456850 Kinetics and Spectroscopic Studies of Methane Partial Oxidation on Ni and Rh Catalysts

Wednesday, November 16, 2016
Grand Ballroom B (Hilton San Francisco Union Square)
Cun Wen1, Jason Hattrick-Simpers2 and Jochen Lauterbach2, (1)Chemical Engineering, University of South Carolina, Columbia, SC, (2)Department of Chemical Engineering, University of South Carolina, Columbia, SC

Kinetics and Spectroscopic studies of Methane Partial Oxidation on Ni and Rh Catalysts

Cun Wen, Jason Hattrick-Simpers, Jochen Lauterbach,*

University of South Carolina, Columbia, SC, 29208, USA

*Corresponding author: lauteraj@cec.sc.edu

Recent exploration of shale gas has led to shockwaves in both energy markets and academic research fields. On the basis of same amount of energy content, shale gas has a much lower price (about 70% lower) compared with that of crude oil, even with todayfs low crude-oil price at $40 per barrel. The price difference between shale gas and crude oil has revived interests to convert methane, as the major component in shale gas, to gasoline and diesel. Methane partial oxidation (POM), in particular, is an preferred processed due to its optimum H2 to CO ratio of 2 for downstream Fischer-Tropsch synthesis and mild heat release. However, the most active catalyst for POM is Rh, which is a nobel metal catalyst with a much higher price tag compared with the next best candidate in-line, Nickle. Here, fundamental studies that compares the reaction kinetics and reaction mechanism between Ni and Rh will be presented, and the possibility of design an Ni catalyst possessing comparable activity of Rh will be discussed.

Series of Rh and Ni catalysts using ƒÁ-Al2O3 as supports were synthesized by following literature.[1, 2] The structures of two catalyst were characterized with ICP, XRD, BET, TEM, to make sure they have comparable metal loadings, particle size, surface area. Their catalytic activity for POM were compared under the same reaction conditions. Consistently with literature,[1, 3] the Rh catalysts showed activity toward POM (T50= 502 ‹C) at a temperature about 100 ‹C lower than that on Ni catalysts (T50= 605 ‹C). The catalytic activity of Rh and Ni catalysts were widely reported to be limited by methane dissociation as the rate-determining step.[4, 5] Therefore, methane-temeprature programmed reduction experiments were design to compare how easily methane can be activated and dissociated by Rh and Ni catalysts. In contrary to the catalytic activity tests, the Rh and Ni catalysts possessed comparable starting temperature for CH4 dissociation at around 200‹C, as shown in Figure 1. Furthremore, Ni catalysts had no activity toward POM until 450 ‹C, at which temperature CH4 could readily dissociate on the Ni catalysts accroding to CH4-TPR. More detailed kinetics and spectroscopic results indicate that Ni catalysts can be partially oxided under the POM condition with CH4 to O2 ratio of 0.5, and loss the activity toward POM. More importantly, methodologies to increase the resistence of Ni to oxidation will be discussed in this presentation.

Figure 1. Methane-temperature programmed reduction on a) Rh/Al2O3 and b) Ni/Al2O3 catalysts.

References:

1.         Li, J.-M., et al., Effect of Rh loading on the performance of Rh/Al2O3 for methane partial oxidation to synthesis gas. Catalysis Today, 2008. 131(1–4): p. 179-187.

2.         Jin, R., et al., Mechanism for catalytic partial oxidation of methane to syngas over a Ni/Al2O3 catalyst. Applied Catalysis A: General, 2000. 201(1): p. 71-80.

3.         Dissanayake, D., et al., Partial oxidation of methane to carbon monoxide and hydrogen over a Ni/Al2O3 catalyst. Journal of Catalysis, 1991. 132(1): p. 117-127.

4.         Wei, J. and E. Iglesia, Isotopic and kinetic assessment of the mechanism of reactions of CH4 with CO2 or H2O to form synthesis gas and carbon on nickel catalysts. Journal of Catalysis, 2004. 224(2): p. 370-383.

5.         Wei, J. and E. Iglesia, Structural requirements and reaction pathways in methane activation and chemical conversion catalyzed by rhodium. Journal of Catalysis, 2004. 225(1): p. 116-127.

 


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