A novel strategy for constructing mesoporous solid superbase catalysts: bimetallic Al-La oxides supported on SBA-15 modified with KF
A novel strategy for constructing mesoporous solid superbase catalysts: bimetallic Al-La oxides supported on SBA-15 modified with KF
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构建介孔固体超强碱催化剂的新策略：KF修饰的SBA-15负载双金属Al-La氧化物
DOI：
10.1039/c6cy02334g
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发表时间：
2017-02-07
影响因子：
5
通讯作者：
Liu, Yuejin
中科院分区：
文献类型：
--
作者：
Liu, Ning;Wu, Zhimin;Liu, Yuejin
采用改进的湿浸法在SBA-15表面预涂Al-La双金属氧化物，然后引入氟化钾，在低温下制备固体超强碱。这打破了KNO 3在高温下分解的传统，并为在SBA-15上产生超碱性位点提供了新的方法。采用FT-IR、XRD、TG-DTG、N2吸附-脱附、TEM、SEM-EDS、酸碱滴定、Hammett指示剂和CO2-TPD等测试手段对KF/Al-La@SBA-15材料的物理化学特性进行了研究。结果表明，Al物种的加入促进了La物种在孔道内的分散行为，La物种的加入可以协同保护SBA-15的介孔结构免受KF的腐蚀。随着Al含量的增加，KF/Al-La@SBA-15呈现出长程有序的孔结构，孔径分布相对较窄，比表面积较高。研究结果表明，KF/Al-La@SBA-15（0.4）催化剂的总碱度为0.79 mmol g（-1），超强碱强度为26.5。在环氧丙烷与甲醇的开环反应中评价了所制备材料的催化活性。结果表明，KF/Al-La@SBA-15（0.4）对环氧丙烷与甲醇的开环反应具有最高的催化活性。这与Al和La物种之间的协同效应以及活性组分在SBA-15载体上的高度分散有关。
Bimetallic Al-La oxides were conjointly precoated on SBA-15 prior to the introduction of potassium fluoride to achieve solid superbases at low temperature by a modified wetness impregnation method. This breaks the tradition of decomposition of KNO3 at high temperature and gives rise to a new approach to generating superbasic sites on SBA-15. The physico-chemical characteristics of the prepared KF/Al-La@SBA-15 materials were investigated using FT-IR, XRD, TG-DTG, N-2 adsorption-desorption, TEM, SEM-EDS, acid-base titration, Hammett indicators and CO2-TPD measurements. The results demonstrated that the addition of Al species promoted the dispersion behavior of La species inside the channels, and the bimetallic species could synergistically protect the mesoporous structures of SBA-15 against KF corrosion. With increasing Al content, KF/Al-La@SBA-15 exhibited a long-range ordering of the pores with relatively narrow pore size distribution as well as high specific surface area. The research results showed that the KF/Al-La@SBA-15 (0.4) catalyst possessed a total basicity up to 0.79 mmol g(-1) and superbasicity with a strength of 26.5. The catalytic activity of the prepared materials was evaluated in the ring-opening reaction of propylene oxide with methanol. Compared with the SBA-15 supported monometallic oxide (Al or La) catalysts, KF/Al-La@SBA-15 (0.4) exhibited the highest catalytic activity for the ring-opening reaction of propylene oxide with methanol. This is associated with the synergistic effects between Al and La species and the high dispersion of active components on the SBA-15 support.