镁铝复合氧化物负载NaAlO2催化剂制备及其催化性能研究

以恒定pH共沉淀法制备的镁铝水滑石为前驱体,NaAlO₂为活性组分,在一定温度下焙烧得到镁铝复合金属氧化物负载铝酸钠催化剂。利用XRD、SEM、BET、CO₂-TPD、DSC-TG等手段对催化剂进行表征,发现通过高温焙烧可实现铝酸钠在镁铝复合金属氧化物表面的稳定分散。该催化剂可在温和反应条件下催化碳酸乙烯酯和甲醇酯交换反应合成碳酸二甲酯（DMC）和乙二醇（EG）,表现出高催化活性及对产物的高选择性。在醇酯物质的量比为10∶1、4 h、65 ℃条件下,DMC收率为74.8%,对DMC和EG的选择性均为100%。循环实验过程中,催化剂表现出较好的稳定性,使用5次后催化活性未见明显下降。该催化剂制备方法简单、成本低,催化剂易与产物分离,可多次重复使用,是一种低温高活性酯交换固体碱催化剂,具有一定的工业应用前景。

Synthesis of Mg-Al mixed metal oxide modified by NaAlO2 catalysts and its catalytic performance

Mg-Al mixed metal oxide modified by NaAlO₂ was prepared at a certain temperature with Mg-Al hydrotalcite that synthesized by constant pH co-precipitation method as precursor and sodium aluminate as the active component.The charac-terization of XRD,SEM,BET,CO₂-TPD and DSC-TG for the catalysts was carried out.It was found that the sodium aluminate prepared at high temperature was dispersed on the metal oxides stably.The catalyst can catalyze the transesterification of ethylene carbonate and methanol to synthesize dimethyl carbonate（DMC） and ethylene glycol（EG） under mild reaction con-ditions,showing high catalytic activity and high selectivity to the product.Under the conditions as follows：the amount-of-substance ratio of methanol to EC was 10∶1,4 h and 65 ℃,then the DMC yield was 74.8%,and the selectivity on DMC and EG both reached 100%.During the cycling experiment,the catalyst showed good stability and no obviously decrease of catalytic activity was observed after reused for five times.The preparation method of the catalyst is simple and cheap.The catalyst is easy to separated from the product and could be reused.It is an efficient transesterification catalyst for synthesis of dimethyl carbonate and glycol,which showing prospective in industrial applications.