US2339846A - Method of and apparatus for the catalytic conversion of hydrocarbons - Google Patents

Description

Jan.;..25, 1944. Du BOIS EASTMAN EAL ,3

METHOD OF AND APPARATUS FOR THE CATALYTIC CONVERSION OF HYDROCARBQNS Filed Sept. 6, 1940 2 Sheets-Sheet l HEATER Q-l I DU B015 EASTMAN d RICHARD E.NAGLE RUFUS L.SAVAGE JR. E INVENTORS i i; M

Patented Jan. 25, 1944 2,339,846 METHOD OF AND APPARATUS -FOR rm CATALYTIC CONVERSIQN F CARBON S Du Bois Eastman, Port Arthur, Tex, and Richard E. Nagle, New York, and Rufus L. Savage, Jr., Hartsdale, N. Y., assignors, by mesne assignments, to The Texas Company, New York, N. Y., a corporation of Delaware Application september 6, 1940,.Seria1 No. 355,568

4 Claims. .(Cl. 196-52) This invention relates to a method of and ap paratus for the catalytic conversion of hydrocar-' bons and particularly with respect to the regeneration of the catalyst employed in the conversion of hydrocarbons such as in the thermal conversion of petroleum hydrocarbons.

The invention has to do with the catalytic conversion of hydrocarbons and particularly the thermal conversion of petroleum hydrocarbons for the production of motor fuel. In accordance with the invention oil heated to a conversion temperature is subjected to contact with two or more catalyst masses alternately, one mass undergoing contact with the oil during on-stream operation while another mass undergoes regeneration during ofi-stream operation.

The cit-stream catalyst mass is regenerated in situ under elevated pressure by contact with a reactivating gas containing a small amount of oxygen, the how of flue gas and its oxygen content being such as to effect regeneration at a temperature not in excess of that at which the catalyst would be injured and such that substantially all of theexothermic heat of regeneration is removed as sensible heat of the gas issuing from. the mass.

The sensible heat is continuously removed from the issuing gas without substantial reduction in' The major proportion the pressure of, the gas. of the cooled gas is continuously recycled through the mass during regeneration by means of a turbine driven impeller while that portion not .so cycled is utilized as a fluid actuating means for the turbine. portion of the gas, still under elevated pressure,

is expanded through the turbine to substantially.

In other words the non-recycled atmospheric pressure, thereby causing the turbine to rotate and thus operate the impeller.

The invention also contemplates an arrangement of apparatus for practising the method of operation involved in the invention as applied to the conversion of hydrocarbon oils.

In the thermal conversion of hydrocarbons, catalytically. the oil, preferably in vaporized form and heated to a conversion temperature, for example, in the range 850 to 1000 F., is passed through a catalyst case containing a solid pulverulent mass of the catalyst. Various catalysts may be employed as for example natural and synthetic silica-alumina catalysts. Specific examples of suitable catalysts will be mentioned later.

During theconversion treatment, higher molecular weight hydrocarbon contained in the feed are converted to lower molecular weight hydro-- ings. Fig. 1 of the drawings represents a diacarbon boiling within the range of ordinary motor fuel. Such conversion is accompanied by the formation of normally gaseous hydrocarbons as well as a certain amount of carbon or carbonaceous material. This carbonaceous material is deposited upon the catalyst particles and as a result of continued carbon deposition the catalyst becomes reduced in eiiectiven'ess so that it is necessary to regenerate the catalyst at intervals in order to restore its efiectiveness inthe conversion reaction.

Regeneration usually involves subjecting the catalyst to contact with an oxygen containing gas so as to remove the carbonaceous deposit by combustion. Accordingly, two or more cases containing catalyst material are maintainedin service, one being kept on stream during conversion while another is off stream undergoing regeneration.

During such regeneration it is essential to avoid gas and during which regeneration a substantial amount of heat is liberated.

The invention will now be described in more detail by reference to the accompanying drawgram of flow for carrying out a process of treating oil involving catalytic cracking to produce motor iuel. Fig. 2 comprises a diagram of flow illustrating the intermittent regeneration of the catalyst employed in the cracking operation illustrated inFig. 1.

Referring to Fig. 1, the gas oil charging stock obtained irom a source not shown is conducted through pipe I to a heater 2 advantageously of the coil or tubular type wherein the oil is vaporized and heated to a temperature ranging from about 900- 1000 F.

The heated vapors pass from the heater through a pipe 3 communicating with the upper portions of catalyst cases 4 and 4'. The catalyst cases comprise vertical vessels co'ntaining a mass of solid pulverulent catalytic material such as The present invention particularly synthetic silica-alumina catalyst. The'catalyst is advantageously supported within the vessels in the form of comparatively shallow beds, one above the other.

The vessels-are manifolded together as indicated to permit maintaining one vessel on stream while the other is off stream and undergoing regeneration, thus vessel 4 may be regarded as on stream in which. case the heated hydrocarbon vapors pass downwardly through-the catalyst mass within the-vessel during which passage' the hydrocarbons undergo conversion. The products of reaction are removed from the bottom of. the,

vessel 4 and are drawn off through a pipe 5 leading to a fractionator 6. I I

In the fractionator 6 the converted hydrocarbons are subjected to fractionation to form a and normally'gaseous hydrocarbonsand a higher boiling liquid fraction comprising gas on which latter is drawn off through a pipe I for such further disposition as may be desirable.

The vapor fraction is drawn off from the top of the fractionator through pipe 8 toa condenser and cooler 9. The resultant condensate and uncondensed gases are drawn off to an accumulator l0. Gaseous constituents collecting in the accumulator are drawn of! through a pipe II from which they may be'passed to a further-processing step which may include, for example, 'further fractionation and catalytic treatment of various constituents thereof. v

The liquid portion collecting in the accumuvapor fraction containing gasoline hydrocarbons through a pipe 32.

Fluegas so produced is forced by mean of a lator is drawn off through a pipe. 12 for such further treatment as desired and=which may include stabilization and/or contact with a refining. cat- -alyst. The-flow of hydrocarbons through. the vessel 4 is continued for a period -of arounda to 8 hours or even up to hours b'rmdre, until it becomes desirable .to regenerate the catalyst, as evidenced by substantial reduction in th-rate of conversion. Shorter conversion periods as low as 20 minutes may be employed if desired.

when regeneration becomes necessary the flow of hydrocarbon vapors is switched from the vessel 4 to the vessel 4' containing fresh or regen- .generation. This-wil1 now be atmospheric pressure up to about 35 pounds per square inch gauge, although higher pressures up to 100 pounds may be employed. 'I'hetregeneration of-the spent catalyst is effected advantaeously under elevated pressure, for example,

around 100 pounds per square inch gauge.

Consequently, in order to effect regeneration following conversion at low pressure, it is necessary after purging the oif-stream catalyst-case to raise the pressure within the off-stream portion of the system'to that prevailing during re- I described by referen'e to Fig. 2 ofthe drawings.

' As indicated in Fig. 2 means are contemplated compressorintogasholders-33, 34 and 35 capable of storing gas under an elevated pressure, for example, around 250 pounds and in sufli'cient vol- .,ume to'pu'rge. and restore the pressure in each catalyst case as well as in theregeneration circuit, prior to and subsequent to regeneration.

The stored flue gas is drawn off as desired through a pipe 36 communicatingwith the pipe l3v to. which reference has been made previously and which communicates with the upper'portion of eachj catalystcase 4 and 4'.

:Thus, assuming that catalyst case 4 is taken onstreariiiorregeneration the first step comprises releasing the pressure to whatever extent I necessary, and discharging to the atmosphere or other freceivr, Thereafter the valves in the pipes l eadingf from: the gas holders are adjusted so as to introduce gas -to the pipe l3 from which it flows through the catalyst case 4 to purge itv -of hydrocarbons remaining from the on-stream .operation. Thi gas, together with hydrocarbons displaced-from the catalyst case is discharged erated catalyst. This is accomplishedby 'adjusting'the valves in the pipe manifolds leading into and away from the vessels 4 and 4'. I The vessel 4 is then off-stream during'which time the catalyst contained therein undergoes regeneration.

Regeneration, as will bedescribed in detail,subse'quently, 'is accomplishedby means" of a reacth vating gas introduced to the vessel containing the spent catalyst from a pipe/l3. The reacti vating gas passesthrough the catalyst mass con-- tained in the vessel and is discharged therefro through pipe l4.

Where the catalyst is new it may be desirable to operate with a relatively short on-stream period during the first few cycles and also at a relatively low conversion temperature. Thus, the new catalyst may-be maintained on stream for a period of around 4 hours with a conversion temperature of around 900 F. after which the hydrocarbon feed is switched to another catalyst case to permit regenerating the off-stream catalyst. After a few cycles with. shortcontact periods and low conversion temperatures the catalyst becomes conditioned so' that the on-stream period may be prolonged and also the conversion temperature may be raised without causing sub- -stantial deterioration of the catalyst.

, The conversion iseffected advantageously under relatively low pressure, for example, around from the bottom of the catalyst case, for example, through a pipe 65 and thus removed from the system, or may be released through valve 59.

Following purging the flow of flue gas from the-gas holders is continued so as to build up apressure in catalyst case 4 and the regeneration system as a' whole to around 100 pounds. When the required pressure has been established in the regenerating circuit, the contr'olvalves are adjusted to discontinue the introduction of further gas to case-4 from thegas holders.

The gas issuing from the-oif-stream catalyst case is at elevated temperature and is passed through the pipe l4 to-waste heat boiler 39 wherein a portion of its sensible heat is removed and the heat so removed used to generate steam which may be used in the process -or for other plant purposes.- From. the waste heat boiler passes through a pipe 40 containing a-screen or other separating means 4| by which means enthe gas passes through a pipe trained dust particles are removed. From there 42 to the suction of an impeller 43. The impeller 43 forces the cooled gas through a pipe 44, containing control valve '45, which pipe communicates with the previously mentioned pipe l3 and through which I the gas is recycled to the off-stream catalyst case. Air is forced by a compressor 46 through a pipe the cooled gas 4 I asaasce 4'8 containing a control valve 4!. and mm "eating with previously mentioned pipe 44. The

air is introduced to the-pipe 44 in amount such that the oxygen content of the reactivating gas leaving the pipe 44 will be around 1-2% by volume. The method of air introduction maybe modifled so that all or a portion of it is introduced to the suction of the impeller 43 tor-the -purp0se or maintaining the gas temperature case, pipe l4, waste heat boiler 39 and pipes 4|! and 42.*The pressure in this circuit is mainpeller. 43, pipes 44, It, the oft-stream catalyst tained at around 100 pounds or at a pressure sufllciently elevated for the purpose of operating the process.

Due to the presence oi oxygen in the reactivating gas carbonaceous material deposited on the oil-stream catalyst is removedirom the catalyst by combustion. The rate of flow and the oxygen content or the circulatin 8&8 is adjusted so as to avoid too rapid combustion which would cause excessive rise in temperature of the catalyst mass. Sumcient volume of inert gas is passed through the catalyst massundergoing regeneration to absorb the exothermic heat of regeneration and remove it therefrom as sensible heat of the gas issuing from the catalyst mass and passing into the pipe l4. More specifically, conditions are maintained such that substantially all of the exothermic heat of regeneration is removed as sensible heat in the gas while maintaining the temperature or the catalyst mass not in excess of about 1200' Accordingly, the 888 passing into the pipe I4 is at a temperature which. may be as high as around 1200 F., and under an elevated pressure of approximately IQO- pounds or whatever pressure is maintained in the catalyst mass during regeneration.

This hot gas thus .passesinto around 900 to 950 F., or to-such lower temperatures as may be desired during theregenerationr.

' erating gas passing to the catalyst mass should be suflicientlyhi h. usually around 900-950 F., to initiate combustion. Once combustion is commenced the-temperature oi. the entering gas may be advantageously reduced, sayto around 150 to 850 F., and suflicient to maintain combustion,

the waste heat, .boiler and is there cooled to'atemperature oi pressure gas from the suction side of the impeller for use in driving the turbine 5|.

- A secondary circuit is therefore provided which I comprises a pipe 53 leading of! from pipe 42 and communicating with a pipe 54 which in turn communicates with a separating vessel or trap 55,

from which a pipe 56 leads to the inlet port of the gas turbine 5|.

A flow control valve'5l is placed in the pipe 54 to control the flow of diverted gas to the turbine 5!. This valve is responsive to the pressure intheregeneration circuit, the purpose being to maintain a substantially constant pressure level;

namely, around 100 pounds in the regeneration circuit. In other words, whenever the pressure in the regeneration circuit at thesuction of the impeller 43 begins to decrease the valve 5'! will close automatically.

."On the other hand provision is also made to avoid a substantial or sudden increase in the pressure in the pipe 42 by providing a discharge valve-fl as well as an emergency relief valve 59. v

Under ordinary circumstances the. volume of gas passing through the valve 51 into the trap 55 and pipe 56 will correspond approximately to the volume of air entering the system from the compressor '46 and will amount to approximately 10% by volume of reactivating gas passing to the catalyst case. This diverted gas is still under elevated pressure corresponding approximately to that maintained at the suction of the impeller 43 and therefore the pressure of the gas is sumciently high so that it can be expanded through the gas turbine Ii as an actuating medium for the turbine. From the turbine 5! the expanded gas isalischarged to'the atmosphere through the p pe v In this way a portion of the flue gas generated during regeneration is utilized directly in the provided by the steam turbine 52. The steam the temperature of the mass undergoing regeneration not being permitted to exceed about 1200 F. As regeneration nears completion it may be necessary to increase thetemperature of the entering gas to around 950 F. or even higher in order to complete the combustion.

;It is desirable to adjust the temperature of the entering gas to keep it at the minimum necessary to support combustion, since the lower the temperature at which it enters the catalyst mass the greater is its heat absorbing capacity.

turbine operates only when there is insuflicient high pressure gas passing to the gas turbine 5|,

an insufllciency of gas for this purpose is reflected by a decrease'in the pressure existing within the pipe 58. Such decrease or fluctuation in this pressure isutilized to control a flow control valve Si in a steam supply pipe 62. Thus, the valve 6| is responsive'to pressure fluctuationsin the pipe 66 and whenever the pressure in the pipe 56 drops, steam is permitted to flow to the steam 1 turbine 52 which then begins to operate and take up the additional load.

Other methods 01'. controlling the turbines II and 52 may be used. Thus the valves in the pipes 54 and62 (supplying gasand steam respectively to the turbines) may be controlled by a. rate of flow controller having an oriflceplate located in the pipe 44 leading from the discharge of the impeller 43. 1 i y In the event that it may be necessary to reduce somewhat the temperature of the flue gas passingto the gas turbine 5i provision is made for introducing boiler feed water from a pipe Ill to, the 'pipe 54 in a small amount. The water so introduced is caused to evaporate upon contact with the hot gas and steam is thus generated accompanied by the desired reduction in The impeller 43 is driven by means 01' gas and steam turbines 5| and 52; respectively. The

Yurbines operate in tandem as indicated and provision is made for diverting a portion or the high gas temperature. The mixture of gas and generated steam passes into the separator 55 where any entrained water is removed. The gas and steam then pass into the pipe 56 leading to the gas turbine 5|.

It is also contemplated that all of the excess through the pipe 54 may be used to drive a turbine operating a motor generator set, rather than to operate a turbine in tandem with the steam turbine as described above. The electricity so generated can be used to advantage in the plant for light and power supply. After completion of regeneration of the catalyst mass, the stream of reactivating gas from the impeller 43 is diverted and the pressure in the catalyst case is released gradually to prevent damage to the catalyst or reactor packing. Oxygen-free flue gas from the purging system is passed through the regeneration circuit so as to displace oxygen from the regenerated catalyst and regeneration circuit, and establish a pressure of oxygen-free flue gas in the system corresponding to that required for the on-stream operation.

In starting up the system it is desirable to warm up the ,cold catalyst cases by passing hot oxygenfree flue gas through them. This gas may be supplied by passing natural gas and air in the proper proportion to a burner 80 wherein combustion under an elevated pressure of around. 100 pounds is eifected. The hot products of combustion flow into a mixing section 8| located in a by-pass 82 in the pipe 44 and wherein they are mixed with the flue gas being circulated through' the regeneration circuit by the impeller 43. Introduction of hot gas from this source may even be continued to some extent during reactivation vof a catalyst mass for the purpose of heating or adjusting the temperature'of the reactivating gas discharged from the impeller. I

While silica-alumina type catalysts have been mentioned it is contemplated that other catalysts may be employed. Various acid-treated and metal-substituted clays, such as the Super-Filtrols, are satisfactory. Likewise, the acid-treated and metal-substituted natural or artificial zeolites, such as the artificial zeolite known as Doucil, can

be used. Various metals can be substituted in the clays or zeolites, such as uranium, molybdenum, manganese, lead, zinc, zirconium, nickel and the like. Likewise, the combination of cer- 2,839,846 gas from the reactivating systemdrawn of! a short interval of time between (a) the closin or the oil inlet andthe opening of the flue gas inlet valves to the case, and (b) the closing of the oil outlet and the opening of the flue gas outlet valves from the case. This interval permits the entering flue gas to sweep out the oil vapors contained in the catalyst chamber and discharge these vapors into the-processing system.

While the maintaining of certain specified pressures has been mentioned above, it is contemplated that the pressure employed in the processing, purging and regenerating steps of the process may be either higher or lower than those disclosed above. If desired, substantially the same pressure may be used throughout the entire process.

While catalytic cracking has been specifically described, it is also contemplated that the invention is applicable to other catalytic treating processes such as dehydrogenatiomfor example.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In apparatus for efiecting chemical reactions by the aid of a regenerative contact mass. in combination, a case having a eontact mass therein and regenerating means for said mass providing a primary circult'includingsaid case, a

turbine operated impeller in said primary circuit arate gas and steam actuated turbines arranged in tandem for operatingsaid impeller, a secondary circuit for diverting a portion of said cooled as to said gas turbine as a turbine'actuating fluid, a valve in said secondary circuit responsive to the pressure in said primary circuit for controlling the volume of cooled gas divertedto the gas turbine, a conduit for supplying steamto said tain acid treated active clays of the character of Filtrol, together with added proportions ofalumina or silica or both can be employed. Aiumina alone may be used under certain conditions; The synthetic silica-alumina catalysts can be improved by the addition of other constituents, such as zirconium oxide or molybdenum oxide. In general, a catalyst is employed which is stable at high temperatures of the order of 1400-1600" F., as determined by calcining in s muille furnace at that temperature, and which is a measure or indication of the ability.,,of the catalyst to,.,maintain its activity under the customary tempe tures of reactivation of the order of 1000-1400 F.,

tions when no ozwgen is present in the flue gas.

accumulating in the system. 'When a catalyst case is being taken ofl-stream for regeneration.

steam turbine and a flowcontrol valve in said steam conduit responsive to the pressure in said secondary circuit at thepoint of gas introduction to the gas turbine. v

2. In the thermal conversion of hydrocarbon oil by contact with a catalyst mass atelevated temperature and under a predetermined and substantial on-stream pressure wherein the oil in vapor phase and heated to a conversion temperature is passed through adjacent contact masses alternately, and the cit-stream mass undergoing regeneration to remove carbonaceous as measured by thermocouples-within the catalyst material deposited upon the catalyst during con tact with the heated oil in on-stream flow, the

method or regenerating the o-stream mass which comprises passing oxygen-free flue gas through the oiI-strearn mass to purge it ot retained bydrocarbons, imposing-"upon the purged mass a substanflally'elevated flue gas pressure, continuously through the mass under said elevated pressure a stream of reactivating gas containing a small amount of oxygen such that the carbonaceous material is removed by combustion at a relatively slow rate, maintaining the volume of gas passing through the mass suiiiciently large to remove the heat of combustion substantially entirely as sensible heat of the. gas issuing from the mass, such that the temperature of the mass the valves may be manipulated so as to permit it does not exceed about 1200' E, reducing the temperature of the issuing gas while still under ofoxygen-containing gas into said stream of major proportion prior to return to the catalyst mass, contimfing the, flow of regenerating gas through the mass until combustion of carbonaceous material is substantially completed,the temperature of at least a substantial portion of the mass upon completion of regeneration being substantially below said elevated temperature, thereafter purging the regenerated mass of oxygen-' containing gas, and then establishing an inert gas pressure within the mass corresponding subbine and operate the impeller, injecting a stream alternately, and the ofi-stream mass undergoing regeneration to remove carbonaceous material deposited upon the catalyst during contact with the heated oil in on-stream flow, the method of regenerating the oil-stream mass which comprises imposing upon the purged m'as's a substantially elevated flue gas pressure, continuously passing through the mass under said elevated pressure a stream of reactivating gas containing a small amount of oxygen such that the carbonaceous material is removed by combustion at a relatively slow rate, maintaining the volume of gas passing through the mass suficiently large to remove the heat of combustion substantially entirely as sensible heat of the gas issuing from the mass, such that the temperature of the mass does not exceed about 1200 F., reducing the temperature of the issuing gas while still under elevated pressure to not less than about 750 to 850'Fr,

' splitting the cooled gas into two streams respectively, one stream comprising a major proportion of the cooled gas and the other stream comprising a minor proportion of .the cooled gas under said elevated pressure, passing the stream of major proportion to a turbine operated impeller for recycling the gas to the catalyst mass, expanding the stream of minor proportion through said turbine thereby to actuate the turbine and operate the impeller, injecting a stream of oxygen-containing gas into said stream of major proportion prior to return to the catalyst mass, continuing the now of regenerating gas through .the mass until combustion of carbonaceous material is substantially completed, the temperature of at least a substantial portion of the mass upon completion of regeneration being substantially below said elevated temperature, thereafter purging the regenerated mass of oxygen-containing gas, and then establishing an inert gas pressure within the mass corresponding substantially to said pre determined pressure prior to re-introduction of feed hydrocarbon vapors for conversion.

DU BOIS EASTMAN. RICHARD E. NAGLE. RUFUS L. SAVAGE, JR.

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