钛硅分子筛TS-1的酸性表征及酸催化性能

Acidity Characterization and Acid Catalysis Performance of Titanium Silicalite (TS-1)

采用Hammett指示剂滴定法表征了钛硅沸石TS-1的酸性.结果表明,TS-1酸强度范围为+3.3<H0≤+4.8.其中,在+3.85<H0≤+4.8范围的弱酸中心可能与TS-1骨架钛有关,而在+3.3<H0≤+3.85的较强酸中心则可能与无定形的六配位非骨架钛有关.TS-1上的较强酸中心能够显著地催化环氧丙烷与甲醇的醚化反应,而TS-1上的弱酸中心对该反应几乎没有催化活性,但弱酸中心对乙二胺环胺化生成哌嗪和三乙烯二胺反应具有高活性和高选择性.这表明TS-1作为一种弱的固体酸催化剂,有可能应用于选择氧化以外的催化反应.

Hammett indicator titration was used for the characterization of TS-1 acidity. The acid strength of the TS-1 studied was ＋3.3 〈 H0 ≤ ＋4.8. The weaker acid sites, ＋3.85 〈 H0 ≤ ＋4.8, were due to the framework Ti of TS-1, while the stronger acid sites, ＋3.3 〈 H0 ≤ ＋3.85, in micron-sized TS-1 samples were due to amorphous extraframework Ti species. The stronger acid sites showed a correlation with the conversion of propylene oxide in the etherification with methanol. The weaker acid sites, although too weak for the etherification of PO with methanol, were active and selective for converting ethyldiamine （EDA） into piperazine （PIP） and 1,4-diazabicyclo[2.2.2]octane （DABCO）. TS-1 as a weak solid acid was shown to be a promising catalyst for reactions like the cycloamination of EDA to PIP and DABCO.