Bio-oil hydrodeoxygenation catalysts produced using strong electrostatic adsorption

Authors: Elkasabi, Yaseen; LIU, QIULI - University Of South Carolina; Choi, Yongsuck; Strahan, Gary; Boateng, Akwasi; REGALBUTO, JOHN - University Of South Carolina

Submitted to: Fuel
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2017
Publication Date: 7/4/2017
Citation: Elkasabi, Y.M., Liu, Q., Choi, Y., Strahan, G.D., Boateng, A.A., Regalbuto, J.R. 2017. Bio-oil hydrodeoxygenation catalysts produced using strong electrostatic adsorption. Fuel. 207:510-521.

Interpretive Summary: Fuels can be produced from agricultural waste products such as corn stalks and manures, using a method called pyrolysis. In pyrolysis, high temperatures in the absence of oxygen are used to break down these solid products into a liquid that resembles crude petroleum (termed ‘bio-oil’). Like petroleum, bio-oil must be chemically converted into a finished fuel, using catalysts that speed up the necessary reactions. Such reactions include the removal of oxygen and the addition of hydrogen. While different methods exist for making these solid-state catalysts, one method that holds promise is called ‘strong electrostatic adsorption’ (SEA). The SEA method has the unique ability to attach metal catalysts of very small sizes onto the catalyst structure material, so much that the specific chemical activity can change due to that small size. This work describes the catalytic refining reactions that were tested on bio-oil, using SEA catalysts. It was found that the SEA catalysts not only showed high stability and strength in the harsh conditions of catalytic fuel refining, but that their specific chemical activities remained active in the presence of bio-oil. In particular, more compounds that have greater fuel energy content were produced using the SEA catalysts than with standard off-the-shelf catalysts. This research could potentially benefit researchers and companies that are trying to develop commercial processes to economically convert biomass into biofuels and higher-value industrial chemicals.

Technical Abstract: We synthesized hydrothermally stable metal catalysts with controlled particle size and distribution, with the goal of determining which catalyst(s) can selectively catalyze the production of aromatics from bio-oil (from pyrolysis of biomass). Both precious and base transition metal catalysts (Ru, Pt, Ni, Cu, 2Pt1Ru, NiCu) were deposited on mesoporous alumina and carbon, respectively, using the strong electrostatic adsorption (SEA) method. Our hypothesis was that controlled bimetallic combinations (precious and/or base metal) could enhance the HDO behavior. As verified by XRD and TPR, the SEA method successfully deposited metal particles that were less than 1 nm in size. Hydrodeoxygenation of pyrolysis bio-oil occurred for 3 hours at 300 degrees C in an aqueous environment. While partial conversion of mesoporous alumina into boehmite phase occurred, the catalysts particles remained between 2 – 3 nm post-reaction, indicating a high degree of anchoring. Base metal particles tended to sinter more over a carbon support. SEA catalysts produced aromatic hydrocarbons at a greater extent than those of Ni/C, or Cu/C, or commercial Ru/alumina, as evidenced by GC-MS and/or NMR. Furthermore, all SEA catalysts produced significantly less non-condensable gases than commercial Ru/alumina, Ni/C, or Cu/C, except for Pt/mA. Bimetallic 2Pt1Ru/mA did not exhibit significantly greater activity than Pt or Ru, whereas NiCu demonstrated improved oil quality and yields over single-metal Ni and Cu.