Propane dehydrogenation method capable of stabilizing sulfur concentration

Abstract

The invention belongs to the technical field of petrochemical industry, and discloses a propane dehydrogenation method capable of stabilizing sulfur concentration, which comprises the following steps: adding a vulcanizing agent into a bubbler, placing the bubbler into a circulating cooler, and adjusting a circulating constant-temperature water bath to a preset temperature T1; an inlet of the bubbler is connected with preset gas G1, and an outlet is connected with the propane dehydrogenation reactor; adding the pre-reduced platinum-containing catalyst into a propane dehydrogenation reactor; after the propane dehydrogenation reactor is heated to the preset temperature T2, the flow of the preset gas G1 is set to be the preset flow F1, and reaction gas is introduced into the propane dehydrogenation reactor, so that the sulfur concentration of the effluent section of the reactor is stabilized at the preset concentration until the reaction is finished. According to the present invention, the ppm-level sulfur content is stably maintained in the reaction atmosphere through the vulcanizing agent saturated steam sample introduction mode at the specific temperature, such that the metal material on the wall surface of the reaction tube is passivated, the cracking and the deep dehydrogenation of propane on the metal material are inhibited to generate coke, and the propylene selectivity and the reaction stability are improved.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, specifically, it relates to a method for propane dehydrogenation with stable sulfur concentration. Background Technology

[0002] Propane dehydrogenation (PDH) is an important industrial process for converting propane into propylene. Propylene is a crucial raw material in the chemical industry, used to produce various chemical products such as polypropylene, epoxy resins, acrylic acid, and its esters. With the continuous growth of global demand for propylene, propane dehydrogenation technology has attracted increasing attention. The advantages of propane dehydrogenation technology lie in its wide availability and relatively low cost of raw materials, especially after the shale gas revolution, which has resulted in abundant and inexpensive propane supplies. Furthermore, this technology can reduce dependence on petroleum resources, providing a more environmentally friendly production route. With continuous technological advancements, propane dehydrogenation has become one of the important sources of propylene in modern chemical production.

[0003] Pt-based catalysts are a class of highly active catalysts for propane dehydrogenation to propylene and are a current research focus. However, in propane dehydrogenation reactors, temperatures can reach over 600 °C, and the cracking of propane within the metal reaction tubes can lead to carbon buildup, which reduces reaction efficiency. Simultaneously, carbon buildup can cause partial or complete blockage of the reaction tubes, increasing system pressure drop and affecting flowability and process control. Furthermore, carbon buildup can poison the catalyst, covering its surface and reducing its activity and selectivity. Excessive carbon buildup can even induce thermal stress concentration, leading to mechanical damage or deformation of the metal reaction tubes. In large reactors, this problem can be mitigated by injecting a sulfurizing agent to maintain a sulfur atmosphere at the ppm level. However, due to the lower gas flow rate in small reactors, maintaining a sulfur content at the ppm level requires an injection rate of 1 × 10⁻⁶ sulfurizing agent. −3 The flow rate is around μL / min, and existing equipment such as syringe pumps cannot achieve the required precision. Summary of the Invention

[0004] This invention focuses on the technical problem of effectively suppressing catalyst coking in a small propane dehydrogenation reactor using a sulfiding agent. It provides a propane dehydrogenation method with stable sulfur concentration by introducing saturated steam of the sulfiding agent to maintain a sulfur content at the ppm level to suppress coking, thereby improving propylene selectivity and reaction stability.

[0005] To solve the above-mentioned technical problems, the present invention is implemented through the following technical solution:

[0006] This invention provides a method for propane dehydrogenation with stable sulfur concentration, comprising:

[0007] (1) Add the vulcanizing agent to the bubbler, which is placed in a circulating cooler, and adjust the circulating constant temperature water bath to the preset temperature T1;

[0008] (2) The inlet of the bubbler is connected to a preset gas G1, and the outlet of the bubbler is connected to the inlet of the propane dehydrogenation reactor;

[0009] (3) Add the pre-reduced platinum-containing catalyst to the propane dehydrogenation reactor;

[0010] (4) After heating the propane dehydrogenation reactor to the preset temperature T2, set the preset gas flow rate G1 to the preset flow rate F1, and introduce the reaction gas into the propane dehydrogenation reactor so that the sulfur concentration in the reactor effluent section is stabilized at the preset concentration until the reaction ends.

[0011] Furthermore, the preset temperature T1 in step (1) and the preset flow rate F1 in step (4) are calculated based on the preset concentration in the propane dehydrogenation reactor and the saturated vapor pressure of the sulfiding agent.

[0012] Specifically:

[0013] First, based on the physical properties of the selected vulcanizing agent, its saturated vapor pressure P at the preset temperature T1 is determined using the Antoine equation. s Among them, P s It is the saturated vapor pressure;

[0014] Secondly, based on Dalton's law of partial pressures and the ideal gas law, the pressure P at the preset temperature T1 and system pressure P is calculated. sys Below, the mole fraction (P) of the saturated vulcanizing agent carried in the carrier gas (passing through at a preset flow rate F1) s / P sys );

[0015] Finally, by combining the relative molecular mass ratio of the vulcanizing agent to the carrier gas, the preset flow rate F1 (the mass flow rate of the gas entering the bubbling gas) is converted into the actual supply of the vulcanizing agent, so as to meet the material balance requirements of the preset sulfur concentration under the total feed flow rate of the reactor.

[0016] In practice, a preset temperature T1 is usually fixed to obtain a stable saturated vapor pressure P. s Then, the required preset flow rate F1 can be calculated; or the preset flow rate F1 can be fixed and the required preset temperature T1 can be calculated, thereby achieving precise control of the concentration of the vulcanizing agent entering the reactor.

[0017] Furthermore, the vulcanizing agent in step (1) is dimethyl disulfide.

[0018] Furthermore, the preset gas G1 in step (2) is hydrogen or nitrogen.

[0019] Furthermore, the platinum catalyst in step (3) is a platinum-containing catalyst supported on alumina.

[0020] Furthermore, the platinum catalyst in step (3) has a platinum mass fraction of 0.1-2.0%.

[0021] Furthermore, the preset temperature T2 in step (4) is 550-620 ℃.

[0022] Furthermore, the reaction gas in step (4) contains propane.

[0023] Furthermore, the preset concentration of sulfur in step (4) is 10-1000 ppm in terms of molar amount.

[0024] Furthermore, in step (4), the preset gas G1 is continuously fed into the propane dehydrogenation reactor throughout the entire reaction process, and the flow rate is kept stable at the preset flow rate F1.

[0025] The beneficial effects of this invention are:

[0026] This invention achieves stable sulfur content at the ppm level in the reaction atmosphere by introducing saturated vapor of the sulfurizing agent at a specific temperature. This passivates the metal material on the reaction tube wall, inhibiting the cracking and deep dehydrogenation of propane to form coke, thus improving propylene selectivity and reaction stability. This advantage is applicable not only to high-flow-rate industrial reactors but also to low-flow-rate laboratory experiments. This invention can precisely control sulfur content in laboratory-scale low-flow-rate reactions, maintaining sulfur concentration fluctuations at the ppm level, thereby achieving the same reaction results as high-flow-rate reactions in low-flow-rate experiments. This high efficiency and stability at low flow rates not only improves the reproducibility and reliability of laboratory research but also provides a strong theoretical foundation and technical support for subsequent industrial scale-up. Attached Figure Description

[0027] Figure 1 The graph shows the effect of sulfur concentration on the performance of propane dehydrogenation to propylene in Examples 1-4 of this invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0029] Example 1

[0030] This embodiment provides a propane dehydrogenation method with stable sulfur concentration, including the following steps:

[0031] Step 1: Add the vulcanizing agent to the bubbler, place the bubbler in the circulating cooler, and adjust the circulating constant temperature water bath to the preset temperature of 0℃;

[0032] Step 2: Connect the bubbler to the front end of the propane dehydrogenation reactor. Connect the inlet of the bubbler to the preset gas and the outlet of the bubbler to the propane dehydrogenation reactor; wherein, the preset gas is hydrogen.

[0033] Step 3: Add a pre-reduced catalyst with a platinum content of 0.3% to the propane dehydrogenation reactor;

[0034] Step 4: The propane dehydrogenation reactor is heated until the temperature reaches the preset temperature of 600℃. Then, a reaction gas containing propane and a preset gas before the bubbler are introduced. The reaction is maintained under these conditions. During the reaction, the sulfur concentration in the reactor effluent section is stabilized at the preset concentration of 100ppm until the reaction is completed.

[0035] The conditions for testing the catalyst's activity in the propane dehydrogenation reaction were as follows: catalyst loading was 100 mg, reaction temperature was 620 °C, molar ratio of propane, hydrogen, and nitrogen was 4:4:17, and total flow rate was 100 mL / min.

[0036] Example 2

[0037] Propane dehydrogenation was performed according to the method in Example 1, except that the sulfur concentration (i.e., the preset concentration) in step four was 0 ppm.

[0038] Example 3

[0039] Propane dehydrogenation was performed according to the method of Example 1, except that the sulfur concentration (i.e., the preset concentration) in step four was 10 ppm.

[0040] Example 4

[0041] Propane dehydrogenation was performed according to the method of Example 1, except that the sulfur concentration (i.e., the preset concentration) in step four was 1000 ppm.

[0042] Example 5

[0043] Propane dehydrogenation was performed according to the method in Example 1, except that the preset gas in step two was nitrogen.

[0044] Example 6

[0045] Propane dehydrogenation was performed according to the method in Example 1, except that the platinum content in step three was 0.1%.

[0046] Example 7

[0047] Propane dehydrogenation was performed according to the method of Example 1, except that the platinum content in step three was 2%.

[0048] Example 8

[0049] Propane dehydrogenation was carried out according to the method of Example 1, except that the preset temperature of the propane dehydrogenation reactor in step four was 550°C.

[0050] Example 9

[0051] Propane dehydrogenation was carried out according to the method of Example 1, except that the preset temperature of the propane dehydrogenation reactor in step four was 620°C.

[0052] The experimental results of Examples 1-9 above were compared horizontally to examine the influence of different parameters on the catalyst reaction performance.

[0053] (1) The effect of sulfur concentration on catalyst activity in Examples 1, 2, 3 and 4. See Table 1 for specific test results.

[0054] Table 1. Effect of sulfur concentration on propane conversion and propylene selectivity of platinum-containing catalysts

[0055]

[0056] Figure 1 The graph shows the effect of sulfur concentration in the reaction system on the performance of propane dehydrogenation to propylene after the injection of the vulcanizing agent in Examples 1-4 of this invention. (From Table 1 and...) Figure 1 It is evident that without the introduction of a sulfurizing agent, the propane conversion rate of the catalyst rapidly decreased from the initial 43.5% to 9.2%, and the propylene selectivity was only 60.2%. The metal tube wall significantly affected the catalytic conversion of propane to propylene by the platinum-containing catalyst. When a sulfurizing agent was introduced into the reaction atmosphere using the method of this invention, reaching a sulfur concentration of 10 ppm, the initial propane conversion rate slightly decreased to 39.8%, but the propylene selectivity significantly increased to 87.1%, and the propane conversion rate remained at approximately 33.2% after 4 hours of reaction. When the sulfur content was increased to 100 ppm, the propylene selectivity further increased to 90.9%, and the propane conversion rate only decreased from 37.8% to 35.2% within 4 hours. Further increasing the sulfur concentration to 1000 ppm also yielded good results. These results demonstrate that introducing a sulfurizing agent into the reaction atmosphere using the method of this invention has a significant positive effect on the propane dehydrogenation to propylene process using a platinum-containing catalyst, with a sulfur concentration of 100 ppm being particularly advantageous.

[0057] (2) The effect of the preset gas used to introduce the sulfiding agent in Examples 1 and 5 on the catalyst activity is shown in Table 2.

[0058] Table 2. Effects of the pre-set gas used to introduce the sulfurizing agent on the propane conversion and propylene selectivity of the platinum-containing catalyst.

[0059]

[0060] As can be seen from the comparison in Table 2, when the preset gas used to introduce the vulcanizing agent is hydrogen or nitrogen, both can achieve a relatively good selective conversion of propane to ethylene, and the selectivity of propylene is much higher than that without vulcanizing agent. This indicates that either hydrogen or nitrogen can be used as the gas introduced by the vulcanizing agent, with hydrogen being the better option.

[0061] (3) The effect of the platinum content in the catalysts in Examples 1, 6 and 7 on the catalyst activity is shown in Table 3 for specific test results.

[0062] Table 3. Effects of catalysts with different platinum contents on propane conversion and propylene selectivity.

[0063]

[0064] As can be seen from the comparison in Table 3, after introducing a sulfiding agent into the reaction atmosphere, catalysts with different platinum contents all exhibited the ability to stably catalyze the production of propylene from propane. The effect was slightly lower with a platinum content of 0.1% than with 0.3%, and the best effect was observed with a platinum content of 2%. Considering both the cost and reaction efficiency of platinum, a platinum content of 0.3% is superior.

[0065] (4) The effect of reactor temperature on catalyst activity in Examples 1, 8 and 9. See Table 4 for specific test results.

[0066] Table 4. Effect of reactor temperature on propane conversion and propylene selectivity

[0067]

[0068] As can be seen from the comparison in Table 4, after introducing a sulfiding agent into the reaction atmosphere, the platinum-containing catalyst exhibited the ability to selectively convert propane to propylene within the temperature range of 550-620℃. This indicates that the method for stabilizing propane dehydrogenation using saturated vapor of a sulfiding agent described in this invention is applicable within a wide temperature range of 550-620℃.

[0069] In summary, the propane dehydrogenation method provided by this invention can introduce sulfiding agent vapor with high stability, effectively reduce coke formation, and significantly improve the selectivity and reaction stability of propane dehydrogenation of propylene using platinum-containing catalysts, thus having broad application prospects.

[0070] The technical solutions disclosed and proposed in this invention can be implemented by those skilled in the art by appropriately modifying the conditions and routes, etc. Although the methods and preparation techniques of this invention have been described through preferred embodiments, those skilled in the art can obviously modify or recombine the methods and technical routes described herein without departing from the content, spirit, and scope of this invention to achieve the final preparation technique. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the spirit, scope, and content of this invention.

Claims

1. A method for propane dehydrogenation with stable sulfur concentration, characterized in that, include: (1) Add the vulcanizing agent to the bubbler, which is placed in a circulating cooler, and adjust the circulating constant temperature water bath to the preset temperature T1; (2) The inlet of the bubbler is connected to a preset gas G1, and the outlet of the bubbler is connected to the inlet of the propane dehydrogenation reactor; (3) Add the pre-reduced platinum-containing catalyst to the propane dehydrogenation reactor; (4) After heating the propane dehydrogenation reactor to the preset temperature T2, set the preset gas flow rate G1 to the preset flow rate F1, and introduce the reaction gas into the propane dehydrogenation reactor so that the sulfur concentration in the reactor effluent section is stabilized at the preset concentration until the reaction ends.

2. The propane dehydrogenation method for stabilizing sulfur concentration according to claim 1, characterized in that, The preset temperature T1 in step (1) and the preset flow rate F1 in step (4) are calculated based on the preset concentration in the propane dehydrogenation reactor and the saturated vapor pressure of the sulfiding agent.

3. The propane dehydrogenation method for stabilizing sulfur concentration according to claim 1, characterized in that, The vulcanizing agent in step (1) is dimethyl disulfide.

4. The propane dehydrogenation method for stabilizing sulfur concentration according to claim 1, characterized in that, The preset gas G1 in step (2) is hydrogen or nitrogen.

5. The propane dehydrogenation method for stabilizing sulfur concentration according to claim 1, characterized in that, The platinum catalyst in step (3) is a platinum-containing catalyst supported on alumina.

6. The propane dehydrogenation method for stabilizing sulfur concentration according to claim 1, characterized in that, The platinum catalyst in step (3) has a platinum mass fraction of 0.1-2.0%.

7. The propane dehydrogenation method for stabilizing sulfur concentration according to claim 1, characterized in that, The preset temperature T2 in step (4) is 550-620 ℃.

8. The propane dehydrogenation method for stabilizing sulfur concentration according to claim 1, characterized in that, The reaction gas in step (4) contains propane.

9. The propane dehydrogenation method for stabilizing sulfur concentration according to claim 1, characterized in that, The preset concentration of sulfur in step (4) is 10-1000 ppm in terms of molar amount.

10. The method for propane dehydrogenation with stable sulfur concentration according to claim 1, characterized in that, In step (4), the preset gas G1 is continuously fed into the propane dehydrogenation reactor throughout the reaction process, and the flow rate is kept stable at the preset flow rate F1.

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