US1964219A - Process for purifying and sweetening hydrocarbon oils - Google Patents

Description

Patented June 26, 1934 umrao smrss PROCESS FOR PURIFYING AND SWEETEN- ING HYDROCARBON OILS No Drawing.

Application December 18, 1930,

Serial No. 503,326

6 Claims.

This invention relates to processes of treating gasoline and other hydrocarbon oils to sweeten the same, and it comprises a process wherein gasoline to be sweetened is treated with solutions of copper compounds in the presenceof relatively high concentrations of chloride ions; it more specifically comprises a process wherein gasoline is sweetened with an aqueous solution of copper sulfate and a soluble chloride such as sodium chloride; it further comprises a process wherein gas" oline is sweetened in accordance with the foregoing process, then treated with sulfuric acid and, if desired, distilled.

Crude gasoline contains appreciable quantities of sulfur compounds, as mercaptans, and it is the usual practice to remove them or convert them to harmless compounds by an appropriate chemical treatment. This process is referred to among oil technologists as sweetening. A sweetened gasoline is sweet to the doctor test. That is, it shows no discolorization when treated with alkaline sodium plumbite and sulfur.

' Plumbite solutions are still used to a very large extent as sweetening agents, since they act to destroy or convert most if not all of the mercaptans present. Just how the plumbite solution acts chemically is not thoroughly understood. While great advances have been made in various other methods, the plumbite treatment still predominates in the refinery.

However, various other sweetening reagents have been proposed. Among the materials ofiering the greatest promise in this connection are copper compounds. Of these, copper oxide has generally been advocated although salts of copper such as the chlorides havealso been suggested. 'Despite the advantages of using compounds of copper, results have not been very satisfactory. This is in part due to the fact that certain reaction products of copper and the sulfur compounds, substances undoubtedly of complex structure, are soluble to some extent in the gasoline. Furthermore, the sweetening action is either incomplete or not of a permanent nature. For example, it has been suggested to use ammoniacal copper sulfate, but gasoline treated therewith will invariably contain solublecopper compounds. Aqueous solutions of cupric chloride in the gasoline, but which do not develop a positive doctor test until the gasoline has been allowed to standfor an hour or so. We have further found that the gasoline, after treatment with cupric chloride and acetate generally contains copper compounds. Any wayof improving the copper method of sweetening so as to avoid the present inherent disadvantages would be of importance technically.

It is therefore an object of our invention to improve the copper method of sweetening gasoline so that the sweetening action is permanent, that is, the treated gasoline gives neither normal nor delayed doctor tests. Other objects of our invention are to avoid the formation of any gasoline-soluble copper compounds, to avoid any appreciable increase in the color of the gasoline as a result of the treatment, to shorten the treatment time, to lessen the reagent cost and to enable the spent copper solutions to be regenerated for reuse economically.

We have found that the sweetening action of copper salts is greatly enhanced provided a high chloride ion concentration is maintained in the copper solution during the treatment.

This we do either by adding a chloride, such as sodium chloride, to the copper solution, or by using strong cupric chloride solutions. The former procedure is more advantageous.

In any event, it is best to have a chloride ion concentration present which is roughly equivalent to the chloride ion concentration in a 15 to 20 percent sodium chloride solution.

Since the essential factor in our process is the presence of a relatively large chloride ion concentration, generally of the order just mentioned, it is apparent that our invention may be practiced in many ways.

We can, for example, treat gasoline with an aqueous solution containing say eight percent of copper sulphate and seventeen percent of sodium chloride and get excellent results, the sweetening being complete in a very few minutes at ordinary room temperature and the treated gasoline being permanently doctor sweet and free of copper compounds.

The volumetric ratio of treating solution to gasoline can vary over wide limits but when using ratios in the neighborhood of one volume of solution to five or more of gasoline, better results are obtained if the acidity of the solution is kept between neutrality and one hundredth normal, that is, 0.01 normal.

the best results when solutions containing very low, concentrations of copper are employed.

Thus, for example, we can treat five volumes of gasoline with one volume of an aqueous solution containing but one percent of copper sulfate and fifteen percent of sodium chloride. A two minute agitation with this solution is suflicient to render the gasoline permanently doctor sweet. The ratio of gasoline to treating solution in this specific example is relatively high and accordingly we find it best to keep the solution neutral or its acidity below one hundredth normal. This is easily done by adding sufficient alkaline material such as sodium hydroxide when the acidity appears to approach the upper limit stated. High ratios of gasoline to treating solution, we find, develop an undesirable acidity, which tends to slow up the sweetening action or even render it incomplete.

When lower ratios of gasoline to treating solutions are employed, say two or three to one, acidity does not develop to such a great extent and the addition of an alkali to control the acidity is unnecessary. However, when an alkali is added, care should be taken to avoid rendering the solution alkaline towards the end of the treatment. In general, our sweetening agents work best in neutral or nearly neutral solutions. While alkali may be added at the start, say enough to neutralize any acidity subsequently developed, the alkali should not be present in suilicient quantity to render the solution alkaline at the 7 termination of the treatment.

Acidity may be controlled more conveniently by adding a buffer substance such as iii-sodium phosphate and a little mineral acid, say hydrochloric, which will keep the acidity of the solution within desired limits. Bufier substances are commonly used in this manner to control the acidity of any particular solution.

We have also found that introducing air or oxygen into the solution, while the sweetening action is progressing, helps to regenerate the copper compounds or restore their reactivity. Vfhen these gases are used, little or no control of the acidity is required.

While the gasoline and copper solution can be briskly agitated together, equally good, if not better results are obtained by allowing the gasoline to issue from orifices in the lower part of a body of treating solution. As the gasolineprogresses upward through the solution, it is in the state of a finely divided dispersion of globules.

Good contact between gasoline and solution is easily obtained in this way.

Ordinary copper sulfate which may contain small amounts of impurities-such as iron cempounds, is the most advantageous copper compound to use for economic reasons, but other soluble copper compounds can of course be employed. Cupric chloride is 'eflicient. If the cupric chloride is used in sufiiciently high concentration, say a twenty percent solution thereof, additional chloride can be dispensed with sincea twenty percent cupric chloride solution contains sumcient chloride ions to satisfy the optimum *chloride concentration stated above.

When cupric chloride is used in a much lower concentration, it is best to add sufficient sodium Provided the chloride ion is present in approximately the quantity indicated, the concentration of copper in the treating solution can vary over rather wide limits from, for example, the chemical equivalent of the mercaptan to be destroyed up to fifteen or twenty percent. The best copper concentration, as well also, as the chloride ion concentration, should be determined for the particular gasoline to be treated. When air is introduced during the sweetening process, as previously described, a large excess of copper is not necessary. This is because the copper solution is being continuously regenerated while the sweetening progresses.

While the optimum concentration of chloride ion has been given as that roughly equivalent to that contained in a fifteen to twenty percent sodium chloride solution, it should be understood that we do not expressly limit ourselves to this concentration. Generally, it has been found to be the most satisfactory, but it is to be expected that some gasolines will require less or more chloride ion present in the solution if the best results are to be obtained.

We find that our invention is also applicable to the treatment of cracked gasoline, kerosene and other hydrocarbon oils, as well as natural gasoline, gaseous or liquefiednatural gas, and hydrocarbon gases, liquefied or not, produced by cracking mineral oils, and in the claims, the term hydrocarbon oils is intended to include such fluids.

The spent treating solutions may be regenerated for further use by adding a copper salt thereto and adjusting the chloride ion concentration and acidity in accordance with the foregoing. Simultaneously treating the spent copper solutions with air to oxidize the copper compounds also acts to regenerate the copper for reuse, and is to be preferred. Spent solutions can be regenerated a number of times in thisway by means of air.

We are aware of the U. S. patent to Colin, No. 744,720, which proposes to treat gasoline with a solution containing copper compounds, sodium chloride and iron saltssuch as ferrous sulfate and we make no claim to that process. Whereas Colin specifically states that all three substances must be present we have found that much better results are secured when the ferrous sulfate is omitted and the concentration of chloride ion maintained as we have described.

Among other things, we have found that our process completely and permanently sweetens the gasoline in a shorter time than when ferrous sulfate is present and that our process is more economical. However, copper sulfate and other copper salts useful in our process may contain traces cf iron, and the accidental presence if iron as an impurity is not detrimental, and is not to be construed as an avoidance of our invention. The presence of large amounts of iron, however, also delays the regeneration of the spent copper solution with air.

After the gasoline or other hydrocarbon oil has been sweetened in accordance with the foregoing process, we find it advantageous to treat the sweetened gasoline with sulfuric acid in ways well known. The sulfuric acid acts as a desulfurizing agent and we find that we can get desulfurization to a greater degree when the acid treatment follows our sweetening process.- This ta s in the gasoline to disulfides and these are more easily removed by the acid than are the mercaptans.

In this acid treatment step, we can follow the usual practice. For example, we can use say 2 pounds of 66 Baum acid per barrel of gasoline, the gasoline being agitated with the acid in the usual way, the sludge allowed to settle and withdrawn, and the gasoline then washed with water until acid free. There are of course many variations on this process, and any particular set of conditions, that is, concentration of acid, and temperature at which the treatment will be effected are dependent upon the character of the gasoline treated.

In the appended claims, we mean the term hydrocarbon oils" to generically define gasoline, 'kerosene, and other petroleum distillates and oils,

Having thus described our invention, what we claim is:

1. The process of sweetening hydrocarbon oils, which includes treating the oil with an aqueous solution of cupric sulphate and a soluble alkaline chloride, said solution being substantially free of iron compounds, the concentration of chlorine as chloride in said solution being approximately equivalent to that in a fifteen to twenty per cent solution of sodium chloride and the cupric copper concentration of said solution being substantially less than equivalent to the chloride concentration, and maintaining the acidity of the solution during the treatment below one hundredth normal.

2. The process as in claim 1, wherein the soluble chloride is sodium chloride.

3. The process as in claim 1, wherein a gas containing free oxygen is passed into the said solution, whereby the latter is regenerated.

4. The process of sweetening hydrocarbon oils, which includes treating the oil with an aqueous solution of cupric sulfate and a. soluble alkaline chloride, said solution being substantially free of iron compounds, the concentration of chlorine as chloride in said solution being approximately equivalent to that in a fifteen to twenty percent solution of sodium chloride while the cupric copper concentration is substantially less than equivalent to said chloride concentration.

5. The, process as in claim 4, wherein the solu-