Avaliação da utilização do processo de explosão a vapor como Pré-Tratamento para extração de lignina Acetosolv do bagaço de cana-de-açúcar

Abstract

The sugarcane bagasse is a source of lignocellulosic biomass. It is mainly composed of cellulose, hemicellulose and lignin. Lignin has aromatic character, making it suitable for a noblest use such as a partial replacement of phenol in phenol formaldehyde resins. However, the lignin is not readily available, requiring the use of physical and chemical methods to extract it from biomass. The aim of this study was extract the lignin from sugarcane bagasse using steam explosion as pre-treatment combined with acetosolv extraction. The use of the pre-treatment was evaluate using central composite design 22 with the center point in triplicate, applicable to the response surface method, to evaluate effects of reaction time and temperature on the total reducing sugars and specific lignin production. Structural and thermal characteristics of lignin were determined by FT-IR and TGA. The results showed that, in the range studied, the independent variables of the steam explosion process caused no significant effects on the extraction of sugars and specific lignin production. However, employing 240 °C for 4 min, it was possible to obtain higher extraction of sugars (39 g/L) and the highest lignin specific production (0,21 g lig/g bagasse). Thus, it was performed an extraction with reduced time (45 min), yielding 0,20 g lig/g bagasse. This result was similar to the result obtained using only acetosolv extraction process with 180 min of reaction time. The results demonstrated that the steam explosion process may be used as a means of reducing energy costs. Acetosolv lignin extracted from the pretreated fiber has similar structural characteristics to the acetosolv lignin extracted from the raw bagasse, showing that the steam explosion process caused no change in lignin monomer units. In addition, the thermal analysis showed a reduction in the content of residual sugars in the lignin extracted from the pretreated bagasse compared to the lignin extracted from raw bagasse.