(699g) A Highly Selective Route from Syngas to Ethanol: Tandem Catalysis Unconstrained By Anderson-Schulz-Flory Distribution
AIChE Annual Meeting
2017
2017 Annual Meeting
Catalysis and Reaction Engineering Division
Catalysis for C1 Chemistry: Methane Reforming and Syngas Conversion
Thursday, November 2, 2017 - 2:18pm to 2:36pm
In many cases of HAS catalyzed by single catalysts, the reaction is believed to proceed by concerted hydrogenation and chain growth (C-C coupling) steps, resulting in co-production of aldehydes, alkenes, and alkanes, with chain-length approximately following the Anderson-Schulz-Flory (ASF) distribution. Such a wide spread in products increases separation costs for targeted HAS, and results in lower-value products (such as methane) competing for feed utilization. Advances in the engineering of the catalyst surface composition and structure have led to significant improvements in selectivities, but, to date, the aforementioned limitations have not been completely eliminated. One approach to break away from the constraints of the ASF distribution in HAS is to spatially separate the hydrogenation and chain-growth steps of the process by pairing catalysts that, individually, selectively catalyze only one of the steps, but, in a multi-bed tandem catalysis scheme, enable both.
In this work, we developed a combination of precious-metal-free, inexpensive, heterogeneous catalysts that, under differential conversions of CO/H2 feed, are able to achieve upwards of 80% selectivity towards ethanol, on a CO2-free carbon basis, with <1% methane selectivity. We will discuss the response of this system to process variables, and its stability. Additionally, some of the thermodynamic and kinetic considerations that are important in the design of such tandem-catalytic schemes for HAS will be highlighted.