Direct observation of catalyst behaviour under real working conditions with X-ray diffraction: Comparing SAPO-18 and SAPO-34 methanol to olefin catalysts

作者：Wragg David S^*; Akporiaye Duncan; Fjellvag Helmer

来源：Journal of Catalysis, 2011, 279(2): 397-402.

DOI：10.1016/j.jcat.2011.02.011

• Heterogeneous catalysis
• X-ray diffraction
• Zeolites
• Methanol to olefins

We have made direct observations of the behaviour of the silicoaluminophosphate framework of the SAPO-18 catalyst under working conditions in the methanol to olefin conversion process. Time-resolved synchrotron powder X-ray diffraction data for the process at 450 degrees C show that the unit cell of the catalyst expands by around 0.9%, significantly less than the structurally similar SAPO-34. The smaller expansion is explained in terms of the cage volume and the rigidity of the structure compared with SAPO-34. Expansion is caused by the build-up of "hydrocarbon pool" intermediates in the cages. The lack of expansion and hence slower build-up of large hydrocarbons is linked to the slower deactivation of SAPO-18 compared with that of SAPO-34. The mechanism for suppressing the formation of the large polycyclic aromatics associated with the deactivation of SAPO MTO catalysts remains open.

• 出版日期2011-4-25