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采用阳离子交换的X-型分子筛作为甲苯和甲醇侧链烷基化反应的催化剂,研究了甲苯侧链烷基化反应的规律。证实了半径大的碱金属离子交换的X-型分子筛,其表面主要显碱性,能够催化甲苯侧链烷基化反应。在Rb-X和Cs-X中引入少量Li~+离子,能够在原分子筛上形成酸碱协调的活性中心,更有利于侧链烷基化活性的提高。对Cs-X催化剂,当Li/(Li+Cs)的摩尔比为0.18时活性最佳。以静电势(e/r)参量表征X-型分子筛表面酸碱的强弱。静电势小,碱性强,静电势大,酸性强;静电势为0.65时,Cs-Li-X催化剂表面酸碱匹配适度,活性最佳。静电势和催化活性的关系与量子化学计算的前沿轨道能量大小和碳原子上的电荷密度分布所作出的预测结论一致。并对甲苯和甲醇侧链烷基化制取乙苯和苯乙烯的适宜条件作了探讨。
The cation-exchanged X-type molecular sieve was used as the catalyst for alkylation of toluene and methanol. The alkylation of toluene was studied. It was confirmed that the X-type molecular sieves exchanged with large radius alkali metal ions are mainly alkaline in their surface, which can catalyze the side chain alkylation of toluene. The introduction of a small amount of Li ~ + ions into Rb-X and Cs-X can form an acid-base coordinate active center on the original molecular sieve, which is more conducive to the side chain alkylation activity. For Cs-X catalyst, the best activity was obtained when the molar ratio of Li / (Li + Cs) was 0.18. Electrostatic potential (e / r) parameters were used to characterize the strength and acidity of the surface of X-type zeolite. Electrostatic potential is small, strong alkaline, strong electrostatic potential, strong acid; electrostatic potential of 0.65, Cs-Li-X catalyst surface acid-base match moderate, the best activity. The relationship between the electrostatic potential and the catalytic activity is consistent with the prediction made by the quantum chemical calculation of the frontier orbital energy and the charge density distribution on the carbon atom. The suitable conditions for alkylation of toluene and methanol to ethylbenzene and styrene were discussed.