Biogas dry reforming over Ni-M-Al (M = K, Na and Li) layered double hydroxide-derived catalysts

Abstract

In this work, Ni-M-Al (M = K, Na, and Li) LDH-derived catalysts were evaluated for the biogas dry reforming. The catalysts were prepared by co-precipitation and characterized by SBET, XRD, TPR, NH3-TPD, CO2-TPD, SEM and TPO. Reactions were carried out in a fixed bed reactor with online GC analysis in step-wise mode in the range of 500–750 °C and the stability tests were performed at 700 °C. All prepared samples exhibited hydrotalcite-type structure. Differences in reducibility and in the acidity of oxides were observed. The acidity of the catalyst was in the order: NiLi > NiNa > NiK, which is in the opposite order of monovalent cation size. The NiLi catalyst showed the highest resistance to sintering during the reactions due to the higher reduction temperature of mixed oxides (Ni2AlO4 and NiAl2O4) which results in smaller Ni° crystallite size after reduction. The results at 700 °C showed that NiLi catalyst deactivation occurs mainly by carbon deposition, whereas the deactivation of NiK and NiNa catalyst occurs mainly by sintering. TPO results indicated different carbon species produced depending on how the reaction is performed. All the catalysts produced carbon nanotubes at 700 °C.