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通过改变硅源和晶化时间的方法,采用水热法合成了系列SAPO-5分子筛材料,用X光衍射(XRD)和27Al MAS NMR对产物的晶相结构进行表征,用13C CP MAS NMR研究了不同阶段的产物中模板剂的存在状态。结果可见:以SiO2凝胶为硅源时;薄水铝石反应物有较高的活性,在48h的晶化时间内,延长晶化时间有助于SAPO-5分子筛的完整结晶,当晶化时间超过48h时,其中已形成的SAPO-5的结构部分被破坏,并转化为SAPO-34.且SAPO-34的量随晶化时间的延长而增多。当以Si(OEt)4为硅源时,铝反应物的反应活性较低,在72h的晶化时间范围内,延长晶化时间有助于SAPO-5产物的形成,使其结构愈加完整,在SAPO-5分子筛的形成过程中,模板剂的状态随分子筛结构的变化而变化,由于三乙胺(Et3N)模板剂中的甲基和亚甲基所处位置不同,其弛豫时间受分子筛结构的影响较大,可用其中甲基的13C MAS NMR诺线的强度及化学位移来表示分子筛结构的完整性。 相似文献
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近年来,人们利用对溶胶凝胶(SolGel)化学的认识,通过表面活性剂调控硅醇盐水解缩聚反应过程和对溶胶表面进行修饰以获得在一定范围内可控结构和可控粒度的纳米材料[1,2],但对SiO2溶胶凝胶过程的改性机理尚待深入研究。在溶胶凝胶过程中,溶胶粒子和网络结构主要受该体系中晶核形成与生长机制以及颗粒之间作用力所控制,这是实施溶胶网络结构形貌控制的理论依据。本文考察了聚氧乙烯醚(PEO)聚氧丙烯醚(PPO)聚氧乙烯醚(PEO)嵌段共聚物(简称EPE)作为改性剂对SiO2溶胶凝胶化过程的修饰行为,探讨了改性SiO2溶胶… 相似文献
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嵌段共聚物对SiO2溶胶-凝胶过程的修饰行为 总被引:4,自引:0,他引:4
By means of TEM, SDP, 29Si NMR etc analysis, the behavior of the Polyethylene Oxide (PEO)-Polypropylene Oxide (PPO)-Polyethylene Oxide (PEO) as organic modifier on SiO2 sol-gel in the basic media was investigated; the effects on sol particle growth and network &morphology control were discussed in detail, and then the model on sol particle growing was suggested on the basis of growth unit theory of anion coordinate polyhedron. The results showed that PEO-PPO-PEO additive limited particle growth but also restrained particle agglomeration and then made the SiO2 sol high stable. It was found that the action of EPE was similar to that of organic structure-directing agent and made the sol cluster cross linked branch network. 相似文献
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通过在SAPO-5分子筛的前身体中加入不同含量不同形式的钯盐方式,直接合成出了分子筛上担载贵金属的双功能催化剂,X光衍射(XRD)结果表明把的加入并不影响SAPO-5分子筛的生成,但降低了分子筛结晶度。当把以碱性介质加入反应物时,使产物中有少量SAPO-34伴生,由MASNMR实验结果可见,反应物中把的加入抑制了硅进入分子筛骨架,使骨架铝配位环境更加对称,并使三乙胺模板分解,改变了其在分子筛中的存在状态。从而导致分子筛结晶度的降低. 相似文献
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Four novel ester-amino ligands were synthesized by bis-acylation of octadecanyl, hexadecanyl, tetradecanyl and dedecanyl L-lysinate with ethylenediaminetetraacetic acid mono-anhydride (EDTA-MA), respectively. The corresponding neutral dimeric Gd(Ⅲ) complexes were gained by reacting these ligands with GdCl3·6H2O. All ligands and complexes were characterized by FTIR, 1H NMR and elemental analysis. The longitunal relaxation time (T1) was measured, and their stability were investigated by competition with Ca2+ and EDTA. The results indicate that the relaxivity of these netral binuclear Gd(Ⅲ) complexes are higher than that of Gd-DTPA. 相似文献
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硫酸交联壳聚糖干膜的13C CP MAS NMR研究 总被引:2,自引:0,他引:2
以不同浓度硫酸交联的壳聚糖干膜为研究对象,在国内首次采用13C CP MAS NMR技术从分子水平上对壳聚糖膜的结构进行研究,结果表明干膜壳聚糖分子的构象能直观地反映出膜的交联状况,交联状况与膜的分离性能密切相关,但仅对干膜的考察还不够全面. 相似文献