Bio-oil hydrodeoxygenation catalysts produced using strong electrostatic adsorption

Our objective was to synthesize hydrothermally stable metal catalysts with controlled particle size and distribution, with the goal of determining which catalyst(s) can selectively produce aromatics. Both precious and transition metal catalysts (Ru, Pt, Ni, Cu, 2Pt1Ru, NiCu) were deposited on mesoporous alumina (mA) and carbon, respectively, using the strong electrostatic adsorption (SEA) method. Due to the alloying that occurs under SEA, our hypothesis was that controlled bimetallic combinations (precious and/or base metal) could enhance the HDO behavior. As verified by XRD, STEM, and TPR, the SEA method successfully deposited noble metal particles less than 2 nm in size onto alumina. Alloying of bimetallic particles was also confirmed. Hydrodeoxygenation of pyrolysis bio-oil was run for 3 h at 300 °C in an aqueous environment. While partial conversion of mesoporous alumina into boehmite phase occurred, the catalyst particles remained between 2 and 3 nm post-reaction, indicating a high degree of anchoring. Over carbon, base metal particles were initially larger in size (about 3.3 nm) and tended to sinter more. Bimetallic SEA catalysts produced aromatic hydrocarbons at a greater extent than those of Ni/C, or Cu/C, or commercial Ru/Al2O3, as evidenced by GC-MS and/or NMR. Bimetallic 2Pt1Ru/mA did not exhibit significantly greater activity than Pt or Ru or control catalysts made by dry impregnation (DI), whereas NiCu demonstrated improved oil quality and yields over single-metal Ni and Cu and DI-method control catalysts. With respect to product compounds, the effect of mA support is stronger than that of carbon support.