镁铝复合氧化物催化剂的制备及催化丙酮缩合反应性能

Preparation of Mg-Al composite oxide catalyst and its catalytic performance in acetone condensation reaction

摘要:

以氨水为沉淀剂，硝酸镁、硝酸铝分别作为镁源和铝源，采用共沉淀法制备系列镁铝二元复合氧化物催化剂（MMO），通过XRD、XPS、TEM、EDS、BET表征了MMO的微观形貌和表面特征。将其用于丙酮缩合制备异佛尔酮的反应中，考察了n(Mg)∶n(Al)、反应温度、反应时间和催化剂用量对异佛尔酮收率的影响。结果表明，n(Mg)∶n(Al)＝2.5∶1制备的co-Mg2.5Al1-MMO-2表现出最佳的催化丙酮缩合制备异佛尔酮反应活性，在反应温度200 ℃，反应时间8 h，催化剂添加量为总质量的5.9%，异佛尔酮选择性可达47.27%，收率为40.74%。co-Mg2.5Al1-MMO-2具有介孔结构，为酸碱协同催化剂，其具有中等强度的碱性位点，强酸性位点占比（74.05%）较高，这些都有利于异佛尔酮的生成。此外，催化剂在放大条件下仍具有良好的催化性能，异佛尔酮选择性可达42.88%，收率为38.29%。

Abstract:

A series of Mg-Al binary composite oxide catalysts (MMO) were synthesized via the co-precipitation method using ammonia as the precipitant, magnesium nitrate as the magnesium source, and aluminum nitrate as the aluminum source. The microstructure and surface properties of MMO were characterized by XRD, XPS, TEM, EDS, and BET analysis. The effects of the Mg/Al molar ratio, reaction temperature, reaction time, and catalyst dosage on the yield of isophorone were systematically investigated. The results demonstrated that co-Mg2.5Al1-MMO-2, prepared with an Mg/Al molar ratio of 2.5:1, exhibited the highest catalytic activity for isophorone synthesis via acetone condensation. The optimal reaction conditions were determined to be: reaction temperature of 200 ℃, reaction time of 8 h, and a catalyst loading of 5.9%. Under these conditions, the selectivity of isophorone reached 47.27%, with a yield of 40.74%. co-Mg2.5Al1-MMO-2 possesses a mesoporous structure, functions as an acid-base synergistic catalyst, and contains medium-strength basic sites along with a high proportion of strong acidic sites (74.05%), which are beneficial for isophorone formation. Furthermore, the catalyst still has good catalytic properties under amplification conditions, with the selectivity of isophorone reaching 42.88% and the yield is 38.29%.