TY - JOUR
T1 - Dynamic atomic scale in situ electron microscopy in the development of an efficient heterogeneous catalytic process for pharmaceutical NSAIDS
AU - Raveendran Shiju, N.
AU - Robert Brown, D.
AU - Yoshida, K.
AU - Boyes, E.D.
AU - Gai, P.L.
PY - 2011/6/1
Y1 - 2011/6/1
N2 - In heterogeneous catalysis the identification of the active site and crucially its location to prevent unwanted sintering and deactivation during the transformation of the precursor to active catalyst require the integration of dynamic in situ imaging at the atomic level and reactivity studies. We report nanostructural and physico-chemical studies towards an efficient low temperature heterogeneous catalytic process for nonsteroidal anti-inflammatory drugs (NSAIDS) such as N-acetyl-p-aminophenol (paracetamol or acetaminophen) on tungstated zirconia nanocatalysts of only a few nanometres in size. We directly visualised, in real-time, the dynamic precursor transformation to the active catalyst, which is of great significance in heterogeneous catalysis, using double aberration-corrected in situ electron microscopy at the atomic level under controlled conditions. We quantified the observations with catalytic activity studies for the NSAIDS. The observations using negative defocus imaging in AC-TEM combined with HAADF-STEM have provided the direct evidence for the presence of surface WO species with dimensions of ≤0.35 nm, nanoclusters and nanoparticles of WO from up to 0.6 to 1 nm, located at grain boundaries on the surface of the zirconia nanoparticles. The observations illustrate that the nanoparticles (NPs) are disordered (distorted) tungsten trioxide. The correlation between the nanostructure and activity of catalysts with different W loadings indicate that surface WO species, nanoclusters and distorted WO nanoparticles create Brønsted acid sites highly active for the low temperature N-acetyl-p-aminophenol reaction, with distorted WO NPs contributing to the activity. The results further elucidate that the anchoring of active sites at grain boundaries of the zirconia nanoparticles prevents undesirable coalescence of the active species and improves the catalyst stability and performance to make more product.
AB - In heterogeneous catalysis the identification of the active site and crucially its location to prevent unwanted sintering and deactivation during the transformation of the precursor to active catalyst require the integration of dynamic in situ imaging at the atomic level and reactivity studies. We report nanostructural and physico-chemical studies towards an efficient low temperature heterogeneous catalytic process for nonsteroidal anti-inflammatory drugs (NSAIDS) such as N-acetyl-p-aminophenol (paracetamol or acetaminophen) on tungstated zirconia nanocatalysts of only a few nanometres in size. We directly visualised, in real-time, the dynamic precursor transformation to the active catalyst, which is of great significance in heterogeneous catalysis, using double aberration-corrected in situ electron microscopy at the atomic level under controlled conditions. We quantified the observations with catalytic activity studies for the NSAIDS. The observations using negative defocus imaging in AC-TEM combined with HAADF-STEM have provided the direct evidence for the presence of surface WO species with dimensions of ≤0.35 nm, nanoclusters and nanoparticles of WO from up to 0.6 to 1 nm, located at grain boundaries on the surface of the zirconia nanoparticles. The observations illustrate that the nanoparticles (NPs) are disordered (distorted) tungsten trioxide. The correlation between the nanostructure and activity of catalysts with different W loadings indicate that surface WO species, nanoclusters and distorted WO nanoparticles create Brønsted acid sites highly active for the low temperature N-acetyl-p-aminophenol reaction, with distorted WO NPs contributing to the activity. The results further elucidate that the anchoring of active sites at grain boundaries of the zirconia nanoparticles prevents undesirable coalescence of the active species and improves the catalyst stability and performance to make more product.
UR - http://www.scopus.com/inward/record.url?scp=79957543488&partnerID=8YFLogxK
U2 - 10.1039/c0cy00063a
DO - 10.1039/c0cy00063a
M3 - Article
AN - SCOPUS:79957543488
SN - 2044-4753
VL - 1
SP - 413
EP - 425
JO - Catalysis Science and Technology
JF - Catalysis Science and Technology
IS - 3
ER -