中空Pt/ZSM-5催化剂用于愈创木酚加氢脱氧合成环烷烃

Hollow Pt/ZSM-5 catalysts for highly selective hydrodeoxygenation of guaiacol to cycloalkanes

采用溶解-重结晶方法合成了不同硅铝比具有级孔壳的中空ZSM-5分子筛,并对其负载Pt催化剂(Pt/HZ-x)催化愈创木酚加氢脱氧制备环烷烃性能进行了探究。通过X射线晶体衍射(XRD)、场发射扫描电子显微镜(SEM)、场发射透射电子显微镜(TEM)、氮气吸附脱附(N_(2)-BET)、氨气程序升温脱附(NH_(3)-TPD)和X射线光电子能谱(XPS)对合成的系列催化剂进行了物化性质表征。得益于特殊的中空级孔结构,中空ZSM-5分子筛具有高外比表面积和介孔孔容,有利于促进活性金属Pt的分散和增强反应物的传质。Pt/HZ-x催化剂表现出了优异的催化性能和愈创木酚加氢脱氧活性,在220℃的低温即可以达到100%的环烷烃选择性。另外,随着分子筛载体酸性的减弱,愈创木酚加氢脱氧产物的二次反应程度降低,增大了环己烷的选择性。

Hollow ZSM-5 zeolites with different Si/Al molar ratios and hierarchical porous shell were fabricated via employing dissolution-recrystallization strategy,and utilized as support to load precious Pt(Pt/HZ-x)for hydrodeoxygenation of guaiacol to cycloalkanes.The physicochemical properties of the as-synthesized catalysts were characterized by powder X-ray crystalline diffraction(XRD),field emission scanning electron microscope(SEM),field emission transmission electron microscope(TEM),nitrogen adsorption and desorption(N_(2)-BET),ammonia temperature program desorption(NH_(3)-TPD)and X-ray photoelectron energy spectroscopy(XPS).Benefit from the special hollow structure,hollow ZSM-5 zeolites exhibited a larger external specific surface area and mesoporous volume,which was favorable to promote the dispersion of metallic Pt and mass transfer of reactants.The Pt/HZ-x catalysts showed excellent catalytic performance and hydrodeoxygenation activity for guaiacol,and could reach 100% selectivity to cycloalkanes at a low temperature of 220℃.In addition,as the acidity of the molecular sieve carrier weakens,the degree of secondary reaction of the guaiacol hydrodeoxygenation product decreases,which increased the selectivity to cyclohexane.