Znd. Eng. Chem. Res. 1992,31, 2127-2133 Eng. Sci. 1986,41 (9),2197-2224. Rosenbrock, H. H. An Automatic Method for Finding the Greatest or Least Value of a Function. Comput. J. 1960,3,175-184. Schnell, H. Chemistry and Physics of Polycarbonates; Interscience: New York, 1964. Turska, E.; Wrbbel, A. M. Effects of Temperature on a Polycondeneation in the Melt. Polymer 1970a,11, 408-414. Tureka, E.; Wrbbel, A. M. Kinetics of Polycondensation in the Melt
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of 4,4-DihydroxyDiphenyl-2,2-Propane with Diphenyl Carbonate. Polymer 1970b,11,415-420. Van Krevelen, D. W.; Hoftyzer, P. J. Properties of Polymers; Elsevier Science: Amsterdam, The Netherlands, 1976.
Received for review November 6,1991 Revised manuscript received February 20, 1992 Accepted June 10,1992
Mild Hydrocracking of an Unstable Feedstock in a Three-phase Fluidized-Bed Reactor: Behavior of the Process and of the Chemical Compounds Guilherme L. M. Qouza,+Jtilio C. Afonso, and Martin Schmal* COPPElPEQlFederal University of Rio de Janeiro, Centro de Tecnologia, Bloco G, Caixa Postal 68502, 21945 Rio de Janeiro, Brazil
Jari N. Cardoso Institute of ChemistrylFederal University of Rio de Janeiro, Centro de Tecnologia, Bloco A, Sala A-603, 21910 Rio de Janeiro, Brazil
The mild hydrocracking (400OC, 125 atm) of an unstable feedstock (shale oil) was performed in a three-phase fluidized-bed reador with a commercial sulfided Ni-Mo catalyst. The hydroprocessing was monitored with respect to the physicochemical properties and the chemical composition of the natural and treated oil. The unit attained steady state after 36 h on stream for almost all parameters (viscosity, density, conversion, selectivity, etc.). Chemical composition data of the feedstock and the treated oil were, in general, in good agreement with the physicochemical characterizations. The mild hydrocracking in a three-phase fluidized-bed reactor is shown to be an alternative process for the treatment of unstable feedstocks. (1) Introduction The worldwide refining profile has been changed as a consequence of different prices of heavy and light crude oils and due to the improvement of processing the bottom barrel of petroleum, in order to supply the rising demand of medium and light distillates with more rigid specifications. In this context, the interest in hydroprocessing heavy unstable feedstocks (which are characteristic of Brazilian petroleums from Campos, Rio de Janeiro (Bruning, 1988)) has gained more importance. As known,these feedstocks are more difficult to treat than the normal crude oils, requiring more severe experimental conditions. As a consequence, the deactivation of the catalyst is faster. Therefore, the operationality and consequently the economicity of the process can be drastically diminished. In the hydroprocessing of heavy and unstable feedstocks, the catalytic system and the reactor design are very important. For this reason, we are studying the mild hydrocracking (MHC) and the hydrotreatment (HDT)of an unstable feedstock, the shale oil, in a pilot-unit three-phase fluidized-bed reactor (Souza et al., 1985). The objective is to maximize the diesel fraction, which is of interest in the context of the actual Brazilian consumption profile. The main advantages of this process compared to that of the fued-bed reactor which is largely employed, are (i) isothermal operation with high conversion of heavy fractions; (ii) addition and withdrawal of the catalyst without perturbation of the hydroprocessing; (iii) higher efficiency of the catalyst due to ita smaller particle size; (iv) better ‘Present address: Petrobrh/CENPES/DICAT, Cidade UnivereitAria, Ilha do FundHo, Quadra 7,21910Rio d e Janeiro, Brazil.
flexibility of the operational conditions, regarding the type of feedstock (that may even contain solids in suspension); and (v) reduction of losses and channeling in the catalytic bed. The hydroprocessing of heavy and unstable feedstocks has long been studied using fluidized-bed reactors (Chervenak et al., 1960; Hellwig et al., 1966). Such nonconventional technologies have been employed in industrial scale by means of the “H-Oil” (Johnson et al., 1985;Embaby, 1990)and the “LC + fining” process (Van Driesen et al., 1979; Boening et al., 1987;Baldassari and Hamilton, 1989). A worldwide effort has been devoted in order to optimize current technologies and in the development of new processes and catalytic systems to reduce the operational severity. In this way, the three-phase fluidized-bed reactor provides better operational conditions, improving the stability and yielding the desired products distribution. In the present work we studied the behavior of a mild hydrocracking process in a three-phase fluidized-bed reactor for over 72 h under a given condition, using a shale oil as a feedstock and a commercial sulfided Ni-Mo catalyt. The chemical classes of organic compounds present in the natural and treated oil were characterized in order to identify possible compounds of low reactivity with regard to the various hydroprocessing reactions. These data were compared with the current product specifications of hydrotreatment. (2) Experimental Section (2.1) Materials. A commercial Ni-Mo/A1203 catalyst (Shell 324) wa8 used,whose main properties are as follows: Ni, 3.2%; Mo, 13.2%; S B E157 ~ , m2/g; pore volume, 0.48 mL/g; average pore diameter, 90 A. The original catalyst was a 1/16-in.unimodal extrudate. After being crushed, it was separated in the fraction -150/+270 Tyler Mesh and
0888-5885f 92/2631-2127$03.O0f 0 0 1992 American Chemical Society
2128 Ind. Eng. Chem. Res., Vol. 31, No. 9, 1992
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S h a l e oil feed r e s e r v o i r D o s i n g pump Catalyst feed reservoir Reactor Condenser High pressure central r e c e i v e r High pressure lateral r e c e i v e r LOW pressure receiver Kerosene reservoir
10 11 12
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13 14 15 16 17 -
Gas collector Dumping chamber oil receiver Hydrogenated Fine metering Valve
Gas cylinder DP'Cell valve Level indicator Gas
cylinder
Figure 1. Schematic diagram of the three-phase fluidized-bed reactor system. Table I. Typical Properties of Natural and Treated Irati Shale Oil natural oil treated oil" 0.86 0.93 density (g/cm3) at 25 OC 1.80 16.43 viscosity (cP) at 40 OC at 80 OC 0.64 4.86 0.50 0.28 iodine index ((g of I)/(g of sample)) 8.6 C/Hratio (w/w) 9.6 0.82 yrene/fluoranthene. ML..., linear aliphatic acids. Mainly alkylnaphthonee and tetralones.
, Lo
I
Oi------T 0
10
20
30
50
40
70
60
T I M E ON S T R E A M ( h )
Figure 4. Selectivities for the diesel fraction (C13/Cm)and naphtha fraction (C5/C12) versus the time on stream.
t
4 60-
40
ra +*I ' x s
-
t20
i 01 0
12
24
36
60
48
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ON
i u
f 4
)?-
II
STREAM ( h )
Figure 6. Aromatic hydrogen (vol W )and C/H ratio (wt %) versus the time on stream.
Figures 3 and 4 show that from 36 to 72 h on stream, the conversion of Cm+ and the selectivities for naphtha/ diesel attained constant levels at 40 and 50 w t %, respectively. In fact, it appears that the stabilization of the conversion of Czo+is achieved more rapidly in a fluid-
ized-bed system than in a fixed-bed one, as shown by Plantega and Sonnemana (1983)for the MHC of a vacuum gasoil and of an atmospheric residue (with Ni-Mo and Co-Mo catalysts). Nevertheless, the time of 72 h (not including the sflidation and the initial time of operation)
2132 Ind. Eng. Chem. Res., Vol. 31, No. 9, 1992 Table IV. Comparative Data of Hydroprocessing of Shale Oils under Various Processesa ref Hellwig et al., 1966 Correa, 1984 Correa and Valle, 1984 Colorado Irati Irati shale oil experimental conditions not given 106*/106 atm 105 atm 300"*/400 "C 400 "C 2* / 1 h-l 1 h-l H2/oil 420*/480 Hz/oil 840 HDS (%) 97 96 87 60 84 77 HDN ( W ) 35 30 conversion of heavy fraction (wt 40 %)
conversion of C/H ratio (w/w) % diesel fraction Drocess catalyst
10 70 (180-380 "C) 65 (170-370 "C) fiied bed (2 stages) H-Oil commercial (not specified) Ni-Mo
12 60 (170-370 "C) fixed bed (1 stage) Ni-Mo
this work Irati 125 atm 400 "C 1 h-' Hz/oil 600 >93 56 40 10 64 (170-370 "C) three-phase fluidized bed Ni-Mo
Values marked with an asterisk are from the first stage.
may not be sufficient to extrapolate conclusionsconcerning the stabilization and deactivation for longer times on stream. It is also dependent on the type of the feedstock, but the experimental conditions play an important role in the behavior of the mild hydroprocessing, the influence on the stability, and the deactivation of the catalyst. The C/H ratio (Figure 51, which is linked to the hydrogenation of hydrocarbons in general, remained constant at a level of 10 w t % after 36 h on stream. However, the hydrogenation of the aromatic rings stabilized after 54 h on stream. Probably, the reaction conditions are very close to the thermodynamic equilibria for hydrogenation and dehydrogenation of these compounds, which makes the stabilization of the aromatic contents difficult. Since the C/H ratio is a global parameter, it may not be sensitive enough to detect differences among the hydrogenation reactions occurring during MHC (although this depends essentially on the chemical composition of the feedstock). Indeed, monitoring of the aromatic content would be of great value in evaluating the behavior of the system (stability) and the quality of the product. Concerning the catalyst itself, no sensitive deactivation was observed from 36 to 72 h on stream, although this period would not be sufficient, as mentioned above. Nevertheless, in a similar experiment (using the same feedstock and experimental conditions), the Ni-Mo catalyst (Shell 327) showed no significant deactivation after 170 h on stream (Schmal, 1988). Moreover, after this period, when the temperature was raised to 410 "C, the system remained stabilized (density, viscosity, gas- and liquid-phase composition, etc.) for over 220 h on stream. After this period, density and Viscosity were increased due to the partial deactivation of the catalyst. These observations reinforce that the three-phase fluidized-bed reactor is very stable even for longer times on stream for hydroprocessing of oils. On the other hand, Plantega and Sonnemans (1983) have observed that in a fixed-bed system, the catalyst (Co-Mo or Ni-Mo) deactivated slightly after 24 h on stream, but stabilized only after about 1 week on stream. Additionally, Yoshimura et al. (1987) have stated that in a trickle-bed system coke, aromatization, and metals deposition are responsible for deactivation. However, in our case, (i) the metal content was very low (elemental analysis) and (ii) the weight percent of coke deposited on the spent Ni-Mo catalyst gave an average value of 4.8% after 72 h on stream. The spent catalyst contained 6.2 wt % sulfur, and after TPO experiments we observed that the ratio S/(Ni + Mo) was 1.33 (Silva, 1992), and thus 75% of the theoretical value. However, considering the fact that the spent catalyst was partiaUy passivated and after exposure to air part of the superficial sulfur was oxidated, we assume that the sulfidation procedure was good and sufficient to activate
the catalyst in NiMoS form. This was also confirmed previously by optimizing the sulfidation procedure of the Ni-Mo catalyst (Henriques et al., 1989). Table IV presents comparative data of hydroprocessing of Irati shale oil or similar oils using different processes. Comparing the fluidized-bed catalytic system with the other fluidized system (H-Oil), the data are very similar. Data are also comparable to the fixed-bed system. On the other hand, several problems were observed in the fixedbed system like blockage, overheating, and metals deposition in catalytic layers (Correa, 1 9 M Correa and Valle, 1984), which are not markedly observed in the fluidizedbed systems. Moreover, as stated above, when compared to fixed-bed system, the three-phase fluidized-bed reactor system attains easily the stabilization of the conversion of heavy fractions (Czo+in our case) and a good stability of the catalyst activity (Schmal, 1988). Higher conversions of heavy fractions were observed in fluidized-bed systems (Table IV),when compared to the fixed-bed systems (even in two stages). This is an important characteristic of fluidized systems: higher conversion of heavy fractions due to their longer residence time in the reactor. The two-stage H-Oil process (Hellwig et al., 1966) presents a higher HDN level for the same conversion of heavy fractions, suggesting a two-stage three-phase fluidized-bedsystem for hydroprocessingof unstable feedstocks, like shale oil. (4) Conclusions
The three-phase fluidized-bed reactor attained good stability after 36 h on stream, remaining constant up to 72 h on stream, as seen by monitoring the viscosity, the density, the conversion of C20+,the selectivities toward naphtha and diesel, the C/H ratio, and the composition of the gas and liquid phases. An exception was the hydrogenation of aromatic compounds, which attained a constant level only after 54 h on stream. The comparison of ow results with data for other fluidized systems and the fixed-bed process justifies the interest and the use of the three-phase fluidized-bed reactor as an alternative process for the hydroprocessing of (heavy) unstable feedstocks like shale oil. Beeidea global parameters (density, viscoeity, conversion) being monitored, it is important to follow the aromatic content, i.e., the quality of the product, during hydroprocessing. The methodology applied to the identification and the quitifcation of the compounds present in the natural and treated shale oil has been shown to be a powerful tool in order to understand and determine the complex chemical reactions during its hydroprocessing. In spite of some critical aspects (losses of volatile compounds during fractionation of samples and difficulties in identifying and
Ind. Eng. Chem. Res., Vol. 31,No. 9,1992 2133 quantifying some chemical compounds, especially those at very low concentrations), the methodology allowed us to identify model reactions for compounds of low reactivity and to determine the HDO level attained.
Acknowledgment We thank Ricardo B. Coelho, Heloisa Freitas, and Carlos Cesar for the GC and the GC-MS analyses at the Institute of Chemistry of the Federal University of Rio de Janeiro, Brazil. The financial support is gratefully acknowledged of FINEP, CNPq, and CAPES. We are also grateful to CENPES (Petrobrk) for support and the physicochemical characterizati0r.s. Nomenclature ASTM = American Society for Testing Materials BTE = low sulfur content D = diesel HDN = hydrodenitrogenation HDO = hydrodeoxygenation HDT = hydrotreatment i.d. = internal diameter MHC = mild hydrocracking NBS = National Bureau of Standards NMR = nuclear magnetic resonance RF = retention fador SBm= specific area BET TPO = temperature-programmed oxidation UV/HPLC = ultraviolet/high performance liquid chromamWPhY Registry No. Ni, 7440-02-0;Mo,7439-98-7. Literature Cited Afoneo,J. C.; Schmal, M.; Cardoso, J. N.; Frety, R. Hydrotreatment of Irati Shale Oil: Behavior of the Aromatic Fraction. Znd. Eng. Chem. Res. 1991a,30,2133-2137. Afonso, J. C.; Cardoso, J. N.; Schmal, M. Comportamento de Compoetos Nitrogenados em Condipbs Severas de Hidrotratamento. 6th Brazilian Symposium on Catalysis, Sept 11-13,1991,Salvador-BA; Instituto Brasileiro de Petroleo: Rio de Janeiro, 1991b; pp 390-399. Afonao,J. C.; Schmal,M.; Cardm, J. N. Acidic Oxygen Compounds in the Irati Shale Oil. Znd. Eng. Chem. Res. 1992,31,1045-1050. Baldasmi, M. C.; Hamilton, G. L. LC-Fining Residue Hydrocracking: The Application of Fine Catalysta for High Conversion Operations. 1989 AZChE Spring National Meeting, April 6,1989, Houston, TX; AIChE: New York, 1989. Boening, R. E.; McDaniel, N. K.; Petersen, R. D.; Van Driesen, R. P. Recent Data on Resid Hydrocracker. Hydrocarbon Process. 1987,66,59-62. Bruning, I. M. R. A. Antecipaflo dos Problemas de ProdugHo e Refino Para os Petroleos de Aguas Profundas da Bacia de Campos. 2nd Latin-American Congress on Hydrocarbons, June 1621,1987,Rio de Janeiro; Instituto Brasileiro de Petroleo: Rio de Janeiro, 1988. Chervenak, M. C.; Johnson, C. A.; Schuman, S. C. H-Oil Process Treata Wide Range Of Oils. Pet. Refin. 1960,39 (lo),151-156.
Cornu, A.; Massot, R. Compilation of Mass Spectral Data. Index de Spectres de Masse, 2nd ed.; Hiyden & Sons Ltd. in Cooperation with SCM Publications: London, 1975;Vole. I and 11. Correa, N. F._Refinaflo de Oleo de Xisto do Irati. Bol. Tec. PETROBRAS, 1984,27,311-321. Correa, N. F.; Valle, A. A. F. Personal communication, 1984 (CENPES/PetrobrBs). Cronauer, D. C.; Young, D. C.; Solash, J.; Seshadrl, K. S.; Danner, D. A. Shale Oil Denitrogenation With Ion-Exchange. 3. Characterization of Hydrotreatad and Ion-Exchange isolated Products. Ind. Eng. Chem. Process Des. Dev. 1986,25,756-762. Embaby, M. Shuaiba Refinery Experiences With H-Oil Unit. In Studies in Surface Science and Catalysts, Vol. 53;m, D. L., Akashah, S., Absi-Halabi, M., Bishara, A., Us.; Elsevier: Amsterdam, 1990; pp 165-174. Harvey, T. G.; Matheson, T. W.; Pratt, K. C.; Stanborough, M. S. Catalyst Performance in Continuous Hydrotreating of Rundle Shale Oil. Znd. Eng. Chem. Process Des. Dev. 1986,25,521-527. Hellwig, K. C.; Feigelman, S.; Albert, S. B. Upgrading Fee& by the H-Oil Process. Chem. Eng. Process. 1966,62,71-74. Henriques, C. A.; Bentes, A. M. P., Jr.; Frety, R.; Schmal, M. Influence of Sulphiding Temperature on NiMo/A1203 for Hydrodenitrogenation of Quinoline. Catal. Today 1989,5, 443-460. Johnson, T. E.; Murphy, J. R.; Tasker, K. G. Combined Cracking Processes Booat Fuel Yields. Oil Gas J. 1985 (July l), 50-65. McCarthy, R. D.; Duthie, A. H. A Rapid Quantitative Method for the Separation of Free Fatty Acids from Other Lipids. J. Lipid Res. 1962,3,117-119. Plantega, F. L.; Sonnemans, J. W. M. Hydroconversion of Vacuum Gasoil and Atmospheric Residua. Symposium on Procesrring Heavy Oils and Residua, Presented before the Division of Petroleum Chemistry, Inc., American Chemical Society Seattle Meeting, March 20-25, 1983; American Chemical Society: Washington, DC, 1983,pp 621-632. Sapre, A. V.;Gates, B. C. Hydrogenation of Aromatic Hydrocarbons Catalyzed by Sulfided Co-Mo/A120B.Reactivities and Reaction Networks. Znd. Eng. Chem. Process Des. Dev. 1981,20,6&73. Schmal, M. HidrogenaqBo do Oleo de Xisto,'1 Relatikio; Technical Report ET-11150;COPPETEC/COPPE/UFRJ: Rio de Janeiro, 1988. Silva, V. L. S. T. Estudo das Condiqhs de Sulfetaflo e Regenera@o de um Catalisador de HDS. M.Sc. Thesis, COPPE/Federal University of Rio de Janeiro, 1992. Souza, G. L. M.; Silva, M. I. P.; Schmal, M. Hidrotratamento Catalitico de Oleo de Xisto em Leito Fluidizado. 3rd Brazilian Symposium on Catalysis, Aug 21-23,1985,Salvador-BA;Inetituto Brasileiro de Petroleo: Rio de Janeiro, 1985;pp 209-223. Stenhagen, E.; Abrahamson, S.; McLafferty, E. W. Atlas of Mass Spectral Data; Interscience Wiley: London, 1969;Vols. I and 11. Van Drieaen, R. P.; Capers, J.; Campbell, A. R.; Lunin, G. LC-Finii Upgrades Heavy Crudes. Hydrocarbon Process. 1979, 58, 107-111. Weast, R. CRC Handbook of Chemistry and Physics, 63rd ed.; CRC Press: Boca Raton, FL, 1982. Yoshimura, Y.; Shimada, H.; Sato, T.; Kubota, M.; Mishijima, A. Initial Catalyst Deactivation on the Hydrotreatment of Coal Liquid Over Ni-Mo and Co-Mo-y-Al2O3Catalysts. Appl. Catal. 1987,29,125-140.
Received for review December 10,1991 Revised manuscript received May 19,1992 Accepted June 14,1992
