非骨架铝在V中心形成过程中的作用

采用电子顺磁共振（ESR）技术，研究了非骨架铝在－HCM－22分子筛上V说生过程中的作用。实验结果表明，H－MCM－22分子筛经过高温处理后，产生一组六重超精细分裂信号（A），该顺磁信号归属为V中心。超精细分裂，是由于与骨架铝相连的氧上的电子空穴与骨架铝相互作用的结果；分裂信号的产生与温度有关，其强度随着温度升高而增强。不同晶体尺寸的H－ZSM－5分子筛的ESR实验证实，容易形成非骨架铝的分子筛易形成的V中心，它产生于已经脱铝的分子筛或伴随着脱铝而产生，非骨架铝的空轨道为电子接受体。

Role of non-Framework Aluminum Species for the Formation of V Center on Zeolites

The role of the non|framework aluminum species for the formation of V center at high temperatures on H|MCM|22 and H|ZSM|5 with different crystal sizes was studied using electron spin resonance technique. A set of six|lines signal (denoted as A, g =2.048) was observed on H|MCM|22 after heat|treatment under flowing helium, and its intensity increased with temperature. The paramagnetic center was identified as a hole of an electron trapped on oxygen atom bonding with a nearby framework aluminum atom. The formation of signal A might be related to the non|framework aluminum species, which was further evidenced on the H|ZSM|5 with different crystal sizes by ESR technique. The mechanism might involve an electron transfer from the lattice oxygen to the vacant orbit of the non|framework aluminum species.