Energy & Fuels 1994,8, 588-592
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New Developments in Deep Hydroconversion of Heavy Oil Residues with Dispersed Catalysts. 1. Effect of Metals and Experimental Conditions Bernard Fixari,’ Sylvie Peureux, Jeanne Elmouchnino, and Pierre Le Perchec Laboratoire des Matgriaux Organiques d Proprigtbs Spkifiques, CNRS, BP24, 69390 Vernaison, France
Michel Vrinat Institut de Recherches sur la Catalyse, CNRS, 2 Av. A . Einstein, 69626 Villeurbanne Cedex, France
Fr6d6ric Morel Institut Francais d u Pgtrole, CEDI, BP3, 69390 Vernaison, France Received October 1, 1993. Revised Manuscript Received February 15, 1994’
A comparative study of the effect of experimental conditions on the deep hydroconversion (up to 90%) of an heavy oil residue (Safaniya) in the presence of dispersed catalysts is reported. Severe thermal conditions are required to obtain a high conversion level. With molybdenum naphthenate as catalyst precursor, a low metal concentration (0.02 wt 5%) and a moderate hydrogen pressure level (7.5 MPa at cold) are efficient to maintain a low coke yield (2 wt 5%). In contrast to molybdenum naphthenate, a higher amount of phosphomolybdic acid is needed to achieve the same result. The reason for its weaker catalytic activity was attributed to a lower sulfidation state of the Mo catalyst, as outlined by physical characterization of the catalyst (XRD, HREM, STEM-EDX). This is in contrast to the rapid formation of numerous slabs of MoSz obtained from molybdenum naphthenate. Nickel and cobalt naphthenate have been studied alone or in association with molybdenum naphthenate. As a pure compound, Mo metal seems to be more appropriate to perform the ultimate hydroconversion step while iron displays a lower activity. For nickel (or cobalt) molybdenum association, a synergism is observed, but the CoMo catalyst is more interesting in terms of conversion parameters and quality of the obtained products.
Introduction Among future challenges, there is the necessity to supply refineries with heavy feedstocks of lower quality, i.e., with elevated values of viscosity, carbon Conradson, heteroelements, and metal contents. Furthermore, from market demand in light petroleum cuts, improved treatment of the “bottom of the barrel” is needed. To achieve a deep thermal conversion of heavy crudes and residues into distillates, it is necessary to activate molecular hydrogen efficiently in the liquid phase. But the overall transformation can be designed as a thermocatalytic hydroconversion process, since it is mainly thermal in nature, while activated hydrogen assists this step likely through hydrogenation,radical capture and hydrogenolysis reactions.’ One of the recently proved ways of hydrogen activation deals with the use of water or oil-soluble metallic or organometallic salts.2 Such precursors decompose under thermal treatment and give rise to a slurry of fine solid particles. Instead of conventional supported catalysts, this active form is known to ensure a better contact between the reactants and. the active phase, and therefore to a Abstract
published in Advance ACS Abstracts, April 1, 1994. (1) Lepage, J. F.; Davidson, M. Rev. Inst. Fr. Pet. 1986,41(1), 131. (2)Bearden, R. Jr.; Aldridge, C. L. Energy Prog. 1981,l (1-4),44.
increase the conversion of residues into light products. Coke amount and asphaltene content are lowered at the same time. Despite the large number of patents that have appeared in this field,3few processes are under advanced industrial development. Fundamental aspects about catalyst particles morphology and their interaction with organic matter are scarce and mostly derived from coal hydroliq~efaction.~ In the framework of the “Fossil Energy Program” of the European Community, studies have been undertaken in order to obtain more information on the scientific background of the hydroconversion process: catalytic activity, reaction nature, and kinetic aspects6as well as on industrial and economic aspects. The description of batch hydroconversion experiments on heavy oil in the presence of various catalyst precursors is presented and covered by a detailed analysis of the quality change of the products. On the basis of physical characterizations, a relation is made between this quality and the modes of the in-situ catalysts production. (3) Del Bianco, A.; Panariti, N.; Di Carlo, S.;Elmouchnino,J.;Fixari B.; Le Perchec, P. Appl. Catal. A: Gen. 1993,94,1-16. (4)Curtis, C. W.;Pellegrino, J. L. Energy Fuels 1989,3,160. (5)Del Bianco, A.; Panariti,N.;Di Carlo, S.Prep.-Am. Chem. Soc., Diu. Pet. Chem. 1993,38,407.
0887-0624/94/2508-0588~04.50/0 0 1994 American Chemical Society
Energy & Fuels, Vol. 8, No. 3, 1994 589
Deep Hydroconversion of Heavy Oil Residues I
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45%
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Figure 1. TPOP thermal analysis: typical profiles obtained for carbon detection (as COz) for initial Safaniya VR (a) and a deeply hydroconverted liquid (b). F1, bp < 500 "C; F2,500 "C < bp < 650 "C; F3, bp > 650 "C (distillates and cracking products detected at 500 "C); F4,nonvolatile products at 500 "C, detected from combustion (residual carbon).
Experimental Section The heavy oil (Safaniya vacuum residue) was furnished by the Institut Francais du PBtrole. The main characteristics of this oil are as follows: (1)viscosity (at 100 "C) 5560 cSt; (2)density (at 25 "C) 1.035;(3)elemental analysis: 84.41% C, 10.07% H, 5.43% S, 0.41 5% N, 45 ppm Ni and 155 ppm V; (4)carbon Conradson content 22.5%; and (5)14.7% n-Ci'-asphaltene. Phosphomolybdic acid (PMoA) was supplied by Aldrich Chemie S.a.r.l., molybdenum naphthenate (MoNaph) by The Shepherd Chemical Co., and Ni, Co, and Fe naphthenates by Strem Chemical Inc., as well as ruthenium acetylacetonate. The reactions were conducted batchwise in a stainless-steel tubing reactor (300 cms) which was heated in a fluidized sand bath and pressurised with Hz (7.5MPa at cold and 12-14 MPa during pyrolysis). About 30 g of feed was charged at 120 "C and the catalyst precursor was introduced into the heavy oil. Run temperature was reached within 10-15 min, while an efficient stirring of the medium ensured a dispersing of the particles liberated from the precursors. The catalyst is sulfided by the H2S liberated from the feedstock below 400 "C. Hydrogen consumption was evaluated from pressure evolution during pyrolysis. At the end of the reaction, gases were vented off and the solid fraction (catalystand coke if any) was separated from the liquid products by centrifugation in toluene. Asphaltenes are obtained by refluxingin n-heptane and filtration at ambient temperature. They were characterized by size exclusion chromatography and NMR as previously described.6 Temperature-programmed oxidative pyroanalysis (TPOP)of the liquids allows to detail fractions distribution (volatile and unvolatile), as well as their elemental compositions (H/C and sulfur content). Therefore, an estimation of the conversionsof the feedstock into light cuts was obtained from TPOP diagrams of liquid (Figure 1): weight of organic solid, and amount of gas. Two conversion numbers of the heavy oil were determined from the following equations: yield 500 O C in the liquid effluent multiplied by the percentage of liquid effluent, and C is the percent of organic solid (insoluble in toluene). yield 650 O C in the initial feedstock (50%) and B' is the percent >650 "C in the liquid effluent multiplied by the percentage of liquid effluent. The residual carbon contents of the liquids (RC) were determined from TPOP analysis (see Figure 1). Such data were (6) Thomas,M.; Fixari, B.; Le Perchec, P.; Lena L.; Bonnamy, S.; Decroocq, D.; Espinat, D. Fuel Sci. Technol. Int. 1991, 9,337. (7)Fixari, B.; Le Perchec, P.; Bigois, M. Fuel Sci. Technol. Znt. 1991, 9,321.
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Figure 2. Effect of the catalyst precursor and Mo contents on the conversion data (440"C, 2 h). previouslyfoundto be correlated to the carbon Conradsonresidue (CCR) data.' Well-known catalyst characterization techniques are used in this work (XRD, HREM, STEM-EDX).
Comparison of Molybdenum Precursors From patents and literature survey, we have chosen to study the catalytic activity of molybdenum naphthenate (MoNaph) and phosphomolybdic acid (PMoA) as molybdenum catalyst precursors.2 Figures 2 and 3 show the results obtained for the hydroconversion of the Safaniya vacuum residue with Mo amount varying from 0 to 1wt 5% of the feed. In this first approach, all the runs have been carried out at 440 O C with a reaction time of 2 h. In the absence of catalyst, a coking-like process is achieved with 17 wt 5% of coke production (insoluble in hot toluene). The conversion levels (as defined in the Experimental Section) are contrasted: 75% of the initial >500 "C is converted and only 57% of the initial >650 "C is transformed into lighter cuts. This exemplifies an
Fixari et al.
590 Energy & Fuels, Vol. 8, No. 3, 1994
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Figure 4. XRD spectra of solids obtained from runs performed with 1%Mo from PMoA or Monaph.
51
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Figure 3. Effect of the catalyst precursor and Mo contents on HDS and coke level (440O C , 2 h).
increase of the global residual carbon content, from an initial value of 14.8-19.3 wt % (coke RC of the liquid effluent). A different situation occurs when a Mo salt is added to the feed. For both precursors (1wt % of Mo to the feed), up to 80% of conversion levels into 6 0 0 "C and even into
