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Simultaneous isomerization of ethylbenzene and zn-xylene on zeolite catalysts, including Pt/mordenite, Pt/USY, Pt/ZSM-5, and Pd/ZSM-5, was studied. Experimental results indicated that Pt/ZSM-5 was the superior catalyst for these reactions. Pd/ZSM-5 is better than Pt/USY, although, both are good enough for the reactions, in comparison with Pt/mordenite. A kinetic model with plausible reaction paths was proposed for the isomerization. The estimated reaction rate constants and activation energies indicated that the transformation of zn-xylene to o-or p-xylene might be limited by the mass-transfer rate of the diphenylmethane-type intermediate, and the formation of o-xylene from ethylbenzene could be restricted by the smaller protonated cyclopropane intermediate. The C8 aromatics consist of four isomers: o-, m-, and p-xylene and ethylbenzene. Their boiling points are very close together, but their melting points are relative far apart. Consequently, in a petrorefinery, zn-xylene and p-xylene are traditionally separated by crystallization. Recently, an adsorptive column for the separation of xylenes and ethylbenzene has become widely used. Mixed xylenes have limited usage, while p-and o-xylene are extensively used for the plasticizer, synthetic fiber, resin, dye, and paint industries.

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The five metalloporphyrins ( T (p- Cl ) PPM , M = Fe , Mn , Co , Cu , Zn ) with different metal nuclei were synthesized, and their catalytic aerobic liquid-phase oxidations of p-xylene into p-toluic acid, p-toluic aldehyde and terephthalic acid using a low concentration of acetic acid as solvent without any halide additives, were studied. The p-xylene conversions and the oxidation product distributions were found to be affected by the structures and concentration of the metalloporphyrins as well as the reaction parameters such as time, temperature and air pressure. The formation of some intermediate oxidation products in the oxidation process also influenced the reaction conversions and the product distribution. Among the metalloporphyrins used, tetrakis(p-chlorophenylporphinato)manganese chloride ( T (p- Cl ) PPMnCl ) was the most efficient catalyst for the oxidation of p-xylene. Under the conditions of 180 °C and 2.0 MPa, 44% conversion of p-xylene and 85% selectivity of p-toluic acid were obtained. Based on the results obtained, a preliminary mechanism of the oxidation of p-xylene over metalloporphyrins was proposed.

Liquid phase catalytic selective hydroxylation of phenol to catechol and hydroquinone was carried out in the presence of metalloporphyrins using hydrogen peroxide as oxidant and water as solvent. Five kinds of metal tetra(p-chlorophenyl)porphrin (T(p-Cl)PPMCl, M = Fe, Co, Mn, Cu, Zn) were studied. It was found that T(p-Cl)PPFeCl had high catalytic activity and diphenol selectivity for the hydroxylation of phenol to catechol and hydroquinone. The influence of various reaction parameters, namely, reaction temperature, solvent, ratio of substrate and oxidant, substrate concentration, the amount of catalyst, reaction time and pH value were investigated systematically. When water was used as solvent (10 mL), the optimum conditions were following: pH = 7, the concentration of phenol was 0.3 g/mL, the molar ratio of phenol and H 2 O 2 was 1/2, the molar ratio of catalyst and phenol was 7/100000, the reaction temperature was 65 °C and the reaction time was 1.5 h. Under above optimum conditions, the phenol conversion was up to 55.1%, and the selectivity of diphenol was almost up to 99.9%, the molar turnover numbers of the catalyst was about 7500. A possible mechanism was also proposed.

Toluene oxidation with molecular oxygen as the sole oxidant, and μ-oxo-bis[tetraphenylporphinatoiron(III)] as the catalyst, are reported. Under the reaction conditions of 438 K and 0.8 MPa, the molar total yields for the products benzaldehyde and benzyl alcohol and the turnover number of the catalyst are 4.35% and 21,830 (based on the metal ion), respectively. Compared with the reaction catalyzed by the corresponding monometalloporphyrin TPPFe III Cl, the total yields of the oxidation products and the catalyst turnover number by the dimeric iron porphyrin were almost twice those by the former. A possible reaction mechanism of the toluene oxidation by μ-oxo-bis[tetraphenylporphinatoiron(III)] is proposed.

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