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Document Type

Open Access

Degree Program

Chemical Engineering

Degree Type

Master of Science in Chemical Engineering (M.S.Ch.E.)

Year Degree Awarded

2012

Month Degree Awarded

September

Keywords

Catalytic Fast Pyrolysis, Biomass Conversion, Green Chemicals

Abstract

The huge energy demand of our society is causing fossil fuel resources to diminish rapidly. Therefore, it is critical to search for alternative energy resources. Biomass is currently both abundant and inexpensive. Biofuels (fuels produced from biomass) have the potential to replace fossil fuels if a cost effective process can be develop to convert biomass into fuels.

Catalytic fast pyrolysis is a technology that can convert biomass into gasoline ranged aromatics in a single step. By heating biomass quickly to an intermediate temperature, biomass will thermally decompose into small molecules which can fit into zeolite catalyst pores. Inside the catalyst pores, these small molecules undergo a series of reactions where aromatics are formed along with olefins, CO, CO2, CH4 and water. Gallium promoted ZSM-5 catalyst has been shown to promote small alkanes aromatization, thus it has the potential to increase aromatic yield in catalytic fast pyrolysis process. The focus of the thesis is to study the behavior of catalyst fast pyrolysis of biomass over Gallium promoted catalyst, and explore various ways to utilize the gas phase olefins to increase the aromatic yield. [CG1]

The effect of reaction parameters (temperature, weight hourly space velocity, and fluidized gas velocity) on catalytic fast pyrolysis of biomass with Ga/ZSM-5 were studied in a fluidized bed reactor using pine saw dust as the biomass feed. The product distribution and hydrocarbon selectivity are shown to be a strong function of temperature and weight hourly space velocity. Compared to ZSM-5 catalyst at the same reaction conditions, Ga/ZMS-5 has been shown to increase the aromatic yield by 40%.

Olefins can be recycled back to the CFP fluidized bed reactor to further increase the aromatic yield. The olefin co-feeding with pine saw dust experiments indicates that co-feeding with propylene can increase the aromatic yield, however, co-feeding with ethylene will cause a decrease in aromatic yield. In both co-feeding experiments, an increase in the amount of coke formed was also observed.

Besides a simple olefin recycle, another possible way to utilize these olefins, while avoiding the high cost to separate them from other gas phase products (CO, CO2 and CH4),is adding a secondary alkylation unit after the fluidized bed reactor. The alkylation unit could provide a way to produce additional ethylbenzene after the main CFP process. Three zeolite catalysts (ZSM-5, Y-zeolite and Beta zeolite) were tested in the alkylation unit, and ZSM-5 catalyst shows the highest activity and selectivity in the alkylation of benzene and ethylene.

First Advisor

George W Huber

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