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An indirect method for measuring gas solubility in liquid media such as heavy oil, bitumen, petroleum residue and low volatility model hydrocarbons is reported. The method is intended for use with an existing X-ray view cell apparatus. With this apparatus it is possible to verify the number of phases present and to ensure that the phases are well mixed. For example, vortices in the impeller region are readily observed using transmitted X-ray imaging, despite the opacity of heavy hydrocarbons to visible light. Gas solubility data is obtained by tracking the location of the liquid–vapour interface. The volume of the view cell, the number of moles of gas added to the cell and the mass of the liquid phase are known. Once the volume of the liquid is obtained, the dissolved gas fraction is computed by difference. The method is applicable over the range of conditions accessible with the view cell apparatus — from ambient conditions up to 450°C and 30 MPa. For sparingly soluble gases such as hydrogen, solubilities measured using this method fall within 5% of values reported in the literature for hexadecane and tetralin at pressures greater than 2 MPa. Measured values are repeatable to within 2%. Hydrogen solubilities in a light virgin gas oil, a heavy virgin gas oil, Athabasca bitumen vacuum bottoms and Gudao atmospheric residuum are reported over a broad range of temperatures (80–380°C) and pressures (0.5–12 MPa). The solubility values obtained for the four cuts differ significantly at low temperatures but fall within a narrow range at elevated temperatures where the values do not differ markedly from values obtained for much lighter fluids such as tetralin.

The thermal decomposition of Athabasca bitumen asphaltenes was investigated in the temperature range 350 to 430 °C. The cracking kinetics of the asphaltenes and their intermediates were analyzed on a total a molar basis, to avoid the assumptions inherent in lumped kinetic models. The apparent first-order activation energy was 176 kJ/mol over the temperature range. Reaction selectivity changed from evolution of hydrogen sulfide to evolution of hydrocarbon gases and liquids over the same range of temperature. This change was consistent with a shift of the controlling reaction mechanism from the cleavage of C-S bonds to the cleavage of C-C bonds as temperature increased past 400 °C. The formation of hydrocarbon gases was the dominant reaction on a molar basis at temperatures over 400 °C, therefore, these reactions require more attention in mechanistic models for cracking of heavy petroleum fractions.

As much as 50 w/w % of bitumen derived from Athabasca oil sands consists of a residuum that cannot be easily upgraded. A better understanding of the chemistry of this material is the key to achieving optimal yields of commercially useful products. In recent years, the application of supercritical fluid extraction (SCFE) with pentane has been successful in separating the residuum into a number of narrow fractions based on their solubility parameters. An important corollary to this separation is that the molecular weight of each fraction increases with the severity of conditions needed to extract the progressively heavier components in each residua. In combination with advanced characterization techniques this approach has proved to be useful in elucidating the complexity of bitumen chemistry. For the work described here, this approach has been applied to residua from commercial operations at the Syncrude Canada Ltd. plant in Northern Alberta. Base samples included virgin bitumen pitch (P) together with residua from the catalytic hydro-cracking (HC) unit and a once-through fluid-coking (CK) test.The SCFE insoluble, heavy subfractions in the pitch contain core structures, comprising condensed polyaromatic rings, associated with heteroatoms and trace metals. In the catalytic hydro-cracking process the cleavage of C-S side chains and the breakage of inter-unit bonds are the prevailing reactions. A comparison between the lighter, SCFE-soluble fractions from catalytic hydro-cracking and thermal cracking shows the latter to have lower unit molecular weights, higher sulfide contents, and shorter alkyl substituents. The highly aromatic, SCFE-insoluble molecules from the CK process are likely formed from condensation reactions involving various fragments of toluene-soluble and -insoluble material. Condensation reactions between heavy core molecules from the SCFE insolubles in pitch lead to formation of coke. In the catalytic hydro-cracking process single unit, highly aromatic, polar cores from pitch SCFE insolubles appear to remain toluene-soluble and thus constitute most of the HC residue. These coke precursors will be converted to coke, or pseudo-solid species, if subjected to the thermal treatment applied in coking or severe hydro-cracking.

Athabasca bitumen is a heavy hydrocarbon recovered from oil sands. During upgrading, bitumen is first distilled to remove lighter components which are processed in hydrotreaters. This distillable portion, heavy gas oil, accumulates nearly 80 w/w% of the saturates present in the original material. The aromatic character and heteroatoms content of the molecules in this fraction increase with the boiling point of the components. The residue from distillation, bitumen pitch, is subjected to thermal cracking followed by hydrotreating. The extractable front fractions from pitch show a trend for increasing aromatic content with a concomitant decrease in H/C atomic ratios. This is a reflection of greater numbers of aromatic rings with a higher degree of condensation and decreasing degree of substitution. The insoluble end- cut from pitch is characterised by the presence of “core” structures comprising condensed polyaromatic rings associated with heteroatoms (N) and trace metals (Ni, V). The heaviest sub-...

Accumulation of fine particles by packed-bed catalytic reactors causes increased pressure drop, sometimes causing premature shut down. Deposition in a reactor, i.e., filtration, is enhanced when the particle suspension is unstable. A model system of 0.68 μm of kaolin in light gas oil was selected to study deposition at hydrotreating conditions. The surface of the kaolin was modified by adsorbing polymeric asphaltene molecules. Particle suspensions were circulated through a packed bed of either glass beads or catalyst in a batch reactor at 375 °C. The filtration mechanism switched from cake filtration to deep-bed filtration when kaolin was pretreated with asphaltene. Deposition of kaolin particles in the bed decreased with increasing asphaltene concentration. These results are consistent with steric stabilization of colloids by adsorbed polymers. Hydrotreating of the liquid phase enhanced desorption of the asphaltene polymer from particle surfaces and increased particle flocculation and deposition along th...

A mechanism for the hot water extraction process is proposed based on new results from extraction tests using model oil sand. It was found that bitumen can be completely liberated from the oil sand matrix and forms aerated droplets during slurrying with water without adding process aids. However, the aerated bitumen droplets were unable to float due to the attachment of sand particles on the surface of the bitumen droplets. When sodium hydroxide (NaOH) was added, the sand particles were released from the bitumen droplets, resulting in bitumen recovery. High recoveries were obtained by adding NaOH to either connate water or slurry water. Bitumen loss was attributed to incomplete bitumen/sand separation and oil-in-water (o/w) emulsification resulting from deficiency and overdose of NaOH, respectively. The use of commercial sodium naphthenate or sodium laurate as process aids had no effect. The size of the aerated bitumen droplets increased as the oil content and/or the size of the sand particles increased. The bitumen recovery and the size of the aerated bitumen droplets increased when the sand was pretreated with NaOH. Liberation of bitumen from the oil-wet model oil sand could be achieved by using excess NaOH, but the liberated bitumen was non-recoverable due to emulsification. Increasing the amount of slurry water had a detrimental effect on aeration.

Electrochemical reduction desulfurization is a promising technology for petroleum refining which is environmental friendly, low cost and able to achieve a high degree of automation. Electrochemical hydrogenation of thiophene was performed in a three-electrode system which SPE electrode was the working electrode. The electrochemical desulfurization was studied by cyclic voltammetry and bulk electrolysis with coulometry (BEC) techniques. The results of cyclic voltammetry showed that the electrochemical hydrogenation reduction reaction occurred at -0.4V. The BEC results showed that the currents generated from thiophene hydrogenation reactions increased with temperature. According to Arrhenius equation, activation energy of thiophene electrolysis was calculated and lower activation energy value indicated it was diffusion controlled reaction. From the products of electrolytic reactions, the mechanisms of electrochemical hydrogenation of thiophene were proposed, consisting of two pathways: openingring followed by hydrogenation, and hydrogenation followed by ring opening.

Bitumen—sand interaction was studied as a function of pH, particle size, temperature and solvent addition to bitumen. Sand particles can be easily detached from the bitumen surface at pH > 6. At pH

Experiments and reaction equilibrium calculations were carried out for the SO2 gas and oilsands fluid coke system. The goal was to develop a coke-based sulfur-producing flue gas desulfurization (SP-FGD) process that removes SO2 from flue gases and converts it into elemental sulfur. The conversion of SO2 to elemental sulfur proceeded efficiently at temperatures higher than 600 degrees C, and the sulfur yield reached a maximum (95%) at about 700 degrees C. An increase of temperature beyond 700 degrees C enhanced the reduction of product elemental sulfur, resulting in the formation of reduced sulfur species (COS and CS2), which lowered the sulfur yield at 900 degrees C to 90%. Although equilibrium calculations suggest that a lower temperature favors the conversion of SO2 as well as the yield of elemental sulfur, experiments showed no formation of elemental sulfur at 600 degrees C and below, likely due to hindered kinetics. Faster reduction of SO2 was observed at a higher temperature in the range of 700-1000 degrees C. A complete conversion of SO2 was achieved in about 8 s at 700 degrees C. Prolonging the product gas--coke contact, the yield of elemental sulfur decreased due to the formation of COS and CS2 while the SO2 conversion remained complete. Equilibrium calculations suggest that the ultimate yield of elemental sulfur maximizes at the C/SO2 ratio of 1, which represents the stoichiometry of SO2 + C--CO2 + S. For the C/SO2 ratio1, equilibrium calculations predict elemental sulfur and CO2 being major products, suggesting that SO2 + C--CO2 + S is the predominant reaction if SO2 is in excess. Experiments revealed that elemental sulfur and CO2 were only major products if the conversion of SO2 was incomplete, which is in agreement with the result of the equilibrium modeling.

Bitumen, separated from oil sands by the hot water extraction process, contains ultra-fine (< 200 nm), inorganic solids (BS). Surfaces of BS particles are coated with toluene insoluble organic matter (TIOM). This organic material is polar and aromatic with contributions from both humic and asphaltene-like components. Although the surfaces of BS particles are dominated by TIOM, the coverage is patchy rather than continuous. As a result, these solids are capable of stabilizing fine water emulsions in the bitumen phase. The nature of the organic matter on the surfaces of the particles is such that it has a high propensity to form coke. Therefore, these particles can also play a role in fouling on equipment and catalysts. Le bitume separe des sables petroliferes par le procede d'extraction a air chaud, contient des solides inorganiques (BS) ultrafins (

Magnetic resonance microimaging (MRM) is used to characterize petroleum coke formed in the upgrading of Athabasca bitumen. Formation of large coke materials poses processing difficulties, and so the study of the structure and formation mechanism is important. The larger, “peas and beans” coke (approximately spherical, 4.1 mm diameter) possesses significant porosity, and is ideal for MRM. Coke is soaked in cyclohexane, and then 7V-, diffusion-, and density-weighted 1H images are collected with an unprocessed image resolution of 24 μm pixel-1. Scanning electron microscopy indicates that the coke is surrounded by a dense, 100 μm-thick outer shell. MRM shows that this shell is permeable to cyclohexane, and that a significant pore volume is present. The cyclohexane diffusion coefficient (Dmax = 1.4 x 10-9 m2 s-1) is roughly one-half of the Dmax in pure solution indicating that the cyclohexane inside the coke is liquid-like. The MRM images indicate that the coke is formed by an agglomeration mechanism from smaller fluid coke particles (nominal diameter 150 μm), which in turn posess microporosity. MRM shows great promise as a non-destructive, structural and dynamic characterization method for petroleum coke. Strategies to enhance resolution will be presented and discussed.

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