Catalytic activity and extra-large pores of germanosilicate UTL zeolite demonstrated with decane test reaction

Abstract

Pyridine adsorption monitored by FTIR spectroscopy revealed germanosilicate UTL type zeolite to contain intrinsic Brønsted acidity required for catalytic activity. Germanosilicate UTL type zeolite was converted into a bifunctional catalyst and evaluated in n-decane isomerization and hydrocracking. To assess the stability of the framework during catalyst preparation and use, three different strategies of converting the zeolite into bifunctional catalyst were followed: incipient wetness impregnation with Pt(NH₃)₄Cl₂ solution before and after evacuation of the template by calcination, and physical mixing of calcined UTL with Pt-containing amorphous silica. All three samples showed catalytic activity but to very different degrees. The possibility of structure degradation during catalyst preparation and catalysis was investigated by XRD and ²⁹Si MAS NMR. The impregnation of as-made germanosilicate UTL zeolite with platinum and pretreatment in the reactor led to superior stability and activity. The n-decane test previously was used to probe zeolite micropore architectures with 8-, 10- and 12-membered rings. Its validity is now extended to the extra-large pore zeolites. The linear trend of increasing ethyloctanevs.methylnonane selectivity with increasing pore size has now been confirmed also for UTL with 14 membered rings.