CN109833904B - A kind of acid-base bifunctional catalyst, its preparation method and application in ethanol conversion reaction - Google Patents

Abstract

The present application discloses an acid-base bifunctional catalyst, its preparation method and its application in the reaction of converting ethylene to olefin. The acid-base bifunctional catalyst is characterized in that it comprises tin-doped beta molecular sieve and magnesium oxide; wherein, the mass content of the tin-doped beta molecular sieve in the acid-base bifunctional catalyst is 10% to 90%; The mass content of magnesium oxide in the acid-base bifunctional catalyst is 10% to 90%. The catalyst is prepared by a deposition precipitation method, and is prepared by compounding tin-doped beta molecular sieve and magnesium oxide in a certain proportion. The acid-base bifunctional catalyst can realize the synergistic effect of acid-base through component modulation, overcomes the problem that the acidity and alkalinity of catalysts in this field are difficult to control in the prior art, catalyzes the conversion of ethanol efficiently, and selectively generates 1,3-butylene Chemicals such as diene, ethylene and 1-butene have simple preparation process and strong operability, and can be used for large-scale industrial production.

Description

A kind of acid-base bifunctional catalyst, its preparation method and its use in ethanol conversion reaction application

technical field

The present application relates to an acid-base bifunctional catalyst and a preparation method thereof, which can be used to catalyze the dehydration, dehydrogenation, and condensation reactions of ethanol to selectively generate 1,3-butadiene, 1-butene, ethylene and other chemicals, belonging to catalytic synthesis field.

Background technique

1,3-butadiene, 1-butene and ethylene are all important organic chemical raw materials, which have a very wide range of uses, and their production mainly depends on the petroleum refining process. With the depletion of petroleum resources and the increasing pressure of carbon emissions, it is of great significance to find other raw material resources or develop new production paths.

Ethanol can be converted to these olefin products with appropriate catalysts (Chem. Soc. Rev., 2014, 43, 7917; ACS Catal. 2017, 7, 3703). However, the traditional ethanol industrial production method is mainly based on biological fermentation process, which makes the conversion of ethanol to produce olefins limited by cost and grain yield. Recently, with the successful research and development of coal-to-ethanol technology, the production cost of ethanol will be further greatly reduced. Therefore, it will be more practical to use ethanol conversion to replace the traditional route to produce high-value olefins.

The traditional catalysts used for ethanol conversion to olefins mainly include composite metal oxides, magnesium oxide/silica and sepiolite (J.Appl.Chem., 1962, 105; Catal. Sci. Technol., 2017, 7, 168; Catal. .Lett., 1995, 34, 359), among which the magnesium oxide/silica catalyst has better activity and selectivity, and has been used in early industrial production, but the acid-base control of the catalyst has always been a difficulty. The reaction process of converting ethanol to olefins requires the synergistic catalysis of acid and alkali. Therefore, whether the acidity and alkalinity of the catalyst can be optimized and controlled will be a key consideration in the development of new catalysts for this reaction process.

SUMMARY OF THE INVENTION

According to one aspect of the present application, an acid-base bifunctional catalyst is provided, which can realize the synergistic effect of acid-base through component modulation, overcomes the problem that the acidity and alkalinity of catalysts in this field are difficult to control in the prior art, and efficiently catalyzes ethanol It can be converted to selectively generate high-value olefins such as 1,3-butadiene, ethylene, and 1-butene. The preparation process is simple, the operability is strong, and large-scale industrial production can be carried out.

The acid-base bifunctional catalyst is characterized in that it comprises tin-doped beta molecular sieve and magnesium oxide; wherein the mass content of the tin-doped beta molecular sieve in the acid-base bifunctional catalyst is 10% to 90%; The mass content of the acid-base bifunctional catalyst is 10% to 90%.

Preferably, the mass content of the tin-doped beta molecular sieve in the acid-base bifunctional catalyst is 30% to 90%.

Preferably, the acid-base bifunctional catalyst is composed of tin-doped beta molecular sieve and magnesium oxide.

Preferably, in the tin-doped beta molecular sieve, the molar ratio of silicon element to tin element is 40-200:1.

According to another aspect of the present application, a method for preparing the above acid-base bifunctional catalyst is provided. The method is simple in process, the prepared catalyst product has stable performance, and can realize large-scale industrial production.

The method for preparing an acid-base bifunctional catalyst at least comprises the following steps:

a) obtaining tin-doped beta molecular sieve;

b) placing the tin-doped beta molecular sieve in a solution containing magnesium ions, and adding an alkaline solution to adjust the pH value;

c) After separating and washing the obtained solid, drying and calcining, the acid-base bifunctional catalyst is obtained.

The tin-doped beta molecular sieve can be purchased commercially, prepared according to the description in the prior art, or prepared according to the method described in this application.

As a preferred way, the tin-doped beta molecular sieve is prepared by a preparation method comprising at least the following steps:

(1) carry out dealumination treatment to H-β molecular sieve;

(2) Mixing and grinding the dealuminated H-β molecular sieve with a tin precursor, and then calcining to obtain the tin-doped β molecular sieve.

Those skilled in the art can select the source of H-β molecular sieve according to the specific situation, which can be obtained through commercial purchase, or can be prepared according to the records in the prior art.

Preferably, the molar ratio of Si to Al of the H-β molecular sieve is SiO ₂ /Al ₂ O ₃ =12.5-50. Further preferably, the molar ratio of silicon to aluminum of the H-β molecular sieve is SiO ₂ /Al ₂ O ₃ =20-30.

As an embodiment, in the dealumination treatment, the H-β molecular sieve is placed in a nitric acid solution with a concentration of 10-14 mol/L, and kept at a temperature of not less than 50-90° C. for not less than 7-30 hours .

Preferably, in the dealumination treatment, the H-β molecular sieve is placed in a nitric acid solution with a mass concentration of 65% to 68%, and kept at a temperature not lower than 75°C to 85°C for not less than 8 to 20 hours.

As an embodiment, in the dealumination treatment, the solid-to-liquid ratio of the H-beta molecular sieve and the nitric acid solution is 1 g: 15-100 mL. Preferably, in the dealumination treatment, the solid-to-liquid ratio of the H-beta molecular sieve to the nitric acid solution is 1 g: 20-40 mL.

As an embodiment, the solution containing magnesium ions is obtained by dissolving magnesium salts in water. Preferably, the magnesium salt is magnesium nitrate and/or magnesium acetate.

Those skilled in the art can select the concentration of the magnesium ion-containing solution and the ratio of the magnesium ion-containing solution to the tin-doped beta molecular sieve according to specific needs. As a specific embodiment, in the step b), the molar ratio of the magnesium element in the solution containing magnesium ions to the mass ratio of the tin-doped beta molecular sieve is 0.25-6 mmol:1 g.

Those skilled in the art can select the type of tin precursor according to actual needs. Preferably, the tin precursor is at least one of crystalline tin tetrachloride, dimethyltin dichloride, stannous chloride or stannous oxalate.

As an embodiment, the mole ratio of the silicon element in the H-β molecular sieve after the dealumination treatment and the tin element in the tin precursor is:

Si:Sn=40～200:1;

As an embodiment, the mass ratio of the dealuminated H-β molecular sieve to the tin precursor is 2:0.05-0.3. Preferably, the mass ratio of the dealuminated H-β molecular sieve to the tin precursor is 2:0.058-0.29.

Preferably, the addition of the alkali solution to adjust the pH value is to add the alkali solution to adjust the pH value of the system to 10-12.

Preferably, the alkaline solution is selected from ammonia water and/or sodium hydroxide solution. Further preferably, the concentration of the ammonia water and/or sodium hydroxide solution is 1 mol/L.

As a specific embodiment, the method for preparing an acid-base bifunctional catalyst is as follows: placing tin-doped beta molecular sieve in an aqueous solution of magnesium precursor, adding an alkaline solution to adjust the pH to 10-12, and the obtained solid product is subjected to After filtering, washing and drying, it was prepared by calcining at 500℃ for 4h in the air.

As a specific embodiment, the preparation method of the tin-doped beta molecular sieve is:

(1) H-β molecular sieve (silicon-aluminum molar ratio 12.5-50) is dealuminated with the nitric acid of 10-14mol/L, and the obtained product is washed and dried;

(2) Mixing and grinding the dealuminated beta molecular sieve with a tin precursor, and then calcining at 550° C. to obtain a tin-doped beta molecular sieve.

According to yet another aspect of the present application, the application of the above acid-base bifunctional catalyst and the acid-base bifunctional catalyst prepared according to any of the above methods as catalysts in the reaction process of ethanol conversion to olefins is provided.

The ethanol conversion includes one of ethanol dehydration, ethanol dehydrogenation, and ethanol condensation.

Preferably, the reaction of converting ethanol to olefins is at least one of converting ethanol to 1,3-butadiene, converting ethanol to ethylene, and converting ethanol to 1-butene.

The beneficial effects of this application include but are not limited to:

(1) The present application provides an acid-base bifunctional catalyst, which can achieve acid-base synergy through component modulation, and efficiently catalyze the conversion of ethanol to selectively generate 1,3-butadiene, ethylene, and 1-butene and other high-value olefins.

(2) The present application provides a method for preparing the above acid-base bifunctional catalyst, the preparation process is simple, the operability is strong, and large-scale industrial production is possible.

Detailed ways

The present application will be described in detail below with reference to the examples, but the present application is not limited to these examples.

Unless otherwise specified, the raw materials used in this application were purchased commercially and used directly without special treatment.

In this application, the used H-β molecular sieve was purchased from Nankai University Catalyst Factory.

The preparation of embodiment 1 catalyst

Disperse 5g of H-β molecular sieve (SiO ₂ /Al ₂ O ₃ =25) into 100 mL of nitric acid solution with a concentration of 14 mol/L, stir at 80° C. for 8 h, filter, wash and dry to obtain dealuminated β molecular sieve; take 2g of dealuminated beta molecular sieve was mixed with 0.29g of crystalline tin tetrachloride and ground for 10 minutes, and the obtained powder was calcined in an air atmosphere at 550°C for 4 hours to obtain tin-doped beta molecular sieve.

Dissolve 1.42 g of magnesium nitrate hexahydrate in 80 mL of deionized water, add 2 g of tin-doped beta molecular sieve, and add 1 mol/L aqueous sodium hydroxide solution dropwise to the above solution until the pH of the system is equal to 12, and continue stirring at room temperature 6h, filtered, washed until the filtrate was neutral, the product was dried at 100°C, and calcined at 500°C for 4h to obtain a Sn-β/MgO catalyst, denoted as sample 1 ^# .

The preparation of embodiment 2 catalyst

Disperse 5 g of H-β molecular sieve (SiO ₂ /Al ₂ O ₃ =25) into 100 mL of nitric acid solution with a concentration of 14 mol/L, stir at 80°C for 8 h, filter, wash and dry to obtain dealuminated β molecular sieve; take 2 g The dealuminated β molecular sieve was mixed with 0.29 g of crystalline tin tetrachloride and ground for 10 minutes, and the obtained powder was calcined in an air atmosphere at 550° C. for 4 hours to obtain a tin-doped β molecular sieve.

Dissolve 2.88g of magnesium nitrate hexahydrate in 80mL of deionized water, add 0.5g of tin-doped beta molecular sieve, and dropwise add 1mol/L ammonia solution to the above solution until the pH of the system is equal to 12, and continue to stir at room temperature for 6h , filtered and washed until the filtrate was neutral. The product was dried at 100°C and calcined at 500°C for 4 h to obtain a Sn-β/MgO catalyst, which was designated as sample 2 ^# .

The preparation of embodiment 3 catalyst

Disperse 5 g of H-β molecular sieve (SiO ₂ /Al ₂ O ₃ =6.25) into 100 mL of nitric acid solution with a concentration of 10 mol/L, stir at 80° C. for 8 h, filter, wash and dry to obtain dealuminated β molecular sieve; take 2g of dealuminated beta molecular sieve was mixed with 0.058g of crystalline tin tetrachloride and ground for 10 minutes, and the obtained powder was calcined in an air atmosphere at 550°C for 4 hours to obtain tin-doped beta molecular sieve.

Dissolve 1.42 g of magnesium nitrate hexahydrate in 80 mL of deionized water, add 2 g of tin-doped beta molecular sieve, and add 1 mol/L aqueous sodium hydroxide solution dropwise to the above solution until the pH value of the system is equal to 10, and continue to stir at room temperature 6h, filtered, washed until the filtrate was neutral, the product was dried at 100°C, and calcined at 500°C for 4h to obtain a Sn-β/MgO catalyst, denoted as sample 3 ^# .

The preparation of embodiment 4 catalyst

Disperse 5g of H-β molecular sieve (SiO ₂ /Al ₂ O ₃ =15) into 100mL of nitric acid solution with a concentration of 12mol/L, stir at 80°C for 8h, filter, wash and dry to obtain dealuminated β molecular sieve; take 2g The dealuminated β molecular sieve was mixed with 0.29 g of crystalline tin tetrachloride and ground for 10 minutes, and the obtained powder was calcined in an air atmosphere at 550° C. for 4 hours to obtain a tin-doped β molecular sieve.

Dissolve 0.22 g of magnesium nitrate hexahydrate in 80 mL of deionized water, add 2 g of tin-doped beta molecular sieve, and dropwise add 1 mol/L ammonia solution to the above solution until the pH of the system is equal to 10, and continue to stir at room temperature for 6 h. Filter and wash until the filtrate is neutral. The product is dried at 100°C and calcined at 500°C for 4 hours to obtain a Sn-β/MgO catalyst, which is designated as sample 4 ^# .

The preparation of embodiment 5 catalyst

Disperse 5g H-β molecular sieve (SiO ₂ /Al ₂ O ₃ =20) into 100mL of nitric acid solution with a concentration of 14mol/L, stir at 80°C for 8h, filter, wash and dry to obtain dealuminated β molecular sieve; take 2g The dealuminated β molecular sieve was mixed with 0.29 g of crystalline tin tetrachloride and ground for 10 minutes, and the obtained powder was calcined in an air atmosphere at 550° C. for 4 hours to obtain a tin-doped β molecular sieve.

Dissolve 5.36g of magnesium acetate tetrahydrate in 80mL of deionized water, add 2g of tin-doped beta molecular sieve, and dropwise add 1mol/L sodium hydroxide aqueous solution to the above solution until the pH value of the system is equal to 12, and continue to stir at room temperature 6h, filter, wash until the filtrate becomes neutral, the product is dried at 100°C and calcined at 500°C for 4h to obtain Sn-β/MgO catalyst, which is designated as sample 5 ^# .

The preparation of embodiment 6 catalyst

Disperse 5 g of H-β molecular sieve (SiO ₂ /Al ₂ O ₃ =25) into 100 mL of nitric acid solution with a concentration of 14 mol/L, stir at 80°C for 8 h, filter, wash and dry to obtain dealuminated β molecular sieve; take 2 g The dealuminated beta molecular sieve was mixed with 0.18 g of dimethyltin dichloride and ground for 10 minutes, and the obtained powder was calcined in an air atmosphere at 550° C. for 4 hours to obtain a tin-doped beta molecular sieve.

Dissolve 1.42 g of magnesium nitrate hexahydrate in 80 mL of deionized water, add 2 g of tin-doped beta molecular sieve, and add 1 mol/L aqueous sodium hydroxide solution dropwise to the above solution until the pH of the system is equal to 12, and continue stirring at room temperature 6h, filtered, washed until the filtrate was neutral, the product was dried at 100°C, and calcined at 500°C for 4h to obtain a Sn-β/MgO catalyst, denoted as sample 6 ^# .

The preparation of embodiment 7 catalyst

Disperse 5 g of H-β molecular sieve (SiO ₂ /Al ₂ O ₃ =25) into 100 mL of nitric acid solution with a concentration of 14 mol/L, stir at 80°C for 8 h, filter, wash and dry to obtain dealuminated β molecular sieve; take 2 g The dealuminated beta molecular sieve was mixed with 0.18 g of dimethyltin dichloride and ground for 10 minutes, and the obtained powder was calcined in an air atmosphere at 550° C. for 4 hours to obtain a tin-doped beta molecular sieve.

Dissolve 1.42 g of magnesium nitrate hexahydrate in 80 mL of deionized water, add 2 g of tin-doped beta molecular sieve, and dropwise add 1 mol/L ammonia solution to the above solution until the pH of the system is equal to 11, and continue to stir at room temperature for 6 h. Filter and wash until the filtrate is neutral. The product is dried at 100°C and calcined at 500°C for 4 hours to obtain a Sn-β/MgO catalyst, which is designated as sample 7 ^# .

The preparation of embodiment 8 catalyst

Disperse 5 g of H-β molecular sieve (SiO ₂ /Al ₂ O ₃ =25) into 100 mL of nitric acid solution with a concentration of 14 mol/L, stir at 80°C for 8 h, filter, wash and dry to obtain dealuminated β molecular sieve; take 2 g The dealuminated beta molecular sieve was mixed with 0.16 g of stannous chloride and ground for 10 minutes, and the obtained powder was calcined in an air atmosphere at 550°C for 4 hours to obtain a tin-doped beta molecular sieve.

Dissolve 1.42 g of magnesium nitrate hexahydrate in 80 mL of deionized water, add 2 g of tin-doped beta molecular sieve, and add 1 mol/L aqueous sodium hydroxide solution dropwise to the above solution until the pH of the system is equal to 12, and continue stirring at room temperature 6h, filtered, washed until the filtrate was neutral, the product was dried at 100°C, and calcined at 500°C for 4h to obtain a Sn-β/MgO catalyst, denoted as sample 8 ^# .

The preparation of embodiment 9 catalyst

Disperse 5 g of H-β molecular sieve (SiO ₂ /Al ₂ O ₃ =25) into 100 mL of nitric acid solution with a concentration of 14 mol/L, stir at 80°C for 8 h, filter, wash and dry to obtain dealuminated β molecular sieve; take 2 g The dealuminated β molecular sieve was mixed with 0.17 g of stannous oxalate and ground for 10 minutes, and the obtained powder was calcined in an air atmosphere at 550° C. for 4 hours to obtain a tin-doped β molecular sieve.

Dissolve 1.42 g of magnesium nitrate hexahydrate in 80 mL of deionized water, add 2 g of tin-doped beta molecular sieve, and add 1 mol/L aqueous sodium hydroxide solution dropwise to the above solution until the pH of the system is equal to 12, and continue stirring at room temperature 6h, filtered, washed until the filtrate was neutral, the product was dried at 100°C, and calcined at 500°C for 4h to obtain a Sn-β/MgO catalyst, denoted as sample 9 ^# .

Example 10 Application of Catalyst

Take 0.5g of Sn-β/MgO catalyst sample 1 ^# , sample 2 ^# , sample 3 ^# , sample 6 ^# , sample 7 ^# , sample 8 ^# , sample 9 ^# (molecular sieve mass content 50%), loaded into a fixed-bed reactor, first pretreated at 450°C for 30min in a nitrogen atmosphere, then the temperature was reduced to 425°C, and the raw material ethanol was introduced to start the reaction, the ethanol flow rate was 0.017mL/min, and the nitrogen flow rate was 50mL/min. min, and analysis was performed after 30 min of reaction.

The products were analyzed using Tianmei gas chromatography 7900 online analysis, FID detector, HP-PLOT Q capillary column.

The results show that the results of sample 1 ^# , sample 2 ^# , sample 3 ^# , sample 6 ^# , sample 7 ^# , sample 8 ^# , and sample 9 ^# are similar, with higher 1,3-butadiene selectivity and higher ethylene Optional.

Taking sample 1 ^# as a typical representative, the reaction results: the conversion rate of ethanol is 77%, the selectivity of 1,3-butadiene is 50%, and the selectivity of ethylene is 34%.

Example 11 Application of catalyst

Take 0.5 g of Sn-β/MgO catalyst sample 4 ^# (the mass content of molecular sieves is 90%) that has been compressed and sieved with 40-60 meshes, and put it into a fixed-bed reactor. Then the temperature was lowered to 425° C., the raw material ethanol was introduced to start the reaction, the flow rate of ethanol was 0.017mL/min, the flow rate of nitrogen was 50mL/min, and the analysis was carried out after the reaction for 30min.

The products were analyzed using Tianmei gas chromatography 7900 online analysis, FID detector, HP-PLOT Q capillary column.

The reaction results: the conversion rate of ethanol is 90%, the selectivity of 1,3-butadiene is 5%, and the selectivity of ethylene is 90%.

Example 12 Application of catalyst

Take 0.5g of the Sn-β/MgO catalyst sample 5 ^# (molecular sieve mass content 30%) that has been compressed and sieved with 40-60 meshes, loaded into a fixed-bed reactor, pretreated at 450° C. for 30min in a nitrogen atmosphere, Then the temperature was lowered to 425° C., the raw material ethanol was introduced to start the reaction, the flow rate of ethanol was 0.017mL/min, the flow rate of nitrogen was 50mL/min, and the analysis was carried out after the reaction for 30min.

The products were analyzed using Tianmei gas chromatography 7900 online analysis, FID detector, HP-PLOT Q capillary column.

The reaction results: the conversion rate of ethanol is 80%, the selectivity of 1,3-butadiene is 60%, and the selectivity of ethylene is 8%.

The above are only a few embodiments of the present application, and are not intended to limit the present application in any form. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Without departing from the scope of the technical solution of the present application, any changes or modifications made by using the technical content disclosed above are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims (11)

1. an acid-base bifunctional catalyst for ethanol conversion to olefin reaction, is characterized in that, is made up of tin-doped beta molecular sieve and magnesium oxide; Wherein, the mass content of the tin-doped beta molecular sieve in the acid-base bifunctional catalyst is 10% to 90%; The mass content of the magnesium oxide in the acid-base bifunctional catalyst is 10% to 90%; In the tin-doped beta molecular sieve, the molar ratio of silicon element to tin element is 40-200:1; The preparation method of the acid-base bifunctional catalyst for ethanol conversion to olefin reaction at least comprises the following steps: a) obtaining tin-doped beta molecular sieve; b) placing the tin-doped beta molecular sieve in a solution containing magnesium ions, and adding an alkaline solution to adjust the pH value; c) separating and washing the obtained solid, and after drying and calcining, the acid-base bifunctional catalyst is obtained. 2. a preparation method of the acid-base bifunctional catalyst for ethanol conversion to olefin reaction as claimed in claim 1, is characterized in that, comprises the following steps at least: a) obtaining tin-doped beta molecular sieve; b) placing the tin-doped beta molecular sieve in a solution containing magnesium ions, and adding an alkaline solution to adjust the pH value; c) separating and washing the obtained solid, and after drying and calcining, the acid-base bifunctional catalyst is obtained. 3. The method according to claim 2, wherein the tin-doped beta molecular sieve is prepared by a preparation method comprising at least the following steps: (1) carry out dealumination treatment to H-β molecular sieve; (2) Mixing and grinding the dealuminated H-β molecular sieve with a tin precursor, and then calcining to obtain the tin-doped β molecular sieve. The method according to claim 3, characterized in that, the molar ratio of silicon to aluminum of the H-β molecular sieve is SiO ₂ /Al ₂ O ₃ =12.5-50. 5. The method according to claim 3, wherein the dealumination treatment is to place the H-β molecular sieve in a nitric acid solution with a concentration of 10-14 mol/L, and keep it at a temperature not lower than 50°C Not less than 7 hours. 6 . The method according to claim 3 , wherein the dealumination treatment is to place the H-β molecular sieve in a nitric acid solution with a mass concentration of 65% to 68% at a temperature not lower than 75° C. 7 . Keep for no less than 8 hours. 7. The method according to claim 3, wherein the tin precursor is at least one of crystalline tin tetrachloride, dimethyltin dichloride, stannous chloride or stannous oxalate. 8 . The method according to claim 3 , wherein the mole ratio of silicon element in the H-β molecular sieve after the dealumination treatment to the mole ratio of tin element in the tin precursor is Si:Sn=40～200 8 . :1. 9 . The method according to claim 3 , wherein the mass ratio of the dealuminated H-β molecular sieve to the tin precursor is 2:0.05-0.3. 10 . 10 . The method according to claim 2 , wherein the pH value adjustment by adding an alkaline solution is to adjust the pH value of the system to 10-12 by adding an alkaline solution. 11 . 11. The acid-base bifunctional catalyst for ethanol conversion to olefin reaction according to claim 1 or a kind of acid-base bifunctional catalyst prepared by the method according to any one of claims 2 to 10 as ethanol conversion to olefin reaction catalyst Applications.