US2739103A - Method of treating gasoline with citric acid to remove copper - Google Patents

Description

METHOD OF TREATING GASOLINE WITH ClTRIC ACID TO REMOVE COPPER John W. Thompson, Kingsport, Tenm, asslgnor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application March 28, 1952, Serial No. 279,211

1 Claim. (Cl. 196-39) This invention relates to a method of improving the quality of petroleum hydrocarbons, and more particularly, to improving the quality of petroleum hydrocarbons which have been treated with copper-containing reagents for the removal or conversion of sulfur compounds.

It is well known to remove sulfur compounds, such as mercaptans, from petroleum hydrocarbons, such as gasoline motor fuels, or to convert such mercaptans into less objectionable compounds .by appropriate chemical treatment, generally referred to as a sweetening operation. One quite common method of sweetening involves the use of a doctor solution made from sodium hydroxide and lead oxide. Treatment of the sour gasoline with this solution and .added sulfur converts the mercaptans to alkyl disulfides. The amount of sulfur used must be very carefully controlled since excess sulfur in the gaso line is harmful with respect tocorrosiveness, lead susceptibility and inhibitor susceptibility. On the other hand, the useof insufiicient sulfur causes lead mercap' tides to be left in'the fuel.

Instead of using the doctor solution method, it has been previously proposed to substitute other sweetening operations employing copper salts for thepurpose of removing the sulfur compounds or converting them into less objectionable substances. This operation is widely used for the treatment of petroleum motor fuels, such as gasoline. Frequently in the copper sweetening process various copper compounds may be carried over into the treated gasoline where they -are very objectionable since even in trace concentrations they catalyze oxidative deterioriation of the treated hydrocarbon. This difficulty is somewhat alleviated through the use of the known antioxidants, although the amount of improvement is not great enough to completely overcome the objections noted above. It is, therefore, desirable to provide some method which would substantially completely remove all heavy metal compounds from the petroleum hydrocarbon, thus allowing the antioxidant to function at its fullest efficiency.

It is, therefore, an object of my invention to provide an improved method of removing. metals, such as copper, from petroleum hydrocarbons. .Another object is to render petroleum hydrocarbons, such as cracked gasoline, more stable to oxidative deterioration catalyzed by metals and to permit more effective use of gasoline antioxidants.

Still another object is to provide a class of new and eifective treating agents for removing such metals from petroleum hydrocarbons, such as cracked gasoline. Other objects will become apparent from a consideration of the following description and examples.

According to my invention, I provide the novel effects mentioned above by treating a petroleum hydrocarbon which has been sweetened with reagents containing copper with a solution containing certain types of aliphatic carboxylic acids. The aliphatic carboxylic acids which are useful in practicing my invention comprise aliphatic hydroxy mouocarboxylic acids, such as lactic, glycolic, e-hydroxy isobutyric acids, etc., and aliphatic polycarboxylic acids selected from those represented by the following general formula:

t-gp.-. (-ihtigs wherein R, R1, R2, R3, R4 and R5 each represents a member selected from the group consisting of a hydrogen atom, a hydroxyl group, a carboxyl group, an alkyl group (e. g. methyl, ethyl, etc.), and an aryl group (e. g.

Advantageously, the petroleum hydrocarbon which has been treated with a copper-containing reagent is washed with an aqueous solution of one of the aliphatic carboxylic acids of my invention. The aliphatic'car boxylic acid reacts with the residual copper reagent in the petroleum hydrocarbon and substantially completely removes said copper reagent from thetreated hydro-' carbon. Since the reaction product between the copper reagent and the aliphatic carboxylic acid has a-higher solubility in the water than it has in the petroleum-hydrocarbon, it is dissolved inthe, water, thus leaving the petroleum hydrocarbon substantially free of copper reagent. Efficient mixing between the aqueous solution 7 containing the aliphatic carboxylic acid and the pet-roleum' hydrocarbon assures substantially complete re moval of the copper reagent.

The aqueous reagent solution contains one or more of the aliphatic carboxylic acids and the concentration of acid can be varied according to the petroleum hydrocarbon being treated. 0.1 up to the weight percent required for a saturated solution of acid in water is effective for the purposes of my invention.

The process of my invention can be carried out in any suitable manner, such as a batch or continuous type operation, wherein suitable contact of petroleum hydrocarbon and washingsolution can be had. As an example of one possible method, the washing solution and petroleum hydrocarbon, such as cracked gasoline, are

intimately mixed-in one chamber and the mixture alor no solubility in the petroleum hydrocarbon.

lowed to settle either in the same or another vessel.

- After separation into two layers, the upper layer comprising the petroleum hydrocarbon, now substantially free of metal content, is Withdrawn for further treatment or disposal as required. In some instances, it may be felt desirable to further Wash the gasoline with water to remove any other remainingtraces of washing solu-' tion, although tests have shown an after treatment with water to be unnecessary. Apparently, the contrasting left in the petroleum hydrocarbon.

until disposal is indicated by high metal content.

solvent can be employed. When an. organic solvent is desired, it is advantageously selected so that it is a solvent for the-aliphatic carboxylic acid but has little It is I thus possibleto effectively separate the organic solvent Patented Mar. 20, 6 j v Generally, a solution of from Instead of using an aqueous solution of the aliphatic, carboxylic acid, a solution of the acid in an organic;

solution containing the aliphatic carboxylic acid from the treated petroleum hydrocarbon.

After treatment of the petroleum hydrocarbon with the solution containing the aliphatic carboxylic acid, the treated petroleum hydrocarbon can then be stabilized against oxidative deterioration by addition of one or more of the known antioxidants ordinarily used for this purpose. Such antioxidants comprise, for example, the p-aminophenols, hydroquinones, p-phenylenediamines,. etc. See,

Efjecz'iveness of organic acids in washing copper from gasoline SECTION A Induction Period Before Washing Induction Period After Washing s 1 Effective- Sample No. S l Sam 10+ amp e ness,

Samole Sample-iamp 8 r Sernp1e+ p Cu+ percent Blank L Cu+ ll ashmg Agent Cu+ Cu BAP BAP Cu BAP 95 55 515 167 water 410 10D 57 525 185 citric aci 555 540 100+ 100 67 530 185 d-tartsric acid. 547 537 100+ 95 55' 517 160 malonic acid. 547 550 100+ 95 55 515 167 oxalic acid 535 100+ SECTION B s5 45 512 so. water 55 s5 4 4....-. 95 45 512 60 citric acid l 130 497 07 for example, Brimer U. 8. Patent 2,496,930, issued February 7, 1950, von Bramer et a1. U. S. Patent 2,323,948, issued July 13, 1943, etc.

The efficiency of the solution containing, the aliphatic carboxylic acid in removing the heavy metal, such as copper, from the petroleum hydrocarbon, such as cracked gasoline, was determined by means of oxygen bomb stability tests on unwashed and solution-washed samples of coppericontaining cracked gasoline, which were inhibited with a gasoline antioxidant just prior to testing. Simultaneously, control tests were made on the cracked gasoline containing various combinations of copper andantioxidant. In the examples described below, the copper was added in the form of a benzene solution of copper oleate and the antioxidant used was N-n-butyl-p-aminophenol, although other antioxidants were found to be equally effective for demonstrating the results of my invention. The washing consisted of shaking the cracked gasoline with 10 volume percent of a 10 weight percent aqueous aliphatic carboxylic acid solution for 5 minutes in a separatory funnel. The treated cracked gasoline was removed and then tested. by means of an oxygen bomb stability test.

In the oxygen bomb stability test, 200 cc. samples of gasoline in glass. bottles were heated at 100 C. in stainless steel bombs. under 100 p. s. i. oxygen pressure. The induction period of the gasoline was measured as the time in minutes before rapid oxidation of the gasoline began, as evidenced by a sharp drop in oxygen pressure. The following table illustrates the effect of various solutions of aliphatic carboxylic acids in removing the copper from the cracked gasoline. Insection A of the table, an amount of copper oleate was employed suificient to give an equivalent of l.() mg. of copper per liter, while in section B, an amount of copper oleate was employed in an amount sufiicient to give 5.0 mg. of copper per liter. The abbreviation BAP stands for N-n-butyl-p-aminophenol. The induction period in minutes is given before washing with the aqueous solution containing the aliphatic carboxylic acid, and similar data are given for the cracked gasoline after washing. The eifectiveness in percent of the particular washing agent is given in the last column, the figure being obtained according to the equation:

(Induction period of) washed gasoline conwashed gasoline containtainmg BAP+Ou ng BAP-k-Cu (Induction period oi) (Induction period of un-) Induction period of 1111-) E11 ectiveness unwashed g as o l l n e washed gasoline containcontaming BAP ing BAI+Ou The purpose of section B in the above table is to show that while water alone does effectively remove some residual copper sweetening agent when the concentration of the agent is low, as is true in section A, this is by no means the case when the concentration of residual copper sweetening agent is higher, suchas might ordinarily be encountered in the treatment of cracked gasoline, as is true in section B. The citric acid used in arriving at the results given in the table was employed as the monohydrate. in the above table was 0.0048 weight percent. The particular gasolines employed were a Pennsylvania cracked gasoline consisting of a blend of catalytically-cracked and thermally-cracked fuels.

The above table is believed to clearly show that the aliphatic carboxylic acids of my invention eifectively reduce the amount of copper sweetening agent in the cracked gasoline to such an extent that the conventional gasoline antioxidants can stabilize the fuel in the desired manner. It will be noted, for example, from the table that while sample No. 7 gave an effectiveness of 97 percent, i. e-., the treatment with the solution of citric acid returned the induction period to within 97 percent of that obtained when the gasoline was completely free of copper oleate, sample No. 6 gave a corresponding induction period return of only 4 percent.

What I claim as my invention and desire secured by Letters Patent of the United States is:

A process of stabilizing cracked gasoline which has been sweetened with a copper-containing reagent which comprises intimately mixing said cracked gasoline with anaqueous solution containing from 0.1 up to the weight percent required for a saturated solution in water of citric acid, and separating said cracked gasoline from said aqueous solution containing the citric acid.

References Cited in the file of this patent UNITED STATES PATENTS The concentration of the BAP where indicated