In-situ catalytic pyrolysis of peanut shells using modified natural zeolite

Abstract

In-situ catalytic pyrolysis of peanut (Arachis hypogaea) shells was investigated employing modified clinoptilolite. Likewise, conventional pyrolysis of the shells was explored to quantify the deoxygenation degree of bio-oil. Two solid catalysts obtained from natural clinoptilolite were used: one which retained most of the native cations and another one subjected to ion exchange treatment to develop Brønsted acid sites. These catalysts were characterized using different techniques, such as scanning electron microscopy with X-ray microanalysis, Fourier transform infrared spectroscopy by pyridine adsorption, and nitrogen sorptometry. Assays in a bench scale installation based on a fixed bed reactor were conducted at 500 °C and the yields of the three kinds of pyrolysis products (bio-oil, bio-char and gases) were determined. Likewise, the composition and other physical properties of the bio-oil and gases were investigated. Both catalysts led to reduce the oxygen content of the bio-oil, improving its high heating value. On the other hand, catalytic pyrolysis promoted a slight reduction in bio-oil production at expenses of an increase in gases generation. The catalyst subjected to ion exchange performed better than the native form as less water was generated in the catalytic cracking.