Membrane technology in bioconversion of lignocellulose to motor fuel components

Abstract

The use of lignocellulosic biomass is one of the promising technologies for the production of energy carriers (bioalcohols, biosyngas) and valuable chemicals. Lignocellulosic biofuels may be thought of as a material capable of substantially replacing oil to provide an efficient consumption of natural energy resources and an improvement of the environment. In the “bioreactor–membrane separator–catalytic reactor (converter)" circuit, all stages are considered to be key: (1) the pretreatment of lignocellulose and the development of fermentation, particularly the cultivation of novel strains of bacteria; (2) the design of energyefficient vapor/gas-phase membrane systems for (a) concentrating bioalcohols and (b) controlling the biosyngas composition; and (3) the development of catalyst systems for the conversion of bioalcohols to motor fuel components. The following sequential tasks are discussed in this brief review: (i) basic approaches to the pretreatment of lignocellulosic biomass aimed at preparing it for fermentation and enzymatic processing of lignocellulose, particularly the cultivation of novel strains of bacteria and their communities, to produce bioalcohols— ethanol and butanol—and thermochemical methods of lignocellulose conversion to products in the form of complex mixtures; (ii) the development of energy-efficient membrane concentrating of bioalcohols using hydrophilic and/or organophilic polymer membranes and the control of the composition of synthesis gas in the form of a multicomponent gas mixture using commercial gas-separation membranes; and (iii) the development of catalyst systems exhibiting high selectivity in the ethanol conversion to alkane and aromatic hydrocarbons (high-quality additives to motor fuels) and valuable olefins, particularly ethylene, propylene, and linear alpha-olefins up to C₁₀.