Hydrogen permselective membranes

E. Kikuchi and Y. Chen, Low-Temperature Syngas Formation by C02 Reforming of Methane in a Hydrogen Permselective Membrane Reactor , Stud. Surf. Sci. Catal. 107 547-53 (1997). 

One is membrane reactor to enhance one pass conversion of equilibrium limited HI decomposition reaction in the gas phase using the hydrogen permselective membrane. The other is concern with the membrane application to enhance the HI molality of HI-I2-H2O mixture in order to facilitate the separation of pure HI. These second application is caused by the lack of capability to distill the Hix solution for the concentration HI more than 56%. To reach the HI concentration of 56% by conventional distillation, even consume a significant huge of heat, the distillation process would be decreased the over all thermal efficiency of the process. 

M. Nomura, K. Ikenoya, S. Kasahara, S. Kubo, K. Onuki, Gab-Jin Hwang, Ho-Sang Choi, and Shin-ichi Nakao, Development of a hydrogen permselective membrane reactor using a silica membrane for the IS process, Proceeding of WHEC15-Yokahama, 242 (2004). 

E. Kikuchi, Hydrogen-permselective membrane reactors, CATTECH, 1997, 1(1), 67-74,... 

C. A. Udovich, Catalytic dehydrogenation of propane in hydrogen permselective membrane reactors, Ind. Eng. 

A growing interest in the membrane-assisted WGSR is manifested by a substantial volume of the published pertinent literature that could be grouped around the two most popular hydrogen permselective membranes, based either on palladium [46-55] or silica [56-59]. The cited references cover only the most recent and most representative examples. 

Microporous silica hydrogen permselective membranes have been extensively studied as a potentially more practical alternative to Pd membranes. Very recently, a comprehensive review was published, tackling various aspects of silica membrane synthesis, application and economics [63]. It was made evident that state-of-the-art silica membranes have good hydrogen flux and separation, as well as respectable thermal stability. However, the hydrothermal stability of a silica hydrogen permselective membrane is a key factor in determining its suitability for a commercial apphcation of membrane-assisted processes. 

It needs to noted, however, that the CO2 permselective membrane, which is in its developmental infancy, is conceptually more difficult than the much more versatile and close to commercialization H2-selective membrane. The principle of molecular size discrimination, which forms the basis of the hydrogen permselective membrane cannot be applied to CO2 separation since CO2 is larger than or of similar molecular size as the species that it must be separated from. The idea of membrane chemical functionalization , which is necessary to achieve selective separation of CO2, is difficult to implement and will most likely result in a significant limitation to the CO2 membrane range of applications. 

The application of a membrane reactor with a hydrogen permselective membrane to intensify H2S decomposition to hydrogen and sulphur at a lower temperature was first considered in the eighties [50, 73, 74]. However, the expected positive effects on H2S conversion observed with the early Vycor-based membranes were insignificant. Also, a zirconia-silica membrane developed more recently and applied to decomposition of H2S by Ohashi et al. [75] had only Knudsen selectivity and produced similar results. 

In the packed bed the catalyst is in a fixed configuration and in contact with a hydrogen permselective membrane. The most used packed bed configuration is the tubular one where the catalyst may be packed either inside the membrane tube or in the shell side, while the permeation stream is collected on the other side of the membrane (in case of hydrogen selective membranes) or one reactant is fed at the other side of the membrane (in case of oxygen selective membrane). 

M. H. Khademi, M. R. Rahimpour and A. Jahanmiri, Differential evolution (DE) strategy for optimization of hydrogen production, cyclohexane dehydrogenation and methanol synthesis in a hydrogen-permselective membrane thermally coupled reactor, Int. J. Hydrogen Energy, 2010, 35, 1936-1950. 

M. R. Rahimpour, H. R. Mottaghi and M. M. Barmaki, Hydrogen production from urea wastewater using a combination of urea thermal hydrolyser-desorber loop and a hydrogen-permselective membrane reactor. Fuel Process. TechnoL, 2010, 91, 600-612. 

The methane combustion configuration is sketched in Figure 3.14 and consists of two sections [44]. Hydrogen permselective membranes are integrated in a fiuidized reform-ing/shift top section where ultra-pure H2 is extracted and the energy required for the SR is supplied via in situ methane oxidation in a separate fluidized bottom section, where oxygen is selectively fed to the methane/steam feed via oxygen permselective membranes. 

Rahimpour, M.R. and Elekaei, H. (2009) Enhancement of methanol production in a novel fluidized-bed hydrogen-permselective membrane reactor in the presence of catalyst deactivation. International Journal of Hydrogen Energy, 34 (5), 2208-2223. 

Collins, J.P., Schwartz, R.W., Sehgal, R. et al. (1996) Catalytic dehydrogenation of propane in hydrogen permselective membrane reactors. Industrial and Engineering Chemistry Research, 35,4398 405. 

The thermodynamic limitations are partially reduced with the help of hydrogen permselective membranes they can remove hydrogen from the reaction mixture, and this produces better performances. Many configurations have been tested in most of the cases, membranes are only a tool to remove hydrogen, and they do not possess any catalytic power, with just a few examples about membranes that act as catalysts to be found in the literature, to our knowledge. 

Choi, H.-S., Ryu, C.-H., Hwang, G.-J. (2013). Obtention of Zr02-Si02 hydrogen permselective membrane by chemical vapor deposition method. Chemical Engineering Journal, 232, 302-309. 

Hydrogen permselective membranes. Hydrogen permselective membranes are used in the reformer to break the thermodynamic equilibrium barrier of the reforming reactions and to produce pure hydrogen in the membrane side. 

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