Why are asphaltenes problematic for refinery operations?

Asphaltenes are problematic for refinery operations due to their tendency to precipitate and deposit, causing fouling of equipment, catalyst deactivation, and operational difficulties. Asphaltenes are complex, high-molecular-weight polycyclic aromatic hydrocarbons that are naturally present in crude oil. They are soluble in aromatic solvents but insoluble in aliphatic solvents, such as propane and butane. Changes in temperature, pressure, or composition can cause asphaltenes to destabilize and precipitate out of solution. These precipitated asphaltenes can deposit on heat exchangers, pipelines, reactors, and other equipment, reducing heat transfer efficiency, increasing pressure drop, and restricting flow. Asphaltene deposition can also lead to catalyst deactivation in catalytic cracking and hydrotreating units, reducing the efficiency of these processes. Furthermore, asphaltene precipitation can cause operational difficulties, such as plugging of filters and pumps, and can require costly shutdowns for cleaning and maintenance. Managing asphaltene stability is a significant challenge in refinery operations, requiring careful control of process conditions and the use of chemical additives, such as asphaltene dispersants, to prevent precipitation and deposition.