Codoped Phosphotungstate as an Efficient Heterogeneous Catalyst for the Synthesis of n-Butyl Oleate

A quaternary ammonium and titanium codoped phosphotungstate (QA(0.5)Ti(0.5)H(0.5)PW) catalyst was prepared by the ion exchange method and used as a solid acid catalyst for the synthesis of n-butyl oleate. The catalyst was characterized by Fourier transform infrared, elemental analyzer, energy-dispersive X-ray spectrometry, Brunauer-Emmett-Teller, scanning electron microscopy, and Hammett indicator methods. QA(0.5)Ti(0.5)H(0.5)PW showed a higher catalytic activity than other phosphotungstate solid acid catalysts reported by literature, and the esterification rate reached 99% under optimized conditions. Moreover, QA(0.5)Ti(0.5)H(0.5)PW exhibited well reusability. An esterification rate of 90.1% was still obtained in the eighth run.