2015 Symposium Abstracts - Chemical Engineering

CHE-01 Determinants Of siRNA Functional Asymmetry

Authors: Phillip A. Angart; Daniel B. Vocelle; Christina Chan; S. Patrick Walton

Abstract: The use of biological molecules as therapeutics (i.e., biologics) is a rapidly expanding area of pharmaceutical research because of their potential for high specificity and low toxicity. Biologics often utilize native cellular mechanisms to amplify their activity while producing minimal perturbation of cellular function. Short interfering RNAs (siRNAs) are a class of biologics that silence targeted mRNAs via the native eukaryotic regulatory pathway called RNA interference (RNAi). Canonical siRNAs are double-stranded with 19 central bases and 2 nucleotide 3’ overhangs. The RNAi pathway recognizes the siRNA structure and then removes one of the RNA strands to form an active complex called RISC, which finds its target through the now free base pairs of the remaining siRNA strand. While the recognition of the siRNA by the RNAi pathway is largely structurally based, siRNA activity can vary greatly with siRNA sequence. Our previous work has identified that the 5’ terminal nucleotide (TN) and the relative terminal hybridization stability (ΔΔG) of the siRNA are independent predictors of siRNA activity. Here we show that both RISC loading and RNAi activity are influenced by both TN and ΔΔG with the stronger influence on functional asymmetry coming from TN. That said, they are not perfect predictors, indicating that other as yet unidentified factors also influence siRNA activity and functional asymmetry.

This work was supported in part by National Institutes of Health (#GM079688, #RR024439, and #GM089866), MSU Foundation, National Science Foundation (CBET 0941055), MUCI, and the Center for Systems Biology

 

CHE-02 Development Of An Association-Based Model For Bio-Derived Chemicals

Authors: Aseel Bala-Ahmed; Carl T. Lira

Abstract: Recently, bio-derived chemicals have gained favor over their petroleum-based counterparts and new processes for their manufacture are being proposed. However, process streams commonly encountered in the bioeconomy consist of polar solutions which hydrogen bond (associate), causing large deviations from ideal behavior. Therefore, a significant amount of capital and time must be invested to reliably predict phase equilibria. This has hindered the industrial implementation of bio-based processes. Many thermodynamic models have been designed to account for association but they often utilize more parameters than can be determined with confidence of physical relevance. Two main approaches for modeling are chemical theory and Wertheim’s theory. Both require accurate representation of the monomer fraction. Various studies have demonstrated the use of spectroscopy to quantify higher order chains in associating mixtures. However, spectroscopy alone is limited by its inability to distinguish between the monomer and end-group donor peaks. A promising approach is to use spectroscopy together with molecular simulation and material balances. Using experimental IR and NMR data to test simulations, force fields can be developed to accurately model molecular behavior and the monomer fraction. In this work, spectroscopy, molecular simulations and isotopic labeling will be utilized to improve the thermodynamic models for associating mixtures, facilitating more accurate and rapid process development.

 

CHE-03 The Impact Of Precursor Solution Additive Choice On Average Infiltrate Oxide Particle Size Nano-Composite Solid Oxide Fuel Cell Cathodes

Authors: Theodore E. Burye; Hongjie Tang; Jason D. Nicholas

Abstract: Recently, precursor nitrate solution desiccation1 and ceria nano-particle pre-infiltration2-4 have been shown to reduce the average size of mixed ionic electronic conducting solid oxide fuel cell infiltrate particles. Two common5-8 solution additives, Triton X-100 (TX) and Citric Acid (CA), were evaluated to determine their impact on the microstructure, phase purity, and long-term performance of infiltrated nano-composite cathodes made using desiccation or pre-infiltration. Cathodes were infiltrated using CA or TX containing La0.6Sr0.4Co0.8Fe0.2O3 (LSCF) precursor solutions, desiccated with CaCl2, and then fired at 700°C. Cathodes with identical Gd0.1Ce0.9O1.95 (GDC) scaffolds containing pre-infiltrated GDC particles were infiltrated with LSCF precursor solutions, and fired at 700°C. In all cases a LSCF loading level of 12.0 vol% was achieved. Cells were characterized through AC electrochemical impedance spectroscopy and scanning electron microscopy. 500 hour, open-circuit, polarization resistance (RP) degradation measurements were also conducted. LSCF particles were phase pure when produced from CA-containing precursor solutions, but secondary phase impurities were produced from TX-containing precursor solutions. Both additives were found to lower RP with desiccation or pre-infiltration, but TX had a much larger impact, lowering RP to 0.1 Ωcm2 at 550°C and reducing the average infiltrate particle size from 50 to 22 nm. For solutions with either additive, the observed performance improvements were found to scale directly with the infiltrate particle size and were not due to changes in gas concentration polarization, infiltrate phase purity, or electronic conductivity. Cells made with TX had a slower RP degradation than CAD, with a 1.2%/1000 hr degradation rate achieved.

This work was supported in part by National Science Foundation (NSF) award number CBET-1254453 and a Michigan State University faculty startup grant to Dr. Jason D. Nicholas

 

CHE-04 Impact Of Xylan O-Acetylation In Arabidopsis Thaliana On Cell Wall Porosity And Response To Alkaline And Liquid Hot Water Pretreatment

Authors: Jacob Crowe; Henry Pan; David Hodge

Abstract: A key obstacle in the utilization of lignocellulosic biomass as a bioenergy feedstock lies in the recalcitrant secondary cell wall structure. Often a combination of mechanical and chemical pretreatment is required to modify the recalcitrant cell wall and render usable polysaccharides from these feedstocks. Another avenue of feedstock modification involves the modification of the genes associated with plant cell wall synthesis to yield feedstocks with reduced cell wall recalcitrance. In this study, modified feedstock lines from Arabidopsis thaliana expressing reduced O-acetylation (Tbl29-1 & Tbl29-2) were subjected to alkaline as well as liquid hot water (LHW) pretreatment, and fermentable sugar yields as well as structural characteristics were quantified and compared to wild type feedstock (WT). Pretreatment conditions resulted in increased deacetlyation and xylan removal from mutant feedstocks, indicating decrease in O-acetylation results in significant changes in the cell wall’s response to pretreatment. Water retention and differential scanning calorimetry were utilized to observe increases in water swellability as well as increased mutant cell wall porosity post-pretreatment. Fermentable sugar yields indicate that in all pretreatment cases, mutant lines exhibited improved yields when compared to wild type. These findings suggest that acetylation of xylan during cell wall growth impacts xylan-cellulose interactions and accessibility within the cell wall matrix as well as impacts acetyl deficient feedstock susceptibility to cell wall disrupting pretreatments.

This work was supported in part by NSF Grant #1336622

 

CHE-05 Thermodynamics And First Principles Based Approach To Develop Silver Free Braze Alloy For Solid Oxide Fuel Cell (SOFC) Application

Authors: Tridip Das; Jason D. Nicholas; Tom Bieler; Yue Qi

Abstract: Commonly used silver based braze alloy in planar SOFC stack has durability issues. The standard 97.5Ag-2.5CuO alloy braze fails due to pore formation during long term application of more than 10,000 hours. A methodology is developed to design a silver free durable and impermeable braze alloy for SOFC application of 40,000 hours at 750 deg C. The study focused on nickel based alloy from the knowledge of nickel superalloys. The search for alloying elements started from periodic table and narrowed down the selection list, based on brazing criteria for SOFC. The binary and ternary alloy phase diagrams are calculated from these selected list of elements based on CALPHAD approach. A list of possible alloy compositions are suggested based on thermodynamic calculations. The suggested alloy compositions are categorized in two systems as Ni-Si and Ni-Mn based. A comprehensive literature review is performed to summarize the present state of the art nickel containing brazing alloys. The literature review shows that the predicted alloy systems in this study are not commercially available according to best of authors’ knowledge. All the predicted Ni-Si based alloy compositions contains more than 30% Si, which makes the alloy brittle. So, any more studies are not performed on them. Ni-Mn based systems are suggested for further experimental studies.

This work was supported in part by DOE

 

CHE-06 Optimized Fiber-Reinforced Polymer Composites For Lightweighting: Toughening Of Aromatic Epoxy Polymers Via Aliphatic Epoxy Copolymers

Authors: Markus A. Downey; Lawrence T. Drzal

Abstract: The new EPA corporate average fuel economy (CAFE) standards will require a target of 54.4 mile per gallon to be met by 2025. Lightweighting has become a central strategy of meeting the CAFE standard, within which fiber-reinforced polymer composites will play an important part. Aromatic diglycidyl ether of bisphenol A (DGEBA) based epoxy polymer matrix systems are important for high-performance and structural applications due to their high strength-to-weight ratios. However, their brittle nature, i.e. lack of toughness, is an issue that needs to be addressed. In an initial stage to toughen the base matrix material, the presented research shows that small additions of a more flexible aliphatic epoxy copolymers, both di- and tri-functional, can significantly increase the notched Izod impact strength (56 to 77%) over the neat DGEBA, while not detrimentally affecting other mechanical properties such as glass transition temperature and flexural properties. The improvement in impact toughness is attributed to the more flexible backbone of the aliphatic epoxy molecules. On the basis of these promising results, carbon fiber reinforced composites with 1 wt% di-functional aliphatic co-polymer in either the fiber sizing or the polymer matrix were produced and tested. The aliphatically toughened sizing showed an increase of 10% in mode 1 fracture toughness, while the aliphatically toughened matrix showed a 90% increase in mode 1 fracture toughness. The enhanced toughness can be either used for a reduction in the amount and weight of material needed for the given application or allow the use of polymer composites in areas that were previously not possible.

This work was supported in part by General Electric Aviation

 

CHE-07 Processing Methods Of High Density Polyethylene-Exfoliated Graphene Nanoplatelet Nanocomposites For Automotive Fuel Tank Applications

Authors: Keith T. Honaker; Frederic Vautard; Lawrence T. Drzal

Abstract: Melt extrusion followed by injection molding was used to manufacture high density polyethylene (HDPE) – exfoliated graphene nanoplatelet (GnP) nanocomposties. To further enhance the composite properties, different processing techniques were explored including microlayer coextrusion and solution sonication followed by extrusion. Modifications to the nanocomposite components were investigated, including cryomilling the HDPE pellets and coating the platelets with a low density wax or elastomer before further processing. Mechanical properties (Izod impact, tensile, flexural) and barrier properties to oxygen were tested to evaluate the relationships between morphology, processing and properties. Melt extrusion of HDPE and GnP yielded a clear increase in stiffness, a decrease in Izod impact resistance, as well as a 50% decrease to both oxygen and fuel permeation with a 5 wt. % GnP composite. Microlayer coextrusion yielded a high alignment of the nanoplatelets in the direction of the flow and resulted in improved permeation resistance at low GnP concentration, but did not result in a further improvement of barrier properties at concentrations above 5 wt. %. Cryo-milling the HDPE pellets into a powder resulted in a minor decrease in mechanical properties with a 35% increase in permeation resistance to oxygen. A wax coating on the platelets before melt extrusion resulted in an increased in Izod impact resistance, but a decrease in flexural modulus and resistance to oxygen permeation. An elastomeric coating of the GnP resulted in retaining the flexural and permeation properties, with a slight improvement to the Izod impact resistance. Presented at 2014 SPE Advanced Composites Conference and Exposition

This work was supported in part by Hyundai Kia America

 

CHE-08 Computationally Analyzing Oxygen Vacancies In Li2MnO3-Delta

Authors: Christine James; Yue Qi

Abstract: The layered-layered cathode material xLi2MnO3∙(1-x)Li(Ni,Co,Mn)O2 has exhibited reversible capacities above 250 mAh/g. This is a high capacity cathode material compared to the commonly used LiCoO2 (~160 mAh/g). It is widely agreed that this extra capacity comes from “activation” due to, atleast in part, the loss of Li2O from the Li2MnO3 component during the first charge cycle at around 4.4 V vs Li/Li+. Experimental studies have shown that Li2MnO3 alone can exhibit high capacities and is “activated” in the same way as the layered-layered cathode material, meaning it is atleast in part activated by the removal of Li2O. Experimental studies have also shown that in the layered-layered cathode material the Li2MnO3 component is the limiting component of kinetics. The creation of oxygen vacancies and the lithium diffusion in Li2MnO3-delta were studied computationally because the atomic effects are difficult to understand experimentally. Density functional theory (DFT) was used to study the effect of oxygen vacancies on the removal of lithium atoms. Ab-initio molecular dynamics (AIMD) and the nudged elastic band (NEB) method were used to study lithium diffusion in Li2MnO3-delta. Lithium vacancies were shown to be more energetically favorable in sites near the oxygen vacancies. Additionally, the oxygen vacancies hindered the diffusion of lithium atoms.

This work was supported in part by NSF/DMR award 1410850

 

CHE-09 Condensed Phase Ethanol Conversion To Higher Alcohols

Authors: Tyler Jordison; Dennis J. Miller; Carl Lira

Abstract: Higher alcohols (C4+) are an important class of chemical feed stocks as well as potential biofuels. Bio-based ethanol offers the opportunity to produce these higher alcohols via condensation pathways collectively known as Guerbet reactions. Numerous studies on Guerbet reactions have been carried out over the past 100 years, mostly in the vapor phase. To date, the highest yields reported for n-butanol are only ~30% of theoretical. In this paper, we focus on characterizing the behavior of gamma-alumina-supported nickel catalysts to carry out Guerbet reactions of ethanol in the liquid phase. The addition of lanthanum oxide as a modifier of gamma-alumina acidity results in catalysts that provide higher alcohol selectivities in excess of 80% at 230oC and autogeneous pressures. At these conditions, which are near the critical temperature of ethanol, the liquid phase is significantly expanded, byproduct gases (CH4 and CO2) are significantly dissolved in the liquid phase, and the vapor phase contains significant quantities of the alcohols. To accurately compute ethanol conversion and product yields in the batch reactor, compositions and quantities of the vapor and liquid phases have been modeled using the S-R Polar equation of state.

This work was supported in part by DOE; National Corn Growers Association

 

CHE-10 Block Copolymers As Toughening Agents For Epoxy Resins

Authors: Nicholas T. Kamar; Lawrence T. Drzal

Abstract: The projected 2019 market value for epoxy resins is $9.2 billion and the aerospace epoxy polymer composite market is projected to reach $5 billion by then as well. Cured epoxy resins have versatile chemistries, high strength, stiffness and good chemical, thermal and electrical resistivities. However, cured epoxies are brittle materials, i.e. they have a low fracture resistance. Therefore, this work explored toughening a model diglycidyl ether of bisphenol-A epoxy resin cured with m-phenylenediamine. Toughening agents included carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) and (poly)-styrene-block-(poly)-butadiene-block-(poly)-methylmethacrylate (SBM). This work explored the effects of processing temperature, high shear rate mixing and concentration on the mechanical, thermomechanical and fracture properties of CTBN and SBM modified epoxies, respectively. It was found that SBM was a more effecient toughening agent than CTBN. That is, at 10 phr SBM, the fracture toughness was increased by 215%, while at 10 phr CTBN, an increase of 90% was observed. Furthermore, the addition of SBM into the epoxy resin at 5, 10 and 15 phr does not result in a loss in glass transition temperature (Tg). Contrarily, when CTBN is added to the epoxy, Tg was decreased. Finally, the morphology of the phase separated copolymers in the epoxy was studied by scanning electron microscopy of compact tension specimen fracture surfaces. Results showed that CTBN phase separated into spheres with particle diameters dependent on CTBN acrylonitrile content. SBM was found to phase separate into worm-like micelles, with particle size dependent on concentration within.

This work was supported in part by General Electric Aviation

 

CHE-11 Non-Precious Metal Catalyst For Oxygen Reduction

Authors: Nathaniel Leonard; Cenk Gumeci; Scott Calabrese Barton

Abstract: Non-precious metal catalysts (NPMC) for proton exchange membrane fuel cells (PEMFC) are explored. Research into NPMCs is motivated by the growing need for cleaner, more efficient energy options. To this end, the morphology and function of metal-nitrogen-carbon (MNC) oxygen reduction catalysts are studied. A porosity study finds that mesoporosity is critical to high performance of autogenic pressure metal-nitrogen-carbon (APMNC) oxygen reduction catalysts. Also, a rotating ring-disk electrode (RRDE) study indicates that the oxygen reduction reaction (ORR) proceeds both via a direct four-electron pathway to water at high potentials and an indirect peroxide pathway at low potentials on an APMNC catalyst. At higher potential, site availability inhibits peroxide generation causing the direct four-electron reduction pathway to dominate, but the net peroxide generation remains relatively low over the entire range due to reduction of peroxide to water. Finally, a PEMFC cathode model is developed for hydrophilic MNC catalysts. Water flooding was studied in terms of its impact on gas-phase transport and electrochemically accessible surface area (ECSA). Fuel cell data is modeled at a variety of pressures and catalyst layer thicknesses. A sensitivity study is performed on the controllable cathode parameters. Sensitivity analysis identified loading and density as critical parameters, and parametric studies indicated that decreased loading would lead to higher catalyst utilization.

This work was supported in part by Department of Energy

 

CHE-12 Silylated Soybean Oil For Industrial Coating Application

Authors: Chetan Tambe; Daniel Graiver; Ramani Narayan

Abstract: Soybean oil is widely available vegetable oil all over the world, thus, it provides a cheap and sustainable source of raw material with compared non-renewable petroleum sources. In addition to being a food source to human being, soybean oil can be made useful in many applications like biodiesel, coatings etc. by chemically modifying it. In this study, a novel solvent free one step silylation process for the preparation of moisture curable soybean oil is introduced. Hydrosilylation is so far the most popular routes in obtaining organosilicon compounds and has been commercially used to graft silanes onto organic compounds by formation of Si-C bonds. Unfortunately, the hydrosilylation reaction is most effective with alkenes containing terminal double bonds. This research focuses on studying, grafting of silane functionality, using vinyltrimethoxy silane, onto the unsaturation present in the fatty acid chains of triglycerides and further developing a coating material. The silylated soybean oil possesses low viscosity, which is ideal for a coating material. The oil was easily moisture curable with at RT and was successfully used as a water repellent coating material for paper coating application. Kraft papers were coated using a direct gravure roll coaters and achieved significant increase on the moisture resistance (by 40%) based on Cobb value characterization. This silylated soy oil is an unsaturated polyester (UP) and provides a low viscosity raw material for synthesizing UP resin. A future work of preparation of UP resin using organo-silicone chemistry for protective coating application is proposed.

This work was supported in part by Department of Defense (contract # N00189-12-C-Z003) and Northern Technologies International Corporation (NTIC), who provided help in scaling up the process and evaluating the performance of the paper bags

 

CHE-13 Engineering Delivery Vehicles For siRNA Therapeutics

Authors: Daniel Vocelle; Olvia Chesniak; Milton Smith; Christina Chan; S. Patrick Walton

Abstract: Given the limitations of small molecule and protein based drugs, new therapeutic approaches are needed for treating disease-associated proteins. One potential candidate, short interfering RNA (siRNA) therapeutics, is capable of highly specific targeting for a wide range of proteins. With the assistance of target specific delivery vehicles, siRNAs are transported from an extracellular environment into the cytoplasm of eukaryotic cells. Utilizing the RNA Interference (RNAi) pathway, siRNA degrades sequence specific messenger RNA (mRNA) and reduces target protein expression. siRNA therapeutics have been developed for cancers, genetic disorders, and infectious diseases, but haven’t received FDA approval due to their dependency on inefficient delivery vehicles. While many types of delivery vehicles have been developed, there is little consensus regarding the mechanisms or characteristics essential for delivery. Using silica nanoparticles (SNPs) varied by size, structure, charge, and functionalized surface, delivery criteria can be investigated among four main categories: siRNA binding affinity, membrane translocation, biodistribution, and protein suppression. Current data indicates that particle binding affinity and location of dextran functionalization are important in facilitating active silencing. Intracellular trafficking data supports SNPs utilizing scavenger receptor mediated endocytosis and preferentially accumulating within acidic organelles, where complex dissociation occurs. To date, our efforts have led to the development of a SNP capable of delivering 10x more siRNA than Lipofectamine 2000, a commercially available delivery vehicle, and achieving comparable silencing over a longer duration at an increased initial rate.

This work was supported in part by National Institutes of Health (#GM079688, #RR024439, and #GM089866)

 

CHE-14 Exploring Sequence-Specificity Determinants Of Enzymes Through Deep Mutational Scanning

Authors: Emily Wrenbeck; Tim Whitehead

Abstract: Enzymes (biocatalysts) are proteins that catalyze specific chemical transformations in biological contexts. Biocatalysts can potentially provide renewable, environmentally friendly, and safe routes for replacement of chemocatalytic reactions. For many potential industrial applications, natural enzymes are not capable of turning over the molecule of interest. Through state of the art protein engineering, novel and improved substrate affinities have been achieved, though the examples are few. To design enzymes that act on user-defined molecules a deep fundamental understanding of substrate-specificity determinants is needed. Using the aliphatic amidase (amiE) from Pseudomonas aeruginosa as a model system, we aim to generate fundamental knowledge of the relationship between a protein’s primary sequence and its substrate specificity. By correlating the fitness of a host organism through its growth rate to protein fitness, a large number of amiE variants (>20,000) can be screened via competitive selection in a single reaction vessel. Multiple selection events will be carried out on different short chain amides, namely acetamide, propionamide, and isobutyramide. The fitness of individual amiE variants will be quantified through next generation sequencing. Through comparative analysis of the different selection data, important positions for selectively will be identified. We expect that specificity determinants will be located in the binding pocket, with additional determinants in neighboring spatial shells. Development of high-throughput methods for designing enzymes with programmable substrate specificities would have significant impact on the transition of industrial chemical reactions towards biosynthetic routes.

This work was supported in part by National Science Foundation (NSF); MSU Plant Biotechnology for Health and Sustainability

 

CHE-15 Synthesis, Characterization And Assessment Of A Fibrous MnOx Catalytic Film Formed On FTO By Dual-Session Cyclic Voltammetry

Authors: Hao Yuan; Robert Y. Ofoli

Abstract: We have developed a new electrodeposition method to synthesize a manganese-based (MnOx) catalytic film in situ on conductive surfaces in aqueous media. This approach uses an electrochemical deposition protocol involving two consecutive cyclic voltammetry (CV) sessions over different ranges of potential (0.0 to 0.6 V and 0.6 to 2.0 V), followed by calcination to increase catalyst crystallinity. The resulting film has a nanoscale fibrous morphology that is uniformly distributed over the conductive surface. The surface morphology and elemental composition were characterized by scanning electron microscopy (SEM), transmitting electron microscopy (TEM) and energy-dispersive x-ray spectroscopy (EDS). The catalytic functionality was assessed by cyclic voltammetry (CV), which showed excellent effectiveness towards water oxidation. Its stability was assessed by consecutive CV and long term amperometry experiments, with the results showing stable catalytic performance over long periods of time. A nucleation-growth theory proposed to explain the mechanism(s) for formation of the fibrous surface morphology has been supported by several preliminary assessments. The effects of other synthesis parameters such as ionic strength, potential ranges, and number of scanning cycles were also evaluated. This protocol has the potential to open avenues for synthesis and optimization of other manganese-based water oxidation catalysts.