摘要
采用TG,NH_3-TPD,FTIR和原位IR考察分析了2,2,6,6-四甲基-4-酮-哌啶(TMPDO)和2,2,6,6-四甲基-4-肟基-哌啶(4-NOH-TMPD)在空心钛硅分子筛/双氧水(HTS/H_2O_2)体系中的吸附作用和机理.结果表明,HTS/H_2O_2体系中的催化剂表面存在Si—OH和Ti—OOH活性位;TMPDO和4-NOH-TMPD分子主要通过碱性的=N—H基与酸性较强的Si—OH中心作用,同时分子中对位的羰基或肟基与Ti—OOH中心作用,形成双位吸附.从而显著地提高活性中心Ti—OOH的稳定性和浓度,并导致催化剂表面强酸位数量明显减少,而弱酸位数量明显增加.因此,通过吸附适当有机碱来修饰催化剂的表面性质,可以提高HTS/H_2O_2体系的催化活性和选择性.
The adsorption mechanisms of 2,2,6,6-tetramethyl-piperdin-4-one（ TMPDO） and 2,2,6,6-tetramethyl-piperdin-4-one-oxime（ 4-NOH-TMPD） in HTS/H_2O_2 system were investigated by thermogravimetry analysis（ TG）,NH_3 temperature programmed desorption（ NH_3-TPD）,Fourier transform infrared spectrum（ FTIR） and in situ IR. The results showed that there were Si—OH and Ti—OOH active sites on the surface of the catalyst in HTS/H_2O_2 system. Two-site adsorption was formed by the interaction of alkali group =N—H of TMPDO or 4-NOH-TMPD with strong acid center Si—OH, and para group —C=O in TMPDO or—N=OH in 4-NOH-TMPD with Ti—OOH center. Such two-center adsorption of TMPDO or 4-NOH-TMPD on surface of HTS significantly increased the stability and concentration of active site Ti—OOH in HTS/H_2O_2 system,and thus caused an evident decrease of strong acid sites and an increase of weak acid sites on surface of the catalyst. Therefore,it is expected to improve the catalytic activity and selectivity of HTS/H_2O_2 system by modifying the surface properties of catalyst with adsorption of appropriate organic bases.
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
2016年第5期946-955,共10页
Chemical Journal of Chinese Universities
基金
浙江省自然科学基金(批准号:LY13B030003)资助~~
