US2966450A - Shale oil refining process using a selective solvent and anhydrous hydrogen chloride - Google Patents

Description

9 c. N. KIMBERLIN, JR., ETAL 2,956,450

SHALE OIL REFINING PROCESS USING A SELECTIVE SOLVENT AND ANHYDROUS HYDROGEN CHLORIDE Filed April 25, 1958 3o HYDROGENATOR SETTLER SOLVENT HCI L.

sHALE Charles Newton Kimberlin, Jr Henry George Ellert Inventors ByWuM Attorney ite SHALE OIL REFINING PROCESS USING A SELEC- TIVE SOLVENT AND ANHYDROUS HYDROGEN CHLORIDE Filed Apr. 25, 1958, Ser. No. 730,897

7 Claims. (Cl. 20810) The present invention relates to the refining of shale oil. More particularly, the present invention relates to a method for improving the characteristics of charging stocks from shale oil for use in catalytic cracking processes while minimizing the loss of suitable cracking feed stocks.

Shale oil as produced by retorting of oil shale contains only a minor proportion of materials suitable for use directly in motor fuels without processing and chemical conversion. An important problem in the use of shale oil for the customary conversions to which petroleum oils are normally subjected is the excessive coke formed when the oil is subjected to catalytic cracking.

Shale oil cannot be satisfactorily refined by standard petroleum processing techniques chiefly because of its high nitrogen content, amounting to about 2%, and its low carbon to hydrogen ratio, and high sulfur content. Only about 20 to 25% of the oil is aliphatic; possibly over 50% is composed of compounds containing nitrogen, oxygen and sulfur.

Considerable Work has been done in attempting to separate undesirable from desirable components of shale oil by a variety of treatments, from thermal soaking, visbreaking, to extraction with liquid solvents. However, those solvents which removed undesirable nitrogenous material were unselective and removed desirable cracking constituents as Well. Thus liquid S liquid ammonia, various organic solvents, strong acids such as H 80 weak acids such as H 80 and acetic or formic acids have all given unsatisfactory results, either because of ineffectiveness or poor selectivity.

It is an important object of the present invention to provide an improved method for the upgrading of shale oil. It is a further object of the present invention to produce from shale oil feed stocks of improved quality for catalytic conversion thereof into motor fuel and other valuable hydrocarbons while minimizing the loss of suitable cracking material.

The foregoing and other objects and advantages of the present invention will be more clearly understood from the detailed description of the invention, made with reference to the accompanying drawing, which repre sents diagrammatically a preferred method for carrying out the invention.

In accordance with the present invention it has been found that shale oil is effectively upgraded by treatment withan acidic gas in the presence of a hydrocarbon solvent under certain conditions discussed hereinafter. There is obtained a sludge or precipitate representing substantially all of the more undesirable coke-forming nitrogen containing constituents; this sludge nonetheless being extremely small in amount. There is further obtained as an extract a maximum amount of high quality cracking stock.

Turning now to the drawing, raw shale oil obtained by retorting oil shale at a temperature of about 800 to 1200 F. for a period of 0.1 to 2 hours is fed by means of line 2 to precipitation zone 4. Though the shale oil tates Pater may be given a preliminary thermal treatment or subjected to visbreaking conditions, this is normally not necessary. In fact, it is one of the advantages of the present invention that the visbreaking operation may be dispensed with. Zone 4 may be an upright vessel provided with means for providing intimate contact of counterflowing streams, such as agitators, packing, perforated plates and the like. Alternately, vessel 4 may be a mixer-settler of conventional design. The shale oil is treated in vessel 4 with from about 0.5 to 10 volumes of a hydrocarbon fraction boiling in the range of from -45 to 250 F. Pentane, hexane, propane, butane or naphtha fractions give good results. This hydrocarbon is introduced through line 5. The temperature is in the range of 0 to 300 F., preferably 50 to F., and pressure sufiicient to keep material in the liquid phase. In further accord with the present invention, an anhydrous acidic gas, such as HCl, HBr, BF and the like, but preferably HCl, is passed into vessel 4 through line 7 in amounts suflicient to saturate the oil. 0.5 to 4.0, but preferably 0.9 to 1.5, equivalents of acid per equivalent of nitrogen in the oil may be used. The oilsolvent-gaseous acid mixture is maintained in a state of agitation, preferably for a residence period of from about 1 to 60 minutes, and then passed to settling zone 8. The extract, containing the oil and solvent, is removed from zone 8 through line 10 to flash distillation zone 12, Where the low boiling hydrocarbon solvent is dis tilled overhead by flash or fractionation and recycled via line 14 to precipitation zone 4. The shale oil fraction may then advantageously be passed to a catalytic cracking zone 18 for conversion by conventional means into valuable fuels and lubricants.

It is to be understood that, although in the above description, solvent precipitation and acid gas treatment were indicated as taking place concurrently, it may often be preferable to complete the solvent precipitation prior to the addition of the acid gas. The latter scheme could be advantageously applied where relatively pure amine salts are the desired by-product.

Returning now to settler 8, the lower layer is a sludgelike material comprising in part high molecular weight hydrogemdeficient material known as Conradson carbon, and also the salt-like reaction product of the HCl and the nitrogen compounds. About 7 to 15 lbs. of HCl per barrel of oil are required in this process.

This low quality sludge, amounting to some 25 to 35% of the total shale oil, may also be utilized to increase the over-all yield of motor fuel and lubricants. In one embodiment of the invention, it is withdrawn as a lower layer from vessel 8 and passed to a hydrogenation zone 30. By operating at about 3,000 p.s.i.g. in a conventional manner and at 650 to 1000 F., preferably 700 to 850 F., the nitrogen content of the sludge is reduced from 5% to 0.5% or less. Alternately, this sludge may be partially hydrogenated at less severe conditions and the product recycled through the precipitation zone.

In still another embodiment of the invention, the salt sludge is passed via line 46 to treating zone 40 for HCl recovery. In zone 40 the salt sludge is heated to 250 to 400 F. or higher and a purge gas stream passed in through line 42. The gas may be an inert gas, N CO a low boiling hydrocarbon or steam. At these temperatures the salt sludge dissociates into the free amines and hydrogen chloride, the latter being withdrawn with the purge gas through line 44. The HCl-rich purge gas is separated for recovery by conventional means, and the recovered I-ICl may be recycled to shale oil treater 4 through line 44. Preferably, vapors of the solvent used in the process comprise the purge gas stream, and in this situation the HCl-rich stream is recycled to the precipitation zone without separation.

Example 1 A sample of shale oil was treated in accordance with the process described in the presence of n-hexane. Four types of acidic treating agents were employed, with the result shown below:

1 4 mols/mol N; in oil.

These data clearly demonstrate the excellent results obtained by the process of the present invention in upgrading shale oil to a catalytic cracking feed stock. It is to be noted that aqueous acid provides a substantially lower oil yield without quality improvement.

Example 2 The necessity of maintaining a solvent in the mixture being acid treated with gaseous HCl is shown by the following data:

Treatment None N 01 H crane-l- 400 F. HCl

Yield, Vol. Percent 67 70 PlOdJCt finality:

ravi y, PI 20. 6 Nitrogen, Wt. Percent 1. 9 3:4 Con. Carbon, Wt. Percent 4.3 3. 9 0.9

1 Added to saturation.

Example 3 The oil prepared as in Example 1 from hexane and HCl was tested as a catalytic cracking feed stock. Reactor conditions included a temperature of 900 F., atmospheric pressure, a feed rate of 2 v./v./hour, a half hour cycle, and fresh alumina-silica cracking catalyst.

Raw Hexane East Feed Shale H Cl- Texas Oil Treated Liglt Gas 011 Conversion (OTC) 40. D+L 1 vol. Percent) 29. 1 it? Dry Gas (Wt. Percent) 9.4 11.2 14.4 Carbon (Wt. Percent) 11.3 5. 4 4. 7

1 Distillate plus loss.

These data show the substantial equivalency of the treated shale oil with the high quality East Texas Light Gas Oil.

Example 4 Shale oil sludge may be hydrogenated to give an upgraded product. Here a cobalt m0lybdateAl O catalyst was employed at 3000 p.s.i.g. H pressure. The effect of temperature is pronounced.

Process Temper- Crudo ature Product Quality Sludge Gravity, API... 2.5 8.3 32. 0 N Wt. Percent" 5.0 2.6 0. 5 S, Wt. Perceut 0.5 0. 4 0.05

Alternately, it may be advantageous to subject this sludge to lower severity hydro-processing, such as hydrotreating at 500 to 1000 p.s.i.g. to form lower molecular weight amines while recovering a part of the nitrogen as N or NH followed by recycle of the product to the precipitation zone.

What is claimed is:

l. A process for treating a crude shale oil containing substantial amounts of nitrogenous constituents and Conradson carbon which comprises agitating said oil with about 0.5 to 10 volumes of a selective hydrocarbon solvent boiling in the range of -45 to 250 F. at a temperature and pressure to maintain said solvent and oil in a liquid state, saturating said mixture with an anhydrous gaseous hydrogen chloride in the amount of about 0.5 to about 4.0 equivalents of acid per equivalent of nitrogen in said shale oil, separating a solvent layer from a sludge layer, and recovering a high quality catalytic cracking feed stock from said solvent layer.

2. An improved process for recovering valuable hydrocarbonaceous products from crude shale oil containing substantial amounts of nitrogenous constituents and Conradson carbon which comprises passing crude shale oil to a first treating zone, passing about 0.5 to 10 volumes of a selective hydrocarbon solvent boiling in the range from about -45 F. to about 250 F. to said zone, agitating said mixture in the presence of a saturating amount of gaseous anhydrous hydrogen chloride at a temperature in the range from about 50 F. to about F., said anhydrous gaseous hydrogen chloride being present in the amount of about 0.5 to about 4.0 equivalents of acid per equivalent of nitrogen in said shale oil, separating an oil and solvent layer from a sludge layer, separating solvent from said oil and passing at least a portion of said separated solvent to the first treating zone, passing said oil to a catalytic cracking zone, passing said sludge layer to a second treating zone and recovering valuable products from said second treating zone.

3. The process of claim 2 wherein said sludge layer is hydrogenated at elevated pressures of 500 to 3000 p.s.i.g. and temperatures of 650 to 1000 F. in said second treating zone and thereafter mixed with the treated oil prior to its passing into the catalytic cracking zone.

4. The process of claim 2 wherein said sludge layer is heated to a temperature in the range of about 250 F. to 400 F. in said second treating zone, purging with vapors of the selective hydrocarbon solvent the liberated HCl from said second treating zone, and passing the mixture of said gases into the first treating zone.

5. The process of claim 4 wherein said treated sludge layer is further treated by hydrogenation at elevated pressures of 500 to 3000 p.s.i.g. and temperatures of 650 F. to 1000 F. in a third treating zone and thereafter mixed with the treated oil prior to its passing into the catalytic cracking zone.

6. The process of claim 2 wherein said sludge layer is hydrogenated in a second treating zone at a hydrogen pressure of about 3000 p.s.i.g, a temperature of about 750 F. and in the presence of a cobalt molybdatc-Al O catalyst and thereafter mixed with the treated oil prior to its passing into the catalytic cracking zone.

7. An improved process for recovering valuable hydrocarbons from shale oil sludge produced by the treatment of the shale oil with anhydrous HCl in the presence of a low boiling hydrocarbon solvent which comprises subjecting said sludge to a hydrogenation reaction at a hydrogen pressure of about 3000 p.s.i.g., a temperature of about 750 F. and in the presence of a cobalt molybdate-Al o catalyst.

References Cited in the file of this patent UNITED STATES PATENTS Thomas June 27, 1944 Castner et a1 Dec. 15, 1953 Wetzel Mar. 22, 1955 Hughes Nov. 5, 1957

Claims (1)

1. A PROCESS FOR TREATING A CRUDE SHALE OIL CONTAINING SUBSTANTIAL AMOUNTS OF NITROGENOUS CONSTITUENTS AND CONRADSON CARBON WHICH COMPRISES AGITATING SAID OIL WITH ABOUT 0.5 TO 10 VOLUMES OF A SELECTIVE HYDROCARBON SOLVENT BOILING IN THE RANGE OF -45* TO 250*F. AT A TEMPERATURE AND PRESSURE TO MAINTAIN SAID SOLVENT AND OIL IN A LIQUID STATE, SATURATING SAID MIXTURE WITH AN ANHYDROUS GASEOUS HYDROGEN CHLORIDE IN THE AMOUNT OF ABOUT 0.5 TO ABOUT 4.0 EQUIVALENTS OF ACID PER EQUIVALENT OF NITROGEN IN SAID SHALE OIL, SEPARATING A SOLVENT LAYER FROM A SLUDGE LAYER, AND RECOVERING A HIGH QUALITY CATALYTIC CRACKING FEED STOCK FROM SAID SOLVENT LAYER.

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