Liquid phase condensation of anisole with p-formaldehyde over benzylsulfonic acid functionalized mesoporous Zr-TMS catalysts

Abstract

The catalytic liquid phase condensation of anisole to 4,4′-dimethoxydiphenylmethane (4,4′-DMDPM) with para-formaldehyde ( p-HCHO) has been studied in a batch reactor at atmospheric pressure using of different loadings of benzylsulfonic acid (BSA) functionalized mesoporous Zr-TMS (Zr-TMS-BSA/(–Zr–O–CH 2–Φ–SO 3H)) catalysts. Conventional catalyst, p-toluene sulfonic acid ( p-TSA) and sulfated zirconia and Zr-TMS (zirconia-based transition metal oxide mesoporous molecular sieves) are also included for comparison. Under identical reaction conditions, Zr-TMS-BSA is considerably more active than Zr-TMS and less active than sulfated zirconia and p-TSA, however, Zr-TMS-BSA showed higher selectivity among all catalysts. The conversion of anisole, rate of anisole conversion (TOF), selectivity to 4,4′-DMDPM and 4,4′-/2,2′-DMDPM ratio over Zr-TMS-BSA-10, after 6 h of reaction time at 100 °C are ca. 28.2 wt.%, 12.04 h −1 mol −1 S, 78.5 wt.% and 27.55, respectively. Acidity and mesoporosity of the Zr-TMS-BSA catalyst play important role in the conversion of anisole, rate of anisole conversion and product distribution. The effect of various parameters such as duration of run, reaction time, catalyst concentration, reaction temperature, anisole/ p-CHCO molar ratio and reuse of catalyst, on the catalyst performance are examined in order to optimize the conversion of anisole and selectivity to 4,4′-DMDPM. The conversion of anisole using Zr-TMS-BSA-10 is increased significantly with the increases in reaction time, catalyst concentration, reaction temperature and decreased with the increase of anisole/ p-HCHO molar ratio. Zr-TMS-BSA-10 catalyst is recycled two times and a decrease in anisole conversion is observed after second cycle, which is related to the minor leaching of anchored benzylsulfonic acid.