Modelling of impregnation kinetics and internal activity profiles: Adsorption of HCl,HReO4 and H2PtCl6 onto γ-Al2O3

This paper presents a rather complete model of impregnation kinetics and internal active ingredient profile. Particle characteristics, operating variables, physical variables and chemical variables are taken into account in our model equations. How the interplay of these variables affects the global kinetics and the distribution will be thoroughly discussed in this paper. Finally, our simulations are compared to the experimental distribution of HCl, HReO₄ and H₂PtCl₆ in γ-Al₂O₃ obtained by Miguel et al. 1984, Appl. Catal.9, 309 and their rate constants of adsorption are found as 0.032, 0.128 and 0.8 min⁻¹ respectively.     

NH3–NO/NO2 SCR for Diesel Exhausts Aftertreatment: Reactivity, Mechanism and Kinetic Modelling of Commercial Fe- and Cu-Promoted Zeolite Catalysts

The activity and the mechanism of the main reactions in the NO/NO₂–NH₃ SCR reacting system were comparatively investigated over a Fe- and a Cu-promoted commercial zeolite catalyst for the aftertreatment of Diesel exhausts. A dynamic micro-kinetic model in close agreement with all the details of the SCR catalytic chemistry was also developed.     

Aqueous mixtures of AMP,HMDA-N,N′-dimethyl and TEG for CO2 separation: a study on equilibrium and reaction kinetics

Abstract

The hindered amine 2-amino-2-methyl-1-propanol (AMP) is a capable CO₂ separation solvent. HMDA-N,N′-Dimethyl (or HMDA-N,N′), which is the dimethyl derivative of 1,6-hexamethyl diamine, is a prospective activator of the absorption rate in AMP/H₂O mixtures. If a less volatile co-solvent such as triethylene glycol (TEG) is used in AMP-based solutions, the regeneration energy constraint will be lowered. In this work, a formulated blend of AMP (2-3?M), HMDA-N,N′ (0.1–0.5 M), TEG (0.7–2?M) and water was suggested for improved CO₂ capture from flue gas in thermal power stations. Kinetics of the CO₂ reaction with the suggested blend was studied in a stirred cell at 35, 40, and 45?°C. The pathway was elucidated using the renowned zwitterion mechanism. Overall, it was envisaged that both AMP and HMDA-N,N′ react with CO₂ in parallel. The values of the pseudo-first order rate constant were determined. It was found that HMDA-N,N′ reacts with CO₂ according to a second-order reaction (rate constant k_2,HMDA-N,N^′ = 79,525?M^?1 s^?1 at 35?°C), whose energy of activation is 38?kJ mol^?1. Lastly, the loading capacity of the suggested blend was measured in an ambient-pressure equilibrium setup. Its highest value was 1.4?mol CO₂/mol amine, when equilibrium CO₂ pressure was 4?kPa.     

Effects of Water and Ion-Exchanged Counterion on the FTIR Spectra of ZSM-5. II. (Cu+–CO)-ZSM-5: Coordination of Cu+–CO Complex by H2O and Changes in Skeletal T–O–T Vibrations

The 2157 cm^–1 (strong) and 2108 cm^–1 (very weak) (CO) IR bands due to Cu⁺–CO in ZSM-5 zeolite with ¹²C and ¹³C isotopes, respectively, are reversibly red-shifted by subsequent adsorption of H₂O at 293 K. On the contrary, the locally perturbed internal (T–O–T) asymmetric stretching framework vibration [ _as ^int (TOT)(Cu⁺–CO)=965 cm^–1] is reversibly blue-shifted. The courses of the band shifts revealed notable features. Charge transfers from water to Cu⁺ ions, changes in coordination spheres of Cu⁺(CO)(H₂O) _n aqua complexes and secondary (solvent-like) effects were considered to explain the results.     

The catalytic activity of Ru and Ir supported on Eu2O3 for the reaction,CO2 + CH4 ⇄ 2 H2 + 2 CO: a viable solar-thermal energy system

Methane and carbon dioxide which often co-exist in nature, constitute valuable potential resources both for the storage of solar (thermal) energy and the convenient production of synthesis gas. Ru and Ir supported on Eu₂O₃ are effective catalysts for the reforming of methane with carbon dioxide to produce synthesis gas with no significant coke formation even after prolonged activity. Ru catalysts show onset of activity around 673 K reaching a maximum at about 973 K. Loadings as low as 1% by weight of Ru are highly effective. Ir catalysts show onset around 823 K reaching a maximum conversion in excess of 94% with respect to CO₂ at 1023 K for a 1% loading of the metal. X-ray absorption studies on the spent Ru/Eu₂O₃ catalysts indicate the presence of the reduced metal, primarily in the form of large spherical particles (> 30 Å) of hexagonal structure. 5% Ir supported on Eu₂O₂ was found to transform an equimolar mixture of H₂ and CO to methane and carbon dioxide with a 42% conversion with respect to H₂ at around 848 K and atmospheric pressure. A 5% loading of Ru on Eu₂O₃ produced a 14% conversion with respect to H₂ at 973 K under similar conditions.Commonwealth Academic Fellow on leave from University of Peradeniya, Peradeniya, Sri Lanka.     

Retention,Thermodynamics and Adsorption Profile of Th(IV) Ions onto 1‐(2‐Pyridylazo)‐2‐Naphthol (PAN) Loaded Polyurethane Foam from Acetate Media and its Separation from Rare Earths

Abstract

The sorption behavior of 2.7×10^?5 M solution of Th(IV) ions on 1‐(2‐pyridylazo)‐2‐naphthol (PAN) loaded polyurethane foam (PUF) has been investigated. The quantitative sorption was occurred from pH 6 to 9 from acetate buffer solutions. The sorption conditions were optimized with respect to pH, shaking time, and weight of sorbent. The sorption data followed the Freundlich, Langmuir, and Dubinin‐Radushkevich (D‐R) isotherms very successfully at low metal ions concentration. The Freundlich isotherm constant (1/n) is estimated to be 0.22±0.01, and reflects the surface heterogeneity of the sorbent. The Langmuir isotherm gives the maximum monolayer coverage is to be 8.61×10^?6 mol g^?1. The sorption free energy of the D‐R isotherm was 17.85±0.33 kJ mol^?1, suggesting chemisorption involving chemical bonding was responsible for the adsorption process. The numerical values of thermodynamic parameters such as enthalpy (ΔH), entropy (ΔS), and Gibbs free energy (ΔG) indicate that sorption is endothermic, entropy driven, and spontaneous in nature. The adsorption free energy (ΔG_ads) and effective free energy (ΔG_eff) are also evaluated and discussed. The effect of different anions on the sorption of Th(IV) ions onto PAN loaded PUF was studied. The possible sorption mechanism on the basis of experimental finding was discussed. A new separation procedure of Th(IV) from synthetic rare earth mixture using batch, column chromatography, and squeezing techniques were reported.     

Study of cerium species in molten Li2CO3–Na2CO3 in the conditions used in molten carbonate fuel cells. Part I: Thermodynamic, chemical and surface properties

The chemical and surface behaviour of cerium oxide, a candidate material for MCFC applications is analysed in Li₂CO₃–Na₂CO₃ carbonate eutectic in reducing (H₂:CO₂:H₂O:CO) and oxidizing (O₂:CO₂) atmospheres. The electrochemical stability domains of cerium species are established at different temperature on the basis of thermochemical calculations. CeO₂ is the stable species whatever the acidity level in both the anode and cathode conditions; nevertheless, a partial solubility of Ce₂O₃ in CeO₂ can be predicted. The solubility of cerium and cerium oxide samples, determined by absorption spectrophotometry, is about 5 × 10^–4 mol kg^–1 in cathodic conditions and 3 × 10^–4 mol kg^–1 in anodic conditions. X-ray diffraction (XRD) confirmed the presence of CeO₂ at the surface of the samples. Incorporation of sodium species in the CeO₂ lattice is likely; the presence of Ce(III) in long endurance tests was detected by X-ray photoelectron spectroscopy (XPS).     

Na(+), K(+)-ATPase Subunit Composition in a Human Chondrocyte Cell Line; Evidence for the Presence of α1, α3, β1, β2 and β3 Isoforms

Membrane transport systems participate in fundamental activities such as cell cycle control, proliferation, survival, volume regulation, pH maintenance and regulation of extracellular matrix synthesis. Multiple isoforms of Na(+), K(+)-ATPase are expressed in primary chondrocytes. Some of these isoforms have previously been reported to be expressed exclusively in electrically excitable cells (i.e., cardiomyocytes and neurons). Studying the distribution of Na(+), K(+)-ATPase isoforms in chondrocytes makes it possible to document the diversity of isozyme pairing and to clarify issues concerning Na(+), K(+)-ATPase isoform abundance and the physiological relevance of their expression. In this study, we investigated the expression of Na(+), K(+)-ATPase in a human chondrocyte cell line (C-20/A4) using a combination of immunological and biochemical techniques. A panel of well-characterized antibodies revealed abundant expression of the α1, β1 and β2 isoforms. Western blot analysis of plasma membranes confirmed the above findings. Na(+), K(+)-ATPase consists of multiple isozyme variants that endow chondrocytes with additional homeostatic control capabilities. In terms of Na(+), K(+)-ATPase expression, the C-20/A4 cell line is phenotypically similar to primary and in situ chondrocytes. However, unlike freshly isolated chondrocytes, C-20/A4 cells are an easily accessible and convenient in vitro model for the study of Na(+), K(+)-ATPase expression and regulation in chondrocytes.     

Semi-rigid N-para-ferrocenyl(benzoyl)amino-acid esters for biomaterials: synthesis and characterization of Fc-C6H4CONHCH(R)CO2Me where Fc = (η5-C5H5)Fe(η5-C5H4) and R=H,CH3,CH2CH(CH3)2,CH2C6H5 and the X-ray crystal structures of Fc-C6H4CO2Me and the l-alanine derivative Fc-C6H4CONHCH(CH3)CO2Me

A series of N-para-(ferrocenyl)benzoyl amino-acid esters, para-Fc(C₆H₄)CONHCH(R)CO₂CH₃ {Fc = (η⁵-C₅H₅)Fe(η⁵-C₅H₄); R = H, CH₃, CH₂CH(CH₃)₂, CH₂C₆H₅}, 3–6 have been prepared by coupling para-(ferrocenyl)benzoic acid to the amino-acid esters (gly, l-Ala, l-Leu, l-Phe) using the standard 1,3-dicyclohexylcarbodiimide (DCC), 1-hydroxybenzotriazole (HOBt) protocol. The compounds were fully characterized by a range of spectroscopic techniques including FAB-MS. The X-ray crystal structures of the parent para-(ferrocenyl)benzoyl methyl ester, Fc-C₆H₄CO₂Me, 1 and a chiral derivative N-{para-(ferrocenyl)benzoyl}-l-alanine methyl ester, Fc-C₆H₄CONHCH(CH₃)CO₂Me, 4 have been determined.     

Fischer�CTropsch Synthesis: Influence of CO Conversion on Selectivities, H2/CO Usage Ratios, and Catalyst Stability for a Ru Promoted Co/Al2O3 Catalyst Using a Slurry Phase Reactor

The effect of CO conversion on hydrocarbon selectivities (i.e., CH₄, C₅₊, olefin and paraffin), H₂/CO usage ratios, CO₂ selectivity, and catalyst stability over a wide range of CO conversion (12?C94%) on 0.27%Ru?C25%Co/Al₂O₃ catalyst was studied under the conditions of 220 °C, 1.5 MPa, H₂/CO feed ratio of 2.1 and gas space velocities of 0.3?C15 NL/g-cat/h in a 1-L continuously stirred tank reactor (CSTR). Catalyst samples were withdrawn from the CSTR at different CO conversion levels, and Co phases (Co, CoO) in the slurry samples were characterized by XANES, and in the case of the fresh catalysts, EXAFS as well. Ru was responsible for increasing the extent of Co reduction, thus boosting the active site density. At 1%Ru loading, EXAFS indicates that coordination of Ru at the atomic level was virtually solely with Co. It was found that the selectivities to CH₄, C₅₊, and CO₂ on the Co catalyst are functions of CO conversion. At high CO conversions, i.e. above 80%, CH₄ selectivity experienced a change in the trend, and began to increase, and CO₂ selectivity experienced a rapid increase. H₂/CO usage ratio and olefin content were found to decrease with increasing CO conversion in the range of 12?C94%. The observed results are consistent with water reoxidation of Co during FTS at high conversion. XANES spectroscopy of used catalyst samples displayed spectra consistent with the presence of more CoO at higher CO conversion levels.     

The adsorption feature and photocatalytic oxidation activity of K1−2xMxTiNbO5 (M = Mn,Ni) for methyl mercaptan in methane

The novel photocatalytic ceramics material K_1?2xM_xTiNbO₅ (M = Mn, Ni) were prepared through Mn²⁺ and Ni²⁺ ion-exchange of KTiNbO₅, which was synthesized by a hydrothermal method. The influence of the ion-exchange process on the structure and morphology of prepared ceramics material were investigated by such physicochemical methods as powder X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), UV–visible diffuse reflectance spectroscopy (UV–vis DRS) and Fourier-transform infrared (FT-IR) microscopy. The adsorption and photocatalytic oxidation of methyl mercaptan (MM) in methane were used to evaluate the catalytic performance of different constitutes. The results revealed that K_1?2xNi_xTiNbO₅ exhibited better adsorption and photocatalytic oxidation activity for MM in methane under both visible and UV light radiation. While the photocatalytic oxidation activity of K_1?2xMn_xTiNbO₅ is similar to that of K_1?2xNi_xTiNbO₅, however it has little adsorption activity for MM in dynamic state.     

N,N,N′,N′-Tetra(2-Ethylhexyl) Thiodiglycolamide T(2EH)TDGA: A Promising Ligand for Separation and Recovery of Palladium from High Level Liquid Waste (HLLW) Solutions

The extraction properties of N,N,N′,N′-tetra(2-ethylhexyl)thiodiglycolamide T(2EH)TDGA have been evaluated for the separation and recovery of palladium from simulated high-level liquid waste (SHLW). T(2EH)TDGA has shown very high selectivity for Pd (II) over other metal ions present in SHLW. The separation factor (SF) for Pd (II) over other metal ions was found to be more than 10⁵. Reusability studies of the extractant indicate that D_Pd remained almost constant even after five successive cycles of extraction and stripping. Palladium was quantitatively recovered from thiourea strip solution by treating it with ammonia and filtering the precipitate of palladium sulphide. The acid uptake constant (K_H) was found to be 0.62 which could be due to the presence of two carbonyl groups of amidic moiety. To account for very high extractability of palladium with T(2EH)TDGA over other ‘S’ donor extractants, namely Bis-(2-ethylhexyl)sulphoxide (BESO), FTIR, as well as Raman studies were carried out. FTIR and Raman studies suggested the ligation through carbonyl as well as the thio-ether group. Conditional extraction constants (log K′_ex) were determined and the thermodynamic parameters were calculated from the dependence of the conditional extraction constant (log K′_ex) on temperature. The calculated values of ΔG_ex, ΔH_ex, and ΔS_ex were ?41.78 kJmol^?1, ?55.12 kJmol^?1 and ?44.04 JK^?1 mol^?1 respectively. The extraction process is indicated to be enthalpy driven with the entropy factor counteracting it.     

The redox pair {(μ4-TCNE)[Fe(CO)2(C5H5)]4}4+/3+: Surprisingly small metal–ligand interaction and the first resolved EPR hyperfine structure (13C, 14N, 57Fe) of a tetranuclear complex with TCNE−

Electrochemistry and absorption spectroscopy (UV/Vis, IR) of the complex {(μ₄-TCNE)[Fe(CO)₂(C₅H₅)]₄}(BF₄)₄ reveal only a small degree of metal-to-ligand π back donation, in contrast to previously characterized compounds [(TCNE)(ML_n)₄]. Accordingly, the one-electron reduced {(μ₄-TCNE)[Fe(CO)₂(C₅H₅)]₄}³⁺ exhibits a very well resolved EPR spectrum at g = 1.9965 with detectable coupling of 0.055 mT for ⁵⁷Fe in natural abundance from four coordinated [Fe(CO)₂(C₅H₅)]⁺ groups.