A reactor system and process for preparing isobutylene from 2-chloroisobutane

Abstract

The present invention relates to the technical field of isobutylene production, and more particularly to a reactor system and process for preparing isobutylene from 2-chloroisobutane. The reactor is subjected to surface modification treatment, comprising the following steps: S1, surface pretreatment; S2, surface oxidation treatment to generate an active oxide layer: the reactor is calcined at a temperature of 500-700°C to generate an oxide layer on its surface; S3, loading active components: the reactor is impregnated with Al2O3 sol, then calcined at 400-600°C to form a porous Al2O3 layer, and then the reactor is impregnated with nickel nitrate solution, freeze-dried, and reduced at 400-600°C in an H2 or Ar atmosphere to form Ni nanoparticles; the material of the reactor is Hastelloy. By surface modification of the reactor, while ensuring a high 2-chloroisobutane conversion rate and isobutylene selectivity, the equipment maintenance cost is reduced, and the reactor coking problem is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of isobutylene production, and in particular to a reactor system and a process method for preparing isobutylene from 2-chloroisobutane. Background Art

[0002] As an important chemical raw material, isobutylene is widely used in industrial production. It is primarily used in the production of rubber products such as polyisobutylene, isoprene rubber, isobutylene rubber, and butyl rubber. It also plays a key role in the preparation of catalysts, antioxidants, pesticides, pharmaceuticals, fragrances, gasoline additives, and lubricants.

[0003] Currently, the raw material for isobutylene production primarily comes from the C4 fraction, a byproduct of naphtha cracking to ethylene plants. However, the boiling points of isobutylene and normal butene in the C4 fraction differ by only 0.4°C, making their effective separation difficult using conventional physical methods and increasing the difficulty of isobutylene extraction.

[0004] In terms of the production process of isobutylene, there are mainly two common methods:

[0005] Isobutane dehydrogenation: This process heats isobutane to approximately 650°C and reacts it with a precious metal catalyst to produce isobutylene. However, this process has significant drawbacks. As the reaction temperature increases, the rate of side reactions accelerates, significantly reducing isobutylene selectivity. It also generates heavy hydrocarbons and coke, which in turn promotes olefin polymerization. These side reactions can lead to coking and deactivation of the catalyst surface, reducing reaction efficiency and increasing production costs. Frequent catalyst replacement is also required, further increasing production complexity and costs.

[0006] Isobutane chlorination to isobutylene: This process first reacts isobutane with chlorine to produce hydrogen chloride and isobutane chloride, which are then separated by distillation to produce isobutane monochloride. Finally, the isobutane monochloride undergoes a HCl removal reaction at high temperature (150-250°C), high pressure (0.2-0.6 MPaG), and a catalyst to produce isobutylene. Compared to isobutane dehydrogenation, this process offers the advantages of higher conversion rates and isobutylene selectivity. Furthermore, due to the relatively low reaction temperature, the catalyst surface is less susceptible to coking and deactivation, allowing the system to operate stably for extended periods of time.

[0007] While the isobutane chlorination process to produce isobutylene has certain advantages, existing processes and equipment still face some practical challenges. For example, catalysts can coke and lose activity after long-term use, requiring replacement, which increases equipment maintenance costs.

[0008] In summary, the existing isobutylene production process has problems such as easy catalyst deactivation, high equipment maintenance cost, low 2-chloroisobutane conversion rate, and low isobutylene selectivity. Therefore, it is of great practical significance to develop an improved process and equipment that can effectively solve the above problems. Summary of the Invention

[0009] In order to solve the above technical problems existing in the prior art, the present invention provides a reactor system and process for preparing isobutylene from 2-chloroisobutane.

[0010] The technical solution of the present invention to solve the above technical problems is as follows:

[0011] A first aspect of the present invention is to provide a reactor system for preparing isobutylene from 2-chloroisobutane, wherein the reactor is subjected to surface modification treatment, comprising the following steps:

[0012] S1, surface pretreatment;

[0013] S2, surface oxidation treatment to form an active oxide layer: calcining the reactor at a temperature of 500-700° C. to form an oxide layer on its surface;

[0014] S3, loading active ingredients: impregnating the reactor with Al2O3 sol, then calcining at 400-600°C to form a porous Al2O3 layer, then impregnating the reactor with nickel nitrate solution, freeze-drying, and then reducing in H2 or Ar atmosphere at 400-600°C to form Ni nanoparticles;

[0015] Wherein, the material of the reactor is Hastelloy, and the oxide layer includes Cr2O3 and / or MoO3.

[0016] The present invention provides a reactor system for preparing isobutylene from 2-chloroisobutane. The reactor adopts Hastelloy as the material of the reactor and the surface of the reactor is modified. A metal matrix oxide layer (Cr2O3 and / or MoO3) and a porous Al2O3 layer are sequentially formed on the reactor surface from the substrate outward. Meanwhile, Ni nanoparticles are loaded and embedded in the porous Al2O3 layer and dispersed in the pores and surface of the Al2O3. That is, the porous Al2O3 layer loaded with Ni nanoparticles is located on the outermost layer. The modified reactor has the function of catalyzing the reaction of 2-chloroisobutane to prepare isobutylene. Specifically, the C in the surface oxide layer is used to form a metal matrix oxide layer (Cr2O3 and / or MoO3). The r2O3 provides weakly acidic sites to promote C-Cl bond cleavage and enhance redox activity through MoO3. The porous Al2O3 layer formed promotes the removal of HCl from 2-chloroisobutane to form isobutylene through surface acid sites. The Ni nanoparticles embedded therein are highly active for C-Cl bond cleavage and C-C bond recombination, while also being low-cost. The reactor after the secondary impregnation is subjected to a reduction reaction in a reducing atmosphere, which can inhibit carbon deposition and promote the stability of the metal active sites. The reactor system is essentially free of catalyst coking and deactivation, greatly reducing equipment maintenance costs and improving feedstock conversion and product selectivity.

[0017] On the basis of the above technical solution, the present invention can also make the following improvements:

[0018] Furthermore, the material of the reactor is Hastelloy C-276, and the calcination time in step S2 is 1 to 5 hours.

[0019] The beneficial effects of adopting the above-mentioned further technical solution are: Hastelloy C-276 has excellent thermal stability and corrosion resistance at high temperatures, and contains a high proportion of molybdenum (Mo) and chromium (Cr), which can resist corrosion in chlorine-containing environments; by controlling the oxidation time, a porous, high-specific surface area oxide layer is formed on the reactor surface, thereby improving the reaction activity.

[0020] Furthermore, the reactor includes at least one pipeline. When the number of the pipelines is greater than one, the pipelines are sequentially connected in series.

[0021] The beneficial effect of adopting the above further technical solution is that the use of a tubular reactor can increase the contact area between the reactor surface and 2-chloroisobutane, thereby improving the reaction efficiency.

[0022] Furthermore, a pipeline mixer is provided in the pipeline.

[0023] The beneficial effect of adopting the above further technical solution is to promote gas disturbance and improve reaction efficiency.

[0024] Furthermore, in step S1, the surface pretreatment includes pickling, ultrasonic cleaning, sandblasting or electrochemical etching.

[0025] The beneficial effects of adopting the above-mentioned further technical solution are: removing the oxide layer and contaminants on the surface of the reactor by pickling, followed by ultrasonic cleaning to ensure surface cleanliness; increasing the roughness of the reactor surface by sandblasting or electrochemical etching, improving the adhesion of the subsequent modified layer and the exposure of active sites.

[0026] Furthermore, the reactor system further comprises a heat exchanger, which is used for heat exchange between 2-chloroisobutane and isobutylene output from the reactor.

[0027] The beneficial effect of adopting the above further technical solution is that the isobutylene output from the reactor is discharged from the reactor outlet and then heat exchanged with the 2-chloroisobutane raw material in a heat exchanger, which can reduce the product temperature while increasing the raw material feed temperature.

[0028] Furthermore, the heat exchanger includes a first inlet and a first outlet, a second inlet and a second outlet, the first inlet is connected to the outlet of the reactor, the second inlet is connected to the 2-chloroisobutane delivery pipeline, the first outlet outputs isobutylene, and the second outlet is connected to the inlet of the reactor.

[0029] The second aspect of the present invention is to provide a process for preparing isobutylene by reacting 2-chloroisobutane, using the above-mentioned reactor system for preparing isobutylene by 2-chloroisobutane.

[0030] Furthermore, the reaction temperature of the reactor is 450-550° C., and the pressure of the reactor is normal pressure-0.5 MPaG.

[0031] The beneficial effect of adopting the above further technical solution is that by increasing the reaction temperature, a higher reaction rate can be achieved, while the reaction conversion rate and product selectivity can be improved.

[0032] Furthermore, the outside of the reactor is heated by far infrared, and the heating temperature is controlled to be 400-800°C.

[0033] Compared with the prior art, the present invention has the following technical effects:

[0034] Based on the existing isobutane chlorination process for producing isobutylene, the present invention performs surface modification on the reactor. By loading the active components on the pipe surface of the reactor, the present invention not only meets the requirements of high conversion rate of 2-chloroisobutane and high selectivity of isobutylene, but also eliminates the need for catalyst replacement and only requires regular cleaning of the reactor for restoration, effectively reducing equipment maintenance costs.

[0035] The reactor pipe of the present invention is made of Hastelloy C-276, which can withstand high temperature and hydrogen chloride gas corrosion on the one hand, and has relatively high catalytic reaction efficiency on the other hand, and can be industrially scaled up and have the ability of large-scale production;

[0036] The process method of the present invention further improves the reaction conditions while ensuring a high 2-chloroisobutane conversion rate and isobutylene selectivity. That is, the reaction temperature and pressure of 2-chloroisobutane are controlled within a suitable range. That is, the reaction temperature is increased but not excessively increased, so as to improve the raw material conversion rate and reaction rate without accelerating the side reaction rate. Therefore, heavy hydrocarbons and coke are not generated, olefin polymerization is avoided, and the coking problem of the reactor is effectively avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic structural diagram of a reactor system for preparing isobutylene from 2-chloroisobutane according to Example 1 of the present invention is shown;

[0038] Figure 2 A schematic structural diagram of a heat exchanger according to embodiment 1 of the present invention is shown.

[0039] Reference numerals:

[0040] 1. Reactor; 2. Pipeline; 3. Heat exchanger; 4. First inlet; 5. First outlet; 6. Second inlet; 7. Second outlet. DETAILED DESCRIPTION

[0041] The following is an explanation of the embodiments of the present invention by specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this invention are limited to this embodiment. On the contrary, the purpose of introducing the invention in conjunction with the embodiment is to cover other options or modifications that may be extended based on the claims of the present invention. In order to provide a deep understanding of the present invention, the following description will contain many specific details. The present invention can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the present invention, some specific details will be omitted in the description. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0042] Example 1

[0043] See also Figures 1 to 2A reactor system for preparing isobutylene from 2-chloroisobutane comprises a reactor 1 and a heat exchanger 3, wherein the reactor 1 comprises four pipelines 2 connected in series, each pipeline 2 being provided with a pipeline mixer, the diameter of each pipeline 2 being DN15 to DN150, the length of a single pipeline 2 being 0.5 to 15 m, and the pipeline mixer being selected from an SK static mixer, an SD static mixer, an SX static mixer, or an SV static mixer; the heat exchanger 3 comprises a first inlet 4 and a first outlet 5, a second inlet 6 and a second outlet 7, the first inlet 4 being connected to the outlet of the reactor 1, the second inlet 6 being connected to a 2-chloroisobutane delivery pipeline, the first outlet 5 outputting isobutylene, and the second outlet 7 being connected to the inlet of the reactor 1; each pipeline 2 being made of Hastelloy C-276 sheet and being formed by welding the Hastelloy C-276 sheets; each pipeline 2 being surface modified, comprising the following steps:

[0044] S1. Surface pretreatment: Remove the oxide layer and contaminants on the surface of pipe 2 by pickling, followed by ultrasonic cleaning to ensure surface cleanliness; then increase the surface roughness by sandblasting to improve the adhesion of the subsequent modified layer and the exposure of active sites;

[0045] S2. Surface oxidation treatment to form an active oxide layer: calcining the pipe 2 at 600° C. for 3 hours to form an oxide layer on its surface, the oxide layer comprising Cr2O3 and MoO3;

[0046] S3. Loading active ingredients: Pipe 2 is impregnated with Al2O3 sol, then calcined at 500°C to form a porous Al2O3 layer. Pipe 1 is then impregnated with nickel nitrate solution, freeze-dried, and reduced in a H2 atmosphere at 500°C to form Ni nanoparticles.

[0047] Example 2

[0048] A process for preparing isobutylene by reacting 2-chloroisobutane, using the reactor system of Example 1, wherein 2-chloroisobutane is transported to the reactor system of Example 1 through a delivery pipeline, and 2-chloroisobutane flows through each pipeline 2 in sequence, reacts in pipeline 2 to obtain isobutylene and hydrogen chloride, and the obtained isobutylene has a higher temperature and enters the heat exchanger 3 through a first inlet 4. The 2-chloroisobutane raw material transported through the delivery pipeline enters the heat exchanger 3 through a second inlet 6. The high-temperature isobutylene and the 2-chloroisobutane raw material are heat exchanged in the heat exchanger 3. After the heat exchange is completed, isobutylene is discharged from the first outlet 5 as a product, and the 2-chloroisobutane raw material is discharged from the second outlet 7 and enters the reactor 1 for reaction; the reaction temperature of the reactor 1 is 450° C. and the pressure is 0.2 MPaG.

[0049] The conversion rate of 2-chloroisobutane can reach over 90%, and the isobutylene selectivity is >85%.

[0050] When coking and carbon deposition occurs on the surface of the reactor 1, the following methods are used to quickly clean the carbon deposition while minimizing damage to the catalytic activity:

[0051] (1) Mild pretreatment (for loose coke): Use mild inert gas purge (N2, Ar) or purge with inert gas at a lower temperature (<300℃) to remove some physically adsorbed hydrocarbons or loose carbon particles, reducing the load and exothermic risk in the subsequent oxidation stage.

[0052] (2) Low temperature controlled oxidation regeneration:

[0053] After pretreatment, the coke is slowly oxidized by using a relatively low temperature (400-450°C) and a controlled oxygen concentration (using diluted oxygen, specifically, a mixture of 1%-3% by volume of O2 and N2 or 1%-3% by volume of O2 and Ar. The low oxygen concentration can control the reaction rate, avoid local overheating, and reduce the potential impact of a strong oxidizing atmosphere on Ni). This avoids triggering violent sintering and phase transformation of Ni and Al2O3.

[0054] In the above low temperature controlled oxidation regeneration process, a high gas space velocity (space velocity range is 2000~4000h -1 ), which is conducive to heat transfer and removal of reaction products (CO2, H2O), preventing local accumulation and overheating; adopt a slow temperature program (1-5℃ / min) from room temperature to the target temperature (400-450℃), and maintain it at the target temperature for a sufficient time (several hours, depending on the amount of carbon deposits) until the outlet CO2 concentration drops to the baseline; moisture control: if conditions permit, the incoming gas can be pre-dried, as high-temperature water vapor will accelerate the hydrothermal aging of Al2O3 and the potential oxidation and migration of Ni.

[0055] (3) Post-processing-reduction:

[0056] After low-temperature oxidation, the system is cooled to a safe temperature (typically <100°C) in an inert atmosphere (N2 or Ar). A reducing gas (a mixture of H2 and Ar, with a volume concentration of 5-10% hydrogen in the inert Ar) is then introduced, and reduction is performed at 400-450°C for a short period of 1-2 hours. During the oxidation regeneration process, the Ni surface may become slightly oxidized. This step is intended to reduce any oxidized Ni back to a metallic state, restoring its activity.

[0057] The above cleaning method can not only protect the Ni nanoparticles from sintering and growing, thereby maintaining catalytic activity, but also protect the Al2O3 porous structure from phase change and destruction. It can also avoid physical damage to the porous Al2O3 layer and the loaded Ni particles due to scratching or peeling, and avoid chemical corrosion, that is, avoid acid and alkaline cleaning solutions that may dissolve Ni particles or corrode the Al2O3 carrier.

[0058] After the above cleaning, the reactor surface can be restored to activity and can continue to be used.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A reactor system for preparing isobutylene from 2-chloroisobutane, characterized in that: The reactor is subjected to surface modification treatment, comprising the following steps: S1, surface pretreatment; S2, surface oxidation treatment to form an active oxide layer: calcining the reactor at a temperature of 500-700° C. to form an oxide layer on its surface; S3, loading active ingredients: impregnating the reactor with Al2O3 sol, then calcining at 400-600°C to form a porous Al2O3 layer, then impregnating the reactor with nickel nitrate solution, freeze-drying, and then reducing in H2 or Ar atmosphere at 400-600°C to form Ni nanoparticles; Wherein, the material of the reactor is Hastelloy, and the oxide layer includes Cr2O3 and / or MoO3.

2. The reactor system for preparing isobutylene from 2-chloroisobutane according to claim 1, characterized in that The material of the reactor is Hastelloy C-276, and the calcination time in step S2 is 1 to 5 hours.

3. The reactor system for preparing isobutylene from 2-chloroisobutane according to claim 1 or 2, characterized in that: The reactor includes at least one pipeline. When the number of the pipelines is greater than one, the pipelines are sequentially connected in series.

4. The reactor system for preparing isobutylene from 2-chloroisobutane according to claim 3, characterized in that: A pipeline mixer is provided in the pipeline.

5. The reactor system for preparing isobutylene from 2-chloroisobutane according to claim 1 or 2, characterized in that: In step S1, the surface pretreatment includes pickling, ultrasonic cleaning, sandblasting or electrochemical etching.

6. The reactor system for preparing isobutylene from 2-chloroisobutane according to claim 1 or 2, characterized in that: The reactor system further comprises a heat exchanger, which is used for heat exchange between 2-chloroisobutane and isobutylene output from the reactor.

7. The reactor system for preparing isobutylene from 2-chloroisobutane according to claim 6, characterized in that: The heat exchanger includes a first inlet and a first outlet, a second inlet and a second outlet, the first inlet is connected to the outlet of the reactor, the second inlet is connected to the 2-chloroisobutane delivery pipeline, the first outlet outputs isobutylene, and the second outlet is connected to the inlet of the reactor.

8. A process for preparing isobutylene by reacting 2-chloroisobutane, characterized in that: A reactor system for preparing isobutylene using the 2-chloroisobutane according to any one of claims 1 to 7.

9. The process for preparing isobutylene by reacting 2-chloroisobutane according to claim 8, characterized in that: The reaction temperature of the reactor is 450-550° C., and the pressure of the reactor is normal pressure-0.5 MPaG.

10. The process for preparing isobutylene by reacting 2-chloroisobutane according to claim 8, characterized in that: The outside of the reactor is heated by far infrared, and the heating temperature is controlled to be 400-800°C.

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