NH4HCO3水热处理对氧化铝孔结构与表面性质的影响

Effect of NH4HCO3 hydrothermal treatment on the pore structure and surface properties of alumina

关键词:  NH₄HCO₃  水热处理  氧化铝  孔结构  表面性质

Key words:  NH₄HCO₃  hydrothermal treatment  alumina  pore structure  surface property

摘要:

分别对硫酸铝-偏铝酸钠法制备氧化铝过程中形成的滤饼、水合氧化铝及氧化铝进行NH₄HCO₃水热处理,并应用XRD、FT-IR、SEM、N₂吸附-脱附、吡啶吸附-脱附等技术分析NH₄HCO₃水热处理对氧化铝孔结构与表面性质的影响。研究发现,不同阶段物料经NH₄HCO₃水热处理后可提高氧化铝的可几孔径及不同程度降低氧化铝表面总酸、弱酸、中强酸含量,并改变氧化铝表面羟基结构。其中,滤饼经NH₄HCO₃水热处理后制得的氧化铝与未处理氧化铝相比,可几孔径由5 nm左右提高至8 nm左右,孔容及比表面积略有降低,表面总酸量由0.47 mmol/g降低至0.30 mmol/g。不同阶段物料经NH₄HCO₃水热处理后都形成了微米级棒状氧化铝,由于微米级棒状氧化铝的生成从而影响氧化铝孔结构与表面性质。 

Abstract:

Filter cake, hydrated alumina and alumina prepared by aluminium sulphate-sodium aluminate method are hydrothermal treated by ammonium bicarbonate solution. The effects of NH₄HCO₃ hydrothermal treatment on the pore structure and surface properties of alumina are analyzed by XRD, FT-IR, SEM, N₂ adsorption-desorption, pyridine adsorption-desorption techniques respectively. It is found that NH₄HCO₃ hydrothermal treatment can increase the most probable pore of alumina, and decrease the total acid content,weak acid content and medium strong acid content, and also change the structure of surface hydroxyl. Compared with untreated alumina, the most probable pore of the alumina prepared from filter cake hydrothermal treated by NH₄HCO₃ is increased from about 5 nm to 8 nm, pore volume and surface area decreased slightly, total acid content decreased from 0.47 mmol/g to 0.30 mmol/g. Micron rod-like alumina is formed when different stage materials hydrothermal treated by NH₄HCO₃ solution. Pore structure and surface properties of alumina are affected by the formation of micron rod-like alumina.