ZnCl2/粘土-SA01催化合成二苯甲烷反应动力学研究

在ZnCl2/粘土-SA01催化剂上合成了二苯甲烷,考察了负载量、苯/苄基氯摩尔比、催化剂用量、反应温度和时间对该反应的影响,研究了以ZnCl2/粘土-SA01为催化剂合成二苯甲烷的反应动力学,为探讨其反应机理和研究烷基化反应动力学提供了依据.结果表明,温度在303-318K时,本征动力学方程为r=k[ZnCl2/粘土-SA01]0.8[C6H6][C6H5CH2Cl],属二级反应,表观反应活化能为88.6kJ/mol;在328-353K时,其本征动力学方程为r=k[ZnCl2/粘土-SA01]0.1,反应属零级反应,表观活化能为52.8kJ/mol.     

Mechanical properties of solvolysis lignin-derived polyurethanes

In order to study the tensile properties of solvolysis lignin polyurethanes, polyurethane (PU) films were prepared from the solvolysis lignin (SL)–polyethylene glycol (PEG)–diphenylmethane diisocyanate (MDI) system, and in addition to this further PU films were also prepared from the SL–MDI system. In the SL–PEG-MDI system, the SL content, the molecular weight of PEG and the NCO:OH ratio were varied in order to control the physical properties. The tensile stress and Young's modulus of the PUs of the SL–PEG–MDI type increased with increasing SL content and NCO:OH ratio. The tensile properties of the PUs from the SL–MDI system showed no NCO:OH ratio dependency; i.e. the mechanical properties of PUs are not influenced by the change in crosslinking. It is possible to control the tensile properties of PUs of the SL–PEG–MDI type by changing the content of PEG and SL at a constant NCO:OH ratio.     

Benzylation of benzene and substituted benzenes by benzyl chloride over InCl3, GaCl3, FeCl3 and ZnCl2 supported on clays and Si-MCM-41

Liquid phase benzylation of benzene by benzyl chloride to diphenyl methane over InCl₃, GaCl₃, FeCl₃ and ZnCl₂ supported on commercial clays (viz. Montmorillonite-K10, Montmorillonite-KSF and Kaolin) or on high silica mesoporous MCM-41 (at 60, 70 and 80 °C) has been investigated. The supported InCl₃, GaCl₃ and FeCl₃ showed high activity for the benzylation of benzene. The redox function created due to the impregnation of the clays or Si-MCM-41 by InCl₃, GaCl₃, FeCl₃ or ZnCl₂ seems to play a very important role in the benzylation process. Among the catalysts, the InCl₃/Mont.-K10 showed both high activity and high selectivity for the benzylation. The activity of this catalyst for the benzylation of different aromatic compounds is in the following order: benzene>toluene>mesitylene>anisole. The InCl₃ (or GaCl₃)/Mont.-K10 (or Si-MCM-41) catalyst showed high benzene benzylation activity even in the presence of moisture in the reaction mixture. The catalyst can also be reused in the benzylation for several times. Kinetics of the benzene benzylation (using excess of benzene) over the supported metal chloride catalysts have also been thoroughly investigated. A plausible reaction mechanism for the benzylation over the supported metal chloride catalysts is proposed.     

Synthesis of Aromatic Ketones from Aromatic Compounds Using Vanadium‐Containing Mesoporous Silicates

Aromatic ketones were synthesized from aromatic compounds via liquid‐phase oxidation at 60 °C and 1 atm over vanadium‐containing MCM‐41 catalysts using a batch reactor. The catalysts were prepared by direct hydrothermal (4V‐MCM‐41) and wet impregnation (9V/MCM‐41) methods. Their physico‐chemical properties were determined with various characterization techniques. For the oxidations of all substrates in this work, 4 V‐MCM‐41 exhibits superior catalytic performance than 9 V/MCM‐41 due to its larger values of unit cell parameter, BET surface area, and vanadium dispersion as well as stronger oxidation ability of vanadium‐oxygen species. Apparently, the single site, isolated vanadium centers in 4V‐MCM‐41 possess much higher activity (based on the turnover number) than those containing more vanadium atoms in 9V/MCM‐41. In addition, the substrate activities decrease in the order of diphenylmethane > fluorene > 9,10‐dihydroanthracene > ethylbenzene ≥ 4‐nitroethylbenzene, which are attributed to their distinct molecular structures.     

Mechanism of W(CO)6 sonolysis in diphenylmethane

The present work analyses the mechanism of W₂C/C nanocomposite formation during sonolysis of W(CO)₆ in diphenylmethane (DPhM) solutions. Carbon supported WC_x nanoparticles attract much interest as an alternative fuel cell electrocatalysts. Sonolysis of neat DPhM under the effect of 20 kHz power ultrasound in argon at 80 °C yields a sonopolymer as a solid product and acetylene, hydrogen, methane, diacetylene and benzene as gaseous products. Diacetylene is formed due to the secondary sonochemical dimerisation of acetylene obtained at the primary stage of DPhM sonolysis. FTIR and μ-Raman studies show that the sonopolymer consists of a mixture of some polymeric partially oxidized aromatic species, and disordered carbon. Sonolysis of W(CO)₆ in diphenylmethane solutions follows the first order kinetics. This process yields monodispersed 2-3 nm X-ray amorphous WC_x nanoparticles embedded in amorphous sonopolymer. The annealing of air sensitive as-prepared solids in an inert atmosphere at 600 °C causes formation of stable W₂C/C nanocomposite with W₂C average particle size in the range of 4-7 nm and hexagonal carbon fine particles with the average size of 30-40 nm. Kinetic study revealed that tungsten carbide is formed inside the cavitation bubble due to the reaction of tungsten nanoparticles originated from primary sonolysis of W(CO)₆ with acetylene produced as a result of diphenylmethane sonochemical degradation.