Extractive removal of both basic and non-basic nitrogens from fuel oil by dicarboxyl-modified polyethylene glycol: Performance and mechanism

Polyethylene glycol [PEG, H(OCH 2 CH 2 ) n OH] like PEG-600, a green extractant for organic N-compounds in fuel oil, was very active for non-basic nitrogens but not effective for basic ones. Modification of PEG that replaced –OH group with –OCH 2 COOH group can produce HOOCCH 2 (OCH 2 CH 2 ) n OCH 2 COOH (dcPEG). For denitrogenation, dcPEG-600 was highly effective for both basic and non-basic nitrogens. N-distribution coefficient [ D N , (μg N ·g dcPEG −1 )/(μg N ·g oil −1 )] of dcPEG-600 to n -octane can reach as high as 200 for indole, 92.6 for pyrrole, 42.0 for quinoline, and 81.5 for pyridine, respectively. Besides, denitrogenation selectivity of dcPEG-600 to toluene ( D N / D toluene ) can amount to 462 for indole, 230 for pyrrole, 146 for quinoline, and 366 for pyridine, respectively. The high performance was ascribed to contribution of active O atom on ether group and active H atom on –COOH group. The active O atom (Lewis basic site) formed H-bond with the non-basic nitrogen (Brønsted acid). The active H atom (Brønsted acidic site) not only interacted with the basic one (Lewis base) but also brought in the good selectivity. Moreover, dcPEG-600 was still effective for real oil and could be recycled for several times without the denitrogenation performance significantly decreasing.