Catalyst multi-bed steady-state grading method in two-stage hydrogenation process in chdm preparation process
By adopting a multi-bed steady-state graded packing method in the CHDM preparation process, the problems of low catalyst utilization and low production efficiency caused by single-bed catalyst packing are solved, achieving high-efficiency catalyst utilization and improved product yield.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA NAT PETROLEUM CORP
- Filing Date
- 2024-02-29
- Publication Date
- 2026-05-29
AI Technical Summary
In the existing CHDM preparation process, the single-bed catalyst loading method results in low catalyst utilization, low production efficiency, and problems such as reaction instability and numerous side reactions.
A multi-bed steady-state graded loading method is adopted, which involves setting up multiple catalyst beds in the two-stage hydrogenation process, and setting temperature gradients and sensors at each bed, combined with a PLC control system to achieve steady-state graded loading of the catalyst.
It improved catalyst utilization and production efficiency, reduced production costs, optimized reactor operating efficiency, reduced by-product generation, and increased product yield and reaction conversion rate.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of CHDM preparation technology. It relates to a method for multi-bed steady-state graded packing of catalysts in the two-stage hydrogenation process during CHDM preparation. Background Technology
[0002] PETG is a non-crystalline copolyester whose products have high transparency and gloss like glass, excellent impact resistance, and excellent processing and molding properties. It is widely used in extrusion molding grade (sheets, sheets), extrusion blow molding grade (cosmetic bottles, etc.), injection molding grade (profiles, etc.), thermoforming grade (carbohydrate films, etc.), alloy materials (electronics, electrical appliances, etc.). In recent years, domestic demand has grown rapidly, with annual consumption reaching 180,000 tons. The product has high added value and good market development potential.
[0003] CHDM is an essential key monomer feedstock for the production of PETG. Industrially, it is mainly produced using a two-step hydrogenation route of dimethyl terephthalate (DMT). The simplified formula of the two-step hydrogenation reaction using DMT as a feedstock is shown below:
[0004]
[0005] CHDM uses DMT as a raw material. First, the benzene ring is hydrogenated to produce dimethyl 1,4-cyclohexanedicarboxylate (DMCD). Then, the ester group is hydrogenated to produce CHDM. Both hydrogenation processes are exothermic reactions. When the catalyst loading is relatively large, if a single catalyst bed is used, the exothermic reaction at the top cannot be removed in time, resulting in high temperatures in the middle and lower catalyst beds. This can easily deviate from the optimal reaction conditions, leading to more side reactions and affecting the final yield of the product.
[0006] In existing CHDM preparation processes, the two-stage hydrogenation process employs the aforementioned single-bed catalyst loading method, which not only affects catalyst utilization but also restricts the improvement of production efficiency. The use of catalysts plays a crucial role in improving reaction efficiency and product quality. Existing catalyst loading technologies also suffer from problems such as uneven loading and unreasonable gradation, leading to instability and low efficiency in the reaction process. Therefore, developing a multi-bed steady-state gradation loading method is of great significance for improving production efficiency and reducing production costs. Summary of the Invention
[0007] To overcome the shortcomings of existing technologies, this invention provides a multi-bed steady-state graded packing method for catalysts in the two-stage hydrogenation process of CHDM preparation. This method offers advantages such as improved production efficiency, reduced production costs, enhanced operator safety, increased catalyst utilization, and optimized reactor operating efficiency. This invention has significant practical value and potential for widespread application.
[0008] The above-mentioned objective of this invention is achieved through the following technical solution:
[0009] The method for steady-state packing of catalysts in the two-stage hydrogenation process of CHDM preparation involves placing multiple catalyst beds in the reactors of both hydrogenation processes. The temperature of the catalyst bed in the reactor of the first hydrogenation process is set at 135-170℃, and the temperature of the catalyst bed in the reactor of the second hydrogenation process is set at 200-210℃. The number of catalyst bed layers in the reactor of the first hydrogenation process is one more than the number of catalyst bed layers in the reactor of the second hydrogenation process.
[0010] Furthermore, the temperature of the catalyst bed in the reactor during the first stage of hydrogenation is set to a gradient increase, with each gradient being 20-30°C.
[0011] Furthermore, in the second stage of hydrogenation, the temperature of the catalyst bed in the reactor is set to increase in a gradient of 5-10°C.
[0012] Furthermore, three catalyst beds are set in the reactor during the first stage of hydrogenation, and two catalyst beds are set in the reactor during the second stage of hydrogenation.
[0013] Furthermore, preferably, the temperature of the catalyst bed in the reactor during the first stage of hydrogenation is set to a gradient increase, with each gradient being 25°C.
[0014] Furthermore, preferably, the temperature of the catalyst bed in the reactor during the second hydrogenation process is set to a gradient increase, with each gradient being 10°C.
[0015] Thickness detectors are installed at adjacent locations of each catalyst bed layer. The thickness detection sensors are used to detect the thickness of each catalyst bed layer, and the actual packing density is obtained by detecting the thickness.
[0016] Each catalyst bed is also equipped with a stabilizing element to support the catalyst bed and keep it stable. The stabilizing element is a mesh structure with dimensions corresponding to the bed, and the mesh surface is uneven. It is made of metal.
[0017] Each catalyst bed is also equipped with a temperature sensor and a weight sensor.
[0018] The method also includes setting up a PLC control system, with the thickness detector, temperature sensor, and weight sensor connected to the PLC control system. None of the sensors are limited to a specific model, as long as their operating functions are implemented.
[0019] The advantages of this invention compared to the prior art are:
[0020] This invention provides a multi-bed steady-state catalyst loading method for the two-stage hydrogenation process in CHDM preparation. Both stages of the hydrogenation process utilize multi-bed catalyst loading. In the first stage, where the reaction is more exothermic, the number of beds is greater than three. The reactor temperature is controlled at 135-170℃, with a maximum temperature rise of only 20-30℃, achieving a conversion rate of 99.5% and a selectivity of 95%. In the second stage, the number of beds is greater than two. The reactor temperature is controlled at 200-210℃, with a temperature rise of only 10℃, achieving a conversion rate of 99% and a selectivity greater than 95%, demonstrating good results. This method better controls reaction deheating and conversion depth, reduces by-product formation, and increases product yield. It also improves the material distribution within the beds, achieving effective control of reaction temperature rise and conversion depth. It offers advantages such as increased production efficiency, reduced production costs, improved operator safety, increased catalyst utilization, and optimized reactor operating efficiency. This invention has significant practical value and potential for widespread application. Attached Figure Description
[0021] To more clearly illustrate the technical solutions in this invention or related technologies, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0022] Figure 1 This is a flow chart of the CHDM production process. Detailed Implementation
[0023] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0024] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.
[0025] In the description of this invention, it should be noted that the terms "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used only for distinction and should not be construed as indicating or implying relative importance.
[0026] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
[0028] In the CHDM preparation process, DMT is used as the main raw material. Firstly, DMDCD intermediates are obtained through dissolution, a first-stage benzene ring hydrogenation, and distillation separation. A portion of this intermediate product is recycled as a solvent in the dissolution unit, while a small portion undergoes a second-stage ester hydrogenation and distillation separation to produce the CHDM product. The CHDM production process flow diagram is shown below. Figure 1 As shown.
[0029] Example 1
[0030] The steady-state graded packing method of catalyst multi-beds in the two-stage hydrogenation process of CHDM preparation was applied to the preparation of CHDM. Multiple catalyst beds were set in the reactors of both hydrogenation processes. The temperature of the catalyst bed in the reactor of the first hydrogenation process was set at 135-170℃, and the temperature of the catalyst bed in the reactor of the second hydrogenation process was set at 200-210℃. The number of catalyst bed layers in the reactor of the first hydrogenation process was one more than the number of catalyst bed layers in the reactor of the second hydrogenation process.
[0031] The reactor inner diameter in the two-stage hydrogenation process is 1.8 m. The catalyst bed size is set to correspond to the reactor inner diameter.
[0032] Three catalyst beds are set in the reactor during the first stage of hydrogenation, and two catalyst beds are set in the reactor during the second stage of hydrogenation.
[0033] In the first stage of hydrogenation, a total of 11.12 tons of catalyst was loaded into the catalyst bed in the reactor. The bulk density was 0.54 g / ml.
[0034] In the second stage of hydrogenation, a total of 25.84 tons of catalyst was loaded into the catalyst bed in the reactor. The bulk density was 1.58 g / ml.
[0035] In the first stage of hydrogenation, the temperature of the catalyst bed in the reactor is set to increase in a gradient of 25°C.
[0036] In the second stage of hydrogenation, the temperature of the catalyst bed in the reactor is set to increase in gradients, with each gradient being 10°C.
[0037] Thickness detectors are installed at adjacent locations of each catalyst bed layer. The thickness detection sensors are used to detect the thickness of each catalyst bed layer, and the actual packing density is obtained by detecting the thickness.
[0038] Each catalyst bed is also equipped with a stabilizing element to support the catalyst bed and keep it stable. The stabilizing element is a mesh structure with dimensions corresponding to the bed, and the mesh surface is uneven. It is made of metal.
[0039] Each catalyst bed is also equipped with a temperature sensor and a weight sensor.
[0040] The method also includes setting up a PLC control system, with the thickness detector, temperature sensor, and weight sensor connected to the PLC control system. None of the sensors are limited to a specific model, as long as their functions are implemented. The preparation results are shown in Table 1.
[0041] Comparative Example 1
[0042] The temperature of the catalyst bed in the reactor during the second stage of hydrogenation was set to 210-220℃, and other conditions were the same as in Example 1. The preparation results are shown in Table 1.
[0043] Comparative Example 2
[0044] The temperature of the catalyst bed in the reactor during the second stage of hydrogenation was set to 190-200℃, and other conditions were the same as in Example 1. The preparation results are shown in Table 1.
[0045] Comparative Example 3
[0046] The temperature of the catalyst bed in the reactor during the second stage of hydrogenation was set to 210-230℃, and other conditions were the same as in Example 1. The preparation results are shown in Table 1.
[0047] Comparative Example 4
[0048] The temperature of the catalyst bed in the reactor during the first stage of hydrogenation was set to 140-180℃, and other conditions were the same as in Example 1. The preparation results are shown in Table 1.
[0049] Comparative Example 5.
[0050] Three catalyst beds were set in the reactor during the first stage of hydrogenation, and three catalyst beds were set in the reactor during the second stage of hydrogenation. Other procedures were the same as in Example 1. The preparation results are shown in Table 1.
[0051] Comparative Example 6
[0052] Two catalyst beds were set in the reactor during the first stage of hydrogenation, and three catalyst beds were set in the reactor during the second stage of hydrogenation. Other procedures were the same as in Example 1. The preparation results are shown in Table 1.
[0053] Comparative Example 7
[0054] The reactor in the two-stage hydrogenation process has an inner diameter of 1.9 m. The catalyst bed in the reactor for the first stage of hydrogenation is loaded with catalyst. The bulk density is 0.64 g / ml.
[0055] In the second stage of hydrogenation, the catalyst bed in the reactor was loaded with catalyst. The bulk density was 1.68 g / ml. Other procedures were the same as in Example 1. The preparation results are shown in Table 1.
[0056] Table 1. Results of DMCD preparation in Example 1 and Comparative Example
[0057]
[0058] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. For those skilled in the art, any obvious modifications made without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims. Although the present invention has been described above with reference to embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no technical conflict, the features in the embodiments disclosed in the present invention can be combined with each other in any way. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.
Claims
1. A method for multi-bed steady-state graded packing of catalysts in the two-stage hydrogenation process of CHDM preparation, characterized in that... Both hydrogenation processes involve the use of multi-bed catalysts in the reactors. The temperature of the catalyst bed in the reactor during the first stage of hydrogenation is set at 135-170℃, and the temperature of the catalyst bed in the reactor during the second stage of hydrogenation is set at 200-210℃. The number of catalyst bed layers in the reactor during the first stage of hydrogenation is one more than the number of catalyst bed layers in the reactor during the second stage of hydrogenation. In the first stage of hydrogenation, the temperature of the catalyst bed in the reactor is set to increase in a gradient of 20-30℃. In the second stage of hydrogenation, the temperature of the catalyst bed in the reactor is set to increase in a gradient of 5-10℃. Each catalyst bed is also equipped with a stabilizing element to support the catalyst bed and keep it stable. The stabilizing element is a mesh structure with dimensions corresponding to the bed, and the mesh surface is uneven. It is made of metal.
2. The catalyst multi-bed steady-state graded packing method for the two-stage hydrogenation process in CHDM preparation as described in claim 1, characterized in that, The catalyst bed size is set to correspond to the reactor inner diameter.
3. The catalyst multi-bed steady-state graded packing method for the two-stage hydrogenation process in CHDM preparation as described in claim 1, characterized in that, Three catalyst beds are set in the reactor during the first stage of hydrogenation, and two catalyst beds are set in the reactor during the second stage of hydrogenation.
4. The catalyst multi-bed steady-state graded packing method for the two-stage hydrogenation process in CHDM preparation as described in claim 1, characterized in that, Thickness detectors are installed at adjacent locations of each catalyst bed.
5. The catalyst multi-bed steady-state graded packing method for the two-stage hydrogenation process in CHDM preparation as described in claim 1, characterized in that, Each catalyst bed is also equipped with a temperature sensor and a weight sensor.