Hydrothermal gasification of glucose for H2 production using Ni–Al2O3 nanocatalyst

Abstract

Hydrothermal gasification is a promising technology for converting biomass into syngas (H2/CO). A substantial challenge of hydrothermal gasification for producing hydrogen is the unwanted deposition of graphitic coke and metal particle agglomeration on the catalyst active sites. In this contribution, we hypothesize and examine controlling the active site nickel nanoparticle size (2, 9, 23 and 32 nm) through synthesis on supported mesoporous alumina (Al2O3). Nanoparticles were synthesized from nickel acetylacetonate (Ni(acac)2) by varying the molar ratio of oleylamine (OA) to trioctylphosphine (TOP) which gave controlled sizes of nanoparticles. Based on catalyst analysis, the 11 wt% Ni–Al2O3 containing 2 nm Ni was further evaluated for hydrothermal gasification of glucose for the production of syngas (H2/CO) at 500 °C temperature and 30 min reaction time. This nanocatalyst was found to significantly increase H2 yield compared to a previously prepared impregnated catalyst having larger Ni active sites. Graphitic coke deposition was minimized while the total organic carbon destruction (TOC) and carbon gasification efficiency (CGE) were both enhanced with the nanocatalyst. Almost double the yield of H2 (1.94 times higher) was achieved compared to the impregnated catalyst. This is attributed to the larger surface area, higher percentage of metal dispersion and uniform size distribution of active metal nanoparticles on the support.