Ph.D., Chemical Engineering, University of Oklahoma
B.S., Chemical Engineering, University of Michigan
- Hydrothermal liquefaction
- Biomass conversion
- Reaction engineering
Thermochemical Conversion of Algal Biomass to High Value Products
Traditional conversion technologies of algal biomass to biofuels have mainly included lipid extraction or pyrolysis for biodiesel, hydrotreated renewable diesel, or bio-oil production. These technology pathways have significant drawbacks when using algal feedstocks. Lipid extraction requires extensive dewatering and organic solvents, diminishing the economics of fuel production and increasing environmental concerns. Whole cell conversion pathways, like pyrolysis, alleviate environmental concerns from solvent extraction but still require extensive dewatering prior to conversion. Hydrothermal liquefaction (HTL) utilizes temperature and pressure in the presence of water to disrupt algae cells and convert the intracellular macromolecules into a carbon-rich biocrude. HTL of algae gives a biocrude with a composition and energy density that more closely resembles petroleum crude than bio-oil from pyrolysis.
The economics and sustainability of a viable algae-based fuel and chemical platform will depend upon a close integration of cultivation and conversion technology. To date, HTL studies of algal biomass have focused on product formation and characterization using fresh monoculture or marine alga feedstocks. The algal biomass has typically been purchased from existing algae producers in the nutraceutical industry, in which the high-value products support the high cost of monoculture cultivation. However, it is generally believed that the renewable fuel industry must utilize low-cost feedstocks to compete with petroleum-derived fuels. Since fertilizer inputs represent a large monetary and environmental cost for cultivation, sustainable algal biomass production should rely on macronutrients provided in wastewater. Wastewater-fed algal cultivation systems also have a dual benefit of performing biological nutrient removal from wastewater. Our team investigates the HTL of polyculture algae cultivated in municipal wastewater and have demonstrated that the effect of the growth media can have significant and beneficial impacts on the biocrude properties (lower oxygen content) and the product distribution (lower gas production) from the HTL reactor. Algae produced from wastewater sources typically have higher ash contents which results in biochar being produced in the HTL reactor. The biochar itself can be a valuable co-product, but also may have some catalytic effects in the reactor helping to reduce oxygen content of the biocrude during HTL processing.
Glycerol Reforming for Syngas and Hydrogen Production
The significant increase in biodiesel production worldwide has resulted in the vast availability of crude glycerol. The conversion of this byproduct glycerol into higher value products could significantly improve the feasibility of continued growth in biodiesel production. In particular, coupling synthesis gas (H2 and CO) from glycerol and Fischer-Tropsch synthesis provides a path to liquid fuels giving economic incentive as well as increase fuel flexibility. This project has looked at catalysts for the steam reforming of glycerol as a means of producing a hydrogen rich synthesis gas stream. Specifically we are interesting in the effect if impurities on the catalyst lifetime and the yield of hydrogen. We are looking at different pretreatments to the crude glycerin to minimize the necessary glycerol processing while maintaining catalyst performance. In addition to the smaller scale reforming reactions that are conducted we are working in collaboration with Dr. Chris Depcik in Mechanical Engineering to evaluate larger scale reforming of glycerin for power generation.
Heterogeneous Materials for Lean NOx Traps
With increasing Mile Per Gallon (MPG) standards for passenger vehicles in the united states Lean-burn diesel engines are becoming more popular as they represent significant fuel savings relative to traditional stoichiometric engines. Emissions from lean burn diesel engine exhaust consistent of much higher amounts of NO/NO2 resulting in difficulties meeting NOx regulation standards. One way to reduce NOx concentrations is through the implementation of a Lean NOx Trap (LNT) catalyst. It is important to understand the processes of NO oxidation as well as LNT catalyst degradation to effectively implement this type of catalyst in Lean Burn Diesel exhausts.
Our research in this area focusses on synthesis, characterization and testing of heterogeneous catalysts for the oxidation of NO. The project is conducted in collaboration with Dr. Christopher Depcik in the mechanical engineering department at the University of Kansas. We are currently investigating the effects of catalyst aging on the effectiveness of supported Pt in LNT catalyst for use in NOx emission reduction in lean burn diesel engine exhausts. We are also investigating the use of novel supports to facilitate oxygen adsorption and reactivity for NO oxidation to increase the efficiency of LNT catalysts.
Electroporation of Algae
As a crucial alternative to petroleum liquid fuels and first generation biodiesel, microalgae represent the most promising renewable source of lipids, thought to be capable of meeting global transportation fuel needs. The most promising characteristics of this alternative energy source are its CO2 neutrality, high biomass growth, high lipid yield, and noncompetitive stance toward food supply. To date, development of economically feasible lipid solvent extraction processes of industrial scale face two significant challenges: green solvent selection with efficient extractive characteristics and requirement of cell disruption pretreatment. This research focuses on the use of greener solvents coupled with the novel utilization of Pulsed Electric Field (PEF) as a membrane permeating technique for extraction intensification. This technology can be applied to increase extraction efficiency not only for lipids but for other compounds that can be used for higher value products.
Fuel Property Modeling
Biodiesel Production Plant
Peer Reviewed Publications
- Sean M. Murphy, David A. Slade, Karen J. Nordheden, and Susan M. Stagg-Williams, Increasing Oxygen Flux through a Dense Oxygen Permeable Membrane by Photolithographic Patterning of Platinum, Journal of Membrane Science, 277 (1-2), 94 (2006).
- Abhishek Jain, Xin Zhao, Shane Kjergaard, and Susan M. Stagg-Williams, Effect of Aging Time and Calcination on the Preferential Oxidation of CO over Au Supported on Doped Ceria, Catalysis Letters, 104 (3-4), 191 (2005).
- John J. Daniels, Andrew R Arther, Brent L. Lee, and Susan M. Stagg-Williams, Infrared Spectroscopy Study of CO and CO2 on Ce- and La- Promoted Pt/ZrO2 Catalysts, Catalysis Letters, 103(3-4), 169 (2005)
- Sean Mueller, Patrick Stallbaumer, David Slade, and Susan Stagg-Williams, Segregation of Pt and Re during CO2 Reforming of CH4, Catalysis Letters, 103(1-2), 69 (2005).
- Wei Wang, Susan M. Stagg-Williams, Fabio B. Noronha, Lisiane V. Mattos, and Fabio B. Passos, Partial Oxidation and Combined Reforming of Methane on Ce-Promoted Catalysts, Catalysis Today, 98(4), 553 (2004).
- Bakul Pant and Susan M. Stagg-Williams, Investigation of the Stability of Pt/LaCoO3 During High Temperature Reforming Reactions, Catalysis Communications, 5, 305 (2004).
- S. M. Stagg-Williams and F. B. Noronha, Pt catalysts for the dry reforming and partial oxidation of methane, in Recent Developments in Catalysis, Vol. 2, ed. S. G. Pandalai (Research Signpost, India, (2003) 205.
- F.B. Noronha, C. Taylor, E.C. Fendley, S. M. Stagg-Williams, and D. E. Resasco, "Catalytic Performance of Pt/ZrO2 and Pt/Ce-ZrO2 Catalysts on CO2 Reforming of CH4 coupled to Steam Reforming or under High Pressure ", Catalysis Letters, Vol. 90(1) 13( 2003).
- Susan M. Stagg-Williams, Fabio Nornoha, Gene Fendley, and Daniel E. Resasco,"CO2 Reforming of CH4 over Pt/ZrO2 Catalysts Promoted with La and Ce oxides", Journal of Catalysis, Vol. 194 (2), 240 (2000).
- Susan M. Stagg-Williams, Ricardo Soares, Enrique Romero, Walter E. Alvarez and Daniel E. Resasco, Metal-Support Interaction on Pt/ZrO2 Catalysts for the CO2 Reforming of CH4, Studies in Surface Science and Catalysis, Vol. 130, 3663 (2000).
- S.M. Stagg and D. E. Resasco, Effects of Promoters on Supported Pt Catalysts for CO2 Reforming of CH4, Studies in Surface Science and Catalysis, Vol. 119, 813 (1998).
- S.M. Stagg, E. Romeo, C. Padro, and D. E. Resasco, Effect of Promotion with Sn on Supported Pt Catalysts for CO2 Reforming of CH4, Journal of Catalysis, Vol. 178, 137 (1998).
- Armando Borgna, Susan M. Stagg, and Daniel E. Resasco, "Interference Phenomena in the EXAFS Spectra of Pt- Sn Bimetallic Catalysts," Journal of Physical Chemistry B, Vol. 102 (26), 5077 (1998).
- Susan M. Stagg and Daniel E. Resasco, Effects of Promoters and Supports on Coke Formation on Pt Catalysts During CH4 Reforming with CO2, Studies in Surface Science and Catalysis, Vol. 111, 543 (1997).
- S. M. Stagg, C. A. Querini, W. E. Alvarez, and D. E. Resasco, Isobutane Dehydrogenation on Pt-Sn/SiO2 Catalysts: Effect of Preparation Variables and Regeneration Treatments, Journal of Catalysis, Vol. 168, 75 (1997).
Additional Peer Reviewed Full Length Manuscripts
- A. Borgna, S. Stagg, and D. Resasco, "Analysis EXAFS de Catalizadores Bimetalicos de Pt-Sn/SiO2," XVI Simposio Iberoamericano Conference Proceedings, (1998).
- S. M. Stagg, C. A. Querini, and D. E. Resasco,Influencia del Sn en Catalizadores de Pt Soportado para Deshidrogenacion de Isobutano, XV Simposio Iberoamericano Conference Proceedings, Vol 2, 1061-1067 (1996).
Limited Peer Reviewed Publications
- Venkatesh Phadnavis, Bakul Pant, and Susan M. Stagg-Williams, "Promoted Pt catalysts for the dry reforming of methane in the presence of oxygen", accepted in Fuel Chemistry Division Preprints, Vol. 41 (1), (2002).
- Susan Williams, "Using Learning Styles to Enhance Education," Teaching Matters, A publication by the University of Kansas Center for Teaching Excellence, Vol 3(4), (2000).