Dehydrogenation process and system with reactor reordering

Abstract

A dehydrogenation system includes a plurality of dehydrogenation reactors, the plurality of dehydrogenation reactors being valve controlled by a plurality of valves to operate in a timed sequence in a system cycle in alternating dehydrogenation and regeneration modes, a digital programmable controller connected to the plurality of valves for sequencing the reactors, and means for determining production rate characteristics of each reactor within the system cycle. The digital controller is operable to re-sequence the reactors to reduce peak production rate or production rate differentials within an initial system cycle. Following re-sequence, production can be increased without exceeding system limitations, for example, without exceeding compressor operating limitations, and the production rate profile of the re-sequenced system is more uniform.

Description

[0001] This application is a divisional application. The original application has the application number CN202080050920.8, the application date is April 30, 2020, and the invention title is Dehydrogenation Process and System with Reactor Reordering.

[0002] Priority Claim

[0003] This application is based on U.S. Patent Application Serial No. 16 / 587,161, filed September 30, 2019, which has the same title. U.S. Patent Application Serial No. 16 / 587,161 is based on U.S. Provisional Application No. 62 / 878,864, filed July 26, 2019, which also has the same title. Priority to the aforementioned application is claimed, and its disclosure is incorporated herein by reference. Technical Field

[0004] This invention generally relates to cyclic dehydrogenation processes and systems with multiple dehydrogenation reactors operating in alternating and synchronous production / regeneration modes. These processes involve the dehydrogenation of alkanes on a fixed bed of catalysts such as supported chromium, gallium, or platinum / tin. This invention relates to sequencing or reordering the reactors to reduce fluctuations in productivity within the system cycle, thereby improving productivity. Background Technology

[0005] Hydrocarbon dehydrogenation processes are typically implemented using systems with compressors and absorbers serving multiple sequenced reactors that operate in alternating production / regeneration modes in a repetitive cycle within the system. For example, GB 794,089 illustrates a process for catalytic dehydrogenation of hydrocarbons in which the catalyst is alternately contacted with the hydrocarbon charge and regenerated by combustion of carbonaceous deposits resulting from the dehydrogenation of the hydrocarbon charge. Each operation is carried out in a set of reactors that operate in a timed sequence with substantially equal durations of hydrocarbon conversion and catalyst regeneration. The sequence of operations for each reactor is as follows: (1) hydrocarbon dehydrogenation, (2) steam purging to remove the catalyst and hydrocarbon products from the reaction vessel, (3) catalyst regeneration in an oxygen-containing gas, (4) venting, and (5) reduction of the catalyst by oxidation in a hydrogen-containing gas. GB 794,089... Figure 2 An exemplary form of a dehydrogenation system is shown. As illustrated, the system comprises five reactors R, which operate in a single cycle, such that two reactors operate simultaneously for catalytic dehydrogenation, two reactors undergo catalyst regeneration, and one reactor is in operation during a phase involving operations such as venting, steam purging, hydrogen reduction, or valve replacement. (GB 794,089) Figure 3 The diagram shows how the reactor operates in a cycle of approximately 22.5 minutes.

[0006] GB 823,626 illustrates another multi-reactor dehydrogenation system. According to the GB 823,626 specification, two or more 3-reactor batteries are used. GB 823,626... Figure 2 An exemplary dehydrogenation system is illustrated. As shown, the system includes six reactors R, arranged in two groups of three reactors each, and operated in a sequence such that two reactors (i.e., one reactor from each group) operate simultaneously for catalytic dehydrogenation, both reactors undergo catalyst regeneration, and both reactors are involved in stages involving operations such as venting, steam purging, hydrogen reduction, or valve replacement. (GB 823,626) Figure 3 The diagrams show how the reactor operates in a 15-minute repeating cycle. See GB 823,626. Figure 3 The circulation diagram shows that reactors 1 and 4, 2 and 5, and 3 and 6 are always in the same stage of a cycle. The desirability of this arrangement, according to GB 823,626, stems from the fact that the paired reactors are opposite each other, as described in GB 823,626. Figure 2 As shown in the diagram. Therefore, the gaseous material introduced into the paired reactors and the gaseous material discharged from the reactors will travel equal distances to reach the main line that introduces and removes the gas. GB823,626 further states that staggered cycle times may be ideal in reducing the need for associated auxiliary equipment such as pumps and compressors, since only one reactor is transitioned at a time.

[0007] Other dehydrogenation systems with programmable controllers can be seen in U.S. Patents 4,581,339 and 7,271,307 and WO 2018 / 203233.

[0008] As understood in the prior art, multiple alternating reactors in a dehydrogenation system operate in a fixed sequence, meaning they always operate in the same consecutive order. This is partly based on the assumption that reactors with identical construction, identical catalysts, feedstocks, and operating conditions will have equal performance in terms of conversion. However, it has been found that similar reactors may not operate in substantially the same way, especially when the catalyst ages. Significant differences can arise in pressure / volume requirements and productivity, which is not irrelevant in gaseous dehydrogenation systems, as an additional mole of hydrogen is produced for every mole of dehydrogenated product. When multiple reactors exhibiting high productivity are operating simultaneously in production mode, differences in pressure drop / volume requirements can overload the downstream product compressor or the upstream regenerator air compressor. This causes the system to shut down when it reaches its power limit, thus limiting productivity based on peak output within a cycle.

[0009] Similarly, in multi-reactor systems, productivity differences between reactors can lead to inefficiencies, productivity losses, and yield losses when the capacity of downstream product recovery equipment, particularly the absorber, is exceeded or underutilized. When the product recovery capacity is exceeded, dehydrogenation products are burned and lost. When the absorber is underutilized, hydrogen is unnecessarily absorbed, increasing the system's energy requirements. Summary of the Invention

[0010] It has been found that significant and unexpected increases in productivity are achieved by reordering the reactors in an alternating cycle multi-reactor dehydrogenation system. In fact, productivity is maximized by reducing the peak conversion rate in the repeated cycles. The overall reactor productivity is balanced to operate close to compressor capacity throughout the cycle, and process variability is reduced, thereby improving absorber performance. In a preferred embodiment, the present invention relates to reordering the reactors to reduce peak conversion and reduce the productivity delta in the system cycle. A preferred system for implementing the invention is a multi-fixed bed, adiabatic endothermic reaction system, referred to in this art as a Houdry dehydrogenation system, as shown in GB 794,089 and GB 823,626.

[0011] By reference Figure 1 To better understand the present invention, Figure 1 This is a graph showing the change in isobutylene yield over time in a seven-reactor system operating for 22 (22) minutes, with different reactor sequences within repeated system cycles. In the initial sequence before reordering, the system exhibited a yield difference of approximately 8%, but after reordering, this difference was reduced to half or less; the peak productivity decreased by approximately 5%, corresponding to a 2.5% yield reduction. Since the system before reordering was limited by peak productivity, in the reordered system, productivity can be increased by increasing the hydrocarbon feed rate, increasing the hydrocarbon feed temperature, increasing the regeneration air temperature, or decreasing the inlet pressure, to produce an additional 5% of product per hour using the same equipment, such as... Figure 1 The mid-productivity is shown by the dashed line.

[0012] The invention can be implemented in various ways by determining and adjusting the productivity of various reactors to improve productivity. For example, in a relatively simple system limited to a yield value of 50 by a downstream product compressor, there are four reactors. Two reactors operate simultaneously in dehydrogenation and regeneration mode, exhibiting a yield of 50. These two reactors alternate with two reactors operating simultaneously in dehydrogenation and regeneration mode in a cycle, exhibiting a yield value of 40. In repeated operating cycles, the peak yield value will be 50, and the yield difference will be 10. If the reactors are reordered within an operating cycle such that one reactor with a yield value of 50 operates simultaneously with one reactor with a yield value of 40 in the same mode, the peak yield value is 45, and the yield difference disappears. Since the system can handle a yield value of 50, productivity can be increased by increasing the hydrocarbon feed rate, increasing the hydrocarbon feed temperature, increasing the regeneration air temperature, etc. Additional capacity is provided without capital expenditure, only incremental operating expense.

[0013] In many implementations, the number of reactors online at any given time is approximately the same before and after reordering; however, if desired, overactive reactors (hot spots) or underperforming reactors can be isolated to allow the system to reach a better balance.

[0014] Further details and advantages will become apparent from the following description. Attached Figure Description

[0015] The invention will now be described in detail with reference to the accompanying drawings, in which:

[0016] Figure 1 The graph shows the yield of isobutene produced from isobutane over time in a multi-reactor system with a cycle time of approximately twenty-two (22) minutes.

[0017] Figure 2 This is a schematic diagram of an individual dehydrogenation reactor connected to a digital controller that is part of a group of reactors, according to the present invention.

[0018] Figure 3 This is a partial schematic diagram according to the invention, illustrating that the data can be reordered using a digital controller. Figure 2 A group of reactors of the type shown (all reactors are as follows) Figure 2 (As shown, connected to the controller).

[0019] Figure 4 It is shown Figure 3 A bar chart showing the yield of each reactor during operation in dehydrogenation mode.

[0020] Figure 5 It is a diagram showing the alternating production / regeneration times of seven reactors in a dehydrogenation system operating in a 22-minute cycle in the initial sequence.

[0021] Figure 6 It is a diagram showing the alternating production / regeneration times of the seven reactors in a dehydrogenation system that operates in a 22 (22) minute cycle after reordering.

[0022] Figure 7 It is a diagram showing the compressor temperature and turbine speed (first stage compressor) of downstream products before and after reordering. Detailed Implementation

[0023] The invention is described in detail below with reference to the accompanying drawings for illustrative purposes only. The invention is defined in the appended claims. Terms used herein in the specification and claims are given their general meanings as supplemented by the following discussion; for example, “conversion,” “selectivity,” and yield are related by the mathematical definition X (conversion) * S (selectivity) = Y (yield), all based on weight or molar calculations; for example, in a reaction, 90% of substance A is converted (consumed), but only 80% is converted to the desired substance B, and 20% is converted to unwanted byproducts. Therefore, the conversion of A is 90%, the selectivity of B is 80%, and the yield of substance B is 72% (= 90% * 80%).

[0024] Characteristic peak productivity refers to the total maximum productivity of a reactor at a given point in time during a production cycle, under given feed rate, operating temperature, and other conditions. If necessary, the characteristic peak productivity of a reordered reactor can be calculated rather than measured.

[0025] Characteristic productivity difference is the difference between the total maximum productivity and the total minimum productivity of the reactors during the system's dehydrogenation cycle, given feed rates, operating temperatures, and other conditions. If necessary, the minimum and maximum productivity of the reordered reactors can be calculated rather than measured.

[0026] Liquid hourly space velocity (LHSV) is based solely on the dehydrogenation reactant feed and is calculated as the hourly volumetric flow rate of liquid dehydrogenation reactants entering the system divided by the volume of the dehydrogenation catalyst bed in the multi-stage system, expressed in hr. -1 The unit is atmospheric density. To calculate LHSV, the liquid density at atmospheric pressure and the boiling point of the reactants are used.

[0027] Unless otherwise indicated, “percentage”, “%” or similar terms refer to a weight percentage of a component or a relative value relative to an initial value.

[0028] The system productivity at any given time refers to the total rate of dehydrogenation products produced by the reactor system operating in dehydrogenation mode, expressed in kg / h or similar units. For a given hydrocarbon feed rate, such as Figure 1 Productivity can be conveniently represented in graphical form by yield, or it can be approximated by conversion rates under a given set of conditions.

[0029] Generally, the main content refers to the term "peak productivity of reordered characteristics is 2% to 20% lower than the initial peak productivity of the system's characteristics," which refers to the difference in productivity compared to the initial peak productivity level of the characteristics. Therefore, if, under a given set of conditions, the peak productivity drops from 50% to 47.5%, we say that the peak productivity has decreased by 2.5 / 50 or 5%, etc.

[0030] The main point is that the characteristic productivity difference of the reordered system, compared to the characteristic productivity difference of the initial system sequence, is at least 25% lower. This refers to the change in the difference between the total peak and minimum productivity within the system cycle. Therefore, if the initial system cycle has a peak productivity of 50% and a minimum productivity of 40%, and the reordered system has a peak productivity of 47.5% and a minimum productivity of 42.5%, we define the characteristic productivity difference as a reduction from 10 to 5, or a 50% reduction, compared to the initial system sequence.

[0031] When sequencing reactors to achieve a productivity difference less than a certain value, the total maximum and minimum production within the cycle must be considered. Therefore, a cycle with a peak production of 100 units and a minimum production of 80 units is referred to as having a productivity difference of 20 units, or 20% of the peak production.

[0032] As can be understood from the foregoing and subsequent discussion, based on the reactor yield or conversion data from the system, the changes in characteristic peak productivity and characteristic productivity difference can be conveniently expressed as a percentage. Therefore, referring to... Figure 1 As shown in Table 1, the reordered system has a characteristic productivity difference of 3.6 / 7.8 or 46% lower than the initial sequence. Furthermore, the characteristic productivity difference of the reordered system is 3.6 / 47.3 or 7.6% of the peak characteristic productivity of the reordered system.

[0033] exist Figure 5 and Figure 6 The diagram illustrates the complete repetitive system cycle. The terms "sequence," "reordering," and similar terms refer to the temporal order in which the various reactors operate in dehydrogenation mode before switching to the reactor's regeneration mode. Therefore, Figure 5 The reactor sequence for the system cycle, which includes seven reactors, is 1, 3, 5, 7, 2, 4, 6. Figure 6The reactor sequence is shown as 1, 5, 4, 2, 7, 3, 6. The system repeats this cycle once the timing sequence is complete.

[0034] This invention can be applied to any suitable cyclic gas-phase dehydrogenation process, for example, as summarized in U.S. Patent No. 4,172,854 to Ellis et al. The dehydrogenation process, which can be reordered according to the present invention, therefore includes the following: isobutane to isobutene; butane to butene and butadiene; propionitrile to acrylonitrile; propionaldehyde to acrolein; ethyl chloride to vinyl chloride; methyl isobutyrate to methyl methacrylate; 2 or 3-chlorobutene-1 or 2,3-dichlorobutane to chloroprene; ethylpyridine to vinylpyridine; ethylbenzene to styrene; cumene to α-methylstyrene; ethylchlorohexane to styrene; cyclohexane to benzene; ethane to ethylene and then to acetylene; propane to propylene or methylacetylene or propadiene; isopentane to isopene and isopendiene; n-butene to butadiene-1,3 and vinylacetylene; methylbutene to isopendiene; cyclopentane to cyclopentene and cyclopentadiene; n-octane to ethylbenzene and o-xylene; monomethylheptane to xylene; ethyl acetate to vinyl acetate; 2,4,4-trimethylpentane to xylene, etc. The preferred compound to be dehydrogenated is a hydrocarbon, particularly acyclic non-quaternary hydrocarbons having 3 to 5 carbon atoms or ethylbenzene, and the preferred products are isobutene, propylene, n-butene-1 or 2, butadiene-1,3-vinylacetylene, 2-methyl-1-butene, 3-methyl-1-butene, 3-methyl-2-butene, isoprene, styrene, or mixtures thereof. Particularly preferred feedstocks are isobutane, n-butane, isopentane, ethylbenzene, or mixtures thereof, for example, hydrocarbon mixtures containing at least 50 mol% of these compounds.

[0035] Suitable catalysts are discussed in Ullman's *Encyclopedia of Industrial Chemistry*, edited by Domenico Sanfilippo and Paul N. Rylander, Volume 18, pp. 451-471, published online: October 15, 2009, DOI: 10.1002 / 14356007.a13_487.pub2, copyright. © 2002 Wiley-VCH Verlag GmbH & Co. KgaA, and described in the references cited herein.

[0036] The two main classes of catalysts used for alkane dehydrogenation (based on Cr and Pt, respectively) do not differ substantially in activity and selectivity, but they do differ substantially in the quality of some byproducts and the processing required to complete regeneration after coke combustion. The maximum level of coke buildup and therefore the length of reaction steps required before regeneration depend on the properties of the specific catalyst used. Furthermore, phenomena leading to irreversible deactivation (sintering, volatilization of active components, and changes in the morphology or state of the support) are generally related to the chemical type characterizing the various catalysts.

[0037] Regarding chromium-based catalysts, the two most widely used supports are ZrO2 and transition alumina (δ-θ). ZrO2 exhibits low acidity and high thermal stability, while transition alumina has been chosen as the practical support for commercial catalysts. Catalyst formulations include co-catalysis with alkali metals, which is the basis for increasing the active sites of chromium and reducing the surface acidity (of both chromium and alumina). Potassium is most effective if an appropriate amount is provided. Generally, increasing the potassium content yields a volcano-shaped profile of activity and selectivity. The nature of the active sites is controversial: it has been pointed out that Cr... 3+ Cr 3+ and Cr 2+ Both, and the coordinatingly unsaturated Cr 2+ It plays a role in catalytic activity. For the dehydrogenation of isobutane on Cr2O3 / Al2O3, a Langmuir–Hinshelwood-type kinetic equation was proposed, which assumes that the adsorption of isobutane represents a slow phase of the reaction and that there is no competition with hydrogen adsorption.

[0038] For platinum-tin catalysts, Pt / Sn is typically supported on alumina, ZnAl₂O₄, or MgAl₂O₄. The catalyst is promoted using alkali metals and other promoters. Sn plays a role in enhancing activity, selectivity, and stability by neutralizing the acidity of the support, interacting electronically with Pt, and reducing the overall effect that favors coke formation. Increasing the Pt+Sn loading, increasing the Sn / Pt ratio, or increasing the reduction temperature leads to a transformation of the system from a separated phase to the formation of a Pt-Sn alloy. The catalyst retains some bifunctional (acidic and noble metal) activity, resulting in a moderate tendency for skeletal isomerization (e.g., isobutyl to n-butyl). Some characteristics of the catalyst have significant implications for industrial implementation: Pt / Sn catalysts undergo dual-mechanism aging through coke fouling and sintering. Pt / Sn catalysts can withstand several percentage points of coke buildup while maintaining sufficient catalytic activity to allow for several hours / day of "on-stream" time before requiring regeneration. Two promoted and optimized catalytic systems (Pt–Sn / Al2O3 and Cr2O3 / Al2O3) exhibited comparable performance in selectivity for olefins. Both catalysts require periodic air regeneration to burn off coke. Therefore, the catalyst undergoes a cycle during which it is exposed to a hydrocarbon atmosphere, followed by a period in the presence of oxygen (and / or some vapor). Consequently, it must maintain its morphology, structure, and chemical stability under harsh hydrothermal conditions. The duration of time in the hydrocarbon stream differs from that of the selected active phase: typically minutes / hour for the Cr catalyst and hours / day for the Pt catalyst.

[0039] Similarly, gallium (Ga) catalysts can be used, as seen in U.S. Patent Application Publication No. 2019 / 0126242 by Xing et al., with or without an additional catalyst metal. See U.S. Patent No. 5,219,816 by Zhou et al., which discloses a Ga / Pt dehydrogenation catalyst.

[0040] The catalyst bed can be undiluted, i.e., composed entirely of a supported active catalyst, or diluted with an inert material if desired, and / or include exothermic materials disclosed in U.S. Patents 7,622,623; 7,973,207; 8,188,328; and 9,725,380. The inert material can be, for example, granular α-alumina material with a particle size similar to that of the supported catalyst. The exothermic material can include metals selected from the group consisting of copper, chromium, molybdenum, vanadium, cerium, yttrium, scandium, tungsten, manganese, iron, cobalt, nickel, silver, bismuth, and combinations thereof. Exemplary supports for the exothermic material include, but are not limited to, various aluminum oxides or hydroxides, such as aluminum hydroxide, boehmite, pseudoboehmite, gibbsite, diaspore, transition alumina or α-alumina, silica / alumina, silica, silicates, aluminates (e.g., calcium aluminate or barium hexyl aluminate), calcined hydrotalcite, zeolites, zinc oxide, chromium oxide, magnesium oxide, and combinations thereof. Optionally, the heating material may further include an accelerator, such as alkali, alkaline earth metal, lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, zirconium, barium, and combinations thereof.

[0041] The dehydrogenation reaction can be carried out in the gas phase at atmospheric pressure, above atmospheric pressure, or below atmospheric pressure. The total pressure of the system is typically about atmospheric pressure or below atmospheric pressure. Generally, the total pressure will be between about 1 p. SiA and about 75 p. SiA. Preferably, the total pressure will be less than about 50 p. SiA. The temperature of the dehydrogenation reaction is typically in the range of about 350°C to 700°C, with excellent results obtained in the range of 400°C to 650°C. Gaseous reactants can be directed through the reaction chamber over a fairly wide range of flow rates. The optimal flow rate will depend on variables such as reaction temperature, pressure, and catalyst particle size. Those skilled in the art can determine the required flow rate. Typically, the flow rate will be in the range of about 0.10 to 10 liquid volumes of the organic compound to be dehydrogenated per hour per volume of the catalyst-containing dehydrogenation zone (referred to as LHSV). Typically, the LHSV will be between 0.15 and about 5. For calculation purposes, the volume of the catalyst-containing fixed-bed dehydrogenation zone is the original void volume of the reactor space containing the catalyst. Dehydrogenation is carried out in a series of cycles, which include: a suitable feedstock on the catalyst of the present invention, dehydrogenation under defined conditions for a period of time, typically about 6 to 12 minutes, followed by a regeneration cycle during which the coke deposited from the dehydrogenation is burned off. The regeneration cycle may be longer or shorter than the dehydrogenation cycle, typically about 6 to 12 minutes is sufficient for coke removal. Coke is removed by passing oxygen at a temperature of 550°C to 650°C through the catalyst. A convenient source of oxygen is air; however, pure oxygen or a mixture of oxygen and an inert gas (e.g., nitrogen) in the same or different proportions as air can be used.

[0042] In a typical implementation, at least two reactors operate simultaneously in dehydrogenation production mode, and at least two reactors are in various different regeneration phases. For a fixed-bed reactor with chromium / alumina catalysis, the entire repeated dehydrogenation / regeneration sequence of the system can be approximately 20 to 25 minutes. A typical cycle for each reactor includes operating the reactor in dehydrogenation mode for approximately 10 minutes, followed by regeneration, which sequentially includes steam purging, regeneration with air and, if necessary, fuel gas, venting, and catalyst reduction. Steam purging lasts for approximately 1 minute, regeneration with air and, if necessary, fuel gas takes place for approximately 10 minutes, venting of the reactor is completed within approximately 30 seconds, and catalyst reduction with hydrogen takes approximately 1 minute. Suitable reaction systems that can be reordered according to the invention include those seen in GB 794,089 and GB 823,626, and those described in this application. Figure 2 , Figure 3 The reactor system shown schematically is a chromium oxide-catalyzed gas-phase dehydrogenation system for the production of isobutene from isobutane.

[0043] Reference Figure 2 , 3 ,exist Figure 2 The connection shown in Figure 3 Catalytic dehydrogenation reactor R1 is one of the other reactors (R2 to R7) shown in the diagram. Reactor R1 is connected to hydrocarbon feed line 12, product discharge line 14, steam line 16, air regeneration line 18, vacuum line 20, reduction line 22, and discharge line 24 for discharging gas from regeneration.

[0044] The operation of reactor R1 is controlled by multiple valves V, and the reactor output is sampled via port S to determine productivity. These valves are connected to a digital controller 100, which sequences various steps in each of the various reactors in the reaction system, as described below. Figure 3 Each of reactors R2 to R7 is also equipped with a valve V and a sampling port S, and is connected to the controller 100 in the same manner as R1, and operates in the same manner.

[0045] The system is conveniently controlled by a digital controller 100, which is connected to valve V via the dashed lines shown in the diagram. The connection to controller 100 is schematically shown only for the seven valves of reactor R1; it should be understood that valve control on other reactors is similarly connected to and controlled by controller 100. Controller 100 is a Delta V DCS controller, model SD+ digital controller. If needed, a second controller can be used to provide additional control integrity for critical characteristics, such as a Triconex controller, model 3008. Both can be used simultaneously and are uniformly and concisely represented as controller 100 in the diagram.

[0046] As can be understood from the diagram, the reordering is achieved by a digital controller because the 49 valves on the reactor must be individually ordered in order to operate the system efficiently.

[0047] like Figure 3 As shown, system 10 includes seven reactors, R1 to R7, which operate in a cycle such that three reactors operate simultaneously for catalytic dehydrogenation, three reactors undergo catalyst regeneration, and one reactor is in a stage involving operations such as venting, steam purging, hydrogen reduction, or valve replacement. Figure 5 The diagram illustrates how the reactor operates within a twenty-two (22) minute (Appx.) cycle; it should be understood that the same operation can be performed within slightly longer or shorter cycle periods. The diagram and cycle times are shown as approximations, meaning that the cycle time for a single system cycle is conveniently represented in two modes, with dehydrogenation extending to regeneration, in order to… Figure 5 , Figure 6 The objectives include purging, air regeneration, and reduction of the catalyst bed.

[0048] Although Figure 5 , Figure 6 As can be seen, at any given time in a cycle, the same number of reactors are in both dehydrogenation and regeneration modes. However, if necessary, the system can be sequenced so that at a given time point in a cycle, there are more reactors in dehydrogenation mode than in regeneration mode. That is, Figure 5 and Figure 6 The diagram shows a general 3-3-1 distribution between the dehydrogenation and regeneration modes, with one reactor in a transition state. However, if a 4-2-1 distribution between the dehydrogenation and regeneration modes would provide a better productivity balance in the system, then the system could be sorted according to this distribution.

[0049] Refer again Figure 2 , Figure 3The hydrocarbon feedstock is supplied to the set of reactors via line 12, which is connected to each of the reactors R1 through R7 in the series via suitable branch lines and valve control settings; the motor-operated valves therein are opened and closed at appropriate times by the operation of the circulation controller 100. The hydrocarbon conversion products are removed from the system via line 14, which is also suitably connected to each of the reactors in the series via suitable branch lines and valve control settings. The reactor effluent from line 14 undergoes a series of steps to recover the desired products, including using a downstream product compressor and an absorption tower (not shown).

[0050] To purge the reactors and catalyst at the end of the operating cycle, steam enters the system through line 16, which is connected to each reactor in reactor R via suitable valved lines. After steam purging, a regeneration medium is introduced to remove contaminant deposits from the catalyst in the reactors. This medium is supplied from supply line 18 to suitable reactors R1 through R7, which is connected to each reactor via suitable branch lines and valve control settings. Typically, air, or air diluted with flue gas, is used as the regeneration medium, which is raised to the required temperature and pressure. Although in some cases the reduction of the oxidized catalyst after regeneration can be achieved via a hydrocarbon feed, in the operation of this system, such reduction is preferably achieved via hydrogen. Therefore, after venting the reactors via line 20 and suitable valve connections after regeneration, hydrogen enters through line 22, which is also appropriately connected. As shown, lines 16 and 22 are connected to individual inlets of the reactors, and therefore suitable valve control devices are designed for selectively introducing steam or hydrogen into these inlets.

[0051] The flue gas from the regeneration is discharged through pipeline 24 and its branch lines controlled by valves connected to each reactor in the reactor. Therefore, as... Figure 5 , Figure 6 As shown, each reactor operates for 9 to 10 minutes for dehydrogenation and approximately 9 to 10 minutes for regeneration, including purging and valve replacement. In other words, 40% to 50% of the total cycle time is used for the actual production of the required hydrocarbon products, while roughly equal time is spent on regeneration, purging, and valve operation. The system is conveniently controlled by a digital controller 100, which is connected to valve V via the dashed lines shown in the diagram. The connection to controller 100 is schematically shown only for the seven valves of reactor R1; it should be understood that valve control on other reactors is similarly connected to and controlled by controller 100.

[0052] Conventional operating systems for dehydrogenation systems with multiple simultaneous reactors typically assume that more or less identical reactors have more or less the same productivity, thus making it unnecessary to change the sequence. However, the various reactors in the system can have different productivity rates, even if they have the same design. By referring to... Figure 4 To understand this, among which Figure 4 This is a bar chart showing the yield of reactors R1 through R7 during production, operating in dehydrogenation mode for approximately 10 minutes. Average yield can be used to determine the productivity. It can be seen that the yield can vary by 10 percentage points or more.

[0053] Figure 2 , Figure 3 The performance of each reactor is determined by sampling (as indicated by the designation S) from the branch lines from each reactor to the output line 14 and comparing the samples with the hydrocarbon feed stream of the reactor. The means used to determine reactor performance can be online or offline and include any suitable analytical techniques, such as chromatography, IR, or any suitable analytical technique. If desired, sampling port S can be used to obtain samples for offline or online analysis by chromatography, nuclear magnetic resonance (NMR), spectroscopy, etc., or for online determination of productivity by optical, infrared, or other spectroscopic detectors.

[0054] Operating system 10 enables the operating limits of downstream product compressors (and other components, such as regenerated air compressors) to accommodate peak productivity during a 22-minute cycle. Figure 1 In the initial sequence shown, peak yield is visible at the beginning of the cycle, and a yield difference of approximately 8 is visible in the middle of the cycle. Once reordered under the same operating conditions, the peak yield decreases by approximately 2.5%, corresponding to a productivity decrease of approximately 5%, while the yield difference decreases as follows: Figure 1 As shown. If productivity can be increased simply by raising the temperature, all other things being equal, productivity can be increased to [a higher percentage]. Figure 1 The dotted line shown will not exceed the compressor limit. (As indicated by the image) Figure 1 As shown, a 2.5% reduction in peak yield results in a 5.5% increase in system productivity:

[0055] Table 1 – Productivity Improvement from Reordering

[0056]

[0057] Although the initial reactor and the reordered reactor have the same average yield, the system can handle a peak yield of approximately 50%. After reordering, due to the reduced peak yield, productivity can be increased by increasing the hydrocarbon feed rate, raising the hydrocarbon feed temperature, and increasing the regeneration air temperature, etc. The resulting productivity increase is 2.5 / 45.4 or 5.5%. A 5.5% productivity increase would generate millions of dollars in additional revenue.

[0058] Figure 2 , Figure 3 The reactor system operates in an initial reactor sequence with a reactor cycle of approximately twenty-two (22) minutes, during which each reactor alternates between dehydrogenation (production) mode and regeneration mode, as shown in Table 2 and Figure 5 As shown. After determining the productivity of each reactor and the system productivity when operating in the initial sequence, Figure 3 The systems are reordered as shown in Table 3 and Figure 6 The sequence. Using the same reactor, reordering and subsequent productivity increases can increase output by any value between approximately 2% and 10% and above, although the peak conversion rate is lower as mentioned above.

[0059] Table 2 – Initial reactor sequence (1, 3, 5, 7, 2, 6)

[0060]

[0061]

[0062] Table 3 – Reordered Systems (1, 5, 4, 2, 7, 3, 6)

[0063] Reactor # 1 2 3 4 5 6 7 Dehydrogenation begins (seconds) 728 1281 359 1096 912 543 175 Regeneration started (seconds) 8 561 930 377 193 1114 745

[0064] By reordering, the downstream compressor can operate at a higher rate and use a higher regenerated air temperature because there is no need to adapt to a higher peak rate. Figure 7 As shown in the figure, Figure 7 This is a diagram illustrating the downstream product compressor turbine speed and temperature before and after reordering. This invention allows for an increase in downstream turbine speed by 20% or more and an increase in temperature by 10% or more without causing system disturbances.

[0065] As can be understood from the preceding description and accompanying figures, the reordering method is based on determining and prioritizing the productivity characteristics of each reactor in order to reduce system productivity deficits within the system cycle, including reducing peak rates. While any specific calculation method can be employed, reordering calculations based on the yield data of all reactors are particularly convenient for a given feed rate and a set of operating conditions.

[0066] Generally, a first aspect of the present invention relates to a method of operating a dehydrogenation system having a plurality of dehydrogenation reactors, the plurality of dehydrogenation reactors alternating between a dehydrogenation mode and a regeneration mode in a system cycle at a timing sequence, the method comprising: (a) operating the plurality of dehydrogenation reactors with an initial system sequence having an initial characteristic peak productivity during the system cycle; (b) determining the productivity characteristics of each of the dehydrogenation reactors; (c) reordering the reactors to operate with a second system sequence having a reordered characteristic peak productivity lower than the initial characteristic peak productivity; and

[0067] (d) Increase the peak productivity of the reordered characteristics to the level of the reordered operation, thereby increasing system productivity within the system cycle compared to the operation in the initial system sequence.

[0068] The method of the first aspect of the invention may include one or more of the features listed immediately following items 2 to 21:

[0069] 2. The peak productivity of the reordered characteristics is 2% to 20% lower than the initial peak productivity of the system.

[0070] 3. The peak productivity of the reordered characteristics is 3% to 6% lower than the initial peak productivity of the system.

[0071] 4. Peak productivity is determined by the yield of the dehydrogenation products.

[0072] 5. The characteristic productivity difference of the reordered reactors is lower than the characteristic productivity difference of the initial system sequence.

[0073] 6. The characteristic productivity difference of the reordered system is at least 25% lower than the characteristic productivity difference of the initial system sequence.

[0074] 7. The characteristic productivity difference of the reordered system is at least 40% lower than the characteristic productivity difference of the initial system sequence.

[0075] 8. The aforementioned characteristic productivity difference is determined by the difference in product yield.

[0076] 9. The step of increasing the peak productivity of the reordered characteristics to the operational level of the reordering includes: (i) increasing the temperature of the regenerated air or (ii) increasing the temperature of the hydrocarbon feed or (iii) increasing the feed rate of the hydrocarbon feed to the dehydrogenation system or (iv) decreasing the inlet pressure of the dehydrogenation system or (v) a combination of two or more of items (i) to (iv).

[0077] 10. The dehydrogenation system therein has 3 to 12 reactors.

[0078] 11. The dehydrogenation system therein has 5 to 10 reactors.

[0079] 12. The hydrocarbon feed to the reactor includes alkanes.

[0080] 13. The hydrocarbon feed to the reactor includes butane.

[0081] 14. The hydrocarbon feed to the reactor includes isobutane.

[0082] 15. The reactor therein contains a catalyst fixed bed selected from supported chromium catalysts, supported platinum-tin catalysts, and supported gallium metal catalysts.

[0083] 16. The catalyst support is selected from alumina, ZrO2, ZnAl2O4 and MgAl2O4.

[0084] 17. Hydrocarbon feed is supplied to each reactor at a liquid hourly space velocity of 0.15 to 5.

[0085] 18. The reactor is operated in dehydrogenation mode at a reactor temperature of 350°C to 700°C.

[0086] 19. The reactor is regenerated with air at a temperature of about 550°C to about 700°C.

[0087] 20. Each reactor operates in dehydrogenation mode for a duration of 5 to 15 minutes within the system cycle.

[0088] 21. At the same time point within the system cycle, there are more reactors operating in dehydrogenation mode than in regeneration mode.

[0089] A second aspect of the invention relates to a method for operating a dehydrogenation system having a plurality of dehydrogenation reactors, the plurality of dehydrogenation reactors alternating between a dehydrogenation mode and a regeneration mode in a system cycle at a timing sequence, the method comprising: (a) determining the productivity characteristics of each of the plurality of reactors; and (b) sequencing the reactors in the system cycle to achieve a productivity difference below a predetermined value in the system cycle.

[0090] The method of the second aspect of the invention may include one or more of the features listed immediately following items 23 to 37:

[0091] 23. The difference in characteristic productivity of the reordered system is less than 25% of the peak characteristic productivity of the system cycle.

[0092] 24. The difference in characteristic productivity of the reordered system is less than 12.5% ​​of the peak characteristic productivity of the system cycle.

[0093] 25. The aforementioned characteristic productivity difference is determined by the difference in product yield.

[0094] 26. The dehydrogenation system therein has 3 to 12 reactors.

[0095] 27. The dehydrogenation system therein has 5 to 10 reactors.

[0096] 28. The hydrocarbon feed to the reactor includes alkanes.

[0097] 29. The hydrocarbon feed to the reactor includes butane.

[0098] 30. The hydrocarbon feed to the reactor includes isobutane.

[0099] 31. The reactor therein contains a catalyst fixed bed selected from supported chromium catalysts, supported platinum-tin catalysts and supported gallium metal catalysts.

[0100] 32. The catalyst support is selected from alumina, ZrO2, ZnAl2O4 and MgAl2O4.

[0101] 33. Hydrocarbon feed is supplied to each reactor at a liquid hourly space velocity of 0.15 to 5.

[0102] 34. The reactor is operated in dehydrogenation mode at a reactor temperature of 350°C to 700°C.

[0103] 35. The reactor is regenerated with air at a temperature of about 550°C to about 700°C.

[0104] 36. Each reactor operates in dehydrogenation mode for a duration of 5 to 15 minutes within the system cycle.

[0105] 37. At the same time point within the system cycle, there are more reactors operating in dehydrogenation mode than in regeneration mode.

[0106] A third aspect of the invention includes a dehydrogenation system comprising: (a) a plurality of dehydrogenation reactors, the plurality of reactors being valve-controlled by a plurality of valves to operate in a timed sequence in alternating dehydrogenation and regeneration modes within a system cycle; (b) a digital controller connected to the plurality of valves for sequencing the reactors; and (c) components for determining the productivity characteristics of each reactor within the system cycle. The digital controller is operable to resequence the reactors to reduce peak productivity or productivity differential within the system cycle.

[0107] The system of the third aspect of the invention may include one or more of the features listed immediately following items 39 to 46:

[0108] 39. The dehydrogenation system therein has 3 to 12 reactors.

[0109] 40. The dehydrogenation system therein has 5 to 10 reactors.

[0110] 41. The dehydrogenation system therein includes an alkane-containing hydrocarbon feed into the reactor.

[0111] 42. The dehydrogenation system therein includes a butane-containing hydrocarbon feed into the reactor.

[0112] 43. The dehydrogenation system therein includes a hydrocarbon feed containing isobutane into the reactor.

[0113] 44. The reactor therein contains a catalyst fixed bed selected from supported chromium catalysts, supported platinum-tin catalysts, and supported gallium metal catalysts.

[0114] 45. The catalyst support is selected from alumina, ZrO2, ZnAl2O4 and MgAl2O4.

[0115] 46. ​​At the same time point within the system cycle, there are more reactors operating in dehydrogenation mode than in regeneration mode.

[0116] In a fourth aspect of the invention, a dehydrogenation system is provided, the dehydrogenation system comprising a plurality of dehydrogenation reactors that alternate between a dehydrogenation mode and a regeneration mode in a timing sequence in a repetitive system cycle, the improvement comprising (a) determining the productivity characteristics of each of the dehydrogenation reactors and (b) reordering the reactors such that the difference in characteristic productivity in the reordered repetitive system cycle is less than a predetermined value, wherein at least two reactors operate in dehydrogenation mode throughout the reordered cycle.

[0117] Improvements to the fourth aspect of the invention may include one or more of the features listed immediately following items 48 to 50:

[0118] 48. The reordering of the reactors includes reducing the number of reactors operating in the system.

[0119] 49. It also includes increasing the productivity of the reordering system by (i) increasing the temperature of the regenerated air or (ii) increasing the temperature of the hydrocarbon feed or (iii) increasing the feed rate of the hydrocarbon feed to the dehydrogenation system or (iv) decreasing the inlet pressure of the dehydrogenation system or (v) a combination of two or more of items (i) to (iv).

[0120] 50. The difference in characteristic productivity of the reordered system is less than 12.5% ​​of the peak characteristic productivity of the reordered system in repeated cycles.

[0121] While the invention has been described in detail, modifications within the spirit and scope of the invention will be readily apparent to those skilled in the art. Such modifications will also be considered part of the invention. Given the foregoing discussion, relevant knowledge in the art, and the references discussed above in conjunction with the background and specific embodiments of the invention (the disclosures of which are incorporated herein by reference), further description is deemed unnecessary. Furthermore, it should be understood from the foregoing discussion that aspects of the invention and parts of various embodiments can be combined or interchanged, in whole or in part. Moreover, those skilled in the art will understand that the above description is given by way of example only and is not intended to limit the invention.

Claims

1. A method for operating a dehydrogenation system having multiple dehydrogenation reactors, the multiple dehydrogenation reactors alternating between dehydrogenation mode and regeneration mode in a timed sequence during a repetitive system cycle, characterized in that, The method includes: (a) During the system cycle process, the plurality of dehydrogenation reactors are operated with an initial system sequence having initial characteristic peak productivity; (b) Determine the productivity characteristics of each dehydrogenation reactor in the dehydrogenation reactor; (c) Reordering the reactors to operate in a second system sequence, the second system sequence having a reordered peak productivity that is lower than the initial peak productivity; and (d) Increase the peak productivity of the reordered characteristics to the level of the reordered operation, thereby increasing system productivity within the system cycle compared to the operation in the initial system sequence.

2. The method for operating a dehydrogenation system having multiple dehydrogenation reactors according to claim 1, wherein the multiple dehydrogenation reactors alternate between dehydrogenation mode and regeneration mode in a timing sequence during a repetitive system cycle, characterized in that, Peak productivity is determined by the yield of the dehydrogenation products.

3. The method for operating a dehydrogenation system having multiple dehydrogenation reactors according to claim 1, wherein the multiple dehydrogenation reactors alternate between dehydrogenation mode and regeneration mode in a timing sequence during a repetitive system cycle, characterized in that, The characteristic productivity difference of the reordered reactors is lower than the characteristic productivity difference of the initial system sequence.

4. The method for operating a dehydrogenation system having multiple dehydrogenation reactors according to claim 3, wherein the multiple dehydrogenation reactors alternate between dehydrogenation mode and regeneration mode in a timing sequence during a repetitive system cycle, characterized in that, The characteristic productivity difference is determined by the difference in product yield.

5. The method for operating a dehydrogenation system having multiple dehydrogenation reactors according to claim 1, wherein the multiple dehydrogenation reactors alternate between dehydrogenation mode and regeneration mode in a timing sequence during a repetitive system cycle, characterized in that, The steps to increase the peak productivity of the reordered characteristics to the reordered operational level include: (i) increasing the temperature of the regenerated air or (ii) increasing the temperature of the hydrocarbon feed or (iii) increasing the feed rate of the hydrocarbon feed to the dehydrogenation system or (iv) decreasing the inlet pressure of the dehydrogenation system or (v) a combination of two or more of items (i) to (iv).

6. The method for operating a dehydrogenation system having multiple dehydrogenation reactors according to claim 1, wherein the multiple dehydrogenation reactors alternate between dehydrogenation mode and regeneration mode in a timing sequence during a repetitive system cycle, characterized in that, The dehydrogenation system has 5 to 10 reactors.

7. The method for operating a dehydrogenation system having multiple dehydrogenation reactors according to claim 1, wherein the multiple dehydrogenation reactors alternate between dehydrogenation mode and regeneration mode in a timing sequence during a repetitive system cycle, characterized in that, The hydrocarbon feed into the reactor includes isobutane.

8. The method for operating a dehydrogenation system having multiple dehydrogenation reactors according to claim 1, wherein the multiple dehydrogenation reactors alternate between dehydrogenation mode and regeneration mode in a timing sequence during a repetitive system cycle, characterized in that, The reactor contains a fixed bed of catalysts selected from supported chromium catalysts, supported platinum-tin catalysts, and supported gallium-containing metal catalysts.

9. The method for operating a dehydrogenation system having multiple dehydrogenation reactors according to claim 8, wherein the multiple dehydrogenation reactors alternate between dehydrogenation mode and regeneration mode in a timing sequence during a repetitive system cycle, characterized in that, The catalyst support is selected from alumina, ZrO2, ZnAl2O4 and MgAl2O4.

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