(544fc) Exploring a Tandem Chemocatalytic Route from Syngas to Ethanol

Selective higher alcohols synthesis (HAS) at high syngas conversions remains an unsolved catalytic challenge after many decades of industrial and academic research.¹ Last year we first reported a highly selective tandem catalytic scheme for ethanol synthesis from syngas that involved a combination of precious-metal-free, inexpensive, heterogeneous catalysts that avoid the selectivity limitations of the Anderson-Schulz-Flory distribution that is often observed on catalysts that do not spatially resolve the hydrogenation and chain-growth steps in HAS.² Namely, this strategy involves a three-bed configuration consisting of 1) a methanol and/or DME synthesis catalyst, 2) a zeolitic carbonylation catalyst for acetic acid and/or methyl acetate synthesis, and 3) an acetate hydrogenation catalyst. We showed that this three-bed configuration could operate in a single isothermal reactor, avoiding the need for inter-stage separations, heat exchange, or pressure swings. Our initial tests of this strategy were able to achieve upwards of 80% selectivity towards ethanol, on a CO₂-free carbon basis, with <1% methane selectivity, but operated under differential conversions of CO/H₂ feed. In this work, we will report our efforts to further understand the dynamic behavior of each of the catalytic beds, and to optimize the system to operate at higher conversions, while maintaining high selectivities and long catalyst lifetimes.

1. Luk, H. T. et al. Soc. Rev. 2017, 46 (5), 1358–1426.
2. Orazov, M.; Jaramillo, T. F. “A Highly Selective Route from Syngas to Ethanol: Tandem Catalysis Unconstrained by Anderson-Schulz-Flory Distribution” AIChE Annual Meeting, 2017, Minneapolis, MN, Oct 29-Nov 3