Time filter

Source Type

Bucharest, Romania

Berger D.,Polytechnic University of Bucharest | Matei C.,Polytechnic University of Bucharest | Voicu G.,Polytechnic University of Bucharest | Bobaru A.,Science Zecasin SA
Journal of the European Ceramic Society | Year: 2010

La1-xSrxMO3 (M = Mn, Fe, Co, Ni, x = 0-0.3) powders were obtained by solution combustion technique using metal nitrates and α-alanine. The as-prepared powders, resulted by the combustion reaction, were annealed at different temperatures to investigate the evolution of crystalline phases. For the strontium-doped lanthanum-based perovskites, higher annealing temperatures than for the corresponding pure lanthanum-based perovskites are needed to obtain single-phase compounds depending on M-site metal and strontium content. The oxide powders were investigated by FT-IR spectra, X-ray diffraction (XRD), scanning electron microscopy (SEM) and specific area measurements. Based on our results we propose different mechanisms for La1-xSrxMO3 (M = Mn, Fe, Ni, x = 0-0.3) obtaining, depending on the intermediary compounds formed in the combustion reaction or during the thermal treatment of the as-prepared powders. © 2009 Elsevier Ltd. All rights reserved. Source

Vasileios M.,University of Bucharest | Bombos D.,University of Bucharest | Bombos M.,Romanian National Institute for Research and Development in Chemistry and Petrochemistry | Ganea R.,Science Zecasin SA | Bolocan I.,University of Bucharest
Revista de Chimie | Year: 2014

Transforming glycerol in oxygenated compounds by production of ether with isobutene, represents an alternative of capitalizing by using as components for fuel. The selectivity in ethers can be improved by selecting a hydrophilic catalytic support which reduces the secondary reactions of isobutene oligomerization. Etherification experiments were conducted in a batch system in the presence of a triflic acid catalyst supported on powdered γ-Al 2O3 The distribution of the reaction products is influenced by triflic acid concentration, in the range of concentrations studied. Thus the increase of triflic acid concentration of catalyst diminishes the selectivity in monoethers and increases the selectivity in di-and tri-ethers. Source

Mangourilos V.,Petroleum Gas University of Ploiesti | Bombos D.,Petroleum Gas University of Ploiesti | Bombos M.,Romanian National Institute for Research and Development in Chemistry and Petrochemistry | Ganea R.,Science Zecasin SA | Bolocan I.,Petroleum Gas University of Ploiesti
Revista de Chimie | Year: 2014

Transforming glycerol in oxygenated compounds presents opportunities for improving the quality of diesel. Manufacturing of glycerol ether with isobutene, represents the alternative of capitalizing by use as components for fuels. The use of an effective catalyst, having a porosity suitable, enhances the performance of the process of glycerol etherification with isobutene. Also the use of catalysts in powder form favours the contact between reactants by improving the stability of emulsions. Etherification experimental program was conducted on two catalysts with the same concentration of triflic acid supported on microporous amorphous support (y-alumina) and mesoporous crystalline support (MCM-41). The selectivity in di- and tri-ethers, products with low polarity suitable as components for diesel fuels, is largely influenced by the porosity of the catalysts. Source

Andrei M.,Science Zecasin SA
Revista de Chimie | Year: 2014

This study dealt with the reaction kinetics of rapeseed oil transesterification with methyl alcohol, temperature, reactants molar ratio and catalyst amount influences upon triglycerides conversion. It was found out that increasing temperature and decreasing alcohol: oil ratio lowered triglycerides final conversion. Reaction rate is increasing with increasing temperature and catalyst amount. On the other hand increasing catalyst amount in reactants mixture also leads to a greater quantity of soap formation, detrimental to biodiesel yield. Kinetic experiments performed at 6:1 methanol : oil molar ratio, 50 and 60 °C reaction temperatures, 0.3% and 0.6% (by weight of reactants) catalyst loading, showed that during the first part, reaction evolved far from chemical equilibrium and on that time frame (0 +30 min) it is proved a second - order kinetics .Also in the same time, reaction rate constant doubles its value at a 10 °C temperature increase and is 21/2 times higher when catalyst load doubles. Source

Bombos D.,Petroleum Gas University of Ploiesti | Ganea R.,Science Zecasin SA | Matei V.,Petroleum Gas University of Ploiesti | Mawnescu C.,Science Zecasin SA | And 4 more authors.
Revista de Chimie | Year: 2014

The use of sodium bentonite to the treatment of wastewater containing anionic dyes, particulary reactive dyes in aqueous solutions, requires the modification of the hydrophilic surface by inorganic cations with organic cations exchange. Thus, the efficiency of adsorption to remove reactive dyes from aqueous solutions occurs. Samples were prepared from bentonite modified with cationic surfactants (cetyltrimethylammonium bromide, CTAB). The results of the adsorption / desorption of nitrogen showed textural changes induced by the treatment of sodium bentonite with quaternary ammonium salt and organic-inorganic hybrid materials (NaB-S) were obtained. The use of bentonite as an inexpensive sorbent for the removal of Reactive Black 5 (RB 5), Reactive Yellow 145 (RY 145) and Remazol Brilliant Blue R (RBBR) from synthetic aqueous solutions has been studied in batch conditions. The influence of some parameters such as: contact time, initial dye concentration, sorbent dose and agitation speed on sorption kinetics for dye removal were systematically investigated. Source

Discover hidden collaborations