CN109701565B - Bismuth oxyhalide-based metal thermal catalyst suitable for one-step synthesis of benzoin ethyl ether - Google Patents

Abstract

The invention discloses a bismuth oxyhalide-based metal thermal catalyst suitable for synthesizing benzoin ethyl ether by a one-step method, which comprises the following molecules: M-BiOX, wherein: m ═ Au, Ag, Pd, Ru, Cu, Mg … …; x ═ Cl, Br, I. Stirring, mixing and dispersing bulk phase or nano bismuth oxyhalide and a metal ion aqueous solution uniformly, and selecting a 500W xenon lamp as a light source to irradiate for more than 3 hours to obtain the bismuth oxyhalide-based thermal catalyst with different metal loading amounts. The length and width of the bismuth oxyhalide are not more than 100nm, the thickness of the bismuth oxyhalide is about 20nm, and metal nano-particles with the size of 2-20nm are uniformly loaded on the surface of the bismuth oxyhalide. The substrate material bismuth oxyhalide increases the activity of the catalyst, reduces the energy barrier of the benzaldehyde catalytic condensation reaction, has the characteristics of low cost, no toxicity, easy treatment and environmental protection, and expands the application of the photoreduction technology in the aspect of thermal catalyst synthesis.

Description

A bismuth oxyhalide-based metal thermal catalyst suitable for one-step synthesis of benzoin ether

technical field

The invention relates to a catalyst for synthesizing benzoin ether, in particular to a bismuth oxyhalide-based metal thermal catalyst suitable for one-step synthesis of benzoin ether.

Background technique

The chemical structure of benzoin ether is 1,2-diphenyl-2-alkoxyethanone, which is a white or light yellow needle-like crystal. In drug synthesis, it is an important synthetic intermediate. At the same time, because it can absorb near-ultraviolet light, it is often used as a photosensitizer in the printing industry, coating industry, etc.

In the prior art, traditional process synthesis benzoin ether is usually divided into two steps:

1. Benzyl alcohol itself forms benzoin through the condensation of benzoin under the action of a catalyst;

2. Benzoin and low-carbon alcohols are used to synthesize benzoin ether under the action of acid catalyst.

The catalysts commonly used in this process are cyanide or vitamin B1. The former has a high yield, but is highly toxic and difficult to handle. The latter is easy to operate, saves raw materials, and reacts quickly, but the yield of the target product is too low, and Because vitamin B1 and benzaldehyde are insoluble, other organic reagents need to be added to help mix evenly, which is accompanied by the risk of a variety of by-products.

In addition, domestic and foreign patent literature reports take phosphorus trichloride, aluminum trichloride, thionyl chloride, phosphorus oxychloride, phosgene etc. as the synthetic method of catalyzer, but in these techniques, require that ethanol is greatly excessive, and the inevitable existence Problems such as long reaction time, unstable yield and environmental pollution.

Later, researchers explored the one-step preparation and synthesis of benzoin ether by using nickel-based and aluminum-based materials such as NiAl/CuAl, which is green, low-cost, highly selective, and has a large specific surface area, but the problem of low conversion still exists.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a bismuth oxyhalide-based metal thermal catalyst suitable for one-step synthesis of benzoin ether.

The purpose of this invention is to realize through the following technical solutions:

The bismuth oxyhalide-based metal thermal catalyst suitable for one-step synthesis of benzoin ether of the present invention selects bismuth oxyhalide containing halogen elements as the base material, utilizes the bismuth oxyhalide to be sensitive to light response, and under the action of light, in situ Reduce metal ions in metal salt solutions, and finally obtain a small size distribution of bismuth oxyhalide-based metal thermal catalysts;

The elemental composition of the catalyst is: M-BiOX, where M=Au, Ag, Pd, Ru, Cu, Mg...; X=Cl, Br, I.

It can be seen from the technical solutions provided by the present invention that the embodiment of the present invention provides a bismuth oxyhalide-based metal thermal catalyst suitable for one-step synthesis of benzoin ether. The bismuth oxyhalide is sensitive to the response of visible light and is easy to generate photogenerated electrons. It is very easy to reduce the metal in the metal salt solution to form an oxyhalide supported by a small-sized metal catalyst, and the catalyst synthesis method is simple, efficient and green. At the same time, bismuth oxyhalide has the characteristics of low cost, non-toxicity and environmental protection, which will greatly reduce the pollution of the catalyst.

Description of drawings

1 is a schematic diagram of the mechanism of one-step synthesis of benzoin ether by a bismuth oxyhalide-based metal thermal catalyst in the embodiment of the present invention, wherein: M=Au, Ag, Pd, Ru, Cu, Mg...; X=Cl, Br, I.

FIG. 2 is a flow chart of the preparation of the bismuth oxyhalide-based metal thermal catalyst in the embodiment of the present invention.

3 is an electron microscope image of a BiOCl-based catalyst in an embodiment of the present invention, wherein: (a) is a scanning image of a Pd-supported bulk BiOCl-based catalyst; (b) is a transmission image of a Pd-supported nano-BiOCl-based catalyst.

Fig. 4 is the EDS electron energy spectrum of BiOCl-based catalyst in the embodiment of the present invention, wherein: (a) is the EDS electron energy spectrum of the Pd-supported phase BiOCl-based catalyst; (b) is the EDS electron energy spectrum of the Pd-supported nano-BiOCl-based catalyst .

Detailed ways

The embodiments of the present invention will be described in further detail below. Contents that are not described in detail in the embodiments of the present invention belong to the prior art known to those skilled in the art.

What the present invention relates to is a bismuth oxyhalide-based metal thermal catalyst suitable for one-step synthesis of benzoin ether, and its preferred specific embodiment is:

The bismuth oxyhalide containing halogen elements is selected as the base material, and the response of bismuth oxyhalide to light is sensitive. Under the action of light, the metal ions in the metal salt solution are reduced in situ, and the small size distribution of bismuth oxyhalide is finally obtained. metal-based thermal catalysts;

The elemental composition of the catalyst is: M-BiOX, where M=Au, Ag, Pd, Ru, Cu, Mg...; X=Cl, Br, I.

The length and width of the bismuth oxyhalide is 60 nm to 7 μm, the thickness is not more than 200 nm, and the surface of the bismuth oxyhalide is uniformly loaded with metal nanoparticles with a size of 2 to 20 nm.

The synthesis of this catalyst comprises the steps:

The bismuth oxyhalide and the metal ion aqueous solution were stirred, mixed and dispersed evenly, and a 500W xenon lamp was selected as the light source for irradiation. The irradiation time and the concentration of the ion solution were adjusted to obtain bismuth oxyhalide-based thermal catalysts with different metal loadings.

The irradiation time of the 500W xenon lamp is greater than or equal to 3h.

The bismuth oxyhalide-based metal thermal catalyst suitable for one-step synthesis of benzoin ether of the present invention utilizes the oxyhalide to absorb visible light to generate photo-generated electrons to reduce metal ions in the ionic salt solution, and can simply and efficiently obtain a small-sized metal catalyst-supported oxyhalide. metal catalysts. Among them, the small size loading of metals greatly reduces the cost of catalysts. When benzaldehyde is used as raw material and ethanol is used as solvent, the catalyst realizes one-step high activity and high selectivity preparation of benzoin ether. As shown in Figure 1, it is a schematic diagram of the mechanism of one-step synthesis of benzoin ether by bismuth oxyhalide-based metal thermal catalyst. Wherein: M=Au, Ag, Pd, Ru, Cu, Mg...; X=Cl, Br, I.

This application is designed for the first time to utilize the easily detached halogen element atoms in the base material bismuth oxyhalide and the metal catalyst supported on the bismuth oxyhalide to form a strong nucleophile, thereby increasing the catalyst activity and reducing the energy barrier of benzaldehyde catalyzed condensation reaction, effectively It promotes the selective and efficient progress of the reaction. At the same time, the base material bismuth oxyhalide has the characteristics of low cost, non-toxicity, easy handling, and environmental protection. On the one hand, the invention provides a new way and basis for the green one-step preparation of benzoin ether, and on the other hand, it also expands the application of photoreduction technology in the synthesis of thermal catalysts.

Specific examples:

This catalyst provides a new effective way and idea for the one-step thermocatalytic preparation of benzoin ether. The bismuth oxyhalide substrates involved are BiOCl, BiOBr, BiOI, etc., and the metals involved are Pd, Au, Ag, Ru, Cu, Mg, etc. The following will select bismuth oxychloride (BiOCl) as the base material and Pd as the metal catalyst to describe the process in detail.

As shown in Figure 2, it is a flow chart for the preparation of a bismuth oxyhalide-based metal thermal catalyst, including the steps:

Select a 500W xenon lamp as the light source, stir and mix different concentrations of bismuth oxychloride (bulk or nano) and sodium tetrachloropalladate aqueous solution to disperse evenly, and adjust the irradiation time of the xenon lamp and the concentration of the ionic solution to obtain different Pd loadings of bismuth oxychloride-based thermal catalysts.

In order to characterize the morphology of the product, the SEM and TEM of the product were made in this application (Figure 3). (a) is the SEM image of the Pd catalyst supported by the bulk BiOCl material. The size of the bulk BiOCl is micron, and the surface-loaded Pd nanometer The particle size is about 2-20nm; (b) is a nano-BiOCl supported Pd catalyst. As can be seen from the figure, the length and width of bismuth oxychloride are not more than 100nm, the thickness is about 20nm, and its surface is uniformly supported with a size of about 2.49 nm Pd nanoparticles. It can be seen from the analysis of the results that the Pd-supported catalyst can be obtained by the photoreduction method whether it is bulk or nano-sized bismuth oxychloride material.

In order to further determine the composition of the product, the present application made the EDS spectrum of the corresponding material (Fig. 4). As can be seen from the figure, the obtained products are all composed of elements such as Bi, O, Cl, and Pd.

Using the same method, the present application obtained a series of bismuth oxyhalide-based metal thermal catalysts, and selected benzaldehyde as a raw material, ethanol as a solvent, and a temperature of 100 degrees Celsius to carry out the thermal catalytic reaction. The results are shown in Table 1. Under the same conditions, when there is no Pd catalyst supported, bismuth oxychloride alone has no catalytic ability. When Pd was loaded and reacted for 5 h, the conversion rate of bulk bismuth oxychloride-based catalyst reached 95.4%, and the selectivity of benzoin ether was 85.3%. The conversion rate of nano-sized bismuth oxychloride catalyst reached 100% in 5h, and the selectivity of benzoin ether reached 97.9%. That is, nano-sized bismuth oxyhalide-based metal catalysts have higher activity and selectivity. The present application also finds that when the nano-bismuth oxyhalide is used as the base material, the activity and selectivity of the reaction also increase with the increase of the electronegativity of the halogen element under the same conditions. Pd-3.3wt%-BiOI can reach 100% conversion and selectivity within 3h. The stronger the polarity of the halogen elements, the stronger the nucleophilicity, which also proves from the reverse that the easily separated halogen elements in the bismuth oxyhalide and Pd form an effective nucleophile catalysis to accelerate the selective synthesis of benzoin ether. To further prove this point, the present application uses the same principle to photoreduce to prepare Pd/TiO ₂ and Pd/C ₃ N ₄ thermal catalysts, and it is found that there is no selectivity for benzoin ether. That is to say, the halogen elements in the bismuth oxyhalide base material play a decisive role in the highly active and highly selective synthesis of benzoin ether.

Table 1: Comparison of catalytic activity and selectivity of different catalysts

The invention utilizes the halogen group element which is easy to be removed from the bismuth oxyhalide base material and the metal catalyst to form a strong nucleophile, so as to synthesize the benzoin ether with high efficiency and high selectivity. Bismuth oxyhalide can be a bulk material or a nanoscale material, wherein the nanoscale halogen-containing base material is more active. Considering the sensitive absorption of bismuth oxyhalide materials to visible light, small-sized metal-supported bismuth oxyhalide-based catalysts can be obtained by a simple photoreduction method. At the same time, the base material bismuth oxyhalide has the characteristics of low cost, non-toxicity, easy handling, and environmental protection. On the one hand, the invention provides a new way and basis for the green one-step preparation of benzoin ether, and on the other hand, it also expands the application of photoreduction technology in catalyst synthesis. The bismuth oxyhalide substrates involved are BiOCl, BiOBr, BiOI, etc., and the metals involved are Pd, Au, Ag, Ru, Cu, Mg, etc. The specific embodiment is based on bulk and nano-sized bismuth oxyhalide substrates. Pd/bulk BiOCl, Pd/BiOCl, Pd-/BiOBr, Pd/BiOI catalysts.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. Substitutions should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (1)

1. A method for synthesizing benzoin ethyl ether by using a bismuth oxyhalide-based metallothermic catalyst in a one-step method is characterized in that benzaldehyde is used as a raw material, ethanol is used as a solvent, and the benzoin ethyl ether is synthesized by the one-step method through the catalyst;

the catalyst selects bismuth oxyhalide containing halogen elements as a substrate material, and utilizes the response sensitivity of the bismuth oxyhalide to light to reduce metal ions in a metal salt solution in situ under the action of light, thereby finally obtaining the bismuth oxyhalide-based metal thermal catalyst with small size distribution;

the catalyst comprises the following elements: M-BiOX, wherein: m ═ Pd or Ru; x ═ Cl, Br, or I; the M content is 3.1 w%, 3.3 w% or 3.46 w%;

the length and width of the bismuth oxyhalide is 60nm to 7 mu m, the thickness of the bismuth oxyhalide is not more than 200nm, and metal nano particles with the size of 2 nm to 20nm are uniformly loaded on the surface of the bismuth oxyhalide;

the synthesis of the catalyst comprises the following steps:

stirring, mixing and dispersing bismuth oxyhalide and a metal ion aqueous solution uniformly, selecting a 500W xenon lamp as a light source for irradiation, and adjusting irradiation time and the concentration of the ion solution to obtain bismuth oxyhalide-based thermal catalysts with different metal loading amounts;

the irradiation time of the 500W xenon lamp is more than or equal to 3 h.

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