Chemical vapour deposition (CVD) of molybdenum into medium pore H-zeolites

Funding Information: Ac k n o wle d ge m e nts BPLN DIKTI and partial support from Dr. Y. Krisnandi through PUPT BPPTN 2018 grant No. 481/UN2.R3.1/HKP.05.00/2018.Peer reviewedPublisher PD

Influence of post-synthetic modifications on the composition, acidity and textural properties of ZSM-22 zeolite

[EN] In this work, an extensive investigation of the preparation of a large body of desilicated ZSM-22 zeolites and their basic characterization is presented. We investigate the effects of the properties of the starting zeolite, and we employ mixtures of NaOH with CTAB or TBAOH as well as subsequent acid washings to create mesoporous zeolites. Scanning and transmission electron microscopy and nitrogen adsorption revealed that the cristal morphology of the starting zeolite appears to be the dominant parameter which influences the mesopore generation. Mesopores were effectively created within the rod-like commercial crystallites, whereas the thinner dimensions of the needle-shaped particles of the lab-made zeolite represent an obstacle for an intra-mesopore creation. The alkaline, surfactant-assisted or combined NaOH/TBAOH desilication methods resulted in mesopores with different shape and size from the commercial zeolite. The sequential acid washing generally resulted in increased micropore volume with respect to the desilicated samples. Elemental analysis showed that extra-framework Al species were generated upon the desilication treatments, which are eventually removed by the acid treatment. The acidity studied by FTIR demonstrated that this occurs without a marked modification of the Brønsted acidity, whereas the concentration of surface silanol hydroxyl groups is increased. The comparison between the total Al concentration and the amount of Al in acidic sites quantified by pyridine adsorption shows that the acidity was recovered after the acid washing and suggests that original non-acidic Al species in the starting materials may have a role in the formation of both Lewis and extra-framework species upon desilication.This publication is a part of the inGAP Centre of research-based Innovation, which receives financial support from the Norwegian Research Council under contract no. 174893. F.R and M.T.N thank to MINECO for financial support through projects MAT2015-71842-P and SEV-2012-0267. All the authors thank the Electron Microscopy Service of the Universitat Politecnica de Valencia.Del Campo Huertas, P.; Beato, P.; Rey Garcia, F.; Navarro, MT.; Olsbye, U.; Lillerud, K.; Svelle, S. (2018). Influence of post-synthetic modifications on the composition, acidity and textural properties of ZSM-22 zeolite. Catalysis Today. 299:120-134. https://doi.org/10.1016/j.cattod.2017.04.042S12013429

Synthesis of reaction-adapted zeolites as methanol-to-olefins catalysts with mimics of reaction intermediates as organic structure-directing agents

[EN] Catalysis with enzymes and zeolites have in common the presence of well-defined single active sites and pockets/cavities where the reaction transition states can be stabilized by longer-range interactions. We show here that for a complex reaction, such as the conversion of methanol-to-olefins (MTO), it is possible to synthesize reaction-adapted zeolites by using mimics of the key molecular species involved in the MTO mechanism. Effort has focused on the intermediates of the paring mechanism because the paring is less favoured energetically than the side-chain route. All the organic structure-directing agents based on intermediate mimics crystallize cage-based small-pore zeolitic materials, all of them capable of performing the MTO reaction. Among the zeolites obtained, RTH favours the whole reaction steps following the paring route and gives the highest propylene/ethylene ratio compared to traditional CHA-related zeolites (3.07 and 0.86, respectively).Li, C.; Paris, C.; Martínez-Triguero, J.; Boronat Zaragoza, M.; Moliner Marin, M.; Corma Canós, A. (2018). Synthesis of reaction-adapted zeolites as methanol-to-olefins catalysts with mimics of reaction intermediates as organic structure-directing agents. Nature Catalysis. 1(7):547-554. https://doi.org/10.1038/s41929-018-0104-7S54755417Stocker, M. Methanol-to-hydrocarbons: catalytic materials and their behavior. Micro. Mesopor. Mater. 29, 3–48 (1999).Tian, P., Wei, Y., Ye, M. & Liu, Z. Methanol to olefins (MTO): from fundamentals to commercialization. ACS Catal. 5, 1922–1938 (2015).Ilias, S. & Bhan, A. Mechanism of the catalytic conversion of methanol to hydrocarbons. ACS Catal. 3, 18–31 (2013).Olsbye, U. et al. Conversion of methanol to hydrocarbons: how zeolite cavity and pore size controls product selectivity. Angew. Chem. Int. Ed. 24, 5810–5831 (2012).Hemelsoet, K., Van der Mynsbrugge, J., De Wispelaere, K., Waroquier, M. & Van Speybroeck, V. Unraveling the reaction mechanisms governing methanol-to-olefins catalysis by theory and experiment. ChemPhysChem 14, 1526–1545 (2013).Song, W., Haw, J. F., Nicholas, J. B. & Heneghan, C. S. Methylbenzenes are the organic reaction centers for methanol-to-olefin catalysis on HSAPO-34. J. Am. Chem. Soc. 122, 10726–10727 (2000).Arstad, B. & Kolboe, S. The reactivity of molecules trapped within the SAPO-34 cavities in the methanol-to-hydrocarbons reaction. J. Am. Chem. Soc. 123, 8137–8138 (2001).Xu, T. et al. Synthesis of a benzenium ion in a zeolite with use of a catalytic flow reactor. J. Am. Chem. Soc. 120, 4025–4026 (1998).Song, W., Nicholas, J. B., Sassi, A. & Haw, J. F. Synthesis of the heptamethylbenzene cation in zeolite beta: in situ NMR and theory. Catal. Lett. 81, 49–53 (2002).Xu, S. et al. Direct observation of cyclic carbenium ions and their role in the catalytic cycle of the metahnol-to-olefin reaction over chabazite zeolites. Angew. Chem. Int. Ed. 52, 11564–11568 (2013).Chen, J. et al. Elucidating the olefin formation mechanism in the methanol to olefin reaction over AlPO-18 and SAPO-18. Catal. Sci. Tech. 4, 3268–3277 (2014).Haw, J. F. et al. Roles for cyclopentenyl cations in the synthesis of hydrocarbons from methanol on zeolite catalyst HZSM-5. J. Am. Chem. Soc. 122, 4763–4775 (2000).Svelle, S. et al. Conversion of methanol into hydrocarbons over zeolite H-ZSM-5: ethene formation is mechanistically separated from the formation of higher alkenes. J. Am. Chem. Soc. 128, 14770–14771 (2006).Teketel, S., Olsbye, U., Lillerud, K. P., Beato, P. & S., S. Selectivity control through fundamental mechanistic insight in the conversion of methanol to hydrocarbons over zeolites. Micro. Mesopor. Mater. 136, 33–41 (2010).Zhang, M. et al. Methanol conversion on ZSM-22, ZSM-35 and ZSM-5 zeolites: effects of 10-membered ring zeolite structures on methylcyclopentenyl cations and dual cycle mechanism. RSC Adv. 6, 95855–95864 (2016).Sassi, A. et al. Methylbenzene chemistry on zeolite HBeta: multiple insights into methanol-to-olefin catalysis. J. Phys. Chem. B 106, 2294–2303 (2002).Sassi, A., Wildman, M. A. & Haw, J. F. Reactions of butylbenzene isomers on zeolite HBeta: methanol-to-olefins hydrocarbon pool chemistry and secondary reactions of olefins. J. Phys. Chem. B 106, 8768–8773 (2002).Bjørgen, M., Olsbye, U., Petersen, D. & Kolboe, S. The methanol-to-hydrocarbons reaction: insight into the reaction mechanism from [12C]benzene and [13C]methanol coreactions over zeolite H-beta. J. Catal. 221, 1–10 (2004).McCann, D. M. et al. A complete catalytic cycle for supramolecular methanol-to-olefins conversion by linking theory with experiment. Angew. Chem. Int. Ed. 47, 5179–5182 (2008).Arstad, B., Kolboe, S. & Swang, O. Theoretical study of the heptamethylbenzenium ion. intramolecular isomerizations and C2, C3, C4 alkene elimination. J. Phys. Chem. A 109, 8914–8922 (2005).De Wispelaere, K., Hemelsoet, K., Waroquier, M. & Van Speybroeck, V. Complete low-barrier side-chain route for olefin formation during methanol conversion in H-SAPO-34. J. Catal. 305, 76–80 (2013).Wang, C. M., Wang, Y. D. & Xie, Z. K. Verification of the dual cycle mechanism for methanol-to-olefin conversion in HSAPO-34: a methylbenzene-based cycle from DFT calculations. Catal. Sci. Technol. 4, 2631–2638 (2014).Wang, C. M., Wang, Y. D., Liu, H. X., Xie, Z. K. & Liu, Z. P. Theoretical insight into the minor role of paring mechanism in the methanol-to-olefins conversion within HSAPO-34 catalyst. Micro. Mesopor. Mater. 158, 264–271 (2012).Ilias, S. & Bhan, A. The mechanism of aromatic dealkylation in methanol-to-hydrocarbons conversion on H-ZSM-5: What are the aromatic precursors to light olefins? J. Catal. 311, 6–16 (2014).Erichsen, M. W. et al. Conclusive evidence for two unimolecular pathways to zeolite-catalyzed de-alkylation of the heptamethylbenzenium cation. ChemCatChem 7, 4143–4147 (2015).Bhawe, Y. et al. Effect of cage size on the selective conversion of methanol to light olefins. ACS Catal. 2, 2490–2495 (2012).Kang, J. H. et al. Further studies on how the nature of zeolite cavities that are bounded by small pores influences the conversion of methanol to light olefins. ChemPhysChem 19, 412–419 (2018).Martin, N. et al. Nanocrystalline SSZ-39 zeolite as an efficient catalyst for the methanol-to-olefin (MTO) process. Chem. Commun. 52, 6072–6075 (2016).Dusselier, M., Deimund, M. A., Schmidt, J. E. & Davis, M. E. Methanol-to-olefins catalysis with hydrothermally treated zeolite SSZ-39. ACS Catal. 5, 6078–6085 (2015).Yokoi, T., Yoshioka, M., Imai, H. & Tatsumi, T. Diversification of RTH-type zeolite and its catalytic application. Angew. Chem. Int. Ed. 48, 9884–9887 (2009).Ji, Y., Deimund, M. A., Bhawe, Y. & Davis, M. E. Organic-free synthesis of CHA-type zeolite catalysts for the methanol-to-olefins reaction. ACS Catal. 5, 4456–4465 (2015).Liu, M. et al. Differences in Al distribution and acidic properties between RTH-type zeolites synthesized with OSDAs and without OSDAs. Phys. Chem. Chem. Phys. 16, 4155–4164 (2014).Gallego, E. M. et al. “Ab initio” synthesis of zeolites for preestablished catalytic reactions. Science 355, 1051–1054 (2017).Zones, S. I. & Nakagawa, Y. Use of modified zeolites as reagents influencing nucleation in zeolite synthesis. Stud. Surf. Sci. Catal. 97, 45–52 (1995).Li, C., Moliner, M. & Corma, A. Building zeolites from pre-crystallized units: nanoscale architecture. Angew. Chem. Int. Ed. https://doi.org/10.1002/anie.201711422 (2018).Zones, S. I. Zeolite SSZ-13 and its method of preparation. US Patent 4,544,538 (1985).Li, Z., Navarro, M. T., Martínez-Triguero, J., Yu, J. & Corma, A. Synthesis of nano-SSZ-13 and its application in the reaction of methanol to olefins. Catal. Sci. Technol. 6, 5856–5863 (2016).Kumar, M., Luo, H., Román-Leshkov, Y. & Rimer, J. D. SSZ-13 crystallization by particle attachment and deterministic pathways to crystal size control. J. Am. Chem. Soc. 137, 13007–13017 (2015).Martínez-Franco, R., Cantin, A., Moliner, M. & Corma, A. Synthesis of the small pore silicoaluminophosphate STA-6 by using supramolecular self-assembled organic structure directing agents. Chem. Mater. 26, 4346–4353 (2014).Schmidt, J. E., Deimund, M. A., Xie, D. & Davis, M. E. Synthesis of RTH-type zeolites using a diverse library of imidazolium cations. Chem. Mater. 27, 3756–3762 (2015).Moliner, M., Franch, C., Palomares, E., Grill, M. & Corma, A. Cu–SSZ-39, an active and hydrothermally stable catalyst for the selective catalytic reduction of NOx. Chem. Commun. 48, 8264–8266 (2012).Zhao, Y. & Truhlar, D. G. The M06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states, and transition elements: two new functionals and systematic testing of four M06-class functionals and 12 other functionals. Theor. Chem. Acc. 120, 215–241 (2008).Ditchfield, R., Hehre, W. J. & Pople, J. A. Self-consistent molecular orbital methods. 9. Extended Gaussian-type basis for molecular-orbital studies of organic molecules. J. Chem. Phys. 54, 724–728 (1971).Hehre, W. J., Ditchfield, R. & Pople, J. A. Self-consistent molecular orbital methods. 12. Further extensions of Gaussian-type basis sets for use in molecular-orbital studies of organic-molecules. J. Chem. Phys. 56, 2257–2261 (1972).Frisch, M. J. et al. Gaussian 09, Revision C.01. (Gaussian, Wallingford, 2009).Van Speybroeck, V. et al. First principle chemical kinetics in zeolites: the methanol-to-olefin process as a case study. Chem. Soc. Rev. 43, 7326–7357 (2014)