Vol.:(0123456789) 1 3 Topics in Catalysis https://doi.org/10.1007/s11244-019-01176-z ORIGINAL PAPER How to Valorize Peanut Shells by a Simple Thermal‑Catalytic Method Carla S. Fermanelli 1  · Emilce D. Galarza 1  · Liliana B. Pierella 1  · María S. Renzini 1  · Clara Saux 1 © Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract In this work, a simple thermal-catalytic system was used to valorize peanut shells (Arachis hypogaea), the residual biomass from the peanut industry. To accomplish this purpose, tin modifed MEL zeolites were synthesized to catalyze pyrolysis vapors reactions in order to improve bio-oil quality. The processes were conducted at 500 °C for 10 min, with biomass-to- catalyst ratio of 1:1. Proximate, ultimate and elemental analyses of the peanut shells were carried out. Biopolymer compo- sition and HHV were also determined. Thermal decomposition behavior of the raw material was assessed by TGA/DTG analysis. Tin was incorporated to the zeolite matrix by the wet impregnation method to obtain loads of 2, 5, 7 and 10 wt%. All the catalysts were characterized by XRD, TPR, FTIR and BET surface area. Liquid products composition was determined by GC–MS. The material with 5 wt% of tin showed the best results. The optimal combination of Lewis and Brönsted acid sites in this catalyst promoted the necessary reactions to enhance bio-oil quality. In this sense, hydrocarbons selectivity in the presence of the 5 wt% tin zeolite was ten times the one reached in the absence of catalysts. Likewise, 5-hydroxymethyl- furfural formation was favored, obtaining the highest selectivity with the same metal load on the catalyst. Keywords Biomass valorization · Pyrolysis · Residual biomass · Tin · ZSM-11 1 Introduction Considering that the term biomass includes all the organic materials that derive from plants, and that plants are the responsible to convert CO 2 into organic matter by photosyn- thesis, it is possible to close the carbon loop when biomass is employed as source of energy or chemicals [1]. Particu- larly, when biomass wastes are employed as raw material, the environmental advantage is improved. In this paper, we propose the valorization of peanut shells, since Argentina is one of the main global producers of this legume. In our country, more than a million tons of peanuts are produced per year [2], and about 25% of this production corresponds to shells [3] which, in general, lack value-added applications [4]. Some production industries send their residues to others that burn them to obtain elec- tricity [3]. Considering the low density of the peanut shells, high volumes of this waste should be transported, increasing the production costs of the legume. Nowadays there are several researches seeking to valorize biomass residues, looking forward to minimize their impact on the environment and trying to obtain fuels or chemicals from them. Diferent processes could be applied in order to convert biomass, such as thermal, biological or mechanical methods. Nevertheless, thermochemical processes seem to be the most promising ways to transform these low value bio-wastes considering their capacity to depolymerize most of the organic compounds [1]. Besides, lower reaction times are required for the reactions. Taking into account that pea- nut shells are mainly composed of cellulose, hemicellulose and lignin [5], from thermal options (combustion, pyrolysis, gasifcation and liquefaction), pyrolysis seems to be the indi- cated process for these rich in lignin materials. This process consists in the thermal decomposition of the biopolymers in absence of oxygen at 400–600 °C to yield char, oil and gaseous products [6]. The liquid fraction of pyrolysis products, called bio-oil, is a blend of organic molecules that could potentially be used as fuel, additives or as fne chemicals source. One major advantage is that the bio-oil is easier to transport than the shells. Nevertheless, high oxygen compounds (such as * Carla S. Fermanelli cfermanelli@frc.utn.edu.ar 1 Centro de Investigación y Tecnología Química (CITeQ), UTN – CONICET, Maestro Marcelo Lopez y Cruz Roja Argentina, 5016 Córdoba, Argentina