US2217727A - Method of preparing high melting point asphalt and high quality bright stock from mixed base residuum - Google Patents

Description

Patented 15, m40

` UNITED `STATES" PATENT OFFICE Y 2,217,727 METHOD oF rnEPAnnvG man MELTING POINT ASPHALT SIDUUM AND BRIGHT STOCK FROM HIGH QUALITY MIXED BASE RE- Arthur B. Brown and Frank C. Croxton, Hammond, Ind., and Bernard Ginsberg, Chicago, I11.. assignors to Standard Oil Company, Chicago, Ill., a corporation oi Indiana .Y Application June a 193s, serian No. 212,656

with the acid treating and neutralization steps.v

A further object is to provide an improved method and means for nishing an acid-treated filter stock to obtain petrolatums and bright stocks of improvedV cast, color stability andoxidation stability. Other objects will be apparent yas the detailed description of the invention proceeds.

In the operation 0f the deasphalting plant at Whiting, Indiana, it was discovered that the amount of propane admixed with 'the oil during the acid treating step had a profound effect on the neutralizing and nishing steps. When operating with a propane-to-oll ratio below 3:1 it was found that ythe sour oil could not be effectively neutralized, even when excess caustic and inti-I mate mixing was employed. This phenomena is unexplainable in'the light of our present knowledge and experience, but it is evident that the propane has some effect in the acid treating step other than that of a simple diluent or thinner.

The neutralization difliculty is not, as might be expected, a function-of the amount of acid used,-it ls a function of the propane ratio during the acid-treating step. However, the amount of acid used is important from the standpoint of color stability. If'large amounts of acid .are employed the oil requires little or no clay -to meet color specifications, but such excessively treated oils are not stable against oxidation, and they. tend to go oli color on standing, We have found thatnot only the propane ratio, but also the amount of acid used must be regulated within close limits, and that the nishing with clay must also bev within certain limits if a stable,

high quality bright stock is to be produced.

In practicing our invention we regulatel the propane ratio in the deasphalting step to produce asphalt of the desired melting point, penetra.

tions etc. Such ratios may, for instance, be in the range of 2:1 to about 4:1. Subsequent to the deasphaltingy step'and prior to the acid-treating i step .we add suillcient propane (if'addition is necessary) to bring the propane-tofoil ratio up to at least 3:1, and preferably to 3.5:1 or more.

The amount of acid should be sufcient to decolorize the oil only partially, and we have found that .25 to .3 pound of 93% sulfuric acidior its equivalent) per gallon of original charging stock meets this requirement when deasphalting is effected in about 3 to 4 volumes of propane at about `90 tti-115 F., preferably at about'llOV F. When lesser amountsof propane are employed in the deasphalting step. the amount of acid required maybe increased to about .3 to .7 pound per gallon of oil. The amount of acid should be regulated so that in the claying step a filter yield of about 400 to 1000, preferably about 600 to 700 gallons per ton is obtained when using average clayA (this may be increased to 1500 gallons Withnew No. l clay). This Aamount of claylng is essential for color and oxidation stability. We prefer to strain the oil through a spent lter `prior to the dewaxing or cold settling step, and

finally to percolate the wax-free oil or petrolatum in a fresh lter at about 100 to 180 F.

` Another feature of our invention, particularlyl when it is applied to therefining of petrolatum,

is our method of handling and eliminating sludge pepper. When heavy oils or petrolatums are acid-treated ln propane we have found that the treated product tends to suspend a sludge pepper" which has-to be removed before proper neutralization can be eiected. We have Y discovered that this sludge pepper may be removed by further settling. if sufficient propane diluent is employed and suiliclent settling time is allowed. Our method includes the provision of a sludge pepper" settling step with a propaneto-oil ratio of at least 3.5:1 and in a settling zone of the type used for deasphalting orcaustic settling.

y The invention will be more clearly understood from the following detailed description read in connection with the accompanying drawing which forms a part of `this specification and which illustrates a ow diagram of our improved system l for bright stock manufacture.

In our preferred embodiment we will describe the preparation of bright stock from a Mid-Continent residuum reduced to about 20% bottoms and having a viscosity of about 350 to 400 seconds Saybolt at 210 F. It should be understood, however, thatth'el inventlon'isequally applicable to other charging stocks and to oils of widely varying compositionm l.

A Mid-Continent reduced crude having a viscoslty @f about 365 to 37o seconds saybolt artt 210 F. is charged to the system through line I0 by means of pump Il and is admixed with about 21/2 volumes of propane from! storage `tank I2, pump I3 and line I4. This mixture is heated in exchanger or heater I5 to a temperature of about 90 to 115 F., preferably about 100 F. to 110 F. and then introduced into asphalt settler I6 which is maintained at about 200 to 350 pounds pressure,-suiiicient to prevent substantial vaporization of propane. With this low propane ratio a high melting asphalt of low penetration is separated out and withdrawn from the base' of the settler through line I1 to a conventional asphalt depropanizer system.

The propane soluble fraction from the asphalt settler is withdrawn through line I8 to rst acid sludge settler I9 but before it is introduced intothe settler it is admixed with enough propane from line to bring the propane-to-oil ratio up to at least 3: 1, and preferably to about 3.5: 1. Instead of using fresh acid at this point We introduce cycle sludge through line 2I from the second acid sludge settler. The intimate mixture of deasphalted oil, propane and cycle sludge'passes down through thefunnel-like center portion 22 'of the rst acid sludge settler into the quiescent zone in the lower part of the settler. Sludge is withdrawn from the base of the settler through line 23 to a conventional sludge depropanizer and hydrolyzer. Sour oil from the upper-part of the quiescent zone is withdrawn through line 24 to the upper part of second acid sludge settler 25. The fresh acid is introduced through line 26 preferably in amounts of about .2.to .5 pound of 93% acid (or equivalent amounts of 98% acid,etc.) per gallon of original oil charged. The amount of acid in all cases should be so regulated that the oil can be finished to the desired color with a percolation yield of about 400 to 1000 gallons per ton of average clay. It may also be desirable to add -additional propane to line 24 through line 21,

particularly if the propane ratio was low in the rst acid sludge settler. It is most important that the propane-to-oil ratio in the second settler be at least 3 or 31/2:1.

`The'sludge from the second settler is recycled through line 2l to line I8, as hereinabove described. If the sour oil from the upper part of the quiescent zonev in the second settler is substantially free of sludge pepper, it is withdrawn through line 28, admixed with caustic from line 29, and .introduced into caustic settler 30. The

amount of caustic will vary with different stocks and amounts of acid used, but we usually employ about .035 pound per gallon (based on original oil charged) in the form of a 3% solution of sodium hydroxide. The used caustic solution is withdrawn from the base of the settler .through line 3l, and the neutralized oiiis withdrawn.

through lines 32 and 33 to propane still 34. Propane is removed from the vtop of the still through line 35 and recovered for reuse. Depropanized oil is withdrawn through line 36 todepropanized filter stock storage tank 31. n

Filter stock from tank 31 is withdrawn -by pump 38 and admixed with light naphtha with" drawn from tank 38 by pump 48, the blend of naphtha and filter stock being introduced through lines 4I and 42 to the top of a used clay nlter 43. The purpose of passing the solution .through the used filter is' to strain out certain color bodies and impurities, thereby improving the quality of the petrolatum to be later .separated. The filter stock solution fromused filter 75 43'is withdrawn lines 44 and 45V to cold settling tank 46 wherein the solution is gradually chilled to low temperatures for the settling of through line 50, heater 5I and line 52 to fresh clay lter 53 where it is percolated through clay at about 100 to 180 F., preferably at about 110 F. to give a yield of about 400 to 1000 gallons per ton, preferably about 500 to 700 gallons per ton. From this clay filter the oil is passed through lines 54, 55 and 56 to naphtha-reducing still 51, the naphtha being returned through line 58 and condenser 59 to naphtha storage tank 39, and the iinished bright stock being withdrawn through line 60 to storage tank 6 I After settler 46 has been charged, as hereinabove described, the clay in filter 43 is revivied and/or fresh clay is added to this lter. Clay filter 53 now becomes the spent filter and the naphtha iilter stock solution from line 4I is charged through lines 4I and 62 into spent filter 53 for the straining step. 'I'he strained oil is withdrawn through lines 54 and 53, 44 and 64 to cold settling tank 65. After the solution has been chilled and settled in this tank the clear solution is withdrawn todewaxed solution tank 48 through line 66 .and the petrolatum is withdrawn from the.

base of the settler through line 61. 'Ihe dewaxed solution now passes `through line 50, heater 5I and line 68 to fresh filter 43, the clayed solution being withdrawn through lines 69 and 56 to the naphtha-reducing still hereinabove described.

The strainingfcold settling and filtering operations hereinabove described are designed for use in low pressure equipment. When high pressure equipment is available the use of naphtha may be entirely avoided and the neutralized cil from caustic settler 30 may be passed directly through lines 32, 18, 4I and 42 for straining in filter 43, or lines 32, 10, 4I and 62 for straining iu clay filter 53. Somewhat higher filter yields may be obtained by the straining and subsequent filtration Y in propane solution, but here again the temperature should be maintained at about 100 to 110 F.

for maimum eiliciency.

'tion arid is characterized by a low carbon residue and an acidity which is so low that it 'is negligible.

By regulating the propane ratio in the acid treating step subsequent to the deasphalting step, we have made it possible to use low propane ratios in the deasphalting step without interfering with the acid treating and neutralization steps. This enables the production of high quality asphalts in addition to the high quality bright stocks.

By operating at about 100-115 F. on a 20% M. C. residuum with a propane ratio lower than 3:1 we can produce an asphalt with a melting point above' 170" F. and a penetration at '17 F. of less than 5. By blending this hard asphalt in the acid treating step, neutralization can be easily eil'ected.

When petrolatums .or heavy oils are acidtreated it sometimes happensthat the sour oil from the second settler contains appreciable Vamounts `of sludge pepper vwhich is suspended or emulsified in the sour oil and which, unless it is removed, seriously impairs the quality o f the nished oil or petrolatum. We have discovered that this pepper" can best be removed by increasing the propane ratio to atleast 3.5:1 and settling the .pepper in a drum of the type used for settling asphalt and used'caustic. If the asphalt settler is available this vessel may be used for the pepper settle and further equipment (except for the necessary lines, valves,

i sour'oil or petrolatum thru line 1| to pepper settler 12, additional propanebeing introduced thru line I3 if necessary. The sludge pepper is settled'and withdrawn thru line Il and may be depropanized and hydrolyzed with the material. fromline 23. The pepper-free oil or petrolatum is returned by line to the caustic mixer and thence to ycaustic settler 30; as hereinabove dewscribed.

Thus, the propane-to-oil ratio should be a least 3:1 in the acid treating step. but if in this f stepa. sludge pepper n L'suspemiea in the on, additional propane may be added and this pepper gsettled out before the neutralization and further nishing steps. While we have described in deaarmav Y pumps, etc.) will not be necessary. .We may, however, close the valve in line 28 andpass the tail a preferred embodiment of our invention, it

should be understood that we do not limit ourpane-v-to-residuum ratio of less than 3:1 at a -temperature of about 90 to 115 E., addingenough propane tothe deasphalted oil vtogincrease the propane-to-oil ratio to at least 3:11, treating the oil in this propane s'olutionwitlr acid at a temperature of about 90 to 110 F. with an amount of acid of about .2 to .7 pound of 93%-98% sulfuric acid per gallon of oil, neutralizing the sour oil and filtering the neutralized oil through lclay at about 100 to 180 F. to .obtain clay yields of about 400 to 1000 gallons per ton of ordinary clay.

2. The `method of claim 1 which includes the further step of dewaxing .the neutralized oil prior tothe final ltering through clay.

3. The method of claim 1 which includespthe' steps' of depropanizing the neutralized oil, `mixing the depropanized oil withnaphtha, straining the-naphtha solution through a spent iilter, dewaxing the strained :naphtha solution, and subjecting the dewaxedso'lution to :the filtration step at about 100 to 180 F. vto obtain clay yields of about 400 to 1000 gallons per tonA of vaverage clay.

4. The method of -obtaining high melting point low penetration asphalts and high quality bright stocks which comprises deasphalting a mixed base residuum with a propane-to-residuuinratio less than 3:-1, adding additional propane to the deto about 3:1 to 3.5:1, 'acid-treating the oil in the resulting propane solution with about .25 to .7

pound'of 90% to 100% sulfuric acid per gallon of oil treated, neutralizing the acid-treated oil and treating said oilv with clay.

ARTHUR BROWN. FRANKg-C. CROXTON. BERNARD GINSBERG.

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