层状粘土负载的金催化剂制备及其常温催化氧化活性

Preparation of Layered Clay-supported Gold Catalysts and Catalytic Activity for CO Oxidation at Room Temperature

为了研究粘土的性质对其负载的金催化剂在CO常温氧化反应中的催化活性的影响,将金溶胶分别负载到类水滑石(LDHs)和经过壳聚糖改性的蒙脱石(CS-MMT)表面,得到纳米金颗粒呈高度分散状态的金催化剂样品.通过XRD、XRF、TEM、XPS等手段表征了金催化剂样品的物相、金的含量、金颗粒的粒径分布及金的存在价态,测试了催化剂样品对CO的常温转化率.结果表明:Au0是粘土负载的金催化剂对CO常温氧化反应的主要活性物种,碱性载体LDHs负载的金催化剂样品1.83%Au/Mg Al-CO32--LDHs表面只检测到Au0,金颗粒的平均粒径为2.6 nm,对CO的常温转化率能够达到100%,而酸性载体CS-MMT负载的金催化剂样品1.71%Au/CS-MMT表面同时存在氧化态和金属态的金,且Auδ+/Au0=1.1,金颗粒的平均粒径为2.1 nm,对CO的常温转化率仅为25%.

In order to investigate the influence of the properties of different clay supports on the catalytic activity of clay-supported gold catalysts for CO oxidation at room temperature,the catalysts with highly dispersed gold nanoparticles were obtained by loading gold sol on the layered double hydroxides（ LDHs） and montmorillonite modified by chitosan（ CS-MMT） respectively. The physical phase,gold loading,diameter distribution of gold particles and valence state of gold element of the catalyst samples supported on the two types of layered clay were characterized by XRD,XRF,TEM and XPS respectively,and the conversion of CO on different catalyst samples at room temperature was tested. The results showed that Au0 is the active species in the clay-supported gold catalysts for CO oxidation at room temperature. Only Au0 was detected on the surface of basic LDHs-supported gold catalyst sample of 1. 83% Au / Mg Al-CO32--LDHs on which the CO conversion at room temperature achieved 100%,and average diameter of gold particles was 2. 6 nm. However,both Auδ ＋and Au0 were found（ Auδ ＋/ Au0= 1. 1） on the surface of acid montmorillonite-supported gold catalyst sample of 1. 71% Au / CS-MMT which CO conversion was only 25%,and average size of gold particles was 2. 1 nm.