Decolorization of synthetic dyes by hydrogen peroxide with heterogeneous catalysis by mixed iron oxides

Heterogeneous catalysts based on magnetic mixed iron oxides (MO·Fe₂O₃; M: Fe, Co, Cu, Mn) were used for the decolorization of several synthetic dyes (Bromophenol Blue, Chicago Sky Blue, Cu Phthalocyanine, Eosin Yellowish, Evans Blue, Naphthol Blue Black, Phenol Red, Poly B-411, and Reactive Orange 16). All the catalysts decomposed H₂O₂ yielding highly reactive hydroxyl radicals, and were able to decolorize the synthetic dyes. The most effective catalyst FeO·Fe₂O₃ (25 mg mL⁻¹ with 100 mmol L⁻¹ H₂O₂) produced more than 90% decolorization of 50 mg L⁻¹ Bromophenol Blue, Chicago Sky Blue, Evans Blue and Naphthol Blue Black within 24 h. The fastest decomposition proceeded during the first hour of the reaction. In addition to dye decolorization, all the catalysts also caused a significant decrease of chemical oxygen demand (COD). Individual catalysts were active in the pH range 2–10 depending on their structure and were able to perform sequential catalytic cycles with low metal leaching.     

Wet oxidation of phenol by hydrogen peroxide using heterogeneous catalysis Fe-ZSM-5: a promising catalyst

This letter presents an original approach to the treatment of phenolic aqueous wastes using H₂O₂ with heterogeneous catalysts. The experimental results indicate that the system using Fe-ZSM-5 zeolite with MFI structure is promising since it allows total elimination of phenol and significant total organic carbon (TOC) removal under mild working conditions. Moreover, Fe-ZSM-5 remains active after after successive runs. Compared with processes using homogeneous catalysis, the possibility of induced pollution caused by the metal ions in the solution is avoided.     

Cu-silicalite-1 catalyst for the wet hydrogen peroxide oxidation of phenol

The aim of the present work is to study the heterogeneous wet hydrogen peroxide catalytic oxidation (WHPCO) of phenol using copper bearing Silicalite-1 type zeolite, prepared by direct hydrothermal synthesis. The catalysts used for this study were three: one (Na)Cu-Silicalite-1 and two (H)Cu-Silicalite-1 prepared by different ion exchange methods. The results on catalytic activity for phenol abatement and hydrogen peroxide consumption of these materials are presented. The copper leaching during the reaction was evaluated for all samples. A comparison with the catalytic activity and stability of a Cu-Silicalite-1 material prepared by ionic exchange method is presented.     

Studies on the potential of coal fly ash as a heterogeneous catalyst in oxidation of aqueous sodium sulfide solutions with hydrogen peroxide

The potential of fly ash procured form coal-fired thermal power plants was studied as a heterogeneous catalyst in the oxidation of aqueous sodium sulfide solutions with hydrogen peroxide in the temperature range of 303–323 K. The effects of various parameters (source of fly ash, fly ash loading, initial concentrations of sodium sulfide and hydrogen peroxide, electrolyte and deactivation of catalytic effect of fly ash) were studied. For an initial sodium sulfide and hydrogen peroxide concentration of 26·98×10⁻² kmol m⁻³ and 24·28×10⁻² kmol m⁻³ respectively, only 4% (w/v) fly ash loading intensified the rate of oxidation by a factor of 4·52 over that without fly ash at 303 K. The deactivation of the catalytic effect of fly ash was found to be less than 20% even after six repeated uses. The kinetics of aqueous phase decomposition of hydrogen peroxide was also studied in the presence of fly ash in alkaline medium. ©1997 SCI     

Kinetics of the oxidative color removal and degradation of bromophenol blue with hydrogen peroxide catalyzed by copper(II)-supported alumina and zirconia

Copper-supported alumina and zirconia catalysts were prepared and their catalytic activity towards the oxidative color removal and degradation of bromophenol blue with H₂O₂ was investigated. The rate of reaction with alumina is greater than that with zirconia, which ascribed to the increased amount of copper loaded on the catalyst as well as to the increased surface area. A brown intermediate (peroxo-compound), formed at the early stages of the reaction, inhibited the reaction rate. The rate of reaction increased with increase in pH of the medium as well as with added chloride ions. Both catalysts are very stable and can be used for several times without notable loss in their catalytic activities.     

蒽醌法双氧水生产氢化催化剂研究进展

蒽醌加氢催化剂分为镍催化剂和钯催化剂两类。早期集中于对活性组分、添加组分的作用原理和催化剂载体类型的研究;近年则结合出现的新氢化工艺,对催化剂载体的形态和活性组分在载体上分布状况进行了大量的研究。本文较详细地介绍了蒽醌法双氧水生产用催化剂近年来的研究进展。     

Oxidation of dibenzothiophene by hydrogen peroxide in the presence of bis(acetylacetonato)oxovanadium(IV)

In the presence of bis(acetylacetonato)oxovanadium(IV), dibenzothiophene was oxidized by hydrogen peroxide to form sulfoxide and sulfone products. The percentage of dibenzothiophene remaining after the oxidation and the ratio of these oxidation products, as determined by ¹H NMR spectroscopy, was largely dependent on the solvent used. Reactions in acetonitrile consumed more than 99% of the dibenzothiophene in the reaction and yielded the sulfone as the major product. The efficacy of biphasic oxidations performed in heptane and acetonitrile were dependent on the ratio of acetonitrile to heptane with a higher proportion of acetonitrile resulting in greater consumption of dibenzothiophene. After multiple oxidations, all of the dibenzothiophene was removed from the heptane solution.     

Improved performances of electrodes based on Cu-loaded copper hexacyanoferrate for hydrogen peroxide detection

Copper hexacyanoferrate thin films were potentiodynamically deposited on glassy carbon electrodes and employed for the chronoamperometric detection of hydrogen peroxide at 0.0 V vs. SCE. A new experimental procedure based on the intercalation of copper ions inside the structure of the films led to sensors with improved performances. The modified electrode displayed an increased sensitivity to hydrogen peroxide detection together with a wider linear response range and a lower detection limit. Furthermore, even if the electrode response decreased with use, the initial activity could be restored by performing a new intercalation procedure.     

过氧化氢氧化苯制苯酚的催化剂研究进展

综述了过氧化氢直接氧化苯制苯酚过程中相关催化剂的研究进展,重点介绍了含钛、钒、铁、铜的催化剂,同时给出了各种催化剂所达到的收率和选择性及其工业化前景。     

Simple and efficient method for the oxidation of sulfides to sulfones using hydrogen peroxide and a Mo(VI) based catalyst

A simple and efficient method for the oxidation of sulfides to sulfones at room temperature using ammonium heptamolybdate and 30% H₂O₂ is developed. The reactions provide excellent yields within short time, also sensitive functional groups such as allyl, vinyl, propargyl, alcohol, ketone, ester, pyridine and nitrile are found to be tolerated.     

The role of acidity in the catalytic hydroxylation of phenol by hydrogen peroxide

The heterogeneous acid catalysis of the hydroxylation of phenol by hydrogen peroxide was investigated over protonic faujasites containing various amounts of aluminium or partially neutralized. Over strong acids, such as dealuminated protonic faujasites, dihydroxybenzenes result, mainly from an acid catalysed electrophilic aromatic substitution. Over weaker acids, an induction period is observed, the length of which is related to the strength of the acid sites. In that case, the initiation of the reaction occurs by the products of the former acid mechanism, and it is demonstrated using protonated and unprotonated electron transfer agents, that the subsequent autocatalysis involving a redox mechanism, also needs acid catalysis.     

Coordination of Cu(II) and Ni(II) in polymers imprinted so as to optimize amine chelate formation

Molecular imprinting has become an established technique. However, little was done on direct investigation of the sorbents produced. In the present work, en ESR method was used for the investigation of the complex formation processes within the sorbents imprinted with copper(II) and nickel(II). The sorbents were synthesized from a mixture of linear low molecular weight polyethyleneimine oligomers. The composition, structure and distribution of complexes in the resin phase were investigated. The effects of the synthesis conditions, loading degree and water content were examined. The presence of certain copper complexes was found to be a convenient characteristic of the imprinting efficiency. The optimum synthesis conditions for obtaining sorbents imprinted with copper(II) or nickel(II) were identified. The imprinting results in the improvement of the stability of the complexes and the selectivity and working capacity of the sorbents. The imprinted samples are also characterized by a more even distribution of chelating sites. The synthesis conditions and loading by ions allow for the regulation of the ratio between individual complexes and magnetic associates in the resin phase. This is a critical point on the future use of the metal containing imprinted sorbents as catalysts.     

钯催化剂双氧水装置生产初期控制要点分析

以台湾南亚公司双氧水装置为例，介绍了钯催化剂固定床生产初期所遇到的一些常见问题及控制手段。即，在开车初期应通过使用氮气来控制氢化塔的压力，氢气的安全量可控制为工作液流量的5倍，氢化塔温度波动范围控制不超过1℃，加强对工作液组分的控制，保证系统的稳定性。     

过氧化氢生产方法的研究进展

介绍了过氧化氢的生产方法,评述了各种方法的优缺点和目前国际研究发展的最新动向。     

Reduction of Cu(II) by photochemically generated phosphonyl radicals to generate Cu(I) as catalyst for atom transfer radical polymerization and azide-alkyne cycloaddition click reactions

The photoinduced electron transfer reactions of acylphosphine oxide type photoinitiators with Cu(II)Cl₂/N,N,N′,N′′,N′′-pentamethyldiethylenetriamine complex for both atom transfer radical polymerization and copper catalyzed azide-alkyne cycloaddition processes is investigated by laser flash photolysis. The photolytically generated phosphonyl radicals are effective in reducing Cu(II) salts to Cu(I) with rate constants of ∼2 × 10⁹ M⁻¹ s⁻¹.     

SiO2/C/Cu(II)phthalocyanine as a biomimetic catalyst for dopamine monooxygenase in the development of an amperometric sensor

A mesoporous carbon ceramic SiO₂/50 wt% C (S_BET = 170 m² g⁻¹), where C is graphite, was prepared by the sol–gel method. This material was used as matrix to support copper phthalocyanine (CuPc), prepared in situ on their surface, to assure homogeneous dispersion of the electrocatalyst complex in the pores of the matrix. Pressed disk electrodes made with SiO₂/C/CuPc was tested as amperometric sensors for dopamine. Under optimized conditions, at −20 mV vs SCE in 0.08 mol dm⁻³ Britton–Robinson buffer (BRB) solution (pH = 6.0) containing 100 μmol dm⁻³ of H₂O₂, a linear response range for dopamine from 10 up to 140 μmol dm⁻³ was obtained with a sensitivity of 0.63 (±0.006) nA dm³ μmol⁻¹ cm⁻² and the limit of detection LOD was 0.6 μmol dm⁻³. The sensors presented stable response during successive determinations. The repeatability, evaluated in terms of relative standard deviation of 1.37% for n = 10 and 10 μmol dm⁻³ dopamine. The response time was 1 s and lifetime 9 months. Finally, the sensor was tested to determine dopamine in the sample, and gives very good results for its determination. The presence of other phenols like catechol and resorcinol did not show any interference in the detection of dopamine on this electrode, even in the same concentration with the dopamine.     

Development of a new biosensor for mediatorless voltammetric determination of hydrogen peroxide and its application in milk samples

A new biosensor for the voltammetric detection of hydrogen peroxide was developed based on immobilization of catalase on a clinoptilolite modified carbon paste electrode using bovine serum albumin and glutaraldehyde. The biosensor response was evaluated according to electrode composition, reaction time, solution pH and temperature. The voltammetric signals were linearly in proportion to H₂O₂ concentration in the range 5.0 × 10⁻⁶–1.0 × 10⁻³ M with a correlation coefficient of 0.9975. The detection limit is 8.0 × 10⁻⁷ M and the relative standard deviation for 4.0 × 10⁻⁴ M hydrogen peroxide was 1.83% (n = 6). The biosensor exhibited high sensitivity, and it was determined that it could be used for more than 2 months. In addition, the biosensor was successfully applied for the determination of hydrogen peroxide in milk samples.     

Fuel cell grade hydrogen from methanol on a commercial Cu/ZnO/Al2O3 catalyst

This paper presents the results of experiments of the methanol decomposition reaction catalyzed by a commercial Cu/ZnO/Al₂O₃ in the absence and presence of water. Methanol decomposition of 100% in the absence of water was obtained at 290 °C and a space velocity of 2 cm³/h g cat. At these conditions, the hydrogen yield was 1.9–2.0. Water addition to the feed increased the yield of hydrogen and reduced the formation of: dimethyl ether; methyl formate and methane. The variation of the catalyst’s activity and selectivity with time, temperature and feed composition was consistent with previous studies of methanol–steam reforming and water–gas shift reaction, however, this appears to be the first study over the same catalyst of methanol decomposition and methanol–steam reforming. XPS analysis of used catalyst samples and time on-stream data showed that the Cu²⁺ oxidation state of copper favors methanol decomposition, and we propose that the deactivation of the catalyst is mainly caused by the change in the oxidation state of copper.     

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.     

过氧化氢催化活化体系及其在危化品消毒中的应用

随着我国化工行业的飞速发展,危险化学品事故时有发生,洗消成为化学应急处置的关键技术环节之一。本文综合考虑化学品的毒性、产销量、洗消的必要性等因素,初步建立了潜在危化品洗消污染物谱系;同时,在论述洗消原理及洗消剂的基础上,重点探讨了无机催化剂和有机活化剂对过氧化氢的催化活化原理。无机催化体系主要包含金属离子、金属盐和金属配位体,活性成分为·OH、¹O₂等;有机活化剂主要有酯类、酰胺类、脒类、胍类和腈类等,活性成分为过氧酸或过氧亚酰胺酸。各类体系在危化品消毒处置和漂白印染等领域都有研究和应用,有望成为未来危化品消毒剂的发展主体。本文可为过氧化物类消毒剂产品的研发提供一定的理论依据,为应对危化品事故应急救援洗消需求奠定技术基础。