US2300240A - Conversion of hydrocarbons - Google Patents

Description

' Patented oa. 27, 1942 UNlTED CONVERSION F HYDROCARBONS Charles L. Thomas, Chicago, gill., assgnor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application August 25, 1939, Serial No. 291,891 `2. Claims. (Cl. 19E-458) This invention relates to a process for converting hydrocarbon oils to high yields of substantially saturated motor fuel having good antiknock properties. More specifically the invention concerns a method of manufacturing motor fuels from petroleum sources although hydrocarbon oils from other sources may also be used.

Although the process may apply to the production of motor fuels for use in any type of internal combustion engine, it nds special application in the manufacture of fuels for use in airplane motors. This is true because of the highly stable character of the finished product as well as its great susceptibility to increase in antiknock Value upon the addition of tetraethyl lead.

Numerous processes have been developed for the production of increased yields of motor fuel from crude petroleum and other hydrocarbon sources. Among these is the non-catalytic thermal cracking process whereby heavy oils are converted to substantial yields of gasoline having relatively high antiknock value. Straight-run gasoline and naphthas which may have poor antiknock properties are noncatalytically reformed to produce gasoline of improved octane number. This process also yields substantial quantities of gases containing polymerizable olefins, and various polymerization processes may be used in conjunction therewith to augment the yields of valuable motor fuel produced.

Other processes of more recent development are catalytic cracking processes by which hydrocarbon fractions .containing substantially no gasoline are converted to high yields of premium grade motor fuel at increased reaction rates.

The octane numbers obtainable by commercial noncatalytic cracking and reforming processes are relatively limited, since improved antiknock f properties beyond a certain point can be gained only at the expense of gasoline yield so that eventually a point is reached wherein it is no longer economical to increase the octane rating in this manner. Catalytic cracking and polymerization processes may be used to producelmotor fuel of higher octane rating than is economically feasible acording to the non-catalytic method of operation.

According to the present invention substantially saturated motor fuels of high antiknock value may be produced in one of the 'following several ways: fa) by processing hydrocarbon oils containing substantially no gasoline, for example,

kerosene, gas oil, topped crude oil, etc., (b) by processing mixture of olefin containing gasolines and heavier hydrocarbon oils, (c) by reforming cracked gasolines, or (d) by treating essentially olefinic mixtures such as polymer gasolines.

In one specific embodiment the present invention comprises a process of hydrocarbon oil conversion which consists in mixing a powdered cracking catalyst with hydrocarbon oil, heating the mixture to a temperature of approximately 50o-900 F. under a pressure of atmospheric to 1000 pounds per square inch in a tubular heater, passing the heated mixture into approximately the midpoint of a vertical contacter such as a bubble tower or a tower containing contacting members such as perforated plates,` baffles, etc., wherein the downwardly flowing hydrocarboncatalyst mixture intimately contacts upwardly flowing vapors, said contactor being'maintained at a temperature of 50G-900 F. and a pressure of about 50 to 300 pounds per square inch,- removing substantially olefin-free gas and gasoline overhead from said contactor, withdrawing insufficiently converted oil containing-suspended catalyst from the bottom of said contacter, separating the oil from the catalyst, returning a portion of the oil for further conversion, and reactivating the catalyst.

Charging stocks suitable for conversion ac-` cording to the present process may comprise (a) gasoline-free hydrocarbon oil fractions such as topped crude, kerosene, gas oil, topped crude oil, etc.; (b) mixtures of high boiling hydrocarbon oils such as kerosene, gas oil, topped crude oil, and the like, vwith cracked gasoline or other olefin containing mixtures of hydrocarbons; (c) cracked gasolines orother olefin-containing hydrocarbon mixtureaas' well as olefinic hydrocarbons alone including pure hydrocarbons, polymer gasoline, etc. The gasolines may beA those produced by catalytic or non-catalytic cracking or hydrocarbon oils under conditions such that oleiin containing gasoline is produced.

The optimum operating conditions will vary with the charging stock being processed, but the overall range of conditions lies within the limits of approximately 50G-900 F. and pressures of about 50-1000 pounds per square inch.

The catalysts which are useful in the present process may include cracking catalysts of various types, such as synthetic precipitated composites consisting essentially of a major portion of precipitated and washed silica hydrogel having added thereto relatively minor portions of precipitated metal hydrogels to form masses consisting of silica-alumina, silica-zinconia, silica-alumina-` zirconia, etc., said composites being substantially free of alkali-metal compounds.

conia" masses are used in a broad sense. Inesmuch as the chemical knowledge of the solid state has not been developed perfectly, it is not possible to give the structure of all solid substances. All that can be said definitely concerningthese masses is that they contain silicon, oxygen, aluminum, and/or zirconium in combination. Generally speaking, however, all these components indicate more or less low catalytic activity individually but in the aggregate display high activity. This activity is not an additive function, it being relatively constant for a wide range of proportions of the components, whether in molecular or fractions of molecular proportions. No one component can be determined as the one for which the remaining components may be considered as the promoters accordingto conventional terminology, nor can any component be determined as the support and the others the catalyst proper.

According to the description of the preparation of the preferred catalysts given below, precipitated hydrated alumina and/or hydrated zirconia are composited with hydrated silica gel,

otherwise known as silica hydrogel, and then the composite is washed, dried, and calcined, producing a catalytic mass. However, the different catalysts which may be so produced therefrom do not necessarily give equivalent results.

A large number of catalysts developed to assist in thermal cracking of hydrocarbon oils tend to accelerate the formation of gas rather than gasoline. Among these are the reduced metal catalysts. such as nickel or iron. A further characteristic of this type of catalyst is that poisoning by sulfur occurs and the catalytic surfaces are rendered inert by coatings of carbonaceous material.

Another type of catalytic mixture which has been used for this process in the activated clay type, wherein naturally occurring earths are activated by treatment with acids or other chemicals.

Under certain conditions still another type of catalytic mixture comprising activated alumina or magnesia supporting various metal oxides such as those of chromium, molybdenum, vanadium, iron, tungsten, etc, may be used, In some instances mixtures of various catalytic masses produce improved results.

The preferred catalysts of this invention are characterized by selectivity and by accelerating gasoline-forming reactions, rather than gas and carbon-forming reactions, by their refractory character which enables them to retain their catalytic activity through many repeated periods of use and'reactivation under severe conditions of temperature, by their not being poisoned by sulfur, and by the ease and simplicity of manufacture and their exact reproducibility.

The finished catalytic masses of the preferred type contain alumina and/or zirconia in amounts varying over a considerable range, for example, from 1 30 weight per cent and are preferably of the order of approximately 5-30 weight per cent of the compound calculated as A1203 or ZrOz.

The 'preferred catalytic masses may be prepared according to a number of alternative methods. Briefly, the method involves the precipitation of hydrogels of silica and 'the added compound, either simultaneously by coprecipitation methods, or by separate precipitation of the hydrogels, followed by mixing in such a manner as to product a more or less uniform mixture. or by the successive precipitation of silica hydrogel and the added alumina and/or zirconia hydrogel constitutent.

A preferred method of preparation is to'precipitate a sllicalhydrogel by the addition of an acid to a solution of Water-soluble silicate. The precipitation of the silica gels should be carried out under controlled conditions in order to produce material which, when composited with alumina and/or zirconia results in a catalytic mass of high degree of activity. In general, when precipitating silica gel from solutions of sodium silicate, it is desirable to add sufficient acid to cause complete gel formation. If the excess of acid:`

used exceeds approximately 20%, the precepitated hydrogel becomes extremely diflicult to filter, and its more desirable properties are partially lost. p

After precipitation the silica gel is preferably washed free of soluble salts. This may be done by washing the hydrogel with dilute solutions of a mineral acid, such as hydrochloric acid, or with water containing small amounts of ammonium chloride or aluminum chloride.

The removal of the alkali-metal ions, particularly those of sodium, from the catalyst composites during preparation is of particular importance, since the presence of these ions apparently causes certain undesirable side reactions to occur and also causes a substantial decrease in catalytic selectivity and activity. This may possibly be caused by reactions resulting in a decrease, at elevated temperatures, in the active surface and porosity of the catalysts to an extent where the predominant reaction is no longer catalytic in character. It may also be possible that other'reactions of an unknown character such as the catalyzing of undesirable reactions by alkali-metal components may account for the observed detrimental effects. Whatever the explanation, we have observed that the removal of alkali-metal compounds if of primary importance and our preferred catalysts are all of this nature.

During theI treatment, carbonaceous deposits develop on the catalyst surfaces with the consequent reduction in catalytic activity of the mass. The activity can be restored by heating at a temperature of 1000 F. or higher in the presence of an oxygen containing gas, whereby the carbon deposits are removed by combustion;

Because of the manner in which the oil and spent catalyst are separated, there is in addition to carbon a considerable amount of hydrocarbon oil adsorbed on the catalyst. It is desirable to remove this oil bothfrom the standpoint which may comprise gasoline or a fraction of gasoline, etc, The catalyst mass maythen be heated to drive oif the adsorbed solvent.

After removal of the hydrocarbons the catalyst mass is heated in the presence of an oxygen-containing gas at a temperature which preferably should not exceed 1500 F. in order to reactivate it. A suitable reactivating gas consists of a mixture of air and flue gas. The reactivated powdered catalyst is then returned to the process.

One embodiment of the present invention is illustrated in the accompanying drawing which is purely diagrammatic and has not been drawn to any scale nor has any attempt been made to proportionate the apparatus exactly. The invention should not be construed as being limited to the exact apparatus shown, nor the conditions given therein.

Referring to the drawing the charging stock is introduced through line I, valve 2, pump 3 and valve 4. A portion of the oil passes through line 5 and valve 6 to slurry pot I wherein it is mixed with catalyst from storage 8 through line 9 and valve I by means of agitator I0'. The slurry of catalyst and oil passes through line II and valve I2 to line I3, where it is mixed with are'- maining portion of the raw oil charged from lineL I3 and valve I3', and thence through valve I4 pump I5 and valve I6 to coil I'I which is disposed in heater I8, wherein it is heated to a suitable temperature such as approximately 500 to 900 F. and at a pressure of approximately 50 to 1000 pounds per square inch. The pressure used is such to maintain the oil in substantially liquid form. The heated mixture leaves the coil through line I9 and valve 20, entering reactor 2I, at a. point approximately midway in the column. This reactor may comprise any suitable type of column containing contacting members such as a bubble column or a tower containing perforated pa'ns, side-to-side baiiles or other suitable meansfor contacting downwardly-flowing liquid with upwardly flowing vapors and at the same time to maintain sufficient turbulence to prevent settling out of the catalyst powder from the oil. The upper section of this contactor constitutes a fractionator which may be the same or different in design from the lower section but is suitably of the bubble-tray type. Gasoline and gas are withdrawn through line 22 and valve 23 through stabilizers, heat exchangers, condensers, etc., which are not shown in the interest of simplifying the drawing. The higher'boiling oil containing the catalyst in suspension passes down through the reactor and further conversion takes place. If desired, a part of the raw oil which may be heated with or without additional catalyst, may be introduced into the reactor at various points, for example, through line 24, valve 25, or line 26, valve 21, heat exchanger 59 and line 60 The oil may be introduced at additional points which are not shown in order to simplify the drawing. The insuiiiciently converted oil having suspended catalyst contained therein passes through line 28 and valve 29 to separator 30 which may be a settling tank, a filtering apparatus or any other suitable type of equipment for separating the oil from the suspended catalyst. A portion o'f the unreacted oil may be withdrawn from separator 30 through line 3|, valve 32, line 33 and valve 34 to storage. If so desired, a portion of the insufficiently converted oil may be passed through line 35, valve 36, pump 31 and valve 38 to line I3 and thence by previously described routes returned to the catalytic reactor for further conversion. Moreover, a portion 0f the oil may be passed through line 40, valve 4I, pump 42, heat exchanger 42', line 24 and valve 25 to the reactor. mixed with a part of the original oil, from line 43 and valve 44. The spent catalyst from sepa- It may berator 30 maybe removed through line 45 and valve 46 to reactivator 41, wherein it is reactivated by contacting with an oxygen containing gas at altemperature in excess of 1000" F. The reactivated catalyst is returned through line 48 and valve 49 to catalyst storage 8. According to one alternative operation a-side cut such as naphtha or kerosene distillate boiling range materials may be withdrawn from reactor 2l through line 50, heat exchanger 5I vand valve 52 to slurry pot 53 wherein it is mixed with catalyst entering through line 54 and valve 55 and which is kept in suspension by agitator 56. The slurry is passed through line v5'I and valve 58 through heat exchanger 59 and 1ine'60 to the reactor. The advantage of introducingthe cata.-v

lyst at this point is that any material which may be insuiilciently reacted while in contact with the catalyst at a point lower in the tower may be given a chance to react in this way. Moreover, under the conditions of temperature which exist at this point, additional treating of the. hydrocarbon vapors may occur so that further reduction of olefin content andsulfur may be accomplished.

The'following example is given to illustrate the y usefulness and practicability of the invention but should not be construed as limiting it to the exact conditions given therein.

Example 1 .column having perforated pans in thev section below the midpoint and conventional bubble-cap trays above this point.

The pressure in the column was 75pounds per square inch and the temperature at the point of introduction of the reaction mixture was 675 F. Gasoline and gas were removed overhead.

The insuiciently converted oil was Withdrawn from the tower and passed through a filter where.. in the spent catalyst was removed. The residual oil was used as fuel oil. The catalyst mass was substantially freed of residual hydrocarbon by washing with a small quantity of naphtha and then reactivated at a temperature of apprfximately l300 F., using a mixture of air and ue gas.

A total yield of 59% of gasoline was produced in this manner. The octane number of the gasoline was 76 which was increased to 93 bythe addition of 6 cc. of tetraethyl lead per gallon.

The bromine number of the gasoline was 2 inf' dicating substantially no olefins present. The

sulfur content was 0.03%.

Example 2 Pennsylvania gas oil of 37.5 A. P. I. gravityV than 1, and sulfur content of less than 0.01%,

was produced. The gasoline waswater white and met all specifications for. an aviation base fuel.

Example 3 A mixture of 75% cracked gasoline produced by the catalytic cracking of a West Texas gas the reactor tower and mixed into a slurry with a part of the catalytic mass. The mixture was then heated and passed into thereactor at a point above that at which the main charge was introduced.

The gasoline produced in` this manner had an octane number of 80 which was increased by 6 4cc. tetraethyl lead to 95. The bromine number was 1.0 indicating substantially complete conversion of olens. The sulfur content was 0.02%.

Example 4 A 400 F. end point cracked gasoline obtained A by the catalytic cracking of a Michigan gas oil had a bromine number of 105 and octane number of 80 which was increased to 86.5 by the addition of 6 cc. of tetraethyl lead per gallon. This gasoline was made into a slurry with a silica-alumina-zirconia cracking catalyst and passed into a reactor similarI tothat used in Example 1 at a temperature of 700 F. and pressure of 200 pounds per square inch. Approximately 90% of gasoline having an octane number of 79.5 was removed overhead. The octane number was increased to 94 by the addition of l 6 cc. of tetraethyl lead per gallon. The bromine -number was less than 1 and the sulfur content was 0.005%.

I claim as my invention:

1. In the catalytic conversion of hydrocarbon oils, the method which comprises mixing the oil with a powdered cracking catalyst, heating the mixture while :lowing in a restricted stream to a conversion temperature under suillcient pressure to maintain the oil substantially in liquid phase,

introducing the thus heated mixture to an intermediate point in the height of a vertically elongated reaction zone maintained under conversion conditions of temperature and pressure, passing unvaporized portions of the mixture downwardly through the lower portion of said zone, passing vaporous products liberated in said lower portion of the reaction zone upwardly in countercurrent contact with the descending oil and catalyst mixture, fractionating the vapors in the upper portion of the reaction zone, removing resultant reflux condensate and mixing the same with additional cracking catalyst, introducing the resultant mixture to the reaction zone above said intermediate point but below the point of removal of the reux condensate, and removing fractionated vapors from the top of said zone and unvaporized-conversion products and catalyst from the bottom thereof.

2. In the catalytic conversion of hydrocarbon oils, the method which comprises mixing the oil with a powdered cracking catalyst, heating the mixture while flowing in a restricted stream to a conversion temperature under suiiicient pressure to maintain the oil substantially in liquid phase, introducing the thus heated mixture to an intermediate point in the height of a vertically elongated reaction zone maintained under conversion conditions of temperature and pressure, passing unvaporized portions of the mixture downwardly through the lower portion of said zone, passing vaporous products liberated in said lower portion of the reaction zone upwardly in counter-current contact with the descending oil and catalyst mixture, removing vapors from the upper portion of said zone, and removing unvaporized conversion products and catalyst from the bottom of the reaction zone, separating unvaporized conversion products from the catalyst and returning the former to said zone below said intermediate point.

CHARLES L. THOMAS.

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