Bi-Reforming of Methane and Natural Gas From Any Source Under High Pressure. Effect of the Catalyst and Reaction Conditions

Bi-Reforming of Methane and Natural Gas from Any Source Under High Pressure. Effect of the Catalyst and Reaction Conditions

Alain Goeppert, Miklos Czaun, Robert B. May, G. K. Surya Prakash, George A. Olah, Loker Hydrocarbon Research Institute, Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA

Bi-reforming of methane, the combination of steam and dry reforming, was used to obtain a syn-gas with a H₂/CO ratio of 2 called “metgas” ideal for methanol synthesis.^[1-3] It was achieved by selecting the right proportions between water, CO₂ and CH₄ and reacting them over a suitable catalyst at high temperature.

Bi-reforming to metgas is adaptable for reforming varied natural gas (containing hydrocarbon homologues) and CO₂ sources.

Bi-reforming could be especially beneficial in the use of natural gas sources containing substantial amounts of CO₂. This CO₂ would, otherwise, have to be separated to allow further processing of the natural gas. Some natural gas sources contain CO₂ concentration from 5% up to 70%. In most cases, once separated, the CO₂ is presently released into the atmosphere.

In order to mimic conditions closer to commercial operations, the bi-reforming reaction was conducted at pressures up to 42 atm in a tubular reactor system specially built for this purpose and able to withstand both high pressure and high temperature in a gas mixture with a high carbon activity. The catalysts used were based on nickel and cobalt deposited on various supports including alumina, alkali earth oxides and combinations thereof. Reaction temperatures ranging from 700°C to 910°C were investigated. A gas feed composition of CH₄/CO₂/H₂O with a molar ratio of 3/1.2/2.4 was typically used. The reaction was followed by an online GC equipped with a TCD. The amount of carbon formed on the surface of the catalyst was also investigated.

The catalysts were typically tested for at least 100 hours to determine their stability as a function of time. In most cases the conversion of methane as well as carbon dioxide was stable over the length of the experiments (Figure 1). The obtained H₂/CO ratio of the reaction gases was close to the desired value of 2.

The effect of pressure, feed gas composition (amount of water, CO₂, methane), temperature, nature of the catalyst were studied and the results obtained reported.

       

Figure 1. Example of Bi-reforming on 15% NiO on MgO at 7 atm. Conversion of methane and carbon dioxide and selectivity to hydrogen and carbon monoxide.

Acknowledgements

Support of our work by the Loker Hydrocarbon Research Institute and the United States Department of Energy is gratefully acknowledged.

References

[1]        G. A. Olah, G. K. S. Prakash, A. Goeppert, J. Am. Chem. Soc. 2011, 133, 12881.

[2]        G. A. Olah, A. Goeppert, G. K. S. Prakash, Beyond Oil and Gas: The Methanol Economy, 2^nd ed., Wiley VCH, Weinheim, Germany, 2009.

[3]        G. A. Olah, A. Goeppert, M. Czaun, G. K. S. Prakash, J. Am. Chem. Soc. 2013, 135, 648