Synthesis of solketal using sulfonic aluminosilicate catalyst

Abstract

The propyl sulfonic functionalized on H-beta was synthesized by grafting with 3-mercaptopropyltrimethoxysilanegroup. Then, thiol moiety (-SH) was oxidized to sulfonic acid group (-SO₃H) using 30% (w/w) hydrogen peroxide (H₂O₂). The synthesized catalyst was characterized by powder X-ray diffraction (XRD), N₂ adsorption/desorption, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), carbon-13 nuclear magnetic resonance Spectroscopy (¹³C NMR) and acid-base titration. The catalytic activity of this catalyst was investigated for acetalization of glycerol with acetone to produce solketal. This reaction was carried out in batch reactor under solvent free condition. A gas chromatography-mass spectrometry (GC-MS) method was used for products characterization. The effect of various type of catalysts, reaction time, reaction temperature, reactants mole ratio and catalyst amount have been studied. The result showed that the highest glycerol conversion (90.8%) and solketal yield (89.9%) with excellent solketal selectivity (99%) were obtained by using H-beta-Pr-SO₃H as catalyst at 32°C, glycerol: acetone mole ratio of 1:10 with catalyst 2.5 wt% based on glycerol and reaction time for 1 h. The reused H-beta-Pr-SO₃H was also investigated. Moreover, the acetalization of glycerol with other ketones or aldehyde such as cyclohexanone, cyclooctanone, cyclododecanone and benzaldehyde were also studied over sulfonated catalysts (H-beta-Pr-SO₃H and MCM-41-Pr-SO₃H) and commercial catalysts (H-beta and Amberlyst-15).