PdPtVOx/CeO2-ZrO2: Highly efficient catalysts with good sulfur dioxide-poisoning reversibility for the oxidative removal of ethylbenzene

The PdPtVOx/CeO2-ZrO2 (PdPtVOx/CZO) catalysts were obtained by using different approaches, and their physical and chemical properties were determined by various techniques. Catalytic activities of these materials in the presence of H2O or SO2 were evaluated for the oxidation of ethylbenzene (EB). The PdPtVOx/CZO sample exhibited high catalytic activity, good hydrothermal stability, and reversible sulfur dioxide-poisoning performance, over which the specific reaction rate at 160°C, turnover frequency at 160°C (TOFPd or Pt), and apparent activation energy were 72.6 mmol/(gPt⋅sec) or 124.2 mmol/(gPd⋅sec), 14.2 sec-1 (TOFPt) or 13.1 sec-1 (TOFPd), and 58 kJ/mol, respectively. The large EB adsorption capacity, good reducibility, and strong acidity contributed to the good catalytic performance of PdPtVOx/CZO. Catalytic activity of PdPtVOx/CZO decreased when 50 ppm SO2 or (1.0 vol.% H2O + 50 ppm SO2) was added to the feedstock, but was gradually restored to its initial level after the SO2 was cut off. The good reversible sulfur dioxide-resistant performance of PdPtVOx/CZO was associated with the facts: (i) the introduction of SO2 leads to an increase in surface acidity; (ii) V can adsorb and activate SO2, thus accelerating formation of the SOx2- (x = 3 or 4) species at the V and CZO sites, weakening the adsorption of sulfur species at the PdPt active sites, and hence protecting the PdPt active sites to be not poisoned by SO2. EB oxidation over PdPtVOx/CZO might take place via the route of EB → styrene → phenyl methyl ketone → benzaldehyde → benzoic acid → maleic anhydride → CO2 and H2O.

Novel Vanadia/meso-Co3O4 catalysts for the conversion of benzene-toluene-xylene to environmental friendly components via catalytic oxidation

Three - dimensional meso-porous Co₃O₄ was prepared by nanocasting pathway based on the use of mesoporous silica (KIT-6) as hard template with different Cobalt concentrations (0.5-2.5 mol ratio based on mesoporous silica KIT-6). The prepared samples was used as supports for preparing V₂O₅/Co₃O₄ (1, 6 wt% of V₂O₅) catalysts. The prepared samples were characterized by different techniques. The catalytic activity of the prepared samples were evaluated in the complete oxidation reaction of toluene, benzene, and/or p-xylene; (as model reactants of volatile organic compounds) in terms of CO₂. The catalytic reaction was carried out in a fixed-bed micro-reactor operated under atmospheric pressure and within the reaction temperature range of 200-400 °C. The data confirmed that the three dimensional-mesoporous Co₃O₄ (1.0 mole ratio) replicated sample possessed improved different parameters compared to those of the Co₃O₄ sample with other mole ratios. The data reflected the yield of Co2 is decreased upon the increase in reaction temperature to 400°C. 1 wt.% V₂O₅/m-Co₃O₄ catalyst shows a reverse direction, the CO₂ yield slowly increased in the range 150-250 °C, then jumped at 300 °C until maximum yield (100%) is observed at 400 °C. 1 wt.% V₂O₅/m-Co₃O₄ catalyst was found to be the active and selective promised catalyst for the complete oxidation of either individual aromatic volatile organic compounds (benzene, toluene, and/or xylene) and/or their mixtures to 100% CO₂.

Catalytic combustion of toluene over CeO2–CoOx composite aerogels

The dispersion of active species and redox cycle of Co³⁺/Co²⁺ in cobalt based aerogels have an important influence on catalytic performance for toluene oxidation.