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Many drilling sites for oil in the world are at remote locations so the crude oil is shipped by trucks or limited pipelines. Natural gas, CH4, is a side product at most oil wells and in the absence of gas lines it becomes very expensive to ship it to the processing plant. Methane also is a greenhouse gas that traps radiation much more effectively than CO2; on mass bases, CH4 has about 20 times more greenhouse effect then CO2. Currently, most of the CH4 is simply burned off but with increased environmental awareness and stricter environmental policies scientist and the industry have started to look at alternative ways to use this stranded natural gas. One approach is to convert the methane to syngas (CO + H2) and then use a complex heterogeneous catalytic process called Fischer-Tropsch (FT) to convert the syngas to longer, (C8-12), hydrocarbon chains. These longer chains are liquid at moderated temperatures and can therefore be mixed in with the crude oil for shipping. Unfortunately, FT suffers from broad product distribution ranging from light gases to very long waxes. We use density functional theory to study the FT reaction mechanism with the goal to look for the optimal catalyst or catalytic structure to narrow that product distribution.
The FT is a complex multi-step reaction with multiple rate determining steps. Using density functional theory we can map out the reaction mechanism and build a micro kinetic model of the carbide chain growth mechanism. Using a degree of rate control analysis determine the critical steps in both chain growth and CH4 and CO2 formation. Once the critical steps are known we study the effects of surface structure, promotors and alloys on the kinetics of the critical reaction steps to determine which structure/promoter or alloys enhances the production of the optimal length chains.