Editorial Feature

Using Coal to Produce Ultra-Clean Transportation Fuel

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Feb 8 2008

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Coal-derived liquid fuel, which is also commonly referred to as coal-to-liquid, is a term used to describe the process in which coal is converted into liquid fuels, such as diesel or gasoline. The development of coal-derived liquid fuels has been largely supported by rising world oil prices and an increased interest in producing liquid fuels from biomass, oil shale and coal sources

Producing Coal-Derived Liquid Fuels

At present, the Fischer-Tropsch process is the main process used for the production of coal-derived liquid fuels. This process involves an initial conversion of coal to syngas, which is a mixture of both carbon monoxide (CO) and hydrogen (H₂) gas molecules. Prior to converting the syngas to a liquid fuel, a percentage of the CO gas undergoes a water-gas shift that converts it to carbon dioxide (CO₂). Like other chemical processes, the Fischer-Tropsch reaction requires the use of a catalyst, which is typically iron-based.

It is important to note that there are also a number of processes currently available for the conversion of coal directly to liquid fuels. A wide range of useful chemicals and transportation fuels such as gasoline, methanol and diesel can be produced using the coal-to-liquids processes.

Benefits of Coal-to-Liquid Fuels

One of the major advantages associated with the use of coal-derived liquid fuel is that it can be used by today’s gasoline and diesel-powered vehicles. Furthermore, this fuel option is also compatible with petroleum distribution infrastructures, and therefore does not require any new or modifications of existing infrastructures, such as storage tanks and pipelines.

A reduction in regulated exhaust emissions from a variety of diesel-powered engines and vehicles can also be achieved by using fuel derived from coal from the Fischer-Tropsch process. Coal-derived diesel has also shown to have a near-zero sulfur content, which allows the use of advanced emission control devices. Because of the low sulfur content, very little to no particulates are emitted.

Recent Advancements in Coal-to-Liquid Fuels

During the typical production of coal-derived liquid fuels by the Fischer-Tropsch reaction, a large amount of CO₂ is often released in large volumes without being captured. In an effort to reduce the amount of CO₂ generated by this process, a ground of researchers from the Eindhoven University of Technology have developed a pure iron carbide catalyst that exhibits low CO₂ selectivity. By eliminating nearly any CO₂ from being generated by this process, the researchers were able to significantly reduce energy requirements associated with the Fischer-Tropsch reaction, which can ultimately save a typical coal-to-liquid plant an estimated 25 million euros each year.