Immobilization of fluorenone derived π-acceptors on poly (GMA-co-EGDMA) for the removal of refractory nitrogen species from bitumen derived gas oil

• π-acceptor immobilized polymers are capable of removing nitrogen compounds from gas oil.
• Charge transfer complexes are formed between π-acceptors and nitrogen species.
• Trinitrofluorenone immobilized poly (GMA-co-EGDMA) has high nitrogen removal efficiency.

A pretreatment process employing porous polymer support coupled with electron withdrawing π-acceptors has been developed for the selective removal of refractory nitrogen compounds from gas oil via charge transfer complex (CTC) mechanism. Copolymer of glycidyl methacrylate and ethylene glycol dimethacrylate, poly (GMA-co-EGDMA) was used as the porous polymer support for the immobilization of fluorenone based π-acceptors. In order to study the effect of various π-acceptors, 2,7-dinitro-9-fluorenone (DNF); 2,4,7-trinitro-9-fluorenone (TriNF) and 2,4,5,7-tetranitro-9-fluorenone (TENF) were immobilized on poly (GMA-co-EGDMA) via hydroxylamine (ON) linker. BET, CHNOS elemental analysis, SEM and TG/DTA were employed for determining the chemical and physical properties of the synthesized compounds. Characterization by FT-IR revealed the immobilization of π-acceptor on the polymers. Total Nitrogen/Sulfur analyzer affirmed the decrease in total nitrogen and sulfur content of bitumen derived light gas oil (LGO) after pre-treatment with immobilized polymers. This decrease in total nitrogen content of gas oil is a direct consequence of the formation of charge transfer complexes between π-acceptors immobilized polymer and heterocyclic nitrogen species present in gas oil. Furthermore, spectroscopic features of the charge transfer interactions between π-acceptors and basic and non-basic nitrogen species were confirmed by UV–vis spectrophotometer. 13C NMR was used to calculate the decrease in aromatic content after treatment. The optimized polymers were successful in removing up to 14.4% of the total nitrogen content in a single contact using 25 wt% of the immobilized polymers with respect to LGO while only 1.4% of the total sulfur moieties were removed at 25 °C.