Monitoring the Activation of Copper-Containing Zeotype Catalysts Prepared by Direct Synthesis Using in Situ Synchrotron Infrared Microcrystal Spectroscopy and Complementary Techniques

Abstract

The use of copper polyamine complexes as structure directing agents for microporous solids offers a direct route to the inclusion of Cu2+ complex cations in their pores: upon calcination, this gives active catalysts for the selective catalytic reduction of NO with NH3. In situ synchrotron IR absorption spectroscopy on crystals of dimensions 25-35 μm has been used to monitor the dehydration of the Cu2+-cyclam complex that acts as a cotemplate for the silicoaluminophosphate SAPO STA-7 and, at higher temperatures (400 C), the calcination that gives the active catalyst Cu,H-SAPO STA-7. Polarized synchrotron IR microspectroscopy reveals strong alignment of N-H bonds of the Cu2+ cyclam in the larger cages of as-prepared STA-7, and complementary X-ray diffraction, ESR, UV-visible spectroscopy, and computer simulation indicate that the hydrated complex acts as cotemplate during crystallization: dehydration leads to removal of its coordinated water by 200 C.