Synthesis of phthalate-free plasticizers by hydrogenation in water using RhNi bimetallic catalyst on aluminated SBA-15

Abstract

In this study, rhodium–nickel bimetallic nanoparticles loaded on aluminated silica (RhNi/Al-SBA-15) were used as catalysts for the hydrogenation of phthalate in water to produce environmentally acceptable non-phthalate plasticizers. Chemical fluid deposition (CFD) was used to dope metals onto the aluminated silica support, which helped to create a uniform structure of RhNi on Al-SBA-15. The introduction of Ni helped to reduce the use of expensive Rh and increase the number of metal active sites by reducing the bimetallic nanoparticle size. Aluminated SBA-15 not only acted as the support for the RhNi bimetallic catalyst but also enhanced the reaction efficiency by introducing Brønsted and Lewis acid sites and the absorption of phthalates on the catalyst in water. The physicochemical properties of prepared catalysts were characterized by N₂ adsorption–desorption isotherm, X-ray diffraction (XRD), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM). The catalytic performance of the synthesized catalysts was evaluated with the hydrogenation of dimethyl phthalate (DMP). Despite the low solubility of DMP in water, the hydrogenation using Rh_0.5Ni_1.5/Al-SBA-15 was carried out with an 84.4% reaction yield (cis- : trans- = 97.5 : 2.5) at 80 °C using 1000 psi of H₂ after 2 h.