Presentation given at the 2022 Spring Technical Meeting of the Eastern States Section of the Combustion Institute, Orlando FL, March 8 2022With the growing importance of climate change, soot emissions from engines have been receiving increasing attention since black carbon is the second largest source of global warming. A sooting tendency can be used to quantify the extent of soot formation in a combustion device for a given fuel molecule, and therefore to quantify the soot reduction benefits of alternative fuels. An interesting category of alternative fuels are phenolic hydrocarbons, which can be readily produced from the lignin portion of lignocellulosic biomass. Phenolics have a hydroxy group attached to a benzenoid ring, so they potentially combine the soot reduction benefits of oxygenated hydrocarbons with the fuel property benefits of aromatics such as high energy density and elastomer compatibility. In this work, we measured sooting tendencies of a diverse group of phenolics. The sooting tendency of each compound was characterized by the yield sooting index (YSI), which is based on the soot yield when a methane/air nonpremixed flame is doped with 1000 ppm of the test fuel. Many phenolics are solids at room temperature, so we developed a procedure to dissolve them in ethanol and then vaporize the solution into the flame. The results confirm that the oxygenated groups reduce soot formation compared to their analogous aromatics. For example, resorcinol (1,3-dihydroxybenzene) has a YSI of 34 versus 100 for benzene. The sooting tendencies of propylphenols and butylphenols were sensitive to the position of the alkyl group relative to the hydroxyl group, and the form of the alkyl group (e.g., n-propyl vs. isopropyl).