Efficient Synthesis of phenylacetaldehyde via interfacial catalysis by surface-active hybrid polyoxometalates

• Published in: Journal of molecular liquids 2024-08, Vol.407, p.125251, Article 125251
• Main Authors: Gao, Yuanxiang, Zhang, Kaokao, Zhang, Yue, Zhou, YingYing, Li, Yifei, Wang, Zanhong, Li, Haitao
• Format: Article
• Language: English
• Subjects: Hybrid; Interfacial catalysis; Phenylacetaldehyde; Polyoxometalate; Styrene oxidation
• ISSN: 0167-7322
• DOI: 10.1016/j.molliq.2024.125251

•Hybrid POMs show surface activity and self-aggregation behavior in [Bmim][BF4].•Preparation of PhAA from styrene in hybrid POM/O2/[Bmim][BF4]/PTSA system.•PhAA yield achieved ∼54 % under optimized reaction conditions. The catalytic production of phenylacetaldehyde (PhAA) from styrene using oxygen (O2) as the oxidant offers advantages such as readily available feedstocks, a concise reaction route, and environmental friendliness. However, the PhAA yield of this multiphase system is generally less than 15 % due to the interfacial limitations between O2, styrene, and catalyst. To address this challenge, Keggin-type polyoxometalates (POMs) of the form [XW11O39]n- (X = B, P, Si; n = 7, 8, 9) were modified with octyl trimethoxysilane (OTMS) to prepare hybrid POMs possessing both surface activity and catalytic potency. In the [Bmim][BF4] ionic liquid, these hybrid POMs effectively reduce surface tension (44.7 mN/m to 31–34 mN/m) and exhibit critical aggregation behavior similar to conventional surfactants. Within the reaction system using [Bmim][BF4] as a co-solvent and O2 as the oxidant, the hybrid [SiW11O39] achieves 76.9 % styrene conversion and ∼54 % PhAA yield after 8 h at 105 ℃. The surface activity of hybrid POM and the sub-nanometer scale effect of POM head groups promote the effective contact of O2, styrene, and catalyst at the phase interface. Based on the two-step reaction mechanism of epoxidation and isomerization, an efficient preparation of PhAA from styrene using O2 as the oxidant was achieved.