Synthesis and characterization of potassium-modified alumina superbases

Abstract

Novel solid superbases can be prepared by dispersing potassium salts such as K₂CO₃ and KHCO₃ on alumina followed by thermal treatments. The resulting materials show an extremely high activity in the isomerization of cis-but-2-ene at 0°C and possess base strength of at least H₋ = + 26.5. X-Ray diffraction (XRD) and Raman spectra of K₂CO₃ or KHCO₃ modified alumina reveal the formation of potassium hydroalumina carbonate, which is the precursor of active species. Decomposition of potassium salts on alumina has been studied by use of thermal gravimetric differential thermal analysis (TG-DTA) and temperature programmed decomposition-mass spectrometry (TPDE-MS). Two CO₂ evolution processes were observed in the TPDE –MS profile, corresponding to the decomposition of potassium hydroalumina carbonate and bulk potassium salt.