无机铝改性Fe₃O₄微球的制备及催化苯甲醇选择性氧化

Synthesis of Al-Modified Fe₃O₄ Microspheres from Inorganic Aluminum Salts for Selective Oxidation of Benzyl Alcohol

摘要: 本文以常用无机铝盐为原料，采用溶剂热法制备了铝原位改性Fe₃O₄微球，并进行了X射线衍射、扫描电镜、能谱分析等表征。以H₂O₂选择性氧化苯甲醇制备高质量无氯苯甲醛为目标反应，考察了无机铝源的类型、铝盐颗粒大小、铝添加量、加入顺序等因素对无机铝原位改性Fe₃O₄微球催化性能的影响，结果表明无机铝改性可以明显提高Fe₃O₄微球的催化活性，以研磨过的Al₂(SO₄)₃•18H₂O为铝源、Fe/Al比为7.4、按铁盐–铝盐–碱源顺序加料为工艺制备的铝改性Fe₃O₄微球(记为Fe₃O₄-AS-1.0)的催化性能和重现性均最佳(对应苯甲醇的转化率和苯甲醛的产率分别为47.3%和41.2%；作为对比，在空白Fe₃O₄微球上的对应值分别为5.7%和5.6%)。Fe₃O₄-AS-1.0微球经乙二醇还原补铝再生后至少可以循环使用5次，催化性能没有明显损失(苯甲醇的转化率为44.2%~50.3%，苯甲醛的选择性80.0%~85.9%)。

Abstract: In this paper, aluminum-modified Fe₃O₄ microspheres were in situ prepared by solvothermal synthesis using inorganic aluminum salts as raw materials, and characterized by X-ray diffraction, scanning electron microscopy and X-ray energy-dispersive analysis. By taking selective oxidation of benzyl alcohol (BzOH) with H₂O₂ in H₂O to produce high-quality chlorine-free benzaldehyde (BzH) as target reaction, the effects of type, particle size, amount and addition sequence of inorganic aluminum sources on the catalytic performance of the Al-modified Fe₃O₄ (Al-Fe₃O₄) microspheres were investigated. The results showed that the modification by inorganic aluminum significantly improved the catalytic activity of Fe₃O₄ microspheres. Under optimized synthesis conditions, that is, use ground Al₂(SO₄)₃∙18H₂O as Al source with the Fe/Al ratio of 7.4 and add raw materials in the order of ferric salt-aluminum salt-alkali, the obtained Al-Fe₃O₄ microspheres (Fe₃O₄-AS-1.0) had the best catalytic performance and reproducibility (BzOH conversion: 47.3%; BzH yield: 41.2%; for comparison, the corresponding values on blank Fe₃O₄ microspheres were 5.7% and 5.6%). Fe₃O₄-AS-1.0 microspheres can be regenerated by reduction-alumination in ethylene glycol and re-used at least for 5 times with stable catalytic performance (BzOH conversion: 44.2%~50.3%, BzH selectivity: 80.0%~85.9%).