US 3367862 A
Description (OCR text may contain errors)
R. B. MASON ETAL 3,367,862 PROCESS FOR DESULFURlZATION BY HYDROLYSIS WITH Feb. 6, 1968 METALS ON CHARCOAL BASE CATALYSTS Filed Oct. 18, 1965 PQDQONE mokonmm BY 6M PArE/vrxrramn' United States Patent 3,367,862 PRUQESS FOR DESULFURHZATIION BY HY- DRQLYSiS WITH METALS 0N CHARCOAL BASE CATALYSTS Ralph Burgess Mason, Dcnham Springs, and Glen Porter Hammer and Clark Edward Adams, Baton Rouge, La., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Oct. 18, 1965, Ser. No. 497,411 8 Claims. (Cl. 208-243) ABSTRAT 0F THE DISCLUSURE Process for des-ulfurizing heavy residual fractions by contacting with water in the presence of a catalyst comprising a metal, metal oxide, or metal sulfide distended on a char base.
This invention relates to a process for the removal of sulfur, nitrogen and metal contaminants from liquid hydrocarbon streams, particularly heavy petroleum oils. More specifically, the invention relates to the desulfurization of heavy petroleum oils by hydrolysis in the presence of certain metals on charcoal base catalyst employing staged operation.
Generally, sulfur occurs in petroleum stocks in one of the following forms: mercaptans, sulfides, disulfides, and as part of a more or less substituted ring, of which thiophene, benzothiophene, and dibenzothio phene are the prototypes. The mercaptans are generally found in the lower boiling fractions, e.g. naphtha, kerosene, and light gas oil. Numerous processes for sulfur removal from these lower boiling fractions have been suggested, such as doctor sweetening (wherein mercaptans are converted to disulfides), caustic treating, solvent extraction, copper chloride treating, and so forth, all of which give a more or less satisfactory decrease in sulfur or inactivation of merc'apt-ans by their conversion into disulfides. When the process results in the latter effect, the disulfides generally remain in the treated product and must be removed by another step if it is desired to obtain a sulfurfree product.
Sulfur removal from higher boiling fractions, however, has been a much more diiiicult operation. Here, the sulfur is present for the most part in the less reactive forms as sulfides, disulfides, and as a part of a ring compound, such as substituted thiophenes. Said sulfur, of course, is not susceptible to chemical operations satisfactory for removal of mercaptans. Extraction processes employing sulfur-selective solvents are also unsatisfactory because the high boiling fractions contain a much higher percentage of sulfur-containing molecules; for example, even if a heavy petroleum oil contains only about 3% sulfur, it is estimated that substantially all the molecules may contain sulfur. Thus, if such a heavy petroleum oil were extracted with a solvent selective to sulfur compounds, the bulk of the oil would be extracted and lost.
Metallic contaminants, such as nickel and vanadium compounds, are found as innate constituents in practically all crude oils associated with the high Conradson carbon asphaltic and/ or asphal'tenic portion of the crude. When the crude oil is topped to remove the light fractions boiling above about 450650 F. the metals are concentrated in the residual bottoms. The residual botforms may also contain nitrogen compounds. The metals, coke formers and nitrogen compounds, all adversely affect catalysts if the residuum is further treated. When the oil is used as fuel, they also cause poo-r fuel oil performance in industrial furnaces by forming coke and sludge and by corroding the metal surfaces of the furnace.
It is an object of this invention to provide a process for the preparation of a low sulfur heavy petroleum oil which is characterized by a low nitrogen and metals content as well. It is another object of this invention to provide a staged process for preparing a fuel oil from heavy oil which is efiicient and economical.
Briefly, the process of the invention involves contacting a heavy petroleum oil in stages with water and/or water vapor in the presence of a catalyst comprising certain metals on a charcoal base.
While we do not wish to be bound by any theory, it is postulated that the desulfurization and denitrogenation obtained in the following examples result from hydrolysis reactions and that the role of the catalyst is to provide an intimate contact between the feed and the water molecule involved in the hydrolysis. The hydrophylic nature of the char support renders it admirably suited to this role.
The invention will be more fully described with reference to the attached drawing which is a flow diagram of one embodiment of the process. The heavy oil is initially fed at a temperature of 600-850" F. by lines 1, 2, 3, 4- and 5 to reactors A, B, C and D. After the units have been on stream for a time the feed will flow to only two or three of the reactors because one or two of the reactors will be off stream for regeneration. Further details regarding regeneration will be given later on in this description. Suitable feed stocks include heavy whole crude oils, atmospheric residuums, vacuum residuums, visbreaker bottoms, deasphalted oils, refinery cycle stocks, and oils derived from oil shale. When required, very viscous oils can be cut back or diluted to a suitable viscosity or gravity with a light diluent oil so that they can be intimately contacted with water and the catalyts. Oils containing 2-10 wt. percent sulfur, preferably 2-6 wt. percent sulfur can be processed to yield an oil containing less than 50 wt. percent of the sulfur and nitrogen content of the original process feedstock. Oils which have been previously deasphalted can be further reduced in metals content to less than 1 ppm. making them suitable stocks for catalytic cracking or they can be used as fuel oil or fuel oil components.
In the embodiment shown in the drawing, reactors A, B, C and D contain fixed beds of catalyst with provisions being made to maintain an equilibrium relationship with water vapor. Water or water vapor can be added by lines 6, 7, 8 or 9. If desired, some or all of the water can be added with the feed or by wetting the catalyst after regeneration. The water content will range from 5-100 wt. percent based on the oil feed.
In another embodiment, not shown, the oil, water and catalyst are worked up into a slurry and the shiny is continuously passed thrcughthe reactors. After contacting at the desired conditions for a period, the catalyst is separated for regeneration and recycle.
The principal feature of the catalyst is the hydrophylic property of the char support which promotes an intimate contact between the oil and the adsorbed water. Suitable chars are those of high surface area which result from pyrolysis of cellulose materials such as wood fibers, cotton fibers, sugars, starches and the nut products of certain plants. Such pyrolysis results in a dehydration of the cellulose structures. Another suitable char is obtained by dehydrochlorination of polyvinylidene chloride polymers (Saran) as disclosed in US. Patent 2,944,031. Chars obtained by low temperature air oxidation of petroleum coke and coal, also, are eminently satisfactory for the catalyst base in this work. The char support used in the experiments subsequently discussed is a commercial product known as Columbia Activated Char and it was employed in the form of extrudate pellets of about inch diameter.
Suitable metals are the metals of Groups I, II, VI and VIII of the Periodic Table. Particularly suitable compounds are those selected from the group consisting of Me, MeO and MeS wherein Me is selected from the group consisting of nickel, cobalt, copper, iron, zinc, molybdenum, tungsten and mixtures thereof. The most preferred catalysts are chars deposited with molybdenum, molybdenum oxide, molybdenum sulfide, tungsten oxide, metallic nickel, nickel oxide, nickel sulfide, metallic copper, copper oxide, metallic cobalt, cobalt oxide, cobalt sulfide, metallic iron, iron oxide and iron sulfide. Mixtures can be used as well. The metal is preferably present on the char in its highest valence state. The catalyst can contain from -500 wt. percent metal based on the total catalyst.
i char material without the molybdenum oxide and (3) an equivalent amount of molybdenum oxide without the char. In these runs a West Texas deasphalted oil was employed as feed. This feedstock was prepared by propane deasphalting a West Texas vacuum residuum bottoms. The deasphalted product used in these experiments contained 1.28% sulfur, 0.4 wt. percent nitrogen and had an API gravity of 17.6, a Conradson carbon value of 4.3 and a metals content of 3 ppm. nickel and 6 ppm. vanadium, respectively. The boiling range of the feed is 950 F. and higher, predominately 950-1300" F.
For part (1) of the experimental work, 200 grams of a commercial catalyst containing 10% molybdenum oxide on Columbia Activated Char was charged to a one-liter The weight ratio of catalyst to oil in a batch system stirred Hastalloy autoclave together with 160 grams of ranges from 0.25-1 at residence time ranging from 0.5-6 Water so as to wet the catalyst prior to hydrocarbon conhours. The pressure in the reactors may vary from 500- tact. Thereupon, 200 grams of the West Texas deasphalt- 5000 p.s.i.g. at temperatures in the range of 500-850 ed residuum was added and the autoclave was assembled. F. In a flow system, the same temperature and pressures Traces of air and oxygen were removed by repeated are desired at oil feed rates of 0.1-1.0 volume per volpressuring and depressuring with nitrogen. Thcreupon, ume of catalyst per hour. the autoclave contents were heated to 690 F. and held Desulfurized oil from reactor A is passed by line 10 at this temperature for two hours. Autogenous pressure to product recovery line 11; however, any desired part of about 3000 p.s.i.g. was developed. of the oil in line 10 can be further treated by diverting it Part (2) of the experiment was conducted in a similar to reactor B by lines 12 and 3. Similarly, oil recovered by 2 manner with 200 grams of Columbia Activated Char conline 13 from reactor B can be recoverey as a product by taining no molybdenum oxide, 165 grams of water and passing it to line 11 or it can be further desulfurized by 190 grams of West Texas deasphalted oil. Pressure dediverting it to reactor C by lines 14 and 4; also, oil reveloped in this operation was about 2800 p.s.i.g. covered by line 15 from reactor C can be recovered or Part (3) of the experiment was conducted in a simifurther treated in reactor D employing lines 16 and 5. lar manner except that the desulfurizing agent consisted Oil recovered from reactor D by line 18 can be passed of 20 grams of molybdenum trioxide with no added char to reactor A for further treatment or it can be recovmaterial. The charge also consisted of 165 grams of waered as a product by lines 17 and 11. ter and 188 grams of the West Texas deasphalted feed.
Periodically each of reactors A, B, C and D are taken Maximum temperature in this two hour operation was off stream for regeneration of the catalyst. Fixed bed 710 F. and the autogenic pressure was 2300 p.s.i.g. reactors are preferably regenerated by burning with air. The results of this study showing superior perform- Air is supplied by lines 10, 20, 21 and Z2. ance for the molybdenum oxide-char support, but ap- The valves and bypass lines employed for bypassing a preciable desulfurization with the char alone, and almost reactor which is being regenerated have not been shown. negligible desulfurization with the molybdenum trioxide The technique of regenerating reactors in a staged series alone, are tabulated below.
TABLE I 10% M003 on Activated Molybdenum Catalyst Feed Activated Carbon Tricxidc Carbon Treating Temp, F 600 690 710 Wt. percent water on feed (liquid product inspecso 90 90 17.6 29. o 24. 2 16. 7 Sulfur, Wt.Pcrcent 1. 28 0.26 0.62 1.2 Percent Sulfur Removal 75 6 Percent Nitrogen Removal 75 Conradson Carbon, Pcrcent. 4. 3 O. 44 Nickel, p.p.m 3 0 Vanadium, p.p.m 6 0 is well known to those skilled in the art. In a three stage, four reactor system like that shown in the drawing, the sequence of operation is as follows:
The catalyst in the reactor of position 4 is undergoing regeneration.
EXAMPLE 1 The runs herein disclosed are designed to show a su perior order of desulfurization by hydrolysis in presence of char supports. To this end experiments were made with (1) molybdenum oxide-char catalyst (2) the same The superiority of the molybdena-char catalyst over the same char but without the sulfur acceptor is demonstrated.
EXAMPLE 2 An experiment similar to part 1) of the foregoing work was conducted with a 75% shale oil distillate which contained 0.71% sulfur and 2.4% nitrogen. In this work, 200 grams of catalyst comprising 10% molybdenum trioxide on Columbia Activ-ated Char was contacted with grams of water and then 210 grams of the shale oil distillate. After purging the air the charge was heated to 680 F. for one hour at an autogenic pressure of about 3000 p.s.i.g. Liquid product recovered had an API gravity of 29.0, sulfur content of 0.5 and nitrogen content of 1.1. This corresponds to 26% to 56% nitrogen and sulfur removal, respectively.
EXAMPLE 3 The foregoing Examples 1 and 2 were with dififerent feedstocks. A further study of the feedstock variable is given in the instant example. In this run, 200 grams of catalyst which comprised molybdenum trioxide on Columbia Activated Char was contacted with 160 grams of water and then with 204 grams of Kuwait vacuum residuum. This feedstock contained 5.9% sulfur. The composite charge, after purging the air, was heated to 675 F. for two hours in which the autogenic pressure was 2500 p.s.i.g. The product contained 4.6% sulfur which corresponds to 22% desulfuriz-ation.
EXAMPLE 4 Examples l-3 have shown a good degree of desulfuri zation when molybdenum oxide char catalyst was employed. This example demonstrates that the molybdenum sulfide-char support is active in this desulfurization system and that loss in activity from sulfiding the oxide is not a limitation to the process. For this run 205 grams of molybdenum sulfide-char catalyst, prepared by contacting the oxide form with a hydrogen-hydrogen sulfide gas at 700 F., was contacted with 160 grams of water and 190 grams of the deasphalted oil used in Example 1. After expelling the air, the charge was heated for 2.5 hours at 705 F., in which the autogenic pressure was 3250 p.s.i.g. The satisfactory performance of the sulfide catalyst is shown by comparison with the results of Experiment 1 as follows:
TABLE H Data Source Inspections Feed Experiment 1 Experiment (Part 1) 4 Gravity 17. 6 29.0 30. 0
Sulfur 1. 28 0.26 0.23
Sulfur Removal, Wt. percent 70 82 EXAMPLE 5 pholted oil by hydrolysis molybdenum sulfide-activated char catalyst 50 wt. percent water on oil feed Temperature, F. 650 Pressure, p.s.i.g 400 Oil feed rate, v./v./hr. 0.5 Volumes of oil/vol. cat. at end of period Wt. percent sulfur removal 16 Wt. percent nitrogen removal EXAMPLE 6 In a further study of the effect of pressure, the flow unit was operated with the molybdenum trioxide char catalyst, 50% water on oil feed, and West Texas deasphalted oil at 2500 p.s.i.g. and 700 F. until 7 volumes of feed had contacted the catalyst at an oil rate of 0.5
v./v./hr. These conditions provide an average residence time of less than one hour. The desulfurization and the denitrogenation at the end of this operation was 24% and 40%, respectively. These results show clearly that the performance is not solely adsorption on the catalyst and further improvements with residence times greater than one hour are visualized.
The foregoing description and examples clearly demonstrate the value of char base catalysts in association with adsorbed water for the desulfurization and denitrogenation of high sulfur heavy petroleum oils.
What is claimed is:
1. A process for the desulfurization of a high sulfur petroleum oil comprising contacting the oil at elevated temperature and pressure with a treating agent consisting of 5-100 wt. percent water based on the oil in the presence of a catalyst comprising a material selected from the group consisting of Me, MeO and MeS wherein Me is selected from the group consisting of metals of Group I, Group II, Group VI and Group VIII of the Periodic Table deposited on a char support.
2. Process according to claim 1 in which the temperature ranges from 500-850 F. and the pressure ranges from 500-5000 p.s.i.g.
3. Process according to claim 1 in which MeO is molybdenum oxide.
4. Process according to claim 1 in which a plurality of reactors are arranged to provide staged contacting.
5. Process according to claim 1 in which the catalyst is maintained in a fixed bed.
6. Process according to claim 1 in which the oil, water and catalyst are mixed together to form a slurry and are then passed through a plurality of staged reactors.
7. A process for the desulfurization of a petroleum residuum containing 2-10 wt. percent sulfur, nitrogen compounds and metal compounds comprising contacting theoil in stages at a temperature ranging from 500-850" F. and a pressure ranging from 500-5000 p.s.i.g. with a treating agent consisting of 5-100 wt. percent water in the presence of a catalyst comprising a material selected from the group consisting of molybdenum, tungsten, nickel, copper, cobalt and iron and oxides and sulfides thereof deposited on a char support.
8. A process for the removal of sulfur, nitrogen and metals for oil derived from oil shale comprising contacting the oil in stages at a temperature ranging from $00- 850 F. and a pressure ranging from 500-5000 p.s.i.g. with a treating agent consisting of 5-100 wt. percent water in the presence of a catalyst comprising a material selected from the group consisting of molybdenum, tungsten, nickel, copper, cobalt and iron and oxides and sulfides thereof deposited on a char support.
References Cited UNITED STATES PATENTS 2,901,423 8/1959 Herbert et al. 208--264 SAMUEL P. JONES, Primary Examiner.