层状H1-xNb1-xW1+xO6固体酸的制备与表征

摘要

采用高温固相法合成Li1-xNb1-xW1+xO6 (x=0.1,0,-0.1),通过H+交换制备出相应的固体酸H1-x-Nb1-xW1+xO6.采用XRD和FT-IR技术表征固体酸的物相和层板骨架结构,NH3-TPD方法表征其酸性特征.结果表明,3种酸样品的物相相同,但它们的主晶面(002)面间距略有变化.与HNbWO6中的NbO6和WO6八面体结构单元相比,H0.9Nb0.9 W1.1O6和H1.1 Nb1.1 W0.9 O6中的NbO6和WO6八面体发生变形.3种酸样品均有两种不同强度的酸位,它们的弱酸位强度基本相等,强酸位强度大小顺序为HL1 Nb1.1W0.9O6 ＞H0.9 Nb0.9 W1.1 O6＞ HNbWO6,两种酸位的酸量大小顺序均为H1.1 Nb1.1 W0.9 O6＞ HNbWO6＞ H0.9Nb0.9W1.1O6.%Layered solid acids H1-xNb1-xW1+xO6 were prepared by proton exchange of Li1-x Nb1-xW1+xO6 (x=0.1,0,-0.1),which were obtained by the high-temperature solid-state method.The phase structure and laminate structure of the as-prepared solid acids were studied by means of powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy(FT-IR).The acid characteristics of the as-prepared sample were characterized with method of ammonia temperature-programmed desorption (NH3-TPD).The results of XRD indicated that there is the same phase structure and slight difference in the (002) crystal plane spacing for the three acid samples.And FT-IR analysis state clearly that the NbO6 and WO6 octahedral unit in H0.9 Nb0.9 W1.1O6 and H1.1 Nb1.1 W0.9O6 are deformed comparing to HNbWO6.The results of NH3-TPD show that there are two acid sites for each as-prepared sample.For the weak acid sites,their strength is almost equal.However,the acid site strength with higher strong is in order of H1.1Nb1.1W0.9O6＞ H0.9Nb0.9W1.1O6＞ HNbWO6.The acid amounts of the two acid sites for the three samples are all in order of H1.1Nb1.1W0.9O6＞ HNbWO6＞ H0.9Nb0.9W1.1O6.