Preparation and identification of magnesium methoxide_industrial additives

Background and overview^[1]

Metal alkoxide can be represented by “M-O-R or M-(O-R)n (where M represents a metal ion and R represents an alkyl group)”, which is a generalized metal organic compound between inorganic compounds and organic compounds.

Metal alkoxides have been widely used as precursors in sol-gel methods, including: ultrafine and nanomaterials, ceramics, metal oxide films, etc., and are also widely used in the preparation of rubber composites, catalysts, etc. aspect. Magnesium methoxide is a metal alkoxide and a water-sensitive solid compound. It is mainly used as a selective substrate in organic synthesis and as a neutralizing agent in anhydrous systems. It is also the main raw material for preparing high-purity magnesium oxide.

Through research, it has been found that magnesium methoxide can often be used as a catalyst in organic synthesis reactions. Quite a few researchers use magnesium methoxide as a catalyst when synthesizing organic compounds, especially in ketoxime compounds (smelting agents). in synthesis research. In the future, economic development will surely promote the development of domestic hydrometallurgical processes, and the demand for metallurgical agents will continue to increase. As a catalyst for the synthesis of mineral processing agents, the demand for magnesium methoxide will grow rapidly. Therefore, the application of magnesium methoxide The prospects are very good.

Preparation^[1]

The synthesis of magnesium methoxide includes direct synthesis, alkyl magnesium method, alcoholysis method, lipolysis method, etc. There are many documents introducing the use of magnesium methoxide as a reaction intermediate product to synthesize mineral processing agents, and most of them use iodine as the initiator, but there are almost no separate reports on the synthesis process of magnesium methoxide. Therefore, based on the synthetic concept of “simple and easily available raw materials, mild reaction conditions, simple process route, and low cost”, a direct method was used to synthesize magnesium methoxide, and the synthesis The magnesium methoxide was characterized by differential thermal analysis and infrared spectroscopy, which is of great significance to the development and application of magnesium methoxide.

The experimental principle is carried out according to the following equation:

Experimental steps: Wash the magnesium ribbon once each with dilute hydrochloric acid, distilled water and methanol; cut the magnesium ribbon into small pieces and place them in a three-necked flask; add a certain amount of methanol solution to the three-necked flask, add methanol The amount is subject to the ability to completely dissolve magnesium; set the reaction temperature and the rotation speed of the magnetic stirrer, and obtain a white powdery substance after a period of reaction; finally dry, oven-dry, weigh and calculate the yield.

Identification^[1]

1 Differential thermal results and analysis of magnesium methoxide

The solid products obtained in the experiment were analyzed by differential thermal experiments, and the results are shown in Figure 3.

The substance undergoes a phase change within this range. From the structural analysis of the substance, it can be seen that magnesium methoxide is a metal-organic compound that is easily decomposed at low temperatures, so the phase change here should be that magnesium methoxide decomposes to form magnesium oxide and carbon dioxide. and water; from the shape of the entire thermogravimetric and differential thermal analysis curves, it can be seen that the phase change process should be an endothermic process. According to these thermal analysis results, it can be seen that the prepared material needs to be dried for post-processing experiments.

2 Infrared results and analysis of magnesium methoxide

Carry out infrared experimental analysis on the solid products obtained in the experiment. The solid products were divided into 4 groups and dried at 50°C, 100°C, 200°C, and 300°C respectively to obtain 4 samples dried at different temperatures. Then, infrared spectrum experiments were performed on the 4 samples respectively. The experimental results are shown in Figure 4.

From the infrared spectrum of the methanol liquid sample in Figure 4, there is an absorption peak near 3341 cm-1 (shown in area B in Figure 4). The peak shape is broad and blunt, which is due to the formation of partial hydrogen bonds. Caused by. According to the literature, the hydrocarbon stretching vibration of saturated carbon generally has 4 absorption peaks, among which 2960 cm^-1, 2870 cm^-1 belong to CH3, and 2925 cm ^-1, 2850 cm^-1 belong to CH2, the C-H bond of saturated carbon appears absorption peak at less than 3000 cm^-1, and unsaturated carbon The C-H bond appears an absorption peak at greater than 3000 cm^-1, so it can be seen from Figure 4 that it is near 2956 cm^-1 (less than 3000 cm^{– 1}) There is an absorption peak (shown in area C in the figure), which is due to the saturated hydrocarbon group; at 1380 cm^-1, 1460 cm^{-1 (shown in area D in the figure), which is caused by the CH3 group. Judging from the solid sample of magnesium methoxide, the prepared magnesium methoxide was post-processed in 4 different ways, respectively: at 50 Bake for about 1 hour under the conditions of ℃, 100 ℃, 200 ℃ and 300 ℃. The spectra obtained in the experiment are basically similar, but the peak shapes are quite different.}

As can be seen from Figure 4, at 50 ℃, there is an absorption peak at 3341 cm^-1, but it is much smaller than the peak of liquid methanol, indicating that there is still some The presence of hydroxyl groups (O-H); when the post-treatment temperature gradually increases, the peak at 3341 cm^-1 becomes smaller and smaller, indicating that there are fewer and fewer hydroxyl groups in the compound. This is consistent with the experiment The results are consistent with the target product. It can also be seen from Figure 4 that after four kinds of post-processing, -H is located at 2956 cm^-1, 1380 cm^-1, and 1460cm^-1 The absorption peak near has always existed, indicating that the CH3 in the compound has not changed, which is caused by the CH3 group. This is consistent with the experimental results and the target product. After these four kinds of post-processing, in area A A sharp absorption peak appeared, which may be due to the Mg-O group. Through the above infrared analysis, it can be seen that the solid product is basically consistent with the target product; in addition, the infrared spectrum of the “solid product with different post-treatment” After analysis, it can be seen that the results are also consistent with the results of differential thermal analysis.

Reference materials

[1]Li Liqing, Wang Yi, Peng Jianghua. Study on the synthesis and characterization of magnesium methoxide [J]. Journal of Jiangxi University of Science and Technology, 2015, 36(05):17-21.