Síntese e caracterização de materiais caralíticos a partir de caulim flint e estudo comparativos do desempenho catalítico na esterificação do eugenol

Abstract

The Amazon flint kaolin, a waste from kaolin mining, is abundant in kaolin extraction areas. Its high content of SiO2, Al2O3 and Fe2O3 makes it an interesting starting material for synthesis of catalytic materials or mesopore as catalytic support via calcination followed by acidification. The use of solid acid catalysts in the esterification of eugenol with acetic anhydride may be a means to produce value-added ester at low cost. The synthesis of compounds such as eugenol ester has many important applications for the pharmaceutical, food, cosmetic and other fine chemicals industries. In this sense, environmentally correct catalysts were prepared from a kaolinite tail, which was calcined at 750 °C and then activated with sulfuric acid (4 mol L-1) under microwave radiation (400 W for 15 minutes). In parallel the flint metakaolinite was activated with 2.5 mol L-1 H2SO4 (conventional method of heating under reflux) to obtain porous metacaulim as precursor for mesoporous aluminosilicate synthesis (AlSiM) as catalytic support for heteropolyacid (H3PM12O40 (HPMo) and (organosulfonic) groups is described in the present manuscript. The different catalysts were characterized by different techniques such as DRX, physisorption of N2, EDX, DRS, UVvisible, IV, TGA/DrTG and acidity analysis by titration of base acid. In the kinetic study, better conversions (> 98 %) were achieved at temperatures of 100 °C, molar ratio (eugenol: acetic anhydride) 1: 5, catalyst concentration from 2 % (w/w substrate) with 60 min of reaction. The results indicated that the chemically modified and supported catalysts are effective for the conversion of eugenol to eugenol ester following a first order kinetics with respect to eugenol with energies of activations of 18,40 KJ mol-1 (MF4W15), 19,96 KJ mol-1 (10HPMo/AlSiM) and 17,13 KJ mol-1 ((3)SO3H/AlSiM) respectively. What is significant in the development of processes that are not aggressive to the environment are classified in the concept of "green chemistry", constituting like heterogeneous catalysts attractive for reaction of organic transformation. Therefore, Amazon flint kaolin showed potential in the synthesis of catalysts and catalytic support efficient in the esterification of eugenol to produce value-added esters