Amorphous Alloys and Their Application in Fine Chemicals Synthesis

Amorphous petrochemical amorphous alloy and its application in the synthesis of fine chemicals ZHANG Xue-hong 12 LUO Lai-tao px' (1. Institute of Applied Chemistry, Nanchang University, Nanchang 330047; 2 Department of Chemical Engineering, Nanchang Institute of Aeronautical Engineering, Nanchang 330034) The application of fine chemical synthesis.

Overview Amorphous alloys are atoms in which the alloy is composed or their mixing arrangement is completely disordered, do not exhibit periodicity and translational in space, and generally refer to a metal alloy obtained by quenching a molten metal, and its structure is similar to that of an ordinary alloy. Glass, it can also be called Metallicglasses. Amorphous alloy catalysts have attracted much attention at home and abroad in recent years as a new type of catalytic material. This material has a promising application prospect due to its potential high activity and high selectivity for certain chemical reactions. Compared to crystalline alloys, amorphous alloys have long-range disorder, short-range order, and isotropy in structure, and are thermodynamically unstable or metastable, which can change the composition of the alloy over a wide range. And thus continuously control its electronic properties in order to obtain a suitable catalytically active center. These characteristics make amorphous alloy catalysts have higher surface activity and different selectivity, and have made remarkable achievements.

In the characterization method of the catalyst, the amorphous structure can be determined by X-ray diffraction. The diffraction peak characteristic of the amorphous alloy is a dispersed broad band, rather than the separated peak represented by the crystalline alloy. Inductively Coupled PLASMA Optical Emission Spectrometer (ICPBFS) can be used to determine the composition of amorphous alloys. Microstructures of the amorphous alloy such as speckles and uniformity can be observed by electron microscopy (TEM or SEM), differential scanning calorimetry ( DSC) can be used to measure the crystallization temperature and crystallization enthalpy during the heat treatment process by measuring the thermal properties of the sample during the endothermic process. XPS and Ramman spectroscopy can be used to study non- Crystalline alloy surface atomic state. In addition, TPD, TPR, etc. are also effective means for the study of amorphous alloy catalysts.

2 Preparation 2.1 Under the liquid quenching method, the alloy is melted by heating in a high-frequency induction furnace, and the pressure of the inert gas at the inlet is controlled. The molten alloy solution is extruded from the lower end of the quartz tube and ejected onto a high-speed rotating metal roll. When the alloy solution contacts the metal roll, it rapidly cools at a cooling rate of (105-108) K/s, so that the disordered structure of the liquid alloy is maintained to form an amorphous state. Then it is thrown out from the tangential direction due to centrifugal action, resulting in thin sheets, ribbons, or filaments that are several microns to several tens of microns thick. This method is currently a major method of preparing various amorphous alloys and has begun to enter the industrial production stage. In the early stage of the study of amorphous alloys as catalysts, most alloys used 17 and Pd-Si alloys.

The use of liquid phase quenching to prepare amorphous alloys has formed industrial scale, but there are still many problems, such as the alloy composition needs to be in the vicinity of its eutectic point, so that the composition is limited; the small specific surface area of ​​the alloy "1m2/g) surface Inhomogeneity; in the preparation of the surface covered by an oxide layer, the catalytic activity is very small, and some have no catalytic activity at all, so must be surface treatment before use, common treatment methods are: alloy smash; acid wash or caustic wash; O2 and H2 were used for pretreatment.

2.2 Chemical reduction deposition method The general chemical reduction deposition method is the use of strong reducing agent KBH4 and HIPH2O2 solution to reduce the soluble salts to obtain amorphous precipitate, after multiple washing and drying, to obtain amorphous ultrafine particle catalyst. There are more and more reports on the preparation of amorphous alloys by chemical reduction deposition methods, mainly due to the fact that this method and other methods are used in the research work of catalyst materials; the crystal alloys are placed in i quartz tubes in inert gas to protect ishingHous! People rightsreserved. Zhang Xuehong and so on. Amorphous alloys and their application in the fine chemical synthesis, compared with simple equipment, easy operation and so on. Moreover, the samples prepared by this method have both the characteristics of ultra-fine particles and amorphous state, and have good catalytic activity and selectivity without pretreatment.

For example, Ni-P119*, Ni-B; addition of Al, Fe, Pd, etc. can be used to catalyze the electrochemical reduction of 1-nitropropane. Ni-P amorphous alloy is loaded onto SiO2 to obtain specific surface and conventional load. The catalyst is the same amorphous catalyst. In addition, it has also produced a high rate of foaming of amorphous Ni-P alloys. With good permeability, large specific surface area, and high activity and selectivity of amorphous alloy catalysts, it is a new type of catalytic material that combines the advantages of the two.In the experiment of hydrogenation of benzene to cyclohexane, continuous reaction for 360 hours There is no significant change in the activity of the foamed amorphous NP alloy catalyst.In addition, this catalyst has no obvious induction period, has good hydrogenation catalytic activity without pretreatment, and has good stability, and is expected to become Industrial catalysts.

Cheng Zhilin of Xiamen University prepared nano-alumina by foaming, and citric acid was used as a blowing agent to synthesize oxidative defects with a particle size of about 15 nm. The nano-alumina was found at a wave number of 400-1000 cm-1 by IR analysis. There is a "broadening" phenomenon.

At present, little research has been done on the preparation of amorphous alloy catalysts using the foaming method at home and abroad, but from the perspective of its advantages, there will be good prospects for application.

3 Application of Amorphous Alloy Catalysts in Fine Chemical Industry 3.1 Synthesis of Amine Acetonitrile is a byproduct of the production of acrylonitrile. At present, there is no report of industrial production by the hydrogenation of acetonitrile to produce ethylamine. The key is that no suitable catalyst has been found. Industrially, selective catalytic hydrogenation of nitriles to produce aliphatic primary amines mainly uses RaneyNi as a catalyst, but there are defects such as serious environmental pollution and poor selectivity. Wang Minghui et al.: 4142 studied the preparation of ultra-fine-B, Co-B, and Ni-Co-B amorphous alloys by catalytic reduction deposition and their catalytic properties for the hydrogenation of acetonitrile to ethylamine. The alloy catalyst can increase selectivity to ethylamine compared to industrial RaneyNi. The ultrafine Ru-B amorphous alloy was prepared by chemical reduction after C(-B amorphous alloy was introduced into the porous support SiO2, and the hydrogenation reaction of glucose was studied. The results showed that its activity was significantly higher than other The catalyst is 50 times that of Raney Ni. Kinetic studies show that the hydrogenation reaction of glucose is a first-order reaction for hydrogen and zero-order reaction for glucose concentration, so the adsorption amount of hydrogenation is beneficial to increase the hydrogenation activity. 3.3 Other Nitta et al. Use NB to catalyze the selective hydrogenation of crotonaldehyde to n-butyraldehyde, but the activity and selectivity are not ideal. Xu Zhiwei et al. Catalytically unsaturated with Ni-BM (M=Pd, Sn, Co, Cu) Hydrogenation of aldehydes showed that the saturated aldehyde yield was higher when unsaturated fatty aldehydes were used as substrates than aromatic aldehydes, and the greater the steric hindrance, the poorer the selectivity of saturated aldehydes, and the use of Ni-BM by Ms. Huang Zongliang (M=PdCu). ) Catalyzed the selective hydrogenation of piperonylpropionaldehyde to synthesize the jasmonate from Xinyang, and compared it with RaneyNi, Pd/C and Pd/SiO2. The results show that Raney Ni has the worst selectivity and the lowest yield; 5%Pd/C The best conversion and selectivity, the highest yield; 10% Pd/Si2 catalysis The reaction also has good selectivity and yield; the selectivity of Ni-B-Pd is close to 5% Pd/C, the yield is between Pd/C and Pd/SiO2; the yield of Ni-Cu catalytic reaction is higher Ni-B-Pd is 4% lower. Considering that palladium is expensive, Ni-B-Cu has far better catalytic performance than RaneyNi, and has similar performance to palladium-based catalysts, and its cost is lower. Therefore, Ni-FCu may be considered as non-catalytic. The use of crystalline alloy catalysts instead of Pd/C in this reaction.

The most successful methods for the formation of amorphous alloys as catalysts are liquid quenching and chemical reduction. The chemical reduction methods are relatively in-depth studied because of their simple preparation methods and their composition is not limited by the eutectic point. A new method for preparing Ni-P and Ni-PB amorphous alloys was first studied by the New Institute of Catalytic Materials, Nankai University. The nickel phosphate was used as raw material to prepare NPs in aqueous solution using its own redox reaction. Amorphous alloys; Ni-PB amorphous alloys can be prepared by adding potassium borohydride solution to nickel hypophosphite solution with an average particle size of about 30 nm and 15 nm. The catalytic hydrogenation reaction of sulfolane shows that Ni The activity of PB amorphous alloy is similar to that of NB, which is higher than that of Ni-P amorphous alloy. The catalytic activity of Ni-P amorphous alloy prepared from nickel hypophosphite as raw material is higher than that prepared by the traditional method, as shown in Table 1. Table 1 Amorphous Alloy Catalyst Hydrogenation Reaction Activity Sample Sulfolane Yield (%) Electronic Effect Considering that some of the electrons in the Co-B-amorphous alloy were prepared by the B conventional method, ghtsreserved. Zhang Xuehong et al. Amorphous alloys and their application prospects in the synthesis of fine chemicals As amorphous alloys have superior catalytic activity and selectivity to the corresponding crystalline alloys, they may become a new type of catalyst material. Among several different preparation methods, the chemical reduction deposition method has the characteristics of simple preparation process, large surface area ratio of the catalyst, etc. Its activity and selectivity are higher than those of Raney Ni in the industry. Increasing the catalytic efficiency and reducing the environmental pollution is the current chemical and chemical industry. The hot spots of workers are also two basic requirements for green chemistry and atomic economy. The development of new catalytic materials for this purpose is a key issue for researchers, and amorphous alloys are one of the most promising new efficient and environmentally friendly catalytic materials.

From some examples that have been successfully applied in fine chemicals, amorphous alloys may be gradually replaced by Raney Ni in the field of fine chemical catalysis.

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