Aldol Condensation Of Aldehydes And Ketones Catalyzed By Solid Catalysts

Aldol reaction is an important response to the formation of one C-C bond, the traditional catalytic reaction process is carried out in acid or alkaline aqueous solution. However, it will lead to many side reactions, resulting in lower reaction selectivity, corrosion of equipment, and producing large amounts of industrial waste water. In post-processing it will also lead to the loss and waste of raw materials and products, et al. Therefore, in this article, from the perspective of green chemical engineering, and in order to design and develop highly selective, recyclable catalyst system, we mainly studied the cross aldol condensation reaction of cyclopentanone and n-valeraldehyde producing 2-pentylidene cyclopentanone under various process conditions by two types of catalyst system:Mg-Al oxides and ion exchange resin.1. Mg-Al hydrotalcite with Mg-Al molar ratios of 2:1 and 3:1 was prepared by coprecipitation, the products were characterized by infrared spectroscopy (FT-IR), X-diffraction (XRD), thermogravimetry-differential thermal analysis (TG-DTA), elemental analysis (ICP), etal. MgO-Al2O3 LDO was obtained after the calcination of the hydrotalcite precursor. Then aldol condensation of cyclopentanone and n-valeraldehyde was studied by the catalyst of LDO, gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) were used for qualitative and quantitative analysis. The optimal conditions are as follows:Mg-Al molar ratio 3:1, calcination temperature 500℃, ketone/aldehyde molar ratio 3:1, the amount of catalyst 8 w%, under the reflux (about 122℃) for 4 hours. And the percentage of 2-pentyledene cyclopentanone in the total products is 85.2%, conversion of n-valeraldehyde is 99.0%. The catalytic activity is higher than MgO and Al2O3, indicats that the acid-base cooperative catalysis had better effects in aldol condensation.2. In the catalytic system of weak base anion exchange resin, various factors containing the selection of catalyst, pretreatment, catalyst amount, reaction temperature, reaction time, ketone aldehyde ratio, feeding methods, metal coordination and so on, were all discussed on the conversion of n-valeraldehyde and the yield of main product 2-pentyledene cyclopentanone. According to the results, we developed a type of heterogeneous catalytic system that contains amine weak base anion exchange resin, acidic compounds and metal ions, and the catalyst can be recycled after parting of the organic phase. The results showed that the catalyst system had satisfactory results in cross-aldol condensation of cyclopentanone and n-valeraldehyde, the yield of main product 2-pentylidene cyclopentanone can be reached to more than 90%.