from first principles PP-I-1

OP-IV-4Ketonization of Valeric Acid over Metal Oxides as a First Step for GreenDiesel Synthesis: Consideration from Mechanistic ViewpointZaytseva Yu.A., Simonov M.N., Simakova I.L., Shutilov A.A., Zenkovets G.A.Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russiasimakova@catalysis.ruTo produce green diesel fuel from renewable organic materials such as carboxylic acids,obtained via aqueous phase reforming of sugars and sugar alcohols, ketonization [1] followedby deoxygenation of formed ketone can be applied. Ketonization is bimolecular reaction inwhich two acid molecules are converted into ketone, carbon dioxide and water. The benefit ofthe process is safety for environment because non-polluting by-products are formed. In thecurrent work, conversion of valeric acid into symmetrical ketone 5-nonanone has been studiedover various metal oxides such as ZrO 2 , CeO 2 , MgO, Al 2 O 3 , CeO 2 /ZrO 2 , MnO 2 /ZrO 2 ,CeO 2 /Al 2 O 3 at T= 573÷673 K under PH 2 =1 bar in fixed bed reactor. Before the reaction, thecatalyst was heated in carrier gas stream to reaction temperature. Then pure valeric acid wasfed using a syringe pump and after a certain period of time the condensable products werecollected in the trap cooled with liquid nitrogen. In the case of catalytic stability tests, reactionproducts were analyzed every 2 hours.The effects of temperature, residence time, nature of carrier gas on the conversion andselectivity toward the desired ketone was investigated. Selectivity toward 5-nonanone of 94%at complete conversion of valeric acid was observed over the most active ZrO 2 at 628 K.Methods of TEM, XRD, BET by Ar adsorption and XPS were applied to elucidate correlationbetween ketonization activity and structure as well as surface properties of the catalyst’sactive component. Here, we discuss possible reaction mechanism involving formation ofβ-keto acid intermediate [2]. First, surface carboxylates are formed, and then α-hydrogenatom is abstracted to form an anion radical which interacts with another carboxylate to giveβ-keto acid followed by decarboxylation to form a ketone. According to this consideration,the ratio between Lewis acid (M x+ ) and base (O -2 , OH - ) sites provides catalytic activity of themetal oxides. The most active catalysts ZrO 2 and CeO 2 /ZrO 2 seem to possess the optimal ratioand strength of acidic and basic surface sites.References:[1] A. Corma, M. Renz, C. Schaverien, ChemSusChem 1 (2008) 739.[2] S. Rajadurai, Catal.Rev.-Sci.Eng. 36 (1994) 385.80