US2346750A - Process for the reactivation of contact catalysts - Google Patents

Description

April 18, 1944. L A, GUYER PROCESS FOR THE REACTIVATION OF CONTACT CATALYSTS Filed April 14, 1941 2 Sheets-Sheet l INVENTOR JESSE AA GUYE'R 5% TORNEY BY M -PY '18, 1944- J. A. GUYER 2,346,750

PROCESS FOR THE REACTIVATION OF CONTACT CATALYSTS JESSE A GUYER TTORNEY Patented` Apr. 1.8, 1944 iTE'D STATE;

am* .orma- PROESS FOR THE llEAC'.IEVJEION OF CONTACT CATALYSTS Jesse A. Guyer, Bartlesville, 0., assignor toA -Phillips Petroleum Company, a corporation of Delaware implication April 14, 1941, sensi No. 388,535 4 ciaims. (ci. 19e-52) This invention relates to the catalytic treatment of hydrocarbons over contact catalyst- `masses to promote conversions commonly classied -as cracking, reforming, dehydrogenation, cyclization, desulfurization;isomerization and the like. More particularly, this invention relates to an improved method and process for the reactivation of catalyst masses employed in said conversions and which are more or `less progressively inactivated by the deposition of carbon and/or.

carbon-containing material on the catalyst particles. i

In catalytic conversions of the ltype indicated,

the nature of the reactants andthe conditions of` treatment are such that carbonaceous materials are formed and deposited on the catalyst mass, l

thereby impairing the catalyst activity. While the amount of carbonaceous material deposited may vary with the hydrocarbonstock undergoing conversion, the original activity of the catalyst, and the conditions, particulagly the temperature of treatment, the ultimate result is a decrease in conversion to an economically unsatisfactory level. From the standpoint of product, quality and yield, it becomes necessary to reactivate the catalyst at suitable intervalsI corresponding to some pre'- determined standard or average value of economically satisfactory conversion. i i

In catalytic conversion processes wherein re activation of the'catalyst at relatively'frequent intervals is necessary, it is common practice to incorporate into the plant design and equipment a sufcient number of catalyst-containing chambers so that a regular cycle of converting and reactivating. operations is possible. ordinarily includes a treating period during which a unit .volume of the catalyst is employed in the conversion anda reactivating period during which the said unit volume-of catalyst is subjected in situ to controlled combustion conditions by the passage of an oxygen-containing gas at or above the ignition temperature of the carbonaceous deposits.

Reactiyation of solid granular catalyst masses by combustion requires careful control of the rate of burning to prevent deterioration of the physical and catalytic properties thereof by excessive temperatures. I -Ieatl transfer within vthe catalyst mass is poor due to the non-conducting vnature of the particles, and temperature control during `combustion is usually attempted by the regulationl 'of the oxygen content of the combustion atmostphere passedthrough the catalyst mass to thereinr limit the exothermic heatgenerated. Inl this manner the combustion atmosphere may serve as- Such a cycleA both the .temperature control mechanism and the principal heat transfer medium. n

The heat of combustion is primarily a measure of the amount of` carbonaceous material burned, or in other terms, o f Vthe amount of oxygen admitted to the catalyst, and reactivation is ordinarily described as carried out in an atmosphere of relatively low oxygen content. The rate Aoi' combustion is thus to be limited and the exothermlc heat to be controlled by the available oxygen in a unit volume of the combustion atmosphere. Also, during the periodoi reactivation it is often desirable to increase the oxygen concentration of the combustion atmosphere as the carbon content of the catalyst decreases to maintain a reasonably constant temperature and 'speed the reactivation operation.

v However, the tremendous operating diicultes in such a procedure are centered in the regulation of the oxygen content oi the combustion atmosphere. The oxygen content-must be maintained at very low values which may be varied-Within known low limits during the reactivation period,

and this degree'oi regulationhas complicated the analytical and control procedures of the proposed reactivation processesin many cases to the point of inoperability. No ordinarily available gases have an oxygen content in the range required during the initial stages of reactivation. Thus,

a source of .substantially oxygen-free gas. Such recycle gas may then be blended with oxygencontaining gas in producing a combustion atmosphere of controlled oxygen content.- This procedure is complicated by the fact that this recycle gas'may have a substantial and iiuctuating oxygen content at variousintervals throughoutthe combustion period. Especially in the reactivation of catalysts disposed in multiple-tube reactors, th' combustion may proceed unevenly due to unequ l pressure drops in the various tubes so that the eiiluent gases from some tubes may contain I,substantially the original concentration of equipment.

oxygen while that from otherv tubes may be oxygen-free. Similarly, in catalyst vessels of relatively'large. cross-sectional area uneven combustion may result from uneven carbon deposition. This fact in turn requires a. constant and accurate determination of the oxygen content of said recycle gas as long as it is being mixed with additionaloxygen-containing gasahead of the catalyst chamber. Such analysis is difficult to make, and the necessary continual re-proportioning oi the gas streams being mixed introduces 'expensive and troublesome operating control. In addition to these difficulties, the recycle gas stream contains corrosive compounds such as hydrogenfsulde and sulfur dioxide and abrasive constituents such as dust which aredestructive to compressors, blowers, controlinstruments and various other parts of the equipment of the system.

Thus, prior to recyclingthe euentcombustion gas from the catalyst being reactivated is ordinarily chemically treated and/or scrubbed, dried, reheatedl and the like to remove components deleterious to the catalyst or to the reactivating A iinal disadvantage is the high carbon monoxide content of said recycledl gases which, as hereinafter explained, is not desirable in the combustion atmosphere.

It has also been proposed to supply the required substantially oxygen-free gas in the form of steam. Such proposals are not feasible in many cases due to the high cost of providing the large amounts of steam required as well as to the frequent deleteriou eiects of high concentrations of steam on t c catalyst. In the latter instance, control of the'steam content as well as ci' the oxygen content' of the combustion atmosphere leads to the multiplication of control problems and to the use of expensive cooling and rev heating procedures to remove excess steam by condensation and to reheat the combustion atmosphere to ignition temperatures.

I have now discovered a method of conducting the reactivation of catalyst masses 4which from the standpoint of simplicity and economy of op eration as well as the utilization 91 various novel` features hereinafter described represents an important improvement in the art. My invention as exemplified in the control of the reactivation equipment andl process has for its objects'the (elimination fof the disadvantages formerly associated with catalyst reactivation by controlled combustion, and the employment ci' novel operating features and economics.

, I have found that the removal of carbonaceous material from a catalyst mass vmay* be expedited and more easily controlled by the use of a com: bustion atmosphere` prepared by mixing an oxy-l gen-containing gas with a substantially oxygen- .free gas furnished from an external'supply of substantially unvarying composition. I have iurther`discovered a novel method of producing said substantially oxygen-ree gas in any required volume and at a temperature level which makes its generation and 'use inexpensive and 'easily controlled. With this constant supply of substantially oxygen-free gas, I am able to control the reactivation process in all'stages o1' combustion with'ease and simplicity of equipment heretofore impossible. Other advantages of my process such as fuel economy and utilization of waste heat togenerate' steam and power for the process will be obvious from' the following description.

I have noted that greatly improved results are obtained in reactivation byI the use of a combustion atmosphere containing, in addition to a regassettovl 1) o+o2 oo2 (+174,6oo B. t. u.) m (2) C+CIO2 2C0 (-70,200 B. t. u.)

When water lis formed yor is present in the combustion atmosphere additional reactions are possible, as follows:

`Equationl'(1) represents the basic combustion re- I action which is substantially instantaneous and 2m is yresponsible for e'xothermic heat during reactivation. Equations (2) and (4) represent reacactions 'which remove carbon from the catalyst y and at the same time absorb heat. Equations (3) and (5) represent reactions which may be disregarded at the, temperature levels of 600 to i500u F. ordinarily employedin reactivation.

Reactions (2) and (4) are highly desirable in that they are endothermic and promote reactivation.. fI'o the extent that these reactions occur, .reactivation is expedited, andthe heat evolved by Reaction (1) is partly absorbed. Both eilects are beneilciaLand the latter even permits a slightly higher oxygen concentration in the combustion atmosphere. I have establishedithe fact that Re- 35 action (2) utilizing carbon dioxide is of far greater signicance in this respect than Reaction (4) utilizing steam due to a greater reaction velocity at the above-mentioned temperature levels. Thus, carbon dioxide is superior to steam as a secondary reaction agent in the combustion atmosphere while the function of carbon monoxide as a product of the secondary reactions is to suppress the said desirable reactions. For these reasons I prefer to utilize a combustion atmos- 5 phere of closely controlled oxygen content prepared by mixing an oxygen-containing gaswith a substantially oxygen-free' gas also containing maximumlquantities of carbon dioxide and minimum quantities of carbon monoxide. The concentration of steam inv said combustion atmosphere 'may not exceed-that present in ordinary flue or stack gases and may be limited to values consistent with operating economy and the susceptibility of the catalyst toward deterioration .of steam.. 4

In one specific embodiment, my process comprises the steps of (1) preparing a substantially oxygen-free gas by the combustion of fuel gas under moderate pressure in an atmosphere of m oxygen-containing stack or spent combustion gases; (2) lpurging. the catalyst space with substantially oxygen-freezes; (3) mixing the substantially oxygen-free gas with the stack gases or air to produce a mixture of limited oxygen conlcentration which is passed at suitable tempera- .l tures over the catalyst to be reactivated; (4) increasing the oxygen content of the combustion atmosphere as the reactivation proceeds to eiectively maintain the rate of combustion; and (5) utilizing the sensible heat of the eiiluent' gases -from the catalyst v4chamber and of variable volumes of the excess 'gas produced by step (1) to lgenerate steam and power for the operation' of the process.

The `various operations outlined maybe illusintegrated.

' essere@ trated by the ow diagrams of Figures l and 2 v which show schematically two arrangements of equipment for the practice of my invention.

With reference to Figure l, gas from stacE I.

which may be part of a heater or furnace em- -ployed in the catalytic process is withdrawn through cooler 2 and line 3 to steam-driven compressor 4. The, compressor delivers the Agas through line 5 to pressure combustion chamber 6.

' In chamber t lthe stack gas is mixed with suicint fuel gas from line 'I to produce combustion products substantially free of oxygen. The gas stream leaving chamber 6 is divided, passing through line il to line I l which leads to the cata/- lyst chambers i2, I3 and through the backpressure regulator 8 to the waste heat boiler Il. The `substantially oxygen-tree. gas` passing through line lll 'is thus available for uses requiring, an inert atmosphere or for mixing with oxygen-containingl gas. The latter may be stack gas from line id or in some cases air from line I5. The gases are introduced to the' catalyst chambers through li'nes I6, I1 and i8.

The catalyst chambers are represented by two vessels although the number is not restricted and will vary according to the conversion being cnducted. These vessels are fitted with inlet manlfold` lines 50 and 5I and outlet manifold lines 52 and 53 and vapor-inlet line 54 and vapor outlet line 55 `for the passage of hydrocarbons undergoing conversion, and also valves as shown for switching the'ilow othydrocarbons and reactivat'ing gases from oneto, the other of the vessels. The catalysts may bedisposed in a single bed or in sections on trays vand 'the like, or in multiple tubes of relativelyy narrow cross section. The cycle of operations may be illustrated with two vessels although in actual operation with -more vessels the time' intervals ci the various `tion, reactivation is commenced by passing through chamber I3 a mixture of oxygen-containing stack gasirom line Il and substantial-` ly oxygen-free gas, from line I0. The proportions of the mixture are regulated to produce the desired oxygen content. Assumingthat a constant volume oi' gas is generated in combustion chamber t, the requisite volume is delivered through line lil by, reduction of the ilow through the back-pressure regulator 9. Theeiliuent gas from chamber i3 passes through lines 2B, 2l and 2c to the waste heat boiler i I. I The gas' stream leaving the boiler consists of the combined ystreams entering.b'y lines fand 2l, and passesthrough line 25 to vent 26. 'f The-steam generated in the boiler II is withdrawn from the accumulator 21 through the pipe 2u and superheated in the heat exchanger 29 by heat exchange with the hotl gases from pipe it. The superheated steam is 'supplied to the prime mover il@ through the pipe 3l. Steam from an external source maybe admitted to thev prime mover from the pipe t2 and used to augment Vthe .-f v4from the waste heat boiler. The cond ate from the prima mover 30 passes through trap tu and line 34 top'ump Il which returns the lcondensate through line 38. yPart of the water passing through line 36 is sent to boiler l I as feed water through line 31 together with make-up waterirom line 38. 'Water is also injected into the-combustion chamber '8 through line 39 for the purpose of cooling the combustion sas produced. Additional cli'ng of the gas passing through line It is obtained by water injection through line Il and heat exchange in the heat exchanger 29.

The excess steam required over that produced l in the waste heat boiler may be supplied from an external source as indicated, or maybe produced wholly within the system by the .supplemehtary combustion of fuel in boiler il by means of auxiliary burnersnot shown. These latter may also be useful in starting up the plant illustrated before waste heat from the gasj streams is avail able.

As the reactivation proceeds, the oxygen concentration of the reactivating combustion atmosphere may be increased, and larger proportions of stack gas introduced through line le. In fact,

Aafter the major portion of `the carbonaceous residue on the catalyst has been oxidized, undiluted stack gaslmay'be used, or still higher oxygen concentrations may be obtained -by the introduction of air through line I5. In these latter stages, the temperature of the combustion atmosphere may bemaintained at the desired levels by relatively small volumes'of hot gases from line it.l When 4reactivation is complete, the catalyst chamber is again purged with substantially oxygen-free sas byclosing lines it and. I5 and passing only the stream from line l0 at the pro'rfertemperature. Thereafter the catalyst is ready tolte placed in conversion service.

Figure 2 shows a modieation of the apparatus in which the waste heat boiler is placed adjacent to or integral with the combustion chamber. rZin this fashion, the injection or water or` steam to lower the temperature of the gas generated in said combustion chambermay be reduced or eliminated. The stack gas Withdrawn from stack l passes through cooler 2 and line 3 to compressor y t. From thecorhpressor the gas passes through line 5 to the combined combustion chamber and boiler unit di wherein combustior'with fuel'from ine l is conducted to produce the substantially oxygen-free gas. `Gaseous products of combustion pass through one tube. bank of the boiler, which' is divided by apartition 42, and the oxygen-free gasV cooled by passage through the boiler tubes then passes'to line I0.

Again'considering the catalyst in chamber I3 -to' be undergoing reactivation, the catalyst bed is iirst purged of volatile hydrocarbons by means of.`

substantially xygen-free gas'passlng from the combustion c amber "of unit el and through lines lil, i6, and I8 into chamber i3. The purged material exists through ,lines 2li, 26, and 2E..

The reactivat'lng combustion lis then commenced by passage of a'mixture of substantially oxygen-free gas and oxygenl-co'ntaln'ing stack gas from lines I0 and. I4. The temperature ofthe' mixture is 'controlled by. the volume of hot gas entering by line I0, and the oxygen content is regulated by the volume of vstack gas from line lli. Any excess of gas in line It above that required ior the mixture is vented through back--y pressure regulator Q to line 25 and vent'gt. The

eihuent gas from chamber Iii passes through lines unit 5H, and thence through line 25 to vent 2t.'

The steam generated in the unit di is taken from accumulator 2 through lines 28 and 3l to the prime mover 30. Steam from' an external source may be supplied through line 32. The condensate from the compressor engine is taken through trap 33, line 34 and pu'mp 35, and re turned to theunit lil through heat exchanger lll and line 36. Exchanger M serves as a feed Water preheater and removes part pf the heat added to the stack gas stream by the compression step. Boiler feed water from line 36 is passed to the unit il through line 3l together with maire-up water from line 38. Water from line 36 may -be injected through line 39 into the combustion chamber of the unit il if desired, although in most cases the necessary reduction in the temperature of the gas is accomplished in the boiler tubes. f o

Combustion of fuel in an atmosphere of stack gas is carried out in combustion chamber d and in unitil il at moderate superatmospheric pres- 'H without further ceung.- The gas stream sures 01515-50 pounds gauge or suicient' to mainv tain iiow ofthe combustion. atmosphere without further compression. The pressure of combus tion may be only slightly below the discharge pressure of. the compressor which delivers the oxygen-containing stack gas to both the combustion chamber and the gas mixing lines ahead cf the catalyst chambers. This condition con forms with equalization of pressure in the mixing operation anchthe use of the compressor to ,flow the combustion atmosphere through'both the combustion chamber and the catalyst chan/mers.

The system pressure from the compressor discharge to the outlet of the waste-heat boiler may be regulated Within the indicated pressure range by suitable back-pressure regulators.

The combustion of fuel gas in'an atmosphere of stack gas having an oxygen content lower than air and usually between 5 and 10 volume per centl vrpassing through line I0 may be further cooled by additional water'injected through 'line 40 prior to lpassage over the catalyst being reactivated. In every case the degree of 'cooling of the gas in line I0 willbe governed by the relative proportions of said gas used in the mixture with stack gas from line I4 and by the desired temperature of the said mixture at the inlet of the catalyst chamber.

Instead of cooling the gas passed into the catalyst `chambers I2, i3 vand comprising the substantially oxygen-free gas issuing from chamber il or unit 4|, by the injection of liquid water through line' 39, by the injection of liquidjwater through line 40, or by heat exchange indexchanger 29 with the steam issuing from accumulator 2l, this gasmay be cooled by the direct addition thereto of water in the form of steam.' The cooling steam may conveniently be made by the injection of steam as such before or after the blending with air or with stack gas.

The stack gas which serves as the combustion medium in chamber 6 and as the source of oxygen-containing gas in, the. combustion atmos-v phere is cooled to a temperature of about 100 to 300 F. 'ahead of the blower 4, The temperature rise, due to compression may be oiset by a heat exchanger inthe blower discharge and the heat extracted-may be utilized in any desired manner,

for example; to pre eat the feed water to the boiler asin the mod cation oflFigure 2. The

` compressor output is regulated according to the produces a substantially oxygenffree gas oi? high y carbon dioxide content at temperatures which are markedly lower than those resulting from 'the combustion of fuel gas in air.. Thus with stack gases containing about 10Y volume per cent of onygen, the combustion temperature in chamber t3 is about 2400" F., whereas if air were used the temu perature would be in the range of 32003500 F. This lowering of the temperature in chamber@ is reflected in savings in the cost of construction and maintenance of chamber` t, because the higher temperatures cause more rapid Vdeterioration of the shell, yrefractory linings,'checkerwork partitions and effluent gas lines.

The lower temperature of the gas generated -in the pressure combustion chamber is also benecial in the reduction of the degree of' cooling which must be done to produce Itemperatures compatible with the various 'reactivation' steps. For example, when it is desired to lower the temperature of the gas leaving chamber Bt about 1400* F., the generation of said gas at 2400 'F'. instead of 3200 F. results in a reduction of about 50 per cent in the weight of steam required for the temperature reduction. When water isomployed there is a corresponding reduction in the amount required. The temperature reduction at the outlet of chamber 6 may bev done in two sta-gesl if A desired. Thus water may be injecteddirectly into the chamberthroush line 39to reduce the gas temperaturesulciently to protect the line 8 and the portion of the gas passing through regulator 9 may be conducted to boilergas' requirements of-the various phases of reactivation, with a constant volume ordinarily being supplied to' the combustion4 chamber 6 or unit 6|. The' amount of fuel introduced is adjusted to the oxygen content of the stack gas. and the gas passing ,tov pipev I0; is substantially oxygen-free when the fuel added requires about per cent or more of the oxygen present for combustion. In this type of operation a constant supply of substantially oxygen-free gas .is available at all'times without the'necessity of any regulation to compensate for other variations throughout the system. Whatever excess of said substantially oxygen-free gas is produced is utilized in the production of steam.

The. basic control of myoprocess is reduced to the proportioning of the gas streams which are mixed to prepare the combustion atmosphere. 'In its simplest aspects, the controlcomprises regulation-o1 the valves orflowcontrollers in the lines I0, i4, and I5 to produce a gas mixture of any desired oxygen concentration 4up to the maximum represented by the stack gases. Beyond this maximum,v air may be'used to produce any desired oxygen concentration upto the oxygen content of air. These ranges cover all ordinary re= activatinsteps and indicate the flexibility and simplicity of operation of my process. Simple operating controls' such as proportioning ilow controllers actuated by the temperature of the eiiiuent gas from the catalyst bed lmay be employed if desired.'

IIfhe initial purge of the catalyst bedprior to reactivation is accomplished. by discontinuing the flow o1' hydrocarbons, releasing the, pressure on the vessel, and .introducing substantially oxygen-:free gas with or without added steam at a temperature usually approximating that .em-

ployed during conversion. In' some instances of treating very heavy material, subatmospheric pressures may be use'd to expedite removal of hydrocarbons.' While the purge gas may be asiatico mixtures of substantially oxygen-free gas with steam, I often prefer to minimizevthe quantities of steam used on account of possible reactions occurring between the catalyst and steam which cause loss of catalytic activity.

A-Iterthe catalyst bed is purged substantially free of volatile hydrocarbons, combustion is initiated by the introduction oi gas containing low percentages of oxygenj The temperature of the catalystmay be raised or lowered'by the purging operation, and the temperature' of te cm1-4 gen-containing combustion atmosphere initially admitted is ordinarily regulated to minimum ig.- nition temperatures in the range of 500 to 1000 F.. depending on the type of catalyst, the nature oi' the catalytic conversion it has promoted and the maximum temperatures desired in reactivation. In general, the service orconversion temperature level will determine the reactivation temperature level for a catalyst.` For example, catalysts used in reactions conducted at temperatures of 900 to 1300 F. may bereactivated at temperatures within that range or only slightly hi'gher while catalysts used at temperatures of 600 to 900 E. are reactivated at substantially `the same temperatures but not greatly' exceeding 1200 F. In either case, the temperature at the beginning of the reactivation will be within the content of the combustion aflcrded by my p rocess flow and eventually reaches ,the end of the catalyst bed. This terminates the nrst phase of reactivation. The second phase. includes the ccmbustion of carbonaceous material mostly beneath the surfacey of the catalyst granules, and higher oxygen concentrations inthe combustion atmospheresere permissible and necessary to rapidly complete the reactivation. Inv this phase the weight of carbonaceous material removed is relaslower'.

at various points within the catalyst mass or by time measurements once the time periods of the successive operations have been established for a given operation. The time required for the actual combustion of carbonaceous material will depend on the weight o! carbon on the catalyst, the type of catalyst and catalyst 'vessels 4and other yfactors involving the maximum desired temperatures during reactivation.. In-any case, adjustv ment of my process toi any existing or desired the maximum permissible temperatures are not I exceeded.

In most cases, catalyst bed temperatures durlng reactivation will not exceed 1200 to 1400* F., and only inexceptional instances will temperatures above 1400 F.'be tolerated without incurring catalyst deterioration. On the other hand,

set of conditions involvfs only proper control of the volume oi' .the indicated gas streams being y mixed at a single point in the system.

At the completion of the reactivating combustion which may be judged by the temperatures of the eiu'ent combustion atmosphere or of the catalyst bedor by any conventional means, the iiow of oxygen-containingrgas is discontinued.

` and the catalyst is again purged with substantialreactivation is often too slow'an'd involves the handling oi excessive volumes of combustion at'- mosphere when temperatures below about 500 to 700". F. are maintained.

/Pressure's in my process are moderate superatmospheric pressures which may range from values at the blower discharge just suicient to overcome the total pressure drop in the System 'to higher values of 150 pounds gauge or more maintainedV by pressureregulators on the eiuent gas lines. In some cases, higher pressures arey beneiicial in shortening the final stages of reactivation;

"The reactivating combustion may be divided intoA two phases according to the potentialrate of combustion. The rst or rapid phase includes the period required for removal of. the surface coating' of carbonaceous material from the cat. alyst granules. In'this period the oxygen con--` tent of the combustion must be very low, gener'-V ally of the order of 0,5 to about 3 volume per cent to prevent excessive temperatures at the-combustion front or zone of intense oxidation. This zone is thatA portion of the catalyst bed in which previously mentioned Reaction (l) isA occurring, involving the oxygen in the vcombustion atmosphere, andthe temperature of this zoner is gov- `erned bythe concentration or oxygen. and adjacent areas are'also the sectors oi? the catalyst bed in which gasification or carbon by vreaction with carbon dioxide and/or steam occurs. l The gas passing through the combustion front is saised in temperature with the result that the entire bed is moreor less gradually heated .to

a level which permits secondary reactions throughout the mass. Y In my process the combustionvfront proceeds uniformly in. the direction of reactivating gas This zone ly oxygen-free gasto prepare said 'catalyst for Y further conversion service. This n nal purge may be of relatively brief duration, and the temperature of the purge ga's may beregulated if desired to bring the catalyst bed to approximately conversion conditions. rIhus, `ii? the reactivation is completed at say F. below or above conversion temperature, the purge gasmay be utilized to raise or lower the catalyst temperature/to the desired range. In thise'case, the.catalyst may be -placed on stream by introducing the hydrocarbon reactants and stoppingtheow of purge gas.-

Such expedients are of value in conversions such' as catalytic cracking and the like wherein the complete cycle of operationswith'a unitofcatalyst may not be longer thanfrom one or less to labout six hours. l

The operation of the pressure combustion chamber as a source of substantially oxygen-free gas requires a'minimum of regulating control.

The oxygencontent of the stack gas delivered to the chamber is essentially constant. and the quantity of -iuel gas required to combine the oxy- 'gen present in a constant volume 0L said stack gas is thus fixed. They combustion temperature produced by stackgas containing about 10 Vol urne per cent of Voxygen is usually in the range of 2300 to 2500 and this range promotes complete oxidation of the fuel to carbon dioxide,

. gas containing maximum concentrations of carbon dioxide substantially'ireeof oxygen and carbon monoxide. In this respect, combustion is more complete than when fuel gas is burned according `to 1 theoretical -airrequirements in' air alone or in air diluted by steam. I

Since the `waste-heat boiler utilizes the excess oi' sensible heat .or the hot effluent gas from the catalyst chambers, a large portion or the steam and power requirements is supplied by waste productsI of the process. The periods onmaximum steam requirement correspond rather close-v ly to the periods of maximum steam production since the largest yolume of substantially oxygen.-a

free gas is supplied to the catalyst duringthe' initial combustion period when the temperature of the eiliuent gas is at a maximum. Conversely, 4, the periods of minimum steam requirements con respond to the periods of minimum steam production. for starting operations may be supplied as shown from an external source or may be generated in Y therwaste-heatboiler by the auxiliary,comlius-1 tion of-fuelgas and air therein or in the combustion chamber if desired..

The following specic examples will serve to illustrate applications o i my process to the reac tivation 'of catalysts used in specic conversions which diier greatly in respect to both conversion and reactivation conditions. Inasmuch as said examples are included toindicate the exibility and operating advantagesof my-process, no limitation is impliedthereby.

Emample I Acatalytic gas-oil cracking operation was conducted with a. silica-alumina type catalyst under conditions such that the conversion-reactivation cycle was six hours. Of this cycle, the conver= sion period was two hours during which carbon deposition amounted to approximately 2 per centby weight o the gas-oil charge. Three catalyst chambers were employed in the operation, and the reactivation equipment was substantially the same as shown in Figure 2 except that gasmixing manifolds were provided for the individual chambers.

After the catalyst'intherst chamber com pleted 2 hours or conversion, the now of' hydro-a carbon reactants was switched to the second chamber. The pressure on said rst chamber was released and'substantially oxygen-free gas delivered from the pressure-combustion chamber Excess steam'requirements and steam assetto vation, with the third chamber being put on stream. The sequence of reactivation operations thus over-lapped With the initial purge and ini-A tial combustion period of said second chamber occurring simultaneously with the ilnal combustionperiod and nal purge or said ilrst chamber. By this scheme of operation the volume requirements for each of. the gas streams used in the sequence of reactivating steps remained essen- ;tially constant.

Example II A bauxite catalyst used in the desulfurization oi crackedgasoline vapors at 750 F. was reat about 2400 F. and cooled to about 050 F..

was introduced for the initial purge gas. The iiow of purge gas and hydrocarbon vapors was directed to a scrubber wherein the hydrocarbons Were separated. n V

The initial purge was complete after 30 'i s utes, and with the catalyst at approximately 950 F., the combustion was initiated by introducing a mixture of stack gas with sufilcienf. substan tially oxygen-free gas to produce an oxygen conn tent of about 2 volume per cent.' This initial mixture was20 per cent of stack' aaa and 't0 percent substantially oxygen-free sas, and was prepared by mixing 80% Oxygen-free gas from the pressure, combustion chamber with 20% cooled stack gas containing about 10% oxygen to produce a. mixture 'temperature or about After a period o '1.5 hours, the initial combustion4 phase was complete with the maximum temperature not substantially exceeding 1100"- 1200 F. and the temperatures of the catalyst mass showed that the combustion front had trav ersed the bed. At this point, the oxygen content of the comlmstion atmosphere was raised to about activated. after 12 hours on stream. extended period of service, dual catalyst chambers of relatively large cross-section were providedand the reactivation was completed ih aboutl 9 hours. The catalyst to be reactivated was-purged free -of gasoline vapors by means of'a`mixture of substantially oxygen-free ,gas prepared. as in 'the foregoing and steam,at a

.temperature of about "100I F. The purged catalyst was then yreactivated for a.' period or 7 hours with a combustion atmosphere composed of stack gas and said Asubstantially oxygen-free gas and steam entering the chamber at about 850 F. During reactivation', the oxygen content of the combustion atmosphere was gradually increased adm 2.5 per cent to 1o per cent', with the erst increase coming after 4 hours. Maximum temperatures -withinv the catalyst bed did not substantially exceed 1400 F. at any period and during the last 2 hours of the 9 hour period the inlet temperature oi the combustion atmosphere was raised to 900 F. The reactivation was completed in 9 hours, and the chamber was purged' again with substantially oxygen-free gas and steam at a temperature of about '150 F. to eliminateoxygen.

My invention is not limited to the reactivation of any particular type of catalyst nor to any specic conversion in which catalysts are deactivated by the deposition of carbonaceous deposits. In generaL-the catalysts to be reactivated according to the terms of the foregoing disclosure are those which are restored to a suitable activity under' the specined controlled conditions' but which are susceptible to deterioration il.' the said specified conditions are exceeded during reactivation treatment. Examples ot such materials are the various contact catalysts classified as clay-type and mineral ore materials and natural or synthetic metal oxides including the difiicultly reducible oxides alone or' in mixtures with each other and/or promoted with other metals or metal salts. Specic examples are bauxite and bauxite impregnated with c mium.

zirconium. and other oxides used in (cracking.`

dehydrogenation; aromatization and desulrurization conversions and composite catalystsl prepared from-silicon and vated silicates.

With this aluminum oxides and'actiasaasso The term "stack gas and "spent combustion gas" as employed in the foregoing disclosure are intended to designate the gases produced by the combustion of fuels with moderate amounts of excess air according to conventional procedures known to the art.' Such gases ordinarily com prise carbon dioxide, nitrogen, oxygen and water vapor with the relative. amounts of' these and other minor components varying according to the type of fuel and the eiiiciency of' the combustion operation. y

The term "moisture as used in certain of the appended claims includes water in the form of either liquid water or steam. A

Having thus described my invention, I claim:

' l. A method of regenerating a catalyst of reduced activity by removing combustiblel deposits from the catalyst which comprises burning fuel in an atmosphere of an oxygen-containing stack gas, the latter containing a substantial amount but not over 10 ',volume per cent of oxygen and prepared by the combustion of fuel with a limited amount of excess air, the proportions of said fuel and said stack gas being so adjusted to produce a substantially oxygen-free and carbon monoxidefree gas, mixing the resultant substantially oxygen-free and carbon monoxide-free gas with an oxygen-containing gas to form a regenerating gaseous mixture having an oxygen content of less than' 10% by volume, and introducingA said mixture into contact with the catalyst to regenerate the catalyst by removal of combustible deposits from thecatalyst. y

2. A method of regenerating a catalyst of reduced activity byremoving combustible deposits from thercatalyst which comprises burning fuel in an. atmosphere of stack gas, the latter containing a substantial amount but not over 10 volume per cent of oxygen 'and prepared by the combustion of fuel with a limited amount. of excess air, the proportion of said fuel and said stack gas being so adjusted to produce substantially oxygen-free and carbon monoxide-freegas,

mixing the resultant substantially oxygen-free andi carbon monoxide-free gas with controlled cunts of said stack gas to form a regenerating gaseous mixture having a controlled oxygen content of less than 10% by volume, introducing the said mixture into contact with the catalyst to regenerate the catalyst by removal of combustible deposits from the catalyst, and adding moisture to the'regenerating gaseous mixture to limit the temperature of the regeneration below a predetermined maximum.,

3. lA method ofmaking a gas suitable for regenerating a catalyst of reduced activity by removing combustibile deposits from the catalyst which comprises burning fuel in an atmosphere of stack gas, the latter containing a substantial amount but not over 10 volume per cent of oxygen and prepared by the combustion of fuel with a limited amount of excess air, to produce a substantially oxygen free and carbon monoxidefree gas, and mixing the resultant substantially oxygen-free and carbon monoxide-free gas with air to form a mixture of combustion 4products and oxygen having an oxygen content of less than 10% by volume.

a. In a process for the reactivation of solid contact catalysts employed in the conversion of hydrocarbons, the activity of which has been substantially reduced by the deposition of oxidizable carbonaceous material thereon, which comprises passing a portion of a gas into contact with the catalyst to purge the catalyst of hydrocarbon vapors, mixing another portion of said gas with'oxygen-containing combustion products -to produce a mixture of suitablereduced oxygen content, and passing said mixture into contact with said catalyst to effect removal of the carbonaceous material by combustion and gasification of said material, the improvement which comprises generating said gas by burning fuel gas in an atmosphere of combustion products having a substantial content but not over 10 volume per cent of oxygen, the proportions of said fuel and said combustion products being so adju'sted to produce a gas containing carbon dioxide and substantially free of oxygen and carbon monoxide.

JESSE A. GUYER.

cmrrreare or conmcron.

Patent No 2,5146 75.0

It is hereby certified that error appears 1n the printed specifi ot the above mmbered patent' requiring correction as follows; Page 5, second' calm; 13u52, foraine rend #eline-m'. A =-exte; page 5, eccomi co1, lne7 for .-ahosph I for "mise" read thie; page 7, f'rst column, line .l and that the seid Letters Patent should .be

phare-5 V11m El..

Apr-11 18, 191th., y

Jesse-moms;

reed with this correction 'therein met the s'emelmay conform to the record of the casein the-Patent Offices signed jam seared this 29th day er ,august-p (Seal)` .D.- 191th. Y

Leslie Frazer Actng'Conmii'ssoner of Patents.

cation line 61|., for exists read eresa reed --etmoscnnnromn on comoon.

Patent No.4 2,5155750. April 18, 19h11.

.mssx1..oum;

It is hereby certifiedl that error appenrs 1n the printed specification of the above numbered. patent requiring correction follows: Page 3, second' column', 11m 52, forine rend 11ne: line 611, for exists read exits-g pogo 5, econrl` column, line 7, for "vanospheros reed --atmoaphoto-g I Line 13.7,.ror 'v'thise" reid -thil; page 7, first column, line 1, for "tu-n' rnd tomar-- qnd mn: the 1d Lettera usent mould b,

I read vdth this correction 'therein that 'the namens; conform to the record of the case 1n hepatent office. l Q

signed'am alga this 29th day of August, 1.11.1191111.

n v Leslie Frazer (Seal) ActingC-ommi'ssioner of Patents.

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