Reaction pathways for the ethanol-to-aromatics conversion of excess bioethanol to BTEX aromatics and jet fuel in a metal-exchanged hierarchical system.

• Applicant: Dr. Michael Dyballa
• Subject Area: Technical Chemistry
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 471005971

Within the next years and due to the use of battery-driven cars, the use of ethanol in fuels will decline. Within this application, a process for the alternative use and upgrade of excess ethanol from fermentation processes will be researched. The direct conversion of ethanol to jet fuel and industrially important BTEX-aromatics has the economic advantage, that aqueous solutions of ethanol can be used as feed directly without energy-intensive purification. The products, jet fuel and BTEX aromatics, are difficultly synthesized CO2-neutral using other routes. However, the direct conversion of ethanol lacks from fast coke formation and rapidly inactivated catalysts. At this point the proposed project seeks to add additional value by synthesizing new, more efficient catalysts and identification of mechanistic particularities of the ethanol conversion.The coking of ZSM-5 zeolites catalysts will be slowed down by combining two post-modification methods. The exchange of the catalysts with zinc and gallium-ions is, from the conversion of methanol, known to enhance the aromatic content of the products. Changes in the direct surrounding of gallium will be directly monitored by 71Ga solid state NMR. The short time on stream until deactivation will be enlarged by desilication that means by use of hierarchical ZSM-5 catalysts. Thereby, a secondary mesopore system is introduced into the catalysts, which multiplies the amount of pore openings and improves in best case the diffusion properties. The location of acid sites will be determined quantitatively by using voluminous probe molecules and will be correlated with catalytic results, for getting first insights I how acid site location alters the selectivity and reaction mechanism.After identification of suitable catalysis systems, mechanistic differences to the methanol-conversion will be elaborated. The mechanism of ethanol-to-aromatics/jet fuel conversion will be investigated by a combination of spectroscopic techniques. The use of in situ UV/Vis gives insights into the formation of aromatics and coke. The technique is combined with the use of in situ DRIFTS and ex situ MAS NMR techniques upon using 13C-marked feed. We want to find out to which extend the reaction pathway involves the intermediate ethene and how this affects the efficiency of the ethanol conversion compared to the use of methanol feed.

• DFG Programme: Research Grants