%0 Journal Article %1 C6CY02564A %A Dai, Weili %A Cao, Ge %A Yang, Liu %A Wu, Guangjun %A Dyballa, Michael %A Hunger, Michael %A Guan, Naijia %A Li, Landong %D 2017 %I The Royal Society of Chemistry %J Catal. Sci. Technol. %K %N 3 %P 607-618 %R 10.1039/C6CY02564A %T Insights into the catalytic cycle and activity of methanol-to-olefin conversion over low-silica AlPO-34 zeolites with controllable Brønsted acid density %U http://dx.doi.org/10.1039/C6CY02564A %V 7 %X Low-silica AlPO-34 materials with similar crystal sizes but different Brønsted acid site densities were prepared and investigated as catalysts in methanol-to-olefin (MTO) conversion. The effect of Brønsted acid site density on catalyst activity and the dominant reaction mechanism during the MTO conversion was investigated via TGA, GC-MS, solid-state NMR spectroscopy, and in situ UV/vis spectroscopy together with the catalytic performance. For the catalysts with lower Brønsted acid site densities, the olefin-based cycle mechanism is the dominant mechanism during the MTO conversion. Long-chain alkenes, e.g., C5–C6 alkenes, act as intermediates that are cracked to lower olefins, or are converted to dienes via hydride transfer reactions, and can also diffuse out of the cages of low-silica AlPO-34 catalysts as the products. With decreasing Brønsted acid site density or reaction temperature, the methylation route of the olefin-based cycle was found to be much more favored than the cracking route. Therefore, a higher selectivity to C5–C6 alkenes (∼50%) is achieved. Simultaneously, dienes are the predominant deposits occluded in the used catalysts. For catalysts with slightly higher Brønsted acid site densities, the long-chain alkenes are rapidly transformed to aromatics and, subsequently, an aromatic-based cycle mechanism contributes to the MTO conversion. Interestingly, the catalyst with the most suitable Brønsted acid site density can well balance the above-mentioned two reaction cycles accompanied by a low deactivation rate, leading to a long catalyst lifetime of up to 15 h.

@article{C6CY02564A, abstract = {Low-silica AlPO-34 materials with similar crystal sizes but different Brønsted acid site densities were prepared and investigated as catalysts in methanol-to-olefin (MTO) conversion. The effect of Brønsted acid site density on catalyst activity and the dominant reaction mechanism during the MTO conversion was investigated via TGA{,} GC-MS{,} solid-state NMR spectroscopy{,} and in situ UV/vis spectroscopy together with the catalytic performance. For the catalysts with lower Brønsted acid site densities{,} the olefin-based cycle mechanism is the dominant mechanism during the MTO conversion. Long-chain alkenes{,} e.g.{,} C5–C6 alkenes{,} act as intermediates that are cracked to lower olefins{,} or are converted to dienes via hydride transfer reactions{,} and can also diffuse out of the cages of low-silica AlPO-34 catalysts as the products. With decreasing Brønsted acid site density or reaction temperature{,} the methylation route of the olefin-based cycle was found to be much more favored than the cracking route. Therefore{,} a higher selectivity to C5–C6 alkenes (∼50%) is achieved. Simultaneously{,} dienes are the predominant deposits occluded in the used catalysts. For catalysts with slightly higher Brønsted acid site densities{,} the long-chain alkenes are rapidly transformed to aromatics and{,} subsequently{,} an aromatic-based cycle mechanism contributes to the MTO conversion. Interestingly{,} the catalyst with the most suitable Brønsted acid site density can well balance the above-mentioned two reaction cycles accompanied by a low deactivation rate{,} leading to a long catalyst lifetime of up to 15 h.}, added-at = {2019-11-05T13:18:37.000+0100}, author = {Dai, Weili and Cao, Ge and Yang, Liu and Wu, Guangjun and Dyballa, Michael and Hunger, Michael and Guan, Naijia and Li, Landong}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/229bee2be8f5f59216b91c596bdf4e900/ingo}, doi = {10.1039/C6CY02564A}, interhash = {ec22c9b9ea76638c469095264e7b7e9f}, intrahash = {29bee2be8f5f59216b91c596bdf4e900}, journal = {Catal. Sci. Technol.}, keywords = {}, number = 3, pages = {607-618}, publisher = {The Royal Society of Chemistry}, timestamp = {2019-11-05T12:18:37.000+0100}, title = {Insights into the catalytic cycle and activity of methanol-to-olefin conversion over low-silica AlPO-34 zeolites with controllable Brønsted acid density}, url = {http://dx.doi.org/10.1039/C6CY02564A}, volume = 7, year = 2017 }