Brønsted acid generation of alumina-supported molybdenum oxide calcined at high temperatures: Characterization by acid-catalyzed reactions and spectroscopic methods

Promoting Li/MgO Catalyst with Molybdenum Oxide for Oxidative Conversion of n-Hexane

In this work, molybdena-promoted Li/MgO is studied as a catalyst for the oxidative conversion of n-hexane. The structure of the catalysts is investigated with X-ray Diffraction (XRD) and Raman spectroscopy. The MoO3/Li/MgO catalyst contains three types of molybdena-containing species, the presence of which depend on molybdena loading. At low Mo/Li ratios (i) isolated dispersed [MoO4]2− anionic species are observed. At high Mo/Li ratios, the formation of crystalline lithium molybdate phases such as (ii) monomeric Li2MoO4 and tentatively (iii) polymeric Li2Mo4O13 are concluded. The presence of these lithium molybdates diminishes the formation of Li2CO3 in the catalyst. Subsequently, the catalyst maintains high surface area and stability with time-on-stream during oxidative conversion. Molybdena loading as low as 0.5 wt % is sufficient to induce these improvements, maintaining the non-redox characteristics of the catalyst, whereas higher loadings enhance deep oxidation and oxidative dehydrogenation reactions. Promoting a Li/MgO catalyst with 0.5 wt % MoO3 is thus efficient for selective conversion of n-hexane to alkenes, giving alkene yield up to 24% as well as good stability.

Catalytic Performance of Bulk and Al2O3-Supported Molybdenum Oxide for the Production of Biodiesel from Oil with High Free Fatty Acids Content

Non-edible vegetable oils are characterized by high contents of free fatty acids (FFAs) that prevent from using the conventional basic catalysts for the production of biodiesel. In this work, solid acid catalysts are used for the simultaneous esterification and transesterification with methanol of the FFAs and triglycerides contained in sunflower oil acidified with oleic acid. Molybdenum oxide (MoO3), which has been seldom considered as a catalyst for the production of biodiesel, was used in bulk and alumina-supported forms. Results showed that bulk MoO3 is very active for both transesterification and esterification reactions, but it suffered from severe molybdenum leaching in the reaction medium. When supported on Al2O3, the MoO3 performance improved in terms of active phase utilization and stability though molybdenum leaching remained significant. The improvement of catalytic performance was ascribed to the establishment of MoO3-Al2O3 interactions that favored the anchorage of molybdenum to the support and the formation of new strong acidic centers, although this effect was offset by a decrease of specific surface area. It is concluded that the development of stable catalysts based on MoO3 offers an attractive route for the valorization of oils with high FFAs content.

Acidic nanomaterials (TiO2, ZrO2, and Al2O3) are coke storage components that reduce the deactivation of the Pt–Sn/γ-Al2O3 catalyst in propane dehydrogenation

Pt–Sn/γ-Al₂O₃ catalysts were physically mixed with various nanostructured metal oxides (TiO₂, ZrO₂, and Al₂O₃) and investigated as catalysts for propane dehydrogenation at 550 °C and atmospheric pressure.

Effect of perimeter interface length between 2D WO3 monolayer domain and γ-Al2O3 on selective hydrogenolysis of glycerol to 1,3-propanediol

The perimeter interface between WO₃ and γ-Al₂O₃ was found to play an important role in selective hydrogenolysis of glycerol to 1,3-propanediol.

Second-generation hexavalent molybdenum oxo-amidinate precursors for atomic layer deposition

The synthesis and characterization of molybdenum oxo-amidinate ALD precursors MoO₂(R₂AMD)₂[AMD =N,N′-di-R-acetamidinate; R = Cy (2; cyclohexyl) andⁱPr (3)] is reported.

Effect of Mo-Doped Mesoporous Al-SSP Catalysts for the Catalytic Dehydration of Ethanol to Ethylene

The catalytic dehydration of ethanol to ethylene over the mesoporous Al-SSP and Mo-doped Al-SSP catalysts was investigated. The Al-SSP catalyst was first synthesized by the modified sol-gel method and then doped with Mo by impregnation to obtain 1% Mo/Al-SSP and 5% Mo/Al-SSP catalysts (1 and 5 wt% of Mo). The final catalysts were characterized using various techniques such as XRD, N2physisorption, SEM/EDX, TEM, and NH3-TPD. The catalytic activity for all catalysts in gas-phase ethanol dehydration reaction was determined at temperature range of 200°C to 400°C. It was found that the most crucial factor influencing the catalytic activities appears to be the acidity. The acid property of catalysts depended on the amount of Mo loading. Increased Mo loading in Al-SSP resulted in increased weak acid sites, which enhanced the catalytic activity. Besides acidity, the high concentration of Al at surface of catalyst is also essential to obtain high activity. Based on the results, the most suitable catalyst in this study is 1% Mo/Al-SSP catalyst, which can produce ethylene yield of ca. 90% at 300°C with slight amounts of diethyl ether (DEE) and acetaldehyde.

Role of Cu, Ni and Co metals in the acidic and redox properties of Mo catalysts supported on Al2O3 spheres for glycerol conversion

Promoters play an important role in the acidity and redox properties of Mo oxide catalysts supported on alumina spheres, and the catalytic performance reveals a potential effect between Cu and Mo oxides reduced partially, which improves the allyl alcohol selectivity.

Genesis of a bi-functional acid–base site on a Cr-supported layered double hydroxide catalyst surface for one-pot synthesis of furfurals from xylose with a solid acid catalyst

The cross boundary between Cr³⁺ oxide and Mg–Al LDH generates highly active bi-functional acid–base sites for xylose isomerization.

The effects of the Mo–Sn contact interface on the oxidation reaction of dimethyl ether to methyl formate at a low reaction temperature

With increasing degrees of Mo–Sn interface contact, the molar ratio of methyl formate (MF) to methanol (MeOH) and formaldehyde (FA) was found to linearly increase simultaneously.

Metathesis of 1-Butene to Propene over Mo/Al2O3@SBA-15: Influence of Alumina Introduction Methods on Catalytic Performance

A series of Mo-based catalysts for 1-butene metathesis to propene were prepared by supporting Mo species on SBA-15 premodified with alumina. The effects of the method of introduction of the alumina guest to the host SBA-15 on the location of the Mo species and the corresponding metathesis activity were studied. As revealed by N2 adsorption isotherms and TEM results, well-dispersed alumina was formed on the pore walls of SBA-15 if the ammonia/water vapor induced hydrolysis (NIH) method was employed. The Mo species preferentially interacted with alumina instead of SBA-15, as evidenced by X-ray photoelectron spectroscopy, time-of-flight secondary-ion mass spectrometry, and IR spectroscopy of adsorbed pyridine. Furthermore, new Brønsted acid sites favorable for the dispersion of the Mo species and low-temperature metathesis activity were generated as a result of the effective synergy between the alumina and SBA-15. The Mo/Al2O3@SBA-15 catalyst prepared by the NIH method showed higher metathesis activity and stability under the conditions of 120 °C, 0.1 MPa, and 1.5 h(-1) than catalysts prepared by other methods.

Molybdenum oxide/γ-alumina: an efficient solid acid catalyst for the synthesis of nopol by Prins reaction

Prins condensation of β-pinene with paraformaldehyde was carried out over MoO_x/γ-Al₂O₃ catalyst in liquid phase.