite Beta that efficiently catalyzes the conversion of the blend (biomass / polyethylene) to low molecular weight hydrocarbons, reaching a high degree of deoxygenation.