配体对铈化合物催化苯甲醇氧化性能的影响

Effect of ligand on catalytic property of cerium compounds for benzyl alcohol oxidation

研究了桥联二酚铈、氯化铈、硝酸铈、三氟甲磺酸铈、硝酸铈铵五种铈化合物,在溴酸钠存在下催化苯甲醇氧化制备苯甲醛反应的性能。发现五种铈化合物均有催化活性,催化活性高低顺序为:三氟甲磺酸铈>硝酸铈>硝酸铈铵>氯化铈>桥联二酚铈。该顺序跟配体吸电子能力一致,意味着配体吸电子能力越强,越有利于提高铈配合物的催化氧化能力。当三氟甲磺酸铈用量为苯甲醇的5%(mol),80℃反应2.0 h,苯甲醇转化率为95.6%,苯甲醛产率达90.9%,反应选择性95.1%。

The oxidation reaction of benzyl alcohol to benzaldehyde catalyzed by bis(bridged bisphenolato)cerium,cerium trichloride,cerium nitrate,cerium trifluoromethanesulfonate and ammonium ceric nitrate were studied in the presence of sodium bromate.It was found that all the five cerium compounds showed catalytic activity,and the activity decreased in the order:cerium trifluoromethanesulfonate>cerium nitrate>ammonium ceric nitrate>cerium trichloride>bis(bridged bisphenolato)cerium.The order accorded with the decrease of electron-drawing ability of ligands,implying that the stronger the ligand’s electron-drawing ability,the better the catalytic oxidation property of cerium compound.When cerium trifluoromethanesulfonate was used as the catalyst and its dosage was 5%(mol)of benzyl alcohol,95.6% conversion of benzyl alcohol,90.9% yield of benzaldehyde and 95.1% selectivity were achieved at 80℃in 2 h.