Vapor phase oxidation of o-xylene on carbon catalysts

A mechanism is proposed for the mild oxidation of o-xylene on carbon catalysts. A characteristic feature of all stages of the mechanism is that they take place on basic (electron donor) centers, to which are bonded all the organic molecules and molecular oxygen participating in the reaction. The strong oxidation of o-xylene also takes place in parallel with the mild oxidation. A substantial difference between the mechanisms of phthalic anhydride and carbon dioxide formation may be caused by the different orientations of o-xylene during its adsorption, which predetermines the different directions of the subsequent attack by the oxygen. A comparison has been made of the catalytic properties of different carbons, and they have been compared with the catalytic properties of an industrial V₂0₅ catalyst.Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 22, No. 5, pp. 619–625, September–October, 1986.     

Effect of diluent and reaction parameter on selective oxidation of propane over MoVTeNb catalyst using nanoflow catalytic reactor

The selective oxidation of propane to acrylic acid over an MoVTeNb mixed oxide catalyst, dried and calcined before reaction has been studied using high-throughput instrumentation, which is called nanoflow catalytic reactor. The effects of catalyst dilution on the catalytic performance of the MoVTeNb mixed oxide catalyst in selective oxidation of propane to acrylic acid were also investigated. The effects of some reaction parameters, such as gas hourly space velocity （GHSV） and reaction temperature, for selective oxidation of propane to acrylic acid over diluted MoVTeNb catalyst have also been studied. The configuration of the nanoflow is shown to be suitable for screen catalytic performance, and its operating conditions were mimicked closely to conventional laboratory as well as to industrial conditions. The results obtained provided very good reproducibility and it showed that preparation methods as well as reaction parameters can play significant roles in catalytic performance of these catalysts.     

Lithium-promoted V2O5?TiO2 catalysts for o-xylene oxidation to phthalic anhydride

A V₂O₅–Li₂O–TiO₂ (a) based catalyst for o-xylene oxidation to phthalic anhydride has been synthesized. The activity and selectivity of the specimen obtained are comparable with those of industrial catalysts.     

醋酸溶液中Pd-CuPc/Y催化甲烷选择氧化制甲醇

以氯化铜、钼酸铵、苯酐、氯化铵、尿素和NaY分子筛为原料,采用苯酐-尿素法制备了酞菁铜/分子筛复合物CuPc/Y.采用等体积浸渍法将金属钯担载在CuPc/Y上制备了Pd-CuPc/Y催化剂,并在醋酸水溶液中考察了其催化甲烷选择氧化合成甲醇反应的性能,结果表明,催化性能与反应温度、溶剂中CH₃COOH与H₂O的混合比例、对苯醌用量、反应时间等因素有关,在0.5%Pd-0.5%CuPc/Y添加量0.5 g、CH₃COOH与H₂O体积比4∶1、对苯醌用量1 000 μmol、反应时间3 h、反应温度150 ℃的条件下,甲醇的最佳生成量为1 840 μmol.Pd-CuPc/Y催化剂可以多次循环使用,但由于催化剂流失和催化剂表面的钯粒子聚集的原因,循环使用后的催化剂催化活性有所下降.Pd-CuPc/Y在醋酸溶液中催化甲烷选择氧化合成甲醇是亲电取代反应和活性氧物种氧化共同作用的结果.     

Kinetics of the Heck reactions of styrene with bromobenzene and iodobenzene in the presence of ligandless catalytic systems: A comparative study

The comparative kinetic study of the Heck reactions of styrene with iodobenzene and bromobenzene has revealed specific features of these reactions that should necessarily be taken into account for the observed data to be interpretable in the framework of a unified mechanistic conception. It has been proved for the styrene-bromobenzene reaction that benzene forms as a by-product via a heterogeneous route and catalytically active Pd(0) undergoes aggregation via an autocatalytic mechanism. The kinetics of the styrene-iodobenzene reaction indicates that benzene in this reaction forms via a homogeneous route, biphenyl forms as another by-product by a bimolecular mechanism, and excessive aryl halide concentration reduces the catalyst formation rate. A nonlinear-law mechanism is suggested for the conjugation of palladium reduction, aggregation, and oxidation in the Heck reaction. This mechanism allows the existence of a “critical” Pd(0) concentration and a “critical” formation rate of this catalytic species above which the catalytic activity begins to decrease.     

Challenges and Development Opportunities for Catalytic Technologies in Petrochemical Industry in the 21st Century

The propellent drive and development opportunities for future catalytic technologies in petrochemical industry in the 21st century are reviewed in this paper. It focuses on the following five aspects:(1) The environmentally-friendly catalytic technologies, such as new technologies for the production of organic chemicals changing the raw material and synthetic process, the chemicals production replacing phosgene and hydrogen cyanide toxicant, and the conversion and utilization of organic wastes etc.(2) Utilization and development of cheaper light alkanes, for example, the chemical use of natural gas and the development technologies of methane chain, the production of acetic acid, ethylene and vinyl chloride from selective oxidation of ethane, as well as the manufacture of acrolein and acrylonitrile from the oxidation and ammoxidation of propane.(3) The new propylene-plus technologies of the low value higher olefins, such as catalytic cracking of C4,C5 olefins and metathesis of C4 olefin.(4) The technologies of high selective oxidation, e.g. production of propylene oxide with TS-1 molecular sieve, oxidation process by lattice oxygen and direct oxidation of benzene to phenol etc.(5) Development and application of novel catalytic materials, especially, mesopore molecular sieve materials for a larger molecule reaction, zeolite catalyst with MWW structure for alkylation of benzene and propylene, ionic liquid, and membrane reactor catalyst etc.Meanwhile,the challenging research subjects for future industrial catalysis and the several viewpoints for development strategy of new catalytic technologies are proposed. These viewpoints are as follows:(1) Catalysis discipline must be integrated with many other disciplines and should be multidisciplinary and transdisciplinary.(2) New preparation methods of catalytic materials must be originally developed.(3) The instrumentation having better time resolution and spatial resolution and applying under reaction conditions must be improved further.(4) Fundamental research for catalysis and catalytic theory must be enhanced.(5) Catalysis science must be closely integrated with catalytic reaction engineering.(6) Knowledge innovation and technical progress must be accelerated.(7) Scientific and technological co-operation between academic, industrial circles and public organization having a common interest in catalysis must be intensified.     

磷钨酸插层Zn/Al类水滑石催化合成邻苯二甲酸二(2-乙基)己酯

以对苯二甲酸根阴离子为预支撑体,制备了磷钨酸插层Zn/Al类水滑石杂化物催化剂,将其用于邻苯二甲酸二(2-乙基)己酯(DOP)的合成反应.研究了原料配比、催化剂用量、反应温度、反应时间等对邻苯二甲酸酐转化率的影响,及催化剂的可重复利用性.结果表明,磷钨酸-Zn/Al类水滑石杂化催化剂对DOP合成的催化效果较好,在催化剂用量为苯酐质量的0.76%,异辛醇与邻苯二甲酸酐的摩尔比为2.5,反应温度为180℃,反应时间为4.5 h,带水剂环己烷约为苯酐质量65%的反应条件下,苯酐转化率可达92.8%;反应10 h转化率可达97.9%.催化剂重复使用时转化率略有下降,经过乙醇洗涤再生,活性即可基本恢复.     

Selective vapor‐phase oxidation of o‐xylene to phthalic anhydride over Co‐Mn/H3PW12O40@TiO2 using molecular oxygen as a green oxidant

The oxidation of o‐xylene to phthalic anhydride over Co‐Mn/H₃PW₁₂O₄₀@TiO₂ was investigated. The experimental results demonstrated that the prepared catalyst effectively catalyzed the oxidation of o‐xylene to phthalic anhydride. Also, the synergistic effect between three metals plays vital roles in this reaction. From a green chemistry point of view, this method is environmentally friendly due to carrying out the oxidation in a fixed‐bed reactor under solvent‐free condition and using molecular oxygen as a green and cheap oxidizing agent. The resulting solid catalysts were characterized by FT‐IR, XRD, XPS, ICP‐OES, FESEM, TEM, EDX, DR‐UV spectroscopy, BET and thermogravimetric analysis. The oxidation of o‐xylene yields four products: o‐tolualdehyde, phthaldialdehyde, phthalide and finally phthalic anhydride as the main product. The reaction conditions for oxidation of o‐xylene were optimized by varying the temperature, weight hourly space velocity and oxygen flow rate (contact time). The optimum weight percentage of phosphotungstic acid (HPW) and Co/Mn for phthalic anhydride production were 15 wt % and 2 wt%, respectively. The best Co/Mn ratio was found to be 10/1. Oxygen flow rate was very important on the phthalic anhydride formation. The optimum conditions for oxidation of o‐xylene were T = 370 °C, WHSV = 0.5 h^?1 and oxygen flow rate = 10 mL min^?1. Under optimized conditions, a maximum of 88.2% conversion and 75.5% selectivity to phthalic anhydride was achieved with the fresh catalyst. Moreover, reusability of the catalyst was studied and catalytic activity remained unchanged after at least five cycles.     

复合金属氧化物催化剂用于甘油氧化制丙烯酸的研究进展

随着化石燃料的短缺及其利用所产生的环境问题,可再生生物质资源逐渐成为生产燃料以及化学品的重要来源。近年来,甘油作为生物柴油生产的主要副产物受到了人们的广泛关注,利用其生产高附加值产品以及开发相关的转化技术也成为了国内外学者研究的热点。在诸多转化技术中,甘油选择性氧化制丙烯酸展现出了广阔的发展前景,对该反应尤其是催化剂开展研究具有重要的经济意义和社会意义。文中综述了用于甘油选择性氧化制丙烯酸复合金属氧化物催化剂的研究现状,介绍了当前用于该反应的催化体系类型以及对甘油氧化制丙烯酸催化反应机理的认识,分析并提出了存在的问题以及对未来的展望。     

Desorption of catalytic oxidation products of o-xylene from the surface of carbon catalysts

In a study of the oxidation of o-xylene on carbons (in the range of 523–573°K) under nonstationary conditions, it was found that considerable amounts of the reaction products (phthalic anhydride and CO₂) are adsorbed on the surface of the catalysts (phthalic anhydride more strongly than CO₂). The adsorption of the products is chemical in nature, like the adsorption of initial o-xylene. The bond between the adsorbates and the surface weakens with increase in the number of acidic groups on the surface. Since the active carbons are characterized by a higher basicity than the oxidized ones, in the first case the oxidation products of o-xylene are adsorbed more strongly and desorbed more slowly.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 4, pp. 499–503, July–August, 1986.     

多相固体催化剂用于甘油氧化制乳酸研究进展

随着新的全球气候协议下的中国双碳行动计划的实施, 开发和利用可再生生物质资源显得极为重要. 甘油作为生物柴油在生产过程中的主要副产物, 将其催化转化成各种高附加值衍生物受到广泛关注, 其中甘油选择性氧化为乳酸具有巨大的应用前景. 近年来, 采用固体催化剂催化氧化甘油制乳酸成为国内外学者研究的热点. 我们综述了固体催化剂用于甘油催化转化制备乳酸的研究现状, 对甘油催化转化为乳酸的反应途径做了分析, 并讨论了影响催化剂活性的因素, 对当前所存在的问题提出建议, 也对未来相关催化剂制备发展进行了展望.     

甘油的催化选择氧化

综述了近年来生物柴油主要副产物甘油的催化选择氧化的研究进展。分析了甘油的化学催化选择氧化的反应网络;介绍了催化甘油选择氧化反应主要的催化剂如负载型金属催化剂、多孔催化剂以及有机酰基-TEMPO催化剂的催化性能及其催化机理;评述了甘油催化氧化过程中各反应条件等对产物选择性和反应物转化率的影响;概括了甘油的电催化氧化、甘油催化氧化聚合生成新型聚合物-聚丙酮二酸盐（Polyketomalonate）等新催化反应及其机理,总结了甘油生物催化氧化的产物二羟基丙酮（DHA）的新进展。最后提出了甘油的催化氧化存在的一些问题,并展望了甘油催化氧化的研究和发展方向。     

Direct arylation of benzene with aryl bromides using high-temperature/high-pressure process windows: expanding the scope of C-H activation chemistry

A detailed investigation on the direct arylation of benzene with aryl bromides by using first-row transition metals under high-temperature/high-pressure (high-T/p) conditions is described. By employing a parallel reactor platform for rapid reaction screening and discovery at elevated temperatures, various metal/ligand/base combinations were evaluated for their ability to enable biaryl formation through C-H activation. The combination of cobalt(III) acetylacetonate and lithium bis(trimethylsilyl)amide was subjected to further process intensification at 200?°C (15?bar), allowing a significant reduction of the catalyst/base loading and a dramatic increase in catalytic efficiency (turnover frequency) by a factor of 1000 compared to traditional protocols. The high-throughput screening additionally identified novel nickel- and copper-based metal/ligand combinations that favored an amination pathway competing with C-H activation, with the addition of ligands, such as 1,10-phenanthroline, having a profound influence on the selectivity. In addition to metal-based catalysts, high-T/p process windows were also successfully applied to transition-metal-free systems, utilizing 1,10-phenanthroline as organocatalyst.     

Pd/γ-Al_2O_3催化剂催化氧化邻-二甲苯

利用纳米γ-Al_2O_3(10 nm)和普通γ-Al_2O_3(200-300 nm),采用浸渍法制备了1%(w)Pd/γ-Al_2O_3催化剂,考察了其催化氧化邻-二甲苯的性能以及催化剂的活性在氢气还原前后的区别。实验结果发现1%(w)Pd/γ-Al_2O_3(nano)在H_2还原后催化氧化邻-二甲苯的活性最高,T_(90)为150℃。利用X射线衍射(XRD)、比表面积(BET)、透射电镜(TEM)、X射线光电子能谱(XPS)等表征手段,研究了1%(w)Pd/γ-Al_2O_3催化剂物性结构与催化性能之间的构效关系。结果表明,还原态Pd是H_2还原后催化剂催化氧化邻-二甲苯的活性物种;Pd的颗粒大小与催化剂活性有显著的关系,小粒径有利于催化剂活性提高;纳米γ-Al_2O_3载体与Pd之间的相互作用强,有利于Pd的粒径控制和分散,从而提高1%(w)Pd/γ-Al_2O_3(nano)催化剂的活性。     

氧化镁上乙酸乙酯和乙酸丁酯氧化反应（英文）

采用新型无溶剂反应和回流的方法制得锰钾矿型氧化镁(K-OMS-2),同时采用常规方法制得氧化镁,并测试不同催化剂对工业排放气中有机挥发性物质(VOCs)中的模型化合物––乙酸乙酯和乙酸丁酯的催化氧性能.采用N2吸附-脱附、X射线衍射、扫描电镜、程序升温还原和X射线光电子能谱等技术对催化剂进行了表征.所有氧化镁样品均表现出很高的催化乙酸乙酯和乙酸丁酯氧化生成CO2的活性,且制备方法对催化剂性能起着重要作用.新型无溶剂法制得的K-OMS-2纳米棒样品比常规的回流法制得样品表现出更好的催化性能,含锰钾矿型氧化镁的样品比常规方法制得样品表现出更高的活性.性能最好的催化剂也表现出较高的稳定性,在213和202 oC条件下,可分别使90%的乙酸乙酯和乙酸丁酯转化为CO2.催化剂性能的显著差异清楚地表明,对于所选VOCs氧化反应,采用新型无溶剂法制得的K-OMS-2纳米棒样品比常规法制备的氧化镁混合物更好,这可能与样品结构中含有更高的Mn平均氧化态有关.本文表明了催化剂性能与其表面化学性质间存在显著的关联,显示了K-OMS-2内在性质决定了其高的催化性能.     

Carbon Nanotubes: An Example of Multiscale Development—A Mechanistic View from the Subnanometer to the Meter Scale

We summarize the catalytic synthesis of multiwall carbon nanotubes (MWCNTs). The current understanding of the reaction mechanism is presented, in particular the catalyst design for the CCVD process is analyzed. To complement that, kinetics and reaction engineering aspects are discussed along with the impact of the reaction and reactor operation on the product properties. All these issues are analyzed from the perspective of the industrial synthesis and implications for the application of carbon nanotubes. Carbon‐nanotube technology is a perfect example of multi‐scale development and covers challenges from the nanometer to the meter scale. Problems, methods, and solutions characteristic for different scales will be highlighted. The Co/Mn catalyst is used as reference as one of the first commercially used technologies for the scalable production of multiwall carbon nanotubes.     

Palladium complex catalyst immobilized on epoxy support under supercritical conditions

The aim of this research was to obtain a new-generation complex catalyst under supercritical carbon dioxide. A new complex catalyst based on epoxy resin cured with multifunctional polythiourethane was prepared. The use of polythiourethane as a hardener allowed us to introduce linking groups into the structure of the polymer without further functionalization of the resin. Additionally, the use of supercritical CO₂ enabled a more accurate and better distribution of the metal complex in the polymer matrix. The presence of the functional groups allowed us to obtain a catalyst wherein the metal centers had a different electronic structure and various degrees of oxidation, so that such a system was characterized by its high selectivity. The catalytic properties of the prepared catalysts were tested in the hydrogenation reaction. Research methods like time-of-flight secondary-ion mass spectrometry (ToF–SIMS), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and nitrogen BET surface area measurements were used to characterize polymeric support and heterogenized catalysts.     

Homogeneous palladium catalyst suppressing Pd black formation in air oxidation of alcohols

In homogeneous catalyst systems, there is the persistent problem that metal aggregation and precipitation cause catalyst decomposition and considerable loss of catalytic activity. Pd black formation is a typical example. Pd catalysts are known to easily aggregate and form Pd black, although they realize a wide variety of useful reactions in organic synthesis. In order to overcome this intrinsic problem of homogeneous Pd catalysis, we explored a new class of Pd catalyst by adopting aerobic oxidation of alcohols as a probe reaction. Herein we report a new catalyst system that suppresses the Pd black formation even under air and with a high substrate to catalyst molar ratio (S/C: more than 1000) in oxidation of alcohols. The novel pyridine derivatives having a 2,3,4,5-tetraphenylphenyl substituent and its higher dendritic unit at the 3-position of the pyridine ring were found to be excellent ligands with Pd(OAc)2 in the palladium-catalyzed air (balloon) oxidation of alcohols in toluene at 80 degrees C. Comparison with structurally related pyridine ligands revealed that introduction of the 2,3,4,5-tetraphenylphenyl substituent at the 3-position of pyridine ring effectively suppresses the Pd black formation, maintaining the catalytic activity for a long time to give aldehydes or ketones as products in high yields.     

Chiral phosphoric acid-catalyzed enantioselective three-component Povarov reaction using enecarbamates as dienophiles: highly diastereo- and enantioselective synthesis of substituted 4-aminotetrahydroquinolines

A chiral phosphoric acid (5)-catalyzed three-component Povarov reaction of aldehydes 2, anilines 3, and enecarbamates 4 afforded cis-4-amino-2-aryl(alkyl)-1,2,3,4-tetrahydroquinolines 1 in high yields with excellent diastereoselectivities (>95%) and almost complete enantioselectivities (up to >99% ee). The reaction was applicable to a wide range of anilines bearing electron-donating (OMe) and electron-withdrawing groups (e.g., Cl, CF(3), NO(2)) and allowed, for the first time, aliphatic aldehydes to be employed in the enantioselective Povarov reaction. With β-substituted acyclic enecarbamates, 2,3,4-trisubstituted 1,2,3,4-tetrahydroquinolines with three contiguous stereogenic centers were produced in excellent diastereo- and enantioselectivities (87 to >99% ee). A detailed study of the active catalytic species allowed us to reduce the catalyst loading from 10% to 0.5% with no deterioration of enantiomeric excess. In addition, mechanistic studies allowed us to conclude unequivocally that the Povarov reaction involving enecarbamate as dienophile proceeded via a stepwise mechanism. The key role of the free NH function of the enecarbamate in the success of this transformation was demonstrated. NMR experiments indicating the catalyst-substrate interaction as well as a linear correlation between catalyst and product ee's were also documented.     

高分子担载水杨醛半胱氨酸希夫碱铜配合物催化氧化环己烯研究

研究了高分子担载水杨醛半胱氨酸希夫碱配合物(PS-Sal-Cys-M)催化氧化环己烯的性能,详细探讨了反应温度、反应时间、催化剂用量、反应添加剂对高分子担载水杨醛半胱氨酸希夫碱铜配合物催化氧化环己烯的反应性能的影响。研究表明,在常压下,用分子氧作作为氧化剂,不需要溶剂及共还原剂,环己烯可以被氧化生成环己烯醇和环己烯酮,产物的分离提纯比较容易,催化剂可以循环使用。