Kumari Swarnima

Bio: Kumari Swarnima is an academic researcher from National Institute of Technology, Rourkela. The author has contributed to research in topics: Catalysis & Cubic zirconia. The author has an hindex of 1, co-authored 2 publications receiving 11 citations.

Ba/ZrO 2 nanoparticles as efficient heterogeneous base catalyst for the synthesis of β-nitro alcohols and 2-amino 2-chromenes

Abstract: Zirconia nanoparticles were synthesized by precipitation, urea hydrolysis, amorphous citrate and combustion synthesis methods. The zirconia surface was subsequently modified by grafting Ba 2+ species. The Ba 2+ modified zirconia (Ba/ZrO 2) materials were characterized using XRD, Fourier analysis, UV-vis-DRS, FESEM and HRTEM techniques. XRD study indicated selective stabilization of the tetragonal phase of zirconia in the presence of Ba 2+ species. Fourier line profile analysis of the XRD peaks revealed that the average crystallite size of the zirconia nanoparticles is in the range of 5-15 nm. The surface area, basicity and barium content of the material depend strongly on the method of synthesis. The Ba/ZrO 2 catalyst prepared by urea hydrolysis method exhibited higher surface area and barium content compared to other samples. The catalytic activity of the Ba/ZrO 2 catalyst was evaluated for synthesis of β-nitro alcohols and 2-amino 2-chromenes. The β-nitro alcohols were synthesized by condensation of aryl aldehydes and nitromethane. Similarly, the 2-amino 2-chromenes were synthesized by condensation of arylaldehydes, α-naphthol and malononitrile. The Ba/ZrO 2 catalyst was found to be highly efficient for synthesis of both classes of compounds providing excellent yield and purity of the products.

Ruthenium catalyst supported on Ba modified ZrO2 for ammonia decomposition to COx-free hydrogen

Abstract: The Ba modified ZrO2 materials were prepared and loaded Ru nanoparticles for ammonia decomposition to COx-free hydrogen reaction. The catalytic activity of Ru supported on Ba ZrO2 derived from sol-gel process (Ru/Ba ZrO2) is found to be several times of those for Ru/ZrO2 without any promoter and Ru Ba/ZrO2 catalysts prepared by conventional immersion method at the identical conditions. It is found that the formation of BaZrO3 phase in Ba ZrO2 can enhance the electron-donating ability of the support and Ru nanoparticles dispersion. Therefore, mobile electrons would be transferred from BaZrO3 to the surface Ru particles, facilitating the recombinative desorption of N over Ru particles, leading to the increase of activity for ammonia decomposition sufficiently. Additionally, the suitable size of spherical Ru particles with average size of 2.4 nm for the formation of active sites are also responsible factors for the higher activity of this catalyst. The catalytic performance of Ru/Ba ZrO2 catalyst can also be further improved by introducing of K and Cs promoters, and the apparent activation energies over Ru/Ba ZrO2 of 94.1 kJ/mol decrease to 70.7 kJ/mol and 64.2 kJ/mol for K and Cs promoted Ru/Ba ZrO2, respectively.

Review of green diesel production from fatty acid deoxygenation over Ni-based catalysts

Abstract: Green diesel is a second-generation biofuel developed in response to the increasing demand for liquid fuel and the predicted decrease in the availability of fossil fuels, especially diesel as the main liquid fuel used in transportation vehicles. Green diesel can be produced via deoxygenation from various feedstocks, such as vegetable oils, animal fats, fatty acids, and waste cooking oils. Normally, the deoxygenation reaction in green diesel production occurs in a multiphase system. There are three main pathways in the liquid phase of the reaction: decarboxylation, decarbonylation, and hydrodeoxygenation, from which liquid alkane hydrocarbons can be derived, and these are known as green diesel. This review paper discusses several deoxygenation pathways in a multiphase-reaction process to produce green diesel. Nickel metal is a non-noble metal catalyst which has been confirmed from many studies for use in deoxygenation with good performance. The performance of the nickel catalyst depends on different factors including the type of catalyst support and promoter, reaction temperature, reaction pressure, and reaction time. Finally, recent progress and future trends in green diesel production are discussed.

Ferrocene-Containing Ionic Liquid Supported on Silica Nanospheres (SiO2@Imid-Cl@Fc) as a Mild and Efficient Heterogeneous Catalyst for the Synthesis of Pyrano[3,2-b]Pyran Derivatives Under Ultrasound Irradiation:

Abstract: A novel heterogeneous silica nanosphere-supported ferrocene-containing ionic liquid catalyst (SiO2@Imid-Cl@Fc) was designed and synthesised and was systematically characterised by Fourier transform...

Luminescence and energy transfer mechanism in Eu 3+ /Tb 3+ -co-doped ZrO 2 nanocrystal rods

Abstract: Nanocrystal rods of Eu3+/Tb3+-co-doped ZrO2 were synthesized using a simple chemical precipitation technique. Both ions were successfully doped into the Zr4+ ion site in a mixed structure containing both monoclinic and tetragonal phases. The Eu3+ or Tb3+ singly doped zirconia produced red and green luminescence which are characteristics of Eu3+ and Tb3+ ions, respectively. The co-doped zirconia samples produced blue emission from defect states transitions in the host ZrO2, red and green luminescence from dopant ions giving cool to warm white light emissions. The phosphors were efficiently excited by ultraviolet and near-ultraviolet/blue radiations giving white and red light, respectively. The decay lifetime was found to increase with increasing donor ion concentration contrary to conventional observations reported by previous researchers. Weak quadrupole–quatdrupole multipolar process was responsible for energy transfer from Tb3+ (donor) ion to Eu3+ ion. No energy back-transfer from Eu3+ to Tb3+ ion was observed from the excitation spectra. Temperature-dependent photoluminescence shows the presence of defects at low temperature, but these defects vanished at room temperature and beyond. The Eu3+/Tb3+-co-doped ZrO2 nanocrystal rod is a potential phosphor for white light application using UV as an excitation source. Thermoluminescence measurements show that the inclusion of Tb3+ ion increases trap depths in the host zirconia.

Strong green-light emitting Tb3+ doped tetragonal ZrO2 nanophosphors stabilized by Ba2+ ions

Abstract: For a balanced white light in a phosphor down-conversion LED, a proper combination of blue, green and red emission is desirable for better colour rendering capability as desired in general illumination. Since ZrO2 has 3 polymorphism, Ba2+ ion was used to stabilize it in the tetragonal phase. A chemical bath deposition technique was employed in the synthesis procedure. X-ray diffraction measurements show pure tetragonal phase at all Tb3+ concentrations. FTIR, Raman spectroscopy, TEM and SAED analyses all confirmed the tetragonal phase of zirconia without impurity phases. Diffuse reflectance spectroscopy show the formation of both host and intraconfigurational line absorption of Tb3+ ion. Photoluminescence emissions (PL) at room and low (77 K) temperatures gave strong green emission emanating from the 5D4 – 7F5 transition. However, PL intensity was quenched at higher concentrations due to dipole - dipole interaction and energy transfer between adjacent ions. Temperature dependence PL show quenching of emission intensity as the temperature increases due to the dominance of nonradiative transitions at higher temperatures. The Ba-ZrO2: Tb3+ nanophosphors were observed to be very stable, losing half of its emission intensity at 350 °C. The CIE coordinate values of the synthesized green phosphor are comparable to the commercial green light emitting phosphors and with a purity of 83%. Hence this phosphor can be used as a green emitter for different device applications, especially in high power white LEDs.