论文部分内容阅读
本文合成了五种不同硅铝比的ZSM-5,并分别用Mg~(2+),Ni~(2+)和K~+离子进行了交换改性。用NH_3和CO_2的TPD技术测定了它们的酸碱性质,并与甲苯甲醇的反应活性进行了关联。实验结果表明,ZSM-5分子筛的酸性和碱性不仅与骨架铝的含量有关,且与其阳离子的性质有关。甲苯与甲醇之间的苯环烷基化反应以及伴生的甲苯歧化反应均发生在ZSM-5的强酸中心上,弱酸中心不呈活性。由于改性后ZSM-5的碱性位少,即使是KZSM-5的碱性位也只有10~(18)/g,故不足以引发甲苯的侧链烷基化反应。
In this paper, five kinds of ZSM-5 with different Si / Al ratios were synthesized and exchanged with Mg 2+, Ni 2+ and K + respectively. Their acid-base properties were determined by the TPD technique of NH 3 and CO 2 and correlated with the reactivity of toluene-methanol. The experimental results show that the acidity and basicity of ZSM-5 zeolite are not only related to the content of framework aluminum, but also to the nature of its cation. The benzene ring alkylation reaction between toluene and methanol and the disproportionation reaction of toluene occurred in the strong acid center of ZSM-5, and the weak acid center was inactive. Since the basic position of the modified ZSM-5 is small, even KZSM-5 has a basicity of only 10-18 / g, it is not enough to initiate side-chain alkylation of toluene.