Gas-solid method for adding titanium to MOR molecular sieve catalyst

Abstract

The application provides a MOR molecular sieve catalyst gas-solid titanium supplementing method, which comprises the following steps: preparing a hydrogen type MOR molecular sieve with a framework hydroxyl vacancy; loading the hydrogen type MOR molecular sieve into at least one layer of catalyst bed in a gas-solid titanium supplementing reaction furnace; the reaction furnace is provided with a plurality of bed loading positions, and a single layer of catalyst bed or a plurality of layers of catalyst bed is selected according to the production scale; a preheating cavity, a reaction cavity and a constant temperature compensation cavity are warmed up to a reaction temperature; after a gas containing TiCl4 is distributed through a gas distribution structure, the gas is introduced into the catalyst bed, so that the TiCl4 and the hydrogen type MOR molecular sieve perform isomorphous substitution reaction, and titanium atoms are introduced into the molecular sieve framework; after the reaction is completed, the temperature is increased for calcination, and a Ti-MOR molecular sieve is obtained. The MOR molecular sieve catalyst gas-solid titanium supplementing method provided by the application aims to solve the technical problems of uneven gas distribution and process gradient amplification existing in the single layer thick bed gas phase titanium supplementing in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve modification and preparation technology, specifically relating to a gas-solid titanium replenishment method for MOR molecular sieve catalysts. Background Technology

[0002] Mordenite (MOR) molecular sieves possess a regular one-dimensional pore structure, excellent thermal stability, and acid resistance. Their 8-membered ring acidic sites serve as active centers for syngas conversion, while their 12-membered ring channels act as transport channels for reactant molecules, making them widely used microporous molecular sieve materials in industrial catalysis. By introducing titanium atoms into the MOR molecular sieve framework to prepare Ti-MOR molecular sieves, it is possible to effectively control the acidic sites, optimize pore polarity, and improve oxidation catalytic selectivity and structural stability.

[0003] Currently, the main method for preparing Ti-MOR molecular sieves in the industry is the gas-phase titanium-supplementation method. Existing gas-phase titanium-supplementation processes typically use fixed-bed reactors with single-layer thick-bed packing, resulting in high gas flow penetration resistance, significant axial temperature differences within the bed, and uneven TiCl4 gas flow distribution. This easily leads to problems such as localized titanium enrichment, low skeletal titanium content, and large batch-to-batch quality deviations. Furthermore, this type of process lacks versatility; a single fixed-bed reactor cannot simultaneously meet the diverse production needs of laboratory pilot-scale, medium-scale, and large-scale mass production. The process scale-up lacks systematic guidance, making it difficult to achieve gradient scale-up. Summary of the Invention

[0004] This invention provides a gas-solid titanium replenishment method for MOR molecular sieve catalysts, which aims to solve the technical problems of uneven gas distribution and the inability to scale up the process in the existing single-layer thick-bed gas-phase titanium replenishment technology.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: to provide a gas-solid titanium replenishment method for MOR molecular sieve catalysts, comprising the following steps: The raw MOR molecular sieve powder was subjected to desodium and dealuminate treatment to obtain hydrogen-type MOR molecular sieve with skeletal hydroxyl vacancies. The hydrogen-form MOR molecular sieve is packed into at least one catalyst bed in a gas-solid titanium-supplemented reactor; the reactor has multiple bed packing positions, and a single-layer or multi-layer catalyst bed is selected according to the production scale; a preheating chamber, a reaction chamber, and a constant temperature compensation chamber are also sequentially arranged in the reactor along the material flow direction; multiple bed packing positions are located in the reaction chamber; the reactor also has a gas distribution structure, which is arranged on the flow path of gas before it enters the catalyst bed, and / or between adjacent catalyst beds; The preheating chamber, reaction chamber, and constant temperature compensation chamber are heated to the reaction temperature. After the TiCl4-containing gas is distributed through the gas distribution structure, it is introduced into the catalyst bed, so that TiCl4 and the hydrogen-type MOR molecular sieve undergo isomorphic substitution reaction, introducing titanium atoms into the molecular sieve framework. After the reaction was completed, the mixture was heated and calcined to obtain Ti-MOR molecular sieve.

[0006] In one possible implementation, the desodiuming and dealuminizing treatment of the MOR molecular sieve powder includes: sequentially subjecting the MOR molecular sieve powder to acid washing for desodiuming, high-temperature dealuminizing, drying, and calcination.

[0007] In one possible implementation, the reactor is provided with three bed loading positions, and single-layer, double-layer, or triple-layer catalyst beds can be selected for loading according to the production scale.

[0008] In one possible implementation, the packing thickness of a single-layer catalyst bed is 80–160 mm; the total packing thickness of a double-layer catalyst bed is 160–320 mm; and the total packing thickness of a triple-layer catalyst bed is 240–480 mm.

[0009] In one possible implementation, heating the preheating chamber, reaction chamber, and isothermal compensation chamber to the reaction temperature includes: simultaneously heating the preheating chamber, reaction chamber, and isothermal compensation chamber to 320–380°C at a heating rate of 3–5°C / min, and maintaining the temperature for 2–4 hours; purging dry nitrogen gas as a carrier gas throughout the heating and isothermal treatment, with the nitrogen space velocity controlled at 120–180 h⁻¹. -1 .

[0010] In one possible implementation, the TiCl4-containing gas is obtained by passing nitrogen gas into a constant-temperature titanium tetrachloride vaporization tank to carry TiCl4 vapor and form a mixed gas; the temperature of the titanium tetrachloride vaporization tank is kept constant at 160–200°C, the TiCl4 mass concentration in the mixed gas is controlled at 8–15%, and the gas hourly space velocity is controlled at 60–110 h⁻¹. -1 .

[0011] In one possible implementation, during the isomorphic substitution reaction, a segmented PID temperature control system is used to maintain the axial and radial temperature differences across the entire reactor at ≤3℃; and when a single-layer bed is filled, the reaction time is 4–6 h; when a double-layer bed is filled, the reaction time is 5–8 h; and when a triple-layer bed is filled, the reaction time is 6–9 h.

[0012] In one possible implementation, the heating and calcination includes: heating the reaction chamber to 580-620°C at a heating rate of 2-4°C / min, and calcining at a constant temperature for 2-3 hours; during the calcination process, the constant temperature compensation chamber is maintained at 420-460°C.

[0013] In one possible implementation, after the reaction is complete, the process further includes: a gradient cooling at a cooling rate of 2–3 °C / min, and purging the reactor with nitrogen gas; the nitrogen space velocity is 100–150 h⁻¹. -1 When the furnace temperature drops below 120℃, stop the nitrogen gas supply, seal and let stand for 2-5 hours for passivation, then unload and collect the Ti-MOR molecular sieve.

[0014] In one possible implementation, the reactor is provided with a support structure for the detachable installation of the catalyst bed; during unloading, the catalyst bed is extracted in stages from bottom to top, so that the Ti-MOR molecular sieve falls down step by step by gravity and is automatically discharged.

[0015] The beneficial effects of the gas-solid titanium replenishment method for MOR molecular sieve catalyst provided by this invention are as follows: Compared with the prior art, by pre-setting multiple bed filling positions in the reactor, single or multiple catalyst beds can be flexibly selected according to the actual production scale, so that a set of equipment and process system can simultaneously adapt to the differentiated needs of laboratory pilot-scale, medium-scale pilot-scale and large-scale mass production. The process parameters can be gradient shifted according to the number of beds, which solves the technical pain point of lack of systematic guidance in the scale-up process due to the fixed equipment structure in the traditional process.

[0016] A gas distribution structure is incorporated within the reactor. This structure can be positioned either along the gas flow path before it enters the catalyst bed or between adjacent catalyst beds. This multi-stage, multi-point gas distribution method enables multiple uniform distributions of the TiCl4-containing gas, eliminating the uneven gas phase distribution, channeling, and flow deviation phenomena commonly found in traditional thick-bed reactors. This ensures uniform contact between TiCl4 vapor and the molecular sieve, thereby significantly increasing the isomorphic substitution rate of titanium atoms within the molecular sieve framework, suppressing the formation of non-framework titanium agglomerates, and enhancing the catalytic activity of the product.

[0017] The reactor is sequentially equipped with a preheating chamber, a reaction chamber, and a constant-temperature compensation chamber along the material flow direction. Three-stage zoned temperature control enables management of the temperature field. The preheating chamber prevents TiCl4 from condensing at low temperatures, while the constant-temperature compensation chamber avoids corrosion of the equipment due to tail gas condensation and compensates for heat loss at the reaction chamber outlet. This ensures small axial and radial temperature differences throughout the reaction chamber and uniform reaction conditions, thereby guaranteeing consistency in titanium content and catalytic performance between different batches of products and overcoming the drawbacks of large batch deviations in traditional processes.

[0018] This application directly prepares hydrogen-form MOR molecular sieves with skeletal hydroxyl vacancies, laying the foundation for subsequent efficient titanium supplementation. Combined with the multi-layered packing structure of the reactor, production time is shortened.

[0019] The flexible configuration of at least one catalyst bed and gas distribution structure allows for optimization of reaction conditions when dealing with molecular sieve raw materials of different varieties or particle sizes. This can be achieved by adjusting the number of bed layers, packing thickness, and gas distribution levels without the need to change equipment, thus enhancing the flexibility of production organization and the ability to handle multi-variety and variable-batch production tasks. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the steps of a gas-solid titanium replenishment method using a MOR molecular sieve catalyst provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a gas-solid titanium-supplementing reactor using MOR molecular sieve catalyst.

[0021] Explanation of reference numerals in the attached figures: 10. Furnace body; 11. Inlet buffer chamber; 12. Constant temperature compensation chamber; 13. Preheating chamber; 14. First gas inlet; 15. Second gas inlet; 16. Gas inlet; 20. Catalyst bed; 21. First catalyst bed; 22. Second catalyst bed; 23. Third catalyst bed; 30. Gas distribution structure; 31. First gas distribution component; 32. Second gas distribution component; 40. Heating unit; 50. Uniform flow layer; 60. Buffer layer; 70. Support grid. Detailed Implementation

[0022] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0023] It should be noted that the terms "length", "width", "height", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "head", and "tail" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element 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 present invention.

[0024] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Additionally, "multiple" and "several" mean two or more, unless otherwise explicitly specified.

[0026] Please see Figure 1 The present invention will now describe a gas-solid titanium replenishment method for MOR molecular sieve catalysts. The method includes the following steps: S10. The raw MOR molecular sieve powder is subjected to desodium and dealuminate treatment to obtain hydrogen-type MOR molecular sieve with skeletal hydroxyl vacancies. S20. Hydrogen-type MOR molecular sieves are packed into at least one catalyst bed 20 in a gas-solid titanium-supplemented reactor. The reactor has multiple bed filling positions, and single-layer or multi-layer catalyst beds 20 are selected according to the production scale. A preheating chamber 13, a reaction chamber, and a constant temperature compensation chamber 12 are also provided in sequence along the material flow direction in the reactor. Multiple bed filling positions are located in the reaction chamber. A gas distribution structure 30 is also provided in the reactor. The gas distribution structure 30 is set on the flow path before the gas enters the catalyst bed 20, and / or set between adjacent catalyst beds 20. S30. Heat the preheating chamber 13, the reaction chamber and the constant temperature compensation chamber 12 to the reaction temperature; S40. After the TiCl4-containing gas is distributed through the gas distribution structure 30, it is introduced into the catalyst bed 20, so that TiCl4 and hydrogen-type MOR molecular sieve undergo isomorphic substitution reaction, and titanium atoms are introduced into the molecular sieve framework. S50. After the reaction is complete, the temperature is raised and calcined to obtain Ti-MOR molecular sieve.

[0027] In this embodiment, a gas-solid titanium supplementation reactor is used, which has multiple installation structures arranged from top to bottom inside the furnace. Catalyst beds 20 can be selectively installed on the installation structures according to the production scale.

[0028] When the catalyst bed 20 is a single layer, a first gas distribution element 31 is provided to uniformly distribute the gas flow, so that the gas flow enters the reactor at a uniform flow rate and distribution. When the catalyst bed 20 is configured with two or more layers, a second gas distribution element 32 is provided between two adjacent catalyst bed layers 20 to uniformly distribute the gas flow after the upper layer reaction.

[0029] When the catalyst bed 20 is a single layer, the first gas distribution element 31 is the gas distribution structure 30. When the catalyst bed 20 is configured with two or more layers, the first gas distribution element 31 and the second gas distribution element 32 are the gas distribution structure 30.

[0030] Step S10: Select sodium-type MOR molecular sieve powder as raw material. First, perform acid washing to remove sodium, typically using dilute hydrochloric acid or dilute nitric acid solution under heating and stirring conditions for ion exchange to remove exchangeable sodium ions from the molecular sieve. Then, perform high-temperature dealuminization treatment, for example, at 500-600℃ in a steam atmosphere, to reduce the skeletal aluminum content and obtain high-silicon or pure-silicon hydrogen-type MOR molecular sieves. Sieve the dealuminized molecular sieve to 20-40 mesh and place it in a forced-air drying oven at 120-150℃ for 6-10 hours to remove surface free moisture.

[0031] The dried molecular sieve is placed in a muffle furnace and calcined at 450–550°C for 3–5 hours to remove crystal water and residual organic template agent from the pores and to form reactive hydroxyl vacancies in the framework, thus obtaining a hydrogen-type MOR molecular sieve with framework hydroxyl vacancies. The sieve is then cooled to room temperature for later use.

[0032] Step S20: The bed structure within the reactor is flexibly selected based on the production scale. For small-scale laboratory tests, a single-layer catalyst bed 20 is used. For medium-to-small-scale mass production, a double-layer catalyst bed 20 is used. For large-scale industrial mass production, a triple-layer catalyst bed 20 is used.

[0033] The molecular sieve prepared in step S10 is uniformly spread on the selected catalyst bed 20. To ensure uniform gas inlet and outlet, inert alumina ceramic rings are filled in the upper, lower or interlayer parts of the catalyst bed 20 to provide gas flow uniformity and support.

[0034] After filling, seal the upper head loading port and the side unloading port of the reactor, and introduce room temperature nitrogen into the furnace to 0.15-0.25 MPa. Hold the pressure for 30 minutes and perform an airtightness test. If the pressure drop does not exceed the standard, the seal is deemed qualified.

[0035] Step S30: Under the condition of continuously introducing dry nitrogen into the reactor, the preheating chamber 13, reaction chamber and constant temperature compensation chamber 12 of the gas-solid titanium-supplemented reactor are simultaneously heated and kept at a constant temperature in a gradient heating manner to replace and purge the air, water vapor and other adsorbed impurities in the furnace. At the same time, the hydroxyl vacancies in the molecular sieve channels are further activated under the purge of hot nitrogen.

[0036] Step S40: Maintain a slightly positive pressure of 0.02–0.05 MPa inside the reactor. Nitrogen gas bubbling carries away TiCl4 vapor at a constant concentration, forming a uniform mixture. This mixture enters from the top of the reactor, first passing through the preheating chamber 13, and then achieving uniform flow through the multi-stage gas distribution structure 30 corresponding to the current bed layer number. This ensures that the molecular sieve particles in each layer can fully contact the TiCl4 vapor.

[0037] After gas distribution is completed, the system enters the isothermal reaction stage. When a single-layer bed is filled, the reaction temperature is 480–510℃. When a double-layer bed is filled, the reaction temperature is 500–530℃. When a triple-layer bed is filled, the reaction temperature is increased to 520–550℃.

[0038] In the three-layer bed mode, each layer can be independently temperature controlled. The interlayer gas distribution structure 30 (second gas distribution element 32) performs secondary uniform flow of the rising gas phase, eliminating channeling and flow deviation phenomena. At high temperature, TiCl4 vapor undergoes isomorphic substitution reaction with the hydroxyl groups in the molecular sieve framework, and titanium atoms are precisely embedded in the framework to form four-coordinate framework titanium active centers, inhibiting the agglomeration of non-framework titanium (anatase TiO2).

[0039] Step S50: After the isothermal reaction is completed, immediately stop the introduction of TiCl4 vapor into the reactor, but continue to introduce nitrogen gas to begin the calcination process. This calcination step can remove adsorbed chlorides (such as HCl) remaining on the surface and in the pores of the molecular sieve, and promote the solidification of the coordination structure of the framework titanium from the metastable state to a stable closed four-coordinate state. At the same time, it repairs any potentially damaged molecular sieve framework and improves the regularity of the crystal structure.

[0040] After calcination, heating is stopped, and the reactor is purged with nitrogen throughout the process. Once the temperature drops below 120°C, the reactor is sealed and left to stand for passivation. This process eliminates the highly active adsorption sites on the surface of the molecular sieve that has just come out of the furnace, making its surface chemical properties more stable and preventing severe oxidation or rapid moisture absorption when it comes into contact with air later, thereby ensuring the storage stability of the product.

[0041] After the furnace body 10 of the titanium-modified gas reactor has cooled naturally to room temperature and passed the nitrogen purging and depressurization test, the side discharge port is opened. The discharged product is collected, sieved to remove trace amounts of powder, and the final product, Ti-MOR molecular sieve, is obtained and stored in a sealed, dry place.

[0042] The present invention provides a gas-solid titanium replenishment method for MOR molecular sieve catalysts. Compared with the prior art, by pre-setting multiple bed filling positions in the reactor, single or multiple catalyst beds 20 can be flexibly selected according to the actual production scale. This allows a set of equipment and process systems to simultaneously adapt to the differentiated needs of laboratory pilot-scale, medium-scale pilot-scale and large-scale mass production. Process parameters can be gradient shifted according to the number of beds, solving the technical pain point of lack of systematic guidance in the scale-up process due to the fixed equipment structure in traditional processes.

[0043] A gas distribution structure 30 is installed inside the reactor. This structure can be positioned either on the flow path before the gas enters the catalyst bed 20 or between adjacent catalyst beds 20. This multi-stage, multi-point gas distribution method can perform multiple uniform distributions of the TiCl4-containing gas, eliminating the uneven gas phase distribution, channeling, and flow deviation phenomena commonly found in traditional thick-bed reactors. This ensures uniform contact between TiCl4 vapor and the molecular sieve, thereby significantly increasing the isomorphic substitution rate of titanium atoms in the molecular sieve framework, suppressing the formation of non-framework titanium agglomerates, and enhancing the catalytic activity of the product.

[0044] The reactor is sequentially equipped with a preheating chamber 13, a reaction chamber, and a constant-temperature compensation chamber 12 along the material flow direction. Through three-stage zoned temperature control, the temperature field is managed. The preheating chamber 13 prevents TiCl4 from condensing at low temperatures, while the constant-temperature compensation chamber 12 prevents tail gas condensation from corroding the equipment and compensates for heat loss at the reaction chamber outlet. This ensures small axial and radial temperature differences throughout the reaction chamber and uniform reaction conditions, thereby guaranteeing consistency in titanium content and catalytic performance between different batches of products and overcoming the drawbacks of large batch deviations in traditional processes.

[0045] This application directly prepares hydrogen-form MOR molecular sieves with skeletal hydroxyl vacancies, laying the foundation for subsequent efficient titanium supplementation. Combined with the multi-layered packing structure of the reactor, production time is shortened.

[0046] The flexible arrangement of at least one catalyst bed 20 and gas distribution structure 30 allows for the optimization of reaction conditions by adjusting the number of bed layers, packing thickness, and gas distribution level when dealing with molecular sieve raw materials of different varieties or particle sizes, without the need to change equipment. This enhances the flexibility of production organization and the ability to cope with multi-variety and variable batch production tasks.

[0047] In some embodiments, the desodiuming and dealuminizing treatment of MOR molecular sieve powder includes: sequentially subjecting the MOR molecular sieve powder to acid washing for desodiuming, high-temperature dealuminizing, drying, and calcination. In this embodiment, the acid washing for desodiuming stage involves: adding commercial sodium-type MOR molecular sieve powder into an acid-resistant reactor equipped with a stirring and heating device, adding a dilute hydrochloric acid or dilute nitric acid solution with a concentration of 0.5–2 mol / L, and continuously stirring at 60–90°C to carry out an ion exchange reaction for 2–6 hours.

[0048] During this process, the H⁺ in the acid solution undergoes a displacement reaction with the exchangeable Na⁺ outside the molecular sieve framework, removing sodium ions from the molecular sieve and converting them into the hydrogen-form intermediate. After the reaction is complete, the solution is repeatedly washed with deionized water until the washings are neutral, and then filtered to obtain a filter cake.

[0049] High-temperature dealuminization stage: The acid-washed molecular sieve filter cake is placed in a high-temperature treatment furnace and dealuminized at 500–650°C under a steam atmosphere for 3–8 hours. The high-temperature steam selectively hydrolyzes the aluminum-oxygen bonds in the framework, causing some of the framework aluminum to be released in the form of Al(OH)3, thereby reducing the aluminum content of the molecular sieve framework and increasing the silicon-to-aluminum ratio.

[0050] Dealumination treatment can regulate the acidic site density of the molecular sieve, providing more skeletal substitution sites for subsequent titanium atoms. It can also pre-form a certain number of hydroxyl vacancies, which are active centers for the subsequent isomorphous substitution reaction between TiCl4 in the gas phase and the framework.

[0051] Drying stage: The dealuded molecular sieves are sieved to 20-40 mesh and placed in a forced-air drying oven, where they are dried at a constant temperature of 120-150℃ for 6-10 hours. The main purpose of this stage is to remove the free moisture physically adsorbed on the surface of the molecular sieves, in preparation for subsequent high-temperature calcination, and to prevent damage to the skeletal structure of the water-containing molecular sieves under rapid heating conditions.

[0052] Calcination stage: The dried molecular sieve is placed in a muffle furnace and calcined at 450–550°C for 3–5 hours under air or nitrogen atmosphere. This process thoroughly removes residual water of crystallization, organic template agents, and other impurities from the molecular sieve pores. It also promotes the condensation or stabilization of silanol vacancy formed during dealumination, resulting in a well-defined and reactive framework of hydroxyl vacancies. This stabilizes the molecular sieve crystal structure and improves its high-temperature thermal stability. After calcination, the sieve is allowed to cool naturally to room temperature and then sealed for storage.

[0053] Acid leaching for sodium removal and high-temperature dealumination resulted in the formation of numerous well-organized hydroxyl vacancies within the molecular sieve framework. These vacancies serve as direct active sites for subsequent isomorphous substitution reactions between TiCl4 in the gas phase and the framework. Sodium removal eliminated sodium ions that hindered titanium atom migration, while dealumination created the necessary spatial and chemical conditions for titanium atoms to successfully embed into the framework, forming four-coordinate framework titanium active centers. This significantly increased the framework titanium content and suppressed the aggregation of non-framework titanium.

[0054] The hydrogen-type MOR molecular sieve with active hydroxyl vacancies obtained directly after calcination can be loaded into the reactor for titanium replenishment after cooling, without the need for additional intermediate processing steps, thus shortening the overall production cycle and improving production efficiency.

[0055] In some embodiments, the reactor has three bed loading positions, and single, double, or triple catalyst beds 20 can be selected for loading depending on the production scale. In this embodiment, during the laboratory pilot stage, a single catalyst bed 20 is typically installed in the third loading position (the uppermost loading position). This loading position is located in the upper middle part of the reaction chamber, with a moderate gas phase flow, a small amount of material fed at one time, which facilitates rapid evaluation of process parameters and catalyst performance, making it suitable for small-batch research and development.

[0056] In the small-to-medium-scale production stage, catalyst beds 20 are installed simultaneously at the second and third loading positions to form a double-bed loading mode. At this time, the material throughput increases significantly, but each bed layer still maintains a relatively thin thickness, resulting in low gas phase penetration resistance. Furthermore, the interlayer gas distribution structure 30 enables two-stage uniform gas distribution, balancing production capacity and reaction uniformity.

[0057] In the large-scale industrial production stage, catalyst beds 20 are installed in the first, second, and third loading positions, forming a three-layer bed loading mode. The three-layer thin-bed design increases the total throughput several times over, while the thinness of each individual bed allows TiCl4 vapor to penetrate each layer of material uniformly in a short time. Combined with the three-stage gas distribution structure 30 and independent temperature control layer by layer, the uniformity of reaction conditions and the consistency of batch product quality are ensured under large-scale production conditions.

[0058] By pre-setting three bed loading positions within the reactor, flexible switching between single-layer, double-layer, and triple-layer catalyst beds is achieved. The same reactor equipment can be used for laboratory pilot-scale testing, medium-scale pilot production, and large-scale industrial mass production, eliminating the need for repeated design and manufacturing of dedicated reactors for different scales, thus reducing equipment investment costs and R&D conversion cycles.

[0059] In some embodiments, the packing thickness of a single-layer catalyst bed 20 is 80–160 mm. The total packing thickness of a double-layer catalyst bed 20 is 160–320 mm. The total packing thickness of a triple-layer catalyst bed 20 is 240–480 mm. In this embodiment, corresponding to a laboratory-scale test, the packing thickness of the catalyst bed 20 is 80–160 mm.

[0060] Single-layer beds are mainly used for small-batch R&D and preliminary optimization of process parameters. Within this thickness range, TiCl4 vapor can smoothly penetrate the entire bed, the contact time between the gas phase and the molecular sieve particles is moderate, and the heat of reaction can be effectively dissipated to the surroundings through the bed, without significant axial temperature differences or local hot spots due to excessive bed thickness.

[0061] For small to medium-sized production scales, the packing thickness of each catalyst bed layer 20 is 80–160 mm, and the total packing thickness is 160–320 mm. Compared to single-layer beds, double-layer beds increase the total throughput by adding an extra bed layer.

[0062] The three-layer bed loading mode is designed for large-scale industrial production. Each catalyst bed layer has a loading thickness of 80–160 mm, with a total loading thickness of 240–480 mm. The three-layer bed increases the total throughput to 2–3 times that of a single-layer bed.

[0063] In some embodiments, heating the preheating chamber 13, the reaction chamber, and the isothermal compensation chamber 12 to the reaction temperature includes: simultaneously heating the preheating chamber 13, the reaction chamber, and the isothermal compensation chamber 12 to 320–380°C at a heating rate of 3–5°C / min, and maintaining the temperature for 2–4 hours. Dry nitrogen is purged as the carrier gas throughout the heating and isothermal treatment process, and the nitrogen space velocity is controlled at 120–180 h⁻¹. -1 .

[0064] In this embodiment, after the segmented heating system of the reactor is turned on, the preheating chamber 13, the reaction chamber, and the isothermal compensation chamber 12 are heated synchronously at a heating rate of 3-5°C / min. This prevents the molecular sieve from generating excessive thermal stress due to sudden heating (direct and rapid heating), thus avoiding damage to the skeleton structure or the formation of cracks. At the same time, the synchronous heating of the three regions ensures the uniformity of the temperature field within the furnace body 10, avoiding uneven gas flow due to thermal expansion and contraction caused by asynchronous heating in different regions, which would affect the stability of the gas flow distribution within the furnace.

[0065] After simultaneously heating the three regions to 320–380°C, maintain the temperature for 2–4 hours to ensure a fully balanced temperature field within the furnace, minimizing the axial and radial temperature differences at various points in the reaction chamber, and providing sufficient time for deep desorption and activation of the molecular sieve channels.

[0066] Throughout the heating and isothermal treatment process, dry nitrogen gas was continuously introduced into the reactor as a carrier gas, and the nitrogen space velocity was strictly controlled between 120 and 180 h⁻¹. -1 Nitrogen is used as a purge gas to replace air and moisture in the furnace, preventing hydrothermal reactions between the molecular sieve and water vapor at high temperatures that could lead to dealuminization of the skeleton. Nitrogen also acts as a heat carrier, promoting convective heat transfer within the furnace and accelerating temperature homogenization.

[0067] As nitrogen flows through the molecular sieve channels, it carries away the desorbed moisture and impurity gases, activating the hydroxyl vacancies in the molecular sieve.

[0068] Space velocity is short for gas volume space velocity, which refers to the gas volume flow rate through a unit volume catalyst bed 20 per unit time.

[0069] In some embodiments, the TiCl4-containing gas is obtained by passing nitrogen gas into a constant-temperature titanium tetrachloride vaporizer to carry TiCl4 vapor and form a mixed gas. The temperature of the titanium tetrachloride vaporizer is kept constant at 160–200°C, the mass concentration of TiCl4 in the mixed gas is controlled at 8–15%, and the gas hourly space velocity is controlled at 60–110 h⁻¹. -1In this embodiment, the titanium tetrachloride vaporization tank is a sealed, corrosion-resistant container with a heating jacket and a temperature control system, which contains liquid titanium tetrachloride.

[0070] By using PID control linked to an external heating device and an internal thermocouple, the temperature of the liquid TiCl4 in the vaporization tank is kept constant at 160–200°C. This constant temperature control ensures that the amount of TiCl4 vapor carried out by nitrogen per unit time remains constant throughout the doping process, thereby ensuring the uniformity of the subsequent titanium supplementation reaction.

[0071] Dry nitrogen gas is introduced into the titanium tetrachloride vaporization tank below the liquid surface through a pipeline. The nitrogen gas passes through the liquid TiCl4 in a bubbling manner, and is fully saturated with TiCl4 vapor during this process, forming a mixture containing TiCl4 vapor. The mass concentration of TiCl4 in the mixture is maintained within the range of 8% to 15% by adjusting the nitrogen flow rate and the vaporization tank temperature.

[0072] It is important to note that all pipelines from the titanium tetrachloride vaporizer to the reactor inlet are fully insulated with heat tracing, with a heating temperature not lower than 160℃. This is to prevent TiCl4 vapor from condensing and flowing back during transport due to temperature drop, ensuring that the concentration of the mixed gas entering the reactor is consistent with that at the vaporizer outlet. After the mixed gas is introduced into the reactor, the gas hourly space velocity is controlled within the range of 60–110 h⁻¹.

[0073] In some embodiments, during the isomorphic substitution reaction, a segmented PID temperature control system is used to maintain the axial and radial temperature differences across the entire reactor region ≤3°C. When a single-layer bed is loaded, the reaction time is 4–6 hours. When a double-layer bed is loaded, the reaction time is 5–8 hours. When a triple-layer bed is loaded, the reaction time is 6–9 hours. In this embodiment, the segmented PID temperature control system consists of multiple independent temperature control loops distributed along the reactor axis, multi-point temperature measuring thermocouples, and a central PID controller.

[0074] Specifically, the preheating chamber 13, reaction chamber and constant temperature compensation chamber 12 of the reactor are each equipped with independent heating elements and temperature measuring points. The temperature signal of each zone is fed back to the central controller in real time. The controller automatically adjusts the output power of each heating circuit according to the deviation between the set value and the measured value through the proportional-integral-derivative (PID) algorithm to achieve precise closed-loop control of the temperature of each zone.

[0075] Throughout the entire range, the axial temperature difference (the maximum temperature deviation between each measuring point along the gas flow direction) and the radial temperature difference (the temperature deviation between the center and the wall measuring point within the same cross-section) are both controlled within ≤3℃. This ensures that the reaction temperature experienced by each layer of molecular sieve is consistent as the gas flows through the entire bed, avoiding uneven titanium replenishment caused by high temperature at the front and low temperature at the back.

[0076] A radial temperature difference of ≤3℃ prevents reaction rate deviations between the center and edge of the bed due to temperature differences, ensuring that the titanium replenishment of molecules at all points within the same bed cross-section proceeds synchronously. When a three-layer bed loading mode is adopted, each catalyst bed 20 is also equipped with an independent temperature control sub-loop, which can be finely adjusted according to the actual temperature of each bed to compensate for the interlayer temperature difference caused by exothermic reaction or gas flow.

[0077] The reaction temperature and time for the isomorphic substitution reaction are set differently depending on the selected bed packing mode. When a single-layer bed is packed, the reaction temperature is 480℃~510℃, and the reaction time is 4~6 hours. When a double-layer bed is packed, the reaction temperature is 500℃~530℃, and the reaction time is 5~8 hours. When a triple-layer bed is packed, the reaction temperature is 520℃~550℃, and the reaction time is 6~9 hours.

[0078] As the number of molecular sieve layers increases, the total catalyst loading in the reactor increases exponentially. TiCl4 vapor needs to pass through more molecular sieve layers sequentially, contacting and reacting with more molecular sieve particles. Therefore, under conditions of increased total titanium source flow, appropriately extending the reaction time ensures that each molecular sieve layer has sufficient time to fully contact the TiCl4 vapor and complete the isomorphous substitution reaction.

[0079] In some embodiments, the calcination process includes: heating the reaction chamber to 580–620°C at a heating rate of 2–4°C / min, and calcining at this temperature for 2–3 hours. During the calcination process, the isothermal compensation chamber 12 is maintained at 420–460°C. In this embodiment, after the reaction is completed, the flow of TiCl4 vapor into the reactor is stopped, while nitrogen is continuously supplied, and the temperature of the reaction chamber is increased from the isomorphic substitution reaction temperature to 580–620°C at a heating rate of 2–4°C / min.

[0080] Nitrogen gas is continuously introduced during the heating process to maintain an inert environment inside the furnace and to carry away the residual TiCl4 and HCl gases that have desorbed from the molecular sieve surface in the early stage of heating.

[0081] Once the temperature in the reaction chamber reaches 580–620°C, it is calcined at a constant temperature for 2–3 hours to ensure that the molecular sieve bed reaches the target temperature from the outside to the inside and completes the solidification of the coordination structure, thus ensuring the calcination effect.

[0082] While the reaction chamber undergoes high-temperature roasting, the downstream isothermal compensation chamber 12 maintains a temperature of 420–460°C. The high-temperature nitrogen gas flowing out of the reaction chamber carries chlorides (including residual TiCl4 vapor and byproduct HCl gas) desorbed from the molecular sieve during roasting. If the temperature of the isothermal compensation chamber 12 is too low, these chloride gases may condense in the pipeline or downstream equipment, forming highly corrosive acidic droplets or solid deposits, severely corroding the inner walls of the equipment and pipelines.

[0083] Maintaining the constant temperature compensation chamber 12 at 420–460°C, which is much higher than the dew point temperature of HCl and residual TiCl4, ensures that gaseous chlorides pass through smoothly in gaseous form and are eventually absorbed by the exhaust gas treatment system, avoiding the risk of low-temperature condensation corrosion.

[0084] In some embodiments, after the reaction is complete, the process further includes: gradually cooling the reactor at a rate of 2–3 °C / min and purging the reactor with nitrogen gas. The nitrogen space velocity is 100–150 h⁻¹. -1 When the furnace temperature drops below 120℃, stop the nitrogen gas supply, seal and let it stand for 2-5 hours for passivation, then unload and collect the Ti-MOR molecular sieve.

[0085] In this embodiment, after the high-temperature roasting is completed, heating is stopped, and the programmed cooling stage begins. The cooling rate is controlled at 2–3 °C / min, using a gradient cooling method.

[0086] Throughout the gradient cooling process, dry nitrogen gas is continuously introduced into the reactor for purging, with the nitrogen space velocity controlled at 100–150 h⁻¹. -1 During the cooling process, a small amount of adsorbed chlorides (such as HCl and residual TiCl4) that were not completely desorbed during the calcination stage remain on the molecular sieve channels and surface. As the temperature gradually decreases, the desorption rate of these substances decreases, and they need to be removed from the molecular sieve surface and bed pores by continuous airflow.

[0087] In addition, continuous nitrogen purging creates a slightly positive pressure inert atmosphere barrier inside the furnace, preventing outside air from being drawn back into the furnace due to the negative pressure generated by the cooling and contraction of the gas inside the furnace, thus avoiding oxidation of the high-temperature molecular sieve upon contact with oxygen.

[0088] When the furnace temperature drops below 120℃, stop the nitrogen supply and close all inlet and outlet valves to keep the reactor in a sealed state and allow it to stand for passivation for 2-5 hours. At 120℃, the water vapor competitive adsorption capacity on the molecular sieve surface weakens, and the thermal motion amplitude of the molecular sieve framework has also decreased. At this time, sealing and allowing it to stand allows the small number of highly active adsorption sites remaining on the molecular sieve surface (such as incompletely coordinated framework titanium sites, surface hydroxyl groups, etc.) to gradually stabilize in an oxygen-free and anhydrous static inert atmosphere.

[0089] After a standing time of 2 to 5 hours, the surface chemical activity of the Ti-MOR molecular sieve becomes mild, preventing severe oxidation or rapid moisture absorption during subsequent unloading and contact with air, thus ensuring the performance stability of the product during storage and transportation.

[0090] After the sealed passivation process is completed, the furnace body 10 has naturally cooled to room temperature. After nitrogen purging and depressurization to confirm safety, the unloading and collection operation can begin. The close connection between passivation and unloading ensures that the entire process from furnace exit to storage is under control, avoiding quality deterioration caused by exposure to air during intermediate stages.

[0091] In some embodiments, the reactor is equipped with a support structure for the detachable installation of the catalyst bed 20. During unloading, each catalyst bed 20 is extracted sequentially from bottom to top, allowing the Ti-MOR molecular sieve to fall under gravity and be automatically discharged. In this embodiment, the support structure is the aforementioned installation structure. The support structure consists of annular support steps pre-set at different heights along the furnace axial direction, and independent support grids 70 that cooperate with them. Each support grid 70 can be independently installed and removed.

[0092] During the loading stage, operators install each layer of support grid 70 in sequence, and then lay the catalyst bed 20 and inert ceramic rings on top. During the reaction stage, the support grid 70 stably supports the material and withstands the impact of airflow and the high-temperature environment. The support grid 70 is made of corundum material, ensuring both structural strength and corrosion resistance in high-temperature, chlorine-containing environments, while also ensuring ease of disassembly.

[0093] During unloading, first open the unloading port of furnace body 10, and then the operator removes each layer of support grid 70 from bottom to top. First, remove the bottommost (first layer) support grid 70, causing the ceramic rings and molecular sieves on that layer to lose their support and fall into the cavity of the lower section of furnace body 10 under their own weight, flowing out from the unloading port. Then, remove the second and third layers of support grid 70 in sequence. With each layer removed, the material in that layer falls and is discharged until all the material in the top layer has been discharged.

[0094] During the process of gradually removing the support grid 70, the upper ceramic rings and Ti-MOR molecular sieve materials fall downwards under their own gravity and flow out automatically through the discharge port without any mechanical stirring, vibration or manual removal or other auxiliary unloading methods.

[0095] The discharged product is collected and screened to remove trace amounts of powder that may be generated due to gravity falling, thus obtaining the final product Ti-MOR molecular sieve, which is then sealed, dried, and stored.

[0096] This application discloses a gas-solid titanium replenishment method for MOR molecular sieve catalysts, which is implemented based on a gas-solid titanium replenishment reactor for MOR molecular sieve catalysts submitted on the same day.

[0097] See Figure 2A gas-solid titanium-supplementing reactor for MOR molecular sieve catalysts includes a furnace body 10, a reaction unit, and a gas distribution structure 30. The internal space of the furnace body 10 is divided from top to bottom into: an inlet buffer chamber 11, a preheating chamber 13, a reaction chamber, and a constant temperature compensation chamber 12. Among them, the inlet buffer chamber 11 is used to receive and initially buffer the gas phase entering the furnace body 10, so that it forms a relatively stable flow field before entering the subsequent regions.

[0098] The preheating chamber 13 is used to heat the airflow introduced into the intake buffer chamber 11 to a preset reaction temperature range. The constant temperature compensation chamber 12 is used to compensate for and keep the temperature of the exhaust gas after passing through the entire catalyst bed 20, preventing the gas in the low temperature zone from condensing.

[0099] The catalyst bed 20 is detachably installed in the reaction chamber and can be configured as at least one layer as needed. Specifically, it can be a single-layer bed (including only the first catalyst bed 21), a double-layer bed (including the first catalyst bed 21 and the second catalyst bed 22), or a triple-layer bed (including the first catalyst bed 21, the second catalyst bed 22, and the third catalyst bed 23).

[0100] Each catalyst bed 20 is arranged in sequence along the vertical direction, with the uniform flow layer 50 located above a single-layer, double-layer, or triple-layer bed, and the buffer layer 60 located below a single-layer, double-layer, or triple-layer bed.

[0101] The flow equalization layer 50 is formed by stacking alumina inert ceramic rings and is used to further equalize the gas flow entering the catalyst bed 20, eliminating flow deviation and channeling. The buffer layer 60 is also composed of alumina inert ceramic rings and is used to buffer and stabilize the gas flow exiting the catalyst bed 20.

[0102] The first gas distribution element 31 is disposed between the inlet buffer chamber 11 and the preheating chamber 13 to uniformly distribute the raw material gas in the inlet buffer chamber 11, so that the gas flow enters the preheating chamber 13 with a uniform flow rate and distribution. When the catalyst bed 20 is configured with two or more layers, a second gas distribution element 32 is also disposed between two adjacent catalyst bed layers 20 to uniformly distribute the gas flow after the upper reaction layer, ensuring that the gas flow entering the next bed layer is uniform and avoiding flow deviation and channeling phenomena.

[0103] The first gas distribution element 31 and the second gas distribution element 32 structurally ensure that each section of the catalyst bed 20 can obtain a uniform gas flow distribution, thereby improving the uniformity of titanium supplementation.

[0104] Heating units 40 are respectively installed in the preheating chamber 13, the reaction chamber, and the constant temperature compensation chamber 12, forming multiple independent temperature control zones. The heating elements of the heating units 40 are high-temperature ceramic radiant heating tubes (or silicon carbide rods), which are evenly distributed along the circumference of the furnace body 10. The furnace body 10 adopts a gradient composite insulation structure, which consists of alumina refractory fiber, a lightweight refractory layer, and a composite insulation board from the inner wall of the furnace body 10 to the furnace shell.

[0105] A first gas inlet 14 and a second gas inlet 15 are provided on the side wall of the furnace body 10. When the catalyst bed is double-layered, the first gas inlet 14 is located between the two catalyst bed layers, and TiCl4 gas flow is introduced into the furnace body 10 through the gas inlet 16 and the first gas inlet 14, respectively. When the catalyst bed is triple-layered, a first gas inlet 14 and a second gas inlet 15 are provided between two adjacent catalyst bed layers, and TiCl4 gas flow is introduced into the furnace body 10 through the gas inlet 16, the first gas inlet 14, and the second gas inlet 15, respectively.

[0106] 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, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for gas-solid titanium replenishment using a MOR molecular sieve catalyst, characterized in that, Includes the following steps: The raw MOR molecular sieve powder was subjected to desodium and dealuminate treatment to obtain hydrogen-type MOR molecular sieve with skeletal hydroxyl vacancies. The hydrogen-form MOR molecular sieve is packed into at least one catalyst bed in a gas-solid titanium-supplemented reactor; the reactor has multiple bed packing positions, and a single-layer or multi-layer catalyst bed is selected according to the production scale; a preheating chamber, a reaction chamber, and a constant temperature compensation chamber are also sequentially arranged in the reactor along the material flow direction; multiple bed packing positions are located in the reaction chamber; the reactor also has a gas distribution structure, which is arranged on the flow path of gas before it enters the catalyst bed, and / or between adjacent catalyst beds; The preheating chamber, reaction chamber, and constant temperature compensation chamber are heated to the reaction temperature. After the TiCl4-containing gas is distributed through the gas distribution structure, it is introduced into the catalyst bed, so that TiCl4 and the hydrogen-type MOR molecular sieve undergo isomorphic substitution reaction, introducing titanium atoms into the molecular sieve framework. After the reaction was completed, the mixture was heated and calcined to obtain Ti-MOR molecular sieve.

2. The gas-solid titanium replenishment method for MOR molecular sieve catalyst as described in claim 1, characterized in that, The process of removing sodium and aluminum from MOR molecular sieve powder includes: sequentially acid washing to remove sodium, high-temperature dealuminization, drying, and calcination of the MOR molecular sieve powder.

3. The gas-solid titanium replenishment method for MOR molecular sieve catalyst as described in claim 1, characterized in that, The reactor is equipped with three bed filling positions, and single, double or triple catalyst beds can be selected to be filled according to the production scale.

4. The gas-solid titanium replenishment method for MOR molecular sieve catalyst as described in claim 3, characterized in that, The packing thickness of a single-layer catalyst bed is 80–160 mm; the total packing thickness of a double-layer catalyst bed is 160–320 mm; and the total packing thickness of a triple-layer catalyst bed is 240–480 mm.

5. The gas-solid titanium replenishment method for MOR molecular sieve catalyst as described in claim 1, characterized in that, Heating the preheating chamber, reaction chamber, and isothermal compensation chamber to the reaction temperature includes: simultaneously heating the preheating chamber, reaction chamber, and isothermal compensation chamber to 320-380°C at a heating rate of 3-5°C / min, and maintaining the temperature for 2-4 hours; purging dry nitrogen gas as a carrier gas throughout the heating and isothermal treatment process, with the nitrogen space velocity controlled at 120-180 h⁻¹. -1 .

6. The gas-solid titanium replenishment method for MOR molecular sieve catalyst as described in claim 1, characterized in that, The TiCl4-containing gas is obtained by passing nitrogen gas into a constant-temperature titanium tetrachloride vaporization tank to carry TiCl4 vapor and form a mixed gas. The temperature of the titanium tetrachloride vaporization tank is kept constant at 160–200°C, the TiCl4 mass concentration in the mixed gas is controlled at 8–15%, and the gas hourly space velocity is controlled at 60–110 h⁻¹. -1 .

7. The gas-solid titanium replenishment method for MOR molecular sieve catalyst as described in claim 1, characterized in that, During the isomorphic substitution reaction, a segmented PID temperature control system is used to maintain the axial and radial temperature differences across the entire reactor at ≤3℃. When a single-layer bed is filled, the reaction time is 4–6 hours; when a double-layer bed is filled, the reaction time is 5–8 hours; and when a triple-layer bed is filled, the reaction time is 6–9 hours.

8. The gas-solid titanium replenishment method for MOR molecular sieve catalyst as described in claim 1, characterized in that, The heating and calcination process includes: heating the reaction chamber to 580-620°C at a heating rate of 2-4°C / min, and calcining at a constant temperature for 2-3 hours; during the calcination process, the constant temperature compensation chamber is maintained at 420-460°C.

9. The gas-solid titanium replenishment method for MOR molecular sieve catalyst as described in claim 1, characterized in that, After the reaction is completed, the process further includes: a gradient cooling at a cooling rate of 2–3 °C / min, and purging the reactor with nitrogen gas; the nitrogen space velocity is 100–150 h⁻¹. -1 When the furnace temperature drops below 120℃, stop the nitrogen gas supply, seal and let stand for 2-5 hours for passivation, then unload and collect the Ti-MOR molecular sieve.

10. The gas-solid titanium replenishment method for MOR molecular sieve catalyst as described in claim 1, characterized in that, The reactor is equipped with a support structure for the detachable installation of the catalyst bed. During unloading, the catalyst bed is extracted in stages from bottom to top, so that the Ti-MOR molecular sieve falls down step by step by gravity and is automatically discharged.

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