US2107713A - Process for refining mineral oils - Google Patents

Description

, Feb. 8,1938. H. R. ROWLAND ET AL 2,107,713

PROCESS FOR REFINING MINERAL OILS Original Filed Dec/10, 1928 2 She'ets-Shect 1 [wax/v: anew/5 \sM/rw,

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Feb. 0, 1935, H. R. ROWLAND ET AL v PRO CESS FOR REFINING MINERAL OILS 2 Sheets-Sheet 2 Original File'd Dec; 10, 1928 695286587 ,2. eon Lawn, AY/GfA/t, deem/E SM 7f,

Patented Feb. a, 1938 Herbert R. Kansas Rowland and Eugene Jerome Smith, City, Mo., assignors to Corona Conversion Corporation, a corporation of Arizona Application December 10, 1928, Serial No. 324,923

Renewed March 7, 1934 14 Claims. (Cl. I 196-42) This invention relates to processes of refining mineral oils; and in particular it has to do with treatment of mineral oils of various kinds for purifying-and stabilizing the same. The process 8 of the invention is applicable to the treatment of oil products of widely varying characteristics, including oils of the motor fuel type, such as gasoline, especially gasoline derived from cracking processes, and also kerosenes, lubricating oils, and

other oil products.

after, however, reference will be made more par,- ticularly to the treatment of crude motor fuels or motor fuel distillates of the gasoline type, since at the present time this is' considered the most important field of application of the invention.

Crude motor fuels of the gasoline type, especially crude gasglines derived from cracking processes, commonly contain a substantial proportion of gums or gum-forming constituents of unsaturated character, such-as certain diolefins, which are highly objectionable for various reasons. These crude motor -,fue1 distillates also often contain substantial quantities of other impurities, notably sulphur, the proportions of which vary considerably depending upon the source of the crude oil from which the distillates are derived. The sulphur is largely present in the form of more or less complex combinations with the hydrocarbons of the gasoline, and its presence causes poor color, disagreeable odor, and

other objectionable characteristics. Itsremoval from gasoline, togetherwith the removal of gumforming constituents, constitutes one of the most troublesome problems of the refiner. Such im- 35 purities must nevertheless be eliminated 'or reduced below certain specified maximum limits in order to comply with standard specifications for the finished product.

The refining methods heretofore customarily ploying it for refining cracked motor fuel dis-' tillates.

One of the principal objects of the present inu vention is to enable mine al il products gener- In, the description hereinally, and particularly crude motor fuels such as cracked distillates, to be refined in a comparative ly simple and economical manner to meet the standard specifications for the respective finished products.

In general, the process of the present invention primarily involves subjecting the oil to be refined to a systematic and thorough-going treatment with chlorine, but in such manner as to effect the desired elimination of impurities or ob- -jectionable constituents without such drastic action upon the oil as a whole that it is fundamentally altered orits general identifying characteristics are destroyed. That is to say, the oil undergoing treatment is not converted into an entirely different class of product but merely becomes a more highly refined product of the same general class. The chlorine, of which only a relatively very small proportion is employed, is most desirably introduced into the oil as free chlorine; but the invention is not limited in this respect, and it is feasible to employ insteada compound yielding chlorine in available form under proper operating conditions. The chlorine acts upon the impuritiesin the oil in a manner not entirely understood. There are some indications that it acts to some extent both as an oxidizing agent and a polymerizing agent, perhaps catalytically. But whatever may be the precise nature of this action, the practical result is' that if the chlorine is employed under proper conditions, there results a very large reduction in the sulphur content of the oil. Furthermore there results also an action of some kind upon the gumforming constituents such that upon subsequent distillation of the oil undergoing treatment it is possible to reduce the content of these to within the tolerance limit if certain conditions to be referred to presently are observed in carrying out the distillation.

An important feature of the chlorine treatment of the oil in accordance with the principles of the invention consists in allowing a relatively long period of digestion or reaction to elapse after introduction of chlorine into the oil to be refined. In the best way of practicing the invention a digestion period of at least twelve hours is allowed after introduction of the chlorine into the oil, and a period of twenty-four hours is still better and is to be generally recommended in practice. If the oil stands quietly during this digestion period, there results considerable settlement of what appear to be complex sulphurchlorine-hydrocarbon compounds which can be drawn off as a sludge from the settling tank.

ditions are employed at this stage.

in the oil, nevertheless ample time must be allowed for the completion of the desired action.

of the chlorine upon impurities and the attainment of a condition of equilibrium, before the succeeding steps of the treatment are proceeded with.

This chlorine digestion treatment, although relatively mild, accomplishes a very substantial reduction in the sulphur content of a crude motor fuel distillate or other oil product to which it is applied. In and of itself, however, it does not bring about at this stage a sufiiciently extensive removal of gum-forming constituents by precipitation and settlement. A materially better result in this respect can be obtained by a light (or incomplete) acid treatment of the oil to be refined, preceding the chlorine digestion. By incomplete treatment is here meant that materially less acidis used than would be required in the customary acid refining process. The combination of the two treatments is found to be very effective in greatly reducing both the gum content and the sulphur content. This preliminary light acid treatment involves not merely the usual refining action characteristic of acid treatment, but it appears also to so modify the oil that the succeeding steps of treating the oil with chlorine and then distilling are both rendered more efiective than they otherwise would be in removing undesirable constituents. Accordingly, although the preliminary acid treatment is not indispensable in the broader aspects of the invention, it is regarded as highly advantageous in many cases, especially where the oil to be refined is high in contaminating impurities.

Furthermore, the preliminary treatment with a.

relatively small quantity of strong sulphuric acid aids in eliminating moisture that may be present in the crude distillate, and it is of great advantage in the present process to avoid the presence of moisture as far as possible. But it is feasible in some cases even to defer the light acid treatment until after the chlorine digestion.

After .the chlorine digestion, either with or without the preliminary light acid treatment, the partially refined oil is most desirably separated from the sludge or settlings and is run into a still. The charge is now distilled off, and the distillation vapors are caused to pass through a permeable mass of contact material having the power to arrest and remove, probably by a polymerizing action, gums or gum-forming constituents carried by said vapors. Zinc in granular or fragmentary form has been found to act most although some of these metals act far less effectively; Alloys of two or more of these metals are also useful, notably alloys of zinc with cadmium and lead. In addition to passing the distillation vapors through contact material, it is.

'requirements for marketability.

highly desirable that the liquid oil in the still also be subjected to the action of such contact material. Therefore, in the best mode of practicing the invention provision is made for this.

The action of the contact materal, both upon the liquid oil in the still and upon the oil vapors, is of vital importance. Besides assisting in removal of sulphur and gums, it appears also to aid in eliminating from the oil such chlorine as may have combined with some of the oil hydrocarbons, and in this sense to exercise a dechlorinating function. It is not intended to imply, however, that there is necessarily any chemical combination formed by the metal or other contact material with chlorine in the present process. In fact, there is some available evidence to the contrary and it is therefore believed that the action of the contact material in assisting in re.- moval of chlorine from the oil, or in so acting upon it as to render easy its removal in a subsequent step, is more that of a catalyst. But whatever the true explanation may be regarding the function of the contact material in favoring removal of the several impurities referred to, the employment of such material, more particularly metallic zinc, in connection with the distillation which follows the chlorine digestion treatment has been found very important in obtaining best results in practicing the new process.

In conjunction with this polymerizing treatment, the vapors are most desirably subjected to fractionation or rectification, the two operations going on together continuously as a combined treatment of great efficiency. This procedure, which will be described in greater detail hereinafter, is believed to be broadly new in oil refining, especially'in refining" cracked motor fuel distillates, irrespective of whether or not the oil has received special treatment with chlorine or other reagent before distillation.-

The distillation vapors after receiving the combined polymerizing and fractionating treatment, are led to a condenser and the resultant motor fuel condensate is then given an alkaline wash by which remaining traces of chlorine are removed, giving a finished product of good color and stability and otherwise meeting the usual In some cases filtration of the condensate through fullers earth is desirable in order to improve the color but this is frequently unnecessary.

In order to further explain the principles underlying the process of the invention, a specific example 'of its application to the refining of a cracked motor fuel distillate will now be given; and while the practice of the process is not confined to any particular type of apparatus, a novel form of apparatus which can be used to great advantage in carrying out the process will be described in connection with this specific illustrative example. This apparatus is illustrated in the accompanying drawings in which Fig. 1 is a general view in side elevation, partly broken away and in section, of a distillation plant embodying features of the invention;

Fig. 2 is a transverse section of the still on the line 2-2 of Fig. 1; and

Fig. 3 is a vertical section of'the combined tower and fractionating column in part, on a larger scale.

In this specific example, it is assumed that the oil to be refined is a cracked motor fuel distillate obtained from a crude oil characterized by very high sulphur content. This distillate contains 0.5% of sulphur and a large percentage of unsaturates including a substantial proportion of gum-forming constituents such as dioleflns. The refining methods formerly considered necessary to use in handling this type of distillate included, first, an acid treatment at the rate of 10 pounds of concentrated sulphuric acid per barrel of 42 gallons, then treatment with doctor solution, then steam distillation, and finally another treatment with doctor solution. Such treatment is so complicated and expensive, both as to procedure and refining losses, as hardly to be commercially feasible with a crude gasoline of this description. v v I In applying the process of the present invention to this crude motor fuelor gasoline distillate, the distillate is first given alight acid treatment, using 2 pounds of sulphuric acid per barrel (42 gallons) of the distillate. The resultant sludge having been drawn ofi, the oil is most desirably given an alkaline wash to neutralize acidity.

1 After this acid treatment, chlorine gas is bubbled into the distillate to the extent of about 2 poundsof chlorine per barrel of the" crude gasoline. It

will be seen that the quantity of chlorineintro- I duced is relatively very small in comparison with the quantity of crude gasoline distillate being treated, being in this particular instance much less than 1 per cent by weight, notwithstanding the high sulfur content and large percentage of unsaturates present in said distillate. The treated gasoline is then allowed to stand quietly in the treating tank for about 24 hours, during which time a sludge settles out which is characterized by a substantial content of sulphur and chlorine, evidently largely combined with hydrocarbons. This sludge is separated from the clear liquid in any suitable manner.

The apparatus employed up to this stage is of such simple and usual character as to require no illustration here.

The treated gasoline separated from the sludge is now run into the still Ill in the lower part of which are vertically arranged a number of metal plates ll, zinc plates in this instance. As here shown, these plates are provided on opposite vertical edges with lugs I 2 by which the plates are carried on supporting bars l3 extending longitudinally within the still. For convenience in inserting or removing the zinc plates ll, an opening l4 having a suitable closure i5 is provided at one end of the still, and by inserting appropriate lifting means through the apertured lugs IS. with which the zinc plates are provided at their upper ends, these plates can be readily lifted and removed through the opening and replaced by others whenever necessary.

The charge of treated crude gasoline in the still is distilled off in the usual manner, leaving a residue containing some gums and sulphur. The distillation vapors pass off through the vapor line l1 into the base of a combined tower and fractionating column iii, the detailed construction of which is best shown in Iflg. 3. As will be seen, this combined tower and column comprises two different types of sections, namely, liquid-vapor contact or fractionating sections A,

and other sections B which may conveniently be;

termed dephlegmating sections. ,The fractionating sections A may take any of the various forms commonly employed in fractionating or rectifying columns. In this instance they are so-called bubbler-cap sections, each comprising "a plate l9 carrying a plurality of bubbler-cap devices having vapor up-fiow tubes 20 and cooperating inverted cups or bells 2i, all of well-known construction and arrangement. The dephlegmating sections are, in general, sections containing permeable contact material through which the vapors are compelled to pass. In the present example they take the form ,of hopper-shaped plates 22 eachcarrying amass 23 of granulated zinc, and provided with central vapor upfiow tube 24 and cooperating inverted bell or cup 25 whose lower edges depend into the mass of granulated zinc. Suitably covered hand-holes 26 permit easy access to the contact material when replacement or adjustment is necessary.

It will be noted that in the lower part of this combined tower and fractionating column the two types of sections are disposed in alternating arrangement which is particularly advantageous as will presently appear. In the upper part of ,the column only the bubble sections are emlployed.

The distillation vapors entering the base of the combined tower and column pass upwardly through the devices 20, 2! of the first bubblercap section and in so doing travel through the liquid on that plate, the level of this liquid being determined by the height of the intake end of the liquid downflow pipe or run-back 21. The vapors pass thence through the vapor upfiow pipe 24 of the first dephlegmating section and are compelled by the inverted bell 25 to travel through the mass of contact material, granulated zinc in this case, in said section. Thence the vapors pass upwardly through the bubbler devices of the second bubbler section and through the liquid standing thereon, the depth of which is determined by the height of the overflow or run-back pipe 28 which carries the overflow from this plate down to the first bubbler plate through the intervening section B, a kind of stuffing box device 29, 30 being provided where the run-back passes through the plate 22 and the contact material carried thereby, such that any vapors tend:

ing to pass upwardly through the plate 22 at this point rather than through the central vapor pipe will likewise be compelled to pass through the granulated zinc carried by the plate.

The upward travel of the vapors through the remainder of the combined tower and fractionating column is similar to that already described, except that in the upper part of the column the vapors pass only through bubbler-cap sections, it being ordinarily unnecessary to provide dephlegmator sections in alternation with thebubbler-cap sections throughout the entire height of the tower-column structure.

In the top of the tower-column structure is provided a temperature-control section 3i in which is disposed a cooling coil 32 through which cooling, water may be passed in greater or less quantity according to the degree of cooling desired. The vapors pass through this cooling coil high-boilingconstituents of the vapors are dis-,-

charged as liquid, from the lowest bubbler-cap section through overflow or run-back'2l and are refluxed through I! to the still l0.

In passing through the several bodies of permeable contact or catalytic material carried by the plates 22, the oil vapors are relieved almost entirely of their gum-forming constituents, ow-

ing apparently to a polymerizing reaction favored by the contact material; and in the bubbler-cap section through which the vapors pass upon leaving each dephlegmating section, the vapors are thoroughly washed and in this way made to drop gummy polymers which may have been condensed in the dephlegmating sections but mechanically carried over by the vapors. This action is in addition to the normal fractionating or rectifying action of the bubbler-cap section.

The gummy polymers removed in the dephlegmating sections remain in liquid condition at the temperatures prevailing in the lower part of the tower-column, draining down through the catalytic material into the annular trough or launder 34 surrounding the central vapor pipe and thence flowing through trapped line 35 into header 36, which carries them either to a suitable collecting tank (not shown) or, by way of connection in, back into still for re-distillation. There is also shown tar line Ill leading as a discharge from the lower part. of still ill. Screen 31 serves to prevent the granular contact material from dropping down into the trough or launder 34. I

Returning now to the vapors leaving the top of the tower-column, these are conducted by vapor line 33 to a condenser 38 from which liquid conand apparatus, contact material (e. g. mossy zinc)- may also be placed in one or more of the fractionating sections A of the tower-column in such manner as to cover the bubbler-caps and compel the vapors leaving vthe bubbler devices to pass through such contact-material on their way to the next section above.

The herein described process is applicable not only to the refining of mineral oils such as crude motor fuel distillates and similar petroleum products, but also to other hydrocarbon mate- .rials, such as benzol and toluol, for example,

containing sulphur or other impurity which it is desired to remove.

It is. to be understood that the specific details herein above given with respect to both the process and the apparatus of the invention are merely illustrative of good practice, and that the invention is in no sense restricted thereto. Thus, it is feasible to use a material such as fullers earth, for example, in some or all of the -dephlegmating sections of the tower-column in densate passes through look-box 39 and line 40 to densate is now given a thorough washing with an alkaline agent in order to remove any remaining chlorine. For this purpose a saturated water solution of sodium carbonate is eifective and is to be recommended, but other suitable alkaline Washes may be used. 1

The refined gasoline thus obtained is of excellent quality and meets all the requirements of standard motor fuel specifications. 'Not only is a finished product of good color andstability obtained by the foregoing procedure but equally important is the fact that such color is stabilized,

there being no appreciable change in the color of products produced by this process even after prolonged or unusual exposure to light. Considering the high sulphur and gum content of the crude motor fuel distillate to which the process was applied in the specific example hereinabove given, this is obviously a remarkable achievement and indicates the great effectiveness of the treatment. In general, the process is particularly well adapted to treatment of crude motor fuel distillates and other oil products which are refinable with only the greatest difilculty,if at all, by prior methods to a finished product meeting standard specifications; but it is of course also applicable to refining of oil products generally. The quantity of chlorine necessary to use in a given instance depends, of course, upon the particular distillate or other oil product to be refined, but

it seldom exceeds 2 pounds per barrel and commonly is much less.

Instead of employing granulated zinc in th tower-column, mossy zinc may be used to good advantage. Also, trays of mossy or granulated zinc may in some cases desirably replace the described zinc plates H in the still.

In another embodiment of the novel process place of or in conjunction with the metallic contact material referred to in the specific example given, and the invention in its broader aspects comprehends such use; but the use of a metallic contact material, especially zinc, offers important advantages. The apparatus herein disclosed constitutes the subject-matter of a divisional application Serial No. 28,758, filed June 2'7, 1935.

What is claimed is:

1. The process of refining a mineral oil containing combined sulphur and gum-forming constituents which comprises subjecting said mineral oil to an incomplete acid treatment, then subjecting the oil to the action of chlorine for from 12 to 24 hours under mild reacting conditions such that the oil as a whole is not fundamentally altered, and separating resultant precipitated matter from the oil.

2. The process of refining a mineral oil containing combined sulphur and gum-forming constituents which comprises removing a portion of the gum-forming constituents from such oil by acid treatment, then digesting the oil with chlorine for from 12 to 24 hours under mild reacting conditions such that the oil as a whole is not fundamentally altered, and distilling the treated.

oil.

3. The process of refining a mineral oil containing combined sulphur and gum-forming constituents which comprises digesting such mineral oil with chlorine for from 12 to 24 hours under mild reacting conditions such that the oil as a whole is not fundamentally altered, then distilling the t'reated oil and passing the resultant oil vapors into operative contact with a metallic polymerizing agent to condense and, separate gummy matter from said vapors, obtaining a liquid condensate from the residual vapors, and subjecting said condensate to an alkaline wash.

4. The process of refining a mineral oil con- ,taining combined sulphur and gum-forming constituents which comprises subjecting such oil to the action of chlorine for from 12 to 24 hours under mild reacting conditions such that the oil as a whole is not fundamentally altered, distilling the thus treated oil, and subjecting the resultant vapors to a combined polymerizing and fraction ating treatment, and obtaining a useful condensate from said vapors.

6. The process of refining a mineral oil containing combined sulphur and gum-forming constituents which comprises digesting such mineral oil with chlorine for from 12 to 24 hours under mild reacting conditions such that the oil as a whole is not fundamentally altered, distilling the treated oil while maintaining the liquid oil in the still in contact with metallic zinc, passing the resultant vapors through a mass of granulated or fragmentary metallic zinc, condensing the vapors, and subjecting the condensate to an alkaline wash.

7. Process as defined in claim 1 further characterized by the fact that-the oil to be refined'is a cracked motor fuel distillate having a substantial content of unsaturates andhcombined sulphur.

8. Process as defined in claim 2 further characterized by the fact that the oil to be refined is a cracked motor fuel distillate having a substantial content of unsaturates and combined sulsulphur.

10. Process as defined in claim 6 further characterized by the fact that the oil to be refined is a cracked motor fuel distillate having a substantial content of unsaturates and combined sulphur.

11. In the refining of liquidhydrocarbon ma.- terials to remove therefrom contained impurities,

such as sulphur and gum-forming constituents,

the process which comprises introducing into sucha liquid hydrocarbon material a relatively small quantity of available free chlorine, allowing the chlorine to act for from 12 to 24 hours under mild reacting conditions such that said hydrocarbon material is not fundamentally altered substantially in the absence of moisture and without employing added reaction-promoting agents or conditions, and separating resultant reaction products from the liquid.

12. In the refining of mineral oils to remove therefrom contained impurities, such as sulphur and gum-forming constituents, the process which comprises introducing into such a mineral oil a relatively small quantity of available free chlorine allowing the chlorine to act for from 12 to 24 hours under mild reacting conditions such that the oil as a whole is not fundamentally altered, substantially in the absence of moisture and withoutemploying added reaction-promoting agents or'conditions, and separating resultant reaction products from the treated oil.

13. Inthe refining of mineral oils to remove therefrom contained impurities, such as sulphur and gum-forming-constituents, the process which comprises introducing into such a mineral oil a relatively small quantity of chlorine gas 'and, substantially in the absence of moisture and without employing added reaction-promoting agents or conditions, allowing the chlorine to act

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