Comparison of Hydrometallurgical Parameters of N,N‐Dialkylamides and of Tri‐n‐Butylphosphate

Straight‐chain N,N‐dihexyloctanamide (DHOA) and branched‐chain N,N‐di(2‐ethylhexyl)isobutyramide (D2EHIBA) have been identified as promising alternatives to tri‐n‐butylphosphate (TBP) for the reprocessing of spent uranium based fuels, and selective extraction of ²³³U from irradiated thorium fuels, respectively. The present work deals with the effects of different hydrodynamic parameters such as viscosity, density, and interfacial tension (IFT) on the phase‐separation time (PST) under uranium and thorium loading conditions. The IFT values have been determined under varying experimental conditions such as the aqueous nitric acid concentration, n‐dodecane purity, ligand concentration, and thorium/uranium loading conditions. These studies have suggested that the quality of n‐dodecane affects the IFT values of different solutions. The IFT values of D2EHIBA changed marginally (23.3 ± 0.9 mNm^?1) against THOREX feed solution for the wide range of D2EHIBA concentration (0.1–1.0 M). However, IFT, viscosity, and PST values increased with uranium loading of 1.1 M DHOA. These studies suggested that a lower phase‐disengagement rate with increased uranium loading was mainly due to the increased viscosity of the loaded 1.1 M DHOA solution.     

Comparison of the catalytic properties of Al‐ZSM‐22 and Fe‐ZSM‐22 in the skeletal isomerization of 1‐butene

The catalytic activities of Al‐ZSM‐22 (Al in the framework) and Fe‐ZSM‐22 (Fe in the framework) were compared in the skeletal isomerization of 1‐butene to isobutene. The catalysts synthesized in the laboratory were characterized by means of XRD, FTIR spectroscopy, SEM and surface area measurements. The activity of the zeolites was investigated using a fixed‐bed microreactor system. Al‐ZSM‐22 demonstrated higher activity in 1‐butene transformation compared to Fe‐ZSM‐22, while the selectivity to isobutene, on the other hand, was higher over Fe‐ZSM‐22. Coke formation was monitored using a microbalance and the results showed that the weight gain of Fe‐ZSM‐22 was slightly higher compared to Al‐ZSM‐22. This revised version was published online in July 2006 with corrections to the Cover Date.     

Shock‐Wave Initiation of Detonation of Double‐Base Propellants

In the known experimental system active charge–target–HE charge to be tested, critical pressures of shock waves initiating detonation of doublebase propellant charges are determined. TNT charges of various density were used as active HE, and copper plates 5 mm thick were used as targets. The pressure of the shock wave acting on the propellant versus the TNT density was constructed; this dependence being known the critical pressure can be readily determined with only the density of the active charge available. It was found that doublebase propellants are close to liquid HE in terms of sensitivity to shock waves; the critical pressure is 6.0–9.0 GPa for a charge diameter of 40 mm and decreases with increasing diameter. By an example of the NDT2 propellant, it is shown that the use of factorypacked propellants in line charges may lead to failure in transfer of detonation from one propellant charge to another.     

Synergistic Extraction of Lanthanides(III) by Mixtures of N‐p‐Methoxybenzoyl‐N‐phenylhydroxylamine and 1,10‐Phenanthroline

Abstract

We conducted a study on the equilibrium extraction behavior of the trivalent lanthanide ions (M³⁺), La, Pr, Eu, Ho, and Yb, from tartrate aqueous solutions into chloroform solutions containing N‐p‐methoxybenzoyl‐N‐phenylhydroxylamine (Methoxy‐BPHA, HL) and 1,10‐phenanthroline (phen). The synergistic species extracted was found to be {ML₂(phen) (HL)}⁺(1/2)Tar^2?, where Tar^2? is tartrate ion. The extraction constants were calculated. The extraction separation behavior and extractability of lanthanides are discussed in comparison with the self‐adducted chelate, ML₃(HL)₂, which was extracted in the absence of phen, and synergistic extraction by mixtures of other extractants such as 2‐thenoyltrifluoroacetone, and neutral donors.     

Enhancement of activity for NO removal of MFI‐type H‐Co‐silicate by high‐temperature pretreatment

The effect of high‐temperature pretreatment in the presence of steam on NO conversion of protonated cobalt‐incorporated silicate having MFI structure (H‐Co‐silicate) and copper‐ion‐exchanged MFI‐type zeolite (Cu/H‐ZSM‐5) was studied. The activity of Cu/H‐ZSM‐5 decreased with an increase of pretreatment temperature. In contrast with Cu/H‐ZSM‐5, the activity of H‐Co‐silicate for NO removal increased with the pretreatment temperature. As for H‐Co‐silicate, the pretreatment at 1000^°C was the optimum condition to enhance the conversion that was four times higher than that without pretreatment. The destruction of framework and loss of cobalt species were not observed after the pretreatment. Some parts of cobalt species migrated from the framework and became active sites that enhance the activity for NO removal. This revised version was published online in July 2006 with corrections to the Cover Date.     

Redox and photo‐redox properties of isolated Mo5+ ions in MoH‐ZSM‐5 and MoH‐beta zeolites: in situ ESR study

Redox and photo‐redox properties of isolated Mo⁵⁺ ions stabilized in H‐ZSM‐5 and H‐beta zeolites are studied by in situ ESR in flowing O₂, NO, H₂, and C₃H₆. Upon oxidation of pre‐reduced samples at 20 °C, NO demonstrates a higher oxidative ability, as compared with O₂. Interaction of Mo⁵⁺ ions with propene at 20 °C results in formation of a chemisorption complex with enhanced reactivity of Mo(V) toward NO. Illumination of the Mo⁵⁺/HZSM‐5 sample with UV‐visible light causes measurable acceleration of Mo(V) oxidation by NO at 20 °C. Therefore, photochemical activation of the oxidation step could be realized, in principle, for Mo/zeolite catalysts. At 500 °C in the reaction mixture NO + H₂, the step of the catalytic site reduction is fast, and the dynamic equilibrium of the redox reaction Mo(VI) ↔ Mo(V) for MoH‐ZSM‐5 and MoH‐beta seems to be strongly shifted to Mo⁵⁺. This revised version was published online in July 2006 with corrections to the Cover Date.     

Theoretical study of the enhanced Brønsted acidity of Zn2+‐exchanged zeolites

The effect of Zn²⁺ exchange on the Brønsted acidity of a protonic zeolite has been studied by the ab initio DFT (density functional theory) approach using the BLYP generalized gradient approximation. Three different zeolite cluster models have been compared: two 6“T” models (two 4“T” rings with an oxygen atom bridge) with Si/Al=1 and Si/Al=2 and a 4“T” model (ring form) with Si/Al=1. The Brønsted acidity has been probed by computation of the acetonitrile adsorption and the cluster deprotonation energy. The presence of Zn²⁺ does not affect the cluster Brønsted acidity but it creates a very strong Lewis site (Zn²⁺) in all models studied. On the other hand, the presence of ZnOH⁺ enhanced the Brønsted site acidity in the case of the 6T model with Si/Al=1. This enhancement is due to a change in cluster geometry and position of OH group in ZnOH⁺ upon acetonitrile adsorption.     

Self‐Propagating High‐Temperature Synthesis of Quasicrystals

With an example of Al–Ni–Co systems of two different compositions, the possibility of obtaining stable decagonal quasicrystals by the method selfpropagating hightemperature synthesis is demonstrated. The burning rate and temperature are determined. Results of an electronmicroscopic and xray diffraction study of the quasicrystals are reported.     

Stereoselective Formation of 1,4‐Anhydro‐2‐C‐carboxytetritols in the Degradation of 1,5‐Anhydroribitol and 1,5‐Anhydroxylitol with Oxygen in Aqueous Alkali

Abstract

In addition to other acid products, degradation of 1,5‐anhydroribitol (5) and 1,5‐anhydroxylitol (6) with oxygen in 1.25 M NaOH produced diastereomeric 1,4‐anhydro‐2‐C‐carboxy‐D‐erythritol (7) and 1,4‐anhydro‐2‐C‐carboxy‐D‐threitol (8) and their enantiomers as major products. However, the ratio of the diastereomers differed for the two reactants. Thus, their formation could not proceed solely by benzilic acid‐type rearrangements through α‐dicarbonyl intermediates as typically proposed for formation of alkyl C‐carboxyfuranosides from alkyl glycopyranosides in similar reactions. The α‐dicarbonyl species that can form from 5 and 6 are identical. Potential mechanisms to account for stereoselective formation of 7 and 8 are presented.     

Characterization of Extraction of Chromatographic Materials Containing Bis(2‐ethyl‐1‐hexyl)Phosphoric Acid, 2‐Ethyl‐1‐Hexyl (2‐Ethyl‐1‐Hexyl) Phosphonic Acid,and Bis(2,4,4‐Trimethyl‐1‐Pentyl)Phosphinic Acid

Abstract

This work describes the uptake of a wide range of metal ions, including alkaline earths, transition metals, post‐transition metals, lanthanides and actinides, from acidic nitrate and chloride media on extraction chromatographic resins prepared from three different acidic organophosphorus compounds: bis(2‐ethyl‐1‐hexyl) phosphoric acid (HDEHP), 2‐ethyl‐1‐hexyl(2‐ethyl‐1‐hexyl)phosphonic acid, (HEH[EHP]) and bis(2,4,4‐trimethyl‐1‐pentyl)phosphinic acid (H[DTMPP]). The data is plotted in a format allowing for the easy comparison of the uptake of all metal ions under a given condition. Additionally, examples of several novel separations using the three extraction chromatographic materials are discussed.     

Shock‐Induced Polarization of Materials

A new computational method of calculating signals of shockinduced electric polarization of materials is proposed and used to analyze previous experimental results on the shockinduced electric polarization of Plexiglas. Experimental results on the shockinduced electric polarization of granite are presented.     

Extraction of Palladium(II) from Nitric Acid Solutions with 1‐Benzoyl‐3‐[6‐(3‐benzoyl‐thioureido)‐hexyl]‐thiourea

The extraction of palladium (II) from HNO₃ solutions with 1‐Benzoyl‐3‐[6‐(3‐benzoyl‐thioureido)‐hexyl]‐thiourea (Ia) and several monodentate thiourea derivatives in 1,2‐dichloroethane has been studied. The effect of HNO₃ concentration in the aqueous phase and that of the extractant in the organic phase on the Pd(II) extraction is considered. The stoichiometry of the extracted complexes has been determined. The increasing number of thioamide groups in the molecule of Ia increases its extraction efficiency towards Pd(II). The potentialities of a polymeric resin impregnated with compound Ia for selective extraction of Pd(II) from nitric acid solutions are demonstrated.     

Cobalt‐catalyzed amination of 1,3‐cyclohexanediol and 2,4‐pentanediol in supercritical ammonia

The onestep procedure of amination of bifunctional secondary alcohols to diamines has been investigated in a continuous fixedbed reactor. Application of supercritical NH₃ as a solvent and reactant suppressed catalyst deactivation and improved selectivities to amino alcohol intermediates, whereas selectivities to diamines remained poor (8–10%). The main reason for the low diamine selectivity of 1,3dihydroxy compounds is water elimination leading to undesired monofunctional products via ,unsaturated alcohol, ketone or amine intermediates. This side reaction does not occur with 1,4dihydroxy compounds which afford high aminol and diamine selectivities under similar conditions. Amination of secondary diols with ammonia was found to be faster, but less selective than that of the corresponding primary 1,3propanediol.     

Effect of Anions on the Extraction of Lanthanides (III) by N,N′‐Dimethyl‐N,N′‐Diphenyl‐3‐Oxapentanediamide

Abstract

The extraction of microquantities of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y by N,N′‐dimethyl‐N,N′‐diphenyl‐3‐oxapentanediamide (DMDPhOPDA) in 1,2‐dichloroethane from aqueous media containing ClO₄ ^?, PF₆ ^?, (CF₃SO₂)₂N^? anions or by DMDPhOPDA in 1,2‐dichloroethane in the presence of 1‐butyl‐3‐methylimidazolium bis[(trifluoremethyl)sulfonyl]imide ([C₄mim][Tf₂N]) and 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([C₄mim][PF₆]) from HNO₃ solutions has been studied. The effect of HNO₃ concentration in the aqueous phase and that of the extractant concentration in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes has been determined. The addition of HPF₆ and (CF₃SO₂)₂NH or their salts to the aqueous HNO₃ or HCl solutions leads to an enchancement of lanthanides (III) extraction by DMDPhOPDA. A considerable synergistic effect was observed in the presence of ionic liquids (IL) in the organic phase containing DMDPhOPDA. This effect is connected with the hydrophobic nature of the IL anion. The distribution of ILs between the equilibrium organic and aqueous phases can govern the extractability of lanthanides (III) in DMDPhOPDA‐IL systems.     

Extraction Properties of 6,6′‐Bis‐(5,6‐dipentyl‐[1,2,4]triazin‐3‐yl)‐[2,2′]bipyridinyl (C5‐BTBP)

Abstract

The extraction of americium(III) and europium(III) into a variety of organic diluents by 6,6′‐bis‐(5,6,‐dipentyl‐[1,2,4]triazin‐3‐yl)‐[2,2′]bipyridinyl (C5‐BTBP) has been investigated. In addition to determining the stoichiometry for the extraction, the dependence of extraction on contact time and temperature was also studied. The resistance of the ligand to gamma irradiation and the possibility to recycle the organic phase after stripping were tested to determine how the molecule would perform in a radiochemical process. Different organic diluents gave different extraction results, ranging from no extraction to distribution ratios of over 1000 for americium(III). In 1,1,2,2‐tetrachloroethane, the extraction and separation of americium from europium and the extraction kinetics were good; a separation factor above 60 was obtained at equilibrium, ～5 min contact time. The extraction capabilities are adequate for C5‐BTBP to be used in a process for separating trivalent actinides from lanthanides. However, C5‐BTBP is susceptible to radiolysis (americium extraction decreases ～80% after a dose of 17 kGy) and may not be the best choice in the processing of spent nuclear fuel. Nonetheless it is a useful starting point for further development of this type of molecule. It could also prove useful for analytical scale separations for which radiolytic instability is less important.     

Hydrothermal deactivation of Ce‐ZSM‐5, Ce‐beta, Ce‐mordenite and Ce‐Y zeolite deNOx catalysts

The hydrothermal stability of Ce³⁺ zeolite catalysts used for selective catalytic reduction of NO _x was investigated. Aging of Ce‐ZSM‐5, Ce‐beta, Ce‐mordenite and Ce‐Y catalysts consisted of steaming in 10 or 12 vol% water at 600°C for 3–99 h. Ce‐ZSM‐5 (Si/Al ratios: Si/Al = 17.1, 22.6 and 146.6) and Ce‐mordenite (Si/Al = 6.4, IE = 77.2%) showed fast deactivation. Ce‐beta (Si/Al = 12, IE = 68.4%) and Ce‐Y (Si/Al = 2.8, IE = 122%) are significantly more stable zeolite catalysts, Ce‐beta being the most active of these two. Ce‐beta and Ce‐ZSM‐5 catalysts – both having high initial activities – were characterized with ²⁹Si‐NMR and ²⁷Al‐NMR. Especially Ce‐ZSM‐5 showed an increase of non‐framework Al, meaning that the zeolite suffered from dealumination. This revised version was published online in July 2006 with corrections to the Cover Date.     

Extraction of Actinides with Different 6,6′‐Bis(5,6‐Dialkyl‐[1,2,4]‐Triazin‐3‐yl)‐[2,2′]‐Bipyridines (BTBPs)

Abstract

The extraction of Am(III), Th(IV), Np(V), and U(VI) from nitric acid by 6,6′‐bis(5,6‐dialkyl‐[1,2,4]‐triazin‐3‐yl)‐[2,2′]‐bipyridines (C2‐, C4‐, C5‐, and CyMe₄‐BTBP) was studied. Since only americium and neptunium extraction was dependent on the BTBP concentration, computational chemistry was used to explain this behavior. It has been shown that the coordination of the metal played an important role in forming an extractable complex into the organic phase, thus making it possible to extract pentavalent and trivalent elements from tetravalent and hexavalent elements. This is very important, especially because it shows other possible utilizations of a group of molecules meant to separate the actinides from the lanthanides. In addition, the level of extraction at very low or no BTBP concentration was explained by coordination chemistry.     

Vapour phase O‐methylation of 2‐naphthol over the solid bases alkali‐loaded silica and Cs‐loaded MCM‐41

O‐alkylation of 2‐naphthol has been investigated in the vapour phase over alkali‐loaded fumed silica and Cs‐MCM‐41. Both SiO₂ and MCM‐41 had low C‐alkylation activities and no O‐alkylation activity. The introduction of alkali ions considerably increases 2‐naphthol conversion with 2‐methoxynaphthalene being the major product. The activity of the catalysts increases with alkali loading and the basicity of the metal (Cs > K > Na > Li). Very high conversion (∼99%) of 2‐naphthol and selectivity (>95%) for 2‐methoxynaphthalene are obtained over Cs‐loaded fumed silica and MCM‐41. A small amount of 1‐methyl‐2‐hydroxynaphthalene is also formed over the Li‐, Na‐ and K‐loaded silica. This revised version was published online in July 2006 with corrections to the Cover Date.