Kenji Haraya

Capillary carbon molecular sieve membranes derived from Kapton for high temperature gas separation

Abstract The degradation of Kapton polyimide leads to a carbon membrane with a dense surface layer suitable for gas permeations. An integral asymmetric capillary carbon membrane was prepared by coagulation of polyamic acid solution which was imidized to a Kapton capillary and finally pyrolized to a capillary carbon membrane. Various preparation conditions have been studied. Single and mixed gas permeation experiments had been performed. The carbon membrane showed high permselectivities of 2000 for He N 2 and about 1000 for H 2 N 2 at 0°C, respectively. Even for a high temperature of about 250°C the He N 2 selectivity reached 170.

Improvement of ethanol selectivity of silicalite membrane in pervaporation by silicone rubber coating

In order to improve the pervaporation performance of silicalite membrane, two types of silicone rubber, KE45 and KE108, were coated on the membrane surface. The initial molecular weight of KE108 is high and vulcanizing starts when it comes into contact with moisture in air, whereas the initial molecular weight of KE45 is low and vulcanizing starts when it is mixed with a catalyst. KE108 was found to be more effective than KE45 in enhancing the ethanol selectivity of silicalite membranes. A membrane coated using a 3 wt.% KE108 hexane solution showed separation factor of α=125 with a total flux of 0.14 kg/m2 h.

Production of highly concentrated ethanol in a coupled fermentation/pervaporation process using silicalite membranes

The fermentation performance of a coupled fermentation/pervaporation process using silicalite membranes, which are ethanol permselective for an ethanol/water solution, was studied. The process exhibited about a 20% increase in an average glucose consumption rate as compared with that without the pervaporation unit. A strong correlation was observed between the membrane flux and the consumption rate. Ethanol concentrations in the permeates reached a maximum of 85% (v/v).

Concentration of fermented ethanol by pervaporation using silicalite membranes coated with silicone rubber

In order to stabilize the production of highly concentrated ethanol, a coupled fermentation/pervaporation process using ethanol permselective silicalite membranes coated with silicone rubber was studied. In case of the silicalite membrane without coating, the membrane flux and the ethanol concentration in the permeate decreased with the fermentation time. The completely recovered ethanol fermentation was 30% (w/w). This behavior partly resulted from the adsorption of succinic acid produced during the fermentation to the membrane. It was effective to coat a naked silicalite membrane with the silicone rubber in the production of concentrated fermented ethanol of constant concentration by pervaporation. During the fermentation, the ethanol concentration in the permeate was almost constant, about 70% (w/w) when the silicalite membrane coated with the silicone rubber was used. Even in the case of the fermentation/pervaporation using the coated silicalite membrane, the flux greatly decreased. It is suggested that the glycerol produced during the fermentation, which is not adsorbed by the membranes, might have affected the pervaporation fluxes.

Effects of preparation condition of photoinduced graft filling-polymerized membranes on pervaporation performance

Abstract Modification of poly(acrylonitrile) membrane was carried out by heterogeneous photoinduced graft polymerization of methyl acrylate from the vapor phase. The technique of transmembrane monomer flow has proved to be effective for filling pores. The effect of preparation conditions like initiator concentration, reaction time and monomer concentration on the membrane separation was investigated. These graft modified membranes showed benzene permselectivity for benzene/cyclohexane mixture (50/50, v/v) on pervaporation.

Alkene/alkane permselectivities of a carbon molecular sieve membrane

A carbon molecular sieve membrane, whose pore dimension is slightly changed upon mild activation, exhibits excellent permselectivities for alkene/alkane gas pairs.

Preparation of polyacrylonitrile ultrafiltration membranes for wastewater treatment

Abstract The preparation conditions of a polyacrylonitrile (PAN) ultrafiltration membrane for wastewater treatment was investigated. The PAN membranes were prepared by the phase-inversion process in a water gelation bath using casting solutions of varying compositions of PAN/polyvinylpyrolidone (PVP)/N,N-dimethylacetamide (DMAc) and showed a molecular weight cut-off of 50,000–500,000. Especially, the membrane prepared from casting solutions with PVP and annealed at 80°C in water showed high water flux with a molecular weight cut-off of 500,000. Furthermore, the composite membranes of PAN-acrylic acid, prepared by the photo-induced graft polymerization technique, improved high performance.

Application of a membrane reactor system to thermal decomposition of CO2

Abstract An yttria stabilized zirconia (YSZ) membrane reactor system was applied to enhance the direct thermal decomposition of CO 2 at high temperature. The decomposition rate of CO 2 and the permeation rate of oxygen through the membrane were measured and their equations were established. The reaction itself and the reactions involved in the separation process were analyzed by computer simulation. It was found that the YSZ-membrane reactor system may improve the final conversion in CO 2 decomposition. The experimental results were in good agreement with the model predictions presented in this study.

Molecular sieving effect of carbonized kapton polyimide membrane

Microstructural investigation implies that the extremely high gas permselectivity (molecular sieving effect) of a carbonized polyimide membrane results from the decrease of the interplanar spacing and voids.

A Study of Concentration Polarization Phenomenon on the Surface of a Gas Separation Membrane

Abstract Mass transfer coefficients on the surface of porous glass membrane were obtained from separation tests of H2-CO mixtures. These data agree with the correlation presented by Ghosh and Upadhyay for mass transfer on an impermeable wall. In addition, effects of the selectivity of membrane and bulk composition on the concentration polarization phenomenon are discussed and the limiting permeability which is affected by the polarization is represented as a function of mass transfer coefficient.