Extractive denitrogenation of fuel oils with dicyanamide-based ionic liquids

• Published in: Green chemistry : an international journal and green chemistry resource : GC Vol. 13; no. 11; pp. 3300 - 3305
• Main Authors: ASUMANA, Charles, GUANGREN YU, YANWEN GUAN, SHENDU YANG, SHAOZHEN ZHOU, XIAOCHUN CHEN
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2011
• Subjects: Applied sciences; Chemistry; Crude oil, natural gas and petroleum products; Energy; Exact sciences and technology; Fuels; Heterocyclic compounds; Heterocyclic compounds with only one n hetero atom and condensed derivatives; Heterocyclic compounds with several n hetero atoms in the same ring, in separated rings or in fused rings; Organic chemistry; Preparations and properties; Prospecting and production of crude oil, natural gas, oil shales and tar sands; Organic cation; Nitrogen heterocycle; Carbazole derivatives; Carbazole; Fuel oil; Pyridine derivatives; Ionic liquid; Oil; Pyridine; Cyclic compound; Fuel; Aromatic compound; Extraction; Recycling; Nitrogen Compounds; Denitrogenation; Hydrodesulfurization
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/c1gc15747g

The removal of nitrogen-compounds (N-compounds), e.g. basic and neutral species, from fuel oils is necessary because of their inhibiting effect on the hydrodesulfurization process. In this work, the extractive denitrogenation performance of four dicyanamide-based ionic liquids (ILs) with different cationic characteristics, i.e., aromatic 1-butyl-3-methylimdazolium dicyanamide ([BMI][N(CN)2]) and 1-ethyl-3-methylimdazolium dicyanamide ([EMI][N(CN)2]), cyclic ethylated tetrahydrothiophenium dicyanamide ([S2][N(CN)2]), and tetrahedral ethyldimethylsulfonium dicyanamide ([EtMe2S][N(CN)2]), is investigated using basic pyridine and neutral carbazole as representative N-compounds. These ILs are capable of effectively extracting the N-compounds from the fuel oils with carbazole being more efficiently extracted than pyridine; also, aromatic imidazolium ILs exhibit better performance than cyclic thiophenium and tetrahedral trialkylsulfonium ILs in the order [BMI][N(CN)2] [EMI][N(CN)2] [S2][N(CN)2] [EtMe2S][N(CN)2]. Under ambient conditions, 1 : 1 (w/w) IL : oil, the N-content in the raffinate phase of the carbazole-containing fuel oil is undetected after 5 min of contact with [BMI][N(CN)2] and [EMI][N(CN)2], while 96.8% and 84.3% N-extraction efficiency is obtained after contact with [S2][N(CN)2] and EtMe2S][N(CN)2] respectively; for pyridine-containing fuel oil, the N-extraction efficiency in the aforementioned ILs is 72.7%, 69.1%, 63.5% and 59.8%, respectively. Compared with other ILs reported, the extractive performance of these ILs is competitive. [BMI][N(CN)2] is selected as a representative IL to undergo a series of parallel experiments to determine the influence of IL : oil mass ratio, temperature, initial N-content, and multiple extractions; a recyclability test is also performed. This work may present a new approach to fuel denitrogenation.