Edgar Lotero

A study of platinum supported on tungstated zirconia catalysts

Abstract The reaction of n-butane with hydrogen at 573 K was studied over platinum supported on tungstated zirconia (PtWZ). A higher Pt dispersion increases the selectivity toward hydrogenolysis products and overall activity. The % coke after 90 min on stream at a H 2 /n-C 4 ratio of 3 was found to be less than 0.1 wt.-% in all cases. The presence of Bronsted acid sites upon reduction is confirmed by diffuse reflectance infrared spectroscopy of adsorbed pyridine. The WO 3 /ZrO 2 (WZ) support consists of a mixture of tetragonal and monoclinic zirconia and tetragonal tungsten oxide regardless of the presence of platinum.

Characterization of palladium supported on sulfated zirconia catalysts by DRIFTS, XAS and n-butane isomerization reaction in the presence of hydrogen

Abstract Palladium supported on sulfated zirconia (PdSZ) has been characterized by the n-butane isomerization reaction in the presence of hydrogen, X-ray absorption spectroscopy (XAS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) of adsorbed carbon monoxide. Catalyst calcination at 873 K followed by hydrogen reduction at 513 K results in the formation of 30–40 A Pd metal clusters, but the surface can only weakly adsorb CO, though stronger than Pd-free, sulfated zirconia catalysts. In the presence of hydrogen, PdSZ has a lower n-butane isomerization activity than SZ, and the Pd function cannot stabilize the reaction at low H 2 /n-butane ratios.

Tungsta supported on zirconia and alumina catalysts: temperature-programmed desorption/reaction of methanol and pyridine DRIFTS studies

The temperature-programmed reaction/desorption of methanol over tungsta supported on zirconia and gamma alumina (WO3/ZrO2 and WO3/γ-Al2O3) catalysts was monitored by mass spectrometry. The selectivity toward dimethyl ether (DME) was found to increase and its desorption maxima to shift toward lower temperatures with increasing catalyst acidity. The latter was probed by diffuse reflectance infrared spectroscopy (DRIFTS) of adsorbed pyridine up to 723 K.

Alcohol dehydration reactions as chemical precursors for coke formation and acidity probes in tungstated zirconia catalysts

The temperature-programmed desorption of low-molecular weight alcohols was studied over tungstated zirconia and acidic zeolites. Tungstated zirconia (WZ) acids have less tendency to deactivate due to carbon deposition and to form oligomeric products. Proton exchange is also less important in WZ.