Biomass pyrolysis oils for hydrogen production using chemical looping reforming

Abstract

This study considers the feasibility of using highly oxygenated and volatile pyrolysis oils from biomass wastes as sustainable liquid fuels for conversion to a hydrogen-rich syngas using the chemical looping reforming process in a packed bed. Pine oil and palm empty fruit bunches oil- ‘EFB’- were investigated with a Ni/Al2O3 catalyst doubling as oxygen transfer material (OTM). The effect of molar steam to carbon ratio (S/C) and weight hourly space velocity were investigated at 600 °C and atmospheric pressure on the fuel and steam conversion, the H2 yield and the H- and C-products distribution. With a downward fuel feed configuration and using a H2-reduced catalyst, maximum averaged fuel conversions of ∼97% for pine oil and 89% for EFB oil were achieved at S/C ratios of 2.3 and 2.6 respectively (on a water-free oil basis). This produced H2 with a yield efficiency of approximately 60% for pine oil and 80% for EFB oil notwithstanding equilibrium limitations, and with little CH4 by-product. Both oils exhibited very similar outputs with varying S/C. Upon a short number of cycles, i.e. starting from an oil-reduced catalyst, the fuel conversion dropped slightly but the steam conversion was constant, resulting in a slow decrease in H2 yield. Despite their high level of oxygen content, the pyrolysis oils were shown to maintain close to 90% reduction of the oxidised catalyst upon repeated cycles, but the rate of reduction decreased with cycling.