John G. Reynolds

Vanadylporphyrins, indicators of kerogen breakdown and generation of petroleum

Abstract Attempts at understanding the transformation of organic material into fossil fuels often relies on biomarkers, organic compounds present in the geological record that can be related to naturally-occurring molecules from specific organisms. While porphyrins were the first biomarkers identified in fossil fuels, no significant use has been made of them in geochemical correlation studies. We believe that one limitation to their usage has been inaccurate models proposed for the fate of porphyrins during catagenesis. Using laboratory pyrolysis experiments we show that the changes observed in vanadylporphyrin distribution during catagenesis is due to increasing dilution of preexisting DPEP vanadylporphyrins by ETIO vanadylporphyrins released from kerogen. In conjunction with a quantitative expression describing the change in vanadylporphyrin distribution during maturation called the Porphyrin Maturity Parameter (PMP), a basis is now provided for the use of vanadylporphyrins as indicators of onset of petroleum generation.

CHARACTERIZATION OF VANADIUM COMPOUNDS IN SELECTED CRUDES I. PORPHYRIN AND NON-PORPHYRIN SEPARATION

ABSTRACT We have applied size-exclusion chromatography (SEC-HPLC) and reversed-phase chromatography (RP-HPLC), with element specific detection, [Inductively coupled and direct current plasma atomic emission spectroscopy (ICP and DCP)], to selected crude oils –– Boscan, Beta, Morichal, Arabian Heavy, and Maya –– and their separated fractions. By these procedures, we have further characterized both the V porphyrin and the V non-porphyrin compounds. From the SEC-HPLC-ICP profiles of the heavy crude oils we found the V compounds generally have a bimodal distribution, with maxima at approx. 800 and 9000 polystyrene equivalent (PS) molecular weight (MW). Arabian Heavy, though, had relatively few of the small V compounds. The crude oils were separated into porphyrin and non-porphyrin fractions by methanol extraction. From the SEC-HPLC-ICP profiles of the porphyrin fraction, we Identified and quantitated the maximum at approx. MW 800 (PS) as being V porphyrins. The remaining V compounds are non-porphyrin.

Analysis of residuum demetalation by size exclusion chromatography with element specific detection

ABSTRACT We analyzed thermally treated heavy residua by element specific size exclusion chromatography (SEC-ICF) to elucidate the fate of the V and Ni compounds. Thermal treatment, in addition to removing metals, significantly reduces the size of the remaining metal-containing compounds.We thermally treated the distillable and nondistillable metals separately. The distilled metals, primarily petroporphyrins, were completely removed under moderate conditions. The non-volatile metal-containing components, which constituted most of the Ni and V, were either removed, or reduced in size.when treating heavy residua over commercial fixed-bed hydroprocessing catalysts, the metal-containing molecules in the size range of the catalyst pore are preferentially removed. Those larger than the pore size appear to demetalate more slowly.The results argue demetalation is a function of the ligand structure and size of the metal-containing species and not necessarily the coordination sphere around the metal center.

EFFECTS OF ASPHALTENE PRECIPITATION AND A MODIFIED D 2007 SEPARATION ON THE MOLECULAR SIZE OF VANADIUM-AND NICKEL-CONTAINING COMPOUNDS IN HEAVY RESIDUA

ABSTRACT Boscan vacuum residuum (VR), and Maya atmospheric residuum (AR), were separated into operationally defined components by an isooctane asphaltene precipitation followed by a modified D 2007-80 separation of the isooctane soluble material. These collected fractions were examined by size exclusion chromatography (SEC) with element specific detection employing inductively coupled plasma emission spectroscopy (ICP) to investigate the effect the separation has on the the V and Ni compounds. The V and Ni SEC-ICP profiles of the asphaltene fractions indicated some of the metal-containing molecules are substantially larger in size than those observed in the residua. The asphaltene precipitation appears to cause an increase in molecular size through agglomeration of smaller constituents, and accomplishes only limited size separation of the metal-containing compounds. The resin fraction, the polar fraction obtained by modified D 2007-80 chromatography of the isooctane soluble portion, contained much of the ...

CHARACTERIZATION OP VANADIUM COMPOUNDS IN SELECTED CRUDES II. ELECTRON PARAMAGNETIC RESONANCE STUDIES OP THE FIRST COORDINATION SPHERES IN PORPHYRIN AND NON-PORPHYRIN FRACTIONS

ABSTRACT We applied electron paramagnetic resonance spectroscopy (EPR) to heavy petroleum fractions to characterize the first coordination sphere around the vanadyl +2 ion. The fractions were generated using a modified porphyrin extraction procedure. For the residual oil from the extraction, which contains the non-porphyrin metals, the first coordination sphere was dominated by 4N and N O 2S for Boscan, Beta, Morichal, and Arabian Heavy crudes. Maya had distinctively different parameters. These findings are significant for determining the overall structure of metal-containing compounds in heavy crude oils. We discuss the difference between the porphyrin and non-porphyrin behavior, possible blogenic precursors, and some process implications.

Effects of asphaltene precipitation and reprecipitation on the metal-containing compounds in heavy residua

ABSTRACT Boscan vacuum residuum (VR) has been separated into isooctane insoluble asphaltenes and isooctane soluble maltenes. The asphaltenes were dissolved in a minimum of toluene and were further separated by two additional reprecipitations using isooctane as the precipitating solvent. We examined the fractions, including the recovered isooctane soluble material, by size exclusion chromatography (SEC) with inductively coupled plasma (ICP) emission spectroscopy to determine the effects, if any, the reprecipitations have on the size distribution of the metal-containing compounds. The asphaltene fractions show little change in size upon reprecipitation, but removal of a small amount of the metal components does occur. The first reprecipitation produces isooctane soluble material which is very similar in size to the original maltene fraction. However, the second reprecipitation removes small amounts of material in the size range of the asphaltenes. When the amounts were weight balanced, the resulting separat...