Ru@G-CS催化剂的制备及在对苯二甲酸二甲酯加氢反应中的应用

Preparation and application in the hydrogenation of dimethyl terephthalate of Ru@G-CS catalyst

采用一步热解法制备了一系列氮掺杂石墨烯包覆的Ru基催化剂(Ru@G-CS),并将该催化剂用于对苯二甲酸二甲酯(DMT)加氢制备1,4-环己烷二甲酸二甲酯(DMCD)的反应中。利用粉末X射线衍射、拉曼光谱、N2吸附-脱附、X射线光电子能谱、扫描电子显微镜和透射电子显微镜对催化剂的组成、结构和表面形貌进行了表征。实验发现:Ru@G-CS(1∶4)催化剂具有最高的活性和优异的稳定性,在160℃、2.5 MPa、mDMT/mRu=833的条件下,反应4 h后DMT的转化率可达100%,DMCD的选择性高于98.5%;且该催化剂的活性经10次循环使用后未见明显下降。表征结果表明,氮掺杂石墨烯骨架中的氮原子可以促进Ru的分散,而且与负载的Ru之间存在较强的相互作用,这种电子-结构的协同效应可能是Ru@G-CS(1∶4)催化剂表现出优异的活性和稳定性的主要原因。

s:A series of nitrogen-doped graphene-coated Ru-based catalysts(Ru@G-CS)were prepared using glucose,melamine,and RuCl_(3) as raw materials in a facile one-step pyrolysis method at 700℃with a varied mass ratio of glucose/melamine in feed.The composition,structure,and surface morphology of these catalysts were characterized with powder X-ray diffraction,Raman spectroscopy,N_(2) adsorption-desorption,X-ray photoelectron spectroscopy,scanning electron microscope,and transmission electron microscope.Characterization results showed that nitrogen in the graphene skeleton can promote the dispersion of Ru,and there was also a strong interaction between nitrogen and loaded Ru.Ru@G-CS(1∶4)catalyst(with the mass ratio of glucose/melamine in feed was 1∶4)possesses the highest surface area(429 m^(2)·g^(-1)),biggest pore volume(0.45 cm^(3)·g^(-1))and highly dispersed Ru particles(about 1 nm)that encapsulated in 1-2 layered graphene film.At the same time,the detected w_(Ru)^(0)/w_(Ru)^(4+)(73.6/26.4),I_(D)/I_(G)(1.30)and I_(2D)/I_(G)(0.32)reached their maximum in Ru@G-CS(1∶4).These catalysts were tested in dimethyl terephthalate(DMT)hydrogenation to 1,4-cyclohexane dimethyl dicarboxylate(DMCD)under mild conditions and compared with those traditional carriers(HZSM-5,Al_(2)O_(3),MgO,ZnO)supported Ru catalysts.Ru@G-CS(1∶4)exhibited high activity and stability at 160℃,2.5 MPa H_(2),m_(DMT)/m_(Ru)=833,the detected conversion of DMT reached 100%and the selectivity of DMCD remained higher than 98.5%within 4 h.The calculated turnover frequency of each Ru was 233.4 h-1.More importantly,Ru@G-CS(1∶4)could maintain its performance at least in 10 cycles.It was concluded that the electronstructure synergistic effect might be the main reason for the excellent activity and stability of Ru@G-CS(1∶4).