Effect of Mesostructured Zirconia Support on the Activity and Selectivity of 4,6-Dimethydibenzothiophene Hydrodesulfurization

In contrast with the conventional CoMoS/alumina catalyst, the use of amorphous mesostructured ZrO2 as support for the dispersion of the CoMoS active phase in deep hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene led to a higher promotion rate and a better sulfidation of the cobalt species. The CoMoS, dispersed over mesostructured amorphous ZrO2 as catalyst, also induced a modification of the main desulfurization way; in this case, a shift towards direct desulfurization selectivity was observed. This result was unexpected regarding the literature. Indeed, the hydrogenated route was observed for commercial zirconia. The designed catalysts are therefore more eco-friendly, since they consume less hydrogen. This implies a better use of the fossil resources.

Alloying Effect of Silver on Zirconia Support Manipulated Palladium Catalyst for Methane Combustion

PdAg/ZrO2 alloy catalysts calcined at different temperatures were employed to elucidate the effect of support-metal interaction (SMI) on methane combustion. Combustion activity was depressed when the sample was calcined at an elevated temperature from 500 °C to 700 °C. However, calcination at 850 °C enhanced the beneficial SMI, which facilitated a more active phase for the oxidation reaction. The high-resolution transmission electron microscopy experiments show that a special micro-domain structure at the interface is formed during the reduction pretreatment. H2-TPR and O2-TPD measurements illustrate that the active phase would undergo reconstruction upon redox cycles. The active phase manipulated by the support is more suitable for combustion reaction in the course of temperature altering.

Physico-Chemical Properties of Nickel Promoted Sulfated Zirconia Powder Prepared using Different Procedures

In this work, nickel promoted sulfated zirconia (Ni/SZ) as catalyst was prepared by either by reflux (Ni/SZ-R) or hydrothermal Ni impregnation (Ni/SZ-H) routes. The aim of this study was to evaluate the influences of two preparative methods on the physico-chemical properties of prepared catalysts. Both the catalysts were characterized by XRD, FTIR, ammonia adsorption, SEM-EDX, TEM-SAED, AAS and BET. It was found that the presence of sulfate and nickel could enhance the Brønsted and Lewis active acid sites. In relation to the effect of Ni impregnation method, acidity, amount of sulfate and Ni found in Ni/SZ-R were higher than those in Ni/SZ-H. Unfortunately, higher impregnated sulfate and nickel on zirconia support led to a decrease in surface area and pore volume and an increase in crystallite size of grainy aggregated mesoporous nickel promoted sulfated zirconia (Ni/SZ).