Pyrolysis–GC/MS of sinapyl and coniferyl alcohol

Herein we report the fast pyrolysis of the lignin monomers sinapyl and coniferyl alcohol, as well as mixtures of the two, at 650 °C using pyrolysis–GC/MS. The total ion chromatogram area % of certain marker pyrolysates for each alcohol were summed and used to calculate sinapyl:guaiacyl (S:G) ratios in the mixtures; these ratios were then plotted against the actual molar S:G ratios of the starting material. 13 coniferyl alcohol marker pyrolysates and 9 sinapyl alcohol marker pyrolysates provided acceptable linear correlation, whereas several other marker groups chosen did not correlate to the actual S:G ratio in the starting material. Results indicated that the demethoxylation of sinapyl alcohol and/or its pyrolysates occurs during pyrolysis at 650 °C; however, the amount of demethoxylated products generated is statistically insignificant. Having obtained the pyrolysis profile of the various S:G mixtures, marker pyrolysates for the calculation of the S:G ratio in lignin can be carefully selected according to unique samples. These marker groups can then be calibrated against known S:G ratios to provide analysis of the actual S:G ratio of lignin in biomass. For example, pyrolysates chosen from the pyrolysis of peach pit lignin were calibrated in order to determine the S:G ratio in peach pit lignin. The resulting S:G ratio was similar to that obtained from capillary electrophoresis of the products from KMnO4 oxidation of the peach pit lignin.

► We studied sinapyl and coniferyl alcohol and their mixtures using pyrolysis–GC/MS. ► Sum area percent ratios of pyrolysates from each alcohol were calculated. ► Linear correlations existed between sum area percent S:G ratios and molar S:G ratios. ► The S:G ratio of lignin was measured via pyrolysis–GC/MS. ► Pyrolysis–GC/MS S:G ratios agreed with capillary electrophoresis of oxidized lignin.