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 of calcium oxide based catalysts for biodiesel production

In this work, synthesis of several types of calcium oxide based catalysts by mechanochemical treatment and subsequent calcination is presented. Prepared nanocomposite CaO·ZnO, calcium containing perovskites CaTiO3, CaMnO3, CaZrO3 and Ca2Fe2O5, a series of CaO·SiO2 mixed oxides and calcium diglyceroxide (CaDG) were characterized and tested in the methanolysis of sunflower oil under different working conditions: catalyst amount, agitation speed, temperature and methanol to oil molar ratio

Synthesis of calcium oxide based catalysts for biodiesel production

In this work, synthesis of several types of calcium oxide based catalysts by mechanochemical treatment and subsequent calcination is presented. Prepared nanocomposite CaO·ZnO, calcium containing perovskites CaTiO3, CaMnO3, CaZrO3 and Ca2Fe2O5, a series of CaO·SiO2 mixed oxides and calcium diglyceroxide (CaDG) were characterized and tested in the methanolysis of sunflower oil under different working conditions: catalyst amount, agitation speed, temperature and methanol to oil molar ratio

Preparation of calcium containing mixed oxides as solid base catalysts for the application in biodiesel synthesis

Biodiesel (fatty acid methyl esters - FAME) has been found suitable for using as an alternative fuel in diesel engine. The conventional method for biodiesel production is transesterification of vegetable oils or animal fats with short-chain alcohols in the presence of catalysts. From an economic point of view, calcium oxide (CaO) is the most widely used and exhibits good catalytic properties for transesterification of triglycerides to biodiesel. In order to study the effect of solid base catalysts for biodiesel production, transesterification of edible sunflower oil with methanol was carried out in the presence of series of CaO-based oxides, obtained by mechanochemical treatment of CaO or CaCO3 with other metal oxides, followed by calcination. Mechanochemical treatment of starting powders mixtures was performed in a planetary ball mill using two different milling media, hardened steel or zirconia vials and balls. The prepared catalysts were characterized by X-ray diffraction (XRD), base strength using Hammett indicator method and the particle size using laser diffraction distribution (PSLD). All the experiments were carried out at different reaction conditions in 300 cm3 batch autoclave equipped with a heater and mixer. The calcium containing mechanochemically prepared catalysts were found to have enhanced activity compared to conventionally prepared catalysts

Biodiesel synthesis based on CaO·ZnO.K2CO3 as catalyst

The mixed oxide of CaO·ZnO and K2CO3 were prepared by ball milling of CaO and ZnO powders and water, with addition of K2CO3 and afterward by calcination at 700 oC. Influence of different molar ratio of K2CO3 and CaO (x=1, 2 and 4 moles of K2CO3 per 10 moles of CaO) was studied . The prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), scanningelectron microscopy/energy-dispersive spectroscopy (SEM/EDS) and the particle size laser diffraction (PSLD) distribution. The addition of smaller amount of K2CO3 at the beginning of ball miling (x≤2), favors the formation of calcium zinc hydroxide hydrate, while it is not the case when K2CO3 larger addition was used (x > 2). A larger amount of potassium carbonate in the initialcomposition of powder mixture negatively affected formation of CaZn2(OH)6·2H2O. Bimodal distribution were detected for all samples after calcination at 700 oC and the results showed that the distribution of elements in the bulk is not homogeneous and that surface of formed mixed oxide CaO.ZnO (XPS analysis) after calcination is mainly covered by potassium species. That evidence indicate that the K2CO3 was not fully incorporated into the matrix. Prepared samples could be used for methanolysis of vegetable oil and fatty acid methyl esters (FAME, i.e. biodiesel) synthesis

Biodiesel synthesis based on CaO·ZnO.K2CO3 as catalyst

The mixed oxide of CaO·ZnO and K2CO3 were prepared by ball milling of CaO and ZnO powders and water, with addition of K2CO3 and afterward by calcination at 700 oC. Influence of different molar ratio of K2CO3 and CaO (x=1, 2 and 4 moles of K2CO3 per 10 moles of CaO) was studied . The prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and the particle size laser diffraction (PSLD) distribution. The addition of smaller amount of K2CO3 at the beginning of ball miling (x≤2), favors the formation of calcium zinc hydroxide hydrate, while it is not the case when K2CO3 larger addition was used (x > 2). A larger amount of potassium carbonate in the initial composition of powder mixture negatively affected formation of CaZn2(OH)6·2H2O. Bimodal distribution were detected for all samples after calcination at 700 oC and the results showed that the distribution of elements in the bulk is not homogeneous and that surface of formed mixed oxide CaO.ZnO (XPS analysis) after calcination is mainly covered by potassium species. That evidence indicate that the K2CO3 was not fully incorporated into the matrix. Prepared samples could be used for methanolysis of vegetable oil and fatty acid methyl esters (FAME, i.e. biodiesel) synthesis

Mechanochemical Preparation of CaO·ZnO – catalyst for Fatty Acids Methyl Esters Synthesis

One of the catalysts that show excellent activity in the methanolysis of vegetable oil under moderate reaction conditions is the mixture of CaO and ZnO oxides. In this study CaO•ZnO catalyst was synthesized by mechanochemical treatment of ZnO and Ca(OH)2 or CaO powder mixture (using molar ratio of CaO (or Ca(OH)2):ZnO of 1:2) with the addition of required water amount to form calcium zinc hydroxide hydrate (CaZn2(OH)6•2H2O) and subsequent calcinations at 700 °C in air atmosphere. The methanolysis of sunflower oil was studied at 60 °C with the molar ratio of methanol to oil of 10:1 and with 2 wt% of catalyst based on oil weight. Characterisation of the catalyst was performed by XRD, TGA/DSC, FTIR, the particle size distribution and Hammett indicator method. The solubility of the catalyst in methanol at 60 °C was also determined by measuring the calcium(II) and zinc(II) concentration. The results showed that whether Ca(OH)2 or CaO were used as a starting material, after calcination an active catalyst composed of CaO and ZnO was obtained. When CaO was used in the starting mixture, basicity was slightly higher, while the amount of present carbonates was lower

Characterization of Mechanochemically Synthesized CaO·ZnO/K2O Mixed Oxides

Room temperature ball milling of CaO and ZnO powder mixture (using molar ratio of CaO:ZnO of 1:2) with the addition of stoichiometrically required amount of water to form calcium zinc hydroxide hydrate (CaZn2(OH)6•2H2O) and subsequent calcination at 700 oC was conducted. In order to improve basicity of mixed oxides, calcium zinc hydroxide hydrate was modified by the addition of promoters. The addition of promoter in initial powder mixture such as K2CO3 and KOH (with molar ratio of promoter to CaO of 1:10) was shown to effect the mechanochemical reaction. The prepared catalysts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), base strength using Hammett indicator method and scanning electron microscopy (SEM and SEM-EDS). The results showed that, during mechanochemical treatment, CaO, ZnO and H2O reacted rapidly to form CaZn2(OH)6•2H2O, and this was the same when promoters were used. Only difference was in basicity of the catalysts, and opposite of the expected, results showed that the addition of promoters did not cause an increase of basicity. On the other hand, addition of KOH to initial powder mixture caused increase of carbonates formation during mechanochemical treatment

Biodiesel synthesis based on CaO·ZnO.K2CO3 as catalyst

The mixed oxide of CaO·ZnO and K2CO3 were prepared by ball milling of CaO and ZnO powders and water, with addition of K2CO3 and afterward by calcination at 700 oC. Influence of different molar ratio of K2CO3 and CaO (x=1, 2 and 4 moles of K2CO3 per 10 moles of CaO) was studied . The prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), scanningelectron microscopy/energy-dispersive spectroscopy (SEM/EDS) and the particle size laser diffraction (PSLD) distribution. The addition of smaller amount of K2CO3 at the beginning of ball miling (x≤2), favors the formation of calcium zinc hydroxide hydrate, while it is not the case when K2CO3 larger addition was used (x > 2). A larger amount of potassium carbonate in the initialcomposition of powder mixture negatively affected formation of CaZn2(OH)6·2H2O. Bimodal distribution were detected for all samples after calcination at 700 oC and the results showed that the distribution of elements in the bulk is not homogeneous and that surface of formed mixed oxide CaO.ZnO (XPS analysis) after calcination is mainly covered by potassium species. That evidence indicate that the K2CO3 was not fully incorporated into the matrix. Prepared samples could be used for methanolysis of vegetable oil and fatty acid methyl esters (FAME, i.e. biodiesel) synthesis

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..