金属盐类对L沸石伴生杂晶的抑制作用

Suppressing effect of metal salts on mixed crystal with growth of zeolite L

在L沸石合成体系中加入不同金属盐,考察它们对杂晶W沸石的抑制作用。采用X射线衍射(XRD)、低温氮吸附和扫描电子显微镜(SEM)对沸石样品进行了表征。结果表明:当合成体系中加入少量的W沸石晶种可造成L沸石的相对结晶度显著下降,W/L值(以W沸石与L沸石XRD特征衍射峰峰强度之比表示W沸石在L-W沸石中的含量)大幅升高;在含有一定量W沸石晶种的体系中加入等量的不同金属盐做比较,其中Mg NO3 2抑制效果好,且当Mg NO3 2含量为150 g/g时,抑制效果达最佳,其L沸石的相对结晶度为88.3%,W/L值为0.047,与未添加抑制剂的空白样相比,W/L值下降率达91.2%;在10L反应釜放大合成L沸石的体系中添加适宜量的Mg NO3 2,可有效抑制W沸石生成,合成样品中无W沸石相出现,其相对结晶度达98.6%。

Different metal salts are introduced into the synthetic system of zeolite L,and the suppressing effects of the mixed crystal W are investigated.X-ray diffraction（XRD）,nitrogen adsorption isotherms and scanning electron microscopy（SEM） are used for the physicochemical characterization of zeolite samples.The results indicate that a small number of zeolite W crytsal seeds added into the synthetic system of zeolite L remarkably decrease the relative crystallinity of zeolite L,leading to the increase of the peak intensity ratio of zeolite W to zeolite L,/.However,zeolite W could be effectively suppressed by the different metal salts among which magnesium nitrate（） is proven to facilitate to suppress the mixed crystal.And the suppressing effect exhibited optimal with,relative crystallinity of zeolite L and / being 150 g/g,88.3%,and 0.047.The decrease rate of the / value is 91.2% compared with the sample without suppressing agents.The results also show that the appropriate amount of Mg NO 3 2 is very effective in suppressing the formation of zeolite W in the synthetic system of 10 L autoclave for zeolite L.Zeolite W phase is not detected in the synthetic sample,where the relative crystalllinity is 98.6%.