Ethanol is the most abundantly produced biofuel and used as a blendstock for gasoline-powered vehicles. It is projected that in the future demand for gasoline will decrease and demand for C
8-22 distillate range-fuels such diesel and jet fuels will increase [1]. As we will show in this presentation, ethanol can be converted to C
4+ linear and α-branched alcohols by C-C coupling reactions (ethanol oligomerization) as well as to C
6+ high molecular weight esters by C-O coupling reactions with Cu/Mg
xAlO
y (CuMMO) catalysts. The C
4+ alcohols may be converted to ethers, which can be used as a diesel fuel blendstock, via bimolecular dehydration in a subsequent step [2]. In this presentation we report on the effect of BET surface area and Cu-loading of the CuMMO catalysts on the activity, selectivity and stability of the CuMMO catalysts for ethanol oligomerization. We have identified more than 160 species in the products including alcohols, esters, aldehydes, ketones, and olefins. Alcohols range from C
4 to C
12. Esters range from C
4 to C
14. Alcohols follow a Schulz-Flory chain growth model at all conversion ranges. We show the relationship between the catalyst properties (BET surface area, acid and base site count, Cu-loading and synthesis method) and the performance in the reactions. We also show that physical mixtures of CuMMO and MMO can have similar product selectivity of low loading CuMMO catalysts. Finally, we demonstrate that diesel fuel precursor (C
4+ alcohols, aldehydes and ketones, C
6+ esters and ethers) selectivities over 70% can be obtained at all conversion ranges with low loadings of Cu (< 0.6 wt%) for CuMMO catalysts.
[1] 2019 Outlook for energy: a perspective to 2040. Exxon Mobil Corporation: 2019.
[2] Eagan, N. M., Moore, B. M., McClelland, D. J., Wittrig, A. M., Canales, E., Lanci, M. P., Huber, G. W., Green Chem. 2019, 21 (12), 3300-3318.
