Process for extraction of naphthenic acids from crudes

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...

Reexamination Certificate

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C528S491000, C528S50200C, C528S50200C, C166S270000, C166S270100, C166S275000, C166S300000, C166S305100

Reexamination Certificate

active

06281328

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for decreasing the acidity and corrosivity of crudes and crude fractions containing petroleum acids.
BACKGROUND OF THE INVENTION
Many petroleum crudes with high organic acid content, such as whole crude oils containing naphthenic acids, are corrosive to the equipment used to extract, transport and process the crude, such as pipestills and transfer lines.
Efforts to minimize naphthenic acid corrosion have included a number of approaches. Examples of such technologies include use of oil soluble reaction products of an alkynediol and a polyalkene polyamine (U.S. Pat. No. 4,647,366), and treatment of a liquid hydrocarbon with a dilute aqueous alkaline solution, specifically, dilute aqueous NaOH or KOH (U.S. Pat. No. 4,199,440). U.S. Pat. No. 4,199,440 notes, however, that the use of aqueous NaOH or KOH solutions that contain higher concentrations of the base form emulsions with the oil, necessitating use of only dilute aqueous base solutions. U.S. Pat. No. 4,300,995 discloses the treatment of carbonous materials particularly coal and its products such as heavy oils, vacuum gas oil, and petroleum residua, having acidic functionalities, with a quaternary base such as tetramethylammonium hydroxide in a liquid (alcohol or water). Additional processes using bases such aqueous alkali hydroxide solutions include those disclosed in Kalichevsky and Kobe,
Petroleum Refining With Chemicals
, (1956) Ch. 4, and U.S. Pat. Nos. 3,806,437; 3,847,774; 4,033,860; 4,199,440 and 5,011,579. Publications WO 97/08270, WO 97/08271 and WO 97/08275 published Mar. 6, 1997, collectively disclose treatment with overbased detergents and Group IA and IIA oxides and hydroxides to decrease acidity and/or corrosion. Certain treatments have been practiced on mineral oil distillates and hydrocarbon oils (e.g., with lime, molten NaOH or KOH, certain highly porous calcined salts of carboxylic acids suspended on carrier media). Whole crude oils were not treated.
U.S. Pat. Nos. 2,795,532 and 2,770,580 (Honeycutt) disclose processes in which “heavy mineral oil fractions” and “petroleum vapors”, respectively are treated, by contacting “flashed vapors” with “liquid alkaline material” containing, inter alia, alkali metal hydroxides and “liquid oil” using mixture of molten NaOH and KOH as the preferred treating agent, with “other alkaline materials, e.g., lime, also employed in minor amounts.” The treatment of whole crudes or fractions boiling at 1050 plus °F. (565
+
° C.) is not disclosed; only vapors and condensed vapors of the 1050 minus °F. (565

° C.) fractions, that is, fractions that are vaporizable at the conditions disclosed in '532 are treated. Since naphthenic acids are distributed through all crude fractions (many of which are not vaporizable) and since crudes differ widely in naphthenic acid content the '532 patent does not provide an expectation that one would be able to successfully treat a broad slate of crudes of a variety of boiling points or to use bases other than NaOH and KOH.
U.S. Pat. No. 2,068,979 discloses a method for preventing corrosion in a petroleum still by adding calcium naphthenate to petroleum to react with and scavenge strong free acids such as hydrochloric and sulfuric acids to prevent corrosion in distillation units. The patent makes no claims with respect to naphthenic acids, which would have been formed when the strong acids were converted to salts. Patents have disclosed, inter alia, the addition or formation of calcium carbonate (Cheng et al, U.S. Pat. No. 4,164,472) or magnesium oxide (Cheng et al, U.S. Pat. Nos. 4,163,728 and 4,179,383, and 4,226,739) dispersions as corrosion inhibitors in fuel products and lubricating oil products, but not in whole or topped crude oil. Similarly, Mustafaev et al. (Sb. Tr. Azerb. Inst, Neft. Khim. (1971) 64-6) reported on the improved detergency and anticorrosive properties of calcium, barium, and zinc hydroxide additives in lubricating oils. Calcium hydroxide (Kessick, Canadian Patent 1,249,760) has been used to aid in separation of water from heavy crude oil wastes. U.S. Pat. No. 3,994,344 (Friedman) discloses the use of low molecular weight polyethylenimine to treat crudes. However, the resulting polyamine with acid groups attached is dissolved in the oil.
There is a continuing need to develop methods for reducing the acidity and corrosivity of whole crudes and fractions thereof, particularly residua and other 650
+
° F. (343
+
° C.) fractions. Applicants'invention addresses these needs.
SUMMARY OF THE INVENTION
The present invention provides for a method for decreasing the acidity of an acidic crude oil by contacting a starting acid-containing crude oil with an effective amount of a crosslinked polymeric amine having a pKa of greater than 9 to extract the acid groups from the oil to produce a treated crude oil having a decreased acid content and a crosslinked polymeric amine having the acid groups attached thereto. The amines are e.g., polyvinyl amine and anionic exchange resins containing amino groups. The crosslinked polymeric amine with acid molecules attached to it, which is insoluble in the crude, can be separated or otherwise isolated from the crude, e.g., by filtration or centrifugation, and regenerated by displacing the acids.
The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed.
DETAILED DESCRIPTION OF THE INVENTION
Some whole crude oils contain organic acids such as carboxylic acids that contribute to corrosion or fouling of refinery equipment. These organic acids generally fall within the category of naphthenic and other organic acids. Naphthenic acid is a generic term used to identify a mixture of organic acids present in petroleum stocks. Naphthenic acids can cause corrosion at temperatures ranging from about 65° C. (150° F.) to 420° C. (790° F.). Naphthenic acids are distributed through a wide range of boiling points (i.e., fractions) in acid containing crudes. The present invention provides a method for broadly removing such acids, and most desirably, from heavier (higher boiling point) and liquid fractions in which these acids are often concentrated. The naphthenic acids may be present either alone or in combination with other organic acids, such as phenols.
Whole crude oils are very complex mixtures in which a large number of competing reactions may occur. Thus, the potential for successful application of a particular treatment or process is not necessarily predictable from the success of other treatments or processes.
The present invention may be used in applications in which a reduction in the acidity would be beneficial and in which oil-aqueous emulsion formation and large solvent volumes are not desirable. The decrease in acidity typically, is evidenced by a decrease in the neutralization number of the acidic crude or a decrease in intensity of the carboxyl band in the infrared spectrum at about 1708 cm
−1
of the treated (neutralized) crude.
The concentration of acid in the crude oil is typically expressed as an acid neutralization number or total acid number (TAN), which is the number of milligrams of KOH required to neutralize the acidity of one gram of oil. It may be determined according to ASTM D-664. Typically, the decrease in acid content may be determined by a decrease in the neutralization number or in the intensity of the carboxyl band in the infrared spectrum at about 1708 cm
−1
. Crude oils with total acid numbers of about 1.0 mg KOH/g and lower are considered to be of moderate to low corrosivity. Crudes with a total acid number of 0.2 or less generally are considered to be of low corrosivity. Crudes with total acid numbers greater than 1.5 are considered corrosive.
The crudes that may be used are any naphthenic acid-containing crude oils that are liquid or liquifiable at the temperatures at which the present invention is carried out. Typically the crudes have TAN of 0.2 to 10 mg KOH/g.

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