Giammatteo P.J.,Process NMR Associates |
Winter G.,TTC Labs. Inc.
Hydrocarbon Processing | Year: 2010
A discussion on improving diesel yields covers the use of spectro-molecular control to maximize profits; advantages of using nuclear magnetic resonance (NMR) analyzers in extracting additional profits; distillate products; 24-hr distillation predictions from one NMR-monitoring process stream from two separate crude distillation units (CDU) and a hydrotreater; exploiting the price differentials by providing feedback control to the crude units as well as both feed-forward and feedback control to the kerosene hydrotreater; low sulfur requirements for gasoline and diesel; refiners constrained at the hydrotreater with respect to sulfur content and to dibenzothiophene content; the CDU diesel rundown streams; NMR predictions for diesel rundown samples; and variables influencing clean diesel production.
Andrews A.B.,Schlumberger |
Edwards J.C.,Process NMR Associates |
Pomerantz A.E.,Schlumberger |
Mullins O.C.,Schlumberger |
And 2 more authors.
Energy and Fuels | Year: 2011
The molecular architecture of asphaltenes is still a matter of debate. Some literature reports provide evidence that the contrast of petroleum asphaltenes versus coal-derived asphaltenes is useful for understanding the governing principles of asphaltene identity. Coal-derived asphaltenes provide an excellent test for understanding the relationship of asphaltene molecular architecture with asphaltene properties. Diffusion measurements have shown that coal-derived asphaltenes are half the size of many crude oil asphaltenes, but there are relatively few studies comparing coal-derived and petroleum asphaltenes using liquid state 13C NMR. 13C NMR confirms that the molecular sizes of these coal-derived asphaltenes are smaller than virgin petroleum asphaltenes. DEPT-45 experiments were performed in order to determine the relative amount of nonprotonated and protonated carbon in the aromatic region of the spectrum. In contrast to previous NMR work on asphaltenes that ignored interior bridgehead carbon, we show this is an important component of asphaltenes and that correctly accounting for this carbon enables proper determination of the number of fused rings. XRS data supports interpreting the NMR data with a model that weighs circularly condensed structures more heavily than linearly condensed structures. Significantly more carbon exists in chains at least 9 carbons long in petroleum asphaltenes (≥7%) compared to coal-derived asphaltenes (≥1%). © 2011 American Chemical Society.
Mullins O.C.,Schlumberger |
Sabbah H.,Toulouse 1 University Capitole |
Sabbah H.,Hoffmann-La Roche |
Sabbah H.,Stanford University |
And 14 more authors.
Energy and Fuels | Year: 2012
The Yen-Mullins model, also known as the modified Yen model, specifies the predominant molecular and colloidal structure of asphaltenes in crude oils and laboratory solvents and consists of the following: The most probable asphaltene molecular weight is ∼750 g/mol, with the island molecular architecture dominant. At sufficient concentration, asphaltene molecules form nanoaggregates with an aggregation number less than 10. At higher concentrations, nanoaggregates form clusters again with small aggregation numbers. The Yen-Mullins model is consistent with numerous molecular and colloidal studies employing a broad array of methodologies. Moreover, the Yen-Mullins model provides a foundation for the development of the first asphaltene equation of state for predicting asphaltene gradients in oil reservoirs, the Flory-Huggins-Zuo equation of state (FHZ EoS). In turn, the FHZ EoS has proven applicability in oil reservoirs containing condensates, black oils, and heavy oils. While the development of the Yen-Mullins model was founded on a very large number of studies, it nevertheless remains essential to validate consistency of this model with important new data streams in asphaltene science. In this paper, we review recent advances in asphaltene science that address all critical aspects of the Yen-Mullins model, especially molecular architecture and characteristics of asphaltene nanoaggregates and clusters. Important new studies are shown to be consistent with the Yen-Mullins model. Wide ranging studies with direct interrogation of the Yen-Mullins model include detailed molecular decomposition analyses, optical measurements coupled with molecular orbital calculations, nuclear magnetic resonance (NMR) spectroscopy, centrifugation, direct-current (DC) conductivity, interfacial studies, small-angle neutron scattering (SANS), and small-angle X-ray scattering (SAXS), as well as oilfield studies. In all cases, the Yen-Mullins model is proven to be at least consistent if not valid. In addition, several studies previously viewed as potentially inconsistent with the Yen-Mullins model are now largely resolved. Moreover, oilfield studies using the Yen-Mullins model in the FHZ EoS are greatly improving the understanding of many reservoir concerns, such as reservoir connectivity, heavy oil gradients, tar mat formation, and disequilibrium. The simple yet powerful advances codified in the Yen-Mullins model especially with the FHZ EoS provide a framework for future studies in asphaltene science, petroleum science, and reservoir studies. © 2012 American Chemical Society.
Dicaprio A.,Process NMR Associates |
Edwards J.,Process NMR Associates
Journal of the Institute of Brewing | Year: 2014
Spontaneous biological acidification has long been a part of the German brewing tradition, and was historically used to optimize the pH of brewhouse mashes. By facilitating the growth of native barley flora, the production of lactic, acetic and succinic acids sours the mash, functioning in a similar way to the addition of food-grade acids, which are prohibited under the Reinheitsgebot of 1516. Traditionally, sour mashes have been performed at the 'optimum' temperature of 49°C. Quantitative proton nuclear magnetic resonance spectroscopy was used for the investigation and quantitation of organic acids produced by acidified mashes over a range of temperatures. All target metabolites demonstrated an inverse relationship with temperature, although lactic acid reached a relative maximum at 49°C, which is in agreement with the customary sour mash temperature. Therefore, it would seem that the optimization of a sour mash is dependent not on absolute acid concentration, which would give the greatest pH regulation potential, but on the relative acid concentration, an important factor influencing the final flavour profile of a beer. © 2014 The Institute of Brewing & Distilling.
De Goede S.,Sasol Limited |
Rabe T.,Sasol Limited |
Bekker R.,Sasol Limited |
Mtongana S.,Sasol Limited |
Edwards J.,Process NMR Associates
SAE Technical Papers | Year: 2010
Direct Injection Spark Ignition (DISI) engine technology is becoming increasingly common in the South African and global vehicle pares. South Africa is in a unique position because a significant portion of all liquid fuels consumed are synthetically produced from coal and gas. These fuels are mainly supplied into the inland regions, particularly the Gauteng province, the economic heartland of South Africa and the most densely populated area in the country. It is important to understand the performance of synthetic fuels in the latest generation engines, in order to ensure that these fuels are fit for use in these new applications. The latest generation DISI gasoline engines (also known as Gasoline Direct Injectionâ.,¢ and Fuel Stratified Injectionâ.,¢) differ significantly in operation to older Port Fuel Injected (PFI) engines. Although there is literature available on the relationship between crude-derived fuel composition and the composition of DISI engine deposits, no such information exists on the possible effects of synthetic fuel composition on such deposits. An on-road vehicle trial was conducted to assess and compare the effect of synthetic and crude-derived fuels on such engine deposits. During the on-road trial, four similar Volkswagen FSI vehicles were tested under similar conditions over a distance of 20 000 km in order to determine the relative performance of the fuels evaluated. Some of the fuels evaluated during this trial were synthetic fuels (one additised with a detergent additive and two unadditised Fischer-Tropsch fuels), while the fourth fuel was a conventional crude-derived fuel. Comprehensive characterisation of these fuels by Nuclear Magnetic Resonance spectroscopy (NMR) and two dimensional GC analysis (GCxGC-TOFMS) showed very significant differences in fuel composition between the synthetic and the crude-derived fuels. The engine deposits were characterised using various solid-state 13 C NMR techniques, thermogravimetric analysis (TGA), Fourier Transform Infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). This study confirmed that the methodologies developed for the characterisation of deposits from PFI engines could also be applied to DISI engines, which is consistent with previous literature findings. The species identified in these DISI deposits were shown to be similar in nature to the deposits formed in PFI vehicles. Similarly, it was shown that the deposits formed during the combustion of synthetic gasoline were similar in composition to those formed during operation on a crude-derived fuel. Some differences in the quantity of the deposits formed were observed between the vehicles that ran on synthetic fuels and those that ran on crude-derived fuels. Despite the differences in composition between the synthetic and crude-derived fuels, the bulk chemical composition of the deposits generated from these fuels are not significantly different. Moreover, the overall performance of these DISI-equipped test vehicles were unaffected by the fuel composition over the 20 000km test period. However, it must be kept in mind that although vehicle preparation, driving conditions and fuel compositions were well controlled, ambient conditions were not controlled. Results are therefore considered to be comparative. Copyright © 2010 SAE International.