摘要
以UiO-66为前体,在N2气氛下焙烧制备了ZrO2@C,以其为载体,利用浸渍法制备了Pd/ZrO2@C催化剂.以Pd/ZrO2@C+SO42-/ZrO2为催化剂,对以甲酸(FA)为氢源、硝基苯(NB)转移加氢合成对氨基苯酚(PAP)的反应进行了研究.通过表征发现,Pd/ZrO2@C载体中的ZrO2为四方相ZrO2,包埋在无定形C中.随着ZrO2@C在空气中焙烧温度的升高和焙烧时间的增加,其C含量和比表面积随之下降,同时Pd颗粒尺寸变大.Pd/ZrO2@C催化剂中Pd以Pd0和Pd2+两种形式存在,且随着C含量的减少,Pd0含量增加,Pd2+含量减少;当Pd0含量明显高于Pd2+,其对PAP的选择性明显下降.在140℃、反应6h的条件下,Pd/ZrO2@C-200-4+SO42-/ZrO2具有较好的催化性能,NB转化率为63.7%,PAP选择性为42.3%.
Abstract
With UiO-66 as the precursor,ZrO2@C was prepared by calcination in N2 atmosphere.Then,Pd/ZrO2@C was prepared by impregnation method.In this paper,the catalytic transfer hydrogenation of nitrobenzene(NB)to p-aminophenol(PAP)over Pd/ZrO2@C+SO42-/ZrO2 was studied with formic acid(FA)as hydrogen source.Characterization results showed that tetragonal ZrO2 was present in ZrO2@C and was embedded in amorphous C.With the increase of calcination temperature and time in the air,the C content and specific surface area of ZrO2@C decreased accordingly,while the Pd particle size became larger.Pd in the Pd/ZrO2@C catalyst was in the form of Pd0 and Pd2+.The content of Pd2+decreased with C content,While the content of Pd0 increased.When the content of Pd0 was higher than that of Pd2+,PAP selectivity decreased obviously.Pd/ZrO2@C-200-4+SO42-/ZrO2 exhibited good catalytic activity at 140℃for 6h.The conversion of NB was 63.7%and the selectivity of PAP was 42.3%.
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