Physicochemical and Catalytic Properties of a Modified Natural Clinoptilolite

Abstract

Samples of natural clinoptilolite modified by treatment with NH4C1 or HCI solutions, followed by thermal treatments, have been characterized, and their catalytic activity evaluated, in o-xylene isomerization and ethanol dehydration reactions. The substitution of the compensating cations by NH4 ~ does not produce structural changes in the original material, but it opens the channels and increases its acidity and thermal stability. The treatment with HCI increases both the acidity and the effective diameter of the channels and pores but it produces an important loss of zeolite phase. Calcination of the acidic forms above 973 K leads to the breakdown of the zeolite structure. Catalytic activity of the samples is related to the surface acidity. For the original and NH4Cl-treated samples, however, the conversion of o-xylene is limited by the access of the reactant inside the channels of the zeolite. A comparative study with modified sepiolite in dehydration of ethanol has also been performed.

Investigation of structural properties of clinoptilolite rich zeolites in simulated digestion conditions and their cytotoxicity against Caco-2 cells in vitro

“…Quartz peak at 2h = 26.62°was also identified. In literature, HCl treatment was reported to decrease the intensities of the characteristic peaks of zeolites [29]. However, results showed that characteristic peak intensities of the clinoptilolite were almost same compared to the control sample after the gastric treatment.…”

“…The water vibrations of zeolite were also observed after 3,450 cm -1 . In literature, acidic treatments were reported to result shifts at characteristic peaks position (at 472 and 1,056 cm -1 ) and reduction in peak intensities were reported as a result of dealumination and partial structural breakdown [29,32]. However, FTIR spectra showed that characteristic peaks of zeolite were preserved for all treatments and there were no significant variations in the frequencies of assigned bands after gastric and intestinal digestion processes.…”

Copper Adsorption and Si, Al, Ca, Mg, and Na Release from Clinoptilolite

“…According to the XRD pattern shown in Fig. 1, the zeolite is identified as clinoptilolite and its characteristic peaks (14) were recognized at 2θ = 9.85…”

Thermal stability of Ag-exchanged clinoptilolite rich mineral

“…On XRD patterns, characteristics XRD lines of the clinoptilolite rich mineral are observed at 9.92, 22.43 and 30.50°2q [15]. aÈlar et al 2006, had studied thermal behavior of zeolitic tuff from Gördes-Manisa in the temperature range of 200-1200°C.…”