US2179008A

US2179008A - Process for refining oil

Info

Publication number: US2179008A
Application number: US179486A
Authority: US
Inventors: Sumner E Campbell
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-12-13
Filing date: 1937-12-13
Publication date: 1939-11-07
Anticipated expiration: 1956-11-07

Description

Nov.i 7, 1939.

Pecci-66 No.

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PROCESS FOR REFINING 011'J Filed Dec.. l5, 1957 3 Sheets-Sheet 2 FRESH REAGENT f/v VEN TOR. SuM/VER. CAMPBELL A Tra/NEX S. E. CAMPBELL y-PRO-CESS FOR REFINING OIL Filed Deo. 1s, 1937 S'Sheets-Sheet 3 [/v VEN To@ UM/VER. E. CA Mpeg/L A TTo/z/VEK Patented Nov. 7, 1939 UNITED STATES PATENT FFICE leum and its distillates, shale oil, its distillates l or the like, wherein selective removal of various compounds, organic or otherwise, is desired.

The cracking of petroleum, its distillates or residua in general accentuates the production of compounds undesired in the iinalproduct and this is largely due to the formation by pyrogenisis of highly reactive unsaturatedhydrocarbons and derivatives thereof.

While it is desirable to retain a high percentage of unsaturated compounds in a final product,

2.3 such as cracked gasoline, yetA other olenic hydrocarbons, diolefines, for instance, are undesired due to their gum-forming propensities.

Also other organic compounds, such as mercaptans and other sulphur compounds, must be removed to minimize the sulphur content of the oil. Initially, petroleum prior to cracking may contain many compounds which are undesired in a nal product such as H25, organic acids both aliphatic and naphthenic, phenols, and nitrogenous bases.

These compounds are regarded as impurities detrimental to the use of the final product whether it be gasoline, kerosene, or other fraction, and the production of these impurities is increased by cracking and with many modifications in composition.

The treatment of petroleum for the removal of these impurities has assumed many forms in which known reagents are used for absorbing or reacting with the impurities but such known processes involve a blanket removal of impurities by each reagent which is often accompanied by the removal of highly desired hydrocarbons.

The underlying theory of the chemical reactions of known reagents with known impurities has therefore only been heretofore broadly applied to the refining of petroleum, or its distillates, with respect to the removal of groups of impurities responding,pfor instance, to an lacid or alkaline reaction with the result that no selective removal of all the impurities has been accomplished or is possible.

This has resulted in secondary reactions with resulting deficiencies in the quality of the products coupled with loss of valuable hydrocarbons 5 and high cost of reagents, and substantially no yield of the segregated impurities in selective classes.

It is therefore one object of this invention tc providea process for the continuous treatment 10 of petroleum, or its distillates, in which impurities are removed selectively in such sequence of steps that no grouping of different classes of impurities which would be diicult or impossible to separate will occur due, for instance, to either 15 their acid or alkaline nature.

Another object of this invention is. to .provide a simplified and highly eicient mode of operation wherein each selective reagent is utilized to the maximum degree in the removal of the particular class of impurities with which it is adapted to react.

Another object is to provide for the selective removal of groups of impurities from hydrocarbon oils to yield a rened distillate when such is desired irrespective of the selective removal of separate classes of impurities or their homologues.

A further object is to selectively remove all of the impurities from petroleum or its distillates, so that the impurities can be more readily separated and recovered as valuable by-products.

Inhibition of the formation of a material volume of alcohols at any stage of the process is an especially designed object of the invention.

The process will be described With particular respect to the treatment of a cracked naphtha or gasoline distillate containing generally HzS organic acids, of the aliphatic type such as acetic, formiz, butyric, valerie, and the like, organic acids of the naphthenic type, phenols, ni- 0 trogenous bases both Water soluble and waterA insoluble, olenes, .dioleiines mercaptans, and other sulphur compounds of unknown structure.

Referring tc the drawings:

Fig. 1 illustrates in printed form two embodiments of the invention in which variations occur to obtain the desired result;

Fig. 2 shows an apparatus suitable for the process; l 5

Figs. 3 and 4 illustrate details-thereof; 0

Figs. 5 and 6 show a preferred form of contact lter for use in connection with the process and apparatus v The selective removal n of each impurity, or

groups of impurities, in a particular sequence is accomplished with a particular reagent preferably in a contact tower of a certain design found to be highly effective for the objects of the process and while but one tower may be used for each step in some cases, the same may be performed in two or more contact towers for maximum efciency or when refining, for example, a cracked distillate containing a high percentage of any impurities as, for instance, one containing a large amount of hydrogen sulphide, the use of more than one tower is advisable and may be necessary.

l It is well known that the chemical constitution of cracked distillates varies widely depending on the nature of the charging stock from which there are obtained certain cracked distillates containing a relatively small amount of the compounds of oxygen, nitrogen and sulphur. With cracked distillates of this character a single tower may sufiice but with more chemically complex distillates such as those obtained by cracking high sulphur oils such as certain California oils, it is necessary to use two or more towers for the desired selectivity of removal of the impurities, for example, I have found in refining a distillate obtained by cracking a crude oil from the Wilmington field in California, which contains about 2.5% sulphur, that much hydrogen sulphide is obtained due to the pyrogenetic decomposition of these sulphur compounds. With such an voil considerable sodium sulphide is formed in the carbonate towers which will later be described in detail, Sodium carbonate solution is; well adapted to combine with organic acids; however, I have found-that hydrogen sulphide tends to displace organic acids with the result that they again dissolve in the distillate and pass on to the next tower. This same condition exists in the case of a caustic alkali solution wherein organic acids or phenols or both may be displaced, with the result that complete removal is impossible except by the use of a plurality of towers so that HzS may be removed in one, and the organic acids or phenols or both, as the case may be, removed in a tower or towers thereafter. This is a highly important part of this invention as it is an object of the invention to employ a sufficient number of contact towers to selectively remove the impurities without contamination one .with another. It is also to be pointed out particularly with such stocks as just above mentioned that there is a selective combination with caustic soda between phenols and mercaptans to the end that one may replace the other if the concentration of the partially exhausted caustic alkali solution reaches a certain point so that with such stocks it is also necessary to employ a plurality of towers in which the oil is contacted with caustic alkali solution.

It is also to be pointed out that in treating certain oils, notably these containing a relatively large amount of organicacids, that when these combine with sodium carbonate solution to form soaps, carbon dioxide may be liberated and pass over with the distillate into the rst tower containing causticv alkali solution, in which solution it will be absorbed and will tend to decompose phenates which had been formed by the reaction between phenols and the caustic alkali. Such a condition naturally will cause the phenols soliberated to again dissolve in the distillate, passing to the next tower, in which they will again be absorbed by the caustic alkali. This is another instance illustrating the necessity for the use of a plurality of towers containing a given reagent for the eflicient treatment of the oil.

The untreated distillate is passed by pump I through pipe II into the base I2 of tower I3 and is initially mixed with a particular reagent supplied by pipe I Ia into base I2 to ow concurrently therewith through a perforated dome I4 covviscosity will require packing of larger sizes to permit proper flow of the oil through the reagent in which the packing material is immersed. As an example, if the packing material is too fine the distillate flowing into the bottom of the tower will tend to push the reagent upward without permitting it to remain in the interstices of the packing. The packing material is of the desired size when the oil to be treated passes upwardly through the reagent between the particles of the packing, still permitting much of the liquid reagent to remain between the packing particles.

Tower I3 is divided into two sections, the lower packed section I1, terminating in a cylindrical overflow neck I8, in which the contact material is held by a screen I9, and an upper separating section 2.0, provided with the launder 20a, wherein the mixture of oil and reagent is separated by' gravity due to a reduction in velocity. The area of neck I8 should be such as not to appreciably increase the velocity of the mixture therethrough and above the upper edge thereof is provided a baiile I8a for diversion of the upward flowing stream to insure relatively quick separation within a limited distance through spaces sufficiently enlarged not to substantially increase velocity.

The separated reagent, with its contained impurities is withdrawnfrom the lower part of the. launder 20a, section 20, through a pipe 2l and the oil, free from the reagent passes out through pipe 22 into the bottom of a second similar contact tower 23, operated in a similar manner, whence it passes to the next stage of treatment, accomplished in similar towers operated in like manner.

After the oil has received sufficient treatment it may be passed from the last of the series of contacting towers in which liquid reagents are employed to the filter shown in Figs. and 6.

Manhole 25 is provided for charging the tower I3 with packing material and manhole 26 is provided for the removal of the packing material when necessary and a gauge glass 21 indicates the level of the liquids in section 20 and launder 20a. A vent 28 provides a gas release port and a pipe 29 serves to drain the tower I3. Similar instrumentalities are provided for the tower 23, and it is understood that any number of manholes may be conveniently located for the purpose of vfilling and emptying the tower I-3, as is well understood in the arts.

The desired reagent for abstracting a particular impurity or group of impurities from the oil may be introduced initially, if two towers are in use, by a pump 30 which forces the same through line 3| into the base of tower 23 in a manner as illustrated in Fig. 3. It will there be seen that the reagent from pipe IIa is mixed with the oil from pipe II within base I2 in a tangential direction as shown in Fig. 4, adapted to impart a whirling motion to the mixture such as to,give a somewhat gentle mixing without excessive agitation which would tend to form emulsions.

' It has been found that such initial mixing is suicient, coupled with correct design, packing material and operation of the contact towers, to provide all the mixing of the oil and reagent necessary to effect complete abstraction of a particular impurity, or group of impurities, because the most efficient contacting is accomplished throughout the bed of contact material which distorts the oil globuleseffected while in concurrent flow. To this end the ratio of diameter to height in each section I'I of each tower may be about l to 4, but the invention isnot limited to the shape or size of any apparatus used therefor.

The concurrent flow of oil and reagent upward- `ly through tower 23 assures intimate mixing and contact to the end that the oil, which has been partially vtreated initially in tower I3, is-completely treated for the removal of a certain irnpurity by the fresher reagent in tower 23 and separated therefrom completely in the separating section and launder of tower 23 to be withdrawn through pipe 24. As will be further explained, the treatment with a particular reagent can be completed-in one tower, depending on the character of the oil being treated as mentioned above.

The partially spent reagent is withdrawn through pipe 32 and forced bypump 33 through the pipeI Ia into tower I3 where a similar contact is effected with the untreated oil and the completely spent reagent is withdrawn through pipe 2l.

In this manner, by continuous flow, all mixing and contacting and separating are done in each tower. While preliminary mixing may be used, it is unnecessary as it is found that the packed sections themselves are amply sucient to give a contact assuring removal of the particular impurity or impurities the reagent is adapted to remove, at the same time exhausting it.

While two towersV are illustrated, obviously more than two towers could be used in the series but are usually unnecessary for the treatment of most distillates.

In this event, suitable valves and mechanisms are provided so that pump 33 may initially provide a charge of fresh reagent to ll packed section I'I of tower I3 apredetermined depth up to the upper overflow level of collar I 8.

Upon starting the flow of oil by pump I0 through tower I3, a circulating pump 34 may be employed topick up-the separated'reagent from pipe 2I and continually circulate the same to exhaustion through tower I3. At the conclusion of a run, the towerJ I3 may be drained of exhausted reagent through pipe 29.

Alternatively, a series of towers so arranged may be used in which a continuous supply of fresh reagent may be fed by pump 30 through the last tower and each tower will be provided with individual circulation. In this case, of course, there will be a continuous withdrawal of exhausted reagent and impurities through pipe 2i reagent in each tower of a series but that it is sufllcient to introduce fresh reagent into the bottom of the last tower of a serles,/ passing par-V tially spent reagent from the launder of the last tower into the bottom of the next preceding tower, the operation b'eing so conducted as regards lconcentration ofl the reagent and amount introduced to permit complete treating of the oil and at the same time withdrawing completely exhausted reagent from the launder of the first tower of the series.

In each case, the object is to obtain a reagent and impurity free oil and an exhausted reagent.

Depending on the desired extent of treating,

the treated distillate may be passed either di-4 rect to storage through pipes 22 or 24, or may go through a vaporizer or heater 24a to be clay treated thereafter, in 'vapor phase, liquid-vapor phase orin liquid phase alone.

A preferred form of apparatus for clay treating the distillate, previously chemically purified, is shown in Figs. and 6 in which' the distillate is passed from pipes'22 and 24 into a manifold 36 within a shell 3l having an annular perforated container 38,(which may if desired be covered peripherally with a gauze screen to retain theclay) filled with a suitable clay, or contact material, adapted primarily to further rene the distillate by polymerizing or decomposing undesired compounds as opposed to decolorizing action although, of course, an improvement'in color occurs due to adsorption and removal of color forming compounds, if decolorizing clay is employed.

What is known as activated clay, or clay that has been'treated with sulphuric acid, aluminum `sulphate solution, or the like, in ways well known treated distillate or vapor it will exercise an undesired cooling action in the clay, thereby minimizing the efciency of the clay, particularly as regards its polymerizing effect. To this end, steam at the desired temperature can be introduced through pipe 2Gb into pipe 24.

Manifold 36 may be provided with a plurality of distributor arms 39 for introducing and distributing the distillate, in liquid or vapor phase, within the annular space between shell l3l and container 38 which latter may be heated to a desired degree through jacket 40 in any suitable manner. Arms 39 are preferably so arranged as to discharge in the same direction so as to give even distribution by a whirling motion on the ex,- terior of perforated container 38.

Centrally of container 38.-'is a perforated discharge pipe 4I leading to a chamber 82, in which any clay may be retained to be withdrawn through pipe M v*while the distillate or vapor to-- gether with polymerized products and steam combined pass out by pipe v43 to storage, or preferably to a fractionating tower to obtain a distillate of desired boiling point range by' the separation of polymers.

The clay tower structure is usedto receive the distillate or vapor and reduce its velocity through the contact material for reaction purposes which is then increased to a'maximum at pipe 4I for emcient removal of polymers' from the clay. It is clear that the resultant of the flow of the fluids through the clay will effectively provide a desired period of contact and finally maintain the clay relatively free of polymers.

Coming now to the complete process of selectively separating al1 the impurities from a cracked distillate by the contact method and means described and referring to Process No. 1, Fig. -1 in particular, in the first tower or iirst series of towers in the system, the distillate is intimately contacted with a solution of a suitable carbonate such as sodium carbonate, or sodium bicarbonate, or other carbonate solution such as potassium carbonate solution, in any desired concentration up to a saturated solution in order to remove all organic acids present in the oil without abstraction of the phenols which are insoluble in carbonates. Such carbonate solution may also remove some HzS which offers no diniculty in after-separation, in well known ways for the recovery of the organic acids in their diierent forms.

The oil thus being selectively freed from organic acids is continuously flowed through the next series of similar towers in which it is contacted with a suitable caustic alkali solution such as sodiumI hydroxide, preferably up to about 10% concentration, although higher concentrations can be used, potassium hydroxide or other suitable caustic alkali solution which selectively removes the phenols present as sodium or potassium phenates as the case may be, and the phenols are recovered in any of a number of well known ways from such compounds.. The caustic alkali solution also removes any remaining H'zS and some of the mercaptans.

Thus far the described steps are shown in my prior Patent No. 1,953,336, April 3, 1934, and in the present case it will be noted that no water washing is necessary after either alkaline treatment because the contact towers are designed to provide a reagent free oil.

However, the next step of. the process employing similar towers utilizesl a water contacting step, the result of which would be adversely affected if the oil contained any of. the exhausted alkaline solutions previously used.

The result of this vwater contacting step is that it removes water soluble nitrogenous bases from the oil,'s`uch as pyridine, lutidine, colldine and other water soluble nitrogen compounds which may then be recovered in well known ways from the water as Valuable by-products.

Theioil, thus freed of acidic impurities and water soluble bases, is next treated in a series of similar towers with a dilute acid, preferably with sulphuric acid of a concentration of not more than about 10% which has the effect of removing water insoluble nitrogenous bases to form sulphates thereof but without material effect on unsaturated hydrocarbons to either polymerize or sulphate the same or to form alcohols therefrom.

The concentration of the sulphuric acid is highly important because with the low concentration used all of the remaining nitrogenous bases may be separately removed and recovered without the formation ofany material amount of.

sulphated olenes or of alcohols. l

Visual indication of this is shown, when 10% or less concentration of sulphuric acid is used, by the recovery of an acid liquor of red color, whereas if a concentration of higher than about .10% is used, for example sulphuric acid of 50% concentration, both a red and a green acid liquor is obtained.

The next step of the process is the removal of certain unstableunsaturated hydrocarbons, such as some of the dioleflnes, which tend to readily oxidize and polymerize with the formation of gums. This is accomplished by contacting the oil in a similar series of towers with sulphuric acid of a concentration insuiiicient to cause undesirable polymerization and sulphation of desired olenes while sulphating undesired hydrocarbons with the 'formation of an acid ,liquor readily hydrolizable to produce alcohols. Such concentration of sulphuric acid to produce the desired results may range between about '75% and 85% and is preferably about to produce an acid liquor containing sulphated unsaturated hydrocarbons without producing any material amount of alcohols although there may also lbe present some free alcohols probably formed by the catalytic action of the acid and due to the presence of sufficient water for hydrolysis when a lower concentration is used.

It will be understood that if the process is so used with only the recovery of purified distillate as the ultimate object a single tower may be employed as described for each step of the process depending on the character of the oil being treated, as has already been pointed out, in which case the distillate is merely passed once through each tower containing a different reagent until the treatments are finished', and also that the treatments with reagents may be conducted with any -desired temperature gradient through the towers for the desired effects. In any event it is preferred to pass the thus treated distillate then in liquid or vapor phase through the clay tower in which certain gum-forming constituents not removed by the acid treatment are polymerized to be removed thereafter by redistillation. The distillate may then be sweetened in well known ways and is ready for use.

The above steps of Process No. 1 assure the following results:

(1) The minimum use of reagents coupled with maximum removal of impurities.

(2) A more eflicient and economical result in the refining of cracked distillates.

(3) The recovery of by-products in sufficient purity and value to substantially offset the cost of refining.

(4) The production of motor fuel of high antiknock value. i

The clay contacting may be conducted at ordinary atmospheric temperatures, or at elevated temperatures up to about 400 F., or at temperatures suicient to maintain the distillate in vapor form. When higher temperatures are employed such `as a temperature suicient to entirely vaporize the distillate, the steps of Process No. 2 are preferred to be used.

In Process No. 2, the steps of treating up to and including the 10% acid refining are the same as Process No. 1, but thereafter the 80% acid treatment may be eliminated and the distillate completely vaporized to be passed through the treated clay in vapor phase, although liquid phase treatment in Process No. 2 may be at times desirable;

As has already been mentioned, the action of the clay on the hot distillate or vapor tends to decompose sulphur compounds with the formation of hydrogen sulphide and since the presence of much Ihydrogen sulphide in the fractionating column, or .bubble tower, in which polymers are removed in the presence of steam causes a corrosive action in the apparatus,l it is desirable to eliminate such hydrogen sulphide. This can be done by passing the eiiluent from the clay through a scrubber interposed between tower 31 and the fractionating column wherein the vapors are adequately contacted with a reagent adapted to unite with the hydrogen sulphite so that the material going to the fractionating column is freed from this corrosive element. Inasmuch as such scrubbing operation reduces the temperature of the effluent materialsto be fractionated. it follows that the thus treated stock should be brought to a desired temperature by suitable heat exchange, or direct heat, in any manner prior to fractionation and if the then fractionated distillate contains traces of hydrogen sulphide, the

same may be washed with caustic alkali solution prior to the usual sweetening step by means of doctor solution, or-otherwise. It is to be noted that in the steps, for example as enumerated in Process No. 2 where a dilute sulphuric acid is used, that on redistillation with steam after the clay treatment the system will be substantially free of acid as evidenced by the fact that the steam condensate is not acid in reaction, whereas when cracked distillates are treated with concentrated sulphuric acid, neutralized, etc., in the usual manner, certain acid hydrocarbon compounds are formed which are soluble in the oiland after neutralizing, -for example with caustic soda, are converted into the sodium salts of these compounds which on redistillation with steam are decomposed, with the formation of acid which is highly corrosive to equipment and necessitates the introduction of some alkali, for instance ammonia, in' the endeavor to neutralize the acids and protect the equipment from corrosion.

The net result of the treatments described. especially on California cracked distillates, is the production of a cracked gasoline of low gum and lowered sulphur content by the use of clay and a recovery, if desired, of valuable by-products. The octane value of the gasoline is not only conserved but may even be higher than that .of the untreated stock. As an example, crude oil from the Wilmington eld in California was cracked to produce a pressure distillate, the boiling point range by the A. S. T. M. method, and octane value of which are given below, compared with the boiling point range and octane value of the distillate after treatment, in accordance with the above described steps:

Untreated pressure Treated pressure distillate distillate u I. B. P 104 F. I. B. P 118 5% 164 F. 5% 170 10% 196 F. 10% 193 20% 238 F. 20% 228 30% 267 F. 30% 252 40% 290 F. 40% 274 50% 310F. 50% 292 60% 327 F. 60% 308 70% 338 F. 70% 322 365 F. 80% 344 385 F 90% 365 400 F. 95% 379 E. P 407 F. E. P 399 Recovery 97.0% Recovery 98.0% Bottoms 1.5% Bottoms 1.0% Loss 1.5% Loss 1.0% Octane No. (C. Octane No.(C. F.

F. R. method) 65.5 R. method) 66.0

clay is possible on California cracked gasoline by' reason of the prior removal of impurities which, heretofore, have poisoned-the clay, thereby rendering the use of clay on such stocks economically prohibitive.

By use of clay activated with sulphuric acid or aluminum sulphate, it has been found possible to reduce the sulphur content materially. For instance, in passing a cracked gasoline containing 1.48% sulphur through the steps of the proc-- ess the sulphur content of the finished gasoline was reduced to 0.4% whereas if the same stock is sweetened before hot clay treatment the distillate will come out sour and have to be resweetened,

and will be found of lower sulphur content after fied distillate by the removal of separate groups of impurities in order to leave the distillate in a form susceptible for emcient and economical clay treatment.

Thus steps Nos. 1 and 2 may be combined in which impurities soluble in, or reactive with, a caustic alkali washare removed together. Likewise, steps 3 and 4 which include treating with 10% HzSO4 may be eliminated and all nitrogenous bases be taken out with 80% H2804. l

In this event the distillate is purified for clay treatment which has never heretofore been practical for most California cracked stocks.

The range' of concentration of the acid used has a large bearing on the success of the process in the individual steps, because otherwise the formation of alcohols causes enhanced losses without commensurate recovery.

When it is desired to retain the cracked distillate in liquid form during clay treatment, or for accelerating the polymerizing or decomposing action ofthe clay on the distillate either in liquid or vapor form, a suitable superatmospheric pressure ranging up to 300 pounds per square inch may be held on the system.

I claim as my invention:

1. A process of treating oil with reagents which comprises: introducing independent streams of,

oil and .reagent into the lower part of a reaction zone containing contact material substantially submerged in the reagent, passing the said streams upwardly through said zone to cause intimate contacting of said oil and said reagent, then separating the oil and reagent by gravity.

3. A process of treating oil with reagents which comprises: introducing independent streams of oil and reagent into the lower part of a reaction zone containing contact material substantially submerged in the reagent, passing the said streams upwardly through said zone to cause intimate contacting of said oil and said reagent, then separating the oil and reagent, land recircomprises: introducing independent streams of culating the separated reagent back to the original point of entry.

4. A process of treating oil which comprises:

passing a stream of oil continuously through a series of towers each containing a zone lled with contact material and a separating zone, the passage of the oil through each contact zone being upwardly, simultaneously passing a stream of heavier liquid reagent upwardly through each contact zone with the oil, introducing fresh reagent into the last tower in the series in the direction of oil ow, separating the oil and reagent in the separating zone in said last tower, and passing the separated reagent to the next preceding towerin the series in the direction of oil flow.

SUMNER E. CAMPBELL