CAJ | 학술논문

用X-射线衍射(XRD)、紫外-可见漫散射光谱(UV-Vis DRS)、程序升温还原(TPR)、CO化学吸附和微反测试等方法研究了Ni2+在γ-Al2O3上的分散状态和负载型Ni/γ-Al2O3催化剂的α-蒎烯加氢催化活性.结果表明,当Ni2+负载量远低于其在γ-Al2O3载体表面分散容量时,Ni2+优先嵌入载体表面四面体空位,随着Ni2+负载量的增加,嵌入载体表面八面体空位Ni2+的比例增大.由于八面体Ni2+易被还原为金属态Ni0,NiO/γ-Al2O3样品的还原度随Ni2+负载量的增加而大幅度地增加,经氢还原所得Ni/γ-Al2O3催化剂的CO吸附量和α-蒎烯加氢催化活性大幅度增加.对La2O3助剂的作用进行了研究,结果表明分散在γ-Al2O3上的La3+物种可阻止Ni2+嵌入γ-Al2O3表面四面体空位,增大了八面体Ni2+物种所占比例,提高了催化剂的还原度,故Ni-La2O3/γ-Al2O3催化剂催化活性高于Ni/γ-Al2O3催化剂.
용X-사선연사(XRD)、자외-가견만산사광보(UV-Vis DRS)、정서승온환원(TPR)、CO화학흡부화미반측시등방법연구료Ni2+재γ-Al2O3상적분산상태화부재형Ni/γ-Al2O3최화제적α-파희가경최화활성.결과표명,당Ni2+부재량원저우기재γ-Al2O3재체표면분산용량시,Ni2+우선감입재체표면사면체공위,수착Ni2+부재량적증가,감입재체표면팔면체공위Ni2+적비례증대.유우팔면체Ni2+역피환원위금속태Ni0,NiO/γ-Al2O3양품적환원도수Ni2+부재량적증가이대폭도지증가,경경환원소득Ni/γ-Al2O3최화제적CO흡부량화α-파희가경최화활성대폭도증가.대La2O3조제적작용진행료연구,결과표명분산재γ-Al2O3상적La3+물충가조지Ni2+감입γ-Al2O3표면사면체공위,증대료팔면체Ni2+물충소점비례,제고료최화제적환원도,고Ni-La2O3/γ-Al2O3최화제최화활성고우Ni/γ-Al2O3최화제.
The dispersion state of nickel ions on γ-Al2O3 and the catalytic hydrogenation activity of supported Ni/γ-Al2O3 catalysts have been studied by means of X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), H2 temperature-programmed reduction (TPR), CO chemisorption and microreactor tests. It has been shown that the supported nickel ions preferentially incorporate into the tetrahedral vacancies ofγ-Al2O3 when Ni2+ loading is far below its dispersion capacity on γ-Al2O3. Increasing Ni2+ loading, the ratio of Ni2+ ions incorporated into the octahedral vacancies of γ-Al2O3 increases. Since the octahedral Ni2+ ions are easier to be reduced to the metallic state, the reduction degree of supportedNiO/γ-Al2O3 sample increases greatly with Ni2+ loading, thus resulting in agreat increase in the CO uptake and catalytic activity of Ni/γ-Al2O3 catalyst for hydrogenation of α-pinene. Thepromotional effect of La2O3 on the catalytic activity of the supported Ni/γ-Al2O3 catalyst has been studied as well. Ithas been suggested that the dispersed La3 + species on γ-Al2O3 may inhibit incorporation of Ni2 + ions into thetetrahedral vacancies of γ-Al2O3 and increases the ratio of octahedral Ni2+ ions to tetrahedral Ni2+ ions, and thus increases the reduction degree of the catalyst precursor. As a result, the Ni-La2O3/γ-Al2O3 catalyst shows higher catalytic activity than the Ni/γ-Al2O3 catalyst with the same nickel loading.