Catalytic Hydrodeoxygenation of Guaiacol as Lignin Model Component Using Ni-Mo/TiO2 and Ni-V/TiO2 Catalysts

摘要

Catalytic hydrodeoxygenation of guaiacol (2-methoxy phenol), an oxygen rich lignin model compound, has been investigated aiming at the elucidation of active catalysts for production of deoxygenated products. All catalysts were synthesized by impregnation technique. Screening of different catalysts unveiled Ni-Mo/TiO2 as the most active catalyst. Ni-Mo/TiO2 was compared with Ni-V/TiO2 to understand the influence of promoter (Mo and V); nevertheless, Ni-V/TiO2 produced no positive effect compared to Ni-Mo/TiO2. Structural investigation was performed using XRD, TEM, BET surface area and TPD measurements. As evidenced by XRD and TEM, all catalysts composed of nano-sized particles. Ni-Mo/TiO2 showed small sized finely dispersed particles, on the other hand large particles and loss of dispersion noted for Ni-V/TiO2 and Ni/TiO2, respectively. BET surface area measurement depicted Ni-Mo/TiO2 catalyst presented high surface area with optimal mesopores than Ni-V/TiO2. The NH3-TPD data revealed that Ni-Mo/TiO2 acidic strength is higher than the Ni-V/TiO2. Influence of catalysts and reaction variables were investigated using both Ni-Mo/TiO2 and Ni-V/TiO2 to determine their potential role on guaiacol conversion. High activity of Ni-Mo/TiO2 during wide range of conditions could be attributed to: (i) small sized and finely dispersed active metal particles, (ii) more mesopores, and (iii) high acidic strength. Water as a solvent, showed no impact on Ni-V/TiO2 performance, while on Ni-Mo/TiO2, guaiacol conversion and phenol selectivity inclined to decrease.