无定型MnO2的制备及其催化苯甲醇选择氧化性能

用KMnO₄和MnSO₄为原料，通过简单的氧化还原过程合成了无定形MnO₂，并用于催化苯甲醇氧化制苯甲醛，发现制得的无定形MnO₂在催化苯甲醇氧化制苯甲醛中表现出较高的活性和苯甲醛选择性（100%）。考察了反应温度、氧浓度、催化剂用量以及反应时间对苯甲醇氧化的影响。结果表明，较高的反应温度和氧浓度以及合适的催化剂用量有利于无定形MnO₂催化苯甲醇氧化生成苯甲醛，在反应温度110 ℃、常压和通氧条件下反应3 h, 苯甲醇转化率和苯甲醛选择性均为100%。     

锰掺杂CeO2-CoO的制备及其催化苯甲醇液相选择性氧化

以硝酸盐作前体,通过均匀共沉淀法制备了掺锰复合氧化物CeO2-MnO2-CoO,采用X-射线粉末衍射(XRD)对复合氧化物进行了表征,并研究了复合氧化物在苯甲醇液相氧化反应中的催化性能.结果表明,复合氧化物的组成、反应时间、溶剂种类和氧化剂用量等对苯甲醇转化率和苯甲醛选择性均有影响.采用叔丁基过氧化氢作氧化剂,正己烷为...     

Pd/NaY催化苯甲醇无溶剂选择性氧化反应

采用离子交换法将[Pd(NH₃)₄]²⁺交换到NaY分子筛中,经焙烧和氢气还原制备金属钯粒径可调变的Pd/NaY催化剂。在(120~500) ℃改变焙烧温度,可以获得金属钯粒径(1.3~11.9) nm的Pd/NaY催化剂。Pd/NaY催化剂能够催化苯甲醇的无溶剂选择性氧化反应,对含不同钯粒径的Pd/NaY催化剂上醇选择性氧化研究发现,在1.6%Pd/NaY催化剂用量0.1 g、反应温度100 ℃、苯甲醇用量48.5 mmol和O₂流速3 mL·min^-1条件下,苯甲醇转化的真实转化频率随粒径变化在3.2 nm处呈最大值,该反应为结构敏感反应。     

High-performance photocatalysts for the selective oxidation of alcohols to carbonyl compounds

With an increase in awareness about the need for green chemistry, there is a shift in focus towards identifying eco-compatible technologies that can improve product yield and eliminate the use or generation of hazardous compounds. An immediate practical example of such an approach is the development of sustainable methods for alcohol oxidation as alternatives to the current processes that are energy intensive and rely on ecotoxic chemicals. In this regard, heterogeneous photocatalysis has been identified as a robust technique to catalyze reactions under benign conditions, which would otherwise require harsh synthesis routes. With the advent of materials sciences and nanotechnology, there has been a tremendous increase in the scope of applicability of photocatalysis in fine chemicals synthesis. Though an attractive choice, much of the fundamental information pertaining to catalyst activity, selectivity and reaction conditions for optimum conversion are still to be investigated for most of these systems. To this end, this review will encompass recent achievements in the selective photocatalytic oxidation of alcohols by harnessing solar radiation as a viable source of energy. The discussion will be arranged based on common types of photocatalysts reported in literature, namely metal oxides (eg, TiO₂ and ZnO, Nb₂O₅), sulphides (eg, CdS, CuS, and Bi₂S₃), and carbonaceous photocatalysts (eg, g-C₃N₄). Several such candidates for photocatalysts will be discussed critically with the aim of providing useful insight into developing selective photocatalysts that can oxidize alcohols via eco-friendly pathways along with high yields.     

Kinetics of the photocatalytic total oxidation of different alkanes and alkenes on TiO2 powder

Although photocatalyzed total oxidation reaction of hydrocarbon species has been discussed in the literature, most of these studies were performed to obtain an appropriate reaction mechanism. Studies on the kinetics of this type of reaction are rare. Using titanium dioxide as the photo catalyst, the kinetics of the total oxidation of methane, ethane, ethene, as well as propene, have been investigated using a continuous‐stirred tank reactor. In the experiments, the hydrocarbon concentrations, the oxygen concentration, and the irradiation intensity were varied. The results obtained are evaluated on the basis of a kinetic model to derive rate equations which can be used for reactor design.     

An effective tri-phasic catalytic system for oxidation of benzyl alcohol under phase transfer conditions

A tri-phasic catalytic system consisting of aqueous hydrogen peroxide, benzyl alcohol and a solid catalyst such as tungsten trioxide has been proved effective for the oxidation of benzyl alcohol in the presence of cetyl trimethyl aniline bromide (CTMAB). At first, the oxide reacts with CTMAB to form a complex, which can be oxidized by aqueous hydrogen peroxide to form a peroxide which effectively oxidizes benzyl alcohol.Trainee of Changchun College of Metallurgical Geology.     

Novel dicopper(II)-tetracarboxylates as catalysts for selective oxidation of benzyl alcohols with aqueous TBHP

A few dicopper(II) tetracarboxylate complexes viz. [Cu₂(µ-O₂CC₆H₅)₄(4-Etpy)₂] (1), [Cu₂(µ-O₂CC₆H₅)₄(4-DMAP)₂] (2), [Cu₂(µ-O₂CC₆H₅)₄(4-CNpy)₂] (3) and [Cu₂(µ-O₂CCH₃)₄(4-CNpy)₂] (4) have been utilised as catalysts for oxidation of benzyl alcohols using aqueous tert-butyl hydroperoxide as the oxidant. Complexes 1 and 2 have shown better catalytic activity than the other two. Unlike other catalysts, these dicopper complexes can catalyse oxidation of alcohols at a very low concentration (0.5 mol%).     

Aerobic oxidation of secondary alcohols to ketones catalyzed by cobalt(II)/ZnO in poly(ethylene glycol)/CO2 system

The aerobic oxidation of benzhydrol, 1-phenylethanol and cyclohexanol to corresponding ketones was carried out in poly(ethylene glycol) (PEG-600)/supercritical CO₂ (SCCO₂) biphasic system using unsupported and supported CoCl₂·6H₂O as the catalysts. It was demonstrated that CoCl₂·6H₂O, Co(II)/Al₂O₃, and Co(II)/ZnO were all active and selective for the reactions. The reactivity of the substrates followed the order benzhydrol > 1-phenylethanol > cyclohexanol. Co(II)/ZnO was most stable and could be reused four times without considerable reduction of activity. The effect of CO₂ pressure, reaction time and solvent was further investigated. The Co(II)/ZnO/PEG-600 system is active, selective, cheap, clean, and recyclable for the aerobic oxidation of secondary alcohols.     

Selective oxidation of benzaldehyde derivatives on TiO2 photocatalysts modified with fluorocarbon group

Fluorocarbon groups were introduced onto surfaces of SiO₂-covered TiO₂ particles (SiO₂–TiO₂). Oxidation of pentafuluorobenzaldehyde on the surface modified TiO₂ powders proceeded much efficiently than that on SiO₂-covered TiO₂ particles without surface modification. In addition, no enhancement of activity level of surface-modified SiO₂–TiO₂ for oxidation of benzaldehyde was observed. The enhancement of the surface-modified SiO₂–TiO₂ is due to the interaction of F atoms between the substrate and fluorocarbon groups introduced on SiO₂–TiO₂.     

Cu(II) bipyridine and phenantroline complexes: Tailor-made catalysts for the selective oxidation of tetralin

Mononuclear Cu(II) complexes have been synthesized, and their structure thoroughly characterized by electrospray ionization mass spectrometry (ESI-MS). These 2,2′-bipyridine and 1,10-phenantroline mononuclear Cu(II) complexes have been tested as catalysts in the partial oxidation of tetralin (1,2,3,4-tetrahydronaphthalene), using hydrogen peroxide as oxidant in acetonitrile/water as solvent.The complexes [Cu(bipy)₃]Cl₂·6H₂O (1), [Cu(bipy)₂Cl]Cl·5H₂O (2), [Cu(bipy)Cl₂] (3), [Cu(phen)₃]Cl₂·6H₂O (4), [Cu(phen)₂Cl]Cl·5H₂O (5), [Cu(phen)Cl₂] (6) were able to oxidize tetralin at room temperature, at high degrees of conversion (62.1% with 2) into α-tetralol and α-tetralon at 91% selectivity (81% in 1-tetralon).Depending on nature and number of ligands (bipyridine or phenantroline) surrounding Cu²⁺ cation, one was able to tailor both the activity toward tetralin oxidation, and the selectivity toward 1-tetralol and 1-tetralone products, but also to raise the yield in valuable α-tetralone.     

Cu(x)/TiO2催化剂NH3-SCR低温脱硝性能

以硝酸铜和二氧化钛为原料,采用浸渍法制备Cu(x)/TiO_2(x为以TiO_2载体质量为基准的铜负载量,下同)催化剂。运用XRD、XPS、NO-TPD、H_2-TPR等对催化剂进行了表征,在微型固定床反应器中评价了Cu(x)/TiO_2催化剂在以NH_3为还原剂的选择性催化还原NO反应(NH_3-SCR)中的脱硝活性。结果表明,铜物种以Cu_2O和Cu O的形式共存于TiO_2载体上;铜负载量影响催化剂的脱硝性能;Cu(6)/TiO_2催化剂(6代表铜的负载量为6%)表现出较好的氧化还原性和对反应物NO的吸附-脱附能力,低温脱硝活性较好,NO转化率达到85%和95%时对应反应温度T85和T95分别为195和218℃,NO转化率大于95%的活性窗口温度为218～270℃,宽度为52℃。     

2,5-二(二乙氨基甲基)对苯二酚在过氧化氢氧化苯甲醇制备苯甲酸中的应用研究

以30%过氧化氢作为氧化剂,对苯二酚与甲醛、二乙胺的Mannich反应产物2,5-二(二乙氨基甲基)对苯二酚与钨酸钠为催化剂,研究了苯甲醇氧化制备苯甲酸的反应,2,5-二(二乙氨基甲基)对苯二酚的辅助催化性能优于对苯二酚。最佳反应条件为:40.5mmol苯甲醇,n(钨酸钠)∶n(2,5-二(二乙氨基甲基)对苯二酚)∶n(苯甲醇)∶n(30%过氧化氢)=0.405∶0.489∶40.5∶273,3mL0.1mol/L硫酸,于95℃反应8h,在无有机溶剂的条件下苯甲醇可以被氧化为苯甲酸,一次结晶率为76.9%,催化体系的重复使用性能不太理想。     

SiO2负载MoP催化剂的制备及其对苯甲醇选择性氧化的催化性能

在SiO2载体上，以乙酰丙酮钼与次磷酸铵为原料，未经煅烧直接还原制备负载型磷化钼（MoP/SiO2）催化剂，通过XRD、N2-物理吸附、TEM和XPS等手段对催化剂进行表征。研究了浸渍液中P/Mo摩尔比（n(P):n(Mo)=1:1，2:1，3:1）、还原温度（500、550、600 ℃）对MoP相的影响，并考察其在苯甲醇选择性氧化生成苯甲醛反应中的催化性能。结果表明，浸渍液中P/Mo摩尔比为2、还原温度为550 ℃时，所获得的MoP/SiO2催化剂（MoP/SiO2-550-2）在苯甲醇选择性氧化生成苯甲醛反应中具有最好的转化率（99.7%）和优异的产物选择性（99.8%），这是由于MoP/SiO2-550-2催化剂上形成了更多小颗粒的MoP相。     

Partial oxidation of methane to synthesis gas via the direct reaction scheme over Ru/TiO2 catalyst

The partial oxidation of methane to synthesis gas has been investigated over various supported metal catalysts. The effects of operational variables on mass and heat transport resistances were investigated for defining the kinetic regime. It is observed that, in the absence of significant mass and heat transfer resistances, high selectivity (up to 65%) to synthesis gas is obtained over Ru/TiO₂ catalysts in the low methane conversion range ( ) whereas only negligibly small selectivity to synthesis gas is observed over all other catalysts investigated under similar conditions. This indicates that the Ru/TiO₂ catalyst possesses unique properties, offering high selectivity to synthesis gas formation via the direct reaction scheme, whereas the other catalysts promote the sequence of total oxidation of methane to CO₂ and H₂O, followed by reforming reactions to synthesis gas. An increase of selectivity to synthesis gas, in the presence of oxygen, is achieved over the Ru/TiO₂ catalyst by multi-feeding oxygen, which is attributed to suppression of deep oxidation of H₂ and CO.     

Effect of calcination temperature on the catalytic activity of Au colloids mechanically mixed with TiO2 powder for CO oxidation

In order to elucidate the role of the contact structure between gold and metal oxide support in low-temperature CO oxidation, a mechanical mixture of colloidal gold with TiO₂ powder was prepared and calcined at different temperatures. The sample calcined at 473 K, which is composed of spherical gold particles with a mean diameter of 5.1 nm and TiO₂ powder, is poorly active for CO oxidation at temperatures up to 473 K. The catalytic activity appreciably increases with an increase in calcination temperature up to 873 K even though gold particles grow to larger ones, reaching a level with almost the same turnover frequency as that of Au/TiO₂ prepared by a deposition–precipitation method. This revised version was published online in July 2006 with corrections to the Cover Date.     

制备条件对Cu/Al2O3 选择性催化还原NO的影响研究

考察了制备方法、活性组分负载量和焙烧温度对Cu/Al₂O₃ 选择性催化还原NO的影响。结果表明，采用溶胶-凝胶+浸渍法制备的Cu/Al₂O₃催化剂活性最好；负载Cu质量分数为15%时，催化剂的活性温域最宽，最大活性温度最低，催化活性最好；最佳焙烧温度为750 ℃。     

Preparation and characterization of TiO2/Ti film electrodes by anodization at low voltage for photoelectrocatalytic application

Multiporous TiO₂/Ti film electrodes were prepared by different anodic oxidation processes at low voltage, in which the micro-structured TiO₂ thick films were prepared in H₂SO₄–H₂O₂–H₃PO₄–HF solution for 2 h and the nano-structured TiO₂ thin films were prepared in H₃PO₄–HF solution for 30 min with post-calcination. Both types of TiO₂/Ti films were characterized by scanning electron microscopy and X-ray diffraction analysis. The photocatalytic (PC) and photoelectrocatalytic (PEC) reactivity of the TiO₂/Ti electrodes were evaluated in terms of bisphenol A (BPA) degradation in aqueous solution. The experimental results demonstrated that the nano-structured TiO₂/Ti thin-film electrodes had higher reactivity in the BPA degradation reaction. The PEC degradation of BPA was further studied using different cathodes, either a reticulated vitreous carbon (RVC) electrode or a platinum (Pt) electrode. The experimental results confirmed that the efficiency of BPA degradation could be significantly enhanced in the TiO₂/Ti–RVC reaction system due to the generation of H₂O₂ on the RVC cathode. It is believed that such a H₂O₂-assisted TiO₂ PEC oxidation process may have good potential for water and wastewater treatment.