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Understanding the Effects of Sample Preparation on the Chemical Structures of Petroleum Imaged with Non-contact Atomic Force Microscopy

preprint
submitted on 23.10.2018 and posted on 24.10.2018 by Yunlong Zhang, Bruno Schuler, Shadi Fatayer, Leo Gross, Michael R. Harper, J. Douglas Kushnerick
This study addresses the effect of sample preparation conditions on the structural integrity and composition of heavy hydrocarbon mixtures imaged by non-contact atomic force microscopy (nc-AFM). We designed and prepared a set of organic molecules mimicking well-accepted key characteristics of heavy oil asphaltenes including molecular architecture, molecular weight, boiling point, atomic H/C ratio and bond strength. We deliberately focused on multi-core molecule structures with long aliphatic linkers as this architecture was largely absent in previous nc-AFM studies of petroleum samples. The results confirm that all these molecules can be successfully imaged and remain intact under the same preparation conditions. Moreover, comparison with ultra-high resolution FT ICR-MS of a steam-cracked tar asphaltene sample suggests that the single molecules identified by nc-AFM span the entire molecule spectrum of the bulk sample. Overall, these results suggest that petroleum molecules within the scope of chosen molecules studied herein can be prepared intact and without bias and the imaged data can be representative.

Funding

European Research Council (Consolidator grant ‘AMSEL’ – agreement no. 682144) and EU projects ‘PAMS’ (Contract no. 610446)

History

Email Address of Submitting Author

yunlong.zhang@exxonmobil.com

Institution

ExxonMobil Research and Engineering Company

Country

USA

ORCID For Submitting Author

0000-0002-3071-8625

Declaration of Conflict of Interest

no conflict of interest

Version Notes

Oct 21, 2018

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