Regeneration method of platinum-based low-carbon alkane dehydrogenation catalyst

Abstract

The invention belongs to the field of catalyst regeneration, and provides a regeneration method of a platinum-based low-carbon alkane dehydrogenation catalyst, which specifically comprises the following steps of: simultaneously carrying out charking and oxychlorination operations before a deactivated catalyst reaches the highest roasting temperature, and adding agent pouring treatment in the regeneration process, and measures for protecting the dispersity of platinum on the catalyst are added in the reaction heating process of the catalyst and after the application is finished, so that the service life of the catalyst is prolonged. According to the regeneration method, the regeneration step of the deactivated catalyst is simplified, chlorine injection, water injection, vulcanization and other operations are not needed, charking, oxychlorination and different reduction depths caused by different positions of the catalyst are avoided, the performance uniformity of the catalyst and the redispersity of platinum are improved, and the regeneration efficiency is improved. The problems that in an existing regeneration method, the dispersity of active components is low, the number of repeated regeneration times is small, and the performance of the catalyst is reduced are solved, the regenerated catalyst obtained through the regeneration method is not lower than that of a fresh catalyst in the aspects of catalyst conversion rate, selectivity and stability, and the regeneration effect is remarkable.

Description

Technical Field

[0001] The invention belongs to the field of catalyst regeneration and provides a regeneration method for a platinum-based low-carbon alkane dehydrogenation catalyst. Background Art

[0002] The dehydrogenation of low-carbon alkanes (C3 / C4) is a strongly endothermic reaction. Limited by thermodynamic equilibrium, it requires high temperature conditions to achieve a high conversion rate. However, high temperature will also promote the occurrence of side reactions such as cracking and coking. Carbon deposits cover the active sites on the catalyst surface or block the pipeline, resulting in catalyst deactivation, affecting the catalyst activity and stability. Carbon burning regeneration is a commonly used catalyst regeneration method, but for platinum-based moving bed alkane dehydrogenation catalysts, the regeneration process not only involves carbon burning treatment, but also the redispersion process of platinum active components. It is necessary to ensure that the metal dispersion, active particle size, specific surface area, and pore volume of the regenerated catalyst are restored to a level close to that of the fresh agent, so as not to affect the catalyst conversion rate, selectivity, and stability. According to statistics, by 2024, the production capacity of domestic moving bed alkane dehydrogenation units that have been put into production and are under construction will reach 21 million tons / year, and the catalyst demand will exceed 3,000 tons / year. The huge catalyst market requires stable catalyst regeneration technology to ensure the stable and continuous operation of industrial units.

[0003] CN105817271A discloses a method for regenerating a low-carbon alkane dehydrogenation catalyst, in which an inert gas containing a reducing gas is used to remove carbon deposits through temperature-variable blowing. However, this method lacks a redispersion treatment technology for precious metal components, and there is a problem that the activity of the catalyst decreases rapidly after multiple regeneration treatments.

[0004] CN105289757A discloses a method for removing carbon deposits during the regeneration process of an alkane dehydrogenation catalyst. In the method, hydrogen peroxide is used as a combustion aid to regenerate the catalyst by burning carbon. Although the treatment conditions are mild and the temperature is 200-400°C, the temperature during the catalyst dehydrogenation reaction is relatively high, especially the propane dehydrogenation reaction temperature is about 580-650°C. This relatively high reaction temperature easily promotes the sintering of active component particles. If the regeneration process lacks a remedial technology for redispersion of the active components, the catalyst still has the problem of rapid decline in activity and stability after multiple regenerations.

[0005] Patent CN103801330B provides a method of calcining in an oxygen-containing atmosphere, first injecting a chlorinating agent and water for chlorination, then injecting water vapor and reducing gas for dechlorination and reduction treatment to obtain a regenerated catalyst. In this regeneration method, carbon burning and oxychlorination are both at high temperatures. Platinum particles are easily sintered during high-temperature calcination. Even if there is a later oxychlorination treatment, the sintered and aggregated platinum particles cannot be completely dispersed. In this method, water injection or water vapor dechlorination is required. This operation accelerates the corrosion rate of the reactor, and the high-temperature hydrothermal environment easily causes the catalyst structure to be damaged. In addition, its last reduction stage also needs to inject water vapor. After the reduction is completed, if the catalyst is not thoroughly dried, the catalyst carbon deposition will be accelerated during the application process of the industrial anhydrous environment, which seriously affects the catalyst activity and stability during the reaction.

[0006] Patent CN104107704A provides a regeneration method for a platinum-containing low-carbon alkane dehydrogenation catalyst. This method is similar to the catalyst regeneration method provided by patent CN103801330B, which is first carbonization and then oxychlorination. Similarly, during the regeneration process, the active components are not prevented from sintering during high-temperature carbonization. Moreover, the carbonization and oxychlorination temperatures of the catalyst exceed 600°C respectively. After multiple regenerations, the active components of the catalyst are severely sintered. Even if oxychlorination is performed to redisperse the platinum active components, the activity and stability of the catalyst still decrease rapidly. At the same time, there is a lack of investigation into the changes in platinum metal dispersion and active particle size caused by changes in regeneration conditions.

[0007] Through a large number of experiments, the inventors found that the high activity and high stability of the catalyst after regeneration are closely related to the high dispersion of platinum. Compared with the regeneration method of platinum-based low-carbon alkane dehydrogenation catalyst proposed in the existing literature, it is found that there is a general lack of consideration of the sintering problem of active components caused by high-temperature charring and research on the redispersion technology of platinum active components. The generation of charring, oxychlorination or uneven reduction degree caused by the unchanged position of the catalyst during the regeneration process is not avoided. The regeneration steps are cumbersome, and water injection or water vapor is not conducive to the stability of the catalyst structure. In the process of reusing the catalyst after regeneration, there is also a lack of technology to inhibit the reaggregation of platinum active particles. In addition, after the catalyst reaction is completed, the feed is usually stopped and hydrogen purge is switched, but at this time, the higher reaction temperature and hydrogen atmosphere will only promote catalyst sintering. Therefore, in order to solve the above problems, the inventors proposed a variety of optimization measures in the regeneration process to improve the platinum dispersion during the catalyst regeneration process, and investigated the relationship between the size and dispersion of platinum active particles and regeneration conditions, providing technical support for industrial production. Summary of the invention

[0008] The present invention aims at the many shortcomings of the existing platinum-based low-carbon alkane dehydrogenation catalyst regeneration method, and provides a regeneration method for the platinum-based low-carbon alkane dehydrogenation catalyst. During the regeneration process, no chlorine injection, water injection, sulfurization and other operations are required. Specifically, before the deactivated catalyst reaches the highest roasting temperature, charcoal burning and oxychlorination operations are performed simultaneously, and the agent inversion treatment is added during the regeneration process. In addition, measures for protecting the platinum dispersion on the catalyst are added during the catalyst reaction heating process and after the application is completed, which helps to extend the service life of the catalyst. In addition, the present invention studies the relationship between the platinum metal dispersion, the active particle size, and the catalyst activity under different regeneration conditions, and provides technical support for industrial production. The regeneration method simplifies the deactivated catalyst regeneration step, avoids charcoal burning, oxychlorination and different reduction depths caused by different catalyst positions, improves the catalyst performance uniformity and the redispersion of platinum, solves the problems of low active component dispersion, few repeated regeneration times, and catalyst performance decline in the existing regeneration method, and the regenerated catalyst obtained by the regeneration method provided by the present invention is not lower than the fresh agent in terms of catalyst conversion rate, selectivity and stability, and the regeneration effect is significant.

[0009] The main inventive concepts of the present invention are as follows: The inventors found that since the platinum-based low-carbon alkane dehydrogenation catalyst is sensitive to factors such as micro-water, sulfur, nitrogen, and arsenic, the C3 / C4 raw materials entering the device will be dried, desulfurized, denitrogenated, and de-heavy metal treated, so there is no problem of catalyst deactivation caused by poisoning or the introduction of moisture, and the catalyst has strong wear resistance, and will not cause the loss of active components due to wear, and then the inventors found that the deactivation of the platinum-based dehydrogenation catalyst is mainly caused by sintering and coking. The coke generated by coking can be removed by roasting, but the simple high-temperature roasting process is prone to sintering of active components, and the active component particles formed cannot be redispersed, and the higher the roasting temperature, the lower the redispersion efficiency when the active components are redispersed. The inventors observed that before the highest roasting temperature was reached, most of the carbon deposits were removed at low temperatures, and chlorine was introduced in advance before reaching high temperatures, which not only ensured that the charcoal was completely burned but also prevented the sintering of active components, and ensured the migration and dispersion of platinum oxychloride on the carrier, so that it had a higher metal dispersion. After the catalyst was oxychlorinated at high temperature, it continued to be purged and cooled in an air atmosphere to avoid switching to an inert gas at high temperatures to affect the platinum dispersion. During the oxychlorination and reduction process, the operation of adding reagent inversion is added, and the position of the catalyst is moved to avoid different oxychlorination or reduction depths due to different positions, thereby ensuring the long-term stability of the catalyst.

[0010] In addition, during the use of the regenerated catalyst in the reaction, it is forbidden to introduce low-carbon alkanes after the high-temperature reduction of hydrogen to the reaction temperature. The high-temperature operation during the reduction will also cause catalyst sintering. Therefore, in order to avoid this problem, the present application proposes to introduce hydrogen, hydrogen sulfide, and low-carbon alkanes at a low temperature of 370-380°C at the same time, and then program the temperature to the reaction temperature for evaluation reaction. The introduction of hydrogen sulfide can passivate the reactor wall, protect the catalyst, prevent the occurrence of side reactions, and slow down the carbon deposition rate. Low-carbon alkanes, hydrogen and hydrogen sulfide are introduced at low temperatures to avoid the occurrence of rapid catalyst sintering caused by the introduction of low-carbon alkanes at high reaction temperatures, thereby improving the stability of the catalyst reaction. Similarly, after the catalyst reaction is completed, avoid direct hydrogen purging and cooling. The material should be cooled, and nitrogen purging can be switched to protect the catalyst when the temperature reaches a low temperature.

[0011] Based on the above invention concept, the specific technical solution of this application is as follows: A method for regenerating a platinum-based low-carbon alkane dehydrogenation catalyst, the specific steps are as follows: (1) The deactivated platinum-based low-carbon alkane dehydrogenation catalyst is loaded into the constant temperature section of the fixed bed regenerator, supported by ceramic balls at the bottom, and heated to 370-420°C in a low-oxygen nitrogen atmosphere. The temperature is maintained for 1-4 hours for low-temperature carbonization treatment to reduce carbon deposition on the catalyst; (2) Continue to raise the temperature to 450-480°C, keep the oxygen content unchanged, maintain this temperature for 2-6 hours, and continue to gradually remove part of the carbon deposits on the catalyst to prevent temperature runaway; (3) Keep the calcination temperature unchanged. To prevent temperature runaway, gradually increase the oxygen content to 5-10% and maintain this oxygen content for 1-4 hours to further reduce carbon deposits inside the catalyst. (4) Continue to increase the oxygen content to 21% (pure air) at the same oxygen extraction rate, introduce chlorine gas under air atmosphere, then program the temperature to 530-580°C, maintain this temperature for 2-6 hours, perform thorough decarbonization and oxychlorination of the catalyst simultaneously, and restore the catalyst to its pre-reduction color; (5) Stop heating and start cooling. Use air purge to cool down. When the temperature drops below 380°C, switch to nitrogen replacement purge. The air and nitrogen air speeds are both 1000-2000h -1 , no need for water injection, dechlorination and other operations, simplifying the operation steps; (6) After the temperature drops below 200°C, turn off the nitrogen and switch to hydrogen for reduction. The purity of hydrogen is ≥98%. Raise the temperature to the reduction temperature of 500-550°C and maintain this temperature for 2-6 hours. After the reduction is completed, the regenerated catalyst is obtained. No sulfurization operation is required after reduction.

[0012] Furthermore, in step (1), the catalyst is loaded into the constant temperature section of the reactor, and the gas space velocity is 1000-2000h-1 , the volume percentage of oxygen in nitrogen is 1-4%, and the heating rate is 1-3℃ / min.

[0013] Furthermore, the gas space velocity in step (2) is 1000-2000h -1 , the volume percentage of oxygen in nitrogen is 1-4%, and the heating rate is 0.5-2℃ / min.

[0014] Furthermore, in step (3), under a nitrogen atmosphere, the rate of increase of the volume percentage of oxygen in nitrogen is 3% / h.

[0015] Furthermore, in step (4), the rate of increase of the volume percentage of oxygen in nitrogen is 3% / h, the volume percentage of chlorine in air is 0.01-2%, more preferably 0.1-1.0%, and the gas space velocity is 1000-2000h -1 The heating rate is 0.5-2℃ / min. During the constant temperature process, the catalyst is poured 2-3 times. The lower outlet valve of the reactor is opened and 10ml of porcelain balls are unloaded each time to achieve catalyst displacement. The catalyst is always located in the constant temperature section of the reactor.

[0016] Furthermore, the heating rate in step (6) is 1-3°C / min, and the hydrogen space velocity is 600-1200h -1 During the constant temperature process, the catalyst is poured 2-3 times, the lower outlet valve of the reactor is opened, and 10 ml of porcelain balls are unloaded each time to achieve catalyst displacement. The catalyst is always located in the constant temperature section of the reactor.

[0017] The platinum-based low-carbon alkane dehydrogenation catalyst targeted by the present invention uses alumina as a carrier, and Pt, Sn and K are loaded on the carrier by an impregnation method. Based on the weight of the catalyst, the content of Pt is 0.1-1.0%, the content of Sn is 0.1-0.5%, and the content of K is 0.1-3.0%; the catalyst in the comparative example used in the following content is an existing industrial catalyst.

[0018] In the present invention, when the regenerated platinum-based low-carbon alkane dehydrogenation catalyst is reused, the regenerated agent is the same as the fresh agent, and both are compared and verified using a fixed bed reactor. The specific start-up and application steps are as follows: The regenerated catalyst was loaded into the constant temperature section of the fixed bed reactor, supported by porcelain balls at the bottom, and dried for 3 h at a program temperature of 260 °C under a nitrogen atmosphere, with a heating rate of 2 °C / min and a nitrogen space velocity of 600 h -1 ; Then switch to hydrogen for reduction, hydrogen space velocity 300h -1When the temperature rises to 370-380℃, hydrogen sulfide and low carbon alkane are introduced, and the temperature is continued to rise to the reaction temperature. During the reaction, hydrogen sulfide accounts for 60ppm of the low carbon alkane feed, the hydrogen-to-hydrocarbon molar ratio is 0.5, and the low carbon alkane volume space velocity is 3.0h -1 .

[0019] In the method of the present invention, after the reaction of the regenerated platinum-based low-carbon alkane dehydrogenation catalyst is completed, the material needs to be cooled down, and after the temperature drops below 380° C., it can be switched to nitrogen purging.

[0020] The above-mentioned low carbon alkane is propane or isobutane.

[0021] In order to prevent the catalyst from sintering at high temperature, inhibit the aggregation and growth of platinum grains, and allow the generated platinum oxychloride to fully migrate and disperse on the carrier, the regeneration method of the present invention does not need to introduce a chlorinating agent during low-temperature charcoal burning. After removing most of the carbon deposits and continuing to heat up the charcoal burning process, the chlorinating agent is introduced in advance. When the temperature reaches the highest temperature, the high-temperature roasting and oxychlorination processes are carried out simultaneously. It has been verified that the size range of the active particles of the regenerated catalyst obtained under this operation is 3-4nm, the platinum metal dispersion is greater than 30%, and the metal dispersion is significantly improved. After regeneration, the catalyst still maintains high stability and activity after multiple cycles. The regenerated catalyst obtained by high-temperature roasting first and then injecting chlorine for platinum dispersion has an active particle size greater than 4nm and a platinum metal dispersion of less than 26%. This may be one of the important factors affecting the low stability of the existing catalyst. It also further proves that the introduction of chlorine in advance can effectively inhibit the sintering of the catalyst at high temperature. Combined with the evaluation results, it is found that the activity of the regenerated agent is consistent with that of the fresh agent, and the stability is significantly improved.

[0022] During the experiment, it was found that when the catalyst is regenerated, due to the fixed position of the catalyst, it is easy to cause uneven heating of the catalyst or gas deviation. After regeneration, the catalyst generally has uneven color, which affects the catalyst performance. To solve this problem, a pouring operation is added during regeneration, and 10 ml of porcelain balls are unloaded each time. This operation causes the porcelain balls to move relative to each other, thereby driving the displacement of the catalyst. However, since the amount of unloaded porcelain balls is not large, and all the unloaded porcelain balls are from the non-constant temperature section, the catalyst will still remain in the constant temperature section and will not affect the regeneration process. The present application promotes catalyst displacement through the above means, effectively solves the above problems, and further ensures the uniformity of the catalyst metal dispersion.

[0023] When the catalyst is used after regeneration, the inventors found that if only the raw material low-carbon alkane is introduced at a higher reaction temperature, the catalyst deactivates quickly, the reaction system is pressurized, and the catalyst is seriously carbonized; while at the same high reaction temperature, the raw material low-carbon alkane and hydrogen sulfide are introduced at the same time, the catalyst activity decreases slowly and the reaction stability is improved; but if low-carbon alkanes and hydrogen sulfide are introduced at the same time under low temperature conditions, further comparison shows that the catalyst activity decreases further slowly, the catalyst reaction time is extended by more than 50%, and the unloaded catalyst has less carbon deposits, proving that the improved feeding method can effectively inhibit catalyst sintering and prevent platinum grain aggregation. In addition, the inventors found that the activity of the catalyst continued to decrease after regeneration in the first two feeding methods, and the size of the platinum grains continued to increase, while the activity of the catalyst and the size of the active particles after regeneration were not affected under the third feeding method. For example, at a reaction temperature of 600°C, only propane was introduced for reaction. The initial propane conversion rate was 39.2%, and the propylene selectivity was 97.3%. After 42 hours of reaction, the propane conversion rate dropped to 30.4%, and the propylene selectivity was 98.1%. However, after 80 hours of reaction, the initial propane conversion rate of the regenerated catalyst that introduced propane and hydrogen sulfide at the same time at low temperature dropped from 39.7% to 37.3%, and the conversion rate dropped slowly. The initial selectivity increased from 98.6% to 99.1%, and the catalyst reaction stability was significantly improved. After the same regeneration operation, the former had a platinum metal dispersion of only 27.3%, a platinum grain size of 4.5nm, and the latter had a platinum metal dispersion of 31.1%, and a platinum grain size of 3.4nm. After multiple regenerations, the platinum metal dispersion of the former continued to decrease, the platinum grain size continued to increase, and the catalyst activity decreased rapidly; while after 20 regenerations, the catalyst activity, platinum metal dispersion and platinum grain size of the latter catalyst fed with hydrogen sulfide and low-carbon alkanes simultaneously remained almost unchanged, proving that the introduction of low-carbon alkanes and hydrogen sulfide at low temperatures effectively protected the catalyst activity.

[0024] In addition, the deactivated catalysts obtained by cooling with and without cooling after the catalyst reaction were regenerated under the same regeneration conditions. The dispersion of the active metal component platinum was relatively low after the regeneration of the catalyst without cooling. Therefore, cooling with and without cooling after the reaction is helpful to inhibit catalyst sintering.

[0025] In summary, the regeneration method of the platinum-based low-carbon alkane dehydrogenation catalyst provided in the present application solves the problems of low dispersion of active components, few repeated regeneration times, reduced catalyst performance, etc. in the existing regeneration method, and also studies the relationship between different regeneration conditions and platinum metal dispersion, active particle size, and catalyst activity. The catalyst obtained by the regeneration method provided by the present invention is not lower than the fresh catalyst in terms of catalyst conversion rate, selectivity and stability, and the regeneration effect is significant. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments.

[0027] In the present invention, by comparing the platinum active instance size, metal dispersion, propane or isobutane conversion rate at the initial 1 hour and 80 hours of reaction of the catalyst, propylene or isobutylene selectivity and reaction stability in the embodiments and comparative examples, the changes in the catalyst body under different regeneration conditions and the influence on the catalyst performance are investigated.

[0028] During the implementation of the method of the present invention, in order to protect the catalytic performance of the fresh agent and the regenerated agent, hydrogen sulfide and low-carbon alkanes are introduced under low temperature conditions, and after the reaction is completed, the temperature of the material is lowered to 380°C, and then nitrogen purging is switched. The specific evaluation method is: A fixed bed reactor is used, and fresh agent or regenerated agent is loaded into the constant temperature section of the reactor for evaluation. The evaluation conditions of fresh agent and regenerated agent are as follows (taking propane as the raw material): Under normal pressure and nitrogen atmosphere, the catalyst was heated to 260 °C at a rate of 2 °C / min and dried for 3 h. The nitrogen space velocity was 600 h -1 , then switched to hydrogen, airspeed 300h -1 When the temperature rises to 380℃, hydrogen sulfide and propane are introduced, and the propane volume space velocity is 3.0h -1 , hydrogen-to-hydrocarbon molar ratio of 0.5, mass fraction of hydrogen sulfide in propane feed of 60ppm, and when the temperature was raised to 600℃ at a heating rate of 2℃ / min, sampling and analysis began, and propane conversion, propylene selectivity and reaction stability were compared between the initial 1h and 80h of reaction. After 80h of reaction, heating was stopped, and the temperature of the feed was lowered to 380℃, and then nitrogen purging was switched.

[0029] Example 1 The preparation of platinum-based low-carbon alkane dehydrogenation catalyst is as follows: 0.36g of tin tetrachloride and 1.86g of potassium chloride were dissolved in 45ml of chloroplatinic acid aqueous solution, and the mass fraction of platinum in the solution was 0.33%. 30g of commercially available alumina ball carrier (particle size 1.8mm, specific surface area 115m 2 / g, pore volume 0.62cm 3 / g) was immersed in the mixed solution prepared above, maintained at 58°C for 8h, with a rotation speed of 20r / min, and slowly evaporated under vacuum until the catalyst pellets were distinct. Then, at the same rotation speed, the temperature was raised to 80°C and maintained at this temperature for 1h. The catalyst was then removed and dried at 120°C for 5h, and then calcined at high temperature in an air atmosphere with a chlorine content of 0.5% (volume percentage) and an air velocity of 1200h. -1 , calcined at 560℃ for 5h. After calcination, nitrogen was purged and the temperature was lowered to 200℃. Then it was switched to hydrogen reduction and the temperature was raised to 540℃ for 5h. The hydrogen space velocity was 300h -1Finally, a light alkane dehydrogenation catalyst containing 0.5% Pt, 0.25% Sn, and 2.0% K was obtained. This fresh agent is recorded as A-0.

[0030] The propane dehydrogenation reaction was carried out according to the above evaluation method. The platinum active particle size, metal dispersion and reaction data of the fresh agent A-0 are shown in Table 1.

[0031] Example 2 After the fresh agent A-0 reacts for 80 hours, the heating is stopped, and after the temperature of the material is lowered to below 380°C, the feeding of hydrogen, hydrogen sulfide and propane is stopped, and nitrogen is switched to purge to room temperature before unloading to prepare for regeneration; the specific regeneration method is as follows: (1) The deactivated platinum-based low-carbon alkane dehydrogenation catalyst was loaded into the constant temperature section of a fixed bed regenerator, supported by ceramic balls at the bottom, and heated to 400°C in a nitrogen atmosphere with an oxygen content of 2.5%, with a heating rate of 2°C / min and a gas space velocity of 1000 h -1 Keep at this temperature for 3 hours to carry out low-temperature carbonization treatment to reduce carbon deposition on the catalyst; (2) Continue heating to 470°C at a rate of 1°C / min and maintain for 4 h in the same nitrogen atmosphere with an oxygen content of 2.5% and a gas space velocity of 1000 h -1 ; (3) Keep the roasting temperature unchanged. To prevent temperature runaway, gradually increase the oxygen content in nitrogen to 7.5% at an oxygen extraction rate of 3% / h, and the gas space velocity is 1000h -1 , maintain this oxygen content for 4h; (4) Continue to increase the oxygen content to 21% (pure air) at the same oxygen extraction rate. Introduce chlorine gas under air atmosphere. The volume percentage of chlorine gas in the air is 0.5%. The total gas space velocity is 1000h -1 , then the temperature was raised to 550℃ at a heating rate of 1℃ / min, and kept at this temperature for 4h. During the constant temperature process, the outlet valve at the bottom of the reactor was opened, and 10ml of porcelain balls were unloaded each time. The above-mentioned pouring operation was performed twice to achieve catalyst displacement, but the catalyst was always located in the constant temperature section of the reactor. After the catalyst was thoroughly decarbonized and oxychlorinated simultaneously, the catalyst returned to its color before reduction; (5) Stop heating and start cooling. Use air purge to cool down. When the temperature is below 380°C, switch to nitrogen replacement purge. The air and nitrogen air speeds are both 1000h -1 , no need for water injection, dechlorination and other operations, simplifying the operation steps; (6) After the temperature drops below 200°C, turn off the nitrogen and switch to hydrogen for reduction. Raise the temperature to 525°C at a heating rate of 1.5°C / min and maintain for 5 hours at a hydrogen space velocity of 600 h. -1During the constant temperature process, the outlet valve at the bottom of the reactor was opened, and 10 ml of the porcelain ball was unloaded each time. The above-mentioned pouring operation was performed twice to achieve catalyst displacement, but the catalyst was always located in the constant temperature section of the reactor. After the reduction was completed, the catalyst returned to blue. After this regeneration, the catalyst was marked as A-1.

[0032] Using propane as raw material, propane dehydrogenation reaction was carried out according to the above evaluation method. The platinum active particle size, metal dispersion and reaction data of the regenerated catalyst A-1 are shown in Table 1.

[0033] Example 3 The deactivated catalyst obtained after the fresh catalyst A-0 was reacted for 80 hours was regenerated by the regeneration method of Example 2, except that the maximum calcination temperature in step (4) was 500°C, and the other conditions remained unchanged. The raw material was propane, and the regenerated catalyst was subjected to propane dehydrogenation reaction according to the above evaluation method. The platinum active particle size, metal dispersion and reaction data of the regenerated catalyst B-1 are shown in Table 1.

[0034] Example 4 The deactivated catalyst obtained after the fresh catalyst A-0 was reacted for 80 hours was regenerated by the regeneration method of Example 2, except that the maximum calcination temperature in step (4) was 600°C, and the other conditions remained unchanged. The raw material was propane, and the regenerated catalyst was subjected to propane dehydrogenation reaction according to the above evaluation method. The platinum active particle size, metal dispersion and reaction data of the regenerated catalyst C-1 are shown in Table 1.

[0035] Example 5 The deactivated catalyst obtained after the fresh catalyst A-0 was reacted for 80 hours was regenerated by the regeneration method of Example 2, except that the maximum calcination temperature in step (4) was 650°C, and the other conditions remained unchanged. The raw material was propane, and the regenerated catalyst was subjected to propane dehydrogenation reaction according to the above evaluation method. The platinum active particle size, metal dispersion and reaction data of the regenerated catalyst D-1 are shown in Table 1.

[0036] Example 6 The deactivated catalyst obtained after the fresh catalyst A-0 was reacted for 80 hours was regenerated by the regeneration method of Example 2, except that the calcination and oxychlorination processes were separated in step (4). After the calcination was completed at 560°C, the temperature was maintained for 4 hours, and chlorine was introduced again. The volume percentage of chlorine in the air was 0.5%, and the other conditions remained unchanged. The raw material was propane, and the regenerated catalyst was subjected to propane dehydrogenation reaction according to the above evaluation method. The platinum active particle size, metal dispersion and reaction data of the regenerated catalyst F-1 are shown in Table 1.

[0037] Example 7 The deactivated catalyst obtained after the fresh catalyst A-0 was reacted for 80 hours was regenerated by the regeneration method of Example 2, except that only the calcination process was performed in step (4), and no oxychlorination process was performed. After the calcination was completed at 560°C, the temperature was purged with air, and the other conditions remained unchanged. The raw material was propane, and the regenerated catalyst was subjected to propane dehydrogenation reaction according to the above evaluation method. The platinum active particle size, metal dispersion and reaction data of the regenerated catalyst G-1 are shown in Table 1.

[0038] Example 8 The deactivated catalyst obtained after the fresh catalyst A-0 was reacted for 80 hours was regenerated by the regeneration method of Example 2, except that there was no inversion operation in step (4) and step (5), and the other conditions remained unchanged. The raw material was propane, and the regenerated catalyst was subjected to propane dehydrogenation reaction according to the evaluation method. The platinum active particle size, metal dispersion and reaction data of the regenerated catalyst H-1 are shown in Table 1.

[0039] Example 9 The deactivated catalyst obtained after the fresh catalyst A-0 was reacted for 80 hours was regenerated by the regeneration method of Example 2, except that the maximum reduction temperature in step (5) was increased by 600°C, and the other conditions remained unchanged. The raw material was propane, and the regenerated catalyst was subjected to propane dehydrogenation reaction according to the above evaluation method. The platinum active particle size, metal dispersion and reaction data of the regenerated catalyst I-1 are shown in Table 1.

[0040] Example 10 The deactivated catalyst obtained after the fresh catalyst A-0 was reacted for 80 hours was regenerated 20 times by the regeneration method of Example 2, and the regenerated catalyst was reacted according to the above evaluation method. The raw material was propane, and the platinum active particle size, metal dispersion and reaction data of the catalyst A-20 regenerated 20 times were shown in Table 1.

[0041] Embodiment 11 The catalyst preparation method of Example 1 was used to obtain fresh catalyst A-0. Under normal pressure and nitrogen atmosphere, the catalyst was first dried at 300°C for 3 h, cooled to 250°C, and then switched to hydrogen at a space velocity of 300 h. -1 When the temperature rises to 380℃, hydrogen sulfide and isobutane are introduced, and the volume space velocity of isobutane is 2.5h -1 , hydrogen-to-hydrocarbon molar ratio of 0.45, mass fraction of hydrogen sulfide in isobutane feed of 80 ppm, and sampling and analysis began when the temperature was raised to 560°C at a heating rate of 2°C / min. The platinum active particle size, metal dispersion and reaction data of fresh agent A-0 are shown in Table 2.

[0042] Example 12 The deactivated catalyst obtained after the fresh catalyst A-0 in Example 11 was reacted for 80 hours was regenerated by the regeneration method of Example 2, and the regeneration conditions remained unchanged. Using isobutane as the raw material, the regenerated catalyst was used to carry out isobutane dehydrogenation reaction according to the evaluation conditions of Example 11. The platinum active particle size, metal dispersion and reaction data of the regenerated catalyst J-1 are shown in Table 2.

[0043] Comparative Example 1 The catalyst preparation method of Example 1 was used to obtain fresh catalyst A-0. Before the reaction, fresh catalyst A-0 was dried only in a nitrogen atmosphere for 3 h, then cooled to 250 °C and switched to hydrogen reduction at a space velocity of 300 h. -1 After the temperature is raised to 600°C, propane and hydrogen sulfide are introduced to participate in the reaction, and the other conditions remain unchanged. The raw material is propane, and the platinum active particle size, metal dispersion and reaction data of fresh agent A-0 are shown in Table 1.

[0044] Comparative Example 2 The catalyst preparation method of Example 1 was used to obtain fresh catalyst A-0. Before the reaction, fresh catalyst A-0 was dried in a nitrogen atmosphere for 3 h, then cooled to 250 °C and switched to hydrogen reduction at a space velocity of 300 h. -1 After the temperature is raised to 600℃, only propane is introduced to participate in the reaction, and the other conditions remain unchanged. The raw material is propane, and the platinum active particle size, metal dispersion and reaction data of fresh agent A-0 are shown in Table 1.

[0045] Comparative Example 3 The deactivated catalyst obtained after 80 hours of reaction of the homemade fresh catalyst A-0 was regenerated by the regeneration method of Example 2, except that there was no cooling with material in step (1). After the reaction was completed, hydrogen purging was directly switched to cooling, and the other conditions remained unchanged. The raw material was propane, and propane dehydrogenation reaction was carried out according to the operating conditions of the regenerated catalyst. The platinum active particle size, metal dispersion and reaction data of the regenerated catalyst K-1 are shown in Table 1.

[0046] Comparative Example 4 The above evaluation method was used to evaluate the propane dehydrogenation reaction of an existing industrial agent. The platinum active particle size, metal dispersion and reaction data of the industrial agent are shown in Table 1.

[0047] Comparative Example 5 The deactivated catalyst obtained after 80 hours of reaction of the existing industrial agent in Comparative Example 4 was regenerated by the regeneration method of Example 2. The regenerated industrial agent was re-evaluated according to the fresh agent evaluation method. The platinum active particle size, metal dispersion and reaction data of T-1 after the industrial agent was regenerated are shown in Table 2.

[0048] The above examples and comparative examples are summarized, and the propane conversion rate and propylene selectivity are compared in the initial 1h and 80h reaction. The effects of changing the calcination, chlorine injection, reduction conditions and adding measures before and after the catalyst reaction on the dispersion of platinum metal, active particle size, catalyst activity and stability of the active component of the regenerated catalyst are investigated. The specific results are shown in Table 1.

[0049] Table 1 From the comparison of the data in Table 1, it can be seen that the method for regenerating the light alkane dehydrogenation catalyst of the present invention exhibits higher catalytic activity and stability in the dehydrogenation reactions of propane and isobutane.

[0050] By comparing Examples 2, 3, 4, 5, and 9, it was found that when the calcination temperature was lower than 500°C or higher than 600°C, the conversion rate, selectivity, platinum metal dispersion and active particle size of the catalyst after regeneration were affected. When the reduction temperature was higher than 600°C, the platinum metal dispersion of the catalyst after regeneration was significantly reduced, and the size of the active particles was larger, which may be related to the sintering of the catalyst.

[0051] Through Examples 2, 6, and 7, it was found that by introducing chlorine gas in advance before reaching the maximum calcination temperature and carrying out the calcination and oxychlorination processes simultaneously, the activity, selectivity, and stability of the obtained regenerated agent were optimal, the size of the platinum active particles was small, and the dispersion of the platinum metal of the catalyst was the highest. There was no chlorination operation during regeneration, the size of the active particles of the obtained regenerated catalyst was the largest, and the catalyst conversion rate, selectivity, and platinum metal dispersion were significantly reduced.

[0052] Through Examples 2 and 8, it was found that without the inversion operation, the performance of the catalysts after regeneration at different positions was not uniform.

[0053] It was found through Examples 2 and 9 that when the reduction temperature is too high, the catalyst is easily sintered, the size of the active particles increases, and the catalytic performance decreases.

[0054] Through Examples 2 and 10, it was found that under the present regeneration method, the performance of the catalyst was relatively stable after multiple regenerations, and the platinum dispersion was relatively high.

[0055] Comparing Examples 1 and 2 with Comparative Examples 1-3, it was found that in the same fresh agent evaluation process, both high-temperature sulfur injection and sulfur-free injection would affect the performance of the regenerated catalyst. At the same time, the material cooling protection measures after the regenerated catalyst reaction were completed could effectively inhibit catalyst sintering and improve the catalyst activity and metal dispersion after regeneration.

[0056] Comparing Comparative Examples 4 and 5 with Examples 1 and 2, it is found that the catalyst activity and selectivity of the existing industrial agent after regeneration under this regeneration method are similar to those of the fresh agent, the platinum metal dispersion is high, and the active particle size is small, indicating that this regeneration method is also applicable to the existing industrial agent.

[0057] According to the scheme designed in Examples 11 and 12, with isobutane as the raw material, the isobutane conversion rate, isobutylene selectivity, platinum metal dispersion and active particle size of the fresh catalyst and the regenerated catalyst were compared at the initial 1 hour and 80 hours of reaction. The specific data are shown in Table 2.

[0058] Table 2 From the comparison of the data in Table 2, it is found that when the catalyst obtained by the regeneration method of the present invention is reacted with isobutane as the raw material, the catalyst conversion rate and the metal dispersion of the selectivity agent are not affected after regeneration, the platinum metal dispersion is high, and the active particle size is no different from that of the fresh agent.

[0059] The above is only an embodiment of the present application and does not constitute any form of limitation to the present application. Although the present application is disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for regenerating a platinum-based light alkane dehydrogenation catalyst, characterized in that: The specific steps are as follows: (1) The deactivated platinum-based low-carbon alkane dehydrogenation catalyst is loaded into the constant temperature section of the fixed bed regenerator, supported by ceramic balls at the bottom, and heated to 370-420°C in a low-oxygen nitrogen atmosphere. The temperature is maintained for 1-4 hours for low-temperature carbonization treatment to reduce carbon deposition on the catalyst; (2) Continue to raise the temperature to 450-480°C, keep the oxygen content constant, and maintain this temperature for 2-6 hours; (3) Keep the roasting temperature unchanged. To prevent temperature runaway, gradually increase the oxygen content to 5-10% and maintain it at this oxygen content for 1-4 hours; (4) Continue to increase the oxygen content to 21% at the same oxygen extraction rate, introduce chlorine gas in an air atmosphere, and then program the temperature to 530-580°C, maintain this temperature for 2-6 hours, and perform a thorough decarbonization and oxychlorination operation on the catalyst simultaneously, and the catalyst returns to its pre-reduction color; (5) Stop heating and start cooling. Use air purge to cool down. When the temperature drops below 380°C, switch to nitrogen replacement purge. The air and nitrogen air speeds are both 1000-2000h -1 ; (6) After the temperature drops below 200°C, turn off the nitrogen and switch to hydrogen for reduction. The purity of the hydrogen is ≥98%. Raise the temperature to the reduction temperature of 500-550°C and maintain this temperature for 2-6 hours. After the reduction is completed, the regenerated catalyst is obtained.

2. The regeneration method of the platinum-based light alkane dehydrogenation catalyst according to claim 1, characterized in that: The catalyst in step (1) is loaded into the constant temperature section of the reactor, and the nitrogen space velocity is 1000-2000h -1 , the volume percentage of oxygen in nitrogen is 1-4%, and the heating rate is 1-3℃ / min.

3. The regeneration method of the platinum-based light alkane dehydrogenation catalyst according to claim 1, characterized in that: The nitrogen gas space velocity in step (2) is 1000-2000h -1 , the volume percentage of oxygen in nitrogen is 1-4%, and the heating rate is 0.5-2℃ / min.

4. The regeneration method of the platinum-based light alkane dehydrogenation catalyst according to claim 1, characterized in that: In step (3), under a nitrogen atmosphere, the rate of increase of the volume percentage of oxygen in nitrogen is 3% / h.

5. The regeneration method of the platinum-based light alkane dehydrogenation catalyst according to claim 1, characterized in that: In step (4), the rate of increase of the volume percentage of oxygen in nitrogen is 3% / h, the volume percentage of chlorine in air is 0.01-2%, and the gas space velocity is 1000-2000h -1 The heating rate is 0.5-2℃ / min. During the constant temperature process, the catalyst is poured 2-3 times. The lower outlet valve of the reactor is opened, and 10ml of porcelain balls are unloaded each time to achieve catalyst displacement. The catalyst is always located in the constant temperature section of the reactor.

6. The regeneration method of the platinum-based light alkane dehydrogenation catalyst according to claim 5, characterized in that: The volume percentage of chlorine in the air in step (4) is 0.1-1%.

7. The regeneration method of the platinum-based light alkane dehydrogenation catalyst according to claim 1, characterized in that: The heating rate in step (6) is 1-3°C / min, and the hydrogen space velocity is 600-1200h -1 During the constant temperature process, the catalyst is poured 2-3 times, the lower outlet valve of the reactor is opened, and 10 ml of porcelain balls are unloaded each time to achieve catalyst displacement. The catalyst is always located in the constant temperature section of the reactor.

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