Preparation of sodium oxyhumates from peat

We studied how the duration of cavitation treatment, the concentration of NaOH, the amount of hydrogen peroxide, and the water duty affect the concentrations of humic acids and fulvic acids in the liquid phase of the oxidation products of peat with hydrogen peroxide in an aqueous alkaline solution using a cavitation technology. The elemental and functional group composition of isolated oxyhumic acids was studied. The resulting preparations were agrochemically tested as growth stimulators.     

Direct Synthesis of Hydrogen Peroxide from Hydrogen and Oxygen over Palladium Catalyst Supported on SO3H-Functionalized SBA-15

Palladium catalyst supported on SO₃H-functionalized SBA-15 (denoted as Pd/SO₃H-SBA-15) was applied to the direct synthesis of hydrogen peroxide from hydrogen and oxygen. For comparison, palladium catalyst supported on SBA-15 (denoted as Pd/SBA-15) was also employed for the direct synthesis of hydrogen peroxide. Selectivity for hydrogen peroxide, yield for hydrogen peroxide, and final concentration of hydrogen peroxide over Pd/SO₃H-SBA-15 catalyst were much higher than those over Pd/SBA-15 catalyst. The high catalytic performance of Pd/SO₃H-SBA-15 catalyst was attributed to the enhanced acid amount of SO₃H-SBA-15 support, which served as an alternate acid source in the direct synthesis of hydrogen peroxide from hydrogen and oxygen.     

Baeyer–Villiger Oxidation of Cyclohexanone in Aqueous Medium with In Situ Generation of Peracid Catalyzed by Perhydrolase CLEA

A perhydrolase, immobilized as a cross linked enzyme aggregate (CLEA), was employed to catalyze the in situ formation of peracetic acid (PAA) from ethylene glycol diacetate (EGDA) and hydrogen peroxide. The produced PAA was used for the Baeyer–Villiger oxidation of cyclohexanone, which afforded caprolactone in 63 % yield. The effect of type and amount of acyl donor, solvent, pH, temperature and ratio of cyclohexanone to hydrogen peroxide on the production of caprolactone was studied. The highest caprolactone yield was obtained with 100 mM EGDA as the acyl donor at pH 6 and room temperature using a ratio of cyclohexanone to hydrogen peroxide ratio of 1:4. Interestingly, the perhydrolase CLEA exhibited the highest activity in aqueous medium in contrast to the well studied lipase B from Candida antarctica. The perhydrolase CLEA proved to be a very efficient catalyst; the K _m and V_max values were 118 mM and 56.3 μmol min^?1, respectively.     

Study of the effect of operative conditions on the decolourization of azo dye solutions by using hydrodynamic cavitation at the lab scale

In the present study, the potentiality of hydrodynamic cavitation (HC) for the degradation of methyl orange from synthetic aqueous solutions is presented. Hydrodynamic cavitation was set up at laboratory scale using a Venturi tube. Solutions of methyl orange (MO) were subjected to cavitation in order to investigate the efficiency and the potential of this technique for azo dye degradation. Moreover, a HC/H₂O₂/TiO₂ hybrid system was tested with the aim to verify its potential positive impact on the decolourization process and define the best conditions, among those investigated, to remove azo dye from synthetic solutions. The results obtained in this study showed that the maximum efficiency was close to 30% using a Venturi tube at an operating pressure of 400 kPa. The presence of additives, such as titanium dioxide and hydrogen peroxide, increased the performance of the degradation process to slightly above 70%.     

Studies of the initiation mechanism of ferric ion–hydrogen peroxide systems in graft copolymerization on cellulose

The decomposition of hydrogen peroxide by ferric ion adsorbed on cellulose, the lowering of the degree of polymerization of cellulose, and the graft copolymerization in the systems containing methyl methacrylate were studied. As the amount of ferric ion adsorbed on cellulose and the concentration of hydrogen peroxide became higher, the amount of decomposition of hydrogen peroxide and the number of scissions of cellulose chains with higher rates at the initial stage of reaction were both observed to increase. It was recognized that the graft copolymerization was hardly initiated, while such initial reactions were proceeding. Assuming that the hydrogen peroxide decomposed with a higher rate was indifferent to the initiation reaction, a certain relationship was found between the amount of ferric ion adsorbed on cellulose ànd the initiation efficiency of hydrogen peroxide in graft copolymerization.     

钛硅分子筛混合溶剂洗涤再生的研究

研究了失活钛硅分子筛采用过氧化氢和甲醇溶剂混合洗涤的再生过程。通过正交实验，系统考察了再生温度、再生时间、过氧化氢与甲醇质量比和混合溶剂量四个因素对再生过程的影响，得到了再生的最佳工艺条件。在此条件下，反应30 min，环氧丙烷选择性为98.55%，环氧丙烷收率为26.35%，H₂O₂转化率为32.4%。     

Electrochemical oxidation of Crystal Violet in the presence of hydrogen peroxide

BACKGROUND: The combination of electrochemical oxidation using a Ti/RuO₂? IrO₂ anode with hydrogen peroxide has been used for the degradation of Crystal Violet. The effect of major parameters such as initial pH, hydrogen peroxide concentration, current density, electrolyte concentration and hydroxyl radical scavenger on the decolorisation was investigated. RESULTS: The decolorisation rate increased with initial pH and hydrogen peroxide concentration, but decreased with electrolyte and radical scavenger concentration. The decolorisation rate increased with current density, but the increase became insignificant after current density exceeded 47.6 mA cm^?2. On the other hand, hydrogen peroxide decomposition rate increased with initial pH and current density, but decreased with electrolyte and radical scavenger concentration. The amount of hydrogen peroxide decomposed during 30 min reaction increased linearly with hydrogen peroxide dosage. The main intermediates were separated and identified by gas chromatography–mass spectrometry (GC–MS) technique and a plausible degradation pathway of Crystal Violet was proposed. At neutral pH, the electrochemical process in the presence of hydrogen peroxide was more efficient than that in the presence of Fenton's reagent (electro‐Fenton process). CONCLUSION: The anodic oxidation process could decolorise Crystal Violet effectively when hydrogen peroxide was present. Almost complete decolorisation was achieved after 30 min reaction under the conditions 2.43 mmol L^?1 hydrogen peroxide, 47.6 mA cm^?2 current density and pH₀ 7, while 62% COD removal efficiency was obtained when the reaction time was prolonged to 90 min. Copyright © 2010 Society of Chemical Industry     

Large‐scale sonochemical reactors for process intensification: design and experimental validation

Acoustic cavitation results in substantial enhancement in the rates of various chemical reactions but the existing knowledge about the application of reactors based on acoustic cavitation is limited to very small capacities (of the order of few millilitres). In the present work, an overview of the application of acoustic cavitation for the intensification of chemical reactions has been presented briefly, discussing the causes for the observed enhancement and highlighting some of the typical examples. A novel reactor has been developed operating at a capacity of 7 dm³ and tested with two reactions, ie liberation of iodine from aqueous potassium iodide and degradation of formic acid. The energy efficiency of the reactor has been calculated and compared with the conventional sonochemical reactors. The effect of frequency of irradiation on the percentage conversion of the reactants has been studied. Due to quite low conversions in the case of formic acid degradation, further intensification was attempted using aeration, addition of hydrogen peroxide, and the presence of solid particles (TiO₂). Compared with conventional reactors the novel reactor gives excellent results and it can be said that the future of using acoustic cavitation for process intensification lies in the development of large‐scale multiple frequency multiple transducer reactors. Copyright © 2003 Society of Chemical Industry     

高纯度二氧化氯制备工艺中稳定剂的研究

采用过氧化氢法制备高纯度二氧化氯,研究了几种抑制过氧化氢分解的稳定剂。确定了DTPMP、PBTCA、HEDP三种稳定剂效果较理想,其最佳用量分别为反应液中过氧化氢质量分数的0.6%、1.0%、0.6%。进一步确定了HEDP是A组分中最理想的双氧水稳定剂,能起到有效稳定A组分的作用。     

Iodine(I) Reagents in Hydrochloric Acid‐Catalyzed Oxidative Iodination of Aromatic Compounds by Hydrogen Peroxide and Iodine

Hydrochloric acid activates the oxidative iodination of aromatic compounds with the iodine‐ hydrogen peroxide system through the formation of an iodine(I) compound as the iodinating reagent. Activation with hydrochloric acid is more powerful than that with sulfuric acid. The formation of dichloroiodic(I) acid (HICl₂) with various forms of hydrogen peroxide was followed using UV spectroscopy. The HICl₂ was used as the iodinating reagent. In the preparative oxidative iodinaton of various aromatic compounds, hydrochloric acid was used in a catalytic amount and the iodine(I) reagent was formed in situ with 0.5 equiv. hydrogen peroxide and 0.5 equiv. molecular iodine. Two types of reactivity were observed in oxidative iodination with iodine(I) species catalyzed by hydrochloric acid: in the iodination of anisole 1a better yields of iodination were observed with a smaller amount of hydrochloric acid, while on the contrary 4‐tert‐butyltoluene 1b gave better yields of iodination upon increasing the amount of hydrochloric acid. Reactivity was further manipulated by the choice of the solvent (MeCN, trifluoroethanol, hexafluoro‐2‐propanol).     

Advanced oxidation of cork‐processing wastewater using Fenton's reagent: kinetics and stoichiometry

This work evaluates Fenton oxidation for the removal of organic matter (COD) from cork‐processing wastewater. The experimental variables studied were the dosages of iron salts and hydrogen peroxide. The COD removal ranged from 17% to 79%, depending on the reagent dose, and the stoichiometric reaction coefficient varied from 0.08 to 0.43 g COD (g H₂O₂)^?1 (which implies an efficiency in the use of hydrogen peroxide varying from 17% to 92%). In a study of the process kinetics, based on the initial rates method, the COD elimination rate was maximum when the molar ratio [H₂O₂]_o:[Fe²⁺]_o was equal to 10. Under these experimental conditions, the initial oxidation rate was 50.5 mg COD dm^?3 s^?1 with a rate of consumption of hydrogen peroxide of 140 mg H₂O₂ dm^?3 s^?1, implying an efficiency in the use of the hydrogen peroxide at the initial time of 77%. The total amount of organic matter removed by Fenton oxidation was increased by spreading the H₂O₂ and ferrous salt reagent over several fractions by 15% for two‐fractions and by 21% for three‐fractions. Copyright © 2004 Society of Chemical Industry     

Decomposition of hydrogen peroxide in the presence of activated carbons with different characteristics

BACKGROUND: Catalytic ozonation promoted by activated carbon is a promising advanced oxidation process used in water treatment. Hydrogen peroxide generated as a by‐product from the reaction of ozone with some surface groups on the activated carbon or from the oxidation of some organic compounds present in the water being treated seems to play a key role in the catalytic ozonation process. Hydrogen peroxide decomposition promoted by two granular activated carbons (GAC) of different characteristics (Hydraffin P110 and Chemviron SSP‐4) has been studied in a batch reactor. The operating variables investigated were the stirring speed, temperature, pH and particle size. Also, the influence of metals on the GAC surface, that can catalyze hydrogen peroxide decomposition, was observed. RESULTS: Chemviron SSP‐4 showed a higher activity to decompose hydrogen peroxide than HydraffinP110 (70 and 50% of hydrogen peroxide removed after 2 h process, respectively). Regardless of the activated carbon used, hydrogen peroxide decomposition was clearly controlled by the mass transfer, although temperature and pH conditions exerted a remarkable influence on the process. Catalytic ozonation in the presence of activated carbon and hydrogen peroxide greatly improved the mineralization of oxalic acid (a very recalcitrant target compound). About 70% TOC (total organic carbon) depletion was observed after 1 h reaction in this combined system, much higher than the mineralization achieved by the single processes used. CONCLUSIONS: Of the two activated carbons studied, Chemviron SSP‐4 with an acidic nature presented a higher activity to decompose hydrogen peroxide. However the influence of the operating variables was quite similar in both cases. Experiments carried out in the presence of tert‐butanol confirmed the appearance of radical species. A kinetic study indicated that the process was controlled by the internal mass transfer and the chemical reaction on the surface of the activated carbon. The catalytic activity of hydrogen peroxide in oxalic acid ozonation promoted by activated carbon (O₃/AC/H₂O₂) was also studied. The results revealed the synergetic activity of the system O₃/AC/H₂O₂ to remove oxalic acid. Copyright © 2010 Society of Chemical Industry     

Room temperature direct oxidation of benzene to phenol using hydrogen peroxide in the presence of vanadium-substituted heteropolymolybdates

The liquid-phase direct catalytic oxidation of benzene to phenol was studied at room temperature using vanadium-substituted heteropolyacids as catalysts. Glacial acetic acid was employed as the solvent for the first time, while hydrogen peroxide was used as the oxidant. A yield of 26% and a selectivity of 91%, respectively, were obtained. The as-prepared phenol was separated by column chromatography and was characterized by infrared and mass spectrometry. The catalysts have been characterized by elemental analysis, thermal gravimetric analysis, infrared spectroscopy, UV–vis spectroscopy, X-ray diffraction, and ³¹P NMR and ⁵¹V NMR techniques. The effects of various reaction parameters, such as solvent, reaction temperature, reaction time and the amount of hydrogen peroxide used, were studied. The effects of different vanadium species on the catalytic performance were also studied. Glacial acetic acid was found to be the most suitable solvent among the solvents used in present work. An appropriate molar ratio of H₂O₂ to benzene of 1.7, and a favorable reaction time of 100 min were optimized. H₄PMo₁₁VO₄₀·13H₂O was found to be the most active in terms of turnover based on vanadium atom and the most stable catalyst.     

The ability of Nb2O5 and Ta2O5 to generate active oxygen in contact with hydrogen peroxide

Amorphous and crystalline niobium(V) and tantalum(V) oxides were treated with hydrogen peroxide and studied by XRD, UV–vis, FTIR and ESR techniques to identify changes on their surface upon interaction with hydrogen peroxide. Differences between amorphous and crystalline materials in the interaction with H₂O₂ depending on the hydroxylation of the surface and the nature of OH groups were evident. The type of radical species formed on hydroxylated amorphous materials treated with H₂O₂ depended on the nature of metal oxide. It was proved that peroxo radical species formed in the interaction of H₂O₂ with amorphous Nb₂O₅ were the active intermediates in the oxidation of glycerol to glycolic acid with hydrogen peroxide. The radicals formed on amorphous Ta₂O₅ surface treated with hydrogen peroxide were poorly active in the oxidation of glycerol. Detailed study of the above mentioned radicals is in progress and will be a subject of a separate paper.     

钨酸钠催化环己酮清洁合成己二酸的研究

研究了Na2WO4·2H2O/H2O2(H2O2浓度为30%)体系催化氧化环己酮制取己二酸的反应。发现配体种类、用量、反应时间、催化剂的用量、双氧水的用量是合成己二酸的主要影响因素。通过一系列实验优选出磺基水杨酸为配体,采用正交设计考察了诸主要因素对己二酸收率的影响,确定n(环己酮)=100mmol时最佳的己二酸收率水平组合为:双氧水量54.5ml,n(催化剂)∶n(磺基水杨酸)=2∶1、催化剂量2.5mmol、反应时间7h。     

Methane oxidative coupling on the Au/La2O3/CaO catalyst in the presence of hydrogen peroxide

Methane oxidative coupling in the presence of the catalyst 1% Au/5% La₂O₃/CaO and gas-phase initiator hydrogen peroxide at the temperature 700–800°C under normal pressure has been studied. It has been shown that hydrogen peroxide remarkably increases the yield of C₂₊ products without the loss of selectivity. The maximal yield of C₂₊ products under the conditions studied was 27% with the formation of a noticeable quantity of benzene. It has been proposed, that the observed effect is due to hydroxyl radical formation from hydrogen peroxide, which could be essential under definite conditions also in a conventional catalytic methane oxidative coupling.     

超声辐射催化合成1,4-萘醌

用超声波辐射氧化1-萘酚合成1,4-萘醌。探讨了环己烷用量、过氧化氢用量、超声辐射时间和超声波辐射功率对产品收率的影响。在1-萘酚用量0.5 g,30%过氧化氢溶液用量10.3 mL,环己烷用量3.4 mL,超声波辐射功率120 W,超声辐射时间60 min,1,4-萘醌产率达72.7%。最佳条件下的产率比微波辐射法的产率(50.9%)高。此合成方法所用氧化剂清洁无污染,反应时间较短而且后处理简单,提供了一种绿色合成1,4-萘醌的方法。     

Purification of Wet‐Process Phosphoric Acid by Hydrogen Peroxide Oxidation,Activated Carbon Adsorption and Electrooxidation

In this work, three technologies are studied for the purification of phosphoric acid produced by the wet process: chemical oxidation with hydrogen peroxide, adsorption onto activated carbon, and electrochemical oxidation by boron‐doped diamond anodes. The treatment of wet‐process phosphoric acid by chemical oxidation with H₂O₂ as oxidizing agent can remove 75 % of the initial TOC as maximum, indicating that this wet‐process phosphoric acid contains an important amount of organics that cannot be oxidized by hydrogen peroxide under the operation conditions used. High temperatures and hydrogen peroxide/TOC ratios close to 150 g H₂O₂/g TOC allow obtaining the best chemical oxidation results. The adsorption onto activated carbon can remove between 40 and 60 % of the initial TOC as maximum. Adsorption times of 2 hours and activated carbon/WPA ratios close to 12 g AC/Kg WTP assure both steady state and maximum adsorption of organics. The electrochemical process is the only technique by which complete mineralization of WPA organics can be achieved. Operating at 60 mA cm^–2 and at room temperature, high current efficiencies are achieved which only seem to decrease by mass transport limitations.     

水合肼中间体丁酮连氮的合成工艺研究

以丁酮、氨气和过氧化氢为原料,研究了在催化剂条件下水合肼中间体丁酮连氮合成的不同工艺条件;考察了催化剂种类及其用量、反应时间、反应温度、双氧水用量各因素对反应收率的影响,结果显示,当催化剂选用甲酰胺,催化剂用量0.5mol,反应时间6h,双氧水用量为0.5mol时,反应温度60℃,丁酮连氮收率达到83.49%。     

Direct synthesis of hydrogen peroxide from hydrogen and oxygen over palladium catalyst supported on SO<Subscript>3</Subscript>H-functionalized MCF silica: Effect of calcination temperature of mesostructured cellular foam silica

Palladium catalysts supported on SO₃H-functionalized MCF silica (Pd/SO₃H-MCF-T (T=450, 550, 650, 750, 850, and 950)) were prepared with a variation of calcination temperature (T, °C) of MCF silica. They were then applied to the direct synthesis of hydrogen peroxide from hydrogen and oxygen. Conversion of hydrogen, selectivity for hydrogen peroxide, and yield for hydrogen peroxide showed volcano-shaped curves with respect to calcination temperature of MCF silica. Yield for hydrogen peroxide increased with increasing acid density of Pd/SO₃H-MCF-T catalysts. Thus, acid density of Pd/SO₃H-MCF-T catalysts played an important role in determining the catalytic performance in the direct synthesis of hydrogen peroxide. Pd/SO₃H-MCF-T catalysts efficiently served as an acid source and as an active metal catalyst in the direct synthesis of hydrogen peroxide.