US2284272A - Process for sweetening light petroleum distillates - Google Patents

Description

May 26, 1942. L. U. FRANK|.|N ErAL 2,284,272

PROCESS FOR SWEETENING LIGHT PETROLEUM DISTILLATES Filed July l2, 1939 2 Sheets-Sheet l WTER 0R ST HM LESLIE UFRHNKLIN WALTER H. WEEKS JACK W. *HARRIS May 26, 1942. 1 UQ FRANKLIN v|51- AL 2,284,272

PROCESS FOR SWETENNG 'LIGHT PETROLEUM DISTILLATES Filed July l2, 1939 2 Shee'lLS-SheeI 2 Syvum/bows LESLIE UTRANKLIN WALTER Hwfxs JACK w. HARRIS Patented May 26, 1942 l V PROCESS FOR SWEETENING LIGHT PETRO- LEUM DISTILLATES Leslie U. Franklin, Walter H. Weeks, and Jack W. Harris, Port Arthur, Tex., assignors to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Application Jul-y 12V, 1939, Serial No. 284,117

12 Claims.

Our invention relates to sweetening sour hydrocarbon oils, more particularly light pe-V troleum 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 Vsulfur impurities, such as mercaptans, t0 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 toV improvements vin what is known in the petroleum art as copper sweetening,V i.V 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 ionizing to form cupric and chloride ions, for example, cupric chloride, together with a substantially inert solid carrying agent.

The earliest proponents of copper-sweetening processesreferred, in the main, to twogeneral types of processes,V i. 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. Y v y Y In processes wherein the oil is treated while in the liquid phase, it is now generally conceded that sufficient 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 so-called percolatiom type processes have not proved commercially successful inlthetreatment of cracked distillates and other oils containing substantial amounts of potential gumand color-forming constituents. The oxygen stabilities of suchV 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. y

A third type of process, known as the slurryfullers earth, adsorbent clay Vor the like, and the if independent aqueous phase.

sweetened gasoline is finally separated and rey moved.4 A limited amount of moisture must be present, but processes of this type do not give rise to serious corrosion problems; there is no i' The prior art slurry-type processes have resulted in littlerv o r no ccmmercialadoption, except vpossibly with respect to certain Aoilsl presenting little orno sweetenirigdifiiculties. Among the factors contributing to this, we believe,were the following:

Y (1) Bad eiects on oxygen stabiliti'es of the oils tested; caused by operation'in such manner as to leave oil-soluble copper in the" oil, plus the diiculty-of removing the same many cases.

(Process features which make it possible to overcome this diiculty are set forth and claimedin the copending application of Leslie U. Franklin and Walter H. Weeks, Serial No. 284,116, filed concurrently herewith.) A Y (2) Thevuse of highly adsorbent solid carrying agents, such as fullers earth, claysand the like. (The use of non-adsorbent, but absorbent, nonpolymerizing, nely divided asbestos in this type of' process ishighly advantageous, as set forth and claimed in the copending application of Lesi (3) Improper regulation and control of moisture content and texture of the solid sweetening agent.

We have discoveredthat certain hitherto unknown considerations affecting factor (3) above are of the utmost importance in maintaining emcient and uniform operation. n

' Thus, in one prior art` process, the moisture content of the treating agent is initially low, but gradually increases to around 9 per cent, followed y by removal of the agent, re-drying it and re-use as before. g f

We have discovered that operation in this manner does not produce satisfactory results, for a Y number of reasons, and that variation in water f content oi the chemical treating agent (other v I conditions such as the nature of thevoil treated, the character of the carrying agent, the type of apparaus used and the like remaining the same) must be held within far narrowerlimits during normal operation in order to achieve Ysatisfactory results.

In a system wherein the moisture content continuously varies'over a wide range, high efliciency is attained only at relatively infrequent intervals and for brief periods. Moreover, the diculty tends to be cumulative in effect, because, when Y advantages are overcome, and more satisfactory operation isachieved than has heretofore been realized.

Operating in all cases within the limits Vof from 0.5 per cent to 9.0 per cent moisture'content, or in the case of asbestos as a carrying agent, between limits of from 0,5"pr cent to 7.0

per centHzO, we do not allow the -moisturecontent of the treating agent to varyover thisl enrange of moisture variation should be carefully controlled for good results.

Moisture is, of course, added when and as necessary. strikingly enough, such moisture addition is often necessary even when operating both at temperatures high enough to remove moisture as formed and Aat lower temperatures; temperature alone does not entirely govern the tendency of the treating agent to gain or lose in moisture cohtent, respectively.

Thus, we have found that if the solid treating agent is efliciently ground as it recirculates in the system, a higher average moisture content,

' with correspondingly llower operating temperatire range, but confine it as far as possible to.

an extremely limited range. More specifically,l

tures, can be' carried and is in fact desirable. The same oil, which without efficient grinding requires an average moisture content in the y treating agent of around 0.8 per cent, and mainwe never permit the maximum andfminimum moisture contents at anyntimes vduring regular continuous operation to yary over -more than a 2:1ratio.,; I

The moisture contents referred to herein represent percentages of H30 bynwl-eight,on a basisyV of the entire mass offsolid: treating agentV'A(including the carrier) A.Tnusgwehave found "that in mcstffuu-sizea commercial apparatus,V withcertain exceptions referred Yto hereinbelow, it is necessaryto maintain them'oisture content at a verylow point.

In many actual instances, ;variationof moisture content .over a rangewider than from A0.5 per cent 1501.0 per cent Vresults in-a serious loss of efficiency; thegstage at whichfthe desired texture ofthe solid Atreating-agent is destroyed isY rapidly, reached in such cases if the variation in moisture content is allowed to exceed the range noted., especially on thehigh side. In other cases.

a rangeof from n1.0 to;2.0 per cent, ory from 3.0.

y gasoline product.

provided in the cycle. VIn one specific case, for example, we found that under these conditions (using asbestos as. the carrying agentithe permissible variation, at least aftervan initial or conditioning period to be referred to'hereinbelow, was from 3 to 6 per cent. Drier material resulted in poor regeneration, withV a greatly augmented tendency to leave oil-soluble, insuiiiciently regenerated cuprous compounds in the final Higher moisture Vcontent resulted in impairment of the texturer of the sweetening agent, which in this casewas maintained in a highly effective and highly fiocculent ture percentage scale varies somewhat las be-Y tween individual carryingl agents.

ReferringV again to the instances mentioned, it may be observed that in many cases the more diicult it is to oxidize the mercaptan content of the oil, the lower will be the actual moisture contentk carried.

Regulation of Ythe moisture content is Yaccomcondition. It may be noted at this point that we always aimto maintain the agent in a occulent or semi-occulent condition, as we have found that best results are secured only when this condition is. reached or approached. With excessive variation in moisture content, vit is impossible to achieve this highly desirable and important result. n l Thev exact causes underlying this particular necessity are not so fully understood as would iustify us in predicating our invention uponany particular-chemical or physico-chemical theory,

and it is. unnecessary forus to do so. We may stateVhowever, that we have discovered that a f high state'of operating eiciency can only be oband down within the'narrow range noted'. On,

` the] contrary, we maintain as uniform a moisat times. In any given operating. instance, the

tained when the chemical treating agent is maintained throughout in a proper physical condition, or-texture, i. e. in a fiocculent or semi-.occulent condition, and that, while the average moisture content effective to give the optimum texture willvary considerably in different cases, too wide a variation of moisture content in any individual case will make it impossible` to maintain the desired texture over commercially satisfactory periods of time. i

We have referred hereinabove to an initial operating period or conditioning period. During .such period the moisture content may sometimes lncrease from a point considerably below the minimum moisture content subsequently maintained, or itrnay decrease from a point considerably above the desired maximum. 'Ihis fact is intimately connected with another feature of our-invention, which We shall now proceed to set forth. l y Y V*We have observed that the treating agents of the. prior art were strongly hygroscopic in character, and that it was very diicult to maintain the desired uniformity of moisture content when they were used. We have discovered, however, that a highly advantageous and effective and less inherently hygroscopic sweetening agent may be prepared by mixing cupric sulfate, NaCl or NHiCl and finely divided asbestos, aging the mixture in the presence of some moisture, and then drying the mixture down to around 0.5 to 1.0 per cent H2O content at a temperature of about 95 to 100 F. or higher. Drying at temperatures substantially below 90 F. is not so effective. When the treating agent has once been treated in this manner, it is, for some reason not fully understood, far less hygroscopic in subsequent operation; that is to say, it does not possess the strong tendency to accumulate moisture in the system that has been characteristic of prior art materials. Hence, such pre-conditioned material aids in carrying out our process, in which excessive variation in moisture content is avoided.

Here again, we do not wish to limit ourselves to any particular theory of operation. The following facts may, however, be significant:

(l) This feature of our invention relates only to mixtures containing Na2SO4 and NaCl;

(2) The decomposition point of Na2SO4.7HzO is garound 65 F.; that of the higher hydrate, NazSO4.10l-I2O, is around 92 F.; Yand Y (3) The addition of anhydrous Na2SO4 to a treating agent comprising fairly dry Na-2SO4 and NaCl (enough water being present to form hydrates) tends to have a strongly dehydrating effect.

It may therefore be that the absence of both the heptaandA deca-hydrates, or the presence of anhydrous Na2SO4, exerts a marked depressing effect upon the water-accumulating or hygroscopic tendency of the sweetening agent, and this in turn may account for the fact that drying at temperatures below 90,-100 F. has not been found effective, while drying at higher temperatures has. But, whatever the theory, this preconditioning step is definitely of value.

When temperatures of 100 F. or more are maintained in the system, kit is not absolutely esj sential that the treating agent be dried prior to use in the process. Such drying or preconditioning takes place reading in the system itself, under such conditions. Moisture should not Abe added, however, until the moisture content of the agent is down to 0.5 to 1.0 per cent; thereafter moisture is added, when and as necessary to maintain the uniformity referred to above.

Where lower temperatures are used (or even where higher temperatures are ,.used, if desired) the partial drying step may be carriedV out prior to adding the chemical agent to the system, and preferably after aging the mixed chemicals and absorbent at a relatively high moisture content, as for example in a humid atmosphere. Such aging is useful in order to complete the reactionV forming CuClz; the presencev of moisture accelerates the rate at which vthe reaction approaches its equilibrium. Aging is therefore best effected prior to drying,` whether suchV drying y moisture content of the treating agent may be operation, we may follow any of the followingl increased to some extent (after the partial dehydration step set forth above) prior to putting it into `the system, Ias for example by ex-V posure to humid atmosphere, by steam treatment, or by spraying it with water. The amount of moisture so added need only be such as to bring the moisture content of the treating agent to a point lying within the desired range.

If desired, however, the partially dried agent may be simply put into the system, moisture being added in somewhat larger amounts than are necessary later, until the moisture content of the treating agent in the system is within the desired range.

Thus, where a low average moisture content (below 2 per cent) is to be maintained in the procedures:

(l) Dry the sweetening material-at a tem` perature of F. or higher-down to a moisture content of from 0.5 to 1.0 per cent prior to putting it into the system;

(2) Introduce the aged material intorthe system without pre-drying it. and effect the drying step in the presence of sweet oil, prior to charging sour oil to be sweetened;

(3) Introduce the aged material into the system without pre-drying it, and reduce the mois- Vture content down to 0.5 to 1.0 per cent in the presence of the sour oil being charged; or

(4) A combination of (2) and (3) above, i. e; drying part ofthe way with sweet oil and the rest of the Way in the presence of the sour oil to be sweetened.

When higher average moisture contents (above 2 per cent) are to be maintained in the system, we may use any of the following procedures:

A (5) rFollow (l) above, and then raise the moisture content to the desired point before intro- 'ducing the material into the system;

(6) Follow (1) above, but raise the moisture content after introducing the material to the system, in the presence of sweet oil, prior to charging some oil to be sweetened;

('7) Follow (1) above, but raisevthe moisture content in the presence of sour oil being sweetresults that at some time prior to or during the initial phases of operation, in the moisturecontent of the sweetening material be at least temporarily reduced tofrom 0.5 to1.0 per cent, by drying at a temperature of about 100 F. or higher. Y

It will be obvious that some of the procedures set forth above involve a preliminary sweetening or conditioningstage. Unfavorable results do not, however, occur during this period, if not unduly prolonged, for reasons which we shall now explain as fully as possible.

We have stated hereinabove that, when the range is, say, from 3 to 6 per cent moisture content, then, in the later stages of the operation, reduction of the water content below 3 per cent tends to cause retention of oil-soluble copperk in compound formed on regeneration, other thanY CuClz, may actually be the effective sweetening agent itself in the later stages, though somewhat less rapid in action than CuClz in most cases. But, during the, initial or conditioning period following introduction of the sweetening agent into vthe system, even when some gasoline is being charged to the system during this period,

the concentration of'CuClz inthe agent is relatively high, and the agent is therefore in a highly active'condition. Consequently, variation i in moisture content is not as harmful at this time as it is lateron. Y Various methods of supplying moisture to th system, when and as required, maybe employed. Thus, it may be introduced directly-'to the treating zone, or in the air or oil supplied to the system. HC1 may also be added. We have found, however, that addition of HCl (the purpose of which is to maintain the copper compound largely in the form of CuCl2), is rendered more difficult when the operating temperatures are high, as for example at 1009 F. orhigher. At lower'operating temperatures, of, say, 60 to 70 F., and in the presence of relatively larger amounts of Water,

cent and 'treating temperatures usually ranging from 100V F. to 150 F., or even somewhat higher, are carried. In this type of operation the amount of cupric chloride (CuClz) actually maintained in the system, except at the start, and for brief periods following the addition of any large amount of fresh chemical, is normally very'low. On the other hand, Vwe have operations in which lower treating temperatures of, for example, from 60 to 70 F., or in any event below 100 F., are carried, and the average moisture contentl of the treating agent is maintained at a relatively high point, for example, from 3 to 6 per cent. In this type of processthe amount of CuClz present as such is considerably higher.

Naturally, many operations will lie intermediate between the two types of operations just referred to. Whether the operation requires relatively high temperatures and low average moisturev content, or relatively low temperatures and relatively high average moisture content, is largely determined in each case by the texture of the solid treating agent, and, fo'r that reason, by

HC1 is more easily added, andthe amount of CuClg in the system may be maintained at a relatively high point.

From several standpoints, there are advantages in maintaininga relatively high average moisture content and a'relatively high CuClz content in the treating agent. But it must be emphasized that mere addition of WaterV will not necessarily produce the desired results. On the v contrary, in many cases attempts to maintain high `average moisture content result most unfavorably. The explanation of this lies in part in the necessity for maintaining the solid treating agent in a proper physical condition or texture. Prior workers in this field do not appear to have recognized the sensitivity and narrow range of Vtexture permissiblelnor to have suggested adequate means or steps for maintaining it. v

From time to time, fresh sweetening material may be added to the system, to replace thatlost mechanically or* otherwise. fresh sweetening `material in relatively small We prefer to add quantities at frequent intervals, approaching Y continuous addition, `rather than to add it in largequantities at infrequentperiods, In this way, we avoid excessive variation of conditions in the system which would be incident to the addition of large quantities at any one time. It should not be inferred, however, that it isV necessary to add fresh treating chemicals in an amount anywhere near thatY amount required to react stoichiometrically with the amount of mercaptans present'in the oil charged.

It will be apparent from rthe above that 4o ur process is capable of beingembodied in two fairly distinct types of operations. -On the one hand, low moisture contents ranging from 0.5 to 1.5 per the presence or absence of mechanical conditioning means. But, except for relatively briefv periods following initial introduction ofthe solid treating agent into the system? (where the moisture content of the agent, as added, mustbe adjusted to that desired to be maintained in the system), the Vlimited range of moisture variation refterred to above must be maintained throughou Y By controlling and regulating the moisture content of the solid treating agent, as set forthabovc, conditions are so maintained as to favor maintenance 'of the treating agent in a proper physical condition or texture, that is to say, in a flocculent or semi-occulent state. But, in almost all cases, it will be necessary, in order to achieve low-temperature operation and relatively high moisture content, to provide means for mechanically conditioning the solid treating agent in the system.

Mere agitation or mere passage of the slurry througha recirculating pump is not enough. This does not mean thatV our process requires more than mere agitation or pumping for good results; it does mean that with such expedients alone we have found it necessary in almost all cases Vto maintain the treating agent at a low moisture content, not exceeding 2 per c ent at the most.V 'l

' 'I'here are advantages in maintaining a somewhat higher average moisture content, when this can be done without destroying the desired texture of the treating agent-one is the fact that the CuClz content of the treating agent can bel Vmeans the more. truly flocculentwill be the condition of the solid treating agent. It might be expected that passing a suspension of asbestos and the solid chemical or chemicals used, in oil, through an eicient grinder would tend to produce a very finely divided material and thereby to destroy whatever flocculentcharacter the suspension possessed. The reverse is actually trueV in copper-sweetening processes of the slurry type. The more'eflcient the grinding means.

`2,5284,27:.2 Athe more iiocculent is the character of the suspension, and the more moisture the suspension can tolerate without losing its flocculent character or texture. Thus, low-temperature, highaverage-moisture-content operations normally require and to a large extent depend upon the use of highly eflcient grinding means; with less efcient grinding means, it is usually necessary to hold the moisture content at a relatively low point, with the temperature correspondingly high.

This may be due in part to the fact that very eflicient grinding tends to exert a'm'echanical dehydrating effect upon the solid treating agent. Also, grinding tends to prevent accumulation of gummy or resinous matter on the individual suspended particles. Whatever be the reason, grinding does assist greatly in maintaining the desired f'locculent or semi-occulent texture referred to, especially in the presence of more than 1 per cent moisture.

When all factors are such as to permit the use of relatively high average moisture content and relatively low operating temperatures, the most efficient and advantageous results are secured. In this type of operation the content of cuprc chloride in the treating agent tends to remain fairly high, with consequent improvement in operating eiciency; regeneration is improved and made more thorough, the tendency toward retention of oil-soluble copper in the treated oil is reduced, and the consumption of chemicals over extended operating periods is also reduced. sweetening takes place more quickly and regeneration is also improved.

The grinding means may be located at various points in the system, as, for example, in the treating zone itself or in the recirculation line which conveys the regenerated treating agent from the separating Zone back to the initial treating zone, or both.

We have also found that if the treating zone is so constituted as to secure a turbulent, cyclic ow of oil and suspended treating agent within the treating zone itself, highly efficient sweetening and regeneration are secured, and apparatus providing for such turbulent, cyclic flow is de-Y scribed hereinbelow.

In any event, the process is carried out by comingling the solid treating agent with a flowing stream of sour oil to be treated, in the presence of oxygen (supplied Vas such or in air or other oxygen-containing gas), and permitting the mixture thus formed to ow in essentially concurrent fashion through a treatingl zone, wherein sweetening and regeneration of the treating agent proceed more or less simultaneously and concurrently. The mixture is then transferred to a separating zone where the flow is suinciently quiescent to permit the separation and withdrawal of the treated oil, free or substantially free from suspended treating agent. The latter, still in suspension in oil, but as a far more concentrated suspension or slurry, is then re-circulated back to the initial contact zone.

As set forth and claimed in the copending application of Leslie U. Franklin and Walter H. Weeks, Serial No. 284,116, led concurrently herewith, it is important not to effect separation of the treated oil from the suspended treating agent at or immediately after that point in the system Where the oil first shows itself sweet to the doctor test, but to maintain the oil undergoing treatment and the suspended treating l,'55 zione until the oil is free from "cuprous chloride and cuprous mercaptides, and contains not more than a slight trace of copper in any form.

With regard to the composition of the treating material itself, We have found that the best results are secured by forming a mixture as follows:

Parts by Weight CuSO4.5H2O 1 NaCl Y 2 to 4 (preferably 3) Asbestos 0.5 to 1 As dis-closed in U. S. Patent No. 744,720, the chemicals employed in the 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.

As pointed out in application Serial No. 285,636, lled July 20, 1939, increasing the amount of asbestos in the mixture above about 20 per cent is neither necessary nor particularly effective. Amounts of asbestos in excess of about 20 per cent simply represent an unnecessary excess of asbestos above and beyond that amountnecessary to serve as an effective carrying or supporting agent.

The same conditions apply Yto mixtures containing fullers earth or the like inthe place of agent undergoing regeneration in contact through a sweetening zone and a subsequent stabilizing asbestos, except that asbestos is preferable from many standpoints and requires the presence of somewhat less moisture than whenhighly ad-v sorbent carrying agents are used.

As aforesaid, the treating agent, after being initially prepared by mixing Ythe Vabove ingredients in the proportions noted, should be preconditioned, either before or aftervadding it to the system, by partial dehydration, preferably after permitting the mixture to age for some time.

By operating in accordance with our invention, we have been able to secure successful continuous operation on a full commercial scaleover extended periods of time, sweeteningV a wide variety of distillates, including both straight-run and cracked gasolines, of varying degrees of sourness Apparatus and processing costshave been reduced, and the nished oils have been of good quality.

In addition to the objects and advantages `specifically referred to hereinabove, our invention has for further objects such additional operative advantages and improvements asmay hereinafter be found to obtain.

In order that our invention may be fully set forth and understood, we now describe, with reference to the drawings accompanying and forming a part of this specification, various preferred forms and manners in which our invention may be practiced and embodied, without however limiting our invention to the details of such exemplications as are described hereinbelow, except as in the claims hereinafter made. In these drawings, y

Fig. l is a more or less diagrammatic elevational view of apparatus for sweetening sour petroleum distillate in accordance with our invention; and

Fig. 2 is a similar view of an alternative form of a portion of the apparatus illustrated in Fig. 1.

Similar reference numerals designate similar or corresponding parts in both figures.

Referring now to Fig. 1,4 sour oil to be treated enters the system through a pipe I and is delivered by a pump 2 through a pipe 3 and a distributor 4 into a vessel 5. A solution of alkali,

such as a per cent aqueous solution of caustic soda is mixed with the' oil entering ther-vessel 5 by means of a pump and a valved line 1. This alkali wash removes HaSfrom the oil, to the extent that the-same has not been removed by prior refining steps. In the -vessel 5, separation takes place, the spent washing solution being withdrawn through a valved line 8 while the separated oil passes through a `valved line 9 into a second treating and separating vessel I0. Water is introduced into the oil passing-to the vessel I9 by means of va pump II and a valved line I2, the purpose being to remove such quantities of alkali solution as may remain in the oil leaving the vessel' 5. After separation in the vessel I0, the wash water is removed through a valved line I3, while the treated oil passes through a line` I4 into a nections for introducing and removing a suitable uid heating medium, such as steam.

The heater I9 may or may not be operated, as desired, depending largely upon the mosture content which it is desired tohmaintain in the subsequent treating stage. Temperatures above 160 F. are rarely if ever necessary in any event, and

the heating should never be carried to such extent as to cause substantial vaporization of the oil under the pressures employed.. We prefer to maintain the oil throughoutthe system under a moderate superatrnospheric pressure ranging from, for example, 10 to 60 pounds per square inch. Such pressures assist in maintaining the air or other gaseous oxidizing agent (subsequently added) in solution inthe oil throughout the treating and regenerating stage.

The oil leaving the heater I 9 passes through a line 2li into the lower part of a treating `vessel or tower 2l. Dry air is also introduced along with the oil. In the instanceshown, such air enters the system, under suitable pressure, through a line 22, having a regulating valve 23 and wherein Vare located one or more drying towers 24. As is true ofthe drying chamber I5, these drying towers -24 may be internally provided with beds of rock salt, calcium chloride or other drying agent.

Various forms of treating apparatus `may .be employed, but that illustrated in Fig. 1 has been found practical and useful. As shown, the tower 2I is provided with a plurality of baiiies` 25 and with agitating means comprising a plurality of blades or paddles 26 mounted onfa vertically disposed shaft 21, which is in turn driven by a motor 28.

The oil to be treated, together with suspended solid treating agent, usually comprising a mixture of the reaction products of copper sulfate and sodium chloride together with finely divided asbestos, or other suitable carrying agent, which is introduced through a line 29 in the form of a relatively concentrated slurry in oil of the same character as that being treated passes upward through the tower 2I. During its upward ow through the tower 2I, the mixture of oxidizing gas, oil and solid treating agent is subjectedto intimate contact and agitation. Sweetening vof Any moisture accumulatingv in the .under the inuence of the oxidizing gas. The i latter is usually in solution in the oil, as aforesaid. l Y

The mixture reaching the top of the tower 2I then passes `through a line 30 into a separating vessel 3|, where, by reason of relatively quiescent flow, the solid treating agent is caused to separate by gravity. from the main body of oil undergoing treatment. Treated oil, free of suspended solid matter, is removed by means of a Weir device 32 and an outlet line 33. The treating agent, in the form of a relatively concentrated slurry in treated oil, is withdrawn from the bottom of separator 3| through a valved outlet line 34A and returned tothe bottom of the treating vessel 2I by means of a pump 35. Valved lines 36 and 31 are provided on the suction and pressure sides of the pump V35,- respectively, for the purpose of introducing and removing solid treating agent (in slurryform), when and as desired.

In the instance shown, the slurry separated at the bottom of the separator 3| and recirculated into tower 2I, is passed, before being reintroduced into the latter, through a suitable grinder 38 located in the line 29. The function and purpose of the grinder 38 have been set forth hereinabove, where it'has also been stated that various types of grinders may be employed. It should be emphasized, however, that the desired function of suchjgrinding means is not Arealized by merely `passing the slurry through an agitating or mixing device or through a pump; a definite grinding action is essential for maintenance of the suspended treating agent in the Vmost advantageousv physical-conditions, i. e., in a occulent or semi-flocculent state.

Suitable vents40 and 4I are provided at the tops of the tower 2| and the separator 3l, re-

spectively. The vent 40 is normally kept closed lbut is provided with a safety valve suitably adjusted in accordance with the pressures to be maintained in the system. The vent 4I is provided with a back-pressure-regulating valve,l and leads to an absorber (referredto hereinbelow).

Where the addition of moisture in regulated quantities is desired, this may be provided for by withdrawing a portion of the treated oil leaving the separator 3I through a line 42 leading to a pump 43, which in turn delivers it through a line 44 `and settling device 45. Water or steam is introducedahead of the device 45 vthrough a valved line 46. A l

It is advantageousto introduce such moisture as may be desired in the main treating system in the form of a foggy suspension of water in hydrocarbon oil, preferably a sweetened oil of the same character' as that undergoing treatment. `The specific means illustrated in Fig. 1 for-moistureaddition is `adapted to operate in this manner.

Any excess `of water separating out of the oil in the device 45 is withdrawn therefrom through a line 41, while Vthe moisture-containing oil is returned through a line 48 into the treating tower 2I. Alternatively, this oil' may be comingledwith the sour `oil prior to its entry into the treating tower 2I.

That portion ofthe treatedoil not employed for the purpose of furnishing a carrying Amedium for introducing moisture into the system, as described-passes througha line 49 'toan aftertreater 58. Various types of after-treatment may be employed, but in the instance shown, the after-treater 50 comprises a vessel adapted to contain one or more beds I of salt, or a mixture of salt and sand, which may or may not be treated with copper compounds or other copperremoving material prior to use. Moisture accumulating at this point in the system may be removed from time to time as necessary, through a valve line 52.

As set forth and claimed in the copending application of L. U. Franklin and W. H. Weeks, Serial No. 284,116, led concurrently herewith, the operation of the treating unit described is so conducted as to maintain the oil undergoing treatment and the treating agent in contact through a sweetening zone and also through a subsequent stabilizing zone, until regeneration has been eifected to an extent indicated by freedom of the oil from cuprous chlorides and cuprous mercaptides. Nevertheless, slight traces of copper compounds, such as copper naphthenates and the like, may persist in the oil leaving the separating zone. The purpose of the aftertreater is to remove such traces, inasmuch as amounts of copper compounds as low as one part or even less per million parts of oil are highly deleterious, and also to oifset any inadvertent or accidental loss of copper compounds from the heating system, through occasional unavoidable entrainment in the oil leaving the separator The oil leaving the after-treater 50 passes through a line 53 into an accumulator 5d, from which sweetened oil is withdrawn into a valved line 55. Any air and vapors separating at this point are preferably passed through a line 56 into an absorber 5l where they are scrubbed to remove valuable hydrocarbon constituents by means of absorbent oil introduced through a line 58. The vent line lil also leads to the absorber 51. The scrubbed vapors leave the absorber 51 through a line 59, while the enriched absorbent oil is removed from the system through a line 60.

The desired pressure in the system is regulated by means of the pump 2, and the settings of the valves 40 and 4I and the valves located in the various outlet lines.

In the somewhat modied form of apparatus illustrated in Fig. 2, means are provided for maintaining a continuous cyclic flow in the initial treating zone.

As shown in this instance the treating vessel 2| is provided with an externally disposed pipe or sweetening tube 10, communicating at its upper and lower ends with the upper and lower portions of the tower 2l respectively, and provided internally with impelling and agitating means 'Il driven by a motor 12. The sour oil enters through the line 20. The-slurry recovered from the bottom of the separator 3l is delivered through the pipe 29 to the tower 2|, and passes down through the tube with the sour oil, and then upward through the tower 2 l.

As in Fig. 1, a grinder similar to that shown at 38 therein may be provided in the line 29. However, in the instance illustrated in Fig. 2, the grinder 38 is located elsewhere, as shown. Slurry is removed from the bottom of the treating vessel 2l through a line 'l5 wherein is located a circulating pump 16 and the grinder 38, After passing through the grinder 38 the slurry thus withdrawn from the tower 2l is returned to the tower 2| through a line 11. Preferably, the pump '16 and grinder 38 are operated continuously throughout the entire operating period, although it may in some cases be sufficient to operate these I conveniently located at or near the bottom of the treating tower 2|.

Operation of the system as described above is conducted in accordance with the disclosure set forth in that portion of this specification immediately preceding the description of the drawings, i. e. to maintain uniformity of moisture content and texture of the solid treating agent within the system, and in accordance with other considerations set forth.

The following specific operating examples will further illustrate the operation and advantages of our process:

Example I In this example, we sweetened a sour, acidtreated re-run gasoline produced by cracking West Texas crude. Analyses of the gasoline, before and after treating in accordance with our invention, were as follows:

The solid treating agent used was initially prepared by mixing 416 lbs. of powdered cupric sull fate pentahydrate, 1250 lbsof powdered sodium chloride, and 334 lbs. of nely divided asbestos. This mixture was allowed to age and react for 48 hours in a humid atmosphere, the moisture content running up in excess of 5 per cent. The aged mixture was then heated on a hot plate for about 6 hours at a temperature of from 175 to 200 F., the moisture content falling to 0.6 per cent. This partially dehydrated material was then introduced into the apparatus, (substantially as illustrated in Fig. 2), together with sweet gasoline, and agitated and recirculated for about three hours at F., to assist in improving the texture of the solid treating agent.

Moisture-containing sweet gasoline was then introduced into the system, until the moisture content of the treating agent reached 1.0 per cent. The actual treating operation was then commenced, .sour gasoline being introduced at a temperature of 80 F. at the rate of 400 barrels per hour, and air at the rate of 2000 cubic feet per hour (measured at 60 F. and 14.7 lbs. per square inch). A gauge pressure of 30 lbs. per square inch or a little higher was maintained throughout the run.

Large quantities of gasoline were treated in this run, which extended over a long period, and the results given above are typical and characteristic.

Example II In this example, analyses of the sour gasoline treated and the gasoline after treatment were substantially as shown in Example I above. Apparatus similar to that illustrated in Fig. 1 vwas used.

The solid treating agent was prepared by mix-V ing the same amounts of Vingredients in the same proportions as in Example I, lbutin this case the aged material was dehydrated from about 6.0 per cent down to 2.0 per cent by agitation in the system in suspension in sweet gasoline at a temperature of 135 F. y

Some gasoline was thenintroduced at a rate of 200 barrels per hour, at a temperature of 135 F., `the gauge pressure being 30 lbs. per square inch, together with air inthe same relative proportion as in Example I. This initial stage was continued until the moisture content. of the treating agent fell to 0.5 per cent. Moisture was then introduced until the moisture content of the treating agent rose to 0.8 per cent, whereupon the oil charging rate was raised to 450 barrels per hour, and the amount of air supplied increased in proportion.

Throughout the remainder of the run, which f continued over a long period of time,emoisture was added as necessary to maintain the treating agent at an average moisture Vcontent of-0.8 per cent, and to avoid excessive variation therein, in accordance with our invention. Fresh quantities of treating material were added from time to time.

. Example III In this example, we treated a sour straightrun gasoline from West Texas crude. Analyses before and after treatment were as follows:

The sweetening agent used was prepared by mixing the following ingredients in the following proportions:

Parts by weight Powdered cupric sulfate pentahydrate 125 Powdered sodium chloride 375 Powdered asbestos 100 After ageing for 48hours in a humid atmosphere the mixture was dehydrated to 0.6 per cent moisture content. It was then suspended in sweet gasoline and impregnated with moisture until the moisture content rose to 5.0 per cent.

The sweetening operation was then started and sour gasoline charged at a temperature of 75 F., at substantially atmospheric pressure, and at a rate equivalent to those shown in the foregoing examples, (In this case, smaller apparatus was used, so that the optimum of oil charged per hour was correspondingly lower). Throughout the run, moisture was added at frequent but intermittent periods to maintain the average moisture content at 5.0 per cent, andthe maximum variation within limits of from 3.0 to 6.0 per cent. Some HC1 was added at one point to replace that lost from `the system. Air was also added, as in Examples I and II. 1

This experimental run was continued for 365' hours, at the end of Which time it was arbitrarily discontinued. The results throughout were entirely satisfactory, and at the end of the'run the solid treating agent was fully active, at though no fresh chemical was added at any time.

The highly successful results attained in this relatively smallfscale run were largely due to the fact that we had available at that time smallscale grinding means far more ei'licient than the grinding means which we then had available for larger-scale operation. Because of that fact. we were able to maintain the solid treating agent in a highly flocculent and efficient condition, with a vhigh CuClz content, yet at a relatively high averagemoisturecontent. But, under these conditions, as under others, regardless of the actual average moisture content maintained, excessive variation in moisture content, beyond the limits referred to hereinabove, has a highly unfavorable elect.

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 wehave set vforth 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 specic operating examples, our in- Vention may be variously practiced and embodied within the scope of the claims hereinafter made.

What we claim is:

1. The process of sweetening sour hydrocarbon oils containing mercaptans, which comprises passing a flow of said oil, oxygen and a suspended solid treating agent comprising (1) a substance capable of ionizing to give cupric ions and chloride ions and (2) a solid, substantially inert carrying agent, through a treating and regenerating zone, maintaining the average moisture content of the solid treating agent between 0.5 per cent and 9.0 per cent, and also regulating the amount of moisture present in the system so that the maximum water content of the treating agent at any time is never more than twice the minimum water content of the treating agent at any time.

2. A process as claimed in claim 1, wherein the carrying agent is finely dividedasbestos, and the average moisture content of the solid treating agent is maintained 'between 0.5 per cent and 7.0 per cent.

3. The process of sweetening sour hydrocarbon oils containing' mercaptans, which comprises passing a ow of said oil, oxygen and a suspended solid treating agent comprising a substancecapable of ionizing to give cupric ions and chloride'ions and a solid, substantially inert carrying agent; through a treating and regenerating zone, maintaining the average moisture content of the solid treating agent between 0.5 per cent and 9.0 .per cent, and also regulating the amount of moisture present in the system so that the maximum water contentof the treating agent at any timeis never more than twice the minimum water content of the treating agent at anytime, separating treated oil from the solid treating agent, and recycling the latter to the initial contact stage.

4. A process as claimedin claim 1, wherein the .supporting material comprises finely divided asbestos, andthe solid treating agent is maintained in an at least semi-flocculent condition.

5. A Aprocess as claimed in claim 1, wherein the solid rtreatiz'ig agent, after separation of treated oilgand inthe presence.` of oilnot separated therefrom, is subjected to grinding prior to recirculation.

6. A process as claimed in claim 1, wherein aV cyclic circulation of oil, oxygen and solid treating agent, without separation, is maintained in the contact stage, the mixture being subjected to mechanical grinding during at least a kportion of the cycle thus established.

7. A process as claimed in claim 1, wherein the solid treating agent, as added, comprises a mixture of cupric sulfate and a chloride selected from the class consisting of NaCl and NH4C1, together with an absorbent but not highly adsorbent solid supporting material in iinely divided form.

8. A process as set forth in claim 1, wherein the oil undergoing treatment is maintained at a temperature not substantially below 100 F., and the average moisture content of the solid treating agent is maintained at from 0.5 to 1.5 per cent.

9. A process as set forth in claim 1, wherein the oil undergoing treatment is maintained at a temperature below 100 F., and the average moisture content of the solid treating agent is maintained at from 3.0 to 6.0 per cent.

10. A process of sweetening sour hydrocarbon oils comprising forming a solid treating agent from cupric sulfate, a chloride selected from the class consisting of NaCl and NH4C1, and a finely divided absorbert but not highly adsorbent solid supporting material, initially drying saidr treating agent at a temperature not substantially below 100 F. to reduce its moisture content to 0.5 to 1.0 per cent, treating sour hydrocarbon oil with said .treating agent, and regulating the amount of moisture present in the system so that the y maximum water content of said treating agent at any time is never more than twice the minimum water content thereof at any time.

11. A process as set forth in claim 10, wherein the-initial drying step is effected prior to introduction of the treating agent into the treating system.

12. A process as set forth in claim 10, wherein said initial drying step is effected during sweetening and after introduction of the treating agent into the treating system.

LESLIE U'. FRANKLIN. WALTER H. WEEKS. JACK W. HARRIS.

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