This project explores the chemical processes responsible for the decomposition of biomass when it is rapidly heated in the absence of oxygen, a process known as fast pyrolysis, to produce gases, liquids, and solids. The liquids from fast pyrolysis from biomass show promise for the production of advanced biofuels and biobased chemicals that resemble conventional gasoline and diesel fuels produced from petroleum. Understanding the chemical reactions that occur during fast pyrolysis and measuring their rates are important for designing future biorefineries that would convert biomass into fuels and chemicals. This project will explore new experimental techniques for probing reactions that occur in solid biomass after it has been rapidly heated to high temperatures in a matter of seconds. By tracking the change in concentration of various decomposition products with time, rates of important pyrolysis reactions can be determined.
The goal of this research is to measure the chemical kinetics of biomass fast pyrolysis through time-resolved measurements of condensed phase reactions. Pyrolysis is the basis for most thermochemical processes including combustion, gasification, fast pyrolysis, and even solvent liquefaction. Among these technologies, fast pyrolysis has gained considerable attention in the last few years for its prospects to produce advanced biofuels and biobased chemicals from lignocellulosic biomass. The reaction mechanisms of pyrolysis have been studied since the 1950s, but only modest progress has been made in determining elementary reaction rates associated with the depolymerization of the biopolymers that make up lignocellulosic biomass. Without rate coefficients and activation energies for these reactions, it is difficult to accurately model and design pyrolysis reactors from first principles. Most previous studies of pyrolysis kinetics have measured weight loss of samples undergoing relatively slow heating, which yields little information about elementary reactions occurring in solid biomass. This research will demonstrate the utility of two versions of Controlled Pyrolysis Duration (CPD) - Quench reactors developed at Iowa State University for studying condensed phase elementary chemical reactions. The first, capable of investigating reactions that occur on the order of a few seconds, will be used to study unzipping of small oligosaccharides to form the anhydro-monosaccharide levoglucosan. The second, capable of investigating much faster reactions, will be used to study cracking of cellulose to oligosaccharides early in the depolymerization process. These apparatus will also be employed to study depolymerization of hemicellulose and lignin.
