Ordered tungsten and aluminum co-doped mesoporous KIT-6 catalysts (W-Al-KIT-6) with different Si/Al molar ratios were successfully synthesized by a one-pot synthesis method. The obtained W-Al-KIT-6 catalysts were tested for catalytic conversion of 1-butene and ethene to propene via isomerization of 1-butene to 2-butene and subsequent cross metathesis of 2-butene and ethene. Various characterization techniques, such as ICP-OES, XRD, BET, TEM, Raman, XPS and NH3-TPD, were used to characterize the catalysts. The introduction of Al did not change the mesoporous structure of KIT-6 when the nominal Si/Al was 10, 20 or 30. Moreover, the sample demonstrated a larger amount of acidic sites. The W-Al-KIT-6 catalysts with suitable Si/Al ratios illustrated a superior catalytic performance to W-KIT-6 catalyst. The origin of catalytic performance enhancement over W-Al-KIT-6 catalysts is preliminarily discussed and ascribed to the highly disperse W species and a large amount of acidic sites. The acidic sites were formed by the introduction of a suitable amount of Al in the W-KIT-6 framework, which accelerated the isomerization of 1-butene to 2-butene and promoted the cross metathesis of 2-butene and ethene to propene.
Shaoqing Wang,Yan Jiao,Zhihe Li,Zhen Wan,Yu Han,Weiming Yi
In this paper, a surface encapsulation method has been developed to synthesize the HZSM-5 @Al-KIT-6 hierarchical zeolites, due to the poor mono-aromatic hydrocarbons (MAHs) selectivity and rapid coke deactivation during the catalytic upgrading lignin pyrolysis vapors. Results showed that the acidity and accessibility of HZSM-5 @Al-KIT-6 hierarchical zeolite can be modulated by changing the TEOS/HZSM-5 mass ratio during catalyst synthesis. The three-dimensional (3-D) cubic mesoporous shell can capture the bulky phenolic oligomers and pre-crack for further reforming. The highest MAH content (44.03%) and lower polycyclic aromatic hydrocarbons (PAHs) (23.79%) were produced when the TEOS/HZSM-5 mass ratio was 1.0. The hierarchical zeolites improved the yield of xylenes due to the enhanced alkylation reaction. In addition, the micro-mesoporous highway reduced the formation of coke deposition. The catalytic mechanism of hierarchical zeolites was then proposed based on the obtained results. This study provides a reference for pilot-scale experiments for the catalytic upgrading lignin pyrolysis vapors.
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