Galen J. Suppes

Nanospace engineering of KOH activated carbon

This paper demonstrates that nanospace engineering of KOH activated carbon is possible by controlling the degree of carbon consumption and metallic potassium intercalation into the carbon lattice during the activation process. High specific surface areas, porosities, sub-nanometer (<1 nm) and supra-nanometer (1-5 nm) pore volumes are quantitatively controlled by a combination of KOH concentration and activation temperature. The process typically leads to a bimodal pore size distribution, with a large, approximately constant number of sub-nanometer pores and a variable number of supra-nanometer pores. We show how to control the number of supra-nanometer pores in a manner not achieved previously by chemical activation. The chemical mechanism underlying this control is studied by following the evolution of elemental composition, specific surface area, porosity, and pore size distribution during KOH activation and preceding H(3)PO(4) activation. The oxygen, nitrogen, and hydrogen contents decrease during successive activation steps, creating a nanoporous carbon network with a porosity and surface area controllable for various applications, including gas storage. The formation of tunable sub-nanometer and supra-nanometer pores is validated by sub-critical nitrogen adsorption. Surface functional groups of KOH activated carbon are studied by microscopic infrared spectroscopy.

Latent heat characteristics of fatty acid derivatives pursuant phase change material applications

Abstract In their natural form, fats and vegetable oils melt at temperatures useful for thermal energy storage. Incremental improvement of their heat release characteristics could pave the way for commercial applications as phase change materials (PCM). These chemicals could provide a biomaterial alternative to a technology dominated by paraffin and salt products. Mixture heats of fusion and melting points were evaluated for single acid derivatives of stearic, palmitic, and oleic acids to develop a fundamental understanding of the solid–liquid transition and to better understand how to convert natural compositions to useful PCM products. Many mixtures of monoacid derivatives of a single fatty acid formed single sharp solid–liquid phase transitions useful for PCM applications. These mixtures also qualitatively exhibited freezing point depression therein allowing the mixture composition to be used as a means to control the temperature of the phase transition. In mixtures of monoacid derivatives from different fatty acids, melting occurred over wider temperature ranges with eventual separation of the solid–liquid transition to at least two different events. This work demonstrates that it is possible to fully convert natural fatty acid mixtures into high performance phase change materials.

Hydrogen storage in engineered carbon nanospaces

It is shown how appropriately engineered nanoporous carbons provide materials for reversible hydrogen storage, based on physisorption, with exceptional storage capacities (approximately 80 g H2/kg carbon, approximately 50 g H2/liter carbon, at 50 bar and 77 K). Nanopores generate high storage capacities (a) by having high surface area to volume ratios, and (b) by hosting deep potential wells through overlapping substrate potentials from opposite pore walls, giving rise to a binding energy nearly twice the binding energy in wide pores. Experimental case studies are presented with surface areas as high as 3100 m(2) g(-1), in which 40% of all surface sites reside in pores of width approximately 0.7 nm and binding energy approximately 9 kJ mol(-1), and 60% of sites in pores of width>1.0 nm and binding energy approximately 5 kJ mol(-1). The findings, including the prevalence of just two distinct binding energies, are in excellent agreement with results from molecular dynamics simulations. It is also shown, from statistical mechanical models, that one can experimentally distinguish between the situation in which molecules do (mobile adsorption) and do not (localized adsorption) move parallel to the surface, how such lateral dynamics affects the hydrogen storage capacity, and how the two situations are controlled by the vibrational frequencies of adsorbed hydrogen molecules parallel and perpendicular to the surface: in the samples presented, adsorption is mobile at 293 K, and localized at 77 K. These findings make a strong case for it being possible to significantly increase hydrogen storage capacities in nanoporous carbons by suitable engineering of the nanopore space.

Plug-in fuel cell hybrids as transition technology to hydrogen infrastructure

Abstract A plug-in fuel cell hybrid with as little as 20 mile of range from rechargeable hydrogen could displace more than 50% of the gasoline consumed in the US. While the well-to-wheel efficiencies are poor, proper utilization of the grid electricity along with electrical infrastructure modifications would lead to acceptable and sustainable overall efficiencies. The limited-range plug-in option provides a viable transition technology toward a hydrogen refueling infrastructure. The technology is also sustainable and available on a short timeline.

Properties of Biobased Rigid Polyurethane Foams Reinforced with Fillers: Microspheres and Nanoclay

The effect of incorporating 1–7% microsphere and nanoclay fillers on the physical properties of polyurethane (PU) foams containing 15% soybean oil-based polyol was investigated. Increasing filler percentage reduced the PU foam density. The compressive strength of PU foams decreased slightly when increasing the microsphere content from 1 to 3% and then increased. At 7% microsphere content, the foams displayed the same compressive strength as the control foams made from 100% petroleum polyol. For PU foams reinforced with nanoclay, their compressive strength changed little from 1 to 5%, but decreased at 7% due to a lower density and weaker matrix structure. Foams containing 5 to 7% microspheres or 3 to 7% nanoclay had density-compressive strength comparable or superior to the control. Foams reinforced with fillers had more cells and smaller cell size than foams made from 15% soy-polyol but without fillers. During the foaming process, the maximal temperatures reached by PU foams were not affected by the presence of 1 to 7% of microspheres or nanoclay, but slightly lower than the control. In addition, foams with fillers displayed roughly the same thermal conductivity as soy-polyol based foams without fillers.

Physical Properties of Soy-Phosphate Polyol-Based Rigid Polyurethane Foams

Water-blown rigid polyurethane (PU) foams were made from 0–50% soy-phosphate polyol (SPP) and 2–4% water as the blowing agent. The mechanical and thermal properties of these SPP-based PU foams (SPP PU foams) were investigated. SPP PU foams with higher water content had greater volume, lower density, and compressive strength. SPP PU foams with 3% water content and 20% SPP had the lowest thermal conductivity. The thermal conductivity of SPP PU foams decreased and then increased with increasing SPP percentage, resulting from the combined effects of thermal properties of the gas and solid polymer phases. Higher isocyanate density led to higher compressive strength. At the same isocyanate index, the compressive strength of some 20% SPP foams was close or similar to the control foams made from VORANOL 490.

HIGH-SURFACE-AREA BIOCARBONS FOR REVERSIBLE ON-BOARD STORAGE OF NATURAL GAS AND HYDROGEN

An overview is given of the development of advanced nanoporous carbons as storage materials for natural gas (methane) and molecular hydrogen in on-board fuel tanks for nextgeneration clean automobiles. The carbons are produced in a multi-step process from corncob, have surface areas of up to 3500 m 2 /g, porosities of up to 0.8, and reversibly store, by physisorption, record amounts of methane and hydrogen. Current best gravimetric and volumetric storage capacities are: 250 g CH4/kg carbon and 130 g CH4/liter carbon (199 V/V) at 35 bar and 293 K; and 80 g H2/kg carbon and 47 g H2/liter carbon at 47 bar and 77 K. This is the first time the DOE methane storage target of 180 V/V at 35 bar and ambient temperature has been reached and exceeded. The hydrogen values compare favorably with the 2010 DOE targets for hydrogen, excluding cryogenic components. A prototype adsorbed natural gas (ANG) tank, loaded with carbon monoliths produced accordingly and currently undergoing a road test in Kansas City, is described. A preliminary analysis of the surface and pore structure is given that may shed light on the mechanisms leading to the extraordinary storage capacities of these materials. The analysis includes pore-size distributions from nitrogen adsorption isotherms; spatial organization of pores across the entire solid from small-angle x-ray scattering (SAXS); pore entrances from scanning electron microscopy (SEM) and transmission electron microscopy (TEM); H2 binding energies from temperature-programmed desorption (TPD); and analysis of surface defects from Raman spectra. For future materials, expected to have higher H2 binding energies via appropriate surface functionalization, preliminary projections of H2 storage capacities based on molecular dynamics simulations of adsorption of H2 on graphite, are reported.

Impact of the maximum foam reaction temperature on reducing foam shrinkage

One of the obstacles to displacing petroleum-based polyols with soy-based polyols in rigid urethane foam formulations is foam shrinkage, especially at displacements greater than 50%. The shrinkage is a result of partial vacuums forming in the closed-cell foam as reaction temperatures dissipate. It was hypothesized that the shrinkage was in part due to inadequate curing of the foam which was due to lower maximum-attained temperatures during the near-adiabatic foaming process. Foam formulation studies were performed to evaluate the correlation of peak temperature foam shrinkage. Two approaches were evaluated to increase peak temperatures: (a) preheating of the monomers prior to reaction and (b) use of bio-based glycerol as a co-reagent to increase the mixture hydroxyl number and respective maximum temperatures. The results show that as the maximum reaction temperature increases, foam shrinkage decreases. Both preheating and use of a glycerol co-reagent were effective for increasing peak temperatures and decreasing shrinkage. Experimental results were supplemented with a simulation of the foaming process to better understand the fundamental phenomena and to evaluate the effectiveness of the simulation to evaluate approaches to better utilize bio-based monomers in thermoset polymers.

Complex pore spaces create record-breaking methane storage system for natural-gas vehicles

P. Pfeifer, L. Aston, M. Banks, S. Barker, J. Burress, S. Carter, J. Coleman, S. Crockett, C. Faulhaber, J. Flavin, M. Gordon, L. Hardcastle, Z. Kallenborn, M. Kemiki, C. Lapilli, J. Pobst, R. Schott, P. Shah, S. Spellerberg, G. Suppes, D. Taylor, A. Tekeei, C. Wexler, and M. Wood University of Missouri, Columbia, Missouri 65211, USA P. Buckley, T. Breier, J. Downing, S. Eastman, P. Freeze, S. Graham, S. Grinter, A. Howard, J. Martinez, D. Radke, and T. Vassalli Midwest Research Institute, Kansas City, Missouri 64110, USA J. Ilavsky Argonne National Laboratory, Argonne, Illinois 60439, USA Received 27 August 2007; published online 27 December 2007 DOI: 10.1063/1.2786007

Simulation of Catalyzed Urethane Polymerization: An Approach to Expedite Commercialization of Bio-based Materials

A MATLAB program was developed to simulate polyurethane foaming reaction. Key reactions (including isocyanate–polyol and isocyanate–water) and dozens of primary side reactions were taken consideration into the simulation of polymerization. The model tracks reaction rates, component concentration profiles and the temperature profile for the reactions under different conditions respect to different catalyst types, amount of catalyst loading, reaction temperature and the reactivities of the monomers with each other. Tin based catalysts and amine based catalysts were applied into gel and foam recipes separately to evaluate the impact of each catalyst on both gel and blow reactions. The model predicts performances of diverse foam recipes and can be effective for “sensitivity studies” useful in designing form formulations. The simulations have been validated for estimating catalyst loadings, identifying the tradeoff between higher catalyst loadings versus preheating of reagents, and providing insight into fundamental mechanisms/reactions.