Advances In The Catalytic Conversion Of Biomass Components To Ester Derivatives Challenges And Opportunities PDF Download

Biomass offers a plethora of opportunities to obtain useful and unique products in a sustainable way, be it chemicals with specialty applications, or molecules that can be blended into our everyday fuels, potentially improving their desired properties. In this work, we study two processes involving the conversion of biomass-derived feedstocks into specialty chemicals and diesel fuel precursors using suitable solid catalysts for each application. In Chapters 2 and 3, we delve into the production of hexane-1,2,5,6-tetrol from levoglucosanol, which is ultimately obtained from a cellulose direct derivate, and a potential application as a polymer precursor. In Chapter 2, we obtain kinetic information for the conversion of levoglucosanol into the polyol using a Pt-WOx/TiO2 catalyst at industrially relevant concentrations (10 - 30wt% reactant in water), showing that with this catalyst we can obtain selectively our product of interests, and also preserve over 90% of the reactant stereocenters. We also demonstrate the relative stability of this catalyst compared to what is known in literature, and its regenerability as well. In Chapter 3, we show a potential application for hexane-1,2,5,6-tetrol in the synthesis of tetrol-boronate copolymers when benzenediboronic acids are used. We prove that a facile synthesis is possible at room temperature with various solvents, and demonstrate that the properties of the polymers are impacted by the choice of a solvent, and the diastereomeric excess of the reactant, managing to obtain a first-known case of a chiral polymer when 98% d.e. (S,R)-hexane-1,2,5,6-tetrol is used. In Chapters 4 and 5, we study the selective conversion of ethanol into larger molecules that can be ultimately converted into compounds that can be blended into diesel by different methods when MgAl mixed metal oxide catalysts that have very low loadings of Cu are used. In Chapter 4, we demonstrate that when Cu loadings less than 0.6wt% are used in MgAl catalysts, very high diesel fuel precursor selectivities may be obtained, with the most significant products being larger alcohols and aldehydes, followed by large esters, and relatively minor amounts of ethyl acetate. We proved that changing the properties of the MgAl support does not greatly impact the performance of the catalyst, instead we found that the loading of Cu is the determinant factor in catalyst performance due to Cu acting more as a promoter of MgAl acid-base chemistry than as an actual catalyst for the Guerbet coupling reaction. The presence of Cu in low amounts also enables the selective production of esters with 6 or more carbons over ethyl acetate. The studied catalysts also promoted high product alcohol linearity, and the alcohol selectivity per carbon number fitted the Schultz-Flory distribution, showing that alcohol growth is dictated by chain growth behavior. In Chapter 5, we studied the performance of a single low Cu loading MgAl catalyst at different contact times, performed tests at varying ethanol-to-hydrogen partial pressure ratios, and performed cofeed studied of ethanol with acetaldehyde and ethyl acetate in order to elucidate the reaction network of ethanol oligomerization to larger oxygenates. We found that selectivity to higher alcohols was greater towards alcohols at all conversions, and alcohols exhibit chain-growth at all contact times. We found that ester and ketone selectivity increase with conversion, with their sizes becoming larger with conversion as well. Esters are series products from alcohols and aldehydes. Finally, we demonstrated that higher linear alcohols will be more selective to esters that ethanol, and that branched alcohols feeds may form esters selectively. Finally, in Chapter 6, we cover the conclusions from all the performed studies, and provide an outlook on future research avenues that enable the effective conversion of biomass-derived feedstocks into products of added value using solid catalysts.