US1963556A - Treatment of hydrocarbon oils - Google Patents

Description

Patented June 19, 1934 7 TREATMENT OF HYDEOCARBON OILS Jacque C. Morrell, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware a No Drawing. Application August 7, 1933,

. Serial No. 684,126

4 Claims.

This invention refers more particularly to the treatment of the relatively low boiling gasolinecontaining distillates produced as a result of the cracking of heavy hydrocarbon oil mixtures. I

In a more specific sense the inventionis concerned with a method of treatment which may be employed either by itself or in conjunction with other treating steps to produce from cracked distillates gasolines acceptable to the trade from the standpoint of such properties as color, odor, gum content, sulphur content, et cetera. The process is particularly effective in sweetening and desulfurizing high sulfur cracked distillates, as will be developed later.

Difficulties in refining cracked distillates, parv v ticularly those produced from high sulfur charging oils, are quite generally known to petroleum refiners. Sulfuric acid of varying strength is the most generally employed treating reagent. However, it is not entirely specific in respect to its action upon the different undesirable groups of compounds present, to-wit, diolefins (gum formers), corrosive and odorous sulfur compounds,

et cetera. Thus, when sufficient sulfuric acid is ut'lized to insure the desulfurization of some cracked naphthas, there is a concurrent removal of too much of the mono olefins which contribute to the anti-knock value of the final product without adding to its gum-forming tendencies or decreasing its stability under normal conditions of exposure to light and air. When using treating solutions according to the present process, the

amount of sulfuric acid necessary can frequently position of soluble sulfur compounds and the pro duction of a sour overhead product.

In one specific embodiment the invention com prises treatment of gasoline-containing hydrocarbon distillates in liquid or vapor phase with aqueous solutions containing both mercury andcopper salts, e. g. mercuric chloride and cupric chloride. Salts of mercury and copper are the most desirable from the viewpoint of their reactivity with sulphur compounds in petroleum. p

The two salts mentioned are used together in treating cracked distillates with particular ad' vantage for several reasons. In the first place, tests have shown that the mercury salt'has a higher limited solubility in water in the presence of the copper. salt than it has alone, which enables the employment of higher concentrations and consequently more intensive and selec-v tive treating action, along with other advantages which will be broughtout more in detail in describing the method of application'of such solutions. The following table shows the composition of four mercuric chloride-cupric chloride solutions at the saturation point at ordinary temperatures and pressures:

Solution i ht Weight percent percent The limit concentration of either salt will be determined by theamount of the other salt present, the table showing two solutions of maximum total concentration as Solutions 2 and 3. These concentrations may be-varied in either direction to take advantage of the particular treating action of either salt upon different types of sulfur compounds and other undesirable groups such as, for example, diolefins. According to this concept the concentration of the treatingsolutions may be varied generally within the limit solubilities of either salt, though obviously each specially prepared solution will exert its own particular treating action which will depend not only upon its concentration and the relative proportion of the two salts, but also upon the conditions under which they are applied such as the presence of liquid, mixed or vapor phase, temperature, pressure,.efiiciency of contact, et cetera. Accordingly, the various. alternatives are not to be considered as exact equivalents in their action upon the same or upon different cracked distillates. The actions of mercuric chlorideand cupric chloride, respectively, upon the various types of sulfur compounds in petroleum and upon unsaturated hydrocarbons of a diolefinic character,

which occur in varying percentages in cracked distillates from difierent sources differ somewhat. Themercury salt is active in combining directly with mercaptans which account principally for the sour character and bad odor of lowv boiling cracked products, the products of this reaction disulfides which remain dissolved in the oil.

being direct molecular addition compounds, fre quently of a semi-crystalline character, which are quite insoluble in the oil. The mercury salt also reacts with olefins, particularly those of a diolefinic character, and by choosing the proper concentration of the composite solution and selecting the conditions of operation it is possible to remove both a sufilcient amount of sulfur and the major portion of the gum-forming olefins without recourse to sulfuric acid. Copper salts as a compound of the treating reagent also have a distinctive action.

The present type of treating solutions may be applied to cracked distillates in liquid or vapor phase and at any desired stage in the refining operations thereon, including their use upon the rerun end point product. Liquid phase treatments may be conducted in the same type of equipment usually employed for sulfuric acid treatment, to-wit, the ordinary batch agitator or the continuous treating plant consisting of alternatemixing and settling units. These types of operation are well known in the industry and need no detailed description.

In treating vapors such as those arising from the fractionators of cracking units or from the rerun stills, several modes of operation are possible. The solutions may be injected into a stream of vapors prior to their entering a fractionating column and the spent reagents and the products of the reaction allowed to settle in an intermediate chamber preceding the fractionator. In other cases vapors may be passed upwardly through filled towers counter-current to descending streams of treating solutions, after which treated vapors are finally fractionated. To maintain the concentration of the treating solutions under the temperature conditions encountered in vapor phase treatments, it may be necessary to introduce a regulated amount of steam, which feature is included within the scope of the invention.

The choice of treating either in liquid or vapor phase will be determined by the results obtained in any given case and it is not to be inferred that these two types of treatment are necessarily equivalent in their action upon any particular cracked distill-ate.

A special advantage in the present type of treatment resides in the fact that mercaptans may be removed directly, in contrast to sweetening processes employing such reagents as sodium plumbite and sulfur, and sodium hypochlorite solutions, both of which convert mercaptans to In the case of sodium plumbite, there is ordinarily an additional hazard in the use of sulfur to break the solution: of mercaptides produced by the; first step of the treatment. Experiments have shown that in many cases the tendency of sweetened cracked gasolines to become cloudy after. exposure to light is: due to dissolved sulfur or to sulfides or disulfides, since complete removal of these classes of sulfur compounds produces a gasoline which remains clear for a much greater period of time.

I he following examples are illustrative of the results obtainable by the use of reagent solutions of'thepresent character in treating cracked distillates. and gasolines.

A cracked naphtha produced: from a California gas oil charging stock was treated with about 1%. to 2 by volumeof an aqueous solution corresponding in composition to that of- Solution No. 2 shown in the tablegiven-above. After-separation Properties of untreated and treated gasolines Gravity A.P.I 53. 6 53. 8 Mg. of gum by copper dish. 250 25 Total sulfur, percent. 0. 0. 15 Doctor tcst Positive Negative. Initial boiling point, F 96 100 Final boiling point, F 410 408 As an example of results obtainable when treating in vapor phase, the following may be cited. The vaporous effluent from the secondary fractionator of a cracking plant operating upon a West Texas residuum may be passed upwardly countercurrent to a descending solution of a composition corresponding to Solution No. 3, using steam to prevent crystallization of the solutes. The temperature of the treater may be approximately 310 F. and the pressures about pounds per square inch. A comparison of the gasoline recovered from this treatment and the gasoline producible from the svapors without chemical treatment is shown in the following table:

Comparison of untreated and treated gaso'lines Gravity A'.P.I 54.2 54.5 Mg. of gum by copper dish 275 30 Total sulfur, percent.... 0. 38 0.1% Doctor test Positive. Negative. Initial boiling point, F 98 103 Final boiling point, F 412 409 1. A step inv the process for the treatment of hydrocarbon oil to the action of an aqueous soa lution containing a mercury salt and a copper salt.

3. A step in a process for the treatment of cracked hydrocarbon oil to refine the same and. to substantially reduce the sulphur content thereof, which comprises subjecting the said cracked hydrocarbon oil to the action of an aqueous solution containing mercruic chloride and a copper salt.

4. A step in the process for the treatment of cracked hydrocarbon oil to refine the same and to substantially reduce the sulphur content thereof, which comprises. subjecting the said cracked hydrocarbon oil to the action of an aqueoussolution containing mercuric chloride and cupric chloride. JACQUE' C. MORRELL.