Design and Fabrication of Ceramic Catalytic Membrane Reactors for Green Chemical Engineering Applications

Catalytic membrane reactors (CMRs), which synergistically carry out separations and reactions, are expected to become a green and sustainable technology in chemical engineering. The use of ceramic membranes in CMRs is being widely considered because it permits reactions and separations to be carried out under harsh conditions in terms of both temperature and the chemical environment. This article presents the two most important types of CMRs: those based on dense mixed-conducting membranes for gas separation, and those based on porous ceramic membranes for heterogeneous catalytic processes. New developments in and innovative uses of both types of CMRs over the last decade are presented, along with an overview of our recent work in this field. Membrane reactor design, fabrication, and applications related to energy and environmental areas are highlighted. First, the configuration of membranes and membrane reactors are introduced for each of type of membrane reactor. Next, taking typical catalytic reactions as model systems, the design and optimization of CMRs are illustrated. Finally, challenges and difficulties in the process of industrializing the two types of CMRs are addressed, and a view of the future is outlined. Keywords: Dense ceramic membrane, Porous ceramic membrane, Catalytic membrane reactor, Gas separation, Heterogeneous catalysi

Decomposition of CO2 coupled with POM in a thin tubular oxygen-permeable membrane reactor

In this study, a SCFA (Al2O3 of 3 wt.% doped in SC0.8F0.2O3-delta) dense mixed-conducting thin tubular membrane was applied to a membrane reactor for coupling the thermal decomposition of carbon dioxide (TDCD) (CO2 double left right arrow CO + 1/2O(2)) with the partial oxidation of methane (POM) to syngas, in which the reaction of CO2 decomposition took place in the tube side of the membrane and the POM reaction occurred in the shell side of the membrane simultaneously. The reaction performance of the SCFA thin tubular membrane reactor was investigated as function of reaction temperature and the feed flow rates of CO2 and CH4. It was found that the CO2 conversion increased with increasing the temperature and decreased with increasing the feed flow rates of CO2 or with decreasing the feed flow rates of CH4. At the temperature of 900 degrees C, the CO2 conversion reached about 12.4%, and the CH4 conversion, CO selectivity and the ratio of H-2/CO were 86%, 93% and 1.8, respectively. Compared with the disc-shaped membrane, the CO2 conversion in the thin tubular membrane is higher at the same operation temperature. The SCFA membrane reactor could be operated for about 62 h at the temperature of 900 degrees C. (C) 2009 Elsevier B.V. All rights reserved

Pore structure control for porous FeAl intermetallics

Pore structure control methods for porous FeAl intermetallics were studied in this paper based on pore formation mechanism. A large range of pore structure parameters can be obtained through fabrication parameter adjustment in porous FeAl preparation procedure. Open porosity and maximum pore size of porous FeAl have a direct proportional relationship to the powder size of raw materials and an inversely proportional relationship to the pressing pressure. The relationship between maximum pore size (d(m)) and raw material powder size (d(p)) can be determined as d(m) = 0.40d(P). Open porosity and maximum pore size decrease with increasing holding time at solid diffusion reactive procedure. The quantitative relationship between open porosity (theta) and holding time (t) at 600 degrees C is theta = 49.7 - 0.1t (6

Double-site yttria-doped Sr1−xYxCo1−yYyO3−δ perovskite oxides as oxygen semi-permeable membranes

New mixed conducting oxides with the composition of Sr1-xYxCo1-yYyO3-delta (x = 0.0-0.8, y = 0.0-0.1) were exploited and synthesized. The resulted materials were investigated by X-ray diffraction, four-probe dc conductivity, temperature-programmed desorption characterization, and oxygen permeability measurement. As compared with the oxides with only one-site (A or B) being Y3+-doped, i.e., Sr1-xYxCoO3-delta and SrCo1-yYyO3-delta, the double-site y(3+)-doped ones show improved phase stability, higher electrical conductivity under reduced atmosphere, and higher oxygen permeability and stability. Particularly, Sr0.95Y0.05Co0.95Y0.05O3-delta oxide demonstrates stable cubic perovskite phase in air, oxygen and nitrogen, high electrical conductivity of similar to 110 S cm(-1) in air and similar to 50 S cm(-1) in nitrogen, and a maximum permeation flux of 1.35 x 10(-6) mol cm(-2) s(-1) at 900 degrees C under an air/helium gradient. Long-term permeation study at 850 C indicates that Sr0.95Y0.05Co0.95Y0.05O3-delta can operate stably as oxygen semi-permeable membrane. (C) 2008 Elsevier B.V. All rights reserved