US2399540A - Precombustion cracking process - Google Patents

Description

April 30, 1946. D- E CARR 2,399,540

PRECOMBUSTION CRACKING PROCESS Filed July 28, 1942 Sr/FAM INVENTOR.

DON/ILD E. CHIP/? ATTORNEY,

neiy divided carbon in the hot combustion Patented Apr. 30, 1946 UNITED STATES PATENT OFFICE 2,399,540 PRECOMBUSTION CRACKING PROCESS Donald E. Carr, Los Angeles, Calif., assigner to Union Oil Company of California,

Los Angeles.

Calif., a corporation of California Application July 28, 1942, Serial No. 452,569 15 Claims. I Cl. ISG-0 7) and other valuable hydrocarbons froml charging stock which is paraiilnic or naphthenic in char-vl acter.

My process consists in burning hydrocarbon fuel containing a metallic organic lcompoundv dissolved therein which uponburning is converted into a nely divided metallic oxide- The spent fuel gas, ata .temperature in the range of 2000 to 3500 F. containing the finely divided metal oxide is then mixed with a speciiic hydrocarbon fraction, which fraction has preferably been preheated. The temperature of the mixture in the mixing zone may vary from 1200 F. to 1600F. After admixture of the fuel gases containing the finely divided metal oxide with the hydrocarbon fraction to be treated this mixture is passed into a reaction zone where its period of residence may vary from .01 second to 5.0 seconds according to the type of products desired. The reaction product is then withdrawn from the reaction zone, the spent catalyst is separated from the reaction product, which is then quenched y to a. lower temperature by means `of a cooling Iiuid, such as water or oil, after which the `quenched reaction product is fractionated into l the desired product.

As anothermodiiication of my invention the ratio of air to fuel may be controlled in the combustion zone so as to maintain the conditions of combustion slightly on the reducing side. When operating under these conditions there is a slight deiiciency in oxygen which results in the formation of iinely divided carbon. yThis gases may be utilized as the catalyst for the treatment of the hydrocarbon fractions in the reaction zone. When operating.v according to this modification hydrocarbon fuel and air are introduced into the combustion zone in such proportions that there is a. deficiency in the amount of oxygen to support complete combustion. This deficiency of oxygen in the combustion chamber results in the formation of finely divided carbon in the hot combustion gases. The hot combustion gases at a temperature in the order of 2500 F. to 3500 F. containing the finely divided carbon is then-mixed with a hydrocarbon fraction to be treated, such as gasoline, naphtha or lighter or heavier hydrocarbons. The resulting mixture at a temperature ranging from 1200 F. to 1600 F. is then passed into a reaction chamber where its residence period ranges from .01 second to 5.0 seconds, depending upon the type of reaction Product desired.- The :reaction product is then withdrawn from the Vreaction zone, quenched to a temperature preferablybelow 800 F. and above 450. ;F.aft'erjwhich.it is fractionated.

Itistherefore an object of the present inven- .'tion to.'thermally treat hydrocarbon fractions with spent fuel gas containing a iinely divided catalyst, lsuch as a metal oxide or nely divided carbon. v

1 Referring to the iigure, air and fuel are introduced in appropriate proportions in combustion chamber I via lines 3 and 4 so that the combustion gases formed in chamber I contain a minimum amount of free oxygen. Incidentally steam, either saturated or superheated, may also be introduced in the combustion chamber via line 2. The fuel introduced in chamber l containing the oil f soluble metallic-organic compounds specified above are burned in the combustion chamber together with the fuel and are converted into the oxides of their corresponding metals. The mixture of spent fuel gases containing the metallic oxides are passed from the combustion chamber via line 5 into mixing chamber 6 where they are mixed with the hydrocarbon fraction to be treated according to this process. 'I'he hydrocarbon fraction to be treated is withdrawn from tank I0 through valve I I and line I2 from whence it passes through preheater I3, line I 4 into the mixing chamber 6. From the mixing chamber the combustion gases and the hydrocarbons being treated pass through duct 8 into reaction chamber 1 where this mixture is permitted suiiicient residence time to obtain a maximum of the products desired. From reaction zone 1 the treated -materials pass via line I5 into the electrical precipitator I6 where the solid catalytic material is precipitated and collected in cone 26 ot tower I8 and withdrawn through valve I8 and line I9. The treated material in the electrical precipitator IB from which the solid catalytic material has been removed then passes via line 20 into quenching zone 2| where it is sprayed with an appropriate liquid, such as a hydrocarbon or water to lower the temperature of the treated materials to a point sumciently low to inhibit any further thermal reaction. From the quenching zone 2I the material passes via line 22 to the fractionation tower 23 where it is fractionated into the desired overhead fractions which are recovered via line 24 and bottom fractions are recovered via line 25. In some instances it may be desirable to return certain of the overhead or bottom fractions from tower 23 back to the treating zone. In such case the materials in tower 23 can either be returned to tank I or line I I from whence they may be recirculated through the process. In the figure, 9 represents an insulating material which surrounds the combustion mixing and reaction zones.

The type of fuel injected in line 4 may be either liquid or gas. When liquid fuels are employed the metallic-organic compounds may be dissolved directly in this fuel. For example, chromium, molybdenum, tungsten, or uranium stearates, oleates or naphthenates may be dissolved directly into the fuel being introduced into line 4 from whence they pass into the combustion zone I wherein they are converted into their corresponding metal oxides. Other metals may be injected into the fuel for conversion into metal oxide in the combustion zone l. For example, manganese, calcium, barium, strontium, aluminum, iron, nickel, zinc, tin, vanadium, copper, lead, mercury, lithium, sodium, potassium, cadmium, silicon, arsenic, antimony, bismuth, and beryllium, salts of stearic acid, naphthenic acid or oleic acid may also be employed depending upon the type of reaction which it is desired to obtain in the reaction zone l. Where high degrees of dehydrogenation or aromatization is desired to be obtained in reaction zone 1, I have found that the oil soluble salts of chromium or molybdenum, either alone or mixed with the oil soluble salts of aluminum and beryllium give highly satisfactory results. Where a combination of desulfurization, dehydrogenation and aromatization is desired, I nd that the oil soluble salts of molybdenum give highly satisfactory results.

Besides the metallic salts of the organic acids I may also use compounds in which the abovev metals are attached to an aryl or an alkyl or an aralkyl group which compound is soluble in the fuel being injected into combustion chamber I. Examples of such compounds are as follows: oil soluble metal phenates, alcoholates, mercaptides, and sulfonates. Furthermore, I may also use the oil soluble metal salts of organic acids produced by oxidizing petroleum hydrocarbons. This method is highly suitable for the production of oleiins and aromatica and also for the removal of sulfur from oils containing high percentages of sulfur. In the production of oleiins, by a careful control of the reaction conditions as to time and temperature and stock selection, relatively large quantities of diolefins, such as butadiene may be produced.

As a specific example of producing butadiene, a gasoline fraction or petroleum fraction containing hydrocarbons within the gasoline boiling point range, is withdrawn from tank I0 through valve Il in line I2 and passed into preheating coil I3 where it is preheated to a temperature of about 1000 F. Simultaneously a medium grade of fuel oil (specific gravity 0.98 and viscosity 65 furol at 122 F.) containing about 1% of chromium naphthenate is introduced into combustion chamber I via line I. Simultaneously air is intraducen inw combustion chamber i via une s. 'I'he mixture in combustion chamber I burns to produce hot combustion gases at a temperature of about 3000 F. and contains finely divided chromium oxide. The hot combustion gases in chamber I then pass through line i into mixing chamber 6 where they are mixed with a gasoline fraction preheated to a temperature of around 1000 F. From the mixing chamber 3 the combustion gases containing the gasoline fraction then pass into reaction chamber 7 at a temperaturel of about 1500 F. The time in reaction chamber 'I will vary according to the temperature employed and the products desired. However, I have found for butadiene production that the reaction time in reaction chamber should be somewhere around .01 to .05 second. Where lower temperature levels are employed, i. e., around 1200 F., the residence time in reaction chamber 'I will be increased. For example, if the temperature in reaction chamber I2 is decreased to about 1200* F. to 1300 F. then the reaction time should be increased to about 2 or 3 seconds. From the reaction chamber the reaction gases are Withdrawn through line I5 and introduced into electrical precipitator II where the finely divided catalyst is precipitated and withdrawn from line I9, as previously described. The reaction gases from which the catalyst has been removed then passes through line 2l into quenching zone 2I where the temperature of the mixture is rapidly dropped by means of either liquid hydrocarbons or water to about 500 to 800 F. From the quenching zone 2| the cooled reaction gases then pass via line 22 into fractionation 0 By proper fractionation in tower 23 or subsequent columns, not shown on the drawing, a fraction of pure butadiene may be recovered.

When the process is used for the production of a high percentage of aromatic lnrdrocarbons, such as benzol, toluol and xylol, a high temperature level is employed in reaction zone I or, as an alternative, the residence time in reaction zone l is materially increased to obtain a higher temperature level in reaction zone l. This is simply accomplished by lessening the amount of feed stock introduced into mixing zone 8 via line I4 in relationship to the combustion gases entering that zone from combustion zone I.

When the process is utilized for the production of such materials as benzol, toluol or xylol, .the particular hydrocarbon fraction. such as gasoline or naphtha in tank I0, is fed into mixing zone 6 at a temperature of about 1000 F.. as Dreviously described, where it is mixed with combustion gases from combustion chamber I at a temperature of about 3000 F. in such proportion that the resulting mixture passing out of duct 3 into reaction zone l is at a temperature of about 1500 F. The time of residence in reaction zone l for the production of the maximum yield of aromatic hydrocarbons at this temperature will be at about .0l to 1.0 second. In the event that va lower temperature level is utilized in combustion zone 1, i. e., either 1200 F. to 1300 F. a residence time of 0.5 to 3.0 seconds will be required in this reaction zone to produce the optimum amount of aromatic hydrocarbons.

Where the process is employed for the production of aromatic hydrocarbons it is seldom necessary to utilize the quenching zone. In other words, the gases recovered from combustion zone I pass to the electrical precipitator I6 for the removal of the catalytic materials present after which these gases then Dass directly to the fractionating zone 23 for the recovery of aromatic hydrocarbons from the reaction product.

Steam may also be injected into the combustion zone I via line 2 since in some cases it aids in the production of olens and aromatics by the process described above. In most instances it is preferable to introduce the steam directly into mixing chamber 6 rather than into combustion chamber I. This is accomplished through line 28.

The spent catalyst recovered from line I9 may be reconverted if desired into oil soluble organic compounds and then reintroduced into the fuel which is employed in combustion chamber I.

By utilizing the process described above a, large number of different kinds of hydrocarbons may be catalytically treated at relatively high temperatures for a selected period of time to produce a large number of highly desirable products. For example, a gas oil having a gravity of 31 to 33 API ai; 60 F. can be catalyticallycracked by this process to produce a high yield of gasoline containing a relatively high percentage of hydrocarbons of the olefin, aromatic and isoparaiilnic types thus yielding a product which has a high anti-knock value. In carrying out the process t cataiytically crack oil a fuel oil containing an oil soluble organic compound of chromium or molybdenum, such as chromium stearate, naphthenate or oleate or molybdenum stearato, naphthenate or oleate is introduced into combustion zone I to convert the metallic-organic compound by burning the fuel into an oxide. The combustion gases in combustion zone I at a temperature of about 3000 F. then pass via line 5 into mixing zone 6 where they are mixed with the gas oil to be catalytically cracked. This gas oil is usually preheated in coil I3 to a temperature of about 800 F. before admixture with combustion gases in mixer i. The quantity of gas oil introduced into mixing zone 6 is such that the resultant temperature of the mixture of gas oil and-combustion gases is about 950 F. This mixture passes into reaction zone 'I where it is allowed to remain for a period of about 0.5 to 5.0 seconds. From the reaction zone l the treated mixture then e passes into a tar separator, not shown, where the tarry and liquid materials are permitted to separate out and the gases then pass into the electrical separator I6 where any solid material present is recovered via line I9.v These gases then pass into the quenching zone 2| where the temperature is dropped to about 550 F. to 650 F. after which the cooled material then passes into the fractionating zone 23 where a superior grade of motor fuel may be recovered.

The apparatus shown in Figure 1 can also be used for carrying out ordinary catalytic reforming operations. For example, a gasoline stock having an end point of about 400 F. may be preheated in coil I3 to a temperature of about 800 F. and. then introduced into mixer 6 together with combustion gases from combustion chamber I containing one of the metal oxides described above, such as for example, chromium oxide or molybdenum oxide; these oxides having been 'formed in combustion chamber I by burning fuel in this chamber containing oil soluble organic compounds oi these metals, such as the stearate, naphthenate, oleate, or phthalate. The temperature in mixing chamber 6 is preferably regulated so that it ranges between 900 F. and l100 F. and the residence time in reaction zone l is usuany between 0.5 second and 5.0 seconds. The reaction products withdrawn from reaction zone 'I are passed from this zone to the electrical separator I6 where the spent catalyst, withdrawn via line I3 and the gases then pass to quenching zone 2| where the temperature is dropped to about 600 F. after which these gases then pass into the 'fractionating zone 23. In some reforming operations it may be desirable to eliminate the quenching zone 2|. Furthermore in some instances it may be desirable to introduce free hydrogen into the mixing zone 6 along with the gasoline-like fractions undergoing operation. In most reforming operations the use of steam either in the combustion zone or in the mixing zone can be dispensed with.

When the gasoline fraction being reformed contains sulfur the fuel is mixed with an oil soluble molybdenum compound which upon oxidation in the combustion zone produces molyb denum oxide. The hot combustion gases containing the molybdenum oxide is then mixed with the sulfur containing hydrocarbon fraction in such proportions that the temperature of the mixture is in the range of from 1200 F. to 1600 F. This mixture then passes to the reaction zone where it is maintained for a period of from .05 to 5.0 seconds after which it is sent to an electrical separator for the separation of the molybdenum (which is now in the sulfide form) from the reaction product. The reaction product is then quenched, as described above and fractionated.

When it is desired to employ nely divided carbon as the catalyst the ratio of air to fuel injected via lines 3 and 4 into combustion space I is so adjusted that there is a slight oxygen deficiency. This results in the formation of finely divided carbon suspended in the spent combustion gases. This mixture of hot spent combustion gases containing the finely divided suspended carbon particles ows via line t into mixer 6 where it is mixed with the hydrocarbon fraction to be treated. The combustion gases are introduced into 6 at a temperature ranging from 2500 F. to 3500 F. and the hydrocarbon to be treated is introduced into mixer 6 via line it at a temperature of about 500 F. to 1000 F. The combustion gases and hydrocarbon lfeed into mixer 6 are so proportioned that the final temperature of the mixture is around 1200 F. to 1600 F. The mixture in 6 then passes to chamber l where it is retained for a period of from .05 to 5.0 seconds after which it then passes to the quencher 2l and then to the fractionation column. Since the finely divided carbon formed the catalyst in this modification it need not be separated by electrical separator I6 but may be removed in the bottom fraction recovered from I line 25 of tower 23.

In many instances I find that the temperature employed in preheater I3 should -be suiciently high to produce a substantial cracking of the stock prior to introduction into the mixing zone 6 together with the combustion gases from combustion zone I containing the finely divided metal oxides or finely divided carbon.

I also find that in many instances it is desirable to employ a substantial pressure in the mixing zone 6 and reaction zone 1. This pressure will vary anywhere from 50 pounds per square inch to about 500 pounds per square inch.

Quenching zone 2| in the figure is merely illustrative of one way of rapidly reducing the temperature a point where the thermal reaction is inhibited. As shown in this figure a cool quenching fluid is introduced via line I1 and sprayed onto the incoming gases into that zone. This quenching fluid may comprise a hydrocarbon fraction such as kerosene or gas oil or in fact it may comprise a portion of the feed stock which is of the same composition as the material in tank I0, in which case this quenching fluid is recovered via line 25 and then either returned to tank i or to line l2, thence to the reaction zone.

In the foregoing I have described a process in which oil soluble metallic-organic compounds, such as organic acid soaps are dissolved in a fuel which is then burned to produce the correspending oxide of the metallic-organic compound. This finely divided metallic oxide in the spent fuel gases then acts as a catalyst when subsequently mixed with petroleum stocks to be treated for the formation of more valuable compounds, such as olefins, mono-olefins, di-olenns, etc. I do not wish to limit myself to the use of oil soluble metallic-organic compounds since I may also use metallic-organic compounds which are oil insoluble but which may be dispersed in the fuel in the form of an emulsion. When the `emulsied fuel is burned these metallic-organic compounds are oxidized to form the corresponding metallic oxide which is then utilized as a catalyst in the same manner as the oxides formed from oil soluble soaps described above. As an example of this modification I propose to add an oil insoluble metallic-organic compound to the fuel'and at the same time add an emulsifying agent, such as sodium oleate to this mixture and then form the emulsion by agitation. This mixture is then used as fuel in the process described above. When this fuel burns the emulsified metallic-organic compound forms a nely divided oxide which forms the catalyst when subsequently mixed with hydrocarbons to be treated, as described above.

I claim:

1. A process for the thermal treatment of hydrocarbons which comprises commingling a liquid fuel with an oil soluble metallic-organic compound, passing the fuel containing the dissolved metallic organic compound into a combustion zone together with oxygen and converting said fuel into products of combustion in the combustion zone containing oxides of said metallicorganic compound, mixing the combustion gases containing the finely divided metallic oxides with a hydrocarbon fraction in the mixing zone, passing said mixture into a reaction zone and thence to a fractionator and separating valuable hydrocarbons therefrom.

c 2. A process for `the production of olefinic hydrocarbons from a hydrocarbon stock which comprises preheating said hydrocarbon stock, mixing said preheated hydrocarbon stock with hot combustion gases containing finely divided metal oxides resulting from prior combustion of a hydrocarbon fuel containing a metallic-organic compound, maintaining the hot combustion gases and preheated hydrocarbon stock in admixture for a sufiicient length of time to convert the hydrocarbon stock into olefinic hydrocarbons, chilling the reaction mixture to a temperature suillciently low to prevent further thermal reaction, passing the cooled mixture to a fractionating zone and recovering olilns therefrom.

3. A process for the catalytic conversion of hydrocarbons which comprises commingling liquid fuel with an oil soluble metallic-organic compound, converting said fuel containing the metallic-organic compound into combustion products containing finely divided metallic oxides by reaction with oxygen, mixing the said hot combustion gases containing the finely divided metallic oxide with a hydrocarbon fraction in such amounts that the resulting mixture is at a conversion temperature, and maintaining said resulting mixture at said reaction temperature for a sufficient length of time to accomplish the desired hydrocarbon conversion.

4. A process for the catalytic conversion of hydrocarbons which comprises mixing a liquid fuel with an oil soluble metallic-organic compound, oxidizing said fuel thereby forming hot combustion gases having a temperature between 2000 F. and 3500 F. containing finely divided metal oxide, mixing said hot combustion gases with a hydrocarbon fraction in such proportions that the resulting mixture has a temperature in the order of 800 F, to 1100 F. and maintaining said resulting mixture at said reaction temperature for a sufiicient length of time to accomplish the desired hydrocarbon conversion.

5. A process for' the thermal treatment of a hydrocarbon fraction which comprises, mixing said fraction with hot combustion gases containing a finely divided metal oxide resulting from prior combustion of a hydrocarbon fuel containing a metallic-organic compound, in such proportions that the temperature of the resulting mixture is within the rangev of from 900 F. to 1600 F. and maintaining said mixture within said temperature range for a period of from .01 second to 5.0 seconds.

6. A process for the thermal treatment of a hydrocarbon fraction which comprises mixing said fraction with combustion gases which are at a temperature between 2000 F. and 3500 F. and which gases contain a finely divided metal oxide in such proportions that the resulting mixture is at a temperature range of 900 F and 1600 F., and maintaining said resulting mixture within said last temperature range for a period of from .01 second to 5.0 seconds.

7. A process for the thermal treatment of a hydrocarbon fraction which comprises mixing said fraction with hot combustion gases which are within the temperature range of 2'000" F. and 3500 F. and which contain a finely divided metal oxide, in such proportions that the temperature of the resulting mixture is within the temperature range of 900 F. to 1600 F., maintaining the resulting mixture within said latter temperature range for a period of from .01 second to 5.0 seconds, and then contacting the thermally treated gaseous mixture with a cooling fluid.

8. A process for the thermal treatment of a hydrocarbon fraction which comprises burning a fuel containing an oil soluble metallic-organic compound and thereby forming combustion gases which are at a temperature between 2000 F. and 3500 F. and which contain finely divided metal oxide, mixing said combustion gases with a hydrocarbon fraction in such proportions that the temperature of the resulting mixture is within the temperature range of 900 F. to 1600 F., passing said resulting mixture into a reaction zone, maintaining said resulting mixture in said reaction zone y"at said latter temperature range for a period of from .01.second to 5.0 seconds, withdrawing the thermally treated products from said reaction zone and contacting said products.

with a cooling iiuid.

9. A process for the production of hydrocarbons of the type of mono-olefin, diolefin, aromatic and like hydrocarbons which comprises commingiing a liquid fuel with an oil soluble metallicorganic compound, passing the fuel containing the dissolved metallic-organic compound into a combustion zone together with oxygen and converting said fuel into products of combustion in the combustionzone containing oxides of said metallic-organic compound, mixing the combustion gases containing the finely divided metallic oxides with a hydrocarbon fraction in the mixing zone, passing said mixture into a reaction zone and thence to a fractionator and separating valuable hydrocarbons therefrom.

10. A process for the production of aromatic hydrocarbons which comprises commingling a liquid fuel with an oil soluble metallic-organic compound, passing the fuel containing the dissolved metallic organic compound into a combustion zone together with oxygen and converting said fuel into products of combustion in the combustion zone containing oxides of said metallicorganic compound, mixing the combustion gases containing the finely divided metallic oxides with a hydrocarbon fraction in the mixing zone, passing said mixture into a reaction zone and thence to a fractionator and separating aromatic hydrocarbons therefrom.

l1. A process for the production of butadiene which comprises commingling a liquid fuel with an oil soluble metallic-organic compound, passing the fuel containing the dissolved metallicorganic compound into a combustion zone together with oxygen and converting said fuel into products of combustion in the combustion zone containing oxides of said metallic-organic compound, mixing the combustion gases containing the finely divided metallic oxides with a hydrocarbon fraction in the mixing zone, passing said mixture into a reaction zone and thence to a fractionator and separating butadiene therefrom.

12. A process for production of butadiene from a hydrocarbon stock which comprises preheating said hydrocarbon stock, mixing said preheated hydrocarbon stock with combustion gases containing nely divided metal oxides which are at a temperature between about 2000 and 3500o F., maintaining the hot combustion gases and preheated hydrocarbon stock in admixture for a.'

sufficient length of time to convert a portion of the hydrocarbon stock into butadiene, chilling the reaction mixture to a temperature sufficiently low to prevent further thermal reaction, passing the cooled mixture to a fractionating zone and recovering butadiene therefrom.

13. A process for the thermal treatment of hydrocarbons which comprises commingling a combustible fuel with a metallic-organic compound, passing the fuel containing the dissolved metallic-organic compound into a combustion zone together with oxygen and converting said fuel into products of combustion in the combustion zone containing oxides of said metallic-organic compound, mixing the combustion gases containing the finely divided metallic oxides with a hydrocarbon fraction in the mixing zone, passing said mixture into a reaction zone and thence to a fractionator and separating valuable hydrocarbons therefrom. l

14. A process for the thermal treatment of a hydrocarbon fraction which comprises burning a fuel containing a metallic-organic compound and therebyforming combustion gases which are at a temperature between 2000 F. and 3500 F. and which contain finely divided metal oxide, mixing said combustion gases with a hydrocarbon fraction in such proportions that the temperature of the resulting mixture is within the temperature range of 900 F. to 1600 F., passing said resulting mixture into a reaction zone, maintaining said resulting mixture in saidv reaction zone at said latter temperature range for a period of from .01 second to 5.0 seconds, withdrawing the thermally treated products from said reaction zone and contacting said products with a cooling Huid.

15. A process according to claim 14 in which hydrogen is introduced along with the hydrocarbon fraction.

DONALD E. CARR.

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