Emulsion neutralization of high total acid number (TAN) crude oil

Abstract

This invention is a method for reducing the total acid number of organic acid containing petroleum oil comprising forming a water-in-oil emulsion comprising an aqueous Group IIA metal hydroxide solution or slurry in a hydrocarbon oil, said water-in-oil emulsion having an aqueous droplet particle size diameter of from 1 to 25μ, adding the water-in-oil emulsion to the organic acid containing petroleum oil and permitting the mixture to stand for a time sufficient to permit the neutralization of the organic acids in the petroleum oil.

Description

[0001] This application claims the benefit of U.S. Ser. No. 60 / 609,624 filed Sep. 14, 2004.FIELD OF THE INVENTION [0002] This invention relates to the neutralization of the organic acids contained in petroleum oils to reduce the acidity and corrosivity of such oils. BACKGROUND OF THE INVENTION [0003] 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. [0004] Efforts to minimize naphthenic acid corrosion have included a number of approaches. U.S. Pat. No. 5,182,013 refers to such recognized approaches as blending of higher naphthenic acid content oils with low naphthenic acid content oils. Additionally, a variety of attempts have been made to address the problem by replacing carbon or low alloy steels by more expensive, highly alloyed stainless steels, using corrosion inhibitors for the metal surfaces of equipm...

AI Technical Summary

Benefits of technology

[0015] It has been discovered that acid neutralization can be accomplished in a process that does not avoid emulsion formation and in fact practices emulsion formation and maintenance as part of the process eliminating the need for chemical demulsifiers.

[0016] The present invention is a method for decreasing the acidity and corrosivity of an acid containing corrosive crude comprising, securing an aqueous alkaline earth metal hydroxide solution or slurry, forming a water-in-oil emulsion of the aqueous alkaline earth metal hydroxide solution or slurry in a hydrocarbon carrier oil, preferably a small quantity of the same corrosive crude to be treated, the water-in-oil emulsion having an aqueous phase droplet size of between about 0.5 to 50μ, preferably between about 1 to 25μ, more preferably between about 1 to 10μ, mixing the water-in-oil emulsion with the crude to be treated in a ratio of about 0.2 to 10 volume of emulsion to 100 volumes of crude to be treated, preferably 0.5 to 5 volume of emulsion to 100 volumes of crude or fraction thereof to be treated, holding the crude or fraction thereof to which the water-in-oil emulsion has been added at a temperature sufficient to promote interaction between the alkaline earth metal hydroxide and the naphthenic acid in the crude to be treated, preferably between about 20° C. to 150° C., more preferably between about 20° C. to 100° C. most preferably between about 20° C. to 60° C. for a time sufficient for the partial or complete neutralization of the naphthenic acids contained in the crude to be treated by conversion of the naphthenic acids into alkaline earth metal naphthenic salts which remain dissolved in the crude oil, e.g., at least about 30 minutes, preferably at least about 1 hour, more preferably at least about 2 hours, still more preferably at least about 4 hours. The treated crude without the addition of a demulsifier can then be passed for further processing using standard techniques in the refinery. It can be dewatered and desalted and then passed on for distillation and subsequent standard processing.

Problems solved by technology

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.

U.S. Pat. No. 4,199,440 notes, however, that a problem arises with the use of aqueous solutions that contain higher concentrations of aqueous base.

Importantly, '532 does not disclose the treatment of whole crudes or fractions boiling at 1050+° F.

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.

The patent goes on to expressly state that the formation of a crude oil-aqueous emulsion (i.e., either water-in-oil or oil-in-water) tends to interfere with the efficient separation of the crude oil and water phases and thus with recovery of the treated crude oil.

Emulsion formation is undesirable and a particular problem that is encountered during treatment of naphthenic acid-containing crudes with aqueous bases.

This is because often emulsions may be stabilized and then become very difficult to “break” or separate into oil and aqueous phases.