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.

A catalytic membrane hybrid system based on a cermet membrane with a channel size 〈d〉 of ∼0.12 μm has been produced using sol-gel processing. A layer of a superfine methanol conversion catalyst with the composition Cr₂O₃ · Al₂O₃ · ZnO has been formed on the inner surface of the channels, and a thin oxide coating of composition P_0.03Ti_0.97O_{2 ± δ} with a homogeneous porous structure and 〈d〉 ∼ 2 nm has been formed on the geometric membrane surface. The methanol conversion rate and the gas permeability of the membrane depend considerably on the methanol vapor and gas (H₂, He, CO₂, Ar, CH₄) flow directions. When methanol vapor diffuses toward the mesoporous layer, the catalytic activity is one order of magnitude higher and the gas permeability coefficients are 3–8 times lower than in the case of the reverse flow of the gaseous molecules. The temperature dependence of the gas permeability taking into account the possible types of mass transfer in porous solids suggests that, when the gases move toward the mesoporous coating consisting of phosphorus-modified titanium oxide, surface flow and activated diffusion dominate, whereas the reverse gas motion is dominated by free molecular flow.

The paper presents the characteristics of a laboratory-made water-selective composite membrane with a selective layer of hydrophobic polyvinyltrimethylsilane (PVTMS) for use in the processes...

Designing hollow fiber (HF) membrane modules occupies one of the key positions in the development of efficient membrane processes for various purposes. In developing HF membrane modules, it is very important to have a uniform HF distribution and flow mixing in the shell side to significantly improve mass transfer and efficiency. This work suggests the application of different textile 3D HF structures (braided hoses and woven tape fabrics). The 3D structures consist of melt-spun, dense HFs based on poly(4-methyl-1-pentene) (PMP). Since the textile processing of HFs can damage the wall of the fiber or close the fiber bore, the membrane properties of the obtained structures are tested with a CO₂/CH₄ mixture in the temperature range of 0 to 40 °C. It is shown that HFs within the textile structure keep the same transport and separation characteristics compared to initial HFs. The mechanical properties of the PMP-based HFs allow their use in typical textile processes for the production of various membrane structures, even at a larger scale. PMP-based membranes can find application in separation processes, where other polymeric membranes are not stable. For example, they can be used for the separation of hydrocarbons or gas mixtures with volatile organic compounds.