Avaliação do uso da argila vermiculita como catalisador no processo de hidrólise do bagaço de cana-de-açúcar.

Abstract

Biomass has been an interesting renewable energy source because it is available in large quantities, has low cost and is presented as a viable alternative for conversion into chemical products with high added value and biofuels. In Brazil, in the short time, the sugarcane bagasse is the source of biomass with the greatest potential for use as an industrial input. Among the methods used for conversion of biomass hydrolysis using solid catalysts have attracted interest in researchers from around the world and is an alternative to commonly used technique. Due to the availability, low cost and surface properties, aimed to evaluate the use of vermiculite clay as a catalyst in the process of hydrolysis of sugarcane bagasse. Performed by acid activation of the clay, using sulfuric (3M) and fluoridric acid (4M) and the chemical, with sodium hydroxide (4%) and sulfuric acid (3%), and the hydrothermal pre-treatments of sugarcane bagasse. The processes were conducted with control of time and temperature. Before and after the treatments application were determined the composition of the bagasse and textural properties of the clay, in addition the material was characterized by XRD, SEM, TG/DTG and DSC analysis. Regarding the composition of the bagasse, when using the chemical method of pre-treatment was achieved 75.88 and 73.88% solubilization of lignin and hemicellulose fractions, respectively, while for the hydrothermal method showed no significant alteration. The XRD analysis allowed to verify changes in crystallinity and SEM analysis showed changes in the morphology of bagasse, for the two types of pre-treatment. The TG / DTG and DSC analysis proven to degradation of hemicellulose and lignin, when using chemical pre-treatment. The characterization of vermiculite showed that acid treatment caused significant changes in the material making it amorphous, with higher surface area and pore volume. The natural clay presented surface area of 14.69 m²/g and treated with sulfuric and phosphoric acid 296.65 and 306.88 m²/g, respectively. The pore volume was 0.019 cm³/g to 0.273 and 0.297 cm³/g, respectively. However, there were no significant changes in thermal stability, the lamellar arrangement and diameter of pores, which presented an average value of 3.8 nm, classified as mesoporous materials. The catalytic tests using natural and activated with acid clay as a catalyst in the hydrolysis of commercial cellulose and in nature and pre-treated sugarcane bagasse were performed in autoclaves and greenhouse where it was evaluated the influence of temperature, time reaction and the amount of catalyst present in the reaction medium. The vermiculite showed catalytic activity in all reactions. The best results in the generation of fermentable sugars were observed when using treated with phosphoric acid clay in the hydrolysis of pretreated bagasse by hydrothermal method, achieving glucose and xylose yields of 38.02% and 80.26% respectively, for times of 2 and 1 h, 200 °C and the mass ratio of the catalyst and biomass 2:1.