【摘要】 利用X射线衍射(XRD),X射线光电子能谱(XPS),原位红外(in situ IR)光谱和CO2程序升温脱附(CO2-TPD)等技术研究了K对Mg-Al水滑石复合氧化物(MgAlO)的表面改性.结果表明,当K负载量≤8%(w)时,K高度分散在MgAlO表面,并与载体作用形成了新的Lewis碱位.其中,K取代MgAlO弱碱位OH上的质子形成弱碱性的Mg(Al)-O-K;与强碱位表面O2-结合形成强碱性的Mg-O-K.当K负载量为5%-8%(w)时,还存在与载体作用较弱并具有更强碱性的准自由KOx.K增强MgAlO碱性的本质是K的电荷转移到了表面氧负离子上.更多还原

【Abstract】 The surface modification of Mg-Al hydrotalcite mixed oxides (MgAlO) with K was investigated using X-ray powder diffraction (XRD),X-ray photoelectron spectroscopy (XPS),in situ infrared (in situ IR) spectroscopy,and temperature-programmed desorption of CO2 (CO2-TPD).We found that K was highly dispersed on the surface of MgAlO when the loading amount was less than 8% (w).New Lewis base sites were formed through the interaction between K and MgAlO.The weakly basic Mg(Al)-O-K resulted from the proton substitution of Mg(Al)-OH with K.Mg-O-K was obtained by combination with strongly basic O2-sites.At a K loading between 5% (w) and 8% (w),the quasi free KOx species that interacted weakly with the support and showed stronger basicity than Mg-O-K was formed.The increase in basicity of K/MgAlO can be attributed to charge transfer from K to the surface oxygen anions,which increases the negative charge of the strongly basic sites.更多还原