@article { ISI:000337637100018, title = {NOx reduction at near ambient temperatures and under lean-burn conditions on modified pd surfaces}, journal = {ChemCatChem}, volume = {6}, number = {2}, year = {2014}, month = {FEB}, pages = {531-537}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

Palladium surfaces that are modified with O atoms in the subsurface broaden the NO reduction temperature regime up to 325 K with O-2-rich NO+H-2+O-2 compositions. Compared to virgin Pd surfaces, up to 150\% higher deNO(x) catalytic activity was observed with modified Pd surfaces at the reaction maximum. Molecular beam instrument and ambient-pressure photoelectron spectroscopy were employed to follow the kinetic and surface changes. These results open up a possibility to realize the cold-start reduction of NOx (deNO(x)). DeNO(x) activity reported in the literature with supported Pd catalysts after a simple calcination in air compares well with our present observations. Surface modification is likely to demonstrate a high potential for other catalytic reactions at relatively low temperatures.

}, keywords = {heterogeneous catalysis, nitrogen, oxygen, Palladium, surface chemistry}, issn = {1867-3880}, doi = {10.1002/cctc.201301033}, author = {Roy, Kanak and Gopinath, Chinnakonda S.} } @article { ISI:000349917900007, title = {Can we shift and/or broaden the catalysis regime towards ambient temperature?}, journal = {ChemCatChem}, volume = {7}, number = {4}, year = {2015}, month = {FEB}, pages = {588-594}, publisher = {WILEY-V C H VERLAG GMBH}, type = {Article}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

An attempt was made to shift the temperature regime of oxidation catalysis towards ambient temperatures by employing surface modification (SM) as a handle. Systematic SM of Pd(111) was performed by O-atom diffusion into the subsurfaces. Virgin and modified Pd(111) catalysts were evaluated for CO oxidation. Typical CO poisoning observed on virgin surfaces was partially lifted, and ambient CO oxidation was observed on the modified surfaces. CO oxidation was followed by the molecular beam method and near-ambient pressure (NAP) photoelectron spectroscopy under different pressure regimes. UV valence band spectral analysis of the SM and the CO+O-2 reaction on modified Pd(111) surfaces under NAP conditions demonstrated changes in the electronic structures of the surfaces with a change in surface potential by 0.35eV and directly probed CO2 formation under the reaction conditions. Supported metal catalysts may be subjected to SM and evaluated for a shift in the catalysis regime for many different reactions.

}, keywords = {heterogeneous catalysis, Oxidation, photoelectron spectroscopy, surface chemistry, surface modification}, issn = {1867-3880}, doi = {10.1002/cctc.201402979}, author = {Gopinath, Chinnakonda S. and Roy, Kanak and Nagarajan, Sankaranarayanan} } @article { ISI:000379531300011, title = {Effect of donors on the activation mechanism in ziegler-natta catalysis: a computational study}, journal = {Chemcatchem}, volume = {8}, number = {10}, year = {2016}, month = {MAY}, pages = {1809-1818}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {

Full quantum chemical calculations, using density functional theory (DFT), have been conducted to explain the effect of donors on the {\textquoteleft}{\textquoteleft}activation mechanism{\textquoteright}{\textquoteright} in the Ziegler-Natta (Z-N) catalyst system. In the activation mechanism, the inactive (TiCl4)-Cl-IV catalyst converts into the active (TiCl2Et)-Cl-III catalyst with the help of the AlEt3 present in the system. The donors that have been considered in this study are: ethyl benzoate (eb), two representative diether cases, a phthalate donor, and a silyl ester donor. The results indicate that eb and the diether donor cases donor have a negative effect on the barriers for the activation mechanism. However, the eb donor can be displaced from the MgCl2 surface by AlEt3, which matches experimental observations. For the phthalate, silyl ester and TiCl3-OC4H8Cl cases, the results indicate that a significant induction period would be present in Z-N systems employing such donors or having such a catalytic center, before catalysis could commence.

}, keywords = {Alkylation, aluminum, Density functional calculations, surface chemistry, titanium}, issn = {1867-3880}, doi = {10.1002/cctc.201600281}, author = {Kumawat, Jugal and Gupta, Virendra Kumar and Vanka, Kumar} }