Reactor evacuation method and system for dehydrogenation reactor

Abstract

The present disclosure provides a method of operating a dehydrogenation reactor requiring vacuum pressure during the dehydrogenation reaction, the method including feeding a hydrocarbon to a reactor comprising a catalyst bed and configured to dehydrogenate the hydrocarbon under vacuum pressure; purging the reactor to remove remaining hydrocarbon; regenerating the catalyst bed with air from a regeneration air source; and evacuating the reactor to induce vacuum pressure, wherein the evacuating comprises passing a motive gas through a reactor evacuation ejector in fluid connection with the reactor, wherein the motive gas is nitrogen or air in the absence of steam. A system for dehydrogenation of a hydrocarbon is also provided, which includes a dehydrogenation reactor and a reactor evacuation ejector in fluid communication with the dehydrogenation reactor and a motive gas source, wherein the motive gas is nitrogen or air in the absence of steam.

Description

REACTOR EVACUATION METHOD AND SYSTEM FOR DEHYDROGENATION REACTORTECHNOLOGICAL FIELD

[0001] The present disclosure relates to methods and systems for dehydrogenation of a hydrocarbon.BACKGROUND

[0002] Fixed bed dehydrogenation units are used for production of olefins and / or alkynes from alkanes and / or olefins. Generally, a fixed bed dehydrogenation unit comprises three or more parallel fixed bed reactors and a catalyst regeneration system. When the fixed bed dehydrogenation unit is in operation, one or more reactors are on line (in dehydrogenation mode), and one or more fixed bed reactors are in regeneration mode.

[0003] A fixed bed reactor in dehydrogenation mode first dehydrogenates the hydrocarbon feed for a period of time. Then, the fixed bed reactor is purged with steam. In a subsequent regeneration mode, heated air is blown through to decoke the catalyst disposed in the fixed bed reactor. The reactor is in turn evacuated and the catalyst in the reactor undergoes reduction. After catalyst reduction, the reactor is placed back on line for dehydrogenation reactions. The same sequence is repeated automatically for each fixed bed reactor using a programmable logic controller (PLC) to ensure continuous production of the entire dehydrogenation unit.

[0004] The dehydrogenation reactors operate under vacuum during the dehydrogenation step. The vacuum in these reactors is created by a steam jet ejector using steam as the motive fluid. WO2016069918 Al discuss about the pressure within the reactor can be reduced to less than atmospheric pressure with one or more steam ejectors. Typically, in large dehydrogenation units, about 20 t / hr of steam at 12-13 bar abs is vented through this ejector. The evacuation is done cyclically because air regeneration of the reactor occurs under nominal pressure, thus requiring evacuation of the reactor during each production cycle. The cyclical steam purge takes place every 4-5 minutes. Since the steam passing through the ejector is vented to atmosphere, use of steam as a motive fluid in such large amounts presents a significant cost. There remains a need in the art to decrease the cost and improve the efficiency of operating dehydrogenation reactors.BRIEF SUMMARY

[0005] Example implementations of the present disclosure are directed to processes and systems for dehydrogenation of a hydrocarbon. Such systems typically include a dehydrogenation reactor comprising a catalyst bed in fluid communication with a hydrocarbon feed source; a regeneration air source in fluid communication with the dehydrogenation reactor; a reactor evacuation ejector in fluid communication with the dehydrogenation reactor; and a motive gas source. The reactor evacuation ejector is adapted to reduce the pressure in the reactor below atmospheric pressure. According to the present disclosure, the motive gas is nitrogen or air in the absence of steam. By replacing steam as the motive gas, venting of steam to atmosphere during the reactor evacuation process is avoided, improving energy efficiency of the process and reducing cost associated with steam production.

[0006] In certain embodiments, the motive gas is air from a bleed air line of a gas turbine comprising an internal compressor and a turbine unit, wherein the bleed air line is in fluid communication with the outlet of the internal compressor. In certain advantageous embodiments, the same gas turbine also drives an external compressor that provides regeneration air to the reactor. Accordingly, the same gas turbine can serve as both the power source for a regeneration air supply and a source of motive gas, such that additional costly equipment is not required.

[0007] The present disclosure includes, without limitation, the following embodiments.

[0008] Embodiment 1 : A method of operating a dehydrogenation reactor requiring vacuum pressure during the dehydrogenation reaction, comprising: feeding a hydrocarbon to a reactor comprising a catalyst bed and configured to dehydrogenate the hydrocarbon (e.g., to produce an olefin) under vacuum pressure; optionally purging the reactor to remove remaining hydrocarbon; regenerating the catalyst bed with air from a regeneration air source; and evacuating the reactor to induce vacuum pressure, wherein the evacuating comprises passing a motive gas through a reactor evacuation ejector in fluid connection with the reactor, wherein the motive gas is nitrogen or air in the absence of steam. This method of operating a dehydrogenation reactor is suitable to operate thesystem for dehydrogenation of a hydrocarbon according to the invention, in particular but not limited to Embodiment 10 to 15 related to the system.

[0009] Embodiment 2: The method of Embodiment 1, wherein the motive gas is nitrogen produced in an air separation process or air from a bleed air line of a gas turbine comprising an internal compressor and a turbine unit, wherein the bleed air line is in fluid communication with the outlet of the internal compressor. In Particular, the dehydrogenation reactor is connected to a gas turbine comprising an internal compressor and a turbine unit, which will generate air stream necessary for the regeneration and evacuation step.

[0010] Embodiment 3: The method of Embodiment 2, wherein the gas turbine drives an external air compressor in fluid communication with the reactor, wherein the external air compressor is the regeneration air source.

[0011] Embodiment 4: The method of any one of Embodiments 1 to 3, wherein evacuating the reactor comprises evacuating the reactor to a vacuum pressure of about 0.6 bar or less.

[0012] Embodiment 5: The method of any one of Embodiments 1 to 4, wherein the motive gas entering the reactor evacuation ejector has a temperature of about 260 to about 370 °C and / or a pressure of about 7 to about 25 bar.

[0013] Embodiment 6: The method of any one of Embodiments 1 to 5, wherein the hydrocarbon is selected from the group consisting of propane, isobutane, pentane, isopentane, n-butane, 1 -butene, and combinations thereof.

[0014] Embodiment 7: The method of any one of Embodiments 1 to 6, wherein purging the reactor comprises passing steam through the reactor.

[0015] Embodiment 8: The method of any one of Embodiments 1 to 7, further comprising reducing the catalyst bed after evacuating the reactor.

[0016] Embodiment 9: The method of any one of Embodiments 1 to 8, further comprising venting the motive gas from the reactor evacuation ejector to atmosphere.

[0017] Embodiment 10: A system for dehydrogenation of a hydrocarbon, comprising: a dehydrogenation reactor comprising a catalyst bed in fluid communication with a hydrocarbon feed source; a regeneration air source in fluid communication with the dehydrogenation reactor; a reactor evacuation ejector in fluid communication with thedehydrogenation reactor and a motive gas source, wherein the motive gas is nitrogen or air in the absence of steam; and, optionally, a purge gas source in fluid communication with the dehydrogenation reactor.

[0018] Embodiment 11 : The system of Embodiment 10, wherein the motive gas source is nitrogen produced in an air separation process or air from a bleed air line of a gas turbine comprising an internal compressor and a turbine unit, wherein the bleed air line is in fluid communication with the outlet of the internal compressor.

[0019] Embodiment 12: The system of Embodiment 11, wherein the gas turbine drives an external air compressor in fluid communication with the reactor, wherein the external air compressor is the regeneration air source.

[0020] Embodiment 13: The system of any one of Embodiments 10 to 12, further comprising a reducing gas source in fluid communication with the dehydrogenation reactor.

[0021] Embodiment 14: The system of any one of Embodiments 10 to 13, wherein the purge gas source is a steam source.

[0022] Embodiment 15: The system of any one of Embodiments 10 to 14, wherein the hydrocarbon feed source provides a hydrocarbon selected from the group consisting of propane, isobutane, pentane, isopentane, n-butane, 1 -butene, and combinations thereof.

[0023] These and other features, aspects, and advantages of the present disclosure will be apparent from a reading of the following detailed description together with the accompanying figures, which are briefly described below. The present disclosure includes any combination of two, three, four or more features or elements set forth in this disclosure, regardless of whether such features or elements are expressly combined or otherwise recited in a specific example implementation described herein. This disclosure is intended to be read holistically such that any separable features or elements of the disclosure, in any of its aspects and example implementations, should be viewed as combinable, unless the context of the disclosure clearly dictates otherwise.

[0024] It will therefore be appreciated that this Brief Summary is provided merely for purposes of summarizing some example implementations so as to provide a basic understanding of some aspects of the disclosure. Accordingly, it will be appreciated that the above described example implementations are merely examples and should not beconstrued to narrow the scope or spirit of the disclosure in any way. Other example implementations, aspects and advantages will become apparent from the following detailed description taken in conjunction with the accompanying figures which illustrate, by way of example, the principles of some described example implementations.BRIEF DESCRIPTION OF THE FIGURES

[0025] Having thus described aspects of the disclosure in the foregoing general terms, reference will now be made to the accompanying figures, which are not necessarily drawn to scale, and wherein:

[0026] FIG. l is a schematic representation of a dehydrogenation reactor system according to an example implementation of the present disclosure;

[0027] FIG. 2 is a schematic representation of an example embodiment of a single dehydrogenation reactor showing the reactor evacuation ejector according to an example implementation of the present disclosure; and

[0028] FIG. 3 is a schematic representation of an example embodiment of an air bleed line of a turbine used to provide motive air to a reactor evacuation ejector according to an example implementation of the present disclosure;DETAILED DESCRIPTION

[0029] Some implementations of the present disclosure will now be described more fully hereinafter with reference to the accompanying figures, in which some, but not all implementations of the disclosure are shown. Indeed, various implementations of the disclosure may be embodied in many different forms and should not be construed as limited to the implementations set forth herein; rather, these example implementations are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout.

[0030] Unless specified otherwise or clear from context, references to first, second or the like should not be construed to imply a particular order. A feature described as being above another feature (unless specified otherwise or clear from context) may instead be below, and vice versa; and similarly, features described as being to the left of anotherfeature else may instead be to the right, and vice versa. Also, while reference may be made herein to quantitative measures, values, geometric relationships or the like, unless otherwise stated, any one or more if not all of these may be absolute or approximate to account for acceptable variations that may occur, such as those due to engineering tolerances or the like.

[0031] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., ranges of “up to 25 wt. %, or, more specifically, 5 wt. % to 20 wt. %”, is inclusive of the endpoints and all intermediate values of the ranges of “5 wt. % to 25 wt. %,” etc.). “Combination” is inclusive of blends, mixtures, alloys, reaction products, and the like.

[0032] As used herein, unless specified otherwise or clear from context, the “or” of a set of operands is the “inclusive or” and thereby true if and only if one or more of the operands is true, as opposed to the “exclusive or” which is false when all of the operands are true. Thus, for example, “[A] or [B]” is true if [A] is true, or if [B] is true, or if both [A] and [B] are true. Further, the articles “a” and “an” mean “one or more,” unless specified otherwise or clear from context to be directed to a singular form. Dehydrogenation Process and System

[0033] The present disclosure relates to improvements in reactor evacuation for a dehydrogenation process used to convert alkanes to alkenes over, for example, a chromium-alumina catalyst. The dehydrogenation process takes place in fixed bed reactors that operate on a cyclic basis to permit continuous flow of the major process streams. Dehydrogenation units typically include multiple reactors operated in parallel multiple reactors at least 2, preferably 3 to 5 wherein the reactors are synchronized in a coordinated way to have difference of at least one step of the dehydrogenation process for example in a dehydrogenation process with two reactors one reactor will be in the purging step, second reactor will be in regeneration step. The goal is to increase the throughput of the dehydrogenation unit by reducing the down time. In one cycle, hydrocarbon vapors are dehydrogenated (dehydrogenation step) for example a period of 7 minutes to 9 minutes and the reactor is then purged with steam (purging step) for example a period of 1 minute to 2 minutes and blown with air to burn off coke (regeneration step) for example a period of 7 minutes to 9 minutes. These steps are followed by anevacuation step for example a period of 2 minutes to 3 minutes and reduction step for example a period in the range of 2 to 3 minutes and then another cycle starts. A cycle timing device actuates hydraulically operated valves to control the operation. Each cycle operates for example a period of 1 minute to 26 minutes or 2 minutes to 24 minutes or 3 minutes to 24 minutes or 4 minutes to 23 minutes, preferably for a period of 2 minutes to 23 minutes, more preferably for a period of 4 minutes to 22 minutes.

[0034] In a typical fixed bed dehydrogenation process, an aliphatic hydrocarbon (e.g., propane, isobutane, n-butane, 1 -butene, or isopentane) passes through a dehydrogenation catalyst bed and is dehydrogenated to a complementary olefin. The olefin is then flushed from the catalyst bed, the catalyst is regenerated and reduced, and the cycle is repeated. The product (dehydrogenated hydrocarbon) of the fixed bed dehydrogenation unit may comprise, for example, propylene, isobutylene, pentene, isoprene, butadiene, or combinations thereof. The dehydrogenation reactions may include reactions (i) and / or (ii) as follows, where “n” in reactions (i) and (ii) is the number of carbon atoms in a hydrocarbon molecule, and “n” is less than 5:

[0035] C IIH2II 2^CHH2II+H2 (i), and / or

[0036] CnH2n^CnH2n-2+H2(ii).

[0037] This process can be run as an adiabatic, cyclic process. Each cycle includes a catalyst reduction step and a dehydrogenation step, and typically further includes a step to purge the remaining hydrocarbon from the reactor, and finally a regeneration step with air. Following this, the cycle begins again with the catalyst reduction step.

[0038] The reactors in dehydrogenation processes operate under vacuum. The pressure within the reactor can be reduced to less than atmospheric pressure using any suitable device, system, or combination of devices and / or systems. For example, the pressure can be reduced with one or more ejectors, e.g., a steam ejector, in fluid communication with the reactor and configured to pull a vacuum on the reactor. The pressure created in the reactor by vacuum is called vacuum pressure or final reactor pressure. The evacuation of the reactors is accomplished using a reactor evacuation ejector, and conventionally, MP steam is used as the motive fluid. As explained more fully below, in the present disclosure, MP steam is replaced with air or nitrogen. The ejector effluent is typically vented to atmosphere and is non-recoverable. The vacuumpressure after evacuation is typically about 0.6 bar or less, such as about 0.2 to about 0.6 bar (Absolute).

[0039] With reference to FIG. 1, a process schematic diagram for an example implementation of a fixed bed dehydrogenation unit 100 is shown, with different reactors at different points in the process cycle. The fixed bed dehydrogenation unit 100 may include a fixed bed reactor 101 in purge mode, a fixed bed reactor 102 in dehydrogenation mode, and a fixed bed reactor 103 in regeneration mode. Each of the fixed bed reactors comprises a catalyst bed. The catalyst may include Cr / Al (chromium oxide over alumina), Sn — Pt / Al (tin-platinum over alumina), or combinations thereof.

[0040] The inlet of fixed bed reactor 102 in dehydrogenation mode may be connected to a heater 110 that is configured to heat a hydrocarbon feed to a reaction temperature, and the outlet of fixed bed reactor 102 in dehydrogenation mode may be connected to a heat exchanger 108 to cool down the effluent from fixed bed reactor 102 in dehydrogenation mode. The combined hydrocarbon stream 13 from a hydrocarbon feed stream 11 and a recycled hydrocarbon stream 12 may be vaporized and heated to a reaction temperature by heater 110. The reaction temperature is typically about 540 °C to about 750 °C. The reaction pressure may be in a range of about 0.2 to about 1.2 bar.

[0041] Fixed bed dehydrogenation unit 100 may further include a regeneration air system comprising an air compressor 104 configured to blow air into fixed bed reactor 103 in regeneration mode, a regeneration air heater 105 configured to heat the air from air compressor 104, a fuel injector 106 configured to inject fuel gas into fixed bed reactor 103 in regeneration mode, and a heat exchanger 107 configured to cool down the effluents from fixed bed reactor 103 in regeneration mode and fixed bed reactor 101 in purge mode. Fuel injector 106 may be disposed between air compressor 104 and air heater 105. A stream 16 leaving fixed bed reactor 103 in regeneration mode may be used for generating steam via heat exchanger 107. The regenerating conditions can include a regenerating pressure of about 0.1 to about 10 bar. The regenerating conditions can include a regenerating period that may be in a range of about 7 to about 18 minutes.

[0042] The fixed bed dehydrogenation unit 100 may further include a compression and recovery system 109 to recover and purify a dehydrogenated hydrocarbon obtained from fixed bed reactor 102 in dehydrogenation mode. Specifically, an effluentstream 14 from fixed bed reactor 102 in dehydrogenation mode may be cooled, recovered, and purified through recovery system 109. Purified dehydrogenated hydrocarbon may flow in a stream 17. Recovered unreacted hydrocarbon may be recycled back to combined hydrocarbon stream 13 via recycled hydrocarbon stream 12.

[0043] The fixed bed dehydrogenation unit 100 may further include a purge gas source 20 (e.g., steam) in fluid communication with each reactor for use in the purge step and a reducing gas source 22 (e.g., hydrogen) in fluid communication with each reactor.

[0044] Process sequence can be controlled, for example, using programmable logic controllers. See, for example, the programmable logic controllers set forth in US Pat. No. 11,370,729 to Ansari et al. and US Pat. Publ. No. 2022 / 0055002 to Bodas et al, which are incorporated by reference herein in their entirety.Evacuation System for Dehydrogenation Reactor

[0045] According to the present disclosure, air or nitrogen is used as the motive fluid for reactor evacuation. An example implementation of a dehydrogenation reactor system 30 using air or nitrogen as the motive fluid passed through the evacuator is shown in FIG.2. For the sake of simplicity, a single reactor is illustrated in FIG. 2, but as shown in FIG. 1, dehydrogenation units typically include multiple reactors operated in parallel. The system 30 includes a reactor 32 in fluid communication with a hydrocarbon feed 34, a regeneration air feed 36, a purge gas feed 38, and a reducing gas feed 40. The reactor 32 has a hydrocarbon effluent stream 42 and an off-gas effluent stream 44.

[0046] Additionally, as shown in FIG. 2, the reactor 32 is also in fluid communication with a reactor evacuation ejector 46. The ejector 46 is adapted for reducing pressure in the reactor 32 by passing a motive gas feed 48 through the ejector. Unlike conventional systems using steam as a motive gas, the present disclosure utilizes an air or nitrogen source 50 as the motive gas feed 48. The motive gas effluent 52 is typically vented to atmosphere. In certain embodiments, the motive gas entering the reactor evacuation ejector 46 has a temperature of about 260 to about 370 °C and / or a pressure of about 7 to about 25 bar (g) (e.g., about 10 bar to about 25 bar or about 15 bar to about 20 bar).

[0047] According to the present disclosure, the motive gas is characterized by an absence of steam, meaning the motive gas is substantially or completely free of steam. Example ranges of steam in the motive gas include 10% by volume or less of steam,based on the total volume of the motive gas, such as 5% or less of steam, or 1% or less of steam, or 0.5% or less of steam, or 0.1% or less of steam, or even 0.0% steam. By replacing steam as the motive gas, venting large amounts of steam to atmosphere is avoided, which increases the energy efficiency of the overall dehydrogenation process and reduces cost associated with steam production.

[0048] The source 50 of the air or nitrogen for use as motive gas feed 48 can vary. In certain embodiments, the motive gas source is nitrogen from an air separation plant. Large chemical plant complexes often include an air separation plant to produce purified oxygen and nitrogen streams useful in various processes. Such air separation processes often produce nitrogen in great surplus, much of which is vented to atmosphere due to lack of demand. This surplus nitrogen can be used as the motive gas feed 48 passed through the reactor evacuation ejector 46.

[0049] In other embodiments, bleed air from a gas turbine can be used. Gas turbines typically include an internal compressor that produces compressed air for combustion within an internal combustor. Diverting a portion of the compressed air from the internal compressor through a bleed line can provide the necessary motive gas for the reactor evacuation ejector 46.

[0050] The regeneration gas demand in a dehydrogenation system is generally quite high, requiring use of a gas turbine to drive a regeneration air compressor (e.g., air compressor 104 of FIG. 1). Example gas turbines for use in driving a regeneration air compressor include GE MS5001 available from General Electric, as well as SGT 750 and SGT 700 available from Siemens. Typically, such gas turbines operate at an efficiency of about 25-45% and have a multi-stage internal axial combustion air compressor that delivers about 10 bar (ga) air pressure or above, such as about 15 bar or above or about 20 bar or above (e.g., about 10 bar to about 25 bar or about 15 bar to about 20 bar). Such turbines are typically adapted to allow air bleed from the effluent from the internal compressor. This bleed air can be used as the motive gas to the reactor evacuation ejector 46 of FIG. 2, which means an existing gas turbine used in the process can be used as the source of motive gas for the reactor evacuation ejector 46.

[0051] Use of an air bleed from a turbine will result in a slight de-rating of the turbine’s capacity. However, this will typically have no appreciable impact on the overallprocess because, even for demand as high as 700 t / hr of air, gas turbines used to drive this compression typically range between 20 and 26 MW in power generation capacity. Since the expected de-rating is no more than 2-5%, there is no meaningful impact on turbine performance as the turbine is under a seasonally varying load much smaller than its maximum load capacity.

[0052] An example implementation of bleed air for this use is shown in FIG. 3, which illustrates a gas turbine 60 comprising an internal compressor 62 receiving air from an inlet 64 and producing a pressurized effluent 66. The pressurized effluent 66 is in fluid communication with an internal combustor 68, with the internal combustor also receiving a combustible fuel 70. The combustor effluent 72 enters an internal turbine 74 that produces work from the energy of the gas. The exhaust 76 from the gas turbine 60 can be fed to a waste heat boiler (not shown). As illustrated, in certain embodiments, the gas turbine 60 can serve dual purposes within the dehydrogenation system. Specifically, the gas turbine 60 can be used to drive an external regeneration air compressor 80, which produces regeneration air to be passed to reactor 32 of FIG. 2 for example, and also used as a source of motive gas for ejector 82.

[0053] As shown, a bleed line 84 from the pressurized effluent 66 from the internal compressor 62 of the gas turbine 60 can be in fluid communication with the ejector 82 and used as a motive gas to pull a vacuum on a reactor, such as reactor 32 of FIG. 2. In other words, the bleed line 84 from the gas turbine 60 can be the air source 50 of FIG. 2.

[0054] In general, the invention may alternately comprise, consist of, or consist essentially of, any appropriate components herein disclosed. The invention may additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants or species used in the prior art compositions or that are otherwise not necessary to the achievement of the function and / or objectives of the present invention.

[0055] Many modifications and other implementations of the disclosure will come to mind to one skilled in the art to which this disclosure pertains having the benefit of the teachings presented in the foregoing descriptions and the associated figures. Therefore, it is to be understood that the disclosure is not to be limited to the specific implementations disclosed herein and that modifications and other implementations are intended to beincluded within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

WHAT IS CLAIMED IS:

1. A method of operating a dehydrogenation reactor requiring vacuum pressure during the dehydrogenation reaction, comprising: a) feeding a hydrocarbon to a reactor comprising a catalyst bed and configured to dehydrogenate the hydrocarbon under vacuum pressure; b) purging the reactor to remove remaining hydrocarbon; c) regenerating the catalyst bed with air from a regeneration air source; and d) evacuating the reactor to induce vacuum pressure, wherein the evacuating comprises passing a motive gas through a reactor evacuation ejector in fluid connection with the reactor, wherein the motive gas is nitrogen or air in the absence of steam.

2. The method of Claim 1, wherein the motive gas is air from a bleed air line of a gas turbine comprising an internal compressor and a turbine unit, wherein air from the bleed air line is in fluid communication with the outlet of the internal compressor.

3. The method of Claim 2, wherein the gas turbine drives an external air compressor in fluid communication with the reactor, wherein the external air compressor is the regeneration air source.

4. The method of any of Claims 1 to 3, wherein evacuating the reactor comprises evacuating the reactor to a vacuum pressure of about 0.6 bar or less.

5. The method of any of Claims 1 to 3, wherein the motive gas entering the reactor evacuation ejector has a temperature of about 260 to about 370 °C and / or a pressure of about 7 to about 25 bar.

6. The method of any of Claims 1 to 3, wherein the hydrocarbon is selected from the group consisting of propane, isobutane, pentane, isopentane, n-butane, 1 -butene, and combinations thereof7. The method of any of Claims 1 to 3, wherein purging the reactor comprises passing steam through the reactor.

8. The method of any of Claims 1 to 3, further comprising reducing the catalyst bed after evacuating the reactor.

9. The method of any of Claims 1 to 3, further comprising venting the motive gas from the reactor evacuation ejector to atmosphere.

10. A system for dehydrogenation of a hydrocarbon, comprising: a) a dehydrogenation reactor comprising a catalyst bed in fluid communication with a hydrocarbon feed source; b) a regeneration air source in fluid communication with the dehydrogenation reactor; c) a reactor evacuation ejector in fluid communication with the dehydrogenation reactor and a motive gas source, wherein the motive gas source is nitrogen or air in the absence of steam; and d) a purge gas source in fluid communication with the dehydrogenation reactor.

11. The system of Claim 10, wherein the motive gas source is air from a bleed air line of a gas turbine comprising an internal compressor and a turbine unit, wherein the air from the bleed air line is in fluid communication with the outlet of the internal compressor.

12. The system of Claim 11, wherein the gas turbine drives an external air compressor in fluid communication with the reactor, wherein the external air compressor is the regeneration air source.

13. The system of any one of Claims 10 to 12, further comprising a reducing gas source in fluid communication with the dehydrogenation reactor.

14. The system of any one of Claims 10 to 12, wherein the purge gas source is a steam source.

15. The system of any one of Claims 10 to 12, wherein the hydrocarbon feed source provides a hydrocarbon selected from the group consisting of propane, isobutane, pentane, isopentane, n-butane, 1 -butene, and combinations thereof.

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