Aerobic liquid-phase oxidation of p-xylene over metalloporphyrins

Abstract

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.

Aerobic Oxidation of p-Toluic Acid to Terephthalic Acid over T(p-Cl)PPMnCl/Co(OAc)2 Under Moderate Conditions

“…In addition, the metalloporphyrins tend to form catalytically inactive dimeric l-oxo-and/or l-peroxobridged dimetal species when its concentration surpassed the critical value, which was not in fovor of the catalysis Aerobic Oxidation of p-Toluic Acid to Terephthalic Acid over T(p-Cl)PPMnCl/Co(OAc) 2 157 [20]. Similar phenomena were also observed in our previous works [6,15].…”

“…So it is feasible to realize the effective oxidation of PX to TPA through two steps. The work we have reported [6,7] has solved the step of the oxidation of PX to PTA, however, the oxidation of PTA to TPA still remains a challenge to the oxidation of PX to TPA. So it is essential to explore how to oxidize PTA to TPA effectively under moderate conditions.…”

Efficient catalytic oxidation of methyl aromatic hydrocarbon with N-alkyl pyridinium salts

“…The distribution of the product is different with those results obtained with metal-containing catalyst being used, in which deep oxidation happened and then considerable amount of 4-carboxylicbenzaldehyde (4-CBA) and terephthalic acid (TPA) produced. 39 For organic catalysts, introduction of substitute was an efficient method to modulate their catalytic activity. 28,40 Effect of different substituted groups was studied in the present work.…”

Solubilities of 5,10,15,20-Tetraphenylporphyrin and 5,10,15,20-Tetraphenylporphyrin Manganese(III) Chloride in Binary Ethanol + Water Solvent Mixtures

“…Since Δ sol H 0 is a well-behaved function of T, the Δ sol H 0 can be properly expressed as a perturbation on the value Δ sol H θ 0 at reference temperature θ using the Taylor's series expansion 26 (11) where A, B, and C are the parameters of Nyvlt equation. The thermodynamic parameters of dissolution for TPP and TPPMnCl in ethanol + water solvent mixtures are listed in Table 2 and Table 3, respectively.…”