Monday, March 07, 2011

New Nano-Wire Catalysts Convert Methane to Ethylene

The oxidative coupling of methane converts methane into ethane and ethylene (C2 hydrocarbons). The basic OCM reaction (which is exothermic) is:

2CH4 + O2 → C2H4 + 2H2O

In the OCM reaction, methane (CH4) is activated on the catalyst surface, forming methyl free radicals (CH3) which then couple in the gas phase to form ethane (C2H6). The ethane subsequently undergoes dehydrogenation to form ethylene and water. _GCC
We are seeing the early stages of a trend which has been long predicted by Al Fin energy analysts: The creation of robust non-biological nano-catalysts which are modeled on a biological template. These newer and tougher catalysts are only possible due to advances in nanotechnological fabrication processes, and they will eventually change the way that synthetic fuels are made -- avoiding the expensive Fischer-Tropsch pathways.

The Siluria advance described in the article below, involves the catalytic production of ethylene from methane -- currently in quite abundant supply due to the ongoing unconventional natural gas bonanza. Ethylene can then be converted catalytically to long chain, high value hydrocarbons.
The catalyst materials are proprietary, doped metal oxides of early transition metals that are designed for compatibility with existing petrochemical industry infrastructure. Siluria has developed a library of compounds with a range of crystal structures, and has tested their behavior in catalyzing the OCM reaction.

The first step is creating the library of organic templates—that’s the phage. Second, you do synthetic prep, so inorganic synthetic chemistry on each of those phages, and you create a diversity of catalyst nanowires: the same composition, but a different active site. Then we take these individual compositions, we combine them with high-throughput screening to screen not some incidental or ancillary property that you then infer; we actually run every single one in the reaction of interest. We get a direct measurement on each one of those little dots [256 per wafer] which is a different catalyst.
—Erik Scher

The excitement and the promise is where we will be 5 years from now. The non-reducible advantages of OCM versus FT and a syngas-based route is threefold. One, [OCM] is a simpler chemistry, in terms of the number of steps required to get to the end product. With OCM, its two steps: methane to ethylene, oligomerize to liquids. In FT, there are three steps: steam methane reforming to syngas, syngas to a mixture, hydrocracking to clean it up. Non-reducible.

Two, [OCM] is a chemistry that is easier to control. Ethylene is a versatile and flexible molecule that is easy through existing technologies to convert to longer chains: detergents, lubricants, fuels. And three, it has a better energy balance. The first step in FT is endothermic; the first in OCM is exothermic.
—Alex Tkachenko

In other alternative liquid fuels news, UCLA researchers are aiming to develop microbes which create advanced biofuels from biomass proteins. Proteins are often found in greater quantity in biomass than either carbohydrates or lipids. By creating microbes to ferment the protein component into fuels, technologists will be able to convert biomass to fuels more completely and efficiently.

Thermochemical conversion of biomass takes a lot of energy -- although it is available now, rather than 10 years from now. But in 10 years, microbes which convert biomass to fuels more efficiently will begin taking over from the less efficient thermochemical processes. And in 20 to 30 years, non-biological nano-catalysts will begin taking over liquid fuels synthesis from many of the microbial fuels approaches -- and from the more efficient thermochemical approaches.

As long as government interference can be kept to a minimum, marketplace incentives should drive synthetic liquid fuels to a high level of replacement for petrol fuels over the next 30 years.

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