Catalytic synthesis of DHHB over home-made catalysts and its kinetic calculations

Abstract DHHB (n-hexyl 2-(4-N,N-diethylamino-2-hydroxybenzoyl) benzoate) is a recently developed UV absorber that demonstrates a high degree of safety, excellent efficiency, and favorable solubility properties. In this paper a catalyst was prepared to catalyze the esterification of DHHB with homemade sulfonic acid modified polystyrene microspheres coated with silica instead of conventional H 2 SO 4 . And the catalyst was characterized by scanning electron microscopy (SEM) and infrared spectroscopy (FT-IR). The effects of different conditions on the reaction rate and equilibrium conversion were also investigated using conventional H 2 SO 4 as a benchmark. The results showed that the catalytic activity of the catalyst did not decrease significantly after 10 consecutive cycles, and the yield of DHHB could reach 90.21 % after 2 h of reaction at 150 °C. Meanwhile, The kinetic experimental data obtained were correlated using a proposed homogeneous phase model. The synthesis of DHHB is a heat-absorbing reaction with heat of reaction and activation energies of 4.6537 kJ/mol, 43.2157 kJ/mol and 37.5735 kJ/mol for the forward and reverse reactions, respectively. It was verified that the proposed homogeneous reaction kinetic model accurately described the kinetic processes of the DHHB esterification reaction.