Matching Items (4)
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- All Subjects: Adsorption
- Creators: Wang, Xuan
- Member of: ASU Electronic Theses and Dissertations
- Status: Published
Description
Post-combustion carbon capture is a viable option for reducing CO2 greenhouse gas emissions, and one potentially promising technology for this route is adsorption using chemically and physically based sorbents. A number of exceptional CO2 sorbents materials have been prepared including metal organic frameworks, zeolites, and carbon based materials. One particular group of capable materials are amine based solid sorbents that has shown to possess high adsorption capacities and favorable adsorption kinetics. A key variable in the synthesis of an amine based sorbent is the support which acts as the platform for the amine modification. Aerogels, due to their high porosities and surface areas, appear to be a promising support for an amine modified CO2 sorbent. Therefore, in order to develop a commercially viable CO2 sorbent, particulate aerogels manufactured by Cabot Corporation through an economical and proprietary ambient drying process were modified with amines using a variety of functionalization methods. Two methods of physical impregnation of the amino polymer TEPA were performed in order to observe the performance as well as understand the effects of how the TEPA distribution is affected by the method of introduction. Both samples showed excellent adsorption capacities but poor cyclic stability for lack of any covalent attachment. Furthermore the method of TEPA impregnation seems to be independent on how the polymer will be distributed in the pore space of aerogel. The last two methods utilized involved covalently attaching amino silanes to the surface silanols of the aerogel. One method was performed in the liquid phase under anhydrous and hydrous conditions. The materials developed through the hydrous method have much greater adsorption capacities relative to the anhydrous sample as a result of the greater amine content present in the hydrous sample. Water is another source of silylation where additional silanes can attach and polymerize. These samples also possessed stable cyclic stability after 100 adsorption/regeneration cycles. The other method of grafting was performed in the gas phase through ALD. These samples possessed exceptionally high amine efficiencies and levels of N content without damaging the microstructure of the aerogel in contrast to the liquid phase grafted sorbents.
ContributorsLinneen, Nick (Author) / Lin, Jerry (Thesis advisor) / Pfeffer, Robert (Thesis advisor) / Lind, Mary (Committee member) / Rege, Kaushal (Committee member) / Nielsen, David (Committee member) / Anderson, James (Committee member) / Arizona State University (Publisher)
Created2014
Description
With the aid of metabolic pathways engineering, microbes are finding increased use as biocatalysts to convert renewable biomass resources into fine chemicals, pharmaceuticals and other valuable compounds. These alternative, bio-based production routes offer distinct advantages over traditional synthesis methods, including lower energy requirements, rendering them as more "green" and "eco-friendly". Escherichia coli has recently been engineered to produce the aromatic chemicals (S)-styrene oxide and phenol directly from renewable glucose. Several factors, however, limit the viability of this approach, including low titers caused by product inhibition and/or low metabolic flux through the engineered pathways. This thesis focuses on addressing these concerns using magnetic mesoporous carbon powders as adsorbents for continuous, in-situ product removal as a means to alleviate such limitations. Using process engineering as a means to troubleshoot metabolic pathways by continuously removing products, increased yields are achieved from both pathways. By performing case studies in product toxicity and reaction equilibrium it was concluded that each step of a metabolic pathway can be optimized by the strategic use of in-situ adsorption as a process engineering tool.
ContributorsVasudevan, Anirudh (Author) / Nielsen, David R (Thesis advisor) / Torres, César I (Committee member) / Wang, Xuan (Committee member) / Arizona State University (Publisher)
Created2014
Description
The large-scale anthropogenic emission of carbon dioxide into the atmosphere leads to many unintended consequences, from rising sea levels to ocean acidification. While a clean energy infrastructure is growing, mid-term strategies that are compatible with the current infrastructure should be developed. Carbon capture and storage in fossil-fuel power plants is one way to avoid our current gigaton-scale emission of carbon dioxide into the atmosphere. However, for this to be possible, separation techniques are necessary to remove the nitrogen from air before combustion or from the flue gas after combustion. Metal-organic frameworks (MOFs) are a relatively new class of porous material that show great promise for adsorptive separation processes. Here, potential mechanisms of O2/N2 separation and CO2/N2 separation are explored.
First, a logical categorization of potential adsorptive separation mechanisms in MOFs is outlined by comparing existing data with previously studied materials. Size-selective adsorptive separation is investigated for both gas systems using molecular simulations. A correlation between size-selective equilibrium adsorptive separation capabilities and pore diameter is established in materials with complex pore distributions. A method of generating mobile extra-framework cations which drastically increase adsorptive selectivity toward nitrogen over oxygen via electrostatic interactions is explored through experiments and simulations. Finally, deposition of redox-active ferrocene molecules into systematically generated defects is shown to be an effective method of increasing selectivity towards oxygen.
First, a logical categorization of potential adsorptive separation mechanisms in MOFs is outlined by comparing existing data with previously studied materials. Size-selective adsorptive separation is investigated for both gas systems using molecular simulations. A correlation between size-selective equilibrium adsorptive separation capabilities and pore diameter is established in materials with complex pore distributions. A method of generating mobile extra-framework cations which drastically increase adsorptive selectivity toward nitrogen over oxygen via electrostatic interactions is explored through experiments and simulations. Finally, deposition of redox-active ferrocene molecules into systematically generated defects is shown to be an effective method of increasing selectivity towards oxygen.
ContributorsMcIntyre, Sean (Author) / Mu, Bin (Thesis advisor) / Green, Matthew (Committee member) / Lind, Marylaura (Committee member) / Arizona State University (Publisher)
Created2019
Description
The aims of this project are to demonstrate the design and implementation of separations modalities for 1) in situ product recovery and 2) upstream pretreatment of toxic feedstocks. Many value-added bioproducts such as alcohols (ethanol and butanol) developed for the transportation sector are known to be integral to a sustainable future. Likewise, bioproduced aromatic building blocks for sustainable manufacturing such as phenol will be equally important. The production of these compounds is often limited by product toxicity at 2- 20 g/L, whereas it may desirable to produce 20-200 g/L for economically feasible scale up. While low-cost feedstocks are desirable for economical production, they contain highly cytotoxic value-added byproducts such as furfural. It is therefore desirable to design facile detoxification methods for lignocellulose-derived feedstocks to isolate and recover furfural preceding ethanol fermentation by Escherichia coli. Correspondingly it is desirable to design efficient facile in situ recovery modalities for bioalcohols and phenolic bioproducts. Accordingly, in-situ removal modalities were designed for simultaneous acetone, butanol, and ethanol recovery. Additionally, a furfural removal modality from lignocellulosic hydrolysates was designed for upstream pretreatment. Solid-liquid adsorption was found to serve well each of the recovery modalities characterized here. More hydrophobic compounds such as butanol and furfural are readily recovered from aqueous solutions via adsorption. The primary operational drawback to adsorption is adsorbent recovery and subsequent desorption of the product. Novel magnetically separable mesoporous carbon powders (MMCPs) were characterized and found to be rapidly separable from solutions at 91% recovery by mass. Thermal desorption of value added products was found efficient for recovery of butanol and furfural. Fufural was desorbed from the MMCPs up to 57% by mass with repeated adsorption/thermal desorption cycles. Butanol was recovered from MMCPs up to an average 93% by mass via thermal desorption. As another valuable renewable fermentation product, phenol was also collected via in-situ adsorption onto Dowex Optipore L-493 resin. Phenol recovery from the resins was efficiently accomplished with tert-butyl methyl ether up to 77% after 3 washes.
ContributorsStaggs, Kyle William (Author) / Nielsen, David R (Thesis advisor) / Lin, Jerry S (Committee member) / Torres, César I (Committee member) / Lind, Mary Laura (Committee member) / Wang, Xuan (Committee member) / Arizona State University (Publisher)
Created2017