氧化镁蒸氨反应的动力学和机理研究

Study on kinetics and mechanism of ammonia evaporation reaction of magnesium oxide

以轻烧粉和氯化铵反应为出发点,研究了氧化镁蒸氨反应过程的动力学和反应机理。结果表明:当反应30 min时,70~90℃条件下溶液中镁离子浓度约为0.14 mol/L,100℃时浓度为0.5 mol/L。XRD结果表明,蒸氨过程中未反应生成Mg2+的氧化镁以氢氧化镁存在于滤渣中。随着煅烧温度的升高,氧化镁水化反应活化能逐渐增加。当煅烧温度为600℃时,反应活化能为64.7899 kJ/mol;当煅烧温度为800℃时,反应活化能为81.3506 kJ/mol。氢氧化镁和氧化镁按不同物质的量比混合进行蒸氨反应时,蒸氨速率随体系中氢氧化镁含量的增加而升高。氧化镁蒸氨体系可分为2个阶段:第一阶段,氧化镁在铵盐体系中进行水化反应生成氢氧化镁,同时部分氧化镁和氢氧化镁进行蒸氨反应生成镁离子;第二阶段,整个体系完全变成氢氧化镁蒸氨体系。

Kinetics and mechanism of ammonia evaporation reaction of magnesium oxide using light burning magnesium powder and ammonium chloride as raw materials were studied.Results showed that when the reaction was carried out for 30 min,the concentration of magnesium ion in the solution was about 0.14 mol/L at 70~90℃,and the concentration was 0.5 mol/L at 100℃.XRD results showed that the magnesium oxide without forming Mg2+in the ammonia evaporation reaction existed in the filter residue in the form of magnesium hydroxide.As the calcination temperature increased,the activation ener gy of the magnesium oxide hydration reaction increased gradually.When the calcination temperature was 600℃,the activa tion energy was 64.7899 kJ/mol;when the calcination temperature was 800℃,the activation energy was 81.3506 kJ/mol.When magnesium hydroxide and magnesium oxide were mixed in terms of different amount-of-substance ratios for the ammo nia evaporation reaction,the rate of ammonia evaporation increased with the amount of magnesium hydroxide in the system increases.Ammonia evaporation reaction of magnesium oxide can be divided into two stages:In the first stage,magnesium ox ide is hydrated in the ammonium salt system to form magnesium hydroxide,and at the same time,part of the magnesium oxide and magnesium hydroxide react with ammonium chloride to form magnesium ions.In the second stage,finally the system completely became an ammonia evaporation system of magnesium hydroxide.