Silver nitrate in situ upgrades pyrolysis biofuels from brewer's spent grain via biotemplating

摘要

Bio-based hydrocarbon fuels made from carbonaceous wastes are a renewable and potentially carbon neutral alternative to conventional fossil fuels. Pyrolysis biofuels are limited largely because of a poor overall energy balance along with the fuel's high viscosity and high oxygen content. This study explores an integrated biorefinery approach to manage Brewer's Spent Grain (BSG) waste that combines in situ catalytic upgrading of pyrolysis fuel with production of value-added products to improve process economics. By incorporating silver nitrate via a wet impregnation method into BSG prior to pyrolysis, non-condensable gas (particularly hydrogen and ethane) production dramatically increases, while the evolution of methane is largely unchanged. Critically, the peak temperatures at which pyrolysis gases evolve are decreased by the incorporation of silver, suggesting that this process could lower required pyrolysis temperatures. The silver-treated pyrolysis bio-oil showed a considerable increase in furfural, an important precursor in many chemical processes. The silver-impregnated biomass also showed a decrease in 2-methyl-propanal and 2-methyl-butanal yields, and virtually eliminated detectable anthracene and pyrene. In conjunction with the evolved gas results, it is likely that molecular rearrangement and dehydrogenation pathways, as opposed to a complete thermochemical cracking of the bio-oil fraction, are responsible for the catalytic behavior observed. After pyrolysis, the biochar can be oxidized to yield bio-templated, green-synthesized silver micro- and nanomaterials. The integrated biorefinery approach offers a novel path for upgrading pyrolysis biofuels, unifying synthesis of micro- and nanostructured materials and fuel production.