Synthesis and characterization of a green composite of H3PW12O40 and starch-coated magnetite nano particles as a magnetically-recoverable nano catalyst in Friedel-Crafts alkylation

Abstract

Preparation and characterization of a magnetic composite of 12-tungstophosphoric acid (HPW) and starch coated magnetite nano particles (SMNs) were reported. Magnetite nano particles coated with starch were prepared using controlled chemical coprecipitation of magnetite phase from aqueous solution in a polymeric starch matrix. HPW was immobilized on this nano particles in order to produce a composite of SMNs and HPW (HPW/SMNs) as a nano catalyst. The as-prepared HPW/SMNs catalyst was characterized by transmission electron microscopy, laser particle size analyzer, Fourier transform infrared spectroscopy, vibrating sample magnetometer and chemical composition of the HPW/SMNs was estimated by elemental analysis. The results show that HPW/SMNs had a well-defined composite structure and an average size of approximately 29nm. The characterization data derived from FT-IR reveal that basic structure and geometry of the Keggin anion are preserved after synthesis of HPW/SMNs. Activity of the catalyst was probed through alkylation of aromatic compounds from benzhydrol. The excellent conversions show that the catalyst has strong acidity, which are responsible for its catalytic performance. The catalyst could be recovered simply by using an external magnetic field and reused several times without appreciable loss of its catalytic activity.