Methanol could become an intermediate fuel source ahead of the advent of the hydrogen economy if only there were a way to make it cheaply and easily at low energy cost. A new catalyst could now open the door to making methanol from methane more efficiently.
The so-called “hydrogen economy” is a hot topic in the environmental debate. Hydrogen could become the ultimate clean fuel if it could be produced using sustainable, energy sources. Using hydrogen to power fuel cells for vehicles and even buildings would produce only electricity and warm water as waste products with no local pollution. Unfortunately, hydrogen is not the easiest substance to store nor transport as it is highly explosive. Being a gas means it also requires compression or complex porous materials for safe storage.
Methanol, on the other hand, could be used as a possible fuel cell fuel or a substitute for petroleum ahead of hydrogen. As a liquid, it can be stored much more easily and cheaply than hydrogen and could be distributed by way of the existing network of filling stations. In one sense, methanol would probably represent an intermediate step on the way to a hydrogen economy as it still relies on finding a renewable carbon source. That aside, methanol will always have a bigger carbon footprint than hydrogen because it is a carbon compound.
Nevertheless, researchers have now developed a new solid catalyst for the direct low-temperature oxidation of methane (natural gas) to methanol, a chemical tool for which researchers have been searching for many years. Ferdi Schüth at the Max Plank Institute of Coal Research in Mülheim, Germany, and Markus Antonietti at the Max Planck Institute for Colloids and Interfaces in Potsdam-Golm, Germany, and their colleagues have developed a novel catalyst that they say could provide a “second wind” for methanol research.
The problem chemists have faced in developing oxidation catalysts for producing methanol from methane is that the bonds in methane are very strong. Moreover, preventing the oxidized methane from simply converting fully to carbon dioxide has proved difficult. A catalyst must be highly active, to keep the reaction conditions mild as well as highly selective to control the products effectively.
The platinum catalysts developed by Roy Periana’s team allowed the low-temperature oxidation of methane in concentrated sulfuric acid at around 200 Celsius to form methyl sulfate, which could then be converted to methanol. However, this approach was plagued with separation and recycling problems for the dissolved catalyst. Schüth explains that, “a solid catalyst that can be easily separated could make such a process viable on a small scale, making possible the efficient, decentralized consumption of natural gas.”
The German team has now developed just such a solid catalyst with high reactivity and selectivity using a recently discovered class of high-performance polymer as a support material for the catalytic platinum particles. Their successful preliminary tests suggest it might be developed into a commercially viable material for producing methanol from methane.
Angew Chem Int Edn, 2009, 48, 6909-6912
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