Influence of thermal treatment conditions on the activity of hydrotalcite-derived Mg–Al oxides in the aldol condensation of acetone

Kuśtrowski, Piotr; Sułkowska, Dominika; Chmielarz, Lucjan; Rafalska-Łasocha, Alicja; Dudek, Barbara; Dziembaj, R.

doi:10.1016/j.micromeso.2004.09.011

Cited by 148 publications

(100 citation statements)

References 33 publications

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“…It can be underlined that the catalytic activity dramatically increases from HT:rGO= 0.5:1 to 1:1 the catalyst with the lowest HT content being poorly active ( Figure 7A). During the reaction time of 480 min, in any case, the equilibrium conversion of 23.1% was reached 26 ; however, the catalytic performance showed by the calcined HT/rGO-xC80 catalysts with HT:rGO= 5:1, 10:1 and 20:1 was superior to that of the calcined bare HT (HTc) or other HT-derived mixed oxides reported previously 12,18,27,28 . Bare GO and rGO did not show any catalytic activity under the reaction conditions tested, which confirms that HT is the active phase of the reaction.…”

Section: Acetone Self-condensationmentioning

confidence: 56%

“…[18][19][20][21][22][23][24][25][26][27][28][29] A slighter influence of the drying and synthesis methods than at low HT loading on the hybrids' catalytic performance was observed, the catalysts submitted to freeze drying presenting the higher DAA yields. Of particular interest is the case of the hybrid catalyst prepared by coprecipitation and freeze dried (HT/rGO-10CFD) which showed the best performance with an average DAA amount of 102.7 mmol/gHTc; that is a specific activity (based on the weight of HT present in the hybrid catalyst) about 2.5 times higher than that of HTc.…”

Section: Acetone Self-condensationmentioning

confidence: 99%

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Role of the synthesis route on the properties of hybrid LDH-graphene as basic catalysts

Álvarez

Tichit

Medina

et al. 2017

Applied Surface Science

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Layered double hydroxides (LDH or HT) or their derived mixed oxides present marked acid-base properties useful in catalysis, but they tend to agglomerate inducing a weak accessibility to the active sites. In this study we report the preparation and characterization of HT/Graphene (HT/rGO) nanocomposites as active and selective basic catalysts for the acetone condensation reaction. The graphene high specific surface area and structural compatibility with the HT allowed increasing the number and accessibility of the active sites and activity. Two series of HT/rGO nanocomposites with 0.5≤HT/rGO≤10 mass ratio were prepared by: i) direct HT coprecipitation in the presence of GO; ii) self-assembly of preformed HT with GO. The prepared HT/rGO nanocomposites were dried either in air at 80 °C or freeze-dried. A series of characterizations showed the great influence of the preparation method and HT/rGO mass ratio on both the nanocomposite structure and catalytic activity. An optimum activity was observed for a HT/rGO = 10 catalyst. Particularly, the highest catalytic activity was found in those nanocomposites obtained by coprecipitation and freeze dried (3 times more active than bulk HT) which can be connected to their structure with a better accessibility to the basic sites.2

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Section: Acetone Self-condensationmentioning

confidence: 56%

Section: Acetone Self-condensationmentioning

confidence: 99%

Role of the synthesis route on the properties of hybrid LDH-graphene as basic catalysts

Álvarez

Tichit

Medina

et al. 2017

Applied Surface Science

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“…Moreover, the (1 1 0) plane can be used to determine the lattice parameter a, corresponding to the average cation-cation distance in a brucite layer. The (0 0 3) and (0 0 6) planes can be used to calculate parameter c, which is related to the total thickness of the brucite-like layer and the interlayer distance [19,20]. The lattice parameter a is 3.04 for all samples, which indicates that the original structure of the brucite-like layer is intact.…”

Section: Catalytic Performance Testsmentioning

confidence: 99%

Comprehensive study of H2S selective catalytic oxidation on combined oxides derived from Mg/Al-V10O28 layered double hydroxides

Zhang

Tang

Qiao

et al. 2015

Applied Catalysis B: Environmental

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a b s t r a c tA series of Mg 2 Al-V 10 O 28 -LDH (named V-LDH) were synthesized using ion-exchange method, and the derived oxides were investigated for H 2 S selective oxidation. The physicochemical properties of the catalysts were assessed by various methods. It was observed that vanadium species existed mainly in the form of isolated V 5+ in distorted [VO 4 ], Mg 3 V 2 O 8 , and Mg 2 V 2 O 7 . Moreover, there was a large amount of V 4+ species (>25%), mainly formed with vanadyl bonds. Significantly, the catalysts exhibited excellent catalytic performances at relatively low reaction temperatures (100-200 • C). Furthermore, the catalyst containing 10.6 wt% vanadium (8V-LDO) was highly durable at a relatively low temperature (160 • C) and a high gas hourly space velocity (GHSV, 24,000 h −1 ), which can proceed consecutively for 100 h without notable deactivation. In the reaction process, the gradually produced sulfate species reacted with V 4+ species to form less active VOSO 4 species, which improved the redox property of V 5+ . The catalysts obeyed a step-wise mechanism for H 2 S selective catalytic oxidation. The excellent durability can be ascribed to the fact that the content of moderate basic sites was kept and the redox property of V 5+ was improved.

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“…Os valores dos parâmetros a e c foram obtidos segundo as Equações propostas por Debye-Scherrer. [22][23][24][25][26] O parâmetro c foi calculado através da multiplicação de d(003) em Å pelo índice 3, ou seja, c = 3d 003 . O parâmetro a foi calculado por meio da multiplicação de d(110) em Å por 2, isto é, a = 2d 110 .…”

Section: Espectroscopia Vibracional Na Região Do Infravermelho (Eiv)unclassified

Hidróxidos duplos lamelares à base de escória de alto forno

Rebelo¹,

Cunha²,

Corrêa³

2012

Quím. Nova

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Recebido em 14/4/11; aceito em 8/11/11; publicado na web em 13/1/12 LAYERED DOUBLE HYDROXIDES PRODUCED FROM BLAST FURNACE SLAG. Hydrotalcite like compounds (HT) were prepared by co-precipitation (Mg/Al = 3.5), using an acid solution with blast furnace slag and MgCl 2 .6H 2 O and aqueous solutions of NaOH. The following synthesis variables were investigated: temperature (30 and 45 °C) and pH (9 and 12). Depending of the temperature two systems were observed: Mg-Al-CO 3 (T = 30 °C); Mg-Al-Cl-CO 3 (T = 45 °C). An increase in the pH of synthesis and Mg 2+ concentration produced HTs well-crystallized and with greater values of all cell parameters. The study showed the potentiality of BFS in the synthesis of well-crystallized LDHs without the presence of other crystalline phases.Keyords: blast furnace slag; layered double hydroxides (LDHs); syntheses. INTRODUÇÃOA atual situação em torno da disposição de resíduos industriais tornou-se uma séria preocupação que ameaça o meio ambiente, a saú-de e a qualidade de vida. Quando os resíduos industriais são dispostos de maneira inadequada, causam graves problemas ambientais como contaminação das águas subterrâneas por lixiviação de metais tóxicos e emissões de material particulado para áreas vizinhas. A reciclagem de resíduos mostra-se como uma alternativa capaz de minimizar os impactos ambientais negativos decorrentes do processo produtivo. 1 A produção de aço gera uma série de resíduos industriais. Entre os vários tipos de resíduos, a escória de alto forno (EAF) tem atraído muita atenção, já que a sua produção ultrapassa a de qualquer outro resíduo. 1A indústria do aço no Brasil, representada por 14 empresas privadas, foi responsável pela produção, em 2010, de 32,9 milhões de toneladas de aço bruto, levando o país a ocupar a 9ª posição no ranking da produção mundial.2 De acordo com análises do Instituto Aço Brasil, a produção acumulada de janeiro a novembro de 2011 totalizou 34,9 milhões de toneladas de aço bruto e 27,3 milhões de toneladas de ferro-gusa, o que representa, em média, um volume total de 13,4 milhões de toneladas de escórias, oriundas do alto forno e da aciaria. 2A EAF é formada pela mistura entre a ganga do minério de ferro com as cinzas do coque ou carvão vegetal e do calcário, utilizado como fundente no processo de fabricação do ferro-gusa.3 Sua composição química é majoritariamente Ca, Si, Al e Mg, bem como uma pequena quantidade de Fe, Ti e Mn.3-5 O tamanho de suas partículas e estrutura variam em função da velocidade de resfriamento da EAF na água ou no ar. Ao ser resfriada bruscamente, a EAF adquire estrutura vítrea e forma granular, apresentando propriedades hidráulicas latentes; mas, se o processo empregado for o resfriamento lento, a escória cristaliza, formando um produto sem atividade hidráulica, constituído por silicatos e aluminossilicatos cálcicos. Nas escórias básicas (CaO/SiO 2 > 1) há predominância de melilitas (akermanita e gehlenita) e merwinita, enquanto que nas ácidas (CaO/SiO 2 < 1) ocorre principalmente wollastonita e anortita. 4,6,7 A E...

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Influence of thermal treatment conditions on the activity of hydrotalcite-derived Mg–Al oxides in the aldol condensation of acetone

Cited by 148 publications

References 33 publications

Role of the synthesis route on the properties of hybrid LDH-graphene as basic catalysts

Role of the synthesis route on the properties of hybrid LDH-graphene as basic catalysts

Comprehensive study of H2S selective catalytic oxidation on combined oxides derived from Mg/Al-V10O28 layered double hydroxides

Hidróxidos duplos lamelares à base de escória de alto forno

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