syngas, biogas, reforming, hydrotalcite, catalyst, coke
Catalytic transformation of methane-carbon dioxide mixture, produced through anaerobic digestion of organic waste, to syngas is a promising route for the production of chemicals and fuels from biogas. Dry reforming of methane is expected to yield a syngas with a H2/CO molar ratio of one. However, occurance of reverse water gas shift reaction (RWGS) decreases hydrogen yield. Minimization of coke formation is another challenge. In the present study, Ni incorporated Mg and Ca based hydrotalcite-like materials were synthesized following one-pot (Ni-MgAlO and Ni-CaAlO) and impregnation procedures (Ni@MgAlO and Ni@CaAlO). Results proved that, catalysts with Ni/Mg or Ni/Ca ratios of 0.2 were highly stable and active in this reaction. Catalysts containing higher Ni contents caused significant coke formation. Catalytic performance of novel Ni-CaAlO was better than Ni-MgAlO, in terms of product distribution and hydrogen yield. Hydrogen and CO selectivities were both close to two with Ni-CaAlO while hydrogen selectivity was less than CO with Ni-MgAlO, due to RWGSR. In terms of coke formation, performance of Ni-MgAlO was much better, without deactivation during reaction, extending upto 50 hours at 600oC. Ni incorporated catalysts synthesized by the one-pot route yielded less coke formation than the materials prepared by impregnation.