Matching Items (17)
Description
Pervaporation is a membrane separation technology that has had industrial application and which is the subject of ongoing research. Two major factors are important in judging the quality of a membrane: selectivity and permeation flux. Although many types of materials can be used for the separation layer, zeolites will be the material considered in this thesis. A simple mathematical model has been developed to demonstrate the inter-relationships between relative permeation flux, reduced selectivity, and the relative resistance to mass transfer of the support to the zeolite layer. The model was applied to several membranes from our laboratory and to two examples from the literature. The model offers a useful way of conceptualizing membrane performance and facilitates the comparison of different membrane performances. The model predicts the effect of different supports on zeolite supported membrane performance.
ContributorsMann, Stewart (Author) / Lin, Jerry (Thesis advisor) / Lind, Mary Laura (Committee member) / Nielsen, David (Committee member) / Arizona State University (Publisher)
Created2014
Description
Membrane-based gas separation is promising for efficient propylene/propane (C3H6/C3H8) separation with low energy consumption and minimum environment impact. Two microporous inorganic membrane candidates, MFI-type zeolite membrane and carbon molecular sieve membrane (CMS) have demonstrated excellent thermal and chemical stability. Application of these membranes into C3H6/C3H8 separation has not been well investigated. This dissertation presents fundamental studies on membrane synthesis, characterization and C3H6/C3H8 separation properties of MFI zeolite membrane and CMS membrane.
MFI zeolite membranes were synthesized on α-alumina supports by secondary growth method. Novel positron annihilation spectroscopy (PAS) techniques were used to non-destructively characterize the pore structure of these membranes. PAS reveals a bimodal pore structure consisting of intracrystalline zeolitic micropores of ~0.6 nm in diameter and irregular intercrystalline micropores of 1.4 to 1.8 nm in size for the membranes. The template-free synthesized membrane exhibited a high permeance but a low selectivity in C3H6/C3H8 mixture separation.
CMS membranes were synthesized by coating/pyrolysis method on mesoporous γ-alumina support. Such supports allow coating of thin, high-quality polymer films and subsequent CMS membranes with no infiltration into support pores. The CMS membranes show strong molecular sieving effect, offering a high C3H6/C3H8 mixture selectivity of ~30. Reduction in membrane thickness from 500 nm to 300 nm causes an increase in C3H8 permeance and He/N2 selectivity, but a decrease in the permeance of He, N2 and C3H6 and C3H6/C3H8 selectivity. This can be explained by the thickness dependent chain mobility of the polymer film resulting in final carbon membrane of reduced pore size with different effects on transport of gas of different sizes, including possible closure of C3H6-accessible micropores.
CMS membranes demonstrate excellent C3H6/C3H8 separation performance over a wide range of feed pressure, composition and operation temperature. No plasticization was observed at a feed pressure up to 100 psi. The permeation and separation is mainly controlled by diffusion instead of adsorption. CMS membrane experienced a decline in permeance, and an increase in selectivity over time under on-stream C3H6/C3H8 separation. This aging behavior is due to the reduction in effective pore size and porosity caused by oxygen chemisorption and physical aging of the membrane structure.
MFI zeolite membranes were synthesized on α-alumina supports by secondary growth method. Novel positron annihilation spectroscopy (PAS) techniques were used to non-destructively characterize the pore structure of these membranes. PAS reveals a bimodal pore structure consisting of intracrystalline zeolitic micropores of ~0.6 nm in diameter and irregular intercrystalline micropores of 1.4 to 1.8 nm in size for the membranes. The template-free synthesized membrane exhibited a high permeance but a low selectivity in C3H6/C3H8 mixture separation.
CMS membranes were synthesized by coating/pyrolysis method on mesoporous γ-alumina support. Such supports allow coating of thin, high-quality polymer films and subsequent CMS membranes with no infiltration into support pores. The CMS membranes show strong molecular sieving effect, offering a high C3H6/C3H8 mixture selectivity of ~30. Reduction in membrane thickness from 500 nm to 300 nm causes an increase in C3H8 permeance and He/N2 selectivity, but a decrease in the permeance of He, N2 and C3H6 and C3H6/C3H8 selectivity. This can be explained by the thickness dependent chain mobility of the polymer film resulting in final carbon membrane of reduced pore size with different effects on transport of gas of different sizes, including possible closure of C3H6-accessible micropores.
CMS membranes demonstrate excellent C3H6/C3H8 separation performance over a wide range of feed pressure, composition and operation temperature. No plasticization was observed at a feed pressure up to 100 psi. The permeation and separation is mainly controlled by diffusion instead of adsorption. CMS membrane experienced a decline in permeance, and an increase in selectivity over time under on-stream C3H6/C3H8 separation. This aging behavior is due to the reduction in effective pore size and porosity caused by oxygen chemisorption and physical aging of the membrane structure.
ContributorsMa, Xiaoli (Author) / Lin, Jerry (Thesis advisor) / Alford, Terry (Committee member) / Chan, Candace (Committee member) / Arizona State University (Publisher)
Created2015
Description
In this study, two novel sorbents (zeolite 4A and sodium polyacrylate) are tested to investigate if utilizing ultrasonic acoustic energy could decrease the amount of time and overall energy required to regenerate these materials for use in cooling applications. To do this, an experiment was designed employing a cartridge heater and a piezoelectric element to be simultaneously providing heat and acoustic power to a custom designed desorption bed while measuring the bed mass and sorbent temperature at various locations. The results prove to be promising showing that early in the desorption process ultrasound may expedite the desorption process in zeolite by as much as five times and in sodium polyacrylate as much as three times in comparison to providing heat alone. The results also show that in zeolite desorption utilizing ultrasound may be particularly beneficial to initiate desorption whereas in sodium polyacrylate ultrasound appears most promising in the after a temperature threshold is met. These are exciting results and may prove to be significant in the future as more novel heat-based cooling cycles are developed.
ContributorsBertrand, Weston Kyle (Author) / Phelan, Patrick (Thesis advisor) / Bocanegra, Luis (Committee member) / Wang, Liping (Committee member) / Devasenathipathy, Shankar (Committee member) / Arizona State University (Publisher)
Created2018
Description
The goal of this research was to study the effect of dilution on ammonium and potassium removal from real hydrolyzed urine. The performance of two natural zeolites, clinoptilolite and chabazite, was studied and compared with the help of batch equilibrium experiments at four dilution levels: 100%, 10%, 1% and 0.1% (urine volume/total solution volume). Further, the sorption behavior of other exchangeable ions (sodium, calcium and magnesium) in clinoptilolite and chabazite was studied to improve the understanding of ion exchange stoichiometry. Ammonium and potassium removal were highest at undiluted level in samples treated with clinoptilolite. This is a key finding as it illustrates the benefit of urine source separation. Chabazite treated samples showed highest ammonium and potassium removal at undiluted level at lower doses. At higher doses, potassium removal was similar in undiluted and 10% urine solutions whereas ammonium removal was the highest in 10% urine solutions. In general, chabazite showed higher ammonium and potassium removal than clinoptilolite. The result showed that ion exchange was stoichiometric in solutions with higher urine volumes.
ContributorsRegmi, Urusha (Author) / Boyer, Treavor H (Thesis advisor) / Delgado, Anca G (Committee member) / Hamilton, Kerry (Committee member) / Arizona State University (Publisher)
Created2019
Description
The influence of mix design on the structural properties of FAU-type (faujasite) zeolite was studied. Samples were synthesized in a forced convection oven using various proportions of coal fly ash, sodium hydroxide (NaOH), and sodium chloride (NaCl). Three faujasite varieties, labeled X, P and S, were prepared for each mix design. Samples were characterized using Fourier transform infrared (FT-IR) spectroscopy and thermo-gravimetric analysis (TGA). Mercury intrusion porosimetry (MIP) was used to obtain porosity information on the samples. Mechanical strength testing was performed on solid blocks of the zeolite samples prepared in a mold. It was found that the S variety in mix design (iv) had the most desirable balance of porosity and strength for engineering applications.
ContributorsRuta, Francesco Luigi (Author) / Neithalath, Narayanan (Thesis director) / Ramakrishna, Bindiganavale (Committee member) / Civil, Environmental and Sustainable Engineering Programs (Contributor) / Barrett, The Honors College (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Department of Physics (Contributor)
Created2015-05
Description
Due to the environmental problems caused by global warming, it has become necessary to reduce greenhouse gas emissions across the planet. Biofuels, such as ethanol, have proven to release cleaner emissions when combusted. However, large scale production of these alcohols is uneconomical and inefficient due to limitations in standard separation processes, the most common being distillation. Pervaporation is a novel separation technique that utilizes a specialized membrane to separate multicomponent solutions. In this research project, pervaporation utilizing ZIF-71/PDMS mixed matrix membranes are investigated to see their ability to recover ethanol from an ethanol/aqueous separation. Membranes with varying nanoparticle concentrations were created and their performances were analyzed. While the final results indicate that no correlation exists between nanoparticle weight percentage and selectivity, this technology is still a promising avenue for biofuel production. Future work will be conducted to improve this existing process and enhance membrane selectivity.
ContributorsHoward, Chelsea Elizabeth (Author) / Lind, Mary Laura (Thesis director) / Nielsen, David (Committee member) / Greenlee, Lauren (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor) / Materials Science and Engineering Program (Contributor)
Created2015-05
Description
Carbon capture is an essential way to reduce greenhouse gas emissions. One way to decrease the emissions is through the use of adsorbents such as zeolites. Dr. Dong-Kyun Seo’s group (School of Molecular Sciences, Arizona State University) synthesized the nanostructured faujasite (NaX). The zeolite was characterized using Scanning Electron Microscopy (SEM) and the physisorption properties were determined using ASAP 2020. ASAP 2020 tests of the nano-zeolite pellets at 77K in a liquid N2 bath determined the BET surface area of 547.1 m2/mol, T-plot micropore volume of 0.2257 cm3/g, and an adsorption average pore width of 5.9 Å. The adsorption isotherm (equilibrium) of CH4, N2, and CO2 were measured at 25ºC. Adsorption isotherm experiments concluded that the linear isotherm was the best fit for N2, and CH4 and the Sips isotherm was a better fit than the Langmuir and Freundlich isotherm for CO2. At 25ºC and 1 atm the zeolite capacity for CO2 is 4.3339 mmol/g, 0.1948 mmol/g for CH4, and 0.3534 mmol/g for N2. The zeolite has a higher CO2 capacity than the conventional NaX zeolite. Breakthrough experiments were performed in a fixed bed 22in, 0.5 in packing height and width at 1 atm and 298 K with nano-zeolite pellets. The gas chromatographer tested and recorded the data every two minutes with a flow rate of 10 cm3/min for N2 and 10 cm3/min CO2. Breakthrough simulations of the zeolite in a fixed bed adsorber column were conducted on MATLAB utilizing varying pressures, flow rates, and fed ratios of various CO2, N2 and CH4. Simulations using ideal adsorbed solution theory (IAST) calculations determined that the selectivity of CO2 in flue gas (15% CO2 + 85% N2) is 571.79 at 1 MPa, significantly higher than commercial zeolites and literature. The nanostructured faujasite zeolite appears to be a very promising adsorbent for CO2/N2 capture from flue gas and the separation of CO2/N2.
ContributorsClark, Krysta D. (Author) / Deng, Shuguang (Thesis director) / Green, Matthew (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Even though access to purified water has improved, there are still many people and locations that do not have this convenience. Approximately 1.2 billion people lack access to safe drinking water and 2.6 billion people have little or no sanitation. Furthermore, breakthroughs in water purification technology are essential to combat these issues. While there are several approaches to water purification, membrane processes are widely used based on their numerous advantages, including high operating temperature and low energy input. In essence, membranes do not require chemical additives, thermal inputs, or regeneration of spent media. The spin coating procedure was used to make a total of 94 membrane samples by adjusting the following variables: membrane support, membrane wetting, solvent, polyacrylonitrile (PAN) content, water contant, Linde Type A (LTA) zeolite content, and the rotations per minute (RPM) of the spin coater. Parameters that were held constant include PAN for the permeable dispersion layer, LTA zeolites as the inorganic filler material, and a spin time of 30 seconds for the spin coater. There were key findings in both the preliminary and core data sets. From the preliminary membrane samples 1 \u2014 40, a baseline was established to use for the core data: polysulfone (PSf) support, 1 \u2014 3% PAN content, and 1 \u2014 3% LTA zeolite content. Flux analysis revealed many inconsistencies in groups 1 \u2014 13 such as unreasonably high error bars (+50%), flow rates that were near zero or extremely high (+15,000 L hr-1 m-2), and lack of a clear trend for membrane specifications. Membranes with a high degree of polymer \u2014 zeolite aggregation on the surface had very low flux values. A higher flux of 4,700 L hr-1 m-2 was correlated to gap and hole formation on the membrane surface. It was shown in group 7 that an increasing degree of surface defects corresponded to an increasing flux of 17,000 L hr-1 m-2. Although the target flux for a defect \u2014 free membrane lies between 500 \u2014 4,000 L hr-1 m-2, there were not any groups with flux values in this range. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) analysis revealed that the observed group similarities could not be attributed to individual membrane specifications. However, this data showed chemical fingerprint overlap across all groups, which were synthesized with varying quantities of the same chemicals. Analysis of flux data, SEM images, and ATR-FTIR data all suggest that the spin coating procedure leads to inconsistent results. Although the spin coater provides flexibility in user control, its advantages are outweighed by the limited control of surface uniformity, zeolite dispersion, and defect formation. It has been shown that the spin coating process is not compatible with the formation of a uniform polymer \u2014 zeolite layer in these experiments.
ContributorsMaltagliati, Alexander Justin (Author) / Lind, Mary Laura (Thesis director) / Durgun, Pinar Cay (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
Unmanned aerial vehicles have received increased attention in the last decade due to their versatility, as well as the availability of inexpensive sensors (e.g. GPS, IMU) for their navigation and control. Multirotor vehicles, specifically quadrotors, have formed a fast growing field in robotics, with the range of applications spanning from surveil- lance and reconnaissance to agriculture and large area mapping. Although in most applications single quadrotors are used, there is an increasing interest in architectures controlling multiple quadrotors executing a collaborative task. This thesis introduces a new concept of control involving more than one quadrotors, according to which two quadrotors can be physically coupled in mid-flight. This concept equips the quadro- tors with new capabilities, e.g. increased payload or pursuit and capturing of other quadrotors. A comprehensive simulation of the approach is built to simulate coupled quadrotors. The dynamics and modeling of the coupled system is presented together with a discussion regarding the coupling mechanism, impact modeling and additional considerations that have been investigated. Simulation results are presented for cases of static coupling as well as enemy quadrotor pursuit and capture, together with an analysis of control methodology and gain tuning. Practical implementations are introduced as results show the feasibility of this design.
ContributorsLarsson, Daniel (Author) / Artemiadis, Panagiotis (Thesis advisor) / Marvi, Hamidreza (Committee member) / Berman, Spring (Committee member) / Arizona State University (Publisher)
Created2016
Description
While the solution diffusion model and pore flow model dominate pervaporation transport mechanism modeling, a new model combining the solution diffusion and viscous flow models is validated using membranes with large scale defects exceeding 2 nm in diameter. A range of membranes was characterized using scanning electron microscopy and x-ray diffraction (XRD) to determine quality and phase characteristics. MFI zeolite membranes of He/SF6 pure gas permeation ideal selectivities of 25, 15, and 3 for good, medium, and poor quality membranes were subjected to liquid pervaporations with a 5% ethanol in water feed, by weight. Feed pressure was increased from 1 to 5 atm, to validate existence of viscous flow in the defects. Component molar flux is modeled using the solution diffusion model and the viscous flow model, via J_i=F_i (γ_i x_i P_i^sat )+(ρ )/M_W ∅/μ_ij x_i P_h. A negative coefficient of thermal expansion is observed as permeances drop as a function of temperature in all three membranes, where ϕ=((ϵr_p^2)/τ∆x). Experimental parameter ϕ increased as a function of temperature, and increased with decreasing membrane quality. This further proves that zeolitic pores are shrinking in one direction, and pulling intercrystalline voids larger, increasing the (ϵ/τ) ratio. Permiabilities of the bad, medium, and good quality membrane also decreased over time for both ethanol and water, meaning that fundamental membrane characteristics changed as a function of temperature. To conclude, the model reasonably fits empirical data reasonably well.
ContributorsWilliams, Suzanne Jean (Author) / Lin, Jerry Y.S. (Thesis advisor) / Emady, Heather (Committee member) / Mu, Bin (Committee member) / Arizona State University (Publisher)
Created2016