Advancing sustainability with inverse vulcanization of waste sulfur catalyzed with TiO2

Abstract

There is a need for sustainable valorization solutions for the problem of excess sulfur arising from abundant natural sources of sulfur and the production of millions of tons of sulfur annually as a byproduct of refineries. Developing sulfur-based polymers with enhanced mechanical properties using the process of inverse vulcanization could be a valuable endeavor, since the poor mechanical properties of current sulfur polymers limit their scale-up and widespread application. Herein, we studied the performance of titanium oxide (TiO2) in improving the mechanical properties of the sulfur polymer through copolymerization with oleic acid. To study the efficacy of TiO2 and oleic acid in copolymerization with sulfur. we used laboratory experiments and a computational approach geared toward the use of the density functional theory (DFT). Based on the DFT results, the coordination of the third and fourth ligands (oleic acid chains) to the Ti4+ ion are not as strong as the coordination of the first two ligands mainly because of the high steric hindrance around the metal ion. The low values of binding energy for Ti2+–di oleate and Ti+–tri oleate make them more accessible to sulfur chains. This in turn, promotes the cross-linking reactions in a process of inverse vulcanization. This was further reflected in an increase of up to 637.3% in sulfur–oleic acid blends in presence of TiO2. This study contributes to the sustainable use of abundant sulfur and the sustainable development of the polymer industry.