OPTICAL AND CONFOCAL MICROSCOPIC STUDIES ON DISSOLUTION OF RICE STRAW PARTICLES IN 1-ETHYL-3- METHYLIMIDAZOLIUM ACETATE

Abstract

Abundant agriculture residue such as rice straw needs an effective pretreatment method in order to efficiently and economically process it into biofuels and chemicals. In order to develop an economical liquefaction process for pretreatment of rice straw, a 3D particle based-dissolution process model needs to be investigated. As a result, this study was undertaken to develop a dissolution model of ball milled rice straw (RS) particles in 1-Ethyl-3-Methylimidazolium Acetate [Emim][OAc], at 120°, 140° and 160°C using optical and confocal microscopes. These results showed the rectangular particle swelled in-plane during the heat treatment in [Emim][OAc] but the thickness and volume decreased with heating time. As the particle swelling progressed, the particle light intensity ratio increased which was confirmed by confocal and optical microscopy. Both the particle light intensity ratio and volume ratio measurement were used to estimate the particle dissolution end point. Heating at 160ºC accelerated particle dissolution and swelling significantly. Decreasing the temperature from 160ºC to 120ºC extended the dissolving time changing from 10 min to 1 h. This new imaging analysis process model utilizing particle light intensity and volume ratios allows significant improvement in dissolution process modeling for endpoint determination and prediction. The dissolution process also has applications to other types of biomass.