CN114749191B - Ni/P-attapulgite clay catalyst and preparation method and application thereof - Google Patents

Abstract

The invention discloses a Ni/P-attapulgite clay catalyst, a preparation method and application thereof, wherein the carrier of the catalyst is phosphate modified attapulgite clay, the active component is metal Ni, and the load amount of the catalyst is 30-60% of the total mass of the catalyst. According to the invention, the attapulgite clay is used as a carrier, the surface property of the attapulgite clay is regulated and controlled by a phosphate through an impregnation method, and the metal Ni is uniformly distributed on the modified attapulgite clay through a precipitation method, so that the Ni/P-attapulgite clay catalyst is obtained, the hydrothermal stability of the catalyst is improved, the surface acidity of the catalyst is enhanced, and the catalytic reaction activity of the amide group hydrodeoxygenation is improved.

Description

A kind of Ni/P-attapulgite clay catalyst and its preparation method and application

technical field

The invention belongs to the technical field of catalyst preparation, and relates to a Ni/P-attapulgite clay catalyst, a preparation method thereof and an application in the reaction of N,N-dimethylformamide hydrodeoxygenation to prepare trimethylamine.

Background technique

As an important chemical raw material, fatty amines are widely used in the fields of pharmaceuticals, daily chemicals and textiles. The industrial fatty amines are usually synthesized by converting fatty acids into amides, which are dehydrated to generate fatty nitriles, and then the fatty nitriles are catalyzed. Hydrogen can be used to obtain fatty amines (ACS Catalysis, Volume 5, 2015, pages 4814~4818). Studies have found that amide groups can also be directly converted into aliphatic amines by catalytic hydrodeoxygenation, and this synthetic strategy can effectively improve the economic efficiency of aliphatic amine synthesis (Journal of Separation Science, 2014, Vol. 37, pp. 558-565). Noble metal Ru, Pd, Pt and metal Ni catalysts have good catalytic activity in the reaction of catalytic hydrodeoxygenation of amide groups directly into aliphatic amines, and metal Ni catalysts are more widely used due to their low price and abundant resources. Prospects (J. Catalysis, 2012, Vol. 292, pp. 130~137). Al ₂ O ₃ is often used as a support for metallic Ni catalysts in industrial production due to its good thermal stability and large specific surface area. However, during the reaction process of amide group through catalytic hydrodeoxygenation, a large amount of water will be generated, so that the catalyst is placed in a hydrothermal environment. The long-term hydrothermal environment will make the unsaturated coordination A1 ³⁺ existing on the surface of Al ₂ O ₃ A hydration reaction occurs (Langmuir, 2002, volume 18, pages 7530-7537), causing changes in the structure of the catalyst, leading to the deactivation of the metal Ni catalyst (Catalysis Today, 2010, volume 158, pages 475-480). At the same time, the amide group can form multiple adsorption bonds with the metal Ni atom in the catalyst, and the surface acidity of the catalyst can reduce the surface electron density of the metal Ni in the catalyst, and greatly increase the adsorption strength of the amide group on the metal Ni atom, thereby improving the catalytic performance of the catalyst. Reactivity to hydrodeoxygenation of amide groups (Angewandte Chemie International Edition, 2013, Vol. 52, pp. 2231~2234).

In order to improve the hydrothermal stability of metal Ni catalysts, the traditional method is to add a small amount of additives to the catalyst, such as adding a small amount of SiO ₂ in the preparation process of the catalyst, which can not only improve the dispersion of metal Ni in the catalyst, but also effectively Improve the hydrothermal stability of the catalyst, but the service life of the catalyst still needs to be improved (Journal of Colloid and Interface Science, Vol. 447, 2015, pp. 68-76). In addition, the addition of metal La as a promoter can also greatly improve the hydrothermal stability of the catalyst, but the catalyst will still be deactivated quickly under harsher reaction conditions. What is more serious is that the metal La will enhance the surface alkalinity of the catalyst and weaken the catalyst. The surface acidity of the catalyst inhibits the reactivity of the catalyst for the catalytic hydrodeoxygenation of the amide group (Journal of Catalysis, 2016, volume 338, pages 1-11).

It can be seen that although the surface structure of Al ₂ O ₃ in industrial catalysts can be changed by adding additives to improve the hydrothermal stability of the catalyst, its internal structure has not been improved, and the hydrothermal stability of the catalyst cannot be fundamentally improved. stability. In addition, the modification of the surface properties of the catalyst by the metal promoter can also inhibit the reactivity of the catalyst for the catalytic hydrogenation of amide groups.

Contents of the invention

In view of the deficiencies in the prior art, the object of the present invention is to provide a Ni/P-attapulgite clay catalyst, which has high hydrothermal stability and has the advantages of being used in the preparation of amine groups by catalytic hydrodeoxygenation of amide groups. Higher conversion rate and selectivity; another object of the present invention is to provide a preparation method of the Ni/P-attapulgite clay catalyst.

The present invention is achieved through the following technical solutions:

A Ni/P-attapulgite clay catalyst, the carrier is attapulgite clay whose surface has been modified by phosphate, the active component is metal Ni, and the loading capacity is 30-60%.

A further improvement of the present invention is:

A method for preparing a Ni/P-attapulgite clay catalyst, the preparation steps are as follows: disperse the attapulgite clay in distilled water, add a phosphate solution under heating and stirring, then dry and calcinate to obtain a phosphate-modified Attapulgite clay: Disperse the modified attapulgite clay in distilled water again, weigh Ni(NO ₃ ) ₂ 6H ₂ O and anhydrous NaCO ₃ respectively, and dissolve them in distilled water respectively. ₃ ) The solution of ₂ ·6H ₂ O and anhydrous NaCO ₃ was added dropwise to the aqueous solution dispersed with modified attapulgite clay to form a precipitate, the obtained precipitate was washed with water until neutral, and dried The solid powder is compressed, sieved and reduced to obtain the Ni/P-attapulgite clay catalyst.

Further, the phosphate solution is an aqueous solution of methyl phosphate, and the heating temperature is 60°C.

Further, the drying temperature is 80-120°C, the calcination temperature is 400-550°C, and the calcination time is 2-4 h.

Further, the mass of Ni(NO ₃ ) ₂ ·6H ₂ O is calculated by the mass of Ni, so that the mass of Ni accounts for 30-60% of the sum of the mass of Ni and the mass of the phosphate-modified attapulgite clay.

Further, during the dropwise addition of the solution containing Ni(NO ₃ ) ₂ ·6H ₂ O and anhydrous NaCO ₃ , the temperature of the reaction solution was controlled at 80°C.

Further, the drying temperature is 80-120° C., and the drying time is 6-12 h.

Further, the sieve needs to pass through a 60-80 mesh sieve.

Further, during the reduction, the temperature is 400-550° C., the reducing gas is H ₂ , and the time is 2 h.

The further improvement scheme of the present invention is:

Application of the above-mentioned Ni/P-attapulgite clay catalyst in the reaction of N,N-dimethylformamide hydrodeoxygenation to prepare trimethylamine.

The beneficial effects of the present invention are:

What the present invention selects is a kind of water-containing magnesium-aluminosilicate porous type chain-layered attapulgite clay as carrier, attapulgite clay has the characteristics of porous, large specific surface area, and contains a large amount of water in the structure, water High thermal stability. However, attapulgite clay contains a large amount of Mg ²⁺ , so it has strong surface alkalinity. As the support of metal Ni, it is used in the catalytic hydrodeoxygenation reaction of N,N-dimethylformamide to prepare trimethylamine, which will inhibit its catalytic activity, so it is necessary to modify the surface properties of attapulgite clay. Phosphate has strong acidity, and modifying it with phosphate can inhibit its surface alkalinity and enhance its surface acidity. Not only can the hydrothermal stability of metal Ni catalyst be improved, but also its catalytic reactivity can be improved.

In the preparation method of the present invention, the surface properties of the attapulgite clay are modified using methyl phosphate by the impregnation method, and it is used as a carrier to uniformly distribute metal Ni in the modified P-attapulgite clay by the precipitation method The Ni/P-attapulgite clay catalyst is obtained, and the catalyst activity and the hydrothermal stability of the catalyst are improved at the same time.

The Ni/P-attapulgite clay catalyst of the invention is used in the reaction of preparing trimethylamine by catalytic hydrodeoxygenation of N,N-dimethylformamide. The data show that at 180 ℃, 4 MPa pressure and 2 h ⁻¹ space velocity, the Ni/P-attapulgite clay catalyst after hydrothermal treatment at 180 ℃ for 12 h still has very high activity, N,N- The conversion rate of dimethylformamide reaches 63%, and the selectivity of trimethylamine is 91%, which has good industrial application prospect.

Detailed ways

Reference example 1

Weigh 2.5 g of commercial Al ₂ O ₃ powder and disperse it in 50 mL of distilled water; take another 5.4 g of Na ₂ CO ₃ and dissolve it in distilled water to make a 50 mL solution; then weigh 12.4 g of Ni(NO ₃ ) ₂ ·6H ₂ O was dissolved in distilled water to make a 50 mL solution. Add the aqueous solution containing Na ₂ CO ₃ and Ni(NO ₃ ) ₂ dropwise to the distilled water dispersed with Al ₂ O ₃ under stirring to form a precipitate, wash the precipitate with distilled water until it is neutral, and dry it at 100°C. Then pressed into tablets and sieved to make 60-80 mesh particles, and then reduced with H ₂ at 450 ℃ for 2 h in a tube furnace to obtain a Ni/Al ₂ O ₃ catalyst with a loading capacity of 50%. The sample number is Ni/Al 2 O 3 . AlO.

Reference example 2

Weigh 2.5 g of attapulgite clay and disperse it in distilled water to make a 50 mL solution; another 5.4 g of Na ₂ CO ₃ is dissolved in distilled water to make a 50 mL solution; then weigh 12.4 g of Ni(NO ₃ ) ₂ · 6H ₂ O was dissolved in distilled water to make a 50 mL solution. Under stirring, the aqueous solution containing Na ₂ CO ₃ and Ni(NO ₃ ) ₂ was added dropwise to distilled water dispersed with attapulgite clay at the same time to form a precipitate, which was washed with distilled water to neutrality and dried at 100 °C. Then it was pressed into tablets and sieved to make 60-80 mesh particles, and then reduced with _H2 at 450 °C for 2 h in a tube furnace to obtain a Ni/attapulgite clay catalyst with a loading capacity of 50%. The sample number is Ni/ ATP.

Example 1

Weigh 2.5 g of attapulgite clay and disperse it in distilled water to make a 50 mL solution, which is heated to 60 °C. Add 20 mL of 0.1 mol/L methyl phosphate solution dropwise under stirring; filter, dry at 100 °C, and finally calcinate at 450 °C for 2 hours to obtain modified attapulgite clay, the sample number is P-ATP.

Example 2

Weigh 2.5 g P-ATP and fully disperse in distilled water to make 50 mL solution; take another 5.4 g Na ₂ CO ₃ dissolved in distilled water to make 50 mL solution; then weigh 12.4 g Ni(NO ₃ ) ₂ · 6H ₂ O was dissolved in distilled water to make a 50 mL solution. Under stirring, the aqueous solution containing Na ₂ CO ₃ and Ni(NO ₃ ) ₂ was added dropwise to distilled water dispersed with attapulgite clay at the same time to form a precipitate, which was washed with distilled water to neutrality and dried at 100 °C. Then pressed into tablets and sieved to make 60-80 mesh particles, and then reduced with H ₂ at 450°C for 2 h in a tube furnace to obtain a Ni/attapulgite clay catalyst with a loading capacity of 50%. The sample number is Ni/ P-ATP.

Reference example 3

The sample Ni/AlO catalyst in Reference Example 1 was transferred to a 100 mL hydrothermal reactor filled with 20 mL water, and the temperature was raised to 180 °C at a rate of 2 °C/min and kept for 12 h. After the hydrothermal treatment, the sample was cooled to room temperature, filtered and dried, and the obtained sample number is Ni/AlO-HT.

Reference example 4

Transfer the sample Ni/ATP catalyst in Reference Example 2 to a 100 mL hydrothermal reactor filled with 20 mL water, raise the temperature to 180 °C at a rate of 2 °C/min and keep it for 12 h. After the hydrothermal treatment, the sample was cooled to room temperature, filtered and dried, and the obtained sample number is Ni/ATP-HT.

Example 3

Transfer the sample Ni/P-ATP catalyst in Example 2 to a 100 mL hydrothermal reactor filled with 20 mL water, raise the temperature to 180 °C at a rate of 2 °C/min and keep it for 12 h. The sample was cooled to room temperature, filtered and dried, and the obtained sample number was Ni/P-ATP-HT.

Reference example 5

Weigh 0.4 g of the sample Ni/AlO in Reference Example 1 and fill it into the reaction tube of a miniature fixed-bed reactor with an outer diameter of 6 mm, feed H ₂ , and heat up to 450 °C at a rate of 2 °C/min for reduction 2 h. After the temperature of the catalyst bed is cooled to the set reaction temperature, i.e. 180 °C, a 20% N,N-dimethylformamide aqueous solution with a mass fraction of n(H ₂ )/n(N , N-dimethylformamide) = 8/1, WHSV = 2 h ⁻¹ , and the pressure is 4 MPa. The conversion and selectivity analysis results of the reaction are shown in Table 1.

Reference example 6

Weigh 0.4 g of the Ni/ATP sample in Reference Example 2 and fill it into the reaction tube of a miniature fixed-bed reactor with an outer diameter of 6 mm, feed H ₂ , and heat up to 450 °C at a rate of 2 °C/min for reduction 2 h. After the temperature of the catalyst bed is cooled to the set reaction temperature, i.e. 180 °C, a 20% N,N-dimethylformamide aqueous solution with a mass fraction of n(H ₂ )/n(N , N-dimethylformamide) = 8/1, WHSV = 2 h ⁻¹ , and the pressure is 4 MPa. The conversion and selectivity analysis results of the reaction are shown in Table 1.

Example 4

Weigh 0.4 g of the sample Ni/P-ATP in Example 2 and fill it into the reaction tube of the miniature fixed bed reactor, the outer diameter of the reaction tube is 6 mm, feed H ₂ , and raise the temperature to 450 °C at a rate of 2 °C/min ℃ reduction for 2 h. After the temperature of the catalyst bed is cooled to the set reaction temperature, i.e. 180 °C, a 20% N,N-dimethylformamide aqueous solution with a mass fraction of n(H ₂ )/n(N , N-dimethylformamide) = 8/1, WHSV = 2 h ⁻¹ , and the pressure is 4 MPa. The conversion and selectivity analysis results of the reaction are shown in Table 1.

Reference example 7

Weigh 0.4 g of the sample Ni/AlO-HT in Reference Example 3 and fill it into the reaction tube of a micro-fixed-bed reactor with an outer diameter of 6 mm, feed H ₂ , and raise the temperature to 450 °C at a rate of 2 °C/min. ℃ reduction for 2 h. After the temperature of the catalyst bed is cooled to the set reaction temperature, i.e. 180 °C, a 20% N,N-dimethylformamide aqueous solution with a mass fraction of n(H ₂ )/n(N , N-dimethylformamide) = 8/1, WHSV = 2 h ⁻¹ , and the pressure is 4 MPa. The conversion and selectivity analysis results of the reaction are shown in Table 2.

Reference example 8

Weigh 0.4 g of the sample Ni/ATP-HT in Reference Example 4 and fill it into the reaction tube of a miniature fixed-bed reactor with an outer diameter of 6 mm, feed H ₂ , and raise the temperature to 450 ℃ reduction for 2 h. After the temperature of the catalyst bed is cooled to the set reaction temperature, i.e. 180 °C, a 20% N,N-dimethylformamide aqueous solution with a mass fraction of n(H ₂ )/n(N , N-dimethylformamide) = 8/1, WHSV = 2 h ⁻¹ , and the pressure is 4 MPa. The conversion and selectivity analysis results of the reaction are shown in Table 2.

Example 5

Weigh 0.4 g of the sample Ni/P-ATP-HT in Example 3 and fill it into the reaction tube of the miniature fixed bed reactor, the outer diameter of the reaction tube is 6 mm, feed H ₂ , and raise the temperature at a rate of 2 °C/min Reduction at 450 °C for 2 h. After the temperature of the catalyst bed is cooled to the set reaction temperature, i.e. 180 °C, a 20% N,N-dimethylformamide aqueous solution with a mass fraction of n(H ₂ )/n(N , N-dimethylformamide) = 8/1, WHSV = 2 h ⁻¹ , and the pressure is 4 MPa. The conversion and selectivity analysis results of the reaction are shown in Table 2.

Table 1. Catalytic activity of catalysts in the reaction of N,N-dimethylformamide hydrodeoxygenation to trimethylamine

Catalyst preparation example catalyst Conversion rate selectivity Reference example 5 Ni/AlO 56% 89% Reference example 6 Ni/ATP 51% 97% Example 4 Ni/P-ATP 71% 93%

Table 2. Hydrothermal stability of catalysts in the reaction of N,N-dimethylformamide hydrodeoxygenation to trimethylamine

Catalyst preparation example catalyst Conversion rate selectivity Reference example 7 Ni/AlO-HT 36% 90% Reference example 8 Ni/ATP-HT 48% 95% Example 5 Ni/P-ATP-HT 63% 91%

It can be seen from Table 1 and Table 2 that the Ni/P-attapulgite clay catalyst prepared by the present invention is used for the reaction of N,N-dimethylformamide catalytic hydrodeoxygenation to prepare trimethylamine, and has higher catalytic activity and hydrothermal stability.

Claims (10)

1. A Ni/P-attapulgite clay catalyst is characterized in that the carrier of the catalyst is attapulgite clay modified by phosphate on the surface, the active component is metal Ni, and the mass loading capacity is 30 to 60 %. 2. a preparation method of Ni/P-attapulgite clay catalyst as claimed in claim 1, is characterized in that, preparation step is as follows: attapulgite clay is dispersed in distilled water, adds phosphate under heating, stirring state solution, then dried and calcined to obtain phosphate-modified attapulgite clay; the modified attapulgite clay was dispersed in distilled water again, and Ni(NO ₃ ) ₂ ·6H ₂ O and anhydrous Na ₂ CO ₃ were dissolved in distilled water respectively, and the solution containing Ni(NO ₃ ) ₂ ·6H ₂ O and anhydrous Na ₂ CO ₃ was added dropwise to the aqueous solution dispersed with modified attapulgite clay to form Precipitation, the obtained precipitate is washed with water to neutrality, and the solid powder obtained by drying is pressed into tablets, sieved and reduced to obtain a Ni/P-attapulgite clay catalyst. 3. The preparation method of a Ni/P-attapulgite clay catalyst according to claim 2, characterized in that: the phosphate solution is an aqueous solution of methyl phosphate, and the heating temperature is 60°C. 4. The preparation method of a Ni/P-attapulgite clay catalyst according to claim 2, characterized in that: the drying temperature is 80-120°C, the calcining temperature is 400-550°C, and the calcined The time is 2 to 4 hours. 5. the preparation method of a kind of Ni/P-attapulgite clay catalyst according to claim 2, is characterized in that: the quality of described Ni(NO ₃ ) ₂ 6H ₂ O is calculated by the mass of Ni, makes Ni The mass of Ni accounts for 30-60% of the sum of the mass of Ni and the mass of phosphate-modified attapulgite clay. 6. The preparation method of a kind of Ni/P-attapulgite clay catalyst according to claim 2, is characterized in that: after adding dropwise containing Ni(NO ₃ ) ₂ 6H ₂ O and anhydrous Na ₂ CO ₃ solution During the process, the temperature of the reaction solution was controlled at 80°C. 7 . The preparation method of a Ni/P-attapulgite clay catalyst according to claim 2 , characterized in that: the drying temperature is 80-120° C. and the drying time is 6-12 hours. 8. The preparation method of a Ni/P-attapulgite clay catalyst according to claim 2, characterized in that: the sieving needs to pass through a 60-80 mesh sieve. 9 . The preparation method of a Ni/P-attapulgite clay catalyst according to claim 2 , characterized in that: during the reduction, the temperature is 400-550° C., the reducing gas is H ₂ , and the time is 2 hours. 10. The application of a Ni/P-attapulgite clay catalyst as claimed in claim 1 in the reaction of N,N-dimethylformamide hydrodeoxygenation to prepare trimethylamine.