一氧化碳还原热解硫酸镁制备高纯氧化镁

利用菱镁矿和工业纯硫酸制备七水硫酸镁,进一步脱水得到无水硫酸镁。以无水硫酸镁和CO气体为原料,经高温煅烧制备高纯氧化镁,考察硫酸镁粒径、CO气体流量、煅烧温度和煅烧时间对硫酸镁转化率的影响。通过单因素实验确定的最佳工艺条件为:粒径51.8μm,CO气体流量30 mL/min,煅烧温度800℃,煅烧时间2.0 h。样品氧化镁经X射线衍射和扫描电镜表征,纯度达到99%,其平均粒径为40nm,单分子表面为多孔蓬松状。经实验和动力学推导得到描述热解过程的经验方程,CO气体还原热解硫酸镁的动力学模型为收缩核动力学模型,热解表观活化能为234.055 kJ/mol,该模型表明热解过程中的控制步骤决定于氧化还原速率。

Preparation of high-purity magnesia by carbon monoxide reduction pyrolysis of magnesium sulfate

The magnesium sulfate heptahydrate prepared by magnesite and commercial sulfuric acid was dehydrated to prepare anhydrous magnesium sulfate.The high-purity magnesia was obtained by commercial magnesium sulfate and carbon monoxide.The influences of the particles diameter,gas flow,calcining temperature and time on the purity of prepared magnesium oxide were investigated.The optimum processing parameters of precipitation were obtained by single factor experiments,and the conditions were as follows: the grain diameter 51.8 μm,the carbon monoxide flow 30 mL/min,the calcining heat 800 ℃,the calcining time 2.0 h.The morphology of the magnesia was characterized by X-ray diffractometry(XRD) and scanning electron microscopy(SEM).The results indicate that sample particle has high purity to 99%,the average particle diameter is 40 nm.The single molecule surface with high specific surface area is porous and fluffy.By means of experiment and kinetic deduction,an empirical equation for the calcining process was established,and the apparent activation energy is 234.055 kJ/mol.The calcining process of magnesium sulfate can be simulated with a shrinking core model,which indicates that the control factor of the calcining process is the diffusion rate of reacting reagents in the redox process.