Influence of the operating parameters over dry reforming of methane to syngas

摘要

The influence of operating parameters over dry reforming of methane reaction was evaluated using a Ni-based catalyst obtained after calcination of a hydrotalcite-like precursor. The studied variables were mass to flow ratio (W/F), reaction temperature and CO_2/CH_4 ratio. Maximum methane and carbon dioxide conversions were achieved at W/F ratios above 0.21 g h L ~1. The higher the W/F ratio was, the lower amount of water was formed, which led to a higher H_2/CO ratio. The increase in reaction temperature produced an increase in conversions. Water concentration in the outlet stream showed a maximum at 600 ℃. At this temperature, reverse water-gas-shift reaction (RWGS) was favoured because it is endothermic. However, steam reforming and carbon gasification were also favoured and they consumed great part of the water produced. CO_2/CH_4 ratios above 1 led to a higher CH_4 conversion but selectivity to hydrogen decreased because RWGS reaction was favoured. When CO_2/CH_4 was below unity, CH_4 conversion decreased but less amount of water was produced so a higher H_2 selectivity was achieved. The catalyst exhibited good stability over dry reforming of methane under all the tested conditions, which may be ascribed to its high basicity. This property improved CO_2 adsorption and then RWGS reaction and carbon gasification.