Investigating the applicability of Athabasca bitumen as a feedstock for hydrogen production through catalytic supercritical water gasification

Abstract

Supercritical water gasification has been a promising technique for hydrogen production using several lignocellulosic biomasses and organic wastes. Various organic wastes such as sewage sludge, lignocellulosic biomass, municipal solid waste, industrial effluents and cattle manure that have been used as feedstocks for supercritical water gasification. With the objective of hydrogen production from alternative and less explored resources, Canadian Athabasca bitumen was used as a feedstock for supercritical water gasification in this study. Bitumen was gasified in supercritical water to examine the impacts of temperature (550–700°C), feedstock concentration (20–35wt%) and reaction time (15–60min) at the reactor pressure of 23MPa. The improvements in hydrogen yields with the use of four different heterogeneous catalysts such as FeCl3, ZnCl2, Ni/Si-Al2O3 and Ru/Al2O3 at 5wt% loading were targeted. Prior to gasification in a tubular batch reactor, bitumen was characterized for determining its ultimate composition (carbon-hydrogen-nitrogen-sulfur-oxygen, CHNSO analysis), surface organic functional groups (Fourier-transform infrared spectroscopy, FTIR) and devolatilization behavior (thermogravimetric analysis, TGA). In non-catalytic gasification, the highest hydrogen yields (2.26mmol/g) and total gas yields (4.68mmol/g) were obtained at 700°C in 60min of reaction time with 20wt% feed concentration. 5wt% ZnCl2 enhanced the gasification rate with hydrogen yields up to 3.57mmol/g. The overall catalyst activity towards maximizing hydrogen yields was in the order of ZnCl2>FeCl3>Ru/Al2O3>Ni/Si-Al2O3. This study is an initial attempt to determine the candidacy of bitumen as a possible resource for hydrogen generation.