Chapter 8
The Effect of Pressure on CO Reforming of Methane and the Carbon Deposition Route Using Noble Metal Catalysts Downloaded by STANFORD UNIV GREEN LIBR on May 17, 2013 | http://pubs.acs.org Publication Date: April 12, 2007 | doi: 10.1021/bk-2007-0959.ch008
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Abolghasem Shamsi and Christopher D. Johnson National Energy Technology Laboratory, U.S. Department of Energy, 3610 Collins Ferry Road, Morgantown, WV 26505-0880
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Dry reforming of methane and C-labeled methane were studied over Pt/ZrO , Pt/Ce-ZrO , and l%wtRh/Al O at several pressures. It appears that carbon deposited on the catalysts resulted from both methane and CO . The presence of approximately equal ratios of C- and C-containing products suggests that the oxygen exchange reaction between CO and CO is very fast. Temperature-programmed oxidation of carbon formed on the catalysts indicates that CO disproportionation contributes significantly to carbon deposition at lower and higher pressures. The Rh/alumina supported catalyst is the most resistant toward carbon deposition both at lower and higher pressures. In all catalysts, methane and CO conversions as well as H /CO ratios decreased with increasing pressure. 2
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U.S. government work. Published 2007 American Chemical Society.
In Ultraclean Transportation Fuels; Ogunsola, O., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2007.
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Introduction Natural gas, which is mostly methane, is primarily used for heating and electrical production. Currently, natural gas reserves are nearly as large as oil reserves and new reserves of natural gas are constantly being found. The economic use of natural gas, however, depends on its locality. It is not normally feasible to ship natural gas from remote areas to population centers. For instance, the north shore of Alaska has large natural gas reserves along with oil, but the natural gas is re-injected because the cost of transporting the gas is too expensive. Two available options at this time for bringing that resource to market are, building a pipeline, or cryogenic liquefaction. An alternative would be to chemically convert the gas to liquid and then transport it with the current infrastructure. To convert methane to liquid, it is first necessary to make synthesis gas and then convert the synthesis gas to liquid by methanol synthesis or Fischer-Tropsch reaction. The most costly part of the overall conversion is the production of synthesis gas. Three different routes, or combinations of these, can be used to produce synthesis gas from methane. These are steam reforming, C 0 reforming and partial oxidation. Each has its advantages and likewise has drawbacks. Steam reforming, which is a common industrial method of synthesis gas production, is very endothermic, as seen in the equations below. It also produces an H /CO ratio of about 3/1, which is good for hydrogen production, but is too high for fuel synthesis. Methanol and Fischer-Tropsch synthesis use a H /CO ratio of about 2/1. 2
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CH4 + C 0 2CO + 2H 2
CH4 + H 0
