Green energy-saving formaldehyde production system and production method
By generating formaldehyde through a dehydrogenation reaction and producing hydrogen as a byproduct, the problem of high energy consumption in existing formaldehyde production is solved, achieving a green and energy-saving production effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LIAOCHENG MEIWU NEW MATERIAL SCI & TECHCO
- Filing Date
- 2023-06-02
- Publication Date
- 2026-06-19
Smart Images
Figure CN116764549B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of formaldehyde synthesis technology, specifically relating to a green and energy-saving formaldehyde production system and production method. Background Technology
[0002] Formaldehyde is an important organic chemical raw material with a wide range of applications in pesticides, pharmaceuticals, coatings, dyes, and defense industries.
[0003] Formaldehyde production processes generally include methanol oxidation, natural gas oxidation, dimethyl ether oxidation, and methanol dehydrogenation. Formaldehyde oxidation involves directly oxidizing methanol, air, and water to formaldehyde at 600-700℃ using a silver catalyst or catalysts such as copper or vanadium pentoxide; or mixing vaporized methanol with alkaline-washed air and water vapor, heating to 115-120℃, and controlling the reaction temperature at 600-650℃ and pressure at 0.3-0.5 MPa under the action of a silver catalyst to produce formaldehyde, which is then absorbed by water to obtain a formaldehyde solution. Natural gas oxidation involves directly oxidizing a mixture of natural gas and vacancy at 600-680℃ using oxide catalysts such as iron or molybdenum to produce formaldehyde, which is then absorbed by water to obtain a formaldehyde solution. Dimethyl ether oxidation uses dimethyl ether, a byproduct of methanol synthesis via high-pressure synthesis of syngas, as raw material, oxidizing it with a metal oxide catalyst. Methanol dehydrogenation directly dehydrogenates methanol to obtain anhydrous formaldehyde, while also producing hydrogen as a byproduct.
[0004] Currently, most formaldehyde production processes in China employ the silver process or the iron-molybdenum catalytic oxidation dehydration method. This process typically uses air as the oxidant, with the air circulation volume being approximately 6-10 times the methanol mass flow rate. Simultaneously, two hydrogen atoms in methanol combine with oxygen to form water molecules, and the removal of hydrogen as water is energy-intensive. Summary of the Invention
[0005] To address the issues of high energy consumption and high cost in existing silver-based or iron-molybdenum catalytic oxidation dehydration methods for formaldehyde production, this invention provides a green and energy-saving formaldehyde production system and method. This method employs a dehydrogenation reaction, resulting in fewer side reactions and producing formaldehyde and high-value-added hydrogen as products, thereby reducing reaction energy consumption and process costs.
[0006] This invention is achieved through the following technical solution:
[0007] A green and energy-saving formaldehyde production system is characterized by comprising a methanol buffer tank, a dehydrogenation feed preheater, a dehydrogenation evaporator, a first preheater, a dehydrogenation reactor, a condenser, a dehydrogenation separator, a preheater, a dryer, a light tower, an aldehyde tower, an alcohol tower, a dehydrogenation condenser, a compressor, and a pressure swing adsorption device.
[0008] The methanol buffer tank is connected to the dehydrogenation feed preheater, which is connected to the dehydrogenation evaporator, the first preheater and the condenser respectively. The dehydrogenation evaporator is connected to the first preheater in sequence, and a circulation loop is set between the first preheater and the dehydrogenation reactor.
[0009] The condenser is connected to the dehydrogenation separator, which is connected to both the preheater and the dehydrogenation condenser.
[0010] The preheater is connected in sequence to the dryer, light tower, aldehyde tower and alcohol tower;
[0011] The dehydrogenation condenser is connected in sequence to the compressor and the pressure swing adsorption device.
[0012] Furthermore, the alcohol tower is connected to a methanol buffer tank, and the recovered methanol enters the methanol buffer tank (1).
[0013] Furthermore, the dehydrogenation feed preheater, dehydrogenation evaporator, and first preheater are shell-and-tube structures.
[0014] The method for producing formaldehyde using the green and energy-saving formaldehyde production system of this invention includes the following steps:
[0015] (1) Methanol is fed to a methanol buffer tank and then preheated in sequence through a dehydrogenation feed preheater, a dehydrogenation evaporator and a first preheater. After being heated to 210~260℃, it enters the dehydrogenation reactor to carry out the dehydrogenation reaction in the presence of a catalyst. After the reaction is completed, the reaction liquid enters the first preheater and the dehydrogenation feed preheater in sequence to recover heat, and then enters the condenser and the dehydrogenation separator in sequence for gas-liquid separation.
[0016] (2) After gas-liquid separation in step (1), the liquid phase enters the preheater, dryer, light tower and aldehyde tower in sequence to obtain formaldehyde product, and the remaining liquid enters the alcohol tower to recover formaldehyde.
[0017] (3) After gas-liquid separation in step (1), the gas phase enters the dehydrogenation condenser, compressor and pressure swing adsorption device in sequence to obtain hydrogen.
[0018] Furthermore, the dehydrogenation reactor is filled with a dehydrogenation catalyst, the catalyst support is Al2O3, the main components are CuO and ZnO, the total content of CuO and ZnO is ≥80%, and the mass ratio of CuO:ZnO is 0.6~0.9.
[0019] Furthermore, the catalyst is an alkali-treated catalyst.
[0020] Furthermore, the alkaline treatment method for the catalyst is to add 0.1-0.5% alkali to the catalyst, or to spray and moisten the catalyst with a 0.5wt% alkali solution.
[0021] Furthermore, in step (1), the dehydrogenation reaction is carried out at a temperature of 210~260℃, a reaction pressure of 5-15KPa, and a space velocity of 0.5~1.2h. -1 .
[0022] Furthermore, the space velocity for the dehydrogenation reaction in step (1) is 0.7~0.9 h⁻¹. -1 .
[0023] Furthermore, in step (1), 2-4% methanol is added to the dehydrogenation reaction process at 230°C saturated water vapor.
[0024] Specifically, the conversion rate and selectivity of methanol dehydrogenation depend on the catalyst used, operating conditions, and the purity of the feedstock. To improve production, dehydrogenation side reactions should be minimized to reduce the impurity content in the dehydrogenation products. This can be achieved through the following approaches: ① Improving methanol purification: Increasing the purity of methanol, the feedstock for dehydrogenation, can significantly suppress side reactions. ② Selecting and suppressing operating conditions: In industrial production, attention should be paid not only to controlling reaction operating conditions and preventing overheating, but also to selecting and controlling the optimal space velocity. Furthermore, since industrial methanol dehydrogenation uses tubular reactors, the axial temperature difference between the reaction bed and the reactor should be avoided as much as possible to prevent local overheating, which can lead to sintering and carbon deposition on the catalyst surface. ③ Adding steam to the dehydrogenation reaction: Dehydrogenation is an endothermic reaction with increased volume. Adding appropriate amounts of steam to the reactants can reduce the partial pressure of organic matter, which is beneficial to the thermodynamic equilibrium of the dehydrogenation reaction, thereby increasing the equilibrium conversion rate. In addition, the addition of steam is beneficial for controlling the reaction temperature, increasing the space velocity of the material, and suppressing major side reactions such as dehydration, condensation, and carbon deposition.
[0025] The beneficial effects achieved by this invention are as follows:
[0026] (1) Producing hydrogen as a byproduct, and using hydrogen as an energy output, is a green and energy-saving production process;
[0027] (2) The addition of water vapor reduces the occurrence of side reactions such as dimethyl ether and carbon deposits. Attached Figure Description
[0028] Figure 1 This is a schematic diagram of the green and energy-saving formaldehyde production system of the present invention;
[0029] The components include: 1. Methanol buffer tank; 2. Dehydrogenation feed preheater; 3. Dehydrogenation evaporator; 4. First preheater; 5. Dehydrogenation reactor; 6. Condenser; 7. Dehydrogenation separator; 8. Preheater; 9. Dryer; 10. Light tower; 11. Aldehyde tower; 12. Alcohol tower; 13. Dehydrogenation condenser; 14. Compressor; and 15. Pressure swing adsorption unit. Detailed Implementation
[0030] The preferred embodiments of the present invention will now be described in detail so that the advantages and features of the present invention can be more readily understood by those skilled in the art.
[0031] A schematic diagram of the green and energy-saving formaldehyde production system in this invention is shown below. Figure 1 It can be seen that, from Figure 1 As can be seen, the green and energy-saving formaldehyde production system of the present invention includes a methanol buffer tank 1, a dehydrogenation feed preheater 2, a dehydrogenation evaporator 3, a first preheater 4, a dehydrogenation reactor 5, a condenser 6, a dehydrogenation separator 7, a preheater 8, a dryer 9, a light tower 10, an aldehyde tower 11, an alcohol tower 12, a dehydrogenation condenser 13, a compressor 14, and a pressure swing adsorption device 15; the methanol buffer tank 1 is connected to the dehydrogenation feed preheater 2, which is connected to the dehydrogenation evaporator 3, the first preheater 4, and the condenser 6 respectively; the dehydrogenation evaporator 3 is connected to the first preheater 4 in sequence, and a circulation loop is set between the first preheater 4 and the dehydrogenation reactor 5; the condenser 6 is connected to the dehydrogenation separator 7, which is connected to the preheater 8 and the dehydrogenation condenser 13 respectively; the preheater 8 is connected to the dryer 9, the light tower 10, the aldehyde tower 11, and the alcohol tower 12 in sequence; and the dehydrogenation condenser 13 is connected to the compressor 14 and the pressure swing adsorption device 15 in sequence;
[0032] The methanol tower 12 is connected to the methanol buffer tank 1, and the recovered methanol enters the methanol buffer tank 1.
[0033] The method for producing formaldehyde according to the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments:
[0034] Example 1
[0035] (1) Preparation of catalyst: The dehydrogenation catalyst support is Al2O3, the main components are CuO and ZnO, the total content of CuO and ZnO is 85%, CuO:ZnO=0.7, 0.2% of the catalyst mass of alkali is added to the catalyst, and the prepared catalyst is filled into the dehydrogenation reactor 5;
[0036] (2) Methanol is fed to methanol buffer tank 1, and then preheated to 50°C in sequence through dehydrogenation feed preheater 2, dehydrogenation evaporator 3, and first preheater 4. Before entering dehydrogenation evaporator 3, 4% methanol of 230°C saturated water vapor is added, and after heating to 250°C, it enters dehydrogenation reactor 5 for dehydrogenation reaction in the presence of catalyst. The dehydrogenation reaction temperature is 250°C, the reaction pressure is 10 kPa, and the space velocity is 1.0 h⁻¹. -1 After the reaction is completed, the reaction liquid enters the first preheater 4 and the dehydrogenation feed preheater 2 in sequence to recover heat, and then enters the condenser 6 and the dehydrogenation separator 7 in sequence for gas-liquid separation.
[0037] The methanol conversion rate in dehydrogenation reactor 5 is 55%, and the formaldehyde selectivity is ≥99.5%.
[0038] (3) After gas-liquid separation in step (1), the liquid phase enters the preheater 8, dryer 9, light tower 10 and aldehyde tower 11 in sequence to obtain formaldehyde product. The remaining liquid enters the alcohol tower 12 to recover formaldehyde. The recovered formaldehyde continues to react in the methanol buffer tank.
[0039] (4) After gas-liquid separation in step (1), the gas phase enters the dehydrogenation condenser 13 and compressor 14 in sequence. The pressurized hydrogen is sent to the pressure swing adsorption device 15 for purification to obtain high-purity hydrogen.
[0040] Example 2
[0041] (1) Preparation of catalyst: The dehydrogenation catalyst support is Al2O3, the main components are CuO and ZnO, the total content of CuO and ZnO is 85%, CuO:ZnO=0.7, 0.2% of the catalyst mass of alkali is added to the catalyst, and the prepared catalyst is filled into the dehydrogenation reactor 5;
[0042] (2) Methanol is fed to methanol buffer tank 1, and then preheated to 40°C in sequence through dehydrogenation feed preheater 2, dehydrogenation evaporator 3, and first preheater 4. Before entering dehydrogenation evaporator 3, 3% methanol of 230°C saturated water vapor is added, and after heating to 260°C, it enters dehydrogenation reactor 5 for dehydrogenation reaction in the presence of catalyst. The dehydrogenation reaction temperature is 260°C, the reaction pressure is 12 kPa, and the space velocity is 1.2 h⁻¹. -1 After the reaction is completed, the reaction liquid enters the first preheater 4 and the dehydrogenation feed preheater 2 in sequence to recover heat, and then enters the condenser 6 and the dehydrogenation separator 7 in sequence for gas-liquid separation.
[0043] The methanol conversion rate in dehydrogenation reactor 5 was 57%, and the formaldehyde selectivity was ≥99.5%.
[0044] (3) After gas-liquid separation in step (1), the liquid phase enters the preheater 8, dryer 9, light tower 10 and aldehyde tower 11 in sequence to obtain formaldehyde product. The remaining liquid enters the alcohol tower 12 to recover formaldehyde. The recovered formaldehyde continues to react in the methanol buffer tank.
[0045] (4) After gas-liquid separation in step (1), the gas phase enters the dehydrogenation condenser 13 and compressor 14 in sequence. The pressurized hydrogen is sent to the pressure swing adsorption device 15 for purification to obtain high-purity hydrogen.
[0046] Example 3
[0047] (1) Preparation of catalyst: The dehydrogenation catalyst support is Al2O3, the main components are CuO and ZnO, the total content of CuO and ZnO is 85%, CuO:ZnO=0.7, 0.2% of the catalyst mass of alkali is added to the catalyst, and the prepared catalyst is filled into the dehydrogenation reactor 5;
[0048] (2) Methanol is fed to methanol buffer tank 1, and then preheated to 50°C in sequence through dehydrogenation feed preheater 2, dehydrogenation evaporator 3, and first preheater 4. Before entering dehydrogenation evaporator 3, 2% methanol of 230°C saturated water vapor is added. After heating to 230°C, it enters dehydrogenation reactor 5 for dehydrogenation reaction in the presence of catalyst. The dehydrogenation reaction temperature is 230°C, the reaction pressure is 8 kPa, and the space velocity is 0.8 h⁻¹. -1 After the reaction is completed, the reaction liquid enters the first preheater 4 and the dehydrogenation feed preheater 2 in sequence to recover heat, and then enters the condenser 6 and the dehydrogenation separator 7 in sequence for gas-liquid separation.
[0049] The methanol conversion rate in dehydrogenation reactor 5 was 54%, and the formaldehyde selectivity was ≥99.5%.
[0050] (3) After gas-liquid separation in step (1), the liquid phase enters the preheater 8, dryer 9, light tower 10 and aldehyde tower 11 in sequence to obtain formaldehyde product. The remaining liquid enters the alcohol tower 12 to recover formaldehyde. The recovered formaldehyde continues to react in the methanol buffer tank.
[0051] (4) After gas-liquid separation in step (1), the gas phase enters the dehydrogenation condenser 13 and compressor 14 in sequence. The pressurized hydrogen is sent to the pressure swing adsorption device 15 for purification to obtain high-purity hydrogen.
[0052] Comparative Example 1
[0053] Compared to the examples, no water vapor was added in the dehydrogenation reaction of Comparative Example 1, while all other operating steps were the same as in Example 1. In Comparative Example 1, the conversion rate of methanol in dehydrogenation reactor 5 was 45%, and the selectivity of formaldehyde was 90%.
Claims
1. A method for producing formaldehyde, characterized in that, Includes the following steps: 1) Methanol is fed to methanol buffer tank (1), and then preheated in sequence through dehydrogenation feed preheater (2), dehydrogenation evaporator (3) and first preheater (4) to 210~260℃ before entering dehydrogenation reactor (5) for dehydrogenation reaction in the presence of catalyst. After the reaction is completed, the reaction liquid enters first preheater (4) and dehydrogenation feed preheater (2) in sequence to recover heat, and then enters condenser (6) and dehydrogenation separator (7) in sequence for gas-liquid separation. 2) After gas-liquid separation in step 1), the liquid phase enters the preheater (8), dryer (9), light tower (10) and aldehyde tower (11) in sequence to obtain formaldehyde product. The remaining liquid enters the alcohol tower (12) to recover formaldehyde. 3) After gas-liquid separation in step 1), the gas phase enters the dehydrogenation condenser (13), compressor (14) and pressure swing adsorption device (15) in sequence to obtain hydrogen; In step (1), the dehydrogenation reaction is carried out at a temperature of 210-260℃, a reaction pressure of 5-15 kPa, and a space velocity of 0.5-1.2 h⁻¹. -1 During the dehydrogenation reaction, 2-4% methanol is added to 230°C saturated water vapor. The dehydrogenation reactor (5) is filled with a dehydrogenation catalyst. The dehydrogenation catalyst support is Al2O3, and the main components are CuO and ZnO. The total content of CuO and ZnO is ≥80%, and the mass ratio of CuO to ZnO is 0.6~0.
9.
2. The method for producing formaldehyde according to claim 1, characterized in that, The catalyst is an alkali-treated catalyst.
3. The method for producing formaldehyde according to claim 2, characterized in that, The method for treating the catalyst with alkali is to add 0.1-0.5% alkali to the catalyst, or to spray and moisten the catalyst with a 0.5wt% alkali solution.
4. The method for producing formaldehyde according to claim 1, characterized in that, The space velocity for the dehydrogenation reaction in step (1) is 0.7~0.9 h⁻¹. -1 .