Method for synthesizing 3-hydracrylic acid

Abstract

The invention relates to a method for synthesizing 3-hydracrylic acid, in particular to a method for preparing 3-hydracrylic acid from formaldehyde and acetic acid. The process comprises the following steps: firstly, carrying out condensation reaction on formaldehyde and acetic acid on a catalyst with a condensation function to generate a mixture of acrylic acid and water; and then carrying out hydration reaction on the mixture of the in-situ generated acrylic acid and water on a hydration catalyst to generate 3-hydracrylic acid.

Description

Technical Field

[0001] The invention relates to a method for catalytically synthesizing 3-hydroxypropionic acid, in particular to a method for preparing 3-hydroxypropionic acid from formaldehyde and acetic acid. Background Art

[0002] 3-Hydroxypropionic acid is an isomer of lactic acid (2-hydroxypropionic acid). Due to the different positions of the hydroxyl groups, its chemical properties are more active. Through oxidation, dehydration, esterification, etc., it can synthesize a variety of important chemical substances, such as malonic acid, acrylic acid, 3-hydroxypropionic acid ester, and polymer poly 3-hydroxypropionic acid. It can also be used as an additive and preservative for food or feed.

[0003] The large-scale production of 3-hydroxypropionic acid has not been reported. Its synthesis methods mainly include biological fermentation and chemical synthesis. Although the biological fermentation method is green and environmentally friendly, it has low production efficiency, cumbersome product separation, and small production scale, which cannot meet the market demand for polymers. The chemical synthesis methods for producing 3-hydroxypropionic acid mainly include: β-hydroxypropionitrile acidification method, 1,3-propylene glycol / propylene alcohol / 3-hydroxypropanal oxidation method, vinyl acetate carbonylation method, and acrylic acid hydration method.

[0004] β-Hydroxypropionitrile acidification method: Ethylene and Cl2 undergo substitution reaction to generate vinyl chloride, which is then added with water and substituted with sodium cyanide to generate β-hydroxypropionitrile; β-hydroxypropionitrile then reacts with water to generate 3-hydroxypropionic acid. This route uses highly toxic sodium cyanide, so it is only suitable for small-scale synthesis and separation in the laboratory, and is not suitable for large-scale industrial production.

[0005] 1,3-propylene glycol / propylene alcohol / 3-hydroxypropanal oxidation method: Supported precious metal catalysts are widely used in the catalytic oxidation of alcohols and aldehydes to prepare carboxylic acids. The production of 3-hydroxypropionic acid using 1,3-propylene glycol as raw material has a high raw material cost, and the large-scale production technology of 1,3-propylene glycol is monopolized by foreign countries. Domestic production technology is under continuous development and research. Degussa reported that using 3-hydroxypropanal as raw material (3-hydroxypropanal is usually obtained by hydration of acrolein, which is an intermediate in the process of propylene oxidation to acrylic acid) has milder reaction conditions than 1,3-propylene glycol, but the oxidation reaction process is not easy to control, and a slight change can lead to over-oxidation to produce malonic acid.

[0006] Vinyl acetate carbonylation method: Vinyl acetate and other vinyl unsaturated products react with CO and H2O in the presence of Pd complex to form hydroxypropionic acid ester (a mixture of 3-hydroxy and 2-hydroxy), which is then hydrolyzed by base to form a mixture of 3-hydroxypropionic acid and lactic acid. In this route, the raw material vinyl acetate is toxic, the carbonylation reaction conditions are harsh, the catalyst cost is high, and the product 3-hydroxypropionic acid and lactic acid have similar properties and are difficult to separate.

[0007] Acrylic acid hydration method: Wanhua Chemical (CN2019112225946.7) reported a method for preparing 3-hydroxypropionic acid by catalyzing the hydration of acrylic acid using a β-molecular sieve catalyst modified with an acid such as maleic acid or citric acid. The preparation of 3-hydroxypropionic acid from acrylic acid through hydration reaction has low requirements on equipment.

[0008] Although the biosynthesis method is the main method for preparing 3-hydroxypropionic acid, the fermentation process is not mature and the preparation time is long. The chemical synthesis method has gradually attracted attention due to its advantages such as relatively simple separation and purification, low cost, and mild conditions. Summary of the invention

[0009] The problem to be solved by the present invention is to provide a method for synthesizing 3-hydroxypropionic acid, a method for preparing 3-hydroxypropionic acid from cheap and readily available formaldehyde and acetic acid. 3-hydroxypropionic acid is prepared by condensation-hydration through a suitable catalytic system and catalytic process.

[0010] The technical solution is:

[0011] Formaldehyde or its aqueous mixture and acetic acid are gasified, diluted with an inert gas or without dilution, and undergo condensation reaction on a catalyst with a condensation function in a first-stage reactor to generate a mixture of acrylic acid and water; a mixture of acrylic acid and water is obtained from the reaction mixture by separation, and then the mixture of acrylic acid and water, or by partially separating water or by adding water to adjust the molar ratio of acrylic acid to water, is gasified, diluted with an inert gas or without dilution, and undergoes hydration reaction on a catalyst with a hydration function in a second-stage reactor to generate 3-hydroxypropionic acid.

[0012] Provide a solution:

[0013] Acrylic acid and water are partially separated or not separated in the mixture after the first stage reactor.

[0014] Provide a solution:

[0015] The formaldehyde or its aqueous mixture includes: trioxymethylene, polyoxymethylene, and 30-99 wt% formaldehyde aqueous mixture;

[0016] The molar ratio of formaldehyde to acetic acid in the formaldehyde or its aqueous mixture is 5:1 to 1:5;

[0017] The inert atmosphere includes: N2, Ar, He;

[0018] The inert gas accounts for 10-80% of the total gas volume;

[0019] The catalyst having condensation function is one or more of tantalum phosphate, niobium phosphate, tantalum phosphate isomorphously substituted with niobium, niobium phosphate isomorphously substituted with tantalum, and supported catalysts thereof;

[0020] The loading amount of the active component in the supported catalyst is 5-50wt%;

[0021] The carrier of the supported catalyst includes: one of SiO2, Al2O3, TiO2, ZrO2 or a mixture of two or more thereof in any proportion;

[0022] The condensation reaction temperature is: 250-450°C;

[0023] The condensation reaction pressure is: 0.5-30atm;

[0024] The mass space velocity of formaldehyde and acetic acid on the catalyst is: 0.2-4h -1 ;

[0025] The molar ratio of acrylic acid to water in the mixture of acrylic acid and water is 1:1 to 1:6;

[0026] The catalyst with hydration function is: SO4 2- / HfO2、SO4 2- / ZrO2、SO4 2- / TiO2、SO4 2- / ZrO2-HfO2, SO4 2- / Fe2O3、SO4 2- / SnO2、SO4 2- / CeO2、SO4 2- / γ-Al2O3;

[0027] The hydration reaction temperature is: 120-350°C;

[0028] The hydration reaction pressure is: 0.5-30atm.

[0029] The mass space velocity of acrylic acid on the catalyst is: 0.2-4h -1 .

[0030] Provide a solution:

[0031] The preparation method of the catalyst with condensation function is as follows: potassium niobate or potassium tantalate is dissolved to form a uniform solution, and then a mixed acid solution of nitric acid and phosphoric acid with a molar ratio of 1:1 is added dropwise thereto until more than 95% of Nb and tantalum metal ions in the solution are precipitated, and then the above-mentioned precipitation suspension is filtered and washed until the filtrate is neutral, and then the precipitate is dried and placed in air or an inert atmosphere and fully calcined to 500-800° C. to obtain niobium oxyphosphate or tantalum oxyphosphate;

[0032] Using a mixed solution of potassium niobate and potassium tantalate, the above method can be used to prepare niobium isomorphously substituted tantalum oxyphosphate or tantalum isomorphously substituted niobium oxyphosphate.

[0033] The preparation method of the supported catalyst is as follows: after potassium niobate or potassium tantalate is dissolved to form a uniform solution, a specific mass of a carrier is added according to the load amount, and then the supported condensation catalyst is prepared by continuing the above process.

[0034] Provide a solution:

[0035] The preparation method of the hydration function catalyst is as follows: dissolving one or more of the corresponding soluble metal salts of Ti, Zr, Hf, Fe, Sn, Ce, and Al in water or ethanol, adding ammonia water or urea or NaOH or KOH and other precipitants, wherein the amount of the precipitant is sufficient to precipitate more than 90% of the metal ions in the metal salt solution; and simultaneously adding (NH4)2SO4 or Na2SO4 or K2SO4 solution, wherein the SO4 2- The ion concentration is 0.5-4.0 mol / L; the obtained precipitation suspension is aged at 30-80°C for 6-24h, then filtered, washed to remove impurity ions, and then dried and fully calcined at 400-800°C in air or nitrogen atmosphere.

[0036] Beneficial technical effects

[0037] The present invention realizes the synthesis of high value-added 3-hydroxypropionic acid by organically combining innovative catalyst design with reaction process with cheap, easily available and simple raw materials formaldehyde and acetic acid.

[0038] Figure 1 .Brief reaction process flow chart. DETAILED DESCRIPTION

[0039] In order to further explain the present invention in detail, several specific implementation cases are given below, but the present invention is not limited to these embodiments.

[0040] according to Figure 1 The reaction process is briefly described as follows: the vaporized formaldehyde acetic acid mixed solution undergoes a condensation reaction on a catalyst with a condensation function in the first reactor; the reacted materials are separated to obtain a mixture of acrylic acid and water, which is introduced into a hydration reactor by controlling the temperature, and the molar ratio of acrylic acid to water is adjusted to an appropriate ratio by partially separating the water; finally, in the second reactor, the mixture of acrylic acid and water undergoes a hydration reaction on a catalyst with a hydration function to generate 3-hydroxypropionic acid, which is then separated to obtain 3-hydroxypropionic acid.

[0041] Example 1

[0042] Potassium niobate is dissolved in water to form a uniform saturated aqueous solution, and then a mixed solution of 68wt% nitric acid and 85wt% phosphoric acid in a molar ratio of 1:1 is added dropwise thereto, and the Nb ion concentration is monitored until more than 95% of the Nb ions in the solution are precipitated, and then the above-mentioned precipitation suspension is filtered, and the solid is washed until the filtrate is neutral, and the precipitate is dried and fully calcined in air at 500°C until the mass loss is stable, thereby obtaining niobium oxyphosphate.

[0043] Dissolve zirconium nitrate in water (10 g / L), gradually add 26 wt% ammonia solution, monitor the Zr ion concentration until more than 90% of the Zr ions are precipitated, and add (NH4)2SO4 to ensure that SO4 2- The ion concentration is 0.5 mol / L; the obtained precipitate is aged at 30°C for 6 hours, then filtered, washed, and the impurity ions are removed, and then fully calcined at 400°C in an air atmosphere until the mass loss is stable, thus obtaining SO4 2- / ZrO2.

[0044] After the mixture of trioxymethylene and acetic acid in a molar ratio of 1 / 5 is gasified, a condensation reaction occurs in the first reactor on the condensation catalyst niobium oxyphosphate at 250°C and 0.5atm. The mass space velocity of formaldehyde and acetic acid on the catalyst is ensured to be 0.2h by controlling the feed amount. -1 A mixture of acrylic acid and water is obtained from the reaction mixture by separation, or by partially separating water or by adding water to adjust the molar ratio of acrylic acid to water to 1:6. After gasification, in the second reactor, at 120°C and 0.5atm, a catalyst SO4 having a hydration function is used. 2- / ZrO2 undergoes hydration to generate 3-hydroxypropionic acid, and the mass space velocity of acrylic acid on the catalyst is ensured to be 0.2h by controlling the feed amount. -1 The conversion rate and selectivity were calculated by chromatographic analysis. See Table 1.

[0045] Example 2

[0046] Potassium tantalate is dissolved in water to form a uniform saturated aqueous solution, and then a mixed solution of 68wt% nitric acid and 85wt% phosphoric acid in a molar ratio of 1:1 is added dropwise thereto, and the Ta ion concentration is monitored until more than 95% of the Ta ions in the solution are precipitated, and then the above-mentioned precipitation suspension is filtered and washed until the filtrate is neutral, and the precipitate is dried and fully calcined in air at 800°C until the mass loss is stable, thereby obtaining tantalum phosphate.

[0047] Dissolve hafnium nitrate in water (10 g / L), gradually add urea, monitor Hf ion concentration, until more than 90% of Hf ions are precipitated, and add Na2SO4 to ensure that SO4 2-The ion concentration is 2 mol / L; the obtained precipitate is aged at 80°C for 12 h, then filtered, washed, and the impurity ions are removed, and then fully calcined at 600°C in a nitrogen atmosphere until the mass loss is stable, thus obtaining SO4 2- / HfO2.

[0048] The mixture of paraformaldehyde and acetic acid in a molar ratio of 1 / 1 was gasified and diluted with N2 (N2 accounted for 10% of the total gas volume). In the first stage reactor, a condensation reaction occurred on the condensation catalyst tantalum phosphate at 300°C and 1atm. The feed rate was controlled to ensure that the mass space velocity of formaldehyde and acetic acid on the catalyst was 1h -1 A mixture of acrylic acid and water is obtained from the reaction mixture by separation, or by partially separating water or by adding water to adjust the molar ratio of acrylic acid to water to 1:3, and after gasification and dilution with nitrogen (nitrogen accounts for 10% of the total gas volume) in a second reactor at 180°C and 10 atm on a catalyst having a hydration function, SO4 2- / HfO2 undergoes hydration to generate 3-hydroxypropionic acid, and the mass space velocity of acrylic acid on the catalyst is ensured to be 1h by controlling the feed amount. -1 The conversion rate and selectivity were calculated by chromatographic analysis. See Table 1.

[0049] Example 3

[0050] Potassium niobate and potassium tantalate are dissolved in water at a metal molar ratio of 1 / 9 to form a uniform saturated aqueous solution, and then a mixed solution of 68wt% nitric acid and 85wt% phosphoric acid at a molar ratio of 1:1 is added dropwise thereto, and the concentrations of Nb and Ta ions are monitored until more than 95% of Nb and Ta ions in the solution are precipitated, and then the above-mentioned precipitation suspension is filtered and washed until the filtrate is neutral, and the precipitate is dried and fully calcined in air at 600°C until the mass loss is stable, thereby obtaining tantalum phosphate isomorphously substituted with niobium.

[0051] Dissolve ferric nitrate in water (200 g / L), gradually add NaOH, monitor the Fe ion concentration until more than 90% of the Fe ions are precipitated, and add K2SO4 to ensure that SO4 2- The ion concentration is 4 mol / L; the obtained precipitate is aged at 60°C for 24 hours, then filtered, washed, and the impurity ions are removed, and then fully calcined at 800°C in an air atmosphere until the mass loss is stable, thus obtaining SO4 2- / Fe2O3.

[0052] A mixture of 30 wt% formaldehyde aqueous solution and acetic acid in a molar ratio of 5 / 1 was gasified and diluted with N2 (N2 accounted for 50% of the total gas volume). In the first stage reactor, a condensation reaction occurred on a condensation catalyst, tantalum phosphate isomorphously substituted with niobium, at 350°C and 10 atm. The feed rate was controlled to ensure that the mass space velocity of formaldehyde and acetic acid on the catalyst was 2 h -1 A mixture of acrylic acid and water is obtained from the reaction mixture by separation, or by partially separating water or by adding water to adjust the molar ratio of acrylic acid to water to 1:1, and after gasification and dilution with nitrogen (nitrogen accounts for 50% of the total gas volume) in a second reactor at 250°C and 20 atm on a catalyst having a hydration function, SO4 2- / Fe2O3 undergoes hydration reaction to generate 3-hydroxypropionic acid, and the mass space velocity of acrylic acid on the catalyst is ensured to be 2h by controlling the feed amount. -1 The conversion rate and selectivity were calculated by chromatographic analysis. See Table 1.

[0053] Example 4

[0054] Potassium tantalate is dissolved in water to form a uniform saturated aqueous solution. At the same time, the amount of Al2O3 carrier added is calculated according to the yield of tantalum phosphate obtained in Example 2, so that the loading amount of tantalum phosphate is maintained at 5wt%; then a mixed solution of 68wt% nitric acid and 85wt% phosphoric acid in a molar ratio of 1:1 is added dropwise, and the Ta ion concentration is monitored until more than 95% of Ta ions in the solution are precipitated, and then the above-mentioned precipitation suspension is filtered and washed until the filtrate is neutral, and the precipitate is dried and placed in air at 800°C for sufficient calcination until the mass loss is stable to obtain 5wt% tantalum phosphate / Al2O3.

[0055] Similarly, supported tantalum phosphate catalysts with different carriers (including SiO2, TiO2, ZrO2) and different loading amounts (5-50wt%) can be prepared.

[0056] Dissolve cerium nitrate in water (300 g / L), gradually add KOH, monitor the Ce ion concentration, until the Ce ions are precipitated by more than 90%, and add K2SO4 to ensure that the SO4 in the solution is 2- The ion concentration is 4 mol / L; the obtained precipitate is aged at 60°C for 24 hours, then filtered, washed, and the impurity ions are removed, and then fully calcined at 800°C in an air atmosphere until the mass loss is stable, thus obtaining SO4 2- / CeO2.

[0057] Similarly, hydration catalysts with different supports (including SnO2, Al2O3, TiO2, and ZrO2) can be prepared using tin chloride, aluminum nitrate, and titanium chloride.

[0058] A mixture of 50 wt% formaldehyde aqueous solution and acetic acid in a molar ratio of 1 / 2 was gasified and diluted with Ar (Ar accounted for 80% of the total gas volume). In the first stage reactor, a condensation reaction occurred on a condensation catalyst of 5 wt% tantalum phosphate / Al2O3 at 450°C and 30 atm. The feed rate was controlled to ensure that the mass space velocity of formaldehyde and acetic acid on the catalyst was 4 h -1 A mixture of acrylic acid and water is obtained from the reaction mixture by separation, or by partially separating water or by adding water to adjust the molar ratio of acrylic acid to water to 1:1, and after gasification and dilution with nitrogen (nitrogen accounts for 50% of the total gas volume) in a second reactor at 350°C and 30 atm on a catalyst having a hydration function, SO4 2- / CeO2 undergoes hydration to generate 3-hydroxypropionic acid, and the mass space velocity of acrylic acid on the catalyst is ensured to be 4h by controlling the feed amount. -1 The conversion rate and selectivity were calculated by chromatographic analysis. See Table 1.

[0059] Example 5

[0060] Potassium tantalate and potassium niobate are dissolved in water at a metal molar ratio of 1 / 9 to form a uniform saturated aqueous solution. At the same time, the amount of ZrO2 carrier added is calculated according to the theoretical yield of tantalum isomorphously substituted niobium phosphate, so that the loading amount of tantalum isomorphously substituted niobium phosphate is maintained at 50wt%; then a mixed solution of 68wt% nitric acid and 85wt% phosphoric acid in a molar ratio of 1:1 is added dropwise, and the concentrations of Ta and Nb ions are monitored until more than 95% of Ta and Nb ions in the solution are precipitated, and then the above-mentioned precipitation suspension is filtered and washed until the filtrate is neutral, and the precipitate is dried and placed in air at 600°C for sufficient roasting until the mass loss is stable to obtain tantalum isomorphously substituted niobium phosphate / ZrO2.

[0061] Dissolve zirconium nitrate and hafnium nitrate in water at a molar ratio of 1 / 1 (total concentration of metal nitrates 10 g / L), gradually add 26 wt% ammonia water, monitor the concentration of Zr and Hf ions, until more than 90% of the Zr and Hf ions are precipitated, and add Na2SO4 to ensure that SO4 2- The ion concentration is 2 mol / L; the obtained precipitate is aged at 80°C for 12 h, then filtered, washed, and the impurity ions are removed, and then fully calcined at 600°C in a nitrogen atmosphere until the mass loss is stable, thus obtaining SO4 2- / ZrO2-HfO2.

[0062] A mixture of 99 wt% formaldehyde aqueous solution and acetic acid in a molar ratio of 1 / 2 was gasified and diluted with N2 (N2 accounted for 50% of the total gas volume). In the first stage reactor, a condensation reaction occurred on a condensation catalyst of tantalum isomorphously substituted niobium phosphate / ZrO2 at 350°C and 5 atm. The feed rate was controlled to ensure that the mass space velocity of formaldehyde and acetic acid on the catalyst was 2 h -1 A mixture of acrylic acid and water is obtained from the reaction mixture by separation, or by partially separating water or by adding water to adjust the molar ratio of acrylic acid to water to 1:3. After gasification, in the second reactor, at 200°C and 15atm, a catalyst SO4 having a hydration function is used. 2- / ZrO2-HfO2 undergoes hydration reaction to generate 3-hydroxypropionic acid, and the mass space velocity of acrylic acid on the catalyst is ensured to be 1h by controlling the feed amount. -1 The conversion rate and selectivity were calculated by chromatographic analysis. See Table 1.

[0063] Example 6

[0064] Potassium tantalate and potassium niobate are dissolved in water at a metal molar ratio of 1 / 9 to form a uniform saturated aqueous solution. At the same time, the amount of ZrO2 carrier added is calculated according to the theoretical yield of tantalum isomorphously substituted niobium phosphate, so that the loading amount of tantalum isomorphously substituted niobium phosphate is maintained at 50wt%; then a mixed solution of 68wt% nitric acid and 85wt% phosphoric acid in a molar ratio of 1:1 is added dropwise, and the concentrations of Ta and Nb ions are monitored until more than 95% of Ta and Nb ions in the solution are precipitated, and then the above-mentioned precipitation suspension is filtered and washed until the filtrate is neutral, and the precipitate is dried and placed in air at 600°C for sufficient roasting until the mass loss is stable to obtain tantalum isomorphously substituted niobium phosphate / ZrO2.

[0065] Dissolve zirconium nitrate and hafnium nitrate in water at a molar ratio of 1 / 1 (total concentration of metal nitrates 10 g / L), gradually add 26 wt% ammonia water, monitor the concentration of Zr and Hf ions, until more than 90% of the Zr and Hf ions are precipitated, and add Na2SO4 to ensure that SO4 2- The ion concentration is 2 mol / L; the obtained precipitate is aged at 80°C for 12 h, then filtered, washed, and the impurity ions are removed, and then fully calcined at 600°C in a nitrogen atmosphere until the mass loss is stable, thus obtaining SO4 2- / ZrO2-HfO2.

[0066] A mixture of 99 wt% formaldehyde aqueous solution and acetic acid in a molar ratio of 1 / 4 was gasified and diluted with N2 (N2 accounted for 50% of the total gas volume). In the first stage reactor, a condensation reaction occurred on a condensation catalyst of tantalum isomorphously substituted niobium oxyphosphate / ZrO2 at 350°C and 5 atm. The feed rate was controlled to ensure that the mass space velocity of formaldehyde and acetic acid on the catalyst was 2 h -1 , a mixture of acrylic acid and water is obtained from the reaction mixture by separation, or by partially separating water or by adding water to adjust the molar ratio of acrylic acid to water to 1:5, and after gasification, in a second reactor, at 200°C and 15atm, in the presence of a catalyst having a hydration function, SO4 2- / ZrO2-HfO2 undergoes hydration reaction to generate 3-hydroxypropionic acid, and the mass space velocity of acrylic acid on the catalyst is ensured to be 1h by controlling the feed amount. -1 The conversion rate and selectivity were calculated by chromatographic analysis. See Table 1.

[0067] Example 7

[0068] Potassium tantalate and potassium niobate are dissolved in water at a metal molar ratio of 1 / 9 to form a uniform saturated aqueous solution. At the same time, the amount of ZrO2 carrier added is calculated according to the theoretical yield of tantalum isomorphously substituted niobium phosphate, so that the loading amount of tantalum isomorphously substituted niobium phosphate is maintained at 50wt%; then a mixed solution of 68wt% nitric acid and 85wt% phosphoric acid in a molar ratio of 1:1 is added dropwise, and the concentrations of Ta and Nb ions are monitored until more than 95% of Ta and Nb ions in the solution are precipitated, and then the above-mentioned precipitation suspension is filtered and washed until the filtrate is neutral, and the precipitate is dried and placed in air at 600°C for sufficient roasting until the mass loss is stable to obtain tantalum isomorphously substituted niobium phosphate / ZrO2.

[0069] Dissolve zirconium nitrate and hafnium nitrate in water at a molar ratio of 1 / 1 (total concentration of metal nitrates 10 g / L), gradually add 26 wt% ammonia water, monitor the concentration of Zr and Hf ions, until more than 90% of the Zr and Hf ions are precipitated, and add Na2SO4 to ensure that SO4 2- The ion concentration is 2 mol / L; the obtained precipitate is aged at 80°C for 12 h, then filtered, washed, and the impurity ions are removed, and then fully calcined at 600°C in a nitrogen atmosphere until the mass loss is stable, thus obtaining SO4 2- / ZrO2-HfO2.

[0070] A mixture of 99 wt% formaldehyde aqueous solution and acetic acid in a molar ratio of 1 / 5 was gasified and diluted with N2 (N2 accounted for 50% of the total gas volume). In the first stage reactor, a condensation reaction occurred on a condensation catalyst of tantalum isomorphously substituted niobium phosphate / ZrO2 at 350°C and 5 atm. The feed rate was controlled to ensure that the mass space velocity of formaldehyde and acetic acid on the catalyst was 2h -1 A mixture of acrylic acid and water is obtained from the reaction mixture by separation, or by partially separating water or by adding water to adjust the molar ratio of acrylic acid to water to 1:6. After gasification, in the second reactor, at 200°C and 15atm, a catalyst SO4 having a hydration function is used. 2- / ZrO2-HfO2 undergoes hydration reaction to generate 3-hydroxypropionic acid, and the mass space velocity of acrylic acid on the catalyst is ensured to be 1h by controlling the feed amount. -1 The conversion rate and selectivity were calculated by chromatographic analysis. See Table 1.

[0071] Example 8

[0072] Potassium tantalate is dissolved in water to form a uniform saturated aqueous solution, and then a mixed solution of 68wt% nitric acid and 85wt% phosphoric acid in a molar ratio of 1:1 is added dropwise thereto, and the Ta ion concentration is monitored until more than 95% of the Ta ions in the solution are precipitated, and then the above-mentioned precipitation suspension is filtered and washed until the filtrate is neutral, and the precipitate is dried and fully calcined in air at 800°C until the mass loss is stable, thereby obtaining tantalum phosphate.

[0073] Dissolve hafnium nitrate in water (10 g / L), gradually add urea, monitor Hf ion concentration, until more than 90% of Hf ions are precipitated, and add Na2SO4 to ensure that SO4 2- The ion concentration is 2 mol / L; the obtained precipitate is aged at 80°C for 12 h, then filtered, washed, and the impurity ions are removed, and then fully calcined at 600°C in a nitrogen atmosphere until the mass loss is stable, thus obtaining SO4 2- / HfO2.

[0074] The mixture of paraformaldehyde and acetic acid in a molar ratio of 1 / 1 was gasified and diluted with N2 (N2 accounted for 10% of the total gas volume). In the first stage reactor, a condensation reaction occurred on the condensation catalyst tantalum phosphate at 250°C and 1atm. The feed amount was controlled to ensure that the mass space velocity of formaldehyde and acetic acid on the catalyst was 1h -1A mixture of acrylic acid and water is obtained from the reaction mixture by separation, or by partially separating water or by adding water to adjust the molar ratio of acrylic acid to water to 1:3, and after gasification and dilution with nitrogen (nitrogen accounts for 10% of the total gas volume) in a second reactor at 180°C and 0.5 atm on a catalyst having a hydration function, SO4 2- / HfO2 undergoes hydration to generate 3-hydroxypropionic acid, and the mass space velocity of acrylic acid on the catalyst is ensured to be 1h by controlling the feed amount. -1 The conversion rate and selectivity were calculated by chromatographic analysis. See Table 1.

[0075] Example 9

[0076] Potassium tantalate is dissolved in water to form a uniform saturated aqueous solution, and then a mixed solution of 68wt% nitric acid and 85wt% phosphoric acid in a molar ratio of 1:1 is added dropwise thereto, and the Ta ion concentration is monitored until more than 95% of the Ta ions in the solution are precipitated, and then the above-mentioned precipitation suspension is filtered and washed until the filtrate is neutral, and the precipitate is dried and fully calcined in air at 800°C until the mass loss is stable, thereby obtaining tantalum phosphate.

[0077] Dissolve hafnium nitrate in water (10 g / L), gradually add urea, monitor Hf ion concentration, until more than 90% of Hf ions are precipitated, and add Na2SO4 to ensure that SO4 2- The ion concentration is 2 mol / L; the obtained precipitate is aged at 80°C for 12 h, then filtered, washed, and the impurity ions are removed, and then fully calcined at 600°C in a nitrogen atmosphere until the mass loss is stable, thus obtaining SO4 2- / HfO2.

[0078] The mixture of paraformaldehyde and acetic acid in a molar ratio of 1 / 1 was gasified and diluted with N2 (N2 accounted for 10% of the total gas volume). In the first stage reactor, a condensation reaction occurred on the condensation catalyst tantalum phosphate at 450°C and 1atm. The feed amount was controlled to ensure that the mass space velocity of formaldehyde and acetic acid on the catalyst was 1h -1 A mixture of acrylic acid and water is obtained from the reaction mixture by separation, or by partially separating water or by adding water to adjust the molar ratio of acrylic acid to water to 1:3, and after gasification and dilution with nitrogen (nitrogen accounts for 10% of the total gas volume) in a second reactor at 180°C and 30 atm on a catalyst having a hydration function, SO4 2- / HfO2 undergoes hydration to generate 3-hydroxypropionic acid, and the mass space velocity of acrylic acid on the catalyst is ensured to be 1h by controlling the feed amount. -1 The conversion rate and selectivity were calculated by chromatographic analysis. See Table 1.

[0079] Example 10

[0080] Potassium niobate and potassium tantalate are dissolved in water at a metal molar ratio of 1 / 9 to form a uniform saturated aqueous solution, and then a mixed solution of 68wt% nitric acid and 85wt% phosphoric acid at a molar ratio of 1:1 is added dropwise thereto, and the concentrations of Nb and Ta ions are monitored until more than 95% of Nb and Ta ions in the solution are precipitated, and then the above-mentioned precipitation suspension is filtered and washed until the filtrate is neutral, and the precipitate is dried and fully calcined in air at 500°C until the mass loss is stable, thereby obtaining tantalum phosphate isomorphously substituted with niobium.

[0081] Dissolve ferric nitrate in water (200 g / L), gradually add NaOH, monitor the Fe ion concentration until more than 90% of the Fe ions are precipitated, and add K2SO4 to ensure that SO4 2- The ion concentration is 4 mol / L; the obtained precipitate is aged at 30°C for 24 hours, then filtered, washed, and the impurity ions are removed, and then fully calcined at 800°C in an air atmosphere until the mass loss is stable, thus obtaining SO4 2- / Fe2O3.

[0082] A mixture of 30 wt% formaldehyde aqueous solution and acetic acid in a molar ratio of 5 / 1 was gasified and diluted with N2 (N2 accounted for 50% of the total gas volume). In the first stage reactor, a condensation reaction occurred on a condensation catalyst, tantalum phosphate isomorphously substituted with niobium, at 350°C and 10 atm. The feed rate was controlled to ensure that the mass space velocity of formaldehyde and acetic acid on the catalyst was 2 h -1 A mixture of acrylic acid and water is obtained from the reaction mixture by separation, or by partially separating water or by adding water to adjust the molar ratio of acrylic acid to water to 1:1, and after gasification and dilution with nitrogen (nitrogen accounts for 50% of the total gas volume) in a second reactor at 250°C and 20 atm on a catalyst having a hydration function, SO4 2- / Fe2O3 undergoes hydration reaction to generate 3-hydroxypropionic acid, and the mass space velocity of acrylic acid on the catalyst is ensured to be 2h by controlling the feed amount. -1 The conversion rate and selectivity were calculated by chromatographic analysis. See Table 1.

[0083] Embodiment 11

[0084] Potassium niobate and potassium tantalate are dissolved in water at a metal molar ratio of 1 / 9 to form a uniform saturated aqueous solution, and then a mixed solution of 68wt% nitric acid and 85wt% phosphoric acid at a molar ratio of 1:1 is added dropwise thereto, and the concentrations of Nb and Ta ions are monitored until more than 95% of Nb and Ta ions in the solution are precipitated, and then the above precipitation suspension is filtered and washed until the filtrate is neutral, and the precipitate is dried and fully calcined in air at 800°C until the mass loss is stable, thereby obtaining tantalum phosphate isomorphously substituted with niobium.

[0085] Dissolve ferric nitrate in water (200 g / L), gradually add NaOH, monitor the Fe ion concentration until more than 90% of the Fe ions are precipitated, and add K2SO4 to ensure that SO4 2- The ion concentration is 4 mol / L; the obtained precipitate is aged at 80°C for 24 hours, then filtered, washed, and the impurity ions are removed, and then fully calcined at 800°C in an air atmosphere until the mass loss is stable, thus obtaining SO4 2- / Fe2O3.

[0086] A mixture of 30 wt% formaldehyde aqueous solution and acetic acid in a molar ratio of 5 / 1 was gasified and diluted with N2 (N2 accounted for 50% of the total gas volume). In the first stage reactor, a condensation reaction occurred on a condensation catalyst, tantalum phosphate isomorphously substituted with niobium, at 350°C and 10 atm. The feed rate was controlled to ensure that the mass space velocity of formaldehyde and acetic acid on the catalyst was 2 h -1 A mixture of acrylic acid and water is obtained from the reaction mixture by separation, or by partially separating water or by adding water to adjust the molar ratio of acrylic acid to water to 1:1, and after gasification and dilution with nitrogen (nitrogen accounts for 50% of the total gas volume) in a second reactor at 250°C and 20 atm on a catalyst having a hydration function, SO4 2- / Fe2O3 undergoes hydration reaction to generate 3-hydroxypropionic acid, and the mass space velocity of acrylic acid on the catalyst is ensured to be 2h by controlling the feed amount. -1 The conversion rate and selectivity were calculated by chromatographic analysis. See Table 1.

[0087] Comparative Example 1

[0088] A mixture of 50 wt% formaldehyde aqueous solution and acetic acid in a molar ratio of 1 / 2 was gasified and diluted with Ar (Ar accounted for 80% of the total gas volume). In the first stage reactor, a condensation reaction occurred on a condensation catalyst of 5 wt% V2O5 / Al2O3 at 450°C and 30 atm. The feed rate was controlled to ensure that the mass space velocity of formaldehyde and acetic acid on the catalyst was 4 h -1A mixture of acrylic acid and water is obtained from the reaction mixture by separation, or by partially separating water or by adding water to adjust the molar ratio of acrylic acid to water to 1:1. After gasification, the mixture is diluted with N2 (N2 accounts for 50% of the total gas volume) and then hydrated on HMCM-48 at 350°C and 30 atm in the second reactor to produce 3-hydroxypropionic acid. The mass space velocity of acrylic acid on the catalyst is ensured to be 4 h by controlling the feed amount. -1 The conversion rate and selectivity were calculated by chromatographic analysis. See Table 1.

[0089] Comparative Example 2

[0090] A mixture of 50 wt% formaldehyde aqueous solution and acetic acid in a molar ratio of 1 / 2 was gasified and diluted with Ar (Ar accounted for 80% of the total gas volume). In the first stage reactor, a condensation reaction occurred on a condensation catalyst of 5 wt% P2O5 / Al2O3 at 450°C and 30 atm. The feed rate was controlled to ensure that the mass space velocity of formaldehyde and acetic acid on the catalyst was 4 h -1 A mixture of acrylic acid and water is obtained from the reaction mixture by separation, or by partially separating water or by adding water to adjust the molar ratio of acrylic acid to water to 1:1. After gasification, the mixture is diluted with N2 (N2 accounts for 50% of the total gas volume) and then hydrated on HZSM-5 at 350°C and 30 atm in the second reactor to produce 3-hydroxypropionic acid. The mass space velocity of acrylic acid on the catalyst is ensured to be 4 h by controlling the feed amount. -1 The conversion rate and selectivity were calculated by chromatographic analysis. See Table 1.

[0091] Comparative Example 3

[0092] A mixture of 50 wt% formaldehyde aqueous solution and acetic acid in a molar ratio of 1 / 2 was gasified and diluted with Ar (Ar accounted for 80% of the total gas volume). In the first stage reactor, a condensation reaction occurred on a condensation catalyst of 5 wt% V2O5-5 wt% P2O5 / Al2O3 at 450°C and 30 atm. The feed rate was controlled to ensure that the mass space velocity of formaldehyde and acetic acid on the catalyst was 4 h -1 A mixture of acrylic acid and water is obtained from the reaction mixture by separation, or by partially separating water or by adding water to adjust the molar ratio of acrylic acid to water to 1:1. After gasification, the mixture is diluted with N2 (N2 accounts for 50% of the total gas volume) and then hydrated on SAPO-34 at 350°C and 30 atm in the second reactor to produce 3-hydroxypropionic acid. The mass space velocity of acrylic acid on the catalyst is ensured to be 4 h by controlling the feed amount. -1 The conversion rate and selectivity were calculated by chromatographic analysis. See Table 1.

[0093] Table 1 Reaction evaluation results

[0094]

[0095] From Examples 5-7, it can be seen that the lower the molar ratio of formaldehyde to acetic acid in the first reactor, the more favorable the conversion is, and the selectivity can be maintained at a similar level; the lower the molar ratio of acrylic acid to water in the second reactor, the more favorable the conversion is, and the selectivity can be maintained at a similar level.

[0096] From Examples 2, 8, and 9, it can be seen that: in the first reactor, the lower the reaction temperature, the lower the conversion rate, and the selectivity is equivalent; the higher the reaction temperature, the higher the conversion rate, but the selectivity decreases. In the second reactor, the lower the reaction pressure, the lower the conversion rate, and the selectivity is equivalent; the higher the reaction pressure, the higher the conversion rate and selectivity.

[0097] From Examples 3, 10 and 11, it can be seen that the calcination process in the preparation of the condensation catalyst requires a moderate calcination temperature; the aging process in the preparation of the hydration catalyst requires a moderately suitable temperature.

[0098] From Example 4 and Comparative Examples 1, 2, and 3, it can be seen that: V2O5 / Al2O3, P2O5 / Al2O 3、 V2O5-P2O5 / Al2O3 as condensation catalyst, HMCM-48, HZSM-5, SAPO-34 as hydration catalyst had poor activity under the reaction conditions.

Claims

1. A method for synthesizing 3-hydroxypropionic acid, characterized in that: Formaldehyde or its aqueous mixture and acetic acid are gasified, diluted with an inert atmosphere gas or not, and undergo a condensation reaction in a first stage reactor on a catalyst having a condensation function to generate a mixture of acrylic acid and water; A mixture of acrylic acid and water is obtained from the reaction mixture by separation, and then the mixture of acrylic acid and water is gasified and then diluted with an inert gas or without dilution, and hydrated on a catalyst having a hydration function in a second reactor to produce 3-hydroxypropionic acid; The catalyst having condensation function is one or more of tantalum phosphate, niobium phosphate, tantalum phosphate isomorphously substituted with niobium, niobium phosphate isomorphously substituted with tantalum, and supported catalysts thereof; the supported catalyst has one or more of tantalum phosphate, niobium phosphate, tantalum phosphate isomorphously substituted with niobium, and niobium phosphate isomorphously substituted with tantalum as active ingredients; The catalyst with hydration function is: SO4 2- / HfO2、SO4 2- / ZrO2、SO4 2- / TiO2、SO4 2- / ZrO2-HfO2, SO4 2- / Fe2O3、SO4 2- / SnO2、SO4 2- / CeO2、SO4 2- / One or more of γ-Al2O3.

2. The method according to claim 1, characterized in that: Acrylic acid and water are partially separated or not separated in the mixture after the first stage reactor.

3. The method according to claim 1, characterized in that: The inert atmosphere includes: one or more of N2, Ar, and He; The inert gas accounts for 10-80% of the total gas volume.

4. The method according to claim 1 or 3, characterized in that: The formaldehyde or its aqueous mixture includes: one or more of trioxymethylene, polyoxymethylene, and 30-99wt% formaldehyde aqueous mixture; The molar ratio of formaldehyde to acetic acid in the formaldehyde or its aqueous mixture is 5:1 to 1:5; The catalyst having condensation function is one or more of tantalum phosphate, niobium phosphate, tantalum phosphate isomorphously substituted with niobium, niobium phosphate isomorphously substituted with tantalum, and supported catalysts thereof; The supported catalyst has one or more of tantalum phosphate, niobium phosphate, tantalum phosphate isomorphously substituted with niobium, and niobium phosphate isomorphously substituted with tantalum as active components, and the loading amount of the active component in the supported catalyst is 5-50wt%; The carrier of the supported catalyst includes: one of SiO2, Al2O3, TiO2, ZrO2 or a mixture of two or more thereof in any proportion; The condensation reaction temperature is: 250-450°C; The condensation reaction pressure is: 0.5-30atm; The mass space velocity of formaldehyde and acetic acid on the catalyst is: 0.2-4h -1 .

5. The method according to claim 1, 2 or 3, characterized in that: The molar ratio of acrylic acid to water in the mixture of acrylic acid and water is 1:1 to 1:6; The catalyst with hydration function is: SO4 2- / HfO2、SO4 2- / ZrO2、SO4 2- / TiO2、SO4 2- / ZrO2-HfO2, SO4 2- / Fe2O3、SO4 2- / SnO2、SO4 2- / CeO2、SO4 2- / one or more of γ-Al2O3; The hydration reaction temperature is: 120-350°C; The hydration reaction pressure is: 0.5-30atm; The mass space velocity of acrylic acid on the catalyst is: 0.2-4h -1 .

6. The method according to claim 1 or 5, characterized in that: SO4 in catalysts with hydration function 2- The mass content of SO4 on the carrier 2- It depends on the saturated adsorption capacity of the ions.

7. The method according to claim 1 or 4, characterized in that: A. The preparation method of the catalyst with condensation function is as follows: potassium niobate or potassium tantalate is dissolved to form a uniform solution, and then a mixed acid solution of nitric acid and phosphoric acid in a molar ratio of 1:1 is added dropwise thereto until more than 95% of Nb and tantalum metal ions in the solution are precipitated, and then the above-mentioned precipitation suspension is filtered and washed until the filtrate is neutral, and then the precipitate is dried, and the precipitate is placed in air and / or an inert atmosphere (including: one or more of N2, Ar, and He) and fully calcined to 500-800° C. to obtain niobium oxyphosphate or tantalum oxyphosphate; Alternatively, B, using a mixed solution of potassium niobate and potassium tantalate, the above method A (with the same process and conditions) can be used to prepare niobium isomorphously substituted tantalum phosphate or tantalum isomorphously substituted niobium phosphate; Alternatively, C, the preparation method of the supported catalyst is as follows: after the potassium niobate and / or potassium tantalate is dissolved to form a uniform solution, the required mass of the support is added according to the loading amount, and then the supported condensation catalyst is prepared by continuing the same process and conditions as the above-mentioned method A or B.

8. The method according to claim 1, 5 or 6, characterized in that: The preparation method of the hydration function catalyst is as follows: dissolving one or more corresponding soluble metal salts of one or more of Ti, Zr, Hf, Fe, Sn, Ce and Al in water and / or ethanol, adding one or more precipitants such as ammonia water or urea or NaOH or KOH with a mass concentration of 28wt%, wherein the amount of the precipitant is sufficient to precipitate more than 90% of the metal ions in the metal salt solution; and simultaneously adding one or more of (NH4)2SO4 or Na2SO4 or K2SO4 to make SO4 2- The ion concentration is 0.5-4.0 mol / L; the obtained precipitation suspension is aged at 30-80°C for 6-24h, then filtered, washed to remove impurity ions, and then dried and fully calcined at 400-800°C in air and / or nitrogen atmosphere.

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