Oriented control of Al locations in the framework of Al-Ge-ITQ-13 for catalyzing methanol conversion to propene

Reaction Mechanism for Direct Cyclization of Linear C5, C6, and C7 Alkenes over H‐ITQ‐13 Zeolite Investigated Using Density Functional Theory

“…The calculated RSE (Table S1) suggests that formation of Ge‐ O ‐Al is favorable. Ge‐OH‐Al and Si‐OH‐Al species have similar proton affinity (1214 vs. 1219 kJ/mol), and hence, show similar acid strength, as confirmed by NH 3 ‐TPD, pyridine adsorption IR (Py‐IR) spectroscopy and DFT calculation results . In this model, one Ge atom is located at T2 site and one Al atom at T3 site, forming Ge‐ O ‐Al species with charge‐balancing proton sited at O8.…”

“…Ge not only plays a structure‐directing role for the formation of the strained double four‐membered rings (D4R), but also assists the incorporation of Al into the framework of ITQ‐13 . We found that ITQ‐13 phase was only formed in the presence of appreciable amounts of Ge (Si/Ge≤40) in the synthesis gel, whereas non‐addition of Ge led to production of EU‐1 . The 27 Al and 29 Si MAS NMR spectroscopy and DFT calculation results show that Ge atoms are preferably located at T2 and T5 sites in the D4R, while Al atoms are positioned at T3 and T6 for the Al‐Ge‐ITQ‐13 sample with excellent MTP catalytic performance .…”

“…We found that ITQ‐13 phase was only formed in the presence of appreciable amounts of Ge (Si/Ge≤40) in the synthesis gel, whereas non‐addition of Ge led to production of EU‐1 . The 27 Al and 29 Si MAS NMR spectroscopy and DFT calculation results show that Ge atoms are preferably located at T2 and T5 sites in the D4R, while Al atoms are positioned at T3 and T6 for the Al‐Ge‐ITQ‐13 sample with excellent MTP catalytic performance . Figure S1 displays the relative substitution energies (RSE) calculated from the ωB97X‐D/6–311+G(d,p) total electronic energy (Gaussian program) by replacing Si with Ge at each site in D4R (T2−1, T2−2, T2−3, T2−4, T5−1, T5−2, T5−3, and T5−4) and taking the substitution with the lowest free energy as reference state.…”

“…This unique pore structure makesi ts how excellent catalytic performance in methanol-to-propene (MTP) process. [30] The propene selectivity reaches 46.7 %w ithout obvious induction period, and the propene/ethene ratio is as high as 9. In addition, the single catalytic lifetime gets to 440 h.…”

“…It has two 10‐MR (4.7×5.1 Å and 4.8×5.3 Å) and one 9‐MR (4.0×4.9 Å) channels with a cavity of 15.5×5.3 Å (Figure ). This unique pore structure makes it show excellent catalytic performance in methanol‐to‐propene (MTP) process . The propene selectivity reaches 46.7 % without obvious induction period, and the propene/ethene ratio is as high as 9.…”