钼系加氢精制催化剂中助剂镍的存在形态

STUDY ON THE EXISTING STATES OF Ni IN Mo-Ni/γ-Al_2O_3 CATALYSTS

利用TPMS、XRD、TEM等手段研究了分浸法制备的镍铝系催化剂的磁化率及物相结构。结果表明,镍钼系催化剂中,氧化铝同氧化镍存在强相互作用,形成了大量的xNiO·MoO_3·yH_2O结构和少量的α-NiMoO_4结构。还原磁化曲线呈现顺磁性。催化剂还原后未见单独的氧化镍晶粒存在,当镍钼催化剂充分硫化后,粒径迅速下降,成为高度分散体系,并未发现单独的硫化镍晶粒,显示了氧化物催化剂和硫化物催化剂的结构继承性。由此,提出了可能的硫化机理和助剂镍的活化模型。

The existing states of Ni in Mo-Ni/γ-Al_2O_3 catalysts prepared by stepwise impregnation method have been studied by means of TPMS,XRD and TEM.The results indicate that strong interaction happens when Ni^(2+)is introduced into the Mo/γ-Al_2O_3 catalysts.Structures such as xNiO·MoO_3·yH_2O and α-NiMoO_4 were found in the Mo-Ni/γ-Al_2O_3 catalysts but no individual NiO and MoO_3 praticles.The reduction-suscep-tibility curve of the catalysts shows paramagnetism.Such a phenomenon can be attributed to that the highly dispersed NiO reacts strongly with MoO_3,even in its reduced state.The average particle diameter of the sulfideform catalysts decreases abruptly after the catalysts have been sufficiently sulfurized.No Ni_xS_y structure was observed in the sulfide-form catalysts.This shows the inheritance of structures between the oxied-form and sulfide-form catalysts.Therefrom,a possible sulfurizing model of MoNi/γ-Al_2O_3 catalysts and acitivation model of Ni has been suggested.