摘要：
在文献中所报道AEL型分子筛无溶剂合成法的基础上,引入低温预处理、机械化学预处理、晶种和双氧水等合成变量进行具有特定形貌或孔结构的高结晶度的FeAPO-11分子筛的合成,并将制备的分子筛作为催化剂应用于苯酚的羟基化反应中.采用XRD、SEM、氮气物理吸脱附以及紫外可见漫反射光谱(UV-Vis DRS)等手段对FeAPO-11分子筛进行表征,深入探讨了催化剂上铁元素含量、铁物种分布和比表面积等因素对苯酚羟基化反应的影响.结果表明,低温预处理和双氧水的引入能显著提高FeAPO-11分子筛的结晶度,在特定条件下能制备出具有规则纳米晶聚集体形貌的FeAPO-11分子筛.催化结果表明,苯酚羟基化反应的诱导期长短主要取决于FeAPO-11催化剂中非骨架铁形式的多核铁的含量.在被考察的5个催化剂中,FeAPO-11-LHSB由于具有规则的纳米晶聚集体形貌、高的外表面积及骨架铁含量,在苯酚羟基化反应中展示出最优的性能,其苯二酚的产率和选择性分别为33.6％和67.6％.%Based on the solvent-free synthesis method of AEL-type molecular sieves in the literature, FeAPO-11 molecular sieves with high crystallinity, specific morphology or pore structure were synthesized by introducing some additional synthetic variables, including low temperature pretreatment, mechanochemical pretreatment, seed crystals and hydrogen peroxide.Their catalytic performance was investigated using phenol hydroxylation as a probe reaction.The synthesized FeAPO-11 molecular sieves were further characterized by XRD, SEM, N2 physisorption and UV-Vis DRS.Moreover, the effects of content and distribution of Fe species, and surface area of the catalysts on the phenol hydroxylation reaction were thoroughly studied.Characterization results indicate that combination of low temperature pretreatment and hydrogen peroxide can significantly improve the crystallinity of FeAPO-11 zeolite.Especially, under some specific conditions, FeAPO-11 molecular sieve with uniform nanocrystalline aggregates morphology can be successfully prepared.The catalytic reaction results suggest that the induction period of phenol hydroxylation reaction is mainly determined by the amount of multi-nuclear iron in the form of non-framework iron species in FeAPO-11 catalysts. Among the five selected catalysts, due to its regular nanocrystalline aggregates morphology, high external surface area and high iron content in the framework, FeAPO-11-LHSB exhibites the best performance with 33.6％ dihydroxybenzene yield and 67.6％ selectivity.
