Author : Yongchun Hong
Publisher :
ISBN 13 :
Total Pages : 211 pages
Book Rating : 4.:/5 (14 download)
Book Synopsis Bimetallic Catalysis in Hydrodeoxygenation of Lignin Derived Molecules by : Yongchun Hong
Download or read book Bimetallic Catalysis in Hydrodeoxygenation of Lignin Derived Molecules written by Yongchun Hong and published by . This book was released on 2016 with total page 211 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrodeoxygenation (HDO) of phenolic compounds is an important model reaction in understanding the fundamental and application of catalysis in lignin based biofuel production. Recently, Fe has emerged as a promising catalyst for HDO of phenolics, due to its low cost and high selectivity in C-O bond cleavage. However, Fe's low HDO activity and poor stability under HDO conditions has limited its application. In this work, we developed an efficient approach to promote Fe's activity and stability without altering its unique selectivity in HDO of phenolics, by doping noble metals such as Pd onto Fe catalyst surface. A series of noble metal doped Fe catalysts were tested in HDO of m-cresol. Noble metals remarkably promoted Fe's activity and stability, while maintaining Fe's high C-O bond cleavage selectivity. To better understand this synergistic catalysis, a systematic study using both experimental and theoretical tools such as reaction kinetics, electron microscopy, in situ spectroscopies and DFT calculation was performed. The Pd-on-Fe nanostructure with sub-nm Pd clusters on reduced Fe surface in Pd-Fe catalyst was evidenced by high resolution STEM and pseudo in situ XPS. A direct C-O bond cleavage mechanism, in which m-cresol decomposes on Fe surface into C7H7* and OH* species and the formed species further reacts with H atoms to form toluene and water, respectively, was proposed based on DFT calculation and kinetic modeling. Kinetic modeling and in situ AP-XPS results suggested that Fe catalyst surface is dominated by OH* species, which ultimately lead to a deactivation of Fe catalyst. Addition of Pd to Fe significantly changes its kinetics by creating new sites for H2 activation and new reaction pathways via reaction between H activated on Pd sites and C 7H7* and OH* on Fe sites, as suggested by kinetic modeling. As a result, the surface of Pd-Fe is no longer dominated by OH* and catalyst deactivation by water induced oxidation is thus avoided. The concept of constructing Pd-on-Fe type nanostructure to stabilize base metal catalysts and at the same time promote their activity without altering their unique selectivity is potentially of border impact in other heterogeneous catalysis applications.
