Comparação estrutural entre amostras de materiais tipo hidrotalcita obtidas a partir de diferentes rotas de síntese

Chagas, Luciano H.; Farias, Stephane B. P. de; Leitão, Alexandre A.; Diniz, Renata; Chiaro, Sandra S. X.; Speziali, Nivaldo L.; Abreu, Heitor A. De; Mussel, Wagner da Nova

doi:10.1590/s0100-40422012000600008

Cited by 6 publications

(6 citation statements)

References 28 publications

(39 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Vibrational spectra for all LDHS are shown in Fig. 3, and they are similar to those presented in previous studies [35]. The strong and broad absorption band between 3500 and 3400 cm −1 is due to the stretching mode of structural OH groups ( OH ) in the metal hydroxide layer and the interlayer water molecules [32,43].…”

Section: Characterization Of Materialssupporting

confidence: 81%

“…The second event occurs in the range 250-550 • C with an average mass loss of 28% due to the decarbonation followed by the dehydroxylation of the lamellae [34]. Above 450 • C, masses were measured at about 60% of the initial mass, the result of the collapse of the lamellar structure and formation of mixed oxides of the spinel type (MgAl 2 O 4 ) as residue [35]. The organic fraction was converted to CO2 and H2O and the minerals remained in the catalyst in very small quantities.…”

Section: Characterization Of Materialsmentioning

confidence: 99%

See 1 more Smart Citation

Mixed metal oxides from sucrose and cornstarch templated hydrotalcite-like LDHs as catalysts for ethyl biodiesel synthesis

Coelho

Perrone

Gomes

et al. 2017

Applied Catalysis A: General

View full text Add to dashboard Cite

Sucrose and cornstarch were used as organic templates in the synthesis of hydrotalcite-like layered double hydroxides (LDHs) prepared by the coprecipitation with partial replacement of Mg by Zn, and Al by Fe. Non-template materials were taken as references. All LDHs were used as precursors of mixed metal oxides (MMOs) by calcination and applied as catalysts for ethyl biodiesel synthesis via transesterification reactions of soybean oil and ethanol. The LDHs were characterized by XRD, TG, FTIR-ATR and the respective MMOs by SEM, BET, basicity and acidity. Crystallographic data from templated LDHs showed lower crystallinity compared to the reference homologous materials, and it was observed that cornstarch decreases the average surface areas (from 173 to 94 m 2 g −1) and the size of the crystallites (from 147 to 92 Å). FTIR spectra indicated carbohydrates were occluded inside the crystals. While this did not influence the number of acidic sites on the MMOs, it enhances the alkaline sites. Under the catalytic conditions of this experiment, cornstarch templated MMOs reach an average ethyl biodiesel conversion of 70% whereas those prepared with sucrose 45%, and the homologous reference materials only 36%. These results demonstrated the great potential of using carbohydrates as biotemplates in the preparation of heterogeneous catalysts for transesterification reactions.

show abstract

Section: Characterization Of Materialssupporting

confidence: 81%

Section: Characterization Of Materialsmentioning

confidence: 99%

Mixed metal oxides from sucrose and cornstarch templated hydrotalcite-like LDHs as catalysts for ethyl biodiesel synthesis

Coelho

Perrone

Gomes

et al. 2017

Applied Catalysis A: General

View full text Add to dashboard Cite

show abstract

“…Absorptions in the 669-455 cm -1 range refer to O-M-O, M-O-M and M-OH vibration modes (where M is Mg or Al). Cd-Te stretching modes are expected near 170 cm -1 , 33,34 thus outside the observed region. Evidences of the presence of MPA-capped CdTe nanocrystals are suggested in Figure 2b.…”

Section: Resultsmentioning

confidence: 76%

Synthesis of Hydrotalcite-Supported CdTe Semiconductor Nanocrystals for Electrochemical Detection of Ciprofloxacin

Carvalho¹,

Santana²,

Matos³

et al. 2019

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

In this work, CdTe quantum dots (QDs) were controllably grown onto the surface of layered double hydroxide (LDH) aiming to develop a sensitive and selective method for the electrochemical detection of ciprofloxacin (CPX). Emission and absorption spectroscopy results as well as high-resolution transmission electron microscopy (HRTEM) images evidenced the formation of LDH/QD hybrid material. Unmodified carbon paste electrodes (CPE) as well as CPE chemically modified (MCPE) with native LDH and with the LDH/QD hybrid were prepared for CPX detection, revealing that MCPE-LDH/QD had the highest sensitivity for the detection of ciprofloxacin. Optimum detection conditions included a modifier dosage of 20% in MCPE, Britton-Robinson (BR) buffer (pH 6.0) as analytical medium, 300 s accumulation time and a scanning rate of 20 mV s-1. Linear current versus concentration curve was observed from 2.5 × 10-8-1.2 × 10-5 mol L-1 (coefficient of determination (R 2) = 0.995), with sensitivity (limit of detection (LOD) = 4.2 × 10-8 mol L-1 ; limit of quantification (LOQ) = 1.3 × 10-7 mol L-1), precision (relative standard deviation (RSD) = 3.0%), accuracy (94.0%) and satisfactory selectivity in the presence of Zn 2+ , Fe 2+ , Cu 2+ , citric acid and ascorbic acid. Tests of CPX determination in commercial 500 mg ciprofloxacin tablets evidenced the applicability of the method.

show abstract

“…O ombro entre 2900 e 3042 cm -1 é atribuído à ligação de hidrogênio entre H 2 O e o ânion carbonato (CO 3 -H 2 O). 31,[34][35][36] A curva TG do material 5:1 MgAlGa50% é mostrada como um exemplo na Figura 5 com indicações dos pontos obtidos por DTG usados na determinação percentual de perda de massa no estudo de degradação térmica. O padrão de decomposição térmica dos HDLs é fortemente dependente da composição do material e do tipo de ânion incorporado no espaço interlamelar.…”

Section: Caracterização Estrutural Dos Hdls E De Seus Ompsunclassified

Óxidos metálicos derivados de materiais tipo hidrotalcitas contendo Ga3+ como catalisadores para síntese de biodiesel etílico

Mancini¹,

Perrone²,

Thoméo³

et al. 2017

Quim. Nova

View full text Add to dashboard Cite

.4H 2 O in different ratios Mg 2+ /M 3+ where M 3+ is Al 3+ , Ga 3+ or both was carried out by the coprecipitation method to be applied in the transesterification reactions for synthesis of ethyl biodiesel from soybean oil and ethanol. The reactions were processed for 12 hours at 120 °C at a molar ratio oil/ethanol (1/20) with 20% (m/m) of the catalyst in relation to the oil mass, and the products were quantified by GC-FID. With the introduction of Ga 3+ in the solid, some physicochemical characteristics of LDHs were kept based in the data from X-ray pattern diffraction (XRD), vibrational spectrometry (ATR-FTIR), and scanning electron microscopy (SEM), but changes from thermogravimetric analysis (TGA), superficial area (BET), and the acidity/basicity properties were observed. Typical hydrotalcite with Mg 2+ /M 3+ = 3 was used as reference material and reach 45.1% of biodiesel conversion. Although the best conversion result (77.6%) was reached from the solid without Ga 3+ and with Mg 2+ /M 3+ ratio 4/1, there is an interesting correlation between the catalytic activities and the physicochemical properties of the solids with Ga 3+ and their respective homologous materials as discussed in this work.Keywords: ethyl biodiesel; bioenergy; hydrotalcites; metal oxides; heterogeneous catalysis. INTRODUÇÃOO biodiesel é um biocombustível composto por mistura de ésteres alquílicos produzidos a partir de álcoois de cadeias curtas, principalmente metanol e etanol, e glicerídeos graxos de origem vegetal ou animal, 1 e reconhecidamente causa menos impacto ambiental que o petrodiesel. Dados divulgados em 2016 pelo Ministério de Minas e Energia indicam que as principais matérias-primas graxas empregadas no Brasil são: óleo de soja (78%), gordura bovina (19%), óleo de algodão (2%), e outros óleos (0,9%). 2 Segundo a ANP (Agência Nacional do Petróleo, Gás Natural e Biocombustíveis), 3 em 2008, a adição de 2% de biodiesel ao petrodiesel passou a ser obrigatória, aumentando para 4% em 2009, 5% em 2010 e 7% em 2014. A produção nacional em 2015 atingiu 3,9 milhões de litros, e o governo brasileiro autorizou o uso voluntário de até 20% de biodiesel em frotas privadas, consumidores rodoviá-rios atendidos por ponto de abastecimento, e de 30% em transporte ferroviário, uso agrícola e industrial.Embora o uso de etanol seja menos frequente para a reação de transesterificação devido a sua higroscopicidade, o etanol é particularmente interessante para o Brasil em função da base industrial sucroalcooleira instalada e também pela baixa toxicidade deste álcool, comparada com a do metanol.A principal rota sintética comercial na produção de biodiesel envolve a reação de transesterificação entre matéria graxa e metanol por catálise alcalina homogênea usando NaOH ou KOH como catalisadores, pois apresenta baixo custo e elevados rendimentos, além da reação ocorrer em condições brandas de temperatura e sob pressão atmosférica. 4 No entanto esta rota apresenta fatores negativos como o não reaproveitamento do catalisador, produção de grande volume de ef...

show abstract

Comparação estrutural entre amostras de materiais tipo hidrotalcita obtidas a partir de diferentes rotas de síntese

Cited by 6 publications

References 28 publications

Mixed metal oxides from sucrose and cornstarch templated hydrotalcite-like LDHs as catalysts for ethyl biodiesel synthesis

Mixed metal oxides from sucrose and cornstarch templated hydrotalcite-like LDHs as catalysts for ethyl biodiesel synthesis

Synthesis of Hydrotalcite-Supported CdTe Semiconductor Nanocrystals for Electrochemical Detection of Ciprofloxacin

Óxidos metálicos derivados de materiais tipo hidrotalcitas contendo Ga3+ como catalisadores para síntese de biodiesel etílico

Contact Info

Product

Resources

About