Pt-M催化剂表面电子密度调控及其肉桂醛选择性加氢性能的研究

The selective hydrogenation of α, β-unsaturated aldehydes to unsaturated alcohol is widely used in synthesizing a variety of fine chemicals. However, the hydrogenation of the C=C bond is more easy than that of the C=O bond. Based on the understanding that the electronic density may be the key factor in deciding the selective hydrogenation of the C=O bond, this project will design a serious of Pt-M（M=Fe, Co, Ni...）catalysts, in which the Pt and M are separated by a carbon or nitrogen doped carbon (C/CN) membrane. The catalysts will be synthesized by atomic layer deposition. The electronic density on the surface of Pt nanoparticles will be regulated by controlling the thickness of the C/CN membrane and the species and size of M by ALD. The catalytic performance of the catalysts will be evaluated by using the selective hydrogenation of cinnamaldehyde as a probe reaction. Then we correlate the selectivity to cinnamyl alcohol and the electronic density of the catalysts to reveal the relationship between the surface electronic density and the catalytic performance on the hydrogenation of C=C and C=O bonds. According to these results, a modal catalyst that can promote the hydrogenation of C=O bond and inhibit the hydrogenation of C=C bond will be structured. And the conclusion will provide guidance for the design of new industrialized catalysts.

α、β不饱和醛选择性加氢制备不饱和醇在精细化工生产过程中占据着重要的位置，但C=O双键的选择性加氢是其难点。在认识到催化剂表面电子密度可能是影响其选择性的关键因素的基础上，本项目提出设计一种具有空间剥离结构的Pt-M（M= Fe、Co、Ni等）催化剂，并利用原子层沉积技术实现可控制备。以Pt-M催化剂为基础，通过改变剥离层—C/CN膜的厚度和助金属的种类等，有望实现对催化剂中Pt表面电子密度的精确调控。以肉桂醛加氢反应为探针，将Pt-M催化剂与肉桂醛加氢活性和选择性关联起来，研究和分析Pt表面的电子密度对肉桂醛中C=C双键以及C=O双键选择性加氢的影响规律。构建出能够促进C=O双键加氢，抑制C=C双键加氢的模型催化剂，为后续的工业化催化剂提供理论指导。

金属表面电子结构对催化剂的催化性能有着本质的影响，而通过催化剂空间结构调控可以实现对催化剂表面金属的电子结构实现精确调控。在本项目的支持下，主要开展了三个方面的工作。一是利用原子层沉积技术，通过硫醇的分子层吸附精确调控了Pt-Co催化剂的空间结构。通过肉桂醛选择性加氢探针反应，我们发现Pt-Co催化剂中Pt主要起活化H2的作用，而以Co2+价态存在的Co主要起吸附C=O双键的作用，并且活化的H经载体溢流到CoO的表面，从而实现C=O双键的选择性加氢。二是通过Pt与TiO2之间的强相互作用实现了对Pt表面低配位Pt原子的电子密度调控。通过丙烷脱氢反应，我们发现低配位的Pt原子是丙烷脱氢制烯烃的主要活性位点，并且具有正电荷的Pt具有更高的活性和选择性。三是通过TiO2纳米管的限域作用实现了对Cu的电子结构调控。通过光催化CO2还原制烯烃的反应，我们发现高分散的Cu+团簇更有利于低碳烯烃的生成。