Effect of acid pretreatment and process temperature on characteristics and yields of pyrolysis products of peanut shells

GUREVICH MESSINA, L.I.; BONELLI, P.R.; CUKIERMAN, A.L.

RENEWABLE ENERGY

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2017

0960-1481

Pyrolysis of acid pretreated peanut (Arachishypogaea) shells was examined inorder to improve the yield of liquids (bio-oils) and the characteristics of thethree kinds of pyrolysis products. Also, pyrolysis of the pristine shells wascomparatively investigated. The acid pretreatment was carried out employing adilute HCl solution and it successfully diminished the ash content of theshells. Pyrolysis assays were performed in a fixed-bed reactor at differentprocess temperatures (400 °C, 500 °C, and 600 °C). The maximum bio-oil yieldwas obtained at a temperature of 500 °C for both the pretreated and the pristine shells, but pyrolysisof the formers yielded more bio-oils than the untreated ones (42 wt% vs. 33wt%). The increase of the process temperature resulted in a reduction of thesolid (bio-char) generation for both samples. Demineralization also led to afurther reduction of the bio-char yield. Regarding the productscharacteristics, neither the pretreatment nor the temperature had a noticeableinfluence on the elemental composition of the bio-oils. However, water content ofthe bio-oils was lower for the ones arising from pyrolysis of the demineralizedshells although it increased with growing process temperature. Likewise,pyrolysis of the demineralized shells resulted in bio-chars with less ash,improving their potentialities as bio-fuels. Also, the bio-chars arising fromthe treated shells at the higher temperatures (500 °C and 600 °C) resulted in higher BETsurface areas (up to 300 m2/g), pointing to their possible use as rough adsorbents or forfurther upgrading to activated carbons.