ausblenden:
Schlagwörter:
Alkali metal cation exchanged faujasite-type zeolites; Isopropanol dehydrogenation; Infrared spectroscopy; X-ray diffraction; CO2 adsorption
Project 4, Basic zeolites
Zusammenfassung:
The conversion of isopropanol in a fixed bed flow reactor was used as a test reaction for a number
of faujasite-type zeolites which were modified in order to increase their basicity. Samples included a
CsY zeolite with an intact faujasite structure and an exchange degree of nearly 100% prepared by
solid-state ion exchange, a CsNaY obtained from CsY through exchange with aqueous NaCl
solution, a CsNaX obtained from NaX and aqueous CsCl solution, and a Na(Ge)X, with Si
replaced by Ge. At 623 K, an isopropanol partial pressure of 5 kPa in He, and a total feed flow of
90 ml/min, a catalyst mass of 50 mg, initial yields were as follows: NaY: 62% propene, CsNaY:
78% propene, NaCsX: 10% propene, 0.37% acetone, Na(Ge)X: 8% propene, 11% acetone.
Conversion in the presence of CsY was <1%. CO2 adsorption and infrared (IR) spectroscopy
were used to probe basicity, and Na(Ge)X was the only sample to form monodentate carbonates
upon CO2 adsorption (bands at 1477 and 1428 cm-1). Further characterization with X-ray
diffraction (XRD), transmission electron microscopy (TEM), thermal analysis, nitrogen sorption, and
isopropanol sorption was necessary to properly interpret catalytic results by identifying samples
which contained impurities, had blocked pore systems, or decomposed partially during activation or
reaction
