Carbon-based membrane reactors

In this chapter, we first give an overview of carbon membrane materials (Section 10.2) and the classification of carbon membranes (Section 10.3). Then, unsupported carbon membranes, based on planar membranes and asymmetric hollow fiber membranes are discussed (Section 10.4). In Section 10.5, the supported CMSMs are reviewed in detail in terms of precursors, supports, fabrications and problems. In Section 10.6, carbon-based membrane reactors are discussed in detail, based on the topics of dehydrogenation reactions, hydration reactions, hydrogen production reactions, H2O2 synthesis, bio-diesel synthesis, and new carbon membranes for carbon membrane reactors (CMRs). In the end, the new concept of using carbon membranes in microscale devices (microcarbon-based membrane reactor) is outlined (Section 10.7). 

Although carbon membranes are still in their infant stage, and have some serious challenges such as weak mechanical strength for unsupported membranes and bad controllability and reproducibihty of the fabrication for supported membranes, they are believed to be promising candidates for porous membrane based membrane reactors because of their ease of fabrication, low cost of both fabrication and raw materials, molecular-sieve separation effect and high permeance. 

The overall goal of this study is to develop superior catalysts suitable for use in modem advanced slurry phase or membrane reactors. Successful investigations have produced an iron-based unsupported catalyst with high activity and extended catalyst life (improved attrition resistance). This catalyst was used by the authors to understand the phase transformations from iron oxide precursors after activation to iron carbide crystallites and to characterize the presence of characteristic amorphous carbon species that have been reported to envelop the spent Fe-FTS catalyst grains in form of surface layers. Previous studies suggest two different phases to be considered as the active phase including iron oxide and a mixture of x snd e -carbides (Table 1) and in some instances minor amounts of metallic iron, however the spatial distribution of the different... 

K. Hwang, C. B. Lee, S. K. Ryi, J. S. Park, Hydrogen production and carbon dioxide enrichment using a catalytic membrane reactor with Ni metal catalyst and Pd-based membrane, Int. J. Hydrogen Energy 37 (2012) 6626-6634. 

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