Engineering Commons^™

The Investigation Of Surface Barrier During Molecular Transport In Hierarchical Zeolites, Xiaoduo Qi

Doctoral Dissertations

Hierarchical zeolites with micropore lengths on the order of nanometers have been synthesized with the aim of reducing mass transfer limitation. However, due to large external surface to volume ratios, the mass transport in these materials can be hindered by a secondary rate limitation step imposed on the external surface of the zeolites. This has led to the general phenomenon referred to as “surface barriers”, which cause the enhancement in mass transport being far lower than expected. In order to fully unlock the potential of hierarchical zeolites, it is imperative to fundamentally understand the molecular transport in these new types …

Engineering Zeolite Catalysts Through Porosity And Surface Acidity Control For Selective Production Of Light Olefins, Xin Li

Doctoral Dissertations

"Zeolites are broadly used as heterogeneous catalysts in various chemical and petrochemical industries to produce value-added chemicals and fuels, mainly due to their large surface area, acid-base properties, high thermal stability, and excellent shape-selectivity. In this dissertation, various zeolite catalysts were engineered through fine-tuning micro-meso-macro-porosity and surface acidity. The engineered zeolites were used as heterogeneous catalysts for production of light olefins such as ethylene and propylene through alcohol dehydration and hydrocarbon cracking reactions.

To control the zeolite porosity and acidity, SAPO-34@ZSM-5 and SAPO-34@Silicalite-1 composites with core-shell structure were synthesized and evaluated in ethanol dehydration reaction. Analysis of catalytic performance revealed …

Nanoporous Solid Acid Materials For Biomass Conversion Into Value-Added Chemicals: Synthesis, Catalysis, And Chemistry, Hong Je Cho

Doctoral Dissertations

Growing environmental concerns associated with diminishing reserves of fossil fuels has led to accelerated research efforts towards the discovery of new catalytic processes for converting renewable lignocellulosic biomass into value-added chemicals. For this conversion, nanoporous solid acid materials have been widely used because of their excellent hydrothermal stability and molecular sieving capability. In the thesis, hierarchical Lewis acid zeolites with ordered mesoporosity and MFI topology (three dimensionally ordered mesoporous imprinted (3DOm-i) Sn-MFI) were successfully synthesized within the confined space of three dimensionally ordered mesoporous (3DOm) carbon by a seeded growth method. The obtained 3DOm-i Sn-MFI showed at least 3 times …

Catalytic Hydrodeoxygenation And Dehydration Of Bioderived Oxygenates To Renewable Hydrocarbon Building Block Molecules: Enabling Renewable Carbon Fiber, Andrew Walter Lepore

Doctoral Dissertations

It is our goal to develop inexpensive catalytic pathways that can effectively remove oxygen from bio-derived carboxylic acids and alcohols under mild reaction conditions to produce propene which can be converted to renewable carbon fibers. Carboxylic acid hydrodeoxygenation and alcohol dehydration are necessary for successfully producing propene from bio-mass derived precursors and are also broadly relevant to bio-oil upgrading. This body of research adds to the understanding of both known and novel catalyst materials and develops and optimizes pathways for valorizing oxygenates. Dehydration and hydrodeoxygenation catalysts were examined under both batch and continuous flow operation. Product selectivity and reactant conversion …

Rational Development Of Carbon-Based Materials For Adsorption-Enhanced Conversion Of Cellulose To Value-Added Chemicals, Paul J. Dornath

Doctoral Dissertations

The increasing demands for transportation fuels and commodity chemicals as well as concerns over diminishing fossil fuel resources have driven research efforts towards the efficient utilization of renewable feedstocks, such as naturally abundant lignocellulosic biomass. Co-impregnation of microcrystalline cellulose with dilute sulfuric acid and glucose catalyzed the formation of a(1→6) branches onto b(1→4) glucan prior to ball-milling and reduce the time needed for ball-milling 4-fold compared to impregnation with acid alone. A three dimensionally ordered mesoporous (3DOm) carbon-based catalyst was developed that rapidly hydrolyzed the water-soluble glucan oligomers to 91.2% glucose yield faster than conventional approaches. A structure-property relationship was …

Rational Development Of Solid Lewis Acid Catalysts For Biomass Conversion, Chun-Chih Chang

Doctoral Dissertations

The need for sustainable production of everyday materials in addition to declining reserves of petroleum-based feedstocks has motivated research into the production of renewable aromatic chemicals from biomass. We have proposed a multistep pathway to produce renewable p-xylene from lignocellulosic biomass using heterogeneous catalysts. The pathway includes formation of glucose by saccharification of cellulose, isomerization of glucose into fructose, dehydration/hydrogenolysis for production of 2,5-dimethylfuran (DMF), and final step for producing p-xylene from reacting DMF with ethylene. Lewis acid zeolite catalysts (e.g. Sn-BEA, a tin containing molecular sieve with zeolite BEA structure) exhibited critical roles in the pathway because …

Production Of Sustainable Aromatics From Biorenewable Furans, Christopher Luke Williams

Doctoral Dissertations

Increasing demand for renewable and domestic energy and materials has led to an accelerated research effort in developing biomass-derived fuels and chemicals. The North American shale gas revolution can provide a domestic source for the manufacture of four of the five major products of the world chemical industry: methanol, ethylene, ammonia, and propylene. However this emerging domestic resource lacks a conversion pathway to the fifth major chemical building block; the larger C6 aromatics benzene, toluene, and xylene (BTX). One sustainable feedstock for renewable C6 aromatic chemicals is sugars produced by the saccharification of biopolymers (e.g., cellulose, hemicellulose). The catalytic conversion …

Production Of Renewable Fuels And Chemicals From Biomass-Dervied Furan Compounds, Sara K. Green

Doctoral Dissertations

Growing concern over the petroleum supply, energy independence, and environmental impacts associated with fossil fuels, has motivated research into the production of renewable fuels and aromatic chemicals from biomass resources. Specifically, furan-based feedstocks such as furfural, 2-methylfuran (MF) and, 2,5-dimethylfuran (DMF) can be derived from biomass and used to produce a wide variety of desired compounds. These furan-based feedstocks are produced by: (a) the hydrolysis of cellulose and hemicellulose form to glucose and xylose, (b) the dehydration of these carbohydrates to form 5-hydroxymethylfurfural (HMF) and furfural, and (c) the reduction of HMF and furfural to DMF, MF, and furan. The …