Absorption of NO into NaClO3/NaOH solutions in a stirred tank reactor

The absorption kinetics of NO into aqueous solutions of NaClO₃/NaOH was investigated under different experimental conditions in a stirred tank reactor. It is proven that the absorption process is a fast pseudo-mth reaction. The reaction was found to be second-order with respect to NO and first-order with respect to NaClO₃. The frequency factor and average activation energy of this reaction were 2.696 × 10⁶ m³/(mol s) and 13.88 kJ/mol, respectively. The addition of NaOH to solutions of NaClO₃ decreased the absorption rate of NO. And the absorption rate of NO increased with increasing reaction temperature. In this study, the flue gas flow rate almost had little effect on the absorption of NO.     

Absorption of lean NO in aqueous slurries of Ca(OH)2 with NaClO2 or Mg(OH)2 with NaClO2

The absorption of lean NO in an aqueous slurry of Ca(OH)₂ or Mg(OH)₂ with NaClO₂ was carried out using a stirred tank absorber with a plane gas-liquid interface at 25°C and 1 atm. The rates of absorption of NO and the accompanying desorption of NO₂ for the Ca(OH)₂ slurry were in close agreement with those for the aqueous mixed solution of NaClO₂ and NAOH with higher OH^? concentration, whereas for the Mg(OH)₂ slurry, the absorption rate of NO noticeably exceeded that for the former systems. Furthermore, the ratio of the NO₂ desorption rate to the NO absorption rate considerably exceeded the theoretical prediction for gas absorption with the consecutive reaction (maximum deviation attained 117%). Also, chlorine dioxide was detected in the gas phase. It was deduced from this experimental evidence that there occurs both desorption of the decomposition product ClO ₂ and gas-phase oxidation of No with ClO₂ to produce NO₂.     

Absorption of NO in aqueous solutions of KMnO4

The absorption of NO in aqueous solutions of KMnO₄ and aqueous mixed solutions of KMnO₄ and NaOH was carried out using a batch stirred vessel w     

Absorption of SO2 by aqueous NaOH solutions in the presence of a surfactant

A report is presented on the influence of liquid flow rate, NaOH concentration, column length and presence of 5 × 10^-3 wt-% of the surfactant SLS on the rate of absorption of pure SO₂ by aqueous NaOH solution in a sphere-and-cylinder column. The presence of sodium lauryl sulphate (SLS) prevented axial turbulence which increased mass transfer in longer columns and was almost independent of the flow rate. The enhancement factor due to the reaction between SO₂ and NaOH with respect to the process of physical absorption was analyzed for the systems with excess OH^- in the outflow. The results obtained in the presence of a surfactant are satisfactorily explained by film theory with a single reaction plane model. Those obtained in the absence of surfactant are best described by a two-plane model using renewal theory.     

Solubility of CO2 in aqueous solutions of NaCl, KCl, CaCl2 and their mixed salts at different temperatures and pressures

The solubility of CO₂ in water and aqueous solutions of NaCl, KCl, CaCl₂, NaCl + KCl (weight ratio = 1:1), NaCl + CaCl₂ (weight ratio = 1:1), KCl + CaCl₂ (weight ratio = 1:1), and NaCl + KCl + CaCl₂ (weight ratio = 1:1:1) was determined at 35.0, 45.0 and 55.0 °C up to 16 MPa, and the concentration of the salt was up to 14.3 wt%. It was demonstrated that solubility increased with increase in pressure, and decreased with increasing temperature. Addition of a salt or salt mixture resulted in reduction in the solubility due to the salting-out effect. At the same salt concentration (wt%), the salting-out effect of KCl was considerably smaller than those of NaCl and CaCl₂. The salting-out effect of a salt mixture is between those of its components.     

Thermodynamic modeling of CO2 solubility in aqueous solutions of NaCl and Na2SO4

A thermodynamic model based on the electrolyte NRTL activity coefficient equation and PC-SAFT equation-of-state is developed for CO₂ solubility in aqueous solutions of NaCl and Na₂SO₄ with temperature up to 473.15 K, pressure up to 150 MPa, and salt concentrations up to saturation. The Henry's constant parameters of CO₂ in H₂O and the characteristic volume parameters for CO₂ required for pressure correction of Henry's constant are identified from fitting the experimental gas solubility of CO₂ in pure water with temperature up to 473.15 K and pressure up to 150 MPa. The NRTL binary parameters for the CO₂-(Na⁺, Cl⁻) pair and the CO₂-(Na⁺, SO₄²⁻) pair are regressed against the experimental VLE data for the CO₂-NaCl-H₂O ternary system up to 373.15 K and 20 MPa and the CO₂-Na₂SO₄-H₂O ternary system up to 433.15 K and 13 MPa, respectively. Model calculations on solubility and heat of solution of CO₂ in pure water and aqueous solutions of NaCl and Na₂SO₄ are compared to the available experimental data of the CO₂-H₂O binary, CO₂-NaCl-H₂O ternary and CO₂-Na₂SO₄-H₂O ternary systems with excellent results.     

Growth and morphology of ZnO nanorods prepared from Zn(NO3)2/NaOH solutions

ZnO nanorods on ZnO-coated seed surfaces were fabricated by a solution chemical method using supersaturated Zn(NO₃)₂/NaOH solution. The seed surfaces were coated on glass substrates by sol–gel processing and PEG addition. The mechanism of crystal growth and the factors affecting the rod growth were elucidated. The morphology and structure of both the seed surface and successive nanorods were analyzed by using SEM, XRD, TEM and SAED. Nucleation on the ZnO seed surface is crucial for rod growth since rods can only be observed on ZnO-coated substrates. Supersaturation is also required for rod growth and the Zn²⁺ ion and NaOH concentrations must be varied synchronously to maintain the high level of supersaturation. The average diameter and length of the ZnO nanorods increase to different degree with increasing precursor concentration. The dependence of rod growth on temperature shows that the maximum rod growth rate at any given concentration of Zn²⁺ occurs at a specific temperature, and the optimal temperature increases with Zn²⁺ ion concentration. Densely thick nanorods oriented perpendicularly to the substrate can be obtained by controlling the seed surface with PEG assistance.     

Dissolution of starch in urea/NaOH aqueous solutions

Dissolution of starch in urea/NaOH aqueous solutions was studied by using polarizing microscope and viscometry. The experimental results revealed that starch could dissolve in urea (2–20 wt %) and NaOH (10–1 wt %) aqueous solutions at temperature ranging from ?12 to 25 °C, where the optimized dissolution condition was in the aqueous solution of mixed urea 14% and NaOH 4% at 0 °C for 30 min or above. Under the conditions, the starch solubility could be 99.0 and 92.1% as the starch weight percent was 1 and 10%, respectively. Measurements for the molecular weight and amylose content of the starch before and after the dissolution indicated that there was no serious degradation during the process. The results from determinations of X‐ray diffraction, Fourier transform infrared, and rapid visco analysis revealed that the recovered starch from the starch solutions was an amorphous solid with a part of V‐type pattern (single‐helix). The urea/NaOH aqueous solvent may have potential significance for starch processing and modification. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43390.     

功能化离子液体-MDEA复配体系吸收CO2

采用一步法合成了两种功能化离子液体四乙铵-丙氨酸盐([N2222][Ala])和四乙铵-丝氨酸盐([N2222][Ser]),利用IR和1H NMR对其结构进行了表征,并测定了其玻璃转化温度和分解温度;同时,在40℃下分别将[N2222][Ala]和[N2222][Ser]与MDEA进行复配,考察复配后的体系对CO2吸收性能;实验结果表明,[N2222][Ala]和[N2222][Ser]的加入对MDEA吸收CO2均有不同程度的增强作用,当加入质量分数为10%时,体系对CO2吸收量分别增加了8.63%和5.40%。此外,研究了20～60℃温度范围内复配体系的密度、黏度等,并比较了吸收前后黏度的变化。     

Rate-based modelling of SO2 absorption into aqueous NaHCO3/Na2CO3 solutions accompanied by the desorption of CO2

A rate-based model of a counter-current reactive absorption/desorption process has been developed for the absorption of SO₂ into NaHCO₃/Na₂CO₃ in a packed column. The model adopts the film theory, includes diffusion and reaction processes, and assumes that thermodynamic equilibrium among the reacting species exists in the bulk liquid. Model predictions were compared to experimental data from literature. For the calculation of the absorption rate of SO₂ into NaHCO₃/Na₂CO₃ solutions and concomitant CO₂-desorption, it is important to take into account all reversible reactions simultaneously. It is clear that the approximate analytical based model cannot be expected to predict the absorption rates under practical conditions because of the complicated nature of the reactive absorption processes. The rigorous numerical approach described here only requires definition of the individual reactions in the system, and subsequent solution is independent of specific assumptions made, or operational variables like pH or compound concentrations. As an example of the flexibility of this approach, additional calculations were conducted for SO₂ absorption in a phosphate-based buffer system.     

Role of Cl− in breakdown of Ni Passivity in aqueous NaOH solutions

Repetitive potentio- and galvanokinetic traces of Ni rods yielded anodic peaks (or arrests) corresponding to probable formations of α and β Ni(OH)₂ and NiO(OH) prior to O₂ evolution. Cathodic half cycles consistently showed only two reduction processes that are attributed to NiO(OH)→ Ni(OH)₂åNi. Potentiostatic polarization resulted in multi-peaks i-t traces, in [NaOH] ? 1 moll^?1; the main peak exhibiting the general form characteristic of instantaneous nucleation processes. The maximum current intensity, i_p, of the potentiokinetic traces as well as the parameter i_mt_m of the i-t curves showed negligible dependence on NaOH in the range 0.01–1 moll^?1. In the range of 1–200 mVs^?1 scan rate, i_p ∝ v. Employing an aqueous media of mixtures of different concentrations of NaCl plus a constant [NaOH] resulted in: (a) significant increases of both i_p and i_mt_m and (b) nearly linear i-v^{$\text{sol1}\text{2}$} relation. Achievement of electrode passivity was retarted by Cl^? but eventually attained. As [Cl^?]/[OH^?] exceeded ～ 3 passivity showed signs of breaking down. The passivation current showed continous rise with increasing [Cl^?]. A mechanism of Cl^? attack involving surface adsorption, increasing solubility of an intermediate Ni hydroxide species that nucleates into passive film and peptization of the deposited oxide, by Cl^?, is discussed.     

The mechanism of the anodic formation of S2O2−8 ions on a Ti-supported IrO2 electrode in mixed aqueous solutions of H2SO4, (NH4)4SO4 and NH4F

The mechanism for the anodic formation of peroxydisulfate ion on a Ti-supported IrO₂ electrode was investigated in mixed aqueous solutions of H₂SO₄, (NH₄)SO₄ and NH₄F.Peroxydisulfate ion can be formed in higher yield at lower overpotential on the Ti-supported IrO₂ electrode, compared with smooth Pt electrode. The most probable mechanism under Langmuir conditions of intermediate adsorption was proposed as

     

A study on the reaction between CO2 and alkanolamines in aqueous solutions

Literature data on the rates of reaction between CO₂ and alkanolamines (MEA, DEA, DIPA, TEA and MDEA) in aqueous solution are discussed. These data induced us to carry out absorption experiments of CO₂ into aqueous DEA, DIPA, TEA and MDEA solutions from which the respective rate constantsThe results for DEA and DIPA were analysed by means of a zwitterion-mechanism which was derived from the mechanism originally proposed by Danckwerts [1The reaction rate of CO₂ with aqueous TEA and MDEA solutions shows a significant base catalysis effect which is also reported by Donaldson and Nguy     

碱性离子液体-NaOH/MEA混合体系的CO2吸收性能

为了改善有机醇胺与无机碱液对生物质燃气中CO2的吸收性能,制备了具有代表性的4种功能化离子液体:[TMG]+ [C3H4N2]-、[TMG]+[TFEA]-、[MEA]+[BF4]-、[MEA]+[CHOO]-,并按一定的比例分别与NaOH溶液和乙醇胺(MEA)溶液复配组成新型CO2吸收剂,以研究其对CO2的吸收特性.实验结果显示,MEA-[TMG]+[C3H4N2]-、MEA-[MEA]+[CHOO]-和NaOH-[MEA]+[CHOO]-对CO2的吸收去除率高于单纯的MEA和NaOH溶液,而MEA-[TMG]+[TFEA]-、MEA-[MEA]+[BF4]-和NaOH-[MEA]+[BF4]-对CO2的去除率则低于单纯碱液吸收剂.同时发现,当离子液体[MEA]+[CHOO]-与MEA的混合比例为2∶3时,混合溶剂对CO2的吸收效果比MEA溶液的显著提高,生物质燃气中CO2去除率从91.3％增加至95.7％.     

Activity measurements in aqueous mixed electrolyte solutions—III. HClCaCl2 mixtures of constant total ionic strength

Emf measurements have been made in cells without liquid junction of the type H₂/HX (m₁), MX_n(m₂)/AgCl, Ag . . (I) containing mixtures of HCl and CaCl₂ in different proportions, but at constant total ionic strength (I = 2, 1, 0.5). The measurements have been carried out at 5°C intervals over the temperature range 5–35°C. AgAgCl electrodes prepared by two different methods (thermal and thermoelectrolytic) were used of which the thermoelectrolytic electrodes were found to give more consistent results. The results when extrapolated properly lead to E° values at the different temperatures which agree well with those reported in literature. The application of the Pitzer method leads to the calculation of the ionic interaction coefficients α₁₂ and α₂₁, at the different constant ionic strengths. The nature of variation of these α's with the total mixture ionic strength at different temperatures has been considered.     

MDEA-二元羧酸离子液体溶液吸收/解吸SO2性能

设计合成了三类N-甲基二乙醇胺（MDEA）-二元羧酸离子液体水溶液,研究了它们的物理性质和SO₂吸收容量。结果表明：MDEA/有机酸的摩尔比及阴离子种类是影响吸收容量的主要原因。碱酸摩尔比越高,离子液体吸收能力越强,解吸能力越差且解吸时间也越长。此外,不同阴离子的离子液体溶液吸收SO₂的容量有如下关系：MDEA-丁二酸>MDEA-戊二酸>MDEA-苹果酸。对于MDEA-戊二酸和MDEA-苹果酸离子液体溶液,最具工业化应用前景的碱酸摩尔比分别为1.2：1和1.4：1。     

Absorption of co2 into aqueous tertiary amine/mea solutions

Absorption rates for CO₂ into aqueous solutions of TEA, MDEA and blends of MEA with MDEA and TEA were measured in a stirred cell by a method similar to that used by Laddha and Danckwerts (1981). Second order rate constants for CO₂-TEA and CO₂-MDEA were obtained from the single amine data for temperatures in the range of 25-60°C. A modified pseudo first order model based on the film theory is used to predict the rate of absorption of CO₂ into mixed amine solutions. This model accounts for the variation of amine concentration in the film and assumes a shuttle mechanism for rate enhancement. Bulk liquid concentrations of the various species present are obtained from a simplified thermodynamic model. The model predicts absorption rates that are in agreement with experimental measurements.     

氢氧化钠沉淀沽制备Bi2O3粉末的研究

对氢氧化钠沉淀法制备Bi2O3粉末进行了详细的研究,大量探索实验发现,反应温度、终点pH值和搅拌速度对Bi2O3的纯度有较大的影响。研究表明,最佳工艺条件控制为反应温度70－90℃,pH值12左右,搅拌速度约300r/min时,制得的Bi2O3为β型、针状、粒度为1－10μm的高纯度粉末。该粉末用于对粒度和纯度有一定要求的无机颜料、阻燃剂、抑烟剂、高折光玻璃和核工程玻璃等领域。     

CO2 capture into aqueous solutions of piperazine activated 2-amino-2-methyl-1-propanol

In this work, experimental data and a simplified vapor–liquid equilibrium (VLE) model for the absorption of CO₂ into aqueous solutions of piperazine (PZ) activated 2-amino-2-methyl-1-propanol (AMP) are reported. The purpose of the work was to find the AMP/PZ system with the highest concentration and cyclic capacity, which could be used in the industry without forming solid precipitations at operational temperatures. The effect of the AMP/PZ ratio and the total concentration level of amine was studied. The highest possible ratio of AMP/PZ, which does not form solid precipitates during the absorption of CO₂ at 40 °C (40 wt% amine), was identified. Considering the maximum loading found in the screening tests for AMP/PZ (3+1.5 M) and for 30 wt% MEA systems, the AMP/PZ system has about 128% higher specific cyclic capacity if operating between 40 and 80 °C, and almost twice the CO₂ partial pressure at 120 °C compared to MEA.