Aldol condensation of acetone over Mg–Al mixed oxides catalyst prepared by a citric acid route

Abstract

Mg-Al mixed oxides with different Mg/Al molar ratios were prepared by using a citric acid route and tested as catalysts for the gas phase self-aldol condensation of acetone to isophorone. The sample with Mg/Al ratio of 1.0 exhibits relatively high activity and stability, and its catalytic performance could be further improved by adding alkali promoter.

Heterogeneous Catalysts for the Guerbet Coupling of Alcohols

“…Aldolization has also been shown to be promoted by bifunctional acid−base materials. Examples of bifunctional solids include Y 3+ added to MgO, 91 Mg/Al mixed oxides, 39,41,70,92 amorphous aluminophosphate, 40 Cs/ZrO 2 , 93 and Mg/Zr mixed oxides. 94,95 The promotion of the reaction on bifunctional catalysts is thought in part to be the result of the stabilization of a surface intermediate through a Lewis acid interaction.…”

“…Aldolization has also been shown to be promoted by bifunctional acid–base materials. Examples of bifunctional solids include Y 3+ added to MgO, Mg/Al mixed oxides, ,,, amorphous aluminophosphate, Cs/ZrO 2 , and Mg/Zr mixed oxides. , The promotion of the reaction on bifunctional catalysts is thought in part to be the result of the stabilization of a surface intermediate through a Lewis acid interaction. This interaction also allows large networks of aldolization products to form at elevated temperatures, since a strong interaction between the oxygenated intermediates and the Lewis acid sites prevents desorption, especially when multiple functional groups exist in one molecule …”

Influence of the Precipitation Method on Acid–Base‐Catalyzed Reactions over Mg–Zr Mixed Oxides

“…As with transesterification, acid–base bifunctional materials appear to be more effective catalysts than traditional solid bases for aldol condensation 12. 13, 43 Some examples of acid–base bifunctional catalysts for aldol condensation include: Y/MgO,44 Mg‐Al mixed oxides,43, 45–47 amorphous aluminophosphate,13 Cs/ZrO 2 ,12 and Mg‐Zr mixed oxides catalysts 3. 9 In many of these studies, a goal of the preparation was to locate a Lewis acid center in proximity to a strong base site.…”

Kinetics of Isophorone Synthesis via Self‐Condensation of Supercritical Acetone

“…The selectivity of isophorone is less than 70 % and the reaction takes 15 min to 4 h 1, 6, 7. Besides, since more than 30 years scientists studied the vapor‐phase aldol condensation of acetone over heterogeneous solid base catalysts 8–16. In contrast, this vapor‐phase method is a greener process with advantages of higher selectivity of isophorone and no alkaline wastewater.…”