The onset of mass transport limitations triggers the stimulus responsiveness of polymer coated catalysts

A series of Pd/Al2O3 catalysts coated with N-isopropylacrylamide polymer (p-NIPAM) brushes increasing particle size the support were prepared to study interplay between mass transport limitations and ability thermo-responsive modify reactivity during reaction. Nitrite hydrogenation in water was chosen as probe reaction, which is a key step reduction nitrites nitrates from drinking water. The results show that apparent activation energy decreases on temperature above LCST, i.e. where undergoes phase change, for catalyst sizes 38 100 ?m, alluding significant increase transfer limitations. In sharp contrast, both p-NIPAM modified smaller uncoated do not this change temperature. Detailed multi-physics reaction modelling indicated limiting reagent, hydrogen case, severely reduced when collapses at temperatures its LCST. It concluded effective control using stimulus responsive polymers requires system be close limitation regime, maximize effect conformation performance achieve reversible transitions active inactive.