Chemical Shifts and Lifetimes for Nuclear Magnetic Resonance (NMR) Analysis of Biofuels

Abstract

Determination of the molecular composition of biofuels is critical to process development. Because biofuels, such as pyrolysis oil, contain hundreds of compounds, quantitative determination of the mixtures is a formidable task and is often not necessary for routine development work. ¹³C and ¹H nuclear magnetic resonance (NMR) offer a reasonable trade-off between functional group identification and analytical measurement effort. However, accuracy depends upon selection of chemical-shift regions, baseline compensation, and correction for incomplete longitudinal relaxation effects. We propose chemical-shift assignments and <i>T</i>₁ correction factors based on ¹³C and ¹H NMR measurements of over 50 compounds that have been previously identified in pyrolysis oils and several plant natural products, especially terpenes. The results are intended to allow for a semiquantitative assessment of molecular composition of bio-oils on a time scale of 1−8 h to provide feedback for process development