Reducing the Carbon Footprint of Air-Blown Bitumen Using Physisorption

This research uses experiments and molecular modeling calculations to study the efficacy of using polyphosphoric acid (PPA) grafted to silica to produce air-blown bitumen with the desired stiffness at a lower air-blowing time and temperature. Lowering the air-blowing time and temperature leads to reductions in the emitted volatile organic compounds (VOCs), the environmental carbon footprint, and the use of energy and resources. Our experiment showed that using PPA-grafted silica reduced the air-blowing time required to achieve the desired penetration [90 (0.1 mm)] and softening point (45 °C) by up to 29 and 50%, respectively, compared to neat vacuum bottom residue (VBR). Molecular modeling calculations showed that the adsorption of PPA to silica changed the intramolecular hydrogen-bond network in the backbone of PPA and promoted the interaction of PPA-grafted silica with VBR molecules, especially with VOCs. Increased intermolecular interactions facilitate the stiffening of VBR, leading to a lower duration of air blowing. Furthermore, these interactions can directly trap the VOCs and reduce their emission to the environment. The study outcomes show the merits of using PPA-grafted silica to produce the desired bitumen grades while reducing the duration of air blowing, to improve the energy efficiency and reduce the environmental impact of the process.