Methane is one of the most important industrial gases. Not only is it directly used for heat generation, it is the primary feedstock for several of the most widely produced commodity chemicals including hydrogen, ammonia, methanol and formaldehyde. Methane activation and conversion is typically accomplished though syngas production by steam reforming, which requires high pressure (typically above 10 bar), high temperature (700-1100 oC) and is very endothermic (~200 kJ/mol). The high energy requirement is typically met through the combustion of methane, which introduces a feedstock inefficiency into the system (~40% of the total methane fed is burned for heat) and results in a very high CO2 footprint for the process. The large amount of methane spent for heat, combined with the number of unit operations to accommodate the circuitous energetic pathway makes methanol production from methane relatively expensive.
Since they allow for control of the catalyst surface free energy, electrochemical methods have the potential to reduce the thermal and overall energy barrier to convert methane to oxygenates [1-3]. Processing conditions for electrosynthesis can also be tailored to selectively and dynamically change the reaction selectivity, meaning that the several unit operations that are currently required for the conversion of methane to methanol or formaldehyde might be reduced to a single step. Methanol is a particularly high value target; it is used to synthesize numerous products, and has been touted as an important energy carrier of the future. Its high energy density and liquid state in atmospheric conditions make it ideal for stable transportation and storage that is compatible with existing petroleum infrastructure [4-5].
In this study, we will present two systems that are able to directly convert methane to methanol at low temperatures in alkaline media. Cell geometries, overall trends and variations in catalytic performance and the product profile will be presented while controlling the reacting environment. Trends from this promising technology will help to guide future cell design with the prospect of improving the applications for methane, natural gas resources and CO2.
1. N. Spinner and W. E. Mustain, J. Electrochem. Soc., 160, 11 (2013).
2. N. Spinner and W. E. Mustain, J. Electrochem. Soc., 159, 12 (2012).
3. N. Spinner and W. E. Mustain, Electrochim. Acta., 56, 16 (2011).
4. G. A. Olah, A. Goeppert and S. K. Surya-Prakash, Beyond oil and gas: the methanol economy, Wiley-VCH (2009).
5. G. A. Olah, Angew Chem Int Ed Engl., 44, 18 (2005).
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