Methane Steam Reforming Kinetics for a Rhodium-Based Catalyst

Abstract

Methane steam reforming is the key reaction to produce synthesis gas and hydrogen at the industrial scale.Here the kinetics of methane steam reforming over a rhodium-based catalyst is investigated in the temperature range 500-800°C and as a function of CH 4 , H 2 O and H 2 partial pressures. The methane steam reforming reaction cannot be modeled without taking CO and H coverages into account. This is especially important at low temperatures and higher partial pressures of CO and H 2 . For methane CO 2 reforming experiments, it is also necessary to consider the repulsive interaction of CO that lowers the adsorption energy at high CO coverage. The CO-CO interaction is supported by comparison with fundamental surface science studies.

Methane dissociative chemisorption and detailed balance on Pt(111): Dynamical constraints and the modest influence of tunneling

“…Thermal dissociative sticking coefficients for CH 4 and CD 4 calculated with the d-PMMT model are shown in Fig. 10(a) along with the kinetic isotope effect (KIE) in Fig.…”

“…11(b) provides a closer analysis of the fraction of the reactive flux in dissociative chemisorption that is predicted to have tunneled across the reaction barrier. Although tunneling is negligible at the higher temperatures relevant to catalysis, as the temperature drops the tunneling fraction increases steadily and by 200 K it reaches 95% for CH 4 and 60% for CD 4 .…”

“…The CH 4 have given rise to a wide range of E 0 values extending from 43 kJ/mol to 121 kJ/mol. Earlier s-PMMT model (assuming active rotations) analyses of supersonic molecular beam experiments gave E 0 = 61.3 kJ/mol, 11 58.9 kJ/mol, 13 and lower values of E 0 = 49 kJ/mol, 65 48.2 kJ/mol 56 for analyses of different effusive molecular beam experiments.…”

“…The activated dissociative chemisorption of methane at catalytic metal surfaces can be a rate-limiting step [1][2][3][4][5] in the catalytic reforming of methane (ca., 95% of natural gas) that is the industrially preferred process to produce hydrogen and synthesis gas. Development of quantitative models for methane dissociative chemisorption has been of long-standing interest [6][7][8][9][10][11][12][13][14][15][16] given that such models might ultimately prove helpful in optimizing catalytic transformations of methane.…”

Steam reforming on reactive carbon nanotube membranes

“…Depending on the initial fuel, and thus its thermal stability, the operational temperatures to reach appreciable conversion can range from about 300 8C (methanol) [16] up to 700 8C and above for more thermally stable molecules such as CH 4 [17]. A plethora of catalysts has been in use to make this transformation as smooth as possible: Pd [18,19], Pt [20,21], Rh [22,23], Ru [24,25], Cu [26,27], Co [28,29] or Ni [30][31][32]. Ni remains the primary choice because of the tradeoff between its relatively low cost and the performance it offers.…”