CN116020356A - Method and system for dehydrogenating low-carbon alkane by countercurrent moving bed - Google Patents

Method and system for dehydrogenating low-carbon alkane by countercurrent moving bed Download PDF

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CN116020356A
CN116020356A CN202111239994.9A CN202111239994A CN116020356A CN 116020356 A CN116020356 A CN 116020356A CN 202111239994 A CN202111239994 A CN 202111239994A CN 116020356 A CN116020356 A CN 116020356A
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reactor
catalyst
dehydrogenation
dehydrogenation reaction
reaction zone
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CN116020356B (en
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刘彤
董晨
黄宇恺
马冲
任坚强
张新宽
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Sinopec Research Institute of Petroleum Processing
China Petroleum and Chemical Corp
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Sinopec Research Institute of Petroleum Processing
China Petroleum and Chemical Corp
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Abstract

The invention relates to the field of petrochemical industry, in particular to a method and a system for dehydrogenating light alkane by a countercurrent moving bed, wherein the method comprises the following steps: introducing a lower alkane from an inlet of the dehydrogenation reaction zone into countercurrent contact with the dehydrogenation catalyst; the dehydrogenation reaction zone comprises at least 2 reactors which are sequentially connected in series, so that a gas phase stream can sequentially pass through each reactor; obtaining a spent catalyst from the most upstream reactor; sequentially regenerating and reducing the spent catalyst to obtain a regenerated catalyst; recycling the regenerated catalyst back to the most downstream reactor; and introducing a coking inhibitor into each reactor, wherein the coking inhibitor is a sulfur-containing compound. The method provided by the invention can sufficiently passivate the inner wall of the reactor, the inner member and the inner wall of the heating furnace tube, inhibit the metal catalytic coking tendency and ensure the stable operation of the device.

Description

Method and system for dehydrogenating low-carbon alkane by countercurrent moving bed
Technical Field
The invention relates to the field of petrochemical industry, in particular to a method and a system for dehydrogenating low-carbon alkane by a countercurrent moving bed.
Background
The moving bed reaction-regeneration process is one of the common processing processes in the fields of petroleum refining and petrochemical industry, and is mainly used in the fields of preparing high-octane gasoline components or preparing olefin by catalyzing and reforming naphtha, preparing arene, preparing low-carbon alkane by dehydrogenation, and the like.
CN102746085a discloses a process for the preparation of propylene from paraffins by mixing a fresh propane feed with a propane-rich material separated from the reaction product, and introducing it into a paraffin dehydrogenation reactor, which may be a moving bed reactor packed with a dehydrogenation catalyst or other reactor configuration for paraffin dehydrogenation, to convert it to propylene at a temperature of 575-675 ℃. However, this method fails to address the problem of metal-catalyzed coking that occurs when hydrocarbons come into contact with metal walls at high temperatures.
CN111170820A, CN110452085a discloses a process for producing propylene by moving bed propane dehydrogenation in which the reaction feed is countercurrently contacted with the regenerated catalyst, wherein the combined reaction feed flow of propane is the same as the serial number sequence of the reactors, the regenerated catalyst is countercurrently contacted with the reaction feed by first entering the last reactor in the opposite direction to the feed. Similarly, this process also fails to address the problem of metal-catalyzed coking that occurs when hydrocarbons come into contact with metal walls at high temperatures.
CN110234432a discloses a method for managing sulfur on a catalyst during light paraffin dehydrogenation by injecting demineralized water at any one of the reactor inlets of a paraffin dehydrogenation reaction system and transferring coked deactivated spent catalyst from the last reactor outlet first to a sulfur stripper, removing at least 50% of the sulfur on the spent catalyst and then to a regenerator for coke burning regeneration, reducing the formation of sulfate on the catalyst during the regeneration coke burning. According to the method, the sulfur-containing passivating agent is injected into the reaction feed to reduce the occurrence probability of metal catalytic coking, and desulfurization is carried out at the outlet of the last reactor to reduce the generation of sulfate in the regeneration process, but the sulfur-containing passivating agent is only injected into the reaction feed, so that the passivation effect is ensured, and the injection amount is higher.
In the actual operation of a moving bed low-carbon alkane dehydrogenation industrial device, the inner wall of a subsequent reactor, the inner member and the inner wall of a heating furnace tube are not thoroughly passivated because sulfur is only injected into reaction raw materials, and the moving bed low-carbon alkane dehydrogenation device is frequently stopped due to metal catalytic coking, so that the stable operation of the device is influenced.
Disclosure of Invention
The invention aims to solve the problems of insufficient passivation of the inner wall of a reactor and the inner wall of a heating furnace tube and easy occurrence of metal catalytic coking in the existing moving bed low-carbon alkane dehydrogenation technology.
The inventors have found in research that in the prior art process flow shown in fig. 1, the countercurrent moving bed low carbon alkane dehydrogenation process injects coking inhibitors only at the inlet of the reaction feed heat exchanger.
Specifically, in fig. 1, the solid line indicates the flow direction of the reactant stream in the moving bed light alkane dehydrogenation reaction device, and the broken line indicates the flow direction of the catalyst in the moving bed light alkane dehydrogenation reaction device;
the low-carbon alkane is mixed with the coking inhibitor introduced through the coking inhibitor pipeline 101 through the raw material pipeline 100, enters the reaction feed heat exchanger 150, exchanges heat with the reaction product from the pipeline 111, then enters the feed heating furnace 151 through the pipeline 103 after being mixed with the hydrogen-rich gas from the gas pipeline 102, enters the first reactor 152 through the pipeline 104 after being heated, enters the second reactor inlet heating furnace 153 through the pipeline 105 after being heated, enters the second reactor 154 through the pipeline 106, enters the third reactor inlet heating furnace 155 through the pipeline 107 after being heated, enters the third reactor 156 through the pipeline 108 after being heated, enters the fourth reactor inlet heating furnace 157 through the pipeline 109 after being heated, enters the fourth reactor 158 through the pipeline 110 after being heated, enters the reaction feed heat exchanger 150 through the pipeline 111, exchanges heat with the reaction raw material, and then goes to the downstream reaction product compression cooling separation device through the pipeline 112;
the catalyst to be regenerated is obtained from the first reactor 152, lifted by a catalyst line 186, enters a regenerator 159 of a catalyst regeneration zone, is regenerated to obtain an oxidized regenerated catalyst, lifted by a catalyst line 181, enters a reducer 160, is reduced to obtain a regenerated catalyst, enters a fourth reactor 158 by a lower catalyst line 182, lifted by a catalyst line 183, enters a third reactor 156, lifted by a catalyst line 184, enters a second reactor 154, lifted by a catalyst line 185, enters the first reactor 152, and is obtained from the first reactor 152, thereby performing a reaction-regeneration cycle of the catalyst.
In the moving bed light alkane dehydrogenation reaction system shown in fig. 1, which typically comprises four reactors, the temperature drop in the first reactor is highest, whether it be a countercurrent moving bed or a conventional concurrent moving bed. In order to achieve the same inlet temperature as the first reactor, the heat load provided by the second reactor inlet furnace to the reaction materials is highest in four reactor inlet furnaces, the heating intensity is the highest, and the metal catalytic coking tendency in the heating furnace tubes is the highest; because the flow rate of the materials in the heating furnace tube is high, the coke generated by metal catalysis is easy to carry into the second reactor, and the coke is continuously grown and grown in the second reactor, so that the inner components of the second reactor are damaged by extrusion, the pressure drop from the inlet to the outlet of the second reactor is increased, and the device cannot normally operate and is stopped.
Moreover, the inventor also found that the temperature drop from the inlet to the outlet of the fourth reactor is the lowest in the four reactors, the weighted average bed temperature is the highest, the metal catalytic coking tendency on the inner wall or the inner member of the reactor is also high, the inner member of the fourth reactor is easy to be crushed and damaged, and the pressure drop from the inlet to the outlet of the fourth reactor is increased, so that the device cannot operate normally and is stopped.
The inventor further found in the study that in the process of circulating and conveying the catalyst of the countercurrent low-carbon alkane dehydrogenation device, the regenerated fresh catalyst has the lowest sulfur content, and after entering the fourth reactor, the adsorption effect on hydrogen sulfide in the reaction material is strongest, so that the concentration of the hydrogen sulfide in the reaction material in the fourth reactor is rapidly reduced, and the passivation effect on metal internals is further weakened.
Accordingly, the inventors believe that metal-catalyzed coking occurs more readily inside the fourth reactor of a countercurrent moving bed low-carbon alkane dehydrogenation process than in a conventional forward moving bed process, in the manner and in the amount of injection of coking inhibitors into the low-carbon alkane dehydrogenation feed.
In view of the above, the inventors provide a scheme of the present invention, and the method provided by the present invention is capable of effectively reducing the total injection amount of the coking inhibitor and improving the overall activity of the catalyst in the reactor on the premise of ensuring sufficient passivation of the inner wall of each reactor, the inner member and the inner wall of the heating furnace tube, by injecting the coking inhibitor into not only the reaction feed line but also the inlet line of the intermediate heating furnace of each reactor, and distributing the injection ratio of the coking inhibitor according to the adsorption tendency of the catalyst in each reactor to sulfur in the countercurrent moving bed low-carbon alkane dehydrogenation process.
To achieve the above object, a first aspect of the present invention provides a countercurrent moving bed low-carbon alkane dehydrogenation method, which is implemented in a moving bed low-carbon alkane dehydrogenation reaction device, comprising:
introducing light alkane from an inlet of a dehydrogenation reaction zone of the moving bed light alkane dehydrogenation reaction device in the presence of hydrogen to make countercurrent contact with a dehydrogenation catalyst, and obtaining a first material flow from an outlet of the dehydrogenation reaction zone; the dehydrogenation reaction zone comprises at least 2 reactors which are sequentially connected in series, so that a gas phase stream in the moving bed low-carbon alkane dehydrogenation reaction device can sequentially pass through each reactor; and
obtaining spent catalyst from the reactor upstream most of the dehydrogenation reaction zone;
introducing the spent catalyst into a catalyst regeneration zone of the moving bed low-carbon alkane dehydrogenation reaction device to sequentially perform regeneration and reduction so as to obtain a regenerated catalyst;
recycling the regenerated catalyst back to the most downstream reactor of the dehydrogenation reaction zone; and
introducing a coking inhibitor into each reactor of the dehydrogenation reaction zone, wherein the coking inhibitor is a sulfur-containing compound; the ratio of the mass rate R1 of the introduced low-carbon alkane to the mass rate R2 of the introduced coking inhibitor calculated as sulfur element is R1: r2=100: 0.001-0.05.
In a second aspect, the present invention provides a countercurrent moving bed system for dehydrogenating light alkanes, the system comprising:
a dehydrogenation reaction zone for countercurrent contacting of the lower alkane with a dehydrogenation catalyst therein, the dehydrogenation reaction zone comprising at least 2 reactors connected in series in sequence;
a catalyst regeneration zone in fluid communication with the most upstream and downstream reactors of the dehydrogenation reaction zone, respectively, for sequentially regenerating and reducing spent catalyst from the most upstream reactor therein to obtain regenerated catalyst and recycling the regenerated catalyst back to the most downstream reactor.
The method provided by the invention can sufficiently passivate the inner wall of the reactor, the inner member and the inner wall of the heating furnace tube, inhibit the metal catalytic coking tendency and prevent shutdown caused by the metal catalytic coking; and the total amount of injected coking inhibitor is lower than that of the conventional method which is only injected at the inlet of a reaction feed heat exchanger, so that sulfur on the spent catalyst before entering a regeneration zone is easy to remove, and the activity influence is small.
The method provided by the invention has the advantages of simple process flow and low investment, and can be used for the transformation of the existing device and the new device.
Drawings
FIG. 1 is a schematic process flow diagram of a conventional countercurrent moving bed low-carbon alkane dehydrogenation process with only the injection of coking inhibitors at the inlet of the reaction feed heat exchanger;
FIG. 2 is a schematic process flow diagram of a preferred embodiment of the process of the present invention with coke inhibitors injected in the heating furnace lines at the inlet of the reaction feed heat exchanger and the inlet of the second and fourth reactors;
FIG. 3 is a schematic process flow diagram of a preferred embodiment of the process of the present invention with coke inhibitors injected in the furnace lines at the inlet of the reaction feed heat exchanger and the inlet of the second, third and fourth reactors.
Description of the reference numerals
100. Raw material pipeline 101 coking inhibitor pipeline
102. Gas line 103 line
104. Line 105 line
106. Pipeline 107 pipeline
108. Line 109 line
110. Line 111 line
112. Pipeline 150 reaction feed heat exchanger
151. First reactor of feed heating furnace 152
153. Second reactor inlet furnace 154 second reactor
155. Third reactor Inlet furnace 156 third reactor
157. Fourth reactor Inlet furnace 158 fourth reactor
159. Regenerator 160 restorer
181. Catalyst line 182 catalyst line
183. Catalyst line 184 catalyst line
185. Catalyst line 186 catalyst line
201. Coking inhibitor line 202 coking inhibitor line
301. Coking inhibitor line 302 coking inhibitor line
303. Coking inhibitor pipeline
Detailed Description
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
In the present invention, the pressures are gauge pressures unless otherwise specified.
As previously described, a first aspect of the present invention provides a countercurrent moving bed process for the dehydrogenation of light alkanes, the process being carried out in a moving bed light alkane dehydrogenation reaction unit comprising:
introducing light alkane from an inlet of a dehydrogenation reaction zone of the moving bed light alkane dehydrogenation reaction device in the presence of hydrogen to make countercurrent contact with a dehydrogenation catalyst, and obtaining a first material flow from an outlet of the dehydrogenation reaction zone; the dehydrogenation reaction zone comprises at least 2 reactors which are sequentially connected in series, so that a gas phase stream in the moving bed low-carbon alkane dehydrogenation reaction device can sequentially pass through each reactor; and
obtaining spent catalyst from the reactor upstream most of the dehydrogenation reaction zone;
introducing the spent catalyst into a catalyst regeneration zone of the moving bed low-carbon alkane dehydrogenation reaction device to sequentially perform regeneration and reduction so as to obtain a regenerated catalyst;
recycling the regenerated catalyst back to the most downstream reactor of the dehydrogenation reaction zone; and
introducing a coking inhibitor into each reactor of the dehydrogenation reaction zone, wherein the coking inhibitor is a sulfur-containing compound; the ratio of the mass rate R1 of the introduced low-carbon alkane to the mass rate R2 of the introduced coking inhibitor calculated as sulfur element is R1: r2=100: 0.001-0.05.
Preferably, the ratio between the mass rate R1 of introduction of the lower alkane and the mass rate R2 of introduction of the coking inhibitor in elemental sulfur is R1: r2=100: 0.005-0.04, more preferably R1: r2=100: 0.008-0.02.
In the dehydrogenation reaction zone, the upstream and downstream directions of the reactors connected in series are the same as the direction of the reactant flow, the feeding side is upstream, and the discharging side is downstream; the serial number of each reactor is also the same as the direction of the reactant flow, i.e. the reactant feed first enters the first reactor at the most upstream, then enters the second reactor and the third reactor in turn until entering the reactor at the most downstream, and the lower alkane dehydrogenation reaction product flow flows out of the reactors.
In the invention, the regenerated catalyst circularly flows through a circulating conveying system in the direction opposite to the direction of the reactant flow, namely, enters the most downstream reactor firstly, then enters the next-to-last reactor and the third-to-last reactor in sequence until entering the first reactor at the most upstream, and becomes a spent catalyst to flow out of the first reactor, and then enters the catalyst regeneration zone for regeneration and reduction in sequence, so as to obtain the regenerated catalyst in a reduced state.
In the present invention, the coking inhibitor is heated to gasify prior to being introduced into each reactor of the dehydrogenation zone.
In the present invention, the mass rate R1 of the lower alkane represents the sum of the mass of the lower alkane-rich material fed with fresh feed of the lower alkane and the reaction product fed into the dehydrogenation reaction zone in unit time after subsequent separation, and the mass rate R1 of the lower alkane may be, for example, kg/h.
In the present invention, the mass rate R2 of the coking inhibitor in elemental sulfur represents the sum of the masses of the coking inhibitor in elemental sulfur in each reactor fed into the dehydrogenation reaction zone per unit time, and the mass rate R2 of the coking inhibitor in elemental sulfur may be in kg/h, for example.
Preferably, the location of introduction of the coking inhibitor is selected from at least one of the inlet of each reactor of the dehydrogenation reaction zone, the line upstream of the inlet of each reactor.
Preferably, the location of introduction of the coking inhibitor is selected from at least one of a reaction feed heat exchanger, an intermediate heating furnace, a pipeline of the dehydrogenation reaction zone upstream of the inlet of the respective reactor.
Preferably, the regenerating operation includes sequentially performing scorching, oxychlorination, and calcination.
In the present invention, the operation of regeneration is performed in a regenerator of the catalyst regeneration zone, the regenerator comprising a burn zone, an oxychlorination zone, and a calcination zone.
Preferably, the sulfur-containing compound is a disulfide, the alkyl group in the disulfide being selected from C 1 -C 3 At least one of the alkyl groups of (a).
Preferably, the disulfide is dimethyl disulfide.
Preferably, the dehydrogenation reaction zone contains 3-5 reactors connected in series in sequence.
Preferably, the reaction conditions in each of the reactors each independently comprise: the reaction temperature is 500-670 deg.c and the reaction pressure is 0.01-1.0MPa.
More preferably, the reaction conditions in each of the reactors each independently comprise: the reaction temperature is 550-650 ℃, and the reaction pressure is 0.02-0.2Mpa.
Further preferably, the reaction conditions in each of the reactors each independently include: the reaction temperature is 600-650 ℃, and the reaction pressure is 0.03-0.1Mpa.
Preferably, the reaction conditions in the most upstream reactor include: the volume ratio of the hydrogen to the low-carbon alkane is 0.5-6:1, the space velocity of the feeding volume is 0.3 to 5h -1 Preferably 0.5-2h -1
Preferably, the dehydrogenation catalyst comprises a carrier and an active component supported on the carrier, wherein the carrier is alumina, the active component comprises platinum element, a second metal component element, a group IA metal component element and halogen, and the second metal component element is at least one of tin, germanium, lead, indium, gallium and thallium; and the content of the platinum element is 0.1 to 2.0 mass%, the content of the second metal component element is 0.1 to 2.0 mass%, the content of the group IA metal component element is 0.5 to 5.0 mass%, and the content of the halogen is 0.3 to 10.0 mass%, based on the total weight of the carrier.
Preferably, the alumina is θ -alumina.
Preferably, the alumina is spherical.
Preferably, the alumina has an average diameter of 1.5-2.0mm.
Preferably, the operation of burning comprises: the spent catalyst is contacted with nitrogen having an oxygen content of 0.5 to 5.0% by volume at 480 to 600 ℃.
Preferably, the oxychlorination operation comprises: and contacting the burnt spent catalyst with nitrogen or air at the temperature of 500-520 ℃, wherein the nitrogen contains chlorine and oxygen, and the air contains chlorine.
Preferably, the firing operation includes: and roasting the spent catalyst which is subjected to the scorching and the oxychlorination in sequence in air at the temperature of 520-565 ℃.
Preferably, the operation of reducing comprises: the regenerated spent catalyst is contacted with hydrogen at a temperature of 350-550 ℃.
In the present invention, the operation of reduction is performed in a reducer of the catalyst regeneration zone.
Preferably, the lower alkane is C 3 -C 5 At least one of the paraffins of (a).
The following provides a process flow of a preferred embodiment of the countercurrent moving bed process for the dehydrogenation of light alkanes according to the present invention in connection with FIG. 2:
the solid line in the figure shows the flow direction of the reactant stream in the moving bed light alkane dehydrogenation reaction device, and the dotted line shows the flow direction of the catalyst in the moving bed light alkane dehydrogenation reaction device;
the low-carbon alkane is mixed with the coking inhibitor introduced through the coking inhibitor pipeline 101 through the raw material pipeline 100, enters the reaction feed heat exchanger 150, exchanges heat with the reaction product from the pipeline 111, then enters the feed heating furnace 151 through the pipeline 103 after being mixed with the hydrogen-rich gas from the gas pipeline 102, enters the first reactor 152 through the pipeline 104 after being heated, enters the second reactor inlet heating furnace 153 through the pipeline 105 after being heated, enters the second reactor 154 through the pipeline 106, enters the third reactor inlet heating furnace 155 through the pipeline 107 after being heated, enters the third reactor 156 through the pipeline 108 after being heated, enters the fourth reactor inlet heating furnace 157 through the pipeline 109 after being heated, enters the fourth reactor 158 through the pipeline 110 after being heated, enters the reaction feed heat exchanger 150 through the pipeline 111, exchanges heat with the reaction raw material, and then goes to the downstream reaction product compression cooling separation device through the pipeline 112;
the catalyst to be regenerated is obtained from the first reactor 152, lifted by a catalyst pipeline 186, enters a regenerator 159 of a catalyst regeneration zone, is regenerated to obtain an oxidized regenerated catalyst, lifted by a catalyst pipeline 181, enters a reducer 160, is reduced to obtain a regenerated catalyst, enters a fourth reactor 158 by a lower catalyst pipeline 182, lifted by a catalyst pipeline 183, enters a third reactor 156, lifted by a catalyst pipeline 184, enters a second reactor 154, lifted by a catalyst pipeline 185, enters the first reactor 152, and is obtained from the first reactor 152 to perform a reaction-regeneration cycle of the catalyst;
introducing a coking inhibitor into line 105 through coking inhibitor line 201 to passivate the interior walls of the furnace tubes of second reactor inlet furnace 153 and the interior walls and internals of second reactor 154; coking inhibitors are introduced into line 109 through coking inhibitor line 202 to passivate the interior walls of the furnace tubes of fourth reactor inlet furnace 157 and the interior walls and internals of fourth reactor 158.
The following provides a process flow of a preferred embodiment of the countercurrent moving bed process for the dehydrogenation of light alkanes according to the present invention in connection with FIG. 3:
unlike fig. 2, the coking inhibitor line 201 and the coking inhibitor line 202 are replaced with a coking inhibitor line 301, a coking inhibitor line 302, and a coking inhibitor line 303, specifically, a coking inhibitor is introduced into the line 105 through the coking inhibitor line 301 to passivate the inner walls of the furnace tubes of the second reactor inlet furnace 153 and the inner walls and internals of the second reactor 154; introducing a coking inhibitor into line 107 through coking inhibitor line 302 to passivate the inner walls of the furnace tubes of the third reactor inlet furnace 155 and the inner walls and internals of the third reactor 156; a coking inhibitor is introduced into line 109 through coking inhibitor line 303 to passivate the interior walls of the furnace tubes of fourth reactor inlet furnace 157 and the interior walls and internals of fourth reactor 158.
As previously described, a second aspect of the present invention provides a countercurrent moving bed system for the dehydrogenation of light alkanes, the system comprising:
a dehydrogenation reaction zone for countercurrent contacting of the lower alkane with a dehydrogenation catalyst therein, the dehydrogenation reaction zone comprising at least 2 reactors connected in series in sequence;
a catalyst regeneration zone in fluid communication with the most upstream and downstream reactors of the dehydrogenation reaction zone, respectively, for sequentially regenerating and reducing spent catalyst from the most upstream reactor therein to obtain regenerated catalyst and recycling the regenerated catalyst back to the most downstream reactor.
Preferably, the dehydrogenation reaction zone contains 3 to 5 reactors connected in series in sequence.
Preferably, the system further comprises:
a reaction feed heat exchanger in fluid communication with the most upstream reactor of the dehydrogenation reaction zone for heat exchange therebetween of the lower alkane and the coking inhibitor and introduction into the most upstream reactor;
an intermediate heating furnace in fluid communication with each of said reactors at each end for heating therein the product stream and coking inhibitors from said reactor upstream and introducing into said reactor downstream adjacent thereto.
The invention will be described in detail below by way of examples.
In the following examples, all of the raw materials used were commercial products unless otherwise specified.
Example 1
This example employs the process flow shown in fig. 2 for countercurrent moving bed low-carbon alkane dehydrogenation.
Spherical low-carbon alkane dehydrogenation catalysts are filled in the first reactor to the fourth reactor of the moving bed low-carbon alkane dehydrogenation reaction device, and the carriers of the low-carbon alkane dehydrogenation catalysts are spherical theta-Al 2 O 3 The diameter range is 1.60mm-1.80mm; the content of Pt element was 0.3 mass%, the content of tin, the second metal component element was 0.3 mass%, the content of potassium, the group IA metal component element was 0.9 mass%, and the content of chlorine element was 1.15 mass%, based on the total weight of the carrier;
the filling volume ratio of the low-carbon alkane dehydrogenation catalyst in the first reactor, the second reactor, the third reactor and the fourth reactor is 1:1:1:1.
the lower alkane reaction raw material adopted in the embodiment is propane, and the coking inhibitor is dimethyl disulfide (analytically pure); the ratio relationship between the mass rate R1 of the introduced low-carbon alkane and the mass rate R2 of the introduced coking inhibitor calculated as sulfur element is R1: r2=100: 0.015, wherein the mass rate R2 of the coking inhibitor introduced in elemental sulfur is the sum of the mass rates of the coking inhibitor in elemental sulfur introduced via coking inhibitor line 101, coking inhibitor line 201, and coking inhibitor line 202, and the ratio between the mass rate of the coking inhibitor in elemental sulfur introduced via coking inhibitor line 101, the mass rate of the coking inhibitor in elemental sulfur introduced via coking inhibitor line 201, and the mass rate of the coking inhibitor in elemental sulfur introduced via coking inhibitor line 202 is 1:1:1, a step of;
the operating conditions of the moving bed low-carbon alkane dehydrogenation reaction device are shown in table 1, and the reaction results are shown in table 2.
Example 2
This example employs the process flow shown in fig. 3 for countercurrent moving bed low-carbon alkane dehydrogenation.
The lower alkane dehydrogenation catalyst, lower alkane reaction raw material and coking inhibitor used in this example were the same as in example 1;
the ratio relationship between the mass rate R1 of the introduced low-carbon alkane and the mass rate R2 of the introduced coking inhibitor calculated as sulfur element is R1: r2=100: 0.012, wherein the mass rate R2 of the coking inhibitor as a sulfur element is the sum of the mass rates of the coking inhibitor as a sulfur element introduced through the coking inhibitor line 101, the coking inhibitor line 301, the coking inhibitor line 302, and the coking inhibitor line 303, and the ratio between the mass rate of the coking inhibitor as a sulfur element introduced through the coking inhibitor line 101, the mass rate of the coking inhibitor as a sulfur element introduced through the coking inhibitor line 301, the mass rate of the coking inhibitor as a sulfur element introduced through the coking inhibitor line 302, and the mass rate of the coking inhibitor as a sulfur element introduced through the coking inhibitor line 303 is 1:1:1:1, a step of;
the operating conditions of the moving bed low-carbon alkane dehydrogenation reaction device are shown in table 1, and the reaction results are shown in table 2.
Comparative example 1
This comparative example employs the process flow shown in fig. 1 for countercurrent moving bed low-carbon alkane dehydrogenation.
The lower alkane dehydrogenation catalyst, lower alkane reaction raw material and coking inhibitor used in this comparative example were the same as in example 1;
the ratio relationship between the mass rate R1 of the introduced low-carbon alkane and the mass rate R2 of the introduced coking inhibitor calculated as sulfur element is R1: r2=100: 0.018, wherein said introduced mass rate R2 of said coking inhibitor in elemental sulfur is the mass rate of said coking inhibitor in elemental sulfur introduced via coking inhibitor line 101;
the operating conditions of the moving bed low-carbon alkane dehydrogenation reaction device are shown in table 1, and the reaction results are shown in table 2.
TABLE 1
Figure BDA0003319090280000141
TABLE 2
Project Example 1 Example 2 Comparative example 1
Single pass conversion of propane, mass% 27.4 27.6 27.0
Total yield of propylene product, mass% 85.8 86.3 85.1
Whether or not coking of the metal walls occurs Does not occur Does not occur Does not occur
Sulfur content of spent catalyst at outlet of first reactor, mass% 0.061 0.054 0.071
The sulfur content of the catalyst at the outlet of the second reactor, mass% 0.077 0.068 0.088
Catalyst sulfur content at outlet of third reactor, mass% 0.086 0.081 0.102
The sulfur content of the catalyst at the outlet of the fourth reactor, mass% 0.102 0.092 0.114
The fourth reactor inlet regenerates the sulfur content of the catalyst, mass% 0.057 0.051 0.065
As is clear from Table 2, in example 1, by injecting dimethyl disulfide as a coking inhibitor into the reaction feed and the lines of the second reactor inlet furnace and the fourth reactor inlet furnace, the conversion per pass of raw propane was increased by 0.4 mass% and the total yield of propylene was increased by 0.7 mass% as compared with comparative example 1, and the respective furnaces and the inner walls of the reactors were sufficiently passivated, and the apparatus was operated smoothly, without coking of the metal walls.
In example 2, compared with comparative example 1, by injecting the coking inhibitor dimethyl disulfide into the reaction feed and the second reactor inlet heating furnace, the third reactor inlet heating furnace and the fourth reactor inlet heating furnace pipelines, the one-pass conversion rate of raw propane is improved by 0.6 mass percent, the total yield of propylene is improved by 1.2 mass percent, the heating furnaces and the inner walls of the reactors are fully passivated, the device runs stably, and metal wall coking does not occur under the condition that the total consumption of the coking inhibitor is reduced by 33 percent compared with comparative example 1.
From the results, the method provided by the invention can sufficiently passivate the inner wall of the reactor, the inner member and the inner wall of the heating furnace tube, inhibit the tendency of metal catalytic coking and prevent shutdown caused by metal catalytic coking; and the total amount of injected coking inhibitor is lower than that of the conventional method which is only injected at the inlet of a reaction feed heat exchanger, so that sulfur on the spent catalyst before entering a regeneration zone is easy to remove, and the activity influence is small.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.

Claims (19)

1. A countercurrent moving bed process for the dehydrogenation of light alkanes, the process being carried out in a moving bed light alkane dehydrogenation reaction unit comprising:
introducing light alkane from an inlet of a dehydrogenation reaction zone of the moving bed light alkane dehydrogenation reaction device in the presence of hydrogen to make countercurrent contact with a dehydrogenation catalyst, and obtaining a first material flow from an outlet of the dehydrogenation reaction zone; the dehydrogenation reaction zone comprises at least 2 reactors which are sequentially connected in series, so that a gas phase stream in the moving bed low-carbon alkane dehydrogenation reaction device can sequentially pass through each reactor; and
obtaining spent catalyst from the reactor upstream most of the dehydrogenation reaction zone;
introducing the spent catalyst into a catalyst regeneration zone of the moving bed low-carbon alkane dehydrogenation reaction device to sequentially perform regeneration and reduction so as to obtain a regenerated catalyst;
recycling the regenerated catalyst back to the most downstream reactor of the dehydrogenation reaction zone; and
introducing a coking inhibitor into each reactor of the dehydrogenation reaction zone, wherein the coking inhibitor is a sulfur-containing compound; the ratio of the mass rate R1 of the introduced low-carbon alkane to the mass rate R2 of the introduced coking inhibitor calculated as sulfur element is R1: r2=100: 0.001-0.05.
2. The method of claim 1, wherein the ratio between the mass rate of introduction of the lower alkane, R1, and the mass rate of introduction of the coking inhibitor, R2, in elemental sulfur, is R1: r2=100: 0.005-0.04, preferably R1: r2=100: 0.008-0.02.
3. The process of claim 1 or 2, wherein the location of introduction of the coking inhibitor is selected from at least one of an inlet of each reactor of the dehydrogenation reaction zone, an upstream line of an inlet of each reactor.
4. The process of claim 3 wherein the location of introduction of the coking inhibitor is selected from at least one of a reaction feed heat exchanger, an intermediate furnace, a pipeline of the dehydrogenation reaction zone upstream of the inlet of the respective reactor.
5. The method of any of claims 1-4, wherein the regenerating comprises sequentially performing a scorch, an oxychlorination, and a bake.
6. The process according to any one of claims 1 to 5, wherein the sulfur-containing compound is a disulfide, the alkyl group in the disulfide being selected from C 1 -C 3 At least one of the alkyl groups of (a);
preferably, the disulfide is dimethyl disulfide.
7. The process of any of claims 1-6, wherein the dehydrogenation reaction zone comprises 3-5 reactors connected in series in sequence.
8. The method of any of claims 1-7, wherein the reaction conditions in each of the reactors each independently comprise: the reaction temperature is 500-670 ℃, and the reaction pressure is 0.01-1.0Mpa;
preferably, the reaction conditions in each of the reactors each independently comprise: the reaction temperature is 550-650 ℃, and the reaction pressure is 0.02-0.2Mpa;
more preferably, the reaction conditions in each of the reactors each independently comprise: the reaction temperature is 600-650 ℃, and the reaction pressure is 0.03-0.1Mpa.
9. The method of any of claims 1-8, wherein the reaction conditions in the most upstream reactor comprise: the volume ratio of the hydrogen to the low-carbon alkane is 0.5-6:1, the space velocity of the feeding volume is 0.3 to 5h -1 Preferably 0.5-2h -1
10. The method according to any one of claims 1 to 9, wherein the dehydrogenation catalyst comprises a carrier and an active component supported on the carrier, the carrier is alumina, and the active component comprises a platinum element, a second metal component element, a group IA metal component element and halogen, and the second metal component element is at least one selected from tin, germanium, lead, indium, gallium and thallium; and the content of the platinum element is 0.1 to 2.0 mass%, the content of the second metal component element is 0.1 to 2.0 mass%, the content of the group IA metal component element is 0.5 to 5.0 mass%, and the content of the halogen is 0.3 to 10.0 mass%, based on the total weight of the carrier.
11. The method of claim 10, wherein the alumina is theta alumina;
preferably, the alumina is spherical;
preferably, the alumina has an average diameter of 1.5-2.0mm.
12. The method of claim 5, wherein the operation of burning comprises: the spent catalyst is contacted with nitrogen having an oxygen content of 0.5 to 5.0% by volume at 480 to 600 ℃.
13. The method of claim 5, wherein the oxychlorination comprises: and contacting the burnt spent catalyst with nitrogen or air at the temperature of 500-520 ℃, wherein the nitrogen contains chlorine and oxygen, and the air contains chlorine.
14. The method of claim 5, wherein the firing operation comprises: and roasting the spent catalyst which is subjected to the scorching and the oxychlorination in sequence at the temperature of 520-565 ℃.
15. The method of any of claims 1-14, wherein the operation of reducing comprises: the regenerated spent catalyst is contacted with hydrogen at a temperature of 350-550 ℃.
16. According to claims 1-15The method of any one of, wherein the lower alkane is C 3 -C 5 At least one of the paraffins of (a).
17. A countercurrent moving bed system for the dehydrogenation of light alkanes, the system comprising:
a dehydrogenation reaction zone for countercurrent contacting of the lower alkane with a dehydrogenation catalyst therein, the dehydrogenation reaction zone comprising at least 2 reactors connected in series in sequence;
a catalyst regeneration zone in fluid communication with the most upstream and downstream reactors of the dehydrogenation reaction zone, respectively, for sequentially regenerating and reducing spent catalyst from the most upstream reactor therein to obtain regenerated catalyst and recycling the regenerated catalyst back to the most downstream reactor.
18. The system of claim 17, wherein the dehydrogenation reaction zone comprises 3 to 5 reactors connected in series.
19. The system of claim 17 or 18, wherein the system further comprises:
a reaction feed heat exchanger in fluid communication with the most upstream reactor of the dehydrogenation reaction zone for heat exchange therebetween of the lower alkane and the coking inhibitor and introduction into the most upstream reactor;
an intermediate heating furnace in fluid communication with each of said reactors at each end for heating therein the product stream and coking inhibitors from said reactor upstream and introducing into said reactor downstream adjacent thereto.
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