采用固体多核13C,27Al及29Si MAS NMR结合吸附气体Xe后的129Xe NMR,详细研究了乙烯和2-丁烯歧化生成丙烯反应过程中6%Mo/Hβ-Al2O3催化剂上积炭的类型和落位.结果表明,积炭以饱和烷烃为主,并随着反应的进行生成更多的支链烷烃,积炭主要分布在Hβ分子筛上,并主要落位在分子筛的交叉孔道处.
A new propene production route from 1-butene metathesis has been developed on heterogeneous 10WO3/Al2O3-HY catalysts with different HY contents.It is found that the catalysts play bi-functionally first for the isomerization of 1-butene to 2-butene and then for the cross-metathesis between 1-butene and 2-butene to propene and 2-pentene.The combination of HY zeolite and Al2O3 is prerequisite for the production of propene.The propene yield keeps increasing with the HY content in the range of 10-70 wt%,where 10WO3/Al2O3-70HY exhibits the highest propene yield.The MS-H2-TPR and MS-O2-TPO characterizations indicate that the increase of HY content in the catalysts weakens the interaction between W species and supports,whereas enhance the probability of coking on the metal species and acid sites.
A series of 3.0Mo/MCM-22-Al2O3 catalysts with γ-Al2O3 contents in the range of 0-100 wt%were prepared and applied in the metathesis reaction of ethene and butene-2.Addition of γ-Al2O3 did not affect the structure of MCM-22 zeolite as evidenced by XRD and N2 adsorption measurements.It was deduced from TPR experiments that γ-Al2O3 phase favored the formation of polymolybdate or multilayered Mo oxide,while more Al2(MoO4)3 species were generated over MCM-22 zeolites.Alumina content in the support was directly related to the metathesis activity of ethene and butene-2 to propene.Mo species with higher valence(Mo6+or Mo5+)contributed more to the excellent performance of catalyst than metallic Mo.The best catalyst activity and stability was obtained over 3.0Mo/(MCM-22-30%Al2O3)under the reaction condition of 1.0 MPa and 125℃ using N2 as the pretreatment gas.
