US2205411A - Process of refining mineral oil - Google Patents

Description

June 25,l 1940. R. D. HcwARD PROCESS OF REFINING MINERAL OIL Patented June 2s, 1940 PROCESS F REFINING MINERAL Roscoe D. Howard, Tulsa, Okla., assignor, by mesne assignments, to Petroleum Research Corporation, Chicago, Ill., a corporation of Delaware Application October 22, 1937, Serial fNo. 170,452 13 Claims. '.(Cl. 196-28) This invention relates to a process of refining mineral oil.` Although the invention is applicable to the refining of mineral oil products generallythat are susceptible of being treatedin the man- Vl0 ing processes or from straight run distillation of crude petroleum.

Raw cracked distillates, produced by high temperature conversion of relatively high-boiling A mineral oil material into` lower-boiling products l for motor fuel of the gasoline type, are commonly characterized by a substantial content of deleterious gums or gum-forming constituents, as well as other objectionable impurities, including sulphur in various states of combination, and are '20 more or less deeply colored-` and evil-smelling in varying degree depending upon the source and character of the mineral oil material employed as cracking stock. In refining raw distillates of this type the problem is to eliminate these objectionable characteristics in order to prepare therefrom a nished merchantable product substantially free from gummy or gum-forming constituents, of good colorand odor, and sweet to the doctor test (sodium plumbite). Where the raw distillate to be'reiined is a sour straight run gasoline, the problem is somewhat less complicated because gum-removal is ordinarily not involved to any great extent, but the matter of effecting satisfactory sweetening economically nevertheless presents practical dimculties that are often serious. Moreover actual reduction of sulphur content is not ordinarily achieved by sweetening treatments heretofore available.

The importance of the problem above referred to is well known toioil refiners and is attested by the numerous methods heretofore proposed, and in some cases employed, in attempting to solve it; but it is also well known that even the best of the refining methods heretofore known falls short of solving it in a completely satisfactory manner, either because of failure to effect the desired rening or purification with the desired completeness or `because of operating 605118100 high to permit profitable operation commercially.

I A general object of the presentinvention is to provide an improved process for purifying or refining mineral oilproducts derived from petroleum, more particularly relatively low-boiling mlneral oil distillates of the type mentioned, for pro- '55 duction of refined commercial mineral oil products, especially of the motor fuel or gasoline type. A more specific object of the invention is to enable efiective and economical refining of 4raw cracked mineral oil distillates for removal therefrom of undesirable and contaminating impuri- 5 ties or constituents such as those above referred to, whereby to produce finished commercial products of the required high grade, especially gasoline that is substantially gum-free, doctor sweet, and of good color, odor and stability. 10

.According to the process of the invention, the crude or raw mineral oil product to be rened or purified is subjected to the required treating steps While it is wholly or to a large extent in vapor phase. In applying the process to produc- 15 tion of merchantable gasoline from a crude cracked gasoline distillate, vapors of the raw distillate, from whatever source derived, are'first subjected to treatment whereby those hydrocarbon compound constituents, including complex 20 sulphur-containing hydrocarbons, chiefly responsible for gum-formation and instability, are attacked selectivelyand so altered as to favor formation of heavy polymers which are Subsc-- quent'ly removed. This initial treatment, which 25 should be relativ'ely mild in order to avoid too far-l reaching action upon the whole body of hydrocarbons composing the'clistillate,- may be accomplished in various specific ways. In general, however, the process of the invention involves employing for this purpose analogen, particularly chlorine, and oxygen (as such, or in available form) conjointly, in' said initial treatment of the vapors; each of these agents being used in proportion relatively small as compared to the quan- 35 tity of raw distillate to be treated. Most desirably, the required small proportions of said agents, in gaseous condition, are mixed with hot vapors of the raw distillate, whereupon reactions 'ensue which are peculiarly effective in s'o altero in'g the character of the complex hydrocarbons sought to be attacked that formation. deposition and removal of gumv and tarry impurities, including complex polymers, as well as' rduction in sulphur content and sweetening of the hydrocars bon vapors, are remarkably promoted and facilitated.

After suiiicient opportunity has been given for the desired reactions to occur to a suiiicient ex-- tentin the initially treated hydrocarbon vapor 50 mixture, the mixture is then subjected, still in 'vapor phase, to treatment with suitable contact material or materials eective' to promote deposition and removal of gummy and tarry products and to accomplish sweetening. This part of the process is most desirably accomplished in a plurality of successive stages because itthereby becomes feasible to employ, more or less separately. contact materials respectively best adapted for gum removal and for sweetening, and in addition to provide for exceptionally economical operation, especially in regard to replacing or revivifying the contact materials employed. The contact materials employed should not only be capable of effecting gum-removal and sweetening,

but should also have the power of removing from the treated hydrocarbon vapors such of their content of chlorine (i. e. in chlorinated hydrocarbons) or hydrochloric acid as is not bound by or combined with the gummy and tarry deposits already referred to. In general, the contact materials comprise essentially metalliferous material having the capabilities hereinabove enumerated, and in at least one stage of the process, It must comprise metal in oxidized condition. Although the practice of the invention in its broader aspects is not confined to the employment of any one specific metalliferous contact material in particular, in respect either to the contained metal or to physical formation, it has been found that a zinciferous K contact material affords marked advantages for the purposes of the invention because of its superior effectiveness in performing al1 the before-mentioned refining and purifying functions.

` Another important characteristic of the novel process in its best embodiments is that it is continuous iny its operation, thus making for slmplicity and smoothness of operation or procedure with consequent economy in operating costs as well as uniformity of final product.

Other important features and' advantages of the invention will appear from the further detailed description to be given hereinafter for the purpose of affording a more complete understanding of the essential underlying principles of the novel process. In order that these underlying principles may be the more readily made apparent, certain particularly desirable practical embodiments of the invention will be referred to in giving said detailed description, but it is to be understood that this is merely by way of concrete illustrative example explanatory of the,

general principles involved and is not to be construed as in any way limiting the scope of the invention defined in the appended claims.

In a typical practical embodiment of the invention, the process is applied to the production of a finished gasoline of high grade from a raw motor fuel distillate obtained by cracking relatively heavy and high-boiling mineral oil by any known or suitable cracking process for conversion of such heavy oil into lighter and lower boiling products. Such raw distillate is strongly colored, ranging from light yellow to darkbrown, and is characterized by an odor that is unpleasaft and often very foul. It also shows a high gum content by the copper dish test, and its sulphur content is ordinarily much higher than is permissible in finished gasoline, a large part of this sulphur content being in complex combination with hydrocarbons in a form rendering the distillate very soun In this typical example, it will be assumed that the'raw distillate to be treated is supplied initially in the form of a. substantially cold liquid condensate'requiring heating and vaporization at the commencement ofy carbon vapors coming direct from a cracklngplant, or it may flow in hot liquid condition from a stabilizer wherein it has undergone treatment for elimination of certain very light hydrocarbon components in the nature of xed gases, and hydrogen sulphide.

The process can be carried out in apparatus plants or installations varying widely in structural details and arrangement. One type of such plant, the use of which will be assumed in the present illustrative example, is shown more or less diagrammatically in Vthe accompanying drawing and will be referred to for the sake of convenience and clarity of explanation in the following detailed description of how the invention may be applied to the refining of a raw cracked distillate of the character above mentioned. l

In the drawing, W Fig. 1 is a side elevation of a typical plain suitable for use in carrying out the process of tin invention, certain parts being shown broken away and in section;

Fig. 2 is a detail, in section and on an enlarged scale, of a. structural feature shown generally in Fig. 1;

Fig. 3 is a side elevation of another type oi unit for vaporizing and reacting upon raw charg ing stock, which may be used in place of the corresponding unit shown in Fig. l;

Fig. 4 is a side elevation of a type of reaction chamber sometimes desirable to employ; and

Fig. 5 is a section on line 5-5 of Fig. 4.

Referring to the drawing, and at first more particularly to Fig. l, raw cracked gasoline distillate enters the system through line I and is forced by charging pump 2 through line 3 and vapor-liquid heat exchanger 4, wherethe cold charge picks up heat from 'the hot vapors of the refined gasoline, thereby having its temperature raised, say, from.80 F. to around v240 F., for example. The raw charge thus preheated and partially (e. g. about 50%) vaporized is then conducted through line 5, the liquid-vapor mixture of hydrocarbons being discharged at 6 into vaporizer 1, which in this instance is shown as an ordinary horizontal shell still suitably supported as by brick setting 8 over lire-box 9 heated by burner means (not shown) in the usual manner. 'I'his shell still vaporizer may be 30 feet long and 10 feet in diameter, in a typical instance.

Through line I0, a mixture of air and chlorine gas also enters the vapor space of the still at 6., in company with the liquid-vapor mixture of hydrocarbons. The chlorine-air mixture is formed at the junction II of lines I2 and I3, through which air and chlorine are respectively supplied in quantity and proportion controllable by air control and meter assembly Il, and chlorine control and meter assembly I5. At I6 is represented a chlorine supply cylinder. 'Y Fig. 2 illustrates in detail one convenient form which the chlorine-air and raw gasoline inlet y assembly, indicated generally at I'I in Fig. l, may

take. The chlorine-air supply tube I0, termihating' in' discharge tip I8, delivers the chlorineair mixture at high velocity into the liquid-vapor stream of hydrocarbons before entry into the vaporizer, thus effecting a preliminary com- -mingling of the treating gases with the hydrocarbons. Since the vapor space above the liquid level Il normally maintained in the vaporizer is relatively large, ample further opportunity isv therein afforded Vfor the desired intimate and uniform commingling of the chlorine and air with hot hydrocarbon vapors, and for the preliminary breakingdowu or pre-treating action to occur to the desired extent.

Since it is sometimes necessary to clear accumulated matter from the discharge tip I8 of tube III, 4suitable provision is made for permitting this to be done without interrupting operation of the plant. As here shown, the tube I is arranged to be removable from inlet assembly I1 for purposes of cleaning its tip. The shutoff cock 20 has the usual passage 20, through which and through cooperating passage I1*l the tube I0 extends with a loose dt. A packing gland and nut 11b seal the point of entry of the tube into the upper end of the body of the inlet assembly. VWhen necessary to clean the discharge tip I3, the packing gland nut is loosened enough to permit pulling the tube I0 up until its lower end is above cock 20, which is then turned t0 close passage 11; whereupon the tube can be completely removed from the assembly.

The pre-treated (i. e. partially oxygenated and chlorinated) hydrocarbon vapors, in mixture with a small amount of nitrogen (from the air) pass from the vapor space of the still through vapor line 2I. In case it is desired further to promote thorough and'uniform commingling of the cracked distillate vapors from the air and chlorine prior to exit of the vapor mixture from the vaporizer, bafde means (not shown) may be provided in the vapor space, in such arrangement relative to the inlet 6 and outlet to vapor line 2| as to compel all the gaseous components to travel together by a circuitous path before reaching said outlet, thus also somewhat prolonging the period of pre-treatment.

Said vapor line 2I delivers the vapor-gas mixture into the lower part of a preliminary treating tower 22; wherein it intimately contacts a body 23 of contact material, in this instance metallic zinc in the form known as moss'y zinc. of such character as to promote precipitation or deposition of gummy' and tarry polymers. This contact material is supported on perforated plate 24 located somewhat above the point where the vapor-gas mixture enters the tower on a tangent, asindicated at 25. In a typical instance, this tower, which serves as a knock-ou box or separator for removal of most of the heavy polymers from the vapor gas mixture prior to its further treatment, may be 3 feet in diameter and 8 feet high, and the body of mossy zinc supported on perforated plate 24 maybe approximately 3 feet thick vertically.

A certain amount of relatively heavy redux oil, derived from a later stage of the process as will be presently explained, is introduced into tower 22 in such manner as to contact with the vapors as they pass through the mass of mossy zinc, and thus to aid the action of the zinc in causing a major portion of the heavy polymer tars and gums carried by the gasoline vapors to drop out. Such heavy redux oil may enter the tower either through line 26 discharging just above the plate 24, or through line 21 discharging above the surface ofthe zinc mass 23', or through both these lines, each of which is suitably valved to afford the necessary control and adjustment.,l In any case, the number and size of the-apertures in plate 24 are so correlated to the volume of vapors passing through the plate that practically none of the redux oil introduced into the tower is permitted to drop through the apertures or perforations in the plate. The hot heavy redux oil dissolves and continuously removes from the zinc mass the tars, gums and section of the tower below plate 24. Especially effective action of the redux oil is attained in dissolving the aforesaid impurities and keeping clean and active the zinc surfaces of the contact mass in tower 22, if all or most of said redux oil is introduced thereinto through the lower inlet 26. Redux oil thus introduced is carried upwardly through the entire mass of contact material, in a state of extreme agitation and turbulence, by the rapid dow of vapors through apertured plate 24.

The vapors, freed in large part, at least, of gummy and tarry polymers, pass from tower 22 through line 29 into the lower part of a second treating tower 30, containing a body 3l of contact material comprising zinc in'oxidized condition. This -mass of oxidized zinc material accomplishes dnal treating of the hydrocarbon vapors insofar as concerns dechlorination, degumming, de-colorizing, sulphur reduction and sweetening. The second tower, and the body of contact material contained therein, are de'sirably much larger than the preliminary treating tower 22 and body 23 of contact material therein contained. In a typical instance, tower 30 may have an inside diameter of 6 feet and vertical length of 26 feet. The mass of oxidized zinc material therein may be 16 to 20 feet in depth, and is supported on a perforated plate or false bottom 32 located above the point of entry or vapor line 29 and spaced 3 feet or so above the tower bottom proper. These figures merely illustrate typical good practice and are in no sense restrictive. A clean-out or discharge opening 33 is provided for removal of the contact material from tower 30 when this becomes vnecessary or desirable. l

After passing upwardly through mass 3| of oxidized zinc material in tower 30, the vapors leave this tower through line 34 and enter the lower part of tower or column 35 which constitutes an after-fractionator and is for the purpose of making final separation of any residual relatively heavy constituents, and controlling the final end point of the dnisned gasoline as may be desired by the rener. This tower 35 may take the' form, for example, of a fractionating column of the bubble tray type; but any type of column suitable for edecting the desired fractionation may be employed.

Refined and fractionated gasoline vapors 'leavl ing the upper part of the column 35 through vapor line 36, give up heat to incoming. raw gasoline charge in heat exchanger 4, and are then condensed in condenser coils, indicated diagrammatically at 31, contained in condenser box 36. The rened gasoline condensate passes, together with uncondensed gas and vapor, through condensate line 39 into separator 40. From this separator, uncondensible gases are vented from the system through line 4I containing regulator 4I which maintains a pre-determined back pressure upon the treating system. The refined liquid gasoline constituting the i'lnished product is conducted from the separator .through line 42 to storage tanks. .A small pump 43 is provided to take some finished gasoline from separator 40 through line 44 and to pump the same through line 45 to the top of the fractionating column 36 to provide redux for said column.

In the column 35, a relatively heavy fraction cated at 46, which is suitable to serve as the heavy reflux oil hereinabove referred to for washing the mossy zinc contained in Vthe preliminary treating tower 22. 'I'his hot fraction collecting in the base of tower 35, or such portion of it as may be desirable to use for the purpose, is accordingly conducted through line 41 and continuously delivered, still hot, to tower 22 through inlet 26, or through both inlets 26 and 21, as hereinabove described. Any surplus not required for use as a reflux or washing medium in tower 22 may be conducted by suitable piping connection (not shown) directly into surge tank 48, into which are also conducted heavy polymer fractions and heavy bottom fractions' from ,towers 22 and 30 through lines 49 and 5U, respectively. From the surge tank, pump 5l picks up these relatively heavy frac'- tions or residues through line 52 and delivers them through line 53 back into the vaporizer 1 where they are denuded of any gasoline naphthas which they may carry. ,Accumulation of'heavy 4bottoms in the vaporizer may be continuously or intermittently withdrawn therefrom through residuum line 54, valved at 55, and delivered to fuel storage or otherwise disposed of. The large body of relatively heavy and high-boiling bottoms or residuum thus accumulated and continuously maintained in the vaporizer, substantially halffllling the same, provides a large-capacity storage medium for heat units supplied thereto by the heating furnace therebelow. The temperature of this large body of residuum can easily be held substantially constant, thus ensuring.

substantially constant or uniform rate of vaporization of the liquid portion of the raw distillate charged to the vaporizer, and a substantially constant supply of cracked distillate vapors for a given rate of feed of such vraw distillate into the vaporizer at inlet 6. This is obviously an important advantage because it greatly facilitates achieving smoothly continuous operation of the process as a whole.

Y Towers 22 and 30 are also provided with valved bottom drain connections `56 and 5.1, respectively, for discharging accumulated heavy liquid matter into sewer or sump 58, when desired. Column 35 may be provided with a cleanout or discharge outlet as indicated at 59.

`Towers 22 and 30 are y desirablyv provided in their upper portions with steam inlet connections 60 and 6I, respectively, for a purpose which will presently appear.

All the parts of the system, from the vaporizer 1 clear through to and including theheat exchanger 4 are desirably heavily lagged with insulation, indicated at 62, for example, in order to maintain the temperature of the vapors saillciently above that at which the desired gasoline product will condense, until after the refined vapor-gas mixture has left the top of the afterfractionator column 35.

The amounts ofchlorine and air employed in operating as above described may vary considerably depending upon the type, analysis and other characteristics of the particular raw distillate to be rened, the required specifications of the nished gasoline to be produced, and similar practical considerations. Very small proportions of chlorine and of oxygen are suliicient to produce very noticeable beneficial effects. n the other hand, it is undesirable to use either chlorine or oxygen in substantially' larger proportion than is necessary to accomplish the desirable action above described. not only because employment of unnecessary excess is wasteful and increases operating costs, especially in the case of chlorine, but also because of undesirable' effects which employment of these agents in too large proportion can have upon the quality and yield of finished gasoline product. 'The use of too much oxygen would adversely affect, for example, the color of the finished gasoline; and it is obvious that it should never be employed in such large proportion as to form a combustible mixture with the hydrocarbon vapors. If too much chlorine is used, the chlorination of hydrocarbons is apt to go beyond that desired for promoting polymerizationand removal of gumforming constituents. In general, the proportion of chlorine used may range, in practice, from as little as 0.01 pound, or even less, to. 1.0 pound, per 42-gallonlbarrel of raw mineral oil to be rened; while the amount of oxygen employed may vary from about 0.1 pound, to about 0.4 pound, per l2-gallon barrel of raw mineral oil to be refined. These ranges are not to be taken, of course, as rigidly xed or absolutely limited, but only as .indicative of bounds outside of which it isv ordinarily unnecessary to go in practicing the invention. It will be observed that even the maximum limits indicated correspond to a relatively very small volume percentage of chlorine and oxygen, respectively, in the initial mixture thereof with the vapors of the mineral oil to be refined. It is to be further understood that the chlorine and oxygen are not necessarily employed in free condition, but that either may be supplied as a compound capable of yielding it or making it available in active form under the conditions of operation. Many such compounds or combinations are known in the art and require no specific description here.

In employing the present process to treat a cracked gasoline distillate of the general type assumed in the specific example above given, the use of about 0.1 pound of chlorine, and. about 0.176 pound of oxygen (represented by l0 cubic feet of air at 60 F. and atmospheric pressure), per i2-gallon barrel of the raw distillate charged to the still or vaporizer, represents average good practice. Otherwise stated, this means that in the hot initial or pre-treating mixture described in the above s pecic example, the concentration of the chlorine is about 0.04 per cent by volume. while air is present in about 1.1 per cent by volume.

In order to ensure thorough distribution or mixing of the chlorine gas-with the mineral oil vapors, and also to avoid localized over-concentration and consequent localized over-chlorination through imperfect mixing, it is very desirable, although not indispensable, that the chlorine be introduced into the oil vapors in highly diluted condition. The use of air in this connection, as in the example hereinabove given, not only accomplishes this purpose effectively but serves at the same time to supply the requisite amount of oxygen. It will be noted that in said egample, the volume ratio of air to gaseous chlorine is about 28:1. The amount and proportioning of the air and chlorine can be measured and controlled very accurately through provision of metering and control devices I4, l; in' the typical installation here illustrated.

'Ihe operating temperatures employed in practicing the process are capable of considerable variation while still realizing in substantial measure the benefits of the invention. l'I'heir should' be high enough, of course, to maintain' substantially in vapor phase the desired components of the raw mineral oil` product to be relined, until the refining treatment of the vapors has been effected to the extent desired. Thus, in the specific example hereinabove given, the body of relatively heavy liquid substantially half filling the still or vaporizer 1 to the level indicated at lmay be maintained at approximately 400 to 425 F.; while the vapor-gas mixture leaving the vaporizer through line 2| may be at a t'emperatureapproximating 390 to 400 F., that is, at approximately the normal mean boiling temperature of the raw distillate, or slightly above. The raw cracked distillate, together with the proper proportion of the chlorine-air mixture, 'is charged into the vaporizer continuously at a substantially constant rate which may be regulated andl controlled as desired by valve means provided in the respective feed lines. Under these conditions, the temperature in the knock-out box or tower 22 is on the order of about 380 to 390 F.; the vapors enter the oxidized zinc contact tower or column at from about 370 to 390 F. and leave the top of the con tact bed at from about 340 to 350 F.; while the vapors leaving the after-fractionator are at a temperature approximating 300 F. The foregoing assumes, of course, efective heat insulation of the various parts of the installation referred to. All the temperatures mentioned are of c ourse variable in practice, depending upon the specific characteristics of the raw charging stock to be refined and what end point is desired for the finished gasoline, as well as upon the operating pressure maintained in the system and other practical considerations. The specic temperatures above given therefore merely represent averagejgood practice in a typical instance, assuming operation under a superatmospheric pressure of about 5 pounds per square inch.

In carrying out the process of the invention, it

is found desirable -to operate the treating system under moderate superatmospheric pressure which, however, need. seldom exceed 15 to 20 pounds as a maximum. More usually, when operating on the Atype of raw distillate and employving the type of apparatus installation described in the above specific example, the operating pressure is on the order of 5 to 10 pounds per square inch above atmosphere, the degree of pressure being capable of close regulation and control through suitable adjustment of a back-pres- 1 sure control valve, for example, such as that indicated at 4|n in Fig. l. Moderate superatmospheric pressure has the advantage, among others, of apparently rendering more eihcient the desired action of the contact materials upon the vapors passed therethrough.

The employment of a plurality (e. g. two) separate bodies of contact material for contact treatment of the vapor-gas mixture in successive stages, as in the illustrative example above described, is a very desirable and important feature of the invention in a particularly desirable practical embodiment thereof, although it is not necessarily characteristic of the invention in its broader aspects. By thus employing a plurality of successive contact treatments, it becomes possible to employ at each stage of the contact treatment a particular kind or form of contact material best adapted to accomplisha desired -part of the complete treatment, as well as to effect certain substantial only a few seconds, say 3 operating economies.'

that are desirable, 'and in some cases vital, for profitable commercial operation. In the present instance, the contact material employed in the relatively small contact tower 22 is adapted and intended to function more particularly to effect deposition and separation of most of the heavy polymers, chiefly gummy and tarry matters, from the vapors without necessarily effecting substantial sweetening action. The sweetening of the hydrocarbon vapors and reduction of total sulphur, together with removal of residual small proportions ofheavy polymers, as well as dechlorination and de-acidifying of the vapor-gas mixture, -are accomplished mainly or almost entirely in the second and larger contact tower 30 which contains contact material of a derent nature adapted more particularly to exert sweetening action. By first accomplishing most oi the heavy polymer removal in tower 22, so that there is comparatively little deposition oi gummy and tarry materials in the oxidized zinc contact mass 3|, the operating life of this latter is greatly prolonged, with resultant important economies in operation. Since it is possible to remove most of the polymers by a comparatively rapid passage of the vapor-gas mixture through the relatively small body of contact material 23 in tower 22, and also since this contact material is of such nature and in such physical form that it can be kept relatively clean and active by the described washing and dissolving action of the reux oil employed in this tower, this body of contact material also can be used for a prolonged period without replacement or revivication; and when it is ilnally necessary to replace it,`there is only a comparatively small amount of material to handie, thus keeping down operating costs'.

In general, the first contact'tower 22 for removing heavy polymer' should most desirably be moderately coarsely granular or fragmentary in physical form to permit reasonably rapid passage of vapors and reflux liquid therethrough. Thus, in actual practice of the present process, it commonly requires to 6 seconds, for the vapor-gas mixture to pass through this body of contact material in tower' 22. The material should also be metalliferous, zinc being particularly effective for the purpose. The mossy metallic zinc employed for this contact mass in the speciiic example hereinabove given combines in a particularly effective way the various properties desirable in acontact material used in effecting this preliminary knock-out contact treatment for removal of heavy polymers; but practice of the invention is not to be understood as limited thereto, other metals besides zinc, such as lead, aluminum, iron, copper, tin and cadmium, for example, being usable in place of or in conjunction with zinc for this primary or knock-out contacting treatment, although usually with less eiciencv and without compensating advantage.

The larger contact mass 3| employed in the second, and in this instance the final, contacting treatment of the vapor-gas mixture should also 'mentioned in describing the speciiic example contact material used in the mass initially. Eventuallyhowever, this em sist, for instance, of small fragments of a mixture of equal parts by Weight of commercial zinc oxide and plaster of Paris with water, which has been allowed to set or harden and has then been crushed and screened to desired size. Typically suitable sizing for such material is such that practically all of it will pass a 5A; inch screen but will be retained on a 1A; inch screen. This gives a mass offering more resistance to vapor flow than does contact mass 23. Furthermore the vapor gas mixture must pass through a much greater thickness of it. Consequently this second stage of contact treatment involves a longer period of time, on the order of several minutes, say two or three minutes in a typical instance; although in the case oi certain types of raw charging material this contacting period can be reduced to one minute or even less with satisfactory results.

Although zinc in oxidized condition is recommended more particularly for use in the second or sweetening contact treatment in tower 30, it

is also very effective in removing gnmmy and tarry polymers andfmay therefore be employed for this purpose, as well as for sweetening, within the broad scope of the invention. But since it is more dimcult to keep contact material consisting largely or mainly of oxidized zinc or other metal free from the extensive deposits of gums, tars, and other heavy carbonaceous polymers etc. which would form thereon if used in the -primary or lknock-out contact. step, considerable advantage is'gained by using essentially metal contact surfaces in the primary tower 22. Neither vzinc metal nor zinc chloride, nor other metals and metal chlorides generally speaking, have any substantial sweetening action whe used alone, but zinc and zinc chloride especially are extremely effective as de-gumming agents, that is, in promoting separation and removal oi heavy polymers, gums, tars, etc. In addition, the metal surfaces, or the mainly metal surfaces, of cony tact mass 23 are comparatively easy to keep clean by employing reflux oil in the manner above described. Hence, this division of contacting work, or separation of contacting function, into the plurality of stages represented by the operation in towers 22 and 30, respectively, has very great practical advantages in commercial work.

After the plant hereinabove described has been started up and the process has been running normally for a time,

noticeably and remains for a long time at a point considerably above that characterizing the ciency begins to decline. that a substantial part of the oxidized zinc in contact mass`3| has been converted into' zinc chloride by the action of the hydrochloric acid resulting from chlorination of certain of the hydrocarbons, so that said contact mass is no longer removing all the hydrochloric acid from the vapor-gas mixture as it should, and consequently re-vivification or reactivation is necessary. In practice, such re-vivication is not delayed until hydrochloric acid begins to be noticeable inthe vapors leaving the after fractionator.

When it is necessary to re-vivify the oxidized zinc contact mass, tower 30 may be simply cut outpf the system and the flow of the vapor-gas mixture through line 29 diverted through a duplicate or spare tower and contact mass (not shown) of. the same character. The method of This is an indication it is found that the efliciency'f ofthe oxidized zinc contact mass3l increases 2,205,411 given hereinabove. This contact mass may conre-vivifying the spent zinc oxide contact mass, although simple and' economical, is` very effective and constitutes an important specific feature of the present invention. Steam is introduced into the tower through inlet connection 6l andforced through the contact mass therein; whereupon a reaction occurs between zinc chloride and the steam whereby the zinc chloride gives up a substantial part, say half, of its chlorine content, with formation of hydrochloric acid which is carried out of the. tower with `theexcess steam, leaving a mixtureos' compoundor series of compounds, consisting ofzinc oxide and zinc' chloride constituting 'what may be generally termed zinc oxychloride. The exact molecular proportioning vof the zinc oxide and zinc chloride in this mixture or combination will depend in a given instance upon the extent of the steaming, thetemperature at which the steam is employed, and other operating conditions. In the practice of the present invention, it is found advantageous 'to use steam at a temperature somewhat higher than 212"o F., say 300-350 F., since this not only speeds up the reaction and shortens the time required for re-vivifying, but it also leaves a zinc oxychloride mass of such chemical composition and physical structure (finely porous) as to render it particularly eiective in using it subsequently for contacting purposes inthe oil ref lning process. Although any heavy liquid polymers adhering to the contact surfaces ofthe oxidized zinc material of contact mass 3l are yalso removed to a considerable extent by steaming the mass as described, it becomes increasingly diicult to effect this cleansing and re-viviflcaexcessive accumulation of heavy tarry and other carbonaceous deposits, it isy feasible to burn these olf under carefully controlled conditions in order to re-vivify thecontact mass.

This oxychloride contact material contains water of hydration in proportions varying with the conditions under which it was produced; and in order to maintain it at highest operating efficienc-y for the maximum period of time, it is therevfore found advisable to ensure thatA the initial vapor-gas mixture leaving vaporizer 1 shall contain a small percentage (e. g. on the order of l0.1

to. l per cent by weight) of moisture which may be introduced continuously at a proper regulated rate into the vapor space of the vaporizer, along with the air-chlorine mixture or otherwise as may be most convenient. In some cases, the raw distillate charged into the vaporizer may contain moisture in quantity wholly or partly sufllcient for this purpose, andthis should of course be duly taken into account. The inclusion of a small amount of water vapor in the initial vaporgasgmixture appears to exercise a benecial action tending to maintain an equilibrium among the crystalline compounds comprised `in the zinc oxychloride mixture or complex. But use of an excessive proportion in the gas-vapor mixture is obviously undesirable as tending to reduce exmaterially to the greater elciency displayed by f:

. tion as time V goes on. However, when the steaml ing action eventually ceases to be effective due to the oxychloride contact material as compared to straight zinc oxide, whether used alone or with a carrier such as plaster of Paris.

l chloride combinations or complexes of theoxychioride type are well known to chemists and require no detailed description here. It may be stated that, in general, oxychloride complexes wherein the molecular ratio ranges from 1ZnCh:'?ZnO to 1ZnCl2z20ZnO have been found' particularly effective for use in a contact mass employed in the type of oil refining process herein described; and whether the complex be prepared outside the treating tower in advance, or by steaming down a previously used contact mass in which the active material consisted initially mainly of zinc oxide, the conditions of its formation are'most desirably controlled and .regulated to attain a molecular ratio within the range above mentioned. However, the invention is in no sense restricted in this regard since that molecularratio range can be departed from substantially in oxychloride contact masses of this general ch'aracter while still realizing the benefits of the invention to a substantial extent.

Although the metallic surfaces of the contact mass contained in the first or primary contact treating tower 22 can be kept substantially free of gums and tars by the washing and dissolving action of the reflux oil employed as described, those surfaces may eventually become coated to a greater or less extent with carbonaceous deposits not soluble in the reflux oil nor easilv dislodged therefrom by its washing action. occurs to such an extent as to noticeably decrease the eiiiciency of this contact mass in its de-gumming action, it is advisable to disconnect this tower from the system and to re-vivify the contact mass, meanwhile running the vapors through a spare or duplicate de-gumming contact tower (not shown) connected in parallel with tower 22. By introducing steam into tower 22 through inlet 80 and forcing it through the contact mass therein, in a manner similar to that hereinabove described ior tower 30. the surfaces of the mossy zinc metal can be effectively freed of practically all such tenaciously adherent carbonaceous deposits of the character above mentioned. Incidentally, any zinc chloride that may be present in the mass as theresult of reaction between the zinc and the hydrochloric acid content of the.'

vapor-gas mixture previously passing through the mass will be converted into zinc oxychloride,

which is' not a disadvantage since this complex material has a de-gumming action fully as erlicientas that of either zinc or zinc chloride, or evenmore eiiicient. If, after repeated steamings, the amount of oxychlo'ride material accumulating on the mossy zinc surfaces of the contact mass in tower 22 becomes great enough to interfere materially, as it may. with the action of the reflux oil in keeping the zinc surfaces free of gummy and tarry deposits, it is a simple matter then to discharge the contactfmass from tower 22, melt the f metallic zinc which has becomecoated with oxychloride, discard the dross and waste, and repour into mossy form the remaining zinc metal, which When this can then be charged back into the primary contact tower for further use in de-g It would of course be possible to use the same type of contact material in tower 22 as in tower 30, and such practice is included within the broad scope of the invention, but this would sacrifice the advantage, hereinabove pointed out, that by using an essentially metallic contact mass to perform the de-gumming or polymer-precipitating action,l the much greater trouble of keeping an oxidized metal contact massfrom becoming clogged and rendered inactive by gum and tar deposits can be readily avoided in the simple and economical manner hereindescribed.

After the plant has been started and normal operating 'conditions have been established, the process can be carried on continuously for long periods of time without any interruption. A condition analogous to equilibrium is attained, in the treating system as a whole, among the var-V ious substances or materials involved, including and controlling the introduction thereinto of the raw mineral oil to be refined, togetherwith the chlorine, air and moisture, in such manner as to ensure maintenance of that equilibrium condition at an. optimum, as indicated by the quality and yield of the refined gasoline product, can be obtained in the manner hereinabove set forth.

The refined gasoline product may be optionally subjected to a washing treatment, either with water alone or with a very dilute solutions-.of a suitable alkaline agent, such as caustic soda, to remove any possible traces of acidity. Such washing is not necessary, however, if the contact mass in th'e tower 30 is not permitted to become highly acidic through formation therein of too large a proportion of zinc chloride.

Therflnished gasoline product obtainable by treating a typical cracked gasoline distillate in accordance with the process of the invention is characterized in general by satisfactory color, pleasant odor, sweetness to doctor solution (sodium plumbite),ksubstantially lower content of total sulphur than the raw distillate (the reduction amounting to -from30 to 50 per cent usually), and substantial freedom from gumming, as well as gum stability and color stability, all as determined by'th'e standard tests for these various properties. For example, such a finished distillate commonly shows a color of 30 plus (Saybolt) a gum content of about 4 or 5 milligrams per 100 cc. as determined by the copper dish test, the `re. duction in gum content, on the basis of gum content of the raw distillate treated, being frequently 98% ormrnore.Y .Y

TheV finished gasoline shows good stability in respect to gum formation during storage periods, the breakdown period as indicated by the standard accelerated oxidation bomb test being ordinarily well over six hours, and quite commonlyI as much as ten hours or more. The color stability is also excellent, no perceptible change in color or appearance of cloudiness occurring after exposure of a sample to sunlight for two hours. In a typical instance, a sample exposed to sunlight for one hundred hours shows a color drop of only five points, and no cloudiness or gum deposition. A specimen gives negative results by It is evident from the foregoing that finished l gasolines resulting from treatment of raw distillates in accordance with the principles of the invention are commercially valuable products of excellent standard characteristics. This is further evident from the following table of test data whichY affords a comparison between the raw distillate and the treated distillate or finished product resulting fro'm application of the process in actual practice to the rening of three typical hydrocarbon sulphur complexes responsible for sourness are converted into compounds of the type represented by the formula R-S-S-R (R being a hydrocarbon radical) which are negative to the doctor test. It appears possible that, by

the present process, the objectionable hydrocarbon-sulphur complexes are converted into pounds of the thioether type represented by the formula Rf-S-R.' also negative to the doctor test. Whether or not this is the correct explanation, thefact remains that the present process produces a sweet finished gasoline of distinctive pleasant odor and,moreover, of substantially reduced sulphur content. This vreduction in sull5 raw distillates: phur content, not achieved in ordinary sweeten- No. I No. II No. III Origin West Texas crude Mid-Continent crude Kansas crude Product Cracked pressure distillate Cracked pressure dis- Straight run gasoline s@ tillate Raw Treated Raw 'Premsa Raw Treated Gravity Baum 53 9 57.0 51.1 5l.5.-- 64.4 64.1. Doctor test Sweet.- Sonn.-. Sweet Sonn--. Sweet. Color 30 Yellow.. 30 30 30.

Sulphur:

T el 0.144% 0.027%.. 0.012%.- 0.033495 001.32%. Mei-captan None.---. 0.005%-. None.--. 0.0125%- None. Gums (mgs. per 100 cc v Copper dish* Glass dish" Copper strip 2 hrs. at 212 F No good. Excellent.

Induction (accelerated oxidation) 90m n 840mm.-. n.- t Sunexposurs (2hrs.) Nodrop-- No drop-- Cloudy. 30. Distillatxon:

I. B. P F 84 F 110 F 98 F 90 F 100 F 107.-. 140 F 134 F 190 F 5'F 148 F 158 F All Residue 1.a 1.1% 1.s% 12% 1o 1.0%

Old method.

(a) After cutting raw P. D. to 400 F. end point. u (b) After cutting raw P. D. to 413 F. end point.

In the specic example of the process hereinabove described in detail, ow of the vapor-gas mixture through the body or bodies of contact material has been indicated as generally upward vertically. Ordinarily this is advantageous because it permits most easily utilizing the reuxing eiect of any relatively heavy liquids separated in or supplied to the contact material, with some resultant fractionation. However, it should be clearly understood that practice of the invention in no sense is limited to such flow of vapors through the contact material, but that they may travel downwardly or laterally through the contact mass or masses wherever, in any given instance, this may be more desirable or convenient.

The sweetening action effected by passage of the-vapor-gas mixture vthrough a metal oxide contact mass, after the mixture has been subjected to the action of chlorine and oxygen, apparently differs in its chemical mechanism from the sweetening action effected by such well known processes as those involving treatment with sodium plumbite or alkaline hypochlorite. This seems tobe evivdenced by the fact that the pleasant odor characterizing iinished gasoline produced by the presentprocess is different and easily distinguishable from the odor of gasoline that has been sweetened by either the sodium plumbite treatment or hypochlorite treatment. It is generally supposed that by these last-mentioned treatments, certain ing" treatments, is a noteworthy and important feature of the present process. A

Although, as pointed out, the practice of the invention is not conned to the employment, in

the treatment of the vapor-gas mixture with a-' agent and also as a de-gumming and de-colorizing agent. In being able to function. satisfactorily in these several different capacities, zinc oxide material is found to be superior to other metal oxide materials, as a rule, for employment in the the present process. The terms metal oxide material and zinc oxide material are to be understood as employed in a broad sense to include not merely oxides per se but other conditions of oxidation broadly, such as basic or Oxy-salts, especially oxychlorides, hydrated oxides, and the like, capable of functioning as de-chlorinating and deacidifying agents under the conditions herein set forth. A

Commercial zinc oxide, commonly containing Varound 5% of basic lead sulphate as an impurity, is typically satisfactory for use in the practice of the present process, usually in'association with a. carrier and binder, such as plaster of Paris, as in the specic example given hereinabove. Its subsequent conversion into flowing et high velocity, and then leading the oxychloride complexes, where chlorine is em- 4played in the pre-treatment, simply increases its effectiveness, as does also re-activation by steaming down. In this connection, it is to be noted that another way of preparing effective zinc oxychloride contact material is to saturate with zinc chloride solution inert porous material such as brick, tile or the like, and then steam the mass thoroughly to produce the desired labile and sensitive basic chlorides or oxychlorides of zinc ,so eiective in their sweetening action. Oxidized ores of zinc constitute another available form of zinc oxide material suitable for use in practicing the process. Among other types of carriers and binders which may be associated with oxidized zinc in any of its forms to pro- Vduce satisfactory zinc oxide contact material, are fullers earth, certain types of cements, clays, and the like, pumice, fire brick, etc. Zinc dust, which commonly contains around 3% of zinc oxide, may be employed to form contact masses having sweetening action initially which increases progressively With use 'where oxygen is employed in the pretreatment of the hydrocarban vapors.

Other metal oxides, in addition to lead oxide; which may also be employed as such or in conjunction with inert carriers, etc. as metal oxide contact material for sweetening, within the scope of the invention in its broader aspects, are the oxides of iron, copper and magnesium, especially in their hydrated forms. However, like lead oxide, these various oxides are not particularly effective as de-gumming or de-colorizing agents, as compared to the highly effective de-gumming and de-colorizing action of zinc oxide andmetallic zinc; and hence, where they are employed as contact agents in the sweetening of a hydrocarbon oil high in gum or gum-forming constituents, or of dark color, treatment of the vapors with an effective de-gumming and de-colorizing agent, such as zinc, should precede the sweetening contact treatment.

In Fig. 3 of the drawing is illustrated another arrangement of apparatus for eecting vaporization of the raw distillate to be. treated, and commixture thereof with the pre-treating gas or gases prior to passing the vapors over contact material. In this arrangement, which can sometimes be employed to great advantage instead of the corresponding part of the system illus- :trated in Fig. 1, the raw distillate coming from heat exchanger 4 passes through line 10 into pipe coil heater 'il where it is heated up to the maximum 4temperature required, passing therefrom through line 12 largely in the form of vapor. At 13 the necessary amount of pre-treating gas,

such as a mixture of chlorine and air, is introduced into the hot hydrocarbons through line 1I, and the mixture is discharged tangentially at 15 into the ash and pre-treating tower 16, where the desired reaction upon the raw hydrocarbons takes place.v The pre-treated vapors leave the upper part of the reaction chamber 16 through line 11, going thence to the knockout tower 22 and through the remainder of the system shown in Fig. 1 and described hereinabove.

Another specific way by which thorough and uniform commingling of the `raw mineral oil vapors and the gaseous modifying agent or agents may be effected is by continuously introducing the gaseous treating agent, such as aproperly proportioned mixture of air and chlomixture into a drum or chamber of relatively large volume, the velocity of now being thus greatly reduced and a suflicient reaction period being thus provided prior to the subsequent contact treatment of the vapors for gum-removal and sweetening. One way of accomplishing this is illustrated in Figs. '4 and 5. Into reaction drum or chamber 18, a stream of raw hydrocarbon vapors is introduced at high velocity line 19, while the required proportion of gaseous treating agent (e.g. chlorine-air mixture) is also introduced through line 80 into said drum as a high velocity jet directed oppositely to the incoming stream of raw vapors. The two streams or jets meet counter-currently and extremely eilicient mixing is thereby secured. 'Ihe drum is of suiiicient size to give ample time for the desired reaction to occur, and the swirling motion of the vapors facilitates the throwing out of any tarry matter that may be formed at this stage. The tangential entry of lines 19 and 80 into the drum as here shown 'is of advantage in this connection. The treated vapors leave the of such a distillate to the conjoint action of small proportions of chlorine and oxygen, separating resultant heavy reaction products from the vapors while passing them in contact with reiiux liquid comprising condensed components of such vapors, then passing the vapors, while still hot, through a permeable mass of solid contact material comprising oxidized metal whereby to effect sweetening, and condensing a refined relatively low-boiling product from the treated vapors.

2. The process of rening a sour crude gasoline distillate which comprises subjecting hot vapors thereof to the conjoint action of a relatively small proportion of chlorine and a larger but still small proportion of air, separating resultant heavy reaction products from said vapors while passing them in contact with reux liquid comprising condensed components of such vapors, then passing the vapors, while still hot, through a permeable mass comprising zinc in oxidized condition to effect sweetening of the vapors and removal therefrom of any residual reavy reaction products, and condensing a refined gasoline from the treated vapors.

3. In the art of rening crude cracked mineral oil distillates of the gasoline type containing gum-forming and color-producing constituents as well as deleterious sulphur compounds, the process which comprises commingling hot vapors of such crude gasoline distillate with a small proportion of chlorine prediluted with a very much larger proportion of air, allowing sufficient time to elapse for a moderate chlorinating action to occur, then passing the mixture through a permeable mass of contact material comprising zinc owchloride, draining from said mass separated heavy liquid products, leading the residual substantially dechlorinated vapor mixture from said mass, and condensing from of good color,

mingling with hot vapors of such a distillate` y relatively small proportions of oxygen and process which comprises mixing with hot vapors v chlorine, separating from the mixture resultant heavy, high-boiling reaction products, then passing the residual mixture.' while still relatively hot, through permeable solid contact material comprising metal 'in oxidized condition, said material being adapted to promote sweetening and also such further separation of heavy reaction products as may be necessary, and .cooling the treated vapors to condense gasoline therefrom.

' 6. The process defined in claim 5, wherein said contact material comprises' metal of.which at least a substantial part is zinc in theform of oxychloride.

'1. In the art oi* refining mineral oil products containing objectionable contaminants, including gum-forming and color-producing constituents as well as deleterious sulphur componds,` the process which comprises mixing with hot vapors of such a product a smal proportion of air and a still smaller proportion of chlorine, separating resultant heavy, high-boiling reaction products from the mixture, passing the residual mixture through permeable contact material comprising an Oxy-chloride o f zinc, and reactivating said contact material by subjecting it, after .a period of use, to the action of steam.

.8. In the art of retin-ing mineral oil products containing -objectionable contaminants, including gum-forming and color-producing constituents as well as deleterious sulphur compounds, the

of such a product a small proportion of air and still smaller proportions of chlorine and water vapor, separating resultant/heavy, high-boiling reaction products from the mixture, passing the residual mixture throughpermeable contact material comprising oxidized zinc, and reactivating said contact material by subjecting it, after a period of use, to the action of steam.

9. The process defined in claim 5, wherein a substantial part of said contact material is zinc in the form of oxychloride, and wherein the oxidized zinc contact material is subjected, after a period of use, to the action of steam to improve its sweetening action.

10. In the art of refining cracked mineral oil distillates of the gasoline type containing -gumforming, color-producing and other objectionable constituents, including deleterious sulphur compounds, the process which comprises commingling with vapors of such a distillate small proportions of oxygen and chlorine, passing the mixture in heated condition iirst through a permeable mass of metallic contact material to remove gums, and then through a permeable mass of metal oxide material to eect sweeten-` -ing, and condensing gasoline from the treated vapors.

11. In the art lof refining cracked mineraloil distillates of the gasoline type containing gumforming, color-producing and other objectionable constituents, including deleterious sulphur compounds, the process which comprises commingling with vapors of such a ,distillate small proportions of oxygen and chlorine, passing the mixture in heated condition first through a permeable mass of metallic zinc contact material to remove gums, and then through a permeable mass of zinc oxide material to eil'ect sweetening, and condencing gasoline from the treated vapors.

12. The process deilned in claim 11, wherein the passage of the vaporous mixture through the metallic contact material is of substantially 'briefer duration than'the passage through the metal ,oxide material.

13. 'I'he process dened in claim 11, wherein hot liquid oil is continuously supplied. to the metallic contact material to wash deposited matter therefrom while the metal oxide material is steamed from time to time to maintain its sweeting activity.

ROSCOE D. HOWARD. v

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