Lignosulfonate-Based Ionic Liquids as Asphaltene Dispersants

Asphaltenes are recognized as being troublesome from upstream to downstream in the oil industry due to their tendency to precipitate and self-associate. Their extraction from asphaltenic crude oil for a cost-effective refining process is a crucial and critical challenge in the oil and gas sector. Lignosulfonate (LS), as a by-product of the wood pulping process in the papermaking industry, is a highly available and underutilized feedstock. This study aimed to synthesize novel LS-based ionic liquids (ILs) by reacting lignosulfonate acid sodium salt [Na]₂[LS] with different alkyl chains of piperidinium chloride for asphaltene dispersion. The synthesized ILs, 1-hexyl-1-methyl-piperidinium lignosulfonate [C₆C₁Pip]₂[LS], 1-octyl-1-methyl-piperidinium lignosulfonate [C₈C₁Pip]₂[LS], 1-dodecyl-1-methyl-piperidinium lignosulfonate [C₁₂C₁Pip]₂[LS] and 1-hexadecyl-1-methyl-piperidinium lignosulfonate [C₁₆C₁Pip]₂[LS] were characterized using FTIR-ATR and ¹H NMR for functional groups and structural confirmation. The ILs depicted high thermal stability because of the presence of a long side alkyl chain and piperidinium cation following thermogravimetric analysis (TGA). Asphaltene dispersion indices (%) of ILs were tested by varying contact time, temperature and ILs concentration. The obtained indices were high for all ILs, with a dispersion index of more than 91.2% [C₁₆C₁Pip]₂[LS], representing the highest dispersion at 50,000 ppm. It was able to lower asphaltene particle size diameter from 51 nm to 11 nm. The kinetic data of [C₁₆C₁Pip]₂[LS] were consistent with the pseudo-second-order kinetic model. The dispersion index (%), asphaltene particle growth and the kinetic model agreed with the molecular modeling studies of the HOMO-LUMO energy of IL holds.