Novel Methodology toward Deep Desulfurization of Diesel Feed

Ind. Eng. Chem. Res. 2004, 43, 7843-7849

7843

SEPARATIONS Novel Methodology toward Deep Desulfurization of Diesel Feed Based on the Selective Elimination of Nitrogen Compounds Mathieu Macaud, Marc Se´ vignon, Alain Favre-Re´ guillon, and Marc Lemaire* Laboratoire de Catalyse et Synthe` se Organique, UMR 5181, Universite´ Claude Bernard Lyon 1, CPE Lyon, 43 boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex, France

Emmanuelle Schulz Laboratoire de Catalyse Mole´ culaire, UMR 8075, Institut de Chimie Mole´ culaire et des Mate´ riaux d’Orsay, 91405 Orsay Cedex, France

Michel Vrinat Institut de Recherches sur la Catalyse, UPR 5401, 2 avenue Albert Einstein, 69626 Villeurbanne Cedex, France

π-Acceptor molecules covalently attached on hydrophilic support were used to selectively remove neutral nitrogen heterocyclic compounds from diesel feed by a charge transfer mechanism. Functionalized hydrophilic polymers can effectively adsorb nitrogen heterocyclic compounds with a high selectivity toward sulfur heterocyclic compounds from model and real feed. The results showed that charge transfer processes coupled with an ion-exchange process to selectively remove basic nitrogen compounds are efficient enough to produce denitrogenated feed in high yield. This study was conducted to determine whether trends in hydrodesulfurization (HDS) activity with lower sulfur content were mainly the result of lower reactivity of hindered sulfur compounds or due to nitrogen species inhibition. The inhibition effects of nitrogen compounds on HDS at conditions commonly used in the hydrotreatment of gas oil feedstocks has been experimentally determined. This study suggests that the selective removal of nitrogen compounds from gas oil strongly enhanced the deep desulfurization. Introduction In recent years deep desulfurization of diesel fuel has attracted much attention due to the gradual reduction of the statutory sulfur content in most western countries. In 2009, the maximum S-content will be limited to 10 ppm compared to today’s value of 350 ppm S.1 The refining industry has demonstrated its capability of adapting hydrotreatment to the stringent regulations by improving catalytic activity, increasing the process severity, especially increasing the hydrogen pressure or designing new reactor configurations.2 However, the limited availability of hydrogen used during hydrodesulfurization (HDS) of petroleum fractions and the more severe regulation of CO2 emission should be also considered in the selection of a new process for the hydrotreating unit. Additionally, the worldwide petroleum reserves are becoming heavier as a result of depletion of traditional resources, increasing their sulfur and nitrogen contents. Two main routes should be considered to improve the HDS process: on one hand, the elimination of refractory * To whom correspondence should be addressed. Tel.: +33 (0)472431407. Fax: +33 (0)472431408. E-mail: [email protected].

sulfur species, such as 4,6-dialkyldibenzothiophenes,3,4 and on the other hand, the elimination of HDS inhibitors5-8 which could limit the performance of HDS catalysts. Indeed, the reactivity of nitrogen-containing compounds is much lower than that of polyaromatic sulfur compounds9-11 although adsorption is stronger. When high levels of desulfurization are reached, the concentration of refractory sulfur compounds is very low and polyaromatics and nitrogen compounds naturally occurring in diesel fuel may inhibit the HDS process through competitive adsorption8 and contribute to the difficulty of meeting the more stringent specifications.2,5-8,10,12 Then we could expect that elimination of HDS inhibitors such as nitrogen compounds could lead to improvement of HDS conditions. Usually, the basic nitrogen compounds have been considered to be stronger inhibitors for the HDS reactions than the nonbasic ones.13-18 However, strong inhibition of these reactions by nonbasic nitrogen compounds has been observed, either due to hydrogenation reactions occurring during this process, which lead to the formation of basic species, or to a strong adsorption of the nonbasic compounds over the support surface, but the results seem to be inconclusive.5,6 Furthermore, the presence of nitrogen compounds in petroleum may also

10.1021/ie049465e CCC: $27.50 © 2004 American Chemical Society Published on Web 10/22/2004

7844

Ind. Eng. Chem. Res., Vol. 43, No. 24, 2004 Table 1. Composition and Physical Properties of Iranian Straight Run

Figure 1. Nitrogen-containing compound in petroleum.

promote tank and pipe corrosion and oil degradation during storage.19,20 The identification of nitrogen compounds in diesel feedstock has been performed.21-27 The nitrogen compounds are present predominantly in heterocyclic aromatic compounds (Figure 1).10,28 These compounds are classed as basic and nonbasic. In the latter (e.g., indole 1 and carbazole 2), the lone-pair electrons on the nitrogen atom are delocalized around the aromatic ring and are unavailable for donation to a Lewis acid. The opposite is true for basic heterocyclic compounds such as quinoline 3 and acridine 4. Nonheterocyclic nitrogen compounds such as aliphatic amines are also present in smaller quantities and are denitrogenated much more rapidly.10 Among nonheterocyclic amines, aniline 5 derivatives which necessarily appear in the hydrodenitrogenation pathway of heterocycles9 are important. The elimination of nitrogen compounds by noncatalytic processes has already been studied. Basic nitrogen compounds can be removed using an ion-exchange resin,23,29-31 by liquid/liquid extraction using volatile carboxylic acid,32 and by metal complexation.33 The simultaneous removal of sulfur- and nitrogen-containing compounds has been studied by alkylation and subsequent precipitation method using excess alkylating agents (CH3I and AgBF4),34-38 and by combination of UV irradiation39,40 or chemical oxidation41 with subsequent liquid-liquid extraction using an oil/acetonitrile two-phase system liquid/liquid extraction. One alternate approach to remove unwanted heterocyclic compounds is to use bacterial cells or enzymes as biocatalysts.42 The difference from biodesulfuration,43 to date, is that no bacterial isolates efficient for biodenitrogenation have been reported.44 The previous methods are efficient for the removal of basic nitrogen compounds, but none of them seemed to be efficient or selective enough to remove neutral nitrogen compounds such as indole 1 and carbazole 2. The primary objective of this study was to selectively remove nitrogen compounds present in petroleum fractions from sulfur and polyaromatic compounds. The selectivity of this first step is essential in order to obtain a high yield during the subsequent refining process. In addition, a second objective was to determine the effects of nitrogen concentration on the HDS process. After description of the elimination process, we report here the preparation of highly denitrogenated feed in order to study the influence of nitrogen species toward deep hydrodesulfurization in industrial conditions. Experimental Section Reagents. The model fuel was prepared by dissolving in a heptane/toluene solution (75/15, v/v) 100 ppm (0.215 mmol) each of the five nitrogen compounds (Aldrich, >96%) listed in Figure 1 and 230 ppm (0.215 mmol) of 4,6-dimethyldibenzothiophene.45 The catalyst used for the hydrodesulfurization test was an industrial NiMo/Al2O3 catalyst (MoO3, 16.5 wt %; NiO, 3.3 wt %), provided as extrudates (bulk density 0.78 g‚cm-3; pore volume 0.44 cm3‚g-1; surface area 205

density (at 288 K) (g/L) sulfur (ppm) total nitrogen (ppm) basic nitrogen (ppm) aromatics (wt %)

870 13 600 360 120 32.6

m2‚g-1). The extrudates were crushed, screened (80125 µm), and then sulfided ex situ in an H2-H2S (15%) flow (4 L‚h-1) at 673 K for 4 h before use. Amberlite IR 120 (H+ form, 1.9 mequiv/mL, 450-600 µm) was purchased from Fluka and used as received. Iranian Straight Run was kindly provided by IFP (Lyon) and was used as feedstock. The relevant properties of this oil are summarized in Table 1. Preparation of the Resins. Details of the preparation were described elsewhere.46,47 The loading of the resins was determined by elemental analysis and quantitative IR spectroscopy and was found to be 0.20 and 0.74 mmol of π-acceptor per gram of resin for polymers 6 and 7, respectively (Figure 2).

Figure 2. Structure of hydrophilic polymer 6 and lipophilic polymer 7 used in this study.

Evaluation of the Resins. Distribution coefficients were determined according to eq 1, where Ci and Cf are the initial and final concentrations of the studied molecule and msol and mresin are the mass of liquid and resin used.

Ds )

Ci - Cf msol Cf Mresin

(1)

The selectivity of the resins toward N-compounds were determined according to eq 2, where DX and DY are the distribution coefficients calculated for compound X and compound Y.

SX/Y )

DX DY

(2)

Analytical Procedures. Gas chromatography (GC) analyses were carried out on a Shimadzu GC-14A equipped with a 15 m apolar column JW DB-5 (95% dimethylpolysiloxane-5% diphenylpolysiloxane) and a flame ionization detector. Gas chromatography-mass spectrometry (GC-MS) analyses were carried out on a Fisons MD 800 mass spectrometer equipped with the same apolar column. Quantitative analysis of the total sulfur concentration was determined by energy X-ray fluorescence spectroscopy with a Horiba SLFA 1800 sulfur in oil analyzer, using 20 mm i.d. PTFE cells with 7 µm Mylar film windows. To eliminate the effect of the matrix on the gas oil, the calibration of the apparatus was made with

Ind. Eng. Chem. Res., Vol. 43, No. 24, 2004 7845

a series of different gas oils containing between 100 and 13 600 ppm of sulfur. For low sulfur and nitrogen concentrations, the sulfur and nitrogen concentrations were analyzed by UV fluorescence and by chemiluminescence, respectively, on an Antek 9000 Series nitrogen/sulfur analyzer equipped with a robotic liquid autosampler. Reactors. Hydrodesulfurization catalytic tests were performed on two different sorts of reactors: one operating in a batch mode and the other one in a continuous mode to mimic industrial conditions. The batch reactor used was a 200 cm3 stirred slurry tank reactor. This autoclave was equipped with a hollow-shaft, six-bladed magnetically driven turbine with four baffles on the wall to prevent vortex formation. The samples were collected through a tube (1/16-in. diameter); hydrogen was introduced through a pressure controller, which maintains a constant pressure during the hydrodesulfurization course. In each run, the autoclave was charged with about 100 mL of diesel feed. Freshly presulfided catalyst was added to the mixture. The reactor was flushed with nitrogen and heated under stirring to reach the reaction temperature. Hydrogen was then introduced (Ptot ) 5 MPa). This step was considered to be the beginning of the reaction. Samples were periodically removed during the course of the HDS test, and determination of the sulfur content of samples was performed as previously described. Determination of the initial rate of sulfur transformation was performed at 543 K with 260 mg of NiMo/Al2O3, and determination of high sulfur conversion was performed at 693 K after 95 h with 500 mg of NiMo/Al2O3. Control of the Kinetic Regime. Previous experiments were carried out to ensure the absence of intraparticle and interphase mass transfer limitations.48 It appeared that there were no diffusional problems under our conditions when the mass catalyst was limited to 1 g and the stirring rate was fixed to at least 900 rpm. Moreover, we have performed the hydrodesulfurization of straight run gas oil at different temperatures and an apparent activation energy of 100 kJ/mol was calculated, indicating that the experiments were performed without mass transfer limitation. On the other hand, gas oil HDS experiments in continuous mode were performed in a trickle-bed microreactor previously described.49 The main feature of this equipment is its high miniaturization, allowing using only a small amount of catalyst, so steady states are reached in several hours rather than a few days, as in larger units. The 2 cm3 reactor was then loaded with about 1 g of catalyst. The tests were performed at different temperatures between 633 and 673 K, under a 3 MPa hydrogen pressure (H2 flow ) 3.2 mL‚min-1). Gas oil feedstock was introduced through the bed catalyst at a rate corresponding to a 1.1 g‚h-1 flow resulting in an operating LHSV of 1 h-1. Results and Discussion Considering their planarity and their electron-rich structure, neutral N-compounds 1 and 2 (Figure 1) can form charge transfer complexes (CTCs) with suitable π-acceptor molecules (Figure 3). Furthermore, electron donor-acceptor complexes of 1 with 1,3,5-trinitrobenzene 850 and 2 with 2,4,7-trinitrofluorenone 951 have already been described. However, diesel fuel contains a large variety of aromatic compounds, with and without heteroatoms, capable of forming CTCs which could in

Figure 3. Structure of π-acceptor molecules.

turn compete with compound 1 or 2. Theoretical calculations3,52 and experimental studies3,53 on synthetic and real feeds have shown that selectivities of CTCs can be correlated to the spatial overlap of the frontier molecular orbitals of the LUMO of the π-acceptor molecules and the HOMO of the donor molecules. Thus symmetrical polynitro-substituted 9-fluorenones (compound 10, Figure 3) are selected for the selective complexation of neutral N-compounds. The HOMO values of dibenzothiophene and carbazole are closed. Furthermore, S-compound derivatives are up to 20 times more concentrated than N-compounds, and thus the carbazole/dibenzothiophene selectivity is expected to be very low. However, the hydrophobic character of a compound can be a key attribute in determining its interaction with a solid. Most commonly, the hydrophobicity of a compound is determined by its ability to partition between water and an immiscible organic solvent. The logarithm of the octanol-water partition coefficient (log P) has been used extensively to describe the lipophilic or hydrophobic properties of a compound. Log P measurement provides a thermodynamic measure of its hydrophilicity-lipophilicity balance.54 The lipophilicity of dibenzothiophene is much more important than that of carbazole as evidenced by the log P value (4.59 and 3.77 for dibenzothiophene and carbazole, respectively).54 Furthermore, log P values for anthracene, phenanthrene, and pyrene are 4.63, 4.53, and 4.88.54 It was then expected that, using synergistic interactions between π-acceptor molecules and hydrophilic polymer 6 instead of lipophilic polymer 7 (Figure 2), the selectivity of charge transfer complex formation toward nitrogen-containing compounds could be enhanced.46 To examine the feasibility of the present process, a model fuel containing equimolar quantities of each of the five nitrogen compounds drawn in Figure 1 and 4,6dimethyldibenzothiophene (4,6-DMDBT) was treated with polymers 6 and 7. GC analyses were conducted as a function of time. The equilibrium was reached after 1 h of contact, in a batch reactor under continuous stirring, between the model fuel and the resins. As shown in Figure 4, polymer 7 showed a high distribution coefficient for 4,6-DMDBT and carbazole, as compared to polymer 6. Even though the total adsorption capacity of polymer 6 was lower than that of polymer 7, the former was more selective for the nitrogen compounds adsorption than the latter. A carbazole/4,6-DMDBT selectivity of 78 and 6 was calculated according to eq 2 for polymers 6 and 7, respectively. As expected, the structure of the polymer functionalized by the π-acceptor molecule, and thus the hydrophilicity/ lipophilicity balance, is of major importance for the selective formation of charge transfer complexes with donor molecules. Single Extraction from Straight Run. Figure 5 shows experimental results obtained for both sulfur and nitrogen removal from straight run sample after 1 h of contact.

7846

Ind. Eng. Chem. Res., Vol. 43, No. 24, 2004

Figure 4. Distribution coefficient of N- and S-compounds from 30 g of model fuel by 1 g of polymers 6 and 7 after 1 h of mechanical stirring at 400 rpm and at room temperature.

Figure 5. Total concentration of nitrogen and sulfur before and after contact of 8.2 g of straight run with 1 g of polymer 6 or 7 after 1 h of mechanical stirring at 400 rpm and at room temperature.

About 60 wt % nitrogen removal from straight run was achieved in a single contact with polymer 6 with the resin feed ratio of 8.2 by weight. Polymer 7, which is more lipophilic, appears to be less efficient than the

hydrophilic polymer 6. Only 30 wt % nitrogen compound removal was achieved with this resin. Under those conditions, the sulfur level was lowered to less than 3 wt %. A selectivity of 72 can be calculated, according to eq 2, for polymer 6, which can be compared to a selectivity of 17 obtained for polymer 7. Thus immobilization of π-acceptor molecules on polar polymers strongly enhanced the selectivity of adsorption of nitrogen compounds observed with real samples. Polymers 6 and 7 could be easily regenerated by washing with toluene. The selectivity could be confirmed by analysis of the toluene fractions. The trapped compounds were analyzed by GC-MS and compared in Figure 6. The nitrogen compounds are predominant in the compounds trapped by polymer 6 (Figure 6), although sulfur derivatives and polyaromatics without heteroatoms are the major components in the compounds trapped by polymer 7. These results highlight the synergistic extraction of N-compounds by π-acceptor molecules and a polar polymer. As expected from the mechanism of complexation,3 the structures of the extracted compounds by polymer 6 were closed to the carbazole and dibenzothiophene derivatives. Some polyaromatics able to form a charge transfer complex with immobilized π-acceptor were also found, but quinoline 3 and aniline 5 derivatives due to their different molecular orbital symmetry were not found in the toluene fractions. Multistep Elimination of Nitrogen Compounds. Neutral nitrogen compounds were effectively removed by formation of charge transfer complex with π-acceptor molecules immobilized on polymer 6. Basic compounds present in straight run are efficiently removed by ionexchange resins.23,29,31 Thus, the two processes were combined to selectively remove the whole nitrogen compounds from straight run (Figure 7). Figure 7 shows the concentration of nitrogen compounds in straight run during a multistep batch procedure. Basic nitrogen compounds are effectively removed by using ion-exchange resins. After 1 h of contact, 130 ppm (36%) of N-compounds was removed. A second batch process with a new ion-exchange resin did not further decrease the total N content of the feed. Then, the feed was contacted with polymer 6 with a straight run/polymer ratio of 3. After 1 h of contact, 140 ppm of

Figure 6. GC-MS of the compounds trapped by polymers 6 (a) and 7 (b) from straight run.

Ind. Eng. Chem. Res., Vol. 43, No. 24, 2004 7847

Figure 8. Evolution of sulfur content of feed as a function of time for different nitrogen compound contents in batch mode: 200 cm3 slurry tank reactor; 100 mL of straight run; 500 mg of freshly presulfided NiMo/Al2O3 catalyst; PH2 ) 5 MPa; 693 K. Figure 7. Batch removal of N-compounds from straight run (13 600 ppm S, 360 ppm N), 1 h of mechanical stirring at 400 rpm and at room temperature. Ion-exchange process: straight run/ Amberlite IR 120 is 17/1; charge transfer process: straight run/ polymer 6 is 3/1.

neutral N-compounds was removed. The obtained feed was then contacted with regenerated polymer 6 and 55 ppm of neutral N-compounds was again adsorbed. After three batch processes, the total N concentration was less than 30 ppm. Using an ion-exchange resin coupled with a charge transfer process, 93% of N-compounds originally present in straight run were successfully removed whereas less than 5% of S-compounds were removed. The global yield of the process is excellent: more than 95 wt % of the feed is recovered after the extraction. To our knowledge, it is the most powerful noncatalytic process for ultradeep denitrogenation. Inhibition Effect of Nitrogen Compounds toward Hydrodesulfurization Process. 1. Catalytic Tests in a Batch Mode. HDS of straight run feed and its denitrogenated analogue was performed under the same experimental conditions (5 MPa hydrogen pressure at 593 K). Examination of the sulfur compound conversion by sulfur analysis in the samples according to time allowed the determination of the initial rate of transformation of sulfur species in a batch reactor. The initial rates of sulfur transformation for straight run feed (13 600 ppm S and 360 ppm N) and for denitrogenated straight run feed (12 900 ppm S and 25 ppm N) were 165 × 108 and 157 × 108 mol‚g-1‚s-1, respectively. Thus, removal of the nitrogen compounds from the feed had no great influence on the initial rate of transformation of sulfur compounds. To evaluate the inhibition of N-containing compounds at deep HDS levels, the hydrodesulfurization tests were performed under more severe conditions (5 MPa hydrogen pressure at 693 K) in order to reach low sulfur levels in the hydrotreated feed (Figure 8). Under those conditions, 99.8% sulfur compound conversion (26 ppm S) was obtained with the denitrogenated straight run feed whereas 97% sulfur compound conversion (410 ppm) was obtained with the straight run feed. Those results were in accordance to studies performed by SK Corporation.55 We observed that the inhibition effect of nitrogen species on HDS reaction occurred mainly when the sulfur content decreased. This certainly implies that the inhibition effect of nitrogen compounds occurred especially at deep HDS conditions when the adsorption

Table 2. Sulfur Concentration Obtained in Continuous Reactor at Different Temperatures (PH2 ) 3 MPa, LHSV ) 1 h-1, 1 g of NiMo/Al2O3) 653 K

673 K

S conversion S conversion (ppm) (%) (ppm) (%) straight run feeda denitrogenated straight run feedb

1250 690

90.8 94.6

510 340

96.2 97.4

a Initially 13 600 ppm S and 360 ppm N. b Initially 12 900 ppm S and 25 ppm N.

competition toward different species (sulfur and nitrogen compounds) is maximal because of their similar concentrations in the feed. At a high level of HDS, competitive adsorption on HDS active sites is high, and then the HDS rate decreases drastically. In a comparison of the straight run and denitrogenated straight run feeds, higher conversion of S-compounds is obtained with the latter. Such a higher conversion is associated with higher H2S production. Therefore, the inhibiting effect of H2S is low compared with the N-compound effect. Demonstration is made that the elimination of inhibiting species, such as N-compounds, could be one way to reach a high level of desulfurization. 2. Catalytic Tests in Continuous Mode. Experiments were then performed in a continuous reactor to mimic industrial conditions. HDS of straight run feed and its denitrogenated analogue at three different temperatures (633, 653, and 673 K), under hydrogen pressure of 3 MPa, were compared (Table 2). As previously observed, the conversion of sulfur derivatives was improved in a continuous reactor when the nitrogen-containing compounds were removed. Results showed that such a removal of nitrogen compounds increased drastically the conversion of sulfur compounds toward hydrodesulfurization. In other words, to reach the same conversion of sulfur compounds, it is possible to work at a reaction temperature in the HDS unit lower than 15 °C. Thus the lifetime of the catalyst should be increased. Conclusion Nitrogen-containing compounds could be selectively removed from diesel feed in a two-step process. The basic nitrogen compounds were removed using strongly

7848

Ind. Eng. Chem. Res., Vol. 43, No. 24, 2004

acidic ion-exchange resins, and the nonbasic nitrogen compounds were selectively adsorbed by the formation charge transfer complexes using synergistic interaction with a hydrophilic π-acceptor polymer. The regeneration of the resins was performed by using toluene. GC-MS analyses of the adsorbed compounds confirmed that the carbazole derivatives were effectively trapped by this functionalized polymer. The highly denitrogenated feed was used to study the influence of the nitrogen compound concentration on HDS of diesel feed. We studied first the inhibition effect of nitrogen compounds toward the HDS process in a batch mode and showed that denitrogenation allowed a significant improvement of the HDS process. Indeed, compared to an untreated diesel feed, lower sulfur content was obtained with weaker time of contact using a denitrogenated feed. Catalytic tests in continuous mode confirmed an improvement of the HDS process. The use of highly denitrogenated feed upstream of the HDS allowed the HDS process to be performed at lower temperatures of at least 15 °C, thus increasing the catalyst lifetime. Although the inhibiting effect of these nitrogen derivatives on HDS is known, very few teams evaluated the elimination of nitrogen compounds from feedstock as an alternative to obtain deeply desulfurized diesel feeds. Acknowledgment The authors acknowledge FSH, IFP, and TotalFinaElf for their financial support of this work. The authors also acknowledge IFP for the donation of the hydrotreated diesel fuel. Literature Cited (1) Regulatory Impact Analysis: Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements; United States Environmental Protection Agency, December 2000; EPA420-R-00-026, (2) Breysse, M.; Djega-Mariadassou, G.; Pessayre, S.; Geantet, C.; Vrinat, M.; Perot, G.; Lemaire, M. Deep desulfurization: reactions, catalysts and technological challenges. Catal. Today 2003, 84, 129-138. (3) Milenkovic, A.; Schulz, E.; Meille, V.; Loffreda, D.; Forissier, M.; Vrinat, M.; Sautet, P.; Lemaire, M. Selective Elimination of Alkyldibenzothiophenes from Gas Oil by Formation of Insoluble Charge-Transfer Complexes. Energy Fuels 1999, 13, 881-887. (4) Shafi, R.; Hutchings, G. J. Hydrodesulfurization of hindered dibenzothiophenes: an overview. Catal. Today 2000, 59, 423-442. (5) Laredo, G.; De los Reyes, A.; Cano, L.; Castillo, J. Inhibition effects of nitrogen compounds on the hydrodesulfurization of dibenzothiophene. Appl. Catal. A 2001, 207, 103-112. (6) Laredo, G.; Altamirano, E.; De los Reyes, A. Inhibition effects of nitrogen compounds on the hydrodesulfurization of dibenzothiophene: Part 2. Appl. Catal. A 2003, 243, 207-214. (7) Turaga, U. T.; Ma, X.; Song, C. Influence of nitrogen compounds on deep hydrodesulfurization of 4,6-dimethyldibenzothiophene over Al2O3- and MCM-41-supported Co-Mo sulfide catalysts. Catal. Today 2003, 86, 265-275. (8) Koltai, T.; Macaud, M.; Guevara, A.; Schulz, E.; Lemaire, M.; Bacaud, R.; Vrinat, M. Comparative inhibiting effect of polycondensed aromatics and nitrogen compounds on the hydrodesulfurization of alkyldibenzothiophenes. Appl. Catal. A 2002, 231, 253-261. (9) Perot, G. Reactions involved in hydrodenitrogenation. Catal. Today 1991, 10, 447-472. (10) Girgis, M. J.; Gates, B. C. Reactivities, reaction networks, and kinetics in high-pressure catalytic hydroprocessing. Ind. Eng. Chem. Res. 1991, 30, 2021-2058. (11) Kasztelan, S.; Des Courieres, T.; Breysse, M. Hydrodenitrogenation of petroleum distillates: industrial aspects. Catal. Today 1991, 10, 433-445.

(12) Furimsky, E.; Massoth, F. E. Deactivation of hydroprocessing catalysts. Catal. Today 1999, 52, 381-495. (13) Satterfield, C. N.; Modell, M.; Wilkens, J. A. Simultaneous catalytic hydrodenitrogenation of pyridine and hydrodesulfurization of thiophene. Ind. Eng. Chem. Process Des. Dev. 1980, 19, 154-160. (14) LaVopa, V.; Satterfield, C. N. Poisoning of thiophene hydrodesulfurization by nitrogen compounds. J. Catal. 1988, 110, 375-387. (15) LaVopa, V.; Satterfield, C. N. Response of dibenzothiophene hydrodesulfurization to presence of nitrogen compounds. Chem. Eng. Commun. 1988, 70, 171-176. (16) Nagai, M.; Sato, T.; Aiba, A. Poisoning effect of nitrogen compounds on dibenzothiophene hydrodesulfurization on sulfided nickel-molybdenum/alumina catalysts and relation to gas-phase basicity. J. Catal. 1986, 97, 52-58. (17) Nagai, M.; Kabe, T. Selectivity of molybdenum catalyst in hydrodesulfurization, hydrodenitrogenation, and hydrodeoxygenation: effect of additives on dibenzothiophene hydrodesulfurization. J. Catal. 1983, 81, 440-449. (18) Gutberlet, L. C.; Bertolacini, R. J. Inhibition of hydrodesulfurization by nitrogen compounds. Ind. Eng. Chem. Prod. Res. Dev. 1983, 22, 246-250. (19) Batts, B. D.; Fathoni, A. Z. A literature review on fuel stability studies with particular emphasis on diesel oil. Energy Fuels 1991, 5, 2-21. (20) Mushrush, G. W.; Beal, E. J.; Hardy, D. R.; Hughes, J. M. Nitrogen compound distribution in middle distillate fuels derived from petroleum, oil shale, and tar sand sources. Fuel Process. Technol. 1999, 61, 197-210. (21) Schmitter, J. M.; Ignatiadis, I.; Dorbon, M.; Arpino, P.; Guiochon, G.; Toulhoat, H.; Huc, A. Identification of nitrogen bases in a coker gas oil and influence of catalytic hydrotreatment on their composition. Fuel 1984, 63, 557-564. (22) Dorbon, M.; Bernasconi, C. Nitrogen compounds in light cycle oils: identification and consequences of aging. Fuel 1989, 68, 1067-1074. (23) Merdrignac, I.; Behar, F.; Albrecht, P.; Briot, P.; Vandenbroucke, M. Quantitative Extraction of Nitrogen Compounds in Oils: Atomic Balance and Molecular Composition. Energy Fuels 1998, 12, 1342-1355. (24) Li, M.; Larter, S. R.; Stoddart, D.; Bjoroey, M. Liquid chromatographic separation schemes for pyrrole and pyridine nitrogen aromatic heterocycle fractions from crude oils suitable for rapid characterization of geochemical samples. Anal. Chem. 1992, 64, 1337-1344. (25) Mao, J.; Pacheco, C. R.; Traficante, D. D.; Rosen, W. Analysis of neutral nitrogen compounds in diesel oil by direct injection high-performance liquid chromatography-mass spectrometry-ultraviolet spectrometry methods. J. Chromatogr. A 1994, 684, 103-111. (26) Mao, J.; Pacheco, C. R.; Traficante, D. D.; Rosen, W. Identification and characterization of nitrogen compounds in Brazilian diesel oil by particle beam l.c.-m.s. Fuel 1995, 74, 880887. (27) Shin, S.; Sakanishi, K.; Mochida, I.; Grudoski, D. A.; Shinn, J. H. Identification and reactivity of nitrogen molecular species in gas oils. Energy Fuels 2000, 14, 539-544. (28) Kabe, T.; Qian, W.; Ishihara, A. Hydrodesulfurization and hydrodenitrogenation: chemistry and engineering; Wiley-VCH: Weinheim, 1999. (29) Cronauer, D. C.; Young, D. C.; Solash, J.; Seshadri, K. S.; Danner, D. A. Shale oil denitrogenation with ion exchange. 3. Characterization of hydrotreated and ion-exchange isolated products. Ind. Eng. Chem. Process Des. Dev. 1986, 25, 756-762. (30) Marcelin, G.; Cronauer, D. C.; Vogel, R. F.; Prudich, M. E.; Solash, J. Shale oil denitrogenation with ion exchange. 2. Evaluation of ion-exchange adsorbents and resin treatment procedures. Ind. Eng. Chem. Process Des. Dev. 1986, 25, 747-756. (31) Prudich, M. E.; Cronauer, D. C.; Vogel, R. F.; Solash, J. Shale oil denitrogenation with ion exchange. 1. Process concept and modeling. Ind. Eng. Chem. Process Des. Dev. 1986, 25, 742746. (32) Qi, J.; Yan, Y.; Su, Y.; Qu, F.; Dai, Y. Extraction of nitrogen compounds from catalytically cracked diesel oil with a volatile carboxylic acid based on reversible chemical complexation. Energy Fuels 1998, 12, 788-791.

Ind. Eng. Chem. Res., Vol. 43, No. 24, 2004 7849 (33) Qi, J.; Yan, Y.; Fei, W.; Su, Y.; Dai, Y. Solvent extraction of nitrogen compounds from catalytically-cracked diesel oil by metal ion complexation. Fuel 1998, 77, 255-258. (34) Shiraishi, Y.; Taki, Y.; Hirai, T.; Komasawa, I. A novel desulfurization process for fuel oils based on the formation and subsequent precipitation of S-alkylsulfonium salts. 1. Light oil feedstocks. Ind. Eng. Chem. Res. 2001, 40, 1213-1224. (35) Shiraishi, Y.; Tachibana, K.; Taki, Y.; Hirai, T.; Komasawa, I. A novel desulfurization process for fuel oils based on the formation and subsequent precipitation of S-alkylsulfonium salts. 2. Catalytically cracked gasoline. Ind. Eng. Chem. Res. 2001, 40, 1225-1233. (36) Shiraishi, Y.; Tachibana, K.; Hirai, T.; Komasawa, I. A novel desulfurization process for fuel oils based on the formation and subsequent precipitation of S-alkylsulfonium salts. 3. Denitrogenation behavior of light oil feedstocks. Ind. Eng. Chem. Res. 2001, 40, 3390-3397. (37) Shiraishi, Y.; Hirai, T.; Komasawa, I. A novel desulfurization process for fuel oils based on the formation and subsequent precipitation of S-alkylsulfonium salts. 4. Desulfurization and simultaneous denitrogenation of vacuum gas oil. Ind. Eng. Chem. Res. 2001, 40, 3398-3405. (38) Shiraishi, Y.; Tachibana, K.; Hirai, T.; Komasawa, I. A novel desulfurization process for fuel oils based on the formation and subsequent precipitation of S-alkylsulfonium salts. 5. Denitrogenation reactivity of basic and neutral nitrogen compounds. Ind. Eng. Chem. Res. 2001, 40, 4919-4924. (39) Shiraishi, Y.; Hirai, T.; Komasawa, I. Photochemical denitrogenation processes for light oils effected by a combination of UV irradiation and liquid-liquid extraction. Ind. Eng. Chem. Res. 2000, 39, 2826-2836. (40) Shiraishi, Y.; Hirai, T.; Komasawa, I. Photochemical Desulfurization and Denitrogenation Process for Vacuum Gas Oil Using an Organic Two-Phase Extraction System. Ind. Eng. Chem. Res. 2001, 40, 293-303. (41) Shiraishi, Y.; Tachibana, K.; Hirai, T.; Komasawa, I. Desulfurization and Denitrogenation Process for Light Oils Based on Chemical Oxidation followed by Liquid-Liquid Extraction. Ind. Eng. Chem. Res. 2002, 41, 4362-4375. (42) Vazquez-Duhalt, R.; Torres, E.; Valderrama, B.; Le Borgne, S. Will Biochemical Catalysis Impact the Petroleum Refining Industry? Energy Fuels 2002, 16, 1239-1250. (43) Song, C.; Ma, X. New design approaches to ultra-clean diesel fuels by deep desulfurization and deep dearomatization. Appl. Catal. B 2003, 41, 207-238. (44) Bressler, D. C.; Gray, M. R. Hydrotreating Chemistry of Model Products from Bioprocessing of Carbazoles. Energy Fuels 2002, 16, 1076-1086.

(45) Meille, V.; Schulz, E.; Lemaire, M.; Faure, R.; Vrinat, M. An Efficient Synthesis of Pure 4,6-Dimethyldibenzothiophene. Tetrahedron 1996, 52, 3953-3960. (46) Macaud, M.; Schulz, E.; Vrinat, M.; Lemaire, M. A new material for selective removal of nitrogen compounds from gas oils towards more efficient HDS processes. Chem. Commun. 2002, 2340-2341. (47) Lemaire, M.; Schulz, E.; Sevignon, M.; Macaud, M.; FavreReguillon, A.; Thomas, M.; Loutaty, R. Polymer-supported π-electron acceptors for charge-transfer-based denitrogenation-desulfurization of petroleum fractions. PCT Int. Appl. 2002024836, 2002. (48) Koltai, T.; Macaud, M.; Milenkovic, A.; Schultz, E.; Lemaire, M.; Vrinat, M. Hydrodesulfurization of diesel fuels by association of a catalytic process and a separation process by using charge-transfer complexes. Catal. Lett. 2002, 83, 143-148. (49) Letourneur, D.; Bacaud, R.; Vrinat, M.; Schweich, D.; Pitault, I. Hydrodesulfurization Catalyst Evaluation in a Upflow Three-Phase Microreactor. Ind. Eng. Chem. Res. 1998, 37, 26622667. (50) Foster, R.; Fyfe, C. A. Electron-donor-acceptor complex formation by compounds of biological interest. III. Indole complexes. J. Chem. Soc. [Sect.] B: Phys. Org. 1966, 926-929. (51) Orchin, M.; Woolfolk, E. O. Molecular complexes with 2,4,7trinitrofluorenone. J. Am. Chem. Soc. 1946, 68, 1727-1729. (52) Milenkovic, A.; Loffreda, D.; Schulz, E.; Chermette, H.; Lemaire, M.; Sautet, P. Charge transfer complexes between tetranitrofluorenone and polyaromatic compounds from gasoil: a combined DFT and experimental study. Phys. Chem. Chem. Phys. 2004, 6, 1169-1180. (53) Meille, V.; Schulz, E.; Vrinat, M.; Lemaire, M. A new route towards deep desulfurization: selective charge transfer complex formation. Chem. Commun. 1998, 305-306. (54) Rekker, R. F.; Mannhold, R. Calculation of Drug Lipophilicity. The Hydrophobic Fragmental Constant Approach; VCH: Weinheim, 1992. (55) Min, W. S.; Choi, K., II; Khang, S. Y.; Min, D. S.; Ryu, J. W.; Yoo, K. S.; Kim, J. H. Method for manufacturing cleaner fuels. PCT Int. Appl. 9967345, 1999.

Received for review June 18, 2004 Revised manuscript received September 8, 2004 Accepted September 10, 2004 IE049465E