Fabrication of new magnetite based sulfonic-phosphotungstic dual-acid catalyst for catalytic acetalization of benzaldehyde with ethylene glycol

Abstract

A new sulfonic-phosphotungstic dual-acid hybrid catalyst based on silica coated magnetite nanoparticles (SCMNPs) containing two types of Bronsted acidic sites i.e. sulfonic acid (–SO3H) and phosphotungstic acid (HPW) groups, was prepared with chemical and electrostatic interactions of these acidic functional moieties with piperazine-grafted propylsilyl spacer groups. Physicochemical techniques including FT-IR spectroscopy, elemental analysis and inductively coupled plasma-optical emission spectroscopy (ICP-OES), vibrating sample magnetometry (VSM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the prepared solid acid catalyst. Acetalization reaction between benzaldehyde and ethylene glycol was done to investigate the catalytic activity of prepared catalyst and 97% conversion toward acetal production was reached in short reaction time. The lower conversion was also achieved for the same catalyst without any HPW species, demonstrated the positive role of the second acidic sites on progression of this reaction. In addition, this easily separable solid acid catalyst reused for four runs with no observable loss in benzaldehyde conversion.