“…There is a tendency to overtitrate using these Hammett indicators; substituted arylmethanols seemed to be better suited as indicators [482]. The use of aryl methanols (aryl carbinols) instead of Hammett indicators had been proposed by Hirschler [483). Triaryl methanols react with strong proton acids according to R3 C-OH + H+ ¢ R3C+ + H 2 0.…”
Section: And Iii)mentioning
confidence: 98%
“…For these indicators, an HR acidity function was defined by Deno et al [484]: (18) This equation contains also the activity of water, and obviously results will be influenced by traces of moisture still more strongly than with Hammett indicators. However, Hirschler [483] claimed better correlation of the titration values with catalytic activity of silica-alumina cracking catalysts when HR indicators were used instead of Ho indicators.…”
“…There is a tendency to overtitrate using these Hammett indicators; substituted arylmethanols seemed to be better suited as indicators [482]. The use of aryl methanols (aryl carbinols) instead of Hammett indicators had been proposed by Hirschler [483). Triaryl methanols react with strong proton acids according to R3 C-OH + H+ ¢ R3C+ + H 2 0.…”
Section: And Iii)mentioning
confidence: 98%
“…For these indicators, an HR acidity function was defined by Deno et al [484]: (18) This equation contains also the activity of water, and obviously results will be influenced by traces of moisture still more strongly than with Hammett indicators. However, Hirschler [483] claimed better correlation of the titration values with catalytic activity of silica-alumina cracking catalysts when HR indicators were used instead of Ho indicators.…”
“…groups (MeOH) follows the Hirschler-Plank mechanism [134,135], i.e., via dissociation of water molecules in the strong electrostatic fields of the multivalent extra-framework cations inside the zeolite pores and cages. This dissociation of water molecules leads to the formation of hydroxyl protons bound to framework oxygen atoms of Si-O-Al bridges and of OH groups bound to extra-framework cations (Scheme 2).…”
Section: Brønsted Acid Sites On Zeolites and Heteropoly Acidsmentioning
“…The strengths of these electric fields are strictly proportional to the ratio of cation charge to cation radius. According to the mechanism of Hirschler [330] and Plank [331] dissociation of water molecules upon adsorption on multivalent cations results in the formation of cation and bridging OH groups. lH MAS NMR spectroscopy has been applied to investigate quantitatively the formation of hydroxyl protons due to water adsorption on dehydrated zeolites MgNa Y and CaNa Y [308] .…”
Section: H Mas Nmr Spedroscopy Of Acidic and Non-acidic Hydroxyl Grmentioning
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