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One of the first instrumental techniques applied to asphaltenes and coal to obtain structural information was X-ray diffraction. The broad asymmetric peaks were interpreted on the basis of the graphite crystalline structure, and the resulting lattice spacings and crystallite dimensions have been published regularly for over 60 years. This review examines the basis for this analytical method and tests the underlying assumptions and hypotheses by comparison to X-ray patterns from model compounds and amorphous polymers. These comparisons show that the X-ray patterns of complex asphaltenes are dominated by inter- and intramolecular scattering and that the published methods to quantitatively analyze these data are invalid. High-temperature processing of asphaltenes and coals can give higher order X-ray peaks consistent with graphite, but prior to this, the structural information is highly ambiguous. The use of full width at half maximum for the broad signal from 10° to 30° is recommended for tracking thermal conversion reactions of such highly complex materials as asphaltenes and coal, to avoid unjustified assumptions of the crystalline structure.

Carbon fibers are materials of paramount importance for composites applied in fields such as aerospace engineering, medicine, and renewable energy. Currently, most of the production of carbon fibers uses polyacrylonitrile, which incurs significant greenhouse gas emissions and high production costs. Therefore, carbon fiber manufacturing from asphaltene-enriched feedstocks is attractive as it could add value to extra-heavy fossil fuels and cut down precursor costs by ∼90%. Recent studies indicate that some asphaltene-rich samples feature rheological properties that make them optimal for melt-spinning and carbon fiber production; in other cases, the spun asphaltene feedstocks are unsuitable for such applications. In this work, bitumen asphaltenes were subjected to upgrading processes under three distinctive conditions to tweak their rheological properties in order to produce carbon fibers. The treated samples were comprehensively studied by separations based on solubility and extrography, and subsequently characterized by ultrahigh-resolution mass spectrometry, gas-phase fragmentation, and thermogravimetric analysis. The results indicate that upon thermal processing, asphaltene-rich feedstocks produced a mixture with diverse solubility, i.e., maltenes, asphaltenes, and toluene-insoluble material. The molecular composition of remnant asphaltenes suggests that thermal treatment dramatically decreased molecular polydispersity in terms of the content of heteroatoms, alkyl chains, and structural motifs, i.e., single-core vs multicore, also known as island vs archipelago. The processed asphaltenes revealed high abundances of alkyl-depleted island species. Such thermally treated samples produced no stable carbon fibers. Conversely, a feedstock treated with molten sodium in a proprietary process designed to remove sulfur, revealed increased content of alkyl-side chains and archipelago structural motifs. This sample produced stable carbon fibers. Furthermore, thermal analysis coupled with mass spectrometry (TGA-HRMS) was conducted to understand thermal desorption and pyrolysis profiles for the samples, as well as the presence of occluded compounds and carbon residue formation. The TGA-HRMS results are consistent with extrography and IRMPD FT-ICR MS studies and confirmed the ultrahigh abundance of multicore compounds in the desulfurized sample. Although the sample size is limited, and thus, correlations between molecular composition and rheology properties are not achieved, this is the first study that aims to understand the role of feed composition in the ability to generate carbon fibers from asphaltene-enriched feedstocks. Collectively, the results indicate that samples comprised of abundant highly aromatic asphaltenes, dominant in alkyl-depleted single-core structures, are unlikely optimal for carbon fiber applications. Conversely, a sample with a marked increase in H/C, a significant decrease in S content, and abundant multicore species could generate stable carbon fibers. More studies are underway to find correlations between molecular features and carbon fiber production.

A MERE 17 YEARS AGO, FEW PEOPLE OUTSIDE THE biological sciences had ever heard of 'biodiversity'. The signing of the UN Convention on Biological Diversity at the Rio de Janeiro [...]

The role of archipelago asphaltene structure in the reactions of petroleum asphaltenes was investigated by comparing yields of products from the conversion of archipelago-rich heavy oils and bitumen to the yields from a sample with predominant island-type structures. The archipelago content of the asphaltenes was positively correlated with the yield of liquid products boiling below 524 °C. The yield of coke solids increased with the fraction of island structures in the asphaltenes. Furthermore, catalytic hydroconversion of Athabasca bitumen gave a residual asphaltene fraction that was highly enriched in weakly aggregating components, on the basis of extrographic separation, and very low content of archipelago structures. High-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis showed that the heteroatom polydispersity of the asphaltenes after conversion was dramatically reduced, and the range of double-bond equivalents and carbon number was close to the limiting boundary of planar polynuclear aromatic hydrocarbons (PAHs). The radical cations from the converted asphaltenes showed significant concentration of high-ring-number/known PAH structures. The results highlight the existence of a positive correlation between the amount of archipelago structural motifs in asphaltenes and the yield of products with a range of boiling points below 524 °C. Moreover, the data demonstrates that advanced hydroconversion methods can be used to obtain asphaltene fractions with decreased polydispersity in terms of heteroatom content, alkyl-substitution, and molecular structure, which could be eventually exploited for material science applications.

A simple, new technique relates product gravity to its elemental composition in a variety of processes, using data for Alberta heavy oils and bitumens. This approach allows integration of material [...]

The molecules in petroleum asphaltenes follow a molecular structure continuum similar to the rest of the oil but differ in the formation of nanoaggregates in solution. The nature of the aggregation, its size distribution, and dimensions of the nanoaggregates is still debated, and the impact of this aggregation on phase behavior, physical properties, and the processing of heavy petroleum fractions remains unclear. This review first discusses the role of nanoaggregates in the phase separation of asphaltenes, then examines the literature on subfractionation of the asphaltene fraction to define how different molecules partition. Efforts to measure the distribution of nanoaggregate size are summarized, and the roles of size distribution in the behavior of asphaltenes during sedimentation, emulsion formation, and refinery processing are examined. Finally, the molecular basis for formation of a distribution of aggregate sizes/properties is considered. The molecular weight ranges as high as 40,000 Da but the size is below 100 nm. Although few direct experimental data are available for the distribution of aggregate properties, three behaviors indicate the importance of portions of the nanoaggregate population. The highest molecular weight aggregates are the least soluble, driving phase behavior when the asphaltenes are partially precipitated. A portion of these large aggregates are also most responsible for the stabilization of asphaltene films at oil–water interfaces, which stabilize oil-in-water emulsions. The vanadium and nickel species that are most resistant to removal during refining of vacuum residues are also found in the most aggregated fraction, although the stability of the aggregates at process temperatures is not yet proven. Average properties for the asphaltene fraction, including both free molecules and nanoaggregates, are sufficient for prediction of onset of asphaltene phase separation, gravity segregation, and properties such as density and viscosity.

Recent advances in instrumentation for high-field Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) have enabled access to ∼70 000 unique molecular formulas in broadband mass spectral characterization of unfractionated/whole asphaltenes. The results accumulated over a decade highlight the need for an asphaltene molecular model that acknowledges the coexistence of (1) monofunctional and polyfunctional species; (2) island and archipelago structural motifs; and (3) heteroatom-depleted/highly aromatic compounds, as well as atypical species with low aromaticity but increased heteroatom content. Collectively, results from FT-ICR MS, preparatory-scale separations (extrography/interfacial material), gel permeation chromatography, precipitation behavior in heptane:toluene, thermal decomposition, and aggregate microstructure by atomic force microscopy (among other techniques), suggest that the strong aggregation of asphaltenes results from the synergy between several intermolecular forces: π-stacking, hydrogen bonding, London forces, and acid/base interactions. This review presents general features of asphaltene molecular composition reported over the past five decades. We focus on mass spectrometry characterization and expose the reasons why early results supported the dominance of single-core motifs. Then, the discussion shifts to recent advances in instrumentation for high-field FT-ICR MS, which have enabled the detection of thousands of species in asphaltene samples, whose molecular composition and fragmentation behavior in ultrahigh vacuum agree with the coexistence of single-core and multicore structural motifs. Furthermore, evidence that highlights the limitations of commercially available/custom-built ion sources and selective ionization effects is presented. Consequently, the limitations require separations (e.g., chromatography, extrography) to gain more-comprehensive molecular-level insights into the composition of these complex organic mixtures. The final sections present evidence for the role of aggregation in selective ionization and suggest that advanced characterization by both thermal desorption/decomposition and liquid chromatography with online FT-ICR MS detection can be employed to mitigate the effects of aggregation and provide unique insights in molecular composition/structure.

In petroleum science, asphaltenes are well-known as the most refractory fraction of crude oil and remain infamous for problems in production, transportation, and refining processes. Hence, they have been continuously analyzed and modeled over more than half a century. Defined only by solubility and characterized by an extremely complex and diverse molecular composition, asphaltenes lack discriminative molecular descriptions and definitive chemical characteristics. Most of the historic research has focused on representative structures in an attempt to yield physical and chemical models of asphaltenes, and thus, conflicting theories of bonding structures and aggregation interactions remain. This review focuses on the aggregation behavior of asphaltenes and attempts to rationalize a structure–property relationship to asphaltene aggregate thermal stability. Herein, the chemical and physical bonding properties of asphaltenes and the contradictory interpretations of their nature and composition are examined, particularly as they impact formation and stability of asphaltene aggregates. We propose a new hypothesis involving free radical interactions, i.e., pancake bonding, as an additional significant contributor to the bonding structure and formation of aggregates in asphaltenes that is consistent with the latest findings based on Fourier transform ion cyclotron resonance mass spectrometry and non-contact atomic force microscopy techniques. Various structural features of polycyclic aromatic hydrocarbons contributing to this interaction involving a stable free radical are highlighted, and suggestions for future research are presented.

Geology is part of the planet's “natural capital”, the stock of global natural assets. These assets provide many benefits for society, often referred to as “ecosystem services”. However, traditionally these have mainly focused on biotic services and have undervalued the abiotic ones. The latter are known here as “geosystem services” and they all derive from the geodiversity of the planet. This paper outlines how society benefits from three aspect of geodiversity – topographies, geological materials and physical processes. It also particularly argues that society benefits from geoconservation of the planet's geoheritage, citing the criteria for designating UNESCO World Heritage Sites, UNESCO Global Geoparks and national protected areas, the public interest in visiting spectacular geological places and the economic benefits this geotourism brings.

A multicomponent cyclocondensation reaction between 2-aminoanthracene, aromatic aldehydes, and 5-α-cholestan-3-one has been used to synthesize model asphaltene compounds. The active catalyst for this reaction has been identified as hydriodic acid, which is formed in situfrom the reaction of iodine with water, while iodine is not a catalyst under anhydrous conditions. The products, which contain a tetrahydro[4]helicene moiety, are optically active, and the stereochemical characteristics have been examined by VT-NMR and VT-CD spectroscopies, as well as X-ray crystallography.

A series of model compounds for the large components in petroleum, with molecular weights from 534 to 763 g/mol, was thermally cracked in the liquid phase at 365–420 °C to simulate catagenesis over a very short time scale and reveals the selectivity and nature of the addition products. The pyrolysis of three types of compounds was investigated: alkyl pyrene, alkyl-bridged pyrene with phenyl or pyridine as a central ring group, and a substituted cholestane–benzoquinoline compound. Analysis of the products of reaction of each compound by mass spectrometry, high-pressure liquid chromatography, and gas chromatography demonstrated that a significant fraction of the products, ranging from 26 to 62 wt %, was addition products with molecular weights higher than that of the starting compounds. Nuclear magnetic resonance (NMR) spectroscopic analysis showed that the pyrene compounds undergo addition through the attached alkyl groups, giving rise to bridged archipelago products. These results imply that the same geochemical processes that generate the light components of petroleum, such as n-alkanes, simultaneously produce some of the most complex heavy components in the asphaltenes. Similarly, thermal cracking reactions during refinery processes, such as visbreaking and coking, will drive addition reactions involving the alkyl groups on large aromatic compounds.

Association of asphaltene molecules to form aggregates is a defining property of this fraction of petroleum, which has impacts on all aspects of production and refining. Association has been detected over a very wide range of concentrations, but the quantitative modeling of this aggregation of molecules has mainly been restricted to fitting relatively high-asphaltene concentration data from vapor-pressure osmometry. This paper examines the capability of the termination/propagation model for association to represent low-concentration behavior. The addition of an additional strongly associating fraction to the model is necessary to obtain dimer formation over the observed range of concentrations. Unfortunately, the data required to fit such a model with confidence are lacking. Data from ultracentrifugation of asphaltene aggregates can also be fitted to a termination/propagation model. Transient measurements of ultracentrifuge concentration profiles have the potential to enable more comprehensive models of association behavior, especially when applied to subfractions with known aggregation behavior.

In the past, transportation of heavy and bitumen to downstream refineries has been accomplished by either adding a diluent or converting the vacuum residue to produce a synthetic crude oil. In Canada, partial upgrading of bitumen to enhance its transportation to downstream refineries is becoming more attractive as production increases from both in situ and mining operations. Similar opportunities exist for inland production elsewhere in the world. This review discusses the relationship between the key properties for transport, which are viscosity and density, and the composition of a crude oil. The potential process pathways to achieve low-cost reduction in viscosity and density are discussed, particularly thermal cracking and partial deasphalting. Thermal cracking is effective for reducing the viscosity, but it is limited by the stability of the processed asphaltenes in the product blend. While thermal cracking has a long history in refining, the lower levels of asphaltene removal to achieve partial upgrading require removal of solid asphaltenes, rather than the viscous liquids produced in current refinery deasphalting plants. The benefits of combinations of reaction and separation approaches are discussed, particularly combinations of thermal cracking, addition of reduced amounts of diluent, and partial deasphalting.

CSChE builds on tradition by supporting chemical engineers in their responsibility to the public. The new Process Safety Management Subject Division was formed to meet members' needs in this area. [...]

This year marks a half-century of continuing success for one of our proudest traditions. The 50th Canadian Chemical Engineering Conference will be held in Montreal, QC from October 15-18, 2000, [...]

THE CONSULTATION DRAFT of the intended replacement for PPG9: Nature Conservation (1) proposes to retitle PPS9 (Planning Policy Statement 9) as Biodiversity and Geological Conservation. This should be hugely welcomed [...]

The adsorption of asphaltenes on dehydroxylated mineral surfaces is an important occurrence during thermal processing of unconventional oil resources such as oil sands bitumen. We investigated the irreversible adsorption of Athabasca asphaltenes from toluene solutions onto untreated and dehydroxylated kaolinite. The adsorption density, percent surface coverage, and mean domain thickness were evaluated using X-ray photoelectron spectroscopy (XPS) and elemental analysis. The dehydroxylated kaolinite gave higher adsorption density and percent surface coverage than the untreated kaolinite, as particularly revealed in multiple contacts of kaolinite with the asphaltene-in-toluene solutions (2 g/L), indicating that dehydroxylation of kaolinite enhanced its adsorption capacity for asphaltenes. The XPS-determined percent surface coverage was 18% and 41% on the untreated and dehydroxylated kaolinite, respectively, corresponding to the maximum adsorption density of 3 and 7 mg/m2. The incomplete coverage even at the highest adsorption density proved that the asphaltene adsorption layer was discontinuous on both materials. After saturation of kaolinite binding sites with the first asphaltene layer, at most two additional layers were adsorbed due to asphaltene-on-asphaltene deposition, forming 15 nm thick domains.

IN MY OPINION, conservation in the UK still places too much emphasis on biodiversity and doesn't take into account the importance of our geological resources. This national failing is encapsulated [...]

Recent controversies over pulp mill and sour gas developments have focused public attention on two aspects of industrial development: the impact of emissions on the environment, and the selection of [...]

It was surprising and disappointing that Charlie Furniss's article on protected areas (Dossier, June 2005) was written almost entirely from the perspective of biological conservation. The fact is that nature [...]

Practical wisdom is essential to occupational and professional practice. However, the emphasis on technical rationality in these domains neglects the necessity of practical wisdom in doing specialized, skilled work. Microdynamic methods for analyzing social action enabled the discovery and examination of practical wisdom in two interactional episodes from community health work. Practical wisdom was found in specific acts: in adaptation to and interpretation of logical forces and interactional rules of these acts; and in deliberation among choices to reach intended outcomes. Cultivating skills in microdynamic methods for finding and analyzing practical wisdom is an essential tool for practitioners and organizations.