超重力反应沉淀法制备氧化锰八面体分子筛

Preparation of Manganese Oxide Octahedral Molecular Sieves by High Gravity Reactive Precipitation( HGRP)

采用氧化还原沉淀法在超重力反应器中制备出氧化锰八面体分子筛(OMS-2),考察了加入的酸量、反应器转速、反应温度对OMS-2晶型和尺寸的影响。研究结果表明,超重力反应器中,当加入硝酸浓度达到2.32mol/L,反应器转速增大到1 200 r/min时才能获得晶型良好的OMS-2产品。而且改变转速对OMS-2晶体的尺寸和形貌无明显调控作用,温度对OMS-2的晶体尺寸有明显影响。反应温度60℃比30℃对应产物沿直径的横向生长速率更快,生成纳米棒直径增大。DSC和H2-TPR分析表明,超重力反应沉淀法相比于普通回流法制备出的OMS-2产物,其在550℃以下可在不破坏晶体结构的前提下更稳定持续地释放出体相氧物种。超重力反应沉淀法以水为溶剂,为实现氧化锰八面体分子筛的规模化清洁制备做出了有益的探索。

Manganese oxide octahedral molecular sieves （OMS-2） were prepared in high gravity reactor by redox precipitation method. The effects of the amount of acid, the rotation speed of reactor and reaction temperature on the properties of OMS-2 were investigated. SEM images and XRD patterns show that the crystal structure of OMS-2 formed well when the concentration of HNO3 added was 2.32 mol/L and the rotation speed of reactor was 1 200 r/min. The size control of OMS-2 was not achieved through changing the rotation speed of reactor, and reaction temperature could significantly alter the size of crystalline materials. The lateral growth rate along the diameter of OMS-2 nanorods rose when the reaction temperature increased from 30 ℃ to 60 ℃. DSC thermogram and Ha-TPR profile indicate that, in comparison with conventional reflux method, the persistent release ability of the oxygen species of OMS-2 materials synthesized by HGRP was better at temperatures below 550 ℃ and without the destruction of crystal structure at the same time. This study provides a new green method to prepare one-dimensional OMS-2 nanorods on a larze scale.