US2056913A - Process of removing soaps from asphaltic still bottoms and purifying the same - Google Patents

Description

Oct. 6, 1936. H. T. TERRELL E1- Al.

PROCESS OF REMOVING SOAPS FROM ASPHALTIC STILL BOTTOMS AND PURIFYING THE SAME Filed April 15, 1935 Patented Oct. 6, 1936 PB0ESS 0F REMOVING SOAPS FROM AS- PHALTIC STILL BOTTOMS AND PURIFY- lNG THE SAME Basson T. Terrell, Edward M. Hughes, and Philip Y L. Carter, Chester, Pa., assignors to Sun Oil' Company, Philadelphia, Pa., a corporation of New Jersey Applicaiinnnpru 15,1935, serial Nit-16,270 2 claims. (ci. s79) The present invention relates to a process for producing cutting oil and more particularly to a process for producing cutting oil comprising a blend of lubricating oil and soaps of petroleum naphthenic acids, and to the method of producing such soaps.

When distilling lubricating oils from a topped residue, or mazoot, derived from a coastal naphthenic or asphaltic base crude which has been treated with caustic soda. before distillation, there is produced an asphaltic still bottom which contains soaps of petroleum naphthenic acids in considerable quantities. `Such a process is described and claimed in the patent to Arthur E. Pew, Jr., No. 1,761,153, issued June 3, 1930. In lthe processl outlined above and described and claimed in thepatent, the topped crude or ma-` zoot is treated with caustic soda before distillation for the purpose of converting any contained petroleum naphthenic acids into their corresponding soaps or sodium salts. This procedure lis followed in order that the distillates .thereby produced will not contain the petroleum naphthenic acids, thereby rendering unnecessary excessive acid treatment and neutralizationof the distillates produced.

The petroleum naphthenic `acids, which are naturally contained in coastal and other similar I crudes, have boiling points which approximate those of the lubricating fractions in such crudes. It is therefore impossible to avoid distilling oi such petroleum naphthenic acids, if the topped crudes or mazoots are distilled without preliminary treatment. The preliminary treatment with caustic soda solution, however, transforms any contained petroleum naphthenic. acids into their corresponding soaps or sodium salts, which soaps have boiling points much higher than any 1,694,463, issued November 11, 1928, wherein the oils or asphaltic bottoms containing the soaps are converted by the addition of water into an emulsion, the emulsion heated under super-atmospheric pressure to a temperature above the boiling point of water and the soap solution settled from the asphalt; or the lubricating distillates containing the fatty acids are treated with sulphuric acid, the precipitate drawn off and the remaining body of naphthenic acid containing oil treated with an alkali to form an emulsion. The emulsion so formed is then settled, and the soap and water layer withdrawn, leaving a soap-free mineral lubricating oil; To the soaps so extracted there,is added a small proportion apl ufacture a cutting oil from the same without re ducing the original starting material, or any of the intermediate products, to emulsion form.-

A better understanding of the invention will be had vby reference `to the accompanying drawing whih'is a diagrammatic representation of one type of equipment in which the present invention may be lcarried out. f

Referring now to the drav. ng:

A, B, and C represent agitators such as are usually used in petroleum reneries for the acid treatment and neutralization of lubricatingoils.

D 'represents' a distillation unit wherein the distilland is heated by means -of the latent heat of condensation of mercury vapor. 'Such an apparatus is described a'd claimed in the patent to Arthur E. PeW,.Jr., No. 1,761,151, issued June 3, 1930.

E also represents an agitator of the 'same type as A, B, and' C.

'The balance of the equipment shown in the Vdrawing consists of storage tanks, run down tanks, condensers, coolers, and heatersv such as form a part of the equipment in any petroleum renery.

lso

y Referring, now more particularly to the drawing, the soap-containing asphalt bottom vsuch as derived from a distillation process, as described and claimed in Pew Patent 1,761,153, are admitted to the process through line I under a pressure imposed by pump 2. These bottoms are fed to a manifold line 3,having valved branches 4, l. and 6 leading to each of the agitators A B, and C, respectively. sulphuric acid is admitted to the process from an acid ball, or any suitable source, .through valved line 'l to manifold l from which it is fed by means of valved branches l, I Il, and I I to each of agitators A, B, and C, respectively. 'I'he agitators A, B, and C are each provided with valved outlets I2, I3, and I4 leading to a manifold line I5 in which is placed a pump I6 for pumping the material from the agitators.

Leading into the manifold I5 is a valved line Il containing a pump I8 which takes suction on a lubricating oil storage tank I9. The line Il leads through a heater or heat exchanger and thence to the distillation plant D. There is also provided a tank 2i, having a valved inlet 22,' and a valved outlet 23 containing pump 24. This tank may be used as storage for a portion or all ot the material flowing from the agitators A, B. and C. and tank I9 toward the distillation unit D.

The distillation unit D consists of a vaporizer 25 having upper and lower portions separated by a flat plate 26. The material to be distilled passes into the vaporizer 25 from line 21 leading from the heater 20. A pool of the material is maintained at one endiof the vaporizer 25 by means of the weir 28. The material to be distilled overiiows this Weir and ilows in a lthin film downwardly over the plate 28, being heated during its travel by means of the latent heat of condensation of mercury vapor which is admitted to the lower portion of the vaporizer 25 through line 29, the liquid mercury formed by the condensation being withdrawn through lineI 30 and returned to the mercury boiler (not-shown). Any

material which is unvaporized in the vaporizer 2l flows out through line 3I which connects with the inlet end of the next vaporizer in series. For the present purposes, there would ordinarily be from 6 to 10 of these vaporizers in series. However, one only is shown in the drawing for the purpose of `simplicity The vapors generated within the vaporizer 23 are withdrawn through lines 32 which lead to a vapor manifold 33 from which-in vturn lines above the vapor inlets 34, therev is placed an annular pan 36 and aseries'oi bubble trays 31, the

pan 3B providing a throat to permit the upward passage of uncondensed vapors. That section oi' the tower below the pan 33 also contains several bubble platesto aid in thepoper separation or liquid and vapor within that sction or the tower.

- That portion of the vapor which is condensed below the pan 36 is drawn oil' from the bottom of the tower through line 3 3 and is returned to the inlet end or the vaporizer. Those vapors which pass up through the throat in pan 33 are fractionally condensed. by means yof redux liquid added to the toppf tbe tower. 'and run down over the plates in the tower and are withdrawn through line 3l and cooler 4l to' run down tank -4I, whence they are periodically `through valved line 42, containing pumplgand delivered to tank 44. The vapors which vare condensed in the tower 35 pass overhead-through line 46 to a condenser 43, whence theyfpto ture within tower 35, and therefore the rate of cooling, is maintained such as .to preclude the passing overhead and cooling of more vapors than are necessary to form the requiredv quantity 'of reflux. If, however, a superfluous amount of reflux accumulates in tank 41 it is withdrawn to storage through valved line 43 by means of pump 50. From the top oi reflux tank 41 there is a valved line 5I which leads to vacuum producing equipment, sincev it is desirable, if not necessary, to maintain the various stills in the series D under absolute pressures which vary from stili to still, but are all very low. g

Leading from the bottom of tank 44 there is 'a valved line 52 containing pump 33. This line leads to and throughs. heater or heat exchanger 54. From the heat exchanger a line '55 leads to the top .of agitator E; Line 56, for the con- A-ior the purpose of blowing the material within agitator E. The bottom of the agitator E is provided with a valved outlet BI containing pump the material from 32 for the purpose of forcing agitator E to storage tank'33.

The apparatus just described is used as follows in carryingout the present process:

Asphaltic products, containing soaps of naphthenic acids, from a lubricating oil distillation process are admitted through line I 'and any of its branch lines 4, 5, and 6 to one or all ot the agitutors A, B, and C. These bottoms are preferably heated to a temperature varying between 300 and 500 1 1'. When a sumcient quantity of bottoms has been admitted to one 0r all oi. the agitators, depending on whether the ilrst portion oi the process is being run, as a batch process or a` Continuous one. 66 B. sulphuric acid (Q6-93% H2804) is added through lines 9, III, or II. acid so admitted is in a quantity not more suillcient (practically a quantity-not quite suillcient) to completely convert the contained soaps to their corresponding petroleum naphthenic acids. This isy quite necessary. since an excess of sulphuric acid would have an exceedingly deleterious corrosive action on the succeeding eqgipment. After the proper quantity of acid has added, the contentsarel agitated until a reaction product. After the reactioniscom- 3 plete, the acidiied` bottoms are withdrawn through lines I2, I3, or I4' to line- I5 by means of pump I3.y To the line I3 is also adde 15%l of a lubricating oil distillate having, or example..

a cash oi 37o-385 F. a nre of, isa-445 F.. and

a saybqi; viscosity at 100l F., of 50o-03o seconds.

oil is preferably heated to about 400 F., or

the approximate temperature of the acidifled bottoms. The mixture so produced is then passed .either'to tank 2I vor-directly tothe distillation` equipmmt D.

As explainedin the first part of vthe present are converted to their corresponding acids. Even pecification, the soaps contained in the bottoms though the. acids have -a much lower lboiling point than the asphalt containing them and are therefore distillable from the bottoms, whereas the soaps have boiling points much too high to be distilled without cracking, the acids are not readily distillable without the admixture of an oil such as, or similar to, that just described, since the asphalt exerts a sufficiently high partial pressure effect to make it extremely dilcult to distill thev acids below cracking temperature without also distilling oi a portion of the asphalts, or at least carrying olf a portion of the asphalt in entrainment. However, by the addition of from to 15% of a lubricating oil as above described', it is possible to readily distill these acids without cracking, due to the fact that the added oilexerts a partial pressureeffect, and is much lower boiling than the asphaltic constituents or the acids being distilled. Since a certain proportion of lubricating oil is requisite in the final product, the addition oi oil at this stage imposes only a slight added burden on the plant, which burdenis more than offset by the added advantages obtained. In certain cases the asphaltic bottoms fed to the process will contain some undistilled lubricating oils, in which case it will be unnecessary to add any oil as above described,

since the oil remaining in the asphalts will exertY vacuum to drive oi a portion of the oil and acids. -V

The dstilland unvaporized in this vaporizer is then passed, by means of line 3|, to the next vaporizer in series. The vapors generated within the vaporizers 25 are withdrawn through risers 32, manifolds 33, and lines 34 to the towers 35, within the lower portion of which a small proportion of the vapors are condensed and returned by means of. lines 33 to the inlet end of the vaporizer wherein they were generated, the remaining portion passing up through the throats in pans 36 and being in the major part condensed by contact with the reux liquid ilowing downwardly over trays 31. The remaining portion passes through lines 45 and condensers and coolers 46 to the reflux lines 41 the condensate with in the reflux tank being withdrawn and returned through lines 48 to the tops of towers 35. The amount of vapors passed overhead is controlled by the temperatures in the towers so as to provide, on condensation and cooling, just suincient reflux to condense the desired side streams within the towers 35. The side streams, which are withdrawn through lines 39 from pans 35, are theA desired acids and oil distilled therewith and are passed through coolers 40 to run down tam 4|. In -the production of the usual grade of cutting oil all ofthe distilled acids are pumped from the ru'n down tank Il to a single storage tank u. However, incertain cases it may be desirable to segregate the various fractions distilled and classify them as to viscosity or saponlilcation number for various other uses, or for making various grades of cutting or emulsiable oils.

Generally the best results are obtained by lamount of lubricating oil remaining therein, or

the amount of lubricating oil added after acidiilcation of the bottoms.

As a specific example, the following inlet temperatures and absolute pressures will serve to demonstrate the method of distilling wherein a battery of seven stills was employed.

Still No. l 570 F. 18-14 mm'. Still No. 2 605 F. 13-11 mm. Still No. 3 630 F. 11-8 mm. Still No. 4 650 F. 10-8 mm. Y Still No. 5 665 F. 10-8 mm. Still No. 6 675 F. 9-6 mm. Still No. 7 680 F. 8-6 mm.

The amount of acids distilled from the bottoms as a whole, or obtained in each cut. will. of course, vary slightly depending upon the crude from which the starting material was derived. The following, however, will serve as an example:

Still numbers No.1 No.2 No.3 No.4 No.5 No.6 No.1

Testa:

Soy. vis. at 210 F- 46 Saponiiition No. 55.9l

When the above acids were combined, the'total showed a viscosity of 75 seconds Saybolt at 210 F., and a Saponication No. of 40.6.

The composite of these cuts is withdrawn from the tank M through line 52 by means of pump 53, and is pumped through a heater 54 and line 55 to the agitator E. The proper quantity of caustic soda solution of 35-41 B. (about 29- 36% NaOH) is then added through line 55. Agi-I tation s then carried out by means of air admitted through line 50, or other suitable means, until lthe acids are completely saponiiled. The amount of sodium hydroxide added, and itsA strength, will vary depending upon the water content of the acids, the water content desired in the nished material. and the saponiilcation value of the acids or mixture of acids and oil. Generally'it has been found that with a composite such as illustrated above, 38 B. caustic soda in the proper proportions gives a product having the required characteristics. It is usually advisable to use a slight excess of caustic soda solution, so that the nished product will be very slightly on the alkaline side. If the'saponied mixture contains too much water, it is blown with air to remove the excess water content.

Aftersaponiflcation, a light mineral lubricating oil having a Saybolt viscosity of 10Q-115 seconds at 100 F. is added in amounts varying from to 50%, depending upon the amount of soaps desirable in the finished product, the viscosity desired inthe finished product, and the emulsifying qualities required. '.l'his oil is added by means of valved line 51, the oil being drawn from tank 53 and pumped by means of pump 53.

The nnished cutting oil (which is an emulsoid jor dispersoid system itself before the addition of water) will have approximately the following characteristics, 4depending'upon the amount-ot oil added in both cases:

Light oil 40%lilhl cil soap and Wren and heavy y vy oil A. P. I. Gravity- -i 16. 3 17. 2 Flash F 340 3N) Fire F .v- 365 366 Vis. at 1(1)" F. S. 2753 1W Vis atl30FS m' lidi Vis,Bt210F S U-- 72 65 Pour test F.-- +10 +5 1.61 1.38 Water 2. i l. 8 Alkalinity NaOH 0.(8 0.07 Sap. value f Sap. equivalent mg. KOB '22 19 adding to said bottoms a mineral acid', thereby effecting the acidification Vot soaps, and adding also a sumcient quantity of lubricating oil ot lower aosems -and'form a mineral'oil and soap emulsion.

2. The process of producing a blend of lubri- .cating. oil and naphthenic acid soaps from asphaltic bottoms containing naphthenic acid soaps produced inthe distillation of naphthenic base oil inthe presence ofan alkali, which comprises adding to. said bottoms a mineral acid in an 'amount not :quite sumcient to completely acidity the soapsand adding also lubricating oil, sub- Jecnng the resultant emulsion of asphalt, oil and naphthenic acids to distillation to vaporize the acldsand oil, condensingthe acid-oil vapors, and

adding to the condensate an alkali adapted to -convert the contained acids to soaps and forni a

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