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

C. FERMANELLI; E. DIGUILIO; L. PIERELLA; C. SAUX

Congreso; 2nd International Bioeconomy Congress 2017; 2017

Argentina is the first worldwide peanut (Arachys hypogaea) exporter, with around 600,000 tons per year of commercialization. Nevertheless, peanut production leaves around 25-vol% of shells as residue of the process. This low density waste (0.10 kg/dm3) is actually burned or buried, causing serious environmentalproblems, or stored in silos but with an important auto ignition risk. As an alternative to solve this issue and to obtain interesting chemical products, a catalytic pyrolysis process is proposed. In this sense, two types of porous solid materials were studied: 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).The pyrolysis reaction generates a liquid fraction (bio-oil), a solid one (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 making 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.ZSM-11 zeolites were obtained from the traditional hydrothermal crystallization method [2].To obtain the hierarchical material, the obtained solid was further desilicated with aqueous NaOH at 65 °C for 30 min. Both materials, as synthesized and desilicated, were finally exchanged with a NH4Cl solution, desorbed in N2 flow and further calcined at 500 °C. The obtained solids were called H-ZSM-11 micro and H-ZSM-11 micro/meso, respectively. The fresh and used materials were widely characterized.The pyrolysis reactions were done in a fixed bed reactor at 500 °C with a 60 mL/min N2 flow for 10 min. For comparison purpose, thermal and catalytic processes were carried out. Condensable products were collected in a bath with refrigerant mixture and then analyzed and quantified in a GC and GC/MS chromatographs.Bio-char yields were quiet similar with both studied catalysts, but bio-oil production was 7 % higher when hierarchical material was employed. Besides, the liquid composition presented higher toluene, styrene, 5-hydroxymethylfurfural concentrations, that are chemical compounds of interest for the fine chemical industry.Better bio-oil yields were obtained when H-ZSM-11 micro/meso was employed as catalyst for peanut shell pyrolysis. Moreover, higher concentrations of desired products on the liquid fraction of products were achieved when the hierarchical zeolite catalyzed the reaction. In this sense, the use of zeolites is beneficialfor interesting chemical production, particularly the desilicated H-ZSM-11.