Preparation, characterization and application of d-gluconic acetal-based self-healing supramolecular ionogels for desulphurization of fuels

Abstract

To prevent the entry of toxic sulphur-containing contaminants into the atmosphere, extractive desulphurization of fuels with an ionic liquid (IL) as an extractor is a benign and efficient strategy, as compared with traditional hydrodesulphurization. However, ILs have some drawbacks like toxicity, non-biodegradability, low recyclability, and partial solubility in the fuel (leading to contamination), which limit their practical applications. Supramolecular ionogels, obtained from the gelation of ILs, not only retain the desulphurization function of ILs, but also prevent the leakage and achieve the renewable utilization of ILs. Hence, they are effective in overcoming the abovementioned limitations. Herein, a series of efficient D-gluconic acetal-based gelators (NG6, 12, 18 and NGO18) that can harden four different ILs at low concentrations was developed. They were thermally reversible and stable at room temperature with self-healing properties. The gelation and self-healing mechanisms of these gels were also systematically investigated. Furthermore, their desulphurization capacities in fuel-mimicking solutions of thiophene (T), benzothiophene (BT) and dibenzothiophene (DBT) in hexane were investigated. The effects of the concentration of sulphur compounds, fuel volume and temperature on the efficiency of sulphur removal were studied. Interestingly, the NG18-IL2 ionogel was the best-performing, which showed outstanding mechanical properties and fast and complete self-healing characteristics, along with 40.99, 49.76 and 51.68% removal efficiencies for T, BT and DBT, respectively, and 100% for T, BT and DBT in a multi-stage approach. Additionally, the ionogel could be reused six times and regenerated, all of which make it a low-cost and environment-friendly desulphurization material for practical applications.