Synthesis of zinc aluminate with high surface area by microwave hydrothermal method applied in the transesterification of soybean oil (biodiesel)

Quirino, Max Rocha; Oliveira, Matheus José Cunha de; Keyson, David V.; Lucena, Guilherme Leocárdio; Oliveira, José de; Gama, L.

doi:10.1016/j.materresbull.2015.10.027

Cited by 37 publications

(12 citation statements)

References 27 publications

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“…Metal aluminate spinels with the formula MAl 2 O 4 , where M represents a divalent metal ion, have attracted great attention for various applications owning to their high chemical and thermal stabilities, high mechanical resistance, high quantum yields with hydrophobic qualities, large surface area, and low surface acidity method, and polymeric precursor synthesis [8][9][10]. Each of these techniques requires its own specialized equipment, imposing significant cost, while further drawbacks include the low surface area of product and lack of homogeneity [3,11].…”

Section: Introductionmentioning

confidence: 99%

Effect of calcination temperature on structural and optical properties of MAl2O4 (M = Ni, Cu, Zn) aluminate spinel nanoparticles

2019

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NiAl 2 O 4 , CuAl 2 O 4 , and ZnAl 2 O 4 aluminate spinel nanoparticles were synthesized by sol-gel auto combustion method using diethanolamine (DEA) as a fuel. The effects of calcination temperature on structure, crystallinity, morphology, and optical properties of MAl 2 O 4 (M = Ni, Cu, Zn) have been investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), UV-visible diffuse reflectance spectroscopy (UV-DRS), and photoluminescence (PL) spectroscopy. The XRD and FT-IR results confirm the formation of single-phase spinel structure of NiAl 2 O 4 , CuAl 2 O 4 , and ZnAl 2 O 4 at 1200, 1000, and 600 ℃, respectively. The direct band gap of these aluminate spinels, calculated from UV-DRS spectra using the Kubelka-Munk function, is found to increase with calcination temperature. The PL spectra demonstrate that NiAl 2 O 4 gives the highest blue emission intensity, while CuAl 2 O 4 and ZnAl 2 O 4 exhibit a very strong violet emission. During fluorescence process, the ZnAl 2 O 4 emits visible light in only violet and blue regions, while NiAl 2 O 4 and CuAl 2 O 4 emissions extend to the green region. It seems therefore that the transition metal type and intrinsic defects in these aluminate powders are responsible for these phenomena.

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Section: Introductionmentioning

confidence: 99%

Effect of calcination temperature on structural and optical properties of MAl2O4 (M = Ni, Cu, Zn) aluminate spinel nanoparticles

2019

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“…Biodiesel production over spinel zinc aluminate (ZnAl 2 O 4 ) prepared by calcination of Zn-Al-LDHs [30,31] has attracted significant attention and was commercialised as a continuous process by IFP [32]. Recent studies suggest that alkali-precipitated Zn-Al-LDHs dehydrated by low temperature calcination at 200 • C (insufficient to form crystalline spinels) exhibit superior performance for triglyceride transesterification, giving a stable 76% FAME yield from soybean oil for over 150 h on-stream [33].…”

Section: Introductionmentioning

confidence: 99%

Alkali-Free Zn–Al Layered Double Hydroxide Catalysts for Triglyceride Transesterification

et al. 2018

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Zn-Al layered double hydroxides (LDHs) of general formula [Zn 2+ (1−x) Al 3+ x (OH) 2 ] x+ (CO 3 2− ) x/2 ·yH 2 O are promising solid base catalysts for the transesterification of lipids to biofuels. However, conventional synthetic routes employ alkali hydroxide/carbonate precipitants which may contaminate the final LDH catalyst and biofuel. The use of (NH 3 ) 2 CO 3 and NH 3 OH as precipitants affords alkali-free Zn-Al-LDHs spanning a wide composition range. The hydrothermal reconstruction of calcined Zn-Al-LDHs offers superior solid basicity and catalytic activity for the transesterification of C 4 -C 18 triglycerides with methanol, compared with cold liquid phase or vapour phase reconstruction. Hydrothermally activated Zn 3.3 -Al-LDH was stable towards leaching during transesterification. Abstract: Zn-Al layered double hydroxides (LDHs) of general formula [Zn 2+ (1x)Al 3+ x(OH)2] x+ (CO3 2− )x/2·yH2O are promising solid base catalysts for the transesterification of lipids to biofuels. However, conventional synthetic routes employ alkali hydroxide/carbonate precipitants which may contaminate the final LDH catalyst and biofuel. The use of (NH3)2CO3 and NH3OH as precipitants affords alkali-free Zn-Al-LDHs spanning a wide composition range. The hydrothermal reconstruction of calcined Zn-Al-LDHs offers superior solid basicity and catalytic activity for the transesterification of C4-C18 triglycerides with methanol, compared with cold liquid phase or vapour phase reconstruction. Hydrothermally activated Zn3.3-Al-LDH was stable towards leaching during transesterification.Scheme 1. Transesterification of triglyceride to biodiesel and glycerol by-product. Scheme 1. Transesterification of triglyceride to biodiesel and glycerol by-product.

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“…The results show that the crystallite sizes are in nanometers scale, 25.6 nm and 6.9 nm, for ZnAl 2 O 4 -MC and ZnAl 2 O 4 -H, respectively. As the working temperature is relatively low in the hydrothermal synthesis, this method leads to the formation of smaller crystallites 22 . Whereas, ZnAl 2 O 4 -MC powders present larger crystallite sizes, probably due to the large amount of heat released during combustion reaction 3 .…”

Section: Resultsmentioning

confidence: 99%

Characterization of ZnAl2O4 Spinel Obtained by Hydrothermal and Microwave Assisted Combustion Method: A Comparative Study

Macedo

Medeiros

et al. 2017

Mat. Res.

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In this work, zinc aluminate spinel was prepared by two methods of directly synthesis (without calcination): microwave assisted combustion and hydrothermal method. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N 2 -adsorption/ desorption isotherms. The XRD patterns confirmed the formation of cubic ZnAl 2 O 4 spinel structure with no secondary phases for both synthesis routes, whereas the hydrothermal method yielded powders with crystallite size 3 times smaller (6.9 nm), as compared to the powders produced by microwave assisted combustion method (25.6 nm). The micrographs revealed agglomerated powders with platelike morphologies for both routes. Nitrogen adsorption/desorption isotherms (BET) revealed higher surface area (183 m 2 .g -1 ) and greater pore volume (0.173 cm 3 .g -1 ) for ZnAl 2 O 4 powders prepared by the hydrothermal method.

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Synthesis of zinc aluminate with high surface area by microwave hydrothermal method applied in the transesterification of soybean oil (biodiesel)

Cited by 37 publications

References 27 publications

Effect of calcination temperature on structural and optical properties of MAl2O4 (M = Ni, Cu, Zn) aluminate spinel nanoparticles

Effect of calcination temperature on structural and optical properties of MAl2O4 (M = Ni, Cu, Zn) aluminate spinel nanoparticles

Alkali-Free Zn–Al Layered Double Hydroxide Catalysts for Triglyceride Transesterification

Characterization of ZnAl2O4 Spinel Obtained by Hydrothermal and Microwave Assisted Combustion Method: A Comparative Study

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