A Liquid Derivative of Phosphotungstic Acid as Catalyst for Benzyl Alcohol Oxidation in Water: Facile Separation and Stability of Benzaldehyde at Room Temperature†

Abstract

Polyetheramines belong to a class of green di-block copolymer with ethylene oxide and propylene oxide moieties along with terminal amine functionality. The polymers are biocompatible and show temperature dependant phase separation properties. Herein, we report the effect of a polyetheramine (Jeffamine®) on the catalytic properties of a well studied polyoxometalate catalysts, phosphotungstic acid (PTA). The catalytic reaction chosen for the test is the hydrogen peroxide-mediated oxidation of benzyl alcohol (BzOH). Modification of PTA with Jeffamine® (PTA-Jeffamine®) resulted in a solvent-less liquid-like material accessible to a wide range of solvents. The PTA-Jeffamine® catalyst was observed to enhance the conversion of BzOH compared to that of pristine PTA and facilitated easy separation of benzaldehyde (BzH) and catalyst from reaction mixture. Stability of synthesized BzH was studied with gas chromatography attached with mass spectrometry (GC-MS). Synthesis of the catalyst is cost-effective and scalable due to easy availability of the individual components and nature of the synthetic protocol. UV-visible spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and field emission scanning electron microscopy (FE-SEM) were used to characterize the catalyst. Surface tension experiment, FE-SEM, ICP-MS and controlled experiments were performed to understand the effect of Jeffamine® in the catalytic process. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim