Mesoporous V‐Zr Catalysts for Selective Formation of 1,4‐Naphthoquinone by Degradation of Naphthalene with Hydrogen Peroxide

Abstract

In order to control the deep oxidation of naphthalene with hydrogen peroxide for increasing the 1,4‐naphthoquinone selectivity, the mesoporous V−Zr samples were prepared by evaporation induced self‐assembly (EISA) method, and their physical chemical properties were characterized by X‐ray diffraction, X‐ray fluorescence spectrometer, N2 sorption, Raman, temperature programmed oxidation, scanning electron microscope‐energy dispersive X‐ray spectroscopy and transmission electron microscope techniques. The characterization results showed that the vanadium species can be successfully homogeneously incorporated into the ordered framework of mesoporous ZrO2, and it would stabilize the tetragonal ZrO2 phase and increase the temperature of phase transformation from tetragonal to monoclinic phase. The highest surface areas and appropriate pore volumes derived from more oxygen vacancies owing to the valence unbalance between the vanadium and zirconium species for the 12V−Zr‐773 sample with the Xm value of 1.1% has a better catalytic performance than other catalysts, whose selectivity of 1,4‐naphthoquinone can reach 67.7%. The catalytic performance would be promoted and the catalytic stability can be kept well even after reaction for five times using ascorbic acid as reducer. This method can provide a valuable reference for the degradation of naphthalene to the protection of the environment.

Influence of Titanium Species on the Ordered Mesoporous Structure of V‐Zr Catalysts for Naphthalene Oxidation with Hydrogen Peroxide

“…It can be seen from Figure 3(A) that except for the 12 V15TZ‐600 sample, other four samples exhibited mesoporous structure although the peak intensity decreased, and the peak would be shifted to higher angle with the calcination temperature increasing, suggesting that the pore size became smaller. As can be observed in Figure 3(B), compared to our previous literature, the amorphous phase for 12 V15TZ‐500 sample was obtained, which can be attributed to the reason that the incorporation of titanium species would lead to the improvement of the crystallization temperature . With the calcination temperature further increasing from 500 to 550 °C, the t ‐ZrO 2 crystal with high crystallinity would be formed.…”

“…In addition, no naphthalene conversion was occurred over 15Ti‐Zr‐550 catalyst even in the presence of ascorbic acid. However, the naphthalene conversion of 14.2 % over 12V‐Zr‐500 catalyst can be obtained, indicating that the vanadium species was the main active sites . Compared to 12V‐Zr‐500 sample, 12.1 % of naphthalene conversion for 12 V15TZ‐500 sample would be reached owing to its amorphous phase.…”

“…In our previous reports, the effect of vanadium species incorporated into different metal oxides on the liquid‐phase oxidation of naphthalene with hydrogen peroxide was investigated, where the highest selectivity of 1,4‐naphthoquinone using ZrO 2 as carrier was obtained, but the conversion of naphthalene was lower owing to the less oxygen vacancies. On the contrary, titanium oxide with most oxygen vacancies can be beneficial to the naphthalene oxidation and the highest naphthalene conversion was earned.…”