An Efficient and Recyclable Sn-Based Phosphotungstic Acid with Tunable Brønsted/Lewis Acidity for Selective Oxidation of Benzyl Alcohol

Yousheng Zhou,Xiaoxiang Han,Zhe Cai,Xiujuan Tang,Xingyu Mei,Haijiang Zhang,Qing Wang,Jiahui Duanmu,Ouyang Kai

doi:10.21577/0103-5053.20200165

Abstract

A series of metal ion (M = Sn2+, Fe3+, Ni2+, Co2+, Ag+, Cu2+) exchanged tungstophosphoric acid (H3PW12O40; TPA) catalysts with tunable Bronsted/Lewis acidity were synthesized and exploited for the oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) using hydrogen peroxide (H2O2) as oxidant. The structure of these M-TPA composite salts was also characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analyses (TGA) and solid-state 31P nuclear magnetic resonance (NMR) probe molecule method. Among these M-TPAs, the Sn1/2H2PW12O40 catalyst, which presented strong Bronsted acidity, the synergistic effect of Bronsted/Lewis and pseudo-liquid characteristic property, exhibited excellent catalytic activity and durability with 98.2% of BzH selectivity and 95.1% of BzH yield. The optimal conditions for the oxidation of BzOH optimized by response surface methodology (RSM) were as follows: n(BzOH)/n(H2O2) = 1:1.25, catalyst amount of 5.5 wt.% to BzOH, water amount of 17 mL, 3.3 h of reaction time, and temperature 393 K. Moreover, further kinetic study confirmed that the reaction order was 2.64 and the activation energy was 21.75 kJ mol-1.

Highlights

Carbonyl compounds are one of the most important intermediates in the fine chemicals such as perfumes, dyestuffs, and agro-processing chemicals industry.[1]
Catalytic properties of metal ion-exchanged tungstophosphoric acid (TPA) catalysts were listed in Table 1 on the oxidation of benzyl alcohol (BzOH) with H2O2
Strong acidic conditions can improve the oxidizability of H2O2.58 The catalytic activities of all metal ion-exchanged TPA and the original TPA were investigated during the oxidation of BzOH and the results were listed at Table 1

Summary

Introduction

Carbonyl compounds are one of the most important intermediates in the fine chemicals such as perfumes, dyestuffs, and agro-processing chemicals industry.[1]. Catalytic properties of metal ion-exchanged TPAs catalysts were listed in Table 1 on the oxidation of BzOH with H2O2.

Results

Conclusion