Issue 7, 2015

Selective hydrodeoxygenation of bio-oil derived products: ketones to olefins

Abstract

The hydrodeoxygenation (HDO) of various ketones (acetone, methyl ethyl ketone and cyclohexanone) to olefins via hydrogenation–dehydration was conducted in a fixed bed reactor at 373–573 K under H2. A ketone can be hydrogenated over the metal function to an alcohol intermediate that is subsequently dehydrated to an olefin over the acidic function. A preliminary study on hydrogenation of acetone to 2-propanol over metal/SiO2 catalysts (Cr, Fe, Co, Ni, Cu and Pd) shows that Ni and Cu are active at >373 K. Although Ni possesses an activity higher than that of Cu, it promotes olefin hydrogenation and alcohol hydrogenolysis at >473 K. Hydrogenolysis of alcohol intermediate is suppressed over the Ni–Cu alloy catalyst. An optimum conversion with 100% selectivity to alcohol, can be obtained at 448 and 473 K for Ni and Cu, respectively. The dehydration of 2-propanol to propylene over proton zeolites (ZSM-5, Y, Mordenite and β) can be achieved at >398 K. The zeolites with three-dimensional pore structure (β and Y) provide relatively higher activity (>90% conversion). However, a bimolecular dehydration to ether is also promoted. Only HZSM-5 shows excellent selectivity to propylene (98%). Hydrodeoxygenation of ketones was tested with (i) a double bed of 5%Ni/SiO2 and HZSM-5 (Si/Al ~ 13), (ii) a physical mixed bed of 5%Cu/SiO2 and HZSM-5 (Si/Al ~ 13) and (iii) a bi-functional catalyst of 5%Cu/HZSM-5 (Si/Al ~ 250). It was found that high alkene selectivity was readily obtained at 448 K. While, over the physical mixed bed and bi-functional catalyst, the hydrogenation activity was enhanced as the alcohol intermediate was removed from the system. The reactivity of the ketone depends on its adsorption on the metal surface and steric hindrance, i.e. acetone > cyclohexanone > methyl ethyl ketone.

Graphical abstract: Selective hydrodeoxygenation of bio-oil derived products: ketones to olefins

Supplementary files

Article information

Article type
Paper
Submitted
12 Mar 2015
Accepted
27 Apr 2015
First published
27 Apr 2015

Catal. Sci. Technol., 2015,5, 3639-3648

Author version available

Selective hydrodeoxygenation of bio-oil derived products: ketones to olefins

A. Witsuthammakul and T. Sooknoi, Catal. Sci. Technol., 2015, 5, 3639 DOI: 10.1039/C5CY00367A

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