Aproveitamento do pó da casca de coco verde para produção de compostos levulínicos

Abstract

Agro-industrial waste is most often widely disposed of in landfills or in an uncontrolled manner. An environmentally friendly alternative can be the use of this residual biomass for the production of sustainable chemicals with high added value. Levulinic acid and its derivatives are examples of these products, which have high added value and can serve as precursors for various industrial products and also used as fuel additives. In this context, the present thesis aimed to study the feasibility of using raw coconut shell in natura in levulin compounds. For this, three studies were developed, the first being the investigation of the viability of catalysts for biomass conversion through degradation kinetics; the second was the synthesis of levulinic acid from green coconut husk and, finally, the synthesis of ethyl levunilate, to ascertain the conditions of the esterification reaction and the viability of using aluminum sulfate as a catalyst. The first step determined the biomass composition before and after esterification through thermogravimetric analysis; there was a reduction in the amounts of cellulose (18.18% to 9.77%) and hemicellulose (44.65% to 26.18%) after the reaction. Then, the degradation kinetics of the coconut husk powder was carried out using the Ozawa–Flynn–Wall method, which demonstrated that the activation energy is directly related to the presence of hemicellulose and cellulose, exceeding 143 kJ.mol-1 for 125 kJ.mol-1. The second stage consisted of the synthesis of levulinic acid generated from the powder of green coconut shell. The reactions took place in a Parr Instruments stainless steel reactor, with a capacity of 300 mL, and the samples were analyzed on HPLC. The reaction conditions were determined according to a factorial design with the addition of 3 points, temperature, time and amount of catalyst being the three significant. The response variable was the yield of levulinic acid, which reached a maximum of 42.94% in the central conditions (190 ºC, 2h, 1:0.25). The third study comprised a three-factor BoxBehnken (PBB) design, with the response being the conversion of levulinic acid into ethyl levulinate. The highest conversion occurred in the time of 1hrs, molar ratio (ethanol: AL) 4:1 and catalyst concentration 0.04mol/L. Then, a comparison was made between the synthesis of methyl and ethyl levulinate, realizing that the only significant factor in both reactions was time. After the analysis, the feasibility of converting green coconut husk powder into levulinic acid was proven, being the ideal aluminum sulfate catalyst for both the synthesis of AL and for the synthesis of ethyl levulinate.