Catalytic conversion of levulinic acid to γ-valerolactone using supported Ru catalysts: from molecular to reactor level
|PhD ceremony:||Ms A.S. Piskun|
|When:||December 16, 2016|
|Supervisor:||prof. dr. ir. H.J. (Hero Jan) Heeres|
|Where:||Academy building RUG|
|Faculty:||Science and Engineering|
Levulinic acid, accessible from C6-sugars, present in a wide variety of biomass sources (e.g. lignocellulosic biomass and starch), is considered a very attractive platform molecule in current and future biorefinery schemes. γ-Valerolactone is one of the most interesting levulinic acid derivatives due to its attractive properties and is typically prepared from levulinic acid by a hydrogenation reaction.
In this thesis, extensive research on the hydrogenation reaction is reported using heterogeneous ruthenium catalysts in batch and continuous set-ups. Experimental results indicate that the conversion of levulinic acid to γ-valerolactone involves two consecutive reactions with one intermediate product (4-hydroxypentanoic acid). A catalyst screening study with nine ruthenium-based catalysts demonstrated that levulinic acid hydrogenations are best performed using a very acidic, highly porous zeolite support (Beta-12.5). Moreover, a detailed study on the hydrogenation with Ru on a titania support revealed that the Ru nanoparticle size is of prime importance for catalytic activity and that it heavily depends on the catalyst synthesis protocol.
Kinetic modelling activities were conducted and a Langmuir-Hinshelwood model was developed for the hydrogenation reaction with good agreement between experimental and model data. An experimental study in a packed bed reactor with mm range catalyst particles demonstrated that intra-particle mass transfer limitation of both hydrogen and LA plays an important role and heavily influences the overall reaction rate. High levulinic acid conversion coupled with acceptable stability for 52 h on stream was observed for a Ru/C catalyst.