Reaction chemistry of ethanol oligomerization to distillate-range molecules using low loading Cu/Mg_xAlO_y catalysts

Journal Article · 09 August 2022 · Applied Catalysis. B, Environmental

DOI: https://doi.org/10.1016/j.apcatb.2022.121821 · OSTI ID:2331252

Cuello-Penaloza, Paolo A. ^[1]; Chavarrio-Cañas, Javier ^[2]; Du, Yi ^[3]; Lanci, Michael P. ^[3]; Maedke, Derek A. ^[2]; Dumesic, James A. ^[2]; Huber, George W.  ^[2]

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1. University of Wisconsin, Madison, WI (United States); University of Wisconsin Madison
2. University of Wisconsin, Madison, WI (United States)
3. ExxonMobil Research and Engineering, Annandale, NJ (United States)

We study ethanol oligomerization to higher alcohols and other oxygenates with a 0.3 wt. %Cu/Mg_2.9AlO catalyst. This reaction involves more than 130 products in a complicated reaction network. The selectivity towards diesel fuel precursor compounds (hereafter ‘DFPC’) increased with conversion until reaching a plateau at an ethanol conversion of ~70 %. Alcohol selectivity was found to follow Schultz-Flory distribution at all studied conversions. Larger sized alcohols then are formed mostly by chain-growth mechanisms via surface reactions of adsorbed oligomers with ethanol-based monomers. Higher esters are formed from alcohols and aldehydes in a series reaction mechanism. Moreover, C₆₊ ester and C₄₊ ketones selectivities increase as conversion increases. We also found that C₄₊ alcohols most likely undergo Guerbet coupling with the studied catalyst to form even higher alcohols once, and that the oxygen of these alcohols is active as a nucleophile, resulting in the selective formation of esters if the starting alcohol is branched. Finally, we performed several cofeed studies varying ethanol-to-H₂ inlet partial pressures, and adding acetaldehyde and ethyl acetate as cofeeds to ethanol at different concentrations. Here, we conclude from these experiments that acetaldehyde concentration controls reaction chemistry, with conditions favoring larger concentrations of the molecule promoting both alcohol coupling and ester formation, and conditions leading to lower concentrations of acetaldehyde resulting in higher alcohol selectivity at the expense of esters and higher aldehydes.

• Research Organization: ExxonMobil Research and Engineering, Annandale, NJ (United States); University of Wisconsin, Madison, WI (United States)
• Sponsoring Organization: USDOE; USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Advanced Automotive Technologies (EE-32); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Sustainable Transportation. Bioenergy Technologies Office (BETO); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Sustainable Transportation. Vehicle Technologies Office (VTO); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Technology Development (EE-20)
• Grant/Contract Number: EE0008480
• OSTI ID: 2331252
• Journal Information: Applied Catalysis. B, Environmental, Journal Name: Applied Catalysis. B, Environmental Vol. 318; ISSN 0926-3373
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English