室溫離子液體於油品氧化脫硫之應用

Oxidative Desulfurization of Oils with Room Temperature Ionic Liquids

魏國佐(Guor-Tzo Wei) ； 羅文亨(Wen-Hen Lo) ； 莊豊霖(Li-Lin Chuang) ； 黃榮富(Jung-Fu Huang)

《化學》 65卷4期 (2007/12) Pp. 445-461

https://doi.org/10.6623/chem.2007045

摘要

降低油品中硫含量可以降低油品燃燒後所造成的空氣污染與及其所導致的酸雨之形成，為了防治酸雨的危害，各國政府立法嚴格管制硫氧化物的排放；面對法規愈趨嚴格要求，各煉油廠對於油品中硫含量的規範更加嚴格；再加上工業上使用的加氫脫硫方法需要在更高溫度與更高氫氣壓力下操作，才能降低油品中的硫含量，此將增加操作成本與風險。因此在傳統加氫脫硫技術外其他更有效的替代製程急需被研究開發。本報告簡略說明各種脫硫技術，再深入探討室溫離子液體於油品氧化脫硫之研究結果。室溫離子液體被歸屬為綠色溶劑Green solvent，因為它具有高熱穩定性及高溫不揮發等特性，且可溶解很多類型的化合物，因此可用來取代傳統的有機溶劑以進行液相－液相的萃取。本研究使用的室溫離子液體為1-烷基-3-甲基咪唑四氟硼酸鹽(1-alkyl-3-ethylimidazotetrafluoroborate)和1-烷基-3-甲基咪唑六氟磷酸(1- alkyl -3-methylimidazohexafluorophosphate)，在氧化脫硫系統中可藉由液相－液相萃取將油品中的硫化物萃取到離子液體中，再經由過氧化氫及有機酸的氧化反應，將離子液體內硫化物氧化形成硫氧化物，氧化後的硫氧化物大多數分佈在離子液體相內，此系統可將油中的硫化物不斷的萃取到室溫離子液體相，並讓氧化反應持續的進行。本方法在溫和條件下，便可將加氫脫硫觸媒很難脫除的二苯基　吩類型的化合物從油品中除去，有效的降低蒸餾柴油的含硫濃度，達到深度脫硫 (小於50 ppm)的目的。

關鍵字

氧化脫硫 ； 室溫離子液體 ； 柴油 ； 綠色製程

並列摘要

Combustion converts the sulfur compounds of oils to SO_x which are the major source of acid rain and air pollution. Hence, the air pollution could be improved by removing sulfurs from oils. The government regulations have set up the limit of the sulfur content in very low levels for oil refineries. Hydrogen desulfurization (HDS) is the only method being employed in oil refineries now. With HDS method, a higher reaction temperature and higher hydrogen pressure are required to produce the light oils that have low levels of sulfur compounds to meet the requirements of strict regulations. This will increase the cost and risk of HDS operation. In order to produce low S, alternative technologies are particular interested in providing potential solutions to replace HDS that is operated at high cost and hazard conditions. Extraction and oxidation have the potential to become the alternative approach for desulfurization of fuel oils. This report describes the desulfurization techniques briefly and presents our recent work of a desulfurization process, based on a combination of chemical oxidation and solvent extraction with RTILs, for fuel oils. RTILs are regarded as ＂green solvents＂. Generally, they are thermally stable, non-volatile, and can dissolve various types of compounds. RTILs have recently gained recognition as alternative traditional solvents for liquid-liquid extraction systems. In our work, 1-alkyl-3-methylimidazolium tetrafluoroborate and 1-alkyl-3-methylimidazolium hexafluorophosphate were empolyed as reaction media for sulfur removal from fuel oils. Dissolving sulfur compounds in hexadecane were employed as model oil for our studies. When oils and ionic liquids were stirred in the presence of H_2O_2 and organic acid, sulfur compounds in oil were extracted into the ionic liquid phase and oxidized there and converted to the corresponding oxidative compounds. These products have rather high polarity and are distributed in the ionic liquid phase, thus providing a successive removal of sulfur from oil. This method was carried out at moderate temperature and can easily treat DBT compounds, which are difficult to be removed by current HDS method. With this process, the sulfur content of the actual light oil can be reduced from 665ppm to less than 50ppm (ultra-deep desulfurization level) in just one batch of operation. This demonstrates the potential of the proposed method for the production of low S oils.

並列關鍵字

Oxidative desulfurization ； Room temperature ionic liquids ； Diesel oils ； Green process