A preparation device and method for continuously synthesizing methyl formate from carbon monoxide and methanol

Abstract

The application discloses a preparation device and a preparation method for continuously synthesizing methyl formate from carbon monoxide and methanol. The device comprises a gas-liquid countercurrent reaction unit, a gas phase circulation unit and a liquid phase treatment and recycling unit. The gas-liquid countercurrent reaction unit adopts a packed tubular reactor, which is internally provided with a packed bed and a gas-liquid distributor to form a gas-liquid countercurrent contact channel. The gas phase circulation unit comprises a condenser, a settling tank, a booster pump, a gas buffer tank and a gas preheater to realize gas phase recycling. The liquid phase treatment and recycling unit comprises a liquid buffer tank, a rectifying tower and a liquid mixer to realize product separation and unreacted substance recycling. The device realizes continuous and efficient synthesis of methyl formate from carbon monoxide and methanol through gas-liquid countercurrent contact reaction, and the purity of the obtained methyl formate product is not less than 97.01%. The application solves the problems of low reaction efficiency and unstable product quality in traditional batch reaction, and realizes continuous and efficient production of methyl formate.

Description

Technical Field

[0001] This application relates to an apparatus and method for the continuous synthesis of methyl formate from carbon monoxide and methanol, belonging to the field of chemical equipment technology. Background Technology

[0002] Methyl formate, as an important chemical intermediate and solvent, is widely used in pharmaceuticals, pesticides, fragrances, and other fields. Currently, the industrial production of methyl formate mainly adopts the carbonylation reaction route of methanol and carbon monoxide, which is usually carried out in the presence of a metal alkoxide catalyst.

[0003] However, existing technologies mostly employ single alkali metal alkoxide catalytic systems, which are prone to forming tight ion pairs, resulting in limited effective nucleophile species concentrations. They are also sensitive to impurities such as moisture and carbon dioxide, and are prone to problems such as activity decay and insufficient catalyst lifetime during long-term operation. Therefore, it is necessary to provide a composite catalyst system in which component A and component B work synergistically to improve reaction rate, volumetric yield, and extend stable operation period while maintaining selectivity.

[0004] Traditional methanol carbonylation processes often use single alkali metal alkoxides (such as sodium methoxide / potassium methoxide) as catalysts. These catalytic systems suffer from problems such as difficulty in separating ion pairs, sensitivity to water / impurities leading to activity fluctuations, and easy deactivation. Higher pressure or longer residence time is often required to obtain higher conversion rates. Therefore, it is urgent to introduce synergistic promoters to construct composite catalyst systems, which can improve reaction rates and catalyst lifetimes while ensuring selectivity.

[0005] Existing methyl formate production technologies mainly include two process routes: batch reaction and continuous reaction. Chinese patent CN107935856B discloses an energy-saving methyl formate production device, which prepares a mixed gas through methanol dehydrogenation, and then separates the methyl formate product in a distillation column. Chinese patent CN103951558B discloses a device for producing methyl formate by gas-phase methanol carbonylation, using a fixed-bed reactor for atmospheric pressure reaction. Chinese patent CN1271038C describes a reaction method of methanol and carbon monoxide at 0.5-10 MPa pressure and 50-150℃ temperature, separating the methyl formate entrained in the gas stream by condensation and recycling the remaining gas stream. Furthermore, Chinese patent CN116265055A discloses a product separation and purification device for methyl formate produced by carbon monoxide esterification, and Chinese patent CN112939777A discloses a continuous reaction device for the one-step oxidation of methanol to produce methyl formate.

[0006] However, existing technologies still have many technical shortcomings in the continuous production of methyl formate: First, the strong backmixing in batch or external circulation mixing reactors leads to more homogeneous components in the reaction zone, causing methyl formate to accumulate throughout the reaction zone, which reduces the driving force of the reaction over time and affects the reaction efficiency. Second, the co-current operation scheme of tubular reactors lacks effective reverse contact and mass transfer enhancement methods. Limited by the effective gas-liquid contact interface area, it is difficult to form a favorable axial product distribution through structure to alleviate product accumulation inhibition. Third, existing continuous production units mostly adopt overall reactor isothermal or single-point temperature control, making it difficult to simultaneously achieve upper kinetic acceleration and lower equilibrium optimization in the same reactor, resulting in a low concentration of methyl formate in the output, increasing the load and energy consumption of subsequent distillation separation. Finally, problems such as circulating gas entraining liquid into the pressurization equipment causing operational risks, mutual transmission of reaction and distillation load fluctuations leading to system fluctuations, and catalyst being carried out with the product leading to increased replenishment amount seriously affect the long-term stable operation of the unit. Summary of the Invention

[0007] To address the technical challenges in existing reactors for the continuous synthesis of methyl formate from carbon monoxide and methanol, such as strong backmixing leading to product accumulation inhibition, insufficient gas-liquid contact, strong coupling between reaction and separation, limited temperature control, and unstable system operation, this paper provides a preparation apparatus and method for the continuous synthesis of methyl formate from carbon monoxide and methanol. This method aims to achieve efficient gas-liquid mass transfer, axial concentration gradient distribution, decoupling of reaction and separation, optimized temperature gradient, and long-term stable operation.

[0008] The technical solution adopted by this application to solve its technical problem is: In a first aspect, this application provides an apparatus for the continuous synthesis of methyl formate from carbon monoxide and methanol, comprising: The gas-liquid countercurrent reaction unit includes a packed tubular reactor, which is provided with a top liquid inlet, a bottom gas inlet, a top gas phase outlet and a bottom liquid phase outlet. The internal structure is provided with a packing bed and gas distributors and liquid distributors for uniform gas-liquid distribution to form a gas-liquid countercurrent contact channel. The gas phase circulation unit has its inlet connected to the top gas phase outlet of the packed tubular reactor, and sequentially includes a condenser and a settling tank for condensing the gas phase and separating entrained liquid along the flow direction, as well as a booster pump and a gas buffer tank for pressurizing and buffering the gas; the outlet of the gas buffer tank is connected to the bottom air inlet of the packed tubular reactor via a gas preheater, and a fresh carbon monoxide inlet is provided upstream of the gas preheater. The liquid phase treatment and reuse unit has its inlet connected to the bottom liquid phase outlet of the packed tubular reactor and includes a liquid buffer tank and a distillation column. The top of the distillation column is used to output methyl formate product, and the bottom outlet of the column is connected to the top liquid inlet of the packed tubular reactor through a liquid mixer. The liquid mixer is also equipped with a fresh methanol inlet. The liquid phase separated from the settling tank is recycled to the liquid phase treatment and reuse unit.

[0009] Furthermore, the packed tubular reactor is configured to form a methyl formate concentration gradient in the axial direction, and the methyl formate concentration at the bottom liquid outlet of the packed tubular reactor is higher than the methyl formate concentration at the top inlet.

[0010] Furthermore, the packed tubular reactor is provided with a temperature gradient along the axial direction, and the temperature of the top reaction zone is higher than that of the bottom reaction zone.

[0011] Furthermore, the reaction pressure of the packed tubular reactor is 1-5 MPa, the temperature of the top reaction zone is 70-150℃, and the temperature of the bottom reaction zone is 50-120℃.

[0012] Furthermore, the packing material in the packed tubular reactor is selected from at least one of Raschig rings, Pall rings, stepped rings, grid packing, and corrugated packing; Preferably, the liquid distributor is at least one of a spray disc, a trough distributor, or a perforated distribution plate; Preferably, the gas distributor is at least one of a porous distribution plate, a sieve plate, or a nozzle distributor.

[0013] Furthermore, the outer wall of the packed tubular reactor is provided with at least two independent temperature control zones along the axial direction, and the set temperature of the upper temperature control zone is 5-40°C higher than the set temperature of the lower temperature control zone.

[0014] Furthermore, the mixture of unreacted methanol and catalyst output from the bottom of the distillation column is mixed with fresh methanol in the liquid mixer and then refluxed to the top of the packed tubular reactor.

[0015] Secondly, this application also provides a method for continuously preparing methyl formate using the preparation apparatus described in the first aspect above, comprising the following steps: A reaction solution containing a composite catalyst is prepared, wherein the composite catalyst comprises component A and component B; wherein component A is sodium methoxide and / or potassium methoxide, and component B is a metal complex / complex type promoter containing multiple coordination sites; the total mass fraction of the composite catalyst is 0.1-10%; recycled carbon monoxide is mixed with fresh carbon monoxide and preheated, and then continuously introduced into the bottom of the packed tubular reactor. The recycled stream from the distillation column bottom is mixed with fresh methanol and preheated before being continuously fed into the top of the packed tubular reactor. In a packed tubular reactor, the gas and liquid phases react in countercurrent contact at a pressure of 1-5 MPa. An axial temperature gradient is formed in the packed tubular reactor, with the temperature in the top reaction zone being 70-150℃ and the temperature in the bottom reaction zone being 50-120℃. The gas phase discharged from the top of the packed tubular reactor is condensed, separated by sedimentation, pressurized, and circulated back to the bottom of the packed tubular reactor; The liquid phase discharged from the bottom of the packed tubular reactor is buffered and then sent to a distillation column for separation. Methyl formate is obtained at the top of the column, and the bottom stream is refluxed back to the top of the packed tubular reactor. Preferably, the catalyst is a composite catalyst composed of two substances, comprising component A and component B; component A is sodium methoxide and / or potassium methoxide (preferably potassium methoxide), and component B is a metal complex / complex-type promoter containing multiple coordination sites, the molecular structure of which is as follows: Figure 3 As shown, the metal center M is Fe, Ni, Co, Mo, W or Mn; Preferably, the mass fraction of component A in the reaction solution is 0.1-10%, and the mass fraction of component B in the reaction solution is 0.001-1%. Preferably, component B is characterized in that: component B is a complex / complex formed by a chelating ligand L with multiple coordination sites and a metal center M, wherein the skeletal structure of ligand L is as follows: Figure 3 As shown, component B activates CO and works synergistically with sodium methoxide / potassium methoxide to increase the rate of key carbonylation steps; at the same time, it stabilizes active species, inhibits deactivation, and extends catalyst lifetime and continuous operation stability. Preferably, component B is prepared by the following method: under a CO atmosphere, ligand L is mixed and reacted with anhydrous metal salt (selected from one or more of chloride, nitrate, acetate, and acetylacetonate) in an alcohol solvent or a polar organic solvent, and the reaction is controlled at 20-120℃ for 0.5-24 h to obtain a metal complex / complex; the complex is obtained by precipitation, filtration, washing and drying.

[0016] Furthermore, the reaction pressure is 2-3 MPa, the temperature of the top reaction zone is 80-120℃, and the temperature of the bottom reaction zone is 60-90℃.

[0017] Furthermore, the methyl formate product obtained from the top of the distillation column has a purity of not less than 97.01%.

[0018] Compared with the prior art, the beneficial effects of the present invention include at least the following: Compared with existing technologies, the packed bed significantly increases the gas-liquid contact area per unit volume and promotes liquid film renewal, improving the volumetric mass transfer coefficient and alleviating the limitation of insufficient gas-liquid contact area. An axial methyl formate concentration gradient is formed through continuous counter-current gas-liquid contact, preventing the product from accumulating uniformly in the reaction zone. High-concentration methyl formate at the bottom is promptly carried out, improving the utilization of reaction driving force and single-pass conversion rate. The carbon monoxide gas phase at the top is condensed and settled, then pressurized, buffered, and circulated back to the bottom of the reactor in a closed loop, reducing tail gas emissions and raw material loss. Pressure and flow stabilization are achieved through a gas buffer tank. Separate setup of the reaction and distillation separation equipment reduces fluctuations caused by strong coupling between reaction and distillation. Decoupling of the liquid buffer tank and mixing / preheating unit facilitates long-term stable operation. An axial temperature gradient accelerates the reaction in the upper part and shifts the equilibrium to the right in the lower part, increasing the methyl formate concentration at the bottom effluent, thereby reducing the load and energy consumption of the external distillation separation. The pressure is increased from 1 MPa to 3 MPa under conditions of 90°C at the top and 70°C at the bottom. At MPa, the single-pass conversion rate of methanol increased from 16% to 80%, and the volumetric yield of methyl formate increased from 260 g / L to 1587 g / L. -1 ·h -1 The purity of methyl formate at the top of the distillation column can reach 97.01%. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process flow of an apparatus for the continuous synthesis of methyl formate from carbon monoxide and methanol, provided in one embodiment of this application. Figure 2 This is a schematic diagram of a method for the continuous synthesis of methyl formate from carbon monoxide and methanol according to one embodiment of this application. Figure 3 This is a schematic diagram of the molecular structure of catalyst component B provided in one embodiment of this application, wherein M is Fe, Ni, Co, Mo, W or Mn; Figure label: 1-Packed tubular reactor; 2-Condenser; 3-Settling tank; 4-Booster pump; 5-Gas buffer tank; 6-Gas preheater; 7-Liquid buffer tank; 8-First liquid pump; 9-Second liquid pump; 10-Third liquid pump; 11-Methanol feedstock tank; 12-Distillation column; 13-Methyl formate product tank; 14-Liquid mixer; 15-Liquid preheater. Detailed Implementation

[0020] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0021] In this application, methyl formate is used for the first time as “Methyl Formate (MF)”, and will be uniformly referred to as MF thereafter; carbon monoxide is used for the first time as “carbon monoxide (CO)”, and will be uniformly referred to as CO thereafter; the booster pump 4 can also be a compressor or other device capable of pressurizing the gas; the hourly volumetric production unit of MF is g·L. -1 ·h -1 .

[0022] Example 1 In this embodiment, please refer to Figure 1 As shown, this application provides a preparation apparatus for the continuous synthesis of methyl formate from carbon monoxide and methanol. The apparatus achieves efficient continuous synthesis of carbon monoxide and methanol through the synergistic effect of three functional units: gas-liquid countercurrent reaction, gas phase circulation, and liquid phase treatment and reuse.

[0023] The preparation device consists of three main parts: a gas-liquid countercurrent reaction unit, a gas phase circulation unit, and a liquid phase treatment and reuse unit.

[0024] As an example, the core of the gas-liquid countercurrent reaction unit is a packed tubular reactor 1, which has four interfaces: a top liquid inlet, a bottom gas inlet, a top gas phase outlet, and a bottom liquid phase outlet. The packed tubular reactor 1 contains a packed bed, using one or more combinations of Raschig rings, Pall rings, stepped rings, grid packing, and corrugated packing to provide sufficient mass transfer area for gas-liquid contact. The packed tubular reactor 1 also includes a gas distributor and a liquid distributor. The gas distributor uses a porous distribution plate, sieve plate, or nozzle distributor, while the liquid distributor uses a spray plate, trough distributor, or porous distribution plate. Together, they ensure uniform gas-liquid distribution within the reactor, forming an efficient gas-liquid countercurrent contact channel. The packed tubular reactor 1 creates a methyl formate concentration gradient in the axial direction, with the methyl formate concentration at the bottom liquid phase outlet significantly higher than that at the top liquid inlet. This concentration gradient is beneficial for the continuous reaction and product enrichment.

[0025] As an example, the packed tubular reactor 1 is equipped with an axial temperature gradient control system, where the temperature in the top reaction zone is higher than that in the bottom reaction zone. Two independent temperature control zones are axially arranged on the outer wall of the packed tubular reactor 1, with the upper temperature control zone set at 5-40°C higher than the lower temperature control zone. The operating pressure of the packed tubular reactor 1 is controlled within the range of 1-5 MPa, the temperature in the top reaction zone is set at 70-150°C, and the temperature in the bottom reaction zone is set at 50-120°C. This temperature gradient design fully utilizes the exothermic characteristics of the reaction, maintaining a higher temperature at the top of the reactor to promote the reaction, while using a lower temperature at the bottom is beneficial for product stability and separation.

[0026] As an example, the gas phase circulation unit is connected to the top gas phase outlet of the packed tubular reactor 1, and sequentially includes a condenser 2, a settling tank 3, a booster pump 4, and a gas buffer tank 5 along the flow direction. The condenser 2 condenses the condensable components in the gas phase and separates entrained liquid, ensuring the purity of the gas phase. The settling tank 3 further separates the gas and liquid phases; the separated liquid phase is recycled to the liquid phase treatment and reuse unit, realizing the recycling of materials. The booster pump 4 and the gas buffer tank 5 work together to pressurize and buffer the gas, ensuring the pressure stability of the gas phase circulation system. The outlet of the gas buffer tank 5 is connected to the bottom inlet of the packed tubular reactor 1 via a gas preheater 6, which heats the circulating gas to a suitable reaction temperature. A fresh carbon monoxide inlet is located upstream of the gas preheater 6 to replenish the carbon monoxide raw material consumed in the reaction.

[0027] As an example, the liquid phase treatment and recycling unit is connected to the bottom liquid phase outlet of the packed tubular reactor 1, and includes two main pieces of equipment: a liquid buffer tank 7 and a distillation column 12. The liquid buffer tank 7 buffers and stabilizes the liquid phase flow rate. Downstream of the liquid buffer tank 7 is a first liquid pump 8, which is connected to the feed inlet of the distillation column 12. The distillation column 12 is a key piece of equipment for product separation, outputting high-purity methyl formate at the top, with a purity of up to 97.01%. The bottom of the distillation column 12 outputs a mixture of unreacted methanol and catalyst. This mixture is then mixed with fresh methanol via a liquid mixer 14 and returned to the top inlet of the packed tubular reactor 1, achieving the recycling of unreacted raw materials. The top of the distillation column 12 is connected to the methyl formate product tank 13, and the bottom outlet is connected to the liquid mixer 14. The liquid mixer 14 also has a fresh methanol inlet to replenish the methanol raw material consumed in the reaction.

[0028] Furthermore, fresh methanol is supplied to the liquid mixer 14 via the second liquid pump 9 from the methanol feed tank 11; the outlet of the liquid mixer 14 is connected to the third liquid pump 10 and the liquid preheater 15, and the outlet of the liquid preheater 15 is connected to the top inlet of the packed tubular reactor 1; the liquid phase separated by the settling tank 3 is recovered to the liquid buffer tank 7 and / or the liquid mixer 14.

[0029] The working principle of this preparation device is as follows: Fresh methanol and recycled unreacted methanol are mixed in liquid mixer 14 and then enter the reactor 1 through the top inlet. Carbon monoxide is mixed with recycled gas, heated by gas preheater 6, and then enters the reactor 1 through the bottom inlet. In the packed bed, the gas and liquid phases come into countercurrent contact and undergo a synthesis reaction under the action of a catalyst. The gas phase after the reaction flows out from the top gas phase outlet, is condensed by condenser 2, separated by settling tank 3, pressurized by booster pump 4, buffered in gas buffer tank 5, and then preheated by gas preheater 6 before being recycled. The liquid phase after the reaction flows out from the bottom liquid phase outlet, is buffered by liquid buffer tank 7, and then enters distillation column 12 for separation. Methyl formate is obtained at the top of the column, and the unreacted material at the bottom is recycled.

[0030] In a preferred embodiment, the preparation apparatus is operated under the following conditions: a reaction pressure of 3 MPa, a top reaction zone temperature of 90°C, a bottom reaction zone temperature of 70°C, and a composite catalyst, wherein component A is 1% potassium methoxide by mass, and component B is 0.05% metal complex / complex promoter (M is Fe). Under these conditions, the single-pass conversion of methanol can reach 80%, the selectivity of methyl formate is 99.5%, and the volumetric yield of methyl formate can reach 1587 g·L⁻¹. -1 ·h -1 .

[0031] In another preferred embodiment, at a reaction pressure of 2 MPa and under the same temperature conditions, the single-pass conversion rate of methanol is 64%, and the volumetric yield of methyl formate is 1075 g·L⁻¹. -1 ·h -1 When the pressure is increased to 4 MPa, the single-pass conversion rate of methanol increases to 86%, and the volumetric hourly yield reaches 1880 g·L. -1 ·h -1 .

[0032] Through the above structural design and optimized operating conditions, this preparation device can achieve efficient and continuous synthesis of carbon monoxide and methanol, with advantages of high conversion rate, good selectivity and high product purity, and is suitable for the industrial production of methyl formate.

[0033] Example 2 In this embodiment, please refer to Figure 2 As shown, this application also provides a method for continuously preparing methyl formate using the preparation apparatus in Example 1. This method adopts the principle of gas-liquid countercurrent reaction and achieves efficient continuous synthesis of carbon monoxide and methanol through cyclic operation.

[0034] The preparation method includes the following steps: Step 1: Prepare the reaction solution A reaction solution containing a composite catalyst (component A + component B) is prepared, with the total mass fraction of the composite catalyst controlled within the range of 0.1-10%. Component A is sodium methoxide and / or potassium methoxide, and component B is a metal complex / complex promoter containing multiple coordination sites. The selection and concentration of the composite catalyst directly affect the reaction activity and stability. Component B can activate CO and synergistically work with component A to increase the carbonylation rate and extend the catalyst lifetime.

[0035] Step 2: Carbon monoxide feed treatment After being mixed with and preheated, recycled carbon monoxide is continuously introduced into the bottom of packed tubular reactor 1. The recycled carbon monoxide comes from the gas phase circulation unit, and mixing it with fresh carbon monoxide can improve the utilization rate of raw materials. The preheating treatment ensures that the gas reaches a suitable reaction temperature.

[0036] Step 3: Methanol Feed Processing The recycled stream from the bottom of distillation column 12 is mixed with fresh methanol and preheated before being continuously fed into the top of packed tubular reactor 1. The recycled stream mainly contains unreacted methanol and catalyst, which are recycled after being mixed with fresh methanol, thus improving feedstock utilization efficiency.

[0037] Step 4: Gas-liquid countercurrent reaction Within the packed tubular reactor 1, the gas and liquid phases react in countercurrent contact, with the reaction pressure controlled at 1-5 MPa. An axial temperature gradient is formed in the packed tubular reactor 1, with the temperature in the top reaction zone set at 70-150℃ and the temperature in the bottom reaction zone set at 50-120℃. This temperature gradient design fully utilizes the exothermic characteristics of the reaction, maintaining a higher temperature at the top to promote the reaction, while using a lower temperature at the bottom to facilitate product stability. The countercurrent gas-liquid contact increases the mass transfer area and improves the reaction efficiency.

[0038] Step 5: Gas Phase Circulation Processing The gas phase discharged from the top of the packed tubular reactor 1 is condensed and separated by sedimentation, then pressurized and circulated back to the bottom of the packed tubular reactor 1. The condenser 2 condenses the condensable components in the gas phase, the sedimentation tank 3 further separates the gas and liquid phases, and the booster pump 4 pressurizes the gas to ensure stable pressure in the circulation system, thus realizing the recycling of unreacted carbon monoxide.

[0039] Step Six: Liquid Phase Separation and Product Recovery The liquid phase discharged from the bottom of the packed tubular reactor 1 is buffered and then sent to the distillation column 12 for separation. Methyl formate is obtained at the top of the column, and the bottom stream is refluxed back to the top of the packed tubular reactor 1. The distillation separation achieves product purification and recovery of unreacted materials. The top product is high-purity methyl formate, and the bottom stream contains unreacted methanol and catalyst. Recirculation improves the overall economic efficiency.

[0040] In a preferred embodiment, the reaction pressure is controlled at 2-3 MPa, the temperature of the top reaction zone is controlled at 80-120°C, and the temperature of the bottom reaction zone is controlled at 60-90°C. Under these optimized conditions, the reaction system operates more stably and achieves better reaction results.

[0041] In another preferred embodiment, the methyl formate product obtained from the top of distillation column 12 has a purity of not less than 97.01%. Through the efficient separation of distillation column 12, product purity is effectively guaranteed, meeting the requirements of industrial applications.

[0042] Through specific operational verification, when using a composite catalyst (component A is 1% potassium methoxide by mass, component B is 0.05% metal complex / complex promoter by mass, and M is Fe) under continuous operation at a reaction pressure of 3 MPa, a top reaction zone temperature of 90℃, and a bottom reaction zone temperature of 70℃, the single-pass conversion rate of methanol can reach 80%, the selectivity of methyl formate is 99.5%, and the volumetric yield of methyl formate reaches 1587 g·L⁻¹. -1 ·h -1 The purity of the product at the top of the column was 97.01%. At a reaction pressure of 2 MPa, the single-pass conversion rate of methanol was 64%, with a volumetric hourly yield of 1075 g·L⁻¹. -1 ·h -1 When the pressure is increased to 4 MPa, the single-pass conversion rate of methanol increases to 86%, and the volumetric hourly yield reaches 1880 g·L. -1 ·h -1 .

[0043] This preparation method achieves efficient and continuous synthesis of carbon monoxide and methanol through the synergistic effect of gas-liquid countercurrent reaction, temperature gradient control, gas phase circulation and liquid phase separation and reuse. It has the advantages of high conversion rate, good selectivity, high product purity and high raw material utilization rate, and is suitable for the industrial continuous production of methyl formate.

[0044] Example 3 Existing liquid-phase carbonylation devices mostly use single alkali metal alkoxides or simple auxiliary agent systems, which have problems such as low effective concentration of active species, difficulty in separating alkali metal ion pairs, and sensitivity to water / impurities leading to activity fluctuations. Higher pressure or longer residence time is often required to obtain higher conversion rates.

[0045] The composite catalyst proposed in this application consists of component A (sodium methoxide and / or potassium methoxide) and component B (metal complex / complex-type promoter), as shown in component B... Figure 3 As shown, it can activate CO and work synergistically with sodium methoxide / potassium methoxide to improve the rate of key carbonylation steps; at the same time, it stabilizes active species, inhibits deactivation, and extends catalyst lifetime and continuous operation stability.

[0046] This embodiment is used to verify the effect of the composite catalyst system and operating conditions on the reaction performance: Component A is potassium methoxide (1% by mass based on the reaction solution), and component B is a promoting component containing a metal center (0.05% by mass based on the reaction solution, with Fe as an example of the metal center M). A comparative example (only component A is added, 1% by mass) is also set up to evaluate the synergistic effect of component B.

[0047] Table 1. Effect of pressure (catalyst: component A 1%, component B = 0.05%)

[0048] Table 2 Effect of temperature gradient (pressure 3 MPa, catalyst: component A 1%, component B = 0.05%)

[0049] Table 3 Comparative Tests (Pressure 3 MPa, Comparative Example: Component A only; Example: Component A + Component B)

[0050] As shown in Tables 1-3, under the conditions of top / bottom temperatures of 90 / 70℃, when using a composite catalyst system (component A = 1% potassium methoxide + component B = 0.05% promoting component), as the reaction pressure increases from 2 MPa to 3 MPa, the single-pass conversion rate of methanol increases from 64% to 80%, and the volumetric yield of methyl formate increases from 1075 g·L⁻¹. -1 ·h -1 Increased to 1587 g·L -1 ·h -1 When further increased to 4 MPa, the conversion rate and volumetric yield per hour reached 86% and 1880 g·L⁻¹, respectively. -1 ·h -1 The gain gradually decreases. Under a pressure of 3 MPa, the conversion rate and volumetric yield are low when the temperature gradient is too low (e.g., top / bottom 70 / 50 °C); the MF selectivity decreases when the temperature gradient is too high (e.g., top / bottom 150 / 110 °C). Therefore, a pressure of 2-3 MPa is preferred, with a top temperature of 80-120 °C and a bottom temperature of 60-90 °C. Furthermore, under conditions of 3 MPa and 90 / 70 °C, compared to the comparative example with only component A added, the addition of component B further improves the methanol conversion rate and volumetric yield (78% / 1170 g·L⁻¹). -1 ·h -1 Increased to 80% / 1587 g·L -1 ·h -1This demonstrates the synergistic effect of component B. In a preferred embodiment, the packed tubular reactor 1 is filled with packing material to enhance gas-liquid contact and mass transfer. The packing material can be selected from one or more of the following: random packing materials such as Raschig rings, Pall rings, and stepped rings; or structured packing materials such as grid packing and corrugated packing. The packing material can be stainless steel, ceramic, or corrosion-resistant polymer material, and the packing specifications can be selected according to the reactor diameter, pressure drop, and mass transfer requirements.

[0051] Liquid distributors can be spray discs, trough distributors, or perforated distribution plates; gas distributors can be perforated distribution plates, sieve plates, or nozzle distributors. By cooperating with the packing bed, the gas and liquid can be evenly distributed in the pipe and a stable axial concentration gradient can be formed.

[0052] In a preferred embodiment, the outer wall of the packed tubular reactor 1 is divided into at least two independent temperature control zones (e.g., an upper temperature control zone and a lower temperature control zone) along the axial direction. Each temperature control zone is connected to an independent jacketed heat exchange medium circuit or an electric heating / cooling circuit, thereby forming a temperature gradient with a high top and a low bottom along the axial direction of the reactor.

[0053] Preferably, the temperature of the top reaction zone of the packed tubular reactor 1 is 70-150℃, and the temperature of the bottom reaction zone is 50-120℃; more preferably, the temperature of the top reaction zone is 80-120℃, and the temperature of the bottom reaction zone is 60-90℃; and the temperature of the top reaction zone is 5-40℃ higher than the temperature of the bottom reaction zone. Under this temperature gradient, the higher temperature at the top can increase the reaction rate; the lower temperature at the bottom can shift the reaction equilibrium towards the formation of methyl formate, thereby increasing the concentration of methyl formate in the bottom effluent, and thus reducing the separation load and energy consumption of the external distillation column.

[0054] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. An apparatus for the continuous synthesis of methyl formate from carbon monoxide and methanol, characterized in that, include: The gas-liquid countercurrent reaction unit includes a packed tubular reactor (1), which is provided with a top liquid inlet, a bottom gas inlet, a top gas phase outlet and a bottom liquid phase outlet. The internal packing bed and gas distributor and liquid distributor for uniform gas-liquid distribution are provided to form a gas-liquid countercurrent contact channel. The gas phase circulation unit is connected to the top gas phase outlet of the packed tubular reactor (1) at its inlet, and includes, in sequence along the flow direction, a condenser (2) for condensing the gas phase and separating the entrained liquid, a settling tank (3), a booster pump (4) for pressurizing and buffering the gas, and a gas buffer tank (5); the outlet of the gas buffer tank (5) is connected to the bottom air inlet of the packed tubular reactor (1) via a gas preheater (6), and a fresh carbon monoxide inlet is provided upstream of the gas preheater (6); The liquid phase treatment and reuse unit is connected to the bottom liquid phase outlet of the packed tubular reactor (1) at its inlet and includes a liquid buffer tank (7) and a distillation column (12). The top of the distillation column (12) is used to output methyl formate product, and the bottom outlet of the column is connected to the top liquid inlet of the packed tubular reactor (1) through a liquid mixer (14). The liquid mixer (14) is also provided with a fresh methanol inlet. The liquid phase separated from the settling tank (3) is recycled to the liquid phase treatment and reuse unit.

2. The preparation apparatus according to claim 1, characterized in that, The packed tubular reactor (1) is configured to form a methyl formate concentration gradient in the axial direction, and the methyl formate concentration at the bottom liquid outlet of the packed tubular reactor (1) is higher than the methyl formate concentration at the top liquid inlet. Preferably, the packed tubular reactor (1) is provided with a temperature gradient along the axial direction, and the temperature of the top reaction zone is higher than that of the bottom reaction zone; Preferably, the reaction pressure of the packed tubular reactor (1) is 1-5 MPa, the temperature of the top reaction zone is 70-150℃, and the temperature of the bottom reaction zone is 50-120℃.

3. The preparation apparatus according to claim 1, characterized in that, The packing material in the packed tubular reactor (1) is selected from at least one of Raschig rings, Pall rings, stepped rings, grid packing, and corrugated packing. Preferably, the liquid distributor is at least one of a spray disc, a trough distributor, or a perforated distribution plate; Preferably, the gas distributor is at least one of a porous distribution plate, a sieve plate, or a nozzle distributor.

4. The preparation apparatus according to claim 1, characterized in that, The outer wall of the packed tubular reactor (1) is provided with at least two independent temperature control zones along the axial direction, and the set temperature of the upper temperature control zone is 5-40℃ higher than that of the lower temperature control zone.

5. The preparation apparatus according to claim 1, characterized in that, The unreacted methanol and catalyst mixture output from the bottom of the distillation column (12) is mixed with fresh methanol in the liquid mixer (14) and then refluxed to the top of the packed tubular reactor (1).

6. A method for continuously preparing methyl formate using the preparation apparatus according to any one of claims 1-5, characterized in that, Includes the following steps: A reaction solution containing a composite catalyst is prepared, wherein the composite catalyst comprises component A and component B; wherein component A is sodium methoxide and / or potassium methoxide, and component B is a metal complex / complex-type promoter containing multiple coordination sites; the total mass fraction of the composite catalyst is 0.1-10%; After mixing and preheating the recycled carbon monoxide with fresh carbon monoxide, it is continuously fed into the bottom of the packed tubular reactor (1); After mixing and preheating the recycled stream from the bottom of the distillation column (12) with fresh methanol, it is continuously fed into the top of the packed tubular reactor (1); In the packed tubular reactor (1), the gas and liquid phases react in countercurrent contact. The reaction pressure is 1-5 MPa. A temperature gradient is formed axially in the packed tubular reactor (1). The temperature in the top reaction zone is 70-150℃, and the temperature in the bottom reaction zone is 50-120℃. The gas phase discharged from the top of the packed tubular reactor (1) is condensed, settled and separated, then pressurized and circulated back to the bottom of the packed tubular reactor (1); The liquid phase discharged from the bottom of the packed tubular reactor (1) is buffered and then sent to the distillation column (12) for separation. Methyl formate product is obtained at the top of the column, and the bottom stream is returned to the top of the packed tubular reactor (1).

7. The method according to claim 6, characterized in that, The reaction pressure is 2-3 MPa, the temperature of the top reaction zone is 80-120℃, and the temperature of the bottom reaction zone is 60-90℃.

8. The method according to claim 6, characterized in that, The catalyst is a composite catalyst system comprising component A and component B; wherein, component A is an alkali metal alkoxide, and component B is a promoting component containing a metal center; Component A is selected from at least one of sodium methoxide, potassium methoxide, sodium ethoxide, and potassium ethoxide; preferably potassium methoxide. Component B is a metal complex or metal compound, and the metal center M is selected from at least one of Fe, Ni, Co, Mo, W, and Mn; preferably Fe or Ni.

9. The method according to claim 8, characterized in that, Based on the reaction solution, the mass fraction of component A is 0.1%-10.0%, preferably 0.5%-2.0%; the mass fraction of component B is 0.001%-1.0%, preferably 0.01%-0.2%. The molar ratio of component B to component A is 0.001-0.5:1, preferably 0.01-0.2:1; Preferably, component B is used to activate carbon monoxide and synergistically promote the methanol carbonylation reaction with component A to improve methanol conversion and / or methyl formate volumetric yield, and extend the stable operating cycle of the catalyst.

10. The method according to claim 9, characterized in that, The volume ratio of carbon monoxide to inert gas in the reaction gas is (50-100):(0-50); preferably, the volume fraction of carbon monoxide is not less than 80%.

Images