US2227089A - Treatment of hydrocarbon oil - Google Patents

Description

Patented Dec. 31, 1940 UNITED STATES PATENT OFFICE 2,227,089 TREATMENT OF HYDROCARBON OIL No Drawing. Application February I, 1938, Serial No. 189,237

15 Claims. (01. 196-29) The present invention relates to the refining of hydrocarbon oils, and is a continuation in part of my application Serial No. 85,325, filed June 15, 1936, and which has issued as Patent 2,122,795,

July 1938. More particularly, as stated in the parent case, the invention pertains to the treatment of the lower boiling straight run or cracked distillates, such as naphthas, gasolines and kerosenes, to impart stability thereto after said distillates have been subjected to a purifying treatment involving the use of copper-containing reagents.

The invention also contemplates an improved method of treating petroleum and similar distillates and particularly those within the gasoline and/or kerosene boiling ranges with certain chemical reagents to render such distillates sufflciently stable and pleasing in appearance and odor from a sales standpoint.

Petroleum distillates, such as naphthas, gasolines and kerosenes, whether obtained by straight run distillation or by cracking of petroleum hydrocarbon oils or of their fractions, usually contain considerable quantities of sulphur derivatives, such as mercaptans, sulphides, thiophenes, etc., most of them being 'malodorous and containing corrosive impurities. The distillates obtained from the aforementioned treatments of petroleum hydrocarbons also contain color imparting substances which may comprise asphaltic and resinous bodies, oxidized hydrocarbons, nitrogenous compounds, etc. All of these undesirable substances must be removed before the distillates are sumciently stable and pleasing in appearance and odor to make them suitable for the particular uses for which they are made. In treating such hydrocarbon oils or distillates copper chloride and other copper salts are frequently employed to remove the sulphur compounds, or, at least, to convert them into non-corrosive and non-detrimental sulphur compounds. In such sweetening processes a large number of copper compounds may be employed either in a dry state or in solution and, while in some cases there may be some actual removal of the sulphur by combination with copper, it is believed that the copper chloride, or like reagent, is recoverable practically quantitatively, the sulphur compounds, particularly of the mercaptan type, being converted to di-sulphides. In the above mentioned copper chloride treatment, the reaction is realized in the present of air or other oxygen-containing gas. Although the copper salts employed for the sweetening operation are insoluble in the hydrocarbon oil treated, the oils treated with these copper reagents, in

spite of their apparent copper-free condition, are found to exhibit a progressive tendency to discolor or to have an increased tendency to form resinous material, polymers or malodorous constituents. Although the exact chemistry of the 5 reaction is not known and although the reaction products causing the above mentioned tendency to discoloration and resinification are not known at the present time, it is known that. some of the copper salts, such as copper chloride, are trans- 10 formed during the sweetening step into oil-soluble copper naphthenates and other oil soluble copper organic compounds which are the cause of the above mentioned undesirable characteristics exhibited by copper treated distillates.

It is, therefore, an object of the present invention to provide a novel reagent for treating such copper sweetened distillates to prevent and reduce the undesirable discoloration, resinification, polymerization, etc., of such copper treated hydro- 20 carbon distillates. Another object of the invention is to reduce, delay and/or prevent the formation of malodorous products in such treated oils.

As stated in the parent application, it was found that a copper-treated oil fraction exhibiting the 25 undesirable discolorizing, resin-forming or polymer producing properties could be stabilized by bringing such oil into intimate contact with alkaline earth or alkali metal carbonates, and particularly with aqueous solutions of said carbonates, 30 subsequent to the treatment of the oil with the copper or similar compounds. Thus, it was stated. that the copper treated oil fractions may be stabilized by contacting them with any of the alkali or alkaline earth metal carbonates which are water soluble.

It has now been discovered that the copper compounds which are known to be oxidizing catalysts and which are found in oils and distillates treated with copper salts of the type of 40 copper chloride, may be removed or rendered nondetrimental by treating these oils and/or distillates with certain other carbonates which are substantially insoluble in water. In fact, this auxiliary treatment of the copper treated distillates, according to the present invention, comprises the use of carbonates of the metals above hydrogen in the electro-chemical series. includes the use of the carbonates of the alkaline earth metals such as barium, strontium, calcium, magnesium and aluminum as well as the carbonates of the heavy metal such as manganese, zinc, chromium, cadmium, iron, cobalt, nickel, tin and lead. All of these carbonates are substantially insoluble in water.

When dealing with different gasoline stocks which have been sweetened by different copper or like compounds, and under difierent methods of operation, some of the carbonates enumerated above may act with greater efflciency than others. Therefore, they cannot be considered as exact equivalents, although they may be employed alternatively. Of thealkaline earth metal carbonates, I have found that calcium carbonates may be used in practically all cases, while among the heavy metal carbonates the carbonates of zinc and iron fall within this preferred class.

It has been further discovered that a copper treated oil fraction exhibiting the aforementioned discoloring, resin-forming or polymer producing characteristics, may be stabilized and rendered pleasing in appearance and odor by bring said oil into intimate contact with a carbonate of the metals above hydrogen in the electrochemical series after the oil has been treated with a copper salt, such as copper chloride or the like. It has been further found that a small blft definite amount of moisture is desirable if not essential to the activity of the solid carbonate reagent employed.

The reasons for the refining action of the above described carbonates and their efiiciency in removing the objectionable by-products from copper sweetened distillates are not entirely understood. However, it has been uniformly observed that this treatment of the copper treated oil with the above carbonates delays, reduces or prevents discoloring and/or the formation of resinous matter, polymers or oxidation products. It is believed at the present time that the treatment of the copper sweetened distillates, such as gasoline, with the carbonate or carbonates of the metals above hydrogen in the electro-chemical series, converts the oil-soluble copper naphthenate into an oilinsoluble copper carbonate and intonon-detrimental naphthenates of the metal employed. Similarly, the other oil-soluble organic copper compounds are also believed to be converted into easily removable compounds which leaves the gasoline sweet and free from any tendency to discolor or to form resinous materials, polymers or other undesirable substances.

It is obvious that I do not desire to be limited by the above theory of the function of the carbonate or carbonates of the metals above hydrogen in the electro-chemical series. Thus, the decolorizing and clarifying of the stocks treated by the process constituting the object of the present invention may be due to some extent to the removal of mechanically entrained finely divided particles or to reactions of a rather obscure character involving the conversion of the dissolved reaction products, such as copper mercaptides, into di-alkyl di-sulphides on the one hand and into oil-insoluble copper compounds on the other hand. In view of the fact that copper is below hydrogen in the electro-chemical series, it is also possible that, at least initially, the reaction or reactions may involve the replacement of the copper in the reaction products by the metal of the carbonate or carbonates employed, the resulting metal reaction products being oil-insoluble so that their removal from the copper sweetened distillate may be realized very simply. In the alternative these metallic reaction products, although oil-soluble, may be non-detrimental in that they do not tend to cause discoloration, etc., of the gasoline. There is a further possibility that the color in the copper sweetened hydrocarbon distillates may be traceable to minute amounts of some of the copper salts originally used for sweetening. In such a case, the treatment with the heavy metal carbonates may cause a reaction which forms an easily precipitatable copper carbonate with the concurrent formation of a metal compound. It is thus obvious that there are many possibilities as to the reaction or reactions which might occur when a. copper sweetened distillate is treated with a carbonate of a metal above hydrogen in the electro-chemical series, the fact, however, remaining that such a treatment delays, reduces and/or prevents discoloration and/or the formation of resinous matter, polymers or oxidation products.

The operation of the process is extremely simple, any method of intimately contacting the oil with the metal carbonate being suitable. Thus the copper sweetened distillate may be merely passed through beds of the metal carbonate at either ordinary or slightly superatmospheric temperatures. The time of contact of the oil with the carbonate compound is relatively short even at room temperature provided intimate contact between the oil and the carbonate compound is obtained. If necessary to maintain substantially liquid phase conditions superatmospheric pressures may be used. The carbonate employed for this treatment may be produced by precipitation or other methods, or may be the natural occurring minerals, for example, in the case of iron, the mineral siderite, and in the case of zinc, the naturally occurring zinc carbonate known as calamine. The carbonates may be employed either alone or commingled with or distributed over the surface of inert carriers, such as clay, fullers earth, etc., the distribution being for the purpose of allowing a better contact with the distillate to be treated.

As an example of the realization of the process constituting the object of the present invention,

a cracked gasoline obtained from a sulphur-bearing crude oil was treated in the following manner:

A stream of cracked gasoline which reacted sour to a doctor test was first commingled with air in the proportion of approximately one cubic foot of air per barrel of gasoline, and then dried, as by passing over a bed of calcium chloride. The oil-air mixture was then brought in contact with solid copper chloride which, in the instant case, was distributed or spread on a carrier of the type of beauxite. Oil thus treated was found to be sweet to the doctor test, that is, exhibited no discoloring upon agitation with aqueous sodium plumbite and sulphur. Evaporation of a sample of this oil, however, showed considerable nonvolatile residium and upon prolonged standing the copper treated gasoline discolored. For the purpose of stabilizing this copper treated gasoline and to prevent its resinification and discoloration, the gasoline, immediately after being sweetened by the above described contacting with copper chloride, was passed over a bed of zinc carbonate distributed on a caI'rieL-such as fullers earth. The contacting was realized at room temperature and the pressure was only sufiicient to cause the passage of the copper sweetened gasoline through said bed. The gasoline recovered from this treatment was found to contain substantially no volatile residue and did not show any discoloration even upon prolonged standing. Also, its induction period was considerably greater than the induction period for the copper sweetened gasoline which was not subjected to the treatment with the zinc carbonate.

It is to be understood that the invention includes all such modifications or substitutions as are within the scope of the appended claims, the specific embodiments described hereinabove being merely illustrative and not deemed to be in any way limiting. Thus, although the above treatment with the metal carbonates has been described in connection with the stabilization of copper treated gasolines or other distillates, the invention may be equally applicable when the sour distillates has been initially treated with other compounds, as for example with mercuric chloride.

I claim:

1. A process for stabilizing oil treated with a copper reagent in the presence of oxygen, which comprises treating the copper sweetened oil with a carbonate of a metal above hydrogen in the electro-chemical series.

2. A process for stabilizing petroleum fractions previously treated with a copper reagent in the presence of oxygen, which comprises contacting said copper sweetened petroleum fraction with a solid relatively water insoluble carbonate of metal above hydrogen in the electro-chemical series.

3. A process for removing copper compounds from copper sweetened hydrocarbon oils sweetened in the presence of an oxygen containing gas which comprises treating the copper sweetened oil, in the presence of water, with a solid relatively water insoluble carbonate of metal above hydrogen in the electro-chemical series.

4. In a process of stabilizing petroleum oils which have been previously subjected to treatment with a copper reagent in the presence of an oxygen containing gas, the step of passing said copper sweetened oil, in the presence of a relatively small quantity of moisture, through a bed of a solid carbonate of metal above hydrogen in the electrochemical series.

5. In a process according to claim 4, wherein the metal carbonate is maintained on a relatively inert carrier, thus permitting a better contact between the metal carbonate and the copper sweetened oil being treated.

6. A process for removing copper compounds from copper sweetened oils sweetened in the presence of an oxygen containing gas which comprises treating the copper sweetened oil with a solid alkaline earth metal carbonate substantially insoluble in water.

7. A process according to claim 6 wherein the treatment is conducted in the presence of a relatively small quantity of water.

8. A process for stabilizing petroleum fractions previously treated with a copper reagent in the presence of oxygen which comprises contacting said copper sweetened fraction, in the presence of water, with a solid carbonate of a heavy metal above hydrogen in the electro-chemical series.

9. A process according to claim 8 wherein the heavy metal is of the class consisting of zinc and iron.

10. A process for treating petroleum distillates containing mercaptans and the like comprising contacting the distillate with a copper reagent in the presence of oxygen to convert said mercaptans and the like, and thereafter contacting the copper treated oil with a carbonate of a metal above hydrogen in the electro-chemical series.

11. A process according to claim 10 wherein the treatment with the carbonate takes place in the presence of a small proportion of water.

12. A process for removing copper compounds from copper sweetened hydrocarbon oils which comprises treating the copper sweetened oil with zinc carbonate in solid form, thereby stabilizing the oil against color deterioration or gum formation.

13. A process for removing copper compounds from copper sweetened hydrocarbon oils which comprises treating the copper sweetened oil with iron carbonate in solid form, thereby stabilizing the oil against color deterioration or gum formation.

14. In the process of sweetening petroleum oil containing mercaptans wherein the petroleum oil is contacted with a copper reagent in the presence of an oxygen-containing gas, the steps of contacting said copper-treated oil with a solid relatively water-insoluble carbonate of a heavy metal above hydrogen in the electrochemical series, thereby stabilizing the oil against color deterioration or gum formation, and separating the stabilized oil from the heavy metal carbonate.

15. The process according to claim 14 wherein the treatment is conducted in the presence of a relatively small quantity of Water, and wherein the metal carbonate is maintained on a relatively inert carrier, thus permitting a better contact between the heavy metal carbonate and the copper sweetened oil being treated.

BASIL HOPPER.