Palladium membrane reactions

The auto-thermal reaction of ethanol occurred in the shell side of a palladium membrane reactor in which a Zn-Cu/AlaOs industrial catalyst (MDC-3) was packed with silica powder. Ethanol-water mixture (nH2o/nEioH=l or 3) and oxygen (noa/nEioH=0.2,0.776 or 1.035) are fed concurrently to the shell side. The reaction temperatures were set at 593-723 K and the pijrasures were 3 10 atm. 

Guryanova, O. S., Y. M. Serov, S. G. Gul yanova and V. M. Gryaznov. 1988. Conversion of carbon monoxide on membrane catalysts of palladium alloys Reaction between CO and H2 on binary palladium alloys with ruthenium and nickel. Kinet. and Catal. 29(4) 728-731. 

Membrane is the catalyst Cation exchange membranes for esterification reactions Palladium membranes for hydrogenation/dehydrogenation reactions... 

Kurungot et al. [48] developed a novel membrane material and a catalytic membrane reactor for the partial oxidation of methane. The driver of the development was the fact that rates of reforming reactions are much higher compared with the low permeability of conventional palladium membranes [49], Silica was previously recognized as a low-cost alternative to palladium [50], Additionally, the conventional... 

Uemiya, S., Sato, N., Inoue, H., Ando, H. and Kikuchi, E. (1991) The water-gas shift reaction assisted by palladium membrane reactor. Industrial e[ Engineering Chemistry Research, 30, 585. 

In addition to packed and wall-coated systems, numerous researchers have investigated the fabrication of membranes, within microchannels, in which catalytic material can be incorporated. Employing a protocol developed by Kenis et al. (1999), Uozumi et al. (2006) deposited a poly(acryla-mide)-triarylphosphane palladium membrane (PA-TAP-Pd) (1.3 pm (wide), 0.37 mmol g-1 Pd) within a glass microchannel [100 pm (wide) x40pm (deep) x 1.4 cm (long)]. Once formed, the membrane was used to catalyze a series of Suzuki-Miyaura C-C bond-forming reactions, the results of which are summarized in Table 21. 

In spite of the advances made by these researchers, it remains unclear how membrane surfaces undergo restructuring and how these changes influence the catalytic and transport properties of the material. Furthermore, there is a need to link surface structure and composition with long-term performance of palladium membranes under continuous reaction conditions. One... 

Membrane reactor models of various configurations, complexity, and ranges of applicability have been previously reported [Sun and Khang, 1988 Itoh and Govind, 1989 Liu et al., 1990], Several previous investigators have presented water-gas shift membrane reactor models. A model of the iron-chromium oxide catalyzed water-gas shift reaction at 673 K in a cylindrical, palladium membrane reactor was developed to demonstrate... 

Uemiya, S. Sato, N. Ando, H. Kikuchi, E. The Water Gas Shift Reaction Assisted by a Palladium Membrane Reactor Ind. Eng. Chem. Res. 30 (1991a) 585-589. 

The use of a membrane reactor for shifting equilibrium controlled dehydrogenation reactions results in increased conversion, lower reaction temperatures and fewer byproducts. Results will be presented on a palladium membrane reactor system for dehydrogenation of 1-butene to butadiene, with oxidation of permeating hydrogen to water on the permeation side. The heat released by the exothermic oxidation reaction is utilized for the endothermic dehydrogenation reaction. 

Itoh et al(S). studied dehydrogenation of cyclohexane in a palladium membrane reactor containing a packed bed of Pt/Al203 catalyst. The removal of hydrogen from the reaction mixture using the pal dium membrane increased the conversion from the equilibrium value of 18.7% to as high as 99.5%. It was shown that for given rates of permeation and reaction, there is an optimum thickness of membrane, at which maximum conversion is obtained. 

Recently, Itoh and Govind(ll.) have reported a theoretical study of coupling an exothermic hydrogen oxidation reaction with dehydrogenation of 1-butene in an isothermal palladium membrane reactor. 

A schematic of a palladium membrane reactor is shown in figure 1. The reversible reaction of 1-butene dehydrogenation occurs on the reaction side of the membrane in which the chrome-alumina catalyst is uniformly packed. The oxidation of hydrogen with oxygen in air occurs in the permeation or separation side on the palladium membrane surface. The... 

The feasibility of the palladium membrane system with an oxidation reaction on the permeation side and 1-butene dehydrogenation reaction on the reaction side in a membrane reactor has been successfully demonstrated. The palladium and its alloy membrane not only can withstand high temperature but also are selectively permeable to hydrogen... 

The permeation flux of oxygen through a mixed oxide membrane described above depends on the oxygen partial pressures across the membrane, membrane thickness and temperature. The dependence, however, is embedded in a complicated implicit equation [Lin et al., 1994]. Only in special cases the permeation Oux shows a pressure dependence similar to that for palladium membranes as given in Eq. (4-10). For example, when electronic conductivity predominates, the value of the exponent, n, is equal to 0.5 for thin membranes and 0.25 [Dou et al., 1985 Itoh et al., 1993] for thick oxide films. If the oxide membrane is essentially an ionic conductor and the surface reaction is the rate-limiting step, n takes on a value of 0.5. 

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