Vanadia Supported on Titania Prepared by Grafting: Influence of Support Properties on the Structure and Activity of Vanadia for the Selective Catalytic Reduction of NO by NH3
Vanadia Supported on Titania Prepared by Grafting: Influence of Support Properties on the Structure and Activity of Vanadia for the Selective Catalytic Reduction of NO by NH3
复制标题
接枝二氧化钛负载氧化钒：负载性能对氧化钒NH3选择性催化还原NO的结构和活性的影响
DOI：
10.1002/bbpc.19920961208
复制
发表时间：
1992
期刊：
影响因子：
--
通讯作者：
A. Wokaun
中科院分区：
文献类型：
--
作者：
B. Handy;I. Gorzkowska;J. Nickl;A. Baiker;M. Schraml;A. Wokaun
通过将氧钒醇盐接枝到形态（表面积、相组成）和杂质浓度不同的三种二氧化钛载体上制备的氧化钒/二氧化钛催化剂，研究了 NH3 对 NO 的选择性催化还原（SCR）。中子活化分析表明二氧化钛载体中存在主要杂质氯和钾。负载型催化剂通过VO(OR)3 (R = i-C3H7, i-C4H9)与载体表面羟基反应制备。关注了各种制备参数（氧化钒前驱体、载体预处理、杂质）的影响及其与沉积的氧化钒的量、还原性和活性的关系。热分析、X射线衍射和拉曼光谱表明，在接枝前对二氧化钛载体进行预处理，如果不在温和条件下进行，会导致锐钛矿相部分转变为金红石。钾杂质似乎在这种转变中稳定了锐钛矿相。对于含有钾作为杂质的二氧化钛，金红石化发生在比用含有氯作为杂质的二氧化钛观察到的温度显着更高的温度下。拉曼光谱表明，在研究的一系列二氧化钛载体中，氧化钒负载是决定固定化氧化钒表面物种结构的最重要因素。小簇和带在低覆盖率下占主导地位（∼ 2μmol V5+/m2）。在较高的覆盖率下，催化活性最强的二维氧化钒层占主导地位。当覆盖率超过 ∼ 3μmol V5+/m2 时，NO 转换达到最大水平。对于沉积在所有三种二氧化钛载体上的氧化钒，观察到这种行为，无论载体的 BET 表面积和污染物水平有多大差异。
The selective catalytic reduction (SCR) of NO by NH3 has been investigated over vanadia/titania catalysts prepared by grafting of vanadyl alkoxides onto three titania supports which differed in their morphologies (surface area, phase composition) and concentrations of impurities. Neutron activation analysis revealed the presence of chlorine and potassium as major impurities in the titania carriers. The supported catalysts were prepared by the reaction of VO(OR)3 (R = i-C3H7, i-C4H9) with support surface hydroxyl groups. Attention was paid to the influence of various preparation parameters (vanadia precursor, support pretreatment, impurities) and their relation to the amount, reducibility and activity of the vanadia deposited. Thermal analysis, X-ray diffraction and Raman spectroscopy revealed that pre-conditioning the titania supports before the grafting, if not carried out under mild conditions, results in partial transformation of the anatase phase to rutile. Potassium impurities appear to stabilize the anatase phase with regard to this transformation. For titania containing potassium as impurity, the rutilization occurs at a significantly higher temperature than observed with titania containing chlorine as impurity. Raman spectroscopy showed that within the series of titania supports investigated, the vanadia loading is the most important factor that determines the structure of the immobilized vanadia surface species. Small clusters and ribbons prevail at low coverages (∼ 2μmol V5+/m2). At higher coverages, the catalytically most active two-dimensional vanadia layers are prevailing. The maximum level of NO turnovers is achieved at coverages exceeding ∼ 3μmol V5+/m2. This behaviour was observed for vanadia deposited on all three titania carriers, irrespective of the largely different BET surface areas and contaminant levels of the supports.