Acid Strength Distribution Studies of Catalyst Surfaces.

Hirschler, Alfred E.; Schneider, A.

doi:10.1021/je60010a038

Cited by 26 publications

(9 citation statements)

References 12 publications

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“…By comparing our results with those given in the literature (Benesi, 1956(Benesi, , 1957Hirschler et al, 1961;Bailey et alo 1968;Solomon et al, 1971Solomon et al, , 1972 it can be seen that there is disagreement in the region of the strongly acidic sites. While the literature reports acid sites in montmorillonite corresponding to pKa values of -5"6 and -8'2 (i.e.…”

Section: Surface Acidity Measurementssupporting

confidence: 65%

“…It is, of course, impossible that there are more acid sites stronger than pKa = -5.6 than sites stronger than pKa = -3"7 or = -1,5. The acid strength distribution curves of montmorillonite in the literature (Benesi, 1957;Hirschler, 1961) are parallel to the abscissa over a wide range of pKa. This implies that only very weak and very strong acid sites occur, which a priori seems improbable, It has previously been proved wrong for cracking catalysts (Kevorkian et al, 1963;Kubokawa, 1962), and in the present study also for montmorillonites.…”

Section: Surface Acidity Measurementsmentioning

confidence: 92%

“…than in the W-montmorillonite interlayers. Hirschler et al (1961), Mortland and Raman (1968), Solomon et aL (1971), Lahav (1972) and others found that the acidity of clay minerals increases as the mineral is dried. We compared the acidity of AI-W dried at 130~ with that of A1-W which was stored over water vapor at room temperature for 24 hr.…”

Section: Surface Acidity Measurementsmentioning

confidence: 97%

“…The estimation c.c.M. 22 5/6--E of acid strength of some clay minerals, including montmorillonite, on the basis of color changes of adsorbed Hammett indicators has been reported (Benesi, 1956(Benesi, , 1957Hirschler et al, 1961 ;Solomon et al, 197 l, 1972). These investigators found very strong sites by using dicinnamalacetone, benzalacetophenone and anthraquinone as indicators.…”

Section: Introductionmentioning

confidence: 96%

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Surface Acidity of Montmorillonites

Frenkel

1974

Clays and clay miner.

120

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Abstract--Surface acidity of almost homoionic montmorillonites was measured by titrating selected Hammett indicators adsorbed on the clay with n-butylamine.As expected, the acidity is strongly affected by the exchangeable cations and the degree of hydration of the clay. Greater polarizing ability of the interlayer cations increases both the strength and number of acid sites per H 0 value. The acidity of 'activated' or heated H-montmorillonite does not exceed that of untreated H-montmorillonite. The origin of the negative charge in the montmorillonite appears to affect the acidity of the clay.It is concluded that the very high acidities reported in the literature (Ho < -5-6) are apparent only and are due to physisorption of the indicator.

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Section: Surface Acidity Measurementssupporting

confidence: 65%

Section: Surface Acidity Measurementsmentioning

confidence: 92%

Section: Surface Acidity Measurementsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 96%

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Surface Acidity of Montmorillonites

Frenkel

1974

Clays and clay miner.

120

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“…For instance the acidity of clay minerals increases as the mineral is dried (Hirschler and Schneider, 1961;Mortland and Raman, 1968;Frenkel, 1974). Further, the influence of the exchangeable cation also plays a role.…”

Section: Ph Of Bulk Solution and Extent Of Adsorption Of Nucleic Basementioning

confidence: 99%

A review of conditions affecting the radiolysis due to40K on nucleic acid bases and their derivatives adsorbed on clay minerals: Implications in prebiotic chemistry

Mosqueira

Albarrán²,

Negrón‐Mendoza³

1996

Origins Life Evol Biosphere

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This paper describes the possible effects of ionizing radiation arising from long-lived soluble radionuclides within clays, in particular 40K, at the epoch of the emergence of life on Earth. The free dispersion of soluble radionuclides constitutes an effective in situ irradiation mechanism that might have acted upon adsorbed nucleic bases and their derivatives on clays, inducing chemical changes on these organic molecules. Several types of well documented reactions for radiolysis of nucleic acid bases and their derivatives are known, even at low doses (i.e., 0.1 Gy). For example, estimates with a dose rate calculated from 40K from deep sea clays at 3.8 Ga ago, indicates that over a period of 1000 years the amount of organic material transformated is 1.8 X 10(-7) moles/kg-clay. Although ionizing radiation may also induce synthetic reactions with prebiological interest, all in all these considerations indicate that nucleic acid bases and their derivatives adsorbed on clays were exposed for long periods to degradation conditions. Such situation promotes decomposition of organic molecules rather than protection of them and enhancement of farther polymerization, as it has been usually taken for granted.

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Catalytically Active Sites: Generation and Characterization

Hunger

2010

Zeolites and Catalysis

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Acid Strength Distribution Studies of Catalyst Surfaces.

Cited by 26 publications

References 12 publications

Surface Acidity of Montmorillonites

Surface Acidity of Montmorillonites

A review of conditions affecting the radiolysis due to40K on nucleic acid bases and their derivatives adsorbed on clay minerals: Implications in prebiotic chemistry

Catalytically Active Sites: Generation and Characterization

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