Kinetics of acid-catalyzed cleavage of cumene hydroperoxide

The cleavage of cumene hydroperoxide, in the presence of sulfuric acid, to form phenol and acetone has been examined by adiabatic calorimetry. As expected, acid can catalyze cumene hydroperoxide reaction at temperatures below that of thermally-induced decomposition. At elevated acid concentrations, reactivity is also observed at or below room temperature. The exhibited reactivity behavior is complex and is significantly affected by the presence of other species (including the products). Several reaction models have been explored to explain the behavior and these are discussed.     

不同形貌CuO纳米粒子的制备与性能

采用CuSO4.5H2O、Cu(NO3)2、(CH2)6N4和NaOH为原料,采用沉淀法分别制备纤维状CuO纳米粒子和纺锤状CuO纳米粒子,用透射电镜和X射线衍射仪对产物的大小﹑形貌和组成进行表征;按质量比为9∶1的比例将黑索金分别与纤维状CuO纳米粒子和纺锤状CuO纳米粒子混合,对样品进行热失重测试分析,根据黑索金热分解温度的变化来衡量催化剂的活性。结果表明,采用沉淀法制备CuO纳米粒子时,反应温度、终点pH值对产物形貌有显著影响;不同形貌的CuO纳米粒子对黑索金的分解催化作用效果不同。     

溶胶-凝胶自蔓延法制备球形纳米铜粉

以硝酸铜、柠檬酸为原料,利用氨水调节pH制备溶胶,将溶胶蒸发干燥得到的干凝胶通过自蔓延法制得金属铜纳米粉体,研究pH在制备溶胶-凝胶过程中对成胶时间的影响,以及pH、自蔓延温度对产物组成的影响;通过差热分析、X射线衍射和扫描电镜分别对凝胶的热分解机制、产物的物相组成以及形貌和粒度进行分析。结果表明,当pH=6～7时,形成的凝胶均一,凝胶时间最短(4 h);当自蔓延反应温度为250℃时,可以制得粒径为50～70 nm的球形纳米铜颗粒。     

Oxidative decomposition of atrazine in water in the presence of hydrogen peroxide using an innovative microwave photochemical reactor

The simultaneous application of microwave (MW) power and UV light leads to improved results in photochemical processes. This study investigates the oxidative decomposition of atrazine in water using an innovative MW and UV photochemical reactor, which activates a chemical reaction with MW and UV radiation using an immersed source without the need for a MW oven. We investigated the influence of reaction parameters such as initial H(2)O(2) concentrations, reaction temperatures and applied MW power and identified the optimal conditions for the oxidative decomposition of atrazine. Atrazine was completely degraded by MW/UV/H(2)O(2) in a very short time (i.e. t(1/2) = 1.1 min for 20.8 mg/L in optimal conditions). From the kinetic study, the disappearance rate of atrazine can be expressed as dX/dt = k(PH)[M](0)(b-X)(1-X), where b ≡ [H(2)O(2)](0)/[M](0)+k(OH)[·OH]/k(PH)[M](0), and X is the atrazine conversion, which correlates well with the experimental data. The kinetic analysis also showed that an indirect reaction of atrazine with an OH radical is dominant at low concentrations of H(2)O(2) and a direct reaction of atrazine with H(2)O(2) is dominant when the concentration of H(2)O(2) is more than 200 mg/L.     

Disproportionation of Pu(VI) and reproportionation of Pu(V), Pu(VII) in aqueous alkali solutions

Disproportionation of Pu(VI) and reproportionation of Pu(V) and Pu(VII) in aqueous NaOH solutions was studied. With an increase in the NaOH concentration in solution over 7.5 M, the equilibrium of the reaction Pu(VII) + Pu(V)?2Pu(VI) is gradually shifted toward formation of Pu(V) and Pu(VII) as products of Pu(VI) disproportionation, and at [NaOH] + 13 M, Pu(VI) disproportionates virtually completely. At [NaOH] + 7.5 M, the equilibrium of the above reaction is shifted toward formation of Pu(VI). Based on the experimental data, the equilibrium constants of the reaction at various alkali concentrations in the solution and the formal potentials ?_{f[Pu(VII)/Pu(VI)]} were calculated. The data obtained showed that, with respect to reduction with water, Pu(VII) is stable in aqueous alkali solutions at NaOH concentrations exceeding 7.5 M.     

Decomposition of urea in sub- and supercritical water with/without additives

Urea was decomposed in sub- and supercritical water in the presence and the absence of hydrogen peroxide at temperatures from 538 to 651 K, 23 MPa and residence times up to 1.5 s in a continuous flow reactor. The initial concentrations of urea varied from 0.005 to 0.5 mol L⁻¹. The major products were carbon dioxide, and ammonia. As a minor product cyanic acid was detected without hydrogen peroxide, and nitric acid and nitrous acid were produced with hydrogen peroxide. The decomposition rates of urea with and without hydrogen peroxide were represented by the first order reaction kinetics. The addition of hydrogen peroxide increased the rates at lower temperatures, but was scarcely effective at higher temperatures. In the absence of hydrogen peroxide, the effects of various additives at concentrations of 0.5 mol L⁻¹ on the decomposition rates at 649 K were examined. The addition of NaOH enhanced them remarkably. The presence of NaCl did not affect the product distribution significantly, but enhanced the rates somewhat, in particular, increasing as approaching to the critical temperature of water. The addition of acids, hydrogen chloride and sulfuric acid, did not increase the rates.     

Decomposition of 2-bromophenol in NaOH solution at high temperature

2-Bromophenol was reacted in aqueous sodium hydroxide at 200-250 degrees C. The decomposition rate was remarkably faster at 250 degrees C than at 225 or 200 degrees C, and the percentage debromination reached almost 100% in 1M NaOH at 250 degrees C for 4h. The percentage increased with NaOH concentration over the range 0.1-1M. Aliphatic compounds, such as 2,2-dimethoxypropane and 4-hydroxy-4-methyl-2-pentanone, and aromatic compounds, such as phenol and cresol, were formed as decomposition products. The formation of carboxylic acids, such as formic, acetic, and propionic acids, in the presence of oxygen was also confirmed. Under a nitrogen atmosphere, the oxidation caused by oxygen in solution was suppressed and hydrolysis became the dominant reaction in the decomposition of 2-bromophenol.     

Change of monochloroacetic acid to biodegradable organic acids by hydrothermal reaction

The feasibility of biodegradability improvement induced from the structural conversion of refractory pollutants by hydrothermal reaction was investigated. Monochloroacetic acid (MCAA) was selected as a preliminary material represented for linear hydrocarbon structured refractory pollutants. Under the tested conditions, MCAA was partially destructed and then converted to biodegradable reaction products by hydrolysis, dehydration and thermal decomposition. The identified products were glycolic acid, citric acid and formic acid. Total organic carbon (TOC) reduction during the structural conversion did not exceed 24%, except the results at the reaction conditions of 350 degrees C and 17 MPa. However, Produced biodegradable organic acids were reduced by thermal decomposition with increasing reaction temperature and time. At the reaction temperature of 250 and 300 degrees C, biodegradability (BOD/COD(Cr)) was reached at 0.51 in 6.9 min and 0.52 in 7.4 min despite the presence of dissociated chlorine ions. The detachment of recalcitrant chlorine ion from MCAA and the production of biodegradable organic acids by hydrothermal reaction were directly related to the biodegradability improvement of reaction products.     

Modification of dispersibility of nanodiamond by grafting of polyoxyethylene and by the introduction of ionic groups onto the surface via radical trapping

To improve the dispersibility of polycrystalline nanodiamond (ND) in solvents, the grafting of polymers and introduction of ionic groups onto ND surface via radical trapping by ND surface were investigated. The grafting of polyoxyethylene (POE) onto ND surface by trapping of POE radicals formed by the thermal decomposition of POE macro azo-initiator (Azo-POE) was examined. The polymer radicals formed by the thermal decomposition of Azo-POE were successfully trapped by ND surface to give POE-grafted ND. The effect of temperature on the grafting of POE onto ND was discussed. In addition, the introduction of cationic protonated amidine groups onto ND was achieved by the trapping of radicals bearing protonated amidine groups formed by thermal decomposition of 2,2′-azobis(2-methylpropionamidine)dihydrochloride (AMPA). The anionic carboxylate groups was introduced onto ND surface by the trapping of the radicals bearing carboxyl groups formed by thermal decomposition of 4,4′-azobis(4-cyonovaleric acid) (ACVA) followed by the treatment with NaOH aqueous solution. The dispersibility of ND in water was remarkably improved by the grafting of POE, based on the steric hindrance of polymer chains and by the introduction of ionic groups, based on the ionic repulsion, onto ND surface.     

Ozonation of Cationic Red X-GRL in aqueous solution: kinetics and modeling

Ozonation of Cationic Red X-GRL was investigated in a semi-batch column reactor under various operating conditions such as gas flow rate Q(G), temperature T, initial concentration C(D,0), and pH. The relative contributions of ozone direct oxidation and OH-facilitated indirect oxidation of the dyestuff were quantified, and the overall rate constant k(T) and the kinetic regime of the reaction were determined by interpreting the experimental data with a newly derived kinetic model. The Hatta number of the reaction was found between 0.053 and 0.080, indicating that the reaction occurred in the liquid bulk, i.e. the slow kinetic regime. The ratio γ of indirect oxidation rate constant k(R) to k(T) decreased from 11.50% at pH 9.24 to 2.47% at pH 3.15. A mechanistically sounder model was derived to describe the reaction kinetics, which takes into account mechanisms of ozone decomposition and dyestuff degradation, and gas-liquid mass transfer. Good agreements were obtained between the experimental and calculated concentrations of Cationic Red X-GRL C(D), dissolved ozone C(A), ozone in off gas C(A,G), and nitrate. Furthermore, a model-based sensitivity analysis of C(D)/C(D,0), C(A), and C(A,G) was performed with respect to various model parameters.     

Synthesis, characterization and properties of nitrogen-rich salts of trinitrophloroglucinol

Five different nitrogen-rich salts of trinitrophloroglucinol (H(3)TNPG) have been prepared by the reaction of ammonia, aminoguanidine (AG), carbohydrazide (CHZ), semicarbazide (SCZ) and 5-aminotetrazo (ATZ) with trinitrophloroglucinol in aqueous solution through the heating method of water bath, with the yield up to 80%. These salts were characterized by elemental analysis, FT-IR, DSC and TG-DTG techniques. Their melting temperature is consistent with the thermal decomposition temperature. Their thermal decomposition process and kinetic parameters from 323 to 673K were investigated under a linear heating rate by DSC. The thermal decomposition of these salts undergoes an intensive exothermic decomposition stage to evolve abundant gas products and the enthalpies of exothermic decomposition reaction are high. The tests of sensitivity properties show these salts are insensitivity. All the properties of five nitrogen-rich salts appeared to depend on molecule structures and interconnection. It can be concluded that the five compounds are worthy of further in-depth studies as the gas-generating composition, emission reagents and propellants.     

Oxidation of Pu(VI) with ozone and stability of the oxidation products,Pu(VII) and Pu(VIII), in concentrated alkali solutions

Oxidation of Pu(VI) with ozone and stability of the oxidation products, Pu(VII) and Pu(VIII), in 4–15 M NaOH solutions were studied. In a wide range of alkali concentrations, from 1 to 15 M, the Pu(VI) ozonation yields a mixture of Pu(VII) and Pu(VIII). It was proved that Pu(VII) exists in aqueous alkali solutions in the form different from that suggested previously. Pu(VII) is readily reduced with ?2? in aqueous alkali solutions with the NaOH concentration of up to 8 M, whereas at [NaOH] + 8 M it is fairly stable. On the contrary, Pu(VIII) is noticeably reduced with water at room temperature throughout the examined range of NaOH concentrations from 1 to 15 M.     

TiO_2纳米带在强碱条件下的水热反应

研究了在不同浓度NaOH溶液中,于不同反应时间和温度的水热条件下,TiO2纳米带发生反应,进一步生成产物的结构和形貌。通过对产物的XRD和SEM的测试结果表明,在强碱条件下水热处理TiO2纳米带很容易生成具有层状结构的钛酸盐纳米带,NaOH溶液的浓度、水热反应时间和温度对产物的形貌影响不大。     

One-step wet chemical method to Cu(OH)2 nanowires

Under controlled temperature and pH of solution, Cu(OH)2 nanowires were successfully fabricated by dropping simply NaOH solution into CuSO4 solution. The morphology and composition of as-synthesized products were controllable by adjusting the pH value, reaction temperature and aging time. The influence of reaction conditions on the products was discussed in detail and optimum synthesis conditions were obtained. A mechanism of reconstruction involving dissolution, reprecipitation and transportation of [Cu(OH)4 ]2- was proposed. OH ions played an important role by absorbing on the surface of crystal planes which resulted in anisotropic growth of Cu(OH)2 crystals. This method with mild conditions was simple and repeatable. This route provides a new perspective to synthesize similar 1-D nanomaterials, such as Co(OH)2 and Ni(OH)2 and so on. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to characterize the products.     

Catalytic decomposition of organic anions in alkaline radioactive waste: III. Oxidation of oxalate and glycolate

Decomposition of oxalate and glycolate ions in alkaline solutions under the action of O₃, H₂O₂, and Na₂S₂O₈ was studied spectrophotometrically and titrimetrically. At 20°C, ozone slowly decomposes oxalate in 0.05 M NaOH. In 1 M NaOH, heating at 90°C is required to oxidize oxalate with ozone. Glycolate is readily oxidized with ozone at 20°C in 0.05–1 M NaOH, predominantly into oxalate. Hydrogen peroxide is ineffective reagent for oxalate and glycolate decomposition. Persulfate oxidizes oxalate ion in 0.5–5 M NaOH at 90°C. The reaction of persulfate with glycolate proceeds at 50°C and higher temperatures and is characterized by an induction period, which shortens with increase in concentration of S₂O ₈ ^2? , OH^?, and temperature, or in the presence of AgNO₃ and K₄Fe(CN)₆. Oxidation involves thermal dissociation of persulfate ions into radical ions followed by a chain reaction.     

Scoring single-nucleotide polymorphisms at the single-molecule level by counting individual DNA cleavage events on surfaces

Single-nucleotide polymorphisms (SNPs) are the most frequent type of human genetic variation. Recent work has shown that it is possible to directly analyze SNPs in unamplified human genomic DNA samples using the surface-invasive cleavage reaction followed by rolling circle amplification (RCA) of the cleavage products. The ability of RCA to produce single-stranded DNA tens of thousands of nucleotides in length from a single cleaved DNA molecule on the surface suggested the possibility of detecting individual cleavage events on the surface. The feasibility of this approach to SNP scoring is shown here. Individual cleavage events on the surface are detected using fluorescence microscopy to visualize the single-stranded DNA product of the RCA reaction labeled with the fluorescent dye SYBR Green I. The surface density of fluorescent features observed is dependent upon the concentration of target DNA. Future reductions of the sample volume and optimization of the reaction conditions offer the potential of being able to perform such analyses on as little as a single copy of genomic DNA target.     

The removal of the indigo carmine dye from aqueous solutions using cross-linked chitosan: evaluation of adsorption thermodynamics using a full factorial design

A 2(3) factorial design was employed to evaluate the quantitative removal of the indigo carmine (IC) dye from aqueous solutions on glutaraldehyde cross-linked chitosan. The variables were chitosan masses of 100 and 300 mg, IC concentrations of 2.0 and 5.0 x 10(-5) mol L(-1) and temperatures of 25 and 35 degrees C. The quantitative and energetic adsorption parameters were analyzed statistically using modeling with bilinear equations. The results indicated that increasing the chitosan mass from 100 to 300 mg decreases the IC adsorption/mass ratio (mol g(-1)) whereas a temperature increase of 25-35 degrees C increases it. The principal effect of the IC concentration did not show statistical significance. The factorial experiments demonstrate the existence of a significant antagonistic interaction effect between the chitosan mass and temperature. The adsorption thermodynamic parameters, namely Delta(ads)H, Delta(ads)G, and Delta(ads)S, were determined for all the factorial design results. Endothermic values were found in relation to the Delta(ads)H. The positive Delta(ads)S values indicate that entropy is a driving force for adsorption. The Delta(ads)G values are also significantly affected by important antagonistic and synergistic effects involving all principal and interactive factors. It is concluded that the thermodynamical spontaneity of the IC adsorption parameters are greatly influenced by the interactive factors and not by the temperature changes alone.     

工业级原料制备碳纳米管的研究

为降低碳纳米管批量制备的原料成本,以焦化苯和二茂铁为主要原料(工业级),采用浮游催化热解法制备碳纳米管,用TEM、SEM、Raman、XRD等对产物的形貌和结构进行观察和表征,着重讨论了二茂铁的分解温度和苯的挥发温度对碳纳米管的制备及其形貌的影响,并对其影响机理进行了分析.研究表明:在噻吩体积分数为0.55 mL/100 mL苯、炉膛反应温度为1170℃的前提下,当二茂铁的分解温度为150℃、苯的挥发温度为50℃时,用工业级原料完全可以制备出碳纳米管,此时,碳纳米管的内径分布在0.88~1.15 nm.     

Dechlorination of hexachlorocyclohexanes with alkaline 2-propanol and a palladium catalyst

Hexachlorocyclohexane isomers (alpha-, beta-, gamma- and delta-HCH) were dechlorinated in 2-propanol by means of stoichiometric reaction with NaOH and subsequent catalytic dechlorination over a supported palladium catalyst (Pd/C). When the HCH isomers (2-10 mmol/l) were reacted with a molar excess of NaOH ([NaOH]/[HCH]>9) in 2-propanol, transformation of alpha-, gamma- and delta-HCH to trichlorobenzenes (TCBs) was complete within 5 min at room temperature, but beta-HCH was less reactive. Analysis of TCB isomers produced from individual HCH isomers showed that 1,2,4-TCB was always predominant (70-90% of the product) and 1,2,3-TCB and 1,3,5-TCB were minor products. The produced TCBs were dechlorinated by subsequently adding Pd/C to the alkaline 2-propanol solution and heating at 55 degrees C for 3 h, resulting in the formation of benzene in high yield (>80%). Technical-grade HCH, which contains these four isomers, was successfully dechlorinated with NaOH and Pd/C at 55 degrees C.     

纳米TiO2制备过程中的若干影响因素

用自行设计的、用于观测由透明均匀相中生成超微粒子的激光测试仪,对水解法制备纳米TiO₂的过程进行了研究,并设定了一系列反应过程的内在参数,如成核温区△T,成核时间△t,反应成核浓度的参数I／I₀等,并记录了这些参数及有关曲线,讨论了这些参数与最后产物性质的关系,研究了反应初始条件如浓度、酸度和阴离子等外部因子的改变对这些参数的影响,以及对最终产物性质（粒子大小、晶型结构）的影响,获得了金红石含量高,粒子直径在100nm的超细TiO₂粉体．