掺杂Fe作为第二种金属组分的V-HMS催化剂的苯羟基化反应

采用浸渍法在V-HMS中引入第二种金属组分(Fe、Al、Cu、Ni、Co、Mo、Cr)以提高催化剂在H2O2为氧化剂的苯羟基化反应中的催化性能.筛选发现,Fe在所研究的金属组分中最为有效.进一步采用共合成法制备了一系列FexVy-HMS催化剂.采用粉末X射线衍射、N2物理吸附、透射电子显微镜、NH3程序升温脱附、H2程序升温还原等手段对催化剂的结构和性质进行表征,结果表明,HMS仍保持介孔结构,Fe的加入在催化剂中产生了新的酸性位和更强的氧化还原性.在苯羟基化反应中,钒物种是反应活性物种,铁物种起助剂作用,其中Fe0.04V0.06-HMS具有最高的催化活性,苯酚收率由不含Fe的Fe0.00V0.06-HMS的13.1%提高到18.1%.提出了Fe、V参与反应过程的可能机理.

Hydroxylation of Benzene over V-HMS Catalysts with the Addition of Fe as the Second Metal Component

Second metals (Fe, Al, Cu, Ni, Co, Mo, Cr) were incorporated into V-HMS catalyst by impregnation to enhance the catalytic activity for the hydroxylation of benzene with hydrogen peroxide as the oxidant. Among the studied second metals, Fe was found to be effective in improving the catalytic performance. Therefore, we synthesized a series of FexVy-HMS catalysts containing different amounts of Fe and V by the co-synthesis method. The catalysts were characterized by powder X-ray diffraction (XRD), N2 physisorption, transmission electron microscopy (TEM), NH3 temperature-programmed desorption (NH3-TPD), and H2 temperature-programmed reduction (H2-TPR). The characterization results show that the mesoporous structure of HMS is maintained and the addition of Fe creates new acid sites and a stronger redox ability. Catalytic tests show that vanadium species are the active species and that the iron species promote the reaction. Under optimal reaction conditions, the Fe0.04V0.06-HMS catalyst gives the best catalytic performance with a highest phenol yield of 18.1% by comparison with 13.1% over the Fe-free catalyst Fe0.00V0.06-HMS. We propose a possible mechanism involving the Fe and V species for the hydroxylation of benzene with H2O2 as the oxidant.