Influence Of La₂O₃/γ-Al2O3Catalysts On Initial Velocity Of Aldol Reaction And Adsorption Behavior Of Citral And Acetone

In our initial research, La2O3/γ-Al2O3catalyst was found good activity for aldol condensation reaction of citral and acetone. The relative literatures about the reaction rate of citral and acetone catalyzed by basic oxieds has been few. In order to explain some reaction rate questions about this reaction, we imagine to arrive it by studying adsorptive behave of reactive components citral and acetone on La2O3/γ-Al2O3catalysts. So, the initial rate of the reaction and some relative factors were studied. And adsorptive behavious of citral and acetone on La2O3/γ-Al2O3catalysts were researched in citral-EtOAc, acetone-EtOAc and citral-acetone-EtOAc solutions too. Some conclusions are drawn as following:1. The investigation on isothermal adsorption kinetics of citral and acetone on La2O3/γ-Al2O3catalyst indicated that adsorption kinetics of citral and acetone could be described by the pseudo-second-order model well at30℃respectively. And the isothermal adsorption behavious of citral and acetone fitted for the Langmuir model in30.0-65.0℃. The saturated adsorption capacity of citral and acetone increased with the rise of adsorption temperature at30.0-65.0℃. The adsorption heats were32.19kJ/mol and23.78kJ/mol respectively for citral and acetone.2. At same experiment conditions, the equilibrium adsorption capacity of citral and acetone are different on La2O3/γ-Al203catalyst. That of citral is higher than that of acetone at given temperature.3. Change of temperature and La2O3content on La2O3/γ-Al2O3catalysts showed sharply effect on equilibrium adsorption capacity of citral and acetone. For citral and acetone, the equilibrium adsorptive capacity and equilibrium adsorptive time drop greatly with temperature elevating. The equilibrium adsorptive capacity of citral and acetone rise with increase of La2O3content on La2O3/γ-Al2O3catalysts.4. The acetone/citral molar ratio, temperature and La2O3content on La2O3/γ-Al2O3catalysts were influence factors on initial rate of the condensation reaction. The initial rate of the reaction arrives the biggest (0.06696mmol/min) when acetone/citral molar ratio is4, La2O3content reaches to22.80wt.%and temperature arrives373.2K.5. IR spectra of the catalyst adsorbed citral and acetone respectively showed citral and acetone in adsorptive state occur chemical adsorption with active sites on catalyst by carbonyl group.6. The surface areas and pore volume of La2O3/γ-Al2O3catalysts drop with increase of La2O3content on La2O3/γ-Al2O3catalysts under preparation conditions. The XRD patters of those catalysts showed La2O3on y-Al2O3support was amorphous. No La2O3grain detected by XRD.