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Znd. Eng. Chem. Res. 1988, 27, 915-920 915 energy values have been determined. These, along with k h e n i u s correlations for the rate constants, are presented in Table V. The calculated activation energy values are consistent with the low values normally observed with free-radical reactions. ConclusionsQuantitative and selective oxidation of styrene to benzaldehyde was achieved with Wilkinson complex. The reaction initiation period was independent of temperature. The reaction induction period strongly depended upon the catalyst concentration below the critical catalyst concentration. Co-oxidation of aldehyde to acid was found to be significant above a temperature of 75 "C and a styrene conversion of 25%. The optimum reaction conditions have been determined as (C/So) = 5.0 X lo4, (So/T) = 0.5, and T = 75 OC. A second-order kinetic model has been found to fit satisfactorily the experimental kinetic data both in the presence and absence of co-oxidation reactions.Nomenclature AI, A2, A3 = constants (B) = concentration of benzaldehyde, mol/L (C) = concentration of the catalyst, mol/L (C/So) = mole ratio of the catalyst to initial styrene kf = first-order rate constant, l / h k'f = pseudo-first-order rate constant, l / h k, = second-order rate constant, L/(mol h) (S) = styrene concentration, mol/L (So) = initial concentration of styrene, mol/L (So/T) = mole ratio of initial styrene to toluene (T) = toluene concentration, mol/L T = temperature, K t = time, h r = [(So) -(S)]/(So) = mole fraction of styrene converted xB = (B)/(So) = mole ratio of benzaldehyde to initial styrene Registry No. RhCl(PPh3)The kinetics and product distributions of the thermal cracking of cyclohexane were investigated in a stainless steel annular reactor using the pulse method. Experiments were conducted a t 1-atm pressure and with excessive nitrogen dilution. Data were obtained at temperatures of 700-860 OC and space times of 0.40-1.14 s. A kinetic analysis of the conversion-space time data revealed that conversion was autocatalytic at 700-800 "C, while at higher temperatures (820-860 O C ) it was governed by first-order kinetics. The activation energies for the two kinetic regimes were 192.5 and 240.0 k J mol-', respectively. The autocatalysis was ascribed to the participation of methylallyl radicals in a new bimolecular propagation sequence. The product distributions and the first-order kinetic rate parameters were consistent with those obtained in the continuous-flow mode.

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Combustion of fossil fuels gives rise to sulfur oxides, which are harmful to the environment. Adsorptive desulfurization (ADS) of diesel was conducted using sewage sludge activated with H 2 O 2 as the oxidizing agent. A full 2 2 central composite response surface design was employed to determine optimum conditions for the production of activated sewage sludge (ASS). The adsorbent (ASS) was characterized using SEM, EDX and FTIR and the results of the analysis showed that it has the capacity to desulfurize diesel significantly. The ASS was subsequently used to conduct batch ADS of diesel with a view to investigate the kinetics, equilibrium and thermodynamics of the process. The optimum conditions established for the production of ASS using H 2 O 2 as the oxidizing agent were: temperature 400 °C and holding time 60 min. The Elovich model gave the best fit to the kinetic data of the ADS of diesel using ASS, while the equilibrium study showed that the Freundlich isotherm fitted the data at 35 °C better than Temkin and Langmuir isotherms. The positive values of the free energy and enthalpy changes revealed that the process was non-spontaneous and endothermic, respectively, while the negative entropy change is evidence of decrease in randomness of the adsorbed species. 33% desulfurization was achieved in 100 min during ADS of diesel showing that the adsorbent developed by activating SS with H 2 O 2 was very good and effective. Thus, ASS can be used to gain more insight into kinetics, equilibrium and thermodynamics of the ADS of middle-distillate petroleum fractions.