Selective formation of fuel BXT compounds from catalytic hydrodeoxygenation of waste biomass over Ni-decorated beta-zeolite

Abstract

Upgrading of bio-oil extracted from the various components of biomass into transportation fuels is typically attained via surface-assisted hydrodeoxygenation (HDO) reactions. Date palm (Phoenix dactylifera) pits constitute an important category of waste biomass in many parts of the world. Herein, we report a comprehensive integrated experimental-simulation approach to investigate HDO process of vapor fraction generated from pyrolysis of date pits over the metal-supported catalyst Ni/H-Beta zeolite. The catalyst was synthesized and characterized using various techniques including XRD, FTIR, SEM-EDX, and TPR. Catalytic tests were carried out in a 2-stage catalytic reactor where pyrolysates from the first reactor flows over the catalyst placed in the second reactor. Selective formation of toluene (and other alkylated benzenes) indicates a profound selectivity towards the formation of benzene-toluene-xylene (BXT) fractions especially in the temperature range 200–400 °C. As the temperature increases, fragmentation and bimolecular reactions involving toluene leads to synthesis of unwanted PAHs, most notably azulene. Considering 3,4-altrosan as a model compound for the lignin content in date pits, governing mechanisms of HDOs, was mapped out using density functional theory (DFT) calculations. Results reported herein are expected to assist in the optimizing operational conditions that leads to the production of the valuable BXT fraction from pyrolysis of date pits.