Nanoporous carbon/zeolite composites for the adsorption of green house gases (GHG) and toxic industrial chemicals (TIC)

LTA (4A) and NaX (13X) zeolite have been grown in the macrostructure of four 'unmodified' carbons (MAST™, willow, pine and rattan) without blocking the meso/micropores of the substrate. A lack of modification reduces environmenta1/production costs, avoids weakening the substrate and prevents side reactions. The :MAST ™/NaX composites can be rapidly regenerated in-situ by electrical heating using the resistivity of the carbon substrate. Calcination of the composites to remove the carbon produces a zeolite-only replica of the carbon substrate and (though fragile) the zeolite structures may be of use jn their own right. Zeolite loading could be increased almost 200% (from 3.3% to 9.6% mass) by extending substrate time in the precursor solution, or further increased (to 28-44% MASTTM) by gravity deposition of the zeolite on the substrate. Extending the synthesis time may have produced a different zeolite inside the pores to that produced externally. SEM on a 5-week synthesised LTA sample suggests that the zeolite hydroxy sodalite (H-SOD) has formed inside the pores while LTA developed externally. Hence, growth rates were found to be different inside the carbon pores as crystal growth continued after it was attested in the external solution. However, XRD and 29Si MAS-NMR analysis indicated that, in the first 14 h, NaX zeolite synthesis was slower inside the carbon pores than the external liquor. Acidity was expected to be important in the ability of a material to adsorb the basic molecule ammonia, so, to assess if this is indeed the case, LTA, carbon and composites were H+ exchanged using Hel before ammonia adsorption. Ammonia adsorption was not found here to be significantly increased by acid exchange. Indeed, Na~ LTA was found to adsorb NHJ just as extensively (6.6mmol/g) as H~LTA (6.8mmol/g) and adsorption in ~ LTA zeolite exchanged using the N H./ LTA method (then heated to remove NHJ was decreased by 50%, and only 3.3nunol/ g was adsorbed (on the 6.6rrunol/g adsorbing LTA) after NH/ exchange. The carbon substrate, however, performed much better when acid treated. Boehm titration results indicated that acidity ranges from 0.14nunol/g to 1.36nunol/g, even in non-acidified synthetic carbons, depended on the activation method performed (steam, CO2, etc.) and when add treated the carbon NH, adsorption increased 10 fold (from O.3mmol/g to 3.3mmol/g). NaX was found to be the best zeolite for NH J adsorption (5. l mmol/g for a 2 h outgas, 9.7mmol/g for a 4 h outgas and 18.6mmol/g for a 10 h+ outgas), if properly pre-conditionedEThOS - Electronic Theses Online ServiceGBUnited Kingdo