Co-pyrolysis characteristics and kinetics of lignin and collagen

• Higher char yield of lignin-collagen blends was obtained in a particular proportion.
• Apparent activation energies for lignin-collagen blends were obtained and their changes presented four stages.
• Evolution of gaseous products produced by lignin-collagen blends was compared with that from pure lignin, or pure collagen.
• Synergic pyrolysis interactions between lignin and collagen were observed.

The authors have investigated apparent activation energies of volatiles emission when using (a) lignin alone, (b) collagen alone, or (c) lignin-collagen blends as a thermally-strengthened binder for high-density carbon product manufacturing. Apparent activation energies (EaEa) computed by the Kissinger, the Weibull, and the Flynn-Wall-Ozawa (FWO) methods showed the same trends: with the highest EaEa for lignin alone (245 kJ/mol), and the lowest for collagen alone (194 kJ/mol). The blends pyrolysis exhibited synergistic presence of collagen, which could help initiate the pyrolysis mass loss reactions at 250–400 °C, and participate in the condensation reactions of aromatic fragments at 400–800 °C, leading to less emission of some gaseous products and more preservation of residual char. In prior Penn State work, it was observed that this thermally-induced preservation and condensation of aromatic structure increased the binding strength of the lignin-collagen binders. The work herein offers thermogravimetric concurrence and insight to this thermal-binding synergism.