摘要:

AbstractKinetic studies on the oxidation of carbon monoxide have been carried out between 413 and 473 K at different partial pressures of carbon monoxide and oxygen by means of the static method using vacuum‐activated, hydrogen‐reduced, and NiO‐doped In2O3semiconductors as catalysts. A strong carbon dioxide inhibiting effect is observed. The experimental data satisfactorily fit an equation derived by assuming the controlling step to be the adsorption of gaseous oxygen on the surface of catalyst. CO and CO2adsorb on the lattice oxygens (O o2−), while O2adsorbs on the oxygen vacancies (V ox) formed by vacuum‐activation, H2‐reduction, and NiO‐doping of In2O3. When CO2formed during the reaction is removed by means of liquid nitrogen trap, the oxidation is found to be first‐order with respect to CO and to be half‐order with respect to O2. The concentration of oxygen vacancy in the solid catalyst is shown to be the controlling factor for the oxidation of carbon monoxide. A possible reaction mechanism can be explained by then‐type character of In2O3and proposed from the experimentally obtained kinetic

ISSN:0538-8066    

DOI:10.1002/kin.550190102

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractAn analysis of thermochemical and kinetic data on the bromination of the halomethanes CH4–nXn(X = F, Cl, Br;n= 1–3), the two chlorofluoromethanes, CH2FCl and CHFCl2, and CH4, shows that the recently reported heats of formation of the radicals CH2Cl, CHCl2, CHBr2, and CFCl2, and the CH bond dissociation energies in the matching halomethanes are not compatible with the activation energies for the corresponding reverse reactions. From the observed trends in CH4and the other halomethanes, the following revised ΔH°f,298(R) values have been derived: ΔH°f(CH2Cl) = 29.1 ± 1.0, ΔH°f(CHCl2) = 23.5 ± 1.2, ΔHf(CH2Br) = 40.4 ± 1.0, ΔH°f(CHBr2) = 45.0 ± 2.2, and ΔH°f(CFCl2) = −21.3 ± 2.4 kcal mol−1. The previously unavailable radical heat of formation, ΔH°f(CHFCl) = −14.5 ± 2.4 kcal mol−1has also been deduced. These values are used with the heats of formation of the parent compounds from the literature to evaluate CH and CX bond dissociation energies in CH3Cl, CH2Cl

ISSN:0538-8066    

DOI:10.1002/kin.550190103

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe reaction of OH and OD radicals with ethylene in the presence of 1 atm argon and 6 Torr water vapor was studied in the temperature range 343–1173 K. The results reveal three kinetically separate temperature regions: (1) 343–563 K, where the disappearance of OH radical is dominated by the addition of OH to the double bond of ethylene; (2) 563–748 K, where concurrent reactions of addition, the reverse reaction of addition and H‐atom abstraction is dominant; and (3) 748–1173 K, where H‐atom abstraction is likely the main reaction. The rate for hydrogen abstraction is 2.4 × 10−11exp[(−2104 ± 125)/T] cm3/molec‐s (for OD 2.1 × 10−11exp[(−2130 ± 172)/T] cm3/molec‐s). There was no obvious pyrolysis of ethylene below 1073 K. The study of OD radical with ethylene s

ISSN:0538-8066    

DOI:10.1002/kin.550190104

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractA recently published kinetic model of the Belousov‐Zhabotinsky reaction was studied by the feature sensitivity analysis of the slow bromide consumption and slow bromide production periods of the relaxing‐type oscillatory system. The computed sensitivities allowed us to reveal the kinetic importance of the 17 individual reactions during the two, “kinetically homogeneous” states of the oscillation. Similarities and differences in the relative kinetic importances of the reaction steps were carefully studied when changing the magnitude of the rate constants (high set and low set). Of the 17 reactions examined, the attack of Ce4+on malonic acid proved to be an essential step of the mechanism. Using the low set, there emerge more reactions which significantly affect the length of the two kinetic

ISSN:0538-8066    

DOI:10.1002/kin.550190105

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe rates of migration of acetyl, propionyl, isobutyryl, and benzoyl substituent in Diels‐Alder adducts of acyl‐1, 4‐benzoquinones, (enediones), (I), to form the corresponding 2‐acyl hydroquinones, (II), in 50% (v/v) ethanolic pyridine have been studied in detail. Rate dependence on pyridine concentration has been established and maximum rate was found at pyridine a volume percent of 25 in an ethanolic reaction mixture. The study indicated first‐order dependence on reactants and fractional dependence on pyridine concentration. The effect of substituents of the acyl group on the rate showed that electronic factors play an important role on the stability of the transition state. A plausible mechanism, which is consistent with the results has been postulated and suitable rate law in consonance with the postulated mechanism have bee

ISSN:0538-8066    

DOI:10.1002/kin.550190106

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe thermal decomposition of acetonitrile was studied behind reflected shocks in a single pulse shock tube over the temperature range 1350–1950 K at overall densities of approximately 3 × 10−5mol/cc. Methane and hydrogen cyanide are the major reaction products. They are formed by an attack of H and CH3radicals on acetonitrile. The initiation step of the pyrolysis is the self dissociation of acetonitrile:for which the following rate constant was obtained:k1= 6.17 × 1015exp(−96.6 × 103/RT)sec−1. WhereRis given in units of cal/K mol. Additional reaction products which appear in the pyrolysis are: C2H2, C2H4, CH2CHCN, CHCHCN, C2H5CN, C2N2, and C4H2. Acetylene is formed from methane pyrolysis and becomes a major reaction product at high temperatures. Acrilonitrile and cyanoacetylene are secondary products originating from the CH2CN radical. Rate parameters for the formation of the reaction prod

ISSN:0538-8066    

DOI:10.1002/kin.550190107

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550190101

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY