PERLITE IMPREGNATED WITH HPA/Α-FE2O3: MAGNETICALLY SEPARABLE CATALYST FOR THE SYNTHESIS OF 3,3,6,6-TETRAMETHYL-9-SUBSTITUTED-3,4,6,7-TETRAHYDRO-2H-XANTHENE-1,8-(5H,9H)-DIONES

Abstract

Phosphotungstic acid (HPA)/α-Fe2O3-loaded Perlite has been prepared as a recyclable heterogeneous catalyst for the synthesis of xanthenes. The prepared catalyst has been characterized by Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM) with selected-area electron diffraction (SAED) pattern analysis, thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) measurements. XRD peaks at 2θ = 9.08° and 26.73° (HPA) and 36.03°, 39.72°, and 62.6° (α-Fe2O3) showed efficient loading of HPA/α-Fe2O3 on the Perlite surface. TEM images of the prepared HPA/α-Fe2O3/Perlite corroborated the successful loading of α-Fe2O3 on the Perlite. Advantages of this new protocol include facile handling, low cost, easy work-up procedure, and remarkable reusability over several cycles without loss of the catalytic activity.