Perrhenic Acid Research Articles

Synthesis of perrhenic acid using solvent extraction

The paper presents results of investigations into production of perrhenic acid from aqueous solutions of ammonium perrhenate of concentration 25 g/L by solvent extraction method. It was demonstrated that perrhenic acid can be obtained by extraction of ReO 4 − with 50% tributyl phosphate (TBP) solution in toluene from aqueous solution of ammonium perrhenate acidified with sulphuric(VI) acid to pH of 1.0 and further stripping of ReO 4 − from organic phase by water of temperature 80 °C. Complete separation of rhenium from ammonium ions was possible after repeated extraction and repeated stripping. In the result perrhenic acid of concentration about 70 g/L Re was obtained, which then was concentrated to reach the level of 300 g/L Re. Thus produced perrhenic acid of concentration 300 g/L Re contained no more than 0.01 g/L of impurities composed of metal (sodium, potassium, magnesium) and ammonium ions.

Selective Synthesis of Cyclic Phosphoric Acid Diesters through Oxorhenium(VII)-Catalyzed Dehydrative Condensation of Phosphoric Acid with Alcohols

The selective synthesis of phosphoric acid diesters has been achieved through the direct catalytic dehydrative condensation of phosphoric acid with two equivalents of alcohols. The present method works especially well for the synthesis of cyclic phosphoric acid diesters. The combination of perrhenic acid and N-methylbenzylamine efficiently catalyzes the dehydrative condensation of phosphoric acid with equimolar amounts of diols to give cyclic phosphoric acid diesters in excellent yields.

Synthesis of perrhenic acid using ion exchange method

The paper presents results of the study for obtaining perrhenic acid from aqueous ammonium perrhenate solutions by ion exchange. Two ways of perrhenic acid synthesis have been examined: sorption of perrhenate anion on selected anion exchange resins (followed by elution of the sorbed rhenium as HReO4), and sorption of ammonium ion on selected cation exchange resins. The method of ammonium ion sorption on cation exchange resins has proved to be more effective. Using C 160 (H) cation exchange resin, perrhenic acid containing >300 g/L of Re (after performing concentration in vacuum evaporator) has been obtained, with impurities concentration at the level of: <1.0 mg/L NH4, ≤0.05 mg/L sodium, ≤0.20 mg/L potassium, ≤0.10 mg/L magnesium and ≤0.20 mg/L calcium.

Perrhenic Acid Catalyzed Dehydration from Primary Amides, Aldoximes, N‐Monoacylureas, and α‐Substituted Ketoximes to Nitrile Compounds.

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Perrhenic Acid-Catalyzed Dehydration from Primary Amides, Aldoximes, N-Monoacylureas, and α-Substituted Ketoximes to Nitrile Compounds

Abstract The dehydration reaction of primary amides is one of the most fundamental methods for the synthesis of nitriles, and the development of environmentally benign catalytic reaction processes is needed. We surveyed a variety of metal catalysts and found that perrhenic acid was extremely effective for the dehydration of not only primary amides but also aldoximes. Typically, 1 mol % of perrhenic acid gave the corresponding nitriles from amides or aldoximes under azeotropic reflux conditions with the removal of water in toluene or mesitylene. In addition, perrhenic acid is an extremely efficient catalyst for the Beckmann fragmentation of α-substituted ketoximes to functionalized nitriles. This new catalytic system can be applied to the gram-scale synthesis of nitriles without further modifications.

Rhenium oxohalides: Synthesis and crystal structures of ReO3Cl(THF)2, ReOCl4(THF), Re2O3Cl6(THF)2, and Re2O3Cl6(H2O)2

Convenient methods to prepare solvated rhenium oxochlorides are described; these compounds should serve as useful starting materials for rhenium chemistry. Treatment of perrhenic acid, HReO(4), with chlorotrimethylsilane or with thionyl chloride, followed by addition of tetrahydrofuran, forms the new oxochloride complexes ReO(3)Cl(THF)(2) and ReOCl(4)(THF), respectively. Small amounts of two dinuclear oxochlorides, which evidently resulted from adventitious hydrolysis, were also isolated: Re(2)O(3)Cl(6)L(2), where L = THF or H(2)O. All four compounds were characterized by X-ray crystallography. The rhenium(vii) complex ReO(3)Cl(THF)(2) adopts a distorted octahedral geometry in which the three oxo ligands are in a facial arrangement; the rhenium(vi) complex ReOCl(4)(THF) adopts a trans octahedral structure. The two dinuclear rhenium(vi) compounds both have a single, nearly linear, bridging oxo group; on each Re center, the three terminal chlorides adopt a mer arrangement, and the terminal oxo and the coordinated Lewis base are mutually trans. The water ligand in the aqua complex is hydrogen bonded to nearby THF molecules. IR data are given.

Perrhenic acid as catalyst for hydrosilylation of aldehydes and ketones and dehydrogenative silylation of alcohols

Abstract Hydrosilylation of aldehydes and ketones with dimethylphenylsilane was catalyzed by perrhenic acid, HReO4, to give silylated ethers in good yields. These hydrosilylation reactions appear to be radical processes, since they were inhibited in the presence of 5,5-dimethyl-4,5-dihydro-3H-pyrrole-N-oxide (DMPO) and Ph2NH, two well-known radical scavengers. Perrhenic acid also catalyzes the dehydrogenative silylation of alcohols in neat conditions at 25 °C. It is selective for the silylation of hydroxyl groups in the presence of alkenes and alkyl halides (RCl).

In situ characterization of the genesis of cobalt metal particles in silica-supported Fischer-Tropsch catalysts using Foner magnetic method

The genesis of cobalt metal particles in silica-supported Fischer-Tropsch catalysts was studied using in situ Foner vibrating-sample magnetic method. The cobalt promoted and unpromoted catalysts were prepared by aqueous (co)-impregnation using cobalt nitrate or acetate, ruthenium nitrosyl nitrate or perrhenic acid followed by oxidative pre-treatment in air and reduction in hydrogen. In several catalyst preparations, sucrose was added to the impregnating solutions. The genesis of cobalt metal phases in these catalysts was monitored in situ by the magnetic method during the temperature-programmed reduction in pure hydrogen. A considerably higher extent of cobalt reduction was found in the catalysts prepared from cobalt nitrate than in those prepared from cobalt acetate. Promotion with ruthenium and rhenium results in a considerable decrease in the temperature of the emergence of cobalt metal phases. Small superparamagnetic, single-domain and multi-domain ferromagnetic cobalt metal particles were observed in the reduced catalysts by the magnetic method. It was found that lower temperature calcination of the cobalt catalysts prepared from cobalt nitrate and addition of sucrose to the impregnating solution lead to a decrease in the concentration of multi-domain cobalt ferromagnetic metal particles and to an increase in the fraction of superparamagnetic cobalt particles. Superparamagnetic cobalt particles smaller than 6–7 nm were detected in the reduced catalysts prepared from cobalt nitrate with sucrose addition and in the catalysts prepared from cobalt acetate. Catalyst characterization using X-ray diffraction and X-ray photoelectron spectroscopy has confirmed the results about cobalt dispersion and reducibility in the cobalt silica-supported catalysts obtained by the Foner magnetic method.

Optimization of the pretreatment procedure in the design of cobalt silica supported Fischer–Tropsch catalysts

The effect of cobalt precursor, catalyst pretreatment and promotion with ruthenium and rhenium on the formation of cobalt metal nanoparticles and catalytic performance of supported Fischer–Tropsch (FT) catalysts was studied using a combination of techniques (DSC–TGA, UV–vis spectroscopy, XPS, XRD, EXAFS–XANES, in situ magnetization measurements, propene chemisorption and catalytic measurements). The cobalt promoted and unpromoted catalysts were prepared by aqueous co-impregnation using cobalt nitrate or acetate, ruthenium nitrosyl nitrate or perrhenic acid. In both unpromoted and Ru and Re-promoted cobalt catalysts after impregnation and drying, cobalt is present mainly in octahedrally coordinated complexes. The repartition of cobalt species between Co 3O 4 and cobalt silicate depends essentially on the exothermicity of precursor decomposition. Cobalt nitrate precursor, with an endothermic decomposition, favors Co 3O 4 crystallites. Lower temperature of cobalt nitrate decomposition and catalyst calcination generally leads to higher dispersion of supported cobalt oxide. Cobalt acetate precursor, with an exothermic decomposition, favors cobalt silicate. By optimizing the conditions of cobalt acetate decomposition, the fraction of cobalt silicate can be decreased favoring a more reducible Co 3O 4 phase. For the catalysts prepared from cobalt nitrate, promotion with ruthenium increases the cobalt dispersion, while maintaining high reducibility. For the catalyst prepared via low temperature decomposition of cobalt acetate, addition of ruthenium increases the fraction of Co 3O 4 crystalline phase and decreases the concentration of barely reducible cobalt silicate. The Fischer–Tropsch reaction rates over unpromoted and promoted cobalt catalysts were found to be primarily a function of the number of cobalt metal sites, which are generated by the reduction of Co 3O 4 crystallites.

Rhenium(VII) oxo complexes as extremely active catalysts in the dehydration of primary amides and aldoximes to nitriles.

An economical and environmentally benign process for the preparation of nitriles by the dehydration of primary amides and aldoximes is catalyzed by rhenium(VII) oxo complexes such as perrhenic acid and trimethylsilylperrhenate (see scheme). The reaction proceeds at azeotropic reflux (with the removal of water) under essentially neutral conditions.

Electroreduction of rhenium from sulfuric acid solutions of perrhenic acid

The electrodeposition of rhenium species from sulfuric acid solutions of ReO4− ions onto polycrystalline Pt and Au surfaces has been studied. The experimental results suggest that ReO2 adsorption takes place and after completion of ReO2 adsorption bulk phase ReO2·xH2O and ReO3 deposition can be observed. From a higher than 10 M sulfuric acid solution of ReO4− ions only Re2O5 can be electrodeposited. In diluted H2SO4 or water media Re2O5 decomposes and ReO2 is formed.

Rhenium catalysed epoxidations with hydrogen peroxide: tertiary arsines as effective cocatalysts

Perrhenic acid in combination with tertiary arsines gives a versatile catalytic system for epoxidation of alkenes with hydrogen peroxide. The best results are obtained with diphenylmethylarsine. A wide range of alkenes could be epoxidised with aqueous hydrogen peroxide (60%) in 60–100% yields with substrate to catalyst ratios of up to 1000.

Rhenium deposition onto platinum surface by reduction of perrhenic acid with methanol in hydrochloric acid media

It has been demonstrated that rhenium deposition onto Pt surface in hydrochloric acid media can also be carried out by reduction of perrhenic acid with methanol. Above 0.5 M Cl− ion concentration, however, it is practical to combine the use of methanol with hydrogen.

Rhenium recovery from Sarcheshmeh molybdenite concentrate

Rhenium, in the form of ammonium perrhenate was recovered from Sarcheshmeh molybdenite concentrates by roasting the concentrates with slaked lime. The effect of the roasting parameters, such as roasting temperature, roasting materials and gas composition was investigated. The roasted materials were leached with water in order to separate the water-soluble calcium perrhenate and the water-insoluble compounds, calcium molybdate and calcium sulfate, that were formed during roasting. Impure rhenium-bearing solution was passed through a column of strong anionic quaternary resin (Dow IRA 410) for selective absorption of rhenium ions from the solution. Stripping of the column was carried out with hypochloric acid. The resultant perrhenic acid solution was exposed to hydrogen sulfide gas in order to precipitate rhenium heptasulfide. To produce ammonium perrhenate, the sulfide was decomposed by ammonia in the presence of hydrogen peroxide. The solution was evaporated and ammonium perrhenate crystals were formed.

Rhenium deposition on platinum surface by reduction of perrhenic acid with methanol

It has been demonstrated that rhenium deposition onto Pt surface can be carried out by reduction of perrhenic acid with methanol and results in the same adsorbed species as its reduction either with hydrogen or with electric polarization.

Thermal and Photochemical Reactions of Methylrhenium Diperoxide: Formation of Methyl Hydroperoxide in Acetonitrile

Compared to the system in aqueous solution, the equilibration reactions in acetonitrile between MTO and the methylrhenium peroxides CH3ReO2(η2-O2) (A) and CH3ReO(η2-O2)2(H2O) (B) are slower but more favored thermodynamically. In CH3CN, small concentrations of water facilitate the formation of A (especially) and B. These species decompose to methyl hydroperoxide and perrhenic acid in CD3CN, rather than to methanol and perrhenic acid as in aqueous solution. The proposed mechanism involves the intramolecular migration of the methyl group to a peroxo oxygen, followed by hydrolysis, and it is facilitated by photolysis. The potential use of B as photocatalyst does not seem promising, however.

SORPTION BEHAVIOR OF PERRHENATE ION ON REILLEX™-HP ANION EXCHANGE RESIN FROM NITRIC ACID AND SODIUM NITRATE/HYDROXIDE SOLUTIONS

ABSTRACT The distribution coefficients (K' d) are reported for perrhenate on the nitrate form of Reillex™-HP, a weak base anion exchange resin, as a function of nitric acid concentration from 0.100 to 10.0 M. Perrhenate K' d values were determined in 1.00 M NaNO3 from pH 2 to 13. The K'd values were determined in solutions containing 1.35 M NaNO3 and variable NaOH, 0.155 to 4.66 M, and in solutions containing 0.655 M NaOH and variable NaNO3,0.46 to 5.35 M. Maximum perrhenate loadings were <2.7% of theoretical capacity. The K' d is defined by the following equation: The total mmol of rhenium initially added is Retotal and [Re]sol is the analytical molarity of rhenium in Vsot mL of solution after a batch contact. At 1.0 M HNO3 the value of K'd is 73 mL/g. The behavior of the perrhenate system in acid can be described by assuming that perrhenic acid, HReO4, is formed with a derived acid dissociation constant of about 6.5 M. In 1.00M NaNO3from pH 2 to 13 the sorption behavior is initially what is expected for a weak base resin with an acid dissociation constant of 1.24 × 10−55 M. Thus, the K' d value decreases with pH values above the pKa value. However, instead of the value of K' d decreasing to zero at higher pH values, it becomes constant at 15 mL/g. In a solution containing 1.00 M NaOH and 1.00 M NaNO3, the value of K'd is 25 mL/g. The unusual behavior of the Reillex™-HP anion exchange resin suggests that the resin's unprotonated pyridine functionality is solvating a {Na+,ReO4 −} ion pair. The interaction of the perrhenate ion with Reillex™-HP is more involved than a simple ion exchange phenomenon and the presence of NaOH affects the resin-perrhenate interactions.

The “Peroxo Perrhenic Acid” H4Re2O13: An Oxygen‐Rich Metal Peroxide and Oxidation Catalyst

AbstractThe rhenium oxides Re2O7 and ReO3 react with hydrogen peroxide solutions yielding peroxo complexes that efficiently catalyze the oxidation of olefins, aromatics, and certain organometallic compounds. In contrast, related oxides of molybdenum (MoO3) and vanadium (V2O5) do not activate H2O2 under comparable conditions. The active rhenium peroxo complex was isolated from the system Re2O7/H2O2: the crystalline red‐orange, explosive compound of formula H4Re2O13 is the most oxygen rich rhenium compound isolated to date. Its structure resembles a “peroxo perrhenic acid”. The binuclear compound could be isolated in the form of a diglyme adduct, structurally defined as two corner‐sharing pentagonal bipyramids with apical oxo and aquo ligands; the equatorial positions are occupied by the bridging oxygen and by n2‐peroxo groups (two [O2]2− ligands per rhenium). In contrast to the known complex [CH3ReO(O2)2].H2O, the new peroxo species [O{ReO(O2)2.H2O}2] decomposes hydrolytically during the catalytic cycle and can thus not compete in terms of catalytic activity in oxidation reactions involving H2O2. Hydrolysis yields “perrhenic acid” Re2O7.2H2O, the diglyme adduct of which compound was also characterized by means of an X‐ray diffraction analysis.

The crystal structure of Solid Perrhenic Acid Monohydrate

AbstractSolid perrhenic acid monohydrate has been characterized by X‐ray single crystal structure analysis (300 K). HReO4 · H2O, Mr = 269.23, tetragonal, I41/a, Scheelite‐type (CaWO4), a = 5.8320(2) Å, c = 12.9384(6) Å, V = 440.06(5) Å3, Z = 4, Dx = 4.063 g cm−3, X‐ray wavelength λ (MoKα) = 0.71069 Å The structure consists of [ReO4]−‐tetrahedra and oxonium ions linked by hydrogen bridges to form a three‐dimensional network.

Synthesis of carrier‐free rhenium‐188(V)DMSA using triphenyl phosphine as a facile reducing agent

AbstractRhenium‐188‐labeled ReOCl3(PPh3)2 is an important reactive complex which can be prepared in &gt; 95% yield by the reaction of perrhenate (188ReO4−) or perrhenic acid with triphenyl phosphine (PPh3) and HCl with subsequent extraction into CH2Cl2 or CHCl3. The yield is dependent upon a high HCl concentration. Because of the potential important use of 188Re(V)DMSA for therapy of tumors of the head and neck, we have used the 188ReOCl3(PPh3)intermediate for the facile synthesis of the ReO(DMSA)2 complex.Although the Re(V)O(DMSA)2 is a monovalent anion, for simplicity the charge is not included and the species denoted as Re(V)DMSA in this discussion Reaction of ReOCl3(PPh3)2 with naturally abundant Re or carrier free Re‐188, with DMSA (meso‐1,2‐dimercaptosuccinic acid) yields ReO(DMSA)2 in high yield. The 188Re(V)DMSA can also be prepared by reaction of Re‐188 perrhenate or perrhenic acid with SnCl2 in the presence of DMSA.