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Activation of Supported Pd Metal Catalysts for Selective Oxidation of Hydrogen to Hydrogen Peroxide 总被引:1,自引:0,他引:1
Catalytic activity of supported Pd metal catalysts (Pd metal deposited on carbon, alumina, gallia, ceria or thoria) showing almost no activity in the liquid-phase direct oxidation of H2 to H2O2 (at 295 K) in acidic medium (0.02 M H2SO4) can be increased drastically by oxidizing them using different oxidizing agents, such as perchloric acid, H2O2, N2O and air. In the case of the Pd/carbon (or alumina) catalyst, perchloric acid was found to be the most effective oxidizing agent. The order of the H2-to-H2O2 conversion activity for the perchloric-acid-oxidized Pd/carbon (or alumina) and air-oxidized other metal oxide supported Pd catalysts is as follows: Pd/alumina < Pd/carbon < Pd/CeO2 < Pd/ThO2 < Pd/Ga2O3. The H2 oxidation involves lattice oxygen from the oxidized catalysts. The catalyst activation results mostly from the oxidation of Pd metal from the catalyst producing bulk or sub-surface PdO. It also caused a drastic reduction in the H2O2 decomposition activity of the catalysts. There exists a close relationship between the H2-to-H2O2 conversion activity and/or H2O2 selectivity in the oxidation process and the H2O2 decomposition activity of the catalysts; the higher the H2O2 decomposition activity, the lower the H2-to-H2O2 conversion activity and/or H2O2 selectivity. 相似文献
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The heterogeneous catalytic wet peroxide oxidation (CWPO), involving total oxidation of organic compounds to CO2 and H2O is a possible path for the treatment of toxic and bio‐refractory wastewater streams. The aim of this work was to synthesize and characterize three Cu/ZSM5 catalysts prepared by direct hydrothermal synthesis. The mass ratio of the active metal component in the zeolite ranged from 1.62–3.24 wt %. These materials were tested for CWPO of aqueous phenol in a stainless steel Parr reactor, in batch operation under mild conditions (at atmospheric pressure and a temperature of 353 K). The catalyst weight was 0.1 g dm–3 and the initial concentration of phenol and hydrogen peroxide were 0.01 mol dm–3 and 0.1 mol dm–3, respectively. The catalysts were characterized by powder X‐ray diffraction (XRD), scanning electron microscopy (SEM), AAS and ICP‐MS. Their catalytic performance was monitored in terms of phenol and total organic carbon (TOC) conversion, hydrogen peroxide decomposition, by‐product distribution and the degree of copper leached into the aqueous solution. The experimental results indicated that within 180 min, these catalysts facilitated almost complete elimination of phenol and a significant removal of chemical oxygen demand, without significant leaching of Cu ions from the zeolite. The Cu/ZSM5‐DHS3 catalyst with the highest copper loading was proven to be the best candidate. The useful fraction of hydrogen peroxide that contributed to the removal of the organic compounds quantified in terms of selectivity, S, indicated that the CWPO selectivity was always less than 100 %, which meant that there was some self‐degradation of oxidant. It was also shown that oxidation of phenol took place on the catalyst surface via a heterogeneous mechanism, and that the contribution of any homogeneous reaction mechanism was not significant. 相似文献
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The direct synthesis of hydrogen peroxide is investigated using ruthenium containing catalysts. Ruthenium is not soluble in Au but forms alloys with palladium. We have therefore investigated Ru?CAu, Ru?CPd as well as trimetallic formulations supported on titania. The addition of ruthenium enhances the direct synthesis activity for all the catalysts studied and the effect is dependent on the amount of ruthenium added. The calcination conditions are shown to affect both activity and reusability. 相似文献
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Massimiliano Comotti Cristina DellaPina Ermelinda Falletta Michele Rossi 《Advanced Synthesis \u0026amp; Catalysis》2006,348(3):313-316
Careful analytical determinations show that the gold‐catalysed aerobic oxidation of glucose occurs through a two‐electrons mechanism leading to gluconate and hydrogen peroxide. This latter decomposes before reaching the critical concentration for competing with O2 in glucose oxidation. A mechanism of glucose oxidation on gold nanoparticles is presented. 相似文献
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综述了醛、酮在过氧化氢做为氧化剂的条件下的Baeyer-Villiger氧化。介绍了环境友好型氧化剂过氧化氢在不同催化剂的催化下对醛、酮的Baeyer-Villiger氧化。 相似文献
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Pattama Saisaha Lea Buettner Margarethe vanderMeer Ronald Hage Ben L. Feringa Wesley R. Browne Johannes W. deBoer 《Advanced Synthesis \u0026amp; Catalysis》2013,355(13):2591-2603
The manganese‐containing catalytic system [MnIV,IV2O3(tmtacn)2]2+ ( 1 )/carboxylic acid (where tmtacn=N,N′,N′′‐trimethyl‐1,4,7‐triazacyclononane), initially identified for the cis‐dihydroxylation and epoxidation of alkenes, is applied for a wide range of oxidative transformations, including oxidation of alkanes, alcohols and aldehydes employing H2O2 as oxidant. The substrate classes examined include primary and secondary aliphatic and aromatic alcohols, aldehydes, and alkenes. The emphasis is not primarily on identifying optimum conditions for each individual substrate, but understanding the various factors that affect the reactivity of the Mn‐tmtacn catalytic system and to explore which functional groups are oxidised preferentially. This catalytic system, of which the reactivity can be tuned by variation of the carboxylato ligands of the in situ formed [MnIII,III2(O)(RCO2)2(tmtacn)2]2+ dimers, employs H2O2 in a highly atom efficient manner. In addition, several substrates containing more than one oxidation sensitive group could be oxidised selectively, in certain cases even in the absence of protecting groups.
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SnO2 nanorod array grown directly on alloy substrate has been employed as the working electrode of H2O2 biosensor. Single-crystalline SnO2 nanorods provide not only low isoelectric point and enough void spaces for facile horseradish peroxidase (HRP) immobilization
but also numerous conductive channels for electron transport to and from current collector; thus, leading to direct electrochemistry
of HRP. The nanorod array-based biosensor demonstrates high H2O2 sensing performance in terms of excellent sensitivity (379 μA mM−1 cm−2), low detection limit (0.2 μM) and high selectivity with the apparent Michaelis–Menten constant estimated to be as small
as 33.9 μM. Our work further demonstrates the advantages of ordered array architecture in electrochemical device application
and sheds light on the construction of other high-performance enzymatic biosensors. 相似文献
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采用停流光谱仪研究了异丙醇在T=298K和pH=3~11范围内O3 / H2O2复合氧化的反应动力学.结果表明异丙醇的O3 / H2O2复合氧化反应动力学随反应体系的pH值不同而不同.在酸性和中性条件下,反应相对于O3浓度、异丙醇浓度都为1级;在碱性条件下,异丙醇较容易被O3/H2O2复合氧化降解,总反应级数为2级,相对于O3浓度、异丙醇浓度和H2O2浓度分别为1级、0级和1级,可见异丙醇的降解速率与它的浓度无关.在T=298K,当pH值从9增大到11, 反应速率常数从3486.1(mol·L-1)-1·s-1增大到38239.2(mol·L-1)-1·s-1. 表明在酸性条件下,异丙醇的O3/H2O2复合氧化是O3分子直接攻击异丙醇的反应占主导;在碱性条件下,自由基型反应占主导. 相似文献
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过氧化氢氧化苯甲醛反应的研究 总被引:10,自引:0,他引:10
研究了在无催化剂及以硫酸铜、金属铜、浓硫酸为催化剂的不同条件下,过氧化氢对苯甲醛的氧化反应。考察了苯甲醛和过氧化氢的摩尔投料比、温度、浓硫酸用量和反应时间对反应的影响.结果表明:温度60℃、反应时间36h、加浓硫酸2滴(以25mL苯甲醛为基准)、投料比为2时,苯甲酸的产率可达86.5%。 相似文献
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Maryam Afsharpour Alireza Mahjoub Mostafa M. Amini 《Journal of Inorganic and Organometallic Polymers and Materials》2009,19(3):298-305
Novel layered materials based on molybdenum oxide have been synthesized using three amino-carboxylate ligands; terephetalic
acid, p-aminobezoic acid and diaminobenzene. On the basis of X-ray diffraction, scanning electron microscopy, thermogravimetry, and
infrared results, the insertion of organic ligands into the interlayer space of molybdenum oxide has been proposed. Moreover,
the influence of organic guests on the oxide structure and also their catalytic performance are discussed. Furthermore, fabrication
of the nanostructured molybdenum oxide is achieved by calcinations of these hybrid materials at 600 °C. Somewhat oriented
nanoplatelets are viewed with different catalytic activity. 相似文献
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用稀土元素铈取代磷钼钒杂多酸合成了Keggin型稀土铈磷钼钒四元杂多酸盐(Ce HPMo11VO40·n H_2O),采用XRD和FTIR对该杂多酸盐的结构进行了表征。并将其作为催化剂应用于H_2O2氧化环己烷制备环己醇和环己酮的反应中,考察了催化剂用量、反应温度、反应时间、H_2O2用量对反应的影响。实验结果表明:反应最佳条件为n(环己烷)=0.1mol,n(Ce HPMo11VO40·n H_2O)=0.2 mmol、反应温度为75℃、反应时间为9 h、n(H_2O2)=0.2 mol(质量分数为30%),在此条件下,环己烷的转化率达到41.29%,环己醇和环己酮的总收率可达27.49%。 相似文献