Standard-Compliant Gasoline by Upgrading a DTG-Based Fuel through Hydroprocessing the Heavy-Ends and Blending of Oxygenates

Methanol-to-gasoline (MTG) and dimethyl ether-to-gasoline (DTG) fuels are rich in heavy
aromatics such as 1,2,4,5-tetramethylbenzene, resulting in low volatilities due to a lack of light ends,
increased emission tendencies and drivability problems due to crystallization. Approaches addressing
these issues mainly focus on single aspects or are optimized for petroleum-based feedstocks. This
research article introduces an upgrading strategy for MTG and DTG fuels through hydroprocessing
(HP) heavy-ends and applying a sophisticated blending concept. Different product qualities were prepared
by HP heavy gasoline (HG) and Fischer-Tropsch wax using commercially available Pt/HZSM-5
and Pt/SAPO-11 catalysts in a fixed-bed reactor. The products were used for blending experiments,
focusing on gasoline volatility characteristics. Accordingly, methanol, ethanol, methyl tert-butyl
ether (MTBE), and ethyl tert-butyl ether (ETBE) were evaluated in a second blending experiment.
The results were finally considered for preparing blends meeting EN 228. HP of HG was found to
improve the amount of light-ends and the vapor pressure of the DTG fuel with increasing reaction
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temperature without, however, satisfying EN 228. The front-end volatility was further improved
by blending methanol due to the formation of near-azeotropic mixtures, while ethyl tert-butyl ether
(ETBE) considerably supported the mid-range volatility. A final blend with an alcohol content of less
than 3 vol.%, mostly meeting EN 228, could be provided, making it suitable even for older vehicles.