Etanólise do ácido levulínico empregando catalisadores de estanho (IV)

• Autor(a) principal: Silva, Evellyn Patricia Santos da
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal de Alagoas (UFAL)
• Texto Completo: http://www.repositorio.ufal.br/jspui/handle/123456789/7953
• topic: Biomassa; Organoestânicos(IV); Ácido levulénico; Catálise; Esterificação (Química); Levulinato de etila; Biomass; Catalysis; Organotin(IV); Ethyl levulinate; Esterification; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA

Lignocellulosic biomass represents an abundant and relatively low-cost renewable carbon resource that can be used to produce chemical inputs such as levulinic acid (LA). This ketoacid is a versatile platform for a wide variety of applications that can replace or complement fossil sources, which is desirable to improve global sustainability. Ester derivatives of levulinic acid can be developed as promising additives to oxygenate fuels, which not only increases the efficiency of the engine, but also decreases gas and particulate emissions. Thus, the present work aims to evaluat commercial tin (IV) based catalytic systems, including butylstannoic acid (BTA), butyltin trichloride (BTC), dibutyltin dichloride (DBDC) and dimethyltin dichloride (DMDC) compared to reactions without the use of catalyst, in the esterification of levulinic acid with ethanol (EtOH) to produce ethyl levulinate. The reactions were conducted at 70, 80, 90 and 110 °C for reaction times ranging from 0.25 to 6 h with AL/EtOH/CAT molar ratios of x/y/z, where x = 1, y = 4, 5 and 6 and z = 0.01 and stirring speed of 1000 rpm. The experiments were carried out in closed glass vial-type reactors. The quantification of the remaining levulinic acid in the reaction mixtures was performed by high performance liquid chromatography (HPLC) and the results were expressed in terms of conversion (%) of AL. The catalysts were characterized by absorption spectroscopy in the mid-infrared region with Fourier transform (FTIR) and it was possible to verify the characteristic vibrations of each one. The results showed that the organometallic complex butyltin trichloride showed better catalytic activity with AL conversion of 92.2 % in 6 hours of reaction using 1/6 AL/EtOH conducted at 110°C and 0.01 catalyst. Such efficiency may be associated with increased Lewis acidity at the metal center due to the presence of electronegative substituents, temperature and alcohol proportion. The apparent rate constant (kap x 103) for the reaction without catalyst at the molar ratio 1/6/0.01 = Al/EtOH/CAT was estimated to be 50.9 h-1 while in the presence of the BTC at the same parameters was 1135.8 h-1 , an increase of 95.5 % to the process. When comparing the reactions in the absence and in the presence of BTC at different temperatures at a molar ratio of 1/5/0.01 = AL/EtOH/CAT, the activation energy was estimated to be reduced by 21 %.