Glycerol acetalization using water-tolerant catalyst
|Abstract:||The commercial application of glycerol has attracted attention of the scientific community in recent years. Glycerol formal, which is produced from glycerol acetalization, is beneficial as fuel additive especially for the low temperature properties of biodiesel. However, the acetalization process is hampered by formation of water which will reverse the reaction and deactivate the acid catalysts. Using water-resistant heterogeneous acid catalyst will be favorable for acetalization of glycerol. In this research work, a comparative study has been carried out using the water-tolerant Cs2.5H0.5PW12O40, AS-MES (arene sulfonic acid ethane-silica), zeolite ZSM-5, H3PW12O40 as a homogeneous model and the commercial catalyst Amberlyst-15. In addition, a preliminary kinetic study was performed in a batch stirred tank reactor, studying the influence of different process parameters including temperature, feed composition and catalyst loading. One of glycerol formal isomers, 1,3 dioxan-5ol may be postsynthetically modified into important chemical products such as 1,3-propanediol. Therefore, the distribution of the two glycerol acetal isomers has also been studied systematically. To further enhance the activity of bulk Cs2.5H0.5PW12O40 for glycerol acetalization, it was supported on mesoporous silica by incipient impregnation method to increase the contact area of reactants and acid sites. Besides, supported Cs2.5H0.5PW12O40 supported on 2D (SBA-15) and 3D (KIT-6 and SBA-16) pore lattice mesoporous silicas have been compared since the topological curvatures of mesoporous silica with 3D structure would reasonably provide good transportation channels to get facilitated access to acid sites, while 2D long channels of SBA-15 may yield transport limitations at the points of connections of elemental particles. The impact of mesopore volume on activity has also been studied. Finding an appropriate aldehyde source is also crucial to improve the activity of the catalyst used. Since formaldehyde solution contains large amount of water which would deactivate the catalyst and favor the reversibility of the reaction, paraformaldehyde (a solid water-free source of formaldehyde) and acetone were studied to replace formaldehyde solution.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||31 August 2018|
|Collection:||Thèses et mémoires|
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