Heterogeneous acid catalysts for esterification in oleochemistry

This thesis aimed at developing heterogeneous catalysts for the esterification of oleic acid (OA) with trimethylolpropane (TMP) to produce an automotive bio-lubricant -trimethylolpropane trioleate (TMPTO). Four groups of catalysts were studied: 1) heteropolyacids (HPA) immobilized onto silica; 2) macroporous Si(HIPE) functionalized with different species (HPA, SO3H-/PO3H2-, zirconium phosphates); 3) functionalized magnetic nanoparticles (MNP); and 4) commercial cation ion-exchange resins. Precisely, we developed a method for the strong immobilization of the HPA onto silica via a link of zirconia and obtained stable-toward-leaching catalysts (first group of catalysts) which can be easily recycled for the further uses. The Si(HIPE)-materials (second group) have convenient shape that makes them easy to operate but they inhibited the reaction due to entrapment of the reagents and products inside their small pores. The work dedicated to MNP (third group) investigated different approaches to protect MNP for the use at the low pH. We found that silica coating of MNP as well as organic silane grafting promote the MNP stability. The surface of coated and grafted MNP was then modified with sulfonic moieties. The MNP-catalysts are recoverable by magnet, active and recyclable. Concerning the ion-exchange resins (fourth group), they possess unique stability and recyclability showing potential for the industrial applications. For the gel-type resin, a so-called “pre-swelling” step was developed to increase the productivity of the resin. We also found that the resins catalyze the formation of mono- and diesters, whereas the final triester is generated thanks to the action of acidity from the residual OA at the high temperature of the system. A cooperative scenario between heterogeneous and homogeneous catalysis is proposed for operating the industrial reaction starting with an ion-exchange resin at low temperature and completing it at higher temperature to obtain the triester.