Preparation Of Anhydrous Chloride Compound Catalyticed By Acetic Anhydride

China is rich in magnesium resources, especially widely distributed in the Qinghai-Tibet Plateau. Salt Lake of Chaerhan in Qinghai, for example, the residues called “brine” after exploitation for sodium and potassium, which contains the main component of magnesium chloride combined with six water molecules. The reasonable way to take advantage of magnesium can not only solve the heavily pollution, but also benefit for the purification of trace elements. Anhydrous magnesium chloride prepared by six water magnesium chloride, which is the key technology of magnesium smelted by electrolytic.Under the existing process, anhydrous magnesium chloride is obtained by two methods, one is to use acidic gases(mainly chlorine and hydrogen chloride) as protection, which causes serious corrosion of the equipment; another one is to introduce ammonia gas in an aqueous solution, complexing with the magnesium chloride crystal instead of water molecules, to form magnesium chloride hexammoniate, for a further deaminase step to get anhydrous magnesium chloride,this process is carried out in an aqueous system, residual water affects quality of the product.In this paper, we use organic systems instead of water to avoid the problem of enough residual water, crystallization water in the anhydride magnesium chloride is removed by acetic. There are two types of crystallization water in agnesium chloride hexahydrate. The four inter-molecular water is easy to remove, but harder for the two intra-molecular ones. According to the difficulty to take away the crystal water,the main contents of this paper is divided into two parts.The first part, acetic acid and acetic anhydride system used, dihydrate magnesium chloride was prepared. And the results showed that ratio of the amount of magnesium chloride and acetic anhydride molar is 1: 9, reflux for 4h, rotary evaporation for 2h under the oil bath temperature of 105 ℃, the detection results in the ratio of magnesium chloride and water in the product reached highest to 1:2.0031.Secondly, we use acetic acid, acetic anhydride and N,N-Dimethylformamidesystem. Conclusion is drew that crystallized water in the product decreases with the increasing of refluxing time, agreeable time makes practical significance. Secondly,the use of complexation agent as catalyst, reducing the difficulty to remove the crystal water molecules in magnesium chloride hexahydrate, which is good for preparation of anhydrous magnesium chloride. Differ according to the nature of the catalyst, the catalyst is divided into basic, neutral and acidic. We inspected the triethylamine and disodium edetate as basic catalyst, ammonium acetate, ammonium chloride and as neutral catalyst, and acid catalyst is citric acid, succinic acid and oxalic acid.The result showed: select acetic anhydride and oxalic acid as catalyst,and the molar ratio is 1:1, reflux for 24 h according by dropping acetic anhydride of1 m L every 20 min, rotary evaporation 2h under an oil bath temperature of 105 ℃.Compared with anhydrous magnesium chloride, the ratio of crystallization water and magnesium chloridethe in the product is 1:0.0177, the content of water is 3.3‰.