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Steam reforming of natural gas for the production of hydrogen at low operation temperature offers significant financial and environmental advantages. However, the presence of higher hydrocarbons as minor components of natural gas can significantly affect the formation of coke and thus the effectiveness of the catalyst. In this study, the effect of the presence of C2–C3 alkanes in the feedstock on the carbon accumulation during low temperature steam reforming of methane is investigated over Ni and Rh catalysts supported on lanthanum doped ceria–zirconia mixed oxide. Both catalysts showed high resistance to coke formation and especially in the case of Rh/La/CeO 2 –ZrO 2 , the carbon accumulation detected was low even after 10 h on stream in steam reforming of all mixtures of hydrocarbons tested. The presence of higher alkanes in methane increased the amount of carbon on Ni(10)CeZrLa compared to pure methane as well as the nature of the carbonaceous species. Increase in the C-number of the additive alkane had almost no influence on the total amount of carbon formed (C/H feed ratio = constant) but favored the formation of filamentous carbon.

The catalytic performance on steam reforming and carbonaceous deposits was examined over Ni/La/CeO2-ZrO2 and Rh/La/CeO2-ZrO2 catalysts, prepared via wet impregnation. The catalytic performance tests were conducted using mixtures of C2–C4 alkanes and CH4 as steam reforming feedstock for 4 h at the temperature range of 400–550 °C and for 10 h at 500 °C, with S/C = 3 and GHSV = 70,000 h−1. Analysis on the used catalysts was carried out via temperature-programmed oxidation (TPO). Both catalysts showed high activity towards the alkane feedstock achieving product distribution close to that predicted by thermodynamics with no significant deactivation during the experiments. TPO of the used catalysts after 10 h on stream showed increased carbon depositions compared to the pure methane reforming but still at very low levels, even though the concentration of the second alkane used was much higher than the real concentration in natural gas.