Reactivity and Composition of Dispersed Ni Catalyst for Slurry-Phase

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Energy Fuels 2010, 24, 1958–1962 Published on Web 03/02/2010

: DOI:10.1021/ef901565x

Reactivity and Composition of Dispersed Ni Catalyst for Slurry-Phase Residue Hydrocracking Dong Liu,* Meiyu Li, Wenan Deng, and Guohe Que State Key Laboratory for Heavy Oil Processing, China University of Petroleum, Qingdao Shandong 266555, China Received December 20, 2009. Revised Manuscript Received February 20, 2010

The composition and reactivity of dispersed Ni catalyst was studied for slurry-phase hydrocracking of the residue. The Ni catalyst was separated at different reaction times and characterized. It was concluded that the water-soluble salts turned into NiS and Ni3S2 after the reaction for 1 or 2 h, respectively. After 3 h of reaction, the crystal of Ni9S8 appeared in the catalyst, and after 4 h of reaction, the catalyst was mainly made up of Ni9S8. The “relative coke restraining ratio” (Cr) was introduced and used to show the coke restraining ability of Ni catalysts at different reaction times. It was concluded that the coke restraining ability of the catalyst containing different kinds of crystals was different. To acquire a higher coke restraining ability of the catalyst, the proper reaction time of residue hydrocracking with dispersed Ni catalyst is 1.0-2.0 h.

dispersed catalysts, such as organic compound and inorganic compound of cobalt, molybdenum, or nickel, are used in the process.9-13 The homogeneous dispersed catalysts are classified as water-soluble dispersed catalysts and oil-soluble dispersed catalysts,14-16 which could be highly dispersed in residues and have a greater surface area/volume ratio.17-19 Coke sedimentation on the surface of the catalyst could cover the reactive center and reduce the coke restraining ability of the catalyst.20,21 Therefore, examination about the deactivation condition of the water-soluble catalyst in slurryphase hydrocracking helps us know about activity changes of the catalyst during the reaction and choose a proper reaction space velocity.22-24 Moreover, a study of the catalyst activity

1. Introduction The slurry-phase hydrocracking process for a residue is a newly developed technique for the processing of heavy oils.1 In the technique, catalysts are highly dispersed in the feedstock oil and suspended in the reactor.2-5 In slurry-phase hydrocracking of a residue, the catalyst is playing an important role in two ways: preventing the residue from coke formation by releasing activated hydrogen (on the other hand, catalysts granules could be used as carriers) and unloading the reactors with coke together.6-8 Generally, the homogeneous *To whom correspondence should be addressed. Telephone: þ860532-86981351. Fax: þ86-0532-86981781. E-mail: [email protected]. com. (1) Schuetze, B.; Hofmann, H. How to upgrade heavy feeds. Hydrocarbon Process. 1984, 62 (2), 75–78. (2) Liang, W. Heavy Oil Chemistry; Petroleum University Press: Jinan, Shandong, China, 2000; pp 318-331. (3) Speight, J. G. New approaches to hydroprocessing. Catal. Today 2004, 98 (1), 55–60. (4) Dohler, W.; Kretschmar, K.; Merz, L. VEBA-Combi-cracking; A technology for upgrading of heavy oils and bitumen. Prepr.-Am. Chem. Soc., Div. Pet. Chem. 1987, 32 (2), 484–489. (5) Rana, M. S.; S amano, 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. (6) 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. (7) 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. (8) Solari, R. B. HDH hydrocracking as an alternative for high conversion of the bottom of the barrel. Presented at the 1990 NPRA Annal Meeting, San Antonio, TX, March 25, 1990. (9) Khulbe, C. P.; Ranganathan, R.; Pruden, B. B. Hydrocracking of heavy oils/fly ash slurries. U.S. Patent 4,299,685, 1981. (10) 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. (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. (12) 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. r 2010 American Chemical Society

(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) Shen, R.; Zhao, H.; Liu, C.; Que, G. Hydrocracking of Liaohe vacuum residue on bimetallic oil-soluble catalysts. China Pet. Process. Petrochem. Technol. 1998, 29 (11), 10–12. (15) Cyr, T.; Lewkowicz, L.; Ozum, B.; Lott, R. K.; Lee, L.-K. Hydrocracking process involving colloidal catalyst formed in situ. U.S. Patent 5,578,197, 1996. (16) 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. (17) 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. (18) Guan, C.; Wang, Z.; Guo, A.; Que, G. Sulfurization of watersoluble catalyst for suspended bed hydrocracking of residue. Acta Pet. Sin. 2004, 20 (2), 75–80. (19) 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. 2001, 17 (4), 82–85. (20) Gatsis, J. G. Catalyst for the hydroconversion of asphaltenecontaining hydrocarbonaceous charge stocks. U.S. Patent 5,288,681, 1994. (21) 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. (22) Dong, Z. X. Hydrocracking of Gudao vacuum residue using oilsoluble catalysts. Ind. Catal. 2003, 11 (4), 27–29. (23) 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.

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pubs.acs.org/EF

Energy Fuels 2010, 24, 1958–1962

: DOI:10.1021/ef901565x

Liu et al.

Figure 1. Diagram of reactors used for hydrocracking: 1, hydrogen bottle; 2, nitrogen bottle; 3, gas inlet; 4, gas outlet; 5, autoclave; 6, stirrer rod; 7, adsorption bottle.

at different reaction times allows us to determine proper slurry catalyst recyclability conditions.25,26 The coke restraining ability of the dispersed Ni catalyst was studied in Karamay atmospheric residua (KLAR) slurryphase hydrocracking, and the expression “relative coke restraining ratio” (Cr) was introduced and used to show the coke restraining ability of Ni catalysts at different reaction times.

Figure 2. Surface area of the Ni catalyst of different reaction times.

2. Experimental Section 2.1. Reaction Conditions. KLAR was taken as the source oil, and water-soluble Ni salts (0.1-1.0 wt %) was dispersed in the source oil. An autoclave with a capacity of 500 mL was taken as the reactor. KLAR with dispersed Ni catalysts of the same mass fraction were hydrocracked at 420 °C in different reaction times from 1 to 4 h, and the initial hydrogen pressure was 5.0 MPa. After the reaction, products were cooled quickly and then the coke restraining ability of the catalyst was evaluated (Figure 1). 2.2. Dispersion and Sulfurization of the Catalyst Precursor. The solution of the dispersed Ni catalyst precursor was added to feedstock oil, in which the mass fraction of nickel was 0.1-1.0%, and the mixture was stirred at 1000 revolutions/ min to make the catalyst precursor highly dispersed in source oil. The solution of sulfurizer was added using the same method, bubbled in the mixture with nitrogen to remove the water at a specific temperature, and then heated for sulfurization and hydrocracking. 2.3. Separation and Analysis of the Catalyst. After sulfurization and reaction, the catalyst was centrifuged from source oil, then washed with toluene, and characterized. A D/MAX-γA X-ray diffractometer was employed to determine the composition of crystalline phase (Cu lamp; Cu KR typical line with a wavelength of 0.154 18 nm). A Coulter LS230 laser particle size analyzer made by the American Beckmann Coulter Corporation was employed to analyze the catalyst size. An ASAP2000 Absorption Instrument made by the American Micromerities Corporation was employed for Brunauer-Emmett-Teller (BET) analysis. 2.4. Evaluation of Catalyst Activities. The catalyst was separated from KLAR hydrocracking products at different reaction times (1.0, 2.0, 3.0, or 4.0 h), and then after the experiment of KLAR hydrocracking with the separated catalyst of the same mass fraction for 1.0 h, the coke restraining ability of the separated catalyst was evaluated. After the reaction, a specific amount of product was dissolved in toluene and then leached. After the filtrate liquor was discarded, filter paper and solids

Figure 3. Median particle diameter of the Ni catalyst at different reaction times.

extract with toluene until the return toluene was colorless. The extraction was vacuum-dried, cooled, and then weighed. The final product is toluene-insoluble (coke). The more the amount of toluene-insoluble products, the more the coke formed during the reaction (the amount of toluene-insoluble product equals the amount of the coke here).

3. Results and Discussion 3.1. BET Analysis. Figure 2 shows the relationship between the reaction time and surface area of the Ni catalyst. As shown, the specific surface area of the Ni catalyst of different reaction times was ranked: 1 h > 2 h > 4 h > 3 h. This is the same order as the exposed reactive center number of the catalyst, probably because the catalyst appeared in the form of microcrystals at the beginning and, as the reaction continued, the crystals formed and became larger, changing the exposed reactive center number on the surface of the catalyst. On the other hand, increasing coke sedimentation on the catalyst brought about decreasing the surface area of the exposed reactive center. Considering the factors above, Figure 2 was easily understood. 3.2. Laser Particle Size Analysis. The Ni catalyst was characterized at different reaction times using a laser particle size analyzer. The changes of the catalyst size with different reaction times or a different covering extent by coke were obtained (Figures 3 and 4). The median particle diameter of the Ni catalyst at different reaction times was shown in the order: 3 h > 4 h > 2 h > 1 h. The same order was found in

(24) Liu, D.; Cui, W.; Zhang, S.; Que, G. Role of dispersed Ni catalyst sulfurization in hydrocracking of residues from Karamay. Energy Fuels 2008, 22, 4165–4169. (25) Liu, D.; Kong, X.; Li, M.; Que, G. Study on water-soluble catalyst for slurry-phase hydrocracking of atmospheric residue. Energy Fuels 2009, 23, 5230–5233. (26) Zhang, S.; Liu, D.; Deng, W.; Que, G. A review of slurry-phase hydrocracking heavy oil technology. Energy Fuels 2007, 21 (6), 3057– 3063.

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Energy Fuels 2010, 24, 1958–1962

: DOI:10.1021/ef901565x

Liu et al.

the particle diameter distribution. According to the data of surface area and particle diameter at different reaction times, we can deduce that most of the surfurized catalyst existed in the form of microcrystals; however, after a long time, the crystals appeared and became larger gradually. The catalyst

might exist in several forms, and the catalyst activity changed with the transformation of crystal kinds during hydrocracking. During hydrocracking of KLAR, the concentration of the toluene-insoluble products rose as the reaction time increased. The catalyst surface was covered by the tolueneinsoluble product, which caused changes of particle size and activity. The results infer that the particle size of the catalyst after 4 h was smaller than that after 3 h. The reason will be further discussed in the next steps. 3.3. XRD Analysis. Sulfurized catalyst usually includes the cystalline phase; therefore, an X-ray diffractometer can be used to characterize Ni catalysts at different reaction times. Figure 5 shows NiS diffraction peaks at 2θ = 18.6, 30.5, 36.0, 40.5, 49.0, 53.0, 57.4, and 59.8 and Ni3S2 diffraction peaks at 2θ = 21.8, 31.5, 38.0, 44.5, 50.4, and 55.0. Figure 5 also shows that, at Ni9S8 diffraction peaks at 2θ = 8.8 and 25.8, the peak value is weak and the peak shape is dispersed. Therefore, after the reaction for 1 h, the catalyst is mainly made up of NiS and Ni3S2. It is shown from Figure 6 that the XRD spectrum of the Ni catalyst after the reaction for 2 h is similar to the XRD spectrum of the Ni catalyst after the reaction for 1 h, with NiS diffraction peaks at 2θ = 18.5, 30.6, 36.0, 40.6, 49.0, 53.0, 57.4, and 59.8, Ni3S2 diffraction peaks at 2θ = 21.8, 31.5, 38.0, 44.5, 50.4, and 55.0, and Ni9S8 diffraction peaks at

Figure 4. Particle diameter distribution of the Ni catalyst at different reaction times: (9) 1 h, ([) 2 h, (2) 3 h, and (1) 4 h.

Figure 5. XRD spectrum of the Ni catalyst after the reaction for 1 h.

Figure 6. XRD spectrum of the Ni catalyst after the reaction for 2 h.

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Energy Fuels 2010, 24, 1958–1962

: DOI:10.1021/ef901565x

Liu et al.

Figure 7. XRD spectrum of the Ni catalyst after the reaction for 3 h.

Figure 8. XRD spectrum of the Ni catalyst after the reaction for 4 h.

2θ = 8.6 and 25.6, where the peak values are weak. From Figures 5 and 6, it is known that the catalyst is mainly made up of NiS and Ni3S2 after 1 or 2 h and their peaks are obvious and similar. Moreover, Ni9S8 has weak diffraction peaks, and the diffraction peaks at 2 h are stronger than those at 1 h. In comparison to Figures 5 and 6, Figure 7 shows NiS diffraction peaks at 2θ = 18.5, 30.6, 32.5, 35.8, 40.6, 49.2, 52.9, 57.6, and 59.8, where the peak values are obviously weaker, Ni3S2 diffraction peaks at 2θ = 22.0, 31.2, 38.0, 44.6, 50.0, 50.4, 54.8, and 55.5, where the peaks are sharper and stronger, and Ni9S8 diffraction peaks at 2θ = 15.4, 26.8, and 34.2, where the peaks are still weak but more obvious than those in Figures 5 and 6. It could be inferred that, after 3 h, diffraction peaks of NiS became weaker and wider, which indicated that the degree of crystallization reduced and the strength of peaks reduced accordingly. Changes of Ni3S2 diffraction peaks show that the Ni3S2 crystal was becoming larger. Therefore, after 3 h, the catalyst was mainly made up of NiS and Ni3S2, and as the reaction continues, the Ni9S8 crystal formed gradually. As is shown in Figure 8, NiS diffraction peaks at 2θ = 18.5, 30.6, 32.5, 35.8, 40.6, 49.2, 52.9, 57.6, and 59.8 disappeared after 4 h of reaction. Ni3S2 diffraction peaks at 2θ = 31.2, 38.0, 44.6, 50.4, and 55.5 also disappeared.

Diffraction peaks at 2θ = 22.0, 50.0, and 54.8 are weak and short. Ni9S8 diffraction peaks at 2θ = 15.8, 19.0, 21.4, 22.6, 24.6, 27.6, 31.6, 32.2, 33.4, 34.5, 38.0, 38.8, 40.5, 41.5, 42.6, 43.2, 46.5, 47.8, 49.8, 50.8, 51.2, 55.5, 58.6, and 57.2 obviously appeared, and the strongest peaks are at 2θ = 27.6, 31.6, 51.2, and 55.5. Therefore, Ni9S8 mainly made up the catalyst after 4 h of reaction. Except for the fact that more and more coke covered the catalyst surface, the transformation of crystal forms is the other reason for the changes of the particle diameter distribution of the Ni catalyst. 3.4. Evaluation about the Catalyst Activity. To show the coke restraining of the catalyst after reaction for different times, the Ni catalyst (1 wt %) was added to KLAR with the initial hydrogen pressure of 5.0 MPa, reacted for 1 h, then analyzed, and evaluated. The expression “relative coke restraining ratio” (Cr) is used to express the activity of the catalyst Cr ðC0 -Cn Þ=C0  100% where Cr is the relative coke restraining ratio (%), Cn is the coke formation ratio for hydrocracking in the presence of the catalyst (%), and C0 is the coke formation ratio for thermal cracking of the source oil in the presence of hydrogen (%). Data are shown in Table 1. 1961

Energy Fuels 2010, 24, 1958–1962

: DOI:10.1021/ef901565x

Liu et al.

From Figure 9, it is also found that the catalyst has the lowest level of coke restraining ability after 3 h of reaction and a better level after 4 h of reaction. The analysis above shows that the crystal kinds of the catalyst change as the reaction time increases and the catalyst is mainly made up of NiS and Ni3S2 after 3 h, while after 4 h, the catalyst has almost turned into Ni9S8. In this condition, the coke restraining ability of the catalyst after 4 h improved mostly.

Table 1. Coke Restraining Ability of the Ni Catalyst at Different Reaction Times for KLAR Hydrocracking pre-current reaction time (h)

Cn (%)

Cr (%)

1.0 2.0 3.0 4.0

0.4984 0.6714 1.1996 1.1737

77.76 70.04 41.47 50.75

4. Conclusion On the basis of the results of this study, the results derived from the hydrocracking of Karamay residue in the presence of dispersed nickel can be summarized as follows: (1) To acquire a higher coke restraining ability of the catalyst, the proper reaction time for Karamay residue hydrocracking with dispersed Ni catalyst is 1.0-2.0 h. (2) The catalysts at different reaction times contain different kinds of crystals. The watersoluble salts turned into NiS and Ni3S2 after 1 or 2 h. After 3 h, NiS decreased and Ni3S2 increased relatively and Ni9S8 began to form, After 4 h, NiS diffraction peaks disappeared and Ni3S2 diffraction peaks became weak, while Ni9S8 diffraction peaks were strong, which inferred that the catalyst was mainly made up of Ni9S8. It was also concluded that the coke restraining ability of the catalyst containing different kinds of crystals would be different. (3) In comparison to the reaction after 1 or 2 h, the coke restraining ability of the dispersed Ni catalyst reaction after 3 h decreased dramatically, but after reaction for 4 h, the coke restraining ability improved, owing to the transformation of the crystal forms and the changes of the number of reactive centers on the catalyst surface in the reaction.

Figure 9. Percentage of coke in the product at different reaction times.

As is shown in Figure 9, the percentage of coke in the product of KLAR hydrocracking at different times is ranked: 1 h < 2 h < 4 h < 3 h. According to the data, the relative coke restraining ratio, Cr, after 2 h is minor compared to 1 h, while after 3 h, the relative coke restraining ratio dramatically reduced to 41.47%. It could be explained that the longer the reaction time, the lower the coke restraining ability of the catalyst. This phenomenon is related to the degree of the catalyst surface covered by coke.

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