Optimization of the preparation of a catalyst under deactivation. 1. Control of its kinetic behavior by electing the preparation conditions (original) (raw)

1987, Industrial & Engineering Chemistry Research

exp(-25943/RT) s-l. The high apparent activation energies common in chemical reactions confirm the assumption of a kinetic regime in this gas-liquid reaction under our experimental conditions. The complete solubility of the reagents and products in the solvent was assured. The high yield and selectivity for this reaction, e.g., 98% at 158 OC, make its application possible for industrial use. The low solubility of reagents and products is nevertheless a problem that must be treated. Solubility data in this system and with other solvents as well as kinetic data in the presence of the solid phase must be obtained. Mechanism Approximation Several authon have suggested mechanisms for this type of oxidation; in every case they look complex and not strictly decided. Koshitani et al. (1982) gave a mechanism through anthrone formation that resulted in impure product. No intermediate acetal is obtained in this system (acetic acid solvent), so it cannot be extrapolated to our experiments. Brossard et al. (1977) obtained the acetal with possible evolution, but no detailed steps for the reaction were given. Rindone and Scolastico (1971) in reactions with cerium catalyst suggested the existence of a carbonium ion that could be easily attacked by the solvent. Thus, from these contributions and on the basis of the kinetic results obtained, for the dependence of reagents and catalyst, we propose a possible mechanism (Scheme 1). Mechanism. This is based on two steps (reactions 1 and 2) to form 9-anthryl radical by Cu2+ catalyst attack (Wilk et al., 1966; Andrulis et al., 1966), as has been shown in some of these types of reactions. Then by typical propagation reactions 3-7 (Koshitani et al., 1982; Lyons, 1977), a 9-anthronyl radical is produced, where Cu(I), Cu(II), and AN are involved. Step 5' might be viewed as a resonance hybrid. On the basis of other works (Gill, 1970), we thought that 9-anthronyl radical might react with Cu(II) to give an 9-anthronyl cation (eq 8). This compound could react with the solvent (eq 9) to obtain the intermediate product I. The solvent has then an important role in the mechanism, as it is obtained. Finally the intermediate gives rise to anthraquinone by means of a hydrolysis equation. This mechanism can be used according to a mechanistic approach and the steady-state principle, for the intermediate production rate, considering reaction 10 as irreversible, This equation agrees with experimental data; there is no dependence on O2 concentration, first order on Cu2+ and AN in the first reaction, but zero order in the second reaction. Registry No. I, 64420-66-2; C a r 2 , 7789-45-9; HO(CH2)20H,