Synthesis and crystallization of a novel poly(ether ketone ether ketone ketone) containing meta-phenylene linkage: PEKEKK(T/I)

Poly(ether ketone ether ketone ketone) containing meta-phenylene linkage (PEKEKK(T/I)) was synthesized by electrophilic Friedel-Crafts acylation condensation of 1, 4-diphenoxybenzophenone with terephthaloyl chloride (T) and isophthaloyl chloride (I) with a T/I ratio of 1 and characterized by LR,DSC,TGA and WAXD. PEKEKK(T/I) has two different crystal structures: a conventional Farm I structure, the same as that observed in PEEK and PEK, wich is usually developed from melt crystallization, and a new Form II structure which can be developed from cold crystallization or solvent induced crystallization (by exposing the glassy sample to methylene chloride).

Studies of the ortho effect in fragmentations of acetyl ion adducts of disubstituted benzenes

The ion-molecule reactions of disubstituted benzenes under chemical ionization conditions with acetyl chloride as reagent gas were examined, and the fragmentation reactions of the adduct ions (mostly proton and acetyl ion adducts) were studied by collision-induced dissociation. Electron-releasing substituents favored the adduct reactions, and electron-withdrawing groups did not. The position and properties of substituting groups had an effect on the relative abundances of the adduct ions. Several examples of the ortho effect were observed. The fragmentation reaction of the adduct ions formed by ortho-benzenediamine with the acetyl ion was similar to the reductive alkylation reaction of amines in the condensed phase. Copyright (C) 2001 John Wiley & Sons, Ltd.

Coking kinetics on the catalyst during alkylation of fcc off-gas with benzene to ethylbenzene

The production of ethylbenzene from the alkylation of dilute ethylene in fee off-gases with benzene has been commercialized in China over a newly developed catalyst composed of ZSM-5/ZSM-11 co-crystallized zeolite. The duration of an operation cycle of the commercial catalyst could be as long as 180 days. The conversion of ethylene could attain higher than 95%, while the amount of coke deposited on the catalyst was only about 10 wt.%. Thermogravimetry (TG) was used to study the coking behavior of the catalyst during the alkylation of fee off-gas with benzene to ethylbenzene. Based on effects of reaction time, reaction temperature, reactants and products on coking during the alkylation process, it is found that the coking rate during the alkylation procedure follows the order: ethylbenzene > ethylene > propylene > benzene for single component, and benzene-ethylene > benzene-propylene for bi-components under the same reaction condition. Furthermore, the coking kinetic equations for benzene-ethylene, benzene-propylene and ethylbenzene were established. (C) 2003 Elsevier B.V. All rights reserved.

Combination of CH4 oxidative coupling reaction with C2H6 oxidative dehydrogenation by CO2 to C2H4

A new process has been suggested for converting natural gas to ethylene by combining oxidative coupling of methane with ethane dehydrogenation to provide an efficient method for the utilization of thermicity and CO2. From their thermodynamics, it is clear that the exothermicity from CH4 oxidative coupling reaction (DeltaH(800degreesC) = -174.3 kJ mol(-1)) can support C2H6 dehydrogenation by CO2 (DeltaH(800degreesC) = + 180.2 kJ mol(-1)). Meanwhile, the two reactions can be conducted under the same reaction conditions, such as the reaction temperature and reaction pressure as well as space velocity. In addition, the CO2 yielded from CH4 oxidative coupling reaction can be directly used for C2H6 dehydrogenation. Two kinds of catalyst are developed for this combined process with an achievement, from which C2H4 content in tail gas can reach attractively 16.4%, which can be used directly to produce ethylbenzene by the alkylation of benzene. (C) 2002 Elsevier Science Ltd. All rights reserved.

Study of the alkylation of isobutane with n-butene over WO3/ZrO2 strong solid acid. 1. Effect of the preparation method, WO3 loading, and calcination temperature

A series of strong solid acids composed of WO3/ZrO2 were prepared. Their crystal structure, surface state, and acidity were determined by the methods of X-ray diffraction, thermal gravimetric and differential thermal analysis, temperature-programmed reduction, laser Raman, and acidity measurement. The results revealed that ZrO2 in WO3/ZrO2 existed mainly in the tetragonal phase, the addition of WO3 plays an important role in stabilizing the tetragonal phase of ZrO2, and all of the samples possessed large surface areas. WO3 in WO3/ZrO2 is mainly monolayer dispersed, and a small amount crystallized on the ZrO2 surface and partly reacted with ZrO2 to form the bond of Zr-O-W, acting as the strong solid acid center. The catalytic properties of WO3/ZrO2 strong solid;acids for alkylation of isobutane with butene at different conditions were investigated. They had a better reaction performance than other strong solid acids; a parallel relationship could be drawn between the catalytic activity and the acid amounts as well as the acidic strength of the catalysts.

Active components and mechanism of isobutane alkylation with butenes in the catalytic system of HPAs plus AcOH

The catalytic active phase (CAP) of a novel liquid catalyst for isobutane alkylation with butenes was investigated, the composition of the CAP was analysized, The components of the catalytic active phase were separated and examined by the methods of FTIR, UV and NMR etc., On the basis of these results, a reaction mechanism based on the formation of protonated heteropolyacid as an intial stage in the isobutane alkylation with butenes was postulated, which is in agreement with the experimental results.

A study on the catalytic behaviors of concentrated heteropolyacid solution - I. A novel catalyst for isobutane alkylation with butene

The catalytic behaviors of a novel liquid acid catalyst (composed of heteropolyacid and acetic acid) for alkylation of isobutane with butene was investigated. As a solvent acetic acid had a synergistic effect. It enhanced the acid strength of HPA and its stability. The conditions for the formation of the catalytically active phase were studied systematically. The content of crystal water of HPA and the quantity of solvent affect the formation of active phase and the catalytic activity. Catalytically active phase consists of HPA, acetic acid and hydrocarbon produced from the reaction, as well as traces of water from the crystal water of HPA. This catalyst system is comparable to the sulfuric acid in catalytic activity.

Studies on the alkylation of isobutane with butene over WO3/ZrO2 strong solid acid (I) - Effect of preparation, load of WO3 and calcination temperature

A series of WO3/ZrO2 strong solid acid prepared under different conditions were studied. Their crystal structures, surface properties and acidities were determined by means of XRD, DTA-TG, H-2- TPR, Laser Raman and acidity measurements. The results revealed that ZrO2 in WO3/ZrO2 existed mainly in tetragonal phase, the addition of WO3 plays an important role to stabilize tetragonal phase of ZrO2 and thus the catalyst had a considerable surface area. WO3 in WO3/ZrO2 was dispersed and crystalized in WO3 crystalite on ZrO2 surface and partly reacted with ZrO2 to form the bond of Zr-O-W, which acts as the strong solid acid site. The catalytic properties of WO3/ZrO2 strong solid acid for alkylation of iso-butane with butene under the different conditions were investigated. They had a better reaction performance than other strong solid acids, a parallel relationship could be drawn between the catalytic activity and the amount of acid sites as well as the acidic strength of the catalysts.

ASYMMETRIC ALKYLATION MEDIATED BY CHIRAL PHASE-TRANSFER CATALYSTS

Seven chiral phase-transfer catalysts, among which three have not been reported so far, have been prepared and applied to the asymmetric alkylation of alpha-isopropyl benzyl cyanide and alpha-isopropyl-p-chlorobenzyl cyanide. The result showed that short reaction time, low temperature, high catalyst concentration and non-polar solvent would improve the optical yield. The influence of structure of the catalyst on the asymmetric reaction was preliminarily studied. The optical purity of the products were evaluated by gas chromatography with a chiral column.

Ferrocenylphosphine-imine ligands for Pd-catalyzed asymmetric allylic alkylation

Ferrocenylphosphine-imine ligands 6 derived front (R,S)-PPFNH2-R 5 and a variety of benzaldehydes were applied in the Pd-catalyzed asymmetric allylic alkylation of 1,3-diphenylprop-2-en-1-yl acetate 7a or pivalate 7b with dimethyl malonate. The substituent effects on the catalytic reaction were investigated, and 96% e.e. with 99% yield was achieved when the m-nitro substituted ligand 6k was used. (C) 2002 Elsevier Science Ltd. All rights reserved.

Numerical Simulation of Gaseous Detonation of H_2-O_2 Mixture with Detailed Chemical Reaction Model

采用高精度的ENO格式和基于基元化学反应的真实化学反应模型求解氢氧混合气体一维爆轰波的精细结构。采用直接起爆方法得到稳定传播的爆轰波,计算的爆轰波阵面参数和实验相当符合。对爆轰波反应区化学反应的研究表明,参与反应的不同组分具有不同类型的变化特征。网格尺寸影响的研究表明,计算结果的精度随着网格尺寸的增加而增加,并能保持较好的收敛性。移动网格研究结果表明,网格运动速度和爆轰速度接近时,两者的相互作用对计算结果产生一定影响。

Microscopic theory of chemical-reaction rate

In this paper we deduce the formulae for rate-constant of microreaction with high resolving power of energy from the time-dependent Schrdinger equation for the general case when there is a depression on the reaetional potential surface (when the depression is zero in depth, the case is reduced to that of Eyring). Based on the assumption that Bolzmann distribution is appropriate to the description of reactants, the formula for the constant of macrorate in a form similar to Eyring's is deduced and the expression for the coefficient of transmission is given. When there is no depression on the reactional potential surface and the coefficient of transmission does not seriously depend upon temperature, it is reduced to Eyring's. Thus Eyring's is a special case of the present work.