Separation method of catalyst for preparing butyraldehyde through propylene carbonylation

Abstract

The invention provides a separation method of a catalyst for preparing butyraldehyde through propylene carbonylation, and relates to the technical field of chemical synthesis. The separation method comprises the following steps: carrying out flash evaporation separation and low-pressure evaporator evaporation on a material obtained by carrying out a propylene carbonylation reaction on propylene and synthesis gas as raw materials, obtaining a gas-phase material from a collecting tank of a low-pressure evaporator, and outputting a liquid-phase catalyst solution; the gas-phase material is subjected to condensation and gas-liquid separation, crude butyraldehyde is output, and obtained non-condensable gas returns to a liquid distribution chamber of the low-pressure evaporator; wherein the catalyst is acetylacetone triphenyl phosphorus silicification carbonyl rhodium, and the operation temperature of the low-pressure evaporator is 85-95 DEG C. By controlling the circulating air volume and the evaporation temperature, high-temperature deactivation of the catalyst is prevented, the service life of the catalyst is prolonged, and the process cost is reduced; the process flow is simplified, and the method is suitable for large-scale process production.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical synthesis, and in particular to a method for separating a catalyst used for preparing butyraldehyde through carbonylation of propylene. Background Art

[0002] Butanol and octanol are important raw materials for organic chemicals, fine chemicals, and chemical additives. They are widely used in the synthesis of lubricants, solvents, defoamers, additives, antioxidants, and other applications, as well as in the photography, printing and dyeing, and paper sizing industries. Both can be produced in the same facility using carbonyl synthesis, hence the common name of butyl and octanol. The widespread use of butyl and octanol has led to an annual increase in both its usage and production.

[0003] Currently, the most widely used process for producing butyraldehyde is the carbonylation of propylene. This process uses n-butyraldehyde as a solvent, and propylene and synthesis gas react over a catalyst to produce n-butyraldehyde and isobutyraldehyde. The reaction equation is as follows:

[0004] This reaction produces propane and butanol as by-products. After the reaction is complete, the catalyst is separated from the butyraldehyde solution through an evaporation process, and the separated catalyst can be recycled. The evaporated and condensed n-butyraldehyde and isobutyraldehyde can first be hydrogenated to produce n-butanol and isobutanol, which are then separated by distillation to obtain n-butanol and isobutanol products. Alternatively, the n-butyraldehyde and isobutyraldehyde can be separated into n-butyraldehyde and isobutyraldehyde through an isomerization column. The isobutyraldehyde, a by-product, undergoes condensation and dehydration under the catalysis of sodium hydroxide to produce octenal. The octenal is then hydrogenated to produce crude octanol, which is then distilled to obtain the final octanol.

[0005] During the overall process, the yield and yield of the propylene carbonylation reaction are key factors restricting the scale-up of the butylene octanol production process. The key points of the propylene carbonylation process are improving the raw material conversion rate, reducing the occurrence of side reactions, improving the catalytic efficiency of the catalyst, reducing waste liquid emissions, and lowering energy consumption. For example, patents such as CN113041962A, CN117049953A, CN114618396A, CN107759640A, and CN117563262A have conducted extensive research in these areas. Among these, the catalyst used in the propylene carbonylation process is a significant production cost. In recent years, separating and recovering the catalyst from the post-reaction materials has become a research focus in butylene octanol production. Summary of the Invention

[0006] In response to the deficiencies in the prior art, the present invention discloses a method for separating a catalyst for producing butyraldehyde by propylene carbonylation. This method can effectively maintain the activity of the catalyst, reduce catalyst loss, and improve process economy during the process of separating the catalyst from the material after the propylene carbonylation reaction. The method has a simple process flow and is conducive to large-scale production.

[0007] To achieve the above technical objectives, the present invention provides a catalyst separation method for producing butyraldehyde by propylene carbonylation, comprising: subjecting propylene and synthesis gas as raw materials to a propylene carbonylation reaction, subjecting the materials to flash separation and evaporation in a low-pressure evaporator, obtaining a gaseous material from a collecting tank of the low-pressure evaporator and outputting a liquid catalyst solution; condensing the gaseous material and subjecting it to gas-liquid separation, outputting crude butyraldehyde, and obtaining non-condensable gas, which is returned to a liquid distribution chamber of the low-pressure evaporator; wherein the catalyst is carbonyl rhodium triphenylphosphinothioate, and the operating temperature of the low-pressure evaporator is 85-95°C.

[0008] In the prior art, the materials after the propylene carbonylation reaction are separated from the catalyst and product through high- and low-pressure evaporation, and the catalyst solution is returned to the reactor. The specific process includes: the reacted materials output from the reactor are fed to the top of the high-pressure evaporator, the product butyraldehyde is vaporized and condensed, and then enters the propylene absorber. The crude butyraldehyde output from the propylene absorber enters the gas stripping tower to separate the propylene and propane dissolved therein, thereby obtaining the butyraldehyde product. The catalyst solution, concentrated in the high-pressure evaporator, is cooled and then fed to the low-pressure evaporator for further separation and concentration, cooling, and return to the reactor. The gaseous products output from the low-pressure evaporator are condensed and then fed to the low-pressure evaporator condensate receiving tank. The separated non-condensable gases are discharged to a flare, and the condensate crude butyraldehyde is fed to the propylene absorber. The overall process involves multiple devices and equipment, including the high-pressure evaporator, propylene absorber, gas stripping tower, and low-pressure evaporator. The process is relatively complex and has high equipment maintenance and repair costs. In addition, the pressure of the high-pressure evaporator is generally approximately 0.7 MPa, which can easily lead to catalyst deactivation.

[0009] The above technical solution uses a specific acetylacetonate triphenylphosphinothioate carbonyl rhodium to catalyze the carbonylation of propylene. The materials after the reaction can be separated into unreacted raw materials through a flash separation process. This part of the raw materials will be returned to the upstream reaction process after condensation and separation. This process not only simplifies the equipment, but also the operating pressure of the flash evaporation process is lower than the operating pressure of the high-pressure evaporator, which is conducive to maintaining the catalytic activity of the catalyst. In addition, the liquid phase material obtained by flash separation is a concentrated catalyst solution. This part of the material is further concentrated in a low-pressure evaporator to obtain a catalyst solution, which can be directly returned to the upstream reaction process for recycling after condensation; the gas phase material obtained by low-pressure evaporation is condensed and subjected to gas-liquid separation, and the obtained non-condensable gas is input into the liquid distribution chamber on the upper part of the low-pressure evaporator as circulating gas, thereby promoting the reduction of the thickness of the liquid film in the low-pressure evaporator to accelerate evaporation, and at the same time reducing and regulating the evaporation temperature to 85~90°C, which can prevent the acetylacetonate triphenylphosphinosilicic acid carbonyl rhodium catalyst from being deactivated at high temperature and extend the service life of the catalyst; the recycling of the non-condensable gas is green and environmentally friendly, saving energy consumption; the liquid phase material obtained by the second gas phase condensation and gas-liquid separation is crude butyraldehyde.

[0010] The above technical solution simplifies the equipment and operation, improves the operating efficiency of the low-pressure evaporator, and achieves a higher liquid output. In practice, it can also reduce the amount of catalyst replenished in the overall process, thereby extending the catalyst's service life and further reducing the process cost of propylene carbonylation. The present invention's examples and comparative examples demonstrate the operational effectiveness of the above technical solution.

[0011] In a further example of the present invention, the control conditions of the catalyst, low-pressure evaporator operation, flash separation operation, etc. in the above technical solution are explored to optimize the effect of the overall process.

[0012] Compared with the prior art, the present invention has the following beneficial effects: it utilizes a flash separation process combined with a low-pressure evaporation process to separate the product and catalyst from the material after the propylene carbonylation reaction. By circulating the non-condensable gas obtained by low-pressure evaporation to the liquid distribution chamber of the low-pressure evaporator, the efficiency of the low-pressure evaporation is improved by controlling the circulating air volume and evaporation temperature. This reduces the low-pressure evaporation temperature, further preventing high-temperature deactivation of the catalyst, thereby extending the service life of the propylene carbonylation catalyst and reducing process costs. The present invention simplifies the high- and low-pressure evaporation equipment used in traditional propylene carbonylation reactions, enhances operability, and is suitable for large-scale, process-based production. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings: Figure 1 A structural diagram of the catalyst separation method for producing butyraldehyde by carbonylation of propylene according to the present invention is shown.

[0014] The above drawings include the following reference numerals: 1-Flash tank, 2-Separation tank, 3-Low-pressure evaporator, 4-Collection tank, 5-Condensate receiving tank, 6-Compressor. DETAILED DESCRIPTION

[0015] To facilitate understanding of the present invention, the present invention will be described in more detail below, with preferred embodiments of the present invention provided. However, it should be understood that these embodiments are merely for the purpose of further explanation and are not to be construed as limiting the present invention in any form, i.e., they are not intended to limit the scope of protection of the present invention.

[0016] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which this invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods described, unless otherwise specified, are conventional methods.

[0017] The present invention provides a catalyst separation method for producing butyraldehyde by carbonylation of propylene. The method comprises the following steps: subjecting propylene and synthesis gas to a propylene carbonylation reaction, subjecting the materials to flash separation and evaporation in a low-pressure evaporator 3, obtaining a gaseous material from a collecting tank 4 of the low-pressure evaporator 3, and outputting a liquid catalyst solution; condensing the gaseous material and subjecting it to gas-liquid separation, outputting crude butyraldehyde, and obtaining non-condensable gas which is returned to a liquid distribution chamber of the low-pressure evaporator 3; wherein the catalyst is carbonyl rhodium triphenylphosphinothioate, and the operating temperature of the low-pressure evaporator 3 is 85-95°C.

[0018] Figure 1 A structural diagram of the catalyst separation method for producing butyraldehyde by carbonylation of propylene according to the present invention is shown. Figure 1 As shown, the material after the propylene carbonylation reaction is fed into a flash tank 1 for flash separation. After flash evaporation and concentration, the resulting gaseous material is output from the gaseous outlet of the flash tank 1. After condensation in a condenser, the gas is separated into liquid in a separation tank 2. Unreacted raw materials (such as propylene and synthesis gas) are separated as a gaseous phase and returned to the upstream reaction process for recycling. The resulting liquid phase is a solution including butyraldehyde. The liquid phase obtained after flash evaporation in the flash tank 1 is fed into a low-pressure evaporator 3 for further evaporation. The gaseous phase obtained from the collecting tank 4 of the low-pressure evaporator 3 is condensed in a condenser and fed into a condensate receiving tank 5 for gas-liquid separation. The resulting non-condensable gas is returned to the liquid distribution chamber above the low-pressure steam to regulate the efficiency of the low-pressure falling film evaporation. This can also promote the regulation and reduce the temperature of the low-pressure evaporation, prevent catalyst deactivation due to high temperature, thereby extending the catalyst service life and saving process costs. The liquid phase obtained from the gas-liquid separation in the condensate receiving tank 5 is crude butyraldehyde, which is fed downstream for subsequent processing. The liquid material obtained from the collecting tank 4 of the low-pressure evaporator 3 is a catalyst solution, which can be directly returned to the upstream reaction process and / or a portion thereof can be input to the downstream catalyst washing process, etc., to achieve the recycling of the catalyst.

[0019] Optionally, the catalyst is prepared by the following preparation method: S1, adding methanol to a 25wt%-30wt% rhodium trichloride aqueous solution, the volume of methanol added being 5-10ml / g based on the mass of rhodium trichloride; S2, heating the reaction solution of step S1 to 40-50°C, then introducing carbon monoxide, stirring, and maintaining for 3-8h; S3, adding sodium acetylacetone to the reaction solution and stirring for reaction, the molar ratio of the sodium acetylacetone to the rhodium element being (3-5):1; then adding triphenylphosphine and an organosilicon compound, reacting for 2-4h to obtain the acetylacetonatotriphenylphosphine silicified carbonyl rhodium; wherein the mass ratio of the triphenylphosphine, the organosilicon compound and the rhodium element is (5-8):(2-5):1, and the organosilicon compound is octaphenylcyclotetrasiloxane or triisopropylsilane.

[0020] The catalyst preparation method of the present invention fully considers the electronic and steric effects of the transition metal and phosphorus-containing ligands in the catalyst. To enhance the reaction activity and stability (i.e., increase the reaction conversion rate) and selectivity (i.e., increase the reaction yield), the catalyst system uses rhodium as the transition metal and introduces silicon into the phosphorus-containing ligand. Silicon has a weaker electronegativity, a larger volume, and possesses vacant 3d orbitals that can accommodate electrons for coordination, thus enhancing the electronic effect of the catalyst system. The acetylacetonate triphenylphosphinosilyl rhodium carbonyl catalyst achieves a conversion rate exceeding 96.8% and a yield exceeding 95.7% in the propylene carbonylation reaction. Furthermore, the acetylacetonate triphenylphosphinosilyl rhodium carbonyl catalyst efficiently catalyzes the propylene carbonylation reaction within a temperature range of 70-90°C. The lower catalyst temperature reduces process energy consumption and saves process costs.

[0021] Further optionally, the catalyst preparation method further comprises: S4, cooling the material after the reaction in step (3), filtering, washing the obtained filter cake, and drying to obtain the acetylacetonatotriphenylphosphanosiliconyl rhodium carbonyl product. In the washing operation, deionized water, an alcohol solvent (such as ethanol), or a hydrocarbon solvent (such as n-hexane) can be optionally used for washing; low-temperature drying, vacuum drying, or the like can be optionally used for drying.

[0022] The present invention optimizes the operating temperature of the low-pressure evaporator 3 based on a large amount of experimental data. Optionally, the operating temperature of the low-pressure evaporator 3 is 85°C, which is conducive to maintaining the activity of the catalyst, increasing the liquid output of the low-pressure evaporator 3, and improving the separation efficiency.

[0023] Optionally, the operating pressure of the low-pressure evaporator 3 is 65-70 kPa. By optimizing the operating pressure of the low-pressure evaporator 3, the operating temperature of the low-pressure evaporator 3 can be controlled synergistically, which is beneficial to lowering the evaporation temperature, improving separation efficiency and saving energy consumption.

[0024] Optionally, the non-condensable gas is compressed by the compressor 6 and returned to the liquid distribution chamber of the low-pressure evaporator 3, wherein the circulating air volume of the output unit crude butyraldehyde is 45~195Nm³ / h·t, that is, the circulating air volume for each ton of the crude butyraldehyde output is 45~195Nm³ / h; preferably 95~195Nm³ / h, further preferably 140~160Nm³ / h. Figure 1 An example is shown in which the non-condensable gas is compressed by the compressor 6 and then returns to the low-pressure evaporator 3 .

[0025] Optionally, in order to promote maintaining the pressure of the low-pressure evaporator 3, in actual operation, a part of the non-condensable gas can be optionally circulated back to the low-pressure evaporator 3 to facilitate regulation of the circulation amount of the non-condensable gas, thereby further regulating the low-pressure evaporation efficiency; the excluded non-condensable gas can be optionally connected to the fuel gas network or input into other processes.

[0026] Optionally, based on a large amount of experimental data, the evaporation capacity of the low-pressure evaporator 3 is 31.05-31.3 t / h. By returning the non-condensable gas, the operating temperature of the low-pressure evaporator 3 can be adjusted to a lower, appropriate control range. At the same time, a higher evaporation capacity of the low-pressure evaporator 3 (output of crude butyraldehyde) can be obtained, thereby improving the catalyst separation efficiency of the overall method.

[0027] Optionally, the flash separation process is carried out in the flash tank 1, which is used to separate unreacted raw materials from the reacted materials; the gaseous material obtained by flash evaporation is the unreacted raw material, and the unreacted raw material is output from the gas phase outlet of the flash tank 1, condensed, separated, and then returned to the upstream reaction process; the liquid material obtained by flash evaporation is input into the low-pressure evaporator 3; wherein, the operating pressure of the flash tank 1 is 0.4~0.45MPa, and the operating temperature is 75~85℃; the optimization of the flash evaporation pressure of the present invention can increase the evaporation rate, and controlling the flash evaporation pressure and temperature within an appropriate range can regulate the concentration effect and prevent overheating from damaging the activity of the catalyst.

[0028] Further optionally, the heating temperature of the flash tank 1 is 120-124°C; further optionally, combined with Figure 1 After the gaseous material obtained by flash evaporation is condensed, it is subjected to gas-liquid separation in the separation tank 2, and the unreacted material is output from the gas phase outlet of the separation tank 2. Further optionally, a first branch for discharging the purge gas is provided on the pipeline connected to the gas phase outlet of the separation tank 2. Through the first branch, some by-products and unreacted materials, such as propane and propylene, can be discharged in a timely and appropriate manner, thereby facilitating the regulation of the upstream reaction process and effectively recovering propylene and reducing the accumulation of propane in the overall process route; further optionally, the first branch can be optionally connected to the fuel gas pipeline network or other processes.

[0029] The propylene carbonylation reaction described herein involves reacting propylene with synthesis gas in the presence of a catalyst to produce butyraldehyde. Optionally, the feed molar ratio of propylene to synthesis gas in the propylene carbonylation reaction is 1:(2-3), the molar ratio of hydrogen to carbon monoxide in the synthesis gas is 1:(1-1.05), and the catalyst concentration is 15-25 ppm. Optionally, the reaction temperature for the propylene carbonylation reaction is 70-90°C, and the reaction pressure is 1.5-1.8 MPa.

[0030] It should be noted that in the present invention, the material after the propylene carbonylation reaction is fed from the upper part of the low-pressure evaporator 3 and input into the liquid distribution chamber; in the liquid distribution chamber, the material to be evaporated is evenly distributed to the surface of each downcomer of the evaporation chamber to promote uniform film falling, thereby helping to improve the heat exchange efficiency and prevent local overheating.

[0031] It should be noted that the present invention is not limited to the specific structure of the equipment such as the flash tank 1, the separation tank 2, the collection tank 4, the condensate receiving tank 5, etc., which can be selected as container-type equipment, and further can be selected as equipment with a demister and a butyraldehyde circulation spray pipe on the top of the container, so as to effectively prevent the loss of the catalyst during the separation process; the present invention is not limited to the specific structure of the low-pressure evaporator 3 used, which can be selected as an effective thin film forming vertical falling film evaporator. Those skilled in the art can select the flash tank 1, separation tank 2, collection tank 4, condensate receiving tank 5 and low-pressure evaporator 3 of suitable structure as needed, and the scope of protection of the present invention is not limited thereby.

[0032] Example 1 This embodiment illustrates a process for separating a catalyst for producing butyraldehyde by carbonylation of propylene under specific working conditions. It should be noted that this embodiment is merely a preferred example and does not limit the scope of protection of the present invention.

[0033] Specifically, in the reaction process, 20.722 t / h of propylene is input into the reactor, the molar ratio of propylene to synthesis gas is 1:2, and the molar ratio of hydrogen to carbon monoxide in the synthesis gas is 1:1.05; n-butyraldehyde is used as the solvent, the catalyst used is acetylacetonate triphenylphosphatosiliconyl rhodium, the reaction temperature is 70-90°C, and the reaction pressure is 1.5-1.8 MPa; the materials after the reaction are completed include propylene, propane, n-butyraldehyde, isobutyraldehyde, additives, trimer, etc., and the pressure is 1.5 MPa and the temperature is 80°C.

[0034] The preparation method of the acetylacetonatotriphenylphosphinosilylcarbonyl rhodium catalyst is as follows: S1, adding methanol to a 28wt% rhodium chloride aqueous solution, wherein the volume of methanol added is 8ml / g based on the mass of rhodium chloride; S2, heating the reaction solution of step S1 to 40-50°C, then introducing carbon monoxide, stirring, and maintaining for 6 hours; S3, adding sodium acetylacetone to the reaction solution and stirring for reaction, wherein the molar ratio of the sodium acetylacetone to the rhodium element is 4:1; then adding triphenylphosphine and triisopropylsilane, wherein the mass ratio of the triphenylphosphine, the organosilicon compound and the rhodium element is 6.7:3.3:1, and reacting for 2 to 4 hours to obtain the acetylacetonate triphenylphosphine silicic carbonyl rhodium.

[0035] After the reacted material is flashed in flash tank 1, the resulting gaseous material is condensed and separated and returned to the upstream reaction process, while the resulting liquid material is fed into low-pressure evaporator 3. The operating pressure of the flash tank 1 is 0.45 MPa and the temperature is 80°C. The flash tank 1 outputs a concentrated catalyst solution with an outlet pressure of 1.2-1.5 MPa, which is fed into the low-pressure evaporator 3.

[0036] In this embodiment, the low-pressure evaporator 3 operates at a temperature of 95°C, and the compressor 6 connected to its top has a circulating air volume of 1500 Nm³ / h. The evaporation capacity (catalyst solution output) of the low-pressure evaporator 3 is 31.3 t / h. Through the subsequent recycling of the separated catalyst solution, the catalyst replenishment rate in this embodiment is 115 g / week.

[0037] Example 2-Example 10 Based on the catalyst separation method for propylene carbonylation to butyraldehyde shown in Example 1, Examples 2 to 10 show the catalyst separation process for propylene carbonylation to butyraldehyde under different working conditions. The process steps and parameter control of these examples are the same as those of Example 1, except that different circulating air volumes of the compressor 6 and operating temperatures of the low-pressure evaporator 3 are used. Table 1 shows the specific parameter control ranges and the evaporation amounts and catalyst replenishment amounts of Examples 2 to 10.

[0038] Comparative Example 1 This comparative example illustrates a method for separating catalyst from the reaction materials after propylene carbonylation to butyraldehyde. This method shares the same process steps and parameter control as Example 1, differing in that the non-condensable gas separated in the condensate receiving tank 5 is not returned to the liquid distribution chamber of the low-pressure evaporator 3. Specific evaporation temperatures, evaporation capacities, and catalyst replenishment amounts are detailed in Table 1.

[0039] Table 1

[0040] The optimal catalytic temperature for the catalyst used in this example is 70-90°C. During the separation process of the materials after the propylene carbonylation reaction to butyraldehyde, separation temperatures exceeding 95°C may cause catalyst deactivation. Table 1 demonstrates that, when the evaporation rate of low-pressure evaporator 3 is the same, the evaporation temperature in Comparative Example 1, which lacks the non-condensable gas circulation feature, reaches 98°C, significantly higher than the controlled temperatures of 85-95°C in Examples 1-10. Furthermore, during catalyst solution recycling, the catalyst replenishment rate in Comparative Example 1 was higher than that in Examples 1-10, confirming that the higher temperature used for catalyst separation in Comparative Example 1 degrades catalyst activity and reduces the overall catalyst lifespan. The catalyst replenishment rate in the present embodiment is significantly lower than in Comparative Example 1. Considering the high preparation cost of catalysts containing rhodium as the active component in propylene carbonylation reactions, the present invention offers superior economic benefits, which will be a significant advantage in large-scale industrial production.

[0041] In addition, by analyzing Examples 1 to 10, it can be confirmed that when the circulating air volume of the compressor 6 is controlled to produce 1500-6000 Nm³ / h, that is, the circulating volume relative to the unit crude butyraldehyde (evaporation amount) is 45~195 Nm³ / h·t, the operating temperature of the low-pressure evaporator 3 is 85-95°C, which can effectively ensure that the evaporation amount of the low-pressure evaporator 3 reaches 31.05-31.3 t / h, and the weekly replenishment amount of the catalyst can be controlled within 110 g; combined with the more simplified equipment and process flow of the present invention compared to the prior art, the catalyst separation method for propylene carbonylation to butyraldehyde of the present invention has excellent operability and economy. Furthermore, when the air volume of the compressor 6 is controlled at 3000-6000 Nm³ / h, that is, the circulation volume relative to the unit crude butyraldehyde (evaporation volume) is 95-195 Nm³ / h·t, the evaporation temperature can be lowered and controlled at 85-90°C (as in Examples 4-10), which is more conducive to maintaining the activity of the catalyst. At this time, the evaporator can still maintain a high evaporation volume and the weekly replenishment of the catalyst can be maintained within 112 g / week. When the air volume of the compressor 6 is controlled at above 4500m³ / h, the evaporation temperature can be reduced to about 85°C (such as in Examples 7-10), which is more conducive to maintaining the activity of the catalyst. At this time, the evaporator can still maintain a relatively high evaporation volume and the weekly replenishment of the catalyst can be maintained within 110g / week; surprisingly, after the circulating air volume rises to 4500Nm³ / h, the evaporation temperature is maintained at 85°C, the replenishment of the catalyst no longer decreases, but the evaporation volume shows a trend of gradually decreasing. Therefore, for economic considerations, the circulating air volume of the compressor 6 in the technical solution of the present invention is more preferably set to 4500-5000Nm³ / h, that is, the circulating volume relative to the crude butyraldehyde (evaporation volume) is 140~160Nm³ / h·t, and the operating temperature of the low-pressure evaporator 3 is 85°C.

[0042] It should be noted that the above is a further detailed description of the present invention in conjunction with specific embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, several simple improvements can be made without departing from the concept of the present invention, and all of these should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for separating a catalyst for carbonylation of propylene to butyraldehyde, characterized in that: The material after propylene carbonylation reaction with propylene and synthesis gas as raw materials is flash separated and evaporated in a low-pressure evaporator, and a gaseous material is obtained from the collecting tank of the low-pressure evaporator and a liquid catalyst solution is output; the gaseous material is condensed and separated into gas and liquid, and crude butyraldehyde is output, and the non-condensable gas is returned to the liquid distribution chamber of the low-pressure evaporator; wherein the catalyst is triphenylphosphosiliconate carbonyl rhodium acetylacetonate, and the operating temperature of the low-pressure evaporator is 85-95°C.

2. The method for separating the catalyst for carbonylation of propylene to butyraldehyde according to claim 1, characterized in that: The catalyst is prepared by the following preparation method: S1, adding methanol to a 25wt%-30wt% rhodium trichloride aqueous solution, wherein the volume of methanol added is 5-10ml / g based on the mass of rhodium trichloride; S2, heating the reaction solution of step S1 to 40-50°C, then introducing carbon monoxide, stirring, and maintaining for 3-8 hours; S3, adding sodium acetylacetone to the reaction solution and stirring for reaction, wherein the molar ratio of the sodium acetylacetone to the rhodium element is (3-5):1; then adding triphenylphosphine and an organosilicon compound, reacting for 2-4 hours to obtain the acetylacetonate triphenylphosphine carbonyl rhodium; The mass ratio of the triphenylphosphine, the organosilicon compound and the rhodium element is (5-8):(2-5):1, and the organosilicon compound is octaphenylcyclotetrasiloxane or triisopropylsilane.

3. The method for separating the catalyst for carbonylation of propylene to butyraldehyde according to claim 1, characterized in that: The operating temperature of the low-pressure evaporator is 85-90°C.

4. The method for separating the catalyst for preparing butyraldehyde by carbonylation of propylene according to claim 1, characterized in that: The operating pressure of the low-pressure evaporator is 65-70 kPa.

5. The method for separating the catalyst for preparing butyraldehyde by carbonylation of propylene according to claim 1, characterized in that: The non-condensable gas is compressed by the compressor and then returned to the liquid distribution chamber of the low-pressure evaporator, wherein the circulating air volume of the output unit crude butyraldehyde is 45~195Nm³ / h·t.

6. The method for separating the catalyst for preparing butyraldehyde by carbonylation of propylene according to claim 1, characterized in that: A portion of the non-condensable gas is input into the gas pipeline network.

7. The method for separating the catalyst for preparing butyraldehyde by carbonylation of propylene according to claim 1, characterized in that: The evaporation capacity of the low-pressure evaporator is 31.05-31.3 t / h.

8. The method for separating the catalyst for carbonylation of propylene to butyraldehyde according to claim 1, characterized in that: The flash separation process is carried out in a flash tank, which is used to separate unreacted raw materials from the reacted materials; the gaseous material obtained by flash evaporation is the unreacted raw material, which is output from the gas phase outlet of the flash tank, condensed, separated, and returned to the upstream reaction process; the liquid material obtained by flash evaporation is input into the low-pressure evaporator; wherein the operating pressure of the flash tank is 0.4~0.45MPa, and the operating temperature is 75~85°C.

9. The method for separating the catalyst for preparing butyraldehyde by carbonylation of propylene according to claim 1, characterized in that: The feed molar ratio of propylene to synthesis gas in the propylene carbonylation reaction is 1:(2-3), the molar ratio of hydrogen to carbon monoxide in the synthesis gas is 1:(1-1.05); and the concentration of the catalyst is 15-25 ppm.

10. The method for separating the catalyst for preparing butyraldehyde by carbonylation of propylene according to claim 9, characterized in that: The reaction temperature of the propylene carbonylation reaction is 70-90° C., and the reaction pressure is 1.5-1.8 MPa.

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