Nano-Silica@PVC-Bonded N-Ethyl Sulfamic Acid as a Recyclable Solid Catalyst for the Hydroxyalkylation of Phenol with Formaldehyde to Bisphenol F

Abstract

Abstract Sulfamic acid functionalized PVC-coated nano-silica (NS) catalyst (NS@PVC-EDA-SO3H) was prepared via multi-step treatment processes and characterized by FT-IR, N2 adsorption-desorption, TGA/DTG, XRD, TEM, STEM-EDS, as well as acid-base back-titration. The hydroxyalkylation of phenol with formaldehyde to bisphenol F was employed to evaluate in detail its acid catalysis performances. The results indicated that the newly constructed NS@PVC-EDA-SO3H possessed richer short mesoporous to macroporous channels and highly exposed sulfamic acids and could exhibit excellent hydroxyalkylation activity and reusability owing to fast mass transfer and reaction rates for the conversion of substrates, as well as excellent structural and chemical stabilities. This new solid acid was obviously superior to the conventional homogeneous concentrated sulfuric acid and heterogeneous sulfonated resin catalysts in catalytic activity and reusability, which could achieve a remarkable formaldehyde conversion (99.9%) and selectivity of bisphenol F (94.5%) under optimal hydroxyalkylation conditions. Furthermore, it could also be recovered easily and used repeatedly at least nine times without an obvious decrease in activity.