Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Xiang, Yizhi

Committee Member

Toghiani, Hossein

Committee Member

Rai, Neeraj

Committee Member

Cui, Xin

Date of Degree

12-10-2021

Document Type

Dissertation - Open Access

Major

chemical engineering

Degree Name

Doctor of Philosophy (Ph.D)

College

James Worth Bagley College of Engineering

Department

Dave C. Swalm School of Chemical Engineering

Abstract

The fact that hydrogen is a clean and versatile fuel offers an attractive carbon-free source of energy and leverages the U.S. economy toward long-term sustainable economic growth. At an industrial scale, hydrogen production is mostly relying on methane steam reforming producing stoichiometric amounts of carbon oxides (CO and CO2), which imposes economic and environmental concerns. To mitigate the issue, we propose NH3 assisted anaerobic reforming of natural gas liquids (ethane and propane) as an alternative approach to produce COx free hydrogen. Here, in the first chapter, through comprehensive performance evaluation, characterization, and transient kinetic studies, it is shown that the atomically dispersed Re-oxo grafted into framework Al of the HZSM-5 zeolite are highly active and stable for the ammonia reforming of ethane and propane at temperatures comparable to steam reforming ≤ 650 °C. In the second chapter, an alternative non- noble Ni/Ga intermetallic compound (IMC) with various Ni to Ga ratios is synthesized through the solvothermal synthesis by forming the oxalate MOF precursor. The result indicates that while Ni-rich samples form pure Ni3Ga IMC with promising catalytic performance, the Ga rich catalyst consists of segregated phases of Ni/Ga IMC and Ga2O3 with ill-defined structure showing lower stability despite the high activity. In chapter 3, a bifunctional Ni/Ga supported ZSM-5 is successfully developed in ethane aromatization. Influence of metal function in early-stage and steady-state activity and stability as well as structure reactivity relation was investigated applying comprehensive characterization, performance test, deactivation modeling, and transient studies. The results suggest that a tandem reaction mechanism between Ni3Ga intermetallic compound, Ga cation, and Bronsted acid sites of zeolite is responsible for the superior performance of bimetallic catalysts compared to their monometallic counterpart. In the last chapter, applying transient kinetic technique, the mechanism of ethane aromatization over Pt and Zn supported ZSM-5 model catalysts was precisely explored. The results reveal that despite mechanistic differences between these catalysts, ethane amortization on both catalysts follows a hydrocarbon pool mechanism.

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