2Laboratorio de Síntesis y Caracterización de Nuevos Materiales

Centro de Química

Instituto Venezolano de Investigaciones Científicas (IVIC)

Caracas, Venezuela

Crystallinity and lignin content are physicochemical barriers that affect the chemical and biochemical reactivity of lignocellulosic materials. In this work, the effect of ammonia on the Crystallinity index (CrI) of ammonia-treated dwarf elephant grass was determined by the X-ray diffraction powder method. Microcrystalline cellulose was used as a reference. The CrI of the untreated grass was 23.4%, which increased to values between 35.2% and 49.6% for the treated grass. Solubilized lignin from the treated material was characterized by IR spectroscopy, showing signals between 2200 and 800 cm^-1: a signal characteristic of the C=O tension of acids or conjugated arilic esters was found around 1648 cm^-1 and that of the aromatic skeletal C=C vibration around 1560-1530 cm^-1. For the untreated material, a signal of an asymmetric C-O-C tension was found between 1000 and 1150 cm^-1, corresponding to glycosidic bonds of polysaccharides. The treatment increased crystallinity, likely due to a reordering in the amorphous region of cellulose, and produced delignification. However, the treated material absorbed more water than the untreated one. The characterized lignin showed spectroscopic signals similar to those of hard wood, confirming great polymerization which decreases the chemical and biochemical reactivity of lignocellulosic materials.