共查询到20条相似文献,搜索用时 629 毫秒
1.
2.
Summary The deaquation-anation of solid aquapentamminecobalt(III) chloride was studied isothermally and non-isothermally. Kinetic data were obtained from t.g.a. and were analysed using 17 rate laws known for solid state reactions. This reaction, long interpreted as SN2, was found to obey an A1.5 rate law from both types of experiments. From the isothermal experiments, an E
a of 97.0 kJ mol-1 was found. 相似文献
3.
本文研究了室温时K~3Fe(CN)~6,K~4Fe(CN)~6在酸碱条件下发生的固相配位化学反应。结果表明:K~3Fe(CN)~6与NaBH~4固相混合物室温下不反应,但加入固体氢氧化钠后,K~3Fe(CN)~6与NaBH~4的固相氧化还原反应在室温下很容易进行。K~4Fe(CN)~6与K~2S~2O~8的固相氧化还原反应在室温下能顺利进行,但当固体KOH存在时,反应明显受到抑制。K~3Fe(CN)~6与K~2C~2O~4.H~2O室温下无反应,但与H~2C~2O~4.2H~2O在室温时即发生固相取代反应。 相似文献
4.
5.
Y Yang N Priyadarshani T Khamatnurova J Suriboot DE Bergbreiter 《Journal of the American Chemical Society》2012,134(36):14714-14717
The studies described here show that a relatively low molecular weight, narrow polydispersity polyethylene (PE) wax (Polywax) can serve as a nontoxic and nonvolatile alternative to alkane solvents in monophasic catalytic organic reactions where catalysts and products are separated under biphasic conditions. In this application, a polymer that is a solid at room temperature substitutes for a conventional alkane solvent at ca. 80 °C. In addition to the advantages of being a nonvolatile, nontoxic, reusable solvent, this hydrocarbon polymer solvent, like heptane, can sequester nonpolar soluble polymer-bound catalysts after a reaction and separate them from products. The extent of this separation and its generality were studied using polyisobutylene (PIB)- and poly(4-dodecylstyrene)-bound dyes and PE-bound Pd allylic substitution catalysts, PIB-bound Pd cross-coupling catalysts, and PE- and PIB-bound metathesis catalysts. Catalytic reactions were effected using single-phase reaction mixtures containing Polywax with toluene, THF, or THF/DMF at ca. 80 °C. These solutions either separate into two liquid phases on addition of a perturbing agent or separate as a solid/liquid mixture on cooling. The hydrocarbon polymer-bound dyes or catalysts either separate into the hot liquid Polywax phase or coprecipitate with Polywax and are subsequently isolated as a nonvolatile Polywax solid phase that contains the dye or the recyclable catalyst. 相似文献
6.
A simple and effective preparation of enamines from bulky ketones and secondary amines has been achieved with the aid of Lewis acid on various solid supports. The optimized yields were higher than those obtained without the solid support. Factors affecting the yield and regioselectivity of these reactions were also studied. Evidence showed that the reaction proceeded simultaneously in solution and on the solid support. 相似文献
7.
The heterogeneous reactivity of HOCl on solid KBr at ambient temperature has been studied using a Knudsen flow reactor. On solid KBr steady-state uptake experiments reveal the formation of Br- and Cl-containing reaction products formed in secondary reactions such as Br(2), BrCl, HOBr, BrOCl, Cl(2) and Cl(2)O with the latter two predominating in the late stages of the reaction. The uptake coefficient gamma spanning a range between 0.15 and 1 x 10(-3) and product yields of HOCl strongly depend on the nature of the solid sample, whether grain, ground grain or thin sprayed film, as well as on sample processing such as pumping and/or heating. Furthermore, the presence of adsorbed halogen species such as Br(2)(a) are crucial for the kinetics of the reaction of HOCl with solid KBr substrates. The presence of surface-adsorbed water (SAW) leads to deactivation of KBr whereas mechanical stress such as grinding leads to the formation of surface defects that become reaction centers. Desorption of SAW at T > 620 K induces high reactivity of the KBr sample at ambient temperature. A reaction mechanism encompassing all significant observations including unusual autocatalytic activity is given as there is no direct reaction of HOCl with solid KBr. It stresses the importance of adsorbed Br-containing species such as Br(2)(a) and HBr(a) that initiate the heterogeneous chemistry of HOCl on solid KBr in the presence of SAW. The role of surface acidity and SAW for the extent of reaction is emphasized. 相似文献
8.
Solvent-free Claisen-Schmidt reactions of cycloalkanones with various substituted benzaldehydes (aryl aldehydes) using solid NaOH (20 mol%) and applying a grinding technique were studied. Quantitative yields (96-98%) of α,α'-bis-(substituted-benzylidene)cycloalkanones were obtained. Aliphatic aldehydes also provided α,α'-bis-(substituted-alkylidene)cycloalkanones in very good yields with minor amounts of a-(substituted-alkylidene)cycloalkanones. The catalytic performance of solid NaOH was examined. The molar ratio of NaOH was optimized. The catalytic effect of solid NaOH was also evaluated by comparing it with KOH, NaOAc, and NH(4)OAc and it turns out that 20 mol% of solid NaOH was good enough to catalyze the Claisen-Schmidt reactions of cycloalkanones with various substituted benzaldehydes. Additionally, the regioselectivity of the Claisen-Schmidt reaction of acetone with benzaldehyde was examined. Using the same method, we could synthesize the corresponding bis-benzylidene- and mono-benzylideneacetone separately in 98% and 96% yields, respectively. 相似文献
9.
J.H. Petropoulos 《Journal of membrane science》1981,8(1):41-50
Simple non-homogeneous irreversible reactions between a mobile reactant A, and immobile reactive groups R, in a solid yielding immobile product B, are considered. The possibilities are discussed of analysing such reactions when they are partially rate-controlled by the diffusion of A. It is shown that the effect of diffusion can be approximately described by a single parameter (“kinetic modulus”) up to a fairly marked degree of diffusion control; so that methods of kinetic analysis analogous to those used for reactions where the solid acts merely as a catalyst can be applied. The “effective reaction constant” previously defined for use as a kinetic modulus (analogous to the “Thiele modulus” of heterogeneous catalytic reactions) is considered further here. An improved, experimentally measurable kinetic modulus, based on the distribution of B across the solid, is also defined and studied. 相似文献
10.
The paper compares building and decomposition pathways of two phosphonic acids, amino trimethylene phosphonic acid (ATMP) and 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP).The theoretical formation reactions were composed using elementary reactions and compared to reaction routes published in literature. As result, summary reaction pathways for both phosphonic acids are proposed which only vary in the number of reaction steps required. These reaction steps include carbonyl reactions, SN2-reactions, and ionic reactions. The synthesis of ATMP proceeds in three reaction steps, whereas HEDP is formed in one reaction. The thermal decomposition of both phosphonic acids in solid state was examined by combination of thermogravimetry coupled with infrared spectroscopy as well as pyrolysis gas chromatography coupled with mass spectrometry. Decomposition mechanisms were deduced and compared to the theoretical findings resulting in the conclusion that the decomposition processes of ATMP and HEDP follows the formation mechanism.Thus, the suitability of theoretical considerations for the understanding of thermal decomposition processes is shown. 相似文献
11.
The objective of this research work was to investigate the kinetics of esterification of acetic acid with n-butanol through the variation of experimental parameters. The reaction mixture was catalyzed heterogeneously by a sulfonated catalyst in batch mode of operation. The catalyst was prepared from abundantly available agro-waste, Cajanus cajan husk by chemical activation process, which produces a carbon-based solid catalyst with high surface area. The catalyst was characterized by a Brunauer-Emmet-Teller surface analyzer and Fourier transform infrared spectroscopy to know the surface morphology. Process parameters such as contact time, reaction temperature, and catalyst loading, which can influence the extent of conversion of reactants, were studied. Furthermore, the kinetic investigation was also carried out to estimate the kinetic parameters for uncatalyzed and catalyzed reaction using the second-order pseudo-homogeneous (P-H), Eley-Rideal (E-R), and Langmuir-Hinshelwood (LH) kinetic models for this research work. The kinetic parameters such as activation energy, preexponential factor, and the thermodynamic parameters such as enthalpy and entropy were estimated for uncatalyzed and catalyzed reactions using these three models. The process conditions were optimized for catalyzed and uncatalyzed reactions to obtain the maximum product yield by minimizing root mean square error of each experimental data using the MS-excel solver tool. Thus, this study reveals the high potential of an agro-waste, Cajanus cajan husk as raw material for the synthesis of catalyst. The results show that the E-R model is more appropriate for predicting the dynamic data of an esterification reaction, as the forward rate of reaction estimated using the E-R model are more modified than P-H and L-H models. 相似文献
12.
13.
原位漫反射红外光谱技术用于气固催化反应机理的研究 总被引:1,自引:0,他引:1
漫反射傅立叶变换红外光谱技术是一种对固体粉末样品进行直接测量的光谱方法,是近年来发展起来的一项较理想的原位表征技术。原位漫反射红外技术由于可直接对催化剂表面的吸附态物种给出红外信号,可方便地跟踪鉴定反应中间态和产物,从而为催化反应体系反应机理的考察给出直接的证据。本文对于原位漫反射红外技术用于低温水煤气变换反应和水汽逆变换反应、醇类的水蒸汽重整、含CO2的合成气制取甲醇、低碳烃制合成气、CO催化氧化以及其他烃类和含氧化合物的氧化等方面进行了综述,认为该技术可很好地剖析气固相催化反应机理。 相似文献
14.
Cyclization reactions of lapachol (1) isolated from Heterophragma adenophyllum have been studied under microwave irradiation under different conditions using alumina (acidic, basic and neutral)/silica gel/montmorillonite (KSF and K-10) as solid support along with neat reaction using 2-3 drops of DMF giving naturally occurring dehydro-alpha-lapachone (2), alpha-lapachone (3), beta-lapachone (4) depending upon the nature of support and irradiation time. A novel naphthoquinone derivative adenophyllone (5) can be synthesized from lapachol using DMF under microwaves. 相似文献
15.
The polyethylene glycol resin (PEG-Resin) which possesses hydrophilic properties was prepared by grafting the polyethylene glycol onto the chloromethylated copolymer of styrene and divinylbenzene in the presence of concentrated sodium hydroxide solution. The proceeding of the graft reaction was identified by IR spectrum analysis. There factors which affected the grafting reactions were investigated. By using the PEG-Resin polymer support, we compared the reactions for the syntheses of a tetra-peptide and a penta-peptide with the Merrifield solid peptide synthesis. We also measured the reaction kinetics of these reactions. The experimental results showed that by employing the PEG-Resin, the reaction rates and condensation yields of these peptide syntheses were improved. 相似文献
16.
Welmoed Beenen Douwe J. v. D. Wal Lon P.B. M. Janssen Ab Buijtenhuijs Andr H. Hogt 《Macromolecular Symposia》1996,102(1):255-263
The graft-copolymerization of styrene on PP in the solid phase has been studied under various reaction conditions using a radical initiator. Polymerization kinetics were investigated by DSC experiments and reactions in glass ampoules. The conversion rate and grafting efficiency of styrene appeared to be strongly influenced by the presence of the PP matrix and the styrene/PP ratio. From reactions in a lab scale reactor the concentrations of styrene and initiator, the dosing rate and the temperature were investigated to be critical parameters determining the grafting efficiency and the average length and number of grafts. The phenomena observed were explained by describing the process in relative rates of diffusion and polymerization, including swelling of the polymer by styrene monomer and diffusion limitations (Trommsdorff effect). 相似文献
17.
18.
19.
S. D. Badmaev A. S. Smorygina E. A. Paukshtis V. D. Belyaev V. A. Sobyanin V. N. Parmon 《Kinetics and Catalysis》2018,59(1):99-103
The gas-phase carbonylation reaction of dimethoxymethane (DMM) to methyl methoxyacetate on different solid acids was studied. It was established that this reaction was accompanied by the occurrence of a side reaction of DMM disproportionation into dimethyl ether and methyl formate. It was shown that the activity of solid acids in both of the reactions depends on the strength of Brønsted acid sites according to an equation like the Brønsted–Evans–Polanyi–Semenov correlations. 相似文献
20.
Solid microparticles of several different insoluble organic compounds were mechanically immobilized on the surface of graphite
electrodes and immersed into a liquid electrolyte in order to study their electrochemical reactions. Cyclic staircase voltammetry
and square-wave voltammetry were used. Quinhydrone was found to be a stable intermediate in the reversible redox reaction
of solid quinone and hydroquinone on the electrode surface. The reaction occurs on the surface of the solid particle which
is in contact with water. Indigo can be reduced to leucoindigo and oxidized to dehydroindigo in two separate reversible redox
reactions. In strongly basic medium indigo dissolves in water upon electroreduction. A hydroacridine radical was detected
as a stable intermediate in the electrochemically irreversible redox reaction of acridine and dihydroacridine. Famotidine
can be electrooxidized and the product of this reaction can be electroreduced in two separate chemically irreversible reactions.
Probucol is oxidized to a semiquinone radical which can be re-reduced in an electrochemically irreversible redox reaction.
Propyl- thiouracil can be also oxidized to an unknown product which can be re-reduced in a chemically reversible, but slow
solid state surface redox reaction. Reductions of solid thionicotinoylanilide and nicotinoylanilide are totally irreversible.
Received September 22, 1998. Revision March 19, 1999. 相似文献