(350c) Kinetic Studies of Succinic Acid Hydrogenolysis Using Multimetallic Catalysts in a Batch Slurry Reactor

Commercial production of succinic acid (SAC) using renewable sugar feedstocks is becoming a reality with recent announcement of bio-based succinic acid plants (BioAmber, Myriant, Succinity, and Reverdia).  This opens an opportunity to produce useful high value added chemicals such as 1,4-butanediol (BDO) and tetrahydrofuran (THF) from renewable resources via the hydrogenation of bio-based succinic acid. However, high activity and selectivities to desired products under mild reaction conditions are some of the major challenges confronting the industrial deployment of bioSAC hydrogenolysis. To this end, the activity and selectivity of multimetallic catalysts containing combinations of metals such as Ru, Re, Pt, Co, and Sn were tested in an isothermal stirred batch slurry reactor using different solvents under a wide range of hydrogen pressures (1-10 MPa) and temperatures (373-523 K). Solvent effects using water, alcohols, and other inert organic compounds were also explored.  Several reactions were conducted using SAC hydrogenolysis intermediates, such as γ-butyrolactone (GBL) and propionic acid (PA), as substrates to provide insight into the reaction pathways and relative importance of the different reactions steps. Finally, intrinsic kinetic parameters for SAC hydrogenolysis were evaluated using a subsystems approach, in which the kinetic parameters of the hydrogenolysis of the intermediates (GBL, PA, BDO, etc.) were evaluated and then used as initial guess values for the overall SAC hydrogenolysis system.  This approach reduces uncertainty in the fitted parameters and increases the reliability and robustness of the models proposed. This presentation will describe optimal conditions (temperature, pressure, catalyst composition, and solvent) for maximum conversion of SAC and selectivity to desired products, address details of different Langmuir Hinshelwood models considered using rigorous and systematic discrimination criteria, and their utility in developing more complete and realistic rate models for SAC hydrogenolysis.