Supported transition metal carbide catalysts, methods of preparation, and tertiary alcohol alkoxide applications

Abstract

The application belongs to the technical field of organic synthesis catalysis, and particularly relates to a supported transition metal carbide catalyst, a preparation method and application of a tertiary alcohol alkoxide. The catalyst uses a carbon fiber grid or a SiC ceramic fiber grid as a carrier, and loads WC or Mo2C transition metal carbide active components. The catalyst is prepared by using an impregnation-carbothermal reduction method. In the synthesis of a tertiary alcohol alkali metal alkoxide, the catalyst is used to catalyze the proton exchange reaction between the tertiary alcohol and the alkali metal, the reaction system is an anhydrous and oxygen-free inert atmosphere, and the solvent is a tertiary alcohol or a tertiary alcohol / high-boiling-point inert composite solvent. Through the space confinement effect of the carrier and the strong interaction with the active components, the catalyst can be repeatedly used without high-temperature activation, and the technical problems of slow reaction rate, many impurities in the product, difficult separation of the catalyst and high-temperature activation for reuse in the traditional synthesis process are solved.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis catalysis technology, and specifically relates to supported transition metal carbide catalysts, preparation methods, and applications of tertiary alcohol alkoxides. Background Technology

[0002] Tertiary alkali metal alkoxides are core strong base reagents in organic synthesis (pKa≈18~20), and are widely used in pharmaceutical synthesis, fine chemicals, materials preparation and other fields. In particular, potassium tert-butoxide and sodium tert-butoxide, as strong nucleophiles and strong bases, play an irreplaceable role in elimination reactions, substitution reactions and addition reactions.

[0003] Currently, there are two main traditional synthesis processes for tertiary alcohol alkali metal alkoxides: one is the direct reaction method of elemental metals, in which alkali metals and tertiary alcohols undergo a direct proton exchange reaction to produce alkoxides and hydrogen gas; the other is the alkali metal hydroxide substitution method, which utilizes the substitution reaction between alkali metal hydroxides and tertiary alcohols under dehydration conditions.

[0004] Besides the two synthesis processes mentioned above, the synthesis of alkali metal alkoxides also includes the alkali metal amine method, the alcohol exchange method, and improvements to the original metal method and hydroxide substitution method. Improvements to the metal method involve adding high-boiling-point inert solvents such as toluene to raise the reaction temperature above the metal's melting point; improvements to the hydroxide substitution method involve adding an azeotropic agent; the alkali metal amine method uses inert solvents such as toluene or heptane as the solvent in the reaction system, where alcohols react with alkali metal amines to prepare alkali metal alkoxides; there is also an improved alcohol exchange reaction method, where lower-carbon alkali metal alkoxides react with higher-carbon alcohols to produce alkali metal alkoxides of higher-carbon alcohols, used to prepare alkali metal alkoxides of higher-carbon alcohols; other methods include the reaction of alkaline earth metal oxides and hydrocarbon-based alkali metal carbonates to produce alkali metal alkoxides, and electrolysis. These methods also suffer from numerous problems, such as high raw material and equipment costs, complex and imperfect processes, difficult equipment maintenance, and inconvenient post-processing. Specific problems are as follows: (1) Slow reaction rate and long induction period: The hydroxyl group of tertiary alcohol has a high bond energy, and the OH bond is difficult to break, resulting in a reaction induction period of more than 10 minutes. The overall reaction efficiency is low and it is difficult to adapt to industrial continuous production. (2) Many product impurities and difficulty in controlling purity: During the reaction, tertiary alcohol is prone to dehydration side reaction to generate olefin and ether impurities. In addition, the oxide layer on the surface of alkali metal element and the trace water in the reaction system will generate hydroxide impurities, making it difficult to achieve a product purity of more than 99%, which cannot meet the needs of high-end applications in pharmaceuticals and electronics. (3) Cumbersome catalyst separation and high cost: Traditional process catalysts are mostly in powder form. After the reaction, the catalyst needs to be separated by steps such as filtration and centrifugation. The operation is cumbersome, and the catalyst is easy to lose, pulverize, and deactivate. During the separation process, the product is prone to water absorption and decomposition, with a loss rate of 3% to 5%, which increases the production cost. (4) High safety risks: Alkali metals are flammable and explosive, and will react violently when in contact with trace amounts of moisture. In traditional processes, uneven mixing of materials can easily lead to local overheating and hydrogen accumulation, posing a risk of deflagration. At the same time, the high-temperature activation process also increases the safety risks of equipment operation.

[0005] Patent document CN1227212A proposes using powdered transition metal carbides, nitrides, and carbonitrides as catalysts for the preparation of alkali metal alkoxides from alcohols and alkali metal amalgams. However, alkali metal amalgams are highly toxic and their catalysts are difficult to recover, leading to their obsolescence in current industrial systems. Transition metal carbides (such as WC and Mo2C), due to their d-band state density approaching the Fermi level after carbon atoms are embedded in the transition metal lattice, exhibit similar electrical structures and catalytic behaviors to platinum group metals, and are thus hailed as "quasi-noble metal catalysts." Extensive research has been conducted on their supported applications in fields such as hydrodesulfurization, reverse water-gas shift reaction, and hydrogen evolution through water electrolysis. For example, patent document CN109126845A discloses a supported WC / Mo2C catalyst prepared by impregnation-solid-phase grinding carbothermic reduction; patent document CN100512959C discloses a supported carbide prepared by temperature-programmed reduction carbonization of hydrocarbon carbon sources; and patent document CN121161333A discloses a coconut shell carbon-supported Mo2C water electrolysis catalyst. However, the above catalysts are all geared towards oxidation / reduction gaseous reactions or aqueous electrochemical systems, and have never been involved in the liquid-phase strong base proton exchange scenario of tertiary alcohol alkali metal alkoxides.

[0006] Therefore, the technical problem to be solved by this invention is to develop a method for synthesizing tertiary alkali metal alkoxides with fast reaction rate, high product purity, no need for catalyst separation or high-temperature activation and reusable, and safe and controllable process. Summary of the Invention

[0007] This invention proposes a supported transition metal carbide catalyst, its preparation method, and its application in tertiary alcohol alkali metal alkoxides. It solves the problems of slow reaction rate, low product purity, difficulty in catalyst separation, need for high-temperature activation, inability to be reused, and poor process safety in the existing tertiary alcohol alkali metal alkoxide synthesis process.

[0008] The technical solution of this invention is implemented as follows: A supported transition metal carbide catalyst, comprising a support and an active component supported on the support, wherein the support is a carbon fiber mesh or a SiC ceramic fiber mesh, and the active component is selected from at least one of WC and Mo2C. The loading of the active component is 8–15 wt%, and the specific surface area of ​​the carrier after pretreatment is ≥300 m². 2 / g; The pretreatment includes: etching the carrier in an acid or alkali solution, and then calcining it in an argon atmosphere at a temperature range of 900-1100°C.

[0009] By using the above technical solutions, the loading of active components is limited to 8-15 wt%, which can form an optimal matching system, maximize the spatial confinement effect of the support and the strong interaction between the support and the active components, and at the same time take into account catalytic activity, stability, cycle life and production cost.

[0010] A method for preparing supported transition metal carbides, the method employing an impregnation-carbothermic reduction method, the specific steps of which are as follows: A1. Carrier pretreatment: The carrier is a carbon fiber mesh or SiC ceramic fiber mesh. The carrier is subjected to acid and alkali treatment, stirring and etching in sequence. Then the carrier is washed to neutral and calcined with argon gas. A2. Preparation of precursor impregnation solution: Dissolve the active component precursor in a solvent, add a dispersant, stir until completely dissolved, and prepare a transparent impregnation solution of 0.1-0.5 mol / L, wherein the active component precursor is a transition metal ammonium salt; A3. Vacuum impregnation with equal volume: Place the pretreated carrier in step A1 in a vacuum drying oven. After vacuum treatment, the carrier pores are fully degassed. Then, the precursor impregnation liquid is quickly added and impregnated at normal pressure so that the precursor is uniformly adsorbed on the carrier surface and in the pores. A4. Drying and pre-calcination: After impregnation, drain excess impregnation liquid from the carrier, dry it with forced air, and then vacuum dry it to completely remove moisture. Then, calcin it under N2 atmosphere and heat up. A5. Reduction and carbonization: The pre-calcined carrier is placed in a tube furnace, and an Ar / H2 mixed protective gas is introduced. After heating, the temperature is maintained to ensure that the transition metal oxide is completely reduced to the transition metal carbide. The carrier is then naturally cooled to room temperature, and the protective gas atmosphere is maintained throughout the process to prevent the product from being oxidized. A6. Post-processing: Take out the product from step A5, ultrasonically wash it to remove unreacted oxides and free carbon on the surface, vacuum dry it, seal it and store it in N2. No additional activation is required, and it can be used directly.

[0011] Using the above technical solution, the supported transition metal carbide obtained in step A6 can be used repeatedly as a catalyst without high-temperature activation. Each reuse only requires washing with anhydrous alcohol at room temperature 2-3 times (liquid-to-solid volume ratio 5-10:1, stirring at room temperature for 20-60 min) and vacuum drying at 60-80℃ for 30-60 min before it can be directly added to the next batch of reaction. After verification by 3 sets of parallel experiments, the average activity retention rate of the catalyst after 10 consecutive reuses was 92.3% (RSD < 2%). After a cumulative reuse of 100 batches, the activity retention rate was still ≥ 85%. The average regeneration rate of slightly deactivated samples after alkaline washing-oxidative decarbonization regeneration was 91.5 ± 2.1%.

[0012] If the supported transition metal carbide catalyst is deactivated, a staged regeneration process can be adopted according to the degree of deactivation: mild deactivation (only surface carbon / impurity adsorption) is regenerated by alkaline washing-oxidative decarbonization, with a regeneration rate ≥90%; moderate deactivation (slight particle agglomeration and a small amount of detachment) is regenerated by ultrasonic dispersion-precursor reloading carbonization, with a regeneration rate ≥80%; severe deactivation (severe particle agglomeration / large amount of detachment, with the support intact) is regenerated by acid dissolution-desorption-reloading, with a regeneration rate ≥75%; when the support is damaged, the single-atom active components are recovered and reloaded onto a new support to achieve resource recovery.

[0013] Supported transition metal carbide catalysts must have a purity of ≥99.5% and be free of metal oxides and other impurities; the oxide layer on the alkali metal surface must be <0.1%; all equipment, fixtures, and seals must undergo a strong alkali corrosion resistance test (5mol / L NaOH, 80℃, 48h without dissolution or deformation) to prevent impurity precipitation.

[0014] Optionally, in step A1, the carrier is cut to a size suitable for the reactor (e.g., 3×3cm, 10×10cm ring or honeycomb shape), etched, cleaned, dried, and inertized for later use; the carbon fiber mesh is etched by stirring at room temperature with 5wt% dilute nitric acid for 1-3 hours; the SiC ceramic fiber mesh is etched by stirring with 1-2mol / L sodium hydroxide solution for 1-2 hours to remove the surface passivation layer, and the processing time must be strictly controlled to avoid dissolution of the carrier matrix; after the sample is cleaned to neutral, it is calcined at 900-1100℃ in an argon atmosphere for 1-3 hours to remove surface adsorbed impurities and residual salts.

[0015] Through the above technical solutions, the preferred supports for supported transition metal carbides are carbon fiber mesh and SiC ceramic fiber mesh, while supports with poor alkali resistance such as Al2O3, SiO2, and molecular sieves are prohibited. The supports need to undergo modification pretreatment, and the specific surface area of ​​the pretreated supports should be ≥300m².2 / g, high temperature resistance ≥800℃, no hydrophilic groups, forms a strong interaction with transition metal active components, and avoids the loss of active components during reaction and washing; Optionally, in step A2, the active component precursor (industrial grade ≥99.5%) is any one or both of ammonium metatungstate and ammonium heptamolybdate, the solvent is anhydrous ethanol or deionized water, the dispersant is polyethylene glycol with a molecular weight of 500 to 1500, and the amount used is 1% to 5% of the mass of the active component precursor.

[0016] Optionally, in step A3, the vacuum treatment conditions are -0.08 to -0.1 MPa vacuum treatment for 30 min, the liquid-solid ratio in the precursor impregnation solution is 0.5:1 to 2:1, so that the carrier is just submerged, and the carrier is impregnated at normal pressure for 6 to 12 h, during which time the carrier is turned over once every 1 to 3 h.

[0017] Optionally, in step A4, the ammonium salt is dried at 80°C for 5–8 hours by forced air drying, and then vacuum dried at 120°C for 10–15 hours. The calcination conditions are as follows: the temperature is increased to 300–400°C at a rate of 2°C / min, and then calcined at this temperature for 2–5 hours to decompose the ammonium salt into transition metal oxides, while the transition metal oxides initially bind to the active sites on the carrier surface.

[0018] Optionally, in step A5, the volume fraction of H2 in the Ar / H2 mixed protective gas is 10%–20%, H2 is used as a reducing agent, Ar is used as an inert protectant, the gas flow rate is 50–100 mL / min, the temperature is increased to 700–900℃ at 1–3℃ / min, and the temperature is maintained for 3–6 h.

[0019] Optionally, in step A6, the prepared supported transition metal carbide is ultrasonically washed three times with anhydrous ethanol or anhydrous tert-butanol for 20-40 minutes each time to remove unreacted oxides and free carbon on the surface, and then vacuum dried at 100-150°C for 3-8 hours.

[0020] The application of a supported transition metal carbide catalyst in the synthesis of tertiary alcohol alkoxides involves using the aforementioned supported transition metal carbide as a catalyst to induce a proton exchange reaction between tertiary alcohols and alkali metals in a tertiary alcohol or a composite solvent of tertiary alcohol and a high-boiling-point inert solvent under the protection of anhydrous and oxygen-free inert gas, thereby generating tertiary alcohol alkali metal alkoxides.

[0021] Through the above technical solutions, existing non-catalytic or ordinary metal salt catalytic processes rely on spontaneous proton exchange between alkali metals and tertiary alcohols. This results in high energy consumption for OH bond breaking, long reaction induction times ranging from tens of minutes to several hours, and a slow overall reaction rate. In contrast, this invention uses supported transition metal carbides as catalysts in the synthesis of tertiary alcohol alkali metal alkoxides. These supported transition metal carbides possess noble metal-like catalytic properties, which can directionally weaken the OH bond energy of tertiary alcohol hydroxyl groups (from 380 kJ / mol to 220 kJ / mol), significantly reducing the proton exchange activation energy and compressing the induction period to less than 5 minutes. This fundamentally accelerates bond breaking and proton exchange rates, solving the problems of slow reaction rates and long induction periods.

[0022] Traditional processes lack selective catalysis, and high-temperature or long-term reactions easily lead to intramolecular dehydration of tertiary alcohols, generating olefin impurities, and excessive decomposition of alkali metals, producing metal oxide impurities. This results in numerous purification steps and poor product purity. In contrast, the catalyst of this invention can directionally activate hydroxyl groups (OH), specifically promoting proton exchange between hydroxyl groups and alkali metals, inhibiting the dehydration side reaction of tertiary alcohols, and reducing the generation of organic impurities and inorganic salts from the reaction source. This eliminates the need for subsequent complex distillation and recrystallization purification, directly improving the purity of the alkoxide product and solving the problems of low product purity and numerous by-products.

[0023] Existing homogeneous catalysts (soluble metal salts, small molecule catalyst promoters) are dissolved in tertiary alcohol liquid systems. After the reaction, they are miscible with the products and cannot be completely removed by distillation or extraction. The catalyst is wasted along with the mother liquor and cannot be recycled and reused. In contrast, the catalyst of this invention is a shaped solid catalyst with activated carbides supported on a carbon fiber / SiC ceramic fiber mesh skeleton. It has a regular network solid phase structure. After the reaction, it can be quickly separated from the liquid reactants / products by simple filtration and scooping. The solid phase of the catalyst is not destroyed and can be recycled and reused. This solves the problems of difficult separation, one-time consumption of catalyst, and inability to be repeatedly recycled and reused.

[0024] Conventional metal oxide and noble metal-based catalysts require high-temperature hydrogen reduction calcination activation at 300℃~600℃ before production, which is energy-intensive and cumbersome. However, the TiC / WC / Mo2C transition metal carbide in this invention has its own noble metal-like electronic structure and catalytic activity, and can exert hydroxyl activation ability at room temperature. No additional high-temperature roasting or reduction activation pretreatment is required before feeding, thus eliminating the high-temperature activation step and solving the problem of catalysts requiring high-temperature pretreatment activation.

[0025] In the process of synthesizing tertiary alcohol alkali metal alkoxides using supported transition metal carbides as catalysts, the entire process is carried out in an anhydrous and oxygen-free environment with an inert gas purity of ≥99.99%. A slight positive pressure is maintained inside the reactor to prevent backflow of air and mixing with H2 to form an explosive gas. The H2 tail gas is ignited and discharged after passing through a flame arrester. The reactor is equipped with a temperature and pressure interlock alarm device that automatically cuts off the heating power and releases Ar gas to relieve pressure in case of over-temperature or over-pressure. During operation, alkali-resistant gloves, goggles, and fireproof clothing are worn, and eyewash stations and emergency showers are provided.

[0026] Optionally, the tertiary alcohol is any one of tertiary butanol, tertiary pentanol, and tertiary hexanol; the alkali metal is any one of lithium, potassium, and sodium; the molar ratio of the tertiary alcohol to the alkali metal is 1.1 to 5:1; the high-boiling-point inert solvent is one or more of saturated alkanes, aromatic hydrocarbons, ethers, and amines; the water content of the high-boiling-point inert solvent is <0.05%; and the volume ratio of the tertiary alcohol to the high-boiling-point inert solvent is 0.5 to 2.

[0027] The above technical solution requires strict dehydration of the reaction system, with the tertiary alcohol having a moisture content of <0.05%. Equipment and pipelines (e.g., raw material storage tanks, reaction vessels, vacuum distillation vessels, solvent receiving tanks, product receiving tanks, buffer tanks, condensers, material conveying pipelines, and gas conveying pipelines) must be vacuum-dried at 150°C for 2 hours to prevent moisture from reacting with alkali metals and products to form hydroxide impurities, which would reduce catalyst activity. The principle for the ratio of tertiary alcohol to alkali metal is to ensure complete reaction, thorough dissolution, and no waste of raw materials. Alkali metals are added in small solid pieces or dropwise to the reaction system under heating. The reaction system can use tertiary alcohol alone as a solvent, or a mixture of tertiary alcohol and a high-boiling-point inert solvent can be used to improve boiling point and solubility.

[0028] The liquid droplet feeding method makes the process more controllable, the temperature and the reaction rate controllable, and transforms the reaction system into a liquid-liquid reaction, which accelerates the reaction rate, increases the contact area of ​​the raw materials, and makes the reaction more complete.

[0029] Using a mixture of tertiary alcohol and a high-boiling-point inert solvent can increase the reaction temperature, accelerate the reaction rate, and shorten the reaction time. By controlling the solvent ratio and distillation timing, granular products can be produced, making the product properties more favorable for downstream applications and reducing dust pollution.

[0030] After adopting the above technical solution, the beneficial effects of the present invention are: 1. This invention uses pretreated carbon fiber / silicon carbide fiber mesh as a carrier to load transition metal carbide active components. Through the spatial confinement effect of the carrier and the strong interaction between the carrier and the active components, the catalyst can be reused repeatedly without high-temperature activation. This solves the technical pain points of traditional synthesis processes, such as slow reaction rate, many product impurities, difficulty in catalyst separation, and the need for high-temperature activation for reuse. This process is simple to operate, safe and controllable, and suitable for the synthesis of various tertiary alcohol alkali metal alkoxides such as potassium tert-butoxide, sodium tert-butoxide, and sodium tert-pentoxide, and has extremely high industrial application value.

[0031] 2. This invention addresses the technical pain points of existing tertiary alcohol alkali metal alkoxide synthesis processes, such as slow reaction rates, numerous product impurities, high safety risks, and high production costs. This invention constructs a strong alkali-resistant and high-temperature-resistant supported transition metal carbide to improve catalytic efficiency, optimize product purity, and enable catalyst reuse without separation or high-temperature activation, thereby reducing production costs and improving production safety.

[0032] 3. The present invention has high catalytic efficiency and fast reaction rate: the active components of the supported transition metal carbide catalyst are uniformly dispersed and the active site exposure rate is ≥90%, which can efficiently activate tertiary alcohol hydroxyl groups, shorten the reaction induction period to <5min, shorten the reaction time by 20% to 30%, the reaction conversion rate is ≥99%, the product yield is ≥98%, and the production efficiency is greatly improved.

[0033] 4. The product of this invention has high purity and low impurity content: the active component has high selectivity and can effectively inhibit the dehydration side reaction of tertiary alcohol, with by-products <1.0%. At the same time, the catalyst does not need to be separated, avoiding catalyst impurities from contaminating the product. The product purity is ≥99.0%, which can meet the needs of high-end applications in pharmaceuticals and electronics.

[0034] 5. The catalyst of this invention can be reused without separation or high-temperature activation, which greatly reduces costs: The catalyst module is fixed inside the reactor, and the product is directly output, eliminating the steps of filtration and centrifugation, and the product loss rate is reduced from 3% to 5% to <0.5%; the catalyst can be reused only by washing at room temperature and drying at low temperature, without the need for high-temperature activation above 800℃, reducing energy consumption by more than 70%, and can be reused continuously for ≥100 batches, reducing the overall production cost by more than 30%.

[0035] 6. This invention is alkali-resistant, high-temperature resistant, and highly stable: the carrier is made of a material resistant to strong alkalis and high temperatures, which forms a strong interaction with transition metals. The catalyst does not dissolve or lose active components in a reaction system with pH > 14 and temperature ≤ 120℃, and the loss rate after a single reuse is < 0.5%.

[0036] 7. This invention is safe and controllable, and suitable for industrial production: the entire process is water-free and oxygen-free, the materials are mixed evenly, avoiding local overheating and hydrogen accumulation, and reducing the risk of deflagration; the equipment modification cost is low (only 5% to 8% of the total equipment price), the modification cycle is short (1 to 3 days), and the operation steps are simplified by more than 50%, making it suitable for the technological upgrading of small and medium-sized enterprises and large-scale industrial production.

[0037] 8. The system of this invention has wide adaptability: it can be directly adapted and applied to the synthesis of various tertiary alcohol alkali metal alkoxides such as potassium tert-butoxide, sodium tert-butoxide, and sodium tert-pentoxide. Only the reaction temperature and material residence time need to be adjusted. The catalytic module does not need to be replaced, which is highly flexible. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0039] This application discloses supported transition metal carbide catalysts, their preparation methods, and applications of tertiary alcohol alkoxides.

[0040] I. Implementation Examples Example 1

[0041] A method for synthesizing potassium tert-butoxide via a supported Mo2C@SiC ceramic fiber mesh catalysis is detailed below: 1. Preparation of supported Mo2C@SiC ceramic fiber mesh catalyst: (1) Carrier pretreatment: Cut the SiC ceramic fiber mesh into a ring-shaped hollow sheet (outer diameter 390mm, inner diameter 60mm, thickness 15mm), add 1-2 mol / L sodium hydroxide, stir for 1-2h to etch, prevent carrier corrosion, wash until neutral, place in 1000℃ argon gas for 1h to remove surface oxide layer, vacuum dry at 105℃ for 12h for later use; (2) Preparation of precursor impregnation solution: Take ammonium heptamolybdate ((NH4)6Mo7O 24 21.8 kg of 4H2O (industrial grade ≥99.5%) was dissolved in 436 kg of anhydrous ethanol, and 1.09 kg of polyethylene glycol 1000 was added. The mixture was stirred at room temperature for 30 min until completely dissolved to prepare a 0.3 mol / L impregnation solution (calculated based on a Mo2C loading of 10 wt%). (3) Vacuum impregnation with equal volume: The pretreated SiC grid is placed in a vacuum drying oven and vacuum-treated at -0.09MPa for 30 min. Impregnation solution is added and impregnated at normal pressure for 8 h. During this period, the grid is turned over once every 2 h. (4) Drying and pre-calcination: Drying at 80℃ for 6 hours, vacuum drying at 120℃ for 12 hours, and then calcining at 350℃ for 2 hours under N2 atmosphere to obtain MoO3 / SiC precursor; (5) Reduction carbonization: The precursor is placed in a tube furnace and Ar / H2 mixed gas (H2 volume fraction 15%) is introduced. The gas flow rate is 80 mL / min, the temperature is increased to 850℃ at 3℃ / min, and the temperature is held for 4 hours. Then it is naturally cooled to room temperature. (6) Post-treatment: Ultrasonic washing with anhydrous tert-butanol three times, vacuum drying at 105℃ for 6h to obtain supported Mo2C@SiC ceramic fiber mesh (Mo2C loading 10wt%), sealed and stored under N2.

[0042] 2. Synthesis method of potassium tert-butoxide: (1) Equipment pretreatment: 50L strong alkali resistant high pressure reactor (lined with polytetrafluoroethylene), pipeline vacuum dried at 120℃ for 4h, high purity N2 (purity ≥99.99%) was introduced, and the flow rate was 50mL / min for 3 to 5 replacements; the prepared catalyst module (6 pieces, total weight 7.2kg, accounting for 10% of the effective reaction volume) was fixed in the reactor to ensure that it could contact the reaction system without affecting the stirring; (2) Feeding: Under N2 protection, add 30kg of anhydrous tert-butanol (moisture < 0.05%) and 30kg of mixed xylene, start stirring (50r / min), and slowly add 10.8kg of small pieces of metallic potassium (250g each time, 2min interval). (3) Reaction: The stirring speed is gradually increased and eventually stabilized at 300-400 r / min, the temperature is stabilized at about 110-125℃, the reaction is carried out for 2.5 h, and the hydrogen tail gas is ignited. (4) Product output: After the reaction is completed, the product is discharged from the bottom outlet under a slight positive pressure of 0.03 MPa N2 and concentrated by vacuum distillation (-0.09 MPa, 45℃) to obtain 30.7 kg of potassium tert-butoxide solid; (5) Catalyst reuse: After the reaction is completed, 160 kg of anhydrous tert-butanol is introduced into the reactor, stirred at room temperature for 20 min and washed, vacuum dried at 60℃ for 30 min, and directly added to the next batch of reaction without activation.

[0043] 3. Testing method: Enterprise testing standard Q / LH0032021 (1) Determination of total alkali: Weigh about 0.5 g of the sample (accurate to 0.0002 g) and place it in a dry 100 mL iodine flask. Add about 20 mL of distilled water (boiled and cooled) to dissolve the sample, shake well and let stand for 5 min. Add 3 drops of 1% phenolphthalein indicator and titrate with 0.5 mol / L hydrochloric acid standard solution until the endpoint is reached. The total alkali content of potassium tert-butoxide is expressed as a mass fraction and calculated by the following formula: X1=C*V*0.11221 / m*100%, where: C represents the concentration of hydrochloric acid standard solution (mol / L); V represents the volume of hydrochloric acid standard solution consumed (mL); and m represents the mass of the sample (g).

[0044] (2) Determination of free base: Add 5 mL of benzoic acid methanol solution and 15-20 mL of methanol as mother liquor to the reaction flask, enough to cover the electrodes. Titrate with Karl Fischer reagent until the galvanometer pointer deflects significantly and remains constant for 30 seconds, which is the endpoint. Do not account for the amount consumed. Then weigh approximately 0.5 g of the sample (accurate to 0.0002 g) and quickly add it to the reaction flask. Titrate with Karl Fischer reagent until the galvanometer pointer deflects as significantly as in the blank experiment and remains constant for 30 seconds, which is the endpoint. Record the volume of Karl Fischer reagent consumed. The water content by mass percentage is calculated using the following formula: X2 = T * V / m * 100%. Where, T represents the titer of Karl Fischer reagent for water (g / mL); V represents the volume of Karl Fischer reagent consumed in titrating the sample (mL); m represents the sample mass (g). The arithmetic mean of two parallel determinations is taken as the determination result, and the difference between the two parallel determinations should not exceed 0.1%. Then, calculate the free alkali content according to the formula X3 = 3.111X2, where 3.111 is the conversion factor for water to potassium hydroxide.

[0045] 4. Test Results: The product yield was 98.5%, the purity was 99.7%, and the free alkali and other byproducts were <0.3%; the reaction induction period was 4 min, and there were no obvious side reactions; the catalyst was reused 10 times, and the activity retention rate was 92.3%, with a single loss rate of 0.42%; after 100 reuses, regeneration was performed, and the activity was restored to over 98%; the overall production cost was reduced by 30% compared with the traditional powder catalyst process.

[0046] Example 2

[0047] The method for synthesizing sodium tert-butoxide via a supported WC-Mo2C@carbon fiber mesh catalysis is detailed below: 1. Preparation of supported WC-Mo2C@carbon fiber mesh catalyst: (1) Carrier pretreatment: carbon fiber mesh is cut into honeycomb modules (pore size 12mm, porosity 78%), 5wt% dilute nitric acid is added and stirred at room temperature for 1h, filtered, washed with anhydrous ethanol until neutral, vacuum dried at 120℃ for 2h, and calcined at 300℃ in N2 atmosphere for 1h for later use. (2) Preparation of precursor impregnation solution: Take ammonium metatungstate and ammonium heptamolybdate and mix them in a molar ratio of 1:2 (total mass 25kg), dissolve them in 500kg of deionized water, add 0.75kg of polyethylene glycol 2000, stir for 30min until dissolved, and prepare a 0.4mol / L impregnation solution; (3) Vacuum impregnation of equal volume: the carrier is degassed under vacuum for 30 min, impregnation liquid is added, impregnated under normal pressure for 10 h, dried and pre-calcined (350℃, 2 h); (4) Drying and pre-calcination: Drying at 80℃ for 8 hours, vacuum drying at 120℃ for 14 hours, and then calcining at 400℃ for 1.5 hours under N2 atmosphere with a temperature increase of 2℃ / min to obtain MoO3-WO3 / carbon fiber precursor; (5) Reduction carbonization: Ar / H2 mixed gas (H2 volume fraction 12%), flow rate 100 mL / min, temperature increased to 780℃ at 2℃ / min, held for 5h, and then naturally cooled to room temperature; (6) Post-treatment: Ultrasonic washing with anhydrous ethanol 3 times, vacuum drying at 120℃ for 5h to obtain the supported WC-Mo2C@carbon fiber mesh (WC-Mo2C loading 15wt%), sealed and stored under N2.

[0048] 2. Synthesis method of sodium tert-butoxide: (1) Raw material pretreatment: 40L of anhydrous tert-butanol (moisture content < 0.05%) and 25L of octane were mixed under N2 protection; (2) Continuous feeding preheating: the preheater temperature is 105℃, the preheating pressure is 0.02MPa, the constant flow feed pump flow rate is 10L / h, and 7kg of preheated liquid sodium is slowly added into the reaction system; (3) Catalytic reaction: The reactor temperature is 100-120℃, the pressure is 0.04MPa, the material reaction time is 3.5h, the stirring speed is 300-500rpm, the guide plate guides the material to flow through the honeycomb catalytic module, and the module ensures that it can contact the reaction system without affecting the stirring. (4) Product output: After the reaction is completed, the product is discharged from the bottom outlet under a slight positive pressure of N2 of 0.02MPa and concentrated by vacuum distillation (-0.09MPa, 45℃) to obtain 28.9kg of sodium tert-butoxide solid; (5) Catalyst reuse: After the reaction is completed, 150 kg of anhydrous tert-butanol is introduced into the reactor, stirred at room temperature for 30 min and washed, and vacuum dried at 90℃ for 30 min. It can then be directly added to the next batch of reaction without activation.

[0049] 3. Testing method: Q / LH004-2021 Enterprise Testing Standard (1) Determination of total alkali: Weigh approximately 0.5 g of the sample (accurate to 0.0002 g) into a dry 100 mL iodine flask, add approximately 20 mL of distilled water (boiled and cooled) to dissolve, shake well, and let stand for 5 min. Add 3 drops of 1% phenolphthalein indicator, and titrate with 0.5 mol / L hydrochloric acid standard solution until the solution becomes colorless. Express the total alkali content of sodium tert-butoxide as a mass fraction, and calculate using the following formula: X1 = C * V * 0.09610 / m * 100%, where: C represents the concentration of hydrochloric acid standard solution (mol / L); V represents the volume of hydrochloric acid standard solution consumed (mL); and m represents the mass of the sample (g).

[0050] (2) Determination of free base: Add 5 mL of benzoic acid methanol solution and 15–20 mL of methanol as the mother liquor to the reaction flask, ensuring the electrodes are submerged. Titrate with Karl Fischer reagent until the galvanometer pointer shows a significant deflection that remains constant for 30 seconds; this is the endpoint, and the amount consumed is negligible. Then weigh approximately 0.5 g of the sample (accurate to 0.0002 g) and quickly add it to the reaction flask. Titrate with Karl Fischer reagent until the galvanometer pointer shows the same significant deflection as in the blank experiment and remains constant for 30 seconds; this is the endpoint, and record the volume of Karl Fischer reagent consumed. The water content by mass percentage is calculated using the following formula: X² = T * V / m * 100%. Where T represents the Karl Fischer reagent titer for water (g / mL); V represents the volume of Karl Fischer reagent consumed in titrating the sample (mL); and m represents the sample mass (g). The arithmetic mean of two parallel determinations is taken as the final result, and the difference between the two parallel determinations should not exceed 0.1%. Then, calculate the free alkali content according to the formula: X3 = 2.222X2, where 2.222 is the conversion factor for water to sodium hydroxide.

[0051] 4. Test Results: The product yield was 98.0%, the purity was 99.3%, and the free base and other byproducts were <0.7%. The reaction induction period was 5.5 min, and there were no obvious side reactions. The catalyst was continuously run 12 times, and the activity retention rate was 91.7%. The single loss rate was 0.39%. After being reused 100 times, the catalyst was regenerated, and the activity was restored to more than 97%.

[0052] Example 3

[0053] The synthesis method of sodium tert-amyl alcohol by supported Mo2C@SiC fiber mesh catalysis is detailed below: 1. Catalyst preparation: The supported Mo2C@SiC fiber mesh catalyst was prepared using the same method as in Experiment 1, resulting in a supported Mo2C@SiC fiber mesh (Mo2C loading 8wt%). 2. Synthesis process: The molar ratio of tert-amyl alcohol to sodium metal is 1.25:1. Sodium metal is added dropwise in liquid form. The reaction temperature is 110-130℃, the stirring speed is 400 r / min, the reaction time is 3h, and other steps are the same as in Example 1. 3. Test methods and results: Tested according to Q / 320411 ATU 002-2017, the product yield was 98.1%, the purity was 99.4%, and the reaction induction period was 6 min; the catalyst was reused 100 times and the activity retention rate was 90.5%.

[0054] II. Comparative Example Comparative Example 1 This comparative example presents a method for synthesizing potassium tert-butoxide via azeotropic distillation. The method includes the following steps: 105.6 kg of tert-butanol and 10.8 kg of potassium hydroxide aqueous solution (50% purity, containing 10.8 kg of water) are weighed and fed into a static mixer via metering pumps from storage tanks, then enter the top of a distillation column; the top vapor is cooled by a condenser and then enters a phase separator for separation. The lower aqueous phase leaves the system, while the upper oil phase, containing tert-butanol and the azeotropic agent cyclohexane, is refluxed into the column for azeotropic distillation and dehydration; the tert-butanol solution of the product potassium tert-butoxide is collected from the bottom of the column, which is heated by steam. The azeotropic agent cyclohexane is added at the phase separator. The top temperature is controlled at approximately 70°C, and the bottom temperature at approximately 87°C. An azeotrope of tert-butanol, water, and cyclohexane was distilled from the top of the column. After reacting for 300 minutes, 100.8 kg of the top condensate was obtained and entered into a phase separator. 166.2 kg of potassium tert-butoxide in tert-butanol was obtained from the bottom of the column and placed in a desiccator. Distillation was continued until complete crystallization, yielding 12.1 kg of granular potassium tert-butoxide with a purity of 98.1%, a yield of 54.9%. This comparative example shows that the traditional azeotropic distillation method, using alkaline solution as raw material, is severely affected by moisture, resulting in incomplete reaction and low product purity and yield. It also has poor process efficiency and no recycling value. Overall, the process economy and product quality are far inferior to the Mo2C@SiC ceramic fiber mesh catalytic process in Example 1.

[0055] Comparative Example 2 This comparative example provides a method for synthesizing sodium tert-butoxide via an amino-alkali metal process. The method includes the following steps: In a 500L reactor equipped with a stirrer, reflux condenser, and thermometer, 240L of dry toluene, 9.8kg of sodium amine, and 19.0g of tert-butanol are added. The mixture is stirred thoroughly until completely dissolved. The temperature is raised to 70℃ to initiate the reaction. The released ammonia gas is absorbed by water or alkaline solution. The reaction temperature is raised to 100-110℃ and held for 1.5 hours to stop the reaction. After the reaction is complete, the reactants are cooled. Most of the reaction medium and a slight excess of tert-butanol are distilled off under normal pressure. The remaining small amount of reaction medium is then distilled off under reduced pressure. Low-temperature nitrogen gas (-20℃) is blown into the reactor through the bottom valve to cool it to below 40℃. The mixture is then discharged under vacuum to obtain 23.2kg of white sodium tert-butoxide solid particles with a purity of 98.6% and a yield of 95.1%. As can be seen from the comparison, although the amino-alkali metal method can produce high-purity products, it has problems such as exhaust gas pollution, special raw materials, and slow reaction start-up. The catalytic process in Example 2 has a fast reaction start-up, no waste gas emissions, and better product indicators. Combined with the advantage of catalyst recycling, the overall production cost is lower, and it is more green and economical.

[0056] Comparative Example 3 This comparative example provides a method for synthesizing sodium tert-amyl alcohol by a metal method. The method includes the following steps: In a 2500L reactor equipped with a mechanical stirrer, thermometer, and reflux condenser, 320kg of tert-amyl alcohol, 1000kg of dried toluene, and 53kg of small pieces of metallic sodium are added. Under nitrogen protection, the mixture is refluxed at 100-110℃ for 10 hours until the metallic sodium is completely eliminated. Excess residual tert-amyl alcohol and toluene mother liquor are distilled off under normal pressure. The remaining small amount of reaction medium is then distilled off under reduced pressure to obtain off-white potassium tert-amyl alcohol solid. Low-temperature nitrogen gas (-20℃) is blown into the reactor through the bottom valve to cool it to below 40℃. Vacuum discharge yields the desired off-white granular sodium tert-amyl alcohol of 245.2kg, with a purity of 98.9% and a yield of 93.9%. As can be seen from the comparative example, conventional metal alkalization reactions do not require catalysts, but the reaction rate is slow, the production cycle is long, and the post-processing is complex. In contrast, the supported Mo2C@SiC fiber mesh catalyst in Example 3 can significantly accelerate the alcohol-base reaction, shorten the working time while ensuring high purity, and the catalyst can be recycled, making it more suitable for large-scale continuous production.

[0057] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A supported transition metal carbide catalyst, characterized in that, The catalyst includes a support and an active component supported on the support, wherein the support is a carbon fiber mesh or a SiC ceramic fiber mesh, and the active component is selected from at least one of WC and Mo2C. The loading of the active component is 8-15 wt%, and the carrier, after pretreatment, has a specific surface area ≥300 m². 2 / g.

2. A method for preparing supported transition metal carbides, characterized in that, This method employs an impregnation-carbothermic reduction process, and the specific steps are as follows: A1. Carrier pretreatment: The carrier is a carbon fiber mesh or a SiC ceramic fiber mesh. The carrier is subjected to acid and alkali treatment, stirring and etching in sequence, and then the carrier is washed to neutral and calcined with argon gas. A2. Preparation of precursor impregnation solution: Dissolve the active component precursor in a solvent, add a dispersant, stir until completely dissolved, and prepare a transparent impregnation solution of 0.1-0.5 mol / L, wherein the active component precursor is a transition metal ammonium salt; A3. Vacuum impregnation with equal volume: Place the pretreated carrier in step A1 in a vacuum drying oven. After vacuum treatment, the carrier pores are fully degassed. Then, the precursor impregnation liquid is quickly added and impregnated at normal pressure so that the precursor is uniformly adsorbed on the carrier surface and in the pores. A4. Drying and pre-calcination: After impregnation, drain excess impregnation liquid from the carrier, dry it with forced air, and then vacuum dry it to completely remove moisture. Then, calcin it under N2 atmosphere and heat up. A5. Reduction and carbonization: The pre-calcined carrier is placed in a tube furnace, and an Ar / H2 mixed protective gas is introduced. After heating, the temperature is maintained to ensure that the transition metal oxide is completely reduced to the transition metal carbide. The carrier is then naturally cooled to room temperature, and the protective gas atmosphere is maintained throughout the process to prevent the product from being oxidized. A6. Post-processing: Take out the product from step A5, ultrasonically wash it to remove unreacted oxides and free carbon on the surface, vacuum dry it, and seal it for storage with N2.

3. The method for preparing a supported transition metal carbide according to claim 2, characterized in that, In step A1, the carbon fiber mesh is etched by stirring at room temperature for 1-3 hours with 5wt% dilute nitric acid, and the SiC ceramic fiber mesh is etched by stirring with 1-2mol / L sodium hydroxide for 1-2 hours to remove the surface silica layer. After washing to neutrality, it is calcined in an argon atmosphere at 900-1100℃ for 1-3 hours to remove surface adsorbed impurities and residual salts.

4. The method for preparing a supported transition metal carbide according to claim 2, characterized in that, In step A2, the active component precursor is any one or both of ammonium metatungstate and ammonium heptamolybdate, the solvent is anhydrous ethanol or deionized water, and the dispersant is polyethylene glycol with a molecular weight of 500 to 1500, and the amount used is 1% to 5% of the mass of the active component precursor.

5. The method for preparing a supported transition metal carbide according to claim 2, characterized in that, In step A3, the vacuum treatment conditions are -0.08 to -0.1 MPa vacuum treatment for 30 minutes, and the liquid-solid ratio in the precursor impregnation solution is 0.5:1 to 2:1, impregnated at normal pressure for 6 to 12 hours, with the sample turned over every 1 to 3 hours during the process.

6. The method for preparing a supported transition metal carbide according to claim 2, characterized in that, In step A4, the ammonium salt is dried at 80℃ for 5-8 hours by forced air drying, and then vacuum dried at 120℃ for 10-15 hours. The calcination conditions are as follows: the temperature is increased to 300-400℃ at a rate of 2℃ / min, and then calcined at this temperature for 2-5 hours to decompose the ammonium salt into transition metal oxides, and at the same time, the transition metal oxides are initially combined with the active sites on the surface of the support.

7. The method for preparing a supported transition metal carbide according to claim 2, characterized in that, In step A5, the volume fraction of H2 in the Ar / H2 mixed protective gas is 10%–20%, H2 acts as a reducing agent, and Ar acts as an inert protectant. The gas flow rate is 50–100 mL / min, and the temperature is increased to 700–900℃ at a rate of 1–3℃ / min and held for 3–6 hours.

8. The method for preparing a supported transition metal carbide according to claim 2, characterized in that, In step A6, the prepared supported transition metal carbide is ultrasonically washed three times with anhydrous ethanol or anhydrous tert-butanol for 20-40 minutes each time to remove unreacted oxides and free carbon on the surface, and then vacuum dried at 100-150°C for 3-8 hours.

9. The application of a supported transition metal carbide catalyst in the synthesis of tertiary alcohol alkoxides, characterized in that, Using the supported transition metal carbide described in claim 1 as a catalyst, under the protection of anhydrous and oxygen-free inert gas, tertiary alcohols and alkali metals undergo a proton exchange reaction in a tertiary alcohol or a composite solvent of tertiary alcohol and a high-boiling-point inert solvent to generate tertiary alcohol alkali metal alkoxides.

10. The application of the supported transition metal carbide catalyst according to claim 9 in the synthesis of tertiary alcohol alkoxides, characterized in that, The tertiary alcohol is any one of tertiary butanol, tertiary amyl alcohol, and tertiary hexanol; the alkali metal is any one of lithium metal, potassium metal, and sodium metal; the molar ratio of the tertiary alcohol to the alkali metal is 1.1 to 5:1; the high-boiling-point inert solvent is one or more of saturated alkanes, aromatic hydrocarbons, ethers, and amines; the water content of the high-boiling-point inert solvent is <0.05%; and the volume ratio of the tertiary alcohol to the high-boiling-point inert solvent is 0.5 to 2.