Showing papers by "Sounak Roy published in 2012"
TL;DR: In this paper, the acid sites on γ-Al2O3 were characterized using FTIR spectroscopy of adsorbed pyridine and temperature programmed desorption (TPD) of 2-propanamine, ethanol, 1-Propanol, 2-methyl-2propanol.
Abstract: The acid sites on γ-Al2O3 were characterized using FTIR spectroscopy of adsorbed pyridine and temperature programmed desorption (TPD) of 2-propanamine, ethanol, 1-propanol, 2-propanol, and 2-methyl-2-propanol, together with density functional theory (DFT) calculations. Following room-temperature adsorption and evacuation, the surface coverages of the adsorbed alcohols were between 2 and 3.2 × 1018 molecules/m2. For each of the adsorbed alcohols, reaction to olefin and water products occurred in a narrow peak that indicated reaction is a first-order process with a well-defined activation energy, which in turn depended strongly on the particular alcohol. DFT calculations on an Al8O12 cluster are in excellent agreement with the experimental observations and show that the transition states for dehydration had carbenium-ion character. The carbenium ion stability in terms of proton affinity (of alkenes) matches well with the activation energy of the dehydration reaction. Adsorption of water on the γ-Al2O3, foll...
193 citations
TL;DR: In this article, various NOx storage-reduction (NSR) catalysts with 1-wt% noble metal loading (Pt, Pd, or Rh) dispersed on MgAl2O4 have been synthesized by single step flame spray pyrolysis.
Abstract: Various NOx storage–reduction (NSR) catalysts with 1 wt% noble metal loading (Pt, Pd, or Rh) dispersed on MgAl2O4 have been synthesized by single step flame spray pyrolysis. The as-prepared powders consisting of nonporous nanoparticles were characterized by X-ray diffraction, scanning transmission electron microscopy, nitrogen adsorption–desorption, CO chemisorption and thermogravimetric methods. Different reduction agents were applied in the fuel rich cycles: H2, CO or C3H6. Processes occurring during fuel rich and lean cycles were analyzed in detail by means of time-resolved diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and thermogravimetry combined with mass spectroscopy. With H2 as reductant, Pt/MgAl2O4 showed the best performance at short regeneration time ( 50 s). NOx storage on these catalysts was mainly restricted to surface species, although bulk nitrate species were identified by DRIFTS as well. The latter were not completely reduced under the experimental conditions used.
15 citations