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.

Raw untreated natural chabazite and clinoptilolite minerals show a more favorable morphology, and a higher strength and density of acid sites compared to the commercially available petroleum cracking agent zeolite Y. These results indicate that raw untreated natural zeolites are capable of performing as effective petroleum cracking agents at a much lower cost than ZY. This can have a great potential for heavy oil and bitumen extraction and upgrading applications.Figure optionsDownload as PowerPoint slideHighlights
► Clinoptilolite and chabazite have platy morphology and substantial external surface.
► These natural zeolites contain large number of strong acid sites.
► Strengths of the sites are higher than/comparable to that of commercial zeolite Y.
► Densities of the sites are much higher than the commercial catalyst.
► Acidic properties of these natural minerals can be modified by ammonium-exchange.