Mineral oils: processes and products – Refining – Organic acid or phenol contaminant removal
Reexamination Certificate
2001-03-09
2002-09-24
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Refining
Organic acid or phenol contaminant removal
C208S299000, C208S307000
Reexamination Certificate
active
06454936
ABSTRACT:
FIELD OF THE INVENTION
The instant invention is directed to the removal of acids, especially organic acids such as naphthenic acids from oils including crude oils, crude oil blends and crude oil distillates using solids.
BACKGROUND OF THE INVENTION
High Total Acid Number (TAN) crudes are discounted by about $0.50/TAN/BBL. The downstream business driver to develop technologies for TAN reduction is the ability to refine low cost crudes. The upstream driver is to enhance the market value of high-TAN crudes.
The current approach to refine acidic crudes is to blend the acidic crudes with non acidic crudes so that the TAN of the blend is no higher than about 0.5. Most major oil companies use this approach. The drawback with this approach is that it limits the amount of acidic crude that can be processed. Additionally, it is known in the art to treat the crudes with inorganic bases such as potassium and sodium hydroxide to neutralize the acids. This approach, however, forms emulsions which are very difficult to break and, additionally, undesirably leaves potassium or sodium in the treated crude. Furthermore, such prior art techniques are limited by the molecular weight range of the acids they are capable of removing.
With the projected increase of acidic crudes in the market (Chad, Venezuela, North Sea) new technologies are needed to further refine higher TAN crudes and crude blends. Thermal treatment, slurry hydroprocessing and calcium neutralization are some of the promising approaches that have emerged. However, these technologies do not extract the acids from the crudes. Instead, they convert the acids to products that remain in the crude.
U.S. Pat. No. 4,752,381 is directed to a method for neutralizing the organic acidity in petroleum and petroleum fractions to produce a neutralization number of less than 1.0. The method involves treating the petroleum fraction with a monoethanolamine to form an amine salt followed by heating for a time and at a temperature sufficient to form an amide. Such amines will not afford the results desired in the instant invention since they convert the naphthenic acids, whereas the instant invention extracts and removes them.
U.S. Pat. No. 2,424,158 is directed to a method for removing organic acids from crude oils. The patent utilizes a contact agent which is an organic liquid. Suitable amines disclosed are mono-, di-, and triethanolamine, as well as methyl amine, ethylamine, n- and isopropyl amine, n-butyl amine, sec-butyl amine, ter-butyl amine, propanol amine, isopropanol amine, butanol amine, sec-butanol, sec-butanol amine, and ter-butanol amine. The cost of such amines for removal of naphthenic acids and the need to regenerate them, makes such a process uneconomical. Hence, a cost effective means for removal of naphthenic acids is needed.
SUMMARY OF THE INVENTION
The instant invention is directed to a process for extracting acids from a starting oil comprising the steps of:
(a) treating the starting oil containing acids with an amount of solids and water under conditions and for a time and at a temperature sufficient to form a water-in-oil emulsion of said starting oil, water and solids wherein said solids are selected from solids having a total average surface area of less than or equal to 1500 square microns;
(b) separating said emulsion of step (a) into a plurality of layers wherein one of such layers contains a treated oil having decreased amounts of organic acids;
(c) recovering said layer of step (b) containing said treated oil having a decreased amount of organic acid and layers containing water and solids.
DETAILED DESCRIPTION OF THE INVENTION
In the instant invention solids are added to starting oil (the oil from which acids are to be removed) along with water to form an emulsion which is then broken, separated into layers and the oil having decreased amounts of acid recovered. Beneficially, the process can be practiced using existing oil/water separation equipment with minor modifications.
The solids may be selected from solids having an average surface area of less than or equal to 1500 square microns, preferably from about 25 to about 1500 square microns, and most preferably about 50 to about 1500 square microns, and more preferably about 100 to about 1500 square microns. Suitably, the solids may be selected from silica, alumina, coke, montmorillonite clays such as bentonite, kaolinite, and mixtures thereof. Although other forms are likewise useable, when clays are selected, especially bentonite clay, the clay will preferably be in the gel form. In the gel form the clay sheets are divided or exfoliated. The procedure to prepare exfoliated or divided gel is know in the art. The main advantage of using the exfoliated clay is that the clay solids are in the form of sheets that are <than 10 nm thick and can be broken to 50 to 200 nm size plates. The solids utilized herein are hydrophilic, hydrophobic or amphiphilic. The solids are preferrably amphiphilic which means that they have a hydrophilic/hydrophobic character. One skilled in the art readily can identify such solids.
The invention is particularly applicable to crude oils, crude oil blends, and crude oil distillates and mixtures thereof. Some crude oils contain organic acids that generally fall into the category of naphthenic acids and other organic acids. Naphthenic acid is a generic term used to identify a mixture of organic acids present in a petroleum stock. Naphthenic acids may be present either alone or in combination with other organic acids, such as sulfonic acids and phenols. Thus, the instant invention is particularly suitable for extracting naphthenic acids.
In the instant invention, organic acids, including naphthenic acids which are removed from the starting oil or blends are preferably those having molecular weights ranging from about 150 to about 800, more preferably, from about 200 to about 750. The instant invention preferably substantially extracts or substantially decreases the amount of naphthenic acids present in the starting oil when the oil is a crude oil or combination thereof. By substantially is meant all of the acids except for trace amounts. However, it is not necessary for substantially all of the acids to be removed since the value of the treated crude is increased if even a portion of the naphthenic acids are removed. Applicants have found that the amount of naphthenic acids can be reduced by at least about 30%, preferably at least about 60% and, more preferably, at least about 86%.
Starting oils (including starting crudes) as used herein include any oil containing acids, and especially crude oils, crude blends, distillates and mixtures thereof. All that is necessary is that the starting oil contain acids, such as organic acids and preferably naphthenic acids. Preferably, if the starting oil is a crude oil, the starting crude will be a whole crude, but can also be acidic fractions (or distillates) of a whole crude such as a vacuum gas oil. The starting oils are treated with an amount of solid capable of adsorbing the acids present in the starting oil. This typically will be from about 0.1 to about 5 wt % based on the amount of oil being treated and the amount of acids present. The instant invention is capable of removing naphthenic acids ranging in molecular weight from about 150 to about 800, preferably about 250 to about 750. The weight ranges for the naphthenic acids removed may vary upward or downward of the numbers herein presented, since the ranges are dependent upon the sensitivity level of the analytical means used to determine the molecular weights of the naphthenic acids removed.
The solids can be added alone or in combination with water. If added in combination, a solution of the solid and water may be prepared. About 5 to 30 wt % water is added based upon the amount of crude oil. Preferrably 5 to 10 wt %. Whether the solids are added in combination with the water or prior to the water, the crude is treated for a time and at a temperature at which a water-in-oil emulsion of water, oil, solids and organic acids will form. Contacting times
Bakun Estelle C.
ExxonMobil Research and Engineering Company
Griffin Walter D.
Nguyen Tam M.
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