US2284271A - Process for sweetening sour hydrocarbon oils - Google Patents

Description

y 1942- L. u. FRANKLIN ETI'AL 2,284,271

PROCESS FOR SWEETENING SOUR HYDROCA RBON'OILS Filed July 12, 1939 6E'PA'RATING 2 ONE awe/"Ms LESLIE FRANKLIN WALTER H.WEEKS Patented May 26, 1942- raoosss FDR SWEETENENG sous. urnno- CARBON OILS Leslie U. Franklin and Walter H. Weeks, Port Arthur, Tex., assignors to Gulf Oil Corporation, Pittsburgh, Pa, a corporation of Pennsylvania Application July 12, 1939, Serial No. 284,116 2 Claims. (01.196-29) Our invention relates to sweetening sour hydrocarbon oils, more particularly light petroleum distillates such as gasolines, naphthas, kerosenes, furnace oils and the like, that is to say, to processes for treating oils of the character indicated, containing sour and malodorous sulfur impurities, such as mercaptans, to convert such impurities into sulfur compounds of less objectionable character, whereby the treated oils are rendered sweet to the doctor test and free from disagreeable odor.

More particularly, our invention relates to improvements in what is known in the petroleum art as copper sweetening, i. e., a process in which sour oil to be treated is contacted with a treating agent comprising a compound or mixture of compounds capable of ionizingto form cupric ions and chloride ions, usually a cupric'chloride, with or without the presence of a substantially inert solid carrying agent.

The earliest proponents of copper-sweetening referred, in the main, to two general types of processes, 1. e., those in which solutions of copper salts were used as the treating agents, and those in which solid copper salts, frequently distributed on adsorbents such as clay, fullers earth or the like, were used.

In processes wherein the oil is treated in the liquid phase, it is now generally conceded that suificient moisture must be present to permit ionization. Naturally, ionization is not a problem in those types of processes in which definite solutions, as distinguished from slurries or solid contact masses are used. However, the solution-type processes involve serious corrosion problems.

For various reasons, the percolation-type processes have not proved commercially successful in the treatment of cracked distillates and other oils containing substantial amounts of potential gumand color-forming constituents. The oxygen stabilities of such oils tend to be seriously reduced after sweetening by this type of process, and the treated oils rapidly develop gum and color upon storage. Nor has this type of process been successful with respect to oils containing relatively high amounts of mercaptans, regardless of whether such oils are cracked or straight-run distillates.

A third type of process, known as the slurrytype process, has also been proposed, in which the sour gasoline is mixed with the treating agent in more or less dry form, usually in the presence of a finely-divided adsorbent material, such as iullers earth, adsorbent clay or the like, and.

the sweetened gasoline is finally separated and removed. A limited amount of moisture must be present, but these processes do not give rise to serious corrosion problems; there is no independent aqueous phase;

However, prior art slurry-type processes have not resulted in-widespread commercial adoption and for the most part have not been successful, except possibly with respect to some oils presenting little or no sweetening difiiculties, such as straight-run distillates of low sourness. In this respect, it, should be noted that, especially with respect to cracked distillates, mere sweetening alone is not a criterion of success. It is relatively easy to make most sour distillates-sweet to the doctor test; it is quite another thing to accomplish this result at a reasonable cost and without increasing the tendency of the oil to go off in color or to form gums, that is to say without decreasing the oxygen stability of the oil. Copper and copper compounds vastly accelerate oxidation reactions in hydrocarbon oils and processes which leave copper (especially oil-soluble copper) in the treated oils yield unstable and unsatisfactory products. Re-running and further refining of these oils tend to make them sour again.

Our invention has also had for other objects such additional operative advantages and improvements as may hereinafterbe found toobtain. Among the objects achieved by our present invention is the provision of a process of cop-' per sweetening in which (1) the sweetening agent is of a substantially non-corrosive type, (2) the sweetening agent can be maintained in a highly efficient condition over considerable operating periods, without substantial losses of the sweetening agent from the system and (3) sweetening is accomplished, even with respect to cracked gasolines and other petroleum distillates having low oxygen stabilities, without adversely affecting the oxygen stabilities of the oils treated.

We have discovered thatthe aforesaid objects may be achieved, and commercially successful sweetening of sour distillates, including cracked distillates and other unstable petroleum distillates, eiiected by passing a mixture of (1) the oil to be sweetened, (2) an oxygen-containing gas such as air or oxygen itself, and (3) a solid compound or mixture of compounds capable of ionizing to give cupric ions and chloride ions, (with or without an inert solid carrier) and containing a limited amount of moisture, in substantially concurrent contact through a sweetening zone, then passing the sweetened oil, the oxygen containing gas and the treating agent through a second or stabilizing zone, wherein regeneration of the treating agent is completed, as indi- In the slurry type of process, to which our invention relates, however, there is no independent aqueous phase. For this reason the presence cated by freedom of the sweetened oil from oila trated slurry insweetened oil, isthen recycled to the sweetening zone fortreatment of fresh quantities of sour distillate. As will be apparent;

the process is most advantageously. carried out .in a continuous fashion, a continuous stream of sour distillate being introducedinto,thesweeten-,

ing zone and an equivalent quantity of the the separating sweetened oil being removed from zone.

We-have discovered-that, in a process of this.

general type, that is to say, a process in which a flowing stream of oil is treated for the conversion of sour sulfur compounds into sweet sulfur compounds by suspending a solid treating agent of the character indicated in a flowing stream of the, sour oil, in the presence of an oxygen-containing gas, sweetening is effected comparatively rapidly, provided the chemical'is fresh or has beenadequately regenerated, but that at that point along the flow of oil and treating agent where the oil first becomes sweet tothe doctor test (i. e. where the oil first shows itself free or substantially free from organic mercaptans) the oil tends to contain very substantial quantities ofcuprous chloride and cuprous mercaptides. Were" the oilto be separated and withdrawn at this point, the separated oil would be {of inferior quality due to the highly adverse effect upon oxygen stability and rate of formation of gums and color imparting bodies which is'exerted by oil-soluble copper compounds, even when present in extremely small amounts. We have'found, however, that if the mixture of oil, oxygen-containinggasand solid treating agent is maintained in contact throughout a stabilizing zone for a considerable period after sweetening has been effected, the reactions which continue for a considerable time after the sweet point has been reached will gradually convert cuprous 'mercaptides and" cuprous chloride bacl; into cupric compounds which are insoluble in oil and therefore remain in the massof solid treating agent maintained in the system instead of being retained in solution in the separated oil. By maintainingcontact of the oil, the oxidizing gas and the solid treatingagent throughout the sweetening and stabilizing zones, as aforesaid, the separated oil can be withdrawn from the system without impairment of its oxygen stability. -In most cases an actual improvement in oxygen stability'is obtained' It should be noted at this point that these considerations do not necessarily apply to solution-type processes, for the reason that cuprous chloride and cuprous mercaptides are quite solu-' ble in the types of solutions commonly employed in such processes. In the latter type'of process it istherefore possible to effect regeneration of thesweetening solution out of contact with the oil, the oil being-withdrawn from the initial treating zone as soon as it is sweet. Some cuprous compounds may, even in such instance, be retained in the oil but can be removed by aftertreatment without great difiiculty.

of cuprous compounds simply means that all or a large portion of such cuprous compounds will dissolve in the oil undergoing treatment. They will remain dissolved in the oil unless and until contact is maintained for a considerable period past the point where the oil becomes sweet, as aforesaid.

Probably because of the fact that sweetening and regeneration are to a certain extent concurrent and tend to take place simultaneously to some extent, operators of prior art slurry-type processes have apparently failed to realize the necessity for establishing a further zone wherein the oil, the air and the solid sweetening agent are maintained in contact for a considerable period past the point where sweetening is complete, and prior to separation. It seems to have beenassumed that the sweetening and regeneration reactions wouldbe'complete at about the same time, whereas inpoint of fact we have discovered that, under actual operating conditions it takes at least 3 or 4 times as much time to effect regeneration tothe point where 'the oil is substantially free of soluble cuprous chloride and cuprous'merca'ptides, than it does to effect sweetening of the oil, that is to say, conversion of the organic mercaptides in the oil into organic disulfides or other free sulfur compounds, and this difference is considerably more marked where air, instead of oxygen, is used. And it was not realized that this stabilization should take place prior to separation of the oil from the treating material. Therefore, prior art slurrytype copper-sweetening processes have uniformly tended to cause impairment of the treated distillates with respect to their oxygen stabilities and their tendencies toward formation of gums and color-imparting bodies.

It may be observed at this point that attempts have been made in the prior art to overcome this disadvantage by various methods of treating the oil after separation from the sweetening this is true. In the first place, removal of the treated distillate as soon as it becomes sweet means thatthere is a continuous and heavy loss of treating chemicals from the system. The dimculty of removing these compounds tends to increase outof proportionto the amount present in-the oil. Consequently such after-treatment, when carried out for the purpose'referred to, has

meant that inaddition to the loss of chemicals from the system, large quantities of after-treating chemicals must be employed. In some instances the amount of cuprous compounds necessary to be removed has been so large that subsequent after-treating methods have not been adequate.

In the second place, any system of the type indicated wherein the oil is removed as soon as it becomes sweet must inherently be ineflicient in operation, because of the fact that the solid treating agent'tends to subsist in a substantially spent" or fouled condition throughout the system, This vastly increases the difliculty of regeneration. 1 l

There .is also a third reason. which has'militated against the success of prior-art processes of the type indicated. This is the fact that, the longer the oil is permitted to retain cuprous compounds in solution, the more difiicult will be the subsequent removal of those compounds or their reaction products. Thus, ifit is necessary to transfer the oil into a subsequent after-treating stage, some time is necessarily consumed in the transfer of the oil from the treating stage to the after treating stage. In our process, the conversion of cuprous compounds back to oilinsoluble cupric compounds is both prompt and rapid, giving less time for the formation of reaction products, which would be very diificultto remove, especiallyif they were present in substantial amounts.

In. any copper-sweeting process, very small traces of such reaction products are to be encountered, even under the most efficient operating conditions. Even as little as one part of a reaction product between copper and non-sulfur containing constituents of the oil, such as a copper naphthenate, per million parts of oil is deleterious with respect to the stability of the oil; that is to say, even such small traces of materials of the character indicated will cause the oil to deteriorate in storage. In order to remove such slight traces of copper naphthenates and the like (and as a factor of safety against accidental entrainment of the treating agent in the oil leaving the system, although in our process the likelihood of such accidental loss is reduced to a minimum) we usually employ a simple form of after-treatment, of more or less conventional type, as will be set forth 'hereinbelow. It must not be inferred, however, that the use of such after-treatment implies a lack of success in reaching the objectives of our process. There is a vast difference between the removal of minute traces of copper naphthenates and the like, which is the primary purpose of after-treatment in our process, and the removal of substantial quantities of cuprous chloride and cuprous mercaptides, which has been the primary purpose of after-treatment in prior art processes, especially prior art processes of the "slurry and percolation types.

An inherent advantage of our process, which results in part from the use of concurrent flow and in part from maintenance of a stabilizing zone as aforesaid, is the fact that the treating agent is never allowed to become reduced to too great an extent at any stage in the cycle, thereby vastly facilitating regeneration. We have found that the amount of time of regeneration required by a given amount of copper-sweetening agent increases out of all proportion to the degree to which the agent has previously been reduced by contact with sour oil. Because of our maintenance of the treating agent in a comparatively active condition through the cycle. the tendency for the oil to pick up substantial quantities of soluble cuprous compounds is greatly reduced as compared with prior art processes of the slurry and "percolation types. It may be noted at this point that the unavoidable tendency toward over-spending of portions of the treating agent is a serious defect in percolation-type processes and also in prior art slurry-type processes wherein the considerations underlying our invention have been neglected,

In practicing our invention, the sour oil to be treated, for example a sour cracked gasoline dis.

cupric ions and chloride ions, with or without (but preferably with) a substantially inert solid carrying agent.

As disclosed in the prior art, a number of compounds and mixtures of compounds may be employed inpreparing the solid sweating agent; thus cupric chloride (CuClz) may be used by itself. We have found. it preferable, however, to employ a mixture of cupric sulfate and sodium chloride, suchmixture'being permitted toreact in the. presence of enough moisture to cause the formation of substantial quantities of cupric chloride. In place of sodium chloride we may use ammonium chloride, and we may expedite the formation of cupric chloride by adding HCl to the mixture. We have'found, however, that potassium chloride is less desirable, possibly because. cuprous chloride is less soluble in aqueous solutions of KCl than in aqueous solutions of NaCl, NHlCl and HCl.

Asdisclosed in U. S. Patent No. 744,720, the

chemicals employed inthe sweetening mixture may comprise iron sulfate in addition to cupric sulfate and sodium chloride, the presence of iron sulfate (either ferric, ferrous or both) being beneficial.

Whatever the nature of the chemical or chemical mixture employed, it is preferably combined prior to use with a finely divided inert solid carrying agent. Various types of carrying agents,

such as fullers earth, clays and the like, may be employed, but we have found it highly advantageous to employ a mixture of (l) finely divided asbestos, (2) cupric sulfate and (3) sodium chloride, as set forth and described in the copending application of Leslie U. Franklin, Serial No. 285,636, filed July 20, 1939. 7

As shown in said application, the use of asbestos as. a supporting means for the coppercontaining chemical mixture is highly advantageous, as compared with the use of highly adsorbent materials, such as clays, fullers earth, silica gel and the like. Asbestos, because of its non-adsorbent, yet highly absorbent character, does'not tend to cause polymerization of potential gum-forming constituents-a tendency apt to be exaggerated in effect when copper is also present. Moreover, it does not tend to hold the treating compounds in such afashion as to prevent or increase the 'difiiculty of regeneration; nor

does it tend to make the agent absorb water to too great an extent. Because of its light and buoyant character, it presents an ideally large surface per unit of weight, is easy to suspend in the gasoline and at the same time easy to separate by decantation, which is particularly important in connection with our process. It is also much less abrasive than the highly adsorbent contact agents, such as clay and the like.

Itis also preferable that the treating agent be preconditioned and maintainedlparticularly with respect to moisture content) as set forth, described and claimed in the copending application of Leslie U. Franklin, Walter H. Weeks and Jack W. Harris, Serial No. 284,117, filed concurrently herewith. Such a mixture can be maintained, by proper steps and procedure, in the form of a flocculent or semi-fiocculent suspension in the oil, of high sweetening and regenerating efliciencyand capable of easy suspension'in concurrently through a sweetening zone pro-* vided'with suitable agitating means for insuring rapidity and intimacyof contact. Regeneration occurs in this zone, but only to a limited extent. After the oil has progressed through this zone only a-short distance, in admixture with the treating agent and air, as aforesaid, sweetening is effectedrthe oil, upon sampling, 'is sweet to the .doctor test. Y

In accordance with our'invention, however, we

do not remove the oil atthis point,'but maintain the oil, the oxidizing gas (which may be in solution in the oil) and the 'solidtreating agent in intimate concurrent contact in a stabilizing zone until regeneration of. the treating agent is complete, as indicated by freedom of the oil from oil-soluble copper, especially cuprous chloride-and cuprous mercaptides. Then, and'then only, do we effect separation of the treated oil from the treating agent.

The separation of the treated oil from the treating agent may be effected in various ways, but we prefer to accomplish it by simple continuous decantation, as .for example by passing the mixture of oil and :air and treating agent to a settling vessel, usuallymore or less conical in shapeand providedwith a vertical baffle between the inlet and the treated gasoline outlet. The treating agent settles to the bottom, and is withdrawn'and recirculated back to the treating zone.

In most cases, at least a portion of the separat ing zone serves as a continuation and extension of the'stabilizing'zone, considerable regeneration taking place in the separating zone in addition to that-taking place in the prior zones. This is not objectionable so long as regeneration is com-' pleted, to the extent indicated; prior to the point where separation is effected.

By virtue of the concurrent-flow and agitation, as well .as by virtue'of the prolonged contactbetween the oil andfthetrea'ting agent in the stabilizing zone of our process,'disadvanta'ges'inherent in prior processes are avoided. In prior counter-current and percolation-type systems, the least active portion of the-treating agent is exposed to contactwith the sourestooilr That might be expected, at first glance, to promote efiicien'cy of sweetening and. the efficiency of the operation as' a whole; but such is not the case.

advantage of our process that there is no definite zonein the system where the treating agent is more or lesscompletely fouled, as'is likely to be the case in the other types of processes referred 1 to above."

' We have found it advantageous to maintain the entire system under a moderate pressure of f-rom,,for example, ten to sixty pounds per square inch or even more, in order to maintain air (oxygen) in solution in the oil throughout the system. This ;use of superatmospheric pressure is especially desirable when operating temperatures, for any reason, are high. 7

We have also found it advantageous to dry the gasoline or other oil to be treated, prior to introducing it into the system, and also to treat the oil prior to sweetening by means of an alkaline wash, to remove HzS, even after refining with acid or clay. Usually we maintain the treating agent in a rather dry condition throughout (always free froman'independent aqueous phase) but controlled moisture addition may be necessary where conditions are such as to entail loss 'of water from the total body of. treating agent in the system. Maintenance of a suitable moisture content formsa part of the invention disclosedin the aforesaid application Serial No.

The regenerated treating agent, after separation and removal fromthe bulk of the treated oil, but of course still existing as a relatively concentrated; slurry in sweetened oil, is withdrawn from theseparating zone and returned to the sweetening zone, entering the latter in admixture with, or at a point'adjacent to the point p of entry of, the souroil to be treated; It is thus re-us'ed-for the'treatment of further quantities of. sour oil.

From time .to time, as necessary, make-up" quantities of fresh treating agent are added to the'system, to replace that mechanically lost during the operation.

' The treated oil, after being separated from the sweetening agent, is best passed through a simple after-treating tower, for the purpose of removing any slight traces of oil-soluble copper naphthenate or the like'which may be retained sweetening itself proceeds so rapidly that it does peated'use and re-use), it is difficult or impos sible to measure the degree of fouling of the treating agent in exact terms. amounts of treating agent, with respect to the sour constituents to be removed, may not'and usually are nob-required. But: it is an inherent Stoichiometric in the oil. Such a tower may comprise a vessel adapted to contain a bed of sand impregnated or coated with salt, a cupric compound such as cupric chloride, or a mixture of cupric sulfate and sodium chloride, of low moisture content. Other types of after-treatment may also be employed.-

In referring to the fact that in our process the oil, the oxygen-containing gas the solid treating agent are maintained in contact, not merely until the oil has been sweetened but throughout a stabilizing zone until regeneration has been completed, we do not mean to infer that in instances where cupric chloride (either as such as in the form of areaction product of cupric'sulfate and sodium chloride or the like) constitutes the sweetening chemical initially added to the system, regeneration necessarily proceeds to such point as tore-form the cupric chlorideinitially added. Inmany instances, there is a certain loss of HCl from the'system, clue in part to the'nature of thereactions taking place, and it is not always possible to supply HCl in such manner as to efiectively regenerate cupric chloride as such. We have observed that in many instances after a short operating period the amount of cupric chloride present in the system may fall to a point where detection of' CuClz is impossible.

Nevertheless, sweetening and regeneration go on, the chemical treating agent being reduced to the cuprous form as a result of the sweetening reactions, and regenerated into some form of cupric compound as a' result of the regenerating reactions. Under different conditions, however, the treating agent can sometimes be maintained at a relatively high CuClz concentration andHCl may be effectively added to maintain this concentration in spite of losses of 101 from the system. But, whether regeneration actually proceeds to the point of forming substantial quantities of CuClz, or whether regeneration merely results in the formation of some other cupric compound capable of sweetening, we have found that a sufficient indication of completion of regeneration, for the purpose of determining the proper time of contact of the oil, the oxidizing gas and the solid treating agent in the stabilizing zone, is found in the freedom of the oil from cuprous chloride and cuprous mercaptides. In other words, separation is not effected until the oil, prior to the point of separation, shows itself upon sampling to be free of cuprous chloride and. cuprous mercaptides, whether or not the treating agent contains substantial quantities of cupric chloride as such.

Whilethe sweetening, stabilizing and separating steps may be conducted in separate apparatus units, if desired, this is not essential. In the usual instance, we provide two apparatus units or vessels. The first of these units is provided with internal agitating means for insuring turbulent fiow, while the second unit, wherein the separation is effected, is usually of larger crosssectional diameter and is not provided with means for agitating, inasmuch as quiescent fiow conditions facilitate settling of the solid treating agent and separation of the final treated oil. With such apparatus, wherein the flow through the first vessel is upward, the lowermost portion of the first vessel constitutes the sweetening zone, while the upper and remainin portions constitute all ora portionof the stabilizing zone, the

separating zone being confined to the second 1 vessel. A considerable portion of the stabilization may, however, be effected in the separating zone itself; it is not absolutely-essential to com plete stabilization before the mixture enters the separating Vessel. Stabilization should, however, be complete prior to the point where final separation takes place.

The advantages of our process are demonstrated by the fact that under actual operating conditions over an extended period of time and on a wide variety of sour oils, we have rarely, if

ever, decreased the oxygenstability 'or color of the oil under treatment (and then only when treating exceptionally unstable oils, and to too slight an extent to be serious), and in a majority of cases we have actually improved the oil with respect to oxygen stability, color stability and potential gum-forming tendency. Such results contrast strongly with the fact that the main factor which has hitherto retarded and substantially prevented commercial adoption of coppersweetening processes of the non-corrosive types for sweetening cracked distillates has been their unfavorable and serious effect upon the quality of the distillates treated.

Operating in accordance with our invention, consumptionofchemicals is low, no corrosion problems are encountered, and the system isuniform in operation and not excessive in size or cost.

and forming" part of this specification, we now describe, by way of exemplification and illustra tion, a preferred form in which our invention may be practiced and embodied, but without limiting our invention to the details of this then washed with water to removetracesof the alkaline wash, and finally dried, as for example by passage through a bed or beds of rock salt.

These steps, being incidental to ratherth'an a part of our invention, are not illustrated in the drawing.

The sour oil then passes through a pipe I into the lower part of a treating vessel 2. In the specific instance shown, this vessel 2 comprises a vertically elongated tower divided into a series of super-imposed compartments by means of a a series of baffle plates 3, and internally provided with an agitating device 4 driven by a motor '5.

The sour oil enters the treating vessel 2 along with a flow of air or'othe'r oxygen-containing gas conveniently introduced through a valved conduit 6, and a suitable quantity of treating agent introduced as a relatively concentrated slurry in oil through a pipe 1. Oxygen, air, or other oxygen-containing gas may also be introducedat other points, ifdesired.- I

Moisture is added to the system, usually in oil solution or suspension, at an appropriate point when and as necessary to replace moisturelos't from the chemical; this being especially necessary when the temperatures of the operation, or

reaching the top of the tower 2 then passes through a pipe 9 into a separating vessel), the upper portion of which is of large horizontal cross-sectional area in comparison with the rate of fiow of oil, so as to insure low velocity of flow, and the lowerpart of which is preferably made in the shape of an inverted cone, as shown. vA wier plate H and an overflow or ofitake pipe l2 maintain a constant level in the vessel l0, and a baflie plate l3, located as shown, prevents liquid introduced through the pipe-8 from passing directly to the overflow wier l i. Preferably, the end of the pipe 9 lying inside the vessel It] is located below the level established by the wier plate I I.

Vents M and 15 are provided for the tower 2 and the vessel I0, respectively, these being pro vided with valves or other devices adapted tomaintain whatever pressures are desired.

No agitation is provided in the separating vesdrawn in the formof. a relatively highly .con-

centrated slurry from the bottom ofthe vessel Referring now to the drawin accompanying in l through a pipe l6 leadingto a pump H, which in turn recirculates :the'material so withdrawn through the pipe 7 back into the tower 2, for treatment of sour gasoline continuously entering the latter.

' By suitably proportioning the size of apparatus and'regulating'the amount of solid sweetening material in the system, the rate of flow of oil therethrough, and the speed of operation ofthe pump 11, thesolid material'can readily be caused to settle out rapidly enough so that the oil leaving the vessel l0 through thepipe l2 contains none of the solid treating agent, or atimost insignificant .quantities thereof. Naturally, the specific gravity of the sweetening material in comparison to that of the oil, as well as other factors. influencing the settling properties of the number required, and their location. a

' tities of CuClz (or a mixture of chemicals con-v pound formed uponiregeneration is perhaps un important; It has been suggested that some form of copper oxychloride is formed under such conditions, but it is unnecessary, in so far as our invention is concerned, either to confirm or deny this possibility; We do known that, under proper conditions, operation may be continued successfully for. long periods without addition of HCl, even wherethe CuClz. content of the treating agent falls to nil, or at least. to a point too low to be determined by ordinary methods.

Even though the; presence of considerable quantities of CllClz facilitates sweetening to a considerable extent, it. is not necessary to repeatedly withdraw the agent from the system for treatment with H0] or otherwise to replenish its content of CuCl;, especially wheresmall quantaining the same as a reaction product) are added to the system from time to time. These re- 7 marks should not be taken to mean that the A valved inlet 24, communicating with the suction side of the pump I1 is provided for introducing fresh solid sweetening material, as for example in the form of aslurry in previously sweetened oil. A valvedofitake pipe 25, on the other side of the pump IT, can be used to withdraw material from the'system whenever desired.

- As the sweetening reactionsfoccur rapidly, the

oil usually shows itself sweet tothe doctor test by the time ithas traversed only a-relatively,

small part of the interior of the tower 2; for example, by the time it reaches the level A-A, which marks the upper limit of the sweetening zone. Experience will show, in'any given unit, just where the sweet level is when the chemicals are fresh, and it should not be allowed ,to rise substantially above this level at any time. Thus, if the sweet level ordinarily lies below the cock I8, then any sourness in a sample taken at this point (provided the supply ofoxygen is adequate and other conditions remain. the same) indicates that the addition .of fresh treating agent is re-' quired, to replace other material lost or rendered inactive in the system. Under proper conditions, this can be reduced to a minimum. At all events, a balance of operating factors should be aimed at.

The mixturethen flows through the upper part of the vessel 2, i. e. through the stabilization zone lying above the level A-A, and thence into the separating vessel I0.

Moisture is added to the system, when and as necessary tomaintain the desired moisture content of the solid treating agent. i V 7 H01 may also be added. At high temperatures tending to cause a loss of HCl, it is sometimes diflicult to add enough HCl to maintain'a high concentration of CuCl in the system, but, as noted above, it is then possible to operate without- HCl addition. At lower operating temperatures,not only is there a reduced tendency toward loss of HCl, but such loss can more easily be replaced, with resultant increase in the amount; of Circl present as such. 7

, When the system is operated without HCl maintenance of a high CuClz contentis initself disadvantageous; the contrary is probably true so long as this result can be secured without incurring serious disadvantages in other respects. It

is not always possible, however, to maintain a high content of CuClz while at the same time maintaining the solid treating agent in a suitable physical condition ortexture.

In any event, when operating in accordance with our invention, as set forth above, the oil,

the oxidizing gas and the solid sweetening material are maintained in contact until regeneration and stabilization are completed ,as far as possible, that is to say untilthe oil is free or substantially free from cuprous chloride and cuprous mercaptides. Separation should not be effected in any event until the oil contains no more than a. slight trace of oil-soluble copper in all forms. It is not essential that this point be "reached in the tower 2, for (especially when considerable quantities of air remain dissolved in the oil, as under pressure) substantial regeneration can be effected in the vessel in. Butthis point must be reached before theoilleaves the vessel ID, as indicated, for example by a sample withdrawnthroughthe cock 22."

' iContro'l'of the process, with the above in mind, and in accordance with the other copending applications-referred'to, is effected by proper regulation of the following factors, in the light of I the degree of sourness of the oil to be treated:

(a) Temperature, 150 F.)

(1)) Rate of flow of. oil,: r

(0) Rate of introduction of oxygen, as such or as' air or other-oxygen-containing gas,

(d) Amount,"physicalcharacter, moisture content and sweetening power-of treating agent in .(normally from A0? to system, a

(e) Extent of agitation, L .0) Pressure,

I j (glAddition of freshltrea'ting agent as readdition, the precise nature of the cupric com;

thenates and the like. v fecting this step have been discussedhereinabove.

quired by mechanical losses,

(h) Rate of. recirculation of treating agent, and V (i) Introductionlof HCl, (where practiced).

After the oil leaves the vessel l0,'it is passed through a stationary bed (not shown) of sand and salt, (with or without oupricchloride), or othermaterial efiective to remove-traces of cop- 'per compounds, suc'has oil -solu'blecopper naph The considerations ef- By way of specific examples of our invention,

the following are typical and will serve to show some of the advantages of our process.

Ezrample I duced during this period.

The sweetening operation was then started,

some gasoline being fed into the system contin- Before treat- After treatment ment Gravity (API) 62. 2 62.0 Color (Saybolt) +28 +28 Color (Saybolt, after 5 hours exposure to sunlight) +25 Doctor test Bad I Good Copper in gasoline Nil Nil Mercaptan sulfur .percent. 0.056 Nil Copper strip test (3 hours at 122 F.). Good Good Oxygen stability rninutes 600+ 600+ The oxygen stability of this gasoline is so high that the test is not ordinarily run to completion. If anything, however, the oxygen stability of this gasoline was increased, rather than decreased, by the sweetening operation. I

Example II In this example, the raw gasoline charged to the unit was an acid-treated and re-run cracked gasoline, produced from the same West Texas crude as the straight-run gasoline of Example I. Analyses of the raw gasoline and the treated gasoline were as follows:

Before treat- After treatment merit Gravity (API) 58. 3 58. 2 Color (Saybolt) +26 +26 Color (Saybolt, after 5 hours exposure to sunlight) +25 +25 Doctor test Sour Sweet Copper in gasoline. Nil Nil Mcrcaptan sulphur percent.. 0. 040 7 Nil Copper strip test (3 hours at 122 F.). Good Good Oxygen stability minutes 580 750 Pounds Powdered CllSO4.5H2O 208 Powdered NaCl 625 Asbestos (Johns-Manville Co. No. 'I-RF' asbestos floats) 167 The mixture thus prepared was allowed to age and react for 48 hours, in the presence of a slight amount of added moisture (about 1 per cent). After aging, the material was placed in the system in the presence of previously sweetened gasoline, and the mixture was agitated at a temuously at'a temperature of 135 F. and at the rate of 50 bbls. per hour, until the moisture content of the solid treating agent was reduced to 0.75 per cent. The charging rate was then increased to bb1s..of gasoline per hour, and moisture was introduced in such amount as to maintain the moisture content of the treating agent substantially constant. A gauge pressure of 30 lbs. per square inch was maintained throughout, and air was continuously introduced at the rate of approximately 5 cubic feet (measured at 60 F. and 14.7 lbs. .per square inch) per barrel of distillate charged. Fresh treating agent was added from time to time.

In the claims hereinafter made, the term oxygen is intended to denote not merely pure oxygen itself, but also oxygen as existing in air or other oxygen-containing gas.

While we have set forth and described our invention hereinabove with reference to numerous operating details (some of which are in accordance with inventions disclosed in the other copending applications referred to herein), and with reference to specific operating examples, our invention may be variously practiced and embodied within the scope of the claims hereinafter made. h

What we claim is: v

1. In a process for sweetening sour oil by means of a solid and substantially dry treating agent comprising a solid substance capable of ionizing to give cupric ions and chloride ions, maintaining a continuous cyclic flow of said solid agent in suspension in oil through a sweetening'zone, a stabilizing zone, and a separating zone, continuously introducing sour oil and oxygen into said sweetening zone, and continuously separating and removing treated oil from the cycle at a point where the oil in the cycle is sweet and free from oil-soluble cuprous chloride and cuprous mercaptides.

2. The process of sweetening sour hydocarbon oil containing mercaptans which comprises passing a mixture of said oil, oxygen, a solid substance capable of ionizing to give cupric ions and chloride ions, together with a substantially inert solid carrier and water in an amount insufficient to produce a separate aqueous phase, through a sweetening and regenerating zone wherein the mixture is intimately commingled to simultaneously sweeten the oil and effect partial regeneration of the treating agent, thereafter subjecting the mixture to continued intimate con tact in an enlarged stabilizing zone for a sufiicient period of time to effect substantially complete regeneration of the treating agent in the presence of the sweetened oil, and then separating and removing treated oil from the treating agent at a point where the treated oil is free from soluble cuprous chloride and cuprous mercaptides.

LESLIE U. FRANKLIN.

WALTER H. WEEKS.

- perature of from to F. for about five

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