US3129060A

US3129060A - Control of conversion in a catalytic hydrogen producing unit

Info

Publication number: US3129060A
Application number: US186817A
Authority: US
Inventors: Jack B Pohlenz
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1962-04-03
Filing date: 1962-04-03
Publication date: 1964-04-14
Anticipated expiration: 1981-04-14

Description

April 14, 1964 1. B. PoHLENz 3,129,060

CONTROL OF CONVERSION IN A OAIALYIIC HYDROGEN PRODUOING UNIT Jac/r B. Pah/enz A TTOR/VEYS April 14, 1964 J. B. PoHLENz 3,129,060

CONTROL OF CONVERSION IN A CATALYTIC HYDROGEN PRODUCING UNIT Filed April 3. 1962 2 Sheets-Sheet 2 F fgure 2 "/,J Carbon 30g //V VEN TOR:

' Jac/r B. Pah/enz zimfagw' A frog/vers United States Patent O CONTRL F CONVERSION 1N A CATALYTC HYDRUGEN PRODUCING UNIT Jack B. Pohlenz, Arlington Heights, Ill., assigner to Universa! Oil Products Company, Des Plaines, Ill., a corporation of Delaware Filed Apr. 3, 1962, Ser. No. 186,817

5 Ciaims. (Ci. 223-212) This application is a continuation-in-part of my presently led application Serial No. 85,154, tiled January 26, 1961, now abandoned.

The present invention relates to an improved process for producing hydrogen, and more particularly to a method for controlling heat release and conversion in a moving bed processing system for effecting the decomposition of methane, natural gas, or other hydrocarbon stream, to hydrogen and coke.

In conventional catalytic conversion systems, such as those used for catalytic cracking of a gas oil to produce an improved cracked gasoline stream, it is customary to provide heat control at the reactor by varying the heat of the hydrocarbon feed stream with heatexchanger or preheater means, as well as by varying they rate of circulation of the hot catalyst being recirculated from the regenerator to the reactor. In the catalytic cracking of oils to provide a gasoline yield, the iluidized cracking units tend to run as heat balanced units Without much diiculty since changes in circulation of particles, and changes in the coke burning rate may be readily carried out. An increased circulation rate increases coke deposition in the reaction zone and provides more coke for oxidation in the regeneration Zone, and, in the reverse situation a decreased circulation rate decreases coke deposition and heat output from burning coke in the regeneration zone, with the variation in coke deposition varying almost linearly with the circulation rate of catalyst in the system for a given gas-oil feed rate. The variations in coke lay-down or deposition seem to occur by reason of the heavier hydrocarbon components in the charge which readily go to coke and are absorbed by the circulating catalyst particles in the cracking zone, such that it is well recognized in the cracking art that coke deposition and heat balance may be varied by changing the circulation rate. However, in the cracking or decomposition of methane to hydrogen and coke and in contrast to catalytic cracking, a change in circulation rate does not provide a Variation in the carbon lay-down rate, and since the operation is highly endothermic and requires a high temperature generally above 1200 F., it is necessary to utilize to an optimum degree the heat available from carbon made in the reaction zone from the decomposition reaction.

In the present improved continuous moving particle system for hydrogen production, carbon is gasied and burned under conditions of incomplete oxidation in the regeneration zone to provide for the production of carbon monoxide and carbon dioxide and to elfect the heating of catalyst particles for return to the reaction zone whereby the system may operate in a self-sustaining manner. It is, of course, undesirable, as Well as uneconomical, to have to burn additional fuel in the regeneration zone to supply heat to the returning catalyst particles, particularly when the regeneration step can be operated to provide the necessary heat from coke being formed in the reaction zone. In contrast to gas oil cracking, it also may be noted in the improved operation to decompose a methane or hydrocarbon stream to hydrogen and carbon in a reaction zone, free of carbon oxides, that catalyst is prevented from passing to the reactor in an oxidized state, or with occluded carbon oxides.

It has been found that in the operation of a catalytic processing system, as in the catalytic decomposition of light gaseous hydrocarbon to hydrogen andl carbon, that the regenerator can be maintained under reducing conditions, with no free oxygen being present in the flue gas stream, and that the carbon dioxide to carbon monoxide ratio within the regenerator flue gas stream can be varied readily, and at will, within certain limitations of carbon deposition on the catalyst particles andwith substantially carbon gasification in the regeneration zone. It has also been found that the ratio of carbon dioxide to the total carbon oxides formed within the regenerator may be regulated or controlled inversely responsive to certain carbon levels retainedl on the regenerated catalyst. In other Words, with a substantially constant quantity of carbon being'gasifed, the CO to CO2 ratio may be varied in accordance with varying levels of carbon maintained on the catalyst particles and that the heat release in the regenerator per mole of carbon gasilied varies accordingly.

It is, therefore, a principal object of the present invention to provide a method for regulating heat release per mole of carbon gasied in the system for a substantially constant carbon gasification rate, by varying the CO to CO2 ratio in the regeneration Zone and in turn varying such ratio by a change in the carbon level retained on the catalyst.

It is a further object of the present invention to proide a method of controlling heat release in the system per mole of carbon gasitied, for any given gasification rate, by varying the level of carbon retention on the regenerated catalyst and regulating and controlling such carbon level by the control of oxygen introduced to the regeneration zone at amounts less than the theoretical amount required to gasify al1 carbon to carbon dioxide from the catalyst particles and precluding free oxygen discharge from the regeneration zone.

Inasmuch as there is a denable relationship between the ratio of carbon dioxide to carbon monoxide obtained in the regeneration zone andthe carbon level maintained on the catalyst, then the present invention also provides for obtaining and controlling a desired heat balance in a continuous hydrogen producing system by relating the heat release per unit of carbon gasied in the system responsive to measurements of carbon level on the regenerated catalyst and the resulting ratio of carbon dioxide to the total carbon oxides being produced within the regeneration zone.

Broadly, the present invention provides in connection with a processing system for catalytically converting a hydrocarbon charge stream to hydrogen and carbon, wherein heat carrying subdivided catalyst particles contact the charge stream at decomposition conditions in a reaction zone, wherein resulting carbonized catalyst particles pass from the reaction zone to the regeneration zone for contact with an oxygen containing stream to effect the gasification of carbon from the catalyst particles and the reheating thereof, an improved method of operation to provide variations in heat release per mole of carbon gasiied in the regeneration zone for a given carbon gasification rate, which comprises, maintaining the oxygen introduction to the regeneration zone at less than theoretical to gasify all of the carbon on the catalyst particles to CO2 and to preclude the discharge of free oxygen from the regeneration zone and controllably varying such oxygen introduction to inversely vary the carbon level retained on the catalyst particles and directly vary the carbon dioxide to carbon monoxide ratio produced in the regeneration ozne.

For comparative purposes, it may be noted that in the operation of conventional lluidized catalytic cracking units, such as brielly set forth hereinbefore in connection with the conversion of a gas oil stream to produce an improved gasoline stream, it is customary to maintain a desired level or quantity of catalyst in the reaction zone, by the use of a level control means at the zone of the catalyst bed in the reactor, and the level control means in turn connecting with a slide valve in the spent catalyst standpipe, whereby the quantity of catalyst leaving the reactor is automatically regulated. At the same time, the catalyst circulation rate in the system is controlled responsive to a temperature control means having a ternperature sensitive element at the reactor, such temperature control means connecting with a valve in the regenerated catalyst standpipe. Thus, temperature in the conversion zone is regualted upwardly or downwardly by either increasing or decreasing the quantity of hot regenerated catalyst being circulated theretofrom the regeneration zone. It is also conventional in all gasoline producing catalytic cracking units to remove substantially all of the carbon deposition on the cracking catalyst particles by contacting them with an air stream, or other stream containing free oxygen, to effect a high carbon dioxide production from the regeneration zone as compared with carbon monoxide. It is not possible to readily Vary to CO2 to CO ratio and provide a control means for varying the heat release in the regenerator and the system. Generally, the regenerated catalyst carbon levels are held below about 0.5% by weight in the gasoline producing units. Higher residual carbon depositions tend to cause a poor product distribution and resulting large quantities ot gas and coke production in the reaction zone. In the present system of operation, as will be further pointed out hereinafter, carbon levels can be substantially higher, generally being above 0.5% by weight, and generally within the range of 1% to 8% or even 10%, although in a particular apparatus, or processing operation with a particular catalyst, the level of carbon may be less than 0.5% by weight. The decomposition of methane or other light hydrocarbon to hydrogen and carbon is, of course, carried out at a higher temperature than is the cracking of gas oil to gasoline, such that the catalyst particles from the regeneration zone must necessarily be circulated and charged to the reaction zone at higher temperatures to supply the required endothermic heat. Also, in the present system, the regeneration zone operates catalytically and at reducing conditions, with no free oxygen being left in the zone to permit oxidation of the metal activating component of the catalyst. For example, with generally steady state operating conditions, when the carbon gasication rate is held steady and there is substantially constant CO to CO2 ratio in the regenerator and carbon level in the catalyst, then a decreased temperature or heat release per unit of carbon gasied can be attained by increasing the amount of CO make with respect to CO2. The oxygen to the regenerator being reduced and carbon being continued to be gasied at a constant rate by reason of a catalytic effect in the regeneration zone in accordance with the reaction of CO2+C 2CO. On the other hand, an increased temperature in the system may be obtained by adjusting the CO2 to CO ratio to a higher level by controlling the regeneration operation such that increased quantities of carbon dioxide are formed from the oxidation of carbon monoxide which in turn is being formed from the gasified carbon deposition. With heat being controlled, or produced, by the catalytic reaction of carbon dioxide to carbon monoxide, or by the oxidation of carbon monoxide to carbon dioxide, there is thus provided a means to vary the total heat in the system, with heat being transmitted from the regenerator to the reactor to in turn provide a decreased or an increased heat level therein. Further, it should be particularly pointed out that suitable types of catalysts are required in the present system, i.e. those which can resist oxidation by CO2, such that C62 can be used to gasify carbon from catalyst particles in the substantial absence of air or free oxygen and such that the flue gas stream from the regenerator can be readily maintained oxygen free.

In accomplishing a change in the carbon dioxide to carbon monoxide ratio in the regeneration zone, it is, of course, necessary to vary slightly the quantity of air or oxygen being introduced to the regenerator to effect the desired gasification of carbon to provide a high or low ratio of carbon monoxide to carbon dioxide. An increased quantity of air will effect an increase in the ratio of CO2 to CO to a higher level and provide simultaneously a lower level of residual carbon deposition on the catalyst particles leaving the regeneration zone. However, as the regeneration step is leveled out to provide, for example, a resulting desired decreased heat release in the system, for a given hydrocarbon conversion rate and a given carbon gasification rate, then the quantity of air may be slightly reduced to provide the prior regeneration operation with a higher carbon monoxide level and a lower carbon dioxide production. At the same time a somewhat higher carbon level occurs on the recirculated catalyst.

For conversion of a light normally gaseous hydrocarbon stream in accordance with present improved control system, the range of variation of oxygen introduction to the regeneration zone is within the limits of not less than about 50% of the theoretical amount to convert the carbon on the catalyst to CO2 (i.e. such that CO may be formed) and not more than of theoretical to form CO2, such that the catalyst will not be oxidized. In order to point out how the heat release varies, it may be noted that the heat release per pound mole of carbon going to CO is of the order of 48,500 B.t.u., and the heat release per pound mole of carbon going to CO2 is approximately 170,000 B.t.u., at 1500 F.

The term theoreticaL as used herein, in connection with the quantity of or amount of oxygen introduced to the regeneration zone for contacting carbonized catalyst particles, has the meaning of that amount theoretically necessary to chemically combine with the carbon present to form CO2.

The present invention may be more clearly explained by reference to the accompanying drawings and the following description set forth in connection therewith.

FIGURE 1 of the drawing is a diagrammatic illustration of a continuous catalytic hydrogen producing system, while FIGURE 2 of the drawing shows a curve illustrating the relationship between carbon level on regenerated catalyst and a resulting carbon dioxide to carbon oxides ratio attained in the operation of the regeneration zone.

Referring now to FIGURE 1 of the drawing, there is shown an inlet line 1 suitable for introducing natural gas, methane, or other light hydrocarbon stream, suitable for cracking to hydrogen and coke in the presence of a subdivided catalyst stream. T he hydrocarbon charge in line 1 becomes admixed with heated catalyst particles being introduced from line 3, having control valve 4, so that a resulting uidized mixture of the charge stream and the catalyst particles pass through the riser line 2 to the lower end of a reaction chamber 5. In the latter, the vaporous stream and catalyst particles are distributed through a grid, such as perforate plate 6, or through other suitable distributing means, such that a uniform dense phase Huidized bed 7 is maintained in the lower portion of the chamber 55, permitting the completion of the conversion of the hydrocarbon stream to provide a high yield of hydrogen and coke.

In an operation where all of the hydrocarbon conversion takes place in a riser line serving as a reaction zone, and no dense phase level is maintained in an enlarged reaction zone, then the product stream from the riser line 2 would discharge directly into one or more particle separators which would have their particle return lines connect directly with the regeneration zone.

Generally, the conversion is carried out at a tentpcrature in the range of from about 1200 F. to about 1700 F.; thus, the heated catalyst particles being introduced into line 2 from line 3 leave the regeneration zone at an elevated temperature of about 1250 F. to about 1800 F.

In a iluidized ssytem the operating pressure is generally maintained low, being only slightly above atmospheric, with pressures maintained inthe reaction and regeneration zones suicient to eliect a desired circulation of particles from one zone to another. Actual operating pressures will thus generally be less than 50 pounds per square inch, and more generally in the range of from about to about 30 pounds per square inch gauge, although higher pressure systems may be utilized.

In the upper portion of the reactor chamber 5, the hydrogen containing product stream is indicated as being separated from catalyst particles by means of a suitable particle separating means 8. The latter permits the return of entrained catalyst by way of dip-leg 9 to dense phase bed 7, while discharging the gaseous stream overhead by way of line 10. The present operation provides approximately equilibrium conversion to hydrogen, such that the only other material of any quantity in admixture with the hydrogen stream comprises methane, there being very little, if any, carbon oxides present. Contacted catalyst particles with a carbon deposition, and with perhaps some entrained coke, pass from the dense phase bed 7 through a catalyst outlet line 11, having control valve 12 such that carbonized catalyst particles may be introduced into a regenerating and heating chamber 13. As previously noted, where no dense phase bed is held in an enlarged reactor, then carbonized catalyst particles pass directly from the particle separators to the regeneration zone.

Air or other oxygen containing stream is introduced in the lower portion of the regenerator 13 by way olf a suitable distributing means such as perforate pipe system 14 that connects with inlet line 15. Air inlet line 16, with control valve 17 is indicated in the drawing as supplying air to compressor 18, which in turn discharges air under pressure to inlet line and the distributing means 14. The carbonized catalyst particles within the chamber 13 are subjected to an upwardly flo-wing yair or oxygen containing stream and thus uniformly contacted in a dense phase fluidized bed of particles 19. Above the dense phase uidized bed 19 is a light phase zone of ilue gas and entr-ained catalyst particles. The latter are separated from the ue gas by means ofk suitable particle separating means 20 and returned to the dense phase bed 19 yby means of a dip-leg 21, while the resulting ilue gas stream passes overhead by way of outlet line 22, having control valve 23. Generally such flue gas stream, which is oxygen free and' contains a high quantity of carbon monoxide, will be sent to a carbon monoxide burner or boiler to provide for further burning to carbon dioxide `and for Ithe generation lof Valuable high temperature steam useable in various units of a renery.

Catalyst particles, `with at least a portion ci the carbon deposition removed, are permitted to descend in a continuous stream from the lower portion of the regenerator 13, and into an elongated stripping section 24. The latter is utilized to remove occluded carbon oxides Iand other entrained material which may contaminate the conversion in the reaction zone and produce carbon oxides therein. Nitrogen or other inert stripping gases may be introduced to the lower end of the stripping section 24 by way of inlet line 25 and valve 26. However, in a desirable operation, a portion of the hydrogen containing product stream from. reactor 5 is used advantageously as `the stripping medium, being transmitted to line 25 and into a stripping section 24 for effecting removal of undesired entrained components. Resulting `stripped and heated catalyst particles pass in Ia continuous manner from the lower end of zone 24, through line 3` and control valve 4 -to the riser line 2 to thus re-enter the reaction zone 5 and maintains a continuously operating iluidized sys-tern of moving catalyst particles.

A continuously operating hydrogen producing system may be controlled, with respect to ilow of catalyst particles in various manners, 'as for example, a system which has been used to advantage in present commercial uidized catalytic cracking systems. The drawing indicates diagrammatically a temperature sensitive element 27 communicating with the interior of reactor 5 and a connection bet-Ween such temperature sensitive element and a temperature controller, indicated as TRC. The latter connects with the control valve `4 which may comprise an automatically actuated slide valve effective in regulating the flow of subdivided particles through a condfuit. The control arrangement thus permits the temperature at the reactor 5 to cause the temperature recording controller TRC to adjust the valve 4 and the rate of circulation oi catalyst particles trom the regenerator to the reactor.

Operating simultaneously and in conjunction with the regulation of catalyst ovv from regenerator to reactor is the slide valve 12 in the conduit 11, which is adjusted automatically to maintain a substantially constant or desired level within the reactor 5. Level control tips 28 and 29 at reactor 5 are indicated as connecting with level control means LRC, which in turn communicates with the automatic control valve 12 so that a controlled quantity of catalyst passes from the reactor to the regenerator 13.

In a system which eliminates :the dense phase bed 7 in reactor 5, then the level control means LRC and slide Valve '1'2 may also be eliminated. The light phase stream in the reactor-riser line 2 carries directly to particle separating means and diplegs from the latter communicate directly to the dense phase zone in regenerator 13, as hereinbefore mentioned, or to a suitable transfer line such as the air line to the regenerator.

In still another apparatus arrangement, the regeneration zone may be operated without a dense phase bed by utilizing ncn-uidized countercurrent ow of catalyst and a regenerating gas inlet stream, or by using a dilute phase contact in a riser section. In the latter case, the iiue gas stream and regenerated and heated particles yall pass to a separation zone and catalyst then passed downwardly through a stripping zone to be subsequently transferred to the reaction zone.

Various types of catalyst may be utilized in the present system to effect the cracking of the hydrocarbon stream to hydrogen and coke. Preferred catalysts are, of course, types which are capable of withstanding high conversion and regeneration temperatures inY la continuous moving particle system where temperatureY may reach the order of 1800 F., or slightly higher. Refractory catalyst base materials which may be used `are alumina, silica-alumina, or silica-magnesia, with an oxide off zirconium, titanium, yand the like, or alternatively, one or more of the foregoing oxides with an oxide of chromium, molybdenum, vanadium, etc. yPreferably one or more metals or metal oxides of Group VIII of the Periodic Table are utilized to provide optimum hydrogen formation. rIhus, nickel, iron, or cobalt compounds are advantageously used with a refractory base material, such as silica-alumina. Also, in view of the catalytic effect necessary in the regeneration zone to ycontrol heat release and the CO to CO2 ratio gasifying carbon from the catalyst particles, the catalyst is necessarily of a type which resists oxidation by CO2 and readily reducible. The size of the catalyst particles will vary in accordance with the conversion system used, but for a lluidized operation the particle size will generally be between 0.01 rand 0.8 millimeter in diameter such that the particle may be readily fluidized and passed from one zone to another.

In accordance with the present invention, the control of the heat release per mole of hydrocarbon converted and/ or per mole of carbon gasiiedy is regulated in the regeneration zone by varying the oxygen addition thereto within a range of about 50% to 100% of the theoretical amount of oxygen to gasify all of the carbon on the. catalyst, with such control being inversely responsive to the carbon level maintained on the catalyst particles that recirculate from the regenerator to the reactor and a direct variation of the CO2 to CO ratio produced in the regeneration zone. The temperature of the catalyst particles themselves, by reason of absorbed heat from the regeneration zone, are in turn regulated and controlled responsive to the ratio of carbon dioxide to carbon monoxide which is effected within the regeneration zone, for a given catalyst circulation rate and/or for a substantially constant carbon gasication rate and uniform tiue gas temperature from the regeneration zone. For example, as will be noted from FIGURE 2 of the drawing, it has been found when using one type of catalyst in a uidized system operating at a constant carbon gasification rate, that for different carbon levels on the catalyst particles above about 0.5% by weight of the catalyst, and more particularly above about 1% of carbon by weight of the catalyst, there is a fairly straight line variation existing between carbon level and the percent of carbon dioxide made with respect to total carbon oxides produced.

In a series of test operations, a natural gas stream, containing about 85% methane, was decomposed at an elevated temperature, in the presence of a catalyst prepared by impregnating 5% nickel on stabilizedv silica-alumina cracking catalyst, to provide hydrogen and carbon, and the regenerator was operated such that there was a substantially constant carbon gasification rate maintained, with a substantially constant temperature in the light phase zone of the regenerator at a temperature of about l265 F. to about 1275 F., as well as a fairly constant rate of circulation for the catalyst particles being maintained between zones. The results of the regeneration operations are tabulated in the following Table I, with the different carbon levels being shown as percent of carbon, by weight, on the regenerated catalyst as returned to the reaction zone, and the amounts of carbon dioxide and carbon monoxide being shown as percentages of the iiue gas stream. The lower line of the Table I provides a resulting ligure indicating the percent of CO2 with respect to the total CO and CO2 content in the flue gas.

reaction zone, there may be continuous or intermittent carbon level measurements and a control of carbon levels responsive to such measurements. In other words, where the circulation rate of catalyst is maintained at a substantially high level and it is desired to increase the heat level in the system, with temperature increases in the reaction zone and regeneration zone, without further increasing the catalyst circulation rate, or carbon gasification rate (for example, by reason of an ambient temperature drop and an increased heat loss from the unit, or perhaps by reason of a feed preheat failure), then the air or oxygen containing stream to the regenerator may be adjusted to temporarily gasify a greater amount of carbon and provide a lower level of carbon on the regenerated catalyst particles and in addition effect a greater burning of CO to CO2. In actual practice this adjustment may require a temporary modification in the air introduction rate to the regeneration zone which substantially increases the oxygen requirements in the regenerator in order to effect rapid gasication of carbon to carbon oxides and to provide the desired lower level of carbon. However, such adjustment will be followed by a cut-back in oxygen introduction to a level which effects a continu ous only slightly increased quantity of air or oxygen that will maintain the increased conversion of CO to CO2. Stated another Way, after the regeneration has once been leveled off to provide a greater CO2 production, then the air may be adjusted to provide a less than stoichiometric or theoretical amount of oxygen which will maintain a substantially constant carbon gasification rate and desired levels of CO and CO2 formation, such adjustment in turn providing a higher temperature level in the regeneration zone and on the regenerated catalyst, with a resulting higher heat input into the reaction zone.

In the reverse situation, where a lesser heat release is desired inthe conversion system (for example, by reason of a reduction in heat losses, or an increased atmospheric temperature), then the regeneration step may be adjusted and controlled to provide a greater CO to CO2 ratio and a carbon level on the regenerated catalyst which is somewhat above that which had been prevailing. In

Table I RunNo 1 2 3 4 5 6 7 siglio 11 Percent Carbon on Regenerated Catalyst 3.27 3.81 2.08 1.79 1.60 1.14 0.94 0.72 0.57 0.45 0.41 Percent C02 in Fine Gas 7.3 8.4 10.1 9.6 0.5 10.3 9.7 10.7 6.5 13.7 13.6 Percent G0 in mue Gas..

15.8 10.1 15.1 11.7 11.0 10.0 10.5 9.1 4.7 4.3 2.4 Percent Cog/Co-j-Coi 31.5 34.3 40.1 45.0 40.5 50.7 43.0 54.3 58.0 70.2 85.0

A plotting of the percent of COZ/CO-l-COZ against the other words, the air and oxygen input to the regeneration respective percentages of carbon depositions is indicated zone is lessened to permit a decreased carbon dioxide in FIGURE 2 of the drawing, together with a resulting production and increased carbon monoxide production curve determined from the plotted points. As indicated, in accordance with catalytically initiated conversion of where the carbon level is held below about 0.5% by rea- CDTi-Ce 2CO, while at the same time there is a resulting son of the regeneration operation, then the CO2 to CO controlled higher level of carbon content on the reratio rises rapidly with the result that considerable heat generated catalyst particles leaving the regeneration zone release may be generated from the CO to the CO2 confor the reaction zone. In all cases, in view of the relaversion. Thus, when the carbon gasification is being tionship which exists, and which is shown in FIGURE 2 held substantially constant there is necessarily a resulting of the drawing, the heat release from carbon gasification, increase in the absorbed heat on the catalyst particles CO2 to CO production, and resulting temperature levels leaving the regenerator, to in turn provide for the reon the catalyst, may be regulated and controlled inversely circulation of higher temperature catalyst to the reaction responsive to measurements of the carbon level on the zone for a greater heat input thereto for a constant circuregenerated catalyst particles. lation rate. For carbon levels above about 0.5% there In still other instances, there may be intermittent is a fairly constant variation in the carbon dioxide pro changes in feed composition, such that it is necessary to duction, the latter decreasing as the carbon level increases, gasify varying quantities of carbon in the regeneration or vice versa, where higher carbon levels are maintained Zone. For example, with a feed stream which is primarily there is a decreasing CO2 production, with the accompany- 70 methane and there is an increase in the ethane content, ing result that there is necessarily a lesser heat release there will be a resulting increase in carbon production on within the regeneration zone than when there is a greater the catalyst and a higher carbon gasification rate needed degree of oxidation of CO to CO2. in the regeneration zone without any substantial increase In effecting the control of the regeneration step, and in heat requirements within the reaction zone. With a in turn the conversion of hydrocarbon to hydrogen in the substantially constant carbon gasification rate there is eifected a production of more CO and a lesser quantity of CO2. This may in turn be accomplished by a4 slight reduction in the air feed to the regeneration zone and slight increase in carbon level held on` the recirculating catalyst.

As a result of pilot plant test operations, where a natural gas feed stream isA utilized at a charge rate of about 4000 s.c.f. per day in. a iiuid system. containing a silica-alumina cracking catalyst base impregnated with approximately nickel, by weight of the composite, there was obtained the accompanying data set forth in Table II. It should be noted that the pilot unit used was designed so that it could operate in a non-adiabatic manner with the rate of heat loss being controlled.

Table 1I Operating Conditions Low C O/ C O2 atio High CO/COz Ratio Reactor Temperature 1, 550 Fd: Regenerator Temperature. 1,60 Fd; Catalyst Circulation Rate (1b. of cab/lb.

of C g/1 Reactor Gas Reactor Charge Gas Component 30 Hydrogen Methane Carbon Dioxide 2. 4 12. 3

It will be noted in Table II that the hydrogen production is substantially the same for both the high and low CO to CO2 ratio operations and that the CO2 production is higher in the low ratio column, in turn indicating that a greater amount of heat was generated and removed from the unit in the latter operation in order to hold the substantially equivalent temperatures in both the reactor and regenerator for the two runs.

It may also be noted that the carbon level on the catalyst utilized in the test runs of Table II are less than those of Table I, however, as indicated hereinbefore, carbon levels may well be less than about 0.5% for certain catalysts, 0r for certain processing arrangements.

lthough it is generally found preferable and safer to hold a carbon level which will assist in preventing catalyst passing to the reactor in an oxidized state.

In a continuously operating system, carbon measurements may be made from continuously operating sampling means or from samples obtained by the use of systematic periodic withdrawal means. Actual carbon content measurements may be carried out by in turn measuring quantities, removed when burning the carbon to substantially complete removal, or by other conventional means. It is not intended to limit the present invention and control to the use of any one means for measuring carbon contents, or to the measurement of CO2 to CO ratios, where such measurements are taken. Further, it should be noted that the present drawing and description indicates a fluidized catalyst operation, but that a continuous system may embody a moving bed or fluidized catalyst lift operation. Still further, a system of fixed bed reactor chambers with one or more of such chambers being regenerated continuously in a switch procedure may also be utilized and it is not intended to limit the invention to the embodiment of the drawing.

I claim as my invention:

l. In a processing systemfor catalytically converting a normally gaseous hydrocarbon charge stream tov hydrogen and carbon wherein subdivided catalyst` particles are contacted in a reaction zone by the hydrocarbon charge stream at decomposition conditions, resulting carbonized catalyst particles are subsequently contacted within a regeneration zone by an oxygen containing stream being introduced thereto to effect the gasification of carbon from said particlesl and such contacted catalyst particles in turn carry heat into the reaction zone, the improved method of operation to provide variations in the heat release per mole of carbon gasitied in thel regeneration zone for a given carbon gasication rate, which comprises, varying the oxygen introduction rate to the regeneration zone within a range below the theroretical required to gasify all of the carbon on the catalyst particles to carbon dioxide, thereby varying the carbon level on the catalyst particles, and varying said heat release per mole of carbon gasied inversely responsive to the carbon level retained on the` catalyst particles and directly responsive to the carbon dioxide to carbon monoxide ratio produced in the regeneration zone.

2. In a processing system for catalytically converting a normally gaseous hydrocarbon charge stream to hydrogen and carbon wherein subdivided catalyst particles are contacted in a reaction zone by the hydrocarbon charge stream at decomposition conditions, resulting carbonized particles are contacted in a regeneration zone by an oxygen containing stream being introduced thereto to effect the gasiiication of carbon from said particles and such contacted catalyst particles in turn carry heat into the reaction zone, the improved method of operation to provide variations in the heat release per mole of carbon gasied, which comprises, varying the oxygen addition to the regeneration zone between an amount which is less than the theoretical required to gasify the carbon deposition on the catalyst particles to carbon dioxide and an amount which is greater than 50% of such theoretical amount, thereby varying the carbon level on the catalyst particles, and varying said heat release per mole of carbon gasified inversely responsive to the carbon level retained on the catalyst particles and directly responsive to the ratio of carbon dioxide to total carbon oxides produced in the regeneration zone.

3. In a processing system for catalytically converting a normally gaseous hydrocarbon charge stream to hydrogen and carbon wherein subdivided catalyst particles are contacted in a reaction zone by the hydrocarbon charge stream at decomposition conditions, resulting carbonized particles are contacted in a regeneration zone by an oxygen containing stream being introduced thereto to effect the gasification of carbon from said particles and such contacted catalyst particles in turn carry heat into the reaction zone, the improved method of operation to provide variations in the heat release per mole of carbon gasified, which comprises, increasing the quantity of oxygen supplied to the regeneration zone while maintaining total oxygen addition thereto at less than the theoretical required to completely gasify all of the carbon from the catalyst particles to carbon dioxide and controlling said heat release per mole of carbon gasiied in response to the resultant decreased level of carbon maintained on said catalyst particles and increase in the ratio of carbon dioxide to total carbon oxides being produced in said regeneration zone.

4. In a processing system for catalytically converting a normally gaseous hydrocarbon charge stream to hydrogen and carbon wherein subdivided catalyst particles are contacted in a reaction zone by the hydrocarbon charge stream at decomposition conditions, resulting carbonized particles are contacted in a regeneration zone by an oxygen containing stream being introduced thereto to effect the gasification of carbon from said particles and such contacted catalyst particles in turn carry heat into the reaction zone, the improved method of operation to provide variations in the heat release per mole of carbon gasiied, which comprises, decreasing the quantity of oxygen supplied to said regeneration zone while maintaining total oxygen addition thereto at less than the theoretical required to completely gasify all of the carbon from the catalyst particles to carbon dioxide and controlling said heat release per mole of carbon gasied in response to the resultant increased level of carbon maintained on said catalyst particles recirculating to said reaction zone and decrease in the ratio of carbon dioxide to total carbon oxides being produced within said regeneration zone.

5. In a processing system for catalytically converting a normally gaseous hydrocarbon charge stream to hydrogen and carbon wherein subdivided catalyst particles are contacted in a reaction zone by the hydrocarbon charge stream at decomposition conditions, resulting carbonized partiales are contacted in a regeneration zone by an oxygen containing stream being introduced thereto to efIect the gasification of carbon from said particles and such contacted catalyst particles in turn carry heat into the reaction zone, the improved method of operation providing variations in the heat release in said system for a given carbon gasification rate While precluding the discharge of free oxygen from the regeneration zone, which comprises, measuring the level of carbon deposition on said catalyst recirculating from the regeneration zone to the reaction zone, controllably changing the carbon level 0n the catalyst particles carrying heat to the reaction zone by inversely modifying the rate of oxygen supply to said regeneration zone in the range of from 50% of theoretical to the full threoretical amount required to gasify all of the carbon deposition to carbon dioxide and effecting a controlled change in the ratio of carbon dioxide to total carbon oxides produced in the regeneration zone directly responsive to such oxygen supply variations, whereby to provide desired corresponding directly responsive changes in the heat release rate within said regeneration zone, with such heat release rate changes being effected inversely responsive to carbon level measurements on said catalyst leaving the regeneration zone.

References Cited in the tile of this patent UNITED STATES PATENTS 2,391,327 Mekler Dec. 18, 1945 2,436,041 Gerhold et al. Feb. 17, 1948 2,449,635 Barr Sept. 21, 1948 2,601,676 Trainer et al. June 24, 1952 2,753,246 Shields et al. July 3, 1956

Claims

1. IN A PROCESSING SYSTEM FOR CATALYTICALLY CONVERTING A NORMALLY GASEOUS HYDROCARBON CHARGE STREAM TO HYDROGEN AND CARBON WHEREIN SUBDIVIDED CATALYST PARTICLES ARE CONTACTED IN A REACTION ZONE BY THE HYDROCARBON CHARGE STREAM AT DECOMPOSITION CONDITIONS, RESULTING CARBONIZED CATALYST PARTICLES ARE SUBSEQUENTLY CONTACTED WITHIN A REGENERATION ZONE BY AN OXYGEN CONTAINING STREAM BEING INTRODUCED THERETO TO EFFECT THE GASIFICATION OF CARBON FROM SAID PARTICLES AND SUCH CONTACTED CATALYST PARTICLES IN TURN CARRY HEAT INTO THE REACTION ZONE, THE IMPROVED METHOD OF OPERATION TO PROVIDE VARIATIONS IN THE HEAT RELEASE PER MOLE OF CARBON GASIFIED IN THE REGENERATION ZONE FOR A GIVEN CARBON GASIFICATION RATE, WHICH COMPRISES, VARYING THE OXYGEN INTRODUCTION RATE TO THE REGENERATION ZONE WITHIN A RANGE BELOW THE THERORETICAL REQUIRED TO GASIFY ALL OF THE CARBON ON THE CATALYST PARTICLES TO CARBON DIOXIDE, THEREBY VARYING THE CARBON LEVEL ON THE CATALYST PARTICLES, AND VARYING SAID HEAT RELEASE PER MOLE OF CARBON GASIFIED INVERSELY RESPONSIVE TO THE CARBON LEVEL RETAINED ON THE CATALYST PARTICLES AND DIRECTLY RESPONSIVE TO THE CARBON DIOXIDE TO CARBON MONOXIDE RATIO PRODUCED IN THE REGENERATION ZONE.