کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
61830 | 47607 | 2011 | 6 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Direct observation of catalyst behaviour under real working conditions with X-ray diffraction: Comparing SAPO-18 and SAPO-34 methanol to olefin catalysts Direct observation of catalyst behaviour under real working conditions with X-ray diffraction: Comparing SAPO-18 and SAPO-34 methanol to olefin catalysts](/preview/png/61830.png)
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 °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.
The closely related silicoaluminophosphate framework catalysts SAPO-18 and SAPO-34 are shown to behave very differently during the methanol to olefin conversion. SAPO-18 shows less expansion despite larger coke molecules being present.Figure optionsDownload high-quality image (147 K)Download as PowerPoint slideHighlights
► Much smaller expansion in SAPO-18 than in SAPO-34 during the MTO process.
► No clear end point to the expansion of SAPO-18, fitting with extended MTO activity.
► Larger quantities of coke in SAPO-18 do not give rise to greater expansion.
Journal: Journal of Catalysis - Volume 279, Issue 2, 25 April 2011, Pages 397–402