Acid site accessibility in sulfonated polystyrene acid catalysts: Calorimetric study of NH3 adsorption from flowing gas stream

• Published in: Journal of molecular catalysis. A, Chemical Vol. 252; no. 1-2; pp. 125 - 131
• Main Authors: Siril, Prem Felix, Brown, David R.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-06-2006; Elsevier
• Subjects: Acid site accessibility; Adsorption kinetics; Amberlyst 15; Ammonia; Catalysis; Chemistry; Exact sciences and technology; Flow adsorption calorimetry; General and physical chemistry; Solid acid catalysts; Sulfonated polystyrene; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Amberlyst 15; Ammonia; Sulfonated polystyrene; Flow adsorption calorimetry; Solid acid catalysts; Acid site accessibility; Adsorption kinetics; Acidic site; Solid; Heterogeneous catalysis; Acids; Adsorption; Calorimetry; Kinetics; Ion exchange resin; Catalyst; Styrene copolymer
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2006.02.050

Calorimetric pulsed NH3 adsorption measurements from a flowing carrier gas have been made on sulfonated poly(styrene-co-divinylbenzene) resin acid catalysts to characterise surface acidity in general and acid site accessibility in particular. Results are interpreted in terms of an adsorption process as depicted below. ▪
Calorimetric pulsed NH3 adsorption measurements from a flowing carrier gas have been made on sulfonated poly(styrene-co-divinylbenzene) resin acid catalysts to characterise surface acidity in general and acid site accessibility in particular. The adsorption and enthalpy profiles associated with each pulse of NH3 show distinct features associated with relatively weak and reversible adsorption of NH3 followed by strongly exothermic reaction with sulfonic acid sites and irreversible adsorption. The rate at which NH3 diffuses from its initial adsorption site to an acid site is shown to depend on catalyst particle size, adsorption temperature and the proportion of unreacted acid sites. By varying the contact time of NH3 with the catalyst the reversibility of the initial NH3 adsorption is demonstrated and an increasing number of the acid sites within the polymer matrix are shown to become completely inaccessible to NH3 as the contact time is reduced.