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Jitianu, Mihaela; Balasoiu, Marina; Zaharescu, Maria; Jitianu, Andrei; Ivanov, Alexandru

doi:10.1023/a:1008703714841

Cited by 29 publications

(5 citation statements)

References 7 publications

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“…It can be seen that this peak produced a weight loss slightly lower in sHT2. In addition, the profile of sHT2 is shifted to higher temperatures This higher thermal stability may be a consequence of the higher crystallinity of the structure [21,30], as XRD characterization showed (Fig. 1).…”

Section: Precursors Characterizationmentioning

confidence: 96%

“…In addition, the interlayered carbonate and the increase in the crystallinity of the structure seem to provide thermal stability to the samples [21]. Precipitation at low supersaturation is performed by slow addition of mixed solutions of divalent and trivalent metal salts with appropriate ratio into a reactor containing an aqueous solution of the desired interlayer anion.…”

Section: Introductionmentioning

confidence: 99%

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Biogas reforming on La-promoted NiMgAl catalysts derived from hydrotalcite-like precursors

Serrano-Lotina

Rodrı̀guez

Muñoz

et al. 2011

Journal of Power Sources

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a b s t r a c tHydrotalcite-like precursors have been synthesized in order to study the influence of lanthanum on the structure and the properties of the precursors, as well as on the catalytic activity and stability of their derived catalyst on biogas reforming. From XRD, and TPO characterization, we confirmed that hydrotalcite-like precursors where obtained. After calcination at 750 • C, Mg(Ni,Al)O solid solution was detected. High surface areas have been obtained finding the highest surface area on the catalyst without lanthanum. TPR experiments were performed in order to study the reducibility of the catalysts. One reduction peak was found in the catalyst without lanthanum while two peaks were observed in the catalysts with lanthanum. A reduction peak at 900 • C was observed over the sample without Ni and La. Catalytic tests, at 700 • C with a feed of CH 4 :CO 2 1:1, were performed after appropriate reduction during 50 h. While a decrease on catalytic activity was observed with the addition and the increase of La content, an enhancement in the stability was observed. No sign of deactivation of the catalyst and no carbon deposition were found on the catalysts doped with lanthanum.

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Section: Precursors Characterizationmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Biogas reforming on La-promoted NiMgAl catalysts derived from hydrotalcite-like precursors

Serrano-Lotina

Rodrı̀guez

Muñoz

et al. 2011

Journal of Power Sources

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“…Their molecular formula is [M 2+ (1−x)M 3+ x(OH)2][A n− ]x/n•yH2O [21,22]. Layered double hydroxides can be prepared by different methods such as coprecipitation, hydrolysis with urea, sol-gel, hydrothermal treatment, combustion and mechanical synthesis, among others, with the most common and economic method being coprecipitation [23][24][25]. Studies have reported that the synthesis method, the conditions of synthesis, the type of cations and structural anions, the metal precursors and the metal ratio M 2+ /M 3+ are determining factors on the properties and applications of LDH [26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Use of Co/Fe-Mixed Oxides as Heterogeneous Catalysts in Obtaining Biodiesel

et al. 2019

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Catalyst-type mixed metal oxides with different compositions and Co/Fe ratios were obtained from layered double hydroxides to be used as heterogeneous catalysts in the production of biodiesel. The effect of the Co/Fe ratio on the precursors of the catalysts was analyzed, considering their thermal, textural and structural properties. The physicochemical properties of the catalysts were determined by thermogravimetric analysis (differential scanning calorimetry and thermogravimetric), X-ray diffraction, Fourier-transform infrared spectroscopy, Scanning Electron Microscopy-Energy Dispersive X-ray spectroscopy and N2-physisorption. The conversion to biodiesel using the different catalysts obtained was determined by diffuse reflectance infrared Fourier-transform spectroscopy and 1H-Nuclear magnetic resonance spectroscopy, allowing us to correlate the effect of the catalyst composition with the catalytic capacity. The conditions for obtaining biodiesel were optimized by selecting the catalyst and varying the percentage of catalyst, the methanol/oil ratio and the reaction time. The catalysts reached yields of conversion to biodiesel of up to 96% in 20 min of reaction using only 2% catalyst. The catalyst that showed the best catalytic activity contains a mixture of predominant crystalline and amorphous phases of CoFe2O4 and NaxCoO2. The results suggest that cobalt is a determinant in the activity of the catalyst when forming active sites in the crystalline network of mixed oxides for the transesterification of triglycerides, with high conversion capacity and selectivity to biodiesel.

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“…To form the gel, the sol undergoes an ageing process, and upon heating the final solid is obtained [24]. The rates of hydrolysis and condensation of the metal precursors determine the properties of the LDH, although these rates can be modified by several parameters such as pH, precursor concentration, temperature or solvent used [114]. The sol-gel method forms LDHs with a larger specific surface area than those formed by the coprecipitation method [115,116].…”

Section: I236 Sol-gel Methodsmentioning

confidence: 99%

Nanorrellenos inorgánicos preparados a partir de LDHS para la obtención de nanocomposites de matriz polimérica. Determinación de la incidencia del método de preparación sobre sus propiedades

Gallego¹

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The present research work has focused on obtaining inorganic nanofillers from Layered Double Hydroxides (LDHs) that can be useful in the preparation of polymer matrix composites and nanocomposites with modified properties. The properties of this type of nanofillers are closely linked to their synthesis conditions; so, parameters such as pH, reaction medium, molar ratio of cations, precipitation rate, synthesis temperature and hydrothermal treatments, etc., have an important impact on the physical and surface properties of the final solids. Thus, in the present work, the synthesis of Zn,Al LDHs with molar ratios 2:1 and 3:1 has been carried out by the coprecipitation method using amines, which are softer bases than the classically used bases. Specifically, amines with different substitution degree and chain length have been used as precipitating agents using a simpler synthesis methodology than the hydrolysis of urea. The resulting solids have been characterised in terms of their morphological and structural properties and their feasibility for use as nanofillers in polymer matrix nanocomposites has been studied. Thus, nanocomposites have been prepared using polypropylene as polymeric matrix, dispersing Zn,Al LDHs synthesised under different conditions. Finally, the impact of the use of these solids as nanofillers on the thermal stability and mechanical properties of the resulting nanocomposites was studied.On the other hand, the synthesis methodology using amines as precipitating agents was extended to the preparation of Ni,Al LDHs which are of great interest as catalyst precursors in the Sabatier reaction of CO2 hydrogenation to obtain methane. The synthesis of this type of solids was carried out using dimethylamine as precipitating agent, since the formation of coordination compounds with Ni(II) was not observed and, in addition, it turned out to be the amine with which the Zn,Al LDHs offered the best properties, in terms of crystallinity degree and particle size distribution. The study of the catalytic activity of this type of solids was extended with the synthesis of catalysts promoted by cations of rare earth elements, such as Ce and La. Thus, the effectiveness of the resulting Ni-Al2O3, Ni-Ce2O3-Al2O3 and Ni-La2O3-Al2O3-Al2O3 catalysts was studied in the production of CH4, taking into account both the conversion and the selectivity towards secondary products. The catalytic test was carried out between 200 and 400 ºC, and it was observed that at 275 ºC a conversion larger than 60% was achieved, maintained up to 400 ºC, with a selectivity of 95% in methane production.

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Untitled

Cited by 29 publications

References 7 publications

Biogas reforming on La-promoted NiMgAl catalysts derived from hydrotalcite-like precursors

Biogas reforming on La-promoted NiMgAl catalysts derived from hydrotalcite-like precursors

Use of Co/Fe-Mixed Oxides as Heterogeneous Catalysts in Obtaining Biodiesel

Nanorrellenos inorgánicos preparados a partir de LDHS para la obtención de nanocomposites de matriz polimérica. Determinación de la incidencia del método de preparación sobre sus propiedades

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