Ind. Eng. Chem. Res. 2009, 48, 3973–3977
3973
SEPARATIONS Selective Extraction of Neutral Nitrogen-Containing Compounds from Straight-Run Diesel Feed Using Polymer-Supported Ionic Liquid Moieties Li-Li Xie,†,§ Alain Favre-Reguillon,†,‡,* Xu-Xu Wang,§ Xianzhi Fu,§ Michel Vrinat,⊥ and Marc Lemaire†,* ICBMS, Institut de Chimie et Biochimie Mole´culaires et Supramole´culairessUMR 5246, Laboratoire de Catalyse et Synthe`se Organique, 43 bouleVard du 11 noVembre 1918, Villeurbanne, F-69622, France, CNRS, UMR5246, UniVersite´ Lyon 1, Laboratoire des Transformations Chimiques et PharmaceutiquessUMR7084, ConserVatoire National des Arts et Me´tiers, 2 rue Conte´, Paris, F-75003, France, Research Institute of Photocatalysis, Fuzhou UniVersity, 523 Gong Ye Road, 350002 Fuzhou, P. R. China, and IRCELYON, CNRS, UMR5256, UniVersite´ Lyon 1, 2 aVenue Albert Einstein, Villeurbanne, F-69626, France
The extraction of trace polar compounds, among them neutral nitrogen-containing compounds (N-compounds), has received much attention from refiners because of their inhibiting effect on the hydrodesulfurization (HDS) process. Recently, we have shown that chloride-based ionic liquids (ILs) can selectively extract N-compounds from straight-run diesel feeds. However, the measurable solubility of ILs in hydrocarbon fuel is not a desired outcome of the process. Thus, the covalent binding of ILs moieties on polymers was studied. Starting from Merrifield resin, three resins were prepared with imidazolium, pyridinium, and triethylammonium chloride functionality. The resins were evaluated using a synthetic solution with dibenzothiophene and carbazole as model compounds, and a high selectivity for N-compounds was found. Imidazolium and pyridinium resins were then further evaluated using straight-run diesel feed containing 13400 ppm S and 105 ppm N. The selectivity toward N-compounds was comparable to the selectivity observed with ILs. Moreover, the resins could be easily regenerated using a protic solvent like methanol. 1. Introduction Efforts to make existing separation methods more efficient and ecofriendly may get a boost from a relatively new class of solvents known as ionic liquids (ILs). ILs exist as liquids over a wide temperature range and interest in them has been prompted both by their unique and useful properties, including negligible vapor pressure, good thermal stability, high heat capacity, high thermal conductivity, and nonflammability.1 ILs have been used as alternative to classical molecular solvents over a range of fundamental research and applications, including synthesis, catalysis, and separation.2-4 We have recently shown that neutral nitrogen-containing compounds could be selectively removed from straight-run diesel feed using chloride-based ILs.5-7 However, the difficult procedures for product purification and ILs recycling as well as the high cost and loss of ILs restrict the industrial application to some extent. In our case, even if the solubility of watersoluble ILs in the hydrocarbon feed were low (down to 40 mg kg-1),5 a small amount of ILs will dissolve and be entrained in the raffinate stream. This loss of ILs in the raffinate will have an impact on the cost of the solvent-raffinate separation system. Furthermore, in our case, the presence of chlorides is expected to cause corrosion and thus an additional liquid/liquid extraction with water should be considered to wash the raffinate. Furthermore the viscosity of ILs can also limit their usefulness as reaction media on the large scale. * To whom correspondence should be addressed. E-mail:
[email protected];
[email protected]. † Universite´ Lyon 1. ‡ Conservatoire National des Arts et Me´tiers. § Fuzhou University. ⊥ IRCELYON.
These constraints can be circumvented by supporting IL moieties on resins. We have explored such a system on a laboratory scale for selective extraction of neutral N-compounds from hydrocarbon feed. Different approaches have been used to support ILs.8-11 Among them, covalent binding between the support and the IL moieties12,13 could solve the problem of leaching and recycling. As part of our ongoing research on selective removal of trace polar compounds in the hydrocarbon feed, we now report the use of a polymeric adsorbent-bearing IL moieties. This study expands on previous work that demonstrated the effectiveness of preliminary treatment of the straight-run feed before HDS.14,15 2. Experimental Details 2.1. Reagents. The model fuel containing 150 ppm N and 150 ppm S was prepared by dissolving 179.2 mg (1.07 mmol) of analytical grade carbazole and 86.3 mg (0.47 mmol) of analytical grade dibenzothiophene in 100 g of a mixture of toluene/n-dodecane (80/20 weight). Arabian light straight run was kindly provided by IFP (Lyon-France) and was used as feedstock. The relevant properties of this oil are summarized in Table 1. 2.2. Resin preparation. Merrifield resin (5.5 mmol Cl/g, 5.5% divinylbenzene, 16-50 mesh) is commercially available (Fluka, ref 63868). The Merrifield resin was first swollen in Table 1. Composition and Physical Properties of Arabian Light Straight Run density (at 293K) (g/L) sulfur (ppm) total nitrogen (ppm) basic nitrogen (ppm) aromatics (wt %)
10.1021/ie900142p CCC: $40.75 2009 American Chemical Society Published on Web 03/23/2009
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