US1954886A - Refining of petroleum oil - Google Patents

Description

Patented Apr. 17, 1934 UNITED STATES PATENT No Drawing. Application May 21, 1931, Serial No. 539,111

6 Claims. (01. 196-36) This invention relates to the treatment of hydrocarbon oils and more particularly is directed to the treatment of petroleum distillates, especially those resulting from the conversion of relatively higher boiling hydrocarbons into lower boiling hydrocarbons by treatment at elevated temperatures, commonly referred to as cracked distillates, by subjecting the same while in vapor formto the action of aqueous solutions of acid sulphates alone or in direct combination with sulphuric acid, to modify and regulate the reactions of the latter.

More particularly the invention relates to the treatment of the said hydrocarbons while in vapor form with solutions containing sulphuric acid and a salt of an alkali metal such as the sulphates of sodium, potassium, ammonium and the like. Presumably, these salts are present as acid sulphates and it is desirable that they always be present in the form of the acid sulphate, preferably with excess sulphuric acid. The use of other salts such as the chlorides, acetates, nitrates, etc., of the alkali metals are contemplated in admixture with sulphuric acid, since to some extent and degree they are equivalent to the sulphates in the presence of sulphuric acid.

Petroleum distillates, especially cracked distillates, contain undesirable compounds, presumably of a highly unsaturated character, which render them unstable with respect to color, gumforming properties and knock rating. Such distillates tend to deposit polymer or gum-like substances while in storage, causing a drop in color which may render the product unsaleable. The development of gums may also prevent proper operation of the motor by plugging or gumming up the fuel lines, carburetor, valves and other parts of the motor. Other objectionable compounds such as those of sulphur, nitrogen and the like may be present in such distillates, and it is among the objects of this invention to remove, or reduce to a minimum, the objectionable substances present in petroleum distillates.

One of the important and desirable developments in petroleum refining is the direct production of a marketable distillate from the cracking process. Many attempts have been made to employ refining agents for this purpose, particularly directed towards the use ofsulphuric acid which, for the most part, have been unsuccessful because they have failed to take into consideration the physical and chemical properties of sulphuric acid under the-conditions of refining. The use of sulphuric acid as a refining agent antedates the' drillingcof the first oil well in the United States but heretofore it has been successfully applied as a refining agent to petroleum and its products only while in the liquid state.

'The following table taken from the 1913 edi-'- tion of the Manufacture of Sulphuric Acid and Alkali by Lunge, a standard work on the subject, shows the relationship between the boiling point and concentration of sulphuric acid:

Table NO. I

Percent H2804 B. Pt. T.

From the above table it is evident that at; a given temperature and at each temperature the sulphuric acid exists at a definite concentration and that irrespective of the concentration of the sulphuric acid fed into a system at a given temperature if it is more dilute than that indicated by the concentration-for the corresponding temperature itwill concentrate to the given concentration; also that for each set of conditions there is acor-respondingminimum concentration. For example, if an approximately 8% solution of sulphuric acid is fed into a tower, the average temperature ofwhich isapproximately 360 F., neg+ lecti-ng the partial pressures of the steam and oil vapors, the sulphuric acidintroduced will concentrate to approximately 75% and under these temperature conditions such aconcentr'a tion of sulphuric acid will immediately attack and destroy the unsaturated hydrocarbons in the immediate vicinity, resultingin an off-colored overhead product of high gum content: and in a charring of the derivatives of sulphuric acid in the hydrocarbons, plugging up the column and rendering the process inoperative. The above indicates only approximately the conditions existing in the tower but is sufiicient to illustrate the trend and direction of the reaction and explain Why previous attempts to refine in the manner described have been unsuccessful.

It is well known that concentrations of sulphuric acid which may be even substantially nonreactive at ordinary temperatures are highly .de-

structive in their reactions at elevated temperatures. Hence, while it is desirable to treat petroleum distillates in the vapor state in order to avoid the expense of redistilling the product, it is imperative that a method of treatment be provided which will enable one to definitely control the concentration and consequently the rate and kind of reaction at the elevated temperatures of treatment. The present invention accomplishes this aim in a new and novel manner which will be hereinafter more fully described.

In a specific aspect the invention comprises treating hydrocarbon vapors, especially cracked hydrocarbon vapors, with an aqueous solution containing dissolved therein sulphuric acid and a sulphate of an alkali metal which is presumably present in the form of the acid sulphate.

In effecting the operation of the invention hydrocarbon vapors from any source, for example, direct from a cracking process, and in general from a distillation process, including vapors from atmospheric distillation or hydrocarbon vapors from rerun stills, may be passed counter-current or concurrent to the solution containing the acid sulphate and the sulphuric acid. The treating solution may be introduced in the form of a spray atomized or otherwise introduced and employed in such manner as to give the most efficient contact of treating agent and vapors undergoing treatment. Under some conditions the hydrocarbon vapors may be bubbled through a pool or pools of the treating agent, preferably feeding in fresh reagent and withdrawing sludge continuously. In the countercurrent operation the vapors may be withdrawn from the top of the treating tower and may be condensed or fractionated and condensed, preferably subjecting the treated hydrocarbons to further treatment with alkalies or combination washing and alkali to remove sulphur dioxide and possibly some entrained treating agent. In the concurrent method of operation, the vapors, reflux condensate and sludge may be passed through a separator, withdrawing the vapors and condensing as described, and separately withdrawing the sludge and/or productsof reaction together with unused treating agent and reflux condensate if present.

Aqueous solutions of the acid sulphates may be mixed with the aqueous solutions of the sulphuric acid or aqueous solutions of the sulphates of sodium, potassium or ammonium may be mixed with sulphuric acid, preferably having a substantial excess of sulphuric acid over that required to produce the acid sulphate. Steam may be introduced into the column during the treatment in order to assist in maintaining an equilibrium between the dissolved substances in the water, namely, the acid sulphate and sulphuric acid. The acid sulphates and part of the acid may be recovered by dilution of the acid sludge with water, heating, separating the oily sludge, and subsequent purification and evaporation of the aqueous solution.

The process may constitute a sole step in the refining of the hydrocarbons or may be combined with other treatments either applied before or after the process of this invention. For example,

the vapors from the treating tower may be subsequently passed through a filter or series of filters containing inert filtering agents, adsorbents, solid alkalies, such as lime, caustic, or mixtures of these, and the like, catalytic materials such as metals and metallic oxides, solutions of alkalies, and the like. Preferably, the vapors are fractionated before passing to the treating stage and may be fractionated after passing to the treating stage. Prior treatments of the hydrocarbons with other reagents, either in the vapor or liquid phase, or subsequent treatment of the condensed liquid may be applied.

For example, the condensed product may be neutralized by treatment with an alkaline solution or besweetened by treatment with plumbite solutions, solutions of copper salts, or other metallic salts, alone or in combination with auxiliary chemical treatments with acids and the like, orv with filtering agents such as fullers earth and like adsorbing agents.

As examples of the conditions of treatment and the results obtained by the operation of the invention, the following are cited. All of the results shown in the tables illustrate the treatment of a cracked distillate from California stock.

The liquid recovery in the above treats varies between 98% and 99%, indicating very low losses during the treatment. The amount of reagent employed varies with the conditions of treatment, the oil to be treated, and the results desired. The reagent may be reused and or recovered for reuse.

Table III 010. so 11. Per- Run Percent per Tem. cent No. NH4HSO4 6 ffg g liter r. Gum sulo i phu oil 16.5 21.2 62.3 160 300 +23 23 0.37 lstpass 35.3 37.5 27.2 145 300 +21 175 0. 39 2d pass 35.3 37.5 27.2 160 300 +23 14 0.38 3d pass Table IV 3 21.7 I 25.7 52.6 120 310 30+ 8 0.33 4 Reusmg SOIIIItiOHS from (3) 205 300 +28 8 0.40

Lamp stability-+23 (Equivalent to 2 hours sunlight) Octane No.72

Bomb stability-No drop in 4 hours.

Air jet gum after oxidation-18 Color after oxidation+12 Octane No. after oxidation70 The solution reused was from Run 3. It was filtered through asbestos to remove as much suspended material as possible.

Run Nos. B and C show that good results can be obtained with lower concentrations of H2804. by increasing the time of contact.

The product from Run 3 after standing 10 days dropped in color to +28 but only dropped five points more when exposed to the ultra violet lamp. The oxygen stability was also very good.

Run 4 shows that the solution can be used over again with good results. Further results have shown that it can be used many times especially when make-up solutions of salts and acid are added.

The quantities of solutions used relative to the oil should be sufficient to maintain good contact. Much smaller quantities give good results and repeated uses of non-regenerated solution is contemplated. Also, regeneration and/ or recovering of the acid sulphate (salts) and sulphuric acid is contemplated.

The above data illustrates that certain combinations and conditions of treatment give better results than others. The results in Run Table No. 2 show a color of the finished product of 30 plus Saybolt with a gum content of only 6 mgs. per 100 cc. The gum content of the original untreated cracked distillate of like boiling range exceeded 400 mgs. per 100 cc. and the color was a dark reddish brown.

The sludge from the treating agent may be recirculated for further treatment to reduce the total percent of treating agent by volume of the oil treated to several percent. In the treatment of a Mid-Continent cracked distillate in the vapor phase employing approximately 3% of a solution containing approximately 20% of ammonium acid sulphate, 50% of sulphuric acid, and 30% of water, a product of plus 30 color containing less than 10 mgs. of gum per 100 cc. of good color stability may be obtained, the raw distillate being dark brown in color and containing in excess of 350 mgs. of gum per 100 cc. Similar results may be obtained with other types of oils.

Similar results may be obtained also with solutions containing sodium sulphate and potassium sulphate with sulphuric acid as with ammonium sulphate and others and the corresponding acid sulphate although the results may vary in degree.

The concentrations of the acid sulphate and sulphuric acid may be varied to suit the particular conditions of treatment, particularly temperatures; generally, the higher the temperature the higher the concentration of sulphuric acid, and in general, the conditions are varied dependcut on the results desired.

Inasmuch as there are many conditions of treatment and variables in respect to the concentrations of dissolved salts and sulphuric acid, temperatures and the like, the above examples are illustrative only and are not to be construed as limitations upon the broad scope of the invention.

I claim as my invention:

1. A process for refining hydrocarbon oil which comprises treating the same in vapor phase with an aqueous sulphuric acid solution to which has been added a water soluble sulphate, the amount of sulphuric acid in the solution being in excess of that required to maintain the sulphate in the form of the acid sulphate.

2. A process for refining hydrocarbon oil which comprises treating the same in vapor phase with an aqueous sulphuric acid solution to which has been added a normal water soluble sulphate, the amount of sulphuric acid in the solution being sufficient to convert the normal sulphate to the acid sulphate.

3. A process for refining hydrocarbon oil which comprises treating the same in vapor phase with an aqueous sulphuric acid solution to which has been added an alkali metal sulphate, the amount of sulphuric acid in the solution being in excess of that required to maintain the sulphate in the form of the acid sulphate.

4. A process for refining hydrocarbon oil which comprises treating the same in vapor phase with an aqueous sulphuric acid solution to which has been added an ammonium sulphate, the amount of sulphuric acid in the solution being inexcess of that required to maintain the sulphate in the form of the acid sulphate.

5. A process for refining hydrocarbon oil which comprises treating the same in vapor phase with an aqueous sulphuric acid solution to which has been added a normal alkali metal sulphate, the amount of sulphuric acid in the solution being sufficient to convert the normal sulphate to the acid sulphate.

6. A process for refining hydrocarbon oil which comprises treating the same in vapor phase with an aqueous sulphuric acid solution to which has been added a normal ammonium sulphate, the amount of sulphuric acid in the solution being suflicient to convert the normal sulphate to the acid sulphate.

JACQUE C. MORRELL.