Ring opening of cyclohexane over ZSM-zeolites followed by reversed-flow gas chromatography

Adsorption Studies of Gases on Pt−Rh Bimetallic Catalysts by Reversed-Flow Gas Chromatography

“…(v) The k 1 CO (100% Pt) values are higher than the k 1 CO (25% Pt + 75% Rh) values, incidating that carbon monoxide is adsorbed more strongly on the pure-Pt catalyst than on the Pt−Rh bimetallic catalysts, in accordancce with previous results. ,− …”

“…Figure c). The latter, which has been also presented previously, , can be attributed to the following reason: The Pt surface concentration in the Pt-rich catalyst (Pt 0.75 + Rh 0.25 ), compared to the Rh surface concentration, according to the surface phonon softening model, , becomes larger with increasing temperature. Considering that the Pt surface in the Pt−Rh alloy catalysts is predominantly covered with CO, while the Rh surface strongly adsorbs oxygen, the adsorption of oxygen on the Pt-rich catalyst decreases with increasing temperature.…”

“…Figure ), at time t where M is the response factor of the detector and g a proportionality constant (usually assumed unity for convenience) pertaining to the detector calibration. Measuring H experimentally as a function of t , one can construct the diffusion band , which in the case of adsorption of the gases CO, O 2 , and CO 2 on the Pt−Rh bimetallic catalysts is described by the equation where In the above equations, m is the injected amount of the adsorbate gases in mol, V̇ is the volumetric flow-rate of the carrier gas, k 1 and k - 1 are the rate constants for adsorption and desorption, respectively, k 2 is the first-order rate constant for a possible surface reaction, ε is the external porosity of the catalyst bed, V G and are the gaseous volumes of empty sections L 1 and L 2 , respectively (cf. Figure ), and D 1 and D 2 are the diffusion coefficients of the adsorbate gases in the carrier gas helium at temperatures T 1 (in the column L 1 ) and T 2 (in the column L 2 filled with the catalyst bed), respectively.…”

Αεριοχρωματογραφικός Προσδιορισμός Σταθερών Ταχύτητας Και Ενεργειακών Μεγεθών Προσροφήσεως Σε Αντιδράσεις Αέριων Ρύπων

“….9.3 το οποίο έχει χρησιμοποιηθεί και σε άλλες μελέτες[186]. Η συντεταγμένη κατά μήκος της ζώνης διαχύσεως χωρίζεται τεχνητώς στα τμήματα ζ και y, για να διευκολυνθεί η μαθηματική περιγραφή.…”