Rare earth cerium-based molecular catalyst and application thereof

Abstract

The invention discloses a rare earth cerium-based molecular catalyst and application thereof, and particularly relates to the field of molecular catalysts. The chemical formula of the molecular catalyst is {[Ce2 (TBDA) 2 (DMF) 2]. Solvents} n, TBDA < 3-> is obtained by removing three protons from 1, 3, 5-tris (4-carboxyphenyl) benzene, two Ce < 3 + > ions, two TBDA < 3-> coordination and two DMF molecules exist in a minimum asymmetric structural unit in the molecular catalyst, and the Ce < 3 + > ions respectively adopt a nine-coordination mode and a ten-coordination mode; adjacent Ce < 3 + > ions firstly pass through the TBDA < 3-> ligand to form a one-dimensional chain structure, and the one-dimensional chain structures further pass through the TBDA < 3-> ligand to form a three-dimensional network structure; the molecular catalyst presents three quadrilateral pore structures with different sizes on a c-axis. By adopting the technical scheme of the invention, the problem that the precious metal catalyst cannot be popularized and applied on a large scale in the conversion of low-concentration non-pure CO2 due to limited precious metal resources and high price in the prior art is solved, and the method has great application value in the aspect of cycloaddition reaction of low-concentration non-pure CO2 and cyanamide compounds.

Description

Technical Field

[0001] The invention relates to the field of molecular catalysts, and in particular to a rare earth cerium-based molecular catalyst and application thereof. Background Art

[0002] With the advancement of global science and technology and the improvement of industrial production levels, more and more CO2 is discharged into the ecological environment. The excessively high CO2 content in the atmosphere has led to a series of environmental and climate problems. On the other hand, CO2 has become a hot topic for scientists because it is a C1 resource with wide distribution, abundant content, low cost, non-toxicity, renewable, safe to use and non-flammable. Under the background of the scientific development goals of "carbon peak" and "carbon neutrality", how to achieve efficient "carbon cycle" and convert CO2 in industrial waste gas into high-value-added chemical products under mild reaction conditions is an important way to alleviate the energy crisis and greenhouse effect and realize resource utilization. People have been committed to developing effective CO2 chemical fixation methods, such as the cycloaddition reaction of CO2 with cyanamide compounds. However, due to the chemical inertness of CO2 and the thermodynamic stability of the carbon-oxygen double bond (bond energy of 805KJ / mol), as well as the high temperature and high pressure reaction conditions, the reaction process and the complicated and lengthy post-treatment procedures, its application is still limited. Therefore, in order to achieve the catalytic conversion of low-concentration impure CO2 under environmentally friendly conditions, the development of efficient catalysts is still urgently needed and of great significance.

[0003] At present, a variety of catalyst systems have been developed, such as highly active precious metal (Pt, Ag, Pd, Ru, Rh) catalysts. This type of catalyst has attracted much attention for its excellent activity, selectivity and stability. However, precious metal catalysts are prone to catalyst "poisoning", easy to sinter at high temperatures, and the active components are lost due to sublimation, which reduces their activity. In addition, precious metal resources are limited and expensive, so they cannot be promoted and applied on a large scale. Compared with traditional precious metal catalysts, rare earth cerium-based catalysts have the advantages of high catalytic activity, good selectivity, low loss, and high catalytic efficiency. They have been widely used in motor vehicle exhaust purification, petroleum catalytic cracking, industrial waste gas treatment, catalytic combustion, fuel cells and other fields. On the other hand, the content of rare earth cerium in the earth's crust is about 0.0046%, which has the advantages of large reserves, complete minerals and rare earth resources, high grade and high abundance. Therefore, under the premise of maintaining good catalytic effects, it is a technical problem that technicians in this field need to solve to find other efficient and inexpensive rare earth cerium-based molecular catalysts to partially or completely replace Pt, Ag, Pd, Ru, Rh and other precious metal catalysts to catalyze the cycloaddition reaction of cyanamide compounds with low-concentration non-pure CO2 under mild conditions. Summary of the invention

[0004] The present invention aims to provide a rare earth cerium-based molecular catalyst and its application, which solves the problem that the existing precious metal resources are limited and expensive, resulting in the inability to achieve large-scale promotion and application of precious metal catalysts in converting low-concentration impure CO2.

[0005] In order to achieve the above object, the present invention provides a technical solution as follows: a rare earth cerium-based molecular catalyst, the chemical formula of the molecular catalyst is {[Ce2(TBDA)2(DMF)2]·solvents} n , of which TBDA 3- It is obtained by removing three protons from 1,3,5-tris(4-carboxyphenyl)benzene, DMF is N,N-dimethylformamide, solvents is a solvent molecule, and n is a natural number from 1 to positive infinity; the molecular catalyst belongs to the monoclinic system, the space group is P21 / c, and the unit cell parameters are: α=90°,β=96.7350(10)°,γ=90°,the crystal volume is Z = 4; there are 2 Ce in the smallest asymmetric structural unit of the molecular catalyst 3+ ions, 2 TBDA 3- With 2 DMF molecules, Ce 3+ The ions adopt nine-coordinate and ten-coordinate coordination modes respectively; the adjacent Ce 3+ Ions first pass through TBDA 3- The ligands form a one-dimensional chain structure, and the one-dimensional chain structure is further connected through TBDA 3- The ligands form a three-dimensional network structure; the molecular catalyst presents three quadrilateral channel structures of different sizes on the c-axis.

[0006] Furthermore, the synthesis method of the molecular catalyst is as follows:

[0007] S1, dissolving organic ligands H3TBDA, Ce(NH4)2(NO3)6 and o-fluorobenzoic acid in N,N-dimethylformamide solvent to obtain a mixed solution; wherein the molar ratio of H3TBDA, Ce(NH4)2(NO3)6, o-fluorobenzoic acid and N,N-dimethylformamide is 1:3:3:32;

[0008] S2. Place the mixed solution in a sealed hydrothermal reactor, react at a constant temperature of 130° C. for 72 hours, take out the product, separate the solid, and wash the solid several times with N,N-dimethylformamide to obtain colorless block crystals.

[0009] Another technical solution provided by the present invention is to use the rare earth cerium-based molecular catalyst to catalyze the reaction of low-concentration impure CO2 and cyanamide compounds under normal pressure to generate quinazoline compounds.

[0010] Compared with the prior art, this solution has the following beneficial effects:

[0011] 1. The rare earth cerium-based molecular catalyst of this scheme can be used to catalyze the reaction of low-concentration impure CO2 and cyanamide compounds to produce quinazoline compounds under normal pressure.

[0012] 2. The rare earth cerium-based molecular catalyst of this scheme has a simple preparation process, high catalytic activity, good selectivity and good stability, and has great potential application value in the cycloaddition reaction of low-concentration impure CO2 and cyanamide compounds.

[0013] 3. The rare earth cerium-based molecular catalyst of this scheme has excellent acid and alkali resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a diagram of the coordination environment of cerium in the rare earth cerium-based molecular catalyst of the present invention;

[0015] Figure 2 It is a three-dimensional structure diagram of the rare earth cerium-based molecular catalyst of the present invention;

[0016] Figure 3 This is a pore structure diagram of the rare earth cerium-based molecular catalyst of the present invention;

[0017] Figure 4 This is a scanning electron microscope image of the rare earth cerium-based molecular catalyst of the present invention;

[0018] Figure 5 It is the X-ray powder diffraction pattern of the rare earth cerium-based molecular catalyst of the present invention. DETAILED DESCRIPTION

[0019] The present invention is further described in detail below through specific embodiments:

[0020] Example 1

[0021] A rare earth cerium-based molecular catalyst, the chemical formula of the molecular catalyst is {[Ce2(TBDA)2(DMF)2]·solvents} n , of which TBDA 3- It is obtained by removing three protons from 1,3,5-tris(4-carboxyphenyl)benzene, DMF is N,N-dimethylformamide, solvents is a solvent molecule, and n is a natural number from 1 to positive infinity; the molecular catalyst belongs to the monoclinic system, the space group is P21 / c, and the unit cell parameters are: α=90°,β=96.7350(10)°,γ=90°,the crystal volume is Z=4; there are 2 Ce in the smallest asymmetric structural unit of the molecular catalyst 3+ ions, 2 TBDA3- With 2 DMF molecules, Ce 3+ The ions adopt nine-coordinate and ten-coordinate coordination modes respectively; the adjacent Ce 3+ Ions first pass through TBDA 3- The ligands form a one-dimensional chain structure, and the one-dimensional chain structure is further connected through TBDA 3- The ligands form a three-dimensional network structure; the molecular catalyst presents three different sizes of quadrilateral channel structures on the c-axis.

[0022] Example 2

[0023] A method for synthesizing a rare earth cerium-based molecular catalyst comprises the following synthesis steps:

[0024] A 0.3 mol / L solution of cerium ammonium nitrate in N, N-dimethylformamide was mixed with a 0.1 mol / L solution of H3TBDA in N, N-dimethylformamide and subjected to ultrasonic treatment for 10 minutes. Under ultrasonic conditions, a 0.3 mol / L solution of 2-fluorobenzoic acid in N, N-dimethylformamide was added to the mixed solution and ultrasonic treatment was continued for 5 minutes. The mixed solution after ultrasonic treatment was placed in a closed hydrothermal reactor and reacted at a constant temperature of 130°C for 72 hours. After the product was taken out, the solid was separated and washed with N, N-dimethylformamide for multiple times to obtain colorless block crystals.

[0025] The properties of the rare earth cerium-based molecular catalyst synthesized in this example are characterized as follows:

[0026] 1. Structural determination of rare earth cerium-based molecular catalysts:

[0027] Table 1 Crystallographic data of rare earth cerium-based molecular catalysts

[0028]

[0029]

[0030] The crystal structure was determined using a Supernova single crystal X-ray diffractometer using graphite monochromatized Mo-Kα radiation. The incident radiation source was used to collect diffraction points in ω-φ scanning mode. The unit cell parameters were corrected by the least square method. The crystal structure was solved by the SHELXL-97 direct method from the difference Fourier electron density map and corrected by Lorentz and polarization effects. All H atoms were synthesized by difference Fourier and determined by ideal position calculation. Detailed crystal measurement data are shown in Table 1.

[0031] Figure 1 This is a diagram of the cerium coordination environment of rare earth cerium-based molecular catalysts. Figure 1It can be seen that there are 2 Ce in the minimum asymmetric structural unit. 3+ ions, 2 TBDA 3- With 2 DMF molecules, Ce 3+ The ions adopted nine-coordinate and ten-coordinate coordination modes respectively.

[0032] Figure 2 This is a three-dimensional structure diagram of the rare earth cerium-based molecular catalyst. Figure 2 It can be seen that the adjacent Ce 3+ Ions first pass through TBDA 3- The ligands form a one-dimensional chain structure, and the one-dimensional chain structure is further connected through TBDA 3- The ligands form a three-dimensional network structure.

[0033] Figure 3 This is the pore structure diagram of rare earth cerium-based molecular catalyst. Figure 3 It can be seen that the rare earth cerium-based molecular catalyst presents three different sizes of quadrilateral channel structures on the c-axis, and the pore sizes are

[0034] 2. Morphology test of rare earth cerium-based molecular catalysts:

[0035] The scanning electron microscope image of the rare earth cerium-based molecular catalyst was tested at room temperature. Figure 4 It can be seen that the rare earth cerium-based molecular catalyst has a regular morphology.

[0036] 3. Phase purity test of rare earth cerium-based molecular catalysts:

[0037] The X-ray powder diffraction pattern of the rare earth cerium-based molecular catalyst was tested at room temperature. Figure 5 It can be seen that the measured powder diffraction pattern is compared with its simulated pattern, except for slight differences in the intensity of some peaks, the peak positions and peak shapes are very consistent, indicating that the rare earth cerium-based molecular catalyst has high phase purity and good acid and alkali resistance.

[0038] Table 2 is the evaluation of the catalytic effect of rare earth cerium-based molecular catalysts

[0039]

[0040]

[0041] The above are only embodiments of the present invention, and the common knowledge such as the known specific structures and / or characteristics in the scheme are not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A rare earth cerium-based molecular catalyst, characterized in that: The chemical formula of the molecular catalyst is {[Ce2(TBDA)2(DMF)2]·solvents} n , of which TBDA 3- It is obtained by removing three protons from 1,3,5-tris(4-carboxyphenyl)benzene, DMF is N,N-dimethylformamide, solvents is a solvent molecule, and n is a natural number from 1 to positive infinity; the molecular catalyst belongs to the monoclinic system, the space group is P21 / c, and the unit cell parameters are: α=90°,β=96.7350(10)°,γ=90°,the crystal volume is Z = 4; there are 2 Ce in the smallest asymmetric structural unit of the molecular catalyst 3+ ions, 2 TBDA 3- With 2 DMF molecules, Ce 3+ The ions adopt nine-coordinate and ten-coordinate coordination modes respectively; the adjacent Ce 3+ Ions first pass through TBDA 3- The ligands form a one-dimensional chain structure, and the one-dimensional chain structure is further connected through TBDA 3- The ligands form a three-dimensional network structure; the molecular catalyst presents three quadrilateral channel structures of different sizes on the c-axis.

2. A rare earth cerium-based molecular catalyst according to claim 1, characterized in that: The synthesis method of the molecular catalyst is as follows: S1, dissolving organic ligands H3TBDA, Ce(NH4)2(NO3)6 and o-fluorobenzoic acid in N,N-dimethylformamide solvent to obtain a mixed solution; wherein the molar ratio of H3TBDA, Ce(NH4)2(NO3)6, o-fluorobenzoic acid and N,N-dimethylformamide is 1:3:3:32; S2. Place the mixed solution in a sealed hydrothermal reactor, react at a constant temperature of 130° C. for 72 hours, take out the product, separate the solid, and wash the solid several times with N,N-dimethylformamide to obtain colorless block crystals.

3. A rare earth cerium-based molecular catalyst as claimed in claim 1 or 2 is used to catalyze the reaction of low-concentration impure CO2 with cyanamide compounds at normal pressure to produce quinazoline compounds.

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