Preparation of Rosin Pentaerythritol Ester Over an Fe3O4-Supported ZnO Catalyst

Abstract

Conversion of rosin to its pentaerythritol ester provides a means of improving its water resistance, alkali resistance, and oxidation resistance, thereby increasing its stability. Rosin pentaerythritol ester is much more amenable to industrial applications than the parent compound. To overcome the difficulty of catalyst recovery and its associated high cost during the synthesis of rosin pentaerythritol ester, Fe3O4-supported ZnO catalysts, such as Fe3O4@ZnO and Fe3O4@SiO2–ZnO, have been designed and synthesized. The structures, morphologies, and compositions of the materials have been characterized by TEM, XRD, and XPS. The results of esterification reactions demonstrate that Fe3O4@SiO2–ZnO has excellent catalytic performance and stability. The degree of esterification in the production of rosin pentaerythritol ester reached 87.9%, far exceeding the yields attained with other catalysts. Moreover, the catalyst could be reused five times without incurring a loss of activity. The effects of zinc source, zinc loading, and reaction conditions on the esterification have been investigated in detail. This study provides a class of heterogeneous catalysts with excellent properties for the synthesis of rosin pentaerythritol ester. In our paper, the optimum process conditions for obtaining rosin pentaerythritol ester have been identified as zinc nitrate as the zinc source, a theoretical loading of zinc source of 0.45 g, a reaction temperature of 250 °C, a reaction time of 5 h, and a catalyst loading of 0.2 g, when starting from rosin (15 g) and pentaerythritol (1.7 g). The conversion rate was 87.9%, and the acid value was 25.0 mg KOH g−1. This research provides an improved protocol for the rosin esterification reaction.