Mechanism of the silver-on-silica catalyzed oxidation of cumene in the liquid phase

Induction Model for the Heterogeneously-Catalyzed Liquid-Phase Oxidation of Aldehydes

“…The induction phenomenon has been observed and discussed not only in the homogeneously-catalyzed but also in the heterogeneously-catalyzed liquid-phase oxidation of hydrocarbons (Sadana and Katzer, 1974a,b;Neuberg et al, 1975;Mukherjee and Graydon, 1967;Vreugdenhil, 1973;Varma and Graydon, 1973). However, few induction models (Sadana and Katzer, 1974a,b) have been proposed for the heterogeneously-homogeneous system.…”

An Analysis of the Heterogeneously Catalyzed Free-Radical Oxidation of Phenol in Aqueous Solution

“…The Critical Catalyst Concentration (CCC) at which hydrocarbon oxidation stops completely generally increases on increasing the initial hydroperoxide (of the hydrocarbon being oxidized) concentration in homogeneously (Betts and Uri, 1968;Kamiya and Ingold, 1968) and heterogeneously catalyzed (Meyer et al, 1965;Mukherjee and Graydon, 1967;Varma and Graydon, 1973;Gorokhovatskii and Pyatnitskaya, 1972;Evmenenko et al, 1972) liquid-phase hydrocarbon oxidations. The hydroperoxide concentration in solution in heterogeneously catalyzed liquid-phase hydrocarbon oxidations may decrease on interaction with the catalyst or its support by (i) excessive free-radical termination generally at high catalyst loadings (Sadana and Katzer, 1974a; (ii) excessive hydroperoxide adsorption Vreugdenhil, 1973), and (iii) excessive hydroperoxide decomposition to nonradical products (Neuberg et al, 1974). The rate of hydroperoxide formation in liquid-phase hydrocarbon oxidations is directly proportional to kinetic chain length (hcl), and at the Critical Catalyst Concentration hcl = 0.5 (Le., rate of hydroperoxide decomposition equals rate of hydroperoxide formation (Neuberg et al, 1972)).…”

“…No comprehensive attempt has, however, been made to analyze heterogeneously catalyzed liquid-phase hydrocarbon oxidations besides determining by the inhibitor method (Betts, 1971), the rate of initiation of free radicals by the solid catalyst in liquid-phase cumene oxidation (Vreugdenhil, 1973;Gorokhovatskii, 1973b), and the oxidizability (defined as the ratio of the rate constants for the propagation and the termination steps (Lloyd, 1973)) for the same system (Vreugdenhil, 1973). No comprehensive attempt has, however, been made to analyze heterogeneously catalyzed liquid-phase hydrocarbon oxidations besides determining by the inhibitor method (Betts, 1971), the rate of initiation of free radicals by the solid catalyst in liquid-phase cumene oxidation (Vreugdenhil, 1973;Gorokhovatskii, 1973b), and the oxidizability (defined as the ratio of the rate constants for the propagation and the termination steps (Lloyd, 1973)) for the same system (Vreugdenhil, 1973).…”

“…The heterogeneously catalyzed liquid-phase oxidation of hydrocarbons involves free radicals (Meyer et al, 1965; Mukherjee and Graydon, 1967;Taylor, 1970;Caloyannis and Graydon, 1971;Neuberg et al, 1972;Varma and Graydon, 1973;Vreugdenhil, 1973;Gorokhovatskii, 1973a,b; Yurchak et al, 1973;Sadana and Katzer, 1974a;Ioffe, 1967; Roginsky and Andrianova, 1968; Gorokhovatskii and Pyatnitskaya, 1972; Neuberg et al, 1974; Shalya et al, 1969; Pyatnitskaya et al, 1970; 'NCL Communication No. 2005. 0019-7882/79/1118-0050$01.00/0 Neuberg et al, 1975).…”

“…Free-radical inhibitors are generally introduced to investigate (i.e., determine the rate constants for each step) liquid-phase hydrocarbon oxidation processes. No comprehensive attempt has, however, been made to analyze heterogeneously catalyzed liquid-phase hydrocarbon oxidations besides determining by the inhibitor method (Betts, 1971), the rate of initiation of free radicals by the solid catalyst in liquid-phase cumene oxidation (Vreugdenhil, 1973; Gorokhovatskii, 1973b), and the oxidizability (defined as the ratio of the rate constants for the propagation and the termination steps (Lloyd, 1973)) for the same system (Vreugdenhil, 1973). The liquid-phase ox- idation of hydrocarbons catalyzed by a solid catalyst constitutes a low temperature and direct method for the production of valuable oxygenated products; hence a detailed analysis of heterogeneously catalyzed liquid-phase hydrocarbon oxidations is desirable to permit optimum utilization of such a process.…”