US2094586A - Process of treating hydrocarbon oils - Google Patents

Description

Oct. 5, 1937.

' W. A. CRAIG PROCESS OF TREATING HY-DROCARBON OILS Filed June 30. 1936 2 Sheets-Shea?l l f O $58 SN oww A TTORNE Oct. 5, 1937. S w. CRAIG 2,094,586

PROCESS OF TREATINGHYDROCARBON OILS Filed June 50, 1936 2 sheets-sheet 2 F/cJ- WMM L 615.44m

ATTORNEY Patented Oct. 5, 1937 UNl'lE .STATES rincones or rnsarrna nrDnocAnBoN ons Application .lune Si), 1,936, Serial No. 88,100

i Claims.

This invention pertains to an improved system 'or method oi treating, purifying and refining hydrocarbon oils with maintained aqueous solutions of metallic salts. More specifically, this invention pertains to improving the treating characteristics of metallic salt solutions in order to maintain deiinite concentrations thereof at the best or more desired treating temperatures, when used to purify and rene mineral hydrocarbon oils in'vapor phase, such as gasoline or naphtha, or other petroleum oil products derived by distillation Yor cracking of mineral oils.

Treatment of hydrocarbon oils in vapor phase with maintained aqueous solutions of metallic salts is generally knownY in the reiining art, in

which the degree of renement by the treatment is determined, in part, by the concentration of the metallic salt maintained in the liquid phase, and the desired concentration of the treating Vsolution has been generally controlled primarily by controlling the temperature of the system` and -the partial pressure of the Water in the vapor phase. n Y Y My invention is an improvement in the method described in U. S. Patent #1,790,622, granted to Arthur Lachman, dated January'Z'l, 1931, for Method of rening mineral cils, and U. S. Patent #1,809,170, granted to Arthur Lachman, dated 1 June 9, 1931, forpProcess of refining hydrocarbons, which disclose methods of refining hydrocarbon oils in vapor phase With Water solutions of the metallic salts ci `zinc, copper, cadmium, mercury, iron, chromium, manganese, aluminum, nickel or cobalt, Which may be the chloride, bromide, sulphate, nitrate, and also any of the Water soluble salts of the above named metals of organic acids, such asl the sulphonic acid of benzol, toluol,

Xylol, or the sulpho acids derived from the treatment oiV petroleum oils with sulphuric acid.

The method described in the aforesaid patents for refining oil comprises, passing the oil, such as gasoline stock, in Vapor phase through and in Contact With a hot water solution of any of the aforesaid metallic salts, in which a tower iilled'v with contact material and a substantially concentrated water solution ofthe metallic salt is employed.

While it is possible to maintain any desired concentration of the metallic salt in the liquid phase by the proper choice of temperature and vpartial pressure of Water vapor, the operating conditions during the treatment of a light petroleum distillate, such as naphtha stocks, are restricted by the characteristics of the latter. In order to maintain the distillate or naphtha stock (Cl. Lilli-36) in vapor phase duringtreatment, certain conditions Yoi temperature and vapor pressure must be observed. 1 It is necessary, therefore, to choose operating conditions that will maintain the concentration of the salt solution at the desired strength and at the same time maintain the distillate or naphtha stock under treatment in vapor phase. The treatment of hydrocarbon mixtures containing unsaturated hydrocarbons with metallic salt solutions causes some of the latter to polymerite or condense to form materials of higher mclecular Weight. The characteristics of the polymers and condensed materials depends upon the characteristics of the original unsaturates and the severityoi treatment, and it has been observed that some of the reaction products are recovered lin the gasoline fraction, While others are removed in the higher boiling portions of the discharged material,V Fractionation will effect the removal of high-boiling polymers and allow the recovery oi a treated distillate having favorable characteristics, such as good color, good color stability when exposed to sunlight, absence of gums and gum forming constituents, etc.

There are times when it is beneficial to maintain the salt solution at a relatively low concentration. If it becomes desirable to lower the concentration within the treating vessel, it may be accomplished by lowering the temperature or increasing the partial pressure oi the water in the vapor phase, or both. However, such changes also affect the liquid-vapor equilibrium of the hydrocarbon oil, as shown in the following Table No. l, which illustrates some of the varying treating conditions which may be employed in purifying a cracked gasoline stock.

Under the chosen conditions, as shown incolumn l of Table No. 1, a zinc chloride concentration of 82.5% is obtained, and the hydrocarbon oil in vapor phase has an average boiling point of approximately 330 F. If the conditions of pressure and Water Vapor pressure are maintained but the temperature is lowered to 335 F., as shown in column 2, the Zinc chloride concentration will be reduced, and at the same time the average boiling point of the hydrocarbons will be reduced, and a portion of the hydrocarbons which Were formerly in vapor phase will condense Within the treater.

Column 3 shows the effect of changing the proportion of water vapor within the treater and maintaining the temperature and pressure constant. Such a change Will reduce the Zinc chloride concentration of the treating solution and increase the average boiling point of the hydrocarbons in vapor phase, provided, of course, that there are. hydrocarbons present in liquid phase to allow this increase to take place.

Column 4 shows the conditions necessary to reduce the zinc chloride concentration, and at the same time maintain the. average boiling point of the hydrocarbons in vapor phase at approximately the same value as that shown in column 1. It is, therefore, evident that conditions of temperature, pressure and Water vapor pressure can be chosen so that the concentration of Zinc chloride in solution and the average boiling point of the hydrocarbons in vapor phase can be controlled to a limited extent. The same sort of control can be achieved if other treating reagents are used when the characteristics of the treating solution are known. It is seen that:-

l. Temperature reduction decreases the concentration of the metallic salt solution;

2. Temperature reduction decreases the average boiling point of the hydrocarbons in the vapor phase;

3. Increase in water vapor pressure decreases the concentration of the metallic salt solution;

4. Increase in water vapor pressure increases the average boiling point of the hydrocarbons in the vapor phase.

From an economical point of View, it is desirable to reduce the steam requirements of the treating system to a minimum. It is shown in the above discussion, however, that higher temperatures would be required to offset the effect of reduced water Vapor pressure upon the average boiling point of the hydrocarbons in the vapor phase. These conditions would affect the treating solution, causing it to become more. concentrated. Inasmuch as the severity of treatment depends in part upon the concentration of the metal salt, it is evident that high temperature and minimum steam addition will give` more severe treatment than will occur with lower teinperature and greater additions of steam. Some hydrocarbons are adversely aiected by severe treatment, and it is necessary to subject stocks of this nature to the milder action of more dilute reagents. One is, therefore., required to sacrice economy in steam consumption in order to avoid over-treatment of such materials.

Now I have discovered that, in the refining of vaporized hydrocarbons such as naphtha or gasoline stocks with aqueous zinc chloride and other like metal salt treating solutions, the aforesaid difficulties may be overcome by dissolving inthe treating solution certain compounds which will decrease the vapor pressure of the treating solution at a given temperature, or modify the ternperature-vapor pressure-concentration relationship. Such compounds, used by my invention to modify the temperature-vapor pressure-concentration relationship, may be inert or non-reactive salts which are soluble in the treating solution, such as calcium chloride, sodium chloride, potassium chloride, and the like, dissolved in treating solutions of zinc chloride, copper chloride, aluminum chloride, and the like, as described in my pending application Serial No. 60,039, led January 21, 1936, for Process of treating hydrocarbon oils.

In treating solutions made from metal sulphate salts, such as Zinc sulphate, copper sulphate, etc., d

non-reactive salts would be employed to modify the temperature-vapor pressure-concentration relationship, such as sodium sulphate, potassium sulphate, and the like, to avoid reactions which would cause precipitation, or removal of any of the components of the treating solution.

I have further discovered that soluble organic salts of the pyridine type will also modify the temperature-vapor pressure-concentration relationship of treating solutions. These compounds may be pyridine, pyridine homologues, or the nitrogen base compounds extracted from petroleum oils, which may be added to the treating solution in the form of bases and allowed to react with the acid which is formed by hydrolysis of the. metal salt treating agent, or these nitrogen bases may be converted into salts by the addition of acid, such, for example, as by the addition of hydrochloric acid to produce hydrochlorides, and then added in this form to the metal salt treating solution.

The following Table. No. 2 illustrates the changes in the boiling points produced by the addition of petroleum base hydrochlorides to zinc chloride treating solution, and the saving in steam eiected thereby in refining gasoline stocks.

TABLE No. 2

Comparison of treating characteristics of eine chloride solution and eine chloride solution containing petroleum base hydrochlorides haring a ratio of base to eine chloride of 0.090

ZDC12 ZIlClg ZIlClz ZIlClz ZDCIQ and base and base and base and base and base Treating solution ZnClg hydro- ZnClg hydro- ZnCl2 hydro- ZnClz hydro- ZnCl2 hydrochlochlochlochlo- 0h10. rides rides rides rides rides Treating temp-ur 335 335 335 335 335 335 35o 35o 379 379 Treating pressure-lb/sq. in. abs. 40 40 33 33 33 33 40 40 40 40 Mol. percent water in vap0rS 36. 7 36.7 23. 5 23. 5 44. 2 44. 2 22.5 22.5 36. 7 36. 7 Abs. vapor pres. of Water lb./sq. f in 14. 7 14. 7 7. 75 7. 75 14. 7 14. 7 9. 0 9. 0 14. 7 14. 7 Abs. vapor pres. of hydrocarbon 1b./sq. in 25.3 25. 3 25.3 25.3 18. 3 18. 3 31. 0 31. 0 25.32 25. 32 Concentration of ZnClz wt. percent 80 74. 6 85 80 80 74. 6 87 80 86. 4 80 Av. boiling pt. at l atmos. of

hydro. in vapors aF 295 295 295 295 320 320 295 295 340 340 Steam required per bbl. hydro 22. 35 22. 35 12.05 12. 05 30. 5 30V 5 11.3 11.3 22.35 22. 35.

F`Ialole No. 2 shows thatat constant conditions of temperature, pressure andV partial pressure of water vapor, the zinc'chloride concentration is lowered by the addition of petroleum base hydrochlorides. At constant zinc chloride concentration, the presence of bases allows operation at lower pressures, or lower partial pressure of water Vapor. At constant zinc chloride concentration, constant pressure and constant partial pressure of water vapor, higher temperatures can be employed.

An object of the invention is to renehydrocarbons in vapor phase at a given temperature, with a water solution of a metallic salt, at a desired vapor pressure.

Another object ofthe invention is to refine hydrocarbons in'vapor Aphase at a given temperature, with a water Vsolution of a metallic salt treating agent, maintained at av desired vapor pressure by the addition of an inert compound which is soluble in the treating solution.

Another object of the invention is to refine hydrocarbon oil Vapor by contact with a reactive salt solution containing a relatively non-reactive salt or compound dissolved therein, in quantities sufficient to modify the temperature-vapor pressure-concentration relationship of the solution to the desired degree.

Various other objects and advantages of the present invention scription of the preferred form or example of the method embodying'the invention; For this purpose reference is made to the yaccompanying drawings.

Figure I shows the relationship at atmospheric pressure of boiling point and concentration of aqueous Zinc chloride solutions in which varying amounts of nitrogen base hydrochlorides are dissolved. The ratios shown in the legend on the figure are calculated from the content of free bases rather than the content of base hyrochlo-V ride. Each curve represents a constant ratio of nitrogen bases to Zinc chloride. Similar curves can be prepared to show the same relationship at pressures other than atmospheric, or for other treating solutions.

Figure II represents which the invention may I represents a treater for contacting hydrocarbon oil vapor with refining agent. The lower section of treater I is filled with bubble cap trays generally apparatus in be performed, in which 2, and provided with a compartment trap 3 stationed above the last tray or row of bubble caps. Pipe 4, controlled by valve 5, connects treater I f near the bottom to a source of hydrocarbon vapor to be treated, such as a fractionating column, still, or other form of vaporizer. Pipe 6, controlled by valve 'I, connects hydrocarbon vapor pipe 4 to a source of the treating solution. Pipe 8, controlled by valve 9, connects pipe 4 to a source of steam. Pipe II), controlled by valve II, connects treater I at the bottom to a storage for waste supply, not shown. Pipe I2, controlled by valve I3, connects the compartment trap section of treater I to a source of steam. A discharge pipe I4, controlled by valve I5, connects the compartment trap section of treater I to a storage for spent treating solution, not shown. Pipe I6 connects treater I at the top to allow the vapors to pass to other equipment for further processing, known in the art.

The preferred operation as carried out in the apparatus just described, is as follows: y

The treating solution is preferably a water solution of zinc chloride and petroleum base hydrowill be apparent from the de-V chlorides, in which the ratio:l of petroleum bases to zinc chloride ranges fromabout 0.09 to 0.65 part by weight of petroleum bases to 1 part by weight of zinc chloride. While the preferred salts employed to make the treating solution are zinc chloride and petroleum base hydrochlorides, it is to be understood that anyof the other salts or mixtures thereof and compounds heretofore enumerated may be used in like manner at` various ratios and concentrations to suit the oil to be treated and the product desired. However, in order to simplify this example, the conditions which arepresented in columns l and 2 of Table No. 2 will be used to illustrate my improved meth- ,od of operation.

Treater I is first lledup to the level of the dischargepipe I4 with the treating solutionto be employed, heated to a desired temperature, preferably ranging from about 360 to 390 F., by a heaterv not shown, which discharges the heated solution through pipe 6, controlledk byvalve l, pipe d, and into said treater I near the bottom.

Hydrocarbon oil vapor, such as gasoline or naphtha stock, coming from any of the known refinery vaporizers, orvaporizer and fractionating` system, at or above the vapor temperatureof the stock to be treated, passes through pipe 4, controlled by valve 5, and into the lower section of treater I. At the same time a regulated quantity of steam, required temperature so as to maintain the oil vapor atfany required treating ,temperature,is continuously passed into the cil vvapor passing through pipe 4, the steam coming through pipe, controlled by valve 9. The treating solution may also be continuously or intermittently introduced into pipe 4 through pipe 6, controlled by valve 1, in quantities sufficient to maintain the treating solution in treater I at the required strength and purity tol continuously effect uniform treatment of the oil vapors.

The hydrocarbon vapors, commingled with steam, pass from pipe 4 into treater I, and are therein intimately contacted with treating solution and treated to the required degree'as they pass up through the bubble cap tray system 2. The contents of the treater are kept at a temperature of 335 F., a pressure of 40 pounds per l square inch absolute, and an absolute water-val por pressure of 14.7 pounds per square inch.

Under these conditions, the aqueous treating solution will contain approximately 74.6 by weight of Zinc chloride, and petroleum base hydrochloride, calculated as free bases, amounting to about 6.7%. The hydrocarbons in Vapor phase will be foundy to have an average boiling point of approximately 295 F. It might be pointed out at this time that, under identical conditions within the treater except that the petroleum bases be absent, the concentration of Zinc chloride in the solution would be approximately 80%, as shown in column l of Table No. 2.

The spent or partially spent treating solution is continuously or intermittently discharged from treater I through pipe I4, controlled by valve I5, to a storage tank not shown, and may be thereafter recovered for reuse by known methods. Steam may also be introduced into the upper section of treater I through pipe I2, controlled by valve I3, to maintain the oil in vapor phase. From treater I, the treated oil vapors and gaseous products of reaction pass through pipe I6 to other equipment known in the art, in which the purified hydrocarbons are separated from undesirable products of reaction.

which may be superheated to any f Cil ouV

The novel feature of my invention is the use of petroleum base hydrochlorides, or other inert compounds, to alter the concentration of the active metallic salt in the treating solution, so that greater flexibility of operation may be obtained. By their use, lower concentrations can be obtained under constant operating conditions, or higher temperature can be employed Without increasing the concentration, and thereby reduce the consumption of steam.

While the process herein described is well adapted for carrying out the objects of the present invention, it is to be understood that various modifications and changes may be made without departing from the spirit of the invention, such, for example, as the use of other forms of contact towers or mechanical mixers, and the invention includes all such modifications and changes as appear within the scope of the appended claims. It also includes the treatment of normally gaseous unsaturated hydrocarbons, by which they can be converted to hydrocarbons of greater molecular weight. By means of my invention it is possible to increase the treating temperature to a marked extent, and still maintain the active treating material as a mobile aqueous solution, and at the same time maintain a relatively low pressure upon the treating vessel.

I claim:

1. A method of rening hydrocarbon oil vapor Which comprises, contacting the oil vapor mixed with steam at refining temperatures With aqueous, reactive, maintained salt solution of a heavy metal Vcontaining petroleum base salts dis- Y chloride salts derived from petroleum oils.

3. In the process of rening hydrocarbon oil vapor mixed With steam, by Contact with a Water solution of Zinc chloride at rening temperatures, maintained at constant concentration, constant pressure and constant Water vapor pressure, the improvement of maintaining a higher treating temperature by adding to the zinc chloride solution salts of petroleum bases, in amounts suii'icientv to refine the oil vapor at a required treating temperature; Y

4. In the process of rening hydrocarbon oil vapor mixed with steam, by contact With a water solution of zinc chloride at reining temperatures, maintained at constant concentration, constant pressure and constant Water vapor pressure, the improvement as in claim 3 in which the petroleum base salts are hydrochlorides.

WALLACE A. CRAIG.

Images