Corrosion inhibitor

Abstract

A composition and method of inhibiting corrosion caused by naphthenic acid in fluids includes using a combination of a thiophosphorus compound and a hydrogen sulfide scavenging compound. The hydrogen sulfide scavenging compound significantly enhances the performance of the thiophosphorus compound and may be included at relatively low levels in the composition. The treatment may be applied to fluids including crude oils and lighter fractions thereof.

Description

CROSS-REFERENCE TO A RELATED APPLICATION [0001] This application claims the benefit of U.S. Provisional Application No. 60 / 741,430, filed Nov. 30, 2005.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to corrosion inhibitors. The present invention particularly relates to corrosion inhibitors useful for applications in which naphthenic acids are present. [0004] 2. Background Art [0005] It is widely known in the art that the processing of crude oil in its various fractions may lead to damage of iron-containing metal surfaces of the processing equipment. This corrosion is frequently associated with, in particular, the presence and activity of naphthenic acid. The corrosion occurs when the amount of naphthenic acids in the hydrocarbon reaches some critical value indicated by total acid number (“TAN”), expressed as milligrams of potassium hydroxide required to neutralize the acids in a one-gram sample. Older literature uses a rule of thumb...

AI Technical Summary

Benefits of technology

[0013] In one aspect, the present invention is a method for inhibiting naphthenic acid corrosion in a fluid containing a corrosive amount of naphthenic acid, the method comprising adding, to the fluid or to a feed therefor, a thiophosphorus compound and a hydrogen sulfide scavenging compound, wherein the thiophosphorus compound and the hydrogen scavenging compound are in amounts effective to inhibit corrosion.

Problems solved by technology

It is widely known in the art that the processing of crude oil in its various fractions may lead to damage of iron-containing metal surfaces of the processing equipment.

(−752° F.) temperatures customarily used to refine and distill the oil, the corrosion problem is typically further exacerbated.

When hydrocarbons containing such naphthenic acid contact iron-containing metals, especially at elevated temperatures, severe corrosion problems arise.

These attempts are generally disadvantageous in that they require additional processing and / or add substantial cost to treatment of the crude oil.

While these tetrahydrothiazoles phosphonic acids or esters offer good corrosion inhibition, they tend to break down under high temperature conditions.

Another disadvantage to using phosphorus-based compounds as corrosion inhibitors is that the phosphorus has been alleged to impair the function of various catalysts used to treat crude oil, such as in fixed-bed hydrotreaters and hydrocracking units.

Thus, crude oil processors are often faced with a dilemma, since corrosion itself, if not inhibited, may result in accumulation in the hydrocarbon fluid of a catalyst-impairing amount of iron, as high as 10 to 20 ppm in some cases.

Unfortunately, while there are a number of commercially available non-phosphorus-based inhibitors, they are known to be generally somewhat less effective than the phosphorus-based compounds.

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