Catalytic Spectroscopy Laboratory, Instituto de Catálisis y Petroleoquímica, Consejo Superior de Investigaciones Científicas, Calle Marie Curie 2, Cantoblanco, 28049-Madrid, Spain.
Phys Chem Chem Phys. 2012 Feb 21;14(7):2128-36. doi: 10.1039/c1cp22608h. Epub 2011 Oct 12.
Alumina-supported VPO materials are efficient catalysts for acrylonitrile production by the propane ammoxidation reaction. In order to understand the structure-activity relationship and the nature of active sites, operando Raman-GC analyses follow the states of vanadium and phosphorous species on an alumina support during ammoxidation. These oxides were supported on γ-alumina by incipient wetness impregnation at a total V + P loading of two monolayers, which led to incipient formation of nanoscaled VPO crystallites possessing a high surface-to-volume ratio. Since catalysis occurs at the catalyst surface, which is related to the surface and outermost layers, this approach allows studying surface species phase transformations near the surface, and relates changes in activity and selectivity to variations in composition and structure. Dispersed surface V(5+) species appear selective to acetonitrile and V(4+) species would promote selectivity to acrylonitrile. This study suggests that V(3+) is probably involved in redox processes during propane ammoxidation and that the balance between these vanadium species would be determined by activation process.
氧化铝负载的 VPO 材料是丙烯腈通过丙烷氨氧化反应生产的高效催化剂。为了了解结构-活性关系和活性位的本质，在氨氧化过程中通过 operando Raman-GC 分析跟踪氧化铝载体上钒和磷物种的状态。这些氧化物通过等体积浸渍法负载在 γ-氧化铝上，总 V+P 负载量为两个单层，这导致具有高表面积-体积比的纳米 VPO 晶种的初步形成。由于催化作用发生在催化剂表面，这与表面和最外层有关，这种方法允许研究表面物种在表面附近的相转变，并将活性和选择性的变化与组成和结构的变化联系起来。分散的表面 V(5+)物种对乙腈具有选择性，而 V(4+)物种将促进丙烯腈的选择性。这项研究表明，V(3+)可能参与丙烷氨氧化过程中的氧化还原过程，而这些钒物种之间的平衡将由活化过程决定。
