STRATEGIES IN CONTROLLING THE HOMOGENEITY OF ZIRCONIA SILICA AEROGELS - EFFECT OF PREPARATION ON TEXTURAL AND CATALYTIC PROPERTIES
STRATEGIES IN CONTROLLING THE HOMOGENEITY OF ZIRCONIA SILICA AEROGELS - EFFECT OF PREPARATION ON TEXTURAL AND CATALYTIC PROPERTIES
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DOI：
10.1006/jcat.1994.1254
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发表时间：
1994-08-01
影响因子：
7.3
通讯作者：
KO, EI
中科院分区：
文献类型：
--
作者：
MILLER, JB;RANKIN, SE;KO, EI
我们采用溶胶-凝胶合成法，然后进行超临界干燥，制备了不同分子比和不同均匀程度的氧化锆-二氧化硅气凝胶。即使含量低至 1-5 mol%，二氧化硅也能延缓氧化锆样品在热处理时通常会发生的表面积损失和相变。在二氧化硅含量为 5 mol% 的情况下，硅前体原硅酸四乙酯的预水解产生混合氧化物凝胶，其结构特性（最显着的是表面积和孔径分布）随凝胶时间变化，其方式与纯氧化锆气凝胶类似。该证据表明预水解有效地匹配前体反应性，进而产生均匀的混合氧化物。选择替代的硅前体、原硅酸四甲酯，或通过用乙酰丙酮处理对锆前体进行化学改性，也可以有效地匹配前体反应性。充分混合的 95 mol% 氧化锆-5 mol% 二氧化硅气凝胶在 1-丁烯异构化中比混合不良的样品或单一组分气凝胶更活跃。 (C) 1994 年学术出版社
We have used a sol-gel synthesis, followed by supercritical drying, to prepare zirconia-silica aerogels with different molecular ratios and varying degrees of homogeneity. Even at levels as low as 1-5 mol%, silica retards surface area loss and phase transformations that would normally occur in zirconia samples upon heat treatment. At 5 mol% silica, prehydrolysis of the silicon precursor tetraethylorthosilicate produces mixed oxide gels whose textural properties, most notably surface area and pore size distribution, vary with gel time in a manner that parallels pure zirconia aerogels. This evidence suggests that prehydrolysis effectively matches precursor reactivities and, in turn, produces homogeneous mixed oxides. Choosing an alternate silicon precursor, tetramethylorthosilicate, or chemically modifying the zirconium precursor by treatment with acetylacetone is also effective in matching precursor reactivity. Well-mixed 95 mol% zirconia-5 mol% silica aerogels are more active in 1-butene isomerization than are poorly mixed samples or either single component aerogel. (C) 1994 Academic Press, Inc.