SSZ-51 - A new aluminophosphate zeotype: Synthesis, crystal structure, NMR, and dehydration properties

A new aluminophosphate zeotype framework structure, SSZ-51 (Al-4(PO4)(4)F.C7N2H11.0.5H(2)O), has been prepared in the presence of 4-dimethylaminopyridine as a structure-directing agent and a fluoride ion-mineralizing agent. The structure of the material was solved using single-crystal X-ray diffraction at a synchrotron source. It is closely related to the structure of SAPO-40 (AFR) and contains intersecting channels delimited by 8- and 12-membered ring windows. The occluded structure-directing agent and fluoride can be calcined to yield a material with appreciable microporosity. The calcination and dehydration of SSZ-51 was followed using variable temperature synchrotron X-ray powder diffraction and showed that the adsorption of water at low temperatures leads to a loss in long-range order of the framework. The long-range order of the framework is regained by dehydration at temperatures above 100 degreesC.