US2377716A

US2377716A - catalytic cracking

Info

Publication number: US2377716A
Authority: US
Publication date: 1945-06-05
Anticipated expiration: 1962-06-05

Description

June 5, 1945. D. READ. JR 2,377,716

CATALYTIC CRACKING Filed Jan. 28, 1942 TO RECEIVER AND FRACTIONATOR VAPORIZING 8.

CHAMBER REACTOR HEATER HEATER HEATER STEAM CHARGING 0R PROCESS STOCK INVENTOR' DAY RED JR.

BY I

ATTORNEY Patented June 5; 1945 CATALYTIC CRACKING V i Davis zRead,'Jrg Chicago, 111., :as signor to Unil tversal-il Products Company Chicag o, 111., as

corporationlof Delaware i a ApplicationJa'nuary 2s, 1942;SerialNo.428,452 a j kciaim (cr ses-5'2) This invention relates tea-process for the catalytic cracking ofhigher boiling hydrocarbon; oils to form gasoline andothervaluable products. It

is more -specifically concerned I with r catalytic cracking 'processesin which the catalyst is em ployedinpowdered-f ormandwherein thecatalyst after contamination is regenerated bythe'oxida tion" of the carbonaceous deposits Lvvhich reduce the activity of the catalyst; p j

Y It is old inthe art'to use cracking-catalysts in the powdered form. In the; processes heretofore disclosed, the catalyst has been used insu'spension in a stream of the hydrocarbons undergoing con- Version and in other cases the hydrocarbons in vaporous state have been bubbled througha rela:

tively dense mass of the catalyst powder thusse curing large weight ratios of catalyst to j hydro;

carbons inthe conversion zonefl t a t The process of my inventioncomprisesga com:

binationy of suspended-catalystcrackingfand cracking-using a fluid catalyst f operation. The high boiling'oilis commirigled with thepowdered cracking catalyst and the mixture,,suppliedltda heating coil under such conditions that asubstans tial quantity of the oil is vaporized, The extent of" this vaporization depends upon the properties of the original chargingystock and ,in the"case.of kerosene "or a gas ,oil

during the vaporization process and thereafter, if desired; a reaction chambermayiollbw theheatingcoil in order to accomplish. further cracking of theihydrocarbons; Theyreaotio'n' chamber is not anindispensable part of the processand may beflomitted or included as desired. The oreaction products *fromj this catalyticjcracking step are then subjected to'a separation .stepin order to obtain a liquid fraction containing the catalyst in suspension and a lower boilingyaporous fraction.

The liquid fraction separated in the aforesaid steptogether with the suspended catalyst is suppliedto a heating coil anda substantialquantity of the liquid. is vaporized. The vaporization in this case may be aided by. diluting the oil with steam or process gases The heated oil and suspended catalyst is then supplied to a second reaction zone containing a relativelyt clense mass of catalyst powder,;thegaseous hydrocarbons bubbling through the relatively densemass of powder under conditions so regulated as. to obtain the desired extent of catalytic cracking. It may be desirable to add highly heated steamer process ases to the powderedcatalyst zone in order to supplythe additional heat necessary-for the vaporization of any residual quantity of liquidbeing the vaporization, mightibe practically completed. cracking takes.p-lace.

state and mayfbe fractionated separately to resupplied; to said zone. The products leaving the second reaction zone are entirely in the yaporous cover the gasoline, normally gaseous products and unconvertedhigherboiling oil. If desired, however, the hydrocarbon conversion products from 7 the second reaction zone may be commingled-with the reaction products from thefirst cracking step and the mixture subjected to joint fractionation: Inonespecific embodiment my invention comprises a process for the catalytic cracking ofa 7 higher boiling hydrocarbon oil to-form gasoline which comprises chargin said higher boiling hydrocarbon oilwith suspended cracking catalyst into an elongated tubular reaction zone and theree in vaporizinga substantial portionof saidoil and simultaneously and immediately thereafter cracking said oil to produce lowerboiling products 111- eluding gasoline, fractionatingthe products :of

said cracking step in cornmingled state vv'ithtl i e products ofzasecond catalytic cracking step;hereinaiter set forth to produce a vaporous fraction and a higher boiling liquid fraction containing the powdered catalyst in'suspension;supplying said higher boilingliquid fraction and suspended cata:

lyst to aheating zone to vaporize" at least a substantial portion of said fractionand thereafter to a reaction zonecontaining a relatively dense mass ofcatalystpowder and bubbling the hydrocarbon vapors upward through said'relatively densemass of catalyst powder under conditions of temperaa ture, pressure and time offcontactregulatedto produce substantial quantities of gasoline and fractionatingthe products from thissecond catalytic cracking stepincommingledstate with the products of the first catalytic cracking step as hereinbeforej set forth.

particular flow for tmyinvention H in p it I {The charging stock plus a small quantityloi The process of my inventionis illustrated by the accompanying diagrammatic. (drawing and follows ing;,specification which shows and describes one catalyst equaltofthat lost due to incomplete sep aration methods is supplied to thesystem byway ofline l and afterpassing throughvalve Z-enters pump 3 which discharges into line, 4. A portion or all of the charging stockjisusedjto scrub the gaseous products of regeneration leaving the pow:

dered catalyst reactivatlng zone for the purpose of removing the catalystsuspended insaidgases. 7

The oil used as the scrubbing mejdiumypasses through valve 5 and is Zsupplledto tiieq-top of column 5 tvhereiniitj is subiefctedito contact-with the previously cool-ed gaseous products of regeneraccomplishing the process of i hydrocarbons and the mixture passed through valve IE to heating coil I6.

The oil i heated in coil l6 by means of furnace I! to a temperature which lies within the broad limits of about 600-1100 F. but which under the usual conditions of operation is included in the more narrow limits of 7'50-1000 F. The temperature to which the oil is heated; depends upon the nature of the products desired, the

higher the temperature, the greater the degree usual and preferred conditions of operation a sub stantial portion and sometimes all of the oil is vaporized in the heating coil, the mixture of heated oil and catalyst being directed from coil [6 to line 18 wherein after passing through valve l9 it is supplied to reaction chamber 20. The purpose of this reaction chamber, the use of ,whichis optional, is to permit furthercracking if desired. In case it isdesired to omit the reaction chamber the heated oil and catalyst, is directed from line l8 to line 2| and after passing through valve 22 is supplied to line 23 wherein after passing through valve 24 it is supplied to vaporizing and separating chamber .25.

In order to accomplish the desiredseparation in chamber 25 it is necessary to reduce the temerature of the hydrocarbon vapors and this may be done by quenching the gases with the side out removed from the fractionating column. Methods for accomplishing such'quenching' are well known in the art and need not be further described. The vaporous fraction separated in chamber 25 is removed by way of line 26, valve 21 and introduced to fractionating column 28. In this fractionating column the gasoline and normally gaseous products are removed as an overhead by way of line 29, controlled by valve 33. This overhead is then cooled, condensed and subjected to a stabilizing operation for the production of gasoline of the desired volatility. The olefinic'constituents as well as the isoparafiinic constituents in the normally gaseous products may be converted to motor fuel by the well known processes of ,alkylation, or polymerization. The products boiling above the range of gasoline are removed as a bottoms product from fractionating column 28 and enter line 3| and after passing through valve 32 enter pump 33 which discharges into line Id. In line I4 this recycle fraction of higher boiling products is commingled with the charging stock and supplied to heating coil I6 as hereinbefore set forth.

The-liquid fraction obtained from separating chamber 25 containing the used catalyst in suspension is removed by way of lin 34 and after passing through valve 35 enters pump 35 which discharges through line 31, valve 33 into heating coil 39. It may be desirable to dilute this liquid fraction with steam or process gases to assist in the vaporization, these diluent gases being added I to line 38 by way of line 5, controlled by valve 4|. The hydrocarbon oil is heated in coil 39 by means of furnace 32 to a temperature from about 750 to about 1000 F. under pressure conditions such that at least part or all of the oil is vaporized. In the event that only partial vaporization is obtained in heating coil 39 it will be desirable to introduce a heat carrying medium into the stream of hydrocarbons. For this purpose steam or process gases may be used, these gases being introduced to the system by way of line 43 wherein after passing through valve 44 they are supplied to heating coil 65 so disposed as to receive heat from furnace 46. These heat carrying gases may besuperheated to'temperatures of the order of 1000-1100 F. and after, being so heated enter line 4? and pass through; valve; 48 to'line 49 wherein they are commingled with the high boiling oil and catalyst powder from heat; ing coil '39. This mixture of high boiling oil and heat carrying gases, if the latter are used, pass through line is-containing valve 50 after which they are commingled with catalyst powderobtained from the regeneration system, the mixture of catalyst, hydrocarbon reactants and heat carrying gases beingintroduced into reactor 5!. 1

The catalyst in reactor 5! is in the form of a powder in a relatively dense mass, the hydrocarbon reactants and heat carrying gases being bubbled through this dense mass in order to catalyze the desired cracking reactions. .In order to secure uniform distribution of "the reactants throughout the mass. of powder, they are caused to bubble through a distributing member 52 from which they flow upwardly through the relatively de'nse'mas's of powder which iskept in a state of constant agitation by the movementof .the gases; The time of contact and proportion of catalyst to gasis so selected that the .desired degree of cracking'takes placefl'pThe reaction products upon being disengaged'from the upper surface] 68 "of the relatively dense mass of catalyst powder enterlline, 53jfrom which they are directed to cyclone separator 54, the function of which is to separate the major portion of the entrained catalyst. The catalyst thus separated enters line 55 from which it is returned to the relatively dense phase present in the reactor. The hydro carbon reaction'products freed from a greater portion of the entrained catalyst leavecyclone separator 54 by way of line 56 and pass through valve 51 to enter line 23'wherein it iscommingled withthe reaction products obtained from the first catalytic cracking zone. 1-"

The catalyst used'in processing the hydrocarbons becomes contaminated by the deposition thereon of carbonajceo'us materials which reduces activity. In order to maintain the catalyst in uniform activity it'is continuously removed from the reactor by'being withdrawn from the dense phase through central conduit58 from which it enters line 59, controlled by "valve 63. The most common method of reactivatin'gthe carbonized 6| and, after passing through valve 62 enters compressorJ63 which discharges through line 34,

controlled by valve 65. After passing through valve 85 the air is commingled with the carbonized catalyst admitted to line 64 by way of line 59, the mixture of air and contaminated powder thereafter being introduced to regenerator 66.

them a certain quantity of catalyst powder in suspension which is removed by the scrubbing action of the liquid charging stock being supplied The general construction of themethod oi operation of the regenerator is similar to that of the responding to the level 68 of the catalyst powder in the reacting zone. In order to prevent channeling, the air enters the dense mass of catalyst powder after passing through distributing member 86, the temperature, pressure and time of contact being so regulated that the desiredoximent of the regenerating gases serves to 'maintain the relatively dense mass of catalyst powder in the state of. agitatiomthe entire mass of powdered catalyst both in the regenerating zone and reacting zone having the appearance of a boiling liquid. The temperature prevailing powder flows through this downtake 19 into line 1 80 wherein a portion is directed into line 82. Afv .dation reactions take place, The upward move? to said scrubber by way of line 4 as hereinbefore set forth. The gaseous products of regeneration leave scrubber 6 byway of line 11 and after passing through valve 18 are removed from thesystem.

The regenerated catalyst is continuously removed from regenerator 66 by means of the downtake 19 the upper end'of which may extend to within a short distance. of the upper surface of the catalyst powder. Thedense mass of catalyst ter passing through valve 83, this portion of the catalyst powder is mixed with thecharging stock.

in line i2, the mixture of catalyst and oil passing through line l4 wherein it is returned to the heater' ll as hereinbefore. set forth; The remainder of the regenerated catalyst powder in line 8!} passes through valve 8| from which it is within the regenerating zone may be within the approximate limits of 900-1150 FL This temperature must be controlled as excessive temperatures, such as for example, 1300-1400 F. has a marked deleterious effect on the life of the catalyst. The gaseous products of regeneration com prise principally carbon dioxide, water and the nitrogen present in the air and are disengaged from the relatively dense mass of catalyst powder,

carryingwith them a certain quantityof the catalyst in suspension. The mixture of gaseous products of regeneration and entrained catalyst leaving regenerating zone 66 by' way of line 69 to enter cyclone separator 10 wherein a major portion of the catalyst powder is separated and returned to theregezierating zone by line ll which dips into the dense phase of catalyst powder thus serving as a seal for the separator. The gases leaving the cyclone separator enterline "I2 and after passing through valve 13 are cooled by indirect heat exchange in cooler 14. The function of this cooler is to reduce the temperature of the gases sufficiently so that they may be scrubbed with the hydrocarbon liquid in a subsequent step. The cooled gases leaving heat exchanger 14 enter ,line I5 and after passing through valve 16 are directed to scrubber 6., These gases carry with directed to line 49 and thereafter supplied to reactor 5| wherein it is used in the fluid catalyst cracking step. Catalyst losses in the system may be made up by supplying catalyst in the form of; a slurry to the system by way of linef84, 'con-. trolled by valve 85, said line discharging into line a I4 and thereafter into heating coil It}. i l

Iclairn as my invention:

A catalytic conversion process which comprises cracking hydrocarbon oil in a first reaction zone in admixture with a powdered cracking catalyst suspended in the oil,- separating resultant vaporous products from residual liquid containing the powdered catalyst, introducing the mixture of residual hydrocarbons and catalyst into a second reaction zone containing a relatively dense} mass of catalyst powder and bubbling the hydrocarbons through said mass under cracking conditions, removing the cracked vapors, substantially free of catalyst, from said second zone and fractionating and condensing the same, removing carbonized catalyst powderfrom the second reaction zone and regenerating the same, supplyinga portion of the regenerated catalyst powder to said first zone and supplying another portion.

thereof to said second zone.

DAVIS READ, JR.