Search

Your search keyword '"Veljkovic, Vlada B."' showing total 36 results
Start Over Author "Veljkovic, Vlada B." Publication Year Range Last 10 years
36 results on '"Veljkovic, Vlada B."'

7. Production of biofuels from sorghum

Author

Stamenković, Olivera S., Siliveru, Kaliramesh, Veljković, Vlada B., Banković-Ilić, Ivana B., Tasić, Marija B., Ciampitti, Ignacio A., Đalović, Ivica G., Mitrović, Petar M., Sikora, Vladimir Š., and Prasad, P.V. Vara

Published
2020
Full Text
View/download PDF

35. Transesterification of used cooking sunflower oil catalyzed by hazelnut shell ash

Author

Miladinovic, Marija R., Krstic, Jugoslav B., Zdujic, Miodrag, V, Veselinovic, Ljiljana M., Veljović, Đorđe, Bankovic-Ilic, Ivana B., Stamenkovic, Olivera S., Veljkovic, Vlada B., Miladinovic, Marija R., Krstic, Jugoslav B., Zdujic, Miodrag, V, Veselinovic, Ljiljana M., Veljović, Đorđe, Bankovic-Ilic, Ivana B., Stamenkovic, Olivera S., and Veljkovic, Vlada B.

Abstract

Hazelnut shell ash was investigated as a new base catalyst for the transesterification of used cooking sunflower oil to biodiesel. To understand its catalytic properties, the prepared ash was characterized by EDX, XRD, TGA/DTA, Hg porosimetry, N-2 physisorption, FE-SEM, and basic strength measurements. The effects of the catalyst loading in the range of 1-5% of the oil weight and the methanol-to-oil molar ratio of 6:1-18:1 on the kinetics of the fatty acid methyl esters synthesis were established. Moreover, the leaching and reusability of the catalyst were assessed. The obtained results revealed that hazelnut shell ash was mostly composed of K, Ca, and Mg. The highest ester content (98%) was achieved at the catalyst loading of 5%, the methanol-to-oil molar ratio of 12:1, and the reaction time of 10 min. The contribution of homogeneous catalysis because of the catalyst leaching was confirmed but did not determine the overall reaction rate. The catalyst can be reused after the recalcination at 800 degrees C for 2 h achieving the high methyl esters content (>96%) in 30 min after three subsequent runs. The overall reaction followed the pseudo-first-order kinetics with respect to triacylglycerols. A linear relationship between the apparent reaction rate constant and the catalyst loading and the methanol-to-oil molar ratio was determined. The determined value of the reaction rate constant was 0.0576 dm(6)/(min.mol(2)).

Published
2022

36. The chicken eggshell calcium oxide ultrasonically dispersed over lignite coal fly ash-based cancrinite zeolite support as a catalyst for biodiesel production

Author

Pavlovic, Stefan M., Marinkovic, Dalibor M., Kostic, Milan D., Loncarevic, Davor R., Mojović, Ljiljana, Stankovic, Miroslav, V, Veljkovic, Vlada B., Pavlovic, Stefan M., Marinkovic, Dalibor M., Kostic, Milan D., Loncarevic, Davor R., Mojović, Ljiljana, Stankovic, Miroslav, V, and Veljkovic, Vlada B.

Abstract

Lignite coal fly ash (FA) from a domestic thermal power plant was converted into a pure cancrinite zeolitic material (ZM(FA)) using a novel, custom-made, rotating autoclave reactor system by a short-term alkali activation process. The obtained ZM(FA) was used as catalyst support of calcium oxide as an active component derived from waste chicken eggshells (ES). The ZM(FA) supported calcium oxide catalyst (xCaO/ZM(FA)) was synthesized by means of the ultrasound-assisted method. The influence of different concentrations of dispersed calcium oxide (x = 5-20 wt%) over ZM(FA) and thermal treatment at different temperatures (450-600 degrees C) were studied. The structural and morphological characterization showed that the original cancrinite structure was preserved. The basicity and textural properties indicated the presence of strong active sites in a well-defined pore network suitable for the reactions of bulky organic compounds such as triacylglycerols (TAGs). The highest activity (96.5% of fatty acid methyl esters) in the methanolysis of sunflower oil was achieved with the 20CaO/ZM(FA) catalyst under reaction conditions: temperature of 60 degrees C, methanol/oil molar ratio of 12:1, catalyst concentration of 4 wt%, and reaction time of 2 h. It was found that the optimal calcination temperature of the catalyst precursor was 550 degrees C. At calcination temperatures above 550 degrees C, the melting of the glassy phase became more intense whereby the molten phase partially reacted with calcium oxide forming the catalytically inactive calcium silicate compounds (wollastonite, larnite, etc.). The rate constants of the two tested kinetic models were correlated with the concentrations of active calcium oxide. The MRPD of both models was low indicating their reliability.

Published
2021

Catalog

Books, media, physical & digital resources
See catalog results