Influência do tipo de ácido usado e da sua concentração na ativação de uma argila bentonítica

Foletto, Edson Luiz; Volzone, Cristina; Morgado, Ayres Ferreira; Porto, Luismar Marques

doi:10.1590/s0366-69132001000400008

Cited by 16 publications

(16 citation statements)

References 6 publications

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“…Some previous studies 5,12 using sulfuric acid and hydrochloric acid report reductions of approximately 75% to 40% in the Fe 2 O 3 content, depending on the type of acid used and the temperature of the treatment. Higher concentrations and higher temperatures result in greater removals.…”

Section: Introductionmentioning

confidence: 94%

“…After the acid treatment of metakaolinite and natural kaolinite, Sabu et al (1999) 18 observed that H 2 SO 4 was more efficient in the removal of Fe. In montmorillonite-rich clays, H 2 SO 4 strongly removed the Al 3+ species, which resulted in partial degradation of the structure 5,12 . The removal of magnesium was similar for all of the different acid treatments.…”

Section: Leaching With Different Acidsmentioning

confidence: 99%

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Acid treatments of montmorillonite-rich clay for Fe removal using a factorial design method

et al. 2013

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Montmorillonite clays are of great interest for industrial processes such as catalysis and adsorption. The textural properties of clays can be modified in an attempt to increase their uses. This paper describes the acid treatment of natural montmorillonite clay. The materials were characterized using X-ray diffraction (XRD), atomic absorption spectroscopy (AA) and BET surface area measurements. Three different acids (HCl, HNO 3 and H 2 SO 4 ) were tested, and HCl and H 2 SO 4 were more efficient for removing Fe from the clay. The results indicate that HCl better preserves the material structure because less Al is removed. A central composite design (CCD) 2 2 was applied to evaluate the treatment using /75 °C, assured that Fe was removed with less damage to the structure.

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Section: Introductionmentioning

confidence: 94%

Section: Leaching With Different Acidsmentioning

confidence: 99%

Acid treatments of montmorillonite-rich clay for Fe removal using a factorial design method

et al. 2013

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“…This is a very common occurrence in natural materials that exhibit, in its composition, a complex of minerals and clay minerals, such as clays 15,[23][24][25][26] . The Figures 3, 4, 5 and 6 show the obtained conversions of oleic acid from the esterification reaction versus the time in 30, 45 and 60 °C for natural montmorillonite clay and treated montmorillonite clay (0.2 -0.8 mol L -1 ).…”

Section: Characterization Of the Materials And Catalytic Testsmentioning

confidence: 99%

Effect of the Acid Treatment of Montmorillonite Clay in the Oleic Acid Esterification Reaction

et al. 2015

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“…The homogenised clays, called BBn and VLn, were acid-activated, without any previous treatment, in a round-bottom flask connected to a reflux condenser. 29 A 10% m/v suspension of clay in 4 mol L -1 sulfuric acid was stirred at 90 °C for 2 h. The solid was filtered under reduced pressure and washed with distilled water until the washing water has the same pH of the first. The material was dried in an oven at 110 °C for 24 h and finally ground until passage through a 60 mesh sieve again.…”

Section: Catalysts Preparationmentioning

confidence: 99%

Preparation, characterisation and evaluation of brazilian clay-based catalysts for use in esterification reactions

Rezende

Pereira

Santos

et al. 2012

J. Braz. Chem. Soc.

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Catalisadores a base de argilas naturais brasileiras foram preparados, caracterizados, e sua atividade catalítica foi avaliada em reações de esterificação. As argilas naturais foram ativadas por tratamento ácido como recebidas, sem qualquer tratamento prévio. As argilas naturais e as argilas ácidas foram caracterizadas por DRX, TPD-NH 3 , termodessorção de n-butilamina, análise de adsorção de N 2 , FT-IR, TGA e DTA. O desempenho catalítico foi investigado em reações de esterificação de diversos ácidos carboxílicos com diferentes álcoois. As reações foram realizadas com razão molar ácido carboxílico/álcool 1:3, a 100 °C e pressão atmosférica, por 3 h. As argilas ácidas forneceram boas conversões e apresentaram desempenho melhor que a argila comercial K10. Natural Brazilian clay-based catalysts were prepared, characterised, and their catalytic activity was assessed in esterification reactions. The natural clays were acid activated as received, without any previous treatment. Both natural and acid-activated clays were characterised by XRD, NH 3 -TPD, thermodesorption of n-butylamine, N 2 adsorption analysis, FT-IR, TGA and DTA. The catalytic performance was investigated in the esterification of several carboxylic acids with different alcohols. The reactions were carried out in a 1:3 carboxylic acid/alcohol molar ratio at 100 °C and atmospheric pressure for 3 h. The acid-activated clays provided good yields and better performance than commercial clay K10. Keywords: acid activation, clay, smectite, esterification IntroductionEsterification reactions are widely employed in a variety of chemical industries. 1 The procedure generally uses either sulfuric, hydrochloric or sulfonic acid as catalyst. These catalysts generate large quantities of acidic waste, which require appropriate treatment before disposal. The most widely used catalyst is sulfuric acid. It is a low cost reagent and is very active. However, it is also corrosive and presents problems of storage and control. 2 To minimise the problems associated with the homogeneous process, intensive research has been recently devoted to the development of heterogeneous catalysts for esterification. Some examples include functionalised mesoporous materials, 3,4 ion-exchange resin, 1 oxides 5-7 and metal complexes. 8,9 There is considerable interest in developing catalysts based on clays. In terms of their environmental aspect, these materials are one of the most friendly solid catalysts. Additionally, clay-based catalysts are very promising because of the low cost of the raw material, ease of properties manipulation and ease of recovery and reuse. 10 Ion exchange capacity and the potential for increased interlayer spacing are important characteristics of clay minerals that strongly influence their physical-chemical and technological properties. These characteristics, as well as their high surface area, have lead clay minerals to be explored as catalysts. The acid activation method is usually employed to modify the textural characteristics of clays.Clays are being employe...

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Influência do tipo de ácido usado e da sua concentração na ativação de uma argila bentonítica

Cited by 16 publications

References 6 publications

Acid treatments of montmorillonite-rich clay for Fe removal using a factorial design method

Acid treatments of montmorillonite-rich clay for Fe removal using a factorial design method

Effect of the Acid Treatment of Montmorillonite Clay in the Oleic Acid Esterification Reaction

Preparation, characterisation and evaluation of brazilian clay-based catalysts for use in esterification reactions

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