Kinetics and Catalysis:
[1] Complete Catalytic Oxidation of Diethyl Sulfide over a 1 % Pt/Al,O,Catalyst
The complete oxidation of diethyl sulfide over a 1% Pt/A1203 catalyst was studied using a fixed bed catalytic reactor. The reaction was studied in dry air between 225 and 300 "C and 1.25 atm of total pressure. The concentration of diethyl sulfide was varied between 6 and 250 ppm (v/v). The reaction was found to be zeroth order in diethyl sulfide concentration over the range of conditions studied, suggesting that, at even low concentrations, the reactant sulfide is strongly adsorbed by the active site. The zeroth-order rate constant was calculated to be 78.8 exp(-19117/RT) mol/(s-g of catalyst).
[2] Catalytic Oxidation of Chloroform over a 2% Platinum Alumina Catalyst
The complete catalytic oxidation of chloroform over a 2% platinum a-alumina catalyst was investigated using a fixed bed catalytic reactor operated at temperatures between 300 and 400ºC and concentrations between 100 and 5000 ppm (v/v) in humid air at atmospheric pressure. a kinetic rate expression was developed to describe the data over the range of conditions investigated. The rate expression was developed by assuming an interaction between gas-phase chloroform and adsorbed oxygen, with the reaction being inhibited by the adsorption of reaction product HC1. The presence of water in the feed stream shifted the reaction products from Cl2 to HC1, suggesting that water plays a role in the reaction scheme.
Adsorption and Filtration
[3] Peterson, G.W. and Rossin, J.A.; “Removal of Chlorine Gases from Streams of Air Using Reactive Zirconium Hydroxide-based Filtration Media.” Ind. Eng. Chem. Res. 51 (2012) 2675
Zirconium hydroxide and zirconium hydroxide impregnated with triethylenediamine (TEDA) were evaluated for their ability to remove toxic chlorine gases, namely Cl2, COCl2, and HCl from streams of air in respirator applications. Zirconium hydroxide displayed a high capacity for the removal of HCl; however, the ability of zirconium hydroxide to remove Cl2 and COCl2 was relatively low. The removal of Cl2 and COCl2 greatly improved upon impregnation of zirconium hydroxide with TEDA. The improved performance was attributed to the ability of TEDA to promote the hydrolysis of Cl2 and COCl2, leading to the formation of HCl which was subsequently removed via reaction with hydroxyl groups associated with zirconium hydroxide. XPS analysis revealed the presence of both terminal and bridging hydroxyl groups associated with zirconium hydroxide, with only the terminal hydroxyl groups participating in the removal of reactant or reaction product HCl.
[4] Peterson, G.W.; Rossin, J.A.; Karwacki, C.J. and Glover, T.G.; “Surface Chemistry and Morphology of Zirconia Ploymorphs and the Invluence on Sulfur Dioxide Removal.” J. Phys. Chem. C. 115 (2011) 9644-9650.
Zirconium hydroxide was calcined at discrete temperatures up to 900 _C to study the effect of thermal treatment on the structure and surface chemistry related to the filtration of SO2. As-received and calcined materials were characterized using multiple techniques that included thermal gravimetric analysis, X-ray diffraction, and nitrogen porosity to determine changes to the zirconium hydroxide structure. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy were used to characterize changes in surface hydroxyl groups. Changes in the morphology and surface chemistry were correlated to sulfur dioxide filtration through chemical breakthrough studies. It was found that as calcination temperature increased, materials become more crystalline, which led to the loss of terminal hydroxyl groups and a decrease in the efficacy for sulfur dioxide removal.
[5] Levasseur, B.; Gonzalez-Lopez, E.; Rossin, J.A. and Bandosz, T.J.; “Effects of Reduction Treatment on Copper-Modified Activated Carbons on NOx Adsorption at Room Temperature.” Langmuir 27 (2011) 5354-5365.
Activated carbon was impregnated with copper salt and then exposed to reductive environment using hydrazine hydrate or heat treatment under nitrogen at 925ºC. On the obtained samples, adsorption of NO2 was carried out at dynamic conditions at ambient temperature. The adsorbents before and after exposure to nitrogen dioxide were characterized by X-ray diffraction (XRD), thermal analysis, scanning electron microcopy/energy dispersive X-ray spectroscopy, (SEM-EDX), X-ray photoelectron spectroscopy (XPS), N2-sorption at -196ºC, and potentiometric titration. Copper loading improved the adsorption capacity of NO2 as well as the retention of NO formed in the process of NO2 reduction on the carbon surface. That improvement is linked to the presence of copper metal and its high dispersion on the surface. Even though both reduction methods lead to the reduction of copper, different reactions with the carbon surface take place. Heat treatment results in a significant percentage of metallic copper and a reduction of oxygen functional groups of the carbon matrix, whereas hydrazine, besides reduction of copper, leads to an incorporation of nitrogen. The results suggest that NO2 mainly is converted to copper nitrates although the possibility to its reduction to N2 is not ruled out. A high capacity on hydrazine treated samples is linked to the high dispersion of metallic copper on the surface of this carbon.
[6] Mahle, J.J.; Peterson, G.W.; Schindler, B.J.; Smith, P.B.; Rossin, J.A. and Wagner, G.W.; “Role of TEDA as an Activated Carbon Impregnant for the Removal of Cyanogen Chloride from Air Streams: Synergistic Effect with Cu(II).” J. Phys. Chem. C 114 (2010) 20083.
The hydrolysis and fate of cyanogen chloride (CK) in the presence of triethylenediamine (TEDA) – a widely used carbon impregnantsin aqueous and nonaqueous (acetonitrile) media has been determined. In the presence of water, anticipated TEDA substitution is not observed; rather, simple base-catalyzed (OH-) hydrolysis to cyanic acid (HOCN; unstable in water, decomposing to CO2 and NH3) is the major reaction, accompanied by a series of complex side reactions (not involving TEDA) to form several persistent compounds. Thus, the role of TEDA, in the presence of water, is primarily a source of OH-. CK substitution at TEDA is observed in acetonitrile, again forming several complex, but quite different, species. Studies examining the removal of CK from humidified air streams by carbon impregnated with TEDA and/or basic Cu2+ (another common carbon impregnant) are consistent with simple hydrolysis being the major CK-removal mechanism; no TEDA substitution is observed in the presence of humidity/water. Considering the reaction stoichiometry apparent at CK breakthrough for the impregnated carbons, the combination of TEDA and Cu2+ is much more effective than the individual impregnants themselves. This synergism is attributed to dissolution of basic Cu2+ by TEDA to form soluble complexes of the type [Cu(TEDA)2(OH)(H2O)]- in the carbon-adsorbed water layer, thus greatly increasing the dispersion and effectiveness of the basic Cu2+ impregnant.
[7] Peterson, G.W.; Wagner, G.W.; Keller, J.H. and Rossin, J.A.; “Enhanced Cyanogen Chloride Removal by the Reactive Zirconium Hydroxide Substrate.” Ind. Eng. Chem. Res. 49 (2010) 11182.
A novel microporous sorbent consisting of zirconium hydroxide impregnated with triethylenediamine (TEDA) was evaluated for the removal of cyanogen chloride. Breakthrough data were collected on packed beds, illustrating the efficacious nature of TEDA and the enhanced cyanogen chloride removal from the basic zirconium hydroxide structure. NMR and XPS analyses revealed the fate of cyanogen chloride, with inorganic chloride byproducts deposited on the surface of the material and polymerized urea condensates physically adsorbed in the pore structure. The zirconium hydroxide media were found to provide significantly enhanced removal capabilities as compared to traditionally impregnated activated carbons, allowing for the development of respirators with reduced encumbrance.
[8] Maxwell, A.H. and Rossin, J.A.; “Effects of Airborne Contaminant Exposure on the Physical Properties and Filtration Performance of Activated, Impregnated Carbon.” Carbon 48 (2010) 2634.
The effects of airborne contaminant exposure in humid air on the physical properties and filtration capabilities of a copper/zinc/molybdenum impregnated carbon were investigated. The impregnated carbon was exposed individually to CO2, NH3 and NO2 in humid air, then evaluated for changes in metal speciation, metal distribution, porosity and water-uptake. The exposed impregnated carbon was further evaluated for changes in its ability to remove SO2 and cyclohexane from air streams. Exposure to CO2 did not impact the physical properties of the impregnated carbon, with changes in filtration performance were not evident. NH3 exposure resulted in the formation of metal amine complexes, which led to a migration of impregnants from within the pores of the carbon granule to the external surface. NH3 exposure increased SO2 filtration while decreasing cyclohexane filtration. The decrease in cyclohexane filtration was attributed to an increase in water uptake and a decrease in porosity. NO2 exposure significantly decreased the porosity of the carbon substrate while increasing the amount of surface oxygen. The increased surface oxygen greatly increased water uptake. NO2 exposure greatly reduced the SO2 breakthrough time and the ability of the material to remove cyclohexane.
[9] Peterson, G.W.; Rossin, J.A.; Smith, P.B. and Wagner, G.W.; “Effects of Water on the Removal of Methyl Bromide using Triethylene Diamime Impregnated Carbon.” Carbon 48 (2010) 81.
The removal of methyl bromide (CH3Br) from streams of dry and humid air was investigated using coconut shell carbon impregnated with triethylene diamine (TEDA). The relative humidity of the air stream had a significant effect on the CH3Br breakthrough time, but not the removal capacity, especially as the relative humidity of the air stream was increased to greater than 50%. The decrease in the breakthrough time was attributed to an increased in the amount of water physically adsorbed by the carbon substrate, leading to a significant decrease in the CH3Br adsorption capacity. NMR results revealed TEDA was reacting directly with CH3Br, leading to the formation of primarily a mono-substituted quaternary amine, with only small amounts of the di-substituted quaternary amine detected.
[10] Peterson, G.W.; Karwacki, C.J; Rossin, J.A. and Feaver, W.B.; “Catalytic Removal of Ethylene Oxide from Contaminated Airstreams by Alkali-Treated H-ZSM-5.” In Nanoscience and Nanotechnology for Chemical and Biological Defense, Chapter 18, 2009, pp 235-248 (ACS Symposium Series, Volume 1016).
Zeolite H-ZSM-5 was treated with sodium hydroxide in order to develop mesoporosity and increase ethylene oxide breakthrough time. An increase in mesoporosity, coupled with optimizing the acidity while maintaining the hydrophobicity of the zeolite resulted in the largest increase in the ethylene oxide breakthrough time.
[11] Peterson, G.W.; Karwacki, C.J; Feaver, W.B. and Rossin, J.A.; “Zirconium Hydroxide as a Reactive Substrate for the Removal of Sulfur Dioxide.” Ind. Eng. Chem. Res. 48 (2009) 1694.
Zirconium hydroxide [Zr(OH)4], with a surface area of 365 m2/g, was evaluated for its ability to remove SO2 from streams of air at room temperature. The SO2 removal capacity of Zr(OH)4 was ~90 mg SO2 removed per cm3 bed volume, which is almost an order of magnitude greater than the value achieved for activated carbon and is more than twice the value achieved for activated carbon impregnated with 10% CuO. Temperature-programmed desorption results indicate that SO2 is strongly retained by Zr(OH)4. X-ray photoelectron spectroscopy results reveals the presence of sulfite (SO3 2-) species following reaction exposure, which suggests the formation of zirconium sulfite. Although the SO2 removal capacity (volume basis) of Zr(OH)4 is high, relative to that of impregnated activated carbon, only 10% of the stoichiometric hydroxyl groups are able to contribute to the removal of SO2.
[12] Peterson, G.W.; Karwacki, C.J; Feaver, W.B. and Rossin, J.A.; “H-ZSM-5 for the Removal of Ethylene Oxide: Effects of Water on Filtration Performance.” Ind. Eng. Chem. Res. 47 (2008) 185.
Zeolite H-ZSM-5 with a SiO2/Al2O3 ratio of 25 was evaluated for its ability to remove ethylene oxide (EtO) from streams of air at 25°C and between 15 and 90% relative humidity (RH). The primary mechanism for the removal of ethylene oxide using H-ZSM-5 involves a catalyzed hydrolysis reaction initiated by the adsorption of EtO onto a Brønsted acid site. Secondary addition reactions leading to the formation of polyglycols are also occurring. The reaction is poisoned by the accumulation of reaction products within the pores of the zeolite, which ultimately leads to elution of EtO from the filter bed. The ability of H-ZSM-5 to remove EtO decreased significantly as the relative humidity increased from 50 to 90%. For example, the EtO breakthrough time decreases from 220 min at 50% RH to 57 min at 90% RH. The decrease in the EtO breakthrough time over the stated RH range is attributed to the increased hydration of the Brønsted acid site. As the extent of Brønsted acid site hydration increases, the reactivity of the site is reduced, leading to a reduction in the EtO breakthrough time.
Decontamination
[13] Bandosz, T.J. ; Laskoski, M.; Mahle,J.; Mogilevsky,G.; Peterson, G.W.; Rossin, J.A. and Wagner, G.W.; “Reactions of VX, GD, and HD with Zr(OH)4: Near Instantaneous Decontamination of VX.” J. Phys. Chem. C. 116 (2012) 11606.
Zirconium hydroxide was evaluated for the ability to detoxify chemical warfare agents GD, HD, and VX. Observed half-lives were 8.7 min, 2.3 h, and 1 min, respectively. Owing to its extremely fast reaction rate, the mechanism for VX was further characterized. Zirconium hydroxide samples were calcined at temperatures ranging from 150 to 900 °C to investigate the effect of surface speciation on VX hydrolysis rates. NMR, TGA/DSC, TEM, and potentiometric tritration reveal the importance of the acidic, bridging OH groups of Zr(OH)4 which are proposed to protonate and catalytically hydrolyze VX in a manner similar to autocatalysis by EMPA in solution.
[14] Brown, R.S.; Rossin, J.A.; Kotary, J.F.; Fitzgerald, G.; Gerhart, K.G.; Mearns, H.A.; Newton, R.A.; Keller, J.H.; Mawhinney, D.B. and Yates, J.Y.; Decontamination of Chemical Warfare Agents using a Reactive Sorbent. U.S. Patent 6,852,903 (2005).
The invention provides reactive sorbents and methods of making and using the same in order to decontaminate surfaces contaminated with toxic agents, such as chemical warfare agents and/or industrial toxins. The reactive sorbents are of two general types, one of which comprises dehydroxylated aluminum oxide and the other comprises porous carbon impregnated with a reactive solution, so that both sorbents take up and then detoxify toxic agents.