GULF OIL CORP OF PENNSYLVANIA
This invention relates to refining of petroleum oils; and it comprises a technique of refining petroleum oils for the production of lubricating oils for example, the said process including acid treating such oils in at the very least two different steps and at two different temperatures, at the least one of said treatments being conducted at temperatures ranging from 130° to 2120 F.; the said process also advantageously including a step of de-acidifying the acid oil derived from one among said acid treating steps by simple heating and reduction; all as more fully hereinafter set forth and as claimed.
In the recovery of lubricating oils from various crudes, the refining step has always contributed ]. a big proportion of the expense. In spite of much effort and time spent to develop better methods, the refining process generally employed is “treatment” with concentrated sulfuric acid, often followed by washing with water and caustic soda solution. The sulfuric acid treatment improves the standard of the oil, especially as regards color and odor. The treatment is usually conducted at temperatures within the neighborhood of 700-1100 F. Temperatures much above this have “, been reported as producing dark colored and inferior products.
Within the sulfuric acid means of refining, a socalled acid sludge is produced which is usually. separated from the remaining oil by the addition of a small proportion of water followed by gravity cettling, etc. The sludge-free oil retains an appreciable content of acid compounds which have to be removed in some fashion. The step of deacidifying this “acid oil” (usually called “sourS3 oil”) often presents considerable difficulties.
One of many customary methods of handling such acid oils includes washing with water and neutralizing with a dilute caustic solution during agitation with air or steam, usually followed by another washing with water. Another method which may be used is described in my copending application, Serial No. 596,093, filed March 1, 1932. This method consists in a clay contacting and reduction step at a maximum temperature of about 300° to 550°’F.
While it has generally not been considered commercially feasible to acid treat a crude oil before reduction, owing to the high cost of the extra sulfuric acid required, I have found that such a Co treatment is frequently advantageous when combined with a second acid treatment after reduction and usually at a better temperature. I’ve also found that the de-acidification of the acid oil resulting from at the least one of the acid treat5, ing steps could be conveniently accomplished by a simple heating which could also be accompanied by reduction. By acid treating in two different steps and at two different temperatures, not less than one among said treatments being conducted at temperatures of 130° to 212′ F. I have found an important improvement in the quality of the refined oil both as to color and carbon residues.
Where lubricating oils are to be produced from a crude at some distance from the oil fields, preliminary acid treatment at or near the oil fields may prove commercially advantageous as a result of lessening in bulk occasioned by such a treatment.
This lessened bulk reduces the transportation costs on the oil of value, as well as the cost of the next reduction. It might also happen that the acid is cheaper on the oil fields or that the fuel oil sludge produced during acid treatment is more disposable at thatpoint.
I’ve found that a more advantageous method of de-acidifying the acid oil resulting from the. above acid treating steps consists in simply passing the oil right into a still and heating to temperatures ranging from about 5000 to 650° F. Reduction could be accomplished simultaneously if desired. It is sometimes advantageous in this process to heat the oil rapidly while in turbulent flow.
This reduces the chance for acid sludge particles to deposit in the still within the form of coke, causing difficulty in the still. This kind of heating could be accomplished in the fashionable tube still, for instance, in which the time of heating to temperatures above 400° F. could be restricted to less than 30 minutes. The still could be equipped with a fractionating tower with the intention to separate the lighter fractions while the heated oil is being de-acidified. If desired, the acid oil could be partially or wholly neutralized with caustic soda, for instance, before being introduced into the reducing still. If the acid oil is one derived from acid treating an unreduced crude such a neutralizati6n is usually advantageous. During deacidification by heating, the color of the oil isn’t appreciably impaired. Some of the color produced could also be removed by simple filtration.
The described method of de-acidifying acid oil represents a fantastic simplification over prior methods. Much of the mechanical handling of the oil is eliminated and any tendency towards the formation of troublesome emulsions is obviated.
The double acid treatment of my invention, certainly one of said treatments being at a better temperature than the opposite, is advantageous in producing lubricating oils of.low carbon residue and of wonderful color characteristics. If desired the second treatment may directly follow the primary although better results are usually secured with using a heat treatment and reduction of the acid oil after the primary acid treatment. A minimum of one of these treatments (usually the second) needs to be conducted at elevated temperatures starting from 1300 to 2120 F. while the other may be carried out at the same old temperatures of 600 to 130* F. If desired, a dewaxing step may follow each acid treatment or only the ultimate treatment. By such a mix of acid treatments high grade lubricating oils can be produced even from many low grade, asphaltic base crudes.
So as as an instance my invention more specifically four embodiments might be described in reference to the accompanying drawings which represent four flow sheets of actual fullscale operations throughout the scope of my invention, wherein various petroleum stocks are treated by a series of successive operations with the last word production of finished bright stocks. The several operations are indicated on the flow sheets by appropriate legends. In this showing: Fig. 1 represents a process wherein a light crude is directly acid treated at low temperatures followed by a second treatment, after de-acidification by heating and reduction, at higher temperatures, Fg. 2 represents the processing of a light, reduced crude stock with two acid treatments at different temperatures.
Fig. 3 shows the treatment of a heavy lubricating stock derived by mixing an unpressable distillate, an overhead cylinder stock and a residuum, while Fig. 4 shows the treatment of a really heavy residuum, which comprises an initial high-temperature treatment followed by a lower temperature treatment, after de-acidification by simple heating.
Starting at the top of the flow sheet of Fig. 1 a crude of fair quality (100 parts) is shown to be acid treated, at a temperature ranging from 80* to 100° F. with a quantity of 98 per cent sulfuric acid amounting to about 0.5 pound per gallon. In this process the loss of sludge was about 10 per cent. The acid oil from the acid treatment was, in this case, partially neutralized by adding 2.5 per cent by volume of 4 per cent caustic soda solution. (If desired, this step will be omitted.) No water settling of sludge was employed on this case, as the oil was of low viscosity and the soft sludge separated and settled readily.
The partially neutralized acid oil was fed, as shown, directly into a continuous tube still by which it was subjected to a fire and steam reduction. A lot of the charge (65 parts) was distilled off and recovered as gasoline, kerosene, gas oil and pressable distillates, leaving bottoms amounting to 24 parts. The latter were subjected to a second acid treatment at the higher temperature of 140° to 150* F. In this case 1 pound of sulfuric acid was used per gallon of bottoms. But the loss to sludge was only 3 parts.
The acid oil derived from the second acid treating step is able to being processed in several ways. As shown on the chart in dotted lines the acid oil might be de-acidified by simple heating and reduction.’ The maximum still temperature utilized in such a step is about 550* F. A small yield of distillate (1 part) is obtained during reduction.
After the de-acidification step it is convenient, as shown, so as to add the naphtha required in the subsequent wax removal operation. This dilution assists within the clay filtration which advantageously follows the step of de-acidification by simple heating. After this filtration the remaining steps followed through within the operation shown in Fig. 1 consisted of the usual chilling, centrifuging, reduction and clay filtration, these steps forming no a part of the current invention.
Several other methods could be employed for deacidifying the acid oil from the second, hightemperature acid treatment. One such method, namely, a clay contacting and reduction step, is illustrated on the flow chart. As there shown in ; full lines, lime and fuller’s earth amounting to 0.05 and 0.6 pound per gallon of acid oil, respectively, might be added to the oil. The acid oil can then be heated under agitating conditions with slight reduction to a maximum temperature of 5500 F. The oil and clay mixture is then cooled to temperatures about 2500-3000 F. and passed through filters for clay removal. After filtration the steps of chilling, centrifuging, etc. are followed as before. The method illustrated in Fig. 2 Is quite just like that of Fig. 1, with the exception that on this operation at light reduced Oklahoma crude was employed. Starting at the top of this figure a reduced crude (100 parts) was first acid treated with 1 pound per gallon of 98 per cent sulfuric acid. In this operation treatment was conducted at a temperature of 1040 to 123* F. The acid sludge was settled for about 5 hours, air blown for 1 hour at 135° F. and again settled for six hours. The acid oil was then drawn off and subjected to a simple heat treatment and reduction at a maximum temperature of around 600″ F. for de-acidification purposes. On this reduction both gas oil and pressable distillates were recovered. If desired the bottoms recovered in this de-acidification step can be dewaxed before in addition to after a second acid treatment. However, I usually prefer to dewax in a single operation after the second acid treatment as shown on the chart when the amount of wax present just isn’t abnormally great.
The bottoms from the above reduction, amounting to 42 parts, were treated under agitating conditions with about 0.75 pound of 98 per cent acid per gallon at temperatures starting from 143° to 154* F. After completion of the reaction, the mixture was diluted with about 10 per cent by volume of heavy, uncracked kerosene distillate. This addition reduced the viscosity and enabled the 60 rapid subsidence of the sludge which was removed by settling, air agitation, and again settling. The acid oil recovered from these operations was subjected to a clay contacting and reduction step using 1 pound of clay per gallon and a maximum temperature of about 600* F. The kerosene which was added within the treating step in addition to a small amount of intermediate distillate were recovered during this reduction. Further processing included the addition of naphtha, chilling, dewaxing by centrifugal force and clay filtering.
The bright stock recovered from this processing was found to have the following characteristics: Gravity: °A. P. I—- ————-24.3 Viscosity, S. U. V.
100° F —————–_____ 2154 210 —- —————125 Flash, open cup: °F———.- —-__ 495 Fire, open cup: OF—————– 570 Pour test: °F——————— +15 Color, N. P. A——-.————-. 5.5 Carbon residue: %——————-1.4 Acid number ———————– 0.01 Figure 3 shows the refining of a mixed lubricating stock comprising an unpressable distillate, an overhead cylinder stock and a heavy residuum.
One crude oil inventory trading of many more important ways in which this process differs from that of ig. 1 is in the dilution of the lubricating stock with about 12 per cent of heavy kerosene distillate previous to acid treatment. In this operation the acid oil from the first acid treatment was de-acidified by simple heating to 6000 F. without the partial neutralization shown within the means of Fig. 1. The second acid treatment was conducted by heating the mixture of acid and oil to temperatures between 155° and 1650 F. under agitating conditions.
Kerosene distillate was added to the reaction mixture to assist within the subsidence of the sludge.
The finished bright stock produced by the operations outlined was found to have the following characteristics: SGravity, A. P. I———————- 22.8 2Vis. 210* F————————— 153 Flash, P. M. °F———————- 515 Flash, O. C. °F———————- 550 Fire, 0. C—————————- 640 Pour, F ————————— +20 Color, N. P. A ————————. 7 Carbon residue-.———————- 1.7 The method shown in Fig. 4 is of a quite different type from that shown in Figs. 1, 2 and three. On this operation a heavy residuum from Oklahoma crude, having a viscosity of 180 S. U. V. at 210° F. was initially treated with a small quantity of acid amounting to only 15 pounds per barrel of the residuum. This treatment was conducted at temperatures from 170-2000 F. The sludge produced on this treatment settled readily, leaving a warm oil practically free from acid and containing just a few particles of fine suspended sludge. On this instance e the acid oil was merely cooled to the temperatures required in a second acid treating step without de-acidification, as shown in full lines on the flow sheet. Another procedure is to digest the acid oil in a still with the intention to de-acidify the same at temperatures within the neighborhood of 500° F. following the dotted lines on the chart. During such a digestion a small distillate (1 part) is recovered, as indicated.
The next step of the above process was a second acid treatment with a bigger proportion of acid amounting to about 1.75 pounds per gallon of the pretreated oil. This treatment was conducted at the lower temperatures of 130 to 150° F. After separation of the sludge, amounting to 24 parts, the resulting acid oil was subjected to a clay contacting and reduction step for de-acidification.
The remaining process steps shown on the chart are conventional.
The finished bright stock produced by the processing of Fig. 4 was found to have the next characteristics: Gravity.———— ————-Vis./210 ——————–Flash, O. C————————65 Fire, O. C————————Pour: ‘F ————————–Color: N. P. A———————-Carbon residue: %——————23.0 155 510 590 +15, 6 1.75 In the two specific embodiments shown in Figs. 70 1 and a pair of, the first acid treatment was conducted with a relatively light product, that is, with a light crude or a light, reduced crude. Within the process of Fig. 3 a heavy lubricating stock was employed, but this stock was diluted with a light 75 distillate previous to acid treatment. The processing of the diluted mixture was then conducted in a manner somewhat similar to that employed in treating the stocks of lower viscosity. The processes shown in Pigs. 1, 2 and 3 are suitable to be used with light crudes, light reduced crudes, diluted heavy residua or with other stocks of similar properties. For such stocks the dual treatment method of my invention is usually conducted by employing an initial treatment at moderate temperatures of say 60° to 130° F. and a final treatment at higher temperatures ranging from about 1300 to 212° F.
The dual method of treatment shown in Figs. 1, 2 and 3 has several important advantages, especially when oils are used with which the entire treating losses are high. The amount of acid employed in the first treatment will be reduced to some extent where the formation of prohibitively large masses of heavy sludge can be avoided.
Any such formation results within the loss of efficacy of the acid, appreciable losses of treated oil in the heavy sludge, poor separation of sludge and the production of sulfonated compounds in undesirable quantities. In my process these excessive losses are obviated by adding acid in the first treatment only sufficient to remove the bulk of the whole asphaltic matter. This leaves within the acid oil not only some colloidal particles of acid sludge but additionally some sulfonated compounds in solution. De-acidification of this acid oil by heating to temperatures of at least 500′ F. is usually important in that both types of those impurities are thereby decomposed to form materials of a secondary nature which respond readily to a subsequent acid treatment. The double acid treatment of my invention, when employed with an intermediate heating step produces a product of higher quality than either a single acid treatment with the total amount of acid or ai r double treatment without the intermediate heating step. Moreover, the acid oil appears to be so conditioned by the intermediate heat treatment that a given amount of refining can often be produced thereafter by a smaller quantity of acid. Less sulfonated copounds are formed in the second treatment. The acid oil resulting from the second treatment is of considerably higher quality than that which can be produced by the use of the full amount of acid in a single treatment. The sludge s ettles more cleanly.
Within the dual method of acid treatment as shown in Figs. 1, 2 and 3, a big proportion of the -asphaltic material is removed by the primary treatment. Throughout the secondary acid treatment I have found that superior results are usually obtained, as regards agglomeration and settling of sludge particles, by the expedient of adding as much as 12 per cent of kerosene distillate to the agitated oil-sludge mixture after the reaction of the acid with the asphaltic and resinous materials has been substantially completed. Such a procedure is shown in Figs. 2 and 3.
The flow sheet of Fig. 4 shows a somewhat different method of treating heavy lubricating stocks. On this method of treatment such stocks are, acid treated without the preliminary diluition shown in Fig. 3. The process is applicable to very heavy residua or to mixtures of such residua and heavy distillates, corresponding to overhead cylinder stocks. In treating such a oils without preliminary dilution the temperature conditions of the two treatments outlined above are advantageously reversed.. For instance, a small amount of acid may be employed in the 17 first treatment at temperatures ranging from 130* to 212° F. This removes a large proportion of the asphaltic material within the form of a really stiff heavy sludge containing little or no free acid, which might be faraway from an agitator after settling while still warm, in a melted condition. A small amount of acid will remove several times its weight of asphaltic material under these conditions. Upon cooling, this sludge usually hardens to a brittle mass which might be conveniently burned in lump form on an ordinary furnace grate, acting somewhat similar to bituminous coal. Very little sulfonation is produced on this initial treatment as a result of effect of mass action of the massive excess of asphaltic matter and the small amount of acid used, and little or no free acid or sludge particles are left in the warm acid oil. This makes it possible to conduct the second acid treatment at lower temperatures without the necessity of an intermediate de-acidification step.
In this type of treatment only relatively small quantities of acid, for example lower than one pound per gallon, must be employed in the first treating step, since, if all or a big proportion of the acid required for complete refining were added in one step, a violent reaction would ensue with the formation of undesirable reaction products and a severe loss of oil. The second treatment should be conducted at lower temperatures to be able to avoid similar difficulties.
A larger quantity of acid is usually used in this second treatment.
Various changes may be made in the particular 3 steps of the processes outlined above without departing from the scope of my invention. For instance the proportions and concentrations of acid used in the treating steps, the temperatures employed within the acid treating and reducing steps, the proportions of naphtha employed in dewaxing, the quantity of fuller’s earth used, etc. may all be varied to a substantial extent. Even the sequence of several of the steps of my process may be altered in some cases. Other variations from the above procedure which fall within the claims will be evident to those skilled within the art.
What I claim is:1. In the recovery of lubricating oils from heavy petroleum oils, a process of refining the lubricating oil which comprises in combination the steps of treating the oil with concentrated sulfuric acid whereby a part of the acid reacts with the oil to form a removable sludge and of deacidifying the acid oil solely by heating it to temperatures between 500* and 650* F.
2. In a strategy of refining petroleum oils, the step which comprises de-acidifying the acid oil derived from a sulfuric acid treatment solely by a simple heating to temperatures starting from 500° to 650* F. the duration of said heating at temperatures above 400* F. being not greater than 30 minutes and said heating being conducted under conditions of turbulent flow.
3. In the recovery of lubricating oils from various stocks the refining steps which comprise treating such a stock with concentrated sulfuric acid, de-acidifying solely by heating the reaction prod7ucts to temperatures between 5000 and 650° F. and again treating said stock with sulfuric acid having the identical concentration as utilized in the first step.
4. Within the refining of petroleum oils the steps which consists in treating an oil with sulfuric 76 acid, de-acidifying the acid oil solely by heating to temperatures of at least 5000 F. and again treating the deacidified oil with sulfuric acid.
5. Within the recovery of lubricating oils from petroleum oil, the refining.steps which comprise treating an oil with approximately 98 per cent concentrated sulfuric acid at ordinary operating temperatures, de-acidifying the acid oil thereby produced solely by a heat treatment at temperatures between about 500″ and 6500 F. and again treating with 98 per cent concentrated sulfuric acid at temperatures between 130* and 2120 F.
6. Within the recovery of lubricating oils from petroleum oil, the refining steps which comprise treating an oil with sulfuric acid of concentration approximately 98 per cent H2SO4 by weight at temperatures between 130″ and 2120 F. cooling and again treating at lower temperatures with sulfuric acid having the same concentration and de-acidifying the resulting acid oil solely by heating to temperatures between 5000 and 6500 F. 7. Within the recovery of lubricating oils by the refining of light reduced crudes and diluted heavy reduced crudes, the three steps in combination which include treating such a crude with concentrated sulfuric acid at temperatures ranging between 60* and 120* F. with separation of sludge deacidifying the acid oil by heating to temperatures of from 500° to 650° F. and again treating at temperatures ranging from 1300 to 2120 F. with a somewhat smaller proportion of concentrated sul- 80 furic acid having the same concentration as that utilized in the first step.
8. The refining steps of claim 7 by which the reaction mixture resulting from acid treatment is diluted with a light distillate in order to facilitate 88 the settling of the acid sludge formed.
9. In the recovery of lubricating oils by refining heavy reduced crudes and petroleum residua, the steps which comprise initially treating such stocks at temperatures from 130° to 2120 F. with a small proportion of the whole amount of 98 per cent concentrated H2SOi ultimately required for refining to the degree desired, de-acidifying the treated oil solely by heating to temperatures of at the very least 500* F. and subsequently treating the de-adidifled oil with a proportion of 98 per cent concentration H2SO4 sufficient to refine it to the degree desired at ordinary operating temperatures.
10. In the recovery of lubricating oils by the refining of reduced crudes, the steps which com- 10 prise treating such a crude with concentrated sulfuric acid of concentration about 98 per cent H2S04 by weight at temperatures between 60* and 130″ F. in a proportion of about one pound sulfuric acid per gallon of crude, deacidifying and reduc- 5U ing the acid oil by heating to maximum temperatures of between 5000 and 6500 F. again acid treating at temperatures of from 1300 to 212* F. using somewhat less sulfuric acid of the identical concentration, and at last de-acidifying the acid oil by a combined clay-contact and reduction step.
11. In the recovery of lubricating oils by refining heavy lubricating stocks the steps which comprise diluting such a crude oil inventory trading stock, treating said diluted stock at temperatures between 60* and 130* F. with concentrated sulfuric acid of concentration approximately 98 per cent H2S04 by weight in the proportior of 0.75 pound of sulfuric acid per gallon of stock, deacidifying by reducing the acid stock at mnximum temperatures between 5000 and 6500 F. treating the reduced stock with concentrated sulfuric acid of the identical concentration at temperatures between 130° and 212″ F. diluting the reaction mixture with a light distillate to advertise settling of acid sludge, separat- 5 ing the sludge and de-acidifying the treated oil.
12. In the recovery of lubricating oils by the refining of heavy reduced crudes, the steps which comprise treating such a crude at temperatures of about 130° to 212* F. with concentrated sulfuric acid of concentration approximately 98 per cent H2SO4 by weight within the proportion of fifteen pounds of acid per barrel of crude, deacidifying the acid oil by heating at maximum temperatures of from 5000 to 6500 F. again treating with concentrated sulfuric acid of the same concentration at somewhat lower temperatures and de-acidifying said treated stock.
13. In the recovery of lubricating oils by the refining of heavy lubricating stocks, the steps comprising treating such a stock at temperatures ranging from 130″ to 212° F.