One-step aldol condensation of ethyl acetate with formaldehyde over Ce and P modified cesium supported alumina catalyst

Roles of ethanol and Si–OH in the aldol condensation of ethyl acetate over a Cs/SBA-15 catalyst

The negative effect of ethanol dehydrogenation and role of Si–OH are explored in the aldol condensation of ethyl acetate.

An Unusually Acidic and Thermally Stable Cesium Titanate Cs xTi2- yM yO4 ( x = 0.67 or 0.70; M = vacancy or Zn)

Proton-free, alkali-containing layered metal oxides are thermally stable compared to their protonic counterparts, potentially allowing catalysis by Lewis acid sites at elevated temperatures. However, the Lewis acidic nature of these materials has not been well explored, as alkali ions are generally considered to promote basic but to suppress acidic character. Here, we report a rare example of an unusually acidic cesium-containing oxide Cs _xTi_{2- y}M _yO₄ ( x = 0.67 or 0.70; M = Ti vacancy □ or Zn). These lepidocrocite-type microcrystals desorbed NH₃ at >400 °C with a total acidity of ≲410 μmol g^-1 at a specific surface area of only 5 m² g^-1, without the need for lengthy proton-ion exchange, pillaring, delamination, or restacking. The soft and easily polarized Cs⁺ ion essentially drives the formation of the Lewis acidic site on the surfaces as suggested by IR of sorbed pyridine. The two-dimensional layered structure was preserved after the oxide was employed in the ethanol conversion at 380 °C, the temperature at which the protonic form could have converted to anatase. The structure was also retained after the NH₃ temperature-programmed desorption measurement up to 700 °C. The production of ethylene from ethanol, well-known to occur over acid sites, unambiguously confirmed the acidic nature of this cesium titanate.

Effect of Mg as Impurity on the Structure of Mesoporous γ-Al203: Efficiency as Catalytic Support in HDS of DBT

This work shows the study of two alumina materials synthesized from aluminum sulfate with different purity by hydrolysis-precipitation route. The main difference between the aluminum salt precursors was the lower cost of one of them which was due to the higher percentage of magnesium species as impurity. Both materials showed different mesoporous structure nano-fibrillar. The physic-chemical properties of these materials were studied by several characterization techniques as XRD, XRF, BET, 27Al MAS NMR, Pyridine adsorption FT-IR, FE-SEM/EDX, TEM and XPS. Furthermore, these materials were used as supports in the formulations of NiMo-based catalysts which were obtained by impregnation by the incipient wetness method of Ni and Mo salts in 3.3 and 15 wt. % respectively. The two NiMo/γ-Al2O3 sulfide catalysts were evaluated as catalysts in the reaction of hydrodesulphurization (HDS) of dibenzothiophene (DBT), using a high-pressure batch reactor at 350 °C and 3.1 MPa and time reaction of 5 h−1. The NiMo/γ-Al2O3 catalyst prepared by aluminum sulfate of low purity and lower cost exhibited the highest HDS efficiencies, 95 %, respectively, which were mainly ascribed to the presence of Mg (0.9 wt. %) as impurity.

Vapor phase aldol condensation of methyl acetate with formaldehyde over a Ba–La/Al2O3 catalyst: the stabilizing role of La and effect of acid–base properties

Vapor phase aldol condensation of methyl acetate with formaldehyde was studied over Ba–La/Al₂O₃ with different amounts of lanthanum catalysts.