Preparation method of rice hull silica supported phosphomolybdic acid catalyst

Abstract

The application discloses a preparation method of a rice hull silica supported phosphomolybdic acid catalyst, which comprises the following steps: (1) dispersing phosphomolybdic acid in an organic solvent; (2) immersing a rice hull silica carrier in the dispersion liquid obtained in the step (1); (3) removing the dispersion liquid which is not absorbed by the rice hull silica to obtain a muddy mixture; (4) heating and drying the product obtained in the step (3) to gradually volatilize the organic solvent, and uniformly dispersing the phosphomolybdic acid on the surface of the rice hull silica substrate; and (5) further heat treating the product obtained in the step (4) to obtain the rice hull silica supported phosphomolybdic acid catalyst. The application does not need to additionally modify the rice hull silica carrier, and the distribution of molybdenum in the obtained catalyst is more uniform.

Description

Technical Field

[0001] This invention relates to the field of metal-based catalysts, and more specifically, to supported molybdenum-based catalysts, particularly a method for preparing a rice husk silica-supported phosphomolybdic acid catalyst. Background Technology

[0002] Silica is a good support for molybdenum-based catalysts. Soluble molybdenum salts can be loaded onto the surface of silica using co-precipitation or impregnation methods, and then dried and calcined to form a supported catalyst. Phosphomolybdic acid is a small-molecule heteropolyacid in which molybdenum is in a high valence state, and it can be used not only as an oxidant but also has certain catalytic activity. Phosphomolybdic acid can also be produced by co-precipitation (Yan Xuemin, Lei Jiaheng, Mi Yuanzhu, et al. Synthesis and catalytic performance of composite mesoporous material phosphomolybdic acid / silica [J]. Modern Chemical Industry, 2009(1):4.) or impregnation (Wang Huanyi, Liu Tao, He Zhanfeng, Wang Dan, Jiang Yi. H3[PMo 12 O 40 Preparation and catalytic performance of nH2O / SiO2 catalyst [J]. Synthetic Chemistry, 2014, 022(001): 97-99, 110.) The catalyst was supported on silica material to obtain an easily recyclable supported catalyst.

[0003] Rice husks contain a unique silicon cell network structure. One method involves treating rice husks with sodium hydroxide to obtain sodium silicate, which is then used as an intermediate to prepare a silica carrier. However, this method destroys the silicon cell network structure. Alternatively, rice husks can be treated with hydrochloric acid, and the silica carrier can be obtained directly after calcination. In this method, the silicon cell network structure is preserved, forming a natural hierarchical pore structure (Liu Houfan, Gan Lu, Li Risheng, et al. Research on a new method for preparing silica from rice husks [J]. Inorganic Salt Industry, 2007, 39(2):3.). This rice husk-based silica carrier, which retains the natural silicon cell structure, loses most of its hydroxyl groups during preparation, resulting in a hydrophobic surface. Its porous structure can adsorb a significant amount of the oil mimicry diethyl phthalate. Summary of the Invention

[0004] To address the problem of loading phosphomolybdic acid onto hydrophobic rice husk-based silica supports, the present invention aims to provide a method for preparing a phosphomolybdic acid catalyst supported on rice husk silica.

[0005] The technical solution provided by this invention is: a method for preparing a rice husk silica-supported phosphomolybdic acid catalyst, comprising the following steps:

[0006] (1) Disperse phosphomolybdic acid in an organic solvent.

[0007] (2) The rice husk silica carrier is immersed in the dispersion obtained in step (1).

[0008] (3) Remove the dispersion that has not been absorbed by the rice husk silica.

[0009] (4) Heat and dry the product obtained in step (3) to gradually evaporate the organic solvent.

[0010] (5) Further heat treatment of the product obtained in step (4) to fully combine phosphomolybdic acid and rice husk silica support to obtain a supported phosphomolybdic acid catalyst.

[0011] Preferably, the organic solvent used in step (2) is an aprotic, highly polar solvent, such as ethyl acetate or diethyl phthalate.

[0012] Preferably, the heat treatment temperature in step (5) is 120 degrees Celsius.

[0013] In this invention, the final heat treatment temperature is lower than the decomposition temperature of phosphomolybdic acid. Therefore, in the final supported catalyst, molybdenum mainly exists in the form of phosphomolybdic acid. Phospholybdic acid is bonded to the support silica through hydrogen bonds and intermolecular forces. Under suitable solvent conditions, phosphomolybdic acid can detach from the support and return to the solution.

[0014] Advantages of the invention:

[0015] (1) No additional modification is required for the rice husk-based silica carrier.

[0016] (2) The molybdenum distribution in the obtained catalyst is relatively uniform. Detailed Implementation

[0017] The present invention will be further illustrated below with reference to specific embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0018] Example 1

[0019] A rice husk silica-supported phosphomolybdic acid catalyst is prepared according to the following steps:

[0020] (1) Using ethyl acetate as a dispersant, 0.1 g of commercially available phosphomolybdic acid powder was dispersed in 10 mL of ethyl acetate. After stirring rapidly in a beaker for 3 h, the mixture was centrifuged to remove the undispersed phosphomolybdic acid solid and obtain a dispersion.

[0021] (2) Transfer the dispersion obtained in step (1) to a covered test tube, place 5 g of rice husk silica particles on a test tube turner and turn continuously for 1 h to fully impregnate them, and then obtain a mud-like mixture.

[0022] (3) Place the resulting mud-like mixture on a multi-layer filter paper to absorb the dispersion that was not absorbed by the rice husk silica particles;

[0023] (4) Dry the product obtained in step (3) at 35 degrees Celsius for 4 h to allow the organic solvent to gradually evaporate, while phosphomolybdic acid molecules form a film on the rice husk silica matrix.

[0024] (5) The product obtained in step (4) is further heat-treated at 120°C for 24 h to fully combine phosphomolybdic acid and rice husk silica support to obtain supported phosphomolybdic acid catalyst particles.

[0025] Example 2

[0026] A rice husk silica-supported phosphomolybdic acid catalyst is prepared according to the following steps:

[0027] (1) Using diethyl phthalate as a dispersant, 0.1 g of commercially available phosphomolybdic acid was dispersed in 10 mL of diethyl phthalate. After stirring rapidly in a beaker for 3 h, the mixture was centrifuged to remove the undispersed phosphomolybdic acid solid and obtain a dispersion.

[0028] (2) Transfer the dispersion obtained in step (1) to a covered test tube, add 5 g of rice husk silica particles, place it on a test tube turner and turn it continuously for 4 h, so that the rice husk silica particles are fully immersed in the dispersion obtained in step (1) to obtain a mud-like mixture; wherein, the rice husk silica carrier is prepared by acid treatment and calcination, wherein a hydrophobic multi-level three-dimensional porous silica network is retained;

[0029] (3) Place the resulting mud-like mixture on a multi-layer filter paper to absorb the dispersion that was not absorbed by the rice husk silica particles;

[0030] (4) The product obtained in step (3) is heated and dried at 85°C for 24 h to allow the organic solvent to gradually evaporate, while phosphomolybdic acid molecules form a film on the rice husk silica matrix.

[0031] (5) Further heat-treat the product obtained in step (4) at 120°C for 24 h to fully combine phosphomolybdic acid and rice husk silica support to obtain supported phosphomolybdic acid catalyst particles.

[0032] The above embodiments are merely examples to clearly illustrate the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a rice husk silica-supported phosphomolybdic acid catalyst, characterized in that, Includes the following steps: (1) Disperse phosphomolybdic acid in an organic solvent to obtain a dispersion; (2) The rice husk silica carrier is immersed in the dispersion obtained in step (1). The rice husk silica carrier is prepared by acid treatment and calcination, wherein a hydrophobic multi-level three-dimensional porous silica network is retained. (3) Remove the dispersion that has not been absorbed by the silicon dioxide in the rice husk; (4) Heat and dry the product obtained in step (3) to gradually evaporate the organic solvent; (5) Further heat treatment of the product obtained in step (4) to fully combine phosphomolybdic acid and rice husk silica support to obtain a supported phosphomolybdic acid catalyst; The organic solvent used in step (1) is ethyl acetate or diethyl phthalate; The heat treatment temperature in step (5) is 120 degrees Celsius.

2. The method for preparing a rice husk silica-supported phosphomolybdic acid catalyst according to claim 1, characterized in that, Prepare according to the following steps: (1) Using ethyl acetate as a dispersant, 0.1 g of commercially available phosphomolybdic acid powder was dispersed in 10 mL of ethyl acetate. After stirring rapidly in a beaker for 3 h, the mixture was centrifuged to remove the undispersed phosphomolybdic acid solid and obtain a dispersion. (2) Transfer the dispersion obtained in step (1) to a covered test tube, place 5 g of rice husk silica carrier particles on a test tube turner and turn continuously for 1 h. After thorough impregnation, a mud-like mixture is obtained. (3) Place the resulting mud-like mixture on multilayer filter paper and absorb the dispersion that was not absorbed by the rice husk silica carrier particles; (4) Dry the product obtained in step (3) at 35 degrees Celsius for 4 h to allow the organic solvent ethyl acetate to gradually evaporate, while phosphomolybdic acid molecules form a film on the rice husk silica matrix. (5) The product obtained in step (4) is further heat-treated at 120°C for 24 h to allow the phosphomolybdic acid and rice husk silica support to fully combine, thereby obtaining supported phosphomolybdic acid catalyst particles.

3. The method for preparing a rice husk silica-supported phosphomolybdic acid catalyst according to claim 1, characterized in that, Prepare according to the following steps: (1) Using diethyl phthalate as a dispersant, 0.1 g of commercially available phosphomolybdic acid was dispersed in 10 mL of diethyl phthalate. After stirring rapidly in a beaker for 3 h, the mixture was centrifuged to remove the undispersed phosphomolybdic acid solid and obtain a dispersion. (2) Transfer the dispersion obtained in step (1) to a covered test tube, add 5 g of rice husk silica carrier particles, place it on a test tube turner and turn it continuously for 4 h, so that the rice husk silica particles are fully immersed in the dispersion obtained in step (1) to obtain a mud-like mixture. (3) Place the resulting mud-like mixture on a multi-layer filter paper to absorb the dispersion that was not absorbed by the rice husk silica particles; (4) The product obtained in step (3) is dried at 85°C for 24 h, so that the organic solvent diethyl phthalate gradually evaporates, and phosphomolybdic acid molecules form a film on the rice husk silica matrix. (5) Further heat-treat the product obtained in step (4) at 120°C for 24 h to fully combine phosphomolybdic acid and rice husk silica support to obtain supported phosphomolybdic acid catalyst particles.