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The conversion of equilibrium-limited reactions can be efficiently improved by selective removal of product using a Pervaporation Membrane Reactor (PVMR), which attracts substantial attentions due to its excellent performance. For modeling the PVMR process, a pseudo-binary system was often assumed, nevertheless, it is inadequate to predict the performance when both the reactant and product have the similar properties and can simultaneous permeate through the membrane. A detailed model was established by coupling multi-component pervaporation and reaction kinetics with the butanoxime hydrolysis reaction employed as the experiment system. A modified Flory–Huggins (FH) approach and the Maxwell–Stefan (MS) formulation were used to describe the pervaporation model. The mass transfer fluxes and the concentration profiles of permeants within the membrane were modeled by a finite difference approach. Two coexisted behaviors, i.e. competitive adsorption and plasticizing effects were considered to influence mass transfer. The PVMR performance was predicted and a good agreement between experiment and calculation was obtained. The mechanism that how the simultaneous permeation of reactant and product influence the PVMR performance were further clarified in different operating conditions, including initial reactant concentration, downstream pressure, membrane thickness, ratio of membrane area to reaction volume, and temperature. [ABSTRACT FROM AUTHOR]

A composite catalytically active membrane was prepared focusing on the reduction of membrane mass transfer resistance to achieve a better esterification-pervaporation coupling performance. The effect of membrane preparation conditions on the membrane morphology was first evaluated. Under an optimized membrane preparation conditions, a “sandwich-like” composite membrane with a highly inter-connected sponge-like catalytic layer on a polyvinyl alcohol / polyethersulfone bilayer was obtained. The porosity of the membrane was found to be as high as 81.6%. A simple resistance-in-series model was developed to analyze the mass transfer resistance distribution in a traditional inert membrane reactor (IMR), a catalytically active membrane reactor (CAMR) with dense catalytic layer and a catalytically active membrane reactor with porous catalytic layer, respectively. Results showed that the preparation of a highly porous catalytic layer decreased the resistance of catalytic layer from 48.5% to 20.6% of overall resistances, leading to an enhanced water removal ability for the composite membrane. Finally, reaction-separation coupling experiments in IMR, CAMR with porous catalytic layer and CAMR with dense catalytic layer showed that, with a faster reaction kinetics and water removal rate, CAMR with porous catalytic layer exhibited a best coupling performance. [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]