Preparation process and application of an iron-lanthanum co-stabilized molecular sieve supported super strong solid acid catalyst

Abstract

The invention provides a preparation process of an iron-lanthanum co-stabilized molecular sieve loaded with a super-strong solid acid catalyst. Through the preparation of an iron-doped molecular sieve and the modification of the solid acid by rare earth lanthanum, a large number of iron element sites introduced into the internal pores of the molecular sieve can be used as water adsorption binding sites around the solid acid, thereby improving the catalytic activity after multiple reactions, reducing the influence of water on the solid acid catalyst in the reaction, and achieving significant economic benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of solid acid preparation, and specifically relates to a method for preparing an iron-lanthanum co-stabilized molecular sieve supported super-strong solid acid catalyst. Background Art

[0002] Solid superacid catalysts have significant application advantages over liquid superacid catalysts and are often used in organic reactions, especially esterification, acylation, isomerization, and polymerization reactions. There are many types of solid superacid catalysts, among which the most common ones are halogen-containing solid superacids, metal oxide-type, and heteropolyacid-type. However, the most widely used and successful catalysts in the industry are metal oxide-type solid superacid catalysts, which mainly convert sulfate ions (SO4 2- ) is adsorbed and bonded to the surface of metal oxide (MxOy). Metal oxide solid acid catalysts have outstanding catalytic activity and have always been a hot topic in catalytic preparation technology.

[0003] The high-valent sulfur atoms and metal ligands in the metal oxide solid superacid catalyst exist by forming a SOM bonding mode. A large number of existing studies have shown that the type of metal element in the oxide, the preparation process and technology will affect the coordination mode and binding energy of the SOM. Common sulfur element binding modes include monomer binding mode, bidentate binding mode and cross-linking mode. In addition, existing studies have also shown that in metal oxide catalysts, SO4 2- / ZrO2 showed high catalytic activity in the esterification reaction. However, SO4 2- / ZrO2 solid acid catalysts do not have a significant specific surface area advantage. Compared with traditional zeolite molecular sieve solid acid catalysts, the smaller specific surface area makes it difficult for solid superacid catalysts to fully exert their superior catalytic performance during adsorption and catalysis, and they are easily deactivated during the reaction. Usually, superacids are loaded on porous carriers to achieve a combination of high-efficiency catalysis and high adsorption. However, after multiple cycles of catalysis, the effect of water molecules on solid acids can easily weaken and reduce the acidity of superacids, which inevitably affects the catalytic performance of solid acid catalysts. Summary of the invention

[0004] In view of the fact that the catalytic performance in the prior art changes during the continuous catalytic process, and even significantly decreases and weakens, the inventors believe after investigation that the decrease in catalytic performance caused by the effect of water on sulfate ions in the solid acid during the esterification process is one of the important reasons. Through various attempts during the research and development process, it was found that by introducing a large amount of transition metal elements into the zeolite molecular sieve as doping elements of the skeleton, the zeolite molecular sieve can be modified. As a result, when the sulfuric acid-metal oxide component is introduced, a better cycle performance can be presented in the esterification process.

[0005] Specifically, the present invention adopts the following preparation process to achieve the solution to the above problem, a method for preparing an iron-lanthanum co-stabilized molecular sieve supported super-strong solid acid catalyst, comprising the following steps:

[0006] (1) Preparation of iron-doped molecular sieves:

[0007] First, add silicon source, alkali, template, iron salt, solvent into the reaction container and stir and mix evenly to obtain a colloidal solution. The stirring and mixing temperature is 20-40°C; stirring is performed for 1-3 hours. The molar ratio of the silicon source, alkali, template, iron salt, and solvent is 10:4-5:1-2:1-2:500-1500. The solvent is deionized water or distilled water; the silicon source is preferably water glass, ethyl orthosilicate, butyl orthosilicate, and propyl orthosilicate; the alkali is preferably ammonia water, sodium hydroxide solution, and potassium hydroxide solution; the iron salt is a soluble iron salt. The template is an ammonium salt template, preferably ammonium bromide, and tetramethylammonium bromide is particularly suitable as the template.

[0008] Secondly, the colloidal solution obtained after the mixing is placed in a hydrothermal reactor for hydrothermal reaction, the temperature of the hydrothermal reaction is 160-180°C, the time of the hydrothermal reaction is 60-96 hours, and a reaction product is obtained after the hydrothermal reaction. The reaction product is filtered, washed, dried, and roasted to obtain a roasted product, and the roasted product is immersed in dilute sulfuric acid for acidification to obtain an iron-doped molecular sieve.

[0009] The drying can be carried out by vacuum drying, microwave drying, electric oven drying, etc., preferably, it is heated to 60-80°C in an electric oven and dried for 5-10 hours. The washing is first washed with an organic solvent, then washed with deionized water, and washed alternately 3-5 times to obtain the washed product, wherein the preferred washing organic solvent is acetone. The roasting is carried out in a muffle furnace, preferably, the roasting temperature and the rate of heating are controlled, and the method of preheating first and then slowly heating is adopted, and the temperature is gradually raised to 500-700°C for roasting for 4-6 hours.

[0010] (2) Preparation of modified molecular sieve catalyst loaded with super strong solid acid: First, a certain amount of ZrOCl2 and LaCl3 are dissolved in deionized water, and the pH is adjusted to 2-3 to obtain an impregnation precursor solution, and the impregnation precursor solution is impregnated with the molecular sieve product prepared in step (1) to obtain a mixed solution, so that the impregnation precursor solution impregnates the molecular sieve product for 3-6 hours, and then, continuously stirs, and adds alkali while stirring, so that the pH of the mixed solution is controlled at 8.5-9.5, and aged for 24-36 hours, and then filtered, and the precipitate obtained by filtration is dried, and after drying, it is impregnated with ammonium sulfate solution for 3-5 hours, and finally, the precipitate after ammonium sulfate impregnation is filtered, washed, and dried, and after drying, it is placed in a muffle furnace for roasting, and the roasted product is cooled to room temperature to obtain a molecular sieve loaded with iron-lanthanum co-stabilized solid super acid. The drying temperature is 80-120°C, and the drying time is 6-10 hours. The concentrations of ZrOCl2 and LaCl3 in the impregnation precursor solution are 0.1-1nol / L and 0.01-0.1mol / L respectively; the concentration of the ammonium sulfate solution is 0.1-1mol / L.

[0011] The iron-lanthanum co-stabilized molecular sieve loaded solid superacid obtained by the present invention has more excellent performance than the molecular sieve loaded supersolid acid in the prior art; the iron-doped molecular sieve selected by the present invention has a large number of iron sites, and the iron is doped into the framework of the molecular sieve and evenly distributed in the molecular sieve. When the precursor solution is impregnated for precipitation and then ammonium sulfate is impregnated, the iron-doped molecular sieve loaded with SO4 2- / ZrO2 super solid acid, during the esterification reaction, thanks to the presence of multiple sulfated skeleton iron inside the molecular sieve, it is easier to adsorb and bind the moisture generated in the esterification reaction, which is beneficial to reduce the moisture on the catalyst surface. 2- / ZrO2, the sites in the molecular sieve that are easy to bind water are more conducive to reducing the impact of water, reducing the effect of water on SO4 2- / ZrO2 catalytic performance; at the same time, by adding rare earth lanthanum, the rare earth modified SO4 formed after calcination 2- The lanthanum element in ZrO2 provides a stable electronic environment, improves the stability of ZrO2, and is beneficial to the cyclic stability of the catalyst. In addition, in the preparation process of fluorinated fatty acid ester solvents, the super-strong solid acid catalyst of the present invention is used to replace sulfuric acid, which reduces the generation of waste acid, has the performance of recycling, significantly simplifies the subsequent treatment process, and saves a lot of costs. Implementation

[0012] Example 1. A method for preparing an iron-lanthanum co-stabilized molecular sieve supported super-strong solid acid catalyst, comprising the following steps:

[0013] (1) Preparation of iron-doped molecular sieves:

[0014] First, add tetraethyl orthosilicate, sodium hydroxide solution, tetramethylammonium bromide, ferric chloride and deionized water into a reaction container and stir and mix them uniformly to obtain a colloidal solution; the stirring and mixing temperature is below 30° C. and the mixture is stirred for 3 hours; the molar ratio of the tetraethyl orthosilicate, sodium hydroxide solution, tetramethylammonium bromide, ferric chloride and deionized water is 10:4:1:2:1000.

[0015] Secondly, the colloidal solution obtained after the mixing is placed in a hydrothermal reactor for hydrothermal reaction, the temperature of the hydrothermal reaction is 180 ° C, the time of the hydrothermal reaction is 72 hours, and the reaction product is obtained after the hydrothermal reaction. The reaction product is filtered, washed, dried, and roasted to obtain a roasted product, and the roasted product is immersed in dilute sulfuric acid for acidification to obtain an iron-doped molecular sieve. The drying is heated to 80 ° C in an electric oven and dried for 10 hours. The washing is first washed with acetone, then washed with deionized water, and the washed product is obtained by alternating washing 3 times. The roasting is carried out in a muffle furnace, the roasting temperature and the rate of heating are controlled, and the temperature is gradually raised to 600 ° C for roasting for 6 hours by preheating and then slowly heating.

[0016] (2) Preparation of modified molecular sieve catalyst loaded with super strong solid acid: First, 0.5 mol / L ZrOCl2 and 0.05 mol / L LaCl3 are dissolved in deionized water, and the pH is adjusted to 3 to obtain an impregnation precursor solution, and the impregnation precursor solution is impregnated with the molecular sieve product prepared in step (1) to obtain a mixed solution, so that the impregnation precursor solution impregnates the molecular sieve product for 4 hours, and then, continuously stirs, and adds alkali while stirring, so that the pH of the mixed solution is controlled at 9, and aged for 30 hours, and then filtered, and the filtered precipitate is dried, and after drying, it is impregnated with 0.6 mol / L ammonium sulfate solution for 4 hours, and finally, the precipitate after ammonium sulfate impregnation is filtered, washed, and dried, and after drying, it is placed in a muffle furnace for roasting, and the roasted product is cooled to room temperature to obtain a molecular sieve loaded with iron-lanthanum co-stabilized solid super acid. The drying temperature is 80°C and the drying time is 10 hours.

[0017] Example 2. A method for preparing an iron-lanthanum co-stabilized molecular sieve supported super-strong solid acid catalyst, comprising the following steps:

[0018] (1) Preparation of iron-doped molecular sieves:

[0019] First, add ethyl orthosilicate, sodium hydroxide solution, tetramethylammonium bromide, ferric chloride and deionized water into a reaction container and stir and mix uniformly to obtain a colloidal solution; the stirring and mixing temperature is below 30° C.; stir for 3 hours; the molar ratio of the silicon source, alkali, template, iron salt and solvent is 10:4:1:1:1000.

[0020] Secondly, the colloidal solution obtained after the mixing is placed in a hydrothermal reactor for hydrothermal reaction, the temperature of the hydrothermal reaction is 170°C, the time of the hydrothermal reaction is 80 hours, and the reaction product is obtained after the hydrothermal reaction. The reaction product is filtered, washed, dried, and roasted to obtain a roasted product, and the roasted product is immersed in dilute sulfuric acid for acidification to obtain an iron-doped molecular sieve. The drying is heated to 80°C in an electric oven and dried for 10 hours. The washing is first washed with acetone, then washed with deionized water, and the washed product is obtained by alternating washing 4 times. The roasting is carried out in a muffle furnace, the roasting temperature and the rate of heating are controlled, and the temperature is gradually raised to 700°C for roasting for 5 hours by preheating and then slowly heating.

[0021] (2) Preparation of modified molecular sieve catalyst loaded with super strong solid acid: First, 0.5 mol / L ZrOCl2 and 0.1 mol / L LaCl3 are dissolved in deionized water, and the pH is adjusted to 3 to obtain an impregnation precursor solution, and the impregnation precursor solution is impregnated with the molecular sieve product prepared in step (1) to obtain a mixed solution, so that the impregnation precursor solution impregnates the molecular sieve product for 4 hours, and then, continuously stirs, and adds alkali while stirring, so that the pH of the mixed solution is controlled at 9, and aged for 30 hours, and then filtered, and the filtered precipitate is dried, and after drying, it is impregnated with 0.6 mol / L ammonium sulfate solution for 4 hours, and finally, the precipitate after ammonium sulfate impregnation is filtered, washed, and dried, and after drying, it is placed in a muffle furnace for roasting, and the roasted product is cooled to room temperature to obtain a molecular sieve loaded with iron-lanthanum co-stabilized solid super acid. The drying temperature is 80°C and the drying time is 10 hours.

[0022] Comparative Example 1. A method for preparing an iron-lanthanum co-stabilized molecular sieve supported super-strong solid acid catalyst, comprising the following steps:

[0023] (1) Preparation of molecular sieve carrier:

[0024] First, add tetraethyl orthosilicate, sodium hydroxide solution, tetramethylammonium bromide and deionized water into a reaction container and stir and mix them uniformly to obtain a colloidal solution; the stirring and mixing temperature is below 30° C. and the stirring is performed for 3 hours; the molar ratio of the tetraethyl orthosilicate, sodium hydroxide solution, tetramethylammonium bromide and deionized water is 10:4:1:1000.

[0025] Secondly, the colloidal solution obtained after the mixing is placed in a hydrothermal reactor for hydrothermal reaction. The temperature of the hydrothermal reaction is 180°C, and the time of the hydrothermal reaction is 72 hours. After the hydrothermal reaction, the reaction product is obtained, and the reaction product is filtered, washed, dried, and roasted to obtain a molecular sieve carrier. The drying is carried out by heating to 80°C in an electric oven and drying for 10 hours. The washing is carried out by first washing with acetone and then washing with deionized water, and washing alternately 3 times to obtain the washed product. The roasting is carried out in a muffle furnace, and the roasting temperature and the rate of heating are controlled. The method of preheating first and then slowly heating is adopted, and the temperature is gradually raised to 600°C for roasting for 6 hours.

[0026] (2) Preparation of modified molecular sieve catalyst loaded with super strong solid acid: First, 0.5 mol / L ZrOCl2 and 0.05 mol / L LaCl3 are dissolved in deionized water, and the pH is adjusted to 3 to obtain an impregnation precursor solution, and the impregnation precursor solution is impregnated with the molecular sieve product prepared in step (1) to obtain a mixed solution, so that the impregnation precursor solution impregnates the molecular sieve product for 4 hours, and then, continuously stirs, and adds alkali while stirring, so that the pH of the mixed solution is controlled at 9, and aged for 30 hours, and then filtered, and the filtered precipitate is dried, and after drying, it is impregnated with 0.6 mol / L ammonium sulfate solution for 4 hours, and finally, the precipitate after ammonium sulfate impregnation is filtered, washed, and dried, and after drying, it is placed in a muffle furnace for roasting, and the roasted product is cooled to room temperature to obtain a molecular sieve loaded with iron-lanthanum co-stabilized solid super acid. The drying temperature is 80°C and the drying time is 10 hours.

[0027] Comparative Example 2. A method for preparing an iron-lanthanum co-stabilized molecular sieve supported super-strong solid acid catalyst, comprising the following steps:

[0028] (1) Preparation of iron-doped molecular sieves:

[0029] First, add ethyl orthosilicate, sodium hydroxide solution, tetramethylammonium bromide, ferric chloride, and deionized water into a reaction container and stir and mix uniformly to obtain a colloidal solution; the stirring and mixing temperature is below 30° C.; stir for 3 hours; the molar ratio of the silicon source, alkali, template, iron salt, and solvent is 10:4:1:2:1000.

[0030] Secondly, the colloidal solution obtained after the mixing is placed in a hydrothermal reactor for hydrothermal reaction, the temperature of the hydrothermal reaction is 180 ° C, the time of the hydrothermal reaction is 72 hours, and the reaction product is obtained after the hydrothermal reaction. The reaction product is filtered, washed, dried, and roasted to obtain a roasted product, and the roasted product is immersed in dilute sulfuric acid for acidification to obtain an iron-doped molecular sieve. The drying is heated to 80 ° C in an electric oven and dried for 10 hours. The washing is first washed with acetone, then washed with deionized water, and the washed product is obtained by alternating washing 3 times. The roasting is carried out in a muffle furnace, the roasting temperature and the rate of heating are controlled, and the temperature is gradually raised to 600 ° C for roasting for 6 hours by preheating and then slowly heating.

[0031] (2) Preparation of modified molecular sieve catalyst loaded with super strong solid acid: First, 0.5 mol / L ZrOCl2 is dissolved in deionized water, and the pH is adjusted to 3 to obtain an impregnation precursor solution, and the impregnation precursor solution is impregnated with the molecular sieve product prepared in step (1) to obtain a mixed solution, so that the impregnation precursor solution is impregnated with the molecular sieve product for 4 hours, and then, the mixture is continuously stirred, and alkali is added while stirring to control the pH of the mixed solution to 9, and the mixture is aged for 30 hours, and then filtered, and the precipitate obtained by filtration is dried, and after drying, it is impregnated with 0.6 mol / L ammonium sulfate solution for 4 hours, and finally, the precipitate after ammonium sulfate impregnation is filtered, washed, and dried, and after drying, it is placed in a muffle furnace for roasting, and the roasted product is cooled to room temperature to obtain an iron-doped molecular sieve responsible for the solid super strong acid catalyst. The drying temperature is 80°C and the drying time is 10 hours.

[0032] The catalysts prepared in Example 1-2 and Comparative Example 1-2 were used for the reaction of formic acid and 3-fluoropropanol ester, respectively. The conversion rates of the reaction products were measured, as shown in Table 1.

[0033] Example / Comparative Example Conversion rate / 1 reaction 2nd reaction 3 reactions 4 reactions 5 reactions Example 1 94.6% 94.5% 93.9% 93.5% 92.9% Example 2 94.3% 94.3% 93.8 92.9 92.5 Comparative Example 1 93.9% 92.1% 90.2% 89.3% 87.1% Comparative Example 2 94.0% 93.1% 92.1 91.3 90.5%

[0034] With reference to the test data listed in Table 1, Example 1 is compared to Comparative Example 1, after using iron-doped molecular sieve, it is obvious that in the use process of multiple cycles, it still has a higher catalytic activity. In large-scale applications, considering the reaction scale of formic acid and 3-fluoropropanol ester, the iron-doped molecular sieve supported lanthanum modified super solid acid used in Example 1 has obtained a significant effect, and can achieve excellent economic benefits when applied in industry. After further testing, the conversion rate of the catalyst prepared by Example 1 in the reaction process of formic acid and 3-fluoropropanol ester is still about 90% after 10 continuous reaction processes, and still has high catalytic activity.

Claims

1. A method for preparing an iron-lanthanum co-stabilized molecular sieve supported super-strong solid acid catalyst, characterized in that: The following steps are involved: (1) Preparation of iron-doped molecular sieves: First, a silicon source, a base, a template, an iron salt, and a solvent are added to a reaction container and uniformly stirred and mixed to obtain a colloidal solution; the stirring and mixing temperature is 20-40° C.; the stirring is performed for 1-3 hours; the molar ratio of the silicon source, the base, the template, the iron salt, and the solvent is 10:4-5:1-2:1-2:500-1500; Secondly, the colloidal solution obtained after the mixing is placed in a hydrothermal reactor for hydrothermal reaction, the temperature of the hydrothermal reaction is 160-180° C., the time of the hydrothermal reaction is 60-96 hours, a reaction product is obtained after the hydrothermal reaction, the reaction product is filtered, washed, dried, and roasted to obtain a roasted product, and the roasted product is immersed in dilute sulfuric acid for acidification to obtain an iron-doped molecular sieve; (2) Preparation of modified molecular sieve catalyst loaded with super strong solid acid: First, a certain amount of ZrOCl2 and LaCl3 are dissolved in deionized water, and the pH is adjusted to 2-3 to obtain an impregnation precursor solution, and the impregnation precursor solution is mixed with the molecular sieve product prepared in step (1) to obtain a mixed solution, so that the impregnation precursor solution impregnates the molecular sieve product for 3-6 hours, and then, continuously stirs, and alkali is added while stirring to control the pH of the mixed solution to be 8.5-9.5, and then aged for 24-36 hours, and then filtered, and the precipitate obtained by filtration is dried, and after drying, it is impregnated with ammonium sulfate solution for 3-5 hours. Finally, the precipitate after ammonium sulfate impregnation is filtered, washed, and dried, and after drying, it is placed in a muffle furnace for roasting, and the roasted product is cooled to room temperature to obtain a molecular sieve loaded with iron-lanthanum co-stabilized solid super acid.

2. The preparation method according to claim 1, characterized in that: The solvent is any one of deionized water and distilled water; the silicon source is any one of water glass, ethyl orthosilicate, butyl orthosilicate and propyl orthosilicate; the alkali is any one of ammonia water, sodium hydroxide solution and potassium hydroxide solution; the iron salt is a soluble metal salt; and the template is an ammonium bromide template.

3. The preparation method according to claim 2, characterized in that: The ammonium bromide salt is tetramethylammonium bromide salt.

4. The preparation method according to claim 1, characterized in that: In the step 1, drying is carried out by any one of vacuum drying, microwave drying, and electric oven drying; washing is carried out by first washing with an organic solvent and then washing with deionized water, and the washed product is obtained by alternating washing for 3-5 times; the roasting is carried out in a muffle furnace, and the roasting temperature and the heating rate are controlled. The temperature is gradually raised to 500-700° C. and roasted for 4-6 hours by preheating first and then slowly heating.

5. The preparation method according to claim 4, characterized in that: The drying in step 1 is performed by heating to 60-80° C. in an electric oven and drying for 5-10 hours.

6. The preparation method according to claim 4, characterized in that: The organic solvent used in the washing in step 1 is acetone.

7. The preparation method according to claim 1, characterized in that: In step 2, the drying temperature is 80-120°C, and the drying time is 6-10 hours; the concentrations of ZrOCl2 and LaCl3 in the impregnation precursor solution are 0.1-1 mol / L and 0.01-0.1 mol / L respectively; and the concentration of the ammonium sulfate solution is 0.1-1 mol / L.

8. A molecular sieve-supported solid superacid catalyst prepared by the method for preparing the catalyst according to any one of claims 1 to 7.

9. Use of the molecular sieve-supported solid superacid catalyst according to claim 8 in the esterification preparation of a fluorinated fatty acid ester solvent.