Extractive Desulfurization With Ionic Liquids

Petroleum is the cornerstone of modern civilization, but sulfur compounds in it have also caused serious environmental problems. Nowadays, hydrodesulfurization cannot meet the requirement of deep desulfurization. Therefore, new desulfurization techniques like extractive desulfurization (EDS) have been heavily studied. Ionic liquids (ILs) are green solvents with excellent properties and can be ideal extractants for extractive desulfurization.In this work, we synthesized four new ILs based on pyrrolidone and alkylphosphate and characterized them with 1HNMR,13CNMR, Elemental Analysis and ESI-MS. We also tested their melting point, thermal stability, viscosity and density. The test results showed that these ILs had wide liquid window, excellent thermal stability and low viscosity therefore were competent for sulfur removal.Then we used these ILs to extract TS, BT and DBT from model oil. All ILs possessed high EDS ability and [NMP][DMP] is the best. We investigated the factors that would influence the EDS performance, including volume ratio, time, temperature, cycles and regeneration times. Explanations of the results were given based on extraction theory and ILs’properties. Through these tests, we proved [NMP][DMP] to be a promising extractant for desulfurization with the optimal extraction condition given.Finally, we conducted EDS tests of FCC diesel with these ILs and known [NMP][H2PO4]. [NMP][DMP] displayed the highest EDS ability and the varying pattern of five ILs’ EDS ability was consistent with that in model oil. The factors were also investigated and the optimal extraction condition was given.