Catalysis Today, Vol.358, 1-9, 2020
Influence of acidity on the performance of silica supported tungsten oxide catalysts assessed by in situ and Operando DRIFTS
The types of acidity on WOx/SiO2 catalysts prepared with different tungsten loadings (5 and 9 wt.% W) and pretreatment atmospheres (N-2 and H-2) were clarified by using the in situ diffuse reflectance infrared Fourier transform spectroscopy with temperature-programmed desorption (in situ DRIFTS-TPD) technique. Ammonia (NH3) acted as probe molecules that could block Lewis acid site type II (1620 cm(-1)) on the studied catalysts. The reactant feed containing 2% trans-2-butene or mixed feed of 2% trans-2-butene and 4% ethylene were used to investigate the reaction pathway on the WOx/SiO2 catalysts. Combining the Operando DRIFTS with gas chromatography-flame ionization detector (Operando DRIFTS-GC-FID) technique and in situ DRIFTS-TPD led to more deeply understanding of the correlation of acid sites and the primary cross metathesis reaction as the main reaction with isomerization of trans-2-butene as the side reaction. The adsorption energy of pulse chemisorption of 1-butene on catalyst by in situ DSC, confirmed the presence of the Lewis acid site type II related to the opportunity of 1-butene adsorption. The results confirmed that the Lewis acid site at 1620 cm(-1) was crucial for the secondary metathesis reaction of 1-butene.