Catalytic Performance of Mg-La Promoted Ni/Al2O3 for Enhanced Tar Conversion to Fuel Gas

The promotion of MgO and La2O3 on Ni/α-Al2O3 catalysts for tar steam reforming reaction were carried out by two different methods, co- and sequential impregnation. By using toluene as a model compound, the findings indicate that conversion of gas products was improved with the use of prepared catalysts especially on syn-gas (H2 and CO) species. Increase in temperature significantly improved product yield and the highest conversions were obtained at the reaction temperature of 800°C. Comparing the efficiency of the co- and sequential impregnated catalysts at 800°C, it can be seen that the catalytic activity of N-L-M is lower than that of L+M+N (La2O3+MgO+Ni/Al2O3), M-N-L (MgO-Ni-La2O3/Al2O3) and L-N-M (La2O3-Ni-MgO/Al2O3). Above 700°C, LHV of gas product in catalytic reaction reached more than 3.69 MJ/m³ with maximum of 5.39 MJ/m³. The maximum energy efficiency was approximately 85-99% which was attained at the higher temperature of 700-800°C with L-N-M catalyst. For catalytic deactivation study in steam toluene reforming for 480 min at 800°C, all catalyst exhibited relatively high and stable fuel gas production rate. The activity of L+M+N, N-L-M and M-N-L in carbon conversion to CO resulted in the conversion of 45% on average. In addition, L+M+N showed the highest hydrogen conversion to H2 of approximately 60%. The order of decreasing converted H2 was found to be L+M+N > N-L-M > M-N-L > L-N-M. The spent L+M+N catalyst showed lesser amount of whisker carbon and encapsulating carbon. The used M-N-L catalyst had large amount of carbon deposition on the surface though the stable activity could be retained. It was reported that whisker coke