Structure sensitivity of the hydrogenation of crotonaldehyde over Pt/SiO2 and Pt/TiO2
Structure sensitivity of the hydrogenation of crotonaldehyde over Pt/SiO2 and Pt/TiO2
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DOI：
10.1006/jcat.1997.1494
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发表时间：
1997-02-01
影响因子：
7.3
通讯作者：
Lercher, JA
中科院分区：
文献类型：
--
作者：
Englisch, M;Jentys, A;Lercher, JA
在 SiO2 和 TiO2 负载的 Pt 催化剂上研究了巴豆醛的氢化。相对于 Pt/SiO2，初级产物丁醛和巴豆醇的选择性主要取决于 Pt 粒径；即，对不饱和醇的选择性随着粒度的增加而增加。对于大金属颗粒，高比例的 Pt(111) 表面有利于通过羰基键吸附巴豆醛。在小 Pt 颗粒上，低配位的高丰度金属原子允许不受约束地吸附两个双键。在这种情况下，C=C键的氢化在动力学上是有利的。低温还原后Pt/TiO2催化剂的活性和选择性与Pt/SiO2相似。高温还原后，对巴豆醇的选择性通常会增强。 Pt/TiO2 催化剂的选择性由金属颗粒尺寸和 TiOx 颗粒对 Pt 的修饰程度决定。这些氧化物颗粒中配位不饱和Ti阳离子的存在增强了C=O键的吸附强度，从而提高了对巴豆醇的选择性。金属颗粒尺寸和 TiOx 促进作用的影响是相加的。 TiOx 对小颗粒催化剂的促进和未促进的大颗粒的存在使得巴豆醇的选择性达到约 45%。用 TiOx 促进大 Pt 颗粒对巴豆醇的选择性为 64%。 (C) 1997 年学术出版社。
Hydrogenation of crotonaldehyde has been studied over SiO2- and TiO2-supported Pt catalysts. Over Pt/SiO2, the selectivity to the primary products butyraldehyde and crotylalcohol depends critically on the Pt particle size; i.e., the selectivity to the unsaturated alcohol increases with increasing particle size. For large metal particles, the high fraction of Pt(111) surfaces is concluded to favor the adsorption of crotonaldehyde via the carbonyl bond. On small Pt particles, the high abundance of metal atoms in low coordination allows unconstrained adsorption of both double bonds. In this case, the hydrogenation of the C=C bond is kinetically favored. Activity and selectivity of Pt/TiO2 catalysts after low-temperature reduction are similar to those of Pt/SiO2. After high-temperature reduction the selectivity to crotylalcohol is generally enhanced. The selectivity of Pt/TiO2 catalysts is then determined by the metal particle size and the extent of decoration of Pt with TiOx particles. The presence of coordinatively unsaturated Ti cations in these oxide particles enhances the sorption strength of the C=O bond resulting in an enhanced selectivity to crotylalcohol. The effects of metal particle size and promotion by TiOx are additive. TiOx promotion of catalysts with small particles and the presence of unpromoted large particles allow reaching of selectivities to crotylalcohol of approximately 45%. Promotion of large Pt particles with TiOx yields 64% selectivity to crotylalcohol. (C) 1997 Academic Press.