Study Of The Reaction Mechanism For The Hydrodeoxygenation Of Glycerol

This thesis mainly focuses on the hydrodeoxygenation (HDO) reaction of glycerol, sincethe investigation of the HDO of glycerol can gain fundamental knowledge for investigation ofthe HDO of polyols like monosaccharide. In this thesis studies can be divided into twosections, with one section dealing with the dehydration step and the other one dealing with thehydrogenation step. The researches are conducted to understand the influence factors as wellas the reaction mechanism for each step, in order to provide guide for designhigh-performance HDO catalysts. The efforts are taken to the following aspects. First is toexamine the apparent activation energy of glycerol dehydration, using different kinds ofmolecular sieves as catalysts in tank reactors. Second is to examine how differentexperimental conditions such as reaction temperature, acid strength of catalyst and porestructure of catalyst, etc., on the dehydration reaction, in fixed-bed reactors. In this part thereaction mechanism of glycerol dehydration is discussed to seek for guide for catalyst design.Third is to understand the role of molecular sieves in the HDO reaction of glycerol infixed-bed reactors, and to seek for the answer to the question that whether the product yieldand selectivity can be tuned by changing the kinds of dehydration catalysts and hydrogenationcatalysts.The experimental results of glycerol dehydration suggest that for similar active sites, i.e.Br nsted acid sites contained in different catalysts used, their apparent activation energies inthe catalytic dehydration reaction are almost the same. In addition to that, the density of acidsites on the catalysts, as well as the pore structure influence mainly on the pre-exponentialfactor in Arrhenius equation, and not on the apparent activation energy. The reaction temperature, the amount of Br nsted acid sites and the pore structure are essential factorsresponsible for the catalyst activity and the product selectivity. In the experiments forstudying glycerol hydrogenation reaction it was found that the addition of H-beta, adehydration catalyst changed the reaction pathways of the glycerol hydrodeoxygenation, andas a consequence, the reaction took place with a manner of deeper deoxygenation. Thereaction pathway and the product selectivity can be changed by adjusting the packing way ofthe catalysts in the HDO reaction of glycerol. These conclusions can be used for guide forcatalyst design. They also implicate the similar methods for obtaining monohydric alcohols oralkanes from polyols heavier than glycerol.