Catalytic decomposition of cyclohexyl and 1-methylcyclohexyl peroxides in the presence of 3d-metal acetylacetonates was studied.A cyclohexanol3cyclohexanone mixture is commercially produced on a large scale by oxidation of cyclohexane with atmospheric oxygen on a cobalt catalyst [1]. Cyclohexyl hydroperoxide (CHP, ROOH) is formed in the first step of this process. Kinetic features of the oxidation and the composition of the oxidation products are mainly determined by the course of catalytic decomposition of this intermediate. Previously, we have shown that the selectivity of cyclohexanone formation in the presence of chromiumcontaining catalysts is higher than that in the presence of industrial cobalt-containing catalysts [2].The oxidation of methylcyclohexane depends on the catalyst present in the system. The reaction yields either a tertiary alcohol (1-methylcyclohexanol) or a mixture of methylcyclohexanols and methylcyclohexanones, formed by reaction of the secondary C3H bonds with oxygen and peroxy radicals [3]. In the latter case, the reaction kinetics and composition of the oxidation products are determined by the course of transformation of tertiary 1-methylcyclohexyl hydroperoxide (MCHP, ROOH) into secondary methylcyclohexyl hydroperoxides.In this study, we examined the catalytic decomposition of CHP and MCHP in the presence of 3d-metal compounds.As shown previously [4, 5], s-and 3d-metal carboxylates form with MCHP complexes ML n 0 mROOH (n, m = 1, 2). This is due to the fact that intermolecular hydrogen bonds in the complexes of s elements and the coordination bond between 3d metals and the a-O atom of hydroperoxide are stronger than the hydrogen bonds in peroxide self-associates. These complexes catalyze decomposition of the hydroperoxide into radicals and molecular products. The catalytic activity of s-metal carboxylates [e.g., stearates (St)] in MCHP decomposition decreases with a decrease in the cation radius in the following order: CsSt > BaSt 2 > NaSt~Na 1 pel > CaSt 2 > LiSt [6].
EXPERIMENTALCyclohexyl hydroperoxide was prepared via intermediate trialkyl borates [7] at 378oC, which were oxidized with H 2 O 2 . MCHP was prepared by the procedure described in [8]. The content of the available oxygen in the hydroperoxides was 100%.3d-Metal acetylacetonates were prepared by the procedure described in [9].Decomposition of CHP and MCHP at 853105oC in the presence of catalysts listed in Table 1 was studied in decane and methylcyclohexane solutions, respectively. The catalyst concentration ranged from 3 0 10 !5 to 3 0 10 !4 and from 6 0 10 !4 to 8.8 0 10 !3 M; and the concentration of hydroperoxides, from 0.01 to 0.1 M. The first concentration range of the catalysts was chosen so as to minimize their association at 853105oC.The representative kinetic curves of overall CHP decomposition are shown in Fig. 1. The fast decomposition in the first steps decelerates with time owing to catalyst deactivation. The limiting degrees of CHP decomposition are determined by the nature and con-ÄÄÄÄÄÄÄÄÄÄÄ 1 Na pelargona...
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