Study On The Preparation Of Nesquehonite And Magnesium Oxide Whiskers In A Rotation Packed Bed

Whisker is a kind of fiber materials with a certain aspect ratio and the characteristics of high aspect ratios, high intensity, good physichemical property and mechanical property. Magnesium carbonate whisker with a good mechanical property is a significant magnesium salt production. And it is wildly applied for the reinforcement and modification of coating, printing ink, rubber, plastics and so on. Magnesium oxide whisker is also an important magnesium salt production with the advantages of high mechanical strength and good anti-fatigue effect. And it is wildly used in the industry of automobile, chemical engineering, building materials and so on.In this study, magnesium carbonate whiskers have been prepared in an RPB by two routes including MgCl2-NH3·H2O-CO2and MgCl2-NaOH-CO2. And MgO whiskers were obtained by calcining the prepared magnesium carbonate whiskers. The effects of different operating conditions including reaction temperature, rotation speed, CO2concentration, initial concentration of MgCl2solution, molar ratio of Mg2+to NH3·H2O (or NaOH) on the morphology and stacking density of magnesium carbonate whiskers was investigated. And the effects of calcination temperature, calcination time and temperature rise rate on the stacking density of magnesium oxcide were investigated too. The optimal operating conditions of a reaction temperature of40℃, a rotation speed of800rpm, a CO2volumetric fraction of20%, an initial MgCl2concentration of0.5mol/L and a molar tatio of ammonia and Mg2+of3(moler ratio of sodium hydroxide and Mg2+of2in MgCl2-NaOH-CO2system) were obtained in this process. The magnesium carbonate whiskers with a complete and uniformity crystal structure, smooth surface, a stacking density of0.1032g/mL, an average length of36μm, an average diameter of1.16μm, aspect ratio of31was prepared under the optimal operating conditions. And the magnesium carbonate whiskers with a stacking density of0.1245g/mL, an average length of23.2μm, an average diameter of1.78μm, an aspect ratio of13was prepared under the optimal operating conditions in the MgCl2-NaOH-CO2system. The optimal calcination conditions of a calcination temperature of800℃, a calcination time of2h and a temperature rise rate of3℃/min were obtained. The magnesium oxide whiskers with complete and uniformity crystal structure, smooth surface, a stacking density of0.125g/mL, an average length of30μm, an average diameter of1μm, an aspect ratio of30was prepared under the optimal operating conditions.