Patent Publication Number: US-2023133426-A1

Title: Process and apparatus for reacting feed with cooled regenerated catalyst

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional Application No. 63/274,936, filed Nov. 2, 2021, which is incorporated herein in its entirety. 
    
    
     FIELD 
     The field is the reaction of feed with fluid catalyst. The field may particularly relate to reacting a feed with a fluid catalyst to catalyze an endothermic reaction. 
     BACKGROUND 
     Light olefin production is vital to the production of sufficient plastics to meet worldwide demand. Paraffin dehydrogenation (PDH) is a process in which light paraffins such as ethane and propane can be dehydrogenated to make ethylene and propylene, respectively. Dehydrogenation is an endothermic reaction which requires external heat to drive the reaction to completion. Fluid catalytic cracking (FCC) is another endothermic process which produces substantial ethylene and propylene. 
     Dehydrogenation catalyst may incorporate a dehydrogenation metal such as gallium with a molecular sieve or an amorphous material. The catalyst must be sufficiently robust and appropriately sized to be able to resist the attrition expected in a fluidized system. FCC catalyst is typically a Y zeolite with an optional MFI zeolite to boost propylene production. 
     In PDH and FCC reactions with fluidized catalyst, coke can deposit on the catalyst while catalyzing the reaction. The catalyst may be regenerated in a catalyst regenerator by combusting coke from the catalyst in the presence of oxygen. In some cases, addition fuel may be combusted in the regenerator to increase the temperature of the regenerated catalyst. The hot regenerated catalyst may then be transferred back to the reactor to catalyze the reaction. If insufficient heat is provided to drive the endothermic reaction, the conversion to desired products will be lower than desired. The extent of conversion therefore relies on the amount of heat introduced to the reaction. 
     For a given temperature in the regenerator, additional heat can be provided to the reaction through increased catalyst circulation. Alternatively, at a given catalyst circulation rate, additional heat can be provided by increasing the temperature of regenerated catalyst. Increased regeneration temperature may be favored to increase the activity of the regenerated catalyst and to lower the cost associated with regeneration by minimizing regenerator catalyst inventory and minimizing excess air requirements. The drawback of increased regeneration temperature is however that contacting feed with regenerated catalyst at higher temperature leads to additional thermal cracking reactions. Catalytic reactions are more selective to the desired products than thermal cracking reactions. Care must be taken to maximize catalytic reactions over thermal cracking reactions. Another drawback of higher regenerated catalyst temperature is that the lower circulation rate increases the residence time of catalyst in the reactor, as the catalyst inventory in the reactor is remains the same. Longer reactor residence time leads to increased catalyst deactivation. 
     There is a need, therefore, for improved methods to permit regeneration at higher temperature will minimizing undesirable cracking reactions and longer catalyst residence times in the reactor. 
     BRIEF SUMMARY 
     A reactant stream is contacted with a cooled regenerated catalyst stream to produce a product gas stream. Spent catalyst is regenerated and cooled before it is passed into the regenerator. The cooled regenerated catalyst stream enters the regenerator at a lower temperature than a temperature of the hot regenerated catalyst stream. Cooling of catalyst enables the catalyst residence time in the reactor to be operated independently of the regenerator temperature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic drawing of a process and apparatus of the present disclosure; 
         FIG.  2    is a schematic drawing of a process and apparatus of an alternative embodiment of  FIG.  1   ; 
         FIG.  3    is a schematic drawing of a process and apparatus of an additional alternative embodiment of  FIG.  1   ; 
         FIG.  4    is a schematic drawing of a process and apparatus of a further alternative embodiment of  FIG.  1   ; and 
         FIG.  5    is a plot of propane conversion in a dehydrogenation reaction vs. time on stream in the reactor for examples utilizing four different regeneration temperatures. 
     
    
    
     DEFINITIONS 
     The term “communication” means that fluid flow is operatively permitted between enumerated components, which may be characterized as “fluid communication”. 
     The term “downstream communication” means that at least a portion of fluid flowing to the subject in downstream communication may operatively flow from the object with which it fluidly communicates. 
     The term “upstream communication” means that at least a portion of the fluid flowing from the subject in upstream communication may operatively flow to the object with which it fluidly communicates. 
     The term “direct communication” means that fluid flow from the upstream component enters the downstream component without passing through any other intervening vessel. 
     The term “indirect communication” means that fluid flow from the upstream component enters the downstream component after passing through an intervening vessel. 
     The term “bypass” means that the object is out of downstream communication with a bypassing subject at least to the extent of bypassing. 
     As used herein, the term “predominant” or “predominate” means greater than 50%, suitably greater than 75% and preferably greater than 90%. 
     DETAILED DESCRIPTION 
     Catalyst residence time in a catalytic reactor can be an important parameter for determining catalyst deactivation. Catalyst residence time in a catalytic reactor is determined by Equation 1: 
         Tr   cat   =W   cat   /F   cat   (1)
 
     where Tr cat  is the catalyst residence time, W cat  is the mass of catalyst in the reactor and F cat  is the mass flow rate of circulated catalyst. Weight hourly space velocity (WHSV) in a reactor is determined by Equation 2: 
       WHSV= F   f   /W   cat   (2)
 
     where F f  is the mass flow rate of feed to the reactor. Combining Equations 1 and 2 into Equation 3 provides the relationship between Tr cat  and WHSV: 
     
       
         
           
             
               
                 
                   
                     Tr 
                     cat 
                   
                   = 
                   
                     
                       F 
                       f 
                     
                     
                       
                         F 
                         cat 
                       
                       * 
                       WHSV 
                     
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
     Consequently, Tr cat  is dependent on F cat  and WHSV required for the reaction. 
     The heat supplied to the reactor is given by Equation 4: 
         Q   rxn   =F   cat   *C   p *( T   regen   −T   rxtr )  (4)
 
     where Q rxn  is the heat supplied to the reactor, C p  is the specific heat constant of the catalyst, T regen  is the temperature of the regenerator and T rxtr  is the temperature of the reactor. Rearranging Equation 4 yields Equation 5: 
     
       
         
           
             
               
                 
                   
                     F 
                     cat 
                   
                   = 
                   
                     
                       Q 
                       rxn 
                     
                     
                       Cp 
                       * 
                       
                         ( 
                         
                           
                             T 
                             regen 
                           
                           - 
                           
                             T 
                             rxtr 
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
     Combining Equations 3 and 5 provides Equation 6: 
     
       
         
           
             
               
                 
                   
                     Tr 
                     cat 
                   
                   = 
                   
                     
                       
                         F 
                         f 
                       
                       * 
                       Cp 
                       * 
                       
                         ( 
                         
                           
                             T 
                             regen 
                           
                           - 
                           
                             T 
                             rxtr 
                           
                         
                         ) 
                       
                     
                     
                       
                         Q 
                         rxn 
                       
                       * 
                       WHSV 
                     
                   
                 
               
               
                 
                   ( 
                   6 
                   ) 
                 
               
             
           
         
       
     
     Consequently, catalyst residence time, Tr cat , depends on the heat requirements of the reaction, Q rxn , and the temperature difference between the reactor and the regenerator, T regen −T rxtr . Thus, one cannot select a catalyst residence time in the reactor independently of the regenerator temperature. 
     Catalyst deactivation in the reactor is dependent on catalyst residence time in the reactor. Catalyst activity falls over time in the reactor as the catalyst accumulates coke and/or the catalyst is deactivated by the deactivating atmosphere in the reactor. For example, for propane dehydrogenation, the catalyst is deactivated both by coke blocking active sites and by exposure to reducing conditions in the reactor. In FCC, catalyst is deactivated by coke blocking active sites. The objective is to select an acceptable catalyst residence time in the reactor independent of other constraints. 
     Catalyst regeneration is governed by the regeneration conditions. The regeneration temperature, T regen , is a key variable. One would generally seek a regeneration temperature as high as practical to favor complete regeneration of the catalyst and, if needed, to promote the rapid burning of the optional fuel gas supplemented to the regenerator to increase enthalpy. As the regeneration temperature is increased, the required catalyst circulation rate to supply heat to the reactor decreases. The effect is increased residence time in the reactor and resulting lower catalyst activity due to catalyst deactivation in the reactor over time-on-stream. We have found the key to independently selecting an acceptable catalyst residence time in the reactor is the capability to decouple the catalyst circulation rate from the temperature in the regenerator, T rxtr . 
     We have discovered a way to decouple the catalyst residence time in the reactor from the regeneration temperature. The process and apparatus can operate both with a short reactor catalyst residence time and with high temperature in the regenerator at a fixed space velocity and constant conversion. The process and apparatus achieve the desired effect by cooling the regenerated catalyst before it is fed to the reactor. In order to be practical, the heat recovered from cooling of the regenerated catalyst should be recovered for use in the process. Most favorably, the heat should be recovered so as to have a minimal impact on the fuel requirement for the regenerator. 
     The teachings herein may be applicable to any process that requires catalyst to be regenerated to provide heat to drive an endothermic catalytic reaction. Cooling of catalyst for an exothermic reactor is well known; however, the invention here demonstrates the surprising benefit of cooling catalyst for a reactor that houses an endothermic reaction. Paraffin dehydrogenation (PDH) and fluid catalytic cracking (FCC) are examples of endothermic processes. FCC catalyst is used to crack larger hydrocarbon molecules to smaller hydrocarbon molecules at around atmospheric pressure and about 427° C. (800° F.) to 538° C. (1000° F.) and a catalyst to oil ratio of about 5 to about 30. PDH catalyst is used in a dehydrogenation reaction process to catalyze the dehydrogenation of paraffins, such as ethane, propane, iso-butane, and n-butane, to olefins, such as ethylene, propylene, isobutene and n-butenes, respectively. The PDH process will be described exemplarily to illustrate the disclosed apparatus and process. 
     The conditions in the dehydrogenation reactor may include a temperature of about 500 to about 800° C., a pressure of about 40 to about 310 kPa and a catalyst to oil ratio of about 5 to about 100. The dehydrogenation reaction may be conducted in a fluidized manner such that gas, which may comprise the reactant paraffins with or without a fluidizing inert gas, is distributed to the reactor in a way that lifts the dehydrogenation catalyst in the reactor vessel while catalyzing the dehydrogenation of paraffins. During the catalytic dehydrogenation reaction, coke is deposited on the dehydrogenation catalyst leading to reduction of the activity of the catalyst. The dehydrogenation catalyst must then be regenerated. 
     An exemplary PDH reactor  10  is shown in  FIG.  1   . The PDH reactor  10  may comprise two chambers, a reaction chamber  14  and a separation chamber  16 . A feed line  8  may charge a reactant stream of feed to the reactor  10 . The reactant stream may predominantly comprise propane or butane, but other paraffins such as ethane may be present in the reactant stream in conjunction with or to the exclusion of other paraffins. Any feed distributor can distribute the reactant stream to the reactor  10 . A domed reactant distributor  20  may be utilized in the reaction chamber  14  of the reactor  10 . The domed reactant distributor  20  receives a gaseous reactant stream and distributes the reactant stream through nozzles in the top dome of the domed reactant distributor  20  to distribute the reactant stream across the entire cross section of the reaction chamber  14 . It is envisioned that other fluidizing gases may be used to also promote fluidization in the reaction chamber  14 . In an embodiment, the distributed reactant stream ascends in the reaction chamber  14  and the reactor  10 . 
     A recycle catalyst pipe  22  has an inlet end  21  located in the separation chamber  16  and an outlet comprising a first catalyst inlet  23  which in an embodiment may be connected to the reaction chamber  14 . The recycle catalyst pipe  22  passes a first stream of recycled spent catalyst that has not undergone regeneration from the separation chamber  16  through the outlet and the first catalyst inlet  23  to the reaction chamber  14  in an embodiment. The first catalyst inlet  23  provides spent catalyst to the reaction chamber  14 . The recycled spent catalyst is fed to the reactor  10  through the first catalyst inlet  23  which is the outlet of the recycle catalyst pipe  22 . The first catalyst inlet  23  may be contained in the first reaction chamber  14 . 
     A second catalyst inlet  25  delivers a second catalyst stream to the reactor  10 . A regenerated catalyst pipe  26  has an inlet  27  in upstream communication with the second catalyst inlet  25 . An inlet end of the regenerated catalyst pipe  26  is connected to the regenerator  60 . The regenerated catalyst pipe  26  passes a second stream of regenerated catalyst from a regenerator  60  to the second catalyst inlet  25 . The regenerated catalyst pipe may be in downstream communication with the regenerator  60 . The second catalyst inlet  25  is contained in and provides regenerated catalyst to the reaction chamber  14 . The reactant stream is contacted with the second catalyst stream and the first catalyst stream in the reaction chamber  14 . The second catalyst inlet  25  may be spaced apart and may be above the first catalyst inlet  23 . 
     In the reaction chamber  14  the reactant stream is contacted with the second stream of catalyst and the first stream of catalyst which mix together, and the reactant paraffins undergo endothermic conversion to olefins, typically propane to propylene. The reactant stream and the first stream of catalyst and the second stream of catalyst rise in the reaction chamber  14  of the reactor  10  impelled by the reactant stream continually entering the reactor. 
     At an interface  28 , the fluid dynamics transition from a dense phase of catalyst below the transition to a fast-fluidized flow regime. The catalyst density in the dense phase of catalyst is at least 200 kg/m 3  (12.5 lb/ft 3 ); whereas the catalyst density in the fast-fluidized flow regime is at least 100 kg/m 3  (6.3 lb/ft 3 ). The superficial velocity of the reactant stream and the first stream of catalyst and the second stream of catalyst in the reaction chamber  14  will typically be at least about 0.9 m/s (3 ft/s), suitably at least about 1.1 m/s (3.5 ft/s), preferably at least 1.4 m/s (4.5 ft/s), to about 2.1 m/s (7 ft/s) to provide the fast-fluidized flow regime. Reactant gas and catalyst ascend in a fast-fluidized flow regime in which catalyst may slip relative to the gas and the gas can take indirect upward trajectories. 
     The dehydrogenation catalyst selected should minimize cracking reactions and favor dehydrogenation reactions. Suitable catalysts for use herein include an active metal which may be dispersed in a porous inorganic carrier material such as silica, alumina, silica alumina, zirconia, or clay. An exemplary embodiment of a catalyst includes alumina or silica-alumina containing gallium, a noble metal, and an alkali or alkaline earth metal. 
     The catalyst support comprises a carrier material, a binder and an optional filler material to provide physical strength and integrity. The carrier material may include alumina or silica-alumina. Silica sol or alumina sol may be used as the binder. The alumina or silica-alumina generally contains alumina of gamma, theta and/or delta phases. The catalyst support particles may have a nominal diameter of about 20 to about 200 micrometers with the average diameter of about 50 to about 150 micrometers. Preferably, the surface area of the catalyst support is 85-140 m 2 /g. 
     The dehydrogenation catalyst may comprise a dehydrogenation metal on a support. The dehydrogenation metal may be a one or a combination of transition metals. A noble metal may be a preferred dehydrogenation metal such as platinum or palladium. Gallium is an effective metal for paraffin dehydrogenation. Metals may be deposited on the catalyst support by impregnation or other suitable methods or included in the carrier material or binder during catalyst preparation. 
     The acid function of the catalyst should be minimized to prevent cracking and favor dehydrogenation. Alkali metals and alkaline earth metals may also be included in the catalyst to attenuate the acidity of the catalyst. Rare earth metals may be included in the catalyst to control the activity of the catalyst. Concentrations of 0.001% to 10 wt % metals may be incorporated into the catalyst. In the case of the noble metals, it is preferred to use about 10 parts per million (ppm) by weight to about 600 ppm by weight noble metal. More preferably it is preferred to use 10-100 ppm by weight noble metal. The preferred noble metal is platinum. Gallium should be present in the range of 0.3 wt % to about 3 wt %, preferably about 0.5 wt % to about 2 wt %. Alkali and alkaline earth metals are present in the range of about 0.05 wt % to about 1 wt %. 
     The reactant stream lifts the first stream of catalyst mixed with the second stream of catalyst upwardly in the reaction chamber while paraffins convert to olefins in the presence of the dehydrogenation catalyst which gradually becomes spent catalyst attributed to the agglomeration of coke deposits on the catalyst. A fluidizing inert gas may be distributed to the reaction chamber to assist in lifting the mixture of catalyst and reactants upwardly in the reaction chamber  14 . The reactant gases convert to product gases while ascending in the reaction chamber  14 . The blend of gases and catalyst ascend from the reaction chamber  14  through a frustoconical transition section  30  into a transport riser  32  which has a smaller diameter than the diameter of the reaction chamber  14 . A blend of gases and catalyst accelerate in the narrower transport riser  32  and are discharged from a primary catalyst separator  34  into the separation chamber  16 . The primary catalyst separator  34  may be a riser termination device that utilizes horizontal, centripetal acceleration to separate spent catalyst from product gas. Arcuate ducts of the primary catalyst separator  34  direct the mixture of product gas and catalyst to exit from the riser  32  in a typically horizontally angular direction to centripetally accelerate causing the denser catalyst to gravitate outwardly. The catalyst loses angular momentum and falls into a lower catalyst bed  36  depicted with an upper interphase. The lighter gases ascend in the separation chamber  16  and enter into cyclones  38 ,  40 . The cyclones  38 ,  40  may comprise first and second cyclonic stages of separation to further remove catalyst from product gases. The product gas is ducted to a plenum  42  from which it is discharged from the reactor  10  through a product outlet  44  in a product line. The superficial gas velocity in the transport riser  32  will be about 12 m/s (40 ft/s) to about 20 m/s (70 ft/s) and have a density of about 64 kg/m 3  (4 lb/ft 3 ) to about 160 kg/m 3  (10 lb/ft 3 ), constituting a dilute catalyst phase. 
     Catalyst separated from the product gas by the primary catalyst separator  34  drops into the dense catalyst bed  36 . In an aspect, primary cyclones  38  may collect product gas from the separation chamber  16  and transport the product gas separated from catalyst to a secondary cyclone  40  to further separate catalyst from the product gas before directing secondarily purified product gas to the plenum  42 . Catalyst separated from product gas in the cyclones  38 ,  40  is dispensed by dip legs into the dense catalyst bed  36 . At this point, the separated catalyst in the separation chamber  16  is considered spent catalyst because deposits of coke are agglomerated thereon. A spent catalyst stream taken from the spent catalyst collected in the dense bed  36  in the separation chamber  16  is transported in a spent catalyst pipe  18  to a catalyst regenerator  60  to have coke burned from the catalyst to regenerate and heat the dehydrogenation catalyst. 
     A recycle catalyst stream is taken from the spent catalyst collected in the dense bed  36  of the separation chamber  16  and enters the recycle catalyst pipe  22  through an inlet  21 . The recycle catalyst stream of the spent catalyst is recycled in the recycle catalyst pipe  22  back to the first catalyst inlet  23  in the reaction chamber  14  of the reactor  10 . The recycle catalyst stream of the spent catalyst is not regenerated before it returns to the reaction chamber  14 . 
     The separation chamber  16  may include a disengagement can  46  that surrounds the upper end of the riser  32  and the primary separator  34 . A vertical wall  47  of the disengagement can  46  is spaced apart from a shell  48  of the separation chamber to define an annulus  49 . Dip legs of the cyclones  38  and  40  may be located in the annulus  49 . The disengagement can  46  serves to limit travel of the product gas exiting the primary separator  34 , so as to reduce its time in the reactor  10 , thereby mitigating unselective cracking reactions to undesired products. The top of the disengagement can  46  may be hemispherical and feed a gas recovery conduit  50  that transports product gases to ducts  52  that are directly ducted or connected to the primary cyclones  38 . The direct ducting from the disengagement can  46  to the primary cyclones  38  also prevents product gas from getting loose in the larger volume of the reactor vessel where excessive residence time may occur to permit unselective cracking. Windows in the lower section of the wall  48  of the disengagement can  46  permit catalyst in the disengagement to enter into the recycle catalyst pipe  22  or the regeneration pipe  18 . A quench fluid such as condensed product liquid, cooled recycled gas, or even cool catalyst may be injected into the product gases through a quench nozzle  54  to cool the product gases to below cracking temperature to limit unselective cracking. Quench fluid is advantageously injected into the gas recovery conduit  50  which directs the separated product gas to a narrowed location. The gas recovery conduit  50  is in downstream communication with primary catalyst separator  34  which separates the predominance of the spent catalyst from the product gases. The primarily separated spent catalyst bypasses quenching to retain heat in the catalyst. The product gases separated from the predominance of the catalyst subjects a reduced mass of material to quenching thereby requiring less quench fluid to achieve sufficient cooling to reduce the temperature of product gas to below cracking temperature. 
     The spent catalyst is transported to the catalyst regenerator vessel  60  to regenerate the spent catalyst into regenerated catalyst and to combust the coke if present. The catalyst regenerator vessel  60  includes a combustion chamber  62 , which may be a lower chamber, and a separation chamber  64 , which may be an upper chamber. The combustion chamber  62  may include a mixing chamber  66  which mixes streams of catalyst and distributes gases to the catalyst. In the separation chamber  64 , the regenerated catalyst is separated from flue gas generated in the combustion chamber  62 . 
     In an exemplary embodiment, the regenerator vessel  60  includes a mixing chamber  66 . The mixing chamber  66  may be located at a lower end of the of the combustion chamber  62  and the regenerator vessel  60 . The mixing chamber  66  may be connected to an outlet end  19  of a spent catalyst pipe  18  which serves as an inlet for the mixing chamber. The spent catalyst standpipe  18  transports spent catalyst from the dehydrogenation reactor  10  to the catalyst regenerator vessel  60  through a control valve. In some cases, the spent catalyst standpipe  18  may transport catalyst to the regenerator vessel  60  via a spent catalyst stripper (not shown). The mixing chamber  66  may also include a regenerated catalyst pipe inlet  67  from a regenerated catalyst standpipe  68  which serves as an outlet for the regenerated catalyst pipe. Heated regenerated catalyst from the separation chamber  64  may be transported back to the catalyst regenerator vessel  60  through a recycle regenerated catalyst pipe  68  through a control valve to further heat catalyst in the regenerator vessel  60  by contact with hot regenerated catalyst. 
     The outlet end  19  of the spent catalyst pipe discharges a stream of spent catalyst from a spent catalyst standpipe  18  into the mixing chamber  66 , and the regenerated catalyst pipe inlet  67  discharges the recycled portion of regenerated catalyst from the regenerated catalyst pipe  68  into the mixing chamber  66 . The mixing chamber  66  receives a stream of spent catalyst and a stream of hot regenerated catalyst and mixes them together to provide a mixture of catalyst. While mixing, the hotter regenerated catalyst heats the cooler spent catalyst which serves to provide a heated catalyst mixture. 
     A mixing baffle  70  may be positioned within the mixing chamber  66  in an embodiment, to facilitate mixing between the spent catalyst and the regenerated catalyst. The mixing baffle  70  may comprise a capped cylinder with openings opposed to catalyst inlets  19  or  67 . 
     An oxygen supply gas line  72  provides oxygen supply gas into the mixing chamber  66 . The oxygen supply gas from the oxygen supply gas line  72  includes oxygen necessary for combustion. The oxygen supply gas may also fluidize the catalyst within the mixing chamber  66  and lift the catalyst from the mixing chamber upwardly into the combustion chamber  62 . 
     Coke on the spent catalyst may be insufficient to generate enough enthalpy from combustion to drive the endothermic reaction in the dehydrogenation reactor. In some cases, the catalyst may deactivate by a mechanism other than coke deposition and require oxidation to regenerate activity, even though very little or no detectable coke is on the spent catalyst. Moreover, higher regeneration temperature results in greater restoration of catalyst activity. Hence, supplemental fuel gas may be added to the mixing chamber  66  in the regenerator vessel  60  to provide additional combustion enthalpy to drive the endothermic reaction in the dehydrogenation reactor and sufficiently restore catalyst activity. A fuel gas from a fuel gas line  74  may be provided to the combustion chamber  62  perhaps through the mixing chamber  66 . Both gas streams lift the catalyst in the combustion chamber  62  into the separation chamber  64 . 
     The fuel gas is combusted with oxygen in the oxygen supply gas in the presence of the catalyst to provide a heated, regenerated catalyst. Moreover, coke on catalyst is also combusted from the catalyst with oxygen in the oxygen supply gas to provide a regenerated catalyst. Combustion of coke and fuel gas generates flue gas. In an embodiment, the fuel gas and the coke on the catalyst are combusted together in the same vicinity, beginning in the mixing chamber  66  and then in the combustion chamber  62 . 
     The superficial gas velocity in the mixing chamber  66  may be about 0.9 m/s (3 ft/s), to about 5.4 m/s (18 ft/s), and the catalyst density may be from about 112 kg/m 3  (7 lb/ft 3 ) to about 400 kg/m 3  (25 lb/ft 3 ), preferably from about 48 kg/m 3  (3 lb/ft 3 ) to about 288 kg/m 3  (18 lb/ft 3 ), constituting a dense catalyst phase in the mixing chamber  66 . 
     In an exemplary embodiment, air is used as the oxygen supply gas, because air is readily available and provides sufficient oxygen for combustion. About 10 to about 15 kg of air are required per kg of coke burned off of the spent catalyst. Exemplary regeneration conditions in the combustion chamber  62  include a temperature from about 690° C. to about 800° C., preferably 705° C. to about 750° C. and a pressure of about 6.9 kPa (gauge) (1 psig) to about 450 kPa (gauge) (70 psig). 
     Catalyst, fuel gas and oxygen supply gas ascend in the combustion chamber  62  while coke is combusted from the catalyst and the fuel gas is combusted to regenerate and heat the catalyst and generate flue gas. The flow regime may be a fast-fluidized flow regime in which catalyst may slip relative to the gas and the gas can take indirect upward trajectories. The superficial velocity of the gases ascending in the combustion chamber  62  is preferably about 1.5 m/s (5 ft/s) to about 6 m/s (20 ft/s) and preferably about 2.1 m/s (7 ft/s) to about 5.4 m/s (18 ft/s), to provide a fast-fluidized flow regime. The catalyst density in a dilute catalyst phase in the combustion chamber  62  will be from about 16 kg/m 3  (1 lb/ft 3 ) to about 192 kg/m 3  (12 lb/ft 3 ). 
     The blend of gases and catalyst ascend from the combustion chamber  62  through a frustoconical transition section  76  into a riser  80  which has a smaller diameter than a major diameter of the combustion chamber  62 . A blend of gases and catalyst accelerate in the narrower riser  80  and are discharged from a riser termination device  82  into the separation chamber  64 . The transition section  76 , the riser  80  and the riser termination device  82  are considered part of the combustion chamber  62 . The riser termination device  82  may utilize centripetal acceleration to separate regenerated catalyst from flue gas. The superficial gas velocity in the riser  80  will be about 6 m/s (20 ft/s) to about 15 m/s (50 ft/s) and constitute a dilute catalyst phase. 
     Regenerated catalyst separated from flue gas by the riser termination device  82  drops into a dense catalyst bed  84 . The catalyst separation chamber  64  may include one or more regenerator cyclones  86  or other solid/gaseous separator devices to separate the regenerated catalyst still entrained in the flue gas. In an aspect, primary cyclones  86  may collect flue gas from the separation chamber  64  and transport the flue gas separated from catalyst to a secondary cyclone  88  to further separate regenerated catalyst from the flue gas before directing secondarily purified flue gas to the plenum  90 . Flue gas is discharged from the regenerator vessel  60  through an outlet  62  in a discharge line. Regenerated catalyst separated from flue gas in the cyclones  86 ,  88  is dispensed by dip legs into the dense catalyst bed  84 . 
     A stream of fluidizing gas may be distributed into the separation chamber  64  to fluidize regenerated catalyst in the dense catalyst bed  84 . The fluidizing gas may be an oxygen supply gas such as air used in the combustion chamber  62  or it may be inert such as steam or nitrogen. 
     A return portion of the regenerated catalyst collected in the dense bed  84  of the catalyst separation chamber  64  may be transported in the return regenerated catalyst standpipe  26  back to the dehydrogenation reactor ready for catalyzing dehydrogenation reactions. The return portion of the regenerated catalyst may exit the separation chamber  64  through an inlet end  27  of the regenerated catalyst pipe  26  to enter the return regenerated catalyst standpipe  26 . 
     A recycle portion of the regenerated catalyst collected in the dense bed  84  of the catalyst separation chamber  64  may be recycled in a recycle regenerated catalyst standpipe  68  back to the combustion chamber  62  of the regenerator vessel  60  via the mixing chamber  66 . The regenerated catalyst is hotter and has a lower coke concentration than the spent catalyst fed to the regenerator vessel in the spent catalyst standpipe  18 . Regenerated catalyst is returned to the reactor  10  at least in part in the regenerated catalyst pipe  26 . 
     The regenerated catalyst pipe  26  has an inlet end  27  connected to the regenerator  20  in the separation chamber  25  through which regenerated catalyst from the regenerator is transported to the reactor  10 . To decouple the regenerated catalyst temperature from the catalyst residence time in the reactor  10 , the regenerated catalyst in the regenerated catalyst pipe  26  may be cooled in a catalyst cooler  92 . The hot regenerated catalyst is fed to the catalyst cooler  92  from the regenerated catalyst pipe  26  through an outlet end  93  of the regenerated catalyst pipe. The outlet end  93  may be connected to the catalyst cooler  92 . The catalyst cooler  92  may be in downstream communication with the regenerated catalyst pipe  26 . A stream of gas such as an oxygen supply gas in line  94  may be fed to the catalyst cooler  92  through a coil  95  in the catalyst cooler  92  to be indirectly heat exchanged with the hot regenerated catalyst. Cooled regenerated catalyst exits the catalyst cooler  92  through an inlet end  97  of a cooled catalyst pipe  96 . The inlet end of the cooled catalyst pipe  96  may be connected to the catalyst cooler  92 . The cooled catalyst pipe may be in downstream communication with the catalyst cooler  92 . The cooled regenerated catalyst pipe delivers the cooled regenerated catalyst stream to the reactor  10  through an outlet end  25  at a flow rate governed by a control valve thereon. The outlet end  25  may be connected to the reactor  10 . The reactor  10  may be in downstream communication with the cooled catalyst pipe  96 . The cooled regenerated catalyst stream is fed to the reactor  10  through inlet  25  at a lower temperature than a temperature of the hot regenerated catalyst stream that exits the regenerator  60  through the inlet end  27 . The oxygen supply gas in line  94  is heated by heat exchange with the hot regenerated catalyst from pipe  26  and exits the catalyst cooler  92  in line  98 . The heated oxygen supply gas may be fed to the regenerator  60  to provide oxygen supply gas requirements perhaps merging in with the oxygen supply gas in the oxygen supply gas line  72 . Heating the oxygen supply gas before entering the regenerator facilitates combustion of coke deposits on catalyst and fuel gas combustion. The oxygen supply gas in line  94  can be heated by about 450 to about 660° C., and the hot regenerated catalyst stream can be cooled by about 20 to about 50° C. Heating the oxygen supply gas may be used in conjunction with heating other streams such as fuel gas or steam to provide sufficient catalyst cooling. 
     In an embodiment, the regenerated catalyst pipe  26  may be equipped with a bypass line  100  with a control valve thereon for regulating the flow rate of catalyst to the catalyst cooler  92  independently of the flow rate of oxygen supply gas to the catalyst cooler in line  94 . 
     The catalyst cooler  92  may also be used to generate steam, superheat steam or provide heat to another area of the process while cooling catalyst to be fed to the reactor  10  in the cooled catalyst conduit  96  to enable a higher catalyst circulation rate independent of catalyst regeneration conditions. 
       FIG.  2    shows an embodiment of an alternative regenerator  60 ′ which employs fuel gas to cool hot regenerated catalyst. Elements in  FIG.  2    with the same configuration as in  FIG.  1    will have the same reference numeral as in  FIG.  1   . Elements in  FIG.  2    which have a different configuration as the corresponding element in  FIG.  1    will have the same reference numeral but designated with a prime symbol (′). The configuration and operation of the embodiment of  FIG.  2    is essentially the same as in  FIG.  1    with the following exceptions. 
     The hot regenerated catalyst is fed to the catalyst cooler  92  from the regenerated catalyst pipe  26  through an outlet end  93  of the regenerated catalyst pipe. A stream of fuel gas comprising light hydrocarbons and/or hydrogen in line  94 ′ may be fed to the catalyst cooler  92  through a coil  95  in the catalyst cooler  92  to be indirectly heat exchanged with the hot regenerated catalyst. Cooled regenerated catalyst exits the catalyst cooler  92  through an outlet  97  into a second regenerated catalyst pipe  96 . The second regenerated catalyst pipe delivers the cooled regenerated catalyst stream to the reactor  10  through an inlet  25  at a flow rate governed by a control valve thereon. The cooled regenerated catalyst stream is fed to the reactor  10  through inlet  25  at a lower temperature than a temperature of the hot regenerated catalyst stream that exits the regenerator  60  through the inlet end  27  of the regenerated catalyst pipe  26 . The fuel gas in line  94 ′ is heated by heat exchange with the hot regenerated catalyst from pipe  26  and exits the catalyst cooler  92  in line  98 ′. The heated fuel gas may be fed to the regenerator  60  to provide fuel gas requirements perhaps merging in with the fuel gas in the fuel gas line  74 ′. Heating the fuel gas before entering the regenerator facilitates combustion of fuel gas because the fuel gas does not require full heating in the regenerator. The fuel gas in line  94  can be heated by about 500 to about 700° C., and the hot regenerated catalyst stream can be cooled by about 2 to about 10° C. Heating the fuel gas may be used in conjunction with heating other streams such as fuel gas or steam to provide sufficient catalyst cooling. 
       FIG.  3    shows an embodiment of an alternative reactor  10 ″ and regenerator  60 ″ which cools hot regenerated catalyst by heat exchanging it with spent catalyst. Elements in  FIG.  3    with the same configuration as in  FIG.  1    will have the same reference numeral as in  FIG.  1   . Elements in  FIG.  3    which have a different configuration as the corresponding element in  FIG.  1    will have the same reference numeral but designated with a double prime symbol (″). The configuration and operation of the embodiment of  FIG.  3    is essentially the same as in  FIG.  1    with the following exceptions. 
     A catalyst cooler  92 ″ comprises a catalyst heat exchanger in downstream communication with the regenerated catalyst pipe  26 ″ and the spent catalyst pipe  18 ″. The catalyst cooler  92 ″ has a first side in communication with the regenerated catalyst pipe  26 ″ and the cooled catalyst pipe  96 ″. An outlet end  93 ″ of the regenerated catalyst pipe  26 ″ is connected to a manifold  102  of the catalyst cooler  92 ″. The manifold  102  receives hot regenerated catalyst from the regenerated catalyst pipe  26 ″ and distributes the hot regenerated catalyst to a plurality of catalyst tubes  104  or channels comprising a first side of the catalyst cooler  92 ″. A collector  108  receives catalyst from the tubes  104 . An inlet end  97 ″ of the cooled catalyst pipe  96 ″ is connected to the catalyst cooler  92 ″ on the first side to receive cooled catalyst from the collector  108 . 
     A second side of said catalyst cooler  92 ″ may be in communication with the spent catalyst pipe  18 ″ and a heated catalyst pipe  106 . Spaces  110  between the tubes  104  receive the spent catalyst from the spent catalyst pipe  18 ″. The catalyst cooler  92 ″ is in downstream communication with the spent catalyst pipe  18 ″. Specifically, an outlet end  17  of the spent catalyst pipe  18 ″ is connected to the catalyst cooler  92 ″ on the second side, and an inlet end  105  of the heated catalyst pipe  106  is connected to the catalyst cooler  92 ″ on the second side. 
     Hot regenerated catalyst from the regenerated catalyst pipe  26 ″ exits an outlet end  93 ″ and enters the manifold  102  and is distributed to the catalyst tubes  104  on the first side of the catalyst cooler  92 ″. Spent catalyst from the spent catalyst pipe  18 ″ exits the outlet end  17  and enters the spaces  110  between tubes  104  on the second side of the catalyst cooler  92 ″. Heat is indirectly exchanged across the tubes  104  from the regenerated catalyst to the spent catalyst thereby heating the spent catalyst and cooling the regenerated catalyst. The heated spent catalyst exits the spaces  110  between the tubes  104  through the inlet end  105  of the heated catalyst pipe  106 , and cooled regenerated catalyst collects in the collector  108  and exits the catalyst cooler  92 ″ through an inlet end  97 ″ of a cooled catalyst pipe  96 ″. The cooled catalyst from the cooled catalyst pipe  96 ″ is passed to the reactor  10  through the outlet end  25 , and the heated spent catalyst stream is passed to the regenerator  60  through the outlet end  19  of the heated catalyst pipe  106 . The catalyst cooler  92 ″ may be in downstream communication with the spent catalyst pipe  18 ″, and the regenerator  60  may be in downstream communication with the heated catalyst pipe  106 . The spent catalyst stream in the spent catalyst pipe  18 ″ can be heated by about 20 to about 60° C., and the hot regenerated catalyst stream in the regenerated catalyst pipe  26 ″ can be cooled by about 20 to about 60° C. 
     Adjusting the flow rate of hot regenerated catalyst in pipe  26 ″ to the catalyst cooler  92 ″ can be used to control the rate of cooling of hot regenerated catalyst. To do so, a regenerated catalyst bypass pipe  112  has an inlet end  111  connected to the regenerated catalyst pipe  26 ″ and an outlet end  113  connected to the cooled catalyst pipe  96 ″. Modulating the rate of hot regenerated catalyst by bypassing a portion of the hot regenerated catalyst in the regenerated catalyst pipe  26 ″ around the catalyst cooler  92 ″ in the bypass pipe  112  by a control valve thereon can control the temperature of the regenerated catalyst entering the reactor  10 ″ through the outlet end  25  of the cooled catalyst pipe  96 ″. Bypassing more of the hot regenerated catalyst in the regenerated catalyst pipe  26 ″ through the regenerator bypass pipe  112  to mix with cooled catalyst in the cooled catalyst line  96 ″ will increase the temperature of the cooled regenerated catalyst in the cooled catalyst line. Bypassing less of the hot regenerated catalyst in the regenerated catalyst pipe  26 ″ through the regenerator bypass pipe  112  to mix with cooled catalyst in the cooled catalyst line  96 ″ will decrease the temperature of the cooled regenerated catalyst in the cooled catalyst line. 
     Adjusting the flow rate of spent catalyst in pipe  18 ″ to the catalyst cooler  92 ″ can also be used to control the rate of cooling of hot regenerated catalyst. To do so, a spent catalyst bypass pipe  116  having an inlet end  115  connected to the regenerated catalyst pipe  26 ″ and an outlet end  117  connected to the heated catalyst pipe  106 . Modulating the rate of spent catalyst by bypassing a portion of the spent catalyst in the spent catalyst pipe  18 ″ around the catalyst cooler  92 ″ in the bypass pipe  116  can control the temperature of the regenerated catalyst entering the reactor  10 ″ through the outlet end  25  of the cooled catalyst pipe  96 ″. Bypassing more of the spent catalyst in the spent catalyst pipe  18 ″ through the spent bypass pipe  116  will provide less cooling of the hot regenerated catalyst in the hot regenerated catalyst pipe  26 ″ to increase the temperature of the cooled regenerated catalyst in the cooled catalyst pipe  96 ″. Bypassing less of the spent catalyst in the spent catalyst pipe  18 ″ through the spent bypass pipe  116  will provide more cooling in the cooled catalyst line  96 ″ to decrease the temperature of the cooled regenerated catalyst in the cooled catalyst line. 
     A fluidizing gas line  130  may feed a distributor on the first side of the catalyst heat exchanger  92 ″ and/or on the second side of the catalyst heat exchanger. One can adjust the degree of heat transfer by varying the degree of fluidization of catalyst on either side or both sides of the catalyst heat exchanger  92 ″. Increasing the degree of fluidization will increase heat transfer between catalyst streams, and reducing the degree of fluidization will decrease heat transfer between catalyst streams. 
       FIG.  4    shows an embodiment of an alternative reactor  10 * which cools hot regenerated catalyst by mixing it with cooled spent catalyst. Elements in  FIG.  4    with the same configuration as in  FIG.  1    will have the same reference numeral as in  FIG.  1   . Elements in  FIG.  4    which have a different configuration as the corresponding element in  FIG.  1    will have the same reference numeral but designated with a star symbol (*). The configuration and operation of the embodiment of  FIG.  4    is essentially the same as in  FIG.  1    with the following exceptions. 
     The recycle catalyst stream of spent catalyst taken in the recycle catalyst pipe  22 * from the inlet end  21  may be cooled in a catalyst cooler  92 * from which it enters through an outlet end  119  of the recycle catalyst pipe. The catalyst cooler  92 * may cool the recycle catalyst stream by heat exchange with a stream of oxygen supply gas or fuel gas intended for the regenerator, regenerated catalyst, water or paraffin feed intended for the reactor  10 *. In  FIG.  4    a reactant stream of paraffin feed in line  6  is preheated by heat exchange with the recycle catalyst stream of spent catalyst in the recycle catalyst pipe  22 *. In the heat exchange, the catalyst cooler  92 * cools the recycle catalyst stream by heat exchange with the cooler reactant stream in line  6  to produce a preheated reactant stream in the feed line  8 *. The cooled recycle catalyst stream may exit the catalyst cooler  92 * through an inlet end  121  of a cooled catalyst pipe  120  and be fed to the reactor  10 * through an outlet end  23 * of the cooled catalyst pipe. 
     The hot regenerated catalyst stream entering the reactor  10 * through inlet end  25 * from the regenerated catalyst pipe  26 * is cooled when it mixes with a cooled recycle catalyst stream entering through the outlet end  23 * of the cooled catalyst pipe  120  to provide the cooled regenerated catalyst stream in the catalyst bed represented by the interface  28 . The cooled regenerated catalyst stream contacts the preheated reactant stream from the feed line  8 *. 
     The foregoing disclosure describes a process and apparatus that enables the regenerator  60  to be operated at the optimal temperature for catalyst regeneration while independently operating the reactor  10  with an optimal catalyst reactor residence time. 
     The paraffin feed in line  6  can be heated by about 300 to about 500° C., and the hot recycle catalyst stream can be cooled by about 50 to about 100° C. 
     The catalyst cooler  92 * may also be used to generate steam, superheat steam or provide heat to another area of the process while cooling catalyst to be returned to the reactor  10 * in the cooled catalyst pipe  120  to enable a higher catalyst circulation rate independent of catalyst regeneration conditions. 
     All the catalyst coolers  92 ,  92 ′, 92 ″ and  92 * may be shell and tube, nested tube, plate heat exchangers or any other type of heat exchanger. 
     EXAMPLE 
     Catalyst was prepared by incipient wetness impregnation of an aqueous solution of gallium nitrate, potassium nitrate, and tetraamine platinum nitrate on a micro-spheroidal spray dried alumina containing 1% SiO 2 . The catalyst support had BET surface area of 134 m 2 /g measured by nitrogen adsorption. Impregnation was followed by calcination in air for 4 hours at 750° C. Catalyst contained 0.0076% Pt, 1.56% Ga, 0.26% K, 0.5% Si (by weight) as measured by inductively charged plasma atomic emission spectroscopy (ICP-AES). Catalyst appearance was white. Carbon and nitrogen content were measured by CHN method D5291. Carbon content of the fresh catalyst was 0.07 wt %, close to the detection limit of 0.05 wt % (likely due to adsorbed carbonates). Nitrogen was not detectable (detection limit 0.05 wt %). 
     Long-term aging of catalyst was simulated by cycling the catalyst between reactor and regenerator conditions as follows: 
     Startup: 2 cm 3  of catalyst was loaded in a quartz tube reactor. Catalyst was heated to 120° C. in nitrogen and held 30 minutes. Temperature was increased to 720° C. in nitrogen at 10° C./min and regeneration conditions were initiated.
 
Regeneration step: Temperature was increased to 720° C. in nitrogen at 10° C./min. Gas composition was changed from nitrogen to 5% O 2 , 24.2% H 2 O, balance Na (by volume) and was flowed for 2 minutes with gas flow rate of 15 standard cm 3  per minute per cm 3  of catalyst. Gas composition was changed back to nitrogen, temperature was held for 0.5 min, and cooling was initiated.
 
Reaction step: Sample was cooled to 620° C. in nitrogen at 13° C./min. Gas composition was changed from nitrogen to propane. Propane was flowed for 2 minutes with gas flow rate of 7.5 cm 3  per minute per cm 3  of catalyst. Gas composition was changed back to nitrogen, temperature was held for 0.5 min, and heating for regeneration step was initiated. 630 cycles of regeneration-reaction were completed, with an additional regeneration at the end of the program. Catalyst was cooled in nitrogen and unloaded for further testing.
 
     We tested the aged platinum-gallium catalyst for activity at different regeneration temperatures in a propane dehydrogenation test apparatus. We simulated catalyst regeneration at various temperatures in an environment of 25 wt % water, 5 wt % oxygen and the balance nitrogen for 1 minute. 150 mg of the aged catalyst described above was loaded between quartz wool plugs in a quartz tube reactor with inner diameter 3.85 mm. Inert alpha alumina spheres were loaded below the catalyst bed to minimize thermal cracking. The reactor effluent composition was analyzed by transmission infrared spectroscopy which identified propane, propene, ethane, ethene, and methane products with data collection approximately every 7 sec. The effluent of the infrared analyzer was directed to a gas chromatograph which was used to occasionally analyze the product stream and check the accuracy of the infrared analyzer on the real product stream. 
     Catalyst was dried in nitrogen and held for 30 minutes at 120° C., then heated to the regeneration temperatures of 690, 705, 720 and 735° C. in nitrogen. The catalyst was then exposed to a mixture of dry gas consisting of 5 mol % O 2  with the balance nitrogen, where the dry gas flow of O 2  and nitrogen was 15 standard cm 3 /min, mixed with 25 mole % steam generated by vaporizing water which was fed from a pump. Exposure to this steam/O 2 /nitrogen mixture was sustained for 1 minute, at which point it was discontinued and replaced with dry nitrogen. 
     After this pretreatment, the catalyst was cooled to 620° C. in dry nitrogen. The catalyst was then exposed to 2 mol % H 2 O in nitrogen, generated by bubbling nitrogen through a saturator in a temperature-controlled bath. The wet pre-treatment of the catalyst was maintained for 60 minutes. The nitrogen/H 2 O mixture was then stopped and replaced with 9 standard cm 3 /min of propane and 1.5 standard cm 3 /min of hydrogen feed. Feed flowed for 2 minutes, after which gas composition was switched to nitrogen. The temperature was increased to the regeneration temperatures of 690, 705, 720 or 735° C. for regeneration. During regeneration, the catalyst was then exposed to a mixture of dry gas consisting of 5 mol % O 2  with the balance nitrogen, where the dry gas flow of O 2  and nitrogen was 15 standard cm 3 /min, mixed with 25 mole % steam generated by vaporizing water which was fed from a pump. Exposure to this steam/O 2 /nitrogen mixture was sustained for 1 minute, at which point it was discontinued and replaced with dry nitrogen. The catalyst was then cooled to 620° C. for the next reaction step. The O 2 /propane cycles were repeated four times. 
     The propane conversion at or near 0.54 min on stream in the fourth cycle is shown in Table 1 for experiments with four different regeneration temperatures. Conversion vs. time on stream, representing reactor residence time, is shown in  FIG.  5   . The legend key for  FIG.  5    is provided in the last column of Table 1. Higher regeneration temperature results in higher propane conversion in the subsequent reaction cycle. At shorter reactor residence times in the reactor, conversion which corresponds to activity is higher. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Regeneration temperature, ° C. 
                 Propane conversion 
                 Key for FIG. 5 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 690 
                 41.52 
                 * 
               
               
                 705 
                 44.66 
                 ♦ 
               
               
                 720 
                 47.00 a   
                 ● 
               
               
                 735 
                 48.32 
                 x 
               
               
                   
               
               
                   a No datapoint at 0.54 min, so reported average of conversion at 0.44 and 0.66 min. 
               
            
           
         
       
     
     Specific Embodiments 
     While the following is described in conjunction with specific embodiments, it will be understood that this description is intended to illustrate and not limit the scope of the preceding description and the appended claims. 
     A first embodiment of the disclosure is a process for contacting a reactant stream with regenerated catalyst comprising charging a reactant stream to a reactor; contacting the reactant stream with a cooled regenerated catalyst stream to produce a product gas stream and a spent catalyst; passing a spent catalyst stream to a regenerator; regenerating the spent catalyst stream by combustion in the regenerator to provide a hot regenerated catalyst stream and a flue gas stream; cooling a catalyst stream; and passing the regenerated catalyst stream to the reactor. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising cooling the hot regenerated catalyst stream by heat exchange. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising cooling the hot regenerated catalyst by heat exchange with air. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising returning heated air from the heat exchange to the regenerator. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising cooling the hot regenerated catalyst stream by heat exchange with the spent catalyst stream to provide the cooled regenerated catalyst stream and a heated spent catalyst stream. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing the cooled regenerated catalyst stream to the reactor and passing the heated spent catalyst stream to the regenerator. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising bypassing a portion of the hot regenerated catalyst stream around the heat exchange and/or bypassing a portion of the spent catalyst stream around the heat exchange. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising cooling the hot regenerated catalyst stream by mixing it with a cooled catalyst stream to provide the cooled regenerated catalyst stream. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising separating a recycle catalyst stream from a spent catalyst and cooling the recycle catalyst stream to provide the cooled catalyst stream. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein contacting the reactant stream with a cooled regenerated catalyst stream produces an endothermic reaction. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the catalyst includes gallium. 
     A second embodiment of the disclosure is a process for contacting a reactant stream with regenerated catalyst comprising charging a reactant stream to a reactor; contacting the reactant stream with a cooled regenerated catalyst stream to produce a product gas stream and a spent catalyst; passing a first spent catalyst stream to a regenerator and optionally returning a second spent catalyst stream back to the contacting step; regenerating the spent catalyst stream by combustion in the regenerator to provide a regenerated catalyst stream and a flue gas stream; and cooling the regenerated catalyst stream or the second spent catalyst stream to provide the cooled regenerated catalyst stream. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the first spent catalyst stream and the regenerated catalyst stream are mixed to provide the cooled catalyst stream. 
     A third embodiment of the disclosure is an apparatus comprising a regenerator for regenerating catalyst; a regenerated catalyst pipe in downstream communication with the regenerator for transferring regenerated catalyst from a regenerator; a catalyst cooler in downstream communication with the regenerated catalyst pipe; a cooled catalyst pipe in downstream communication with the catalyst cooler; and a reactor in downstream communication with the cooled catalyst pipe. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph wherein the regenerated catalyst pipe has an inlet end connected to the regenerator and an outlet end connected to the catalyst cooler. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph wherein the cooled catalyst pipe has an inlet end connected to the catalyst cooler and an outlet end connected to the reactor. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph further comprising a first side of the catalyst cooler in communication with the regenerated catalyst pipe and the cooled catalyst pipe and a second side in communication with a spent catalyst pipe and a heated catalyst pipe. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph wherein the catalyst cooler is in downstream communication with the spent catalyst pipe and the regenerator is in downstream communication with the heated catalyst pipe. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph further comprising a regenerated catalyst bypass pipe having an inlet end connected to the regenerated catalyst pipe and an outlet end connected to the cooled catalyst pipe. An embodiment of the disclosure is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph further comprising a spent catalyst bypass pipe have an inlet end connected to the spent catalyst pipe and an outlet end connected to the heated catalyst pipe. 
     Without further elaboration, it is believed that using the preceding description that one skilled in the art can utilize the present disclosure to its fullest extent and easily ascertain the essential characteristics of this disclosure, without departing from the spirit and scope thereof, to make various changes and modifications of the disclosure and to adapt it to various usages and conditions. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limiting the remainder of the disclosure in any way whatsoever, and that it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims. 
     In the foregoing, all temperatures are set forth in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.