电化学漂白的研究进展

对电化学漂白的研究进行了简要的综述,包括电化学含氯漂白、电化学氧气漂白和电化学产生过氧化氢漂白。重点对电化学氧气漂白机理和过渡金属催化剂在电化学氧气漂白中的作用进行了概述。     

紫胶漂白的研究(第三报) 改进的漂白技术

改进的漂白技术本研究所不久前报道了 Parsad 和 Khanna 试验单用过氧化氢或过氧化氢与次氯酸钠结合使用来漂白紫胶,但是,只获得部分的成功。Murray 曾报道过氧化氢的温和的氧化作用可通过某种金属催化剂和螯合剂而加强。与过氧化氢一道试用过的活化剂有硫酸亚铁、硫酸铜、醋酐、硫酸铜——吡啶-2-羧酸等。只有用最后提到的催化系统,才取得一些结果。     

过氧化氢催化分解的研究进展

本文概述了过氧化氢催化分解的研究现状及进展,包括过氧化氢酶、仿酶、杂多酸盐、复合体系催化剂等高效能并能重复使用的研究状况。最后指出了今后研究重点:开发新型环保、廉价、重复使用良好的催化剂。     

卡尔斯鲁理工学院开发用于制备过氧化氢的新型钯催化剂

正通过详查用纳米粒子催化剂将氢和氧转化为过氧化氢的过程,研究人员发现了有关驱动该过程机理的新信息,从而提供了可廉价制备过氧化氢的工业催化剂设计。过氧化氢在商业上通常被用于漂白或用作消毒剂和氧化剂。据全球工业分析家网站报道,到2022年过氧化氢的产量将超过550万t。当前过氧化氢主要通过能耗大、步骤多的蒽醌法制备,而直接从氢气和氧气合成该化合物只需要极少的     

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ZSM系列和TS系列催化剂、含铁和含铜催化剂以及钒取代杂多酸盐催化剂，同时给出了各种催化剂所达到的收率和选择性；最后探讨了这些新型催化剂的工作应用前景以及今后研究的方向。     

一种少氯漂白精制漂白紫胶的工艺

在当前精制漂白紫胶常规漂白方法的基础上,为了得到一种精制漂白紫胶的少氯漂白工艺条件,采用次氯酸盐(H)和过氧化氢漂白(P)相结合的两段漂白方法对紫胶进行漂白制得精制漂白紫胶。通过正交试验探讨了精制漂白紫胶HP漂白工艺过程中次氯酸盐用量,过氧化氢用量,过氧化氢漂白温度及其过氧化氢漂白时间等。结果表明,利用次氯酸盐和过氧化氢漂白相结合的漂程,并且在次氯酸盐用量为5.5%,过氧化氢用量为11.0%,过氧化氢的漂白温度为65℃以及过氧化氢漂白时间为1h时,制得的精制漂白紫胶性能最佳,其主要质量指标为:加纳颜色11号,酸值81.1 mg/g,热乙醇不溶物0.15%,冷乙醇可溶物97.5%,氯含量0.61%,蜡含量0.05%,热硬化时间368s。     

废纸脱墨浆H_2O_2漂白的影响因素

研究了脱墨浆过氧化氢漂白特性。研究结果表明 ,脱墨浆采用过氧化氢漂白时 ,过氧化氢的无效分解的程度大。脱墨浆采用过氧化氢漂白时 ,过氧化氢同氢氧化钠用量比为 1∶0 .6,漂白反应时间为 2h ,漂白反应温度为 70℃ ,浆浓为 1 0 %比较合适     

杂多酸盐催化合成对苯二酚和邻苯二酚

用十六烷基吡啶杂多酸盐作催化剂，用苯酚和过氧化氢为原料制备对苯二酚和邻苯二酚，考察了催化剂组成、溶剂、反应时间等反应条件对苯酚差劲基化的影响，在实验范围内苯酚的转化率可达13%，产品中只有对苯二酚和邻苯二酚。     

过氧化氢用于废水处理的前景

过氧化氢又名双氧水,分子式为 H_2O_2,是一种重要的化工产品,主要用于纺织品、纸浆等的漂白、化学产品的合成和废水的处理。过氧化氢作为处理废水的氧化剂,与其他废水处理的氧化剂相比具有很多明显的优点:1.在催化剂或超声波辅助作用下,能够产生具有极强氧化     

环己烯液相环氧化催化剂的研究进展

烯烃环氧化是一类重要的有机合成反应 ,其中环己烯经催化环氧化制得的环氧环己烷可广泛用作合成精细化学品的原料。阐述了Mo(Ⅵ )、V(Ⅴ )、Ti(Ⅳ )络合物、过渡金属卟啉络合物等环氧化用催化剂以及无机过氧酸盐、过氧化氢、分子氧、有机过氧酸及烷基过氧化氢等常用氧化剂在环己烯液相环氧化中的应用研究进展。还介绍了无机固体负载催化剂和高分子负载催化剂的负载化方法。最后展望了烯烃环氧化的研究开发趋势。     

An evaluation of the effectiveness of applying a gelatin–copper complex in the low-temperature bleaching of cotton with hydrogen peroxide

A gelatin–copper complex was prepared and then added as catalyst to a hydrogen peroxide bleaching bath. Cotton fabric was bleached with the new system at low temperature (70 °C). The effects of the gelatin–copper complex on the whiteness, capillary effect, damage, and bleaching rate of the bleached fabric and on the decomposition ratio of hydrogen peroxide were evaluated. These effects were compared with the effectiveness of traditional high-temperature bleaching and low-temperature bleaching without the gelatin–copper complex. The results showed that the gelatin–copper complex enhances the bleaching effectiveness of hydrogen peroxide. The whiteness of cotton fabric bleached with the catalytic complex is comparable with the whiteness achieved with a conventional peroxide system. The catalytic bleaching technology not only realises low-temperature and low-alkali bleaching of cotton with hydrogen peroxide but also reduces fabric strength loss, which meets the requirements of industry for continued development of the wet processing of textiles.     

Influence of hydrogen peroxide-based bleaching agents on the bond strength of resin–enamel/dentin interfaces

This study evaluated the effect of different bleaching techniques on the bond strength of pre-existing adhesive restorations in enamel and dentin. Hydrogen peroxide-based bleaching gels with different concentrations (7.5% and 35%) were used on composite restorations of Adper Single Bond 2 (3M/ESPE, St. Paul, USA) and Filtek Z250 (3M/ESPE, St. Paul, USA). Twenty human third molars were randomly divided into 8 groups: GE—enamel control; GE7.5—bleaching using 7.5% hydrogen peroxide; GE35—bleaching using 35% hydrogen peroxide; GE 7.5+35—bleaching using 7.5% and 35% hydrogen peroxide; GD—dentin control; GD7.5—7.5% hydrogen peroxide; GD35—35% hydrogen peroxide; and GD 7.5+35—7.5% and 35% hydrogen peroxide. Bleaching was performed using long clinical application-time to low concentration gel, and short clinical application-time to high concentration gel. Unbleached specimens were stored in artificial saliva for 14 days. Specimens subject to micro-shear testing and data were analyzed by Analysis of Variance and Tukey's test (p=0.05). Enamel micro-shear bond strength was reduced after 7.5% hydrogen peroxide and after association of 7.5% and 35% hydrogen peroxide. Bleaching treatment altered dentin bond strength only when using 7.5% hydrogen peroxide. The results suggest that the bond strength of the restorations was influenced by the clinical extent of bleaching-gel application time and was not dependent on bleaching-gel concentration.     

Zur Problematik des Blondierens menschlicher Haare

Problems Concerning Bleaching of Human Hair The bleaching of human hair using alkaline hydrogen peroxide involves a chemical change of the coloring pigments eumelanin and pheomelanin – the bleaching proper – as well as a chemical effect on the keratinous material – i. e. hair damage. The oxidation by alkaline hydrogen peroxide may proceed by different mechanisms and via different intermediates. It is discussed whether the reactions leading to bleaching or hair damage, respectively, show preferences for particular mechanisms of hydrogen peroxide decomposition.     

Formation of Hydroxyl Radicals from Hydrogen Peroxide and their Effect on Bleaching of Mechanical Pulps

The formation of hydroxyl radicals from hydrogen peroxide in alkaline solutions and under the conditions of hydrogen peroxide bleaching of pulps was investigated. The results lend support to the generally accepted view that the decomposition of alkaline hydrogen peroxide is catalyzed by redox processes involving transition metal ion species. The formation of hydroxyl radicals by one-electron reduction of hydrogen peroxide in this process is believed to be catalyzed primarily by mononuclear transition metal ion complexes, polynuclear species being far less efficient in this respect. It was found that a certain formation of hydroxyl radicals during alkaline hydrogen peroxide bleaching of pulp may have a beneficial effect on the final brightness. This finding is ascribed to the cleavage of crosslinks in the rigid lignin matrix which facilitates penetration of the bleaching reagent(s). Silicate does not appreciably suppress the formation of hydroxyl radicals in alkaline hydrogen peroxide solution. The stabilizing effect of this additive is probably due to deactivation of finely dispersed colloidal particles of metal hydroxides and hydrated oxides which decompose hydrogen peroxide to give mainly molecular oxygen and water.     

木素醌型发色基团与过氧化氢反应特性的研究进展

概述了木素醌型发色基团与过氧化氢反应特性的研究进展。指出木素中醌型发色基团,特别是邻醌结构是高得率浆颜色的主要来源,只要能有效提高过氧化氢破坏木素中醌型发色基团的效率,就能得到高白度的高得率浆,降低高得率浆过氧化氢漂白成本。建议利用木素模型物与过氧化氢反应,并研究其反应特性,为高得率纸浆过氧化氢漂白的应用研究积累一定的理论基础。     

The final bleaching of eucalypt kraft pulps with hydrogen peroxide: relationship with industrial ECF bleaching history and cellulose degradation

BACKGROUND: The process of chemical pulp bleaching is based for the most part in chlorine dioxide within elemental chlorine free (ECF) technologies. The use of greener alternatives such as bleaching with hydrogen peroxide (P stage) is not widely used owing to selectivity concerns related to transition metal‐catalyzed decomposition reactions. Even at the final stage where peroxide is recognized to boost brightness and improve the brightness stability of the bleached pulp, cellulose degradation often overcomes these advantages. This paper presents the results of studies intended to optimize final peroxide bleaching performance considering two standard ECF industrial bleaching sequences: the conventional DED and the ECF‐light OQ(PO)D (stages name: D—chlorine dioxide; E—alkaline extraction; O—oxygen; Q—chelation, (PO)—hydrogen peroxide pressurized with oxygen). RESULTS: The addition of sodium diethylenetriaminepentaacetate (DTPA) was the most effective option in terms of DED pulp bleachability and selectivity with hydrogen peroxide, as well as in terms of brightness reversion. As regards the OQ(PO)D pulp, a blend of DTPA and magnesium was the most beneficial in those properties. CONCLUSIONS: The choice of the best hydrogen peroxide stabilizer, among the different tested combinations of magnesium and chelants (EDTA and DTPA) studied, in terms of pulp bleachability, bleaching selectivity and brightness reversion is dependent on the impact of the previous bleaching stages on metallic nature and content. The pulp Mg/(Fe + Cu) ratio was highlighted as a process parameter controlling cellulose degradation in peroxide bleaching. Copyright © 2010 Society of Chemical Industry     

Enhanced PAA bleaching of cotton by incorporating a cationic bleach activator

Peracetic acid is a well-known alternative to hydrogen peroxide as a bleaching agent for cotton. In this study, a novel cationic bleach activator, N -[4-(triethylammoniomethyl)benzoyl]butyrolactam chloride, was used in combination with peracetic acid to investigate the enhancement of cotton bleaching efficiency. The effects of temperature, pH and concentrations of activator and peracetic acid on the bleaching performance were studied using a statistical design of experiment. Adding activator to a peracetic acid bleaching bath improved the resultant whiteness of the substrate and at optimal conditions produced less fibre damage than when peracetic acid was used alone. In addition, the bleaching performance of both peracetic acid and hydrogen peroxide in the presence of activator was compared. In the absence of activator, the peracetic acid performance was considerably superior to a conventional hydrogen peroxide bleach system in which no bleach activator is present. However, addition of activator to the hydrogen peroxide bath increased the whiteness to a level comparable to peracetic acid.     

非硅过氧化氢稳定剂在桉木TMP浆漂白过程中的应用研究

以桉木热磨机械浆(TMP浆)为研究对象, 探讨了非硅过氧化氢漂白稳定剂G1、G56替代硅酸钠用于桉木TMP浆漂白的可行性, 并对漂白工艺条件进行了优化。结果表明:桉木TMP浆过氧化氢漂白采用稳定剂G1、G56替代硅酸钠是可行的。在浆浓(质量分数)20%、H₂O₂用量9.0%(以绝干浆质量计,下同)条件下优化的漂白工艺条件为:G1用量0.5%, G56用量0.5%, NaOH用量5.85%, 温度90 ℃和时间30 min。在此工艺条件下桉木TMP浆单段过氧化氢漂白后, 浆的白度达到77.47% (ISO), 比原浆白度高38.89个百分点, 比2%硅酸钠用量下漂后浆的白度高1.75个百分点, 与2%硅酸钠和2%DTPA同时用作稳定剂的白度(79.88%(ISO))相当。     

Dyeing in catalase-treated bleaching baths

The conventional rinsing after bleaching to remove the residual hydrogen peroxide, harmful to the reactive colorants, was replaced by enzymatic cleaning using catalases. The catalase-treated bleaching liquor was reused for dyeing. Though no hydrogen peroxide was detected after the enzymatic process, the bleaching bath composition caused unacceptable colour changes on dyed fabrics. By varying the parameters of the dyeing process – dye, salt, alkali and enzyme concentrations – the colour difference could be reduced significantly and a good dyeing result could be achieved.