Overall kinetics of hydrogen peroxide formation by direct combination of H2 and O2 in a microreactor

Direct combination (DC) of hydrogen and oxygen over a heterogeneous catalyst in a microreactor is a novel method of producing hydrogen peroxide with significant economic advantages over the currently dominant anthraquinone autoxidation method. A kinetic rate expression for this reaction is required for design and modeling of a microreactor for the DC process. Since the formation of H₂O₂ by the DC process involves four simultaneous reactions (synthesis of H₂O₂, synthesis of water, reduction of H₂O₂ by H₂ and decomposition of H₂O₂), the overall rate expression must take into account each of these reactions. In this work, we describe a reactor model that involves the four component reactions as well as mass transfer effects. The model is verified by comparing the predicted reactor performance with experimental data. In addition to providing a tool for reactor design, the model also confirms important assumptions regarding the mechanism of DC reaction.     

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。     

硫酸铜催化过氧化氢氧化联氨实验

联氨是电厂常用的锅炉除氧剂,因此电厂在冲洗、保养、换水等操作中会产生大量含联氨废水。而联氨是一种环境污染物,直接排放含有联氨的废水会使得水体COD值升高。实验中发现,通过硫酸铜催化过氧化氢氧化联氨的方法去除废水中的联氨效果不错。处理之后的废水pH值接近中性,可以直接排放,而无需再进行加酸调节。     

非均相湿式过氧化氢氧化H-酸废水的研究

为研究催化剂对湿式过氧化氢氧化印染废水效果的影响,采用共沉淀法制备了TiO2-CeO2催化剂,并用浸渍法制备了不同铁负载量的Fe/TiO2-CeO2系列催化剂。以过氧化氢湿式催化氧化法处理COD=10 125 mg/L的H-酸模拟印染废水,结果表明:以TiO2-CeO2催化剂处理水样,当催化剂质量浓度为4 g/L,n(Ti)∶n(Ce)=9∶1,水样初始pH=5,反应温度80℃,反应时间2 h,COD去除率达44.3%;以Fe/TiO2-CeO2处理水样,当催化剂质量浓度为4 g/L,n(Ti)∶n(Ce)=9∶1,w(Fe)=2.0%,在水样初始pH=5,反应温度100℃,反应时间1.5 h的条件下,COD去除率可达86.9%。     

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。     

New catalytic systems for selective oxidation of aromatic compounds by hydrogen peroxide

Some new water-soluble catalytic systems based on iron complexes of polyethylene oxide and block copolymers of ethylene oxide and propylene oxide functionalized by catechol or β-cyclodextrin have been developed. These complexes were examined as catalysts for biomimetic hydroxylation of benzene and phenol by hydrogen peroxide. It is shown that the introduction of β-cyclodextrin into the polyethylene oxide molecule is favourable for rate and selectivity of hydroxylation of aromatic compounds in a two-phase system.     

催化湿式过氧化氢氧化预处理有机磷农药废水的研究

以自制Fe2O3-Ce O2/γ-Al2O3为催化剂,采用催化湿式过氧化氢氧化法(CWPO)预处理有机磷农药废水,通过单因素和正交试验研究了过氧化氢投加量、起始p H、反应温度和反应时间对COD的去除效果及影响规律。结果表明,反应最优条件为H2O2投加量2 m L、起始p H=5、反应温度80℃、反应时间40 min,在此条件下COD的去除率可达85.8%,可生化性提高到B/C=0.43。运用一级动力学模型和Arrhenius经验公式,建立了催化湿式过氧化氢氧化降解COD的动力学方程。     

双氧水催化氧化合成频哪醇工艺条件优化

以四甲基丁烯为原料,双氧水为氧化剂,采用活性高、选择性强的复合过渡金属作催化剂,合成高纯度的频哪醇,研究了反应温度、分子筛催化剂Pd/Pt复配量、反应时间等因素对频哪醇收率影响。结果表明,最佳合成条件为:Pd-Pt/Hβ作为复合催化剂,铂∶钯=4∶1(摩尔比),原料配比四甲基丁烯∶30%双氧水∶催化剂=1∶1.4∶0.015(质量比),反应温度75℃,反应4 h,频哪醇产品收率可达90%。本工艺具有产率高、各原料及催化剂无毒、生产过程无三废排放、成本低等特点,具有广阔的市场推广应用前景。     

双氧水催化氧化合成频哪醇工艺条件优化

以四甲基丁烯为原料,双氧水为氧化剂,采用活性高、选择性强的复合过渡金属作催化剂,合成高纯度的频哪醇,研究了反应温度、分子筛催化剂Pd/Pt复配量、反应时间等因素对频哪醇收率影响。结果表明,最佳合成条件为:Pd-Pt/Hβ作为复合催化剂,铂∶钯=4∶1(摩尔比),原料配比四甲基丁烯∶30%双氧水∶催化剂=1∶1.4∶0.015(质量比),反应温度75℃,反应4 h,频哪醇产品收率可达90%。本工艺具有产率高、各原料及催化剂无毒、生产过程无三废排放、成本低等特点,具有广阔的市场推广应用前景。     

氢氧直接合成过氧化氢技术的工业化概况

简单介绍了氢氧直接合成过氧化氢(DSHP)技术的优缺点,结合有关专利分别详细介绍了杜邦公司和Evonik–Headwaters公司的DSHP工艺。最后指出,DSHP是一种值得广泛而深入进行研究和开发的、代表过氧化氢合成工艺未来发展方向的绿色合成工艺。     

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.     

不同沉淀剂制备Pd/TiO_2催化剂对直接合成过氧化氢催化性能的影响

以不同沉淀剂Na_2CO_3、NH_3·H_2O和尿素,通过沉积-沉淀法制备催化剂Pd/TiO_2-CD(X),使用CO脉冲、孔结构分析、H_2-TPR、XRD等表征手段分析催化剂的性质,讨论不同沉淀剂制备的催化剂Pd/TiO_2-CD(X)对直接合成过氧化氢催化性能的影响。结果表明,催化剂Pd/TiO_2-CD(Na_2CO_3)有较高的金属分散度、较小的Pd晶粒粒径、较大的比表面积和平均孔容,分散度为17.22%,晶粒粒径为5.42 nm,比表面积为54.136 m²/g,平均孔容为0.437 cm2/g,平均孔容为0.437 cm³/g,有较好的催化性能,产率达到852.3 mmolH_2O_2/(g_(Pd)·h)。     

A perovskite-type KNbO3 nanoneedles based biosensor for direct electrochemistry of hydrogen peroxide

A KNbO₃ nanoneedles (KNs) based hydrogen peroxide (H₂O₂) biosensor was first proposed. Perovskite-type KNs can directly catalyze H₂O₂. The mechanism can be explained by Molecular Orbital Principles, with the formation of σ-bonding between the e_g orbital of surface niobium ions and surface adsorbed oxygen-related intermediate species. Direct electron transfer between the Horseradish peroxidase (HRP) and electrode surface was achieved. Co-catalyst system of both HRP and KNbO₃ was introduced to the oxidation of H₂O₂, thus the as-prepared biosensor exhibited high sensitivity (750 μA mM⁻¹ cm⁻²) and ultrafast response (1–2 s) to H₂O₂. Therefore, KNs provide a promising material for enzymes assembly and sensing application.     

Prediction of the chemical equilibrium constant for peracetic acid formation by hydrogen peroxide

An expression for temperature dependence of the chemical equilibrium constant for peracetic acid synthesis from acetic acid and hydrogen peroxide in an aqueous solution, derived on the basis of the van't Hoff and Kirchhoff equations, was proposed. The reverse trend of the chemical equilibrium constant vs. temperature was apparent when the predicted values of the constant were compared with experimental ones taken from the literature. However, using the proposed model to calculate the chemical equilibrium constant resulted in better prediction of the equilibrium composition for peracetic acid synthesis at 297.5 K than using experimental data from the literature.     

直接合成过氧化氢Pd/TiO2催化剂的制备

常温和常压下,氢氧直接合成过氧化氢过程中,采用浸渍沉淀法制备Pd/TiO₂催化剂。考察了pH、搅拌时间t₁、静置时间t₂及焙烧温度等制备条件对催化剂活性的影响。正交实验结果表明,影响催化剂活性的顺序为：pH＞搅拌时间＞焙烧温度＞静置时间。在pH=8、t₁=0、t₂=0和（250～300）　℃焙烧3 h的条件下,制备的催化剂活性最好。     

Bimetallic catalysts for the catalytic combustion of methane using microreactor technology

Pt–W and Pt–Mo based catalysts were evaluated for methane combustion using a sandwich-type microreactor. Alumina washcoated microchannels were impregnated with platinum in combination with and promoted with tungsten and molybdenum and compared with commercially available Pt/Al₂O₃ catalysts. Catalysts were tested in the range of 300–700 °C with flow rates adjusted to GHSV of 74,000 h⁻¹ and WHSV of 316 L h⁻¹ g⁻¹. Catalysts containing tungsten were found to be the most active and the most stable possibly due to a metal interaction effect. A Pt–W/γ-Al₂O₃ containing 4.6 wt% Pt and 9 wt% W displayed the highest activity with full conversion at 600 °C and a selectivity to CO₂ of 99%.     

双氧水装置的化学清洗技术

对福州一化化学品有限公司双氧水装置新、旧系统投产前的清洗实例表明,该法对蒽醌法生产过氧化氢的装置进行清洗,可满足双氧水生产的要求。介绍了双氧水的生产流程、清洗原理和工艺。     

过氧化氢催化氧化甲基叔丁基醚脱硫

利用过氧化氢为氧化剂,甲酸为催化剂,对甲基叔丁基醚进行氧化脱硫实验。分别考察反应温度、甲酸用量和过氧化氢用量对反应的影响,同时对最佳反应体系进行短暂寿命实验。结果表明,最佳反应条件为：反应温度80 ℃,甲酸用量为甲酸与过氧化氢总质量的1.0%,过氧化氢用量为反应物总质量的15%,此条件下连续反应12 h,催化体系可以保证产品硫含量低于50 ng·μL^-1。     

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.     

Comparison of catalytic decomposition of hydrogen peroxide and catalytic degradation of phenol by immobilized iron oxides

Immobilized iron oxides on silica matrixes in fluidized bed reactors, including SiG1, SiG2, C1, and the commercial catalyst FeOOH, were used in the catalytic decomposition of H₂O₂ and the catalytic degradation of phenol. They were characterized using XRD, SEM, N₂-sorption, and elucidation of the kinetics of dissolved iron by oxalic acid in dark surroundings. XRD patterns reveal that SiG1, SiG2, and C1 exhibit amorphous structures, and FeOOH exhibits the poor crystallinity of goethite. The SEM images reveal that the surfaces of all the iron oxides are smooth and that the iron oxides are aggregated by the iron oxide floc. The N₂-sorption isotherm indicates that SiG1 and SiG2 are non-porous materials, and that C1 and FeOOH are typical type II and typical type IV materials, respectively. A kinetic model for iron dissolved by oxalic acid is established. The order of apparent first-order dissolution rate constants (k_c) is SiG1 > SiG2 > FeOOH  C1. The immobilized iron oxides, SiG1 and SiG2, are weakly bonded to the support (silica sand) in the presence of oxalic acid. The decomposition of H₂O₂ follows pseudo-first-order kinetics. The number of active sites for the decomposition of H₂O₂ is similar among all iron oxides at a particular k_app (1.8 × 10⁻³ min⁻¹). There are no interactions between phenol and iron oxides in the absence of hydrogen peroxide at pH 4. SiG1 and SiG2 exhibit much higher catalytic activities in phenol degradation than either C1 or FeOOH. The reactivity of iron oxides in catalyzing the phenol degradation by H₂O₂ relates to the tendency of iron to be dissolved by oxalic acid. The intermediates of phenol degradation, such as catechol and oxalic acid, promote the dissolution of iron from SiG1 and SiG2 by reductive and non-reductive pathways and lower the pH values. The catalyses of SiG1 and SiG2 involve heterogeneous and homogeneous reactions.