59th Annual Report on Research 2014

In the time frame of the last report, the principal investigator has conducted extensive research on the topic, on sulfur elucidation in different fossil fuels using X-ray Absorption Near-Edge Structure (XANES) spectroscopy, involving two graduate students. The students worked on active x-ray absorption data acquisition at a synchrotron radiation site at Advanced Photon Source (APS) at Argonne National Lab (ANL), and on data analysis at Rose-Hulman Institute of Technology. The PI worked on data acquisition at APS and Advanced Light Source (ALS) at Lawrence Berkeley Lab (LBL), and on data analysis. This has resulted in three poster presentations, and two peer-reviewed publications. The main idea of this project was to study sulfur chemistry on asphaltenes, kerogens, and resins extracted from different depositional sites and prepared using different laboratory techniques.

Data Acquisition:

During summer 2013 for XANES data collection, three students had accompanied the PI to APS at ANL, and the PI made a separate trip to ALS at LBL. The three students had also worked on the analysis of the data.

During summer of 2014 Eric Kercher and the PI collected sulfur K-edge x-ray absorption data on a set of different sulfur standards diluted at different concentrations, oils, kerogens, bitumens, and asphaltenes. The sample standard samples were obtained from Sigma Aldrich, and the fossil fuel samples came from collaborators at Schlumberger-Doll Research Labs (SDR), American Refining Group, and Conoco Phillips. The x-ray data acquisition was done at the APS at ANL. Eric learned about the proper synchrotron beamline techniques, and how to collect good quality data, working almost round the clock for 3 days. Three collaborators from SDR joined in with Rose-Hulman (RH) group. In the end the group ended up with a set of good reproducible data.

One set of samples that were studied at APS was a set of sulfur standards with different dilution amounts; this set included samples that had not been studied before. This was necessary as every beamtime can be different, and a good set of different samples will make analysis procedures of the fossil fuels more robust. The second set of samples was of different oils with different degrees of biodegradation. This will help us learn about the geochemical processes better. A third set of samples consisted of asphaltenes that were both in pristine and demineralized forms.

In July-August 2014, the PI collected sulfur XANES data at ALS at LBL. This study concentrated on asphaltenes and resins obtained from a series of heavy crude oils.

Beamline 9-BM at APS, and 9.3.1 at ALS, which span an energy range of ~2-6 KeV, were used. Si (111) crystals were used in the double crystal configuration at both beamlines. At APS, a Lytle detector was used for fluorescence measurements. There the samples were mounted on a Teflon sample holder. The liquid samples were diluted in methyl dichloro-methane, or toluene. The kerogens were crushed at liquid nitrogen temperatures, and mixed with boron nitride to avoid self-absorption effects. At ALS a silicon drift detector was used, and the samples were studied under high vacuum conditions.

On-campus work

During the later part summer of 2013 Grant Brodnik spent several weeks studying the collected XANES data. He rewrote a computer program, and analyzed two sets of samples that were collected under different vacuum conditions at two different synchrotron radiation locations, viz. ALS and APS (both sets of data collected in earlier in 2013). The fitting analysis was first done with various sulfur model spectra and then on the fossil fuels. Dr. Andrew Pomerantz of SDR was consulted periodically on several issues. The PI oversaw the entire analysis procedure, including the testing of the new program, as well as independently analyzing the spectra.

The overall results that were obtained from this part of the project were:

1. There are marked differences between kerogens and bitumens. Bitumen, the organic part of the shale that is soluble in organic solvents, showed large percentages of the polar sulfoxide structures. Kerogens, the insoluble organic parts of shales, showed more elemental and thiophenic sulfur forms.
2. Acid demineralization of the samples did not alter the XANES results for the sulfur standards, the kerogens and the bitumens.
3. There are no big differences between the different petroleum asphaltenes. This is despite the fact that there the samples were extracted from oils that have undergone different geochemical processes.
4. A novel way to prepare diluted samples with small particle sizes produced excellent XANES results.

Presentations

• Grant Brodnik presented two posters on the results from asphaltenes, oils, kerogens, and bitumens.
• A poster presentation was made by the PI at the Petrophase Conference in Texas, in August, 2014.
• Two publications:

1. Sulfur Chemistry of Asphaltenes from a Highly Compositionally Graded Oil Column

Andrew E. Pomerantz, Douglas J. Seifert, Kyle D. Bake, Paul R. Craddock, Oliver C. Mullins, Brian G. Kodalen, Sudipa Mitra-Kirtley,Trudy B. Bolin. Energy & Fuels. 07/2013; 27(8):4604–4608.

1. Sulfur speciation in kerogen and bitumen from gas and oil shales. Andrew E. Pomerantz, Kyle D. Bake, Paul R. Craddock, Kurt W. Kurzenhauser, Brian G. Kodalen, Sudipa Mitra-Kirtley, Trudy B. Bolin. Organic Geochemistry 01/2013.

The next step of the project will be to

1. Analyze all data sets collected in August 2014 at ALS and APS.