Comparison of volatile stream compositions obtained by the thermal and catalytic pyrolysis of date palm seeds

Abstract

The thermal and catalytic pyrolysis of date palm seeds have been studied in a Py-GC/MS equipment and the components formed in their degradation have been identified and quantified to a certain extent. Thermal pyrolysis has been studied in the 450–600 °C range. Catalytic pyrolysis on a HZSM-5 zeolite have been carried out at 450 °C, with the catalyst/biomass ratios used being 1, 2 and 5. The temperature of 450 °C has been chosen in order to minimize energy requirements.Concerning thermal pyrolysis, acids, ketones, furans and anhydrosugars are the most abundant compound families in the condensable fraction, with their relative content being almost constant with temperature, except that of the anhydrosugar family, which decreases as temperature is increased. Concerning catalytic pyrolysis, the HZSM-5 zeolite has a great influence on product distribution, with the hydrocarbon yield, especially that of aromatics, being higher than in the thermal cracking and that of oxygenate compounds lower. In the gas fraction, the high content of propene and butenes is remarkable. Concerning the condensable fraction obtained in the catalytic pyrolysis, a detailed analysis of the aromatic compounds has been conducted, as it is a key factor for the bio-oil potential applications. Thus, the content of mononaromatic compounds increases more sharply than that of polyaromatic ones when the C/B ratio is increased. The relative content of all aromatic compounds or compound families increases as the C/B ratio is increased, except benzene derivatives, whose content peaks for C/B = 2, and then decreases for C/B = 5.