@article {45527, title = {Operando X-ray absorption spectroscopy study of the Fischer-Tropsch reaction with a Co catalyst}, journal = {Journal of Synchrotron Radiation}, volume = {26}, year = {2019}, month = {JAN}, pages = {137-144}, type = {Article}, abstract = {

This article describes the setting up of a facility on the energy-scanning EXAFS beamline (BL-09) at RRCAT, Indore, India, for operando studies of structure-activity correlation during a catalytic reaction. The setup was tested by operando X-ray absorption spectroscopy (XAS) studies performed on a Co-based catalyst during the Fischer-Tropsch reaction to obtain information regarding structural changes in the catalyst during the reaction. Simultaneous gas chromatography (GC) measurements during the reaction facilitate monitoring of the product gases, which in turn gives information regarding the activity of the catalyst. The combination of XAS and GC techniques was used to correlate the structural changes with the activity of the catalyst at different reaction temperatures. The oxide catalyst was reduced to the metallic phase by heating at 400 degrees C for 5h under H-2 at ambient pressure and subsequently the catalytic reaction was studied at four different temperatures of 240, 260, 280 and 320 degrees C. The catalyst was studied for 10h at 320 degrees C and an attempt has been made to understand the process of its deactivation from the XANES and EXAFS results.

}, keywords = {catalysis, EXAFS, Fischer-Tropsch reaction, in situ studies, structure-activity correlation, XANES}, issn = {1600-5775}, doi = {10.1107/S1600577518015588}, author = {Nayak, Chandrani and Jain, Preeti and Vinod, C. P. and Jha, S. N. and Bhattacharyya, D.} } @article {46715, title = {Spectroscopic evidences for the size dependent generation of pd species responsible for the low temperature CO oxidation activity on Pd-SBA-15 nanocatalyst}, journal = {Applied Catalysis B-Environmental}, volume = {272}, year = {2020}, month = {SEP }, pages = {118934}, type = {Article}, abstract = {

A comprehensive size dependent CO oxidation activity has been demonstrated for Pd-SBA-15 catalysts with Pd NPs of varying sizes such as 1-2, 4-6 and 7-10 nm. Pd-SBA-15 catalyst with smallest sized NPs (Pd-S-N) has been synthesized by modified deposition precipitation method recently developed in our lab. Pd-S-N catalyst (reduced at 400 degrees C) demonstrated CO oxidation activity with lower light off temperature (50 degrees C), clearly one of the best reported for a Pd-silica system. A detailed XPS and in-situ DRIFTS analyses further supported by XAS and DFT calculations reveal the presence of easily decomposable highvalent Pd-oxide on co-ordinatively unsaturated Pd sites (Pdcus). Weak binding of CO on Pdcus sites in small Pd NPs leaving sites for oxygen activation is attributed to the low temperature activity of Pd-S-N for CO oxidation.

}, keywords = {CO oxidation, high-valent Pd species, Pd nanoparticles, SBA-15, under coordinated Pd atoms}, issn = {0926-3373}, doi = {10.1016/j.apcatb.2020.118934}, author = {Soni, Yogita and Pradhan, Sumanta and Bamnia, Mahesh K. and Yadav, A. K. and Jha, S. N. and Bhattacharyya, D. and Khan, Tuhin Suvra and Haider, M. A. and Vinod, C. P.} } @article {48765, title = {MnXWO4 nanostructure-based catalysts for single-step oxidation of cyclohexane and methane to oxygenates}, journal = {ACS Applied Nano Materials}, volume = {6}, year = {2023}, month = {APR}, pages = {7245-7258}, type = {Article}, abstract = {

Activation of the C-H bond in cyclohexane (CYH) and methane is a crucial step to obtain desirable oxygenated products using nanostructured catalyst and is a great challenge and an efficient route to mitigate the inauspicious effects of climate change. The active sites were identified using XRD, HR-TEM, SEM, N2 sorption analysis, TPR, Raman, XPS, TGA, in situ DRIFT, XAS, etc. In optimal reaction conditions, 46\% of CYH was converted into adipic acid (AA) on MnxWO4 nanostructures within 6 h. The recyclability test confirmed the catalyst heterogeneity, which revealed no appreciable loss of catalytic activity even after three consecutive reactions. In situ DRIFT study reveals that CYH is oxidized to cyclohexanone and cyclohexanol (KA oil) and is further oxidized to AA via carboxylate intermediates. DFT studies disclosed that MnOx species are responsible for the C-H activation of CYH, and the Mn2+/Mn3+ redox centers play a vital role in the absorption of KA oil to form AA. Herein, we demonstrated the significant role of the {\textquoteleft}{\textquoteleft}MnOx{\textquoteright}{\textquoteright} species and that adequate Lewis and Bronsted acidic sites, redox centers of (Mn2+/Mn3+), and lattice oxygen are accountable for the CYH conversion toward the AA. Additionally, we have reported the oxidation of methane to methanol (146 mu mole per gram of catalyst) in the presence of water at 75 degrees C without over-oxidation products.

}, keywords = {Adipic Acid, C-H bond activation, Cyclohexane oxidation, methane activation, MnOx chain, Redox center}, doi = {10.1021/acsanm.3c00319}, author = {Prabu, Marimuthu and Manikandan, Marimuthu and Samal, Pragnya Paramita and Gurrala, Lakshmi Prasad and Mekala, Siva Prasad and Archana, Ramakrishnan and Nayak, Chandrani and Bhattacharyya, D. and Jha, S. N. and Krishnamurty, Sailaja and Raja, Thirumalaiswamy} }