Y型分子筛结晶度和晶胞常数随温度变化规律

Effect of temperature on crystallinity and cell constant of Y Zeolites

选取1种NaY分子筛和3种Si Cl4气相超稳法制得的DY分子筛作为研究对象,通过X荧光光谱(XRF)、N2吸附-脱附、热重(TG-DSC)和场发射扫描电镜(SEM),考察4种Y型分子筛物化性质的差异,利用原位升温粉末X射线衍射(in-situ XRD)考察相对结晶度(室温升至1 000℃)和晶胞常数(室温升至600℃)随温度变化的规律。结果表明,升温过程中4种Y型分子筛相对结晶度均表现为先升后降,NaY型分子筛在900℃时晶体结构完全消失,硅铝比较高的DY分子筛在1 000℃时,相对结晶度仅15%~35%;随着温度升高,NaY分子筛晶胞常数先减后增,而DY-1和DY-2分子筛晶胞常数先增后减,DY-3分子筛晶胞常数一直减少。(555)晶面衍射峰的偏移也随温度和骨架硅铝比变化呈规律性改变。

One NaY zeolite and three DY zeolites prepared by high-temperature gas-phase SiCl 4 were characterized by X-ray fluorescence(XRF),N 2 adsorption-desorption,TG-DSC and scanning electron microscopy(SEM).Relationship of relative crystallinity(from room temperature to 1000℃)and unit cell constants(from room temperature to 600℃)with temperature change was explored by in-situ XRD.The results showed that relative crystallinity of four Y zeolites firstly increased and then decreased with heating process.Crystal structure of NaY zeolite disappeared completely at 900℃,while relative crystallinity of DY zeolites with high molar Si/Al ratio was only 15%to 35%at 1000℃.Unit cell parameters of NaY zeolite firstly decreased slightly and then increased with increase of temperature,by contrast,unit cell constants of DY-1 and DY-2 zeolites firstly increased then decreased.Unit cell constants of DY-3 zeolite decreased.Diffraction peak of(555)plane shifted with change of temperature and Si/Al ratio.