A green process for chlorine-free benzaldehyde from the solvent-free oxidation of benzyl alcohol with molecular oxygen over a supported nano-size gold catalyst

Benzyl alcohol is oxidized selectively to benzaldehyde with high yield, with a little formation of benzylbenzoate, by molecular oxygen over a reusable nano-size gold catalyst supported on U3O8, MgO, Al2O3 or ZrO2 in the absence of any solvent

Steam and oxysteam reforming of methane to syngas over Co<SUB>x</SUB> Ni<SUB>1-x</SUB>O supported on MgO precoated SA-5205

Catalytic steam and oxysteam reforming of methane to syngas studied involves coupling of exothermic oxidative conversion and endothermic steam-reforming processes over Co<SUB>x</SUB> Ni<SUB>1-x</SUB> O (x = 0.0-0.5) supported on MgO precoated commercial low surface area (&lt;0.01 m<SUP>2</SUP> g<SUP>-1</SUP>) macroporous silica-alumina SA-5205 catalyst carrier. The influence of the Co/Ni ratio of the catalyst on its performance in steam and oxysteam reforming processes (at 800 and 850&#176;C) was studied. For the steam reforming process, the Co/Ni ratio influences strongly on the methane and steam conversion and CO selectivity and product H<SUB>2</SUB>/CO ratio, particularly at lower temperature. When the Co/Ni ratio is increased, the methane and H<SUB>2</SUB>O conversion and CO selectivity are decreased markedly. For the oxysteam reforming process, the influence of the Co/Ni ratio on the performance is smaller and depends on process conditions. When the Co/Ni is increased, the methane conversion passes through a maximum at the Co/Ni ratio of 0.17. The influence of the reaction temperature (800 and 850&#176;C) and CH<SUB>4</SUB>/O<SUB>2</SUB> and CH<SUB>4</SUB>/H<SUB>2</SUB>O ratios on the conversion, selectivity, H<SUB>2</SUB>/CO product ratio, and net reaction heat (&#916; H<SUB>r</SUB>) was studied in the oxysteam reforming (at space velocity of 47,000 cm<SUP>3</SUP>.g<SUP>-1</SUP>.h<SUP>-1</SUP>) over the catalyst with an optimum Co/Ni ratio (0.17) and a higher Co/Ni ratio (1.0). The oxysteam reforming process involves coupling the exothermic oxidative conversion of methane and the endothermic methane steam reforming reactions, making the process highly energy-efficient and nonhazardous. This process can be made thermoneutral, mildly exothermic, and mildly endothermic by manipulating process conditions

Oxidative coupling of methane over supported La<SUB>2</SUB>O<SUB>3</SUB> and La-promoted MgO catalysts: influence of catalyst-support interactions

Methane-to-C<SUB>2</SUB>-hydrocarbon conversion activity and selectivity (or yield) of MgO and La-promoted MgO catalysts in the oxidative coupling of methane and strong basicity of the catalysts are decreased appreciably when these catalysts are deposited on commonly used commercial low surface area porous catalyst carriers containing Al<SUB>2</SUB>O<SUB>3</SUB>, SiO<SUB>2</SUB>, SiC, or ZrO<SUB>2</SUB> + HfO<SUB>2</SUB> as the main components. The decrease in the strong basicity and catalytic activity/selectivity or yield is mostly due to strong chemical interactions between the active catalyst component (viz. MgO and La<SUB>2</SUB>O<SUB>3</SUB>) and the reactive components of the catalyst support (viz. Al<SUB>2</SUB>O<SUB>3</SUB> and SiO<SUB>2</SUB>), resulting in the formation of catalytically inactive binary metal oxides on the support surface. However, the influence of support on the activity/selectivity of La<SUB>2</SUB>O<SUB>3</SUB> is relatively very small, and also the chemical interactions of La<SUB>2</SUB>O<SUB>3</SUB> with the supports (except that containing a high concentration of SiO<SUB>2</SUB>) are almost absent. The catalyst-support interactions are thus found to be strongly dependent upon the nature (chemical composition) of both catalyst and support. For developing better supported catalysts for the oxidative coupling of methane, supported La<SUB>2</SUB>O<SUB>3</SUB> with some promoters shows high promise

Oxidative coupling of methane over a Sr-promoted La<SUB>2</SUB>O<SUB>3</SUB> catalyst supported on a low surface area porous catalyst carrier

Oxidative coupling of methane (OCM) to higher hydrocarbons over Sr-promoted La<SUB>2</SUB>O<SUB>3</SUB> supported on commercial low surface area porous catalyst carriers (containing mainly alumina and silica) at 800 and 850&#176;C and a space velocity of 102 000 cm<SUP>3</SUP>.g<SUP>-1</SUP>.h<SUP>-1</SUP> has been thoroughly investigated. Effects of support, catalyst particle size, linear gas velocity (at the same space velocity), Sr/La ratio, CH<SUB>4</SUB>/O<SUB>2</SUB> ratio in the feed, and catalyst dilution by inert solid particles on the conversion, yield, or selectivity and product ratios (C<SUB>2</SUB>H<SUB>4</SUB>/C<SUB>2</SUB>H<SUB>6</SUB> and CO/CO<SUB>2</SUB>) in the OCM process have been studied. The catalysts have been characterized for their basicity, acidity, and oxygen chemisorption by the TPD of CO<SUB>2</SUB>, ammonia, and oxygen, respectively, from 50 to 950&#176;C and also characterized for their surface area. The supported catalysts showed better performance than the unsupported one. The best OCM results (obtained over Sr-La<SUB>2</SUB>O<SUB>3</SUB>/SA-5205 with a Sr/La ratio of 0.3 at a space velocity of 102 000 cm<SUP>3</SUP>.g<SUP>-1</SUP>.h<SUP>-1</SUP>) are 30.1% CH<SUB>4</SUB> conversion with 65.6% selectivity for C<SUB>2+</SUB> (or 19.7% C<SUB>2+</SUB>-yield) at 800&#176;C (CH<SUB>4</SUB>/O<SUB>2</SUB> = 4.0) and 12.8% CH<SUB>4</SUB> conversion with 85.1% selectivity for C<SUB>2+</SUB> (or 10.9% C<SUB>2+</SUB>-yield) at 850&#176;C (CH<SUB>4</SUB>/O<SUB>2</SUB> = 16.0). The basicity is strongly influenced by the Sr/La ratio; the supported catalysts showed the best performance for their Sr/La ratio of about 0.3. The methane/O<SUB>2</SUB> ratio also showed a strong influence on the OCM process. However, the influence of linear gas velocity and particle size is found to be small; it results mainly from the temperature gradient in the catalyst. The catalyst dilution has little or no effect on the conversion and selectivity. However, it has beneficial effects for achieving a higher C<SUB>2</SUB>H<SUB>4</SUB>/C<SUB>2</SUB>H<SUB>6</SUB> ratio and also for reducing the hazardous nature of the OCM process because of the coupling of the exothermic oxidative conversion reactions and the endothermic thermal cracking reactions and also due to the increased heat transfer area

Low temperature complete combustion of dilute methane over Mn-doped ZrO<SUB>2</SUB> catalysts: factors influencing the reactivity of lattice oxygen and methane combustion activity of the catalyst

Complete combustion of methane (1.0 vol.% in air) over Mn-doped ZrO<SUB>2</SUB> catalysts with different Mn/Zr mole ratios (0-1.0) at different temperatures (400-600&#176;C) and space velocities (51,000-150,000 cm<SUP>3</SUP> g<SUP>-1</SUP> h<SUP>-1</SUP>) and also over Mn-impregnated ZrO<SUB>2</SUB> have been thoroughly investigated. Reactivity of the lattice oxygen of the catalysts was studied by temperature-programmed reduction (TPR) with H<SUB>2</SUB> and also by the temperature-programmed reaction of lattice oxygen with pure methane (TPRLOM), both from 100 to 600&#176;C. Such reactivity is drastically increased due to the doping of Mn in ZrO<SUB>2</SUB>, particularly when the resulting catalyst is in cubic form. The methane combustion activity of the catalyst is first increased, passes through a maximum and then decreases with increasing the Mn/Zr ratio from 0 to 1.0, the maximum activity was observed for the Mn/Zr ratio of about 0.25. Similar trends were also observed for the variation of the catalyst surface area, stabilization of ZrO<SUB>2</SUB> in its cubic form and also for the shift in the TPR peak (at higher temperatures) towards the lower temperature side, indicating higher reactivity and/or mobility of the lattice oxygen. However, when the calcination temperature of the Mn-doped ZrO<SUB>2</SUB> (cubic, Mn/Zr=0.25) is increased from 500 to 800&#176;C, its surface area is decreased continuously, but its methane combustion activity passed through a maximum at the calcination temperature of 600 &#176;C, its cubic form is also converted into a mixed monoclinic and cubic form at 800&#176;C

Influence of support on surface basicity and catalytic activity in oxidative coupling of methane of Li-MgO deposited on different commercial catalyst carriers

Deposition of Li-MgO catalyst on commonly used supports (containing SiO2, Al2O3, SiC, ZrO2, HfO2, etc.) causes a drastic reduction in the catalytic activity/selectivity for the oxidative methane coupling reaction and also in both the total and strong surface basicity. The decrease in the catalytic activity/selectivity and basicity is attributed to strong chemical interactions between the catalyst and support which occur during the high temperature (750&#176;C) calcination/pretreatment of the catalyst. The chemical interactions result in catalytically less active binary and ternary metal oxides containing Li and/or Mg, thus deactivating the Li-MgO catalyst by consuming its active components

Coupling of endothermic thermal cracking with exothermic oxidative dehydrogenation of ethane to ethylene using a diluted SrO/La<SUB>2</SUB>O<SUB>3</SUB> catalyst

The energy-efficient and safe conversion of ethane into ethylene is possible by simultaneous exothermic oxidative dehydrogenation and endothermic cracking of ethane in the presence of steam and limited amounts of O2, by using the thermally and hydrothermally stable supported catalyst SrO/La2O3/SA 5205 diluted with an inert support. Because the exothermic and endothermic reactions are coupled, this process requires only very little or no applied energy

Low-temperature complete combustion of methane over Mn-, Co-, and Fe-stabilized ZrO<SUB>2</SUB>

Activity comparable to that of noble metal catalysts is shown by the Mn-, Co-, or Fe-stabilized ZrO<SUB>2</SUB> catalysts for the low-temperature combustion of methane. The incorporation of the transition metal into the ZrO<SUB>2</SUB> bulk structure not only stabilizes the cubic (fluorite) modification, but also increases the reactivity of the lattice oxygen atoms drastically