晶种参与合成SAPO-34分子筛

在加入晶种的体系中,研究了模板剂用量、磷源用量和晶种加入量对合成SAPO-34分子筛的影响。实验结果表明,模板剂是形成SAPO-34分子筛骨架的必要条件;在加入适量模板剂的条件下,加入晶种可提高SAPO-34分子筛的结晶度;在一定范围内增大模板剂用量,可提高SAPO-34分子筛的结晶度,过量的模板剂反而会降低结晶度;降低磷源用量可增强晶种的作用、降低模板剂用量和缩短晶化时间;增加晶种加入量,能提高生成SAPO-34分子筛的选择性,当晶种干基与SiO_2质量比为0 39时,SAPO-5分子筛杂晶消失,得到纯SAPO-34分子筛,且晶化时间缩短了24 h,但晶种加入量达到一定值后,SAPO-34分子筛的结晶度不再明显增加。

Synthesis of SAPO-34 Molecular Sieve in Presence of Crystal Seed

SAPO-34 molecular sieves were synthesized in presence of crystal seed. Effects of dosages of the template, phosphorus source and crystal seed on the synthesis were investigated. The experiments showed that template was the key substance for formation of SAPO-34 framework. With a proper amount of template the addition of crystal seed enhanced the crystallinity of SAPO-34. Although increasing a certain amount of template could improve crystallinity of SAPO-34 to a certain extent, excess of it would contrarily cause undesirable result. Reducing the addition amount of phosphorus source material could bring the role of crystal seed into prominence, save some amount of template and shorten the crystallization time. Properly increasing the amount of crystal seed was preferable to selectivity to SAPO-34. When the mass ratio of crystal seed(dry basis) to SiO_2 was 0.39, the formation of miscellaneous crystal of SAPO-5 molecular sieves was inhibited, pure SAPO-34 molecular sieve was obtained, and a crystallization period shortened by 24 h. But when amount of crystal seed reached a certain limit,the raising of crystallinity of SAPO-34 smoothed out.