A Life Cycle Assessment Of Ionic Liquid Pretreatment For Lignocellulosic Biomass

Author : Thehazhnan K. Ponnaiyan
Publisher :
ISBN 13 :
Total Pages : 173 pages
Book Rating : 4.:/5 (17 download)

DOWNLOAD NOW!

Download or read book Aspects Critical to Advancing Ionic Liquid Pretreatment Technique as a Viable Approach for Lignocellulosic Biomass Conversion written by Thehazhnan K. Ponnaiyan and published by . This book was released on 2016 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: Declining nonrenewable petroleum resources combined with political and environmental concerns over fossil fuels have necessitated the search for alternate energy sources. Plant (lignocellulosic) biomass, which includes the fibrous, woody, and generally inedible portion of plant matter, is an abundant, inexpensive, and sustainable source of organic carbon that can be processed to produce fuel ethanol and a variety of other chemicals. The biological conversion of cellulosic biomass to ethanol could offer high yields at low costs, but only if more improvement is seen in technology for releasing simple sugars from recalcitrant biomass. Lignocellulosic biomass is composed of three major components- cellulose, hemicellulose, and lignin. The cellulose and hemicellulose portions when hydrolyzed into glucose and pentose sugars, can be fermented to produce fuel. The pretreatment of biomass is a crucial step, and in recent years, ionic liquids (ILs) have been gaining recognition as environmentally benign solvents for biomass pretreatment, owing to their favorable properties. Although a promising route, IL pretreatment still harbors several critical aspects that require further investigation, and the goal of this dissertation is to address these concerns. A key aspect that influences the economic viability of the ionic liquid pretreatment technique is the recovery and reuse of ILs. The extent of recovery of the IL under investigation, 1-ethyl-3-methylimidazolium acetate (EMIM-Ac), is investigated and the results are presented in chapter 3. It is shown that the ionic liquid does not irreversibly adsorb onto the biomass and can be recovered in the displacement solvent (water is used as antisolvent for separating ionic liquid from the biomass after pretreatment) at different biomass loadings. Nearly complete recovery of IL in wash solutions is achieved and no appreciable loss in its effectiveness for subsequent pretreatment is observed for over 9 recycle stages. However, the water from the IL-water wash mix needs to be separated from the IL to facilitate its continued efficiency for further pretreatment. From a techno-economic point of view, when such separations are employed on an industrial scale, the energy aspects involved in the recovery of ionic liquids become important. A better understanding of the driving force for separation between the ionic liquid and the antisolvent requires the availability of vapor liquid equilibrium (VLE) for the binary mixture.This provides the motivation to develop a novel and rapid method for the generation of (VLE) data using thermogravimetric analysis, and the results are discussed in chapter 4. VLE data over almost the entire composition range of EMIMAc-water mixtures at five different temperatures (60.0, 70.0, 80.0, 90.0 and 100.0 °C) is generated. This method may be extended to other hydrophilic IL-water systems or to IL-ethanol binary mixtures as well. In the instance when ethanol is used as the antisolvent during the pretreatment step, again, it is necessary to separate the ethanol from the IL by suitable means before the IL can be reused. In light of this, it is of interest to quantify the amount of ethanol remaining in the IL, if any, after the separation. This motive led to the development of a simple and rapid method for the determination of residual ethanol content in hydrophilic ILs, and the results are presented in chapter 5. The method utilizes headspace solid-phase microextraction coupled with gas chromatography to quantify ethanol in ILs. In an integrated biorefinery, another key aspect that can reinforce economic viability is the complete utilization of all components of the biomass, including the lignin portion, to produce value added products. Lignin, given its interesting functionalities and properties owing to its complex aromatic nature, has ample potential to be converted in a wide array of value-added products ranging from adhesives and surfactants to flame retardant material and aromatic acids. Since the IL pretreatment technique is relatively new, the kind of lignin resulting from such a pretreatment needs to be better understood as it is important to assess its usability for further processing. This motive resulted in the characterization of lignin produced from IL pretreated biomass, as discussed in chapter 6. Techniques employed include Scanning Electron Microscopy (SEM), Elemental Analysis, Elemental CHN (Carbon Hydrogen Nitrogen) analysis, Nuclear Magnetic Resonance Spectroscopy (13NMR), Thermo-gravimetric Analysis (TGA), and MatrixAssisted Laser Desorption/Ionization Mass Spectroscopy (MALDI-MS). A better understanding of these key aspects mentioned above will help facilitate further advancement of the IL pretreatment technique as a viable approach for lignocellulosic biomass conversion.