• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.204-208
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• 2014

This study investigated the effect of hydrogen permeance and selectivity, catalyst amount, $H_2O/CO$ ratio in a feed stream, and Ar sweep gas on the performance of a water gas shift reaction in a membrane reactor. It was observed that a minimum hydrogen selectivity of 100 was needed in a membrane reactor to obtain a hydrogen yield higher than the one at equilibrium and the hydrogen yield enhancement gradually decreased as the hydrogen permeance increased. The CO conversion in a membrane reactor initially increased with the catalyst amount and reached a plateau later for a membrane reactor with a low hydrogen permeance while the high CO conversion independent of a catalyst amount was observed for a membrane reactor with a high hydrogen permeance. For the $H_2O/CO$ ratio in a feed stream higher than 1.5, a hydrogen permeance had little effect on the CO conversion in a membrane reactor and it was found that a minimum Ar molar flow rate of $6.7{\times}10^{-6}mol\;s^{-1}$ was needed to achieve the CO conversion higher than the one at equilibrium in a membrane reactor.

• Korean Membrane Journal
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• v.6 no.1
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• pp.10-15
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• 2004

We developed a water-selective ceramic composite membrane for use as a dehydration membrane reactor for dimethylether (DME) synthesis from methanol. The membranes were modified on the porous stainless steel support by the sol-gel method accompanied by a suction process. The improved membrane modification process was effective in increasing the vapour permselectivity by removal of defects and pinholes. The optimized alumina/silica composite membrane exhibited a water permeance of 1.14${\times}$10$^{-7}$ mol/$m^2$.sec.Pa and a water/methanol selectivity of 8.4 at permeation temperature of 25$0^{\circ}C$. The catalytic reaction for DME synthesis from methanol using the membrane was performed at 23$0^{\circ}C$, and the reaction conversion was compared with that of the conventional fixed-bed reactor. The reaction conversion of the membrane reactor was much higher than that of the conventional fixed-bed reactor. The reaction conversion of the membrane reactor and the conventional fixed-bed reactor was 82.5 and 68.0%, respectively. This improvement of reaction efficiency can last if the water vapour produced in the reaction zone is removed continuously.

• International Journal of Industrial Entomology and Biomaterials
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• v.27 no.2
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• pp.322-325
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• 2013

In the present study, we report that the selection of operation mode is important to take the full advantage of nanofibrous membrane in enzyme immobilization. Silk fibroin nanofibrous membrane has been prepared by electrospinning, and a-chymotrypsin was immobilized as a model enzyme. When the immobilized enzyme was operated in the membrane reactor mode, the Michaelis constant, Km, was lower and the Vmax was higher compared to the batch reactor mode. No concentration gradient was observed in the membrane reactor mode and the immobilized enzyme was stable even after 7 times of re-use. Our results suggests that the enzyme immobilized nanofibrous membrane should be operated in the membrane reactor mode rather than in the bath reactor mode.

• Bulletin of the Korean Chemical Society
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• v.23 no.5
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• pp.674-678
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• 2002

The dehydrogenation of propane to propylene has been studied in an isothermal high-temperature shell-and-tube membrane reactor containing a Pd-coated ${\psi}$-Al2O3 membrane and a Pt/K/Sn/Al2O3 packed catalyst . A tubular Pd-coated ${\psi}$-Al2O3 membrane was prepared by an electroless plating method. This membrane showed high hydrogen to nitrogen permselectivities (PH2N2 = 10-50) at 400 $^{\circ}C$ and 500 $^{\circ}C$ with various transmembrane pressure drops. The employment of a membrane reactor in the dehydrogenation reaction, which selectively separates hydrogen from the reaction mixture along the reaction path, can greatly increase the conversion and enable operation of the reactor at lower temperatures. High hydrogen permselectivity has been confirmed as a key factor in determining the reactor performance of conversion enhancement.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.282-287
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• 2005

Palladium membranes, which are permselective to hydrogen separation, were used for the hydrogen purification and in membrane reactors for improving conversions by shifting the reaction equilibrium. Palladium/ceramic composite membranes were prepared by electroless plating technique and then etched in titanium chloride ($TiCl_4$) as a post treatment to enhance the membrane's durability. These membranes were used for membrane reactors in water gas shift (WGS) reaction. CO conversions for the membrane reactor were obtained according to experimental parameters and compared to the traditional reactor without a palladium/ceramic membrane. As a result, CO conversion using palladium membrane reactor at an appropriate condition was over 20~25% greater than that without the membrane reactor. The stability in the long-term test of up to 120 h for WGS reaction with the membrane reactor was good without the degredation of CO conversion.

• Journal of the Korean Institute of Gas
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• v.20 no.6
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• pp.95-101
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• 2016

For a natural gas steam reforming, comparative studies of the performance in a conventional packed-bed reactor and a membrane reactor, a new conceptual reactor consisting of a reactor with series of hydrogen separation membranes, have been performed. Based on experimental kinetics reported by Xu and Froment, a process simulation model was developed with Aspen $HYSYS^{(R)}$, a commercial process simulator, and effects of various operating conditions like temperature, $H_2$ permeance, and Ar sweep gas flow rate on the performance in a membrane reactor were investigated in terms of reactant conversion and $H_2$ yield enhancement showing improved $H_2$ yield and methane conversion in a membrane reactor. In addition, a preliminary cost estimation focusing on natural gas consumption to supply heat required for the system was carried out and feasibility of possible cost savings in a membrane reactor was assessed with a cost saving of 10.94% in a membrane reactor.

• Korean Membrane Journal
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• v.5 no.1
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• pp.68-74
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• 2003

Methane steam reforming (MSR) reaction for hydrogen production was studied in a membrane reactor (MR) using two tubular membranes, one Pd-based and one of porous alumina. A higher methane conversion than the thermodynamic equilibrium for a traditional reactor (TR) was achieved using MRs. The experimental temperature range was 350-500$^{\circ}C$; no sweep-gas was employed during reaction tests to avoid its back-permeation through the membrane and the steam/methane molar feed ratio (m) varied in the range 3.5-5.9. The best results (the difference between the MR conversion and the thermodynamic equilibrium was of about 7%) were achieved with the alumina membrane, working with the highest steam/methane ratio and at 450$^{\circ}C$. Silica membranes prepared at KRICT laboratories were characterized with permeation tests on single gases (N$_2$, H$_2$ and CH$_4$). These membranes are suited for H$_2$ separation at high temperature.

• Clean Technology
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• v.19 no.4
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• pp.379-387
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• 2013

Ethanol steam reforming reaction considered as a clean hydrogen production method is introduced in this paper. Reactivity and reaction rate equation of ethanol steam reforming reaction using various catalysts, reaction temperature, and molar ratio of ethanol and water will be discussed. In addition to introducing a membrane reactor combining a reactor and a separator, the effect of the use of a membrane reactor on an ethanol conversion and hydrogen yield will be compared to those from a conventional packed-bed reactor.

• Membrane Journal
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• v.8 no.3
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• pp.170-176
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• 1998

A study on the bioconversion of soluble starch to cyclodextrin(CD) homologue by CGTase was performed in the membrane-enzyme reactor equipped with a dead-end type membrane module. in the batch reactor, the total conversion of soluble starch to CD homologue was decreased rapidly from a maximum value of 45 % with increasing reaction time due to the product inhibition and breakdown of CD homologue to the reducing sugars. However, in the membrane-enzyme reactor, the total conversion of soluble starch was maintained at a constant value of 35 % throughout the reaction, since the membrane(MWCO = 10,000) promptly separated CD homologue from the reaction mixture. After the macdon for 24 hr in the membrane-enzyme reactor using a 10 % soluble starch solution, the cumulative production amount of CD homologue was about 3.7 kg/m$^2$ at the operating pressure of 2 atm.

• Journal of the Korean Institute of Gas
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• v.8 no.3 s.24
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• pp.16-23
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• 2004

A membrane reactor concept, which combines the typical characteristics of chemical reaction with separation process, has been analyzed and simulated in this study. The advantages of the use of a membrane reactor include chemical equilibrium shift towards higher reactant conversion and purer product than the traditional reactors. A membrane reactor model which incorporates a catalytic reaction zone and a separation membrane is proposed. The water-gas shift reaction to produce hydrogen was chosen as a model reaction to be investigated. The membrane reactor is divided into smaller parts by number of n and each part (named cell), which contains both reaction and product separation function is modeled. One of the membrane outlet streams is connected to the next cell, which is repeated up to the last cell. The simulation results can be used for various purposes including decision of optimum operating condition and membrane reactor design.