Hydrogen permselectivity

Hydrogen-permselective silica membranes [8,10] can be, as well, synthesized by a particular application of solgel techniques [142,143], Additionally, hydrogen permselective asymmetric membranes composed of a dense ceramic of a proton-conducting perovskite over a porous support have been developed [40], However, some difficulties with respect to their stability is possible in certain reactive environments [121],... 

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). 

S. Morooka, S. Yan, K. Kusakabe and Y. Akiyama Formation of Hydrogen-Permselective Si02 Membrane in Macropores of a-Alumina Support Tube by Thermal Decomposition of TEOS , J. Membrane Sci., 101 89-98 (1995). 

S. Yan, H. Maeda, K. Kusakabe, S. Morooka and Y. Akiyama, Hydrogen-Permselective Si02 Membrane Formed in the Pores of Alumina Support Tube by Chemical Vapor Deposition with Tetraethyl Orthosilicate , Ind. Eng. Chem. Res., 33 2096-101 (1994). 

Membrane surface contamination. Although not as hydrogen selective as Pd and its alloys, other metals such as niobium and vanadium in dense form also have moderate to high hydrogen permselectivity and potentially can be considered as membrane materials. Inevitably the membrane surface is contaminated with non-metal impurities prior to or during separation or membrane reactor applications. 

Figure 11.7 Comparison of co-current and counter-current porous membrane reactors for decomposition of ammonia with a hydrogen permselectivity determined by Knudsen diffusion at 627 C [Collins ct al., 19931...

H.Y. Ha, S.W. Nam, S.A. Hong and W.K. Lee, Chemical vapor deposition of hydrogen-permselective silica films on porous glass supports from tetraorthoethyl silicate. /. Membr. Sci., 85 (1993) 279-290. 

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. 

In this study, the silica membranes to apply for HI decomposition reaction was investigated, and prepared by the sol-gel and the thermal chemical vapor deposition (CVD) methods. The objective of this work is to study the characteristics of the silica membrane preparation and the hydrogen permselectivity of the membrane reactor used for HI decomposition in the thermochemical water splitting IS 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). 

Dehydrogenation of paraffins extracts a mole of hydrogen from each molecule and introduces an olefinic double bond in the conversion to olefins. Since this reaction is reversible, conversion is limited by thermodynamics [2]. Carrying out the process in a membrane reactor having hydrogen-permselective walls would allow... 

For a composite membrane that is relatively free of pinholes, there is apparently a limiting palladium thickness that depends primarily on support quaUty and somewhat on deposition method. For example, unmodified PSS requires at least 10 pm of palladium to bridge a majority of the pores [149, 227]. Invariably, a few macrodefects remain that preclude the attainment of perfect hydrogen permselectivity. On porous asymmetric a-alumina supports with 100-200 nm pore size on the surface, approximately 7 pm appears to be the limiting thickness that is proba-... 

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. 

N. Itoh, T. Akiha, T. Sato, Preparation of thin palladium composite membrane tube by a CVD technique and its hydrogen permselectivity, Catal. Today 2005, 104, 231-237. 

S. Araki, H. Miyanidii, H. Yano, S. Tanaka, Y. Miyake, Water gas shift reaction in a membrane reactor using a high hydrogen permselective sUica membrane, Sep. Sci. Technol. 48 (2013) 76-83. 

Itoh N, Akiha T, Sato T (2005) Preparation of thin palladium composite membrane tube by a CVD technique and its hydrogen permselectivity. Catal Today 104 231-237 Kleinert A, Grubert G, Pan X, Hamel C, Seidel-Morgenstern A, Caro J (2005) Compatibility of hydrogen transfer via Pd-membranes with the rates of heterogeneously catalysed steam reforming. Catal Today 104 267-273... 

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