Filling method for retarding coking of hydrogenation catalyst and reducing basic pressure difference of reactor

Abstract

The invention discloses a filling method for retarding coking of a hydrogenation catalyst and reducing basic pressure difference of a reactor, which comprises the following steps: an inert material is selected according to the size and bulk density of the hydrogenation catalyst, and the inert material comprises at least one of a Raschig ring, a Pall ring and an inert ceramic ball; calculating the ratio of the inert material to the hydrogenation catalyst, and mixing the inert material with the hydrogenation catalyst according to the ratio; and filling the mixed catalyst mixture into a tube nest. The inert material is used for diluting the active center of the catalyst, dispersing reaction heat and reducing the accumulation of heat at the upper part of the tube nest, so that the reaction intensity is actively reduced, the coking speed is directly slowed down, the basic pressure difference of the reactor is reduced, and the problems that the catalyst is easy to coke and the bed resistance is increased in the process of preparing ethylene glycol by hydrogenation of dimethyl oxalate are effectively solved; reaction conditions are optimized from a filling source, and the service life of the catalyst is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalyst technology, in particular to a loading method for slowing down coking of hydrogenation catalyst and reducing the base pressure difference of a reactor. BACKGROUND

[0002] From the operation of domestic coal-to-ethylene glycol industry devices, the carbonylation process of carbon monoxide and methyl nitrite to synthesize dimethyl oxalate is relatively mature, and the performance of the catalyst is relatively stable; the dimethyl oxalate hydrogenation process to ethylene glycol faces the problems of catalyst coking and selectivity decline. The service life of the hydrogenation catalyst is generally 6-14 months, and the shortest is only 2-3 months. Most hydrogenation systems will increase the bed resistance due to catalyst coking after a period of operation, and eventually be forced to replace the catalyst due to too large resistance. The dimethyl oxalate hydrogenation to ethylene glycol is an exothermic reaction, and effective heat removal to slow down the coking rate of the catalyst is an important means to improve the service life of the hydrogenation catalyst. At present, the process conditions of hydrogenation reaction and the quality of raw materials are mostly adjusted to alleviate the coking rate, and less adjustments are made from the source loading. Since most processes have limited process parameters that can be optimized, the main purpose of the present application is to seek a method for slowing down the coking of the catalyst from the loading, to reduce the difficulty of process adjustment in the later period, and to prolong the service life of the hydrogenation catalyst.

[0003] A reduction method of a dimethyl oxalate hydrogenation catalyst for preparing ethylene glycol is disclosed in Chinese patent document CN101927200B, which includes: the dimethyl oxalate hydrogenation catalyst for preparing ethylene glycol is obtained by a co-precipitation method, the proportion of the reducing agent added during the reduction process is adjusted in time according to the reaction, the reduction reaction temperature is T=120℃-350℃, the reduction reaction pressure is 0.01-1.6MPa, when the reaction temperature suddenly and rapidly rises, nitrogen or helium or argon should be immediately used to replace the reducing agent, the present application solves the problem of the hydrogen source of the reducing agent, fully utilizes the characteristics of thermodynamics and kinetics of the catalyst reduction reaction, and uses chemical, physical and process means to meet the needs of generating different active centers. By using the reduction method of the present application, the conversion rate of dimethyl oxalate reaches more than 80%, the selectivity of ethylene glycol reaches more than 90%, the service life of the catalyst is greatly prolonged to 1 year, and has good industrialization prospect, but the reduction method of the dimethyl oxalate hydrogenation catalyst for preparing ethylene glycol only aims at the catalyst loading stage, and the inert porcelain balls and other dilution active centers are mixed in the upper part of the tube to disperse the reaction heat, which cannot effectively solve the root cause of catalyst coking.

[0004] A process and apparatus system for producing dimethyl oxalate and then hydrogenating it to ethylene glycol using high-pressure carbonylation of industrial syngas is disclosed in Chinese patent document CN104098441B. This system uses industrial-grade NO, O2, and methanol as raw materials for an esterification reaction to generate methyl nitrite. Then, industrial-grade CO and methyl nitrite are used in a plate reactor for a carbonylation reaction to generate carbonylation products mainly consisting of dimethyl oxalate and dimethyl carbonate. The carbonylation products are separated to obtain dimethyl carbonate. Dimethyl oxalate is then hydrogenated in the plate reactor to produce ethylene glycol. The waste acid from the esterification reaction and the purge gas from the carbonylation reaction are coupled and recycled. The system includes an esterification reaction system, a carbonylation reaction system, a purge gas and waste acid coupling recovery system, and a hydrogenation reaction system. This process is characterized by significant savings in equipment consumption, especially the high coupling and separation of nitric acid waste liquid recycling and purge gas recycling, as well as the recovery and recycling of raw materials in the reaction waste gas, which are highly effective. However, the process and equipment system for high-pressure carbonylation of industrial syngas to produce dimethyl oxalate and hydrogenation to ethylene glycol removes the coking material by chemical cleaning (solvents such as tetrahydrofuran / methanol) after catalyst coking. This is a "stopgap" treatment method, which requires shutdown for treatment and affects production efficiency.

[0005] A method for removing coking from a dimethyl oxalate hydrogenation catalyst is disclosed in Chinese patent document CN116689043B. The method comprises the following steps: first, using a mixed solvent consisting of 70%-90% tetrahydrofuran, 5%-20% ethylene glycol monomethyl ether, and 5%-20% methanol to dissolve and elute the coking aggregated on the hydrogenation catalyst; then, purging with an inert atmosphere containing tetrahydrofuran, methanol, and water to remove high-boiling-point esters and organic acids adsorbed on the catalyst; and finally, purging with an inert atmosphere containing tetrahydrofuran and methanol to remove high-boiling-point alcohols adsorbed on the catalyst, thereby achieving the removal of the coking. This method can remove coking deposits from dimethyl oxalate hydrogenation catalysts, restoring the activity lost due to the coking deposits and thus significantly extending the catalyst's lifespan. The method is simple, inexpensive, and effective. However, this method for removing coking deposits from dimethyl oxalate hydrogenation catalysts involves chemical cleaning (using solvents such as tetrahydrofuran / methanol) after coking, which is a "stopgap" treatment and requires shutdown, affecting production efficiency.

[0006] To address the shortcomings of the existing technology, providing a loading method that slows down coking of hydrogenation catalysts and reduces the basic pressure differential of the reactor is a problem worthy of study. Summary of the Invention

[0007] The purpose of this invention is to overcome the disadvantage of catalyst coking leading to increased bed resistance, and to provide a loading method that slows down coking of hydrogenation catalysts and reduces the basic pressure difference of the reactor, thereby achieving the technical effect of slowing down catalyst coking.

[0008] The objective of this invention is achieved through the following technical solution: A loading method for mitigating coking of hydrogenation catalysts and reducing reactor base pressure differential includes the following steps: Step 1: Select an inert material based on the size and packing density of the hydrogenation catalyst. The inert material includes at least one of Raschig rings, Pall rings, and inert ceramic balls. Step 2: Calculate the ratio of inert material to hydrogenation catalyst, and mix the inert material and hydrogenation catalyst according to the ratio; Step 3: The mixed catalyst mixture is loaded into the tubes. The active centers of the catalyst are diluted by the inert material, the heat of reaction is dispersed, and the heat accumulation in the upper part of the tubes is reduced, thereby actively reducing the reaction intensity, directly slowing down the coking rate, and reducing the basic pressure difference of the reactor. This loading method effectively solves the problems of easy coking of catalyst and increased bed resistance in the hydrogenation of dimethyl oxalate to ethylene glycol. It optimizes the reaction conditions from the loading source and extends the catalyst life. It can be used in the industrial loading of catalysts for the hydrogenation of dimethyl oxalate to ethylene glycol.

[0009] Optionally, the hydrogenation catalyst is used in the hydrogenation of dimethyl oxalate to ethylene glycol, focusing on industrial applications, avoiding efficiency losses caused by method generalization, and ensuring stable operation in high-pressure, exothermic reactions.

[0010] Optionally, in step two, the volume percentage of Raschig rings, Pall rings, or inert ceramic balls in the catalyst mixture ranges from 10% to 50%, which balances the dilution of active centers and reaction efficiency, achieves the best coking mitigation effect, precisely controls the proportion of inert materials, and maximizes catalyst lifetime while ensuring reaction selectivity.

[0011] Optionally, in step three, the loading height of the catalyst mixture is 1m to 5m. The height range of 1m to 5m ensures that the heat of reaction is evenly distributed in the upper part of the tube, controls the reaction area, avoids rapid coking caused by local overheating, and maintains the overall performance of the reactor.

[0012] Optionally, the packing density of the hydrogenation catalyst is between 0.4 and 0.9 g / mL. The packing density is coordinated with the size of the inert material to ensure uniform mixing and prevent bridging or voids during loading, thereby reducing the base pressure difference and improving reaction stability. By standardizing the physical parameters, the repeatability of loading and industrial feasibility are improved.

[0013] Optionally, the size range of the Raschig ring, Pall ring, or inert ceramic ball is 3 to 10 mm, which reduces the pressure difference, optimizes heat and mass transfer efficiency, and avoids local coking or pressure difference increase caused by size mismatch.

[0014] Optionally, the filling method further includes pre-filling the bottom of the tube with pure hydrogenation catalyst before filling with the mixed catalyst, which enhances bed stability, prevents bridging or over-compaction, reduces pressure differential, improves the filling sequence, enhances the reliability of long-term reactor operation, and reduces shutdown and maintenance requirements.

[0015] The filling method of the present invention is used in an industrial plant for the hydrogenation of dimethyl oxalate to ethylene glycol. The application method includes the following steps: The reaction takes place in a tube-shaped hydrogenation reactor. Springs and ceramic balls are installed at the bottom of the tubes, which are then filled to a certain height with pure catalyst, followed by a further layer of mixed catalyst. After filling, the empty height of each tube is 1-2 meters. The catalyst packing height and density are basically consistent within each tube, without bridging, voids, or over-compaction. At room temperature, a stable, clean, and inert gas is passed through each tube at a constant flow rate. After filling, a differential pressure sensor measures the pressure required for the gas to flow through a single tube; this pressure value is the base differential pressure for that tube.

[0016] Positive and beneficial effects: 1. This loading method, which slows down coking of hydrogenation catalysts and reduces the basic pressure difference of the reactor, dilutes the active centers of the catalyst with inert materials, disperses the heat of reaction, and reduces the accumulation of heat in the upper part of the tubes, thereby actively reducing the reaction intensity, directly slowing down the coking rate, and reducing the basic pressure difference of the reactor. It effectively solves the problems of easy coking of catalysts and increased bed resistance in the hydrogenation of dimethyl oxalate to ethylene glycol, optimizes reaction conditions from the loading source, and extends the catalyst life.

[0017] 2. This loading method, which slows down coking of the hydrogenation catalyst and reduces the basic pressure difference of the reactor, is specifically designed for the exothermic reaction of dimethyl oxalate hydrogenation in the coal-to-ethylene glycol industry. It ensures that the selection of inert materials and loading parameters match the thermodynamic characteristics of the reaction, thereby improving the applicability and effectiveness of the method.

[0018] 3. The loading method that slows down coking of the hydrogenation catalyst and reduces the pressure difference of the reactor base ensures that the heat of reaction is evenly distributed in the upper part of the tubes within a height range of 1m to 5m, controls the reaction zone, avoids rapid coking caused by local overheating, and maintains the overall performance of the reactor. Attached Figure Description

[0019] Figure 1 This is a diagram illustrating the method steps of the present invention; Figure 2 This is a comparison chart of the catalyst performance of Examples 1 to 8 of the present invention. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] like Figure 1 As shown, a loading method for mitigating coking of hydrogenation catalysts and reducing the base pressure differential of the reactor includes the following steps: Step 1: Select an inert material based on the size and packing density of the hydrogenation catalyst. The inert material includes at least one of Raschig rings, Pall rings, and inert ceramic balls. Step 2: Calculate the ratio of inert material to hydrogenation catalyst, and mix the inert material and hydrogenation catalyst according to the ratio; Step 3: The mixed catalyst mixture is loaded into the tubes. The active centers of the catalyst are diluted by the inert material, the heat of reaction is dispersed, and the heat accumulation in the upper part of the tubes is reduced, thereby actively reducing the reaction intensity, directly slowing down the coking rate, and reducing the basic pressure difference of the reactor. This loading method effectively solves the problems of easy coking of catalyst and increased bed resistance in the hydrogenation of dimethyl oxalate to ethylene glycol. It optimizes the reaction conditions from the loading source and extends the catalyst life. It can be used in the industrial loading of catalysts for the hydrogenation of dimethyl oxalate to ethylene glycol.

[0022] The hydrogenation catalyst is used in the hydrogenation of dimethyl oxalate to ethylene glycol. It is specifically designed for the exothermic reaction of dimethyl oxalate hydrogenation in the coal-to-ethylene glycol industry, where the hydrogenation of dimethyl oxalate is significantly exothermic. The catalyst ensures that the selection of inert materials and the loading parameters match the thermodynamic characteristics of the reaction, thereby improving the applicability and effectiveness of the method. It focuses on industrial application scenarios, avoids efficiency losses caused by method generalization, and ensures stable operation in high-pressure, exothermic reactions.

[0023] In step two, the volume percentage of Raschig rings, Pall rings, or inert ceramic balls in the catalyst mixture ranges from 10% to 50%. By specifying that the volume percentage of Raschig rings, Pall rings, or inert ceramic balls in the catalyst mixture ranges from 10% to 50%, the dilution of active centers and reaction efficiency are balanced, achieving the best coking mitigation effect. The proportion of inert materials is precisely controlled, maximizing catalyst lifetime while ensuring reaction selectivity.

[0024] In step three, the loading height of the catalyst mixture is 1m to 5m. The loading height affects heat dispersion and pressure difference. If the height is too low (e.g., below 1m), the heat dispersion may be insufficient. If the height is too high (e.g., above 5m), the overall catalyst activity may be reduced. The height range of 1m to 5m ensures that the heat of reaction is evenly dispersed in the upper part of the tube, controls the reaction area, avoids rapid coking caused by local overheating, and maintains the overall performance of the reactor.

[0025] The packing density of the hydrogenation catalyst is between 0.4 and 0.9 g / mL. The packing density is coordinated with the size of the inert material to ensure uniform mixing and prevent bridging or voids during loading, thereby reducing the base pressure difference and improving reaction stability. By standardizing the physical parameters, the repeatability of loading and industrial feasibility are improved.

[0026] The size range of the Raschig rings, Pall rings, or inert ceramic balls is 3 to 10 mm. The size matches the catalyst particles, reducing the bed porosity, promoting uniform fluid distribution, further reducing the pressure difference, optimizing heat and mass transfer efficiency, and avoiding local coking or pressure difference increase caused by size mismatch.

[0027] The loading method further includes pre-loading pure hydrogenation catalyst at the bottom of the tube, followed by loading the mixed catalyst. The pure catalyst layer provides the reaction basis, while the mixed layer is responsible for thermal dispersion, forming a gradient loading structure. This enhances bed stability, prevents bridging or over-compaction, reduces pressure differential, improves the loading sequence, enhances the reliability of long-term reactor operation, and reduces shutdown and maintenance requirements.

[0028] Example 1 The mixed catalyst is packed to a height of 2m (10% Raschig ring - 90% catalyst). Catalyst loading: a) Select a suitable Raschig ring based on the size and bulk density of the hydrogenation catalyst; b) The volume fraction of the Raschig ring is 10%, and the volume fraction of the catalyst is 90%. c) The mixed catalyst is loaded into the upper 2m of the tube.

[0029] d) After filling, the empty height of each tube is 1-2m. Measurement of the base pressure difference in the reactor tubes: The reaction takes place in a hydrogenation reactor tube set. Springs and ceramic balls are installed at the bottom of the tubes, and a certain height of pure catalyst is filled, followed by a certain height of mixed catalyst. After filling, the empty height of each tube is 1-2m. The catalyst filling height and density in each tube are basically consistent, without bridging, voids, or over-compaction. At room temperature, a stable, clean, and inert gas is passed through each tube at a constant flow rate. After filling, a differential pressure sensor measures the pressure required for the gas to flow through a single tube. This pressure value is the base pressure difference of that tube. The results are shown in [Figure showing results]. Figure 2 .

[0030] Example 2 The mixed catalyst is packed to a height of 2m (5% Raschig rings - 5% Pall rings - 90% catalyst). Catalyst loading: a) Select appropriate Raschig rings and Pall rings based on the size and packing density of the hydrogenation catalyst; b) The volume percentage of Raschig rings is 5%, the volume percentage of Pall rings is 5%, and the volume percentage of the catalyst is 90%. c) The mixed catalyst is loaded into the upper 2m of the tube.

[0031] d) After filling, the empty height of each tube is 1-2m. The method for measuring the differential pressure at the reactor tube base is the same as in Example 1, and the results are shown in [see figure]. Figure 2 .

[0032] Example 3 The mixed catalyst is packed to a height of 2m (10% Pall rings - 90% catalyst). Catalyst loading: a) Select a suitable Pall ring based on the size and packing density of the hydrogenation catalyst; b) The volume percentage of the Pall ring is 10%, and the volume percentage of the catalyst is 90%. c) The mixed catalyst is loaded into the upper 2m of the tube.

[0033] d) After filling, the empty height of each tube is 1-2m. The method for measuring the differential pressure at the reactor tube base is the same as in Example 1, and the results are shown in [see figure]. Figure 2 .

[0034] Example 4 The mixed catalyst is packed to a height of 3m (10% Pall rings - 10% inert ceramic balls - 80% catalyst). Catalyst loading: a) Select appropriate Pall rings and inert ceramic balls based on the size and packing density of the hydrogenation catalyst; b) The volume percentage of Pall rings is 10%, the volume percentage of inert ceramic balls is 10%, and the volume percentage of catalyst is 80%. c) The mixed catalyst is loaded into the upper 3m of the tube.

[0035] d) After filling, the empty height of each tube is 1-2m. The method for measuring the differential pressure at the reactor tube base is the same as in Example 1, and the results are shown in [see figure]. Figure 2 .

[0036] Example 5 The mixed catalyst is packed to a height of 2m (10% inert ceramic balls - 90% catalyst). Catalyst loading: a) Select appropriate inert ceramic balls based on the size and packing density of the hydrogenation catalyst; b) The volume percentage of inert ceramic spheres is 10%, and the volume percentage of catalyst is 90%; c) The mixed catalyst is loaded into the upper 2m of the tube.

[0037] d) After filling, the empty height of each tube is 1-2m. The method for measuring the differential pressure at the reactor tube base is the same as in Example 1, and the results are shown in [see figure]. Figure 2 .

[0038] Example 6 The mixed catalyst is packed to a height of 2m (10% Raschig rings - 10% inert ceramic balls - 80% catalyst). Catalyst loading: a) Select appropriate Raschig rings and inert ceramic balls based on the size and bulk density of the hydrogenation catalyst; b) The volume percentage of Raschig rings is 10%, the volume percentage of inert ceramic balls is 10%, and the volume percentage of catalyst is 80%. c) The mixed catalyst is loaded into the upper 2m of the tube.

[0039] d) After filling, the empty height of each tube is 1-2m. The method for measuring the differential pressure at the reactor tube base is the same as in Example 1, and the results are shown in [see figure]. Figure 2 .

[0040] Example 7 The mixed catalyst is packed to a height of 1m (30% Raschig rings - 70% catalyst). Catalyst loading: a) Select a suitable Raschig ring based on the size and bulk density of the hydrogenation catalyst; b) The volume fraction of the Raschig ring is 30%, and the volume fraction of the catalyst is 70%. c) The mixed catalyst is loaded into the upper 1m of the tube.

[0041] d) After filling, the empty height of each tube is 1-2m. The method for measuring the differential pressure at the reactor tube base is the same as in Example 1, and the results are shown in [see figure]. Figure 2 .

[0042] Example 8 The mixed catalyst is packed to a height of 5m (10% inert ceramic balls - 90% catalyst). Catalyst loading: a) Select appropriate Raschig rings, Pall rings, and inert ceramic balls based on the size and bulk density of the hydrogenation catalyst; b) The volume percentage of inert ceramic spheres is 10%, and the volume percentage of catalyst is 90%; c) The mixed catalyst is loaded into the upper 5m of the tube.

[0043] d) After filling, the empty height of each tube is 1-2m. The method for measuring the differential pressure at the reactor tube base is the same as in Example 1, and the results are shown in [see figure]. Figure 2 .

[0044] Comparing Examples 1, 3, and 5, it can be seen that when Raschig rings, Pall rings, and inert ceramic balls are added individually, the inert ceramic balls have the best performance and the lowest base pressure difference.

[0045] Comparing Examples 5 and 8, it can be seen that the filling height has a certain impact on the base pressure difference. Considering the activity of the entire tube catalyst, a filling height of 1m-5m is more suitable.

[0046] Comparing Examples 2, 4, and 6, it can be seen that the effect of mixed filling is not ideal.

[0047] Comparing Examples 1, 6, and 7, it can be seen that the proportion of Raschig rings, Pall rings, and inert ceramic balls is between 10% and 50%, and it is not recommended to exceed 50%. Firstly, if the proportion is too high, it will reduce the effective proportion of the catalyst. Secondly, if it exceeds 50%, the basic pressure difference will not decrease significantly.

[0048] from Figure 2 Overall, the analysis shows that this invention relates to a loading method for slowing down coking of hydrogenation catalysts and reducing the base pressure difference in the reactor. It is mainly used to slow down the rate of catalyst coking and improve the lifespan of the dimethyl oxalate hydrogenation to ethylene glycol catalyst. This loading method effectively dilutes the active sites of the catalyst, slows down the coking rate, and reduces the base pressure difference in the reactor. It can be used in the industrial loading of dimethyl oxalate hydrogenation to ethylene glycol catalysts.

[0049] The above is only used to illustrate the technical solution of the present invention and not to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention, as long as they do not depart from the spirit and scope of the technical solution of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A loading method for mitigating coking of hydrogenation catalysts and reducing the base pressure differential of the reactor, characterized in that, Includes the following steps: Step 1: Select an inert material based on the size and packing density of the hydrogenation catalyst. The inert material includes at least one of Raschig rings, Pall rings, and inert ceramic balls. Step 2: Calculate the ratio of inert material to hydrogenation catalyst, and mix the inert material and hydrogenation catalyst according to the ratio; Step 3: Fill the tubes with the mixed catalyst mixture.

2. The loading method for mitigating coking of hydrogenation catalyst and reducing reactor base pressure differential according to claim 1, characterized in that: The hydrogenation catalyst is used in the hydrogenation reaction of dimethyl oxalate to ethylene glycol.

3. The loading method for mitigating coking of hydrogenation catalyst and reducing reactor base pressure differential according to claim 1, characterized in that: In step two, the volume percentage of Raschig rings, Pall rings, or inert ceramic balls in the catalyst mixture ranges from 10% to 50%.

4. The loading method for mitigating coking of hydrogenation catalyst and reducing reactor base pressure differential according to claim 1, characterized in that: The loading height of the catalyst mixture in step three is 1m to 5m.

5. The loading method for mitigating coking of hydrogenation catalyst and reducing reactor base pressure differential according to claim 1, characterized in that: The packing density of the hydrogenation catalyst is between 0.4 and 0.9 g / mL.

6. The loading method for mitigating coking of hydrogenation catalyst and reducing reactor base pressure differential according to claim 1, characterized in that: The size range of the Raschig ring, Pall ring, or inert ceramic ball is 3–10 mm.

7. The loading method for mitigating coking of hydrogenation catalyst and reducing reactor base pressure differential according to claim 1, characterized in that: The filling method also includes pre-filling the bottom of the tube with pure hydrogenation catalyst, and then filling with the mixed catalyst.

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