Now showing 1 - 5 of 5
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    Ordered Mesoporous Carbon-supported Morphologically-controlled Nano-Gold: Role of Support as well as the Shape and Size of Gold Nanoparticles on the Selective Oxidation of Glycerol
    (22-03-2022)
    Murthy, Palle Ramana
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    Glyceric acid is one of the important intermediates of glycerol oxidation. However, it is extremely difficult to achieve high glyceric acid selectively as the reaction follows a complex pathway with the formation of a variety of undesired products. In this context, periodic mesoporous carbon-supported gold catalysts show promise for selective formation of the targeted product. Therefore, in this investigation, an effort has made to study the effect of particle size and shape of a series of carbon supported with varied sized/shaped gold catalysts on the liquid-phase oxidation of glycerol. Further, the role played by the surface of gold-nanoparticles has prompted us to investigate in detail the isotropic (nanocube/nanosphere) and anisotropic (nanoslabs/nanorods) gold supported onto both activated/amorphous carbon (Au/AC) and ordered mesoporous carbon (Au/CMK-3) towards glycerol oxidation. It was observed that the CMK-3 supported gold nanocube exhibited the highest yield towards glyceric acid with an excellent stability in terms of recyclability/reusability.
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    Publication
    Immobilization of Recombinant Endo-1,4-β-xylanase on Ordered Mesoporous Matrices for Xylooligosaccharides Production
    (17-10-2019)
    Shivudu, Godhulayyagari
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    Khan, Sourav
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    Xylooligosaccharides (XOS) are emerging prebiotics, widely used in food, medicine and health care. XOS are produced by hydrolysis of xylan by acid or endoxylanase enzyme. Xylanase hydrolysis is preferred over acid due to its high specificity and absence of formation of non-toxic byproducts. Immobilized xylanase improves enzyme-stability and efficacy of XOS production through its repeated use. Though there are a few xylanases immobilized on conventional organic polymers for XOS production, immobilization of xylanse on mesoporous inorganic materials have not been investigated for XOS production. In this study, the recombinant endo-1, 4-β-D-xylanase (XynC) of B.subtilis KCX006 was purified and immobilized on ordered mesoporous matrices of carbon (CMK-3), silica (SBA-15) and zirconia (ZMF-127). The immobilized-XynC was characterized and used for XOS production by recycling. The recovered activity (RA) of immobilized-XynC varied between 55 to 84%. The maximum RA was observed for XynC immobilized on ZMF-127 matrix. All immobilized-XynC had optimum pH similar to that of free-XynC. But all immobilized-XynC gained broader temperature range (50-65°C) for optimal catalytic activity when compared with the free-XynC. Immobilization of XynC resulted in higher Km due to substrate diffusion limit. All immobilized-XynC produced free-XOS of DP 2–6 (X2-X6) and substituted-XOS from beechwood xylan and extracted crude xylans from sorghum stalks and sugarcane bagasse (SCB). The XynC immobilized on SBA-15 produced higher proportions of X2-X6 compared to ZMF-127 and CMK-3. The XynC immobilized on SBA-15 and CMK-3 retained higher activity of 85–93% after four batches of repeated use. The observed efficiency of XynC immobilized on CMK-3 and SBA-15 are higher than the reported values. The results showed that XynC immobilized on mesoporous carbon and silica matrices would be useful for production of XOS by enzyme recycling.
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    Publication
    The Enhanced Catalytic Performance and Stability of Ordered Mesoporous Carbon Supported Nano-Gold with High Structural Integrity for Glycerol Oxidation
    (01-09-2019)
    Murthy, Palle R.
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    Ordered mesoporous carbon (OMC) supported gold nanoparticles of size 3–4 nm having uniform dispersion were synthesized by sol-immobilization method. OMCs such as CMK-3 and NCCR-56 with high surface area and uniform pore size were obtained, respectively, using ordered mesoporous silicas such as SBA-15 and IITM-56 as hard templates, respectively. The resulting OMC supported monodispersed nano-gold, i. e., Au/CMK-3 and Au/NCCR-56, exhibited excellent performance as mild-oxidizing catalysts for oxidation of glycerol with high hydrothermal stability. Further, unlike activated carbon supported nano-gold catalysts (Au/AC), the OMC supported nano-gold catalysts, i. e., Au/CMK-3 and Au/NCCR-56, show no aggregation of active species even after recycling. Thus, in the case of Au/CMK-3 and Au/NCCR-56, both the fresh and regenerated catalysts showed excellent performane for the chosen reaction owing to an enhanced textural integrity of the catalysts and that with remarkable selectivity towards glyceric acid. The significance of the OMC supports in maintaining the dispersion of gold nanoparticles is explicit from this study, and that the activity of Au/AC catalyst is considerably decreased (∼50 %) upon recycling as a result of agglomeration of the active gold nanoparticles over the disordered amorphous carbon matrix.
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    Electrochemical performance of nano-LiFePO4 embedded ordered mesoporous nitrogenous carbon composite as cathode material for Li-ion battery applications
    (01-09-2019)
    Khan, Sourav
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    Raj, Rayappan P.
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    Mohan, Talla V.R.
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    Bhuvaneswari, Subramani
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    We report here the preparation and electrochemical characterization of nano-sized LiFePO4, starting from Fe(III) precursor, embedded in ordered mesoporous nitrogenous carbon (LFP/MNC-31). For comparison, LFP nanoparticles embedded in nitrogen-free ordered mesoporous carbon (LFP/CMK-3) was also prepared and studied. Both these composites were characterized using XRD, FT-Raman, TEM, SEM and nitrogen sorption studies prior to electrochemical testing. The ordered and mesoporous nature of the carbon in the composites was established by small-angle XRD and BET isotherms. Reitveld refined XRD data reveals single phase formation of LFP with good crystallinity. TEM studies show that the LFP nanoparticles are embedded in the mesopores of the carbon matrix. Electrochemical studies in half-cell mode (vs. Li+/Li) reveal that the Li-ion diffusion coefficient values in the composites are remarkably higher (6–7 orders of magnitude) compared to pristine LFP. Furthermore, the LFP/MNC-31 composite shows relatively better electrochemical properties in terms of specific capacity, rate capability and cyclic stability vis-à-vis LFP/CMK-3 highlighting the importance of nitrogen doping in the carbon matrix in enhancing the electrochemical performance.
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    Publication
    Platinum-supported mesoporous carbon (Pt/CMK-3) as anodic catalyst for direct methanol fuel cell applications: The effect of preparation and deposition methods
    (01-01-2012)
    Kuppan, Balaiah
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    Platinum-supported ordered mesoporous carbon catalysts were prepared employing colloidal platinum reduced by four different reducing agents, viz., paraformaldehyde, sodium borohydride, ethylene glycol and hydrogen, and deposited over ordered mesoporous carbon (CMK-3) synthesized by silica hard template (SBA-15). The resulting platinum nanoparticles supported mesoporous carbon, designated as Pt/CMK-3, catalysts were tested for the electocata-lytic oxidation of methanol. The effect of the various reduction methods on the influence of particle size vis-à-vis on the electrocatalytic effect is investigated. All the catalysts were systematically characterized by XRD, BET and TEM. The results of the synthetic methods, characterization techniques and the electrocatalytic performance indicate that the Pt/CMK-3 catalysts are superior to that prepared with activated carbon (Pt/AC) as well as with that of the commercial platinum-supported carbon catalyst (Pt/E-TEK). In particular, the catalyst, Pt/CMK-3, prepared using paraformaldehyde reduced platinum showed much higher activity and long-term stability as compared to the other reducing methods.