Y型分子筛的有机酸脱铝改性

利用有机酸对Y型分子筛进行改性,采用XRD、XRF、XPS和IR等对其进行表征,结果表明,分子筛经过离子交换降低钠含量,水热焙烧后,采用有机络合剂进行处理,更有利于得到结晶度高和非骨架铝含量低的分子筛;在相同柠檬酸或草酸比例下,采用柠檬酸处理的样品,其硅铝物质的量比和结晶度均高于草酸处理样品;有机酸处理有利于分子筛非骨架铝的脱除,尤其分子筛外表面非骨架铝的脱除,提高分子筛结晶度和硅铝物质的量比。m(柠檬酸)∶m(分子筛)=a∶1~(a+0.10)∶1时,晶胞尺寸变化不大;m(柠檬酸)∶m(分子筛)=(a+0.15)∶1时,分子筛晶胞进一步收缩,结晶度降低;随着柠檬酸比例增加,脱铝处理分子筛的B/L降低。

Modification of zeolite Y by organic acid dealumination

The dealumination of zeolite Y was carried out with aqueous solutions of oxalic acid and citric acid,respectively. The zeolite samples before and after dealumination were characterized by XRD,XRF,XPS and IR.The results showed that the zeolite with high relative crystallinity degree and low extra framework aluminium could be obtained after ion exchange to reduce sodium content,and hydrothermal treatment and calcinations to remove aluminium with organic acid.The zeolite treated with citric acid possessed higher molar ratio of silica to alumina and higher relative crystallinity degree than that treated with oxalic acid under the same ratios of citric acid or oxalic acid to zeolite.The extra framework aluminium,especially on external surface of the zeolite,could be removed by organic acid treatment,and the molar ratio of silica to alumina and relative crystallinity degree of the zeolite were increased.The crystal cell size of zeolitechanged little after being treated with citric acid under the condition of m(citric acid)∶m(zeolite)=a∶1～(a+0.10)∶1..But with the enhancement of mass ratio of citric acid to zeolite to (a+0.15)∶1,the crystal cell size of zeolite and the relative crystallinity degree reduced.The ratio of B/L acid reduced with the increase of the mass ratio of citric acid to zeolite.