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The role of water in the reusability of aminated silica catalysts for aldol reactions

(2018) JOURNAL OF CATALYSIS. 361. p.51-61
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Abstract
The reusability of methylaminopropyl active sites grafted on mesoporous amorphous silica, either with cooperative silanol groups or trimethylsilated, was assessed in the aldol reaction of acetone with 4-nitrobenzaldehyde. Raman, C-13 NMR, and UV-Vis spectroscopy demonstrated the presence of stable enamines on the spent catalysts. These enamines are produced as a side product from iminium intermediates in the catalytic cycle. Water co-feeding enhances the desorption of the iminium intermediates and, hence, suppresses the formation of these stable enamine species. The reusability of the cooperative catalyst increased to 70% with co-feeding 0.69 wt% water, while an almost complete reusability was achieved for the trimethylsilated catalyst. Continuous-flow experimentation showed that the cooperative effect of the silanol groups was lost during the first 7 h on-stream, yet activity losses continued, most likely due to silica hydrolysis. Activity losses persisted on the more hydrophobic trimethylsilated catalyst, but were significantly less pronounced.
Keywords
Cooperative catalysis, Aminated silica, Reusability, Aldol reaction, Deactivation, Enamine, ACID-BASE COOPERATIVITY, MG-AL HYDROTALCITES, MIXED OXIDES, HETEROGENEOUS CATALYSTS, CONDENSATION-REACTIONS, FUNCTIONAL-GROUPS, ACETONE, SURFACE, ALDEHYDES, ZEOLITES

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Chicago
De Vylder, Anton, Jeroen Lauwaert, Dolores Esquivel, Dirk Poelman, Jeriffa De Clercq, Pascal Van Der Voort, and Joris Thybaut. 2018. “The Role of Water in the Reusability of Aminated Silica Catalysts for Aldol Reactions.” Journal of Catalysis 361: 51–61.
APA
De Vylder, A., Lauwaert, J., Esquivel, D., Poelman, D., De Clercq, J., Van Der Voort, P., & Thybaut, J. (2018). The role of water in the reusability of aminated silica catalysts for aldol reactions. JOURNAL OF CATALYSIS, 361, 51–61.
Vancouver
1.
De Vylder A, Lauwaert J, Esquivel D, Poelman D, De Clercq J, Van Der Voort P, et al. The role of water in the reusability of aminated silica catalysts for aldol reactions. JOURNAL OF CATALYSIS. 2018;361:51–61.
MLA
De Vylder, Anton, Jeroen Lauwaert, Dolores Esquivel, et al. “The Role of Water in the Reusability of Aminated Silica Catalysts for Aldol Reactions.” JOURNAL OF CATALYSIS 361 (2018): 51–61. Print.
@article{8556384,
  abstract     = {The reusability of methylaminopropyl active sites grafted on mesoporous amorphous silica, either with cooperative silanol groups or trimethylsilated, was assessed in the aldol reaction of acetone with 4-nitrobenzaldehyde. Raman, C-13 NMR, and UV-Vis spectroscopy demonstrated the presence of stable enamines on the spent catalysts. These enamines are produced as a side product from iminium intermediates in the catalytic cycle. Water co-feeding enhances the desorption of the iminium intermediates and, hence, suppresses the formation of these stable enamine species. The reusability of the cooperative catalyst increased to 70\% with co-feeding 0.69 wt\% water, while an almost complete reusability was achieved for the trimethylsilated catalyst. Continuous-flow experimentation showed that the cooperative effect of the silanol groups was lost during the first 7 h on-stream, yet activity losses continued, most likely due to silica hydrolysis. Activity losses persisted on the more hydrophobic trimethylsilated catalyst, but were significantly less pronounced.},
  author       = {De Vylder, Anton and Lauwaert, Jeroen and Esquivel, Dolores and Poelman, Dirk and De Clercq, Jeriffa and Van Der Voort, Pascal and Thybaut, Joris},
  issn         = {0021-9517},
  journal      = {JOURNAL OF CATALYSIS},
  keyword      = {Cooperative catalysis,Aminated silica,Reusability,Aldol reaction,Deactivation,Enamine,ACID-BASE COOPERATIVITY,MG-AL HYDROTALCITES,MIXED OXIDES,HETEROGENEOUS CATALYSTS,CONDENSATION-REACTIONS,FUNCTIONAL-GROUPS,ACETONE,SURFACE,ALDEHYDES,ZEOLITES},
  language     = {eng},
  pages        = {51--61},
  title        = {The role of water in the reusability of aminated silica catalysts for aldol reactions},
  url          = {http://dx.doi.org/10.1016/j.jcat.2018.02.016},
  volume       = {361},
  year         = {2018},
}

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