氢氧直接合成过氧化氢催化剂研究进展

从性组分和载体两方面,总结了近年来氢氧直接合成过氧化氢催化剂的研究进展,重点介绍了Au-Pd、Pt-Pd双金属催化剂在氢氧直接合成过氧化氢中的应用研究。指出负载型纳米双金属催化剂将是氢氧直接合成过氧化氢催化剂研究的发展方向。摘要：从活性组分和载体两方面，总结了近年来氢氧直接合成过氧化氢催化剂的研究进展，重点介绍了Au—Pd、Pt—Pd双金属催化剂在氢氧直接合成过氧化氢中的应用研究。指出负载型纳米双金属催化剂将是氢氧直接合成过氧化氢催化剂研究的发展方向。     

氢氧直接合成过氧化氢用催化剂的研究进展

过氧化氢（H₂O₂）是一种高效的绿色氧化剂,广泛应用于化学品合成、印染纺织、污水处理等领域。近年来,氢氧直接合成过氧化氢作为一种简单、环保、原子效率高的合成方法,成为一大研究热点。本文系统性地介绍了近年来氢氧直接合成过氧化氢催化剂的催化反应机理,负载金属的不同结构和性质对直接合成过氧化氢的催化性能与作用机理,重点讨论了与催化剂载体相关的载体结构、载体酸性、载体添加物、载体与金属相互作用等方面对反应活性和选择性的影响。最后对比了近年来直接合成过氧化氢用催化剂的催化性能,认为合成高选择性、高产率的催化剂仍是未来直接合成过氧化氢工业化应用的发展方向。     

国外氢氧直接化合法制过氧化氢工艺研究开发新进展

介绍了近几年国外氢氧直接化合法制过氧化氢工艺技术研究开发进展情况,重点介绍有关专利技术。     

氢氧直接合成法制备过氧化氢过程中的催化剂探究

通过氢氧直接合成过氧化氢法常见应用于印染纺织、污水处理以及化学合成等方面。作为一种简单高效且环保的绿色氧化剂,过氧化氢的合成成为了社会研究热点。通过对过氧化氢氢氧直接合成的路径进行研究,并对这一过程中的催化剂金属进行分析,包括单金属以及双金属。随后对催化剂的载体进行研究分析,分析载体酸性、表面物质以及掺杂物等对催化剂性能所产生的影响,发现今后过氧化氢直接合成过程中催化剂的发展方向将定位为高选择性与高产率。     

由氢与氧直接合成过氧化氢研发新进展

综述了2016年以来国内外由氢与氧直接合成过氧化氢的研发进展,其中主要包括所用催化剂性能提高、合成装置和方法改进以及合成反应机理。介绍了多种不同催化金属(仍以Pd为主)、不同载体的催化剂和催化金属纳米颗粒(簇)形态及粒径、载体多种选择等对提高催化性能尤其是生成过氧化氢选择性的影响,以期获得更理想的催化剂。简要介绍了不同形式反应器和不同反应条件对反应结果尤其是反应选择性的影响。最后介绍了一些学者对直接合成过氧化氢过程中化学反应途径和机理所进行的较为详细和深入的研究以及所取得的结果和新发现。     

国外氢氧直接化合法制过氧化氢工艺研究开发新进展

介绍了近几年国外氢氧直接化合法制过氧化氢工艺技术研究开发进展情况，重点介绍有关专利技术。     

国外由氢氧直接催化合成过氧化氢研究概况

概述了国外由氢氧直接催化合成过氧化氢的研究近况;详述了以溴化物为促进剂由氢氧直接催化合成过氧化氢的工艺过程与试验结果。此外,还对合成所用某些催化剂的制备方法作了介绍。     

反应介质对氢氧直接合成过氧化氢的影响研究

以超声浸渍法制备的PdO／γ-Al2O3-U为催化剂,考察不同无机酸、不同硫酸浓度对氢氧直接合成过氧化氢的影响。结果表明：酸性介质有利于氢氧直接合成过氧化氢,当反应介质为H2SO4溶液时,氢氧直接合成过氧化氢收率好于其他,其最佳浓度为0．35mol／L。     

氢氧直接合成过氧化氢贵金属催化剂的研究

采用浸渍法制备了一系列负载型钯催化剂，用于催化氢气和氧气直接合成过氧化氢的反应。分别考察了钯负载节、溶剂、载体预处理对反应的影响；结合XPS分析推断了催化剂活性组分价态。结果发现钯最佳负载量为1．88％（质量分数）；氢气在溶剂中的溶解度越大其反应转化率也越高，其中甲醇和丙酮都是良好的溶剂；载体经过卤化铵预处理可大幅度地提高催化剂的选择性；金属态钯为具有催化活性的价态。     

Epoxidation of propylene and direct synthesis of hydrogen peroxide by hydrogen and oxygen

The autoreduction of palladium–platinum-containing titanium silicalite leads to an effective catalyst for the epoxidation of propylene to propylene oxide by O₂ in the presence of H₂. The one-pot reaction is favoured compared to the two-step reaction path.     

Direct synthesis of hydrogen peroxide from hydrogen and oxygen over palladium-exchanged insoluble heteropolyacid catalysts

Palladium-exchanged insoluble heteropolyacid (Pd_0.15Cs_xH_2.7?xPW₁₂O₄₀) catalysts were prepared with a variation of cesium content (x = 2.0, 2.2, 2.5, and 2.7), and were applied to the direct synthesis of hydrogen peroxide from hydrogen and oxygen. Pd_0.15Cs_xH_2.7?xPW₁₂O₄₀ showed high catalytic performance even in the absence of H₂SO₄ additive, indicating that Pd_0.15Cs_xH_2.7?xPW₁₂O₄₀ acted as an efficient catalyst and served as an alternate acid source in the reaction. The catalytic performance of Pd_0.15Cs_xH_2.7?xPW₁₂O₄₀ increased with increasing surface acidity of the catalyst. Among the catalysts tested, Pd_0.15Cs_2.5H_0.2PW₁₂O₄₀ catalyst with the largest surface acidity showed the highest yield for hydrogen peroxide.     

Direct synthesis of hydrogen peroxide from hydrogen and oxygen over a Pd core-silica shell catalyst

Pd core–silica shell particles (Pd@SiO₂) were prepared by encapsulating Pd colloids with a silica shell through the Stöber method. The palladium core particles were well dispersed (Dispersion = 43%) and had uniform size (4 nm) and shape inside the porous silica shell. Pd@SiO₂ showed good catalytic activity (554 mmol H₂O₂/g Pd·h) for the direct synthesis of H₂O₂, which was better than those of impregnated Pd catalysts (Pd/SiO₂ and Pd/Al₂O₃). It is expected that the stabilization of less coordinated Pd crystals in a highly dispersed state by core-shell formation is effective for the improvement of H₂O₂ production.     

Direct synthesis of hydrogen peroxide from hydrogen and oxygen: An overview of recent developments in the process

Hydrogen peroxide (H₂O₂) is an important commodity chemical and its demand is growing significantly in the chemical synthesis due to its “green” character. Currently, H₂O₂ is produced almost exclusively by the anthraquinone auto-oxidation (AO) process. The AO process involves indirect oxidation of hydrogen and thus avoids potentially explosive H₂/O₂ mixture. However, this large-scale process presents significant safety issues associated with the transport of bulk H₂O₂. Moreover, the AO process can hardly be considered an environmentally friendly method. In view of this, more economical and environmentally cleaner routes have been explored for the production of H₂O₂. The liquid-phase catalytic direct synthesis of H₂O₂ from H₂ and O₂ offers an attractive green technology for small-scale/on-site production of H₂O₂. However, the direct synthesis process suffers from two major drawbacks: (i) potential hazards associated with H₂/O₂ mixtures and (ii) poor selectivity for H₂O₂ because the catalysts used for H₂O₂ synthesis are also active for its decomposition and hydrogenation to water as well as for H₂ combustion. These serious issues and the recent developments in the direct H₂O₂ synthesis are discussed in this review. The roles of protons (H⁺) and halide ions in promoting the H₂O₂ selectivity are also examined in detail.     

A study of the palladium size effect on the direct synthesis of hydrogen peroxide from hydrogen and oxygen using highly uniform palladium nanoparticles supported on carbon

Highly monodisperse carbon-supported palladium nanoparticles with controllable size (3 nm, 6.5 nm, 9.5 nm) were prepared using a simple colloidal method, and the size dependence of the catalytic performance for the direct synthesis of hydrogen peroxide from hydrogen and oxygen was studied. Smaller-sized supported palladium nanoparticles showed both higher conversion of hydrogen and selectivity for hydrogen peroxide, compared to larger-sized supported particles. Among the catalysts tested, 3-nm Pd nanoparticles supported on carbon showed the highest yield for hydrogen peroxide because of the small size and high crystallinity.     

Direct production of hydrogen peroxide from oxygen and hydrogen applying membrane-permeation mechanism

Direct synthesis of hydrogen peroxide is conducted using a palladium membrane reactor. The palladium membrane is prepared on the external surface of the porous α-alumina tubing, by electroless plating (ELP) or chemical vapor deposition (CVD). Thus prepared membrane is immersed into aqueous reaction solution. Hydrogen is supplied from inside of the palladium membrane, while oxygen was bubbled in the reaction solution. Both reacted at the surface of the membrane to produce hydrogen peroxide. Hydrogen peroxide is produced steadily for more than 80 h and the selectivity based on the amount of reacted hydrogen was estimated to be ca. 50%. The reactor performance is investigated in correlation with membrane properties and the hydrogen/oxygen supply pressures.