A dual catalyst packing method for improving the selectivity of metaselectroisomerization of pseudocumene to quadricylene

Abstract

The present application belongs to the technical field of aromatic hydrocarbon production, and provides a double-catalyst packing method for improving the selectivity of hemimellitene to quadricylene, comprising: after the first catalyst is passivated in water vapor at 400-410 DEG C, it is packed in the upper layer of a fixed bed reactor; taking HZSM-60 as a carrier, after calcination, a transition metal is loaded to obtain a second catalyst; the second catalyst is packed in the lower layer of the fixed bed reactor, and the method is completed; wherein the mass ratio of the first catalyst and the second catalyst is 1:1-1.3. The combined catalysts are packed in the fixed bed reactor, and the advantages of the two catalysts can be combined. The upper catalyst has high alkylation efficiency, and the main function of the lower catalyst is to select type, which is beneficial to reducing side reactions and improving the selectivity of hemimellitene and quadricylene.

Description

Technical Field

[0001] This invention belongs to the field of aromatic hydrocarbon production technology, and specifically relates to a method for producing pseudotrimethylbenzene and mesitylene by alkylation. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Pseudotrimethylbenzene and mesitylene are important fine chemical raw materials. Pseudotrimethylbenzene is mainly used to synthesize trimellitic anhydride, trimethylhydroquinone, and mesitylene. 95% of mesitylene is used to synthesize pyromellitic dianhydride, which is then used to produce high-end specialty new materials such as polyimide resins or films.

[0004] Currently, the most commonly used industrial methods for producing pseudotrimethylbenzene and mesitylene are the C9+ heavy aromatics separation method, pseudotrimethylbenzene alkylation method, pseudotrimethylbenzene disproportionation reaction method, and methanol synthesis method. These methods have drawbacks: high cost, low profit, and significant pollution. Furthermore, the technology is immature and cannot be industrialized. Therefore, developing new, low-cost, and industrially feasible processes is essential. Toluene-methanol alkylation is a very good technical solution, using inexpensive and readily available raw materials, producing fewer byproducts and higher product purity compared to direct methanol aromatication. However, selecting suitable catalysts and fully utilizing their catalytic effects still require improvement. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a dual-catalyst packing method to improve the selectivity of pseudotrimethylbenzene and mesitylene, thereby resolving the issues of low selectivity in existing toluene-methanol methylation for pseudotrimethylbenzene and mesitylene as mentioned in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A first aspect of the present invention provides a method for improving the selectivity of a dual-catalyst packing material for pseudotrimethylbenzene / trimethylbenzene, comprising:

[0008] The first catalyst was passivated in steam at 400–410 °C and then packed into the upper layer of the fixed-bed reactor.

[0009] Using HZSM-60 as a support, after calcination, a transition metal was loaded to obtain a second catalyst.

[0010] The second catalyst is loaded into the lower layer of a fixed-bed reactor to obtain the product;

[0011] The mass ratio of the first catalyst to the second catalyst is 1:1 to 1.3.

[0012] In a second aspect, the present invention provides a fixed-bed reactor prepared by the method described above.

[0013] A third aspect of the invention provides the application of a compound catalyst in improving the selectivity of a catalyst for pseudotrimethylbenzene and mesitylene, the compound catalyst comprising: a first catalyst and a second catalyst, wherein the first catalyst is packed in the upper layer of a fixed-bed reactor and the second catalyst is packed in the lower layer of the fixed-bed reactor.

[0014] Beneficial effects of the present invention

[0015] (1) The combined catalyst of the present invention is packed into a fixed-bed reactor, which achieves the effect of combining the advantages of two catalysts. The upper catalyst has high alkylation efficiency, while the lower catalyst mainly functions as a catalyst selector, which helps to reduce side reactions and improve the selectivity of pseudotrimethylbenzene and mesitylene.

[0016] One catalyst used in this reactor is HZSM-60 supported and calcined before being loaded with a transition metal. This catalyst, prepared by this method, is packed in the lower layer of the fixed-bed reactor, primarily for type-selective catalysis. The other catalyst, passivated with 400°C steam, is packed in the upper layer of the fixed-bed reactor. Its main advantage is that it effectively reduces the content of ethylbenzene, propylbenzene, and methylbenzene, while promoting methylation on the benzene ring. This catalyst combination can efficiently produce pseudotrimethylbenzene or mesitylene while reducing impurities.

[0017] The catalytic reaction process of this invention is carried out in a multiphase two-stage fixed-bed reactor under a specific N2 atmosphere, at a reaction pressure of 0.5-3 MPa and a mass hourly space velocity of 0.2-10. After preheating by a preheater, a gas-solid two-phase reaction is carried out. After a single-pass evaluation, the selectivity of polymethyl aromatic hydrocarbons (particulate trimethylbenzene and mesitylene) is as high as 56%, and the catalyst life is greater than 200 hours. This catalytic process is simple to operate and is easy to carry out for large-scale industrial continuous production.

[0018] (2) The preparation method of the present invention is simple, practical and easy to promote. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 This is a structural diagram of the dual-catalyst packing method in Embodiment 1 of the present invention, wherein 1 is the first catalyst, 2 is the second catalyst, and 3 is quartz sand. Detailed Implementation

[0021] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] A dual-catalyst packing method includes a first catalyst and a second catalyst. The first catalyst is packed in the upper layer of a fixed bed reactor, and the second catalyst is packed in the lower layer of the fixed bed reactor. The feedstocks toluene and methanol are efficiently converted into pseudotrimethylbenzene and mesitylene in a single pass under the action of this catalyst.

[0023] In some embodiments, the first catalyst support is one of HMCM-22, Hβ, HY, and mordenite;

[0024] In some embodiments, the first catalyst support is passivated with water vapor at 400 degrees Celsius for 3 hours to improve catalyst life.

[0025] In some embodiments, the second catalyst support is HZSM-60 with a special pore structure.

[0026] In some embodiments, the second catalyst support is loaded with one or two of the metals La, Cu, Zn, and Ni, and the preparation method of catalyst B is as follows:

[0027] Step 1: Crush the purchased catalyst carrier into strips of 0.5-1cm, and then calcine them in a muffle furnace at 150 degrees Celsius for 2 hours and at 550 degrees Celsius for 2 hours.

[0028] Step 2: Impregnate the catalyst by loading it at a ratio of 0.5 to 7% molar metal per gram of support. Before loading, test the saturated water absorption capacity of the catalyst support and prepare a salt solution containing metal cations with the maximum water absorption capacity. Then, spray the prepared salt solution evenly onto the catalyst support and let it stand for two hours to allow the salt solution to be fully absorbed.

[0029] Step 3: Place it in a forced-air drying oven and bake at 80 degrees for 3 hours, then place it in a muffle furnace and bake at 150 degrees for 2 hours, then at 550 degrees for 2 hours.

[0030] A dual-catalyst packing method for improving the yields of pseudotrimethylbenzene and mesitylene consists of a top layer of quartz sand, followed by a first catalyst, then a second catalyst, and finally another layer of quartz sand.

[0031] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0032] In the following examples, all catalysts are commercially available products.

[0033] Example 1

[0034] A single catalyst packing method for producing pseudotrimethyltetramethylene includes 0 g of catalyst HMCM-22, 210 g of catalyst HZSM-60, and catalyst HZSM-60 support loaded with 2% metallic La.

[0035] The specific preparation process of catalyst HZSM-60 is as follows:

[0036] Step 1: Crush the purchased HZSM-60 catalyst support into strips of 0.5-1cm, and then calcine them in a muffle furnace at 150 degrees Celsius for 2 hours and at 550 degrees Celsius for 2 hours.

[0037] Step 2: Impregnate the lanthanum catalyst with a loading ratio of 2% molar metal per gram of support. Before loading, test the saturated water absorption capacity of the catalyst support to be 0.48g water per gram of support. Prepare a salt solution containing lanthanum nitrate (48.5g water + 4.7g La(NO3)3) with the maximum water absorption capacity. Then, spray the prepared salt solution evenly onto the catalyst support and let it stand for two hours to allow the salt solution to be fully absorbed.

[0038] Step 3: Place it in a forced-air drying oven and bake at 80 degrees Celsius for 3 hours, then place it in a muffle furnace and bake at 150 degrees Celsius for 2 hours, and then at 550 degrees Celsius for 2 hours.

[0039] Example 2

[0040] A dual-catalyst packing method improves the selectivity of pseudotrimethylbenzene and mesitylene, comprising 100g of catalyst HMCM-22 and 110g of catalyst HZSM-60. The HMCM-22 catalyst is packed in the upper layer of a fixed bed, and the HZSM-60 catalyst is packed in the lower layer. Under the action of this catalyst, toluene and methanol are efficiently converted to pseudotrimethylbenzene and mesitylene in a single pass. The HMCM-22 catalyst support is passivated with 400°C steam for 3 hours before packing to improve catalyst lifetime. The HZSM-60 catalyst support is loaded with 2% metallic La.

[0041] The specific preparation process of catalyst HZSM-60 is as follows:

[0042] Step 1: Crush the purchased HZSM-60 catalyst support into strips of 0.5-1cm, and then calcine them in a muffle furnace at 150 degrees Celsius for 2 hours and at 550 degrees Celsius for 2 hours.

[0043] Step 2: Impregnate the lanthanum catalyst with a loading ratio of 2% molar metal per gram of support. Before loading, test the saturated water absorption capacity of the catalyst support to be 0.48g water per gram of support. Prepare a salt solution containing lanthanum nitrate (48.5g water + 4.7g La(NO3)3) with the maximum water absorption capacity. Then, spray the prepared salt solution evenly onto the catalyst support and let it stand for two hours to allow the salt solution to be fully absorbed.

[0044] Step 3: Place it in a forced-air drying oven and bake at 80 degrees for 3 hours, then place it in a muffle furnace and bake at 150 degrees for 2 hours, then at 550 degrees for 2 hours.

[0045] A dual-catalyst packing method for improving the selectivity of pseudotrimethylbenzene and mesitylene consists of a top layer of quartz sand, followed by catalyst HMCM-22, then catalyst HZSM-60, and finally another layer of quartz sand.

[0046] Example 3

[0047] A dual-catalyst packing method to improve the selectivity of pseudotrimethylammonium-methyltetramethylene includes 210g of catalyst HMCM-22 and 0g of catalyst HZSM-60. The catalyst HMCM-22 support is passivated with 400°C water vapor for 3h before packing to improve catalyst lifetime.

[0048] Comparative Example 1

[0049] The difference from Example 2 is that the catalyst Hβ is used instead of HMCM-22.

[0050] Comparative Example 2

[0051] The difference from Example 2 is that catalyst HY is used instead of HMCM-22.

[0052] The catalyst prepared in the above manner was used in the alkylation reaction of toluene and methanol to synthesize pseudotrimethylbenzene and mesitylene in a fixed-bed continuous reaction. The reaction conditions were: temperature 400℃, liquid hourly space velocity 2.3 h⁻¹. -1 The ratio of toluene to methanol (molar ratio) was 1:3, the reaction time was 4 hours, the unit was shut down and the pressure was released, and all the product was collected. The reaction results are shown in Table 1.

[0053] Table 1. Performance Study of Catalysts for Alkylation of Toluene and Methanol to Prodextrimethylbenzene and Mesitylene

[0054]

[0055] As shown in Table 1, the composite catalyst effectively improved the selectivity of pseudotrimethylbenzene and mesitylene in the toluene-methanol alkylation reaction, with the selectivity of pseudotrimethylbenzene and mesitylene reaching as high as 56% after catalyst composite.

[0056] Meanwhile, compared with other catalysts, the HMCM-22 catalyst passivated by water vapor has a better combination effect with HZSM-60 supported with transition metals, and has higher selectivity for pseudotrimethylbenzene and mesitylene.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for using a dual-catalyst packing to improve the selectivity of pseudotrimethylbenzene / me-tetramethylbenzene, characterized in that, include: After passivating the first catalyst in steam at 400-410℃ for 3-4 hours, it is loaded into the upper layer of the fixed-bed reactor. The support for the first catalyst is at least one of HMCM-22 and Hβ; Using HZSM-60 as a support, after calcination, a transition metal was loaded to obtain a second catalyst. The second catalyst is loaded into the lower layer of a fixed-bed reactor to obtain the product; The specific roasting conditions include: roasting at 150~180℃ for 1.5~2 hours, and then roasting at 550~600℃ for 1.5~2 hours. The mass ratio of the first catalyst to the second catalyst is 1:1 to 1.

3. The transition metal is selected from at least one of La, Cu, Zn, and Ni.

2. The method for improving the selectivity of pseudotrimethylbenzene / me-tetramethylbenzene using dual catalyst packing as described in claim 1, characterized in that, The mass of the transition metal is 0.5% to 7% of the carrier.

3. The method for improving the selectivity of pseudotrimethylbenzene / me-tetramethylbenzene dual catalyst packing as described in claim 1, characterized in that, The specific steps for loading transition metals include: spraying a transition metal salt solution onto a catalyst support, placing it for 2-3 hours to allow the salt solution to be fully absorbed, drying it at 80-85°C for 3-4 hours, and finally calcining it at 150-180°C for 1.5-2 hours and at 550-600°C for 1.5-2 hours.

4. The method for improving the selectivity of pseudotrimethylbenzene / me-tetramethylbenzene using dual catalyst packing as described in claim 1, characterized in that, In the fixed-bed reactor, the top layer is quartz sand, followed by the first catalyst, then the second catalyst, and finally another layer of quartz sand.

5. The fixed-bed reactor prepared by the method according to any one of claims 1-4.

6. The application of compound catalysts in improving the selectivity of catalysts for pseudotrimethylbenzene and mesitylene, characterized in that, The compound catalyst includes a first catalyst and a second catalyst. The first catalyst is passivated in water vapor at 400-410℃ for 3-4 hours and then loaded into the upper layer of the fixed bed reactor. The second catalyst is loaded into the lower layer of the fixed bed reactor. The support for the first catalyst is at least one of HMCM-22 and Hβ; The second catalyst is obtained by loading at least one transition metal selected from La, Cu, Zn, and Ni after calcination using HZSM-60 as a support. The calcination includes calcination at 150-180°C for 1.5-2 hours and then calcination at 550-600°C for 1.5-2 hours. The mass ratio of the first catalyst to the second catalyst is 1:1 to 1.3.

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