Catalytic steam reforming of biogas – Effects of feed composition and operating conditions

• A study of the steam reforming of biogas was conducted with a rhodium catalyst.
• The effects of temperature, feed composition (S/C, CO2/CH4), and GHSV were studied.
• 99% of the methane was converted at 650 °C, 19,600 hr−1, and [H2O/(CO2+CH4)] = 3.87.
• Net conversion of CO2 is favored at high CO2/CH4 ratios, high temperatures, and low H2O/C ratios.

A study was conducted on the steam reforming of biogas mixtures over a 4 wt.% Rh/La–Al2O3 catalyst, where the effects of temperature (590–685 °C), steam (S/C molar ratio = 1.28–3.86), CO2/CH4 molar ratio (0.55–1.51), and the gas hourly space velocity (9810–27,000 hr−1) on the conversions and product yields were evaluated. Within these ranges, temperature and steam had the most pronounced effect on methane and carbon dioxide conversions. The highest methane conversion observed was 99%. Low temperatures and high S/C resulted in a net CO2 production. The water gas shift reaction appeared to have a stronger effect on the CO2 conversion than the CO2 reforming reaction. Experimental methane conversions were lower than the equilibrium predicted values. Lower temperature operations yielded a lower carbon balance suggesting the tendency to form carbonaceous species other than CO, CO2, and CH4. The presence of CO2 in the biogas contributed to the CO yield (beyond that from CH4 steam reforming) only above certain CO2/CH4 ratios.