Steam reforming of bio-alcohols over Ni-M (Cu, Co, Pt)/MCF-S (MgO, La2O3, CeO2) for renewable and selective hydrogen production: Synergistic effect of MCF silica and basic oxides on activity and stability profiles

In the current investigation, highly active, and stable catalyst-support systems were developed by employing the benefits of the 3D mesoporous arrangement of MCF silica and O2- Lewis basic sites of MgO, La2O3, and CeO2 in a single system for renewable and selective H-2 production via steam reforming (SR) of bio-alcohols, viz., ethanol (SRE), glycerol (SRG), n-butanol (SRB), and ethylene glycol (SREG). The impact of aging time [24, 48, and 72 h] on structural and surface features of MCF silica was also investigated to develop novel type of mesoporous materials with the best textural properties, viz., Cu-Ni-Co/MCF-MgO for SRE, Ni-Cu/MCF-La2O3 for SRG, Pt-Ni-Cu/MCF-La2O3 for SRB and Ni-Cu/MCF-CeO2 for SREG which were characterized by several physio-chemical techniques; for instance, BET, H-2-TPD, H-2-TPR, TGA, XRD, TEM, SEM, EDX as well as high-resolution XPS analysis. The efficacy of the combination of MCF silica with basic metal oxides was evident from the results showing nearly complete reactant conversion, no coke formation, high selectivity (>84 % H-2 yield), and longterm stability beyond 680 h (> 68 h time on stream (TOS) for one cycle over > 10 cycles) for all bio-alcohols whereas MCF silica without any basic metal oxides, i.e. Ni-Cu/MCF was stable only up to < 64 h (< 16 h TOS for one cycle up to <= 4 cycles) due to the absence of O2- Lewis basic sites leading to coking. Such a huge difference in catalytic stability between MCF-S (MgO, La2O3, CeO2) and Ni-Cu/MCF catalysts clearly justifies the synergistic effect of the 3D mesoporous structure of MCF silica and O2- Lewis basic sites on high metal dispersion, strong metal-support interaction (SMSI), coke inhibition. It proved their efficacy as potential commercial SR catalysts for sustainable H-2 production from bio-alcohols. Finally, catalytic reaction mechanisms were developed for SRE, SRG, SRB, SREG and intrinsic reaction kinetics were studied over their corresponding catalyst-support systems in the absence of external mass transfer and intra-particle diffusion resistancs. The apparent activation energies for SRE, SRG, SRB, and SREG were calculated as 7.2, 11.2, 10.5, and 12.1 kcal/mol, respectively.