Acid-modified clinoptilolite as a support for palladium–copper complexes catalyzing carbon monoxide oxidation with air oxygen
Samples of natural clinoptilolite were modified by an acid–thermal method at nitric acid concentrations of 0.25, 0.5, 1.0, and 3.0 M and a contact time of 30 min. A series of catalysts, K2PdCl4–Cu(NO3)2–KBr/S (S = 0.25H-CLI, 0.5H-CLI, 1H-CLI, and 3H-CLI) was obtained. All samples were investigated by X-ray phase and thermogravimetric analysis, FT-IR spectroscopy, water vapor ad/desorption and pH metric method. Besides, K2PdCl4–Cu(NO3)2–KBr/S samples were tested in the reaction of low-temperature carbon monoxide oxidation. It have been found that, owing to special physicochemical and structural-adsorption properties of 3H-CLI, it promotes formation of the palladium–copper catalyst providing carbon monoxide oxidation at the steady-state mode down to CO concentrations lower than its maximum permissible concentration at air relative humidity varied within a wide range.
Thermal and gas (CH 4 and C 2 H 4 ) adsorption characteristics of nitric acid-treated clinoptilolite
In this study, in order to consider the effect of the time of the nitric acid treatment on thermal, structural and gas adsorption properties, clinoptilolite was modified with 1.0 M acid solutions at 80 °C for 2, 4, 6, 12 and 24 h. Structural and thermal properties of natural and acid-treated clinoptilolites were investigated by powder X-ray diffraction, X-ray fluorescence, thermogravimetric analysis, differential thermal analysis and nitrogen adsorption methods. Methane (CH4) and ethylene (C2H4) are hazardous gases for human and plant health, respectively. Therefore, some measures should be taken to reduce emissions of methane and ethylene. CH4 and C2H4 adsorption capacities of clinoptilolite (CLN) from Turkey and that of acid-treated forms at 273 K up to 100 kPa were found between 0.556–0.683 and 0.470–1.295 mmol g−1, respectively.
Isomerization of α-pinene over ion-exchanged natural zeolites
Abstract Catalysts prepared by ion exchange of clinoptilolite-based natural zeolite tuffs with NH 4 + , Ba 2+ and Pb 2+ were investigated in the isomerization reaction of α-pinene at atmospheric pressure under nitrogen flow. Activity and selectivity to mono-, bi- and tricyclic products were correlated with acidity strength.