Mesoporous nanocrystalline TiO2 supported metal (Cu, Co, Ni, Pd, Zn, and Sn) catalysts: Effect of metal-support interactions on steam reforming of methanol

Abstract

Mesoporous TiO2 supported Cu, Co, Ni, Pd, Sn and Zn catalysts (M-TiO2) were synthesized using facile one-step synthesis method and were characterized using BET, XRD, TGA-DSC, TEM, SEM-EDX, ICP-OES, and H2-TPR studies. The catalysts were further tested for steam reforming of methanol (SRM) to investigate their comparative catalytic performance. Depending on the nature of the metal component, the catalysts exhibited surface area, pore sizes, and TiO2 crystallite sizes in the range of 99–309m2/g, 2.63–4.69nm and 6.8–17.2nm, respectively. N2-physorption, TGA-DSC and XRD analysis demonstrated that the presence of metal in the TiO2 matrix stabilized the mesoporous structure by hindering the crystal growth during heat treatment and thereby preventing the collapse of porous structure. Furthermore, the characterization of 5–20% Zn-TiO2 catalysts indicated that there exist an optimum Zn loading to obtain highest surface area which was found to be 15% in the present study giving a high surface area of ∼258m2/g. This was consistent with the SRM studies where the activity increased up to 15% and then decreased significantly with further increase in Zn loading to 20%. The results of the SRM studies coupled with extensive TPR analysis of different M-TiO2 catalysts suggest that the specific metal-support interactions play a crucial role in controlling its performance on H2 production. The SRM activity order for different metals incorporated in mesoporous TiO2 was observed to be: Pd>Ni>Zn>Co>>Cu>>Sn. The Zn-TiO2 catalyst showed the lowest CO selectivity among the different catalysts studied.