Date of Completion

7-13-2020

Embargo Period

7-13-2020

Keywords

FTS, structured monolith catalysts, gasoline production, bifunctional catalysts

Major Advisor

George Bollas

Associate Advisor

Puxian Gao

Associate Advisor

Brian Willis

Associate Advisor

Julia Valla

Associate Advisor

Luyi Sun

Field of Study

Chemical Engineering

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Gasoline accounts for more than half of U.S. transportation energy usage and its consumption continues growing. Crude oil is where gasoline originates from. However, crude oil reserves are limited in most of the countries around the world. U.S. imports thousand barrels of gasoline per day, making it highly dependent on foreign oil import which imposes a threat to U.S. homeland security. To make the U.S. gasoline independent, alternative processes such as Fischer-Tropsch Synthesis process (FTS) can be promising to mitigate high gasoline demand on transportation fuel and increase fuel diversity. However, scalable, selective, and more efficient FTS technologies are required to align with the need for high gasoline production.

Energy independence and security are some of the merits of making FTS a more efficient and less centralized process. Among the many challenges in FTS catalysis, selectivity to gasoline-range products is vital to be addressed. FTS uses synthesis gas (syngas, CO and H2) as feedstock. Normally, it follows the Anderson-Schulz-Flory (ASF) distribution. FTS can be environmentally benign and friendly, since there is no sulfur or nitrogen in the products. While FTS is conceived as a diesel-producing process, using either a cobalt or an iron catalyst. A bifunctional catalyst can be formulated and applied to improve gasoline selectivity via oligomerization, aromatization, and isomerization reactions. This thesis aims at exploring the potential of structured catalysts as candidates for intensified FTS process selective to gasoline production.

In this thesis, structured bifunctional catalysts consisting of a monolith support, cobalt catalyst, and ZSM-5 with micro- or mesoporosity were synthesized and tested in a fixed bed reactor. Fine-tuning of the catalyst and process condition led to desirable gasoline selectivity. However, the CO conversion was hindered due to the mass transfer limitations in the microporous zeolite. Mesopores were, thus, introduced later to relax mass transfer limitation. CO conversion increased to near 90%, while maintaining high gasoline selectivity with the introduction of the mesopores. A highly active and selective structured catalyst was formulated. After successful synthesis and testing of the bifunctional structured catalysts, modeling was performed to assess the techno-economic feasibility and potential of the new catalytic process. The experimental data was used in a modular Gas-to-Liquid (GTL) plant to further study the potential of the structured catalysts for an intensified process, aiming to monetize stranded natural gas.

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