Abstract

The staged crystallization of aluminophosphate AlPO₄-11 from a commercially available aluminum source based on boehmite is studied for the first time by means of X-ray diffraction, ²⁷Al and ³¹P magic-angle spinning nuclear magnetic resonance, low-temperature nitrogen adsorption–desorption, and scanning election microscopy. It is shown that the synthesis of AlPO₄-11 proceeds via the formation of an intermediate phase based on crystalline aluminophosphate with a layered structure. It is found that AlPO₄-11 with a high degree of crystallinity and phase purity forms in 6–24 h at 200°C. Lengthening the time of crystallization at 200°C to more than 48 h results in the transformation of AlPO₄-11 into nonporous cristobalite. The results can be used to develop means for directional control of the phase purity and degree of crystallinity of commercially important silicoaluminophosphate molecular sieves SAPO-11 with desired properties. These can be used as a base for the synthesis of promising domestic catalysts for the commercial hydroisomerization of higher n-paraffins.

中文翻译：

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通过勃姆石基磷酸铝凝胶结晶形成AlPO 4 -11的关键阶段

摘要

通过X射线衍射，²⁷ Al和³¹ P魔角旋转核磁共振，低温氮吸附，首次研究了从市售的基于勃姆石的铝源中磷酸铝AlPO ₄ -11的分阶段结晶。-解吸，并扫描选显微。结果表明，AlPO ₄ -11的合成是通过形成基于具有层状结构的结晶铝磷酸盐的中间相而进行的。已发现具有高结晶度和相纯度的AlPO ₄ -11在200°C的6–24小时内形成。将200°C的结晶时间延长至48小时以上会导致AlPO ₄的转变-11成无孔方石英。该结果可用于开发用于对具有所需性质的商业上重要的硅铝磷酸盐分子筛SAPO-11的相纯度和结晶度进行定向控制的手段。这些可以用作合成用于高级正构烷烃的商业加氢异构化的有前景的家用催化剂的基础。