类水滑石衍生酸-碱复合氧化物催化尿素醇解合成碳酸二乙酯OA

A series of composite oxides with distinct acidic-basic properties were prepared via co-precipitation followed by the hydrothermal method using hydrotalcite-like compounds as precursors.Then,they were characterized by XRD,SEM,N2 adsorption-desorption,NH3/CO2-TPD techniques and their catalytic performance on urea and ethanol to synthesize diethyl carbonate(DEC)was evaluated.Experimental results show that as typical mesoporous catalysts,the composite oxides are relatively high in pore volume and specific surface area.The DEC yield and selectivity were highly affected by the matching way of metal ions.Among the catalysts,ZnAl-O has well-balanced acidic-basic property and gives the best catalytic performance with a DEC yield of 61.2 mmol/g at 190℃.The activity for the metal composite oxides to convert ethanol to ethoxy anion depends on the number of basic sites,while the activity for activated urea to transform into isocyanate species relies on the number of acidic sites.However,excessive acidic sites can cause catalyst poisoning,while excessive strong acidic sites can lead to severe side reactions that consume DEC.Thus,the acidic-basic synergism is required for the synthesis of DEC from urea and ethanol catalyzed by metal composite oxides.