Method for low pressure synthesis of propynol under acetylene atmosphere and catalyst thereof

Abstract

A method for synthesizing propynol under low pressure in acetylene atmosphere and a catalyst thereof, which uses 35%-40% formaldehyde aqueous solution as a starting material, uses a supported copper oxide-chromium oxide (CuO-Cr2O3) as a catalyst, and makes the formaldehyde aqueous solution flow through the surface of the catalyst carrier in a way of flowing through but not accumulating in a vertical pipe type reactor filled with acetylene gas atmosphere under a pressure lower than 0.05 MPa, and makes the formaldehyde aqueous solution react with acetylene to generate propynol. After the reaction, the material aqueous solution is separated by rectification to collect the product, and the yield of propynol in the product can reach 83%-92%. The Cu / Cr in the copper oxide-chromium oxide (CuO-Cr2O3) catalyst is 9 / 1-7 / 3 (mass ratio).

Description

TECHNICAL FIELD

[0001] The present application relates to a synthesis method of propynol, in particular a safe and high yield synthesis method of propynol from aqueous formaldehyde solution by reaction with acetylene. BACKGROUND

[0002] Propynol, also known as 2-propyn-1-ol or acetylenic methyl alcohol, is a colorless transparent liquid at room temperature, and is an important organic intermediate raw material. In the pharmaceutical industry, propynol is an important intermediate for the synthesis of sodium fosfomycin, calcium fosfomycin and sulfadiazine; in the pesticide industry, propynol can be used to synthesize the pesticide kermite and fungicides; in the electroplating industry, propynol and its downstream derivatives are excellent copper or nickel plating brighteners; in the steel industry and oil exploitation, propynol and its downstream compounds are also used as rust inhibitors and acidizing corrosion inhibitors.

[0003] The most widely used method for preparing propynol at home and abroad at present is the co-production method, that is, aqueous formaldehyde solution and acetylene gas are reacted under the catalysis of a catalyst to generate a mixture of propynol and 1,4-butynediol, and then propynol is separated from the mixture. Due to the low solubility of acetylene in aqueous solution, the speed of acetylene migrating from the gas-liquid interface into the aqueous phase is also slow. In order to promote the entry of acetylene into the aqueous phase and increase the solubility of acetylene in the aqueous phase, the acetylene pressure must be increased. In addition, during the synthesis reaction, the generated propynol is very active and is easily further added to formaldehyde to form 1,4-butynediol, especially when the acetylene pressure is low, the reaction product is basically 1,4-butynediol. Therefore, there is no synthesis process method for generating propynol as the main product from aqueous formaldehyde solution at low pressure at present. At present, the co-production method is basically used to separate and collect propynol product. In order to improve the yield of propynol, the alkyne-aldehyde synthesis method of using low formaldehyde concentration and increasing acetylene pressure is widely used in industrial production, that is, using acetylene copper (or copper oxide-bismuth oxide, etc.) as a catalyst, using 6% to 10% (or 9% to 15%) aqueous formaldehyde solution as formaldehyde raw material, and performing synthesis reaction in 0.5 MPa to 2 MPa high pressure acetylene gas at a temperature of 90°C to 130°C, the total reaction time is several hours to ten hours. After the reaction is completed, the catalyst residue is separated by pressure filtration, and the reaction material liquid containing less than 10% of the total reaction product is collected, in which the content of the target product propynol is only 3% to 4% at most, and the rest is 1,4-butynediol and impurities. Then the reaction material liquid is separated by rectification to collect propynol and 1,4-butynediol, respectively.

[0004] The synthesis process method has the following main disadvantages:

[0005] 1. There is a serious safety hazard: due to the low solubility of acetylene in water, if the acetylene pressure is lower than 0.15 MPa, the concentration of acetylene dissolved in water is very low, and the reaction mainly generates 1,4-butynediol. In order to achieve sufficient dissolved acetylene in water to meet the needs of the reaction, usually a higher acetylene pressure (above 0.5 MPa) is used, because acetylene gas exceeding 0.15 MPa pressure is explosive, plus the use of acetylene copper catalyst, and acetylene copper is easy to burn and explode when dry and subjected to external impact, which poses a serious safety hazard.

[0006] 2. Low yield of propynol product: In the synthesis reaction process, the generated propynol is chemically active and easily further adds with formaldehyde under the action of the catalyst to generate 1,4-butynediol, so the production ratio of propynol to 1,4-butynediol obtained by this process method is usually 1:9~1:2, that is, the yield of propynol is usually less than one third of the final product.

[0007] 3. Low production efficiency and high energy consumption: In order to improve the yield of propynol, this process method reduces the formaldehyde concentration in the water solution while increasing the acetylene pressure to inhibit the generation of 1,4-butynediol, and usually controls the initial formaldehyde concentration to be 6%~10%, so the product concentration is also low, resulting in a large amount of water in the subsequent rectification separation, low production efficiency and high energy consumption.

[0008] The process method of the invention patent CN202111004168.6 "A method for synthesizing propynol" effectively solves the problems existing in the current production process, but the patent method uses formaldehyde organic solution as the starting material and potassium hydroxide or potassium alcoholate as the catalyst, and the waste potassium hydroxide solution needs to be treated after each batch reaction, and corresponding measures need to be taken during production to prevent the volatilization and escape of organic solvents from affecting the production environment. SUMMARY

[0009] The purpose of the present application is to provide a synthesis technical method which uses formaldehyde aqueous solution as the starting material, the catalyst can be used for a long time, the acetylene pressure is low, and the reaction time is short, and the product is mainly propynol.

[0010] The present application adopts the following technical solutions:

[0011] Using formaldehyde aqueous solution and acetylene gas as starting materials, and using supported copper oxide-chromium oxide as catalyst, the production and synthesis of propynol are carried out according to the following technical scheme.

[0012] 1. Preparation of supported copper oxide-chromium oxide (CuO-Cr2O3) catalyst

[0013] (1) Using copper nitrate and chromium nitrate as raw materials, dissolving them in water to prepare a mixture aqueous solution for standby use.

[0014] (2) The carrier particles are first saturated by immersion in a 10-15% aqueous solution of sodium hydroxide (or potassium hydroxide). The particles are then removed and filtered to remove the water trapped in the interstices of the particles. The particles are then dried at 90-100°C for 1-2 hours to remove most of the water from the particles.

[0015] (3) The carrier particles are then immersed in the mixed aqueous solution of copper nitrate and chromium nitrate of (1) above. The copper and chromium salts react with the basic salt on the surface of the carrier particles and in the pores of the particles to form copper hydroxide and chromium hydroxide which are deposited on the surface of the particles. The particles are then dried at 100-120°C and then calcined at 400-450°C for 3-4 hours to convert the metal salts and their hydroxides on the surface of the particles to the oxides of the metals, i.e. CuO-Cr203.

[0016] The metal salts used in (1) above are anhydrous or hydrated copper nitrate and chromium nitrate. The Cu / Cr ratio in the mixed aqueous solution of the metal salts is 9 / 1 to 7 / 3 by weight.

[0017] The carrier used in (2) above is activated alumina (γ-Al203) or silica (Si02). The carrier particles have a diameter of 4-6 mm. This size of carrier particles provides a void space of about 1 / 3 of the total volume of the particles which provides sufficient space for the acetylene gas atmosphere in the reaction tube of the present application.

[0018] The present inventors found that even if the reaction method under the vertical-pipe ethylene atmosphere of the present application is used, if pure copper oxide or copper oxide-bismuth oxide is used as the supported catalyst, the reaction product is mainly 1,4-butynediol, and many impurities are produced. Through analysis of the catalytic mechanism of different metals and many experiments, the present inventors found an effective method of adding an appropriate amount of chromium oxide to copper to form a copper-chromium supported catalyst. The present inventors found that the added chromium oxide can inhibit the further reaction of propynol with formaldehyde and inhibit other side reactions during the reaction of the present application, and as the amount of chromium oxide added increases, the amount of propynol produced in the reaction product also increases, but the reaction rate of formaldehyde and ethylene decreases. Through many experiments, the present inventors found that if the mass ratio of Cu / Cr in the copper oxide-chromium oxide catalyst is 9 / 1 to 7 / 3, the yield of the target product propynol and the reaction rate are optimal. Using the copper oxide-chromium oxide supported catalyst found by the present application, and the unique synthesis reaction operation method under the vertical-pipe ethylene atmosphere of the present application, 35% to 40% high-concentration formaldehyde water can be used as the starting material, and the amount of propynol in the total reaction product (propynol and 1,4-butynediol) is more than 83%, and other impurities are less than 2%.

[0019] 2. Making a special vertical-pipe reactor

[0020] The synthesis reaction of the present application needs to be carried out in a special reactor. The reactor is composed of several parallel stainless steel reaction pipes, which are nested in a stainless steel cylindrical shell, similar to a tube condenser. The total length of the reactor is 12 to 16 meters, and the inner diameter of a single reaction pipe is 40 to 60 mm, and the length is 12 to 16 meters. The reaction pipe is filled with the previously prepared copper oxide-chromium oxide (CuO-Cr2O3) supported catalyst particles. The reaction pipe must be straight and cannot be bent, and the reactor must be vertically placed to avoid the accumulation of formaldehyde water in the reaction pipe. When in use, the ethylene gas and formaldehyde water are both introduced from the top of the reaction pipe and flow out from the bottom of the reaction pipe after passing through the reaction pipe. The reactor shell is filled with heat transfer medium (heat conducting oil), which is pumped from the bottom of the reactor to the top of the reactor.

[0021] 3. Synthesis reaction operation method

[0022] The synthesis reaction operation of the present application is combined with a special reactor and adopts a unique operation method under an ethylene atmosphere:

[0023] (1) The first time the reactor is used, the supported metal catalyst in the reaction tube needs to be pre-activated. The pre-activation method is as follows: close the bottom end of the reactor, fill the reaction tube with clean water (the purpose of filling the reaction tube with clean water is to accelerate heat conduction), heat the flow medium in the reactor shell to 80-90°C and maintain for 0.5 hours, then open the valve at the bottom end of the reactor to discharge the clean water in the reaction tube. Continue to maintain the temperature of the heat transfer medium in the shell at 80-90°C, and at the same time, introduce acetylene into the reaction tube from the top end of the reaction tube, maintaining the acetylene filled in the reaction tube, with a small amount of acetylene escaping from the bottom end of the reaction tube. The acetylene pressure is ≤0.05 MPa. Maintain for 1-2 hours to allow the acetylene to react with the copper oxide in the catalyst to form acetylene copper complex, and the pre-activation is complete. The supported catalyst that has been pre-activated only needs to be used continuously, or the valves at both ends of the reactor are closed during the period of suspension, and the reaction tube remains with acetylene gas and the catalyst particles remain wet, so that the catalyst does not need to be pre-activated again the next time it is used.

[0024] (2) Continuous synthesis reaction operation: maintain the temperature of the flow heat transfer medium in the reactor shell at 80-90°C, continuously introduce acetylene gas from the top end of the reactor, and always maintain the state of acetylene gas filling the internal void space of the reaction tube, with an acetylene pressure of ≤0.05 MPa. Then add the formaldehyde aqueous solution from the top end of the reactor, allowing the formaldehyde to react with the catalyst in the reaction tube. The addition of the formaldehyde aqueous solution must meet the following two conditions:

[0025] ① The formaldehyde aqueous solution is added continuously for 1-2 minutes, then paused for 1-2 minutes, then added continuously for 1-2 minutes, then paused for 1-2 minutes, and so on in this intermittent addition manner;

[0026] ② The addition rate (addition amount) of each batch of formaldehyde aqueous solution is maintained so that the formaldehyde aqueous solution does not accumulate in the reaction tube, i.e. the formaldehyde aqueous solution only flows down the surface of the catalyst particles from top to bottom, does not accumulate in the reaction tube, and the formaldehyde aqueous solution only randomly flows through 50-80% of the surface of the catalyst particles, the remaining surface of the catalyst particles and the interface between the formaldehyde aqueous solution flowing through the surface of the catalyst particles are exposed to the acetylene gas atmosphere at any time. At the same time, the addition amount of each formaldehyde aqueous solution is controlled to ensure that the formaldehyde in the formaldehyde aqueous solution has been converted by more than 98% when it flows to the bottom end of the reactor.

[0027] According to the above adding method of formaldehyde water solution, no liquid is accumulated in the reactor, and acetylene gas always fills the void space of the whole reaction tube, i.e. the catalyst particles and the formaldehyde liquid surface flowing through the surface of the catalyst particles are always exposed to the acetylene atmosphere. The formaldehyde water solution is in the form of thin liquid layer and flows randomly on the surface of the catalyst particles in the reaction tube. In a certain period of time, formaldehyde contacts with the active metal (acetylene copper) on the surface of the catalyst particles flowing through, reacts to convert into propargyl alcohol, and then falls into the water solution. The copper active points on the surface of the catalyst particles which have reacted are exposed to the acetylene atmosphere in the following period of time to be activated again to form acetylene copper complex. In this way, the generation of catalyst acetylene copper complex and the conversion of formaldehyde into propargyl alcohol can occur simultaneously in the reaction tube, which is essentially different from the slurry bed reaction process and the fluidized bed reaction process for synthesizing propargyl alcohol and 1,4-butynediol in terms of ideas, equipment and specific operation modes.

[0028] Here, the concentration of the reaction starting formaldehyde water solution is 35% to 40%.

[0029] The formaldehyde water solution flows into the reactor from the top end and flows out from the bottom end of the reactor, which takes about 5 to 7 minutes. After the reaction material liquid flows out from the bottom end of the reactor, it immediately flows through the cooling tube to be cooled to room temperature, and then flows into the collector for collection. The acetylene gas escaping from the bottom end of the reactor is also collected for reuse.

[0030] The amount of formaldehyde water solution is controlled so that the conversion rate of formaldehyde after passing through the reaction tube is above 98%. In the reaction product, the target product propargyl alcohol can account for more than 82% of the total product.

[0031] 4. Subsequent operation

[0032] The reaction material water solution flowing out from the bottom end of the reactor is collected, and the product propargyl alcohol is separated by distillation according to the conventional method.

[0033] Since the catalyst particles in the reaction tube are in a static state, the mechanical impact of the reaction material formaldehyde water solution on the catalyst particles is weak during use, which is not easy to cause the catalyst particles to be broken. In addition, the residence time of the reaction material in the reaction tube is only a few minutes, which is not easy to form polymerized carbon on the surface of the catalyst particles. Moreover, since the catalyst particles are always in the acetylene atmosphere and at a suitable temperature, the reaction activity can be kept stable for a long time. Therefore, the catalyst particles can be used continuously for a long time after being packed.

[0034] The technical scheme of the present application can achieve the following effects:

[0035] 1. High-concentration formaldehyde water solution is used as the starting raw material, and the amount of material for subsequent distillation treatment is greatly reduced, the production energy consumption is obviously reduced, and the production efficiency is obviously improved.

[0036] 2. The synthesis reaction process keeps the acetylene gas close to normal pressure (≤0.05 MPa), and the catalyst particles are packed in the reaction tube and always in a closed and humid state, which ensures the safety of production.

[0037] 3. The reaction material liquid stays in the reaction tube for only 5-7 minutes before flowing out to terminate the reaction by cooling, effectively inhibiting the polymerization side reaction of the material. The formaldehyde conversion rate in the reaction system reaches more than 98%, and the target product propynol in the generated product can reach 85%-94% of the total product.

[0038] 4. The catalyst particles are not easy to break and deactivate, and can be used for a long time. DETAILED DESCRIPTION

[0039] Example 1:

[0040] In this example, a reaction tube is used for synthesis operation, the length of the reaction tube is 14 m, and the inner diameter of the tube is 50 mm. The packed catalyst particles in the reaction tube are 4-5 mm in diameter, the carrier is active alumina, and the loaded metal catalyst is copper oxide-chromium oxide, Cu / Cr=9 / 1 (mass ratio). Before initial use, the catalyst is pre-activated according to the method described above.

[0041] During the synthesis reaction operation, the heat transfer medium temperature of the reactor shell is controlled at 82℃±2℃, and the acetylene gas pressure entering the reaction tube is always maintained at 0.02 MPa-0.04 MPa, and the acetylene gas fills the internal void space of the reaction tube throughout the reaction operation process.

[0042] The 35% concentration formaldehyde aqueous solution is continuously and intermittently added from the top of the reactor according to the method of adding 1 minute and pausing 1 minute each time, and the amount of formaldehyde aqueous solution added each time (1 minute) is about 400 g, and the material liquid flows through the reaction tube for about 5-6 minutes. The reaction material liquid flowing out from the bottom of the reaction tube is cooled to room temperature by a cooling tube and collected. After the reaction, the material is separated by rectification in an experimental rectification device, and propynol and 1,4-butynediol are collected respectively.

[0043] The example added 20 Kg of formaldehyde water solution with concentration of 35%, which contained 7 Kg of formaldehyde. The residual formaldehyde content in the effluent reaction material was 0.4%, and the conversion rate of formaldehyde was 98.8%. The reaction material was separated by distillation to obtain 11.1 Kg of propynol material with water content of 6.3%, which contained 10.4 Kg of pure propynol. 1.95 Kg of 1,4-butynediol material with water content of 12.9% was obtained, which contained 1.7 Kg of pure 1,4-butynediol. About 80.4% of the converted formaldehyde was propynol, about 17.7% was 1,4-butynediol, and the rest 1.9% was by-product impurities. The main reaction alkyne alcohol product of the example was propynol / 1,4-butynediol = 85.8 / 14.2 (mass ratio).

[0044] Example 2:

[0045] The reaction tube had the same size as in Example 1, and the loaded catalyst particles in the reaction tube had a diameter of 5-6 mm, a carrier of silica, and a loaded metal catalyst of copper oxide-chromium oxide with Cu / Cr = 7 / 3. Before initial use, the catalyst was pre-activated according to the method described above.

[0046] During the synthesis reaction operation, the heat transfer medium temperature of the reactor shell was controlled at 88°C ± 2°C, and the acetylene gas pressure entering the reaction tube was maintained at 0.02 MPa-0.04 MPa at all times. The acetylene gas filled the internal void space of the reaction tube throughout the reaction operation.

[0047] Formaldehyde water solution with concentration of 37% was continuously and intermittently added from the top of the reactor at a rate of 2 minutes of addition and 1 minute of pause. The amount of formaldehyde water solution added during each 2-minute addition was about 330 g, and the material stream took about 6-7 minutes to pass through the reaction tube. The effluent reaction material stream from the bottom of the reaction tube was cooled to room temperature by a cooling tube and collected. The post-reaction material was separated by distillation in a laboratory distillation apparatus to obtain propynol and 1,4-butynediol, respectively.

[0048] This example was carried out with a total formaldehyde aqueous solution of 20 Kg at a concentration of 37%, which contained 7.4 Kg of pure formaldehyde. The residual formaldehyde content in the effluent reaction mixture was 0.7%, which gave a conversion of 98.1% of the initial formaldehyde. The reaction mixture was separated by distillation to give 13.2 Kg of propargyl alcohol containing 5.8% of water, which contained 12.4 Kg of pure propargyl alcohol. The distillation also gave 0.85 Kg of 1,4-butyne diol containing 17.5% of water, which contained 0.7 Kg of pure 1,4-butyne diol. Of the formaldehyde that had been converted, about 91.7% had been converted to propargyl alcohol, about 6.9% to 1,4-butyne diol, and the remaining 1.4% to by-products. The main reaction product of this example was propargyl alcohol / 1,4-butyne diol = 94.5 / 5.5 (mass ratio).

Claims

1. A method for preparing a supported copper oxide-chromium oxide (CuO-Cr2O3) catalyst for synthesizing propargyl alcohol, characterized in that: The following steps are involved: (1) using copper nitrate and chromium nitrate as raw materials, dissolving them in water to prepare a mixture aqueous solution for standby use; (2) Using alumina particles or silica particles as carriers, first saturate the carrier particles with a 10% to 15% sodium hydroxide or potassium hydroxide aqueous solution, remove the alkaline aqueous solution that has accumulated in the gaps between the particles, and bake at 90°C to 100°C for 1 to 2 hours to remove most of the water in the carrier particles; (3) The carrier particles are immersed in the copper nitrate-chromium nitrate mixed aqueous solution of the above (1) until they are saturated. The copper salt and chromium salt therein react with the alkaline salt on the surface of the carrier particles and the surface of the internal pores to generate copper hydroxide and chromium hydroxide, which are deposited and attached. The carrier impregnated with the mixed metal salts is then dried at 100°C to 120°C and then calcined at 400°C to 450°C for 3 to 4 hours to convert the metal salts and their hydroxides attached to the surface of the carrier into metal oxides, thereby obtaining a supported copper oxide-chromium oxide (CuO-Cr2O3) catalyst.

2. The method for preparing the supported copper oxide-chromium oxide (CuO-Cr2O3) catalyst according to claim 1, characterized in that: In the step (1), the metal salts used are anhydrous salts or salts containing crystalline water of copper nitrate and chromium nitrate, and the mass ratio of Cu to Cr in the mixed metal salt aqueous solution is 9:1 to 7:

3.

3. The method for preparing the supported copper oxide-chromium oxide (CuO-Cr2O3) catalyst according to claim 1, characterized in that: In the step (2), the carrier used is activated alumina (γ-Al2O3) or silicon dioxide (SiO2), and the diameter of the carrier particles is between 4 mm and 6 mm.

4. A method for synthesizing propargyl alcohol, characterized in that: The following steps are involved: (1) Preparation of supported copper oxide-chromium oxide (CuO-Cr2O3) catalyst Prepare a supported copper oxide-chromium oxide (CuO-Cr2O3) catalyst according to the method of claim 1; (2) Fabrication of vertical tube reactor The reactor consists of several stainless steel reaction tubes arranged parallel to the reactor axis, with a stainless steel cylindrical shell nested outside. The reaction tubes are filled with previously prepared supported copper oxide-chromium oxide (CuO-Cr2O3) catalyst particles. The reaction tubes must be straight without any bends, and the reactor must be placed vertically to prevent the reaction liquid from accumulating in the reaction tubes. During use, acetylene gas and formaldehyde aqueous solution are allowed to enter from the top of the reaction tubes, pass through the reaction tubes, and then flow out from the bottom of the reaction tubes. The reactor shell is filled with heat transfer medium heat transfer oil, which is pumped from the bottom of the reactor to the top. (3) Synthesis reaction operation At the specified reaction temperature, acetylene gas is continuously introduced from the top of the reactor to ensure that the acetylene gas always fills the void space inside the reaction tube. Then, formaldehyde solution is added from the top of the reactor to allow the formaldehyde to fully contact and react with the catalyst during the process of passing through the reaction tube. The method of adding formaldehyde solution must meet the following two conditions at the same time: ① Add formaldehyde solution continuously for 1 to 2 minutes, stop adding for 1 to 2 minutes, then continue adding for 1 to 2 minutes, and then stop adding for 1 to 2 minutes, and dosing in this intermittent manner; ② The addition rate and dosage of each batch of formaldehyde solution should be maintained so that the formaldehyde solution does not accumulate in the reaction tube. That is, the formaldehyde solution only flows from top to bottom along the surface of the catalyst particles and does not accumulate in the reaction tube. In addition, the formaldehyde solution only randomly flows through 50% to 80% of the catalyst particle surfaces in the reaction tube, and the interface between the remaining catalyst particle surfaces and the formaldehyde solution flowing through the catalyst particle surfaces is exposed to the acetylene gas atmosphere at any time. At the same time, the formaldehyde in the formaldehyde solution should have been converted by more than 98% when it flows out of the bottom of the reactor. The formaldehyde aqueous solution enters from the top of the reactor, flows for 5 to 7 minutes, flows out from the bottom of the reactor, immediately flows through the cooling pipe to cool to room temperature, and then flows into the collector. The reaction materials are separated by distillation to collect the target product.

5. The method for synthesizing propargyl alcohol according to claim 4, wherein In the step (2), each reaction tube of the reactor is 12 to 16 meters long and has an inner diameter of 40 to 60 mm.

6. The method for synthesizing propargyl alcohol according to claim 4, wherein: In the step (3), the prescribed reaction temperature is 80° C. to 90° C., and the acetylene pressure is ≤0.05 MPa.

7. The method for synthesizing propargyl alcohol according to claim 4, wherein: In the step (3), the concentration of the formaldehyde solution is 35% to 40%.