Membranes perovskite

The magnitude of the engineering task involved is indicated by the assumptions for the calculations [53] a sealed vessel, containing 1000 1-in. diameter tubes, each 31 ft long, coated inside with perovskite membrane, in which the tubes are 1.5 in. apart, with a lower preheated section of 6 ft, a central reaction section of 18 ft, and an upper cooling section of 7 ft. The construction of such a vessel is neither simple nor cheap. 

Xu, S.J. and Thomson, W.J. (1999) Oxygen permeation rates through ion-conducting perovskite membranes. Chemical Engineering Science, 54, 3839-3850. 

J.E. ten Elshof, H.J.M. Bouwmeester and H. Verweij, Oxidative Coupling of Methane in a Mixed-Conducting Perovskite Membrane Reactor , Appl. Catal. A, 130 195-212 (1995). 

Industry is continuously in search for suitable membrane materials which may produce high purity oxygen at low cost and preferably at low temperamre. This type of material is yet to be developed. Presently the zirconia and perovskite membranes... 

Ma YH. Dense palladium and perovskite membranes and membrane reactors. MRS Bulletin March 1999 46 9. 

Perovskite membranes are interesting systems not only for their possible applications (e.g., fuel cells, oxygen generators, oxidation catalysts) but also for the fundamental fascination of fast oxygen transport in solid-state ionic. 

In the catalytic partial oxidation of methane to produce syngas the use of permselective dense perovskite membranes avoids (or minimizes) the need of air separation, the most costly step in the process. Although both these O2- and H2-permeoselective membranes (based on perovskites or thin supported Pd-based dense films, respectively) have still to be further developed for commercial applications the outlook appears quite interesting for intensifying various large chemical processes. 

In bottom and side feeds to control temperatures in two sections t Temperature -1000 °C Suitable for perovskite membranes... 

Dixon et al. simulated the partial oxidation of o-xylene to phthalic anhydride over a vanadium pentoxide catalyst supported on alumina, in a dense perovskite membrane tube. A non-isothermal model was used, which included the effect of temperature on the permeation rate. The competing reaction, complete oxidation to combustion products, is favored at higher temperatures. Comparisons were made to fixed bed reactors operated under the same conditions. For the fixed bed with inlet temperature 630 K, the usual hotspot near the front of the bed was seen, as shown in Figure 11. 

The motivation for both was the report of high rates of O2 permeation through perovskite membranes of the formula Lai tSr Coi >,Fe j,03 5 by Teraoka et al. which have been discussed above. 

Vente JF, Haije WG, Rak ZS. Performance of functional perovskite membranes for oxygen production. J Membr Sci. 2006 276 178. 

In addition to the challenges mentioned above, the thermochemical stability of the perovskite membranes in syngas environment is a major hurdle that needs to be overcome for successful implementation of membrane technology for hydrogen separation. Both SrCeOs and BaCe03 based compositions are shown to be unstable in the presence of CO2 and H2O [16-18]. It was shown that replacing a fraction of Ce in the perovskite with Zr also provided improved stability [19]. However this... 

Because the physical parameters such as the diffusivities and the equilibrium constants for the BCN membranes are not readily available in the literature, modeling analysis of hydrogen permeation through the MPEC membrane was carried out for the SrCe0.95Y0.05O3 X (SCY) perovskite membrane. The required physical parameters are taken from the literature [15-19] and are listed in Table 7.1. 

M. van der Haar, Mixed-Conducting Perovskite Membranes for Oxygen Separation, Ph.D. Dissertation, Universiteit Twente, The Netherlands, 2001. 

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