Characterization of destructured heavy oil and study of asphaltenes adsorption over solid adsorbents.

摘要

The presence of asphaltenes in heavy oil is related to its high viscosity which is a major constraint in heavy oil processing and transportation. Moreover, problems associated with the deposition of asphaltenes at different stages of the heavy oil refining steps increase the cost of heavy oil processing. In this research project, we have achieved viscosity reduction of heavy oil by treating it through the novel JetShear destructuring process. Subsequently we have studied the adsorption of the asphaltenes over specific solid adsorbents. Characterization of the raw and treated heavy oil has been conducted. We have experimentally shown that the JetShear destructuring process reduces diluent requirements (up to 50%), decreases the initial viscosity of heavy oil and lowers the oil density (increasing its API degree) thus providing a solution for pipeline transportation. The asphaltenes content of the treated product oil was also found to decrease slightly during the JetShear destructuring as per SARA fractions determination. This implies incipient cracking of the heavy oil induced by the JetShear treatment. Adsorption of asphaltenes over practical adsorbents was conducted to determine whether asphaltenes could be selectively removed from the oil aiming at establishing the basis of a process that could lead to breakthrough technology in heavy oil processing. Investigations of adsorption of asphaltenes were centered onto two objectives: firstly, asphaltenes characterization based on molecular size and separation of asphaltenes into acidic and basic fractions; secondly, asphaltenes interaction with adsorbents was studied. Experiments using virgin and destructured heavy oil showed that asphaltenes were preferentially removed following a multilayer adsorption model in the pores with significant and practical yields (0.25∼0.36 g asphaltenes/g adsorbent) in the 150°C range. Maximum uptake required 200 min of contact time at heavy oil/adsorbents ratios in the 5:1 range. The adsorption reduced the asphaltenes remaining in the treated heavy oil by allowing the asphaltenes to lodge in the pores as well as getting adsorbed on the surfaces of the adsorbent particularly the lower molecular weight asphaltenes. The combined treatment (i.e. destructuring and adsorption) also changed the functional group of the asphaltenes, and induced loss of heteroatoms lowering sulfur content in the final oil.;Keywords. Destructured heavy oil, adsorption of asphaltenes