Kinetics of Absorption of Carbon Dioxide into Sodium Metaborate Solution

Carbon dioxide capture potential of sodium metaborate, which is the main product of the process by means of which hydrogen is obtained from sodium borohydride, was investigated. This work aims at both carbon dioxide capture and finding an alternative use for sodium metaborate. The products of this chemical absorption are sodium carbonate, sodium bicarbonate, and boric acid; all of which are industrially important chemicals. In this study, the kinetics of the reaction between sodium metaborate and carbon dioxide was investigated at atmospheric pressure and temperatures between 17 and 50°C while initial sodium metaborate concentration was changed as 0.5, 1, and 2.5 wt%. The frequency factor and activation energy for this reaction were found as 1.97 × 10⁻³ m³/mol‐s and 18,062 J/mol, respectively.     

Copper‐Catalyzed Coupling of Oxime Acetates with Sodium Sulfinates: An Efficient Synthesis of Sulfone Derivatives

Sulfone derivatives are important synthetic intermediates. However, the general method for their preparation is through traditional coupling reaction: the alkylation of sodium sulfinates with phenacyl halides. Based on our previous work on sodium sulfinates and oxime acetates, we herein report a novel method for sulfone derivatives by oxidative coupling with sodium sulfinates and oxime acetates using copper as catalyst. The sulfonylvinylamine products could be formed in excellent yields. Upon hydrolysis by silica gel in CH₂Cl₂, β‐ketosulfones could also be efficiently constructed. Various sulfonylvinylamines and β‐ketosulfones were obtained in good to excellent yields under the optimized reaction conditions. Mechanistic studies indicated that this transformation involved copper‐catalyzed N? O bond cleavage, activation of a vinyl sp² C? H bond, and C? S bond formation. The oxime acetates act as both a substrate and an oxidant, thus the reaction needs no additional oxidants or additives.     

Simultaneous determination of arsenic,mercury, antimony and selenium in biological materials with prior collection of gaseous products followed by neutron activation analysis

A method combining prior collection of gaseous products with subsequent neutron activation analysis has been developed for simultaneous determination of traces of arsenic, mercury, antimony and selenium in biological materials. The generation of hydrides of arsenic, antimony and selenium and cold vapor of mercury in the vapor generaion and collection system was investigated by the use of radiotracers of the respective elements. The result indicates that selenium and mercury can be completely evaporated from the digested sample solution in 5M HCl with the addition of 5% sodium tetrahydroborate solution, while additional reduction proces by potassium iodide and ascorbic acid is needed for complete evaporation of arsenic and antimony. The gaseous products were collected in a quartz tube for neutron irradiation. The detection limits of these elements were fount to be in the range of 10^–7 to 10^–8 g under the present experimental conditions. The reliability was checked with NBS standard reference materials.     

Preparation and degradation of copolymers of methyl methacrylate with alkali metal methacrylates—IV. The relationship of product yields to sequence distribution

Experimental yields of methanol and methyl methacrylate (MMA), produced in degradation to 500° of copolymers of MMA with lithium, sodium and potassium methacrylates (KMA) respectively, have been compared with the amounts expected on the basis of composition and sequence distribution. Rates of formation of these products under isothermal conditions have also been measured and activation energies for MMA formation at various compositions in the KMA-MMA copolymer series have been evaluated. The activation energy changes from 35 ± 5 kcal mole^?1 in PMMA to 52 ± 5 kcal mole^?1 in a 75 mole% KMA copolymer, indicating increasing difficulty in depolymerization to MMA as the MMA sequences become shorter. The primary route to methanol is by a cyclization involving adjacent ester and salt units in the chain, giving anhydride rings and metal methoxide as the initial products. Methanol yields and the positions of the maxima in the yield vs copolymer composition curves, however, are found to be inconsistent with those predicted from sequence distribution calculations. It is argued that water retained by the copolymers plays a key part in the reaction scheme by converting the metal methoxide to methanol and hydroxide; the latter then causes conversion of ester groups to salt units, so permitting further cyclization in copolymers initially rich in MMA. Mechanisms are discussed in detail.     

Kinetics of sulfuric acid breakdown of beryllium raw material activated by fusion with sodium carbonate

The kinetics of sulfuric acid breakdown of a mixture of beryl and bertrandite–phenakite–fluorite concentrates, activated by fusion with sodium carbonate, was studied. The apparent activation energy of the reaction of the granulated fusion cake with sulfuric acid was determined (E _app = 9.1 kJ mol^–1). This value of E _app is typical of diffusion-controlled processes and suggests that the process is controlled by the rate of diffusion of acid molecules to the reaction surface through the layer of the forming reaction products.     

Cellulase Activity in Different Buffering Media During Waste Paper Hydrolysis by HPLC

The activity of cellulase has traditionally been described by pH and temperature; however, the buffering medium is also an important factor, Taking plain water as a reference medium, three kinds of buffer including KH₂PO₄/K₅HPO₄, citric acid/sodium citrate, and acetic acid/sodium acetate were adopted to survey their effects on the activity of cellulase. Chromatographic assays indicated that xylose, glucose, and cellobiose were the major products and that minor products such as cellotriose and cellotetraose were present in some cases. The activities of cellulase based on glucose production showed that the phosphate buffer acted as a deactivator for cellulase and each of the two organic acid buffers acted as activators for cellulase. The concentration of activation buffer should be high to reach a high cellulase activity; however, this effect would be compensated for by the product inhibition of cellulase. The highest activity obtained was 4.16 ± 0.08 (× 10^?3) IU mg^?1 for the citric acid/sodium citrate buffer under pH 4.80, 40 °C and an agitation speed of 150 rpm.     

Thermal decomposition of sodium azide

The thermal decomposition of sodium azide has been investigated in the temperature range 240–365°C. Three values for the activation energy, 37.0, 59.0 and 14 kcal mol^?1 have been obtained depending on the temperature range of study. The mechanism of decomposition seems to involve excited azide ions (through internal conversion) and excitations. The activation energy of 14 kcal mol^?1 appears to be associated with the promotion of electron in the presence of sodium metal.     

INAA of Zr,La, Ce and Nd in geological samples in the presence of different uranium concentratios

Rock samples which contain relatively high concentrations of uranium may create problems of interference produced by fission products, when instrumental neutron activation analysis is used. The isotopes⁹⁵Zr,¹⁴⁰La,¹⁴¹Ce, 143Ce and 147Nd, which are commonly used in the neutron activation analysis of the corresponding elements, are also produced as fission products of²³⁵U. For each of these radioisotopes, a contribution factor is calculated theoretically and meaured experimentally using geological samples with different uranium contents.     

Deuterium kinetic isotope effect in the oxidation of sodium (2-D2)propionate with permanganate in water solutions

Kinetic parameters characterizing the oxidation of sodium(2-¹H₂) propionate and the oxidation of sodium (2-²H₂) propionate with permanganate in water solutions have been determined and compared with kinetic parameters derived from the investigation of the deuterium isotope effect on the activation parameters in the permanganate and manganate oxidation of sodium (2-³H₂) propionate in water solutions of sodium hydroxide.     

A Novel Process for CO2 Capture by Using Sodium Metaborate,Part II: Carbonation Reaction and Kinetic Studies

In Part II of this two‐part series of papers, optimization of carbonation reaction with sodium metaborate and kinetics of the reaction are studied and compared to the structural properties, which were reported in Part I. This paper presents a comprehensive study on the optimization of reaction conditions and determination of reaction parameters of sodium metaborate (NaBO₂) and carbon dioxide (CO₂). Both hydrated and dehydrated forms of NaBO₂ have high sorption capacities of CO₂ up to 400°C. Decomposition of the products starts beyond 400°C and completes at 600°C. The shrinking core model is used to explain the kinetics of the noncatalytic heterogeneous reaction. The reaction progresses in two stages: one is surface reaction controlled and the other is diffusion controlled. The apparent activation energy and preexponential factor for reaction‐controlled and diffusion‐controlled regions are calculated as 11.8 kJ/mol and 3.5 × 10⁶ cm²/min and 18.2 kJ/mol and 6.5 × 10⁻⁵ cm²/min, respectively.     

Rapid activation product separations from fission products and soil matrixes

A rapid method for the separation and qualitative analysis of several neutron activation products (¹⁹⁸Au, ¹⁹²Ir, ⁷²Ga, ⁵¹Cr, ^191/195m/197Pt, ⁵⁴Mn, ⁵⁷Co, and ⁵⁹Fe) from fission products and soil matrixes has been developed. Analytes were isolated within 20 h using ion exchange chromatography. After separation, the activation products were characterized by γ-spectroscopy and inductively coupled plasma-optical emission spectroscopy. Validation experiments demonstrated versatility of the method, showing that the activation products could be isolated from fresh fission products and other contaminants associated with complex soil matrixes.

     

Fluorine analysis of bone and other biological materials: A cyclic activation method

Fluorine is measured in a bone matrix using cyclic activation in a reactor system. The detection limit and hence precision is considerably improved when compared with other neutron activation techniques and includes an accurate method for correction of sodium matrix interference due to²⁰F (T=11 s) by measurement of the²⁴Na and²³Ne photopeaks. In an interference free matrix the sensitivity is 0.6 μg F. Cyclyc activation, also applied to standard biological materials, will detect ≥10 other elements simultaneously.     

Synthetic studies in the alkaloid field—IV: The sodium dithionite reduction of 1-[2-(3-indolyl)-ethyl]-3-methoxycarbonyl pyridinium bromides

The preparation of racemic indolo[2,3-a]quinolizine derivatives by sodium dithionite reduction of appropriate pyridinium bromides has been studied, A method has been found of influencing with high degree of stereoselectivity the C(12b)-C(2) stereochemical relationship in the products formed. The determination of the stereochemistry of the products by comparative examination of their ¹³C NMR spectra is described. The convenience of the sodium dithionite reduction method for the preparation of vallesiachotamine 1 models is discussed.     

Studies on the kinetics of UO2 dissolution in carbonate-bicarbonate medium using sodium hypochlorite as oxidant

The dissolution of UO₂ in carbonate-bicarbonate solutions containing sodium hypochlorite as an oxidant has been investigated. The effect of temperature, sodium hypochlorite concentration and stirring speed was examined. In the temperature range of 303 to 318 K, the leaching reaction displayed linear kinetics. Apparent activation energy obtained from the differential approach was found to be 57 kJ mol^?1. This relatively high activation energy value indicates a chemically controlled behavior of UO₂ dissolution. The order of reaction with respect to sodium hypochlorite concentration was found to be unity.     

Vergleichende Betrachtung der bisher bekannten cis-Dihydrogenchalkogenido-Komplexe der d8-Metalle

Comparision of the Hitherto Known cis-Dihydrogenchalcogenido Complexes of d⁸ Metals Phosphine-coordinated d⁸ metal dichlorides react in different ways with hydrogen-sulfide, sodium hydrogensulfide and sodium hydrogenselenide respectively. The phosphine ligand and the YH-providing reactand cut a great figure to get the monomere products. Some reactions of the dihydrogenchalcogenido platinum(II) compounds with sodium ethanolat and elemental sulfur respectively are investigated. I.r. and ¹H-n.m.r. spectra are reported.     

Elucidation of the Structure of Products of Triphenylphosphine Electrooxidation in the Presence of Camphene

The structure of the products of anodic oxidation of triphenylphosphine in the presence of camphene carried out in acetonitrile with sodium perchlorate as supporting electrolyte has been studied. The major product, triphenylphosphine oxide, has been isolated from the solution in the form of cocrystals of free triphenylphosphine oxide and its complex with sodium perchlorate. The molecular structure of the cocrystals has been studied by X-ray diffraction analysis. Triphenylcamphenylphosphonium perchlorate, bornylacetamide, and a terpene compound with triphenylphosphonium and acetamide substituents in the cycle have been detected by NMR ¹³C as the electrolysis side products.

     

Determination of some kinetic parameters of the thermal decomposition of alkali persulfates from DTA curves

Using the DTA curves the thermal decomposition of alkali persulfates for the corresponding pyrosulfates is shown to be a second order reaction with activation energies of 72.7–75.6 kcal mol^?1 for sodium persulfate and 67.7–69.1 kcal mol^?1 for potassium persulfate.     

二茂锆羧酸配合物的合成——二茂锆氢化物与α,β—不饱和酸或钠盐反应的研究

本文研究了Cp₂ZrH₂与丙烯酸和Cp₂Zr(H)Cl与丙烯酸钠、巴豆酸钠的反应。产物由IR ¹H和¹³CNMR、ESR谱、气相色谱以及化学方法分析鉴定。产物水解得到与底物相应的饱和酸.用¹H NMR方法考察了Cp₂ZrH₂与丙烯酸的反应过程,用IR方法考察了Cp₂Zr(H)Cl与丙烯酸钠的反应过程。实验结果表明,上面两种反应首先消除H₂或NaCl,形成锆氧健,然后碳碳双键还原生成二茂锆羧酸盐配合物,其中羧酸根离子与二茂锆桥式双齿配位。     

Studies on the kinetics of UO2 dissolution in carbonate-bicarbonate medium using sodium hypochlorite as oxidant

The dissolution of UO₂ in carbonate-bicarbonate solutions containing sodium hypochlorite as an oxidant has been investigated. The effect of temperature, sodium hypochlorite concentration and stirring speed was examined. In the temperature range of 303 to 318 K, the leaching reaction displayed linear kinetics. Apparent activation energy obtained from the differential approach was found to be 57 kJ mol^–1. This relatively high activation energy value indicates a chemically controlled behavior of UO₂ dissolution. The order of reaction with respect to sodium hypochlorite concentration was found to be unity.