Mineral oils: processes and products – Refining – Organic acid or phenol contaminant removal
Reexamination Certificate
1999-09-21
2001-07-10
Myers, Helane E. (Department: 1764)
Mineral oils: processes and products
Refining
Organic acid or phenol contaminant removal
C208S047000, C208S348000, C208S0480AA
Reexamination Certificate
active
06258258
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for neutralizing petroleum acids.
BACKGROUND OF THE INVENTION
Whole crudes and crude fractions with high petroleum acid content such as those containing naphthenic acids are corrosive to the equipment used to extract, transport and process the crude.
Efforts to minimize naphthenic acid corrosion have included a number of approaches for neutralizing and removing the acids from the oil. For example, U.S. Pat. No. 2,302,281 and Kalichevsky and Kobe in
Petroleum Refining with Chemicals
(1956), Chapter 4, disclose various base treatments of oils and crude fractions, e.g., using bases such as ammonia (page 170). U.S. Pat. No. 4,199,440 discloses treatment of a liquid hydrocarbon with a dilute aqueous alkaline solution, specifically dilute aqueous NaOH or KOH. U.S. Pat. No. 5,683,626 teaches treatments of acidic crudes with tetraaylammonium hydroxide and U.S. Pat. No. 5,643,439 uses trialkylsilanolates. PCT US96/13688, US/13689 and US/13690 (Publ. WO 97/08270, 97/08271 and 97/08275 dated Mar. 6, 1997) teach the use of Group IA and IIA oxides and hydroxides to treat whole crudes and crude fractions to decrease naphthenic acid content. U.S. Pat. No. 4,300,995 discloses the treatment of carbonous material particularly coal and its products, heavy oils, vacuum gas oil and petroleum resids having acidic functionalities with a dilute quaternary base, such as tetramethylammonium hydroxide in a liquid (alcohol or water). This patent was aimed at improving yields and physical characteristics of the products and did not address the question of acidity reduction.
U.S. Pat. No. 4,457,837 to Farnham teaches a process for treating corrosive aqueous condensate acid released from petroleum following distilation, i.e., acidic materials such as HCl and H
2
S, not organic condensate. In the process the concentration of water is very high as evidenced by the requirement of a separate aqueous ammonia phase and a hydrocarbon phase. Farnham is silent on the need to form amides in the treatment process and, indeed the presence of large quantities of water disfavors such a reaction.
U.S. Pat. No. 4,634,519 to Danzik teaches a neutralization reaction of naphthenic acids upon extraction into the aqueous methanolic phase to produce ammonium salts of the naphthenic acids and requires the presence in critical ratios of alkanols, water and ammonia. Danzik indicates that about 20% water is required which is consistent with Danzik's teaching of an aqueous ammonia phase. The reference is selective and specifically states that it cannot be successfully applied to treatment of crude oils in general.
While these processes have achieved varying degrees of success there is a continuing need to develop more efficient methods for treating acidic crudes.
SUMMARY OF THE INVENTION
The present invention relates to a process for decreasing the acidity of an acidic crude oil by contacting the acidic crude oil with an effective excess of ammonia in the presence of water in an amount not to exceed the solubility limit of the water in the crude (i.e., essentially anhydrous) at a temperature and under conditions sufficient to form the corresponding amide of the naphthenic acids. Additionally, the process may be carried out in two steps by pretreating an acidic crude oil with an effective excess of ammonia in the presence of water in an amount not to exceed the solubility limit of the water in the crude (i.e., essentially anhydrous) at a temperature and under conditions sufficient to form the corresponding ammonium salts of the naphthenic acids, and then treating the resulting crude containing ammonium salts of the naphthenic acid at a temperature and under conditions sufficient to form the corresponding amides of the naphthenic acid.
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 crude oils contain organic acids that contribute to corrosion or fouling of refinery equipment and that are difficult to separate from the processed oil. The 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 may be present either alone or in combination with other organic acids, such as phenols. Naphthenic acids alone or in combination with other organic acids can cause corrosion at temperatures ranging from about 65° C. (150° F.) to 420° C. (790° F.).
Applicants have discovered that if a crude is treated with ammonia at conditions at which an excess of ammonia is not present the resulting ammonium salt of the naphthenic acid is formed, and on subsequent heating in the absence of additional (or a sufficient excess of) ammonia or at insufficient temperature as can occur, for example, in further refining of a crude oil, this salt decomposes to give ammonia and the naphthenic acid. Thus, a critical step of Applicants' invention is to ensure that the corresponding amide is produced. This is accomplished by heating the crude oils under conditions such that any ammonium salt of the naphthenic acid is converted into the corresponding amide. This requires the presence of ammonia and in sufficient excess concentration in the presence of only trace amounts of water, i.e., in the presence of water in an amount not to exceed the solubility limit of the water in the crude, at a temperature to produce the corresponding amide. Prior art processes using higher levels of water (i.e., aqueous ammonia or predominately water containing systems) produce naphthenic acid salts rather than amides. The resulting amide is heat stable in that it does not decompose to ammonia and the naphthenic acid.
The crudes that may be used are any naphthenic acid-containing whole crude oils that are liquid, liquifiable or vaporizable at the temperatures at which the present invention is carried out. As used herein the term whole crudes means unrefined, non-distilled crudes. The acidic crudes are preferably whole crudes. However, fractions of whole crudes also may be treated. An additional benefit of the treatment process is the minimization of ash formation in the event that resulting crude or fraction is to be subsequently burned.
Crudes typically contain amounts of water but also may be anhydrous or essentially anhydrous. Suitable crudes may be anhydrous or may contain traces of water (i.e., water in an amount not greater than the solubility limit of the water in the crude and thus is insufficient to form a separate aqueous, phase). Dewatering/desalting of water-containing crude to the required level for use in Applicants' process may be carried out by methods known to those skilled in the art.
Applicants' treatment can be carried out using a staged or sequential treatment of the acidic crude with a sufficient excess of ammonia. The temperature in any given stage should not exceed the cracking temperature of the oil. When a one step treatment is used the conditions must be sufficient to form the amide of the naphthenic acid. Typically, treatment at temperatures above about 150-350° C., preferably above about 180-350° C. and in the presence of an effective excess of ammonia are used. Typically, for the two stage treatment in the first stage the temperature is from about 10° C. to 100° C. preferably 20° C. to 50° C. and in the second stage the temperature is greater than the temperature in the first stage and sufficient to produce amidation, typically above about 150-350° C., preferably above about 180-350° C. Pressures are autogenous pressures, typically from 100 to 300 kPa and may be the same or different in the two steps. In the two step process, the ratio of crude to ammonia is sufficient to produce the corresponding ammonium salt in the first step, and sufficient to produce the corresponding amide in the second step. Typically, a large molar excess of ammonia to the naphthenic acid (or
Ballinger Bruce Henry
Dalrymple David Craig
Olmstead William Neergaard
Robbins Winston Karl
Sartori Guido
Exxon Research and Engineering Company
Myers Helane E.
Scuorzo Linda M.
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