Low temperature oxidation of athabasca bitumen

The kinetics of low temperature oxidation in the Athabasca oil sands were investigated over the temperature range 373 K to 459 K. Oxidation experiments, in which the sand-free bitumen was vigorously stirred to obtain a homogeneous oxygen concentration throughout the bitumen, were carried out. It was concluded that the oxidation reaction is governed by three different kinetic expressions depending on temperature and past oxidation history. These are: (i) a high rate first order regime which is obeyed at low extents of oxidation and at temperatures below approximately 423 K; (ii) a second order regime, obeyed at low extents of oxidation and at temperatures greater than 423 K; and (iii) a low rate first order regime, obeyed for extents of oxidation greater than 1.7 moles O₂/kg bitumen over the entire temperature range investigated. The partial molar enthalpy of low temperature oxidation was also evaluated, and was found to be constant over the range of oxidation extents studied.     

Influence of radiation intensity upon photo-oxidation of unstabilised PVC

Films of unstabilised PVC have been exposed to xenon-arc irradiation at various levels of intensity within a limited temperature range, and the rates of photo-oxidation have been determined by infra-red spectroscopy. It has been found that the rate of reaction is directly proportional to radiation intensity measured in absolute units, and that transposition of time and radiation intensity is valid. The consequences of this finding have been discussed in terms of reaction mechanism and acceleration of the time scale for oxidation of PVC under artificial exposures to the xenon-arc, compared with outdoors exposure to solar radiation at Melbourne and London.     

Monitoring ultraviolet radiation with polyvinylchloride

The photo-oxidation of unstabilised polyvinylchloride has been shown to be sensitive only to the ultraviolet region of xenon-arc radiation, and the rate of oxidation as determined by an infrared spectrophotometer is approximately linear with radiation intensity. Since both spectrum and intensity of the xenon arc closely simulate terrestrial solar radiation, PVC has been examined as a simple monitor of ultraviolet radiation for use in characterising outdoor sites at which the durability of building materials is assessed. PVC films have been exposed at London, Melbourne, and Pretoria and the extent of oxidation compared with solar radiation recorded at the sites; in the case of Melbourne the extent was also compared with ultraviolet radiation.     

Effect of low-temperature oxidation on the composition of Athabasca bitumen

The effect of low temperature oxidation on the composition of Athabasca bitumen was examined. Oxidation temperatures in the range 125–135 °C and extents of oxidation up to 100mg $\text{O}{}_2\text{g}$ bitumen were investigated. The aromatics concentration was observed to decline steadily and the concentration of asphaltenes to increase, during oxidation. The saturates were unaffected by low-temperature oxidation. The resins concentration displayed a strange behaviour, first dropping and then increasing to a maximum and again dropping as oxidation proceeded.     

Ageing by UV radiation of an elastomer modified bitumen

Laboratory methods to simulate the short- and long-term ageing occuring during the service life of pure and polymer modified bitumens in a pavement are standardized but none of them takes into account the influence of UV radiations. If the impact of thermal ageing on the degradation of SBS elastomers in bitumens has been extensively studied, there is not study dealing with the photo-oxidation of these copolymers in a bituminous matrix. So, the aim of our study was to investigate, by FTIR spectrometry and SEC chromatography, whether the architecture of elastomers (linear or radial) might have any influence on their ageing by UV radiation in a bituminous matrix. The results show that the elastomers oxidation kinetic, unlike the disappearance kinetic of trans-butadiene double bond, does not depend on their architecture. But, when putted into the same base bitumen, the two copolymers show exactly the same oxidation kinetic and the same decreasing kinetic of trans-butadiene double bond. So, this study has revealed that inside the bituminous matrix, on the one hand, the elastomers architecture does not influence on its degradation when submitted to UV radiation and, on the other hand, there is a “protection” of the elastomers by the studied bitumen towards UV radiation.     

Viscosity of compressed cold lake bitumen

Viscosity data over a temperature range of 37-115°C and a pressure range of 0-10 MPa gauge are presented for a Cold Lake bitumen sample. These data show that the compression of Cold Lake bitumen results in a significant increase in its viscosity. Results are compared with those from a similar study on an Athabasca bitumen sample. Also presented are two correlations for the effects of pressure and temperature on the viscosity of Cold Lake bitumen.     

Ultraviolet-Enhanced Ozonation of Organic Compounds: 1,2-Dichloroethane and Trichloroethylene as Model Substrates

1,2–Dichloroethane (DCE) and trichloroethylene (TCE) were used as model compounds to study the oxidation of organic chemicals by ozone/ultraviolet radiation, ozone, and hydrogen peroxide/ultraviolet radiation. It was found that ozone/ultraviolet radiation oxidized both 1,2–dichloroethane and trichloroethylene in batch systems, at pH = 2 (phosphate buffer). At ozone concentrations in the 1 to 5 mg/L range, the reaction was first order in both ozone and substrate. At pH = 2 and initial ozone concentration 2.2–2.6 mg/L, rate constants (k)Q = 25 and 130 M^-1sec^-1 were observed for the ozone/ultraviolet radiation oxidation of DCE and TCE, respectively. The rat e constants for ozone oxidation of DCE and TCE without ultraviolet radiation were 4.3 and 47 M^-1sec^-1, respectively.

The higher rate of TCE oxidation implies that direct reaction occurs with the double bond. Finite reaction rate of DCE with ozone, and substantial increases in rate at higher pH imply the participatation of hydroxyl radicals in the oxidation of both compounds. For example, at pH = 7, initial ozone concentration of 2.3 mg/L, the k_o for TCE oxidation by ozone/ultraviolet radiation is approximately 500 M^?1 sec^?1 almost too fast to measure in a batch system.The rate also is increased by increased ultraviolet radiation intensity, and by the presence of hydrogen peroxide, which acts as a catalyst.     

Kinetic Study of Hydroperoxide Degradation in Edible Oils Using Electron Spin Resonance Spectroscopy

Lipid oxidation is a complex phenomenon involving free radicals which are highly reactive molecular species. The life-time of these radical species is extremely short and their detection is therefore difficult. Several electron spin resonance (ESR) spectroscopy methodologies make it possible to identify, quantify and measure the reactivity of radical species formed during oxidation–reduction reactions. In this study we took advantage of the specificity of ESR spectroscopy to detect radical compounds in order to determine the rate constants of hydroperoxide degradation, a key reaction involved in lipid oxidation. The interaction of 5-doxyl stearic acid and lipid-derived radicals was studied by following the intensity of ESR spectra. A kinetic model was developed to simulate data analysis obtained by ESR and values of rate constants for hydroperoxide degradation were determined at 100 and 110 °C. This quantitative approach of ESR spectroscopy has produced useful information about new rate estimates for hydroperoxide degradation in edible oils.     

Photocatalytic oxidation of multicomponent solutions of herbicides: Reaction kinetics analysis with explicit photon absorption effects

The intrinsic reaction kinetics of the photocatalytic oxidation (PCO) of the herbicides isoproturon, simazine and propazine over irradiated TiO₂ (Degussa P25) suspensions was studied in single-component and in multicomponent systems. Experiments were carried out at different photon fluxes and different herbicide concentrations in the range below 1 mg L⁻¹. The results were analyzed in terms of a Langmuir–Hinshelwood (L–H) kinetic model previously established for multicomponent solutions of herbicides, but including the explicit effect of photon absorption. This was accomplished by modeling the radiation field in the reactor with the Six-Flux Absorption-Scattering Model (SFM) (i.e., scattered photons follow the route of the six directions of the Cartesian coordinates) using optical parameters averaged across the spectrum of the incident radiation. The intrinsic reaction kinetic constants of isoproturon, simazine and propazine independent of the radiation field in the reactor were determined. The oxidation rate of the herbicides was found to follow half-order dependence with respect to the local volumetric rate of photon absorption (LVRPA), in the range of photon fluxes investigated. The established model was found to be appropriate to predict the time-dependent degradation profiles of the herbicides in single- and multicomponent systems not only at all radiation intensities investigated in this study but also when one or two herbicides were present in excess of the others in the mixture. Using this simple approach, intrinsic kinetic data can be obtained.     

Processing,rheology, and storage stability of recycled EVA/LDPE modified bitumen

The optimum processing conditions for the manufacture of polymer‐modified bitumens (PMBs), as well as the rheological properties of the final polymer‐bitumen blends, strongly depend on the characteristics of the mixing device used. The present work is focused on the comparison among the kinetics of the mixing process and the rheological properties and microstructural characteristics of PMBs manufactured in two different mixers. Thus, blends of 60/70 penetration grade bitumen and recycled EVA/LDPE were processed in both high and low‐shear devices. Knowledge on the evolution of shear viscosity and microstructure with time, as well as on the mechanical properties of the final polymer‐bitumen blends, was gained from rheological and modulated DSC tests, and optical microscopy. The results obtained demonstrate that processing in the high‐shear device yields a significant decrease in the time needed for the polymer‐bitumen blend to reach the final stage of the manufacturing process, as well as an important reduction in bitumen oxidation and enhanced properties in a wide range of in‐service temperatures. However, polymer‐bitumen blends manufactured in the high‐shear device are not stable during its storage at high temperature. POLYM. ENG. SCI., 47:181–191, 2007. © 2007 Society of Plastics Engineers     

Studies on bitumen production from North Rumaila crude oil

In the present investigation, the effect of three process variables viz., air rate, temperature and time of oxidation has been studied to determine the possibility of making paving bitumens from North Rumaila Crude Oil. In order to have flexibility in the choice of proper feedstock for bitumen production, the effect of these process parameters was studied on three different vacuum residues. Air rate and temperature of oxidation were optimised to produce a bitumen product having less temperature susceptibility. The composition studies of typical feeds and oxidised products indicate that mainly “saturates” components get converted to “asphaltics” on air blowing.     

Effect of ore quality on non-aqueous oil sand extraction performance

Current commercial aqueous based extraction processes are energy and greenhouse gas (GHG) intensive and require large tailings ponds. Non-aqueous extraction (NAE) of bitumen from mineable oil sands is an alternative that eliminates tailings ponds with potentially lower energy requirements and GHG emissions. The economics of the NAE process depend partly on the impact of ore quality on bitumen recovery and product quality (low water and solids content). It has been claimed that NAE performance is insensitive to the quality (bitumen content) of the oil sand ores. However, the available data are ambiguous because different extraction methods and solvents were used in different studies and, in many cases, a limited range of ore qualities was examined. In this study, bitumen was extracted from eight ores of different quality with cyclohexane using a multistage method equivalent to a countercurrent process with a solvent/ore ratio of 0.67 w/w. The bitumen recovery and the water and solids content of the product bitumen were determined for each ore. It was found that bitumen recovery correlated negatively to clay content of the ore. The loss of recovery was attributed to bitumen adsorption on clays. The product quality was insensitive to the ore quality and instead depended on the density of the fluid medium, as expected with a centrifuge-based separation method. The recovery and product quality from the NAE method were similar to those from aqueous extractions.     

Effect of oxidation on the viscosity of athabasca bitumen

The effect of low temperature oxidation on the viscosity of Athabasca bitumen was investigated over the temperature range 320 to 370K, and to extents of oxidation as high as 41.7 × 10⁻³ kg-O₂/kg-bitumen. Even at this relatively low extent of oxidation, the viscosity was observed to be more than two orders of magnitude higher than that of unoxidized bitumen. It was found that the Andrade viscosity model could adequately characterize the temperature dependence of the viscosity at all extents of oxidation. However, the pre-exponential constant in the model was observed to be a strong function of extent of oxidation.     

Viscous characteristics of a Utah tar sand bitumen

The viscous behaviour of an extracted tar sand bitumen has been experimentally examined and the results summarized in this Paper. The material studied was from the Asphalt Ridge, Utah area. The viscosity of the bitumen has been determined as a function of temperature (293–422 K), toluene (solvent) content (0–10%), composition (0–14.6% asphaltenes), oxidation and shear history. In all cases studied, the Arrhenius plots were significantly non-linear at temperatures s> 373 K, with viscous behaviour becoming less sensitive to toluene content with increasing temperature. Low temperature behaviour was strongly dependent on toluene content. The presence of asphaltenes in the bitumen was shown to be a strong viscosity enhancer. Oxidation and shear history were also shown to measurably increase the bitumen viscosity.     

The effects of temperature and shear rate on the apparent viscosity of Nigerian oil sand bitumen

The apparent viscosities of Nigerian oil sand bitumen were measured over a temperature range of 50–110°C and a shear rate range of 60–320 s⁻¹. Apart from temperature which is the most important variable influencing the viscosity of a liquid, the viscosities of the bitumen are affected by shearing effects. The apparent viscosity of the bitumen depended on the rate of shear at which it is measured, that is, it has an unlimited number of apparent viscosity values as the shear rate was varied. The shearing effects decreased as the temperature increased; that is, the bitumen became more Newtonian in the higher temperature region.     

Oxidation reaction kinetics of Athabasca bitumen

The oxidation reaction kinetics of bitumen from Athabasca oil sands have been investigated in a flow-through fixed bed reactor using gas mixtures of various compositions. The system was modelled as an isothermal integral plug-flow reactor. The oxidation of bitumen was found to be first order with respect to oxygen concentration. Two models were examined to describe the kinetics of bitumen oxidation. In the first, the Athabasca bitumen is considered to be a single reactant and the oxidation reaction a single irreversible reaction. The activation energy for the overall reaction was found to be 80 kJ mol^?1. This model is limited to calculating the overall conversion of oxygen. Because the fraction of oxygen reacting to form carbon monoxide and carbon dioxide increases with temperature, a more sophisticated model was proposed to take this into account. The second model assumes that the bitumen is a single reactant and that the oxidation of bitumen may be described by two simultaneous, parallel reactions, one producing oxygenated hydrocarbons and water, the other producing CO and CO₂. The activation energy for the first reaction was found to be 67 kJ mol^?1, and for the second, 145 kJ mol^?1. This more sophisticated model explains the result that at higher temperatures more oxygen is consumed in the oxidation of carbon, because this reaction has a higher activation energy than the reaction leading to the production of oxygenated hydrocarbons and water. This model can also predict the composition of the product gases at various reaction conditions.     

Coking of athabasca bitumen: effect of oxidation and sand

The effect of low temperature oxidation on the ultimate coke residue from Athabasca bitumen was examined quantitatively for extents of oxidation up to 100 mg O₂/g bitumen. The residue yield was found to increase linearly with extent of oxidation. When sand was introduced during the oxidation or pyrolysis processes, a smaller increase in coke yield was observed.     

Method for the determination of elemental sulphur in bitumen

The absorption in the range λ = 262 nm (in cyclohexane) of elemental sulphur (S_el), added to bitumen extracted from the Athabasca tar sands, at concentrations ranging from 0.2 to 4.0%, was used to determine its concentration with a reasonable accuracy. The selective concentration of (S_el) in a small fraction of the total bitumen was accomplished by chromatography on charcoal, eluting with a light naphtha. The concentration of (S_el) in the naphtha-soluble fraction (NSF) of bitumen was determined by the reduction in the absorption at λ = 262 nm obtained before and after extracting this fraction with a 30% aqueous sodium sulphide solution and by the use of a preconstructed calibration curve.     

Kinetics of the thermo-oxidative and thermal cracking reactions of Athabasca bitumen

The thermo-oxidative and thermal cracking reactions of Athabasca bitumen were examined qualitatively and quantitatively using differential thermal analysis (DTA). Reaction kinetics of low temperature oxidation (LTO) and high temperature cracking (HTC) were determined. The rate of the LTO reaction was found to be first order with respect to oxygen concentration. The activation energy and the Arrhenius pre-exponential factor were 64 MJ kg^?1 mol^?1 and 10^5.4 s^?1, respectively. The effects of atmosphere, pressure, heating rate and support material on the thermal reactions of bitumen were studied. In general, it was found that partial pressures of oxygen > 10% O₂ favoured exothermic oxidation reactions. High pressure increased the rates of LTO and HTC as well as the exothermicity of these reactions. A major contribution of this study to thermal in-situ processes is that heating rate can be used effectively to control the extent of low temperature oxidation and hence fuel availability during in-situ combustion. Low linear heating rates (2.8 °C min^?1) favoured low temperature oxidative addition and fission reactions. The reaction products readily formed coke and combusted upon heating. High linear heating rates (24.5 °C min ^?1) led to rapid oxidation reactions in the high temperature zone; the high temperature and the energy released during oxidation appeared to promote combustion. Finally, when sand was used as the support material there appeared to be a catalytic effect in both LTO and HTC reactions.     

Effect of weathering on oil sands processability

Effect of weathering on oil sand processability was studied using a good processing ore, a laboratory weathered ore and a naturally weathered ore. The laboratory weathered ore was prepared by weathering the good processing ore in an oven under controlled conditions to study the nature of ore weathering. It was found that the bitumen recovery, bitumen flotation rate, and bitumen froth quality were greatly reduced due to ore weathering. It was also observed that the fresh bitumen coating on a silicon surface could recede and liberate from the silicon surface easily even in a warm water of 35°C. However, after weathering of the bitumen coating, its liberation became more difficult and effective liberation of bitumen from the silicon surface could only occur at higher temperature of 65°C. The current study further confirms that weathering enhanced adhesion of bitumen with solids, causing difficulties for bitumen liberation from sand grains and hence poor processability of weathered ores.