Low temperature oxidation of athabasca bitumen

Abstract

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.

Desulfurization of heavy oil

“…At 150°C, there is change in reaction order. There is a high-rate first-order autoxidation regime below 150°C and second-order autoxidation regime at low extent of oxidation at temperatures above 150°C (Babu and Cormack 1983). For example, compared with a straight run kerosene fraction where thiol removal increases with oxidation temperature, sulfur removal from bitumen does not monotonically increase with autoxidation temperature (Paniv et al 2006).…”

Hydrocarbon Addition Reactions during Low-Temperature Autoxidation of Oilsands Bitumen

“…The change at ∼150 °C coincided with a reported change in bitumen oxidation selectivity. 10,16 (c) There was an increase in the oxygenate functionality in the oxidized bitumen. An increase in both C−O and CO bonds were apparent from infrared spectroscopy, with some increase in SO bonds also being noted.…”

“…Previous work on low-temperature bitumen oxidation also indicated that there is a change in the oxidation selectivity and kinetics at ∼150 °C. 10,16 The effect of oxidation temperature on the properties of oxidized bitumen was investigated by performing oxidation for only 6 h at 140, 150, and 160 °C. The mass loss observed was in the range of 0.6−0.8 wt %.…”

“…The NMR results corroborated the previously reported change in bitumen oxidation selectivity at ∼150 °C. 10,16 The question that was not resolved, was whether the carbonyl formation caused the increase in viscosity, or did it just happen to correlate with the viscosity increase (see eq 1).…”

“…The first part of the study evaluated prolonged low-temperature autoxidation (oxidation with air) of bitumen. This line of investigation was based mainly on the success that was reported with oxidative degradation of coal under mild reaction conditions. − Although bitumen is dissimilar to coal in various respects, previous studies on the low-temperature oxidation (LTO) of bitumen indicated that oxygen is readily incorporated in the bitumen and that prolonged LTO exhibits first-order kinetics, with respect to oxygen. − A yield of 30 wt % of water-soluble material was reported for the chemical oxidation, albeit not autoxidation, of oilsands bitumen-derived asphaltenes . The objective of the study was to empirically evaluate the changes in bitumen properties by autoxidation.…”