US2692226A - Shale oil refining process - Google Patents

Description

Oct. 19, 1954 O( L SHALE- W. M. SMITH SHALE OIL REFINING PROCESS Filed 001;. 7, 1950 QETOQTING HYDRO- 65 N ATOR,

ACHD

TQEATING PLANT Patented Oct. 19, 1954 SHALE OIL REFINING PROCESS Warren M. Smith, Baton Rouge, La., assignor to Standard Oil Development Company, a corporation of Delaware Application October 7, 1950, Serial No. 188,960

Claims.

The present invention relates to an improved process for the recovery of valuable fuels including gasoline, gas oil, and fuel oil range hydrocarbons by the distillation of oil-bearing minerals, particularly oil shale, wherein the raw solids are retorted, preferably in the form of subdivided particles maintained in a highly turbulent state fluidized by upwardly flowing gases to resemble a boiling liquid, and the distillate produced is subjected to a refining treatment to isolate products of the type mentioned above. More particularly, the invention relates to improvements in the refining stage whereby increased operational efficiency and higher quality products in higher yields are obtained.

Organic matter in oil shale is believed to exist in the form of kerogen, a solid consisting of hydrocarbons in combination with sulfur, nitrogen, and oxygen, thus difiering from crude petroleum,

which exists as such in the pores of porous sands.

Crude shale oil produced from the oil shale by decomposition of the kerogen by means of heat also differs from crude petroleum mainly in its extremely high content of nitrogen compounds which probably are responsible for its poor color stability and its disagreeable odor. It is this property of crude shale oil which requires additional treating when shale oil is refined by conventional petroleum refining techniques and procedures.

Established shale oil refining procedures generally involve a combination of distillation for separation of crude shale oil into the various boiling range products, and treatment of these products with sulfuric acid for removal of nitrogen compounds. Such chemical refining treatment must of necessity be very carefully controlled in order to prevent excessive losses of valuable reactive unsaturated hydrocarbons which occur in shale oil as a result of the destructive distillation of the kerogen. In an attempt to minimize treating losses and thereby preserve volume, since crude shale oil is a relatively expensive raw material when compared with present day crude petroleum, it has been proposed to hydrogenate the total crude shale oil mainly in order to reduce the sulfur and nitrogen content to the levels usually met with in crude petroleum, in order to produce a refined shale oil which would then be amenable to further processing by conventional crude refining techniques, as cracking, reforming, etc. Hydrogenation of the shale oil was found to effect some improvement in odor and color. At lower levels of hydrogenation, it was found that the hydrogenated products tended to darken on standing in contact with air. Color stability was found to increase with increase in degree of hydrogenation, but this required excessive amounts of hydrogen, and tended to increase the cost of the process.

It is the principal object of the present invention to disclose an improved economic process for refining shale oil without excessive use of hydrogen.

It is also an object of the present invention to disclose a chemical process for treating shale oil wherein losses due to sludge formation are minimized.

Other objects and advantages of the present invention will become apparent from the more detailed description hereinafter.

It has now been found that the above advantages and results may be achieved by hydrogenating the crude shale only to the point wherein the reactive olefinic hydrocarbons are saturated and some of the nitrogen compounds decomposed to ammonia and hydrocarbons or to more basic type nitrogen compounds, and then subjecting the resulting product to a relatively light acid treat. By operating in accordance with this process, it has been found that only small treating losses occur during the acid treatment, as against large losses when the unhydrogenated crude shale is acid treated. On the other hand, by restricting hydrogenation only to the saturation of the olefins and a mild hydrogenation of the nitrogen compounds, large quantities of hydrogen and expensive hydrogenation equipment are minimized. Again, hydrogenation alone, particularly of the low boiling fractions, did not produce a color and odor-stable product in the presence of air, but, in accordance with the present invention, when the hydrogenated product was given a light acid treat, color stability and improvement were achieved with relatively little loss in product, due to the material being new highly saturated.

The invention may be more clearly understood when read in conjunction with the attached drawing which is a diagrammatic representation of preferred embodiments of the invention. Referring now to the figure, crude shale oil resulting from the retorting of oil shale by any conventional means, preferably by the fluid solids technique, is passed from the distillation and retorting sections to the refinin section. Crude shale oil and distillate, as stated above, are customarily subjected to conventional refining treatments, such as thermal or catalytic cracking, alkylation, polymerization, isomerization, hydroforming, dehydrogenation, etc. by methods known to the petroleum refining art. However, these refining procedures are detrimentally affected by the high nitrogen and sulfur contents of the shale oil, and, in accordance with the present invention, the total oil product from the efiluent is hydrogenated and then acid treated.

The total effluent from the oil shale distilla tion retort it may be passed to a hydrogenation vessel i2, wherein the olefins present in the total product are hydrogenated and the nitrogen compounds mildly hydrogenated to produce some ammonia and some more basic type nitrogen compounds. If desired, a mild vis-breaking treatment to decrease the oil viscosity and pour point, may follow the retorting operation, particularly if the shale oil must be transferred a considerable distance to the refining site. A good hydrogenation catalyst is composed of the mixed sulphides of nickel and tungsten or nickel and molybdenum. Hydrogenation over these catalysts gives a product of considerably decreased olefinicity together with some lowering of nitrogen and sulfur content. Hydrogenation may be accomplished with satisfactory catalyst life at about 2000 to 4000 p. s. i. g., for instance at 3000 p. s. i. g. and temperatures of about 700 to 800 F., depending upon the degree of hydrogenation desired. Space velocities of from 0.5 to 2 v./v./hr. at these conditions are satisfactory, while hydrogen consumption rates are maintained at a level about 500 to 1500 cubic feet of hydrogen per barrel oil fed.

The partially hydrogenated material which is now highly saturated, out which may still contain significant quantities of sulfur and nitrogen impurities, is then passed via line i l to acid treater it, wherein the saturated crude shale oil is contacted preferably with sulfuric acid. Treating conditions preferably include temperatures of from 50 to 100 F. and acid/oil ratios of about 2 to 20 pounds concentrated H2504 per barrel of hydrogenated oil. Other treating min oral acids, such as IiBPO l, may be employed.

The acid treated hydrogenated shale oil with its sulfur and nitrogen content considerably reduced as a result of the combined hydrogenation and acid treatment, is now passed from treater it to the shale oil refining plant for further conversion as is customary in the petroleum refining operation, such as distillation, cracking, hydroforming, reforming, etc., all in a manner known per se.

Instead of treating the total crude shale product to the hydrogenation-acid treating process, it may under certain circumstances, be desirable'to separate the crude shale oil by distillation into appropriate fractions, such as a gasoline and gas oil fraction and higher boiling fractions, and separately hydrogenate and acid treat the respective cuts. genate the total crude shale oil resulting from the retorting operation, then fractionate into the desired products and separately acid treat the resulting cuts.

' The superior results obtained by partially hydrogenating the crude shale oil and following this treatment with a light acid treat may be illustrated by the following specific example.

In the above runs, the crude shale oil was hydrogenated to the extent of 1400 cubic feet of Or, if desired, one may also hydro- 4 H2 per barrel of oil. The acid treating was light, 5 pounds of 98% H2SO'4 being employed per barrel of oil.

Hydrogenation alone results in some increase in volatility of the shale oil at the expense of the 700 F.+ fraction, and also considerable removal of nitrogen as ammonia. In addition, hydrogenation converts residual nitrogen compounds apparently into a form more readily amenable to removal by acid extraction.

The color stability of the diesel fuel fraction prior to acid treatment was unsatisfactory, but by the acid treat it was put into form meeting established specifications. As for the color of the gasoline fraction, this was lower than normal but, since its volume is low, it may readily be blended ofi. Alternatively, a slightly greater acid treat may be employed, whereby an improved color (water white 01' +30 Saybolt) would be obtained.

The example shows, therefore, that at even the moderately high hydrogen consumption level of M00 cubic feet per barrel, the preparation of distillate fuel of satisfactory quality by distillation alone was not possible, but that by the use of a light acid wash, a considerable improvement was obtained without significant loss in yield. In order to obtain products of comparable characteristics from the crude shale oil alone without an intermediate hydrogenation step, a much more severe acid treatment would be required and a considerably greater loss in yield would result.

Various modifications of the system described above may occur to those skilled in the art Without deviating from the spirit of the invention. The above description and exemplary operations have served to illustrate specific embodiments of the invention but are not intended to be limiting in scope.

What is claimed is:

1. In the process of producing oil from oil shale by subjecting the oil shale to distillation temperatures in a distillation zone and recovering the crude oil distillate comprising olefinic hydrocarbons and nitrogen and sulfur compounds from said distillation Zone, the improvement which consists essentially of contacting at least a portion of said distillate in a hydrogenation zone at a space velocity of about 0.5 to 2 v./v./hr., a pressure of about 2000 to 4000 p. s. i. g., and temperatures of about 700 to 800 F. with hydrogen in the presence of a nickel sulfide containing hydrogenation catalyst until up to about 1500 cubic feet of hydrogen is consumed per barrel of oil, whereby said olefinic hydrocarbons are substantially saturated and nitrogen compounds partially hydrogenated, passing said hydrogenated material to an acid treating zone, contacting said material with a minor amount of acid selected from the group consisting of sulfuric and phosphoric acid, and recovering high yields of superior liquid fuel.

2. The process of claim 1 wherein said acid is H2SO4.

3. The process of claim 2 wherein said acid is added to said oil in the ratio of about 2 to 20 pounds of 98% H2SO4 per barrel of oil.

4. The process of claim 1 wherein said hydrogenation catalyst is a mixed sulfide of nickel and a metal selected from the group consisting oftungsten and molybdenum.

5. In a process for improving a crude shale oil containing olefinic hydrocarbons as Well as nitrogen and sulfur compounds, the improvement which consists essentially of passing at least a portion of said crude shale oil to a i=hydrogena-- tion zone at a space velocity of about 0. 5 to 2.0 v./v./hr., contacting said oil in said hydrogenation zone with a nickel sulfide containing hydrogenation catalyst in the presence of hydrogen at a pressure of about 2000-4000 p. s. i. g. and at a temperature of about ZOO-800 F. until about 500-1500 cubic feet of hydrogen are consumed per barrel of oil feed, passing the resulting hydrogenated oil to an acid treating zone, mixing the hydrogenated oil with concentrated sulfuric acid in a ratio of about 2 to 20 lbs. of acid per barrel of oil, separating the acid treated oil from the mixture and distilling the separated oil to isolate therefrom a gas oil having a greatly reduced nitrogen content.

6. A process according to claim 5 wherein the catalyst is a mixed sulfide of nickel and a metal selected from the group consisting of tungsten and molybdenum.

7. A process according to claim 6 wherein the shale oil being treated is a diesel fuel fraction having a boiling range between 400 and 700 F.

8. A process according to claim 6 wherein the shale oil being treated is a gasoline fraction having an end point of about 400 F.

9. A process according to claim 5 wherein the feed to the hydrogenation zone is the total crude oil obtained by distillation of an oil shale.

10. A process according to claim 9 wherein 98% sulfuric acid is used in a ratio of about 5 lbs. per barrel of oil treated.

References Cited in the file of this patent UNITED STATES PATENTS I Number Name Date 2,106,013 Ocon Jan. 18, 1938 2,206,200 Ocon July 2, 1940 2,242,504 Benedict et al May 20, 1941 OTHER REFERENCES Kalichevsky et al., Chemical Refining of Petroleum, Reinhold Publishing Corp. (1942), pages 49, 57, 59.

Claims (1)

1. IN THE PROCESS OF PRODUCING OIL FROM OIL SHALE BY SUBJECTING THE OIL SHALE TO DISTILLATION TEMPERATURES IN A DISTILLATION ZONE AND RECOVERING THE CRUDE OIL DISTILLATE COMPRISING OLEFINIC HYDROCARBONS AND NITROGEN AND SULFUR COMPOUNDS FROM SAID DISTILLATION ZONE, THE IMPROVEMENT WHICH CONSISTS ESSENTIALLY OF CONTACTING AT LEAST A PORTION SAID DISTILLATE IN A HYDROGENATION ZONE AT A SPACE VELOCITY OF ABOUT 0.5 TO 2V./V./HR., A PRESSURE OF ABOUT 2000 TO 4000 P. S. I. G., AND TEMPERATURES OF ABOUT 700 TO 800* F. WITH HYDROGEN IN THE PRESENCE OF A NICKEL SULFIDE CONTAINING HYDROGENATION CATALYST UNTIL UP TO ABOUT 1500 CUBIC FEET OF HYDROGEN IS CONSUMED PER BARREL OF OIL, WHEREBY SAID OLEFINIC HYDROCARBONS ARE SUBSTANTIALLY SATURATED AND NITROGEN COMPOUNDS PARTIALLY HYDROGENATED, PASSING SAID HYDROGENATED MATERIAL TO AN ACID TREATING ZONE, CONTACTING SAID MATERIAL WITH A MINOR AMOUNT OF ACID SELECTED FROM THE GROUP CONSISTING OF SULFURIC AND PHOSPHORIC ACID, AND RECOVERING HIGH YIELDS OF SUPERIOR LIQUID FUEL.

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