The growing dependence in the U.S. on foreign crude oil supplies and increased concerns regarding greenhouse gas emissions has generated considerable interest in research to develop renewable and environmentally friendly liquid hydrocarbon transportation fuels. One of the strategies for achieving this is to produce intermediate compounds such as alcohols and other simple oxygenates from biomass-generated synthesis gas (mixture of carbon monoxide and hydrogen) and further convert them into liquid hydrocarbons. A typical mixed oxygenate stream is expected to contain water (up to about 50%), alcohols, such as methanol and ethanol and smaller quantities of other oxygenates such as acetaldehyde, acetic acid and ethyl acetate. However the composition of the mixed oxygenate stream generated from synthesis gas varies significantly depending on the catalyst used and the process conditions. Conversion of alcohols over HZSM5 is very well studied. It is essential to understand the mechanisms of other oxygenates that are present in a mixed oxygenate synthesis product stream over the HZSM5 to successfully convert the mixture into hydrocarbon fuels. The conversion of dilute acetaldehyde, acetic acid and ethyl acetate over HZSM5 in a fixed bed reactor with and without co-fed ethanol was investigated using HZSM5 catalysts with various Si/Al ratios and different feed compositions. The aqueous products were analyzed by liquid chromatography to measure the conversion level of the feed material against the feed composition and the Si/Al ratio of the catalyst tested. The presence of acetaldehyde in the feed stream deactivated the catalysts faster followed by acetic acid and ethyl acetate. However, the deactivation rate, when acetaldehyde is present in feed, is faster for the 15:1 Si/Al ratio zeolite compared to 40:1 ratio zeolite. This behavior did not occur with either acetic acid or ethyl acetate in the feed stream. Proposed deactivation mechanisms explaining these differences are discussed.

Deactivation mechanism of mixed oxygenates over HZSM5

245th National Meeting (2013)

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