摘要
V_2O_5-TiO_2催化剂在 Cs^+(Cs/PVT=0.012)和 P_2O_5协同作用下,V_2O_5晶相 V=O 键的特征伸缩振动1020cm^(-1)明显地位移到1005cm^(-1),与此同时,V-O-V 键的特征伸缩振动由879cm^(-1)红移到859cm^(-1)。说明一部分 V_2O_5在 TiO_2表面上转为非晶相,V=O 键长由1.58伸长到1.61。NH_3-TPD 谱与 NH_3-IR 谱的结果表明,Cs^+与 P_2O_5的协同作用还显著地加强了催化剂表面的 B 酸和 L 酸的强度。但 Cs/V 原子比如大于0.012时,ESR 谱中游离 V^(4+)的超精细结构讯号明显加强,对催化反应不利。Cs^+渗入到TiO_2晶格间隙,能提高联结有 VO_4四面体的 TiO_2的n 型电导,对于 VO_4捕捉气相氧原子有利。当 Cs^+接近 P-OH、V-OH 或 Ti-OH 的氧原子时,能极化氢氧基,提高了 B 酸强度。当 VO_4四面体氧原子缺位时,Cs^+接近 V-O-Ti 键的桥氧原子,则可提高 L 酸 V⊕的强度。
Under the synergistic action of Cs^+ and P_2O_5,on Cs^+-P_2O_5-V_2O_5-TiO_2 as Cs(0.012)/PVT,the characteristic stretching vibration 1020 cm^(-1) of V=O bondfor crystal phase has prominently red-shifted to 1005 cm^(-1) while the stretch-ing vibration 879 cm^(-1) of V-O-V bond has also red-shifted to 859 cm^(-1),sug-gesting that part of V_2O_5 on TiO_2 surface has transformed into noncrystalphase and the V=O bond distance has elongated from 1.58(?)to 1.61(?).TPD spectra and IR spectra of ammonia adsorbed on Cs/PVT indicate thatthe synergistic action has also enhanced the intensity of B and L acids of thecatalyst.When the Cs/V atomic ratio exceeds 0.012,the signal of superfinestructure of free V^(4+) ion will be remarkably intensified.It is unfavorable tocatalytic reaction.In the case of Cs^+ ion permeating into the lattice space of TiO_2,the n-type conductance of TiO_2 that has VO_4 tetrahedron combined on its surfacewill be increased.It favors the grasp of oxygen atom from gas phase.whenCs^+ ion comes close to the oxygen atom of Ti-OH,P-OH and V-OH,the Cs^+ion can polarize the hydroxyl group and thus enhance the intensity of B acid.Under conditions that the VO_4 tetrehadron is deficient in oxygen atom,Cs^+ion comes close to the bridged oxygen atom of V-O-Ti,and the intensity ofL acid of V is increased.
出处
《石油学报（石油加工）》
EI
CAS
CSCD
北大核心
1990年第3期74-81,共8页
Acta Petrolei Sinica(Petroleum Processing Section)
基金
国家自然科学基金资助的课题
