Colin R. Phillips

Kinetic models for the thermal cracking of Athabasca bitumen: The effect of the sand matrix

Abstract Athabasca bitumen and bitumen-derived products were thermally cracked with and without sand at 360, 400 and 420 °C. The products were separated into six pseudo-components: coke, asphaltenes, heavy oils, middle oils, light oils and gases. The data from cracking bitumen-sand mixtures were compared with data obtained from this work and from the literature on bitumen cracking in the absence of sand. The yields of coke and gases from cracking bitumen-sand mixtures were higher than those from cracking bitumen alone. The presence of sand also affected the yields of the other pseudo-components. Two kinetic models were developed to describe the results. The activation energies for the reactions involved in cracking bitumen-sand mixtures were lower than those involved in cracking bitumen alone. The nature of the effect of sand on the cracking of bitumen is discussed.

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 105.4 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.

Kinetics of non-catalytic hydrocracking of Athabasca bitumen

Abstract The kinetics of non-catalytic hydrocracking of Athabasca bitumen were studied in a batch reactor at 648–693 K and at an initial hydrogen pressure of 7.2 MPa. The reaction products were separated into coke, asphaltenes, resins, aromatics, saturates and gases. Reaction time versus product yield curves were obtained for the above six product groups. Two simple reaction models were proposed. In the first, bitumen is considered to be a single reactant and the hydrocracking reaction a single irreversible reaction. The activation energy for bitumen consumption was found to be 150 kJ mol −1 . In the second model, coke, asphaltenes, maltenes and gases are treated as components. Activation energies for the reactions were found to be in the range 142–284 kJ mol −1 . Hydrocracking reactions were found to be first order. Activation energies for the hydrocracking reactions are compared with those for thermal cracking reactions.

Kinetic models for the non-catalytic hydrocracking of Athabasca bitumen

Abstract Kinetic models for the hydrocracking of Athabasca bitumen were developed based on pseudo-components having similar properties. The pseudo-components were separated bitumen fractions (asphaltenes, resins, aromatics, saturates) and lumped fractions (heavy ends = coke + asphaltenes + resins; heavy oils = asphaltenes + resins; light oils = aromatics + saturates; and saturated fractions = saturates + gases). Hydrocracking reactions were considered to be first order with respect to the pseudo-components and zero order with respect to hydrogen. Arrhenius activation energies and frequency factors were determined for each kinetic model examined. Activation energies for the reactions, heavy ends → light oils, heavy oils → light oils, heavy oils → aromatics, resins → light oils and resins → aromatics, were found not to change under the experimental conditions studied when coke, asphaltene and resin fractions or asphaltene and resin fractions were lumped together in the hydrocracking reactions. This result suggests that these two fractions have similar reactivities in hydrocracking. The aromatic and saturate fractions behaved similarly.

Methods of Cell Immobilization

Methods of cell immobilization roughly parallel those of enzyme immobilization and can best be classified by the nature of the mode of attachment, that is, as mechanical, chemical or ionic. In mechanical immobilization, the cells are localized by means of physical barriers. In chemical immobilization, covalent bonds are formed among cells or to a solid phase. In ionic immobilization, electrostatic, van der Waal’s or London forces of attraction are present. Cells can also attach themselves to solid supports in the course of natural growth, using a combination of these means. This classification is obviously not clear-cut but does serve the purpose of organizing the diverse methods of immobilization available. In Table 2.1, examples of cell immobilization are classified by mode of attachment.

Oxidation reaction kinetics of Athabasca bitumen

Abstract 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.

Diffusive collection of aerosol particles on Nuclepore membrane filter

(29) Rainey, R. H., Science, 155, 1242-3 (1967). (30) Robbins, J. A., Edgington, D. N., “Radiological and Environmental Research Division Annual Report (Part 111) January1211-12 (1965). December 1972”, pp 31-53, Argonne National Laboratory, ANL7960,1973. (31) Agnew, R. P., “Differential Equations”, 180 pp, McGrawHill, New York, N.Y., 1942. (32) Edgington, D. N., Robbins, J. A., unpublished data. (33) Davis, R. B., In “Quarternary Paleoecology”, E. J. Cushing and H. E. Wright, Eds., pp 153-7, Yale University Press, New Haven, Conn., 1967.

A technique for calculation of aerosol particle size distributions from indirect measurements

Abstract A mathematical technique is presented for the interpretation of diffusion battery data to define submicron aerosol size distributions. Lognormal distributions of submicron aerosols are obtained by use of an iterative random search and reduction of search area optimization routine. Testing of the method by retrieval of predetermined functions indicates that the method is rapid and accurate. Data obtained from diffusion battery measurements in a Canadian uranium mine are used to demonstrate the technique.

Enthalpies of pyrolysis and oxidation of Athabasca oil sands

Abstract Thermal degradation of Athabasca oil sands, bitumen, and its fractions have been investigated in N 2 and in air, at 25–600 °C and at pressures up to 6.9 MPa, using thermogravimetry (TG) and high pressure differential scanning calorimetry (PDSC). These conditions are likely to occur during in-situ recovery of bitumen by underground combustion processes. Two regions of weight loss are detected using both gases. The endothermic low temperature volatilization reactions (150–400 °C) absorbed +26 mJ mg −1 for oil sand to +2319 mJ mg −1 for medium oil. The heats of reaction for high-temperature cracking and volatilization reactions (400–550 °C) were similar. The heats of reaction for the low-temperature oxidation reactions (150–375 °C) were −405 mJ mg −1 for oil sand to −30200mJ mg −1 for medium oil. Values for the high-temperature oxidation reactions (400–550 °C) were slightly higher. Increasing the pressure of nitrogen and air caused an increase in the endothermicity and exothermicity of the respective reactions.

Non-catalytic hydrocracking of asphaltenes: 2. Reaction kinetics

Abstract The kinetics of the non-catalytic thermal hydrocracking of Athabasca asphaltenes were studied over the temperature range 350–425 °C in a batch autoclave reactor. Gas, resins, oils (saturates + aromatics), coke and unreacted asphaltenes were separated. Product concentrations were determined as a function of reaction time for the above pseudoproducts. Two simple reaction models are proposed. In the first, the asphaltene fraction is considered to be a single reactant and the hydrocracking reaction a single irreversible reaction. The activation energy for asphaltene consumption was found to be 161 kJ mol −1 . In the second, more complex model, four pseudoproducts are used [asphaltenes, maltenes (oils + resins), coke and gas]. Activation energies for the reactions were found to be in the range 8–200 kJ mol −1 . Asphaltene hydrocracking reactions were found to have first-order kinetics. Experimental and calculated product distributions were in good agreement.