多级孔Fe-HBeta分子筛的合成及其催化性能探究

采用软模板法一步合成了一系列铁同晶取代的多级孔Beta分子筛(nFe-HBeta,n=Fe/Al),并通过等体积浸渍法制备出系列Ni基催化剂(10Ni/nFe-HBeta)。结果表明,系列nFe-HBeta均为结晶度高、孔道结构丰富的片状结构。异质铁原子的引入在降低介孔相有序度的同时,促使沸石颗粒粒径下降,中强酸性位点数量显著减少。对于10Ni/nFe-HBeta催化剂而言,骨架铁与NiO之间存在协同作用,可增强活性组分Ni与载体间的作用力,提高活性金属Ni的分散度,降低NiO颗粒粒径。在乙醇水蒸气重整催化反应中,铁元素的引入可规避酸性位以抑制乙醇脱水反应,同时加强CO和CH_4的水蒸气重整反应,有效提高H_2选择性。其中,10Ni/0.15Fe-HBeta催化剂在500℃时,H_2选择性高达72.15%,C_2H_5OH转化率为99.6%,反应12 h后的积炭量仅为4.3%。

Synthesis of the hierarchical Fe-substituted porous HBeta zeolite and the exploration of its catalytic performance

A series of hierarchical isomorphically Fe-substituted porous beta zeolites (BEAs) was synthesised in a one-step process via soft-template approach (nFe-HBeta, n=Fe/Al) and a series of Ni-based catalysts (10Ni/nFe-HBeta) was prepared by equal volume impregnation. The results showed that the nFe-HBeta zeolites possessed a sheet-like structure with a high crystallinity and numerous porous channels. The introduction of the heterogeneous iron atoms could reduce the degree of order of the mesoporous phase and decrease the size of the zeolite particles and the number of moderate and strong acidic sites. For the 10Ni/nFe-HBeta catalyst, a synergistic effect existed between the framework iron and NiO species, which could enhance the interaction between the active Ni and HBeta support, increase the dispersion of the active metal Ni, and reduce the NiO particle size. In the ethanol steam reforming (ESR) reaction, Fe introduction could inhibit the ethanol dehydration reaction through the shielding of acidic sites and could promote the steam reforming reaction of CO and CH₄, effectively improving the H₂ selectivity. Among the Fe-containing catalysts, 10Ni/0.15Fe-HBeta showed a H₂ selectivity of up to 72.15% and an ethanol conversion rate of 99.6% at 500 ℃, while the amount of coke deposition was only 4.3% after a 12 h reaction.