Natural zeolites for oilsands bitumen cracking: Structure and acidity

Clay minerals are well known for their ability to breakdown heavy oils by catalytic cracking, but not much is known of the potential of natural zeolites for oilsands bitumen cracking. Our previous work shows that natural zeolites can effectively crack oilsands bitumen into lighter, less viscous products, while producing fewer residues than analogous thermal cracking reactions. In this follow up study we have investigated the potential of both ion-exchanged and untreated forms of natural zeolites as solid acid agents for petroleum cracking. We compared the acid properties of various treated and untreated natural zeolites (particularly chabazites and clinoptiolites from different deposits) with the commercial petroleum cracking catalyst, zeolite Y. Energy dispersive X-ray analysis, inductively coupled Argon plasma-atomic emission spectrometry, acid-base titration using Hammett indicators and temperature programmed desorption of ammonia revealed that natural zeolites, both treated and untreated, have higher or comparable strength and density of acid sites compared to commercial zeolite Y. We propose that higher acid strength and site density, combined with a favorable morphology and a high fraction of accessible surface area contribute to the unique cracking ability of these extraordinary minerals. (C) 2011 Elsevier Inc. All rights reserved.