Energy & Fuels 1988,2, 278-282
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High-Temperature Chelation of Stainless-Steel Reactor Walls with 8-Hydroxyquinoline R. H. Schlosberg,*t W. N. Olmstead, M. A. Francisco, and A. Lindgren Corporate Research, Exxon Research and Engineering Company, Clinton Township, Route 22E, Annandale, New Jersey 08801 Received January 27,1987. Revised Manuscript Received November 20, 1987
The high-temperature chemistry of 8-hydroxyquinoline has been studied. This amphoteric (containing both basic and acidic functionalities) compound was chosen as a model representative of the kinds of functionality present in hydrocarbon materials such as heavy petroleum fractions, oil shales, and coals. The dominant feature in the thermal chemistry of 8-hydroxyquinoline is that it readily undergoes redox and chelation chemistry with metals and metal oxides, especially at the elevated temperatures normally employed in heavy hydrocarbon conversion processing. Characterization of the thermally generated chelates revealed that extensive condensation of the organic ligands also occurred. The formation of chelates with 8-hydroxyquinoline may provide a model for the fate of some metallic species, both those from reactor walls and those inherent in the feed (especially heavy oils and residua), during hydroprocessing. One important implication of this work is that reactor corrosion can be enhanced if substantial amounts of amphoteric, chelating moieties are present in a feed. Additionally, it is noted that the presence of hydrogen suppresses this chelation chemistry.
Introduction The heterocyclic compound 8-hydroxyquinoline (8quinolinol) has been studied extensively in terms of its chelating ability. In fact, a major use is as a chelating agent in the determination of trace metal ions.' Since multifunctional molecules containing both basic aromatic nitrogen and acidic aromatic hydroxyl groups are known to be present in hydrocarbon materials such as heavy petroleum fractions, shale oils, and coals,2 we wanted to understand the thermal chemistry of model compounds for these amphoteric molecules. Since some amphoteric compounds, such as 8-hydroxyquinoline, are capable of chelating metal ions and hydrocarbon materials can contain metals, we wanted to study the impact of chelation on the thermal chemistry. Furthermore, since in any conversion process the heavy hydrocarbons are subjected to temperatures of 400-500 "C (750-930O F ) in metal reactors, we were curious as to the interaction of 8hydroxyquinoline and chelated 8-hydroxyquinolines with reactor walls as models for what may occur in heavy hydrocarbon conversion. Experimental Section Pyrolysis treatments were carried out by placing the compounds into small 316 stainless-steel batch autoclaves, sealing the autoclaves, and plunging the autoclaves into a preheated fluidized sand bath. The small batch autoclaves (tubing bombs) have been described in detail? Following the pyrolysis, the autoclaves were rapidly quenched and the products washed out of the reador with methylene chloride. After the solvent was distilled off, the remaining material was subjected to a vacuum distillation (250 "C, 200 pmHg) using a short-path Kugelrohr (Biichi Model GKR-BO) distillation apparatus. This separation provided a volatile and a nonvolatile (nondistillable) fraction with an atmosphericpressure cut point of approximately 500 "C (930 OF). In the MCR (microcarbon residue) analysis, the test material is pyrolyzed in an open reactor under an inert atmosphere at a maximum temperature of 500 0C.4 Thermogravimetric analysis (TGA) was done on a Perkin Elmer TGS-2 instrument at a heating rate of 20 "C/min to 800 "C in 'Present address: Exxon Chemical Co., P.O. Box 536,Linden, NJ 07036.
argon followed by introduction of 30% oxygen in argon. Elemental analysis was done by the Analytical Division of Exxon Research and EngineeringCo. by combustion methods (C,H,N,S),neutron activation (0),and inductively coupled plasma atomic emission spectroscopy (ICPAES, metals). Deuterium analysis was performed by Gollob Analytical Service (Berkeley Heights, NJ). Molecular weights were determined by vapor-phase osmometry in o-dichlorobenzeneat 130 "C. Infrared spectra were taken on material dispersed in KBr pellets by using a Digilab FTS-15E spectrophotometer. 8-Hydroxyquinoline,4-hydroxyquinoline,p-cresol, and quinoline were obtained from Aldrich Chemical Co. and used without further purification. Bis(8-hydroxyquino1inato)vanadiumoxide was obtained from ICN Pharmaceuticals, Inc. and used without further purification. Bis(&hydroxyquinolinato)iron(III) chloride was prepared by adding over 1h a methanol solution of iron(II1) chloride hexahydrate (14.9 g, 0.055 mol) to a stirred methanol solution of 8-hydroxyquinoline(34.8 g, 0.240 mol). The reaction was stirred for 4 days, filtered, washed with methanol, and dried at 110 "C for 24 h in a vacuum oven to yield 21.62 g (theoretical yield 21.03 9,) of product. Elemental analysis indicated that the iron has slightly more than two organic ligands and slightly less than one chlorine. Anal. Calcd for Fe(C9H6N0)2C1:C, 56.9; H, 3.2; N, 7.4; C1, 9.3. Found C, 58.8; H, 4 .O; N, 7.5; C1, 7.9. Derivatization of the nonvolatile residue was done as follows. Tetrahydrofuran (THF) from Fischer was distilled from lithium aluminum hydride under a nitrogen atmosphere. Tetra-n-butylammonium hydrogen sulfate (TBAHS) was used as received from Aldrich Chemical Co., and 50 wt % Aqueous sodium hydroxide was used as received from Fischer Scientific. Deuterium-enriched methyl iodide (99.5 atom % D) was used as received from Merck isotopes. All solvents and excess reagents were removed from reaction products by rotary evaporation under reduced pressure and dried at 100 "C (
