气相法制备ZIF-8纳米膜包覆Pt/SiO2催化剂及其炔烃半加氢性能

Synthesis of ZIF-8-coated Pt/SiO2 by vapor deposition for alkyne semi-hydrogenation

  • 摘要: 以原子层沉积技术与气相转晶法相结合的方法,制备出ZIF-8/Pt/SiO2催化剂。该催化剂中Pt纳米颗粒沉积在SiO2纳米线表面,进一步通过气相法被厚度可控的ZIF-8纳米薄膜包覆后形成三明治结构。通过XRD、TEM、BET、ICP-MS、XPS、CO-DRIFT等表征对催化剂结构进行了系统的分析,以1-庚炔加氢为探针反应研究了ZIF-8薄膜对Pt催化性能的影响。结果表明,Pt颗粒高度分散在SiO2纳米线上,所制备的ZIF-8薄膜厚度可控,能够实现Pt/SiO2纳米催化剂表面的均一、保形性包覆。ZIF-8薄膜改变了Pt电子状态,提高了 Pt表面电子密度。在1-庚炔加氢反应中,ZIF-8包覆后, Pt催化庚炔加氢制庚烯的选择性由14%增加到70%。此外,降低ZIF-8纳米薄膜厚度能够提高反应的活性,几乎不影响烯烃的选择性。

     

    Abstract: In this work, ZIF-8/Pt/SiO2 catalysts were prepared by combining atomic layer deposition (ALD) and vapor phase conversion methods. First, Pt metal nanoparticles were deposited on SiO2 nanowires by ALD. Then, ZnO was further deposited, also by ALD. Subsequently, the ZnO film was converted into ZIF-8 film by vapor phase crystallization to form a sandwich structure (ZIF-8/Pt/SiO2). The microstructures of the catalysts were characterized by XRD, TEM, BET, IC-MS, XPS, and CO-DRIFT. It was shown that the Pt particles were highly dispersed on the SiO2 nanowires before and after coating with ZIF-8, and the ZIF-8 film was coated continuously on the entire catalyst with high conformity. The performance of the catalyst was studied by using the semi-hydrogenation of 1-heptyne as a probe reaction. The ZIF-8 film induces an electron density increase in the Pt component, leading to an increase of the olefin selectivity from 14% to 70% in the 1-heptyne hydrogenation reaction. A reduced thickness of the ZIF-8 film increases the catalytic activity but does not affect the selectivity of 1-heptylene.

     

/

返回文章
返回