3 research outputs found
Synthesis and characterization of calcium based mixed oxide catalysts and their application in heterogenously catalyzed biodiesel synthesis
U ovom radu proučavana je primena mehanohemije u sintezi prekursora aktivnih
katalizatora reakcije transesterifikacije suncokretovog ulja. Ispitivan je uticaj različitih
metoda sinteze – mehanohemijske, sa i bez dodatka vode i, radi poređenja, taložne – na
osobine dobijenog prekursora CaZn2(OH)6·2H2O. Smeša prahova Ca(OH)2 i ZnO u
molskom odnosu od 1:2 je podvrgnuta mlevenju u planetarnom mlinu tokom
vremenskog perioda od 7 h, uz dodatak stehiometrijski potrebne količine vode, kao i
bez dodatka vode. Izvršena je i sinteza prekursora katalizatora koprecipitacijom
Ca(OH)2 i ZnO u vodenom rastvoru KOH radi poređenja. Prekursorski prahovi dobijeni
u sve tri sinteze su višefazni, a njihova aktivacija izvršena je na temperaturi od 700 °C,
čime su prevedeni u mešoviti oksid CaO·ZnO. Nakon kalcinacije, katalizatori su
primenjeni u sintezi metil estara masnih kiselina (MEMK) suncokretovog ulja. Izvršena
je i detaljna fizičko-hemijska karakterizaciju pripremljenih prahova, pre i posle
kalcinacije: strukturna karakterizacija dobijenih prahova urađena je metodom
rendgenske strukturne analize (XRD), dok je morfološka karakterizacija prahova nakon
žarenja urađena skenirajućom elektronskom mikroskopijom (SEM/EDS). Takođe,
primenjivana je i termijska analiza (TGA/DSC), i infracrvena (IC) spektroskopija radi
dobijanja dodatnih informacija o strukturi i sastavu katalizatora. Kako pomenuti
katalizatori daju različite prinose u reakciji transesterifikacije triglicerida sa metanolom,
utvrđena je bitna povezanost između baznosti katalizatora pripremljenih različitim
metodama i katalitičke efikasnosti. Mehanohemijska sinteza se, u odnosu na
konvencionalnu koprecipitaciju, pokazala kao jednostavnija metoda koja ne uključuje
rastvarač i dodatak alkalija koje mogu ometati uvid u stvarnu katalitičku aktivnost, a
ujedno i kao efikasnija metoda za dobijanje aktivnih prekursora mešovitih oksida.
Pored Ca(OH)2, kao polazni prah korišćen je i CaO, dobijen nakon žarenja
Ca(OH)2 na 700 °C, kao i negašeni kreč, a sve sa ciljem smanjenja količine prisutnih
karbonata u sintetisanim prekursorima. Uticaj dodatka promotora (K2CO3) tokom
mehanohemijske sinteze na strukturu i katalitičku aktivnost je ispitivan variranjem odnosa K:Ca...The use of mechanochemical synthesis to obtain active catalyst precursors and
testing their activity in transesterification of sunflower oil with methanol was
investigated. The effect of different methods for preparation of catalytic precursor
(CaZn2(OH)6·2H2O) – mechanochemical, with or without the addition of water and
coprecipitation were investigated. A powder mixture of Ca(OH)2 and ZnO, with the
molar ratio of 1:2, with, as well as without stoichiometrically required addition of water
were milled in a planetary ball mill for a period of 7 hours. The classical coprecipitation
procedure of Ca(OH)2 and ZnO powders in KOH solution was also performed for
comparison.
Precursor powders obtained after above mentioned procedures were multiphase,
and their activation was carried out at temperature of 700 °C, in order to convert them to
CaO·ZnO mixed oxide. After calcination, the catalytic activity was tested in the
synthesis of fatty acid methyl esters (FAME) from sunflower oil. Structural
characterization of obtained powders was done by X-ray diffraction (XRD) analysis,
while morphology was observed by scanning electron microscopy (SEM/EDS).
Thermal analysis (TG / DSC) was also applied, as well as infrared spectroscopy (IR) in
order to obtain additional information on the structure and composition of the catalysts.
The difference in the activity of mechanochemically synthesized catalysts and catalyst
prepared by coprecipitation procedure could be related to the difference in their basicity.
Mechanochemical synthesis has an advantage over the coprecipitation due to its relative
simplicity – solid phase reactions without usage of solvents or precipitants which can
interfere with catalytic activity.
Using CaO, obtained after calcination of Ca(OH)2 at 700 °C, and lime as a
starting powders was investigated in order to reduce the amount of carbonates present in
the synthesized precursors. Influence of promoter (K2CO3) added to starting mixture of
lime and ZnO for mechanochemical synthesis on precursor structure and catalytic
activity was examined by varying the ratio of K:Ca..
Synthesis and characterization of calcium based mixed oxide catalysts and their application in heterogenously catalyzed biodiesel synthesis
U ovom radu proučavana je primena mehanohemije u sintezi prekursora aktivnih
katalizatora reakcije transesterifikacije suncokretovog ulja. Ispitivan je uticaj različitih
metoda sinteze – mehanohemijske, sa i bez dodatka vode i, radi poređenja, taložne – na
osobine dobijenog prekursora CaZn2(OH)6·2H2O. Smeša prahova Ca(OH)2 i ZnO u
molskom odnosu od 1:2 je podvrgnuta mlevenju u planetarnom mlinu tokom
vremenskog perioda od 7 h, uz dodatak stehiometrijski potrebne količine vode, kao i
bez dodatka vode. Izvršena je i sinteza prekursora katalizatora koprecipitacijom
Ca(OH)2 i ZnO u vodenom rastvoru KOH radi poređenja. Prekursorski prahovi dobijeni
u sve tri sinteze su višefazni, a njihova aktivacija izvršena je na temperaturi od 700 °C,
čime su prevedeni u mešoviti oksid CaO·ZnO. Nakon kalcinacije, katalizatori su
primenjeni u sintezi metil estara masnih kiselina (MEMK) suncokretovog ulja. Izvršena
je i detaljna fizičko-hemijska karakterizaciju pripremljenih prahova, pre i posle
kalcinacije: strukturna karakterizacija dobijenih prahova urađena je metodom
rendgenske strukturne analize (XRD), dok je morfološka karakterizacija prahova nakon
žarenja urađena skenirajućom elektronskom mikroskopijom (SEM/EDS). Takođe,
primenjivana je i termijska analiza (TGA/DSC), i infracrvena (IC) spektroskopija radi
dobijanja dodatnih informacija o strukturi i sastavu katalizatora. Kako pomenuti
katalizatori daju različite prinose u reakciji transesterifikacije triglicerida sa metanolom,
utvrđena je bitna povezanost između baznosti katalizatora pripremljenih različitim
metodama i katalitičke efikasnosti. Mehanohemijska sinteza se, u odnosu na
konvencionalnu koprecipitaciju, pokazala kao jednostavnija metoda koja ne uključuje
rastvarač i dodatak alkalija koje mogu ometati uvid u stvarnu katalitičku aktivnost, a
ujedno i kao efikasnija metoda za dobijanje aktivnih prekursora mešovitih oksida.
Pored Ca(OH)2, kao polazni prah korišćen je i CaO, dobijen nakon žarenja
Ca(OH)2 na 700 °C, kao i negašeni kreč, a sve sa ciljem smanjenja količine prisutnih
karbonata u sintetisanim prekursorima. Uticaj dodatka promotora (K2CO3) tokom
mehanohemijske sinteze na strukturu i katalitičku aktivnost je ispitivan variranjem odnosa K:Ca...The use of mechanochemical synthesis to obtain active catalyst precursors and
testing their activity in transesterification of sunflower oil with methanol was
investigated. The effect of different methods for preparation of catalytic precursor
(CaZn2(OH)6·2H2O) – mechanochemical, with or without the addition of water and
coprecipitation were investigated. A powder mixture of Ca(OH)2 and ZnO, with the
molar ratio of 1:2, with, as well as without stoichiometrically required addition of water
were milled in a planetary ball mill for a period of 7 hours. The classical coprecipitation
procedure of Ca(OH)2 and ZnO powders in KOH solution was also performed for
comparison.
Precursor powders obtained after above mentioned procedures were multiphase,
and their activation was carried out at temperature of 700 °C, in order to convert them to
CaO·ZnO mixed oxide. After calcination, the catalytic activity was tested in the
synthesis of fatty acid methyl esters (FAME) from sunflower oil. Structural
characterization of obtained powders was done by X-ray diffraction (XRD) analysis,
while morphology was observed by scanning electron microscopy (SEM/EDS).
Thermal analysis (TG / DSC) was also applied, as well as infrared spectroscopy (IR) in
order to obtain additional information on the structure and composition of the catalysts.
The difference in the activity of mechanochemically synthesized catalysts and catalyst
prepared by coprecipitation procedure could be related to the difference in their basicity.
Mechanochemical synthesis has an advantage over the coprecipitation due to its relative
simplicity – solid phase reactions without usage of solvents or precipitants which can
interfere with catalytic activity.
Using CaO, obtained after calcination of Ca(OH)2 at 700 °C, and lime as a
starting powders was investigated in order to reduce the amount of carbonates present in
the synthesized precursors. Influence of promoter (K2CO3) added to starting mixture of
lime and ZnO for mechanochemical synthesis on precursor structure and catalytic
activity was examined by varying the ratio of K:Ca..
Supercritical fluid extraction of curry flowers, sage leaves, and their mixture
Yield and composition of curry flower (Helichrysum italicum) and sage leaves (Salvia officinalis) extract obtained by supercritical CO2 extraction (SFE) at 15 MPa and 40 degrees C were analyzed and compared to composition of curry flowers and sage essential oil isolated by hydrodistillation. Furthermore, the SFE performed using a mixture of curry flowers and sage plant and SFE of mixture of curry flowers and essential oil of sage were analyzed, too. It was shown that the average selectivity of monoterpenes and some individual sesquiterpenes and diterpenes present in pure sage or pure curry extract were significantly changed when mixture of these plants was used for SFE. The goal of SFE realized with mixture of curry flowers and sage essential oil was to explain effect of essential oil used as co-solvent changing the solubility of different compounds or characteristic group of terpenes in supercritical CO2. Increased extraction of heavier compounds from curry flower which is actually not present in pure essential oil of sage was also detected. The pseudo-kinetic model was proposed and corresponding parameters which define the rate of extraction were determined and compared to the parameters obtained according to Sovova's model usually used in literature for predicting yield of SFE from different plants