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Title: Catalytic upgrading of basic oleochemicals to fatty alcohols over supported cobalt catalysts
Author: Rahmawati, Zeni
ISNI:       0000 0004 7967 6715
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2019
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Conversion of basic oleochemicals such as fatty acids and fatty acid methyl esters to fatty alcohols is a very important transformation as fatty alcohols are widely used in fragrances, detergents, emulsifiers, lubricants, health supplements and pharmaceuticals. Fatty alcohol is commercially produced through the hydrogenation of fatty acid or fatty acid methyl esters over chromite-based catalysts. However, this process requires harsh reaction conditions with elevated temperatures (200-300oC) and high pressures (20-300 bar). Additionally, the use of chromite is associated with environmental problems. In this study, the selective hydrogenation of stearic acid and methyl stearate as model compounds to produce stearyl alcohol was studied over a series of cobalt alumina and cobalt silica catalysts at 300oC and 50 bar. Catalysts were prepared by wetness impregnation and characterised by XRD, TPR, H2 chemisorption, N2 adsorption-desorption, MP-AES, and FTIR. It was observed that stearyl alcohol was the main product of reaction along with heptadecane, octadecane, and stearyl stearate. The results showed that the catalyst support significantly influenced the selectivity of products. Hydrogenation of stearic acid over cobalt alumina confirmed that selectivity of the product was influenced by the availability of Lewis acid sites on the support surface which were responsible for ester formation. Increased cobalt loading diminished the number of Lewis acid sites and enhanced the selectivity to stearyl alcohol. Whereas the hydrogenation of stearic acid over cobalt silica suggested that silica support did not promote ester formation. Moreover, cobalt loading influenced the conversion by providing more available metal area and enhanced the initial reaction rate. Overall, the result showed a high selectivity of stearyl alcohol over 93% which was obtained within the range of cobalt loading 4-8 wt%. The significant influence of catalyst support was also found in the hydrogenation of methyl stearate. Cobalt alumina exhibited improved performance in term of conversion and stearyl alcohol selectivity compared to cobalt silica. However, the selectivity of alkane was dominant as the reaction ran for longer time and conversion increased. Interestingly, the results provide a promising route to upgrade the methyl ester to green diesel.
Supervisor: Howe, Russell ; McCue, Alan J. Sponsor: Ministry of Finance ; Republic of Indonesia
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Fatty acids ; Fatty alcohols ; Oils and fats ; Stearic acid ; Cobalt catalysts ; Catalysis