Hydrogen production from a combination of the water-gas shift and redox cycle process of methane partial oxidation via lattice oxygen over LaFeO3 perovskite catalyst.
ABSTRACT A redox cycle process, in which CH4 and air are periodically brought into contact with a solid oxide packed in a fixed-bed reactor, combined with the water-gas shift (WGS) reaction, is proposed for hydrogen production. The sole oxidant for partial oxidation of methane (POM) is found to be lattice oxygen instead of gaseous oxygen. A perovskite-type LaFeO3 oxide was prepared by a sol-gel method and employed as an oxygen storage material in this process. The results indicate that, under appropriate reaction conditions, methane can be oxidized to CO and H2 by the lattice oxygen of LaFeO3 perovskite oxide with a selectivity higher than 95% and the consumed lattice oxygen can be replenished in a reoxidation procedure by a redox operation. It is suggested that the POM to H2/CO by using the lattice oxygen of the oxygen storage materials instead of gaseous oxygen should be possibly applicable. The LaFeO3 perovskite oxide maintained relatively high catalytic activity and structural stability, while the carbonaceous deposits, which come from the dissociation of CH4 in the pulse reaction, occurred due to the low migration rate of lattice oxygen from the bulk toward the surface. A new dissociation-oxidation mechanism for this POM without gaseous oxygen is proposed based on the transient responses of the products checked at different surface states via both pulse reaction and switch reaction over the LaFeO3 catalyst. In the absence of gaseous-phase oxygen, the rate-determining step of methane conversion is the migration rate of lattice oxygen, but the process can be carried out in optimized cycles. The product distribution for POM over LaFeO3 catalyst in the absence of gaseous oxygen was determined by the concentration of surface oxygen, which is relevant with the migration rate of lattice oxygen from the bulk toward the surface. This process of hydrogen production via selective oxidation of methane by lattice oxygen is better in avoiding the deep oxidation (to CO2) and enhancing the selectivity. Therefore, this new route is superior to general POM in stability (resistance to carbonaceous deposition), safety (effectively avoiding accidental explosion), ease of operation and optimization, and low cost (making use of air not oxygen).
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ABSTRACT: Perovskite-type LaFeO(3) and alpha-Fe(2)O(3) with high specific surface areas were directly prepared with appropriate stearic acid-nitrates ratios by a novel stearic acid solution combustion method. The obtained powders were characterized by XRD, FT-IR and XPS techniques. The catalytic activities of perovskite-type LaFeO(3) and alpha-Fe(2)O(3) for the thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) were investigated by TG and TG-EGA techniques. The experimental results show that the catalytic activity of perovskite-type LaFeO(3) was much higher than that of alpha-Fe(2)O(3) because of higher concentration of surface-adsorbed oxygen (O(ad)) and hydroxyl of LaFeO(3). The study points out a potential way to develop new and more active perovskite-type catalysts for the HMX thermal decomposition.Journal of hazardous materials 11/2008; 165(1-3):1056-61. · 4.14 Impact Factor
Conference Paper: Decompositional logic synthesis approach for look up table FPGAs[Show abstract] [Hide abstract]
ABSTRACT: In this paper, a technology driven logic synthesis approach for look up table FPGAs is presented. Decomposition and bottom-up construction are the key concepts of this approach. By using functionally complete compact modeling with set systems, technology mapping is trivial. The method offers correctness by construction and easy post-synthesis verification and uses a multiple criteria search algorithm for constructing near optimal solutionsASIC Conference and Exhibit, 1995., Proceedings of the Eighth Annual IEEE International; 10/1995
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ABSTRACT: Maintenance insurance is a recent development that has achieved some cost savings for hospitals in the area of equipment maintenance. In this article the authors demonstrate the greater cost savings that can be achieved by a centrally managed self-insurance program that crosses departmental lines. The benefits of having this program run by a technical rather than a financial person is also illustratedEngineering in Medicine and Biology Society, 1995., IEEE 17th Annual Conference; 10/1995