Eco-friendly bitumen binders from heavy crude oil and a relaxation approach to predicting their resistance to rutting and cracking

Abstract

Solvent deasphalting of crude oil is an environmentally unfriendly and hazardous process because of the volatility and explosiveness of the involved hydrocarbons (propane, butane, etc.), which also have low efficiency due to the proximity of their nature to the crude oil itself. A possible way to improve the efficiency of heavy compound removal is to switch from hydrocarbons to low-energy organosilicon liquids whose eco-friendliness can be enhanced by increasing the molecular weight up to the transition to polymers. This paper comparatively examines the deasphalting of heavy crude oil with hexamethyldisiloxane (HMDSO) and its polymeric form—polydimethylsiloxane (PDMS) of various molecular weights—with an assessment of the rational disposal of resultant heavy byproducts as construction materials. The use of HMDSO leads to a brittle heavy product, which contains resins and other heavy oil compounds in addition to asphaltenes, with a high total yield of 38.7%. The use of oligomeric or polymeric PDMS (with a viscosity of 10, 100, or 1000 mm2/s) increases the yield of the heavy product to 50–62% by precipitation of a greater quantity of non-asphaltene compounds that make it more flexible, flowable when heated, and potentially applicable as a bitumen binder with a high heat resistance reaching 70 °C. All obtained heavy products are glass-forming liquids subject to the time–temperature superposition principle, allowing a rapid assessment of their operating properties at low and high temperatures for quick determination of the resistances to cracking and rutting, respectively. At the same time, deasphalting with siloxanes significantly reduces the viscosity of heavy oil (by 390 and 45 times with PDMS and HMDSO, respectively) at lower specific energy consumptions than those for deasphalting with traditional aliphatic hydrocarbons.