Bio-oil upgrading to hydrogen via steam reforming
Hydrogen production from renewable bio-oil is an attractive idea for fuel, energy, and agricultural applications. Hydrogen is a common energy carrier and is prime matter for numerous applications. Hydrogen can be directly used in fuel cells in different kind of scenarios. Hydrogen can also be used as a precursor of ammonia for use in fertilizers.
Bio-oil is mainly composed of two fractions: a carbohydrate fraction (water soluble) and a lignin-derived fraction (water insoluble). That derived from lignin fraction (pyrolytic lignin) is considered a high-value product by itself. This lignin can be easily separated and used as a direct precursor of gasoline-like products. The remaining water-rich carbohydrate fraction can be steam reformed over a catalyst to generate hydrogen. One attractive scenario is to use this hydrogen to catalytically upgrade the lignin products to fuels in the same centralized facility.
The main objective is to understand the fundamentals of bio-oil reforming. In general this means that we want to understand the process so we can optimize it and eventually design reactors for industrial applications. This involves the study of chemical reaction kinetics and catalyst deactivation (by coking). But due to the complex nature of the bio-oils and the variability depending on type of feedstock, pre-treatments, pyrolysis conditions, etc; these kind of study cannot be performed directly.
Figure 1. Flow chart showing overview for steam reforming of bio-oil
Different bio-oil fractions can be collected during pyrolysis containing different physical and chemical characteristics. Some physical and chemical properties are determined for each fraction. Also chemical species can be identified. These fractions can be studied to determine which factors affect the reforming ability of the bio-oils. It is also important to understand the role of different components in both reforming and coking mechanisms.
Overall bio-oil steam reforming reaction
Experiments are being performed in both a fixed bed and fluidized bed reactors loaded with reforming catalyst. The reactors are designed to inject liquids to the catalyst bed. One major advantage of the fluidized bed reforming is that if minimizes the effect of catalyst coking on the overall yield of product. Different parameters can be controlled like temperature, pressure, feed rates, steam to carbon ratios, etc. Gas analysis is performed by on-line GC. The above results will be complemented by the catalyst characterization on order to better understand the catalysis and catalyst deactivation.
- Figure 2. Fixed bed reformer at CSET
- Figure 3. Fluidized bed reactor system at CSET
Reaction kinetic studies can also be performed with bio-oil model compounds to be able to understand the role of different types of chemical species found in bio-oils. Later an ideal reforming fraction of bio-oil can be defined. This concept can be coupled to the design of biomass treatments and pyrolysis units to selectively produce these desired bio-oil fractions.
Research done By:
Pedro Ortiz and Satyakrishna Jujjuri
Principal Investigators:
Robert C. Brown, Brent Shanks, Iowa State University
For inquiries related to this research program, please contact:
Dr. Robert C. Brown
iastate.eduDr. Justinus A. Satrio
Iowa State University CSET, 0411 Marston Hall, Ames, Iowa 50011-2153
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