Theses and Dissertations

Yongwu Lu

Issuing Body

Mississippi State University

Advisor

Yu, Fei

Committee Member

DuBien, Janice

Committee Member

Mlsna, Todd E.

Committee Member

Schneider, Judith A.

Committee Member

Srinivasan, Radhakrishnan

Date of Degree

12-13-2014

Document Type

Dissertation - Open Access

Major

Biological Engineering

Degree Name

Doctor of Philosophy

College

James Worth Bagley College of Engineering

Department

Department of Agricultural and Biological Engineering

Abstract

Higher alcohol synthesis (HAS) from syngas or biomass-derived syngas is an important process for the production of oxygenate fuels, fuel additives and other intermediates for valueded chemical feedstock to produce medicine, cosmetics, lubricants, detergents, and polyesters. Chapter I reviews biomass to liquid fuels technology, higher alcohols being used as alternative fuels and fuel additives, the historical perspective and commercial status of higher alcohols, the catalyst system and the reaction mechanism for HAS from syngas. Chapter II discusses the Zn-Mn promoted Cu-Fe based catalyst that was synthesized by the co-precipitation method. The reaction temperature has been tested to study the influence on the catalytic performance. The maximal CO conversion rate was 72%, and the yield of alcohol and hydrocarbon was also very high. Cu was the active site for alcohol synthesis, iron carbide was the active site for olefin and paraffin synthesis. The reaction mechanism of HAS from syngas over Zn-Mn promoted Cu-Fe based catalyst was proposed. Chapter III documents the three-dimensionally ordered macroporous (3DOM) Cu-Fe catalyst developed using a glyoxylate route colloidal crystal template method. The high intrinsic activity was ascribed to three factors. First, the unique ordered structure has a large pore size and interconnected macroporous tunnels of the catalyst with a large accessible surface area to improve the catalytic activity. Second, a high density of uniformly distributed defective Cu0 and Fe5C2 nanoparticles derived from the glyoxylate route helps to provide abundant, active, and stable dual sites. Third, atomic steps on the Cu surface, induced by planar defects and lattice strain, serve as high-activity oxygenation sites. Active Fe5C2 chain-growth sites intimately surround the defective and strained form of the Cu surface, which results in a synergetic effect between the active and stable Cu–FexCy dual site for HAS. In Chapter IV, in situ ambient pressure x-ray photoelectron spectroscopy and in situ synchrotron powder diffraction were applied to identify the active site of 3DOM Cu-Fe catalyst for HAS. The results show that after syngas pretreatment of the 3DOM Cu-Fe catalyst, Cu0 is the active oxygenation site for alcohol synthesis, and Fe5C2 is the active site for carbon chain growth.

URI

https://hdl.handle.net/11668/19420

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