Hydroisomerization of n-heptane over bifunctional catalysts of Pt supported on heteroatomic zeolite MnAlβ

The bifunctional catalysts of heteroatomic zeolite MnAlβ with supported Pt were prepared by the static hydrothermal method and the co-impregnation method,and characterized by X-ray diffraction(XRD),nitrogen adsorption,inductively coupling plasma(ICP),temperature programmed desorption of ammonia(NH3-TPD),and CO chemisorption techniques.The catalytic activities were evaluated with the hydroisomerization of n-heptane in an atmospheric fixed-bed reactor.Results demonstrated that bifunctional catalysts of Pt supported on heteroatomic zeolite MnAlβ exhibited excellent catalytic performance,and the catalytic selectivity was higher than those of Mn-exchanged or Mn-impregnated β zeolite catalysts supported with Pt.At the reaction temperature of 230 ℃,liquid hourly space velocity(WHSV) of 2.7 h-1,and n(H2)/n(n-heptane) of 7.9,the catalyst with a Pt loading of 0.4%,and a molar ratio of MnO to SiO2 of 0.011 showed a high conversion of n-heptane of 62.1% coupled with a very high selectivity for isomerization products of 92.0%.The introduction of Mn into the framework of β zeolite could modify the pore structure of the catalyst,and improve the dispersion of the supported Pt.