Solar Fuels Through Mixed Reforming of Biogas

Abstract

Solar reforming of biogas is a promising route for the carbon-neutral generation of syngas, with tailored fractions of hydrogen and carbon monoxide, as a versatile intermediate toward fuels and chemicals with low environmental impact, such as sustainable aviation fuels. The process features mixed steam and dry reforming, which are not yet industrially established. A catalyst test setup above lab scale was designed to facilitate catalyst performance tests and characterization under a wide range of practical conditions and to promote catalyst optimization. The catalyst test setup features a catalyst bed volume of 0.45 L and is close to industrial operation conditions, with effects such as limited heat transfer and potential pressure drop being relevant. In this setup, the feasibility of employing nickel-based catalysts for reaction conditions with increased amounts of carbon dioxide can be investigated in the temperature and absolute pressure ranges from 700 to 1000 °C and from 1 to 5 bar, respectively. With the beginning of the endothermic reforming reactions, the temperatures in the respective catalyst bed decreased by up to 100 K in comparison to the temperature of the heating source, showcasing the limited heat transfer that comes with larger setups. In addition, the setup allows the calculation of the formation rate of undesired coke at each moment during the experiment, ranging from 27.20 ± 9.78 g/min in a dry reforming experiment to 4.14 ± 4.45 g/min in a mixed reforming experiment. While methane conversion reached 73.0 ± 3.1%, carbon dioxide conversion did not exceed 28.2 ± 3.1%, highlighting the need for catalysts specifically tailored for the mixed reforming conditions and the option to test them under industrially relevant conditions as featured in the test rig introduced in this work.