US2111487A - Process for sweetening hydrocarbon oils - Google Patents

Description

March15, 38- V 1 L. v. CHANEY ETAL 2,111,487

PROCESS FOR SWEETENING HYDROCARBON OILS Filed July 25, 1936 2 Sheets-Sheet 1 INVENTOR. LOVELL M CHANEK Y ALBERT E. BUELL IR W ' ATTORN S.

March 15, 1938. L. v. CHANEY ET AL 4 PROCESS FOR SWEETENING HYDROCARBON 0114s 2 Sheets-Sheet 2 Filed-July 25, 1956 R KU Y m M w E N A B N m m m m v Mn T A LMQ. I W M o A L I Y B Patented Mar. 15, 1938 UNITED STATES PATENT OFFICE PROCESS FOR SWEETENING HYDE-OCAR- BON OILS Lovell V. Chaney and Albert E. Buell, Bartlesville, kla., assignors to Phillips Petroleum Company, a corporation of Delaware Application July 25, 1936, Serial No. 92,630

7 Claims.

kerosenes, petroleum solvent naphthas, liquefied petroleum gases; and the like. Such unrefined petroleum products contain mercaptans which 15 give the products undesirable odors and render them corrosive and unstable. Petroleum hydrocarbon products containing mercaptans are com monly termed sour. Conversion of these mercaptans partially or entirely to disulfides, or zocompletely removing them, is usually termed sweetening. customarily, these sour compounds are' altered, or removed, by chemical treatment of the 'sour hydrocarbon fluid with 2 alkali plumbite and sulfur. In some instances,

accomplished with alkaline hypochlorite solutions but, like the alkali plumbite method; this method has proved to be not only unecondmical and cumbersome but also has been found to introduce undesirable constituents into the products being sweetened, such constituents in many instances of high mercaptan content products being as detrimental to the petroleum products 35 treated as those present originally. Still other methods have been suggested for the removal or conversion of mercaptans but in nearly every instance these methods involve numerous treating steps, requiring close control, so that the increase 40 in operating costs renders them uneconomical.

' The object of this invention is to provide an economical and easily operated method for refining sour petroleum hydrocarbon oils.

A further and more specific object is to provide improvements in the method of sweetening sour petroleum hydrocarbon oils by means of a moist refining agent consisting of carrying agents impregnated with cupric chloride, said refining agent being retained in a constantly active state by air dissolved in the sour hydrocarbon oils.

In co-pending application Serial No. 725,405, a novel method of sweetening petroleum hydrocarbon products was described, whereby sweet- 55 ening is accomplished by passing a sour petroparticularly with natural gasoline, sweetening is leum product through a bed of moist treating agent comprising cupric chloride carried on fullers earth, or other porous and adsorbent carrier, and the treating agent maintained in an active or sweetening state by means of air added 5 to the petroleum hydrocarbon oil being sweetened.

The petroleum products to be sweetened,'and to which air or other gas containing'free oxygen has been added, are passed through beds of this treating agent, the petroleum products flowing either upward or downward through the beds.

' On emerging from the treating agent bed, the

gasoline or other petroleum hydrocarbon fluid, is sweet to the well known doctor test, has an excellent odor and does not contain any of the undesirable constituents, many of which are unstable to light or heat, usually introduced into the sweetened product by the aforementioned customary sweetening methods.

As disclosed further in co-pending application Serial No. 725,405, the principal chemical reactions in sweetening sourpetroleum hydrocarbon oils with cupric chloride carried on an adsorbent material are believed to be as shown in 5 the following equations:

(1) 2GuClz-l- 4RSH )2RSCu +R-S-SR+ 4HCl Cupric Mercaptan Cuprous Alkyl Hydrochloric chloride mercaptide disuliide acid 1 (2) 2RSCu+2CuClr- RSSR+4Cu0l Cuprous Cupric Alkyl Cuprous mercaptide chloride disulfide chloride In the first step of the reaction, one-half of the mercaptan is converted to the alkyl disulfide and the rest is left as cuprous mercaptide. The latter then reacts (as shown in Equation 2) with additional cupric chloride to give alkyl disulfide and cuprous chloride. On .combining the two equations into one, the ultimate .reaction is:

(3) 4CuCI -I- 4RSH -)2RSSR+ 4Cu0l 41101 Oupric Mercaptan Alkyl cuprous Hydrochloric chloride disulfide chloride acid Since cuprous chloride and hydrochloric acid are formed in the reaction at the expense of the cupric chloride, the. reagent, when treating petroleum oil without the addition of air, will gradually lose its activity, and finally become spent, as the amount of mercaptan sulfur in the oil passed through the reagent becomes more nearly equivalent to the cupric chloride used on the reagent. When the petroleum oil contains only a very small quantity of mercaptan sulfur the.

'life of the reagent is comparatively long, but

when the mercaptan content is high the life of the reagent is quite short.

Spending of the reagent is prevented and its activity maintained over long periods by dissolving air in the petroleum oil previous to its passage through the reagent bed. In this manner the cuprous chloride and hydrochloric acid, formed as shown above in the sweetening step, react with the oxygen in the air to give cupric chloride and water.

(4) 4CuCl+ 41301 I O: )4CllClg+2HaO Cuprous Hydrochloric Oxygen Cupric Water chloride acid (from air) chloride The treating agent contains a substantial quantity of water and. the hydrogen chloride formed as shown in Equation 1 is dissolved in the water or, rather, in the solution of the copper salt. The cuprous chloride likewise remains in solution at the same point in the bed. The oxygen needed to convert the cuprous chlorid and hydrochloric acid back to cupric chloride is furni'shed by the oxygen in solution in the oil and the reagent is immediately and continuously regenerated. If insuflicient water is present, the hydrogen chloride passes oif as a gas dissolved in the oil and the cuprous chloride is precipitated in the solid form. -When the hydrogen chloride is carried away from the cuprous chloride the regeneration does not take place and the reagent therefore soon becomes spent. In this petroleum oil treating process suflicient moisture is maintained in the treating agent such that it has a water content substantially greater. than that of an adsorbent mixture of cupric chloride hydrate crystals and substantially dry adsorbent material. Continuous regeneration of the cupric chloride is obtained and the treating agent remains in a highly active state over long periods of time during which many equivalents of mercaptan sulfur are sweetened by one equivalent of cupric chloride.

Spending of the treating agent, due to insufflcient water, has been observed in the commercial application of this process where the Detroleum oil was exceptionally free from .dissolved water and it was, therefore, necessary to add water to the oil being processed or to the solid treating agent.

In the commercial practice of the process as described in said co-pending application the volume of petroleum oil which can be treated per volume of the cupric chloride sweetening agent varies widely in different instances where the oil and sweetening agent are identical. This variation is due to variations in the rate at which the petroleum oil is passed through the sweetening agent bed. For example, when treating a very sour petroleum oil a greater volume can be treated per volume of sweetening agent when the oil as it had originally, indicating that small channels had formed in the bed of sweetening material and set up a condition equivalent to sweetening at high rates through the local areas in the bed where channelling had occurred.

We have found that this failure in sweetening due to channelling can be prevented by passing the oil at a relatively high rate upward through the bed of sweetening agent for periods of short duration at relatively frequent intervals. serves to lift the reagent bed slightly and to disturb the granules thereof suificiently to break up incipient channels in the bed.

Where the treating agent has failed to sweeten the petroleum oil, due to the formation of these channels, we have obtained a large increase in volume of oil sweetened, per volume of treating agent, by passing the oil up through the treating agent bed at rates between 0.7 and 2.5 ft. per minute. When the flow rate of the oil up through the bed is less than about 0.7 it. per minute, the velocity is not high enough to disturb the granules of treating agent sufliciently to break up the channels, and rates in excess of about 2.5 ft. per minute cause so much lifting that particles of the treating agent are carried out of the container by the oil stream. We prefer to carry out this step in the process by passing the petroleum oil up through the treating agent bed at rates between 1.0 and 1.8 ft. per minute, although the preferred rate in individual cases is influenced somewhat by the size and shape of the treating agent granules, by the depth of the treating agent bed and by the density of the petroleum oil.

We prefer to treat at rates such that the linear velocity of the petroleum' oil through the sweetening agent is less than 0.5 ft. per minute where the oil contains only a moderate concentration of mercaptans and less than 0.2 ft. per minute where the oil is very sour, or contains a relatively high concentration of mercaptans.

As an example of the utility of this step in the refining of petroleum hydrocarbon products with a refining agentconsisting of cupric chloride carried on fullers earth, a treating plant processing a very sour (0.05 per cent, by weight, mercaptan sulfur) West Texas natural gasoline at an average rate of 14,000 gallons per day through a bed of this refining agent 4 ft. deep and 4 ft. in diameter consistently sweetened approximately 200,000 gallons of gasoline after each filling of the treating tank with cupric chloride refining agent before failing to completely sweeten the gasoline. In this normal treating the gasoline was passed through the refining agent bed at rates approximating a linear velocity of 0.13 ft. per minute. A pump was then installed and gasoline passed up through the refining agent bed for 20 to 30 minutes every 3 or 4 days, or after approximately every 50,000 gallons of gasoline had been sweetened, at a rate of 150 gallons per minute, or at approximately 1.6 ft. per minute. Other than this periodical short cessation of normal sweetening operation, the cupric chloride treater operated continuously for over 8 months and sweetened over 3,500,000 gallons of this very sour natural gasoline without once opening up the treater or otherwise disturbing the refining agent This ings are for the purpose of illustration only, and

indicate one manner in which applicants invention can be carried out, and that other systems and apparatus suitable for carrying out the invention as described and claimed may be substituted.

Fig. 1 illustrates the operation of our improved method of sweetening petroleum hydrocarbon oils with cupric chloride solution on a solid carrier. In normal sweetening operation, sour petroleum oil enters the oil and air contacting chamber 3 through pipe I. A controlled amount of air enters contacting chamber 3 through pressure reducing regulator 4, valve 5 and check valve 8. Automatic proportioning of air into the hydrocarbon oil is accomplished by proportional,

control 9 working in conjunction with diaphragm valve 1 motivation for which is furnished by differentials across hydrocarbon oil orifice 2 and air orifice 6,,co-acting through an' air block or pilot valve actuated by an external source of air at constantmoderate pressure, so that every change in the fiow rate of hydrocarbon oilv causes a proportional change in air rate. proportion of air to petroleum hydrocarbon oil is established by drilling the orifices in the orifice plates'in the air and petroleum oil lines to. the proper sizes for the desired proportions.

Sour petroleum oil containing the air passes then from contacting chamber 3 through line I 0, through valves .H and I2 (and through line l3 into the top of tank l4 in which is contained a bedof moist sweetening agentconsisting of cupric chloride solution on a carrier material. Petroleum oil passes down through the bed of refining agent and emerges, sweetened, from treating tank l4 through line l5, valve l6 and through line I! to sweet oil storage. Valves l8, I9, 20, 2|, 23 and 24 are closed.

After a predetermined volume of petroleum oil has been sweetened through treating tank It, for example, valve I2 is closed and valves I8, 32, 34, 36 and H are opened so that oil through line l0, line 31, tank 33, centrifugal pump 35 and line 38 will completely fill tank l4 when air and vapors are-vented from tank I! by opening valve 30.'

When tank I4 is liquid full, valves H and 30 are closed, valve I2 is opened and pump 35 is started. Circulation of oil is then in the reverse direction to that in normal sweetening, oil being drawn from the top of tank [4 through lines I3 and 31 into surge tank 33. Pump 35, taking suction from the bottom of surge tank 33, discharges oil through line 38 and line l5 into the bottom of treating tank l4 below the sweetening agent bed. Flow rate of 011 up through the tank is determined by orifice 26 and manometer, or recording flowmeter, 21 and the flow rate regulated by valve 36 so that the velocity of 011 up through the treating tank is approximately 1.5 ft. per minute. Orifices 26 and 28 are square-edged so that the flow of -oil in either direction can be measured with them in conjunction with a manometer or The desired that the total normal petroleum oil sweetening requirement can be sweetened in the remaining treating tanks while any one is out of service" for the short period of reverse flow.

Flow of air into the petroleum oil is also controlled and recorded by means of a needle valve, not shown, in the air line to the oil and air contacting chamber 3, Fig. 1, orifice 5 and a'recording fiowmeter or a manometer, also not shown in Fig. 1.

Automatically proportioning the air into the gasoline is essential where the quantity of mercaptans in the gasoline is of such magnitude that the air required to maintain the cupric chloride treating agent in a continuously regenerated state is approaching the solubility of air in the hydrocarbon oil being processed. Without an automatic proportioner, the tendency in this critical range would be either to add too much air to the oil, and raise the vapor pressure of the oil, or to add too little, with the possible chance, of permitting the treating agent to become spent. Automatically proportioning the air into the hydrocarbon oil is preferred where the mercapr tan content of the oil is of the order of 0.04 per cent by weight. Where the mercaptan content is around 0.002 per cent, air is satisfactorily added to the oil by manual control.

Sometimes sweetening is also carried out by admitting the sour petroleum oil into the bottom of treating tank I4, Fig. 1, and passing the oil up through the sweetening agent bed at a relatively low rate, removing the sweetened oil from the top of the tank. Fig. 1 is not complicated with the extra lines and valves -to show treating in this manner. After normally treating up-fiow at a relatively low rate for a predetermined time, upward flow of petroleum oil is increased periodically to the desired high rate by means of a pump, or other means for obtaining this high rate, for a relatively short time, after which nor-' mal treating is resumed.

Where the sour hydrocarbon oil can be supplied to the treating agent, inthis reverse flow step, in sufiicient quantity to maintain the required upward'flow rate for the desired length of time,

the oil is passed up through the cupric chloride treating agent bed but once and then passed on to sweet storage, rather than recycled, for even 'at the higher rates required for the slight disturbance of the treating agent bed the oil is com- 'pletely. sweetened. In this manner of maintaining the high flow rate up through the treating agent bed, air is added to the gasoline in the required proportion to maintain the treating agent in a regenerated state, whereas in the recycling method no regenerating air is necessary.

In sweetening through two or more treaters in parallel, valves 20, 22 and 23, controlling the fiow of petroleum oil into and out of treating tank 25, are open as are correspondingly placed valves on other treating tanks if more are in the system. Square-edged orifices 26 and 28, with corresponding m'anometers or fiowmeters 21 and,

29, are conveniently placed in the lines into the top of the treating tanks in order to determine that the desired amount of petroleum oil is passing through each of the treating tanks arranged in parallel and to regulate the periodical relatively high rate of upward flow of oil through the sweetening agent for the prevention of channelling.

Fig. 2 illustrates in detail a typical device for mixing air, or other oxygen-containing gas, with the petroleum oil to be sweetened with the cupric chloride treating agent. Petroleum oil enters through conduit i into chamber 3 where it is intimately commingled with air entering the chamber through conduit 40 and porous plate 4|, the porous plate serving to subdivide the air stream many times to greatly increase the contact surface between air and petroleum oil. Porous plate 4| is composed of Alundum, or other similar material, and is maintained in a swedge nipple with babbitt 42. The petroleum oil and air mixture leaves chamber 3 through conduit Ill.

Fig. 3 shows the construction of a typical treating tank containing cupric chloride sweetening agent. During sweetening operation sour petroleum oil, partially saturated with air, enters tank l4 through conduit l3, impingingagainst baflle 43 to prevent disruption of the granular treating agent bed by the flow of oil. The sour petroleum oil is sweetened in passing through sweetening agent 44, and the sweetened oil passes through perforated wooden plates 45, hair-felt 46 and leaves tank !4 through conduit l5. Sweetening agent 44 is supported by two perforated wooden plates 45, consisting of perforated boards arranged to form a floor, the two plates being held apart by spaced boards 41, and the whole supported by steel beams 48 resting on an angle iron ring 49. Hair-felt 46, or the like, packed tightly between the perforated plates prevents the granular sweetening agent from passing through the plate perforations.

During the step of periodically passing petroleum oil up through the sweetening agent bed at a relatively high rate to break up incipient channels in the bed, oil enters through conduit l5, Fig, 3, impinging upon batlle plate 50, passes up through sweetening agent 44 and leaves treating tank l4 through conduit l3. Oil partially saturated with air, is also passed up through the sweetening agent bed at lower rates during the normal sweetening operation.

Manholes 5|, Fig. 3, are provided for admitting sweetening agent to treating tank l4 through the top and for removing it therefrom at the side. Drain 52 is provided for completely emptying tank I4 of liquid.

Having described our invention what we claim and desire to secure by Letters Patent is:

1. A process for sweetening mercaptan-bearing petroleum oil, comprising impregnating a solid adsorbent carrier material with a sweetening agent consisting of a solution of a copper salt and a chloride adapted to react to form cupric chloride, said impregnated adsorbent material being maintained in a moist condition and having a water content substantially greater than that ofan adsorbent mixture of cupric chloride hydrate crystals and substantially dry solid adsorbent material, admixing a free oxygen-containing gas with said mercaptan-bearing petro leum oil, contacting said oil and free oxygencontaining gas with said impregnated adsorbent material, thereby converting the mercaptans in said oil to disulfides and simultaneously maintaining the sweetening agent active, and collecting the sweetened petroleum oil, discontinuing contacting said petroleum oil and admixture of free oxygen-containing gas with said impregnated adsorbent material, subsequently passing said petroleum oil up through said impregnated adsorbent material at arelatively high velocity for a relatively short duration of time, discontinuing said relatively high velocity of upward passage of petroleum oil through said impregnated adsorbent material and resumingcontacting of said admixture of petroleum oil andfree hydrate crystals and substantially dry solid adsorbent material, comprising admixing a free oxygen-containing gas with said mercaptanbearing petroleum oil, contacting said oil and free oxygen-containing gas with said impregnated adsorbent material, thereby converting the mercaptans in said oil to disulfides and simultaneously maintaining said sweetening agent active, and continuously collecting the sweetened petroleum oil, discontinuing contacting said mercaptan-bearing petroleum oil and admixture of free oxygen-containing gas with said impregnated adsorbent material, subsequently passing a petroleum oil up through said impregnated adsorbent material at a relatively high velocity for a relatively short duration of time, discontinuing said relatively high velocity of upward passage of petroleum oil through said impregnated adsorbent material, and repeating the process.

3. A process forv sweetening mercaptan-bearing petroleum oil, comprising impregnating fullers earth with a solution of copper sulfate and a soluble alkaline chloride, maintaining the water content of said impregnated fullers earth substantially above that of a mixture of cupric chloride hydrate crystals and substantially dry fullers earth, mixing air with said petroleum oil, filtering said petroleum oil and air downward through said impregnated fullers earth at a rate in the range of 0.05 to 0.4 ft. per minute, whereby the mercaptans in said oil are converted to disulfides, and collecting the sweetened oil, discontinuing contacting of said admixture of petroleum oil and air with said impregnated fullers earth, passing said petroleum oil up through said impregnated fullers earth at a rate in the range of 0.7 to 2.5 ft. per minute for approximately one-half hour, discontinuing said upward passage of petroleum oil and resuming downward passage of said admixture of oil and air through said impregnated fullers earth, and collecting the sweetened oil.

4. A cyclic process for'sweetening mercaptanbearing petroleum oil with a solid adsorbent carrier material impregnated with a sweetening agent consisting of a solution of a copper salt and a chloride adapted to react to form cupric chloride, said impregnated adsorbent material being maintained in a moist condition and having a water content substantially greater than that of an adsorbent mixture of cupric chloride hydrate crystals and substantially dry solid adsorbent material, comprising admixing air with said mercaptan-bearing petroleum oil, contacting said oil and air with said impregnated adsorbent material, thereby converting the mercaptans in said oil to disulfides-and simultaneously maintaining said sweetening agent active, and collecting the sweetened petroleum oil, discontinuing contacting said petroleum oil and admixture of air with said impregnated adsorbent material, subsequently'passing said petroleum oil up through said impregnated adsorbent material at a relatively high velocity for a relatively short duration of time, discontinuing said relatively Y high velocity of upward passage of petroleum oil through said impregnated adsorbent material, and repeating the process.

5. In a process -for sweetening mercaptanbearing petroleum oil with asolid adsorbent carrier material impregnated with a sweetening agent consisting of a solution of a copper salt and a chloride adapted to react to form cupric chloride, said impregnated adsorbent material being maintained in a moist condition and having a water content substantially greater than that of an adsorbent mixture of cupric chloride hydrate crystals and substantially dry solid adsorbent material, comprising admixing air with said mercaptan-bearing petroleum oil, passing said oil and air downward through said impregnated adsorbent material at a relatively low rate, thereby converting the mercaptans in said oil to disulfides and simultaneously maintaining said sweetening agent active, and continuously collecting the sweetened petroleum oil, the step of discontinuing the normal relatively low rate of passage of petroleum oil downward through the impregnated adsorbent material and passing said petroleum oil upward through the impregnated adsorbent material at a predetermined relatively high rate, thereby preventing the formation of 6. In a process for sweetening mercaptanbearing lightpe'troleum oil, comprising impregnating fullers earth with a solution of cupric chloride, maintaining the water content of said impregnated fullers earth, substantially above that of a mixture of cupric chloride hydrate crystals and substantially dry iullers earth, addin air to said oil, filtering said oil and air downward through said impregnated fullers earth at a rate less than approximately 0.4 ft. per minute, thereby converting the mercaptans to disulfides, and continuously collecting the sweetened oil, the step of periodically discontinuing filtering said oil and air through said impregnated fullers earth, and subsequently passing a light petroleum oil up through said impregnated fullers earth at a rate in the range of 0.7- to 2.5 ft. per minute for approximately one-half hour, thereby preventing'permanent channelling of said impregnated fullers earth.

7. In a process for sweetening mercaptanbearing petroleum oil partially saturated with air, the steps which comprise passing said oil at a rate less than approximately 0.4 it. per minute up through a sweetening agent consisting of a solid adsorbent material impregnated with a solution oi a copper salt and a chloride adapted to react to form cupric chloride, said impregnated adsorbent material being maintained in a moist condition and having a water content substantially greater than that of an adsorbent mixture of cupric chloride hydrate crystals and substantially dry adsorbent material, periodically increasing the rate of passing said oil, partially saturated with air, up through said sweetening agent to a rate in the range of 0.7 to 2.5 ft. per minute for approximately one-half hour, decreasing said rate of upward passage of said oil through said sweetening agent to a rate less than approximately 0.4 ft. per minute, and repeating the steps.

LOVEIL V. CHANEY.

ALBERT E. BUELL.

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