US2504058A - Process of removing sulfur from oils - Google Patents

Description

April 11, 1950 H. M. UNSCHULD EIAL 2,504,058

PROCESS OF REMOVING SULFUR FROM OILS Filed April 4, 1946 2 Sheets-Sheet l VACUUM PUMP VACUUM INVENTORS HENRY M. UNSOHULD JOSEPH G. ALTHER ATTO NEY April 11, 1950 H. M. UNSCHULD ETAL 2,504,058

PROCESS OF REMOVING SULFUR FROM OILS 2 Sheets-Sheet 2 Filed April 4, 1946 INVENTORS HENRY M. UNSCHULD JOSEPH G. ALTHER. 5&5; /Qamm ATTORNEY Patented A p 11, 1950 5. PATENT OFFICE PROCESS OF REMOVING SULFUR FROM OILS Henry M. Unschuld, Chicago, and Joseph G. Alther, Evanston, 111.; said Alther assignor to said Unschuld Application April 4, 1946, Serial No. 659,446

14 Claims. (01. 204-168) This invention relates to the treatment of hydrocarbons and more particularly refers to a new and improved process and apparatus for removing sulfur from .petroleum hydrocarbons, such as crude oil and their fractions.

Many crude petroleum oils contain sulfur in combined form in percentages ranging from a fraction of a per cent to more than per cent. Examples of high sulfur oils are West Texas and Santa Maria crudes. A wide variety of different sulfur compounds occur naturally in mineral oils including such types as hydrogen sulfide, mercaptans, disulfides, polysulfides, thioethers, and thiophenes.

When treating such sulfur oils by distillation or cracking or similar process, the sulfur compounds corrode the apparatus causing rapid deterioration and rupturing of the equipment with consequent frequent shutdown and loss of money and time. Many'serious fires resulted from the action of sulfur compounds on the metal. thinning it to the point where it burst, spilling the hot oily contents into the atmosphere where they flashed into flame. Resort in some instances was had to high chrome alloy metals to retard the corrosive effect of sulfur in the oil but these alloys are expensive and do not remove the sulfur which finds its way into the products from the crude oil.

One feature of the present invention resides in the, removal of sulfur from oils prior to its conversion into other products. Another feature of this invention resides in the improved method and means of efiiciently and economically removing sulfur from hydrocarbons.

One specific embodiment of the present invention comprises heating hydrocarbon oil containing sulfur to a temperature of approximately 200 F., in the presence'of catalysts consisting of alloys of nickel and silver, and lead and zinc, removing a portion of the sulfur compounds from the oil by distilling the oil under a vacuum, passing the residual oil into a tube containing spaced electrodes connected to a source of. electrical nergy, introducing steam into said tube, subjecting the oiland steam in the tube to the electrical energy imposed on the electrodes of 2500 volts,

2000 cycles, and 100 milliamperes for approximately .05 of a second, and removing the oil from the tube.

Figure 1 is a schematic flow diagram illustrating one apparatus and method for practicing this invention. Charging stock is introduced through line I and valve 2 into vessel 3, wherein the oil is heated to a temperature of approximately 190 to 240 F., by means of enclosed electrical resistance elements 4 connected by wires 5 to a source of electric power. Thermostatic control,

not shown in the drawing, may be utilized to obtain better control of the temperature of the liquid. The heated oil in vessel 3 is constantly agitated by stirrers 6 driven by motors 1. Vessel 3 is provided with manholes 8 to permit access to the vessel. At the bottom of vessel 3 are catalysts 9 and I0, consisting of metal alloys of nickel and silver, and lead and zinc, respectively. Vapors and gases evolved from the liquid oil are sucked through line H and valve 12 by means of vacuum pump l3 and forced through lines II and I6 and valves l5 and I1, then through cooling coil l8 contained in box 19 to effect condensation ofthe vapors. The gases and liquid entering receiver 20 are separated therein; the gases being released by valve 2| in line 22 and the condensate withdrawn from the bottom of receiver 20 through line 23 and valve 24.

Partial desulfurization of the oil is accomplished in the vessel 3 by heating the oil in the presence of metal catalysts which have the effect of converting the sulfur compounds into more volatile components which are distilled off. With some oils, substantial desulfurization may be effected by vacuum distillation without catalysts. The temperature to which the oil is heatedis preferably below that at which decomposition takes place. The preferred temperature range is to 240 F. A vacuum is maintained on the oil undergoing distillation. Other well known methods may be employed to effect distillation at reduced temperatures such as 'steam distillation or the introduction of gases to lower the partial pressure of the vapors. Only a small portion of the oil is distilled off, in an amount preferably not to .exceed 20 per cent. The combined eflect of heat, catalytic action and removal of vapors high in sulfur content substantially reduces the sulfur content of the residual oil. The time necessary to effect desulfurization in the vessel 3 will vary with the type of oil and nature of the sulfur in the oil. In general, five minutes will be ample to complete the reaction. Where light oils, such as high gravity gas oil, kerosene, naphtha and gasoline are charged into the system, superatmospheric pressure may be imposed to retard vaporization of the light oils. Benzene, toluene and other liquid coal tar products may also be successfully treated to reduce their sulfur content.

The distillation process may be batch, semicontinuous or continuous operations. In the batch type operation, a fixed quantity of chargin stock is fed into vessel 3 throu h line and then valve 2 is closed until the reaction is completed. The still contents are emptied through lines II and and a fresh charge of oil introduced. When operating semi-continuously, fresh oil is pumped through line continuously to maintain a constant level by replacing the evolved vapors leaving through line In the continuous type operation, vapors and residual oil are continuously withdrawn through lines II and 25 respectively, and raw oil simultaneously fed into the system through line I.

Although the apparatus and method herein described illustrates a shell still type operation, other well known distillation methods may be employed, as for example, the pipe still and fractlonating type operation.

Most oils, particularly the high sulfur oils, will require a two-stage treatment, the distillation just described and an electrical bombardment later described, to accomplish substant al reduction of the sulfur in the oil. Frequently, sufficient sulfur reduction will occur in the distillation reaction; especially with certain raw oils which do not require maximum desulfurization. In such case, the partially desulfurized oil is sent to storage through line 26 and valve 21. Line 28 may also be employed as an emergency drop out line or to relieve the system of any oil not desired to be sent directly to the electrical bombardment stage.

After a portion of the sulfur from the oil has been removed in the distillation operation, the partially desulfurized oil in the presence of steam is subjected to an electrical bombardment obtained by spaced electrodes connected to a source of electrical current.

Referring to Figure l, residual oil from vessel- 3, while still in a heated condition, flows through line 25, automatic valve 28 and header 30 into a series of vertical tubes until they are filled. Simultaneously, superheated steam from an external source is injected in the flowing stream of oil through line 32 controlled by automatic valve 33. During this period of charging, automatic valves 34 and 35 remain closed. After the charge of oil to the tubes 3| has been completed, valves 28 and 33 are shut and the mixture of steam and oil is electrically bombarded in tubes 3| by imposing an electrical current on the electrodes in the tubes, said electrodes being connected to a source of electrical energy by leads 36. Upon completion of the reaction, valve 34 is opened and the treated oil discharged into header 31, line 38 and thence into receiver 39. Immediately thereafter valve 35 is opened and the vapors and gases in the tubes 3| are evacuated through lines 46, 41, and 49. During its passage from the tubes, the oil is cooled by coils externally wound around the bottom necks of tubes 3|, more fully illustrated in Figures 2 and 3. Receiver 39, wherein separation of gases and vapors from liquid is effected, is provided with heat exchange coil 40 to cool the products of the reaction. The liquid products are sent to storage through line 4| and valve 42. Vacuum pump 43 serves the dual purpose of maintaining subatmospheric pressure on the system and withdrawing the gases and vapors through conduits 46, header 41, vapor line 48 and line 49. The gases and vapor are discharged from pump 43 into receiver 20 through lines 50 and I6 and valves 5| and i1 and coil I8.

To avoid cracking of the oil entering the. electrical bombardment system, the oil should be kept at a temperature below that atwhich decomposition takes place. The preferred temperature range is from 150 to 275 F. A heating or cooling coil, not shown in the drawing, may be interposed to precondition the oil prior to its entrance in the electrical bombardment system. The steam injected into the bombardment tubes 3| is preferably superheated to a temperature equal to or greater than that of the oil. An alternating current with a voltage in excess of 1500 and a frequency greater than 1000 cycles per second are imposed on the electrodes. An amperage greater than I is seldom required. The preferred operating conditions are in the 1 range of 2500 to 3100 volts," 1800 to 2200 cycles per second and approximately .100 milliamperes. Electrodes made of platinum and tungsten have been found to give good results. The lower the pressure on the oil undergoing treatment, the more rapidly and completely will the reaction take place and for this reason subatmospheric pressure is maintained on the system. The time required for the removal of sulfur from the oil is very short, usually less than one minute. Substantial amounts of sulfur have been extracted from oils in periods as low as .03 to .06 of a second. Cooling at the bottom of tubes 3| is carried out to arrest further reaction of the oil.

The operation illustrated in Figure 1 and described above is of the continuous intermittent type whereby a continuous series of batches of oil are charged to the tubes 3|, subjected to electrical bombardment for the required length of time, withdrawn and a fresh batch of oil introduced into the tubes. To facilitate the treatment of oil, another bank of tubes similar to tubes 3| may be connected to the feed line 25 and operated in conjunction with tubes 3| in such manner that when the tubes 3| are being exhausted of their treated oil the second bank of tubes will be taking a charge of fresh oil and vice versa. A series of vessels similar to vessel 3 may be employed to assure'a constant feed of oil to the tubes.

As an alternative method of operation, oil may be continuously fed through the tubes, the rate of now being regulated to permit the oil during its course through the tube to be exposed to the electrical bombardment for a sufficient length of time to effect the desired desulfurization.

In some instances, particularly with oils of low boiling point, it will be desirable to eliminate the first distillation step and introduce the raw 0" directly into the electrical bombardment system.

Figure 2 is a side view of tube 3| showing in detail the construction of the tube.

Figure 3 is a transverse section through the tube, taken on the line 33 of Figure 2.

Figure 4 is a transverse section taken on line 4-4 of Figure 2.

Both ends of the tube 3| are secured to outside conduits 52 and 53 by flanges and 55 and 55 and 51, respectively and fastened by bolts 59. Interpo'sed between flange 54 and 55 and 56 and 51 are expansion joints 59 and 50 to allow for expansion and contraction. In the body of the tube are four axially spaced ring-shaped electrodes numbered GI and 62, 63 and 64. The distance between each pair of electrodes is approximately 3 inches. Conductors 65 leading from electrodes 6|, G2, 63 and 64 pass through small openings in integral bosses 66, 61, 68 and 69 of tube 3| to outside of tube 3| where the conductors are joined to metal caps 10. H. "and I3, which in turn are connected by lead wires to a source of electrical current in such fashion that'electrodes BI and 63 are of opposite polarity to that of electrodes 62 and 64. The electrodes are alternately of different metals. for example, electrodes GI and 63 are platinum and electrodes 62 and 64 are tungsten. Near the entrance end of tube 3| is opening 46 which leads to vacuum pump 43, more fully shown on Figure 1. Tube 3| is provided with ports 14 to permit ingress to the tube to facilitate cleaning. The ports are kept air tight by plugs held in place by springs 16. A cooling coil ll made of copper or any good heat conductor is externally wound around the neck of tube 3| at its outlet end. A cooling medium is passed through coil 11 to cool the products of the reaction by indirect heat exchange. Tube 3| is preferably made of quartz.

The invention is, of course, not limited to the use of all of the various steps above outlined in combination since alternative but non-equivalent methods of operation are provided and some of the steps may be modified or omitted without departing from the scope of the invention.

An example of the operation of this invention is as follows: A Santa Maria crude oil of 14.2 gravity with 14.93 per cent boiling in the gasoline range and a sulfur content of 5.20 per cent was electrically heated to a temperature of 225 F., and stirred in a closed vessel in the presence of two catalysts, an alloy of nickel and silver, and an alloy of zinc and lead, at subatmospheric pressure. During the heating of the oil, the evolved vapors were removed from the vessel. A sample of the residual oil was analyzed and it was found that the sulfur content of the oil was reduced by 28.5 per cent. The residual oil toether with added superheated steam was introduced into a quartz elongated tube containing spaced electrodes made of platinum and tungsten. The electrodes were connected to an alternating electric current of 2700 volts, milliamperes and a frequency of 2000 cycle per second. After exposing the oil to the electrical bombardment for .05 second, the oil was immediately chilled and withdrawn from the tube. The sulfur in the oil was further reduced by 47.3 per cent. The remaining sulfur in the oil was of a noncorrosive type.

We claim:

1. A process for the treatment of hydrocarbon oil which comprises heating said oil to a temperature of to 275 F., subjecting said oil in the presence of steam for a period of less than one minute to an electrical bombardment obtained from an electric current between spaced electrodes within an enclosed zone in the range of 2500 to 3100 volts, 1800 to 2200 cycles per second and approximately 100 milliamperes to desulfurize said oil, and immediately chilling the oil to prevent any reaction with the products of desulfurization.

2. A process for the treatment of hydrocarbon oil which comprises subjecting said oil in the presence of steam at a temperature in the range of 150 to 275 F., and subatmospheric pressure to an electrical action obtained by spaced platinum and tungsten electrodes within an enclosed zone connected to an electric current in the range of 2500 to 3100 volts, 1800 to 2200 cycles per second and approximately 100 milliamperes for a period of time of from .03 to .06 second to desulfurize said oil. and immediately chilling the oil to 6 prevent any reaction with the products of desulfurization.

3. A process for desulfurizing hydrocarbon oil which comprises subjecting said oil at an elevated temperature of to 240 F. to the action of catalyst consisting of alloys of nickel and silver, and zinc and lead respectively.

4. A process for desulfurizing hydrocarbon oil which comprises subjecting said oil at elevated Ill temperatures of from190' to 240 F., and subatmospheric pressure to the action of catalysts consisting of alloys of nickel and silver, and zinc and lead respectively.

5. A process for the treatment of hydrocarbon oil to remove objectionable sulfur therefrom which comprises heatingsaid hydrocarbon oil in the presence of metal catalysts consisting of alloys of nickel and silver, and lead and zinc from 190" to 240 F. to convert the sulfur compounds in the hydrocarbon oil into a more volatile state, and distilling the hydrocarbon oil to separate the lower boiling sulfur compounds therefrom respectively.

6. A process for the treatment of hydrocarbon oil to remove objectionable sulfur therefrom, which comprises treating said oil at an elevated temperature in the range of 190 to 240 F., in the presence of metal catalysts consisting of alloys of nickel and silver, and lead and zinc, respectively, subjecting said oil to distillation under subatmospheric pressure conditions, and separating from the residual oil the evolved vapors which are high in sulfur content. 7

7. A process for the treatment of hydrocarbon oil which is high in sulfur content which com prises distilling said oil and separating a relatively light fraction and a heavier fraction, and subjecting said heavier fraction in the presence of steam at a temperature in the range of 150 to 275 F., and subatmospheric pressure to an electric action obtained by spaced platinum and tungsten electrodes within an enclosed zone connected to an electric current in the range of 2500 to 3100 volts, 1800 to 2200 cycles per second, and approximately 100 milliamperes for a period of from .03 to .06 second to desulfurize said oil, and immediately chilling the oil to prevent any reaction with the products of desulfurization.

8. A process of continuously treating hydrocarbon oil which is high in sulfur content, which comprises continuously and successively feeding batches of said oil into a closed vessel maintained at subatmospheric pressure, maintaining said oil in a state of constant agitation, heating the oil to a temperature in the range of 190 to 240 F., in the presence of a catalyst consisting essentially of alloys of nickel and silver, and lead and zinc respectively, removing the evolved vapors, passing the residual oil into a tube maintained at subatmospheric pressure, subjecting the residual oil with added steam to an electrical bombardment for a period of .03 to .06 second, which bombardment is obtained by imposing electrical energy upon electrodes in the tube in the range of 2500 to 3100 volts, 1800 to 2200 cycles per second, and approximately 100 milliamperes, and immediately thereafter rapidly chilling said residual oil to desulfurize the same and to prevent any reaction with the products of desulfurization, and removing said chilled oil from the system.

9. A process of treating hydrocarbon oil to desulfurize the same, which comprises introducing said oil into a closed vessel maintained atsubatmospheric pressure, maintaining said oil in a state of constant agitation, heating the oil to a 7 temperature between 190 to 240 F1, in the presence of a catalyst consisting essentially of alloys 01 nickel and silver, and 1 ad and zinc respectively, removing the GVOIVM; vapors, passing the residual oil into a tube maintained at subatmos pheric pressure, subjecting the residual oil with added steam to an electrical discharge between electrodes disposed within said tube for a period of .03 to .06 second, which discharge is obtained by imposing electrical energy upon the electrodes in the tube in the range of 2500 to 3100 volts, 1800 to 2200 cycles per second and 100 milliamperes to 1 ampere, and immediately thereafter rapidly chilling the products in the tube to desulfurize said 011, and to prevent any reaction with the products of desulfurization.

10. A process of refining hydrocarbon oil high in sulfur content, comprising subjecting said 011, in the presence of catalysts consisting essentially of alloys of nickel and silver, and zinc and lead, respectively, to a temperature insufllcient to decompose the oil chemically but suflicient to distill otf volatile sulfur compounds, separating and removing the volatile low boiling components, and subjecting the residual oil in the presence of steam to an electric action obtained by spaced platinum and tungsten electrodes within an enclosed zone connected toan electric current in the range of 2500 to 3100 volts, 1800 to 2200 cycles per second and approximately 100 milliamperes for a period of from .03 to .06 second to desulfurize said oil, and immediately chilling the oil to prevent any reaction with the products of desulfurication.

11. A process of treating hydrocarbon oil to desulfurize the same comprising heating the oil to a temperature insufficient to decompose the oil chemically but sufllcient to distill off volatile sulfur compounds while subjecting the so-treated oil in the presence of water vapor to an electrical discharge generated by a current having a frequency between 1000 cycles per second and 2200 cycles per second, said discharge being obtained from'spaced electrodes within an enclosed zone connected to a current source having a voltage in excess of 1500 volts and an amperage between 100 milliamperes and one ampere, and immediately chilling the oil to prevent any reaction with the products of desulfurization.

. 12. A method defined in claim 11 in which the spaced electrodes are platinum and tungsten.

13. A process of desulfurizing hydrocarbon oil high in sulfur-content comprising separating said oil into a relatively light fraction and a heavier fraction, heating said heavier fraction to a temperature between about 150 F. and about 275 F. in the presence of water vapor, subjecting the sotreated heavier fraction to an electrical discharge generated by a current having a frequency be-- tween 1,000 cycles per second and 2200 cycles per second, said discharge being obtained from spaced electrodes within an enclosed zone connected to a current source having a voltage in excess of 1500 volts and an amperage between milliamperes and one ampere, and immediately chilling the oil to preventany reaction with the products of desulfurization.

14. A process of desulfurizing hydrocarbon oil high in sulfur-content comprising subjecting said 011 in the presence of catalysts consisting essentially of alloys of nickel and silver, and zinc and lead, respectively, to a temperature insuflicient to decompose the oil chemically but sufflcient to distill off volatile sulfur compounds, and thereafter subjecting the so-treated oil in the presence of water vapor to an electrical discharge generated by a current having a frequency .between 1000 cycles per second and 2200 cycles per second, said discharge being obtained from spaced electrodes within an enclosed zone connected to a current source having a voltage in excess of 1500 volts and an amperage between 100 milliamperes and one ampere, and immediately chilling the oil to prevent any reaction with the products of desulfurization.

HENRY M. UNSCHULD. JOSEPH G. ALTHER.

' REFERENCES CITED The following references are of record in the file of this :patent:

UNITED STATES PATENTS Number Name Date 1,472,882 Moody Nov. 6, 1923 1,753,859 Gray Apr. 8, 1930 1,803,964 Egloif May 5, 1931 1,920,247 Day Aug. 1, 1933 1,920,248 Day Aug. 1, 1933 1,996,008 Kaehler et a1 Mar. 26, 1935 2,045,343 Darrah June 23, 1936 2,161,987 Tilton et a1. June 13, 1939 2,420,218 Ayers May 6, 1947 FOREIGN PATENTS Number Country Date 224,901 Great Britain Oct. 22, 1925 644,281 France June 4, 1928 OTHER REFERENCES Ellis, Hydrogenation of Organic Substances (1930), p. 596.

Gruse et al., Chemical Technology of Petroleum (1942), Pp. 316, 318.

Kalichevsky et al., Chemical Refining of Petroleum, A. C. S. Monograph Series 63 (1942), pp. 229-237.

Claims (2)

1. A PROCESS FOR THE TREATMENT OF HYDROCARBON OIL WHICH COMPRISES HEATING SAID OIL TO A TEMPERATURE OF 150* TO 275*F., SUBJECTING SAID OIL IN THE PRESENCE OF STREAM FOR A PERIOD OF LESS THAN ONE MINUTE TO AN ELECTRICAL BOMBARDMENT OBTAINED FROM AN ELECTRIC CURRENT BETWEEN SPACED ELECTRODES WITHIN AN ENCLOSED ZONE IN THE RANGE OF 2500 TO 3100 VOLTS, 1800 TO 2200 CYCLES PER SECOND AND APPROXIMATELY 100 MILLIAMPERES TO DESULFURIZE SAID OIL, AND IMMEDIATELY CHILLING THE OIL TO PREVENT ANY REACTION WITH THE PRODUCTS OF DESULFURIZATION.

3. A PROCESS FOR DESULFURIZING HYDROCARBON OIL, WHICH COMPRISES FOR DESULFURIZING HYDROCARBON OIL WHICH COMPRISES SUBJECTING SAID OIL AT AN ELEVATED TEMPERATURE OF 190* TO 240*F. TO THE ACTION OF CATALYST CONSISTING OF ALLOYS OF NICKEL AND SILVER, AND ZINC AND LEAD RESPECTLY.

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