In this study, pervaporation, a membrane-based process was studied for in-situ separation of butanol. This technique has a great potential due to its high selectivity, low energy requirement and high efficiency. The primary objective was to improve the performance of the Polydimethylsiloxane (PDMS) membrane for the pervaporation separation and the recovery of butanol by adding nanoparticles into its matrix to make mixed matrix membrane (MMM). These nanoparticles included zinc-based Metal Organic Frameworks (MOFs) and zinc oxide. Different particle sizes of zeolitic imidazolate framework (ZIF-8) were synthesized. The separation performance of MMMs incorporating different sizes of ZIF-8 nanoparticles was compared to the performance of mixed matrix membranes incorporating zinc oxide as well as pure PDMS membrane. Different characteristics of ZIF-8 and their impact on the performance of the host membrane were discussed. Result showed that the presence of nanoparticles improves the PDMS membrane performance up to a certain particle loading. Moreover, it was shown that the particle size and interfacial bond between polymer and particles have a major impact on the pervaporation membrane separation process. The best membrane for pervaporation separation of butanol from binary aqueous solutions was obtained for the 8 wt% small-size ZIF-8/PDMS MMM where the total permeation flux and butanol selectivity were increased by 350% and 6%, respectively, compared to neat PDMS membranes. In addition to the MOFs, nanotubes are considered emerging nanostructured materials for use in membrane separation applications due to their high molecular diffusivity and unique geometry. Recent progress has also been made on the modification of nanotube surface functionality, and the fabrication of nanotube mixed matrix membranes as well as the ability to align them in MMMs. Since numerous types of nanotubes are available and the process of producing well-aligned nanotube MMMs is very challenging, a theoretical model using finite difference method (FD) was used to gain a deeper understanding on the effect of nanotubes on the separation performance of mixed matrix membranes. A series of numerical simulations were performed and the effects of various structural parameters, including the tubular filler volume fraction, orientation, length-to-diameter aspect ratio, and permeability ratio, were assessed. The results showed that the relative permeability is enhanced by vertically-aligned nanotubes and further increased with an increase of the permeability ratio, filler volume fraction and the length-to-diameter aspect ratio. In addition, comparing the simulation results with existing analytical models for the prediction of the relative permeability acknowledges a need to develop a new correlation that would provide more accurate predictions of the relative permeability of MMMs with embedded nanotube fillers.

The incentives and policies spearheaded by the U.S. government have created abundant opportunities for renewable fuel production and commercialization. Bio-butanol is a very promising renewable fuel for the future transportation market. Many efforts have been made to improve its production process, but seldom has bio-butanol research discussed the integration and optimization of a cellulosic bio-butanol supply chain network. This study focused on the development of a physical supply chain network and the optimization of a green supply chain network for cellulosic bio-butanol. To develop the physical supply chain network, the production process, material flow, physical supply chain participants, and supply chain logistics activities of cellulosic bio-butanol were identified by conducting an onsite visit and survey of current bio-fuel stakeholders. To optimize the green supply chain network for cellulosic bio-butanol, the life cycle analysis was integrated into a multi-objective linear programming model. With the objectives of maximizing the economic profits and minimizing the greenhouse gas emissions, the proposed model can optimize the location and size of a bio-butanol production plant. The mathematical model was applied to a case study in the state of Missouri, and solved the tradeoff between the feedstock and market availabilities of sorghum stem bio-butanol. The results of this research can be used to support the decision making process at the strategic, tactical, and operational levels of cellulosic bio-butanol commercialization and cellulosic bio-butanol supply chain optimization. The results of this research can also be used as an introductory guideline for beginners who are interested in cellulosic bio-butanol commercialization and supply chain design. / Ph. D.

Butanol production by four different Clostridium sp. strains was investigated using glucoseP2-medium supplemented with increasing concentrations of butyric acid, added as cosubstrate.Batch fermentations were carried out in serum bottles (freely-suspended cellcultures) and fibrous-bed bioreactor (FBB) with medium recirculation (immobilized cells).Butyric acid clearly revealed to inhibit cellular growth with all specific growth rates decliningupon the increase of butyrate concentrations. However, the presence of low and moderatelevels in the medium can readily enhance the ABE-fermentation and increase butanolproduction through a shift induction towards the solventogenic phase controlled by themedium pH. In all cases it was found that 4.0 g⋅l-1 is the optimal concentration of butyratethat maximizes the yields for all ABE-solvents and butanol productivities. The non-mutant C.acetobutylicum ATCC 824 was singled out as the most efficient butanol productive strainamong all bacteria tested (10.3 g⋅l-1 butanol versus 0.72 g⋅l-1 with and without 4.0 g⋅l-1butyrate, respectively) showing a productivity augment in the order of 0.078 g⋅l-1⋅h-1 (78.5%)and yields of 0.3 g⋅g-1 from substrate and 7.6 g⋅g-1 from biomass versus 0.072 g⋅g-1 and 0.41g⋅g-1 with and without the optimal butyrate concentration, respectively. This strain alsorevealed the best overall tolerance over increasing butyrate concentrations up to ∼6.0 g⋅l-1 andthe highest glucose uptake (65.5%) among all bacteria. Furthermore, the beneficial effects ofbutyric acid were also observed through the use of a fibrous bed-bioreactor when the mutatedstrains of C. beijerinckii ATCC 55025 and BA 101 were tested. The use of this immobilizedcell system effectively improved butanol production over the free system with butanol titersin the fermentation broth around 11.5 g⋅l-1 and 9.4 g⋅l-1 for the two bacteria, respectively,roughly doubling the values attained with the corresponding suspended cell cultures when themedia were supplemented with 4.0 g⋅l-1 of butyrate. All these results confirm theenhancement of butanol formation using either free or immobilized cell culturessupplemented with butyric acid concentrations up to 4.0 g⋅l-1 in the media.