Sorption enhanced aqueous phase reforming of glycerol for hydrogen production over Pt-Ni supported on multi-walled carbon nanotubes

• Pt and Pt-based bimetallic catalysts are screened for H2 production in CAPR.
• Reaction pathways in CAPR over Pt-based bimetallic catalysts are proposed.
• 5Pt1.5Ni/CNT showed high glycerol conversion rate and carbon conversion to gas.
• Adding CaO in 5P1.5Ni/CNT significantly promoted hydrogen yield and selectivity.
• CO2 sorption facilitated water-gas shift reaction and inhibited methanation.

In this study, multi-walled carbon nanotubes supported Pt and Pt-based bimetallic catalysts were prepared and their catalytic activities were investigated to screen effective and economical catalyst for H2 production in catalytic aqueous phase reforming (CAPR) of glycerol. Nickel promoted Pt catalyst with optimized Ni:Pt molar ratio afforded highest glycerol conversion rate (81.21%) and carbon conversion to gas (15.3%) although hydrogen gasification ratio (7.2%) was poorer than that of noble metals promoted Pt-based bimetallic catalysts. Adding CaO significantly enhanced the fraction and selectivity of H2 over Pt-Ni catalyst and those of CH4 were reduced to a negligible level, which was possibly attributed to the facilitated water-gas shift reaction and inhibited methanation through in-situ CO2 sorption via carbonation. Results suggested that Pt-Ni bimetallic catalysts improved dehydrogenation–decarboxylation and dehydration–hydrogenation reactions, leading to high glycerol conversions. Introducing CaO further favored C–C bond cleavage towards high H2 yield. The catalytic performance can be completely recovered after regenerating the catalyst and adding sacrificial CaO. In terms of reduced consumption of precious metal catalyst, excellent catalyst performance and hydrothermal stability, combination of Pt-Ni bimetallic catalyst and CaO additive was identified as an effective catalytic system for H2 production in CAPR of glycerol.

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