New catalysts for syngas production from carbon dioxide and methane

Abstract

The performance of cobalt tungsten carbide material was investigated for CH 4 /CO 2 reforming. The catalyst was found to convert to a very stable, very active, form when heated in CH 4 /CO 2 at 850 o C and 5 atm.. Even after 90 hours on stream, CH 4 and CO 2 rates of 1.3 and 1.25 mmol/min/g respectively are obtained, with CO yields of 76 % and H 2 /CO ratio close to unity. XRD patterns suggest a phase transformation to WC+Co+C. SEM images suggest formation of encapsulated carbon and whisker carbon. I am grateful to Jean Cropley, member of my research committee, for his valuable suggestions and recommendations in this research study. The financial support from US Department of Energy under cooperative agreement contract DE-FC26-99FT40540 with Consortium for Fossil Fuel Liquefaction Science is gratefully acknowledged.

Kinetic Modeling for Methane Reforming with Carbon Dioxide over a Mixed-Metal Carbide Catalyst

“…The model fits the observed data quite well. Further, the apparent activation energy (E a ) obtained for each of the species H 2 , CO, and H 2 O is comparable to those obtained earlier 40 from the initial catalyst activity over a wider temperature range, 500-850 °C.…”

“…The next step, eq 25d, is assumed to be in equilibrium because the net rate of carbon formation is small compared to the rate of formation of other products. This was confirmed 40 from the carbon balances for the system at different temperatures. The reaction between adsorbed oxygen and gaseous H 2 to produce water in eq 25e is assumed to be reversible, but not in equilibrium, because the RWGS reaction was assumed to be not in equilibrium, previously.…”

“…The details of the calculation for the partial pressures and the rates of formation are given elsewhere. 40 Figures 2-4 show the observed rates of formation for each of the product species, H 2 , CO, and H 2 O, at 600, 550, and 500 °C, respectively. The rate of formation of CO is always higher than that of H 2 and H 2 O combined, at all reaction conditions.…”

“…The equilibrium constant, K a , for every reaction was obtained as a function of temperature from the software CHEMEQ.BAS developed by Sandler. 44 The details of the calculations are given elsewhere 40 and are computed as per the procedure outlined by Sandler. 44 For the MR reaction (eq 24a), the value of the ratio of the observed partial pressures is found to be considerably less (by 3-4 orders of magnitude) than the calculated value of the thermodynamic equilibrium constant (K a ) for all of the experimental runs.…”

“…The advantages and disadvantages of each formulation are discussed elsewhere. 40 The kinetic model used in the current work is described in detail in a later section. In brief, this model uses a few elementary steps, combined to comprise dry reforming in parallel with three other reactions: RWGS, methane decomposition, and the reverse Boudouard (RB) reaction, i.e., eq 10a,b,e and the reverse of eq 10f.…”