Experimental Characterization of Catalysts for Combined Reforming of Methane in Respect to Carbon Deposition

Abstract

The increasing demand for more environmentally friendly transportation particularly in the aviation sector and its impact on global warming urge for the production and utilization of sustainable fuels. This study investigated the incorporation of CO2 into the reforming process of methane to produce syngas, a key intermediate in the chemical industry. The aim was to investigate the influences of changes in the process parameters such as temperature, pressure and feed gas ratio and the impact on carbonaceous deposits which deactivate the catalysts. The preliminary thermal tests revealed that the limiting flow rate regarding an appropriate temperature dispersion within the tubular reactor lied below 25 sl/min, whereas flows of 5 sl/min and 1.5 bar revealed the best thermal distribution, lying within close proximity of three standard deviations of the mean temperature in the catalytic bed. The chemical experiments were conducted in between 1 bar and a maximum pressure of 4.5 bar, lower than typical downstream processes in the chemical industry, with a focus on thermal profiles within the reactor and the catalyst characterization based on conversion levels, carbon deposits and space-time-yields. Catalyst A was evaluated under varying process conditions, showing that elevated pressures and higher CO2 concentrations in the feed gas led to carbonaceous deposits on the catalysts. The observed reactions occurred within the kinetic regime, away from the thermodynamic equilibrium position. Generally, higher pressures positively influenced the conversion of the reactants, particularly of CO2. The experiments conducted at 1000 °C unveiled the highest conversion levels of CH4 and CO2, but simultaneously associated with a higher carbon deposition rate, based on the molar mass balance calculations. The results in dry reforming of methane revealed, that decreasing conversion levels due to coke deposits were accompanied with severe destruction of the catalyst pellets. When considering the production of Sustainable Aviation Fuels via Fischer Tropsch Synthesis, the experiments conducted between 800 °C and 900 °C and with a feed gas ratio of 1:0.9:2 denoting CH4, CO2 and H2O, respectively, showed the most suitable syngas range. Additionally, these results revealed to be amongst the lowest carbon deposition rates detected.