三维贯穿结构大孔氧化铝的制备与性质表征
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摘要
以聚环氧乙烷为诱导剂引发固-液两相分离形成以无定形水合羟基铝为骨架的三维贯通大孔氧化铝,经水热处理使水合羟基铝转化为拟薄水铝石(AlOOH),在温和焙烧条件下制备了具有贯穿大孔孔道的高结晶度γ氧化铝材料。采用XRD、SEM、N_2吸附-脱附和~(27)Al MAS NMR等测试手段对制备的大孔氧化铝材料的性质进行了表征。表征结果显示,所得材料不但具有300～600 nm之间的连续大孔孔道,大孔具有空间分布均匀且三维贯穿的结构特点,大孔氧化铝比表面积达到379 m~2/g;而且孔壁含有9.5 nm的介孔孔道,说明所得材料具有介孔/大孔多级孔道分布;焙烧后的试样铝物种具有四配位、五配位及六配位三种配位状态。实验结果表明,试样在500℃常规焙烧条件下即可转变为高结晶度的γ氧化铝,且抗压强度较高,基本满足多相催化对载体强度的要求。
Polyethylene oxide was used as inducer to initiate solid-liquid two-phase separation to form three-dimensional interconnected macroporous alumina with amorphous hydrated hydroxyl aluminium as framework. After hydrothermal treatment,the hydrated hydroxyl aluminium was converted into pseudo-boehmite(AlOOH). The AlOOH was transformed into high crystallinityγ-alumina materials with three-dimensional interconnected macropores under mild calcination condition. The samples were characterized by XRD,SEM,N_2 adsorption-desorption,and ~(27)Al MAS NMR. The results revealed that the alumima possessed continuous macropores(300-600 nm in size) with uniform spatial distribution and three-dimensional interconnected structure. The specific surface area of macroporous alumina reached 379 m~2/g. The pore wall contained 9.5 nm mesoporous channels,which indicated that the obtained material has mesoporous/macroporous multistage porous channel distribution. For the calcined sample,the three aluminium species of AlO_4,AlO_5,and AlO_6 had been formed by the result. The sample can be converted into high crystallinity γ-alumina by conventional calcination at 500 ℃,and the high crushing strength of alumina can meet the requirements of heterogeneous catalysis for carrier strength.
Polyethylene oxide was used as inducer to initiate solid-liquid two-phase separation to form three-dimensional interconnected macroporous alumina with amorphous hydrated hydroxyl aluminium as framework. After hydrothermal treatment,the hydrated hydroxyl aluminium was converted into pseudo-boehmite(AlOOH). The AlOOH was transformed into high crystallinityγ-alumina materials with three-dimensional interconnected macropores under mild calcination condition. The samples were characterized by XRD,SEM,N_2 adsorption-desorption,and ~(27)Al MAS NMR. The results revealed that the alumima possessed continuous macropores(300-600 nm in size) with uniform spatial distribution and three-dimensional interconnected structure. The specific surface area of macroporous alumina reached 379 m~2/g. The pore wall contained 9.5 nm mesoporous channels,which indicated that the obtained material has mesoporous/macroporous multistage porous channel distribution. For the calcined sample,the three aluminium species of AlO_4,AlO_5,and AlO_6 had been formed by the result. The sample can be converted into high crystallinity γ-alumina by conventional calcination at 500 ℃,and the high crushing strength of alumina can meet the requirements of heterogeneous catalysis for carrier strength.
引文
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[2]Wei J.Modeling of hydrodemetallation[J].Stud Surf Sci Catal,1991,68:333-341.
[3]Rana M S,Navarro R,Leglise J.Competitive effects of nitrogen and sulfur content on activity of hydrotreating CoMo/Al2O3catalysts:A batch reactor study[J].Catal Today,2004,98(1):67-74.
[4]王鼎聪,刘纪端.贯穿性框架式渣油脱金属催化剂氧化铝载体的研究[J].石油炼制与化工,2010,41(1):31-35.
[5]Reijen J E,Keijzer P H,Jongh P E.Pore structure stabilization during the preparation of single phase ordered macroporousα-alumina[J].Materialia,2018,4:423-430.
[6]Takahashi R,Onishi A,Sato F,et al.Preparation of bimodal porous alumina using propylene glycol oligomers[J].J Ceram Soc Jpn,2017,125(10):742-746.
[7]Sun Mingling,Zhao Tianbo,Li Zunfeng,et al.Sol-gel synthesis of macro-mesoporous Al2O3-SiO2-TiO2 monoliths via phase separation route[J].Ceram Int,2016,42(14):15926-15932.
[8]白秀玲,马波,杨卫亚,等.三维贯通大孔氧化铝的制备与表征[J].当代化工,2013,42(3):253-255.
[9]吴俊升,李晓刚,杜伟,等.介孔/大孔Al2O3-SiO2复合氧化物的制备与表征[J].催化学报,2006,27(9):755-761.
[10]杨卫亚,凌凤香,张会成,等.具有三维贯通多级孔道结构大孔氧化铝的制备与表征[J].燃料化学学报,2018,46(5):558-563.
[11]Hashimoto H,Yazawa K,Asoh H,et al.NMR spectroscopic analysis of the local structure of porous-type amorphous alumina prepared by anodization[J].J Phys Chem C,2017,121(22):12300-12307.
[12]Samain L,Jaworski A,Edén M,et al.Structural analysis of highly porousγ-Al2O3[J].J Solid State Chem,2014,217:1-8.
[13]Digne M,Sautet P,Raybaud P,et al.Use of DFT to achieve a rational understanding of acid-basic properties ofγ-alumina surfaces[J].J Catal,2004,226(1):54-68.
[14]赵琰.氧化铝、改性氧化铝及硅酸铝的酸性特征(续)[J].工业催化,2002,10(3):56-62.
[15]郝志显,刘辉,郭彬,等.以无机铝盐为前驱体用溶胶凝胶法合成中孔氧化铝[J].物理化学学报,2007,23(3):289-294.