(583cr) Catalytic Conversion of Bioethanol to 1-Butanol and Higher Alcohols: Effect of Water and Intermediates On Yield

Catalytic Conversion of Bioethanol to 1-Butanol and Higher Alcohols: Effect of Water and Intermediates on Yield

Tyler L. Jordison and Dennis J. Miller

Department of Chemical Engineering and Materials Science, Michigan State University,

East Lansing, Michigan 48824, USA

(jordison@msu.edu)

            With the recent increase in demand for renewable fuels, there has been a surge in corn-based bioethanol production.  Unfortunately, the energy density of ethanol is much lower than gasoline, resulting in poor fuel economy. Gas mileage could be improved if ethanol was upgraded to 1-butanol and other higher alcohols, as these alcohols have energy values close to gasoline [1]. Bioethanol thus has potential to be a platform feedstock for higher alcohol production, which have broad applications as both fuels and chemicals. The current method for producing higher alcohols is the oxo process, which uses petroleum-derived propylene as the feedstock [2]. The oxo process is complicated, requires high energy input, and is costly [2].

A greener process needs to be realized that directly converts ethanol to higher alcohols.  Carbon-carbon coupling of alcohols is commonly regarded as the Guerbet reaction [2].  In the ethanol Guerbet reaction, ethanol is oxidized to acetaldehyde, the acetaldehyde undergoes an aldol condensation to crotonaldehyde, and then the crotonaldehyde is hydrogenated to butanol [3].  Product alcohols can subsequently undergo Guerbet reactions with themselves and ethanol. 

Early experiments over La/Ni/Al2O3 catalyst gave high selectivity (>80%) towards C4, C6, and C8 higher alcohols, with gas formation, acetaldehyde, and ethyl acetate as primary co-products.  To further improve selectivity to alcohols, the effects of water and the co-products on yield during reaction have been investigated. Partial water removal during reaction was accomplished by adding a recirculating flow loop containing a 3A molecular sieve bed to a 300ml Parr reactor. Co-products acetaldehyde and ethyl acetate quickly form and then remain at nearly constant concentration over the course of reaction, indicating they are likely in equilibrium with ethanol in the reaction phase. Their addition to the initial reaction mixture will thus improve overall alcohol yield from ethanol.  

References

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[4]  K. Koda, T. Matsu-Ura, Y. Obora, Y. Ishii, Chemistry Letters 38 (2009) 838-839.

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