FY2010 - Oak Ridge National Laboratory

Director’s R&D Fund—
Systems Biology and the Environment
05548
Catalytic Conversion of Lignin Feedstocks for Bioenergy Applications
Wei Wang, Tommy J. Phelps, Abhijeet P Borole, Timothy J. Tschaplinski, Ji-Won Moon, and Baohua Gu
Project Description
Annual production of 60 billion gallons of biofuels results in the generation of about 200 billion
kilograms of wet lignin residue of low value (~$0.01/kg), which mostly goes to boiler. Value from lignitic
waste may benefit from metal-based nanoparticle catalytic depolymerization. We will investigate novel
photocatalytic approaches by transforming lignin to value-added fuel or feedstocks. Our hypothesis is that
lignin may provide value-added chemicals through photochemically catalyzed depolymerization reaction
using structurally modified TiO 2 nanocatalysts under visible light. While current methodology uses TiO 2
and UV light for complete oxidation of organics, we investigate novel transition metal–doped
nanocatalysts, which lowered the bandgap energy with effective sunlight absorption and increased lignin
conversion efficiency. To further advance catalysis of lignin for value-added components, we also
investigate mechanisms to reduce or displace light-mediated catalytic activation with alternatives such as
electrochemical means to degrade lignin. Compared to conventional thermochemical processes,
knowledge gained through this project from both experiments and mechanistic studies is expected to yield
an effective pathway to convert lignin into value-added products at lower temperature, pressure, and
lower energy input.
Mission Relevance
The goal of this project is to develop an efficient photocatalytic pathway to breakdown low-value
biopolymers such as lignin into value-added chemicals or feedstocks and to obtain a fundamental
understanding of the mechanisms of the photo-catalytic depolymerization processes. The project is thus
directly relevant to the Biomass Program of the DOE Office of Energy Efficiency and Renewable Energy
(EERE) Biomass Program aimed at transforming the nation's renewable and abundant biomass resources
into cost-competitive, high-performance biofuels, bioproducts, and biopower. The research is also
expected to benefit in the general area of renewable energy for developing new technologies for biomass
(e.g., plant-derived material) conversion into valuable chemicals and fuels.
Results and Accomplishments
During the first year of the project, we made progress in the following areas.
Screen conventional TiO 2 catalysts on lignin depolymerization. We studied photodegradation of lignin
with commercially available TiO 2 catalysts from different sources including Degussa P-25 TiO 2 , Nanotek
TiO 2 , and Sigma-Aldrich products and also studied synthesized TiO 2 by conventional methods with
different structures (rutile, anatase, and amorphous) and with different morphologies (nanoparticles,
nanorods, nanotubes, and nanowires). These pure TiO 2 catalysts could degrade organic dyes and lignin
under UV light, but none of them showed observable efficiency under visible light. We also observed that
catalytic efficiency of phase-mixed TiO 2 (e.g., anatase-rutile mixed phase) is higher than single-phase
TiO 2 catalysts under UV light.
Development of new structurally modified TiO 2 nanocatalysts. We have developed new wet-chemical
methods to synthesize band-gap-narrowed TiO 2 catalysts in the forms of nanoparticles, nanotubes, or thin
films on electrodes by introducing metal and nonmetal elements (Cr, V, N, C) into the lattice of TiO 2 .
Light absorption of these doped TiO 2 has been characterized, and enhanced visible light adsorption and
remarkable photocurrents under visible light have been confirmed. Our studies revealed that the band gap
energy of pure TiO 2 (~3.2 eV) could be remarkably reduced to ~2eV. Compared with pure TiO 2 , which
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