Assessment of acid–base strength distribution of ion-exchanged montmorillonites through NH3 and CO2-TPD measurements

Azzouz, Abdelkrim; Nistor, Ileana Denisa; Miron, Doru Neculai; Ursu, Alina-Violeta; Sajin, Tudor; Monette, Frédéric; Niquette, Patrick; Häusler, Robert

doi:10.1016/j.tca.2006.07.019

Cited by 111 publications

(66 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…weaker in acidity that the ]) cations (Azzouz et al, 2006), then the presence of multivalent cations is an essential requirement for higher bleaching activities, in agreement with previously reported data (Güler and Tunç, 1992;Liew et al, 1982). A possible explanation should consist of the polarizing effect of multivalent cations.…”

Section: Assessment Of the Optimum Activation Parameterssupporting

confidence: 90%

“…These removed groups are well known for displaying stronger acidities than terminal silanols (Azzouz et al, 2006) and are presumably involved in absorption sites (Taylor et al, 1989). Consequently, both the acidity strength and negative charge of the clay surface will rather decrease, in contrast with results reported by these authors (Kheok and Lim, 1982).…”

Section: Introductionmentioning

confidence: 87%

“…The occurrence of such electrostatic fields is presumably the cause of molecule attraction and adsorption. Such a phenomenon must be very similar to coagulation-floculation processes in water (Assaad et al, 2007), or gas adsorption in dry media (Azzouz et al, 2006). Therefore, adsorption on the ion-exchange sites must involve not only their strong acidity (Taylor et al, 1989) but also their partial charges.…”

Section: Assessment Of the Optimum Activation Parametersmentioning

confidence: 99%

“…Some authors reported that the acidity of the clay surface seems to enhance the adsorption of β-carotene from acetone (Liew et al, 1982) and chlorophyll from hexane (Güler and Tunç, 1992) into the clay. Nonetheless, unless traces of water are present in the oil to be treated, their attempts to explain the role of the acidic sites in dry media were not satisfactory, inasmuch as acid-base interactions similar to those occurring in gaseous phase are involved (Azzouz et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Acid activation of Bentonite for use as a vegetable oil bleaching agent

Makhoukhi¹,

Didi²,

Villemin³

et al. 2009

Grasas y Aceites

Self Cite

View full text Add to dashboard Cite

SUMMARY Acid activation of Bentonite for use as a vegetable oil bleaching agentThe design of various experiments in order to assess and simulate the effects of the acid activation of an Algerian bentonite on the bleaching capacity of Colza oil is described. Three key parameters of the acidic activation, namely acid concentration, contact time and temperature, were considered. The calculations made indicated that all variables display advantageous effects up to a certain level on the effectiveness of bleaching, regarded as the responsefunction. The acid concentration exerts a predominant individual effect as compared to the other parameters. Some small interactions between parameters were considered. High bleaching capacity reached 99% as optimal activation. Under accurate statistical measurements, synergy phenomena could be observed. Excessive activation is discussed in terms of loss in both porosity and acid strength. KEY-WORDS: Acid activation -Bentonite -Design of experiments -Oil bleaching.

show abstract

Section: Assessment Of the Optimum Activation Parameterssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 87%

Section: Assessment Of the Optimum Activation Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Acid activation of Bentonite for use as a vegetable oil bleaching agent

Makhoukhi¹,

Didi²,

Villemin³

et al. 2009

Grasas y Aceites

Self Cite

View full text Add to dashboard Cite

show abstract

“…The TPD patterns show major desorption peaks differing by samples in their positions and profiles, suggesting changes not only in the total acidity but also in the distribution of the acid strength in the samples. The TPD peaks for the Zn 0.95 Mn 0.05 O and Zn 0.93 Mn 0.07 O samples appear in the region of LT and also in HT, indicating the presence of both weak and strong acid sites on these catalysts (Azzouz et al, 2006).…”

Section: Methodsmentioning

confidence: 96%

Microwave hydrothermal synthesis, characterisation, and catalytic performance of Zn1−x MnxO in cellulose conversion

et al. 2014

View full text Add to dashboard Cite

Wurtzite-type Zn1−xMnxO (x = 0, 0.03, 0.05, 0.07) nanostructures were successfully synthesised using a simple microwave-assisted hydrothermal route and their catalytic properties were investigated in the cellulose conversion. The morphology of the nanocatalysts is dopant-dependent. Pure ZnO presented multi-plate morphology with a flower-like shape of nanometric sizes, while the Zn0.97Mn0.03O sample is formed by nanoplates with the presence of spherical nanoparticles; the Zn0.95Mn0.05O and Zn0.93Mn0.07O samples are mainly formed by nanorods with the presence of a small quantity of spherical nanoparticles. The catalyst without Mn did not show any catalytic activity in the cellulose conversion. The Mn doping promoted an increase in the density of weak acid sites which, according to the catalytic results, favoured promotion of the reaction.

show abstract

Oxidative Esterification of Methacrolein to Methyl Methacrylate over Gold Nanoparticles on Hydroxyapatite

et al. 2017

View full text Add to dashboard Cite

The catalytic production of methyl methacrylate through the direct oxidative esterification of methacrolein is important in terms of green chemistry and sustainable development. In the present work, Au nanoparticles supported on three needle‐like, lamella‐like, and rodlike hydroxyapatites were synthesized. We demonstrated that needle‐like hydroxyapatite could facilitate the higher dispersion of Au species because of its high specific surface area, and the strong interaction between the Au nanoparticles and the support resulted in the formation of more surface defects because of the existence of partially encapsulated Au particles by the needle‐like hydroxyapatite. The surface defects were related closely to the generation of strong basic sites. Compared with the other two materials, the Au supported on the needle‐like hydroxyapatite catalyst, which had a large amount of surface acid–base sites, exhibited a much higher catalytic activity and selectivity to methyl methacrylate in the direct oxidative esterification of methacrolein with methanol under mild reaction conditions (i.e., ambient pressure, low reaction temperature of 70 °C, and low methanol/aldehyde ratio of 8:1). The superior catalytic performance of the Au supported on needle‐like hydroxyapatite catalyst was attributable to a cooperative effect between abundant acid–base sites for the preferential chemisorption of methacrolein and highly dispersed active Au species for the favorable formation of β‐hydride and oxygen activation. The present findings open a new and promising route for the practical production of methyl methacrylate using high‐performance hydroxyapatite‐supported metal catalyst systems.

show abstract

Assessment of acid–base strength distribution of ion-exchanged montmorillonites through NH3 and CO2-TPD measurements

Cited by 111 publications

References 19 publications

Acid activation of Bentonite for use as a vegetable oil bleaching agent

Acid activation of Bentonite for use as a vegetable oil bleaching agent

Microwave hydrothermal synthesis, characterisation, and catalytic performance of Zn1−x MnxO in cellulose conversion

Oxidative Esterification of Methacrolein to Methyl Methacrylate over Gold Nanoparticles on Hydroxyapatite

Contact Info

Product

Resources

About