An Overview on the Dehydrogenation of Alkylbenzenes with Carbon Dioxide over Supported Vanadium–Antimony Oxide Catalysts

Hydrogenation of carbon monoxide over vanadium oxide-promoted rhodium catalysts

Support and dispersion effects on the CO-H 2 reaction-on silica and alumina supported pt catalysts

Dehydrogenation of ethylbenzene with carbon dioxide over MgO-modified Al 2O 3-supported V–Sb oxide catalysts

Modification of alumina support with an appropriate amount of magnesia (Mg/Al = 0.1) leads to the stable activity of the supported vanadium–antimony oxide catalyst for the dehydrogenation of ethylbenzene into styrene in the presence of carbon dioxide as oxidant. Correlation between catalytic performance and surface acidity has been found.

Phosphorus poisoning of molybdenum sulfide hydrodesulfurization catalysts supported on carbon and alumina

This work shows that carbon dioxide, which is a main contributor to the global warming effect, could be utilized as a selective oxidant in the oxidative dehydrogenation of ethylbenzene over alumina-supported vanadium oxide catalysts. The modification of the catalytically active vanadium oxide component with appropriate amounts of antimony oxide led to more stable catalytic performance along with a higher styrene yield (76%) at high styrene selectivity (>95%). The improved catalytic behavior was attributable to the enhanced redox properties of the active V-sites.

The production of toxic shock syndrome toxin 1 (TSST-1) by Staphylococcus aureus MN8 exposed to a range of oxygen concentrations (0 to 21% [vol/vol]) was examined in batch and thin-film cultures. The response of S. aureus to this range of oxygen concentrations was studied in the absence and in the presence of 7% (vol/vol) carbon dioxide. In the absence of carbon dioxide, TSST-1 production in batch cultures increased from negligible levels in the presence of oxygen concentrations of 1% or less to 500 ng/ml in the presence of 2% oxygen and then decreased to 70 ng/ml or less in the presence of oxygen concentrations of 6% and higher. In the presence of carbon dioxide, however, toxin production increased from negligible levels in the presence of 1% oxygen to 1,900 ng/ml in the presence of 21% oxygen. In thin-film cultures, TSST-1 production increased from nearly undetectable levels under anaerobic conditions to 1 and 10 microg/ml under 21% oxygen in the absence and presence of carbon dioxide, respectively. This study demonstrates the controlling effects of both oxygen and carbon dioxide on TSST-1 production.

Mixed metal oxides are important industrial catalysts for the selective oxidation and ammoxidation of aromatics and alkenes and often contain Sb oxides as a component. For the preparation of a catalytically relevant system on the basis of monolayer-type catalysts, an alternative route as compared to the conventional impregnation was chosen by milling the dry compounds in a planetary mill. To get a closer insight into the spreading and oxidation properties of antimony oxide on titania, only the binary oxidic compounds Sb oxide and TiO2 as support were investigated in the present study. Photoelectron spectroscopy (XPS) investigations for surface analysis and X-ray absorption spectroscopy (XANES) for bulk phase analysis were applied. The various Sb oxides (Sb2O3, Sb2O4, and Sb2O5) show totally different spreading behavior. Only with the Sb(III) oxide on titania a significant increase of dispersion was detectable by means of XPS and temperature programmed reduction (TPR). The temperature of oxidation of the supported Sb(III) oxide in air was 100 °C lower as compared to the bulk phase oxidation. The final formula after oxidation of Sb(III) oxide can be calculated from XANES results as Sb6O13 and does not end up at a stoichiometry of Sb2O4.

Evaluation of the Role of the Metal–Support Interfacial Centers in the Dry Reforming of Methane on Alumina-Supported Rhodium Catalysts

The effectiveness of alumina-supported noble metal catalysts for the destructive oxidation of organic pollutants in effluent from a softwood kraft pulp mill was evaluated in a slurry reactor at 463 K and an oxygen pressure of 1.5 MPa. The effects of catalyst preparation procedures, such as metal loading, calcination, or reduction treatment on the catalytic activities, were also tested. Alumina-supported palladium catalysts were found to be more effective than supported manganese, iron, or platinum catalysts. The rate of oxidation over Pd/alumina catalyst was significantly higher than that of the uncatalyzed reaction. Adding Ce on the alumina support was found to promote the activity of alumina-supported Pt catalyst but inhibit the activity of alumina-supported Pd catalyst. The reaction mechanisms for the catalytic wet oxidation process and the roles of Ce on catalytic activity for destructive oxidation of organic pollutants in wastewater are discussed.

A series of bulk oxides (Sb2O3, Sb2O4, VSbO4, and V2O5) and alumina-supported oxides (Sb−O, V−O, and Sb−V−O) were synthesized by conventional methods. The resulting catalysts were characterized with XRD, BET, Raman, and CH3OH-temperature programmed surface reaction (TPSR) spectroscopy. XRD and Raman spectroscopy confirmed that the bulk oxides are present as crystalline phases and the alumina-supported oxides consisted of two-dimensional surface metal oxide species on the alumina support. In the case of alumina-supported Sb−V−O, VSbO4 nanoparticles were formed from the solid-state reaction between the two oxides. CH3OH-TPSR spectroscopy was employed to determine the number (Ns) and chemical nature of active surface sites (redox and acidic) present in the formed catalysts. The bulk and alumina-supported antimonates were found to contain very few active surface redox and acid sites. In contrast, the bulk and alumina-supported vanadium oxides possess a significant number of surface redox sites with a minor amount of surface acid sites. Catalysts that possess both antimonates and vanadium oxides, however, were found to exhibit enhanced redox activity from promotion of the redox surface Vx sites by the antimonates. The series of bulk and alumina-supported catalysts was examined for their performance for the selective ammoxidation of propane to acrylonitrile. Only the catalysts containing both vanadium oxide and antimonates were found active and selective for acrylonitrile formation. The enhanced performance of these catalysts is related to formation of crystalline VSbO4 phases that promote the surface vanadia redox sites.

Catalytic Reforming of Biogas for Syngas Production McKenzie Primerano Kohn Biogas is a mixture of methane and carbon dioxide produced from the anaerobic microbial digestion of biomass. It is an inexpensive, local source of energy but is usually wasted because the CO2 content dilutes the quality of the fuel. Dry and auto-thermal reforming are catalytic methods that convert both the CH4 and CO2 into H2 and CO, or syngas, a valuable product that can be used to produce liquid fuels, provide H2 for fuel cells, or improve the combustion of biogas. A Rh/γAl2O3 catalyst is successful in dry reforming biogas to syngas without deactivation from carbon formation at CH4/CO2 ratios of one or lower. In CH4 rich mixtures, auto-thermal reforming (ATR) is effective because it provides additional oxidant that eliminates carbon formation and combusts a portion of the CH4 in-situ to provide the heat needed for the endothermic reforming reactions. In addition to CH4 and CO2, biogas also contains chlorocarbons that are potential catalyst poisons. Chlorocarbons are unique to biogas and bio-derived fuels due to the natural presence of chlorinated compounds in organic material that are released during decomposition or thermal treatment. Despite their presence in biogas in 10-50ppm concentrations, the effect of chlorocarbons on the dry reforming reaction has not been extensively studied. This work investigated the effect of CH3Cl in particular on the activity and selectivity of CH4 dry and autothermal reforming using a Rh/γAl2O3 catalyst. It was determined that CH3Cl introduction into the reforming reaction deposits chloride on the alumina catalyst support, which increases the surface acidity, poisons the water-gas shift reactions by replacing basic hydroxyl groups, and poisons the dry reforming reaction by reducing hydrogen mobility and the affinity of CO2 for the alumina support. CH3Cl also likely competes and reacts preferentially over CH4 for dry reforming sites. In CO2 rich environments, the reverse water gas shift reaction is poisoned, resulting in an increase of the H2/CO ratio, while in H2O rich environments, the forward water gas shift reaction is poisoned, resulting in a decrease of the H2/CO ratio. With 50 ppm addition of CH3Cl into a dry reforming reaction, the H2/CO ratio increases by 53% at a relatively low temperature of 350°C and increases by only 3% at 700°C. The poisoning of the water gas shift and dry reforming reactions, and the resulting changes in product selectivity and dry reforming activity, are completely reversible upon removal of CH3Cl from the feed. Therefore, the amount of chlorocarbon expected in a biogas mixture, between 1050ppm, is not particularly harmful for the 4% Rh/γAl2O3 catalyst. The degree of chloride poisoning is directly proportional to CH3Cl concentration and inversely proportional to H2O concentration and temperature. Therefore, O2 or air co-feeding minimizes chloride poisoning because it produces H2O and additional heat from the CH4 combustion reaction, both of which decrease chloride poisoning. Auto-thermal reforming is therefore more effective than dry reforming biogas because it keeps the Rh/γAl2O3 catalyst clean of carbon and chloride deposition, thereby maintaining the activity and selectivity of the catalyst for conversion of biogas into syngas.

Optimal biodiesel-additive synthesis under infrared excitation using pork bone supported-Sb catalyst: Engine performance and emission analyses

Antimony oxide dispersed on Ti02 was characterized using FTIR, Raman, and Auger spectroscopies as well as XRD. They indicate that the electronic environment about Sb is perturbed at low concentration suggesting that the structure of Sb oxide on TiOr is somewhat distorted as compared to Sb60t3. The oxidation of labeled propene such as CHr==CH--CD,, ‘%ZHFCH-CH~, and cisCHD==CD-CH, was examined on Sb,O,, and Sb-Ti oxide catalysts. The results indicate that the first hydrogen abstraction is rate determining and that there is little or no isotope effect in the second hydrogen abstraction over Sb and Sb-Ti oxide catalysts. The oxidation kinetics was discussed on the basis of a modified redox mechanism. The reduction step was promoted by a factor of ca. 50 over Sb oxide dispersed on TiOr as compared to that on unsupported Sb60,,. Rate promotion was mainly attributed to the increase in the amount of active sites for the reduction step.

This work presents that carbon dioxide, which is a main contributor to the global warming effect, could be utilized as a selective oxidant in the oxidative dehydrogenation of ethylbenzene. The dehydrogenation of ethylbenzene over alumina-supported vanadium-antimony oxide catalyst has been studied under different atmospheres such as inert nitrogen, steam, oxygen or carbon dioxide as diluent or oxidant. Among them, the addition of carbon dioxide gave the highest styrene yield (up to 82%) and styrene selectivity (up to 97%) along with stable activity. Carbon dioxide could play a beneficial role of a selective oxidant in the improvement of the catalytic behavior through the oxidative pathway.