An inorganic membrane element and a pretreatment process are provided. The inorganic membrane element includes a tubular structure having an inner separating layer, an outer supporting layer, and at least one intermediate layer interposed between the separating and supporting layers, where the separating layer is nanoporous to selectively retain solutes while permitting the transfer of high-temperature solvents therethrough. The pretreatment process utilizes the inorganic membrane element to provide solubilized organics in concentrated form for the subsequent conversion into bio-fuels and other chemicals.
A process for the pretreatment of lignocellulosic biomass is provided. The process generally includes flowing water through a pretreatment reactor containing a bed of particulate lignocellulosic biomass to produce a pressurized, high-temperature hydrolyzate exit stream, separating solubilized compounds from the hydrolyzate exit stream using an inorganic nanoporous membrane element, fractionating the retentate enriched in solubilized organic components and recycling the permeate to the pretreatment reactor. The pretreatment process provides solubilized organics in concentrated form for the subsequent conversion into bio-fuels and other chemicals.