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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. 相似文献
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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。 相似文献
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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%。 相似文献
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New catalytic systems for selective oxidation of aromatic compounds by hydrogen peroxide 总被引:4,自引:0,他引:4
E. A. Karakhanov T. Yu. Filippova S. A. Martynova A. L. Maximov V. V. Predeina I. N. Topchieva 《Catalysis Today》1998,44(1-4):189-198
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. 相似文献
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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。 相似文献
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《化学推进剂与高分子材料》2015,(6):14-23
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。 相似文献
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Epoxidation of propylene and direct synthesis of hydrogen peroxide by hydrogen and oxygen 总被引:2,自引:0,他引:2
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. 相似文献
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《应用化工》2022,(2)
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)。 相似文献
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A perovskite-type KNbO3 nanoneedles based biosensor for direct electrochemistry of hydrogen peroxide
Bin Cai Minggang Zhao Ye Wang Yu Zhou Hui Cai Zhizheng Ye Jingyun Huang 《Ceramics International》2014
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 eg 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. 相似文献
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Prediction of the chemical equilibrium constant for peracetic acid formation by hydrogen peroxide 总被引:1,自引:0,他引:1
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. 相似文献
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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%. 相似文献
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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. 相似文献
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Comparison of catalytic decomposition of hydrogen peroxide and catalytic degradation of phenol by immobilized iron oxides 总被引:1,自引:0,他引:1
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 (kc) 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 kapp (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. 相似文献