JP7416824B2 - System and process for maintaining ethylbenzene dehydrogenation catalyst activity - Google Patents

Description

Embodiments disclosed herein generally relate to the dehydrogenation of alkyl aromatics to produce alkenyl aromatics, such as the dehydrogenation of ethylbenzene to produce styrene. More specifically, embodiments herein relate to processes and systems for maintaining catalyst activity within a dehydrogenation reactor.

When ethylbenzene is dehydrogenated to produce styrene, the iron oxide catalyst is deactivated. One of the main reasons for catalyst deactivation is the migration of potassium promoter in the catalyst. It has been proposed to inject a small amount of potassium solution along with the ethylbenzene/water (steam) mixed feed to suppress potassium migration and keep the catalyst in an active state for a long period of time. Steam, methane, and inert gases have been proposed as carriers to transport the solution to the EB feed. However, when a solution of potassium hydroxide or a potassium salt is heated and vaporized, the salt may precipitate and clog the transfer pipe.

US Pat. No. 5,001,000 teaches that the life of a potassium or chromium stabilized dehydrogenation catalyst can be extended by injecting 0.1 to 10 ppm of a "catalyst life extender". Potassium acetate is mentioned as a life extender.

Patent Document 2 discloses that the life of an iron-based/alkali metal stabilized catalyst is extended by continuously injecting an alkali metal or an alkali metal compound, such as injecting about 0.01 to 100 ppm of an alkali metal or an alkali metal compound. It has been suggested that it can be extended. Examples of the compounds include potassium hydroxide, potassium carbonate, and potassium oxide. Further, as the metal, potassium or sodium metal is mentioned. According to U.S. Pat. No. 5,301,300, inert nitrogen can be used to transport vaporized alkali metals or alkali metal compounds into the reactor feedstream.

US Pat. No. 5,300,501 teaches that the injection of potassium salts must be done carefully or else there is a risk of potassium salts depositing on the injection device. In the example, when injecting a 10% potassium acetate solution, the temperature of the vaporizer needed to be between 200°C and 480°C.

Patent Document 4 discloses that the life of a Fe-based dehydrogenation catalyst can be extended using a Cs compound.

If a potassium hydroxide or potassium salt solution is heated and vaporized, the salt may precipitate and clog the transfer tube. As a solution to this problem, studies have been presented in the above-mentioned patent documents including Patent Document 3. However, since the melting point is very high, it is difficult to volatilize potassium salts. For example, KOH melts at 360°C, K2CO3 melts at 891°C, K acetate melts at 292°C, and K2SO4 melts at 1069°C. Therefore, in the system of Patent Document 3, if there is any operational trouble or if a compound other than potassium acetate is used, clogging may still occur easily.

US Patent No. 6,936,743 US Patent No. 5,739,071 US Patent No. 8,648,007 US Patent Application Publication No. 2006/0224029

Therefore, in order to avoid clogging the injection system, a process and system has been developed to inject potassium either as pure metal, dissolved hydroxide, or dissolved salt. Embodiments herein differ from existing systems by directing molten potassium metal, or solutions of potassium salts or potassium hydroxide, into the EB feed, main steam line, or main EB/steam feed that enters the reactor. Can be injected. The injection nozzle can be designed to limit heat transfer to the potassium or potassium solution so that the potassium or potassium solution does not boil until it passes through the nozzle into the hot stream of steam, EB, or EB/steam. After injection, the potassium or potassium compound evaporates in the process tube before reaching the catalyst bed and mixes well with the feed stream so that the potassium is well distributed throughout the catalyst bed. While traditional methods have focused on vaporizing the material and then injecting it into the reactor feed, embodiments herein use a different approach to remove potassium, potassium compounds, or Do not evaporate the potassium solution.

In one aspect, embodiments disclosed herein relate to a process for dehydrogenating ethylbenzene. The process may include mixing a steam stream and an ethylbenzene stream to form an ethylbenzene/steam feed mixture. The ethylbenzene/steam feed mixture may then be fed to a dehydrogenation reactor containing an alkali metal promoted catalyst to convert a portion of the ethylbenzene to styrene. Injecting a liquid selected from an alkali metal liquid, an alkali metal compound liquid, or an alkali metal-containing solution into the feed stream comprising at least one of the vapor stream, the ethylbenzene stream, or the ethylbenzene/steam feed mixture. Good too. After injection, the liquid vaporizes and disperses into the feedstream upstream of the dehydrogenation reactor. The liquid (the alkali metal, the alkali metal compound liquid, or the alkali metal-containing solution) may be maintained in a liquid state from a point upstream of injection to the injection nozzle. The liquid is dispersed in liquid form through the injection nozzle to form droplets of liquid dispersed in the feedstream. The liquid then evaporates and/or dissolves into the vaporous feedstream.

In another aspect, embodiments disclosed herein relate to a system for maintaining catalyst activity in an ethylbenzene dehydrogenation reactor. The system may include a liquid alkaline feedstream, optionally heated or insulated, selected from at least one of an alkali metal, a liquid alkali metal compound, and a solution containing an alkali metal. Maintain liquid alkaline feed in liquid state. The system may also include an injection nozzle for injecting the liquid alkali feed as a liquid into a process feedstream selected from a vapor stream, an ethylbenzene feedstream, and an ethylbenzene/vapor feedstream to form an alkali-containing feed. . The system also includes a dehydrogenation reactor comprising an alkali metal promoted catalyst and having an inlet for receiving the alkali-containing feed or a mixture comprising the alkali-containing feed.

The alkaline feed stream may be vapor traced, adiabatic, or coolant traced upstream of the injection nozzle to maintain the liquid feed in a liquid state. The vapor trace, insulation, etc. may continue up to the injection nozzle, or as close as possible.

In some embodiments, the system may further include a water feedstream fluidly connected to the injection nozzle. In some embodiments, a control system may be included to alternately supply the liquid alkaline feed and the water feedstream to the injection nozzle.

In another aspect, embodiments disclosed herein relate to a process for maintaining catalyst activity in a reactor. The process may include injecting a liquid containing a catalyst regeneration compound into a vaporous feedstream containing an inert material and/or a reactant upstream of a reactor inlet. vaporizing and dispersing the liquid into the vaporous feedstream in a flow tube upstream of the reactor to form a vaporous mixture comprising the catalyst regeneration compound and at least one inert material or reactant; Good too. The activity of the catalyst in the reactor may be increased by contacting the catalyst contained in the reactor with the vaporous catalyst regeneration compound at the same time that the catalyst in the reactor carries out the desired reaction. good.

Other aspects and advantages will be apparent from the following description and the appended claims.

1 is a simplified process flow diagram illustrating a system for dehydrogenating ethylbenzene to produce styrene according to embodiments herein; FIG. 1 is a simplified process flow diagram illustrating a system for injecting compounds into a dehydrogenation process according to embodiments herein; FIG. 2 illustrates the results of simulating the injection of compounds into a flow stream of a dehydrogenation process according to embodiments herein; FIG.

Embodiments disclosed herein generally relate to the production of alkenyl aromatics by dehydrogenation of alkyl aromatics such as alkylbenzenes, for example, the production of styrene by dehydrogenation of ethylbenzene. More specifically, embodiments herein relate to processes and systems for maintaining catalyst activity within a dehydrogenation reactor. Even more specifically, embodiments herein relate to the injection of catalyst regeneration compounds into a reaction system. For example, embodiments herein may relate to the injection of potassium or potassium compounds to maintain catalyst activity within a dehydrogenation reactor.

Embodiments herein are described below in connection with the production of styrene by dehydrogenation of ethylbenzene. However, those skilled in the art will appreciate that the processes disclosed herein are similar to processes for dehydrogenating other alkyl aromatic hydrocarbons to produce alkenyl aromatic hydrocarbons, such as dehydrogenating cumene to produce α- It can be easily seen that the process can be applied to produce methylstyrene, dehydrogenate ethyltoluene to produce vinyltoluene, and numerous other alkenyl aromatic compounds. Other conversion processes such as the dehydrogenation of butane to produce butadiene, the dealkylation of alkyl aromatics, the synthesis of ammonia, the synthesis of maleic anhydride, etc. may also benefit from embodiments herein. .

Referring now to FIG. 1, there is shown a simplified flow diagram illustrating the typical structure of a dehydrogenation reaction area of a styrene plant. Styrene monomer is produced by dehydrogenation of an ethylbenzene (EB) feed, which is an endothermic reaction. A vaporized azeotrope of ethylbenzene and water is supplied to the reaction zone through a flow line 24. The reaction zone may include 2 to 4 dehydrogenation reactors 26,28. The effluent from each reactor 26 may be reheated with steam before entering the next reactor 26 or final reactor 28. The steam used to reheat the reactor effluent, commonly referred to as Main Steam (MS), is supplied from steam superheater 30 through flow line 32 and coil 38, and is ultimately combined with the vaporized EB/water mixture. Enter inlet 34 of first reactor 26 . The vaporized EB/water mixture may also be preheated in exchanger 36 with the effluent from final reactor 28. Although FIG. 1 is an example of a dehydrogenation system, other processes and systems for dehydrogenating ethylbenzene may also benefit from the embodiments herein.

As discussed above, the catalyst contained in reactors 26, 28 may lose activity due to migration of catalyst or cocatalyst components. It is desirable to inject compounds to help maintain or retain the activity of the catalyst, thereby increasing the catalyst life and the total operating time of the reaction system before shutdown and catalyst replacement is required. For example, potassium stabilized dehydrogenation catalysts can benefit from introducing potassium or potassium compounds into the reactor. Embodiments herein can provide potassium in a useful form with minimal or no accumulation of potassium or potassium salts in the injection system or associated piping.

Accordingly, using the processes and systems disclosed herein, molten potassium metal, or a solution of potassium salt or potassium hydroxide, is directly introduced into the vaporized reactor feed stream via one or more injection systems 50. May be injected. For example, the liquid metal or solution may be introduced into the ethylbenzene (EB) feed 24/25 entering the reactor 26, the main vapor line 40, or the main EB/steam feed 42 via one or more injection systems 50. . In some embodiments, for example, molten liquid potassium may be injected into the EB/vapor stream.

Potassium metal melts at about 63.5°C. A vapor-traced container may be used to store the potassium metal, and vapor-traced or insulated piping may maintain the metal in a liquid state and allow it to flow into the process unit. Liquid potassium may be metered directly into a tube containing the EB/steam feed to the dehydrogenation reactor, such as stream 42 shown in FIG. 1, for example. Potassium boils at approximately 759°C. Generally, the temperature of the feed to the dehydrogenation reactor ranges from 500°C to about 650°C. The EB/steam process temperature is high enough to keep the potassium in a molten state, but not high enough to boil the potassium.

Potassium metal may be atomized or atomized, for example, with nitrogen or another suitable inert gas through a nozzle into the EB/steam feed mixture. Potassium metal does not boil or vaporize in the piping leading to the nozzle, so no contaminant deposits remain and clog the lines. The expected feed rate of potassium to the system may be, for example, 50 to 1000 g/hour, depending on the reactor size and catalyst amount; therefore, the feed rate can be controlled with commonly available components. You may.

In other embodiments, a solution of potassium salt or potassium hydroxide may be injected into the EB/steam stream upstream of reactor 26. Potassium salts dissolved in water may begin to boil or mostly vaporize in the tube leading to the injection nozzle, resulting in precipitated potassium salts or potassium hydroxide depositing in the tube and clogging the system. . The boiling point of a 50% by weight aqueous KOH solution is about 145°C, which is much lower than the temperature of the feed to the reactor, which is 500°C to 650°C. However, according to embodiments herein, the potassium solution is injected into the reactor feed through an insulated tube at a temperature sufficiently low that the solution does not boil and the nozzle is not contaminated. Keep the potassium solution at

FIG. 2 shows a simplified flow diagram of a system 50 for non-boiling injection of potassium solution. Main EB/steam feed 8 passes through tube 7 towards reactor inlet 6. Potassium solution 1 is supplied through an injection nozzle assembly. The injection nozzle assembly may include a supply tube 4 , a nozzle 5 , a shell 2 and an insulation 3 . The insulation layer 3 surrounds and maintains the temperature of the potassium solution in the supply pipe 4 below the boiling point all the way to the nozzle 5 . At nozzle 5, the solution is atomized into EB/steam feed 8. Since the potassium solution is maintained as a liquid in the tube 4 all the way to the nozzle 5, nozzle contamination can be minimized or eliminated.

The type of insulation and thickness of the insulation layer required to prevent boiling of the potassium solution will depend on the potassium salt or compound used and the expected flow rate of the solution through the tubing to the injection nozzle. The higher the boiling point of the solution and the faster the solution flow rate, the less insulation is required. Depending on the solution flow rate, one may aim to inject potassium into the reactor feed at a concentration of 0.01 to 10 ppm by weight. In some embodiments, the solution supply line may be insulated. In other embodiments, the solution supply line may be cooled by heat exchange with a cold heat exchange medium, such as water. For example, cooling may be provided by a heat exchange trace, which may include annular tubing or coils wrapped around the solution supply tube. The ring piping or coils should be at least close to the EB, steam, or EB/steam injection location (e.g., at least several feet away) to eliminate heat exchange with significantly hotter EB, steam, or EB/steam piping and feeds. (within) the solution supply line may be enclosed.

As mentioned above, the system shown in FIG. 2 may be used to continuously or intermittently inject potassium solution into the feedstream. A tube 4 comprising a jacket 2 can also be used, in which case a heat exchange medium 3 circulates through the tube to maintain the potassium solution as a liquid up to the injection nozzle 5. Based on the above description, a person skilled in the art can also envisage using the jacket 2 to supply a heating medium 3 (such as a steam trace) in the annular region to maintain the potassium metal in a molten state up to the injection nozzle 5. . When injecting intermittently, a continuous flow of water may maintain the movement of the solution or fluid through the tube 4.

Also, for both molten potassium injection and potassium solution injection, it is important to ensure that the solution or potassium is vaporized and mixed with the reactor feed. Therefore, the spray angle of the nozzle can be configured to provide good dispersion and to atomize the injected metal or solution to a suitable particle size for mixing and vaporization without accumulation on the EB/steam supply pipe wall.

In some embodiments, a single central spray nozzle 5 may be installed in the middle of the EB/steam supply pipe. In other embodiments, multiple injection nozzles may be placed around the tube to spray toward the center of the supply line. This method can be a good way to distribute potassium when the diameter of the feed tube is very large (several inches). However, in either embodiment, the spray nozzle should be oriented so that the salt solution or molten metal is as far away from the tube wall as possible to minimize deposits and corrosion.

In some embodiments, it has been found to be advantageous to use highly dilute solutions of potassium salts or potassium hydroxide. For example, a 0.02 to 0.5% by weight solution may be used. Although it seems counterintuitive, lowering the solution viscosity can help atomize the solution as finer droplets, making it easier to disperse/vaporize, since the boiling point of the solution can be lower than that of a concentrated solution. Understood. Lower solution concentrations also mean that pure or substantially pure water can be continuously supplied from the injector to keep the injector clean. In some embodiments, potassium salt or potassium hydroxide may be introduced intermittently to maintain catalyst activity. Even if the solution is quite dilute, this has little effect on the process conditions. Additionally, dilute solutions may require faster flow rates to introduce the same amount of potassium, thereby reducing the insulation requirements to maintain the potassium solution below its boiling point.

As mentioned above, embodiments herein relate to a process for dehydrogenating alkylbenzenes, such as ethylbenzene, while maintaining catalyst activity. The process may include mixing a steam stream and an ethylbenzene stream to form an alkylbenzene/steam feed mixture. The alkylbenzene/steam feed mixture may then be fed to a dehydrogenation reactor containing an alkali metal promoted catalyst to dehydrogenate a portion of the alkylbenzene (eg, dehydrogenate ethylbenzene to produce styrene).

To maintain the activity of the alkali metal promoted catalyst, processes according to embodiments herein add an alkali metal to a feedstream comprising at least one of a steam stream, an alkylbenzene feedstream, or an alkylbenzene/steam feed mixture. The method includes the step of injecting a liquid selected from a liquid, an alkali metal compound liquid, or a solution containing an alkali metal. The liquid is injected as a liquid into the feedstream and vaporized and dispersed into the feedstream upstream of the dehydrogenation reactor.

In some embodiments, the alkali metal promoted catalyst includes a potassium promoted catalyst. In some embodiments, the alkali metal promoted catalyst may include an iron-based dehydrogenation catalyst. U.S. Pat. No. 5,739,071 describes many examples of suitable iron-based catalysts, including various catalysts, including, for example, potassium-promoted Fe2O3. Other catalyst systems may also benefit from the injection methods disclosed herein, such as, for example, injection of vanadium or vanadium compounds into a maleic anhydride reactor.

In some embodiments, the alkali metal is injected as a solution. The solution may be, for example, a highly dilute aqueous solution of an alkali metal compound or alkali metal salt. For example, the solution containing an alkali metal may be an aqueous solution containing 0.01 to 1.0% by weight, such as 0.02 to 0.5% by weight, of an alkali metal in water.

The injection system herein may be configured to maintain the liquid (i.e., alkali metal, alkali metal compound liquid, or alkali metal-containing solution) in a liquid state from a point upstream of injection to the injection nozzle. good. The injection system may then be used to disperse the liquid through an injection nozzle to form dispersed droplets of liquid in the feedstream, at which point the injected liquid is in the vaporized feedstream. May be dissolved or evaporated.

In various embodiments, the injection nozzle may be configured to disperse droplets of the liquid, the droplets having an initial particle size of 100 microns or less, 75 microns or less, or 50 microns or less. Good too. As will be appreciated, the droplet size may become smaller as the liquid is dispersed into the vapor, dissolved, or otherwise evaporated. The "initial" particle size therefore relates to the particle size of the droplet particles as they are expelled from the injection nozzle.

In some embodiments, the injection nozzle may be centrally located within the feedstream (eg, proximate the longitudinal axis of the feedstream tube). In other embodiments, the liquid may be dispersed through two or more injection nozzles placed around the periphery of the feedstream, the nozzles directing the feed (EB, steam, or EB/steam, etc.). Co-current injection allows the liquid to be drawn downstream with a significantly larger vapor/hydrocarbon mixture being fed to the reactor. Furthermore, co-current injection may be configured to minimize the accumulation of liquid droplets in the transfer piping by preventing the liquid from being sprayed directly onto the pipe walls.

In some embodiments, continuous injection of alkali metal or alkali metal compound may be required to maintain or restore catalyst activity. In other embodiments, only intermittent injections of the alkali metal or alkali metal compound may be necessary to maintain or restore catalyst activity. In some embodiments, for example, the processes herein may include alternating injection of the liquid and injection of a pure water stream through an injection nozzle. In other words, the process may include the step of intermittently stopping the injection of the liquid and instead injecting pure water from the injection nozzle. Injection of water may be carried out in a similar manner, in which case the water is maintained as a liquid up to the injection nozzle and is dispersed at the injection nozzle. The intermittent presence of a pure water liquid stream helps keep the piping walls and injection nozzles clean and removes alkali metal or alkali metal compound build-up that may result from normal operation or trouble.

In some embodiments, the process of injecting the liquid may include atomizing the liquid with an inert gas. For example, gases considered inert to the reaction system of interest may be used, such as nitrogen, carbon dioxide, steam, argon, and the like. Mixing an inert gas with the liquid immediately upstream of or within the sparge nozzle can improve the dispersion of the liquid into the vapor/hydrocarbon transfer tube at the desired initial particle size.

After the droplets are dispersed into the steam or steam/hydrocarbon feedstream, the droplets may evaporate and disperse as steam into the feedstream. In order to distribute the alkali metal or alkali metal compound throughout the catalyst bed and to avoid settling of the liquid only on catalyst particles close to the inlet, it is possible to completely vaporize the liquid upstream of the reactor inlet. desirable. For example, in some embodiments, evaporation of the liquid may be approximately 5 m It has been found that this can be achieved within a distance of , 10m, or 15m. Accordingly, in various embodiments, the injection nozzle assembly and associated components are located at a reasonable distance upstream from the reactor inlet, such as at least 5 m upstream of the reactor inlet, at least 10 m upstream of the reactor inlet, or at least 10 m upstream of the reactor inlet. It may be located at least 15 meters upstream. In some embodiments, the injection nozzle is located in the main ethylbenzene/steam feedstream about 5 m to 10 m upstream from the dehydrogenation reactor inlet.

In other embodiments, such as where the liquid can be injected into the main vapor line 40, it is preferred to vaporize and disperse the liquid into the stream well before the mixing section, bend, etc. of the piping system. If the distance of introduction of the liquids is too short before such parts of the piping system, the atomized liquids may directly impinge on each other, resulting in undesirable build-up, flow restriction, or clogging of piping components. There is a risk of Accordingly, in various embodiments, the injection nozzle assembly and related components are located at a reasonable distance upstream from the piping component, such as a bend, tee, etc., e.g., at least 5 meters upstream of the piping component, at least 10 meters upstream of the piping component, or at least 10 meters upstream of the piping component. It may be arranged in a straight pipe section at least 15 m upstream of the member.

Embodiments herein also relate to systems for maintaining catalyst activity in a reactor. The system may include a liquid feedstream, such as a liquid alkaline feedstream. The liquid alkaline feedstream may be configured to maintain a liquid alkaline feed selected from at least one of an alkali metal, an alkali metal compound liquid, and a solution comprising an alkali metal in a liquid state. The system also injects a liquid alkali feed as a liquid into a process feed stream selected from a vapor stream, an alkyl aromatic (ethylbenzene) feed stream, and an alkyl aromatic (ethylbenzene)/vapor feed stream upstream of the reactor. and an injection nozzle for forming the alkali-containing feed. The systems herein may also include a dehydrogenation reactor comprising an alkali metal promoted catalyst and having an inlet for receiving an alkali-containing feed or a mixture comprising an alkali-containing feed.

Systems according to embodiments herein may include an alkaline feed stream that is vapor traced, adiabatic, or coolant traced to maintain the alkaline feed as a liquid upstream of the injection nozzle. In some embodiments, the injection nozzle may be located proximate the axial center of the process feedstream. In other embodiments, more than one injection nozzle may be installed around the process feedstream.

The systems herein may also include a water feedstream fluidly connected to the injection nozzle. A control system and associated valves may also be used to intermittently inject a liquid water feedstream in place of the alkaline feedstream. For example, the control system may be configured to alternately supply a liquid alkaline feed and a water feed stream to the injection nozzle.

The injection of an aqueous potassium hydroxide solution (1996 ppm KOH aqueous solution, by weight) was simulated. The solution was simulated as being injected into a tube transporting the main steam feed to the reactor, and the solution was injected with a droplet size of 75 microns. We simulated a main steam line temperature of 860° C. and found that the droplets evaporated while traveling approximately 21.9 feet down the tube. The simulated droplet diameter is shown in Figure 2. In the figure, particle trajectories are colored by particle residence time.

As mentioned above, according to embodiments herein, catalyst activity can be maintained by injecting a liquid agent into the vaporous feedstream. Embodiments herein have the advantage of delivering the liquid agent as a liquid to the vaporous feedstream to minimize salt and metal build-up in and around the injection system and associated piping.

Although described above with respect to dehydrogenation of ethylbenzene, the injection system disclosed herein may be used in other applications where small amounts of non-volatile components need to be injected into the gas phase. For example, using the system herein, small amounts of vanadium may be injected into the feed of a maleic anhydride reactor.

Although this disclosure depicts only a limited number of embodiments, those skilled in the art who have the benefit of this disclosure will appreciate that other embodiments may be devised without departing from the scope of this disclosure. . Accordingly, the scope should be limited only by the claims appended hereto.

Claims (17)

A process for dehydrogenating ethylbenzene, the process comprising:
mixing the steam stream and the ethylbenzene stream to form an ethylbenzene/steam feed mixture;
feeding the ethylbenzene/steam feed mixture to a dehydrogenation reactor containing an alkali metal promoted catalyst to convert a portion of the ethylbenzene to styrene;
Injecting a liquid selected from an alkali metal liquid, an alkali metal compound liquid, or an alkali metal-containing solution into a feedstream comprising at least one of the vapor stream, the ethylbenzene stream, or the ethylbenzene/steam feed mixture. vaporizing and dispersing the liquid into the feedstream upstream of the dehydrogenation reactor;
maintaining the liquid in a liquid state from a point upstream of injection to the injection nozzle; and
A process comprising alternating injection of said liquid and injection of a pure water stream through said injection nozzle. 2. The process of claim 1, wherein the alkali metal promoted catalyst comprises a potassium promoted catalyst. The process of claim 1, wherein the alkali metal-containing solution comprises 0.02-0.5% by weight of alkali metal in water. The above injection process is
2. The process of claim 1, comprising dispersing the liquid through the injection nozzle to form dispersed droplets of liquid in the feedstream, and evaporating the liquid into the feedstream. 5. The process of claim 4, wherein the initial particle size of the dispersed droplets is 75 microns or less. 5. The process of claim 4, wherein the injection nozzle is centrally located within the feedstream. 5. Dispersing the liquid through two or more injection nozzles arranged around the periphery of the feedstream and configured to spray in co-current with the feed towards the center of the feedstream. Process described. 5. The process of claim 4, wherein the step of injecting includes atomizing the liquid with an inert gas. 5. The process of claim 4 , wherein said evaporating step comprises evaporating said dispersed droplets into said feedstream within a distance of about 10 meters. A system for maintaining catalyst activity in an ethylbenzene dehydrogenation reactor, the system comprising:
A liquid alkali feed configured to maintain a liquid alkali feed selected from at least one of an alkali metal, an alkali metal compound liquid, and a solution containing an alkali metal in a liquid state;
an injection nozzle for injecting the liquid alkali feed as a liquid into a process feedstream selected from a vapor stream, an ethylbenzene feedstream, and an ethylbenzene/vapor feedstream to form an alkali-containing feed;
a water feedstream fluidly connected to the injection nozzle;
a control system configured to alternately supply the liquid alkaline feed and the water feedstream to the injection nozzle; and
A system comprising a dehydrogenation reactor comprising an alkali metal promoted catalyst and having an inlet for receiving the alkali-containing feed or a mixture comprising the alkali-containing feed. 11. The system of claim 10, wherein the liquid alkaline feed is vapor traced, adiabatic, or coolant traced to maintain the liquid alkaline feed as a liquid upstream of the injection nozzle. 11. The system of claim 10, wherein the injection nozzle is located proximate an axial center of the process feedstream. 11. The system of claim 10, comprising two or more injection nozzles disposed around the process feedstream. 11. The system of claim 10, wherein the nozzle is configured to disperse the liquid alkaline feed in the form of droplets having an initial particle size of 75 microns or less. 11. The system of claim 10, further comprising an inert gas feedstream fluidly connected to the injection nozzle. 11. The system of claim 10, wherein the injection nozzle is located in the main ethylbenzene/steam feedstream about 5 m to 10 m upstream from the dehydrogenation reactor. 11. The system of claim 10, wherein the injection nozzle is configured to maintain a spray of liquid droplets within a central portion of the process feedstream.

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