Heteropolyacids and sulfonic acid-bifunctionalized organosilica spheres for efficient manufacture of cellulose acetate propionate with high viscosity

Abstract

Cellulose acetate propionate (CAP), a high value-added chemical, is traditionally prepared using H2SO4 as catalyst. Replacement of the mineral acids by solid acids is current research focus for green and sustainable production of CAP. Herein, we reported the fabrication of novel solid acid catalyst HPW/Si(Et)Si-Dim-SO3H (Si(Et)Si = ethyl-bridged organosilica and Dim = dihydroimidazole) by incorporating phosphotungstic acid (HPW) and sulfonic acid-based Bronsted acidic ionic liquids onto the organosilica nanospheres of the designed catalyst for efficient manufacture CAP via esterification. The results indicated that the as-prepared HPW/Si(Et)Si-Dim-SO3H with 7.5% HPW loading showed the best catalytic performance at 45 °C in 3 h and the resulting CAP exhibited viscosity of 447 mPa s, Mw of 102,882 and DS of 2.69. Most importantly, the HPW/Si(Et)Si-Dim-SO3H exhibited high catalytic stability over six consecutive cycles and the obtained products were stable too with similar DS, Mw and viscosity. As such, the designed heteropolyacids and sulfonic acid-bifunctionalized heterogeneous catalyst is highly promising for biomass conversion under mild conditions.