Role of poly(N-vinyl-2-pyrrolidone) in Ni dispersion for highly-dispersed Ni/SBA-15 catalyst and its catalytic performance in carbon dioxide reforming of methane

Abstract

A poly(N-vinyl-2-pyrrolidone) (PVP)-assisted wet impregnation method has been developed for preparing highly-dispersed supported Ni/SBA15-PVP (1/X) catalysts, in which 1/X indicates the molar ratio of PVP polymer to Ni. XRD and TEM results of as-prepared samples showed that PVP addition could dramatically promote the dispersion of NiO on SBA-15, with the nPVP/nNi ratios in the range of 1/5000–1/1000. Whereas, severe sintering of NiO could be observed on Ni/SBA15-PVP (1/X) catalysts prepared with no PVP (1/X=0), insufficient PVP (1/X=1/7500) or superabundant PVP (1/X=1/100). These catalysts were employed to catalyze the carbon dioxide reforming of methane (CRM) reaction, and the optimized Ni/SBA15-PVP (1/X) catalysts (1/X=1/5000–1/1000) exhibited much better stability than others during the 25h test. Besides, the role of PVP addition during the preparation process was illustrated detailedly with Raman, 1H NMR, UV–vis, FTIR, and TPO characterizations. PVP would interact with Ni(NO3)2.6H2O to form complexes through the coordination of the oxygen and nitrogen atoms in the ring of PVP, with Ni2+, NO3− and H2O from the precursor during the drying step. Moreover, this complex could improve the stabilization, inhibit the redistribution and affect the decomposition behavior of the precursor, which ultimately led to a significantly improvement of the NiO dispersion on SBA-15 support.