US2198545A - Process for the treatment of light distillates - Google Patents

Description

April 23, 1940.

M. LEVINE PROCESS FOR THE TREATMENT OF LIGHT DISTILLATES Filed Nov. 27, 1936 a w WM% a fm/ 2 f m m6 9L5 fan/605 f flarralslemv'rzq.

ww w Patented Apr. 23, 1940 UNITED STATES PATENT OFFICE PROCESS FOR THE TREATMENT OF LIGHT DISTILLATES Morris Levine, Pampa, Tex., assignor to Danciger Oil & Refineries, Inc., Tulsa, Okla.

Application November 27, 1936, Serial No. 113,057

1 Claim. (Cl. 196-50) This invention relates to the treatment of light petroleum distillates, such as gasoline, naphtha or kerosene, or similar substances, more particularly to the treatment of such light distillates for the purpose of increasing the octane number.

In the past, two general methods have been suggested for increasing the octane number of gasoline. One method comprises the addition of anti-knock dope, such as tetraethyl lead. This procedure is subject to certain disadvantages. The gasoline treated with such materials has a deleterious effect upon the automobile engine and tends to react with or corrode certain parts, such as valve heads and seats, and the like. This action obtains even when the highly resistant steels are utilized for these parts.

A second procedure which has been suggested for increasing the octane number of gasoline comprises subjecting the gasoline to a high temperature at atmospheric or superatmospheric pressure to effect chemical modification, resulting in an increase in the octane rating of the fuel. However, such processes involve a considerable loss of gasoline, due to its conversion into uncondensable gases. For example, in such processes losses of from 15 to 20% are commonly encountered, although this loss may be compensated for by the increased value of the resulting gasoline, as compared with the untreated material.

It is an object of the present invention to provide an improved method of treating light hydrocarbon fuels designed particularly for employment in internal combustion engines, and especially those of a high compression ratio.

Another object of the invention is to increase the octane number of such fuels with relatively little loss in the products treated.

For the purpose of explaining the invention, particular reference will be made to the treatment of gasoline, but it is to be understood that this is given as illustrative of any similar or equivalent fuel in which comparable improvements in characteristics are sought.

With these and other equally important objects in view, the invention comprehends the concept of subjecting the fuel to be treated, in the vaporous phase, to a catalytic treatment whereby molecular modification or rearrangement is effected, with the ultimate production of a fuel of improved octane rating.

Catalysts which have been found to be very efllcient are compounds consisting of one :or more oxides, or salts, of the metals of thefith group of the periodic table, including compounds of the type RxMyoz where M is a metal of the heating the ammonium derivatives of the metals 5 of the 6th group. One or more of the oxides described in this paragraph may be admixed with one or more salts and still remain within the scope of this invention when used as a catalyst for increasing the octane number of motor fuel.

Among the compounds which come within the scope of this invention the following may be cited: Chromium trioXide, chromium sesquioxide, corresponding oxides o fgmolypdenum, the dioxides of molybdenum 'and tungsten trioxide, potassium chromate, potassium dichromate, potassium molybdate, potassium tungstate and the corresponding sodium and ammonium derivatives of all of these salts and also the products obtained upon heating the ammonium derivatives of all of these salts. These compounds are listed as examples of the catalyst described more generally in the above paragraph.

The catalysts described above may either be used alone or admixed with other compounds that may themselves act as catalysts or in some cases be inoperative as catalysts alone but yet have the ability to improve the activity of the main catalyst. It is found, for instance, that magnesium oxide acts in such capacity. The 30 catalyst may consist of onepr morenftllcoxides or other"compounds of th metals of the 6th group alone or distributed on a support such as charcoal, silica gel, pumice stone, infusorial earth, al wa sand, etc. Such substances as sponge min or brucite may also act as supports for the catalysts.

The temperature at which the operation may be effected, i. e. the temperature at which the gasoline, or other fuel, vapors are brought in contact with the gasoline, may be varied over a relatively wide range from approximately the vaporization temperature of the fuel to a point at which the treating losses become so great that the process becomes uneconomical. A useful operative range of temperature is substantially between 600 F. and 1050 F. It will be recognized that the particular temperature range that is most effective will be established, to a considerable degree, by the other factors of a particular operation, more especially the particular conditions of vapor velocity. For instance, at a velocity such that gasoline is charged to the system at the rate of 20 gal. per hr. per cu. ft. of space in the catalytic tower, the most effective temperature range is between approximately 600 F. and 950 F. At higher gasoline velocities the temperature should be correspondingly raised to produce the most effective results.

In the preferred form of the invention the gasoline is transformed into the vapor phase before contacting with the catalyst. However, the improved process of the present invention may be applied at such a point in petroleum refining procedure where .the gasoline is already in the vapor phase. For example, the tower containing the catalyst may be connected to the vapor line of a bubble tower so that overhead vapors from this tower may be immediately processed. A furnace may be disposed between the top portion of the bubble tower and the reaction tower in order to heat the gasoline vapors to any desired increased temperature before being contacted with the catalyst.

The reaction tower may also be connected to a cracking system, at such point where the cracked gasoline is still in the vapor phase. For instance, the reaction tower may be disposed between the bubble tower and condenser. Here also, means of heating the cracked gasoline vapors to any desired temperature may be disposed ahead of the reaction tower.

However, if the gasoline before treatment is in the liquid phase, it must be transformed into the vapor phase by any known means, such as by passage through the tubes of a commercial pipe still. While this furnace may be so operated that the gasoline vapors leave it at any temperature above that temperature at which it is converted into the vapor phase, it is preferable to operate it so that the gasoline leaves the furnace at such temperature above the optimum reaction temperature that the vapors enter the reaction tower at the desired reaction temperature. This increase in temperature will compensate for the heat lost by radiation, or by any other means, during the passage of the gasoline from the furnace to the reaction tower.

The reaction tower may be disposed vertically or horizontally. If disposed vertically, the gasoline vapors may be conducted through the tower either in an upward or downward direction. If disposed horizontally, it is preferable that the tower be equipped with a number of bafiles, alternately open at the top and bottom, so that the gasoline vapors are contacted with the catalyst in as efiicient a manner as possible, by the prevention of channeling.

The tower may be maintained at the reaction temperature by any known means, such as by placing it in a furnace and applying heat to the tower in the usual manner, or it may be equipped with a coil of resistance wire and heated electrically, or it may be heated by hot combustion gases, or other type of gases, with direct or indirect heat exchange. Good control on the temperature of the reaction chamber may be maintained by disposing the tower vertically inside a chamber, and admitting hot combustion gases into such chamber at a number of points throughout the height of the chamber. The hot combustion gases enter the chamber and travel upward within the annular space between the outside wall of the reaction tower and the inside wall of the chamber in which the tower is disposed.

The treated gasoline vapors issuing from the reaction tower may be conducted successively through a condenser and gas separator in the usual manner, and passed to storage. However, before being passed to storage the gasoline may be subjected to any other treatment that may be deemed necessary. For instance, if sour, it may be treated with doctor solution or any other like agent, in order to sweeten it. Such sweetening treatment and also any other treatment, for instance, for removal of impurities responsible for high gum content and discoloration, may either precede or succeed treatment in accordance with the new process for increasing the octane number of the treated gasoline.

In accordance with one advantageous manner of conducting this series of treatments, the gasoline from the vapor line of a bubble tower forming a part of a cracking system, is treated for removal of substances responsible for gum and discoloration, superheated if necessary, conducted through the catalytic reaction tower, condensed, stabilized to a suitable vapor pressure, and then sweetened. A high grade straight run gasoline may be similarly treated to yield a similar high grade gasoline, but in general with a lower octane number than that obtained by treating gasoline produced in a cracking process. In both cases, however, the octane number is measurably increased by treatment in accordance with this invention. The increase in octane number for straight run gasoline is greater than that obtained in the case of cracked gasoline.

As indicated, the process may be effectively carried out in a number of different apparatus, illustrated for example by that shown in the single figure of the accompanying drawing. As shown, I represents a storage tank containing gasoline to be treated in the case it is in liquid phase before treatment; 2 is a charge pump; 3 is a furnace of current type; 4 is the reaction tower, substantially filled with the catalyst; 5 is the chamber in which the reaction tower is disposed; 6 represents thermocouples, with the help of which the temperature of the reaction chamber is controlled; l, 8 and 9 are valves, by the proper operation of which the reaction tower 4 may be bypassed at any time such action is desired; [9, 20 and 2| are valves that permit flexibility in operation in case the gasoline being treated is already in vapor phase, in a manner more fully to be explained; I0 is a condenser for cooling and condensing the treated gasoline vapors; H is a gas separator; 24 is a furnace employed for the preparation of the hot flue gases used for maintaining the temperature of the reaction tower 4; [6 represents flues, through which hot combustion gases employed for heating the reaction tower, escape to the atmosphere; 23 are dampers for controlling the quantity of hot combustion gases being employed for heating the reaction tower.

In the operation of this plant, the gasoline to be treated is withdrawn from storage tank I by means of a pump 2, and charged to furnace 3, wherein the gasoline is converted to the vapor state and heated to a temperature sufficiently above the desired reaction temperature as to compensate for any losses of heat that may occur in the passage of the gasoline vapors from furnace 3 through line l2, into the upper portion of reaction tower 4.

In furnace 24 hydrocarbon gas, or any other fuel that may be available, is burned, and the combustion gases are conducted through line [3, and enter the annular space M between chamber 5 and reaction tower 4, at a multiplicity of points I5. Three such points are indicated in the drawing, but more or less can be inserted in accordance with the ratio of the volume and temperature of the combustion gases prepared in furnace 24, as compared with temperature and volume of gasoline vapors passing through reaction tower 4. The controlling factor is the ability to maintain a substantially constant temperature in the reaction tower 4. Each of the flue gas inlets I5 is provided with a damper 23, whereby better control of the temperature of tower 4 can be obtained. It will be appreciated that when the present unit is used directly in conjunction with a cracking unit, flue gases from the main cracking furnace or from a viscosity breaker, or other type of furnace unit, may be passed through line l3 to supply the heating medium for the reaction chamber 4.

The hot combustion gases enter the annular space M, circulate around the reaction tower 4, passing in an upward direction, and leave chamber 5 through the flue gas outlets I6.

Returning once more to the path of the gasoline vapors, these vapors enter the upper portion of reaction tower 4, substantially filled with the catalyst, and proceed downward through the tower, receiving necessary heat from the hot flue gases in the annular space l4. The treated vapors leave the reaction tower 4 and proceed successively through line H, condenser l0 and gas separator H, in the usual manner.

The treated gasoline is withdrawn from the bottom of gas separator II and conducted to a run down tank. The small amount of gases inescapably made during the treating process is removed from the upper portion of gas separator H, and. is advantageously passed to a vapor recovery plant to recover any gasoline hydrocarbons that may be present therein, and the residue gases from this step may be admixed with like gases in the refinery and subjected to a polymerization step.

As aforementioned, in the case that it becomes desirable because of operating conditions in connection with the reaction tower system, or for other reasons, to by-pass reaction tower 4, the gasoline vapors may be conducted directly from furnace 3 to line I by proper manipulation of the valves 7, 8 and 9. For instance, the tower 4 can be by-passed by opening valve 8 and closing valves 1 and 9.

As has also been mentioned, the gasoline may be introduced into the reaction tower 4 before condensation has been allowed to take place, as through line 8, leading for instance from the vapor line of a bubble tower connected with either a topping unit or a cracking system. By proper manipulation of valves 1, 8, 9, I9, 20 and 2|, furnace 3 and/or reaction tower 4 may be included in or excluded from the treating system. For instance, if gasoline vapors are obtained from any source, as from the vapor line of a bubble tower, at too low a temperature for the best operation of reaction tower 4, they are advantageously conducted successively through lines l8 and 22, furnace 3 and line 2, into the reaction tower. Under such circumstances, valves 20 and 8 would be closed and valves l9, 2|, 1 and 9 would be open. If the gasoline vapors are at a sufiiciently high temperature, so that no further heat is necessary, they are conducted through lines l8 and I2 directly into the tower. Under these circumstances, valves 2| and 8 are closed. Furthermore, in case of trouble with reaction tower 4, the vapors are passed directly from line |8 into line H, and. thence to the condenser and gas separator. This can be accomplished by closing valves 1, 2| and 9. Again, if desired, the charge to the reaction chamber 4 may be made up in part of vapors drawn from a bubble tower through line l8 and in part by liquid gasoline from tank I which is vaporized in furnace 3. By raising the temperature of the. vapors in furnace 3 to a predetermined degree, these may be utilized to further heat the vapors coming through line l8 so as to charge gasoline vapors to the reaction chamber at any desired uniform temperature. As has already been explained, the apparatus described is but one suggestion of a type of plant in which the new treating process can be conducted.

Although only one reaction tower is represented in the drawing, two or more connected in series or parallel may be advantageously employed. Under conditions of a multiplicity of towers, the operation would not have to be stopped when the catalyst has lost a portion or all of its efliciency, for when this happens a tower containing reactivated catalyst can be introduced into the system, and the tower with the spent catalyst can be shunted by the manipulation of a series of valves (not shown) in a known manner. Thus, while the operation is being conducted the spent catalyst can be revivified, as by means of the passage of a current of air through the tower, following by a water wash. Connections for the introduction of air, and its removal from the tower, are not shown in the drawing. Their presence is to be understood, however.

As an example of the results that may be expected from the treatment of gasoline in accordance with the described process, a straight run gasoline of 48.1 octane number was passed through reaction tower 4, the temperature of which was 955 F. at the bottom. The resulting gasoline had an octane number of 59.5, indicating a rise of 11.4 points. The catalyst used in this case was produced by heating zinc nitrate.

Without in any way limiting the scope of the invention, I may add that the rise in octane number, brought about by the process described above, may be due partly to dehydrogenation,resulting in the formation of olefinesfrom parafiin hydrocarbons. Conversion to aromatic hydrocarbons may also take place in this process, in accordance with results reported in an abstracted form in Chemical Abstracts, vol. 30, page 6713 (1936) the original article being written by B. L. Moldavskii and H. Kamusher. Such change, as is well known, would result in an increase in octane number. This explanation of the mechanism of the action taking place in the process is supported by the fact that the hydrogen content of the effluent gases is tremendously high, as compared with other refinery gases. However, other reactions may take place, including cracking.

It will be appreciated, therefore, that the present improvement is productive of improved results. As noted, by the relatively simple expedient of contacting light hydrocarbons, in vapor phase, with improved catalysts, a marked increase in octane rating is secured.

While preferred methods of operation and improved catalysts have been described, it is to be understood that these are given didactically to explain the principles of the invention and not as the exclusive methods of utilizing these principles. It is to be understood also that the invention is intended to comprehend not only the catalysts specifically listed, but also those which function in an equivalent manner to produce similar results.

I claim:

A process of treating gasoline-like hydrocarbon fractions of low anti-knock value to increase the 75 an; M 4,

distillate, effecting such contact while maintaining the vapors at a temperature of substantially 950 F. and maintaining the velocity of the vapors through the tower at a rate of substantially 20 gallons per hour per cubic foot of space in the tower and condensing and recovering the tr t d vapors. *lVIORRIS LEVINE.

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