@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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