NOx and N2O precursors (NH3 and HCN) from biomass pyrolysis: Co-pyrolysis of amino acids and cellulose, hemicellulose and lignin

Nitrogen in biomass is mainly in forms of proteins (amino acids). Glycine, glutamic acid, aspartic acid, leucine, phenylalanine and proline are the major amino acids in agricultural straw. The six amino acids were pyrolyzed individually at 800 °C in a tubular reactor in an argon atmosphere. Each amino acid sample was then pyrolyzed individually with cellulose, hemicellulose or lignin with 1:1 mixing ratio by weight under the same condition. The emissions of HCN and NH₃ were detected with a Fourier transform infrared (FTIR) spectrometer. The extent of interaction between the amino acids with cellulose, hemicellulose or lignin was determined by comparing the yields of HCN and NH₃ from co-pyrolysis with those from single amino acid pyrolysis under the same condition. The results indicate that the structure of the amino acid has a significant effect on the nitrogen transformation during pyrolysis. The mixtures undergo solid-state decomposition reactions during co-pyrolysis. The extent of interaction between the amino acids with cellulose, hemicellulose or lignin depends on the amino acid types and the components in biomass. Although single proline and leucine form no char, they give a significant amount of nitrogen-containing char when co-pyrolyzed with cellulose, hemicellulose and lignin. HCN and NH₃ yields and nitrogen conversion pathway from amino acid pyrolysis are influenced by cellulose, hemicellulose and lignin.