Catalytic Synthesis Of Propylene Glycol Monoethyl Ether Over Hydrotalcite-like Compounds

Hydrotalcite-like compounds (HT1cs) can be described as positively charged hydroxide layers with the interlamellar space being occupied by anions and water, and they have been widely studied as catalyst and catalyst precursor.In this thesis, series of Mg-Al and Cu-Cr hydrotalcites were prepared by coprecipitation method and characterized by means of XRD, thermal analysis and CO2-TPD. The reaction for the synthesis of propylene glycol monoethyl ether with ethanol and propylene oxide was carried out in a pressure fixed-bed reactor in the presence of hydrotalcites and calcined hydrotalcites as solid-base catalysts. The effect of calcination temperature, anion exchange as well as the chemical composition on the catalytic performance was studied. The relationship between the activity and the basicity of the catalysts was also studied.The results showed that the home-made hydrotalcites catalysts all had the typical hydrotalcite structure. The Cu-Cr hydrotalcites had better catalytic activity than the Mg-Al hydrotalcites. After the calcination, the calcined Mg-Al hydrotalcites exhibited excellent activity for the synthesis of propylene glycol monoethyl ether. The strength and quantity of the basicity center were enhanced with the increasing of the calcination temperature from 350℃to 550℃, the performance of the catalyst was also significantly improved, but the further raising of calcination temperature caused the decrease of basicity and catalytic activity.According to the evaluation results, we found that the sample named as MA2-550 (Mg/Al molar ratio 2, calcined at 550℃) was the most active catalyst with propylene oxide conversion 98.88%, propylene glycol monoethyl ether selectivity 98.20%, and 1-ethoxy-2-propanol selectivity 79.50%.