Aromatic coal, thermodynamic

From a thermodynamic point of view [145] the manufacture of synthetic transportation fuels should aim at a minimum change of the hydrogen content of the feedstock to that of the product (typically around H/C=2). It means that, in principle, it is more efficient to convert natural gas to paraffinic diesel than to aromatic rich gasoline. For coal the indirect conversion via syngas appears less efficient than the direct hydrogenation routes. However, these theoretical considerations should be supplemented with an analysis of the process steps and selectivities involved [145]. 

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