Co2 treatment to remove organically bound metal ions from crude

Details Co2 treatment to remove organically bound metal ions from crude Co2 treatment to remove organically bound metal ions from crude

2000-01-18

2001-02-13

Griffin, Walter D. (Department: 1764)

Mineral oils: processes and products

Refining

Metal contaminant removal

C208S252000

Reexamination Certificate

active

06187175

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a process to remove certain organically bound metal ions from crude oil.
Basic metals such as calcium, when present in crudes can lead to fouling of heaters and heat exchangers and poison catalysts used in crude processing. When present as inorganic salts, e.g., chlorides, usually in an oil-encapsulated water phase, the salts can hydrolyze to release corrosive mineral acids. Such salts are customarily removed by refinery desalters. However, oil-soluble metal salts such as naphthenates are not removed by conventional desalting. Therefore, oil-soluble, basic metal-rich crudes are less valuable than crudes with low levels of such metals. A process for metal ion removal enables the increase of the value of such crudes.
Hung et al. used fixed bed catalysts in the presence of hydrogen to remove oil-soluble calcium from hydrocarbon feeds (U.S. Pat. Nos. 4,741,821, 4,830,736, 5,102,852). Reynolds et al. removed calcium and/or iron from hydrocarbon feeds to an aqueous phase using aqueous acid and/or salt solutions of hydroxycarboxylic acids (U.S. Pat. No. 4,778,589), aminocarboxylic acids (U.S. Pat. Nos. 4,778,590; 4,778,592), carbonic acid (U.S. Pat. No. 4,778,591), dibasic carboxylic acids (U.S. Pat. No. 4,853,109), and monobasic carboxylic acids (U.S. Pat. No. 4,988,433). These chemical treatments all required pH adjustment to greater than 2, preferably between 5-9 along with a commercial demulsifier in order to overcome the problem of emulsion formation. In another approach, Eckerman et al. (Chem. Eng. Technol. (1990), 13(4), 258-64) and Funk (Am. Chem. Soc. Div. Fuel Chem., (1985) 30(3), 148, 148a, 149, 149a, 150-3) reported on the use of supercritical CO
2
fluid to deasphaltene heavy oils accompanied by some removal of only porphyrin metals (Ni, V) associated with the asphaltenes. As known to those skilled in the art, supercritical CO
2
has different properties and different separation selectivity from aqueous CO
2
. Finally, in the pending application (U.S. Ser. No. 961,816, WO 98 14534, published Apr. 9, 1998), oil-soluble calcium removal was effected with CO
2
where no water was added. This treatment maintains one liquid (oil) phase and results in the formation of solid CaCO
3
enabling separation from the oil phase.
It would be desirable to develop a process for removing oil-soluble metals such as calcium that addresses and overcomes the problem of emulsion formation without the need to add demulsifier agents and agents to maintain the pH of the solution. Applicants' invention addresses these needs.
SUMMARY OF THE INVENTION
Applicants have discovered a process to remove +2 ionically charged, organically bound metals from a petroleum feed. One embodiment includes the steps of contacting the petroleum feed at a temperature between 40° C. and 200° C. and autogenous pressure with an effective amount of an aqueous solution of CO
2
under conditions sufficient to minimize the formation of a crude oil in water emulsion to produce a treated crude having a decreased metals content. The aqueous CO
2
solution is formed by dissolving an effective amount of CO
2
in water.
A volume ratio of water to organic phase of greater than 2:1 eliminates emulsion formation. An acidic pH is produced by the addition of the CO
2
dissolved in a sufficient volume of water. The aqueous CO
2
solution or the individual components thereof may be combined with the petroleum feed within the volume ratios specified herein.
In a preferred embodiment the oil-soluble metal is a Group IIa (alkaline earth) metal. In particular, the oil-soluble metals to be removed are Group IIa metals, Mn, Zn and Fe.
The present invention may comprise, consist or consist essentially of the steps recited herein.
DESCRIPTION OF THE PREFERRED EMBODIMENT
One embodiment of the present invention is a process to remove +2 ionic charged metals from a petroleum feed by adding aqueous carbon dioxide, i.e., a solution formed by dissolving CO
2
in an effective amount of water, to a +2 metals-containing petroleum feed in a ratio of aqueous CO
2
to petroleum feed effective to avoid emulsion formation. The CO
2
typically is added in the form of dry ice in water.
In another embodiment, CO
2
in a liquid or gaseous form is used to make the aqueous solution. In another embodiment, the aqueous CO
2
solution is made in situ by combining stepwise the petroleum feed with water and solid carbon dioxide. In another embodiment, CO
2
is added to the crude and then water is added. In another embodiment, the petroleum feed is added to the aqueous CO
2
solution. In another embodiment of the present invention the CO
2
and water are co-added with the petroleum feed forming aqueous CO
2
in situ. The volume and molar ratios are as specified below. The choice of the method to use depends on the field situation and can be made by one skilled in the art.
The amount of water used in the process of the present invention is in excess of that naturally occurring in the petroleum feed. The volume ratio of water to petroleum feed is preferably equal to or greater than 2:1, more preferably between 2:1 and 10:1, most preferably between 2:1 and 5:1. The molar ratio of CO
2
to metal ions is preferably between 500:1 and 2:1, more preferably between 200:1 and 10:1, The oil-soluble metals to be removed include Group Ia metals, notably Ca and Mg, as well as Zn, Fe and Mn. Calcium is particularly important. The metals to be removed may be in several forms, including naphthenates and phenolates.
The reaction is carried out in any suitable reactor, e.g., an autoclave under autogenous pressure. The temperatures should be high enough to permit easy stirring of the crude. The reaction temperature is typically from 40° C. to 200° C. The reaction probably occurs as follows in the petroleum feed, using calcium as an example:
(RCOO)
2
Ca+2CO
2
+2H
2
O→2RCOOH+Ca(HCO
3
)
2
wherein R is any suitable organo or hydrocarbyl group present in the feed, as is known to those skilled in the art.
Applicants' process provides an advantage in comparison to prior art processes in that by mixing the petroleum feed with CO
2
and water (i.e., as an aqueous CO
2
solution) rather than CO
2
as basic salts of carbonic acid, the need to control the pH by treatment with agents is avoided, and the need for addition of a demulsifier is eliminated since the process minimizes the problem of emulsion formation by using a higher volume ratio of water to petroleum feed.
The process produces a treated petroleum feed in the essential absence of emulsion formation and without the need for using an agent to reacidify the solution.
This invention is particularly valuable when a calcium-rich crude is processed in a corrosion-resistant environment, where the increase in acidity accompanying the process of the present invention is not a drawback.


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patent: 4191639 (1980-03-01), Audeh et al.
patent: 4228002 (1980-10-01), Vaidyanathan et al.
patent: 4464251 (1984-08-01), Kukes et al.
patent: 4465589 (1984-08-01), Kukes et al.
patent: 4518489 (1985-05-01), Hitzman
patent: 4778591 (1988-10-01), Reynolds
patent: 4853109 (1989-08-01), Reynolds
patent: 5976358 (1999-11-01), Sartori et al.
patent: 6093311 (2000-07-01), Blum et al.
patent: 496779 (1938-12-01), None
patent: WO 98/4534 (1998-04-01), None
Eckerman, et al., Chem. Eng. Technol. 13(4) (1990) 258-64 -no month.
Funk, Am. Chem. Soc., Div. Fuel Chem. 30(3) (1985) pp. 148, 148a, 149, 149a, 150-153 -no month.

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