过渡金属氧化物修饰的金纳米催化剂苯甲醇氧化性能

采用一步法合成介孔二氧化硅负载的金纳米催化剂,以氯化锡为前驱体,通过浸渍法向金纳米催化剂中引入助剂氧化锡,得到过渡金属氧化物修饰的金纳米催化剂。通过N2吸附-脱附、X射线衍射、透射电镜和固体紫外漫反射光谱等对催化剂结构进行表征。将所合成的催化剂用于苯甲醇选择性氧化反应,考察助剂组分对催化剂性能的影响,结果表明,氧化锡的引入改变了金纳米颗粒的表面电子结构,增加了催化剂活性与选择性;但随着氧化锡含量继续增加,催化剂活性降低,这主要是因为金纳米颗粒表面过渡金属氧化物覆盖度增加,减少了催化剂活性组分与苯甲醇的接触。当氧化锡质量分数0.2%时,催化剂效果最佳,在100℃和氧气压力0.2 MPa下反应3 h,苯甲醇转化率25.7%,苯甲醛选择性75.9%,苯甲酸选择性15.8%,苯甲酸苄酯选择性6.3%。     

硼杂碳包镍负载钯催化芳香醇需氧氧化

以硼杂碳包镍(Ni@BC)为载体,采用乙醇还原前驱体H_2PdCl_4法制备了一种新型磁可分离Pd/Ni@BC催化剂,并对其进行AAS、TEM、XRD和XPS表征,选取苯甲醇需氧氧化为探针反应,考察催化剂用量、反应温度和反应时间对催化性能的影响,研究催化剂对其他芳香醇的催化性能和循环使用性能。AAS结果表明,Pd负载质量分数为9.1%,与理论负载量一致。TEM结果显示,Pd纳米颗粒均匀分散在载体表面,平均粒径为4 nm。XRD和XPS结果均表明,催化剂的活性物种为Pd0。在反应温度80℃、O2_压力101.325 k Pa(流速20 m L·min~(-1))、CH_3CN为溶剂和K_2CO_3为碱性助剂条件下,Pd/Ni@BC对多种芳香醇的氧化反应表现出很高的催化活性和选择性,能将苯甲醇、对甲基苯甲醇、对乙基苯甲醇、对异丙基苯甲醇、肉桂醇、安息香、二苯甲醇以及邻甲基苯甲醇等定量转化为相应的醛或酮。催化剂重复使用5次,苯甲醇转化率由97.3%降至78.9%,Pd的少量脱落和部分氧化是催化剂活性降低的主要原因。     

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%。     

Probing Active Sites During Palladium-Catalyzed Alcohol Oxidation in “Supercritical” Carbon Dioxide

Structural information has been gained during aerobic benzyl alcohol oxidation in “supercritical” carbon dioxide at 150 bar on alumina-supported palladium by X-ray absorption spectroscopy while monitoring simultaneously the performance of the catalyst. The reduction of the catalyst by benzyl alcohol could be monitored by the analysis of the near-edge region of the Pd K-edge. The palladium constituent was mainly in metallic state under operating conditions. Partial reoxidation was observed when only oxygen in “supercritical” carbon dioxide in the absence of alcohol was fed. The catalytic activity of the PdO_x/Al₂O₃ catalyst during benzyl alcohol oxidation was comparable to that in a conventional continuous fixed-bed reactor and depended on the oxygen concentration in the feed. The rate of alcohol conversion went through a maximum when the oxygen concentration was increased. At maximum rate, part of the palladium was in the oxidized state. Upon further increase of the oxygen concentration, the activity decreased because of the formation of surface palladium oxide. The reaction rate in “supercritical” carbon dioxide was strikingly higher than that observed for the corresponding liquid-phase oxidation.     

Microwave-accelerated solvent-free aerobic oxidation of benzyl alcohol over efficient and reusable manganese oxides

A new facile and cost-effective process involving the solvent-free oxidation of benzyl alcohol using molecular oxygen as oxidant under controlled microwave irradiation has been developed for the production of chlorine-free benzaldehyde. Influence of different catalyst parameters (different manganese oxides and other kinds of transition metal oxides) and reaction conditions (reaction period and temperature) on the process performance has been studied. Under optimized reaction conditions, the MnO₂ catalyst showed a superior catalytic performance in the highly selective oxidation of benzyl alcohol as compared to other manganese oxide materials such as MnO, Mn₂O₃ and Mn₃O₄. Moreover, a very stable catalytic activity as a function of cycling test was observed for the MnO₂ catalyst.     

金属卟啉催化空气氧化甲苯制取苯甲醛及苯甲醇的新工艺

在少量简单金属钴卟啉的催化下,无需外加溶剂及反应引发剂,甲苯可由空气直接选择性液相催化成为苯甲醛及苯甲醇。反应结果表明反应时间、反应温度、压力、催化剂用量及空气流量等工艺参数的变化对反应都有影响。在165℃、0．8MPa、3．4ppm及40L／h空气流量的最佳反应条件下,甲苯的转化率可以达到8．7％,同时醛醇选择性可以达到近60％。同传统空气氧化甲苯制取苯甲醛体系相比,此催化体系工艺条件简单、清洁无污染,产品质量好。研究结果表明,金属卟啉存在下的催化空气氧化甲苯制取苯甲醛及苯甲醇的反应经历了一个由金属卟啉引发的自由基反应历程。     

甲苯氧酰化反应制备苯甲醇研究进展

烯烃和芳香烃通过氧酰化反应直接制备羧酸酯具有简单、直接和高效的特点。甲苯通过氧酰化反应制备苯甲醇醋酸酯是该反应的重要应用之一,反应产物苯甲醇醋酸酯和苯甲醇醋酸酯水解生成的苯甲醇是重要的化工原料,工艺路线绿色环保。对甲苯氧酰化反应机理、催化剂组成和载体对催化剂活性的影响、工艺条件的优化以及催化剂失活及再生等方面的研究进展进行综述,现有的甲苯氧酰化催化剂活性较高并可通过再生循环使用,降低了催化剂应用成本。随着苯甲醇醋酸酯、苯甲醇以及苯甲醛等需求的增大和环保要求提高,甲苯氧酰化工艺工业应用前景广阔。     

Partial oxidation kinetics of m-hydroxybenzyl alcohol with noble metal catalysts in supercritical carbon dioxide

Partial oxidation of m-hydroxybenzyl alcohol was studied over several supported noble metal catalysts in a temperature range from 373 to 413 K, up to 2 MPa of oxygen pressure and 20 MPa of carbon dioxide pressure. The major product detected was m-hydroxybenzaldehyde. A charcoal supported palladium catalyst gave the highest yield of the aldehyde. For high temperature above 393 K and high oxygen pressure above 0.5 MPa, total oxidation was observed, which caused the selectivity of m-hydroxybenzaldehyde to decrease. Supercritical carbon dioxide medium seemed to improve heat dissipation of the reaction to allow the partial oxidation of m-hydroxybenzyl alcohol to occur under mild conditions. The partial oxidation of benzyl alcohol over a charcoal supported palladium catalyst was also examined for comparison and the major product formed was benzaldehyde. The conversion of benzyl alcohol and the selectivity to benzaldehyde was higher than those for the case of partial oxidation of m-hydroxybenzyl alcohol.     

Continuous gas–liquid aerobic oxidation of toluene catalyzed by [T(p-Cl)PPFe]2O in a series of three stirred tank reactors

The liquid-phase catalytic aerobic oxidation of toluene by [T(p-Cl)PPFe]₂O was studied in a series of three stirred tank reactors. The effects of operation mode (including semi-batch and continuous operation), reaction temperature, catalyst concentration, average residence time, and air flow rate on the oxidation process were examined. The experimental results showed that continuous oxidation had no advantage over the total yield and selectivity of benzaldehyde and benzyl alcohol in comparison with semi-batch oxidation. And the reaction temperature was the most significant factor influencing on continuous oxidation of toluene. It is also found that adopting sequentially decreased temperature in the three series reactors could improve the yield and selectivity of benzaldehyde and benzyl alcohol in this process. Under which at the higher conversion of toluene, the total yield to benzaldehyde and benzyl alcohol increased 17.05% or 43.62% respectively in comparison with adopting sequentially increased or same temperature in the three series reactors.     

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.     

氮杂碳包铁负载钯催化苯甲醇无溶剂氧化

以氮杂碳包铁(Fe@NC)为载体、聚乙烯吡咯烷酮为稳定剂,通过液相还原H_2PdCl_4和后续焙烧法制备新型的磁可分离Pd/Fe@NC催化剂,并进行AAS、TEM、XRD和XPS表征,将制备的催化剂用于苯甲醇无溶剂需氧氧化反应,考察焙烧温度、反应温度、催化剂用量和碱性助剂对其催化性能的影响,研究催化剂的循环使用性能。结果表明,Pd负载质量分数为4.86%,Pd有效负载比例为97.2%;Pd颗粒在载体上分散均匀,平均粒径为5 nm;催化剂活性物种组成包括Pd~0和含量较低的络合Pd(Ⅱ)及PdO。在无溶剂、无碱性助剂、O_2分压101.325 kPa(O_2流量为20 m L·min~(-1))和低催化剂用量[n(Pd)∶n(苯甲醇)=1∶2 000]条件下,Pd/Fe@NC可高效催化苯甲醇的氧化反应,100℃反应24 h,苯甲醇转化率达86%,苯甲醛选择性为87%,反应过程中无任何有毒物质产生与排放。催化剂循环使用7次后,催化活性略有提高,催化过程中络合的Pd(Ⅱ)向Pd0的转化是其活性提高的主要原因。     

Enhancing the catalytic activity of carbon nanotubes by nitrogen doping in the selective liquid phase oxidation of benzyl alcohol

Nitrogen-doped carbon nanotubes (N-CNTs) were prepared by chemical vapor deposition method and employed as carbon-based catalysts for selective oxidation of benzyl alcohol to benzaldehyde with molecular oxygen as the terminal oxidant under the mild reaction conditions. The results showed that the N-CNTs exhibited much higher activity than the undoped CNTs, and the improved catalytic activity was probably attributed to the introduction of electron-rich nitrogen atoms in the graphitic domains enhanced electron transfer. Moreover, N-CNTs displayed excellent stability without an obvious loss in activity and selectivity for benzyl alcohol oxidation after eight cycling reactions. The results presented herein pave the way for the development of novel carbon catalyst for the liquid-phase oxidation of benzyl alcohol.     

金属卟啉催化的甲苯氧化及工艺优化

Catalytic activities of a series of metalloporphyrin complexes in selective aerobic oxidation of toluene were investigated.The effects of different central metal ions in metalloporphyrins[T（p-Cl）PPMCl（M=Fe,Co,Mn,Cu）] on the reaction course had been examined and it was found that T（p-Cl）PPCu presented the highest catalytic activity in the reaction.The reaction conditions of toluene oxidation were optimized by using orthogonal experiment design.Five relevant factors were investigated：temperature,air pressure,catalyst loading,air flow rate and reaction time.The effects of the five factors on both toluene conversion and total yield of benzaldehyde and benzyl alcohol were discussed.The research results showed that the reaction temperature was the most significant factor influencing toluene oxidation.On the basis of the margin analysis,the optimum conditions for the toluene conversion and the total yield of benzaldehyde and benzyl alcohol respectively were achieved,under which the toluene conversion was up to 14.67%and the total yield of benzaldehyde and benzyl alcohol reached 5.89%.     

Anchoring of Copper(II) Schiff Base Complex into Aminopropyl-Functionalised MCM-41: A Novel,Efficient and Reusable Catalyst for Selective Oxidation of Alcohols

A copper(II) complex containing tetradentate N₂O₂ Schiff base ligand immobilized into aminopropyl-functionalised MCM-41 (mobile crystalline material number 41), was prepared and characterized by Fourier-transform infrared, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, N₂ adsorption–desorption and inductively coupled plasma analysis techniques. The novel heterogeneous catalyst, MCM-41-pr-NH₂-CuL, can be successfully applied for efficient and selective oxidation of different primary and secondary alcohols to the corresponding carbonyl compounds using hydrogen peroxide as an oxidant in acetonitrile at 60 °C. The effect of reaction parameters such as solvent, amount of catalyst, temperature and kind of oxidant on the oxidation of benzyl alcohol was also studied. The prepared catalyst could be recovered and reused four times without important loss of its catalytic performance. The heterogeneous MCM-41-pr-NH₂-CuL catalyst was found to be catalytically more active in the oxidation of alcohols compared to the similar type of copper(II) Schiff base complex in homogeneous media under the same reaction conditions.     

苯甲醇液相氧化合成苯甲醛的连续流工艺

在液相条件下以苯甲醇为原料,次氯酸钠溶液为氧化剂,2,2,6,6-四甲基哌啶-1-氧自由基（TEMPO）为氧化催化剂,在连续流微通道反应器中液相氧化合成苯甲醛。考察了苯甲醇与次氯酸钠溶液的物质的量配比、催化剂用量、反应温度、溶剂以及停留时间对苯甲醛合成的影响,并进行了工艺优化。结果表明：当次氯酸钠与苯甲醇的物质的量比为1.25∶1、苯甲醇与TEMPO的物质的量比为1∶0.01、苯甲醇与DMF的体积比为1∶10、 pH=8、反应温度为0℃、停留时间为10min时,苯甲醛的收率可达95.1%。     

十聚钨酸季铵盐催化苯甲醇合成苯甲醛的研究

研究了以十聚钨酸季铵盐为催化剂、30%过氧化氢为氧源催化氧化苯甲醇合成苯甲醛的反应,考察了不同催化剂的催化效果、反应温度、反应时间、十聚钨酸季铵盐的用量和过氧化氢的用量等对苯甲醇选择性催化氧化反应的影响。结果表明,以十聚钨酸季铵盐（[BunPy]4W10O32）为催化剂,在60℃,十聚钨酸季铵盐用量为0.08mmol,反应15h,30%过氧化氢用量为45mmol,苯甲醇的用量为30mmol时,苯甲醇的转化率为96.7%,苯甲醛的选择性达到91.5%。     

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。     

A quantitative method of photoadsorption determination for irradiated catalyst in liquid–solid system

A method for determining the amount of substrate adsorbed onto the catalyst surface in liquid–solid photocatalytic system under reaction conditions (photoadsorption) is proposed. The method has been applied to the photocatalytic oxidation of benzyl alcohol carried out in aqueous suspensions of a home prepared TiO₂ catalyst. The influence of alcohol concentration, catalyst amount and irradiation power on photoadsorption was investigated. The photoadsorption per unit mass of catalyst increased by increasing concentration of benzyl alcohol and irradiation power but it decreased, increasing the catalyst amount. By taking into account the photoadsorption phenomena, the kinetic modeling of the photooxidation process has been carried out and the parameters of the model have been determined. The results indicate that all these parameters are favorably affected by an increase of the photon flow absorbed per unit mass of catalyst.     

Aerobic oxidation of alcohols catalyzed by gold nano-particles confined in the walls of mesoporous silica

Gold nano-particles confined in the walls of mesoporous silica (GMS) catalysts were successfully prepared by a novel and simple technique utilizing thioether functional groups in the walls of mesoporous silica to anchor HAuCl₄. Calcination of the materials removed organic moieties and reduced the gold salt to gold nano-particles. In this procedure, the thioether groups were introduced into the silica wall via a co-condensation of tetraethyl orthosilicate (TEOS) with 1,4-bis(triethoxysily)propane tetrasulfide. These gold containing mesoporous catalysts have unusually high surface area and pore volume. The catalysts were evaluated for the solvent free liquid phase oxidation of benzyl alcohol by molecular oxygen. High selectivity to benzaldehyde was obtained under the reaction conditions of 403 K, 15 atm and 5 h in an autoclave. The 1.5% GMS catalyst was also evaluated for oxidation of alcohols using toluene as solvent under flowing oxygen at atmospheric pressure at 353 K in a two-necked flask. Under these conditions the conversion of benzyl alcohol reached 100% after 2 h and it was demonstrated that the catalyst can be recycled three times without significant loss of activity.     

聚合物微球固载的N-羟基邻苯二甲酰亚胺在分子氧氧化苯甲醇反应过程中的催化特性

以甲基丙烯酸缩水甘油酯(GMA)和甲基丙烯酸甲酯(MMA)的交联共聚微球GMA/MMA为基质,经过几步大分子反应在微球表面合成与固载了N-羟基邻苯二甲酰亚胺(NHPI),形成固载有NHPI的聚合物微球GMA/MMA-NHPI。将GMA/MMA-NHPI与Co(OAc)₂组成共催化体系,用于分子氧氧化苯甲醇的反应过程。研究结果表明,GMA/MMA-NHPI与Co(OAc)₂所构成的共催化体系在温和条件(65℃和常压氧气)下可有效地实现苯甲醇的分子氧氧化过程,将其深度氧化为苯甲酸,显示出较好的催化活性和高的选择性(苯甲酸的选择性为96%)。主催化剂GMA/MMA-NHPI固载的NHPI与助催化剂Co(OAc)₂适宜的摩尔比为20:1;主催化剂所含NHPI的摩尔分数为底物的10%时催化剂的用量比较适宜。固体催化剂GMA/MMA-NHPI还具有良好的再循环使用性能。