Mass spectrometric methodology was developed for the determination of the primary products of fast pyrolysis of G-lignin model compounds ranging in size from trimers to octamers as well as a synthetic lignin polymer with �-O-4 and/or 5-5 linkages. The lignin model compounds were synthesized using literature methods. To determine the primary pyrolysis products, a very fast heating pyroprobe was coupled with a linear quadrupole ion trap mass spectrometer through a custom-built adaptor. The pyrolysis products were quenched and ionized in an atmospheric pressure chemical ionization (APCI) source infused with ammonium hydroxide to aid in ionization. During APCI in negative ion mode, ammonium hydroxide facilitates deprotonation of aromatic lignin units with phenolic moieties. For small lignin molecules, such as a trimer and tetramer containing �-O-4 linkages, trimeric, dimeric and monomeric products were predominantly generated. The major pyrolysis products of the trimer and tetramer are similar to the product anions formed upon collisionally activated dissociation (CAD) of the deprotonated trimer and tetramer in the ion trap, suggesting that the pyrolysis mechanism is ionic rather than radical type. However, more H2O and CH2O losses were found for the pyrolysis products compared to the CAD product ions. For larger lignincompounds, such as a hexamer and an octamer with both 5-5 and �-O-4 linkages, dimers and monomers are the major pyrolysis products (MW < 400 Da). The pyrolysis of a synthetic G-lignin polymer (about 20 monomeric units) with only b-O-4 linkages showed similar results as the lignin dimers and monomers but with different degrees of H2O and CH2O losses.

On-line mass spectrometric method for the determination of the primary fast pyrolysis products of synthetic lignin oligomers with �-O-4 and 5-5 linkages

247th National Meeting (2014)

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