Nano-cobalt materials play an important role in the hydrogenation of ethyl lactate to 1,2-PDO.Herein,Co3O4 nanomaterials with different morphologies were synthesized,which were further reduced under hydrogen atmosphere to form nano-cobalt.The TEM results indicated that nano-cobalt materials obtained from Co3O4 at a low temperature kept original morphologies.The TPR results showed that the Co3O4 nanoparticles reduced at a low temperature were easier to generate metal cobalt than Co3O4 nanorods.Hence,cobalt nanoparticles gave an excellent conversion for the hydrogenation of ethyl lactate while cobalt nanorods had no activity.Furthermore,the effect of reduction temperature of Co3O4 on the nano-cobalt crystal structures was investigated.XRD and TEM results showed that the hcp phase can be produced at a lower temperature.With increasing the reduction temperature,the transformation from hcp phase to fcc phase would take place.The effect of cobalt nanoparticles reduced at different temperature on the performance of hydrogenation of ethyl lactate was studied.Experiments proved that the cobalt nanoparticles had a positive effect on the hydrogenation performance till the reduction temperature increased to 300 ℃ with a 71％ conversion of ethyl lactate.However,when the reduction temperature increased continually,the conversion of ethyl lactate decreased.It indicated that the hcp phase was beneficial to the hydrogenation of ethyl lactate while the fcc phase hampered the hydrogenation of ethyl lactate.In addition,aggregation may also lower the catalytic activity above 300 ℃.%Co纳米材料是乳酸乙酯加氢制备1,2-丙二醇的重要催化剂.合成了不同形貌的Co3O4纳米材料,利用氢气热还原的方法制备了不同形貌的Co纳米粒子.TEM结果表明低温下还原不同形貌的Co3O4制备得到的Co纳米材料形貌保持不变;TPR结果表明颗粒状的纳米Co3O4比棒状的更易在低温下还原得到纳米Co.通过对乳酸乙酯加氢反应的测试表明,低温还原制备的Co纳米颗粒比纳米棒具有更高的加氢活性.此外,考察了Co3O4的还原温度对纳米Co颗粒中金属晶型的影响,XRD和TEM结果表明低温还原得到的Co纳米颗粒中先出现hcp晶型的金属Co,随着还原温度的升高,hcp晶型金属Co逐渐向fcc晶型转变.乳酸乙酯加氢反应结果表明,随着还原温度的增加,Co纳米颗粒的乳酸乙酯加氢转化率先增加后减小,在300℃时达到最大值71％,即低温下还原得到的hcp晶型有利于乳酸乙酯加氢,而高温下生成的fcc晶型不利于乳酸乙酯加氢,此外,高温下催化剂颗粒的聚集也可能造成乳酸乙酯加氢活性降低.
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