Crotonaldehyde hydrogenation by gold supported on TiO2: structure sensitivity and mechanism
Crotonaldehyde hydrogenation by gold supported on TiO2: structure sensitivity and mechanism
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DOI：
10.1016/j.jcat.2004.01.033
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发表时间：
2004-04
影响因子：
7.3
通讯作者：
R. Zanella;C. Louis;S. Giorgio;R. Touroude
中科院分区：
文献类型：
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作者：
R. Zanella;C. Louis;S. Giorgio;R. Touroude
研究了NaOH （DP NaOH）沉积-沉淀（~ 3wt %）和尿素（DP urea）沉积-沉淀（~ 8wt %）制备的Au/ tio2系列催化剂在常压下对巴丁醛加氢反应的催化性能。在给定的活化处理下，DP尿素和DP NaOH样品的活性（molgAu−1s−1）和选择性没有差异。这是由于DP尿素和DP NaOH样品表现出相似的金粒度分布，尽管DP尿素催化剂中的金负载远高于DP NaOH催化剂。DP尿素样品在不同温度下（120-500℃）进行h2o2还原，或在300℃空气中以不同流速处理，平均粒径在1.7 - 8.7 nm的大范围内变化。在5-50%的转化范围内，对丁醇的选择性（羰基键的选择性加氢）为60 - 70%，且与还原温度无关，并且作为粒度的函数几乎不变。相反，TOF取决于金粒度，当金粒度为~ 2 nm时，TOF急剧增加。并将Au/TiO2催化剂与Pt/TiO2催化剂的这些特性进行了比较。讨论了巴豆醛可能的吸附方式。氢解离被认为是速率决定步骤，并且发生在金粒子的低配位原子上。
The catalytic properties of two series of Au/TiO2catalysts prepared by deposition-precipitation with NaOH (DP NaOH) (∼3 wt%) and by deposition-precipitation with urea (DP Urea) (∼8 wt%) were evaluated for the reaction of crotonaldehyde hydrogenation at atmospheric pressure. There is no difference in activity (molgAu−1s−1) and selectivity between the DP Urea and DP NaOH samples for a given activation treatment. This is due to the fact that the DP Urea and DP NaOH samples exhibit a similar gold particle size distribution, although the gold loading in DP Urea catalysts is much higher than in DP NaOH. The DP Urea samples were reduced under H2at different temperatures (120–500°C) or treated in air at 300°C with various flow rates, to vary the average particle size within a large range, 1.7 to 8.7 nm. The selectivity to crotyl alcohol (selective hydrogenation of the carbonyl bond), in the 5–50% conversion range, is high, 60–70 %, and is independent of the reduction temperature, and almost constant as a function of the particle size. In contrast, the TOF depends on the gold particle size, drastically increasing when the gold particle size is ∼2 nm. These characteristic features of Au/TiO2catalysts in this reaction are compared with those of Pt/TiO2. The possible adsorption modes of crotonaldehyde are discussed. Hydrogen dissociation is proposed to be the rate-determining step, and to take place on the low-coordinated atoms of the gold particles.