Collaborative Research: Experimental and computational methods to study chemical transformations of solid xylose into useful compounds

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

The long-term security of our economy requires a portfolio of domestic feedstocks to produce fuels and chemicals. Biomass is a promising choice; however, conversion technologies that are reliable, reproducible and economical have yet to come to market. Because of its low cost and versatility, biomass fast pyrolysis technology is an ideal choice for producing a renewable stream of fuels and chemicals. One issue with this technology that limits its implementation is that the underlying physical and chemical properties of the biomass transformations remain largely unknown. This project is a collaborative research study involving engineering groups at the Universities of Minnesota and Washington. In parallel, the teams are carrying out a detailed fundamental investigation using experimental (Minnesota) and computational (Washington) methods. The research has the overall goal of determining the mechanism of the chemical transformation of xylan, a major constituent of renewable biomass, into small molecule compounds that are precursors for fuels and chemicals. The research will also benefit other high temperature conversions of similar feedstocks to form a wide product slate. The educational benefits of this project are impacting graduate and undergraduate researchers. The collaborative project mechanism is an ideal way to enrich the training of students who specialize in experimental or theoretical methods through regular interactions and joint publication of research. The outcomes of this research project will also enrich chemical engineering coursework by the addition of real world problems and mini-projects stemming from the research results. The objective of this fundamental research project is to elucidate all of the key pyrolysis reaction pathways in the evolution of xylan, a biopolymer, to products. The experimental effort is based a new technique called PHASR (Pulsed heated analysis of solid reactions), that is capable of measuring rates of conversion in a regime totally free from transport limitations. The simulations and modeling combine graph theory, ab initio dynamics with the metadynamics method, and kinetic Monte Carlo modeling. The team is first investigating the physics of forming a liquid intermediate phase and the properties of the liquid intermediate with experiments and simulations. After determining the structure and dynamics of the transient intermediate, the project will focus on the kinetics and mechanism of biomass conversion. Detailed PHASR analysis is combined with graph theory to determine suggestions for how intermediate and final small molecule products are formed. Building on this, ab initio molecular dynamics (MD) and cutting edge methods developed by the researchers are used to discover individual reaction pathways and characterize their rates. The final step combines the experiments and new mechanistic insights to build a detailed overall model capable of describing both the overall physics and chemistry of this process.