Cheng Liu,Jiale Huang,Daohua Sun,Yao Zhou,Xiaolian Jing,Mingming Du,Haitao Wang,Qingbiao Li
Anatase type extra-framework titanium in titanium silicate-1 (TS-1) molecular sieves has been observed to cause adverse catalytic impediments such as carbon–carbon bond cleavage and low H 2 O 2 efficiency during the epoxidation of terminal alkenes. In this study, a series of TS-1 sieves were synthesized, and used as catalysts for styrene epoxidation. Among the catalysts, the TS-1 with a Si/Ti molar ratio of 35 and 0.21 mol% of anatase type extra-framework titanium exhibited the best styrene conversion and styrene oxide (SO) selectivity. The results suggests that, framework Ti species have no effect on the stabilization of SO selectivity, whereas the synergetic interaction between the framework Ti species and the anatase type extra-framework titanium is essential for the outstanding catalytic performance of TS-1 in styrene epoxidation. In addition, our results demonstrate that the usage of tetraethyl orthosilicate (TEOS), tetrabutyl titanate (TBOT), and isopropyl alcohol in the synthesis of TS-1 does not guarantee the absence of extra-framework Ti species. Instead, the asynchronous degrees of hydrolysis between TEOS and TBOT might account for the formation of the anatase type extra-framework titanium. The influence of H 2 O 2 amount, reaction temperature and time, as well as the types of solvent, oxidant, and catalyst amount, on the catalytic performance of TS-1 with anatase type extra-framework titanium was likewise investigated.
Zheng Zhang,Xiao-Xin Kong,Miao Feng,Zhao-Hui Luo,Hui Lu,Gui-Ping Cao
In this Article, TS-1 was successfully synthesized on carbon nanotubes decorated nickel foam via in situ strategy forming the monolithic TS-1 (MTS-1). To the best of our knowledge, situ synthesis of the MTS-1 has not been reported. Carbon nanotubes decorated nickel foam has many aggregated pores (confined pores formed in aggregated structure) and a large surface area, and TS-1 particles could be dispersed on the surface of CNT@NF. MTS-1 had the characteristics of ultrafine nanoparticle and high content of skeleton titanium. High absorptive property and electrostatic interaction between CNT@NF and gels could accelerate the crystallization rate. The TS-1 particles were solidly immobilized on the CNT@NF, and the conversion rate was almost constant even after multiple reactions. The catalyst is easy to separate from liquid products after reaction, which offers an economical application prospect.
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