Photocycloaddition of dichloromaleic anhydride to benzene

Conclusions In the photocycloaddition of dichloromaleic anhydride to benzene the processes of addition and substitution in the benzene ring proceed in parallel, and also the subsequent photoreaction of the obtained products to give compounds of the tricyclo[6.2.0^5,6.0^4,7]decene series.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1618–1620, July, 1976.     

Cycloacylation of chloro-substituted hydroquinone dimethyl ethers with dichloromaleic anhydride

Under the drastic conditions of Zahn—Ochwat cycloacylation of 2-chloroand 2,3-dichlorohydroquinones with dichloromaleic anhydride (a melt of anhydrous AlCl₃ and NaCl, 185—195 °C), the substrates undergo various degrees of disproportionation, which reduces the yields of the target triand tetrachloronaphthazarins. Quantum chemical calculations showed that the cycloacylation in question proceeds as a double aromatic electrophilic substitution of the vicinal protons with the corresponding oxocarbenium ions (acylium cations).     

An electron diffraction investigation of the molecular structure of dichloromaleic anhydride

The molecular structure of gaseous dichloromaleic anhydride has been investigated by electron diffraction at a nozzle-tip temperature of 164–170°C. The molecule is planar to within experimental error, but small deviations from planarity corresponding to torsion up to about 10° around the carbon-carbon single bonds cannot be ruled out. Values of the more important r_α distances and angles with estimated 2σ uncertainties are r(CO) = 1.188(2) Å, r(CC) = 1.332(5) Å, r(C-O) = 1.389(3) Å, r(C—C) = 1.495(3) Å, r(C—Cl) = 1.685(2) Å, ∠CC-Cl = 129.4(2)°, ∠C-CO = 128.5(4)° and ∠CC—C = 107.9(2)°. The shortening of the carbonyl bond relative to that in maleic anhydride itself is discussed in terms of a possible general effect of vicinal substitution.     

Mathematical simulation of the oxidation of ortho-xylene to phthalic anhydride in a fluidized catalyst bed

Kinetics and Catalysis - The oxidation of ortho-xylene to phthalic anhydride in a catalytic fluidized-bed reactor was simulated. The mathematical model implied that the reactor was separated into...     

Mechanism of phthalic anhydride formation in the oxidation of n-pentane on a vanadium-phosphorus oxide catalyst

The reaction paths of product formation in the partial oxidation of n-pentane on vanadium-phosphorus oxide (VPO) and VPO-Bi catalysts are considered. The condensed products of n-pentane oxidation were analyzed by chromatography-mass spectrometry, and the presence of C₄ rather than C₅ unsaturated hydrocarbons was detected. It was found that the concentration of phthalic anhydride in the products increased upon the addition of C₄ olefins and butadiene to the n-pentane-air reaction mixture. With the use of a system with two in-series reactors, it was found that the addition of butadiene to a flow of n-butane oxidation products (maleic anhydride, CO, and CO₂) resulted in the formation of phthalic anhydride. The oxidation of 1-butanol was studied, and butene and butadiene were found to be the primary products of reaction; at a higher temperature, maleic anhydride and then phthalic anhydride were formed. The experimental results supported the reaction scheme according to which the activation of n-pentane occurred with the elimination of a methyl group and the formation of C₄ unsaturated hydrocarbons. The oxidation of these latter led to the formation of maleic anhydride. The Diels-Alder reaction between maleic anhydride and C₄ unsaturated hydrocarbons is the main path of phthalic anhydride formation.     

Asymmetric oxidation of cyclobutanones: modification of the Sharpless catalyst

Oxidation of prochiral and racemic cyclobutanones with t-BuOOH and Ti-TADDOL-based complexes afforded lactones in up to 44% ee. The enantioselectivity of the reaction clearly depends on the amount of the reagent and the highest enantioselectivities were obtained with stoichiometric amounts of the complex. Modification of the TADDOL structure and use of the mixed complex derived from TADDOL and a tartaric ester led to more reactive but less selective oxidation systems.     

Effect of carbon dioxide on the catalytic oxidation of ethylene over silver. Kinetic reaction model accounting for the modification of catalyst surface by carbonate groups

Changes in the character of catalytic oxidation of ethylene over silver upon increasing pressure of reaction mixture, reflected in increased ethylene oxide selectivity, are due to the modifying effect of suface carbonate groups. A kinetic reaction model is suggested based on the individual investigations of reaction steps.

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Selective oxidation of CO under conditions of catalyst surface ignition

The oxidation of CO in the presence of an excess of hydrogen and to 20% CO₂ and H₂O in the starting mixture was studied in flow reactors with high and low rates of heat removal. The ignition of the catalyst surface was observed in the reactor with a low rate of heat removal; catalyst surface ignition initially occurred at a “hot” spot (section) of the catalyst bed and gradually propagated along the bed. Experimental data on the relaxation dynamics of residual CO concentration and temperature in a catalyst bed under conditions of small heater temperature disturbances near and at the critical temperature of ignition and the effect of oxygen concentration in the starting mixture on this process are reported. It was found exprimentally that the ignition regime in the tested cases was more favorable for the selective oxidation of CO in an excess of hydrogen than the reaction in an isothermal reactor; this was likely due to the more favorable temperature distribution over the length of the catalyst bed.     

催化剂对原油低温氧化的影响

在模拟地下油藏条件下,加入催化剂进行重质原油低温氧化反应实验研究,对氧化前后的气体组成及含量变化、原油组分变化进行分析.结果表明,加入催化剂后在150℃以下显著提高了原油低温氧化效率,且与未加入催化剂的低温氧化反应对比,加入催化剂后氧气消耗更多,生成二氧化碳含量增加.200℃以下原油重质组分含量下降,饱和烃、芳香烃轻质组分含量增加.     

Routes of catalytic oxidation of o-xylene to phthalic anhydride

Relative reactivity of o-xylene, o-tolualdehyde, phthalide, and phthalane and the rate of phthalic anhydride formation from them have been determined. The main route of o-xylene oxidation to phthalic anhydride is due to the o-arrangement of methyl groups, proceeding through bicyclic products, such as dihydrobenzofuran (phthalane) and 3,4-benzofuran.

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Effect of surface oxidation on the interaction of 1-methylaminopyrene with gold nanoparticles

The effect of the surface chemistry of gold nanoparticles (GNPs) on the GNP-amine (-NH(2)) interaction was investigated via conjugating an amine probe--1-methylaminopyrene (MAP) chromophore--with three Au colloidal samples of the same particle size yet different surface chemistry. The surface of laser-irradiated and ligand-exchanged-irradiated GNPs is covered with acetonedicarboxylic ligands (due to laser-introduced citrate oxidization) and citrate ligands, respectively, and both surfaces contain oxidized Au species which are essentially lacking for the citrate-capped GNPs prepared by the pure chemical approach. Both laser-irradiated samples show inferior adsorption capacity of MAP as compared with the purely chemically prepared GNPs. Detailed investigations indicate that MAP molecules mainly complex directly with Au atoms via forming Au-NH(2)R bonds, and the oxidization of the GNP surface strongly influences the ratio of this direct bonding to the indirect bonding originating from the electrostatic interaction between protonated amine (-NH(3)(+)) and negatively charged surface ligands. The impact of the oxidized GNP surface associated with the laser treatment is further confirmed by aging experiment on GNP-MAP conjugation systems, which straightforwardly verifies that the surface oxidation leads to the decrease in the MAP adsorption on GNPs.     

Effect of weak base modification on ZSM‐5 catalyst for methanol to aromatics

The effect of weak base modification on the catalytic performance of ZSM‐5 catalyst for conversion of methanol to aromatics was investigated. The catalysts were characterized using X‐ray diffraction, X‐ray fluorescence, N₂ adsorption–desorption, NH₃ temperature‐programmed desorption, Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetry. The results showed that catalysts treated with weak base (NaHCO₃, Na₂CO₃ and NH₃⋅H₂O) exhibited a pore structure with interconnected micropores and mesopores. The existence of mesopores was beneficial for improving the diffusion of reactants and products, and the coke deposition resistance capacity of treated catalysts was enhanced greatly. Meanwhile, compared to traditional ZSM‐5 zeolite, the ratio of Brønsted to Lewis (B/L) acid sites of ZSM‐5/NH₃⋅H₂O (B/L = 7.35) zeolite slightly increased but the amount of acid sites reduced, while those of ZSM‐5/NaHCO₃ (B/L = 0.127) and ZSM‐5/Na₂CO₃ (B/L = 0.107) significantly reduced. Further, the catalyst treated with NH₃⋅H₂O solution was evaluated in the methanol to aromatics reaction and led to an enhanced aromatization reaction rate. The liquid hydrocarbons product distribution exhibited higher aromatic hydrocarbons yield (56.12%) and selectivity (40.28%) of benzene, toluene and xylene (BTX) with isoparaffin content reducing to 26.17%, which could be explained by appropriate B/L acid sites ratio, higher pore volumes and higher surface area.     

Active surface formation on a promoted copper catalyst of the partial oxidation of ethanol

The catalytic properties, chemical composition, and morphology of the surface of electrolytic copper crystals promoted with phosphorus as catalysts of the partial oxidation of ethanol into acetaldehyde were studied. A mechanism of active copper surface formation under the action of the promoting admixture was suggested. Promotion was shown to cause the formation of copper polyphosphates on the surface. Particles of copper metal responsible for selective alcohol transformation are formed in a promoter layer under the action of the reaction medium.     

Effect of CO on surface oxidation of uranium metal

The surface reactions of uranium metal with carbon monoxide at 25 and 200 °C have been studied by X-ray photoelectron spectroscopy (XPS); respectively. Adsorption of carbon monoxide on the surface layer of uranium metal leads to partial reduction of surface oxide and results in U4f photoelectron peak shifting to the lower binding energy. The content of oxygen in the surface oxide is decreased and O1s/O4f ratio decreases with increasing the exposure of carbon monoxide. The investigation indicates the surface layer of uranium metal has resistance to further oxidation in the atmosphere of carbon monoxide.     

Relaxation of the rate of o-xylene oxidation to phthalic anhydride on vanadium catalysts

Based on numerical analysis of experimental data, the main ideas of the reaction mechanism have been confirmed and kinetic principles of the non-steady=state reaction have been determined.

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Effect of surface modification on the reactivity of MCF-supported IndaBOX

MCF-immobilized indaBOX-copper complexes, which show high enantioselectivities in asymmetric Diels-Alder and cyclopropanation reactions and have reactivities strongly affected by their environment, were prepared using various linker groups and silanol capping agents.     

Ce金属改性对Cu-SAPO-34催化剂水热稳定性能的影响

采用浸渍法制备系列铜铈复合氧化物分子筛催化剂（Cu-Ce/SAPO-34）,探讨了Ce负载量对Cu/SAPO-34催化剂的水热稳定性的影响,通过XRD、SEM、H₂-TPR、XPS和NH₃-TPD等表征手段分析不同催化剂活性和稳定性差异的原因。研究表明,750℃水热老化未造成Cu-Ce/SAPO-34催化剂菱沸石（chabazite,CHA）骨架坍塌,但破坏了部分孔结构和酸性位点,使催化剂表面结晶度下降。水热老化促使催化剂晶格发生拉伸畸变,使Cu²⁺迁移到催化剂表面,Cu²⁺和Ce⁴⁺团簇形成CuO和CeO₂,造成催化剂的Cu活性物种减少和氧空穴浓度降低,所以Cu-Ce/SAPO-34的NH₃选择性催化还原（NH₃-Selective Catalytic Reduction,NH₃-SCR）性能下降。掺杂Ce能提高Cu/SAPO-34催化剂表面的Cu²⁺和Cu⁺活性物种量,减少Cu物种团簇形成CuO,改善催化剂表面活性Cu物种分布性。提高Ce的负载量能稳固Cu-Ce/SAPO-34催化剂的结构,使中、弱强度酸位点得以维持,从而提高其水热稳定性。结果表明,在研究的系列Cu-Ce/SAPO-34催化剂中,Cu/Ce质量比为4：5时具有最佳的水热稳定性。     

Ir-in-CeO_2催化剂上CO氧化过程中表面碳酸盐的量热研究

应用Tian-Calvet热流量热仪与脉冲微反系统相结合的脉冲量热装置研究了Ir-in-CeO2(Ir主要包裹在CeO2里)催化剂上CO氧化过程表面碳酸盐的形成及其转化.结果表明,碳酸盐的吸附强度与CeO2表面价态直接相关.在反应中首先形成约0.07个单层覆盖度的不可逆吸附碳酸盐,随后形成约0.02个单层覆盖度的可逆吸附碳酸盐并随着Ce3+转变为Ce4+而分解.     

Catalyst optimization strategy: selective oxidation of o-xylene to phthalic anhydride

The oxidation of o-xylene and/or naphthalene to phthalic anhydride is one of the important industrial processes based on catalytic selective oxidation reactions. Vanadia--titania catalysts have been used in the industrial phthalic anyhdride process for the last 50 years. The operation parameters like the temperature range of operation, reactor inlet pressures, contact times, o-xylene loadings, etc. were constantly improved during this period of continuous process optimization so as to optimize catalyst performance and increase its life time. However, a fundamental understanding of the mutual interaction of the rather complex reaction network and the catalyst formulation is still missing. Recently, a detailed study of by-product formation as function of process conditions allowed us to develop a novel, improved reaction scheme for the catalytic oxidation of o-xylene. Based on this understanding, a detailed investigation was conducted for the first time of the by-product formation under varying operation conditions and as a function of the active mass variation exploiting high-throughput, as well as bench scales reactors. This high-throughput testing allowed us to relate reaction kinetics to novel catalyst formulations.