Green and Atom Economical Route to High Compressive Strength Lignin Oil-Sulfur Composites

Lignin is the most abundant natural source of aromatics but remains underutilized. Elemental sulfur is a plentiful by-product of fossil fuel refining. Herein we report a strategy for preparing a durable composite by the one-pot reaction of elemental sulfur and lignin oil comprising lower molecular weight lignin derivatives. A lignin oil-sulfur composite (LOS₉₀) was prepared by reacting 10 wt. % lignin oil with 90 wt. % elemental sulfur. The composite could be remelted and reshaped over several cycles without loss of properties. Results from the study showed that LOS₉₀ has properties competitive with or exceeding values for commercial ordinary Portland cement and brick formulations. For example, LOS₉₀ displayed impressive compressive strength (22.1 MPa) and flexural strength (5.7 MPa). LOS₉₀ is prepared entirely from waste materials with 98.5% atom economy of composite synthesis, a low E factor of 0.057, and lignin char as the only waste product of the process for its preparation. These results suggest the potential applications of lignin and waste sulfur in the continuous efforts to develop more recyclable and sustainable materials.