Influence of the solid catalyst porosity on the products yields and composition from peanut shells pyrolysis

Abstract

Argentine is the first worldwide peanut (Arachis hypogaea) exporter, with around 600,000 tons per year of commercialization. Nevertheless, peanut production leaves around a 25 vol% of shells as residue of the process. This low density waste (0.10 kg/dm3) is actually burned or buried, causing serious environmental problems, or stored in silos but with an auto ignition risk characteristic of this kind of material. As an alternative in order to solve this issue and to obtain interesting chemical products, a catalytic pyrolysis process is proposed. In this sense, two type of porous solid materials were studied as catalysts for the reaction: a traditional microporous ZSM-11 zeolite (H-ZSM-11 micro) and a hierarchical form of the same class of MEL zeolite (H-ZSM-11 micro/meso). From the pyrolysis reaction three products lines are obtained: a liquid fraction, called bio-oil; a solid one, known as bio-char, and gases. The bio-oil is a high energy density liquid fuel, which could be used as substitute of fuel-oil [1]. However, high oxygen compounds concentration is obtained from the thermal process that makes this product of reduced stability and poor heating value. We propose the use of the above mentioned zeolites as catalysts for the in situ cracking reactions for the deoxygenation of the components and to obtain high value chemical products.