Selective catalytic hydrodeoxygenation (HDO) is an important process for future biorefinery based on lignocellulosic biomass feedstock. Guaiacol (2-methoxyphenol) as a model compound is a representative product from lignin-derived bio-oils. Hydrodeoxygenation of guaiacol can produce three classes of products determined by the catalyst selectivity: (1) saturated hydrocarbons, (2) aromatics, and (3) phenolics. In this work, we report the effect of titania overlayer on Ni catalyst by changing the typical Ni HDO selectivity from saturated hydrocarbons to phenolics after Ni encapsulation. We discovered that Ni nanoparticle (100-200 nm), a well established industrial hydrogenation catalyst, can selectively hydrodeoxygenate guaiacol to phenolic products when mixed with anatase TiO2 (TiO2-A) nanoparticle under hydrogen pressure. However, when the Ni nanoparticle was mixed with ZrO2, Al2O3, CeO2, even rutile TiO2, the main products were only saturated hydrocarbons. Temperature programmed reduction profiles of the TiO2-A in the presence of Ni showed that a fraction of TiO2-A was reduced at much lower temperature (near 573 K). A mixed Ni /TiO2-A catalyst showed a guaiacol conversion of 85% and the phenolic selectivity of 100% when it was prereduced at 673 K for 30 minutes. XRD and XPS characterization of the catalyst indicated that TiO2 was highly dispersed at the surface of Ni nanoparticle and formed an overlayer at the surface. At the same time, some Ni migrated to the surface of TiO2-A. The Ni nanoparticle was encapsulated by titania due to the strong metal- support interaction. Detailed mechanism will be discussed.

Titania-encapsulated nickel nanoparticle as catalyst for selective hydrodeoxygenation of guaiacol to phenolics

255th National Meeting (2018)

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