硅源及晶化时间对SAPO-5分子筛模板剂、酸性及催化性能的影响

EFFECTS OF Si SOURCES AND CRYSTALLIZATION TIME ON THE STATE OF TEMPLATE, ACIDITY AND CATALYTIC PERFORMANCE OF SAPO_5

改变硅源和晶化时间合成了系列ＳＡＰＯ５分子筛．用原位红外光谱和ＮＨ３ＴＰＤ研究了不同样品的酸碱性，用ＴＧＤＴＡ和ＭＡＳＮＭＲ考察了硅源及晶化时间对分子筛模板剂的影响，评价了不同样品对正己烷裂解的催化活性．结果表明，ＳＡＰＯ５分子筛孔道不仅与模板剂的胺基有作用，而且与其甲基也有作用．以硅凝胶为硅源时，在４８ｈ内，延长晶化时间可使分子筛中硅含量和强酸中心数目增加，低温下正己烷裂解活性提高；晶化７２ｈ时，分子筛的酸性减弱，正己烷裂解活性降低．以正硅酸乙酯为硅源时，延长晶化时间可使ＳＡＰＯ５的酸性增强，正己烷裂解性能提高．

A series of SAPO_5 have been synthesized by changing Si source and crystallization time. Using NH_3 as the probe molecule, the acidity of SAPO_5 was characterized by insitu IR. TGDTA and 13C MAS NMR were employed to study the effect of crystallization time on the state of template. The acidcatalytic performance of SAPO_5 was evaluated with n-hexane cracking. The results show that not only the amine group interacts with the channel of SAPO_5, but the methyl group interacts with the framework of SAPO_5. The 13C MAS NMR can be used to show the crystallinity of SAPO_5. Si sources have effects on the state of template, acidity and catalytic performance of SAPO_5. When using SiO_2 gel as Si source, within 48 h, prolonging the crystallization time can increase the Si content and the amount of acidity, and improve the activity for n-hexane cracking at lower temperature. When the crystallization time exceeds 48 h, the acidity and catalytic activity of SAPO_5 decrease. While using Si(OEt)_4 as Si source, the acidity and the catalytic activity of SAPO_5 rise with crystallization time.