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United States Patent 3,679,577 MOLTEN SALT HYDROFINING PROCESS Charles F. Wantland, Pasadena, Tex., Frank E. Juge, Jr., Maitland, Fla., and William H. Hinds, Houston, Tex., assignors to Shell Oil Company, New York, N.Y. No Drawing. Filed Nov. 29, 1968, Ser. No. 780,256 Int. Cl. C10g 13/08, 23/02, 29/12 US. Cl. 208-408 Claims ABSTRACT OF THE DISCLOSURE A process for conversion of heavy hydrocarbon fractions containing hetero-atom impurities comprising contacting the fractions in the presence of hydrogen, at elevated temperature and pressure with a molten salt comprising cadmium halides, an alkali metal halide and optionally one or more additional salts as diluents or cocatalysts.
BACKGROUND OF THE INVENTION Field of the invention This invention relates to a process for hydrofining heavy petroleum oils using a molten salt catalyst mixture comprising cadmium halide, an alkali metal halide and optionally other metal salts as diluents and/ or co-catalysts.
Description of the prior art A steadily increasing demand for distillate petroleum products and decreasing supply of crude oils of low residue content provides increasing incentive for processes which upgrade high-boiling residual polynuclear hydrocarbon stocks. There are available large quantities of naphthenic, aromatic or mixed based crudes from which some distillate products are recoverably by traditional means. However, the residual fraction, in which is concentrated relatively large quantities of materials containing sulfur, oxygen, nitrogen, and organo-metallic compounds must be disposed of. In the past, low-value stocks have been used for industrial and marine fuels but the supply exceeds demand. Moreover, air pollution restrictions imposed on many industrial areas prevent the use of these high sulfur and nitrogen fuels.
Current technology for upgrading these fuels, such as thermal cracking, catalytic cracking, and catalytic hydrogenation are less than satisfactory. Cracking or hydrogenation is relatively costly when applied to residual stocks due to rapid catalyst deactivation by the high content of contaminants and catalyst poisons found in residues.
The use of molten salt catalytic systems has long been recognized as a method to obviate many of the difiiculties encountered in more conventional refining techniques. In the main, previous work has concentrated on the use of molten caustics, such as sodium hydroxide, for example U.S. 3,051,645, issued August 1962. More recently, acidic molten salt systems, such as zinc chloride, have been proposed for hydrocarcking (Gorin et al., US. 3,355,376, issued November 1967). Use of a molten salt catalyst offers many advantages over conventional heterogeneous catalyst systems as, for example, continual renewal of catalyst surface, close temperature control by better and more uniform heat transfer and the possibility of continuous removal and relatively easy handling of contaminants, such as metals, which seriously interfere with catalyst performance in conventional heterogeneous phase catalytic systems.
The use of acidic salt systems also presents a number of problems. The salt must have reasonably high catalytic activity and the ability to retain activity without sub- "ice stantial decline over a period of use. The hydrocarbons and salt should be easily separated and the salt should be easily regenerated or otherwise restored for reuse after contamination or deactivation.
Th solubility of heavy hydrocarbons in some molten salt systems makes separation difficult. This feature alone is a serious economic deterrent to proposed molten salt hydroconversion processes and represents a major drawback of such systems.
We have now invented a process for hydrofining and/ or cracking heavy petroleum oils using a molten salt mixture possessing the required characteristics and advantages enumerated above. By hydrofining is meant, within the context of the present invention, hydrogenation, desulfurization, denitrification, and metals removal.
SUMMARY OF THE INVENTION The process of the invention in broad aspect comprises contacting heavy petroleum fractions with a molten salt mixture or solution comprising cadmium halide and other metal halides as later specified, in the presence of hydrogen at elevated temperature and pressure.
The heavy petroleum fraction feed to the present process may be any high boiling hydrocarbon oil at least about 50% by volume of which boils above about 450 F. Though lighter hydrocarbons can, in principle, be processed, the present process is most advantageous for treatment of oils containing materials which cannot be distilled in commercial equipment without extensive cracking, e. g., residual materials and hydrocarbon oils, containing asphaltenes, resins and the like. The process finds its greatest utility in the treatment of stocks containing appreciable amounts of hetero-atoms and/or metals. It is, therefore, particularly useful for the treatment of reduced crudes, pitch, vacuum residues, cracked gas oils, residues, and the like which cannot otherwise be deeply flashed without excessive carryover of metal contaminants. In addition, certain crude petroleum oils which contain only small amounts of gasoline and kerosene boiling-range hydrocarbons and which have been topped to remove lighter components may also be processed. Certain petroleum crude oils from tar sands and oils from shale or coal thus may be processed.
The metal salt catalyst of the invention comprises cadmium halide (chloride, bromide or iodide) which is mixed with and dissolved in alkali metal halides. Examples of suitable alkali metal halides are halides (chlorides, bromides, or iodides) of lithium, sodium, and potassium. additional metal salts as diluents or co-catalysts as, for example, any mineral acid salt of metals of Group I, H, HI, IV-B, VI-B, VII-B, and VIH of the Periodic Table of Elements. The preferred co-catalytic additional salt is zinc halide. In general, at least about 5% w. alkali metal salt should be contained in the mixture. The alkali metal halide functions to reduce markedly the solubility of hydrocarbon in the salt melt, thus providing a mixture which can easily be separated from the hydrocarbon feed and products, as for example, by phase separation. The pres ent process requires the use of an amount of molten salt mixture in excess of that required for stoichiometric reaction with the non-hydrocarbon elements of the heteroatom components in the feed, i.e., greatly in excess of that required for reaction with nitrogen, oxygen and sulfur in the feed. The invention lies in the catalytic eifect of the salt and not in the stoichiometric reactions which concurrently occur. The use of a relatively large excess of salt, relative to feed, characterizes one of the distinctions of the present process over previously known process for hydrogenation of hydrocarbonaceous material, such as coal, by impregnation of the material to be hydrogenated with a small quantity of metallic salt.
The process is carried out in the presence of hydrogen at elevated temperatures and pressures and is characterized by very short reaction contact time.
Temperatures in the range of about 650-850 F. are used and preferably in the range from about 750-810 F. Hydrogen pressures of between about SOD-5,000 p.s.i.g. shouldbe used-the total pressure depending, inter alia, upon the purity of the hydrogen used. It is an especially noteworthy characteristic of the present invention that shown in Table I. From these data it can be seen that the salt mixtures containing cadmium halides eifectively increase API gravity (indicating lower molecular weight), reduce the sulfur and nitrogen content of the feed, remove vanadium, and increase hydrogen content of the products. Run number N-ll illustrates that the absence of cadmium halide leads to thermal cracking only (note the negative hydrogen consumption denoting a positive hydrogen production) with little or no removal of sulfur, nitrogen or reaction contact time is very short. In general, a contact 10 metals.
TABLE I.MOLTEN SALT REACTIONS Run Number Feed N-7 N-8 N-9 N-10 N-ll C dI2 (31.2) CdClz (80.0) CdIz 71.3) CdBrz (65. 4) L101 (45. 5 (Pmmt W9 K01 (2o. K1 E28. 7 NaBl a4. 6 nor 54. 53 Temp., F... 5100' s00 566 Pressure, p 2, 000 2, 000 2, 000 2, 000 2, 000 WHSV feed/gm salt/hr. 0. 31 0. 19 0. 18 0. 23 0. 22 Hzloil (mole) 16. 6 16. 6 16. 6 l6. 6 16. 6 Conversion, percent w.
00-4 39. 6 19. 0 24. 9 33. 7 23. 7 H; consumption, s.e.f.lbb1 667 254 519 -428 API at 60 F 22. 9 34. 4 28. 0 31. 32. 7 28. 4 Sulfur, percent w 1. 82 1. 09 1. 31 1. 02 0. 95 1. 44 Tot N, p.p.rn 1. 500 950 1,400 900 1,200 1, 500 Metals, (p.p.m.) V V 5) V 5) V 5) V 5) V (11) 1 5 ppm. is the analytical senstlvity. time of between about 1.0 to 10 seconds is suflicient to EXAMPLE II V obtain the desired results. By contact time is meant the time in which the feed and molten salt catalyst are .in contact in the reaction zone. Longer contact time may, of course, be used depending, inter alia, upon the specific nature of the feed (i.e., boiling range, hetero-atom and metallic impurities), the degree of conversion desired and the temperature and contact efliciency of the specific reactor system employed.
. As inother hydroconversion processes, excess hydrogen is usually recovered, at least in part, from the reaction zone efiluent and recycled to the reaction zone together with additional makeup hydrogen. Pure hydrogen is not required and any suitable hydrogen-containing gas which is predominantly hydrogen can be used. For example, hydrogen-rich gas containing on the order of about 70% v. or more hydrogen which is obtained from a catalytic reforming process can be used.
Various methods of contacting the hydrocarbon feed with the molten salt catalyst may be employed. One simple method comprises merely passing the hydrocarbon into a molten salt bath. Various types of reactors may be used as will readily occur to those skilled in the art. Reactors employing a dispersed gas/liquid system have been found suitable. Reactors employing concurrent plugflow of the fluid (molten salt, hydrogen and hydrocarbon feed) with a high degree of gas-liquid and liquid-liquid contacting are especially useful. The process may be operated continuously or batchwise but is most efliciently and desirably conducted continuously in a short contact time plug-flow reactor system.
The following examples serve to further illustrate the practice and advantage of the invention and are not to be construed as limitations thereof.
'7 EXAMPLE I 'metal halide eificiently reduces hydrocarbon solubility.
Salt composition, operating conditions and results are The following experiments illustrate the hydrocracking potential of a molten salt system containing cadmium halide and zinc halide as co-catalysts. A Straight Run Residue (properties shown in Table II) was hydrocracked TABLE II Run Feed N-22 4 N-23 znBn (80.0) ZnBr (80.0) Salt composition, (percent w.) CdB1'2 (15.0) NaBr (5.0) NaBr (20.0) Operating conditions:
Suliur, percent w 1. 82 0. 14 0. 42 Nitrogen, p.p.m.w 1, 500 25 72 Vanadium, p.p.m 15 7 5 As these data show, the salt melt containing cadmium bromide produced significantly better sulfur and nitrogen removal and was more effective in reducing heavy (900 F. plus) boiling-range materialat these conditions down to 1.6% w. basis feed.
These examples illustrate the potential of the process of the invention. Many ways of utilizing this process in conversion catalysts), and large amounts of heavy fractions boiling above 900 F. is an increasing economic necessity. The process of the invention is a process useful for that purpose. The process may be employed, for example, under mild conditions to remove metals and hetero-atom impurities making a product suitable for further more conventional processing. On the other hand, the process is capable of extensive cracking directly (as shown in Example H) and may be so employed. Various combinations of such operation may be chosen depending on individual requirements.
We claim as our invention:
1. A process for the conversion of heavy hydrocarbon fractions having at least 50% boiling above about 450 F. comprising contacting the fraction with a molten salt mixture consisting essentially of cadmium chloride, cadmium bromide, or cadmium iodide dissolved in the alkali metal chloride, bromide or iodide corresponding to the cadmium salt in the presence of added hydrogen at elevated temperatures and pressures resulting in net hydrogen consumption.
2. The process of claim 1 wherein the mixture contains additional salt selected from the group of zinc chloride, zinc bromide, and zinc iodide.
3. The process of claim -1 wherein the temperature is in a range from about 650 to 850 F. and hydrogen pressure is in the range of 500-6000 p.s.i.g.
References Cited UNITED STATES PATENTS 2,749,288 6/1956 Watkins 208l25 2,987,468 6/1961 Chervenak 208-213 3,355,376 11/1967 Gorin et al 20810 3,371,049 2/1968 Gorin et al. 252-413 DELBERT E. GANTZ, Primary Examiner G. E. SCHMITKONS, Assistant Examiner U.S. CL X.R.