用粉末XRD,FT—IR,^(29)Si MAS NMR,对高硅HZSM—5沸石及疏水硅沸石Silicalite-Ⅰ进行结构性质表征.在室温下,疏水硅沸石具有ZSM—5的单斜对称性.它的红外骨架振动谱及高分辨^(29)Si固体核磁共振谱均显示出高的分辨率.在红外光谱中,3700...用粉末XRD,FT—IR,^(29)Si MAS NMR,对高硅HZSM—5沸石及疏水硅沸石Silicalite-Ⅰ进行结构性质表征.在室温下,疏水硅沸石具有ZSM—5的单斜对称性.它的红外骨架振动谱及高分辨^(29)Si固体核磁共振谱均显示出高的分辨率.在红外光谱中,3700和3500^(-1)左右的表面Si-OH基振动消失.表明疏水硅沸石晶格中的[SiO_4]四面体排列完美.由—Si—O—Si—构成的微孔表面,具有优良的疏水性.展开更多
A post-synthesis modification method, named ion etching, is proposed to adjust the morphology of titanium silicalite TS-1 for a better catalytic activity. The new method mainly involves treating titanium silicalite TS...A post-synthesis modification method, named ion etching, is proposed to adjust the morphology of titanium silicalite TS-1 for a better catalytic activity. The new method mainly involves treating titanium silicalite TS-1 with an ammonia-containing aqueous solution in autoclave under the conditions of ca. ammonia aqueous solution concentration 0.5-14 mol/L NH 3, volume ratio of liquid/solid 20-100, hydrothermal temperature 100-180 ℃ and contact time 24-500 h. According to the characterizations by SEM, XRF, XRD, FTIR and UV-Vis, the modification can transform a well-defined large crystal TS-1[1 μm×2 μm×6 μm, n(Si)/n(Ti)=53.62] into fine grains which can avoid falling off from the matrix if the conditions of the treatment are properly controlled. The effect of ion etching upon TS-1 morphology is attributed to the OH - ion(derives from NH 3·H 2O) catalyzed hydrolysis of the T-O-T bridge bond of the silicic zeolitic framework. Its main advantages over mechanical ball-millingthe conventional zeolitic morphology modification method, include actually fully retained crystallinity and almost intact coordination state of the active Ti sites of the remained framework, as confirmed by XRD, FTIR and UV-Vis. Probe reaction shows that, the large crystal TS-1 modified by the present method at 170 ℃ for 129 h, when used as the catalyst for epoxidation of propylene, could be operated at propylene weight hourly space velocity of 0.5 h -1, and 97.85% hydrogen peroxide conversion and 96.87% propylene oxide selectivity were obtained. However, to reach comparative hydrogen peroxide conversion, the intact zeolite could only be operated under propylene weight hourly space velocity of 0.2 h -1. The remarkable increase of the catalytic activity of the modified TS-1 may be attributed to the improved intra-crystal diffusivity and the excellent preservation of the crystallinity and active Ti sites by the present modification.展开更多
文摘用粉末XRD,FT—IR,^(29)Si MAS NMR,对高硅HZSM—5沸石及疏水硅沸石Silicalite-Ⅰ进行结构性质表征.在室温下,疏水硅沸石具有ZSM—5的单斜对称性.它的红外骨架振动谱及高分辨^(29)Si固体核磁共振谱均显示出高的分辨率.在红外光谱中,3700和3500^(-1)左右的表面Si-OH基振动消失.表明疏水硅沸石晶格中的[SiO_4]四面体排列完美.由—Si—O—Si—构成的微孔表面,具有优良的疏水性.
文摘A post-synthesis modification method, named ion etching, is proposed to adjust the morphology of titanium silicalite TS-1 for a better catalytic activity. The new method mainly involves treating titanium silicalite TS-1 with an ammonia-containing aqueous solution in autoclave under the conditions of ca. ammonia aqueous solution concentration 0.5-14 mol/L NH 3, volume ratio of liquid/solid 20-100, hydrothermal temperature 100-180 ℃ and contact time 24-500 h. According to the characterizations by SEM, XRF, XRD, FTIR and UV-Vis, the modification can transform a well-defined large crystal TS-1[1 μm×2 μm×6 μm, n(Si)/n(Ti)=53.62] into fine grains which can avoid falling off from the matrix if the conditions of the treatment are properly controlled. The effect of ion etching upon TS-1 morphology is attributed to the OH - ion(derives from NH 3·H 2O) catalyzed hydrolysis of the T-O-T bridge bond of the silicic zeolitic framework. Its main advantages over mechanical ball-millingthe conventional zeolitic morphology modification method, include actually fully retained crystallinity and almost intact coordination state of the active Ti sites of the remained framework, as confirmed by XRD, FTIR and UV-Vis. Probe reaction shows that, the large crystal TS-1 modified by the present method at 170 ℃ for 129 h, when used as the catalyst for epoxidation of propylene, could be operated at propylene weight hourly space velocity of 0.5 h -1, and 97.85% hydrogen peroxide conversion and 96.87% propylene oxide selectivity were obtained. However, to reach comparative hydrogen peroxide conversion, the intact zeolite could only be operated under propylene weight hourly space velocity of 0.2 h -1. The remarkable increase of the catalytic activity of the modified TS-1 may be attributed to the improved intra-crystal diffusivity and the excellent preservation of the crystallinity and active Ti sites by the present modification.
