US2441666A - Powdered catalyst process - Google Patents

Description

May 18, 1948. JOHNSON 2,441,666

POWDERED CATALYST PROCESS Filed Dec. 9, 1939 Attorney Patented May 18, 1948 POWDERED CATALYST PROCESS S ration of Delaware Frank B. Johnson, Baton Rouge, La., aulgnor to tanllard Oil Development Company, a corpo- Applicationllecember a, 1939, Serial N0. 308,375

IClalm.

This invention relates to the cracking of hydrocarbon oils and pertains more particularly to a method of cracking such oil in the presence of a finely divided catalytic material. It has heretofore been proposed to catalytically crack hydrocarbon oils in the presence of a cracking catalyst by suspending the catalyst in finely divided form in the stream of oil to be cracked and passing the resulting suspension through a cracking zone. In some cases the finely divided catalytic material is added to relatively cold oil to form a liquid slurry and the resulting slurry passed through a cracking zone. In other cases, the oil is first vaporized and the powdered catalyst then injected into the vapor stream.

In either case, advantages can be often realized by carrying out the cracking operation at relatively high temperature, such as from 900 to 1000. Difilculty has been encountered, however, in bringing the oil to the desired cracking temperature without subjecting the oil to a substantial amount of cracking before reaching these temperatures. Many types of oil begin to actively crack at temperatures of 750 and the rate of cracking increases rapidly as the temperature is raised. As a resu1t,a perceptible amount of low temperature cracking is unavoidable according to prior practices in raising the temperature of the oil from the initial active cracking temperature up to the final desired temperature. This low temperature cracking reduces the quality and yield of the product produced.

One of the objects of the present invention is to provide a means of rapidly raising the temperature of the oil vapor from the initial incipient cracking temperature to the final desired temperature so as to avoid or reduce the amount of low temperature cracking carried out in the operation.

A further inter-related object of the invention is to provide an improved method for catalytic be regulated to give the final'equilibrium temperature corresponding to the desired operating temperature. a 1

According to one of the more specific phases of. the invention, the desired heat is imparted to the powdered catalytic material by regenerating the catalytic material to remove carbonaceous deposits contained thereon resulting from the previous cracking operation. The temperature to which the catalyst is heated and the relative amount added to' the oil will depend upon the nature of the feed stock, the degree of preheating of the oil vapor, the desired operating temperature, the percentage conversion desired, and other factors so that it is not possible to give any specific example which will be applicable to all cases. In many cases, the activity of the catalyst is impaired if it is subjected to too high a temperature. For example, activated clays, such as acid treated bentonite clays, lose their activity when subjected to heat at a temperature above about 1200 F. The maximum permissible temperature without loss of activity of the catalyst therefore is a limiting factor determining the extent to which the catalyst may be preheated before injecting into the oil stream.

The final equilibrium temperature of the resulting suspension can also be controlled by regulating the relative amount of catalyst introduced into the oil stream. However, since any change cracking of oils which will produce a better yield of high grade products with less degradation of charge stocks.

In accordance with the present invention, the oil is initially preheated to incipient cracking temperature only and then rapidly raised to the final desired cracking temperature by injecting into the stream of oil a powdered catalyst having a temperature materially higher than the temperature of the oil vapor, so that the oil is rapidly heated by direct contact with a more highly heated catalytic material to the final desired operating temperature. The temperature of the catalyst and the quantity employed may the increase in quantity compensated for by tem-- pering the activity of the catalyst such as by incompletely regenerating the same. As for example, when cracking virgin gas oils it is usually undesirable to preheat the oil vapors above 800 in order to avoid a substantial amount of cracking. When employing acid treated clays as a catalyst, as a safety measure it is desirable not to preheat the catalyst to a temperature much in excess of 1000 F. Now, if the oil vapor at 800 F. is contacted with catalyst at 1000 F.,' it is necessary to employ about four parts of catalyst for each part of oil by weight in order to 2,441,eco

bring the resulting mixture to an equilibrium temperature of 900 F. This quantity of catalyst may, however, be excessive and bring about overcracking. In such a case, the activity of the catalyst introduced into the vapors can be tempered by stopping the regeneration before .all of the carbon is removed from the catalyst so that the activity of the catalyst is reduced to a point such that overcracking is not obtained.

Other objects and advantages of the invention will be apparent from the more detailed description hereinafter in which reference will be made to the accompanying drawing, which is partly schematic and partly diagrammatic, of an apparatus suitable for carrying the invention into effect. Referring to the drawing, the reference character It! designates a charge line into which the oil to be cracked is introduced into the system. The charged oil may be a condensate stock which is completely vaporizable or it may be a residual stock such as topped or reduced crude.

The oil introduced into the system through line I is forced by means of pump H to preheating coil l2, located in furnace I3. The oil during its passage through heating coil I2 is preferably preheated to incipi ng tempe ature, the time of contact and temperature within th coil being insufficient to obtain any substantial degree of cracking.

The products from the heating coil 12 are thereafter transferred through line [4 to a separator I5 wherein the vapors separate from unvaporized residue. Residue collected in the chamber [5 is withdrawn therefrom through line I 6 and may be rejected from the system or treated in any desired manner outside the purview of the present invention.

Vapors liberated in the separator l5 are passed overhead through line I! leading to a cracking chamber l8 which for illustrative purposes has been shown in the form of an elongated vertical tower.

In accordance with the present invention, there is injected into the stream of oil vapors passing through the cracking chamber l8 a powdered catalytic material such as acid treated clays, synthetic gels containing similar chemical components, or the like. The temperature and the amount of catalyst introduced into the oil stream is such that the equilibrium temperature of the resulting suspension is that desired for carrying out the cracking operation. Referring to the drawing, the powdered catalytic material is injected into the oil stream by any suitable feeding mechanism such as a screw conveyor IS.

The suspension of catalyst and oil vapors is passed through the cracking chamber 18 at a rate sufficient to maintain the catalyst in suspension within the oil vapors. Also, the length of the reaction zone and the velocity of the suspension is controlled to obtain the desired time of contact to produce the desired conversion.

After passing through the cracking chamber l8, a suspension of cracked products and catalyst is removed therefrom through line 20 and is passed to a suitable solid-gas separator such as a cyclone separator 2|. The temperature of the cyclone separator 2| is preferably maintained sufficiently high to avoid any substantial condensation of the oil vapors so that the catalyst separated therein is in substantially dry state.

The cracked products after the removal of the powdered catalyst therefrom are removed from the cyclone separator 2| through line 22 and passed to the conventional fractionating tower 23 in which insufficiently cracked constituents are condensed as reflux condensate.

While there has been shown a single cyclo separator for effecting the removal of the powdered material from the oil vapors it will be understood that the gas-solid separator should be capable of removing the bulk of the powdered material in dry form. In some cases. it may be desirable to provide a plurality of cyclone separators in series through which the oil vapors pass.

Condensate formed in the fractionating tower 23 is withdrawn from the bottom thereof through line 24 and may be removed from the system or recycled to the inlet side of the heating coil l2 through line 25, pump 28 and line 21.

Vapors remaining uncondensed in the fractionating tower 23 are removed overhead through line :8 leading to a condenser 29 wherein the desired liquid distillate is condensed. Products from the condenser 23 pass to a receiver 30 wherein the liquid distillate separates from the normally gaseous constituents formed in the operation. Gases separated in the receiver 30 are vented therefrom through line 3| and may be sent to suitable recovery apparatus for removal of motor fuel constituents therefrom. Liquid distillate collected in the receiver 30 is removed therefrom through line 32 and may be passed to storage or subjected to any finishing treatment.

Returning to the cyclone separator 2|, the catalyst separated therein is withdrawn therefrom through conduit 33 which may be provided with a suitable feeder such as a star feeder 34. The catalyst so removed is passed into a purging chamber for the removal of volatile hydrocarbons thereof prior to passing the same to the regenerating circuit. As illustrated in the drawing the purging chamber comprises the upper section 35 of repressuring and purging tower 36. The purging section 35 of the tower 36 is preferably provided with a line 31 for introducing a suitable stripping medium such as steam. The stripping gases containing the volatile hydrocarbons may be-passed from the stripping section 35 through line 38 and returned to the cyclone separator 2|.

The purging section 35 of the tower 36 is preferably provided with the conical bottom having a valve opening 39 through which the products from the purging section may be periodically transferred to the intermediate section 40 of the tower 36. An equalizing line 4! having a valve 42 is preferably provided so that the pressure between the two sections can be equalized before discharging the powdered material from the top section 35 to the intermediate section 40.

After a predetermined amount of catalyst has been discharged from the upper purging section 35 to the intermediate section 40 the valve 39 is closed and valve 42 in the equalizing line 4| is closed thus sealing'the intermediate section 40 from the purging chamber 35.

The intermediate section 40 of the tower 36 is also preferably provided with a conical bottom having a closure valve 43 for permitting passage of catalysts from the intermediate section into the lower portion of the tower. After the intermediate section 40 has been sealed from the purging section 35, the closure valve 43 in the bottom of the intermediate section 40 may be opened and the catalyst discharged into the bottom section 44 of the tower 36 which serves as a storage bin for the catalyst passing to the regenerating zone. The intermediate section 4| of the tower l is preferably provided with a valved line 45 whereby any desired pressure may be imposed on the catalyst beforepassing the same to the regenerating zone.

The catalyst collected in the bottom section 44 of the tower 36 may be withdrawn therefrom by a suitable feeding mechanism such as star feeder 46 and passed to a suitable transfer mechanism such as screw conveyor 41 through which the catalyst is introduced into a stream of regenerating gases.

The regenerating gas may comprise of air or a mixture of air and diluent gas such as steam, combustion gases or the like, or any other type of gas containing free oxygen capable of buming the carbonaceous deposit from the catalyst mass.

The regenerating gas may for example be introduced through line 48 and blower 49. The suspension. of regenerating gas and catalyst to be regenerated is then passed to a suitable regenerating zone which for illustrative purposes has been shown in the form of an elongated vertical tower 50 similar to the cracking chamber l8.

It will be understood that both the cracking chamber and the regenerating chamber may take any desiredform capable of maintaining the catalyst material-in suspension within the vapors. For example, either the cracking chamber or the regenerating chamber, or both may be in the form of a coil or a baille tower.

The regenerating chamber 50 is maintained at a temperature sufllcient to ignite the carbonaceous deposit contained on the catalyst as a result of the cracking operation and an oxidizing atmosphere is maintained within the chamber as to burn that carbonaceous deposit. when employing a powdered catalyst as hereinbefore described the relative amount of carbon deposit on the catalyst during a single passage through the cracking zone is relatively small so that in most cases the temperature can be readily controlled to prevent exceeding a temperature which would deactivate the catalyst. If desired, however, suitable cooling means may be provided for insuring proper temperature control within,

the regenerating chamber to maintain the regenerating temperature below the desired maximum.

In accordance with one of the more specific phases of the present invention, the degree of regeneration within the regenerating chamber 50 is controlled to remove a part or all of the carbonaceous deposit to thereby regulate the activity of the catalyst following the regeneration.

The product after passing through the regenerating chamber 50 is transferred through line 5| to a suitable solid-gas separator which for illustrative purposes has been shown in the form of a cyclone separator 52 for separation of the regenerated catalyst from the gaseous products of regeneration. These latter products after being stripped of regenerated catalyst are removed from the cyclone separator 52 through line 53 and may be rejected from the system or other wise utilized in a manner outside of the purview of the present invention.

The combined purging and pressuring tower 56 may be of a construction similar to the tower 38 heretofore described. Thus, for example, the tower may be divided into three sections, the upper section 51, an intermediate section I, and

a lower section 59, with communicating closure.

valves 60 and 6! between the upper section 51 6! is also preferably provided between the upper section 51 and the intermediate section II. Also a line 66 may also be provided for the intermediate section-ll to impose any desired pressure on this section of the tower before passing the catalyst back to the cracking zone.

The bottomsection N of the tower 56 may be provided with a suitable heating means such as coil 61 for maintaining or heating the catalyst to the desired initial temperature for contacting with a the cracked product. In many cases, however, the temperature of the regeneration can be controlled to give the desired maximum temperature to the catalyst returned to the cracking zone.

The catalyst after being transferred through the tower I in a manner similar to that described with reference to tower 38 may be charged through a suitable feeding mechanism such as a star feeder 88 to the screw conveyor I! which injects the catalyst into the oil stream to be cracked.

It is desired to again point out with respect to the foregoing that the present invention comprehends a method of rapidly heating the oil vapors from the incipient cracking temperature to the final desired temperature by the residual heat of the catalyst introduced into the oil stream. The amount of heat added to the oil vapors in this manner can be controlled by regulation of the temperature of the catalyst introduced into the stream, and the quantity of the catalyst so introduced. Furthermore, the amount of cracking or conversion obtained during the passage of the suspension through the cracking zone can be controlled independently of the ratio of catalyst to oil vapors introduced by regulating the activity of the catalyst introduced therein. This regulation can be accomplished for example by regulating the regenerating conditions so as to completely or partially remove the carbonaceous deposits thereon.

In order to take full advantage of the heat liberated during regeneration for carrying out the cracking operation, it is preferred to introduce the powdered catalyst into the oil stream at substantially the maximum regenerating temperature which will not adversely affect the activity of the catalyst. Such a temperature, in the case of acid treated clays, may be of the order of 1200 F.

As a guide in carrying out the invention to obtain the greatest benefit therefrom, the following example may be helpful. It will be understood, however, that the values and conditions given therein are illustrative rather than limitive.

Example An East Texas'virgin gas oil having an A. P, I. gravity of about 33.4 is passed through a reheating and vaporizing coil and heated to a temperature of about 800 F. at a rate which will avoid any substantial cracking therein. Into the vapor so formed there is injected a powdered catalyst comprising acid-treated clay of the type known as Super Filtrol at a temperature of about 1000 F.

' accuses and in an amount corresponding to about 4 parts of catalyst per part of oil by weight. The equilibrium temperature of the resulting suspension will be approximately 900 F. so that the oil vapors will be raised from a temperature of 800 F. to a temperature of 900 F. in a very short time. The resulting suspension can then be passed through the cracking chamber and the time of contact controlled to give the-required conversion. After this, the products may be fractionated to separate the desired motor fuel product therefrom.

Having described a specific embodiment of the invention, it will be understood that it embraces such other variations and modifications as come within the spirit and scope thereof.

What is desired to be protected by Letters Patent is:

A method of cracking hydrocarbon oil which comprises vaporizing the oil to be cracked at a temperature substantially below the final cracking temperature and at a rate sufiicient to avoid any substantial cracking thereof, thereafter injecting a finely divided catalytic material into said oil vapors while said catalytic material is at an initial temperature materially above the final cracking temperature, adjusting the relative proportion of catalyst and oil vapors and the initial temperature of the catalyst to rapidly increase the temperature of the oil vapors to the final desired cracking temperature, passing the resulting sus- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 15 Number Name Date 1,799,858 Miller Apr. 7, 1931 1,981,144 Held Nov. 20, 1934 2,027,552 Roberts Jan. 14, 1936 2,073,638 Houdry Mar. 16, 1937 20 2,136,382 Houdry Nov. 15, 1938 2,161,676 Houdry June 6, 1939 2,231,231 Subkow Feb. 11, 1941 2,231,424 Huppke Feb. 11, 1941 2,247,097 Menshih June 24, 1941 5 2,253,486 Belchetz Aug. 19, 1941 2,289,329 Prickett July 7, 1942 FOREIGN PATENTS Number Country Date 30 254,011 Great Britain June 25, 1926

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