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University of New South Wales

1. Kok, Shiyun Esther. The influence of alumina supported cobalt catalysts on synthetic fuel production.

Degree: Chemical Sciences & Engineering, 2012, University of New South Wales

A range of γ-alumina supported (Norton type SA 6176 and Puralox SBA 200) cobalt-based Fischer Tropsch catalysts were synthesized via an impregnation method. Initially, catalyst preparation involved (aqueous) impregnation conducted at pH 2 using 3 M nitric acid with cobalt promoted with either lanthanum and/or ruthenium on Norton γ-alumina support. The presence of promoters (La, Ru) improved the methanation activity with the combination of La and Ru giving the best performance. The presence of promoters altered the physicochemical properties, Co crystallite size and the extent of Co3O4 reduction (to metallic Co) of the catalyst. Impregnation using a non-aqueous technique (ethanol and acetone mix, ratio 1:4) was performed on Puralox γ-alumina support with the catalysts experiencing a similar effect as for aqueous impregnation. Non-aqueous synthesis was found to influence methanation activity due to the modification of surface properties leading to variations in cobalt crystallite size and improved cobalt metal dispersion. The enhancement derived primarily from differences in the pore structure and its influence on Co crystallite size. The Puralox γ-alumina gave a better catalytic performance compared to Norton with CoRu/La/Puralox being the best catalyst and promoter combination. Catalyst reduction conditions (H2 partial pressure, holding time, final reduction temperature and ramp rate) were varied and the impact on performance for the atmospheric Fischer Tropsch reaction on CoRu/La/Puralox was assessed. Changes to these parameters altered the extent of cobalt reduction, the interaction between cobalt-cobalt atoms and cobalt-support and the Co° crystallite size. The optimum catalyst activity was obtained at 100 % H2, 450 °C reduction temperature, 50 hr holding time and 0.5 °C/min ramp rate and represented a balance between the extent of cobalt reduction and cobalt sintering. Ultilisation of a reduction-oxidation-reduction (ROR) strategy to activate the catalyst for the atmospheric Fischer Tropsch reaction was also investigated. Re-oxidising and then re-reducing a previously reduced catalyst was observed to improve its activity. A re-oxidation temperature of 135 °C gave the highest activity improvement. A decrease in the temperature of the second reduction step (from 450 °C to 300 °C) was also found to improve catalyst performance, likely due to a decrease in Co° sintering. Advisors/Committee Members: Amal, Rose, ARC Centre for Functional Nanomaterials, Faculty of Engineering, UNSW, Scott, Jason, ARC Centre for Functional Nanomaterials, Faculty of Engineering, UNSW, Cant, Noel, Macquarie University, Department of Chemistry and Biomolecular Sciences.

Subjects/Keywords: Promoters; Cobalt; Alumina; Impregnation methods; Reduction condition

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APA (6th Edition):

Kok, S. E. (2012). The influence of alumina supported cobalt catalysts on synthetic fuel production. (Doctoral Dissertation). University of New South Wales. Retrieved from http://handle.unsw.edu.au/1959.4/52367 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:11040/SOURCE01?view=true

Chicago Manual of Style (16th Edition):

Kok, Shiyun Esther. “The influence of alumina supported cobalt catalysts on synthetic fuel production.” 2012. Doctoral Dissertation, University of New South Wales. Accessed June 20, 2019. http://handle.unsw.edu.au/1959.4/52367 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:11040/SOURCE01?view=true.

MLA Handbook (7th Edition):

Kok, Shiyun Esther. “The influence of alumina supported cobalt catalysts on synthetic fuel production.” 2012. Web. 20 Jun 2019.

Vancouver:

Kok SE. The influence of alumina supported cobalt catalysts on synthetic fuel production. [Internet] [Doctoral dissertation]. University of New South Wales; 2012. [cited 2019 Jun 20]. Available from: http://handle.unsw.edu.au/1959.4/52367 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:11040/SOURCE01?view=true.

Council of Science Editors:

Kok SE. The influence of alumina supported cobalt catalysts on synthetic fuel production. [Doctoral Dissertation]. University of New South Wales; 2012. Available from: http://handle.unsw.edu.au/1959.4/52367 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:11040/SOURCE01?view=true

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