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A mathematical model was proposed to elucidate the mass transfer of a hollow fiber membrane absorption process taking the effect of membrane porosity into account. This model was derived based on the mass transfer differential equation and discretized considering the micropores on the membrane wall. The model was numerically solved by using upwind difference technique, and the solute concentration profiles were obtained. Effects of porosity under various conditions, including membrane pore size, fiber length, pH of absorbent and liquid velocity on the mass transfer process, were quantitatively investigated. The results indicated that the porosity plays an important role in forming the solute concentration profile, and thus influenced the mass transfer performance. Low porosity (or high pH and liquid velocity, or low fiber length) corresponded to the heterogeneous profiles, while opposite conditions led to the homogeneous profiles. The model gave calculation results in good agreement with experimental results. [ABSTRACT FROM AUTHOR]

Catalytically active membranes can realize chemical reaction and membrane separation simultaneously and have been recognized as an effective strategy for process intensification to offer smaller footprint, lower energy consumption, and enhanced process efficiency. Reaction-separation coupling involving high temperature reactions has traditionally evolved around inorganic membranes. However, great advancements have also been achieved on development of more versatile and abundant polymeric catalytically active membranes (pCAM) for a range of niche applications. This review is the first attempt to provide an overview of reaction-separation coupling by pCAM. Liquid phase reactions often occur at mild temperatures and the majority of studies dealing with pCAM are focused on these reactions. Research progress of reaction-separation coupling using pCAM for liquid phase reactions including fine chemical synthetic, photocatalytic and biocatalytic reactions is first examined. The limited studies on the use of pCAM for gas phase reactions are also summarized. Perspectives on the future development of pCAM and their potential applications are also highlighted. Image 1 • Polymeric catalytic membranes for reaction-separation coupling were reviewed. • Principles of different reaction-separation coupling processes were discussed. • Catalytic membranes for liquid phase reactions were critically examined. • Catalytic membranes for gas phase reactions were also summarized. • Perspectives on future development of catalytic membrane were highlighted. [ABSTRACT FROM AUTHOR]

Bioethanol is a promising substitute for fossil fuels and is mainly produced through yeast fermentation. However, in conventional batch fermentation process extracellular ethanol accumulation restricts yeast excretion of intracellular ethanol, and results in suppressed yeast viability and ethanol productivity. The present study reports a yeast-immobilized catalytically active membrane for efficient extracellular ethanol removal towards enhanced bioethanol productivity in pervaporation membrane reactor. The membrane was fabricated by immersion phase inversion through coating a porous yeast/polyethersulfone catalytic layer on a polydimethylsiloxane (PDMS) pervaporation membrane. Benefited from the high porosity of biocatalytic layer, the immobilized yeast exhibited superior fermentation capacity in high substrate concentration when compared with free yeasts. Most importantly, by comparing the fermentation performances in catalytically active membrane reactor (CAMR), inert membrane reactor and batch reactor, CAMR exhibited the highest ethanol productivity (3.05 g L−1 h−1) and yeast mass concentration (26.41 g L−1), indicating a superior yeast growth rate and viability in CAMR. We attribute this to a "genuine" in situ removal ability of the bio-catalytically active membrane: the extracellular ethanol was promptly removed from the vicinity of the yeast, promoting a more rapid excretion of the inhibitor (intracellular ethanol) and thus maximally eliminated undesirable inhibition of the intracellular ethanol. • A yeast-immobilized catalytic membrane was fabricated by immersion phase inversion. • Superior fermentation capacity was obtained in high substrate concentration. • The catalytic membrane enhanced ethanol productivity in PVMR. • An increase of 35% in ethanol productivity was achieved. • The membrane exhibited a robust durability during long-time coupling process. [ABSTRACT FROM AUTHOR]