Study On Kinetics Of Hydration Reaction Of Magnesium Oxide And Mechanism Of Ammonia Evaporation

As an additive inorganic flame retardant,magnesium hydroxide is widely used in polymer composites due to its unique structure and properties.the light calcined powder?main component:MgO?prepared by calcining magnesite,it is more about the experimental conditions for preparing magnesium hydroxide from magnesium salt solution,and The reaction process of burning magnesia and ammonium salts has rarely been reported.Therefore,the mechanism of the reaction process of light burned magnesia and ammonia is discussed,which provides a reference for actual production.In this paper,the magnesium chloride solution and filter residue are prepared by the steaming ammonia reaction with light calcined powder and ammonium chloride as raw materials.The effects of steamed ammonia temperature,reactant ratio,stirring rate and steamed ammonia time on the concentration of magnesium ions were studied?The results show that steamed ammonia temperature=100°C,steamed ammonia time=3 h,The ratio of ammonium nitrate to light burnt powder?MgO?was 2.1:1,and the stirring rate was 400 r/min for the condition of the ammonia reaction;XRD analysis shows that Magnesium oxide is the form of hydrogen oxide in the residual matterMagnesium oxide?purity>99%?prepared by magnesium hydroxide of two shapes at different calcination temperatures was used as raw material,and the kinetics of magnesium oxide hydration reactions were studied.The results show that with the increase of calcination temperature?from 500°C to 800°C?,SEM image of magnesium oxide shows that it maintains the crystal morphology of the magnesium hydroxide precursor.The specific surface area of flaky magnesium oxide is 106.248 m²/g at 500°C,and the bulk magnesium oxide is42.741m²/g;when the temperature is increased to 900°C,the specific surface area of the flaky magnesium oxide is 23.939 m²/g,and the bulk magnesium oxide 22.915 m²/g?the activation energy of magnesium oxide hydration reaction increases with the increase of calcination temperature.The flaky magnesium oxide hydration activation energy was 47.5061 kJ/mol at500°C,bulk magnesium oxide is 25.8938 kJ/mol;when calcination temperature is 800°C,The flaky magnesium oxide hydration activation energy was 81.3506 kJ/mol,The flaky magnesium oxide was 66.7397 kJ/mol.The magnesium oxide hydration activation energy is greater than 25.12 kJ/mol.According to Bebson principle,magnesium oxide hydration reaction belongs to the mechanism of chemical reaction rate control.The explore the concentration of ammonium salt,different ammonium salts and magnesium salts during hydration reaction.The effect of magnesium oxide hydration rate and ionic conductivity.The results show:The effect of ammonium salt on the hydration rate of MgO isNH₄ NO₃?29?NH ₄Cl?29?NH ₄SO₄?29?NH ₄HCO₃?29?CH ₃COONH₄?29??N H₄?₂C ₂ O₄;With the increase of ammonium salt concentration,the hydration rate of magnesium oxide increase from 26.4%to 69.51%;different magnesium salt solutions are beneficial to hydration of magnesium oxide.The effects on the hydration reaction of magnesium oxide are Mg?N O₃?₂?29?MgCl₂?29?MgSO₄;With the increase of calcination temperature,the ionic conductivity of magnesium oxide suspension increases first to a maximum value and gradually decreases.Experiments were carried out on the reaction mechanism of magnesium oxide and magnesium hydroxide and ammonium chloride.The results show that the magnesium oxide ammonia reaction is divided into two stages:in the first stage,part of the magnesium oxide is hydrated in the ammonium salt solution to form magnesium hydroxide,and the other part of the magnesium oxide and the formed magnesium hydroxide are combined to carry out the ammonia reaction.In the second stage,the magnesium oxide is completely hydrated to magnesium hydroxide,and the ammoniated reaction is converted into a magnesium hydroxide vaporized ammonia system.