Highly selective and clean synthesis of nopol over well-ordered mesoporous tin silicatecatalysts

Abstract

Two-dimensional SnSBA-15(CVD) catalyst was synthesized by the chemical vapor deposition (CVD) method using calcined SBA-15 with anhydrous tin(IV) chloride. For comparison studies, two mesoporous tin silicate catalysts, Sn/SBA-15(SC) and Sn/SBA-15(SA) were synthesized under the incipient wetness impregnation (IWI) method using calcined SBA-15 with different tin sources. SnMCM-41(40) was also synthesized by basic hydrothermal conditions. The synthesized mesoporous catalysts were characterized by ICP-AES, XRD, N₂ adsorption, UV vis DRS, ²⁹Si MAS NMR, FE-SEM and TEM for the proof of standard mesoporous catalysts with nature of tin on the silica pore walls. For highly selective synthesis of nopol (N–OH), the Prins condensation of β-pinene (PE) with paraformaldehyde (PF-CHO) was performed over different mesoporous catalysts such as SiSBA-15, SnSBA-15(CVD), Sn/SBA-15(SC), SnSBA-15(SA) and SnMCM-41(40), and it was conducted using a variety of optimal parameters such as amount of catalyst, reaction time, reaction temperature, ratios of reactant (PE/PF-CHO), solvents and recycles. In addition, SnSBA-15(CVD) was used in the Prins condensation of PE with PF-CHO in the presence of propyl cyanide (PrCN) with water to investigate its catalytic activity. On the basis of all catalytic results, SnSBA-15(CVD) is found to be a highly active, water-resistant and recyclable heterogeneous catalyst for selective synthesis of N–OH.