US2029758A - Treatment of hydrocarbon oils - Google Patents

Description

Feb. 4, 1936.

R. B. DAY

TREATMENT OF HYDROCARBON OILS 3 Sheets-Sheet 1 Filed June ll 1934 INVENTOR ROLAND B. DAY wax;

' I ATTORNE$ Feb. 4,.1936. R. B. DAY

TREATMENT OF HYDROCARBON OILS Filed June 11, 1954 3 Sheets-Sheet 2 mafiam 45.2.

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1 TREATMENT OF HYDROCARBON OILS Feb. 4, 1936.

Filed June 11, 1954 3 Sheets-Sheet 3 4 I m I 3 a B I II 7 l I 0 w 9 m m W B 3 Em m F- A W 7 H mm M w Mm -T LF A o m 6 RW W A S T GF Drum b D mPm PT R c 4 SM WOW EUE LPL mm www 3 moo ccc 0B l 4 m m m w w m m w w w z m 0 LBS. PER BBL.OF 93% SULFURIC ACID ATTORN Patented Feb. 4, 1936 UNITED STATES PATENT OFFICE 2,029,758 TREATMENT OF HYDROCARBON OILS Roland B. Day,

Chicago; 111., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware This application is a continuation in part of my application Serial No. 566,872, filed October 5, 1931, and refers more particularly to the treatment of the light distillates produced in the cracking of heavy hydrocarbon oils to effect their more efficient desulfurization.

More specifically the invention has reference to improvements in processes for the treatment of hydrocarbon 011 distillates, particularly cracked hydrocarbon oil distillates, by a method which enables the reduction of total sulfur content and gum-forming constituents to be accomplished with minimum losses and generally increased efficiency over processes at present in vogue in the oil industry.

Lower boiling petroleum distillates, more particularly those produced from the cracking of the heavier portions of crude petroleums and containing material amounts of components boiling within the range of commercial gasoline commonly contain representatives of well-known groups of sulfur derivatives such as the mercaptans, sulfides or sulfur ethers, thiophenes, thiophanes, etc., and also hydrocarbon derivatives of a straight chain and cyclic structure which vary in their degree of unsaturation and reactivity with sulfuric acid, and it is the purpose of all commercially used methods of treatment to reduce the content of these classes of compounds in the distillates so that the sulfur content is brought to a point corresponding to a minimum requirement while removing only those unsaturated hydrocarbons which have definite gumforming tendencies without affecting such hydrocarbon compounds as the mono olefins which are stable and have good antiknock characteristics.

The method of treatment of longest standing for accomplishing these objects consists in treatment with sulfuric acid of commercial grade after a preliminary washing with caustic soda solution to remove hydrogen sulfide and to some extent the mercaptans. This type of treatment, however, possesses numerous well recognized disadvantages in the cost of the reagents employed and the lack of selectivity in their action, particularly sulfuric acid, the latter not only forming addition compounds with olefins; but-also inducing polymerization and condensation reactions between mono as well as dioleflns under ordinary conditions of treatment to cause high losses in material and form tarry sludges due to its powerful oxidizing and dehydrating action, the sludges being difiicult to treat for the recovery of the acid without large losses thereof by reduction. Furthermore, a redistillation oi the treated oil is practically always necessary owing to the presence in solution of a certain amount of high boiling compounds formed by the induced polymerization and condensation reactions among the unsaturated hydrocarbons. The present inven- 5 tion is concerned with a more efficient method of treating cracked distillates by means of which the more highly unsaturated di and tri olefinic constituents are selectively polymerized prior to the use of sulfuric acid so that the latter may 10 exert a maximum selective influence for the removal of sulfur compounds.

In one specific embodiment the invention comprises the treatment of cracked hydrocarbon oil distillates by passing them in heated vaporous 15 condition while mixed with hydrochloric acid over solid metallic contact materials to cause selective polymerization of highly unsaturated gum-forming hydrocarbon compounds while leaving mono olefins substantially unaffected, fractionating to 20 remove heavy polymerization and condensation products, recovering gasoline boiling range material by condensation and treating the condensate with sulfuric acid to effect a reduction in its sulfur content., 25

I have heretofore disclosed a process for the treatment of cracked hydrocarbon distillates in the vapor phase with hydrochloric acid in the presence of various metallic contact and catalytic materials such as, for example, certain 30 metals, particularly copper, zinc and mercury which I showed to have a catalytic effect upon polymerizing and condensing reactions induced by hydrochloric acid. I have also previously indicated that improved such treatments by-the use of alloys containing metals above and below hydrogen in the electrochemical series, ordinary brass being an example of such alloys. I have now found that the selective polymerization reactions thus induced upon 40 the unsaturated constituents of low boiling gasoline vapors effect the removal of highly unsaturated gum-forming compounds which otherwise consume large amounts of sulfuric acid and prea vent its action in removing sulfur compounds. 45 By the use of the present process, therefore, high etficiency in removal of both gum-forming and. "sulfur compounds is attained.

The term hydrochloric acid as used in the present connection has reference to aqueous solu- 60 tions of hydrogen chloride and the corresponding mixtures of water vapor and hydrogen'chloride resulting from their vaporization. Thus the first step of the process is distinguished from processes employing dry hydrogen chloride, it

results are obtained in 35 having been found that definite amounts of water (or steam) are necessary for the efficiency of the treating reactions. The acid added to the vapors undergoing treatment in the first stage may therefore be obtained by the injection of aqueous solutions or the separate addition of hydrogen chloride and water or steam to the reaction zone.

The attached diagrammatic drawings have been provided to assist in describing a type of operation characteristic of the invention and shows in side elevation by the use of conventional figures an arrangement of elements in which the process may be conducted. The layout shown, however, is merely typical of many different forms of plants which may be employed and while the nature of the invention will be clear from the description with reference thereto, it is to be understood that no limitation of the process is implied.

Referring to the drawings, it will be seen that it consists essentially of two successive interconnected treating units, the first provided for treating with hydrochloric acid and contact materials in the vapor phase and the second for the subsequent sulfuric acid treatment of the distillates in the liquid phase. Line containing control valve 2, indicates any line through which vapors or liquids to be treated may be admitted to the process. Vapors from a cracking process .after preliminary fractionation may be admitted through this line, and if at the temperature suitable for treatment may be by-passed through a line 5, containing a control valve 6 to enter a vapor phase treater l3 through a line 9, containing a control valve 0, leading to the upper end of the treater and another branch line H, containing a control valve I2, leading to the lower end of the same. In case it may be necessary to raise the temperature of 'the entering vapors or in case liquids are admitted to the process they may be passed through a heating element 3 disposed to receiveheat from a furnace 4 and brought to the required temperature and/or desired vapor phase condition as the case may be, the heated products passing to line 9 by way of line 1 containing control valve 8.

Treater |3 preferably contains a stationary body of metallic catalytic material in the space 4, the material being supported upon a conical perforated plate M. The treater is provided with upper and lower manheads I! and I8 to permit the admission and rejection of fresh and spent solid catalytic material when necessary. When downflow treatments are desired vapors are admitted from line 9 into upper space l5 above the metallic contact mass, passed downwardly through the same and enter lower vapor space |6, in which a preliminary or rough separation of reaction products and treated uncondensed vapors occur. The hydrochloric acid necessary for the reactions may be supplied through a line I9, containing a control valve 20, to a feed pump 2| which discharges through a line 22, containing control valve 23, and having branch line 24, containing control valve 25, entering upper vapor space 5 and branch line 26, containing control valve 21, leading to lower vapor space l6. Since either an aqueous solution of hydrochloric acid or the gas itself along with steam may be supplied, .pump 2| may be in' the one case of a type adapted to pump corrosive liquids and in the other case a suitable gas blower or compressor. If the anhydrous gas is pumped in,

the necessary amount of steam may be added at any point along its line of flow.

When downflow treatments are conducted, subsequent fractionation of treated vapors is practically always necessary and in such cases they may be conducted through a line 28, containing a control valve 29, which joins with a line 32, containing a control valve 33, leading to a fractionator 34.

When treatments are conducted with the v8.- pors flowing upwardly through a contact mass a certain degree of fractionation will take place so that in some cases the subsequent fractionator may not be necessary, in which case the fractionated vapors leaving the upper vapor space l5 of treater l3 may pass by way of line 36, containing control valve 3|, and line 31, containing control valve 38, to vapor line 39 for direct condensation, as will presently be described in more detail. When the fractionation has been insufficient to produce vapors of the required boiling range they may be diverted from line 3| through line 28, containing control valve 29, to line 32 which leads to the fractionator as already described.

Polymers and heavy reaction products accumulating in the bottom of the treater may be withdrawn therefrom through a line 52, containing a control valve 53, and be led to an intermediate accumulator 54 which provides temporary storage for the products from whence they may be withdrawn to a suitable disposition'through a line 52','containing a control valve 53, for example, they may be returned to the heating zone of a cracking process to undergo further decomposition reactions with resultant increased yields of light products, in case their carbon-forming tendencies are not too high. Refiuxes from the bottom of fractionator 34 which will contain further amounts of materials of boiling point range too high for use as gasoline may also be led to the accumulator 54 through a line 55, containing a control valve 56, and be disposed of along with the products from the treater. This will usually be the case if vapors of naphthas are treated which contain substantial amounts of materials boiling higher than those desired in the finished product. This material is quite uniformly of a grade suitable for further pyrolysis. The accumulator may have a vapor connecting line 84 permitting the return of any gaseous or vaporous products to the treater, thus'preventing vapor lock.

Vapors from fractionator 34 may pass through a line 35, containing control valve 36, and enter line 39, containing control valve 40, and leading to condenser coil 4|, which is provided to effect liquefaction of condensible constituents, liquids and gases from the condenser passing through a line 42, containing a control valve 43, to a. receiver 44. This receiver may be provided with a. gas

release line 45, containing a control valve 46, through which fixed gases may be withdrawn and the development of excess pressure thus prevented. To assist in controlling the boiling point range of the vapors from the fractionator a por-- tion of the condensed liquids may be returned to the top of the fractionator by way of a line 41, containing a control valve 48, a recirculating pump 49, and a discharge line 50, containing a control valve 5|.

The description thus far has covered the first stage of the treatment which produces in general a gasoline boiling range distillate from which the more reactive and readily polymerizable unsaturated hydrocarbons have been removed by the experiments have shown method and means disclosed. The temperatures utilized in this first stage may vary over a considerable range, for example, from 200 to 600 F., though it has been found that in the case of vapors arising from a cracking process they may be treated under substantially the conditions under which they arise or under somewhat reduced temperature conditions due the vapors to the vapor phase treating equipment. In all cases the conditions will be selected which to produce the best results.

The second stage of the treatment consists in the use of sulfuric acid to further treat the gasoline with the object of effecting a substantial reduction in the total sulfur content, in the absence of olefin compounds readily reactive with the acid. To this end the distillates may be transferred to a treater 66 of any common type employed in the oil industry for sulfuric acid treatments, the drawing showing the well known cone-bottomed agitator. The distillates to be treated may be transferred to the agitator by a pump 59 which takes suction on receiver 44 through a line 51, containing a control valve 58 and discharges into line 60, containing a control valve 6! and GI. Line 50 may be provided with branch line 62, containing control valve 63, for discharge of the distillates into the upper part of the agitator and branch line 64, containing control valve 65. which may be used when the oils are discharged into the bottom of the agitator for any reason.

Assuming the transferred oil to occupy the space 61 below the dotted line, treating and washing reagents may finished product. Pump 16 may take suction upon a line 68, containing a control valve 69; and having branch suction lines [0, containing control valves H, valves 13 and 14 containing control valve 15. Through these manifolded lines treating liquids may be introduced in proper succession. to suit the needs of the treatment, for example, line 68 may serve for the admission of sulfuric acid, line I for wash water, line 12 for caustic soda solutions, and line 14 for sweetening reagents such as sodium plumbite. Pump 16 may discharge the treating liquids through-a line 11, containing control valve 18, and terminating in distributing means 19 which is provided with the object of producing an increased efficiency of contact. To further insure the complete utilization of the strength of the added reagents the partially spent solutions may be taken from the cone of the agitator through a line 80, containing a control valve 8|, and returned by pump 16 to the top of the agitator. Branch line 82, containing control valve 83, is a line which provides for the ultimate removal of sludge reaction products either continuously or intermittently.

The description of the second stage of the treatment just preceding has been given in the most simple manner and is merely typical of any of the methods which may be employed for subjecting the vapor phase treated gasoline to treatment with sulfuric acid. Any other type of liquid phase treating plant may be used such as the continuous plants which are now in general use throughout the oil industry wherein the oils to be treated are passed in a continuous stream through alternate mixing and settling devices with treating, neutralizing, sweetening and washing reagents. added at proper points.

' To show the beneficial results obtainable by to lowering of the cracking plant pressure prior to the admission of then be applied to produce a 12 containing control the use of the process of the invention, the appended curves have been provided which show graphically the results obtained in treating a California cracked distillate for desulfurization by the process of the invention. This distillate had an end boiling point of 437 F., a total sulfur content of 0.45% and a gum-content of 300 mgs. by the copper dish method, indicating a rather high percentage of readily polymerizable and gum-forming oleflns. The curves show generally a comparison between the results obtainable by the use of sulfuric acid alone upon such a distillate and corresponding results obtainable by treatment according to the process of the invention wherein the gum-forming constituents of the vapors are selectively polymerized prior to sulfuric acid treatment.

Referring to curve I the relation between the sulfur reduction by the two methods of treatment is shown for amounts of sulfuric acid ranging from zero to fourteen pounds of 93% sulfuric acid per barrel of gasoline. It will be observed that the vapor phase treating alone without any sulfuric acid treatment reduced the sulfur content from 0.45 to 0.31. It will also be observed that without the preliminary vapor phase treatment that the minimum sulfur content attainable by the use of sulfuric acid alone is 0.16% whereas if the acid treatment is preceded by the vapor phase treatment described a content of 0.11% can be reached.

Curve 2 shows the relation between the total treating, vaporizing and polymerizing losses which occur by the two methods of treatment which are being compared and it will be observed again that the comparison is distinctly in favor of the method of treatment characteristic of the present invention, when it is desired to produce a gasoline meeting a minimum sulfur requirement. It will be observed that without the removal of the gum-forming compounds by the first step of the process that the usual 0.10 of sulfur was not attainable by using what is ordinarily considered to be a prohibitive amount of sulfuric acid, to wit, 12 pounds per barrel, and that according to the curve, added amounts of acid effected no further reduction in sulfur. At the critical point where the 0.10 sulfur percent is reached the overall treating loss-with 10 pounds of sulfuric acid was 7% as compared with only 4% when the first step of the process had been employed.

Curve 3 shows a relationship between the gum content and the pounds of 93% sulfuric acid used per barrel for the two types of treatment. Whileit is difficult to obtain concordant results by means of this test, several deductions can be made from the curves. In the first place it will be observed that the gum content when sulfuric acid is used alone as a treating agent varied much more widely than when the acid treatment has been preceded bythe vapor phase treatment. This is to be expected owing to the great reactivity of the unsaturated hydrocarbon constituents removed by the vapor phase treatment. It is further to be noted that for the particular distillate treated that the lowest gum content is obtained with approximately eight pounds of sulfuric acid per barrel in both cases.

The foregoing description of an operation characteristic of the invention and the example of results obtainable by its use will serve to indicate the novel features and the utility of the process, but since the disclosure and examples are largely illustrative and, other types of operation and examples of results therefrom might be given, the specification is not to be construed as embodying limitations upon the generally broad scope of the invention.

I claim as my invention:

1. A process for refining cracked hydrocarbon distillates which comprises treating the distillate with added aqueous hydrogen chloride in the presence of brass under conditions such as to remove therefrom gum-forming olefins which are readily reactive with sulphuric acid, and thereafter desulphurizing the distillate by sulphuric acid treatment.

2. A process for refining cracked hydrocarbon distillates which comprises treating the distillate with added aqueous hydrogen chloride in the presence of zinc under conditions such as to remove therefrom gum-forming olefins which are readily reactive with sulphuric acid, and thereafter desulphurizing the distillate by sulphuric acid treatment.

3. A process for refining cracked hydrocarbon distillates which comprises treating the distillate with added aqueous hydrogen chloride in the

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