莫来石-刚玉催化剂载体制备及其性能研究

Study on preparation and performance of mullite-corundum catalyst carrier

以我国特色高铝粉煤灰为原料,采用酸-碱联合法制备莫来石-刚玉催化剂载体,利用比表面积全自动物理吸附仪(BET)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)、电感耦合等离子体质谱仪(ICP-OES)等系列表征手段进行了深入分析。结果表明,采用酸-碱联合法制备工艺,即首先在硫酸浓度为1.5 mol/L,反应温度为85℃,液固比为7,反应时间90 min;随后在NaOH浓度为200 g/L、反应温度为95℃、液固比15、反应时间150 min条件下预处理粉煤灰,二氧化硅的脱除率达到58.51%,非晶态二氧化硅脱除率为83.49%。所获得的以莫来石和刚玉为主要成分的催化剂载体具有较高的比表面积和吸水率,分别为39.35 m^(2)/g和70.01%。耐热温度达到1100℃,颗粒大小在20~50μm之间,呈由短棒相互黏结在一起的多孔球形结构。X射线衍射表征结果显示,载体矿物相只有莫来石和刚玉,表明具有较好的化学稳定性和机械强度。孔分布分析结果表明,催化剂载体具有较宽的孔径分布,孔大小主要集中在约10 nm。

In order to realize the resource utilization of high-aluminum fly ash and alleviate the huge demand for catalyst carriers,this work developes a new process.That is,using Chinese characteristic high-alumina fly ash as raw material,the mullite-corundum catalyst carrier is prepared by the acid-alkali combined method,and a series of characterization methods such as specific surface automatic physical adsorption instrument(BET),scanning electron microscope(SEM),X-ray diffractometer(XRD),inductively coupled plasma mass spectrometer(ICP-OES)are used for in-depth analysis.The results show that when the acid-alkali combined process is adopted,that is,the acid process conditions are sulfuric acid concentration 1.5 mol/L,the reaction temperature 85℃,liquid-to-solid ratio 7,and the reaction time 90 min;subsequent pretreatment alkali process conditions are NaOH concentration 200 g/L,reaction temperature 95℃,liquid-to-solid ratio 15,and reaction time 150 min,the leaching rate of silica reaches 58.51%,and the leaching rate of amorphous silica is 83.49%.The obtained catalyst carrier with mullite and corundum as the main components has a higher specific surface area and water absorption.They are 39.35 m^(2)/g and 70.01%,respectively.Its heat-resistant temperature reaches 1100℃,revealing that it has the advantages of good heat stability.From the SEM pictures,it can be seen that particle size is between 20~50μm,and porous spherical structure is bonded by short rods.The X-ray diffraction characterization results show that the carrier mineral phase contains only mullite and corundum,indicating that it has good chemical stability and mechanical strength.The pore distribution analysis results reveal that the catalyst carrier has a wide pore size distribution,and the pore size is mainly 10 nm around.A mullite-corundum catalyst carrier with excellent performance has been prepared successfully,as finding a new way for the high-value utilization of secondary resource fly ash.