(7fu) Membranes As Phase Contactors and Catalytic Interfaces

Membrane science is a rapidly growing area in the field of separations and fundamentally is the study of mass transfer through nano- to micro-scale materials. The physical and chemical properties of permeating species and their interactions with the membrane material dictate the fluxes that are observed. Separation of a mixture of chemical species is possible when the fluxes of the various species are different. Applications for membranes range from water treatment and desalination to chemical separations to controlled drug delivery. Membrane reactors are a unique application where the membrane functions as a phase contactor and is utilized to either selectively remove a reaction product or to selectively supply a reactant into a reactive system. When acting as a reactant deliverer, parameters such as membrane composition, thickness, pore size, and catalyst location allow selective control of reactant flux and targeted delivery to catalytic sites if they are integrated with the membrane. Three-phase heterogeneous hydrogenation is an example of a system that benefits from such control. Hydrogen solubility in liquids, especially water, is inherently low, thus these systems often suffer mass transfer limitations or necessitate extremely high pressures to obtain appreciable reaction rates. Utilizing a membrane to deliver hydrogen directly from the gas phase to membrane-integrated catalytic sites avoids potentially rate limiting dissolution and diffusion in the liquid phase.

My doctoral research focused on the development of polymeric membranes with integrated noble metal catalysts for three-phase hydrogenation reactions. Integrally-skinned asymmetric polyimide membranes, porous polytetrafluorethylene (PTFE) membranes, and composite ceramic/polymer thin film membranes were explored. Porous PTFE membranes were proven highly effective in the aqueous phase hydrogenation of levulinic acid demonstrating reaction rates several factors higher than catalytically equivalent packed bed reactors under identical conditions. A notable challenge to effective utilization of the asymmetric polyimide membranes was solubility of the liquid phase solvent in the membrane material. Many organic solvents exhibited relatively high solubility in the polyimide thus significantly altering and decreasing hydrogen transport. This motivated an intensive investigation into the solubility and diffusivity of a variety of organic species in thin films of the polymer. Short chained alcohols (C1-C8) were identified as a class of solvents that produced only moderate swelling in the polymer and an additional study was conducted to further mitigate this effect by chemically cross-linking the polymer chains.

My postdoctoral research is exploring a variety of separation methods relevant to refining bio-oil from the fast pyrolysis of biomass. The unique fast pyrolysis reactor and fractional collection system developed at Iowa State University has created several novel bio-oil product streams and has thus required innovative separation approaches to separating and purifying the desired products from mixtures of hundreds of chemical species. One important separation is the recovery of sugars from a bio-oil “heavy-ends” organic phase. To accomplish this a combination of solvent extraction and liquid phase adsorption processes were investigated and pilot-scale studies are currently being developed.

Teaching Interests:

I have always thought of myself as an educator and thoroughly enjoy sharing my knowledge and experience with others. It is truly gratifying as an educator to help students overcome learning barriers and reach new heights in understanding. This may be as simple as stating ideas in different language or as complex as deconstructing complex or highly abstract ideas into fundamental concepts and helping the student to ‘see’ the pieces and understand how to rebuild them into complex scientific and engineering principles. I believe that making mistakes is integral to learning and developing oneself into an original and independent thinker. Failure is not something to fear, and the willingness to fail encourages the ability to take calculated risks and to self-correct when the results are not desirable.

My experience as an educator began during my undergraduate education where I tutored young students in a children’s psychiatric unit and coached youth soccer. Concurrently I worked for several years at a company providing services for intellectually disabled individuals and worked closely with clients with a range of intellectual disabilities. In graduate school I was a teaching assistant for materials science and mechanical properties courses. I mentored three undergraduate research assistants in laboratory research over the course of three years and also mentored four REU students in the summers between academic terms. I encouraged the students to test their own ideas in the lab and to draw conclusions from their work. As a postdoctoral researcher I oversee several undergraduates in the lab and work closely with two associated with my research projects, while also mentoring graduate students in our research group. As a faculty I would be comfortable teaching undergraduate courses in any of the core chemical engineering curriculum and would be interested in developing specialized or graduate courses in membranes and advanced separations. I believe educators are students as well and that teaching is a two-way communication. To obtain the best outcome the teacher must be able and willing to understand concepts from the student’s perspective and not just give the student the correct answer, but help him/her to develop the tools to find the answers on his/her own.

Future Directions:

As a faculty I plan to continue pursuing membrane based separations and more specialized applications of membranes integrated in reactive systems. There are many fundamental questions to investigate in this area, including catalyst integration, catalyst/membrane interactions, gas and liquid mass transfer through the membrane and at the membrane surface interface, and catalytic site location, functionality, and activity. Biomass based renewable chemicals is a burgeoning area where novel and innovative catalytic upgrading and separation strategies will help renewable chemicals become economically competitive with their fossil fuel counterparts. As my undergraduate degree is in biomedical engineering, I hope to expand membrane based investigations into biological systems. This may include enzyme immobilization on a membrane for a biologically reactive system, controlled release or selective delivery of drugs, removal of toxins or inhibitory species, or building cellular scaffolds that simultaneously offer controlled nutrient supply. Besides fundamental studies, I also greatly appreciate the need for practical solutions to current scientific and engineering challenges. As an adviser and mentor to undergraduate and graduate students, I will encourage my lab to conduct detailed and meticulous fundamental studies with an overarching constraint that the investigations support practical and rational solutions to real world problems regardless if the timeframe is the near or distant future.

Education

B.S. 2010 University of Iowa Biomedical Engineering
B.A. 2010 University of Iowa Music Performance
Ph.D. 2016 Kansas State University Chemical Engineering

Publications

Stanford, J. P., Soto, M. C., Pfromm, P. H., Rezac, M. E. “Aqueous phase hydrogenation of levulinic acid using a porous catalytic membrane reactor”, Catalysis Today, (2016).

Stanford, J. P., Maier, A. L., McDonald, L. A., Pfromm, P. H., Rezac, M. E. “Kinetic and equilibrium sorption of organic liquids and vapors in Matrimid”, Journal of Membrane Science, (2016).

Stanford, J. P., Pfromm, P. H., Rezac, M. E. “Effect of vapor phase ethylenediamine cross-linking of Matrimid on alcohol vapor sorption and diffusion,” Journal of Applied Polymer Science, (2017).

Stanford, J. P., Hall, P. H., Rover, M. R., Smith, R. G., Brown, R. C. “Separation of fast pyrolysis derived sugars and phenolic species from an aqueous product stream using polymeric resin adsorbents”, (2017, in preparation).

Stanford, J. P., Rover, M. R., Smith, R. G., Brown, R. C. “Modeling and experimental validation of a continuous adsorbent based separation of sugars and phenolic species in an aqueous product stream in a pyrolysis biorefinery”, (2017, in preparation).