Energy & Fuels 2008, 22, 4165–4169
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Role of Dispersed Ni Catalyst Sulfurization in Hydrocracking of Residue from Karamay Dong Liu,* Wenlong Cui, Shuyi Zhang, and Guohe Que State Key Laboratory of HeaVy Oil Processing, UniVersity of Petroleum China, Dongying, Shandong 257061, China ReceiVed June 4, 2008. ReVised Manuscript ReceiVed August 14, 2008
A hydrocracking study of Karamay residue using a batch reactor in the presence of dispersed Ni catalysts with different sulfurization methods is reported. Using two different courses of dispersion and sulfurization, the water-solubility Ni catalyst is dispersed in heavy oil and the dispersed catalyst is separated and characterized. Results showed that the water-solubility salts turn into NiS and NiS2 at the sulfrization temperature of 300 °C, regardless whether the emulsion breaking was achieved by multiple stages or a single stage after dispersion, and while the sulfurization temperature is at 300 °C and breaking the emulsion is by one stage, the better crystal of nikel pyrite is formed and the average particle size of the crystal is smaller than breaking the emulsion by multiple stages. The colloidal sol catalytic system of nikel pyrite is also synthesized in the experiment, and the sol of nikel pyrite can be highly homodisperse in oil and can restrain coke forming effectively.
1. Introduction Hydrocracking of petroleum residues is a recognized longterm necessity resulting from the contradictory evolution of supply, consisting of heavier crudes, and an increasing demand for transport fuels and reduced amounts of heating fuels.1-4 The slurry-phase hydrocracking process for residue is a newly developed technique for the processing of heavy oils.5 The technique, which adopted unsupported dispersed catalysts, has been developed. Generally, the homogeneous dispersed catalysts, such as an organic compound and inorganic compound of cobalt, molybdenum, or nickel, are used in the process.6-12 The homogeneous dispersed catalysts are divided into water-soluble * To whom correspondence should be addressed. Telephone: +86-05468399302. Fax: +86-0546-8396054. E-mail:
[email protected]. (1) Liang, W. HeaVy Oil Chemistry; Petroleum University Press: Shandong, China, 2000; pp 318-331. (2) Speight, J. G. New approaches to hydroprocessing. Catal. Today 2004, 98 (1), 55–60. (3) Dohler, W.; Kretschmar, K.; Merz, L. Veba-Combi-crackingsA technology for upgrading of heavy oils and bitumen. Prepr. Pap.-Am. Chem. Soc., DiV. Pet. Chem. 1987, 32 (2), 484–489. (4) Rana, M. S.; Sa´mano, V.; Ancheyta, J.; Diaz, J. A. I. A review of recent advances on process technologies for upgrading of heavy oils and residua. Fuel 2007, 86 (9), 1216–1231. (5) Schuetze, B.; Hofmann, H. How to upgrade heavy feeds. Hydrocarbon Process. 1984, 62 (2), 75–78. (6) Solari, R. B. HDH hydrocracking as an alternative for high conversion of the bottom of the barrel. Presented at the 1990 NPRA Annual Meeting, San Antonio, TX, March 25, 1990. (7) Khulbe, C. P.; Ranganathan, R.; Pruden, B. B. Hydrocracking of heavy oils/fly ash slurries. U.S. Patent 4,299,685, 1981. (8) Matsumura, A.; Kondo, T.; Sato, S.; Saito, I.; de Souza, W. F. Hydrocracking Brazilian Marlim vacuum residue with natural limonite. Part 1: Catalytic activity of natural limonite. Fuel 2005, 84 (4), 411–416. (9) Matsumura, A.; Sato, S.; Kondo, T.; Saito, I.; de Souza, W. F. Hydrocracking Marlim vacuum residue with natural limonite. Part 2: Experimental cracking in a slurry-type continuous reactor. Fuel 2005, 84, 417–421. (10) Yves, J.; Davidson, M.; Le Page, J. F. Process for hydrotreating heavy hydrocarbons in liquid phase in the presence of a dispersed catalyst. U.S. Patent 4,285,804, 1981. (11) Montanari, R.; Marchionna, M.; Panariti, N. Process for the conversion of heavy feedstocks such as heavy crude oils and distillation residues. World Patent WO2004056946, 2004.
dispersed catalysts and oil-soluble dispersed catalysts,13,14 which could be highly dispersed in residues and have a greater surface area/volume ratio.15-17 The sulfurized transition-metal catalysts have higher hydrogenation and hydro-desulfurization reactivity than the oxidation catalysts;18,19 thus, most of the dispersed catalysts need to be presulfurized to sulfides with high catalytic activity,20 such as pyrrhotine for ferrous salt,21,22 MoS2 for molybdate, etc. It becomes a major study direction to speed the sulfurization, to promote the sulfurization ratio, and to improve the dispersivity of the sulfurization products. Because the oil-soluble dispersed catalysts are expensive, the water-soluble dispersed catalysts are widely investigated in slurry-phase hydrocracking of heavy (12) Marchionna, M.; Delbianco, A.; Panariti, N. Process for the conversion of heavy charges such as heavy crude oils and distillation residues. U.S. Patent Application 20030089636, 2003. (13) Li, Y.; Wang, J.; Jiang, L.; Zhang, Z.; Liu, J.; Ren, S.; Zhao, B.; Jia, Y. Hydrocracking of heavy oil and residuum with a dispersing-type catalyst. U.S. Patent 6,004,454, 1999. (14) Que, G.; Men, C.; Meng, C.; Ma, A.; Zhou, J.; Deng, W.; Wang, Z.; Mu, B.; Liu, C.; Liu, D.; Liang, S.; Shi, B. Heavy oil hydrocracking process with multimetallic liquid catalyst in slurry bed. U.S. Patent 6,660,157, 2003. (15) Strausz, O. P. Process for hydrocracking heavy oil. U.S. Patent 6,068,758, 2000. Strausz, O. P. Oil-soluble catalysts for the hydrocracking of Athabasca bitumen. Fuel Energy Abstr. 1996, 37 (3), 176. (16) Cyr, T.; Lewkowicz, L.; Ozum, B.; et al. Hydrocracking process involving colloidal catalyst formed in situ. U.S. Patent 5,578,197, 1996. (17) Shen, R.; Zhao, H.; Liu, C.; Que, G. Hydrocracking of Liaohe vacuum residue on bimetallic oil-soluble catalysts. Pet. Process. Petrochem. 1998, 29 (11), 10–12. (18) Dong, Z. X. Hydrocracking of Gudao vacuum residue using oilsoluble catalysts. Ind. Catal. 2003, 11 (4), 27–29. (19) Gatsis, J. G. Catalyst for the hydroconversion of asphaltenecontaining hydrocarbonaceous charge stocks. U.S. Patent 5,474,977, 1995. (20) Gatsis, J. G. Catalyst for the hydroconversion of asphaltenecontaining hydrocarbonaceous charge stocks. U.S. Patent 5,288,681, 1994. (21) Wang, X.; Li, Y.; Zhang, Z. Study on homogeneneous catalyst and process for residue suspended bed hydrocracking. Pet. Refin. Eng. 2000, 30 (4), 50–52. (22) Guan, C.; Wang, Z.; Guo, A.; Que, G. Sulfurization of water-soluble catalyst for suspended bed hydrocracking of residue. Acta Pet. Sin., Pet. Process. Sect. 2004, 20 (2), 75–80.
10.1021/ef800427j CCC: $40.75 2008 American Chemical Society Published on Web 11/04/2008
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Liu et al.
Table 1. Properties of Atmospheric Residue of Karamay Petrochemical Complex common properties
wt %
F20 (g m-3)
υ100 (mm2 s-1)
solidifying point
carbon residue (wt %)
ash (wt %)
C
H
S
N
0.9442
108.7
2.0
7.0
0.085
86.6
12.5
0.13
0.41
metal wt (µg g-1)
common properties SARA (wt %)
saturates
aromatics
resin
n-C7 asphaltene
Ni
V
Fe
Ca
KLAR
50.4
22.2
27.2
0.2
11.8
0.35
10.2
346
oil.23,24 Many water-soluble catalyst precursors for slurry-bed hydrocracking, such as ferrous salts, nickel salts, or molybdates, are readily resolved in water and react with water-soluble sulfides in solution; thus, it may be a good idea to perform the sulfurization based on these reactions. In this paper, the studies on presulfurization and reactivity of dispersed Ni catalyst for slurry-phase hydrocracking of residues are carried out.
residues with different catalysts is carried out using a autoclave, which is charged with hydrogen to 7.0 MPa under normal temperature and heated to 435 °C. After 1.0 h, the reactor is cooled with water to cease the hydroreaction. The products are leached, and the solids are extracted with hot toluene to obtain the insoluble toluene, which is the coke. The coke is dried in vacuum and weighed. The filtrate liquor is distilled to obtain the naphtha fraction (C5-180 °C), light gas oil (180-360 °C), vacuum gas oil (360-500 °C), and distilled bottom (>500 °C).
2. Experimental Section 2.1. Raw Material. Karamay atmospheric residue (KLAR) is taken as source oil for hydrocracking. The typical characteristics of KLAR are shown in Table 1. Nickel chloride [NiCl2 · 12H2O] is taken as a test sample of the catalyst precursor. Sodium sulfide [Na2S · 9H2O] is taken as a sulfurizer for sulfurization. 2.2. Dispersion and Sulfurization of Catalyst Precursor. 2.2.1. Breaking the Emulsion by Multiple Stages (Sulfurization a). The aqueous solutions of catalyst precursor (0.05-0.5 wt % Ni based on NiCl2 · 12H2O) were added into the feedstock in a homemade apparatus with a slurry-stirrer (heated if necessary). After the mixture was stirred for a specific time, the mixture was heated to 120 °C and bubbled with nitrogen to remove the water. Then, the aqueous solutions of sulfurizer (1.0 wt % sulfur) were added using the same method. After the mixture was stirred for a specific time, the mixture was also heated to 120 °C and bubbled with nitrogen to remove the water. 2.2.2. Breaking the Emulsion by One Stage (Sulfurization b). The aqueous solutions of catalyst precursor (0.05-0.5 wt % Ni based on NiCl2 · 12H2O) were added into the feedstock in the homemade apparatus. After the mixture was stirred for a specific time, the aqueous solutions of sulfurizer (1.0 wt % sulfur) were added without removing the water added with the catalyst solutions. Then, after the mixture was stirred for a specific time, the mixture was also heated to 120 °C and bubbled with nitrogen to remove the water. 2.2.3. Preparation of Nickel Sulfide Colloidal Sol Catalyst. A proper complexing agent, such as NH3 or CN-, was selected to react with 0.5-1.0 mol/L Ni2+, and the complex compound of Ni was formed. Then, the aqueous solutions of sulfurizer (1.0 wt % sulfur) are added and reacted with the complex compound of Ni. The production of NiS is in the granularity range of 1-100 nm and is homodisperse in the solution. Therefore, the nickel sulfide colloidal sol catalyst is formed, added, and dispersed in the feedstock oil using the same methods as sulfurizations a and b. All of the catalysts were presulfided at a temperature in the range of 100-300 °C for 30 min before reaction. 2.3. Characterization of Sulfurized Catalysts. The fllowing methods are employed to characterize the sulfurized catalysts: (1) particle size distribution (PSD), using a Brinkmann LS230 granulometer. (2) X-ray diffraction (XRD), using a D/MAX-IIIA diffractometer. 2.4. Hydrocracking of Karamay Residue. To evaluate the hydrocracking activity of the catalysts, hydrocracking of Karamay (23) Liu, C.; Que, G.; Liang, W.; Zhu, Y. Hydrocracking of Gudao residue by using dispersed-phase catalysts. I. Preliminary evalution of catalysts. Pet. Refin. 1993, 24 (3), 57–62. (24) Zhou, J.; Deng, W.; Liu, D.; Liang, S.; Que, G. Effect of vacuum bottom residue recycling on slurry bed hydrocracking of residue. Acta Pet. Sin., Pet. Process. Sect. 2001, 17 (4), 82–85.
3. Results and Discussion 3.1. XRD Analysis of Sulfurized Catalysts. To slurry-phase hydrocracking of residues, the active ingredient is the sulfurization products of the catalyst precursor. The main effects of the catalytic reactivity are the PSD, the specific surface area, and the dispersivity of the catalyst dispersed in the residues. In different sulfurization methods and different sulfurization temperatures, the sulfurized catalysts are obtained and XRD patterns are as indicated in Figures 1 and 2. While the sulfurization temperature is 100 °C, XRD patterns (Figure 1) show some unidentified diffraction peaks according to the power diffraction file. It is deduced from Figure 1 that the sulfurized products of nickel solution are probably amorphous state after sulfurization a or b at 100 °C. After heated to 300 °C and sulfurized in the method of sulfurizations a and b, respectively, two patterns of the catalysts (Figure 2) show the diffraction peaks at 2θ ) 31.8°, 35.0°, 39.0°, 45.4°, and 53.6°, which indicate that the crystallite of NiS2 existed, and at 2θ ) 23°, 30.2°, 46°, and 53.6°, which show that the crystallite of NiS is present. Thus, the sulfurized
Figure 1. XRD patterns of Ni sulfurization products at 100 °C: (a) Sulfurization a and (b) sulfurization b.
Hydrocracking of Residue from Karamay
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Figure 5. TEM patterns of nickel sulfide colloidal sol catalytic system (100000×; the content of element Ni is 2000 µg g-1).
Figure 2. XRD patterns of sulfurized Ni products at 300 °C: (a) Sulfurization a and (b) sulfurization b.
products of both sulfurization methods are NiS and NiS2 crystallite. However, from the XRD patterns of Figure 2, it is also found that the strengths of NiS and NiS2 peaks with sulfurization a are weaker, while the half-maximum height widths (HMHWs) are wider than that with sulfurization b, which shows that the crystallization degree of sulfurization a is lower and the size of the crystallite is smaller.
3.2. PSD Analysis of Sulfurized Catalysts. The PSD of dispersed Ni catalysts with different methods is studied using a Brinkmann LS230 laser particle analyzer. While the sulfurization temperature is 100 or 300 °C, the PSDs of the catalysts are shown in Figure 3. Figure 3a depicts the PSD of catalysts when the sulfurizing temperature is at 100 °C. The patterns show that about 25% of the particles of the catalysts are 2.0 µm, the average particle size of the catalyst with sulfurization b is bigger than that with sulfurization a. Figure 3b shows the PSD of catalysts when the sulfurizing temperature is 300 °C. The patterns indicate that about 70% of the particles of the catalysts are 200 > 100 °C. It can be deduced from the results of PSD analysis that, regardless of sulfurization a or sulfurization b method, the average diameter of the catalyst increased significantly with the increasing sulfurized temperature. With different sulfurized temperatures and different sulfurization methods, a different sulfurized catalyst with different PSD would be obtained, and the average diameter of the catalyst is correlative with the dispersivity of the catalyst in feedstock oil and the activity of the catalyst in hydrocracking of residues. Thus, a proper sulfurization method and proper sulfurization conditions should be tested and selected for a hydrocracking of catalytic residues. 3.3. Nickel Sulfide Colloidal Sol Catalyst. Because the solubility product constant of nickel sulfide is very small, the equilibrium constant of the sulfurization reaction of Ni2+ and S2- is very large and, thus, the product NiS is formed rapidly. The newly formed solid clusters easily. Thus, the formed NiS has a larger granularity and lower catalytic reactivity for hydrocracking of residues. In this experiment, SCN- or NH3
Figure 7. Microphotographs of the product oil in the hydrocracking reactions (400×): (a) with the sulfurization a catalyst, (b) with the sulfurization b catalyst, and (c) with the colloidal sol catalyst.
(or CN-) is selected as a complexing agent. Once the complexing reaction with Ni2+ has occurred, then S2- is added and reacted with the free Ni2+ in the solution. In this sulfurization method, the equilibrium constant of the sulfurization reaction is smaller (eq 3) and the formation speed of NiS becomes slower. The nickel sulfide formed in this way has a tiny granularity and high dispersivity in feedstock oils. The transmission electron microscopy (TEM) patterns of nickel sulfide colloidal sol catalyst using a Brinkmann LS230 transmission electron microscope are shown in Figure 5, and the PSDs of nickel sulfide colloidal sol catalyst and a sulfurizated Ni catalyst of sulfurization b after reacting at 300 °C for 1.0 h in Karamay residue are shown in Figure 6. 4R + Ni2+ f Ni(R)42+ Kstability 2+
Ni
+S
2-
(1) -19
f NiS 1/Ksp ) 1/3 × 10
Ni(R)42+ + S2- f 4R + NiS K ) 1/Kstability × Ksp
(2) (3)
3.4. Hydrocracking Catalysis for Karamay Atmospheric Residue. Table 2 shows the product yields in the hydrocracking of the atmospheric residue that was conducted at 440 °C for 1.0 h with different catalysts using an autoclave. The yield of the liquid 360 °C fraction reached ∼40 wt % in this hydrocracking series with different catalyst. The black run, where no catalyst was used, provided a higher yield of the C5-360 °C fractions than that of any of the catalytic runs. In
Hydrocracking of Residue from Karamay
addition, the yields of the TI fraction, the n-C7 asphaltene, and the C1-C4 fraction were all greater for the blank run than those for any of the catalytic runs, respectively. The results indicated that the molecule of hydrogen was activated and the radicalquench reaction was catalyzed over any of the Ni sulfide catalyst. In the series of catalytic runs, the yield of the TI fractions was the lowest for colloidal sol catalyst and the total of n-C7 asphaltene and resins of the 500 °C+ fractions known as the precursor of the coke was also the lowest for colloidal sol catalyst. Because the hydrogenating activity was essential to the acceleration of the radical-quench reaction in the hydrocracking, from Table 2, it could be inferred that the colloidal sol catalyst was more active in the radical-quench reaction than the sulfurization b catalyst and the sulfurization b catalyst was more active than the sulfurization a catalyst. Figure 7 shows the microphotographs of the product oil in the Karamay residue hydrocracking reactions with different catalyst, and the catalyst covered with coke was found dispersed in the product oil. It was found that the colloidal sol catalyst has a higher degree of dispersion in the oil than that of the sulfurization b catalyst and the sulfurization a catalyst and the sulfurization b catalyst is highly homodisperse in oil compared to the sulfurization a catalyst. With regard to the particle size of the catalyst covered with coke in the product oil, it was the biggest for the run with the sulfurization b catalyst and some gelatinous substance known as the precursor of the coke existed between two particles of catalysts. The particle size of the catalyst in the product oil for the run with colloidal sol catalyst was the smallest and distributed in the product oil equably. The
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appearances of the hydrocracking product oil with different catalyst indicated that, the more active the hydrogenating catalytic ability of catalyst, the less coke produced in the products oil and less coke covered on the catalyst. With regard to the hydrogenating catalytic ability of different dispersed catalysts, the colloidal sol catalyst is more active than the sulfurization b catalyst and the sulfurization b catalyst is more active than the sulfurization a catalyst. 4. Conclusion (1) Using two different courses of dispersion and sulfurization, the water-solubility Ni catalyst dispersed in oil is separated and characterized. It infers that the water-solubility salts turns into NiS and NiS2 at the sulfrization temperature of 300 °C. In addition, while the sulfurization temperature is at 300 °C and breaking the emulsion by one stage during the dispersion course, the better crystal of nikel pyrite is formed and the average particle size of the crystal is smaller than breaking the emulsion by multiple stages. (2) The nickel sulfide colloidal sol catalyst is synthesized in the experiments, and the sol of nikel pyrite can be highly homodisperse in oil and restrain coke forming effectively. (3) With regard to the hydrogenating and radical-quenching catalytic ability of different dispersed catalyst, the colloidal sol catalyst was more active than the sulfurization b catalyst and the sulfurization b catalyst was more active than the sulfurization a catalyst. EF800427J
