US2017610A - Refining of cracked petroleum products - Google Patents

Description

Patented o... 15, 1935,

. BEFINING F.

CRACKED PETROLEUM PRODUCTS Donald in. Stevens, Pittsburgh, and William A.

Gruse, Wllkinsburg, Pa., assignors to Gulf lie-- fining Company, Pittsburgh, Pa., a corporation of Texas No Drawing. Application February fin-1932,

' Serial No. 591,928

This invention relates to refining petroleum products; and it comprises processes of refining cracked petroleum products such as gasoline distillates, kerosene distillates and the like, wherein such products are reacted with sulfuric acid and with hydroxylated aromatic compounds, such as phenols or coal tar acids., in admixture, at temperatures up to 300 F., the amount of hydroxylated compounds employed 'varying between 0.25 and 600 per cent or thereabouts by weight of the sulfuric acid used and the gravity of the sulfuric acid varying between about 45 and 66- B. or heavier; and it also includes the products resulting from the described processes, said products being refined cracked petroleum distillates, having a low gum content,

a high oxygen stability and being free from gumforming constituents reactive with mixtures of hydroxylated aromatic compounds and sulfuric acid; all as inore fully hereinafter set forth and as claimed.

. The commercial refining of cracked gasoline distillates has received a large amount of study. While many different methods have been suggested, the art as a whole has never departed from the use of sulfuric acid as a refining agent. While this reagent may not be the best for the purpose, it is at least one of the cheapest-and thus economic reasons have dictated its use.

Sulfuric acid, as used in the refining of cracked gasoline distillates produces rather heavy losses. Part of the gasoline becomes combined, dissolved or mechanically trapped in the/acid sludge, this loss being greater the larger the quantity of acid used. Another loss is generally ascribed to a polymerization of unsaturated compounds to form heavy ends, that is higher boiling substances, and is thereforecalled the polymerization loss. The sum of these two losses in certaininstances may run as high as 7.0 per cent, for example.

All cracked distillates, whether from pressure stills or from the so-called vapor phase cracking processes, contain appreciable quantities of unsaturated compounds. This is true also of thefinished products obtained by redistillation of these distillates. A considerable portion of this unsaturation is due to stable olefinic hydrocarbons and these are desirable components. The

remainder is due to small proportions of much less stable hydrocarbons which are mainly responsible for color, development of gum and oxldative changes. The action of the sulfuric acid does not stop with the removal of these un desirable constituents but extends in some degree to all types of hydrocarbons present. It is 22 Claims. (01.106-40) of cracked diflicult to control conditions so that merely the highly unsaturated and unstable bodies are affected while the other stable and valuable constituents are unaffected. With the more highly cracked distillates, sulfuric acid itself is relatively ineffective.

We have found that the reactivity of sulfuric acid with these oils can be restrained and directed in a desirable manner by the addition of certain hydroxylated aromatic compounds to the reaction mixture; The hydroxylated compounds useful in this invention include various phenols and naphthols. The phenols in general, including homologues within this term, are particularly advantageous. These compounds can be'added directly during refining or separately to either the acid or the oil before refining. The use of these compounds causes several specific effects. For example, for a given amount of acid used, there is a considerable decrease in the tendency to subsequently develop and deposit gum.

Valuable improvement in the refining operation results from the addition of hydroxylated compounds in amount as small as 0.25 per cent by weight of the acid used. The losses to sludge and to higher boiling liquid polymers are both reduced. In another method of utilizing our discovery smaller proportions than usual of sulfuric acid may be advantageously employed when hydroxylated compounds are present in quantity up to molecular proportion, Still other applicatior'ls of our invention will appear in the following discussion.

In the use of our process, due to the restrained activity of the sulfuric acid, higher temperatures may be employed than in the usual sulfuric acid refining. And contrary to teachings of prior refinery art, in the present invention the use of high temperaturesup to about 300 F., actually 1 produces improved results.

There are several possible explanations for the efiects'caused by our hydroxylated compounds.

It is possible that the latter may condense or combine specifically with certain unsaturated gum-forming hydrocarbons. Such condensation products would be expected to be high boiling compounds and hence would fall outside the gasoline range. The sulfuric acid may thenact merely as a condensing agent. It is possible that our hydroxylated compounds may form compounds, such as phenol sulfonic acids, with the sulfuric acid and that such compounds are the active agents in the refiningxreactions. It appears probable, however, that the hydroxylated compounds or their sulfonic derivatives may con- 5 dense with some constituents of the gasoline to form some type of antioxidants, Whatever the real explanation may be, the facts as stated remain. Our invention is therefore not based on any theory which may be suggested for its operation.

The materials effective in our invention apabout two-thirds phenol and one-third cresolscontaining varying proportions-of hydrocarbons.

, The latter appear to have no harmful effect on the refining action and may be beneficial. Tar

acid oils of high hydrocarbon content have been employed successfully.

In a series of experlmentamade to test the eflicacy of various amounts of acid in combination with varying quantities of hydroxylated compounds, a pressure still cracked distillate, very difiicultto refine by ordinary methods was treated at room temperature with 66 B. sulfuric acid, with and without tar acid for 5 minutes, under uniform conditions of agitation. The results obtained are summarized in Table 1.

66 B. acid per barrel of material treated and heavy end, or non-gasoline residue obtained on redistillation.

- Table 2 Amount sulfuric Amount tar acid acid #lbarrel Polymeroxygen ization gum loss Copper Sludge dish gum I loss 0 10 Molecular. 36

These data show that 6 pounds per barrel of acid did not satisfactorily reduce the copper dish gum while 4 pounds, in the presence of a molecular proportion of. tar acid, were satisfactory. This table also shows a reduction in polymerization loss caused by the addition of the tar acid. The sludge loss was reduced to zero in this experiment.

Other experiments recorded in Table 3 were made upon a pressure still distillate which had a copper dish gum test of 467 before treatment. These tests were made to determine the eflect of temperature when treating with different strengths of acid, and the copper dish gum test was used as a measure 'of the degree of refining achieved. In every test the amount of sulfuric acid used was equivalent to four pounds of the tar acid used was in excess of this uniform Table 1 J quantity of sulfuric acid. The time of treat- Amount Bub ment was five minutes for each test except the mm acid Amg lg t g ng; ggf Sludgeloss one recorded in the first line of the extreme 35 #I r1ght hand column, which latter was thirty minutes. Comparable tests were made at room temc o its 3.2 perature (referred to as "cold in Table 3) and 3 8 3? 9% a; at atemperature of F. (referred to as hot 6 5 ms 339 2.2 in Table 3). .It will be observed that just a 40 g 8?; i trace of phenolic bodies has a very pronounced a Molecular. 11 5 1.1 eflect refining the distillate. Table 3 follows:

It is seen from this table that 10 pounds of Table 3 Cold plus Cold plus Hot plus Hot plus 1 P t Acid Acid'B flbmel Cold k822i); tar T tracii tar 66.0 also 4.0 29 1s 14 12 16 50 69.4 71.0 so 121 47 51 11 11 50.2 72.0 5.4 250 171 14s 25 21 63.8 01.4 5.7 104 230 71 32 I 49.6 .01.: 0.2 293 210 232 114 32 "heating timaaominutes. 0

sulfuric acid per barrel (used alone) were required' to properly refine this particular distillate; that is to attain acceptable non-gumming characteristics When 5 per cent of tar acid was added, calculated as a percentage of the sulfuric acid employed, the amount of sulfuric acid required to give an acceptable result was only 8 pounds. The presence of 10 per cent of tar acid reduced the required amount of sulfuric acid to produce like results to about 6 pounds per barrel. The use of molecular proportions of tar acid (practically equal weights of tar acid and sulfuric acid) produced improvement and in particular a considerable reduction in the loss to sludge. I

In experiments under the same conditions on a fresh vapor phase cracked distillate the results shown in Table 2 were obtained, the column marked polymerization loss representing the At higher temperatures, as is seen from the above table, satisfactory copper dish gums cam be obtained with acid concentrations as low as 49.5 B. when molecular proportions of tar acid are employed; Sulfuric acid having gravities as 00 low as 45 B. can be employed in a similar manner. Fuming sulfuric acid is likewise applicable in our invention. The most advantageous range of acid concentration appears to' be betweengravities of about 51 and 66 B. 65

Recovery of finished gasolines from the treated, cracked distillates obtained as described above I may be accomplished by conventional refinery practices. The acid sludge is usually removed by settling, the sour oil being decanted off 70 from the sludge residue. Any reduction in the quantity of distillate present after removal of the sludge is referred to as sludge loss in the tables given above. The sour-oil remaining after separation of the sludge is washed with a dilute 75 alkali solution and then with water, or with water alone. The washed product is then redistilled or re-run as usual. The non-gasoline residues remaining after this distillation are referred to as polymerization loss" in the above tables. It has further been found that, when molecular quantities of tar acid are added to 563 B. (72 per cent) sulfuric acid, good refining is obtained at 190 F. with quantities as low as 2 pounds acid per barrel. When 495 B. (61.8 per cent) acid is used with molecular proportions of tar acid, as small quantities as 4 pounds aeidper barrel can be employed, the refining losses remaining small.

Experiments have been made with tar acid which has been heated with sulfuric acid prior to its addition to the oil. In fact when sulfuric acid having a gravity lower than about 60 B. is employed it has been found desirable to heat the acid and the hydroxylated aromatic compounds together until a homogeneous solution is formed before adding the mixture to the oil. During such a heating operation doubtless some sulfonation takes place. But in other experi-. ments tar acid was added to the oil prior to the addition of the acid with but little difference in ultimate result. These experiments show that sulfonated hydroxylated aromatic compounds are applicable in our process as well as the unsulfonated compounds.

If a substantial amount oftar acid is used in the refining process the quantity of sulfuric acid can be reduced to minor proportions. Thus, good refining has been obtained with 0.? pound of sulfuric acid per barrel-of oil together with 3 to 4 pounds per barrel of phenols. If the phenol is reduced to 2 pounds per barrel the acid remaining at 0.7 pound per barrel, the results are only fair. It is evident from this that, in the presence of a small quantity of acid, the phenol is a somewhat more effective refining agent than is the sulfuric acid alone.

Our experiments have shown that our process can be operated satisfactorily from, room temperatures up to about 300 F. At the higher temperatures pressure apparatus is required; the pressure, as such, apparently producing no effect. We generally prefer to employ temperatures slightly below the boiling point of the products to be refined. A reflux condenser may be employed to prevent evaporation losses if desired or sufiicient pressure may be used to maintain the petroleum products in liquid phase.

The oxygen stability of the products refined by our process is highly satisfactory. In one experiment in which a vapor phase gasoline was refined with 6 pounds per barrel of ordinary sul.

,oxygen of 100 pounds per square inch (army aviation test) was 550 mg. per 100 cc. The same material, refined with two lots of 2-pounds per barrel of tar acid and 0.7 pound per barrel of sulfuric acid, gave a residual gum test of only 3.4. It has also been found that the anti-knock value of the product is not impaired by the use of. hydroxylated aromatic compounds in the refining.

The sludge from one refining operation may be used for further treatment of a new distillate but it is sometimes desirable to add some fresh sulfuric acid to it in using it for this purpose. A second treatment with new reagents may then be applied. We have also found that an economy This may be caused by the setting up of an equilibrium, some of the unsaturated compounds and some of the phenols remaining uncombined when all the reagents are added in on it oh. Unused phenols are sometimes present in e treated distillate before alkali washing and may be recovcred-from the alkali solution used.

Various advantageous embodiments of our in- 10 vention will become evident to those skilled in the art after reading the above description. In commercial use the relative costs of sulfuric acid and of the various hydroxylated compounds applicable as well as thedegree of refining desired will largely determine the method to be employed. We have found that loss to sludge can be completely eliminated by the use of approximately half molecular proportions of tar acid, for example, at elevated temperatures. This proportion also produces favorable results uponthe polymerization loss, degumming, etc. Even a trace of tar acid, such as 0.25 per cent by weight of the acid used, produces an improved product. On the other hand, if the cost of the hydroxylated compounds should be lower than that of the acid, or if a high degree of refining is desired, the pro-' portion of tar acid can be considerably increased with a corresponding reduction in the amount of sulfuric acid employed. Proportions of tar acid up to six times the weight of the acid (600 per cent) are feasible. It is also possible to vary the procedure by employing sulfuric acid of considerably lighter gravity than that usually used if such acid is available. i

What we claim is:-

1. In-the refining of cracked petroleum distillates, the process which comprises reacting coal tar acids with sulfuric acid and treating said distillates with the resulting reaction products to 40 obtain a finished product having a-low gum content and substantially free from gum-forming constituents.

2. In the refining of cracked petroleum products, the process which comprises adding a small 5 amount of coal tar acids to such products and reacting said mixture with sulfuric acid to obtain a finished product having a low gum content and substantially free from gum-forming constituents. I

3. The process-of claim 2 in which said treatment is carried out at temperatures varying from room temperature up to 300 F.

4. In the refining of cracked petroleum products, the process which comprises mixing such 5 products with asmall amount of a phenol and sulfuric acid, and reacting said mixture to obtain a finished product having a low gum content and substantially free from gum-forming constit- I uents.

5. In the refining of cracked petroleum products, the process which comprises mixing such products with a small amount of coal tar acids and sulfuric acid, and reacting said mixture to obtain a finished product having a low gum content and substantially free from gum-forming constituents.

6. In the refining of cracked petroleum products, the process which. comprises mixing such products with a small amount of a phenol and sulfuric acid, and reacting said mixture at temperatures ranging from about room temperatures to 300 F. to obtain a finished product having a low gum content and substantially free from gum-forming constituents.

' products with a small amount of a phenol and sulfuric acid, and reacting said mixture to obtain a finished product having a low gum content and. substantially free from gum-forming constituents, said phenol amounting to from 0.25 to 600 per cent by weight of the sulfuric acid employed.

9. In the refining of cracked petroleum products, the process which comprises mixing such products with a small amount of coal tar acids and sulfuric acid, and reacting said mixture to obtain a finished product having a low gum content and substantially free from gum-forming constituents, said coal tar acids amounting to from 0.25 to 600 per cent by weight of the sulfuric acid employed.

10. In the refining of cracked petroleum prod-. ucts, the process which comprises mixing such products with a small amount of sulfuric acid and a hydroxylated aromatic compound, selected from a group consisting of tar acid, phenols and naphthols, and reacting said mixture to..obtain a finished product having a low gum content and substantially free from gum-forming constituents.

11. In the refining of cracked petroleum products, the process which comprises mixing such products with a small amount of sulfuric acid and a hydroxylated aromatic compound, selected from a group consisting of tar acids, phenols and naphthols, and reacting said mixture at temperatures ranging from about room temperatures to 300 F. to obtain a finished product having a low gum content and substantially free from gumforming constituents.

12. In the refining of cracked petroleum products, the process which comprises mixing such products with a small amount of sulfuric acid and a hydroxylated aromatic compound, selected from a group consisting of tar acids, phenols and naphthols, and reacting said mixture to obtain a finished product having a low gum content and substantially free from gum-forming constituents, said hydroxylated aromatic compound amounting to from 0.25 to 600 per cent by weight of the sulfuric acid employed. 7 p

13. In the refining of cracked-petroleum products, theprocess which comprises mixing such products with a small amount of sulfuric acid and a hydroxylated aromatic compound, selected from a group consisting of tar acids, phenols and naphthols, and reacting said mixture to obtain a finished product having a low gum content and substantially free from gum-forming constituents, said sulfuric acid varying in gravity from 56$, to-66 B.

14. In the refining of cracked petroleum products, the process which comprises mixing such products witha small amount of a mixture, of sulfuric acid and a hydroxylated aromatic compound, selected from a group consisting of tar acids, phenols and naphthols and reacting said mixture at temperatures ranging from about room temperatures to 300 F. and under sufilcient presproducts in successive stages with small propor- 5 tions of a mixture of sulfuric acid and hydroxylated aromatic compounds, selected from a group consisting of tar acids, phenols and naphthols, to obtain. a finished product having a low gum content and substantially free from gum-forming 10 constituents.

16. In the refining of cracked petroleum distillates, the process which comprises reacting a hydroxylated aromatic compound, selected from a group consisting of tar acid, phenols and naphl5 thols, with sulfuric acid and treating said petroleum distillates with the resulting reaction products to obtain a finished product having a low gum-content and substantially free from gum-forming constituents.

17. In the refining of cracked petroleum distillates, the process which comprises adding a: small amount of a hydroxylated aromatic compound selected from a group consisting of tar acid, phenols and naphthols, to said distillates and 25 reacting said mixture with sulfuric acid to obtain a finished product having a low gum content and substantially free from gum-forming constituents.

18. In the refining of cracked petroleum prod- 3 ucts, the process which comprises mixing such products with a small amount of a naphthol and sulfuric acid, and reacting said mixture to obtain a finished product having a low gum con tent and substantially free from gum-forming 35 constituents.

19. In the process of recovering, from cracked petroleum distillates, refined cracked gasolines having a low gum content, a high oxygen stability and being substantially free from gum,-forming constituents,the steps which comprise adding to such distillates small amounts of sulfuric acid and a hydroxylated aromatic compound selected from a'class consisting of phenols, naphthols and tar acids and causing the components of the resuiting mixture to react together.

' 20. In the process of recovering, from cracked petroleum distillates, refined cracked gasolines having a low gum content, a high oxygen stability and being substantially free from gum-forming constituents, the steps which comprise adding to such distillates small amounts of sulfuric acid anda phenol and causing the components of the resulting mixture to react together.

21. In the process of recovering, from cracked petroleum distillates, refined cracked gasolines having a low gum content, a high oxygen stability and being substantially free from gum-form- DONALD R. STEVENS. M A. GRUSE.