From Biomass to Hydrogen

The Science

Hydrogen production through steam reforming biomass-derived compounds is an economically feasible and environmentally benign way to efficiently use renewable energy resources. A recent study combined experimental and theoretical approaches to compare the hydrogen yield achieved by several different metal catalysts used for steam reforming ethylene glycol.

The Impact

The findings show a cobalt (Co) catalyst had a much higher hydrogen yield than rhodium (Rh) or nickel (Ni) catalysts, making it a promising catalyst for steam reforming ethylene glycol for hydrogen production. Ethylene glycol is a component found in aqueous phases that are produced from the direct liquefaction of plant-derived cellulose or cellulosic oxygenates. The study could lead to the development of more efficient strategies to produce hydrogen from bio-derived aqueous phases as an environmentally friendly strategy to power diverse energy needs.

Summary

Steam reforming biomass-derived compounds is a promising strategy for hydrogen production. To realize the full potential of this approach, scientists must identify which catalyst is optimal for producing the highest yield of hydrogen. To address this question, a team of researchers from Pacific Northwest National Laboratory (PNNL) combined experimental and theoretical methods to study steam reforming ethylene glycol over MgAl₂O₄-supported Rh, Ni and Co catalysts. Computational work and advanced catalyst characterization were performed at EMSL, the Environmental Molecular Sciences Laboratory, a Department of Energy (DOE) national scientific user facility. Compared to the highly active Rh and Ni catalysts which achieve 100 percent conversion of ethylene glycol, the steam reforming activity of the Co catalyst was comparatively lower, with only 42 percent conversion under the same reaction conditions. However, the use of the Co catalyst rather than the Rh and Ni catalysts resulted in a three-fold drop in methane (CH₄) selectivity—a measure of the percentage of ethylene glycol converted to CH₄. Calculations revealed the lower CH₄ selectivity for the Co catalyst, as compared to the Rh and Ni catalysts, is primarily due to the higher barrier for CH₄ formation. The findings demonstrate that the Co catalyst leads to a higher yield of hydrogen, at the expense of CH₄, compared with the Rh and Ni catalysts. Additionally, the Co catalyst was also found to offer enhanced catalyst stability compared with the more conventional Ni and Rh catalysts. This information could be used to develop efficient methods for converting biomass-derived compounds into hydrogen for petroleum refining, the production of industrial commodities such as fertilizers, and electricity production via fuel cells.

Funding

This work was supported by DOE’s Office of Science (Office of Biological and Environmental Research), including support of EMSL, a DOE Office of Science User Facility; the DOE Office of Energy and Renewable Energy, Bioenergy Technologies Office; PNNL; and the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility.

Publications

D. Mei, V.L. Dagle, R. Zing, K.O. Albrecht, R.A. Dagle. “Steam Reforming of Ethylene Glycol over MgAl2O4 Supported Rh, Ni, and Co Catalysts.” (2015). ACS Catalysis:315-325 [DOI: 10.1021/acscatal.5b01666]