The catalytic activity of poly(N-vinylimidazole)/SiO2-supported metalloporphyrins in ethyl benzene oxidation

Abstract

In this paper, novel kind of supports for immobilizing metalloporphyrin catalysts, poly(N-vinylimidazole)/SiO 2 (PVI/SiO 2 ) were prepared in the manner of ''grafting from''. Then, various metalloporphyrins (MPs), such as cobalt, iron and manganese tetraphenylporphyrins (CoTPP, FeTPP, MnTPP), cobalt tetra (paranitrophenyl) porphyrin (CoTNPP), and cobalt tetra (para-chlorophenyl) porphyrin (CoTClPP), were immobilized on the supports PVI/SiO 2 via the axial coordination reaction between MPs and the imidazole groups of the grafted PVI, resulting in the heterogenized catalysts MPs-PVI/SiO 2 . The supported catalysts were characterized by IR and UV-Vis spectra. The catalytic performances of MPs-PVI/SiO 2 for the oxidation of ethyl benzene in the absence of any reductant and solvent were investigated and compared in detail. The experimental results revealed that MPs-PVI/SiO 2 could effectively activate dioxygen, and obviously catalyze the oxidation of ethyl benzene to acetophenone. The catalytic activities of MPs-PVI/SiO 2 increased with increase of the electron-deficient degree of the peripheral substituent attached to the benzene ring outside the porphyrin ring. The catalytic activities of MPs-PVI/SiO 2 differed among the different metals and the different substitutional groups according to the following sequences: Co(II) [ Fe(III) [ Mn(III), and CoTNPP [ CoTClPP [ CoTPP. In comparison, the catalytic activity of CoTNPP-PVI/SiO 2 was the best. Under the reaction conditions of 120°C and the ordinary pressure of oxygen, the catalyst CoTNPP-PVI/SiO 2 gave wonderful results with 33.4 mol% yield of acetophenone.

Mesoporous chitosan‐immobilized iron tetrakis(4‐carboxyphenyl)porphyrin as a model of cytochrome P‐450 enzyme for oxidation of ethylbenzene

“…The ethylbenzene conversion, TON, selectivity (ketone + alcohol), and yields subsequently respectively decreased, as the Fe TCPP amount continued to increase from 0.75 to 1.5 mg. The decrease in yields at high amount of Fe TCPP can be ascribed to that excessive addition of Fe TCPP may improve interactions between activated intermediates and suppress the formation of ketone and alcohol …”

Design of oxophilic metalloporphyrins: an experimental and DFT study of methanol binding

“…The free porphyrins were metallated using known methods. 21,[43][44][45][46][47][48][49][50] Mn(III) meso-tetraphenylporphyrin chloride (Mn(TPP)Cl), Zn(II) meso-(tetrapentafluorophenyl)porphyrin (ZnTPFPP) and Sn(IV) meso-tetraphenylporphyrin dichloride (Sn(TPP)Cl 2 ) were purchased from Porphyrin Systems GbR, Germany. Ni(II) meso-tetraphenylporphyrin (Ni(TPP)) was purchased from Frontier Scientific.…”

A zinc sulfide-supported iron tetrakis (4-carboxyl phenyl) porphyrin catalyst for aerobic oxidation of cyclohexane

“…Excessive addition of Fe TCPP may improve interactions between activated intermediates and suppress the formation of cyclohexanone and cyclohexanol. 47 The results indicate that the polymer microenvironment of metalloporphyrins catalysts is an important factor inuencing product yields. This microenvironment not only facilitates catalytic action but also effectively protects metalloporphyrins from dimer formation and destruction, thereby resulting in high catalytic activity.…”