In situ synchrotron-based IR and UV/Vis micro-spectroscopy combined with isotopically labeled reactants have been used to identify the different hydrocarbon species formed as well as to assess the activity and accessibility of individual 50 μm-sized SAPO-34 crystals. For the methanol-to-olefins process, two reaction stages can be distinguished. The first involves the formation of methoxy species, protonated dimethyl ether, and polyalkylated benzene (PAB) carbocations, which do not affect the accessibility of the SAPO-34 crystal. In addition, methoxy species are very dynamic during this stage. The second stage is related to the formation of polyaromatic (PA) species concentrated in the outer rim of the crystal, which are bulky and interact with the acid sites and thus alter the overall accessibility of the crystal. In contrast, the ethanol-to-olefins process only consists of one major stage, as the formation of PAB and PA species cannot be separated. Furthermore, the formation of these species is more internal, and coke formation is mainly concentrated in a layer located in the inner part of the SAPO-34 crystal.
If you can't find a tool you're looking for, please click the link at the top of the page to "Go to old article view". Alternatively, view our Knowledge Base articles for additional help. Your feedback is important to us, so please let us know if you have comments or ideas for improvement.