Chang Samuel Hsu

17.alpha.(H)-21.beta.(H)-hopane as a conserved internal marker for estimating the biodegradation of crude oil

Hopanes are common constituents of crude oils, and they are very resistant to biodegradation. They can therefore serve as conserved internal standards for assessing the biodegradation of the more degradable compounds in the oil. Here we address two important questions that attend such use. The first is whether the [open quotes]internal standard[close quotes] is being created during the biodegradation process itself, for this could result in an overestimate of the extent of biodegradation. The second is whether the internal standard is indeed relatively resistant to biodegradation on time scales of relevance to the biodegradation process under study; for if it was not, this could result in an underestimate of the extent of biodegradation. We find that 17[alpha](H),21[beta](H)-hopane is neither generated nor biodegraded during the biodegradation of crude oil fractions on time scales relevant to estimating the cleansing of oil spills, and so it has the appropriate characteristics to serve as an internal standard for studying the biodegradation of crude oil in the environment. 20 refs., 4 figs.

Petroleomics: advanced molecular probe for petroleum heavy ends

To look into complex mixtures of petroleum heavy ends at the molecular level, ultra high-resolution mass spectrometry, i.e. resolving power > 50,000, is needed to resolve overlapping components for accurate determination of molecular composition of individual components. Recent progress in Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) incorporated with soft ionization techniques adaptable to liquid chromatography enables analysis of petroleum high ends, i.e., heavy oils, residua and asphaltenes. FT-ICR MS at the Future Fuels Institute of Florida State University and the National High Magnetic Field Laboratory (NHMFL) routinely provides 1,000,000 resolving power at 400 Da, with root mean square (rms) mass measurement accuracy between 30 and 500 ppb for 5000-30,000 identified species in a single mass spectrum. Phase correction of the detected ion signal increases resolving power 40-100%, improving mass accuracy up to twofold. Overlapping ionic species that differ in mass by as little as one electron mass (548 µDa) can be resolved. A database of more than 100,000 components of different elemental composition has been generated at NHMFL.

Analytical advances for hydrocarbon research

This review of Analytical Advances for Hydrocarbon Research, edited by C.S. Hsu is based on material presented at the 220th American Chemical Society Symposium held in Washington DC, August 2000. Fossil fuels and crude oils in particular are complex mixtures of hydrocarbons and heteroatomic compounds covering a wide range of molecular weights, polarities, melting points, boiling points and other physical properties. Detailed characterization of these complex mixtures is essential for all areas of exploration, production and refining. Since the earliest discovery of crude oil, methods have been continually developed and improved for this purpose. In the early days, the techniques available were very facile compared to the complex tools available today. Properties such as gravity, color, optical activity were used to differentiate or characterize products. Various distillation techniques were used to provide an indication of the fractions present in the oils and their boiling point distributions. Significant breakthroughs started to occur in the mid-1900s with the development of techniques such as gas chromatography (GC) and mass spectrometry (MS). By the early 1970s, hyphenated techniques such as GC-MS started to become commercially available and a quantum leap was made in our ability to characterize complex mixtures on a molecular level. This book, in my opinion, is very timely since it provides a compilation of 18 chapters dedicated to many of the latest developments in analytical techniques widely used in areas of the petroleum industry concerned with exploration, production, refining, and, more recently, environmental concerns. The chapters in the book cover virtually all of the techniques being used today in these areas. However, I was a little disappointed that coverage on supercritical fluid chromatography (SFC) and high temperature gas chromatography was not adequately provided. Both topics are relatively important in many areas of hydrocarbon characterization. One of the appealing aspects of this volume is that fact that is covers such a wide range of techniques, many of which are often not described in detail in the mainstream literature. The techniques may be described in specialist journals but here they are all together in one readily accessible reference volume. For example, Chapter 1 describes methods to characterize and estimate thermodynamic and physical properties of hydrocarbon and petroleum products through the use of properties such as boiling points, viscosity, refractive index and others. A chapter such as this is extremely useful for reference purposes for those of us who may encounter these properties on an irregular basis but occasionally need more information on such properties. Chapter 2 is valuable for the same reason. We all make use of elemental analyses, but most of us, at least those working with the organic fractions tend to think of C,H,N,O and S when we think of elemental analyses. In this chapter we are provided a summary of methods and developments to determine a wide range of elements in both crude oils and refined products, both new and used. It also provides a brief but useful explanation of techniques such as ICP/MS and XRF which again is useful for non-experts in the field. Chapter 3 focuses on N and S containing compounds and their detection by GC with a brief description of the various N and S specific detectors available and advances made in these areas, such as the nitrogen chemiluminescence detector (NCD). Chapter 4 is the first of many chapters concerned with mass spectrometric techniques in hydrocarbon characterization. Chapter 5 provides an excellent overview on thin-layer chromatography (TCL)—again, a tool we all use routinely but one which most of us pay little attention to when it comes to new developments. Geochemists and other analytical chemists would be well-advised to look into the section on the use of berberineimpregnated plates for the detection of saturate hydrocarbons. A useful summary of ASTM standard methods utilizing GC, SFC, LC (liquid chromatography) and TLC for characterizing various low boiling fractions is given in Chapter 6. As with the other chapters in this book, having all of this information in one place is very useful for those of us who need the information occasionally and do not want to spend a lot of time searching widely-dispersed sources of information. The importance of retention indices in identifying compounds in complex mixtures such as crude oils and other liquid fuels is described in Chapter 7. Retention indices are also provided for over 150 compounds for use in conjunction with GC and GCMS data as an aid in identifying these compounds. Simulated distillation GC is described and a standard method introduced for this purpose. In view of the ever-increasing environmental concerns related to S containing compounds in refined products, Chapter 8 provides a useful summary of the Published online September 17, 2003

Molecular transformation in hydrotreating processes studied by on-line liquid chromatography/mass spectrometry

Molecular transformation in petroleum hyrdrotreating was studied using LC/MS (low-energy electron impact ionization). Changes in the molecular structure of hydrocarbons and heteroatom compounds were effectively analyzed by this method.

Atmospheric Pressure Laser-Induced Acoustic Desorption Chemical Ionization Mass Spectrometry for Analysis of Saturated Hydrocarbons

We present atmospheric pressure laser-induced acoustic desorption chemical ionization (AP/LIAD-CI) with O(2) carrier/reagent gas as a powerful new approach for the analysis of saturated hydrocarbon mixtures. Nonthermal sample vaporization with subsequent chemical ionization generates abundant ion signals for straight-chain, branched, and cycloalkanes with minimal or no fragmentation. [M - H](+) is the dominant species for straight-chain and branched alkanes. For cycloalkanes, M(+•) species dominate the mass spectrum at lower capillary temperature (<100 °C) and [M - H](+) at higher temperature (>200 °C). The mass spectrum for a straight-chain alkane mixture (C(21)-C(40)) shows comparable ionization efficiency for all components. AP/LIAD-CI produces molecular weight distributions similar to those for gel permeation chromatography for polyethylene polymers, Polywax 500 and Polywax 655. Coupling of the technique to Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) for the analysis of complex hydrocarbon mixtures provides unparalleled mass resolution and accuracy to facilitate unambiguous elemental composition assignments, e.g., 1754 peaks (rms error = 175 ppb) corresponding to a paraffin series (C(12)-C(49), double-bond equivalents, DBE = 0) and higher DBE series corresponding to cycloparaffins containing one to eight rings. Isoabundance-contoured plots of DBE versus carbon number highlight steranes (DBE = 4) of carbon number C(27)-C(30) and hopanes of C(29)-C(35) (DBE = 5), with sterane-to-hopane ratio in good agreement with field ionization (FI) mass spectrometry analysis, but performed at atmospheric pressure. The overall speciation of nonpolar, aliphatic hydrocarbon base oil species offers a promising diagnostic probe to characterize crude oil and its products.

Introduction to Petroleum Technology

When people consider petroleum, they first think of energy. Petroleum and other fossil fuels now provide more than 86% of the energy consumed by mankind. In addition, fossil resources, especially petroleum and natural gas, serve as the organic source of tens of thousands of consumer products, which enrich our daily lives.

Gasoline Production and Blending

Gasoline is a volatile, flammable mixture of liquid hydrocarbons primarily obtained from refining petroleum. Most gasoline is consumed as a fuel in spark-ignition engines, primarily those which power automobiles and certain airplanes. For engine performance, important gasoline properties include volatility (Reid vapor pressure), octane number and heat content. Reid vapor pressure (RVP) is one of the gasoline specifications for performance in engine. Reformulated gasoline laws now protect the environment by limiting smog precursors, banning tetraethyl lead (TEL ) and regulating concentrations of sulfur, olefins, benzene and oxygenates in gasoline. Refineries produce gasoline from blendstocks derived from various processes – crude oil distillation, catalytic reforming, fluid catalytic cracking (FCC), thermal cracking, hydrocracking, alkylation, isomerization and catalytic polymerization. Finished products sold in the market include additives, which inhibit oxidation, inhibit corrosion, passivate trace metals, reduce deposition of carbon on intake valves and combustion chambers, and minimize the formation of ice in cold weather. Relative gasoline demand is highest in North America, while automotive diesel is preferred in most of the rest of the world.

Molecular Science, Engineering and Management

All organic materials, living and nonliving are made of molecules. Hence, the composition and structure of the organic molecules, either in pure compounds or different in complex mixtures, determine the properties, behavior, and reactivity of the compounds and mixtures. Chemistry is a science to study the changes of molecules and the relationship of those changes with physics, mathematics, biology, geology, and other disciplines. Chemistry controls how molecules can be used in exploration/production, refining engineering/processing, chemical production, drug discovery, disease controls, etc.

Comment on “Laser Desorption/Ionization Coupled to FTICR Mass Spectrometry for Studies of Natural Organic Matter”

In a recent paper, Blackburn and coauthors reported a comparative FT-ICR MS analysis of NOM using laser desorption/ionization (LDI), matrix assisted laser desorption/ionization (MALDI), and electrospray ionization (ESI). The results should that the ESI compounds belong to higher oxygen classes (maximum number of species for O14-O16)and the ESI mass spectrum of the SRFA showed a bimodal distribution (200-400 Da and 400-800 Da, respectively). We were failed to reproduce the result using ESI FT-ICR MS. According our experimental results and many published data in references, we suspect that Blackburn and coauthors did not carried out the experiments at an optimized condition. We present this comment to avoid the misunderstanding on ESI technique, as well as the molecular composition of netural organic matter(NOM).