Method to Synthesize Micronized Spherical Carbon Particles from Lignin

Spherical carbon particles are versatile products that are of interest in polymer modification and scaffolding, catalysis, and energy storage applications. Despite various complex synthesis methods available currently, there is a need for simplified synthesis techniques to develop spherical carbon particles from sustainable feedstock. Here, we report a simple method for manufacturing micronized carbon particles from lignin, a plant biomass derived phenolic oligomer. By careful selection of a good, high boiling solvent that can fully solvate and stabilize lignin, we were able to create spherical free-flowing carbon particles from lignin by a simple solvothermal process and subsequent carbonization. During solvothermal reaction, lignin degrades into fragments via its thermally sensitive bonds. Simultaneously, the residual lignin and its fragments repolymerize, condense into highly cross-linked structures, and eventually precipitate out of solution with a spherical shape. Infrared and NMR spectroscopy data in combination with the rheological properties of thermally condensed, solvated oligomer elucidate evolution in the chemical architecture of lignin. The coarse-grained molecular dynamics simulations revealed the growth of spherical char from lignin in a good solvent through intermolecular condensation. X-ray diffraction and electron microscopy data show the morphology of the carbonized product - an increase in the carbonization temperature enhances the structural order.