Increasing the basicity and catalytic activity of hydrotalcites by different synthesis procedures

Climent, María J.; Corma, Avelino; Iborra, Sara; Epping, K; Velty, Alexandra

doi:10.1016/j.jcat.2004.04.027

Cited by 305 publications

(71 citation statements)

References 33 publications

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“…Similar cavitation phenomena have allowed obtaining a better catalytic reactivity of solids in the Fischer-Tropsch reaction. Recently, microwaves radiation heating [27][28][29] and ultrasound [27,30,31] have been applied to the synthesis of hydrotalcites with different chemical compositions as an alternative to the conventional hydrothermal treatments. Several of the advantages listed above have been observed, especially the shorter treatment times needed to achieve enhanced crystallinity degrees, the higher specific surface area and the improved metallic dispersions [28,32,33].…”

Section: Introductionmentioning

confidence: 99%

Co-Al Mixed Oxides Prepared via LDH Route Using Microwaves or Ultrasound: Application for Catalytic Toluene Total Oxidation

et al. 2015

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Co6Al2HT hydrotalcite-like compounds were synthesized by three different methods: co-precipitation, microwaves-assisted and ultrasound-assisted methods. The mixed oxides obtained after calcination were studied by several techniques: XRD, TEM, H2-TPR and XPS. They were also tested as catalysts in the reaction of total oxidation of toluene. The physico-chemical studies revealed a modification of the structural characteristics (surface area, morphology) as well as of the reducibility of the formed mixed oxides. The solid prepared by microwaves-assisted synthesis was the most active. Furthermore, a relationship between the ratio of Co 2+ on the surface, the reducibility of the Co-Al mixed oxide and the T50 in toluene oxidation was demonstrated. This suggests a Mars Van Krevelen mechanism for toluene total oxidation on these catalysts.

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Section: Introductionmentioning

confidence: 99%

Co-Al Mixed Oxides Prepared via LDH Route Using Microwaves or Ultrasound: Application for Catalytic Toluene Total Oxidation

et al. 2015

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“…As condições de síntese, ou seja, temperatura, pH, composição de metais e envelhecimento do precipitado, estão associadas às propriedades físico-químicas desses minerais. Os HDLs podem ser convertidos por decomposição térmica em óxidos metálicos mistos, que possuem elevada área superfi cial e propriedades básicas [14,15]. Os HDLs possuem diversas aplicações, dependendo de suas propriedades (cristalinidade, composição, estabilidade térmica e outras), tais como catalisadores heterogêneos, precursores para catalisadores, adsorventes, aditivos para polímeros, e como agentes para o tratamento de úlceras gástricas, entre outras.…”

Section: Introductionunclassified

Síntese de hidróxidos duplos lamelares do sistema Cu, Zn, Al-CO3: propriedades morfológicas, estruturais e comportamento térmico

Santos

Corrêa

2011

Cerâmica

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ResumoHidrotalcitas são argilas aniônicas, também conhecidas como Hidróxidos Duplos Lamelares (HDLs) e possuem estrutura semelhante ao mineral brucita. Os HDLs do sistema Cu, Zn, Al-CO 3 foram sintetizados em condições que favorecem a formação de cristais pequenos e de elevada área superfi cial. A caracterização foi feita por difração de raios X, análise termogravimétrica, espectroscopia na região do infravermelho e microscopia eletrônica de varredura. A síntese foi feita pelo método de coprecipitação em pH variável, utilizando sulfatos de cobre e zinco, soluções de alumínio e solução de hidróxido sódio. Os difratogramas de raios X mostram que os compostos sintetizados possuem alta cristalinidade; a intensidade e a largura dos picos comprovam que os materiais se apresentam bem organizados e com empilhamento das lamelas. Os espectros de infravermelho apresentaram bandas associadas ao ânion carbonato presente na região interlamelar dos HDLs. Palavras-chave: hidróxidos duplos lamelares, hidrotalcitas, argilas aniônicas. Abstract Hydrotalcite-like compounds are anionic clays, also known as layered double hydroxides (LDH),

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“…anions [3][4][5][6]. The acid-base properties and, as a consequence, the catalytic activity and selectivity of these Mg,Me,Almixed oxides depend on chemical composition (type of Me cation and Mg/Me/Al molar ratio) and on the conditions of the thermal treatment used to decompose the hydrotalcite precursor.…”

Section: −mentioning

confidence: 99%

“…So, they can be tailored to the process under study aiming at increasing their activity and/or selectivity. Their main applications as basic catalyst include aldol, nitroaldol, Knoevenagel, and Claisen-Schmidt condensations, alkylation of ketones and phenols, Michael additions, glycerolysis of fats for the manufacture of monoglycerides, selective reduction of unsaturated ketones/aldehydes by hydrogen transfer from alcohols, and more recently transesterification of vegetable oils for biodiesel production [2,[4][5][6][7][8][9][10].…”

Section: −mentioning

confidence: 99%

Influence of the Incorporation of Transition Metals on the Basicity of Mg,Al-Mixed Oxides and on Their Catalytic Properties for Transesterification of Vegetable Oils

Veiga

Sousa

Polato

et al. 2013

Journal of Catalysts

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The transesterification of vegetable oils produces fatty acid methyl esters (biodiesel). Biodiesel is a nonpolluting alternative fuel produced from renewable resources whose chemical and physical properties closely resemble those of the petroleum diesel fuel and does not contribute to the greenhouse effect. The use of solid catalysts makes biodiesel production processes environmentally friendly. In this work, Mg,Al-mixed oxides derived from Mg,Al-hydrotalcite-like compound with an M 3+ /(M 2+ + M 3+ ) molar ratio of 0.25, in which Mg or Al was partially replaced by Co 2+ , Cu 2+ , Cr 3+ , or Fe 3+ , were prepared, characterized, and evaluated as catalysts for the transesterification of soybean oil with methanol. The results have indicated that the incorporation of transition metal influenced both textural and base properties. All the evaluated catalysts were active for the studied reaction. The catalytic activity followed the order Cr-MO < Co-MO < Cu-MO < Fe-MO < MO and could be explained by mesoporous volume.

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Increasing the basicity and catalytic activity of hydrotalcites by different synthesis procedures

Cited by 305 publications

References 33 publications

Co-Al Mixed Oxides Prepared via LDH Route Using Microwaves or Ultrasound: Application for Catalytic Toluene Total Oxidation

Co-Al Mixed Oxides Prepared via LDH Route Using Microwaves or Ultrasound: Application for Catalytic Toluene Total Oxidation

Síntese de hidróxidos duplos lamelares do sistema Cu, Zn, Al-CO3: propriedades morfológicas, estruturais e comportamento térmico

Influence of the Incorporation of Transition Metals on the Basicity of Mg,Al-Mixed Oxides and on Their Catalytic Properties for Transesterification of Vegetable Oils

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