Kinetics study on reactive extraction of hydroxy-(2-methyl-phenyl)-acetic acid enantiomers from organic solution by HP-β-CD

Kinetics data is important for the reliable scale-up of a lab-scale process and for selection, design and operation of related equipment. This paper reports on the kinetics study for reactive extraction of hydroxy-(2-methyl-phenyl)-acetic acid (HA) enantiomers by hydroxypropyl-β-cyclodextrin (HP-β-CD) from the organic phase to the aqueous phase. The theory of extraction with chemical reaction was used. The effects of agitation speed, interfacial area, pH value of aqueous phase, initial concentration of HA enantiomers and initial concentration of extractant on the specific rate of extraction were investigated. The reactions have been found to be first order in HA and second order in HP-β-CD with the forward rate constants of 4.873 × 10⁻⁴ m⁶/(mol² s) for R-HA and 4.343 × 10⁻⁴ m⁶/(mol² s) for S-HA, respectively.     

Direct extraction of Mo(Ⅵ) from sulfate solution by synergistic extractants in the rotation column

Direct extraction of molybdenum from sulfate solution with synergistic extractants(mixture of D_2EHPA and TBP)was studied in the rotation column. The influence of extractant concentration and initial pH of aqueous phase was studied in the bench scale experiments. The outcomes demonstrated that the synergistic solvent extraction enhances the constancy of the extracted complexes for transfer into the organic phase. In the continuous experiments, the effect of different operating parameters such as speed of agitation, inlet solvent flow rate and inlet aqueous flow rate on the holdup, mean drop size, drop size distribution, slip and characteristic velocities and extraction percentage were examined. Modified correlations were proposed for prediction of hydrodynamic parameters with consideration of reaction extraction condition in the rotation column. Furthermore, these correlations were compared with the experimental data. According to the results, the direct extraction of Mo(Ⅵ) from aqueous solution and sulfuric media with extraction efficiency of 90.4% was obtained at higher rotor speed(240 r·min~(–1) rpm) in this column.     

The synthesis of (η5-cyclopentadienyl)titanium(IV) alkoxides by alcoholysis of the Ti–π-ligand bond in permethyl η3:η4-allyldiene-(η5-cyclopentadienyl)titanium(II)

The η³:η⁴-allyldiene-(η⁵-cyclopentadienyl)titanium(II) complex [Ti(η⁵-C₅Me₅){η³:η⁴-C₅Me₃(CH₂)₂}] (1) reacts with three molar equivalents of substituted propargylic alcohols FcCCCMe₂(OH) (2a) and PhCCCH₂OH (2b) at elevated temperature to give (η⁵-pentamethylcyclopentadienyl)titanium(IV) alkoxides [Ti(η⁵-C₅Me₅)(FcCCCMe₂O-κO)₃] (3a) and [Ti(η⁵-C₅Me₅)(PhCCCH₂O-κO)₃] (3b), respectively. The crystal structure of 3a has been determined by single-crystal X-ray diffraction.     

Kinetic study of Hg(II)-promoted substitution of cyanide from hexacyanoferrate(II) in an anionic surfactant medium by 2,2′-bipyridine

The kinetic investigation of Hg(II)-promoted reaction between [Fe(CN)₆]⁴⁻ and 2,2′-bipyridine (Bipy) has been performed in anionic sodium dodecyl sulfate (SDS) micellar medium by recording the surge in absorbance at 400 nm, corresponding to ultimate reaction product [Fe(CN)₄ Bipy]²⁻ using UV–visible spectrophotometer. Pseudo-first-order condition has been used to examine the progress of reaction as a function of temperature, [Fe(CN)₆⁴⁻], ionic strength, [SDS], pH, [Hg²⁺], and [Bipy] by changing one parameter at a time. The results exhibit that [Hg²⁺], [SDS], and pH are the decisive parameter showing maximum reaction rate at 1.5 × 10⁻⁴ mol dm⁻³, 6.0 × 10⁻³ mol dm⁻³, and 3.8, respectively. [Fe(CN)₆]⁴⁻ does not show any appreciable effect on the critical micellar concentration (CMC) of SDS as the polar head of SDS and [Fe(CN)₆]⁴⁻ both are negatively charged. Variable order kinetics was observed for [Fe(CN)₆]⁴⁻ and Bipy in their examined concentration range. The reverse response observed in the reaction rate with [KNO₃] shows a negative salt effect. The K⁺ provided by K₄[Fe(CN)₆] and KNO₃ decreases the repulsion between the negatively charged heads of the surfactant molecules thereby decreasing the CMC of SDS. The negative value for the entropy of activation also supports the interchange dissociative (I_d) mechanism recommended by us.     

Separation of Pt(IV), Pd(II), Ru(III), and Rh(III) from chloride medium using liquid–liquid extraction with mixed imidazolium-based ionic liquids

A reasonable project was presented for the extraction and separation of Pt(IV), Pd(II), Ru(III), and Rh(III) from the mixed imidazolium-based ionic liquids (ILs) [C₆mim]Cl, [C₆mim][NTf₂], and [C₆mim][DDTC]. Pt(IV) was first separated from other three platinum group metals with a mixture of [C₆mim]Cl and [C₆mim][NTf₂]. Then, separation of Pd(II) and Ru(III) from Rh(III) was realized by changing the concentration of [C₆mim][DDTC]. Back-extraction of Pt(IV), Pd(II), and Ru(III) from loaded hydrophobic phase and the recovery of Rh(III) in aqueous phase were also investigated. Mechanisms between Pd(II)/Ru(III) and [C₆mim][DDTC] were further explored using ultraviolet spectrophotometry (UV-Vis), infrared spectrophotometry (FTIR), the method of continuous variations, ab initio quantum chemical studies, and X-ray crystallographic analysis. The results afford more directions for extracting and separating metals by introducing devisable functionalized group into ILs.     

Synthesis of UHMW-PE by a Highly Active Homogeneous System: η5-(C5H5)2Ti(η1-OC(O)C6H5)2/MAO

Summary The complex ⁵-(C₅H₅)₂Ti (¹-OC(O)C₆H₅)₂ was synthesized and activated with MA0 for ethylene polymerization. The resultant polymer is UHMW-PE with a viscosimetric molecular weight of Mv = 6.8 x 10⁶ to 0.7 x 10⁶ g/mol dependent on the temperature of the reaction. The effects of the Al/Ti molar ratio and temperature of the reaction on the catalytic activity and polymer properties were studied.     

Synthesis of a (Ti,Mo)B2 coating by electro-codeposition in NaCl–KCl–AlCl3–MoO3 melt containing TiB2 nanoparticles

This paper demonstrates the availability of electro-codeposition (i.e., the simultaneous occurrence of electrophoretic deposition of nanoparticles and electrochemical deposition of metal ions) in molten salts without the assistance of stirring of the bath. In molten NaCl–KCl–AlCl₃–MoO₃ system containing TiB₂ nanoparticles at 710°C, the electro-codeposition of TiB₂ nanoparticles and Mo(VI) ions has been achieved, and a (Ti, Mo)B₂ coating has been prepared.     

Solvent Extraction Separation of Niobium(V), Tantalutn(V) or Titanium(IV), and Vanadium(V) by 2′-Hydroxy-4-methoxy-5′-methyl Chalkone Oxime (HMMCO) from Their Binary Mixtures

Abstract

2′-Hydroxy-4-methoxy-5′-methyl chalkone oxime (HMMCO) has been used for the solvent extraction separation of Nb(V), Ta(V) or Ti(lV), and V(V) from their binary mixtures. V(V) can be quantitatively extracted with HMMCO from 9 M hydrochloric acid. The green-colored chloroform extractable V(V)-HMMCO complex absorbs at a maximum at 630 nm. Nb(V), Ta(V), and Ti(IV) are not extracted at these conditions. However, these metals can be extracted from strong hydrochloric acid medium in the presence of potassium thiocya-nate. The yellow-colored complexes of Nb(V), Ta(V), and Ti(IV) absorb at a maximum at 380, 390 and 390 nm, respectively. The method is simple, rapid, and selective, and affords a clean-cut separation of vanadium from niobium, tantalum, or titanium which are usually present in alloys and ores.     

Fabrication and in vitro degradation study of novel optically active polymers derived from amino acid containing diacids and 4,4′-thiobis(2-tert-butyl-5-methylphenol)

Chiral bioactive poly(ester-imide)s (PEI)s were synthesized from N,N′-(pyromellitoyl)-bis-(L-phenylalanine) and N,N′-(pyromellitoyl)-bis-(L-leucine) diacids derived from amino acids with 4,4′-thiobis(2-tert-butyl-5-methylphenol) via direct polycondensation reaction in a system of tosyl chloride, pyridine and N,N-dimethylformamide as a condensing agent. The structures of these polymers were confirmed by FT-IR, ¹H-NMR, specific rotation, elemental and thermogravimetric analysis (TGA) techniques. TGA showed that the 10% weight loss temperature in a nitrogen atmosphere was more than 390 °C, which indicates that the resulting PEIs have a good thermal stability. The biodegradability of the monomers and prepared polymers was investigated in culture media and soil burial test for assessing the susceptibility of these compounds to microbial degradation. The results showed that the synthesized monomers and theirs derived polymers are biologically active and they are nontoxic to microbial growth.     

The corrosion inhibition of maraging steel under weld aged condition by 1(2E)-1-(4-aminophenyl)-3-(2-thienyl)prop-2-en-1-one in 1.5?M hydrochloric acid medium

The influence of 1(2E)-1-(4-aminophenyl)-3-(2-thienyl)prop-2-en-1-one (ATPI) on the corrosion behavior of weld aged maraging steel in 1.5 M hydrochloric acid was studied by potentiodynamic polarization method and AC impedance (EIS) technique at different temperatures. The results showed that the inhibition efficiency of ATPI increased with the increase in the concentration of inhibitor and decreased with the increase in temperature. ATPI acts as a mixed type inhibitor without affecting the mechanism of the hydrogen evolution reaction or iron dissolution. The adsorption of ATPI on a weld aged maraging steel surface obeys the Langmuir adsorption isotherm equation. Both activation and thermodynamic parameters were calculated and discussed. ATPI inhibits the corrosion through both physisorption and chemisorption on the alloy surface. The surface morphology of the weld aged maraging steel specimens in the presence and the absence of the inhibitors was studied by the respective SEM images.     

Structure and molecular weight of catenapoly [diphenoxy-λ5-phosphazene-co-bis(sulfophenoxy)-λ5-phosphazene] obtained from catenapoly (diphenoxy-λ5-phosphazene) in very strong acid medium

Acid polymers, –[N=P(OC₆H₅)_2–x (OC₆H₄SO₃H) _x ] _n (II), having an entirely inorganic chain of fifth-group elements, with acid equivalent values between 2.90 and 5.19 mEq/g and molecular weights (M _w) of 10⁵–10⁶ (205n3582), have been obtained from –[N=P(OC₆H₅)₂]– _n (I), 4325n 20,300, in very strong acid medium (SO₃/–P=N –=1.15–3.10 mol/mol). Sulfonation of the pendant substituents occurs first in the meta position and successively at the para carbons, presumably due to reduced conformational mobility as the degree of substitution (x) in II increases.     

Photoluminescence enhancement in a Na5Y(MoO4)4:Dy3+ white-emitting phosphor by partial replacement of MoO42− with WO42− or VO43−

A series of Na₅Y(MoO₄)_4-yA_y:Dy³⁺ (A = WO₄^2?, VO₄^3?; y = 0–0.05) phosphors were synthesized by the combustion method. Some of the MoO₄^2? sites were occupied by WO₄^2? and VO₄^3? anions, which enhanced the luminescence property of Dy³⁺-doped Na₅Y(MoO₄)₄. XRD results show that the crystal structures of the samples were consistent with the standard Na₅Y(MoO₄)₄ phase. Under excitation at 352 nm, the Na₅Y(MoO₄)_4-yA_y:Dy³⁺ phosphors exhibited a characteristic blue emission at 485 nm and a yellow emission at 577 nm, which originated from the ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2 transitions of Dy³⁺ ions, respectively. White light can be achieved by combining these blue and yellow emissions. After replacing MoO₄^2? with WO₄^2? and VO₄^3? anions in Na₅Y(MoO₄)₄:Dy³⁺, the luminescence intensity of Dy³⁺ was significantly improved due to the crystal field effect. The results indicate that Na₅Y(MoO₄)_3.97(WO₄)_0.03:Dy³⁺ and Na₅Y(MoO₄)_3.97(VO₄)_0.03:Dy³⁺ phosphors have good prospects for application in n-UV-excited w-LEDs.     

Electrochemical and physical characterisation of lead-based anodes in comparison to Ti–(70%) IrO2/(30%) Ta2O5 dimensionally stable anodes for use in copper electrowinning

The suitability of various dimensionally stable anodes (DSAs^?) was investigated in comparison to the conventional lead alloy anodes in the electrowinning of copper. DSA^? plate and mesh specimens of composition Ti–(70%) IrO₂/(30%) Ta₂O₅ and lead–(6%) antimony were evaluated. The electrochemical behaviour of these anodes was studied by carrying out open circuit potential measurements, galvanostatic chronopotentiometry, cyclic voltammetry and chronoamperometry. Physical characterisation was done using a scanning electron microscope. It was observed that the DSA^? plate anode exhibited the highest corrosion resistance followed by the DSA^? mesh and lead anodes, respectively. The results also showed that during copper electrowinning using lead anodes, dissolution of the anode occurs while for both DSAs^? marginal loss of coating was observed. The lead anode had the highest anode potential followed by the DSA^? plate and mesh anodes, respectively. Overall, it was demonstrated that the DSA^? plate anode is the most suitable anode for copper electrowinning.     

Asymmetric Intramolecular C?H Insertion of α‐Diazoacetamides in Water by Dirhodium(II) Catalysts Derived from Natural Amino Acids

The asymmetric dirhodium(II)‐catalyzed intramolecular C H insertion of α‐diazo acetamides in water is described for the first time. The use of natural α‐amino acids as chiral ligands allowed the preparation of novel dirhodium(II) homochiral complexes by a simple procedure consisting of the in situ ligand exchange starting from dirhodium tetraacetate. The catalytic system was further reused up to 7 cycles and β‐lactams were obtained in good yields and enantiomeric excess.     

Influence of cation order on crystal structure and microwave dielectric properties in xLi4/3Ti5/3O4-(1-x)Mg2TiO4 (0.6 ≤ x ≤ 0.9) spinel solid solutions

Effect of order/disorder transition on microwave dielectric characteristics is reported to develop a deeper understanding of structure-property relationship in spinel ceramics. Dense xLi_4/3Ti_5/3O₄-(1-x)Mg₂TiO₄ (0.6≤x≤0.9) spinel ceramics were synthesized and characterized for structural and dielectric properties. The critical order/disorder structural transition was induced when x < 0.8, resulting in the ceramic crystallized into a primary cubic spinel phase, while when x> 0.8, the ceramic crystallized into a disordered face-centered cubic phase. The cation occupation caused this order-disorder transition, which directly influenced the variation in microwave dielectric properties. At x = 0.75 the maximum degree of order was achieved resulting in a maximum quality factor of 55,000 GHz and a near-zero τ_f = 2.9 ppm/^oC. Dielectric properties decreased sharply after x = 0.8 when the disorder face-centered cubic phase started to crystallize. All the results indicated that cation ordering/disordering plays a critical role in determining the optimum microwave dielectric properties in spinel ceramics.     

The formation of [RuCl(p-cymene)(Me2HPz)(PPh2OR)]Cl (Me2HPz=3, 5-dimethylpyrazole; R=H,Me and p-Tol) complexes from the cleavage of the P–N bond of a P-coordinated P(Me2Pz)Ph2 ligand by ROH molecules in a ruthenium(II) complex. Crystal structure of [RuCl(p-cymene)(Me2HPz)(PPh2OH)]Cl

The complex [RuCl₂(p-cymene)]₂ reacts with 1-(3,5-dimethyl)pyrazolyldiphenylphosphine (P(Me₂Pz)Ph₂) to give the complex RuCl₂(p-cymene)(P(Me₂Pz)Ph₂). This compound reacts with ROH molecules (R=H, Me and p-Tol) to give [RuCl(p-cymene)(Me₂HPz)(PPh₂OR)]Cl (R=H, Me and p-Tol) complexes, which contain both Me₂HPz and PPh₂OR coordinated molecules.