BIOMASS DERIVED SMALL OXYGENATES TO FUEL RANGE HYDROCARBONS OVER HZSM-5

Karthikeyan Ramasamy

In recent times a great deal of research has focused on the development of renewable energy resources. Renewable fuels from biomass are generated through thermochemical and biological pathways. All the thermochemical processes generates aqueous phase containing oxygenate compounds as by products and biological process generates oxygenates at dilute concentrations. So it is important to develop a process to convert these aqueous streams into compounds that are compatible with the current fuel infrastructure and/or to increase the overall carbon yield. Methanol to Gasoline (MTG) process via HZSM-5 catalyst is well understood. The HZSM-5 catalyst provides a suitable compromise among activity, shape selectivity, and better hydrothermal stability. HZSM-5 is also amenable to regeneration by simply burning the catalyst in air to remove the coke. These same characteristics make HZSM-5 zeolite an interesting catalyst to investigate for the dilute oxygenate aqueous stream of interest in this study. Our focuses on examining the reaction and deactivation mechanism for C1 to C4 alcohols, acetic acid, acetaldehyde, acetone and ethyl acetate conversion over HZSM-5 catalyst using dilute aqueous feedstocks at moderate operating conditions. The alcohol transformation process involves a complex set of reaction pathways. In the early stage of the catalyst life time the reaction mechanism was similar all the alcohols. The catalyst life time is higher for the alcohols > C2 because the oligomerization of propylene and butylene, parent dehydration product, has lower activation energy and can readily take place on weaker acidic sites to form higher hydrocarbon. The conversion of alcohol and aldehyde deactivates the catalyst primarily via pore blocking mechanism but the rate of deactivation is orders of magnitude higher for aldehydes. Acetic acid deactivates the catalyst through an active site poisoning mechanism. Both the deactivation and the reaction mechanism are different for different functional group compounds. Oxygenates, primarily alcohol compounds, generated via biological conversion process can be converted to fuel blend stocks over HZSM-5. In addition the hierarchical zeolites can be used for higher catalyst life time and catalytic activity. Thermochemical conversion generated aqueous phase contains several different functional groups requires further pre-treatment or different reaction mechanisms to generate fuel range hydrocarbons.

BIOMASS DERIVED SMALL OXYGENATES TO FUEL RANGE HYDROCARBONS OVER HZSM-5

Files and links (1)

Abstract

Metrics

Details