What's that black stuff? Investigating the deposits on nickel methane-reforming catalysts with inelastic neutron scattering.

Ian Silverwood (University of Glasgow)

Methane steam reforming is of huge commercial interest to form products such as ammonia, methanol and hydrogen on a multi-million ton scale1. Any improvement in the catalysts used in this reaction can therefore lead to significant savings in both financial and environmental resources. Deactivation of the catalyst over time, and the high energy cost associated with steam production are key disadvantages to the technique. Replacement of steam with carbon dioxide, either wholly or partially has the benefit of consuming a pollutant whilst reducing the energy requirements of steam. Dry reforming uses CO2 as the sole oxidant, and has been attracting increased interest for this reason. Additionally, there is the possibility that it may be useful for conversion of bio-gas to artificial fuels via the Fischer-Tropsch synthesis. Spectroscopic investigation of the deposits formed on Ni/Al2O3 catalysts under steam and dry reforming reactions has been carried out using IR, Raman and Inelastic Neutron Scattering (INS). The catalysts were reacted for an extended period without significant deactivation before being quenched, isolating an immobile overlayer representative of the reaction chemistry2. INS is uniquely sensitive to hydrogen, allowing development of a method capable of quantification of hydrogen in its individual chemical states3, and determination of the partitioning of hydrogen within the catalytic system. Separate quantification of the carbon content is obtained through Temperature Programmed Oxidation (TPO). These linked results then provide a carbon to hydrogen ratio of the deposited overlayer material and conclusions may be drawn regarding the kinetic aspects of the reaction, leading to the proposal of a generalised reaction scheme.

1. Yorke, P.E., Catal. Rev., 49, 511 (2007)

2. Sivadinarayana, C.; Choudhary, T.V.; Daemen, L.L.; Eckert, J.; Goodman, D.W., J. Am. Chem. Soc., 126, 38 (2004)

3. Silverwood, I.P.; Hamilton, N.G.; Laycock, C.J.; Staniforth, J.Z.; Ormerod, R.M.; Frost, C.D.; Parker, S.F.; Lennon, D., Phys. Chem. Chem. Phys., 2010, 12, 3102, (2010)

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