@article { ISI:000239224100005, title = {Silica-supported bis(imino)pyridyl iron(II) catalyst: nature of the support-catalyst interactions}, journal = {Polymer International}, volume = {55}, number = {8}, year = {2006}, month = {AUG}, pages = {854-861}, publisher = {JOHN WILEY \& SONS LTD}, type = {Article}, address = {THE ATRIUM, SOUTHERN GATE, CHICHESTER PO19 8SQ, W SUSSEX, ENGLAND}, abstract = {

Ethylene polymerizations were performed using silica-supported 2,6-bis[1-(2,6-diisopropylphenylimino) ethyl] pyridine iron(II) dichloride with methylaluminoxane (MAO) as co-catalyst. Silica was calcined at 600, 400 and 200 degrees C under vacuum for 8 h. The effect of calcination temperature of silica on the polymerization activity and the properties of the polymers obtained were examined. Catalyst-support interactions were examined by both a chemical method and XPS. It was observed that upon supporting the catalyst on the surface of silica, there is an increase in the binding energy of the metal center. However, no change in the metal binding energy was observed on supporting the catalyst to silica calcined at different temperatures. Ethylene polymerizations were performed using MAO as co-catalyst. Catalysts were also prepared by first pretreating silica with NIAO, followed by addition of the Fe(II) catalyst and contacting a complex of Fe(II) catalyst-MAO with silica previously calcined at 400 degrees C for 8 h. The results indicate that there is no chemical bonding between the support and the catalyst. (C). 2006 Society of Chemical Industry.

}, keywords = {bis(imino) pyridyl iron(II) complex, Polyethylene, silica, supported catalyst, XPS}, issn = {0959-8103}, doi = {10.1002/pi.2020}, author = {Ray, Saptarshi and Sivaram, Swaminathan} } @article { ISI:000243821700012, title = {Structural evolutions of hydrothermally prepared mesostructured MCM-48 silica using differently manufactured amorphous silica powders}, journal = {Journal of Non-Crystalline Solids}, volume = {353}, number = {2}, year = {2007}, month = {FEB}, pages = {194-199}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The hydrothermal synthesis of Si-MCM-48 mesoporous molecular sieves was carried out using a ternary SiO2:CTAOH:H2O System wherein differently manufactured amorphous silica powders such as fumed silica (FMDS), spray dried precipitated silica (SDPS) and flash dried precipitated silica (FDPS) were used as silica source materials. The changes in structural/textural properties were evaluated using powder XRD, N-2 adsorption-desorption and scanning electron microscopy techniques. Studies on the progressive development of MCM-48 mesophases revealed that, the reactivity of the silica source follow the trend: FMDS \> SDPS \> FDPS. MCM-48 synthesized using low cost FDPS has exhibited thicker pore walls but poorer orderness, while MCM-48 prepared from relatively expensive FMDS has thinner pore walls and more ordered structure. Moreover, the extent of contraction caused by calcinations, agglomerate size and structural stability were found to depend on the reactivity of the silica source used. (c) 2006 Elsevier B.V. All rights reserved.

}, keywords = {long-range order, micelles, scanning electron microscopy, silica, silicates, sol-gels (xerogels), X-ray diffraction}, issn = {0022-3093}, doi = {10.1016/j.jnoncrysol.2006.10.005}, author = {Taralkar, U. S. and Jha, Ratnesh Kumar and Joshi, P. N.} } @article {44630, title = {Continuous flow synthesis of micron size silica nanoparticles: parametric study and effect of dosing strategy}, journal = {Journal of Flow Chemistry}, volume = {8}, year = {2018}, month = {JUN}, pages = {59-67}, abstract = {

This work for the first time reports continuous flow synthesis of silica nano-particles of size over 1 mu m using a simple tubular reactor. The systematic approach involves the study of effect of various parameters like: ammonia concentration, water concentration, electrolyte concentraton, temperature, solvent, residence time and mode of TEOS injection over a wide range. A combination of ethanol and butanol was used as the medium with relatively lower polarity. Various process parameters were optimized to obtain highly monodispersed particles of size up to 600 nm and high yield (up to 90\%). Attempts of reducing the reaction time by increasing temperature or concentrations of any of the reagents resulted in significant polydispersity and even in the formation of random shape agglomerates. At the optimized conditions almost complete conversion of TEOS happenned within 40 min and further growth of particles was achieved by adding TEOS using multipoint injection approach. While multipoint dosing resulted in the formation of very small number of secondary particles, the larger particles continued to grow beyond 800 nm. Further reduction in the polarity of reaction medium was achieved by adding 20\% v/v of toluene, which without changing homogeneity of the solution resulted in particles as large as 0.9-1.1 mu m.

}, keywords = {Flow synthesis, Multipoint injection, silica, TEOS, Tubular reactor}, issn = {2062-249X}, doi = {10.1007/s41981-018-0008-3}, author = {Jundale, Rajashri and Bari, Atul and Thara, Chinnu and Kulkarni, Amol} } @article {45533, title = {Process development of silica extraction from RHA: a cradle to gate environmental impact approach}, journal = {Environmental Science and Pollution Research}, volume = {26}, year = {2019}, month = {JAN}, pages = {492-500}, type = {Article}, abstract = {

India is one of the major rice-producing countries. Rice husk is a major agricultural by-product from rice production, which is used as a fuel in boilers. Its use as fuel produces huge amounts of silica-rich rice husk ash (RHA). This paper aims at providing an overall assessment of environmental impacts associated with the extraction of silica from RHAa process developed by our study group. The functional unit used in this study is production of 100kg of silica. The analysis included the extraction and transportation of other raw materials; RHA was assumed to be processed at the site. The study was conducted in accordance with the international ISO 14040 procedural framework. LCA is performed using GaBi Education software, and five midpoint indicators are chosen to assess the environmental impacts of silica extraction. The overall climate change (CC) of the extraction process is 7.26kg CO2 equivalent per kg of silica produced. A high contribution of calcination to CC is attributed to the use of electricity. The comprehensive environmental impacts of silica-rich RHA resulting from processing of RHA and improvement options to achieve sustainable production are presented. The negative impacts that can be avoided during silica extraction are also discussed. It is observed that calcination is a major contributor to the overall environmental indicators. The work also stresses on the use of renewable energy for electricity generation, which would help in decreasing the overall greenhouse gas emissions during extraction while ensuring waste utilization.

}, keywords = {Environmental impacts, Life cycle assessment, Rice husk ash, silica}, issn = {0944-1344}, doi = {10.1007/s11356-018-3648-9}, author = {Joglekar, Saurabh N. and Kharkar, Rhushikesh A. and Mandavgane, Sachin A. and Kulkarni, Bhaskar D.} }