Catalyst and Material Development for Warm Cleanup of Biomass or Coal-Derived Syngas: Tar, Methane, Inorganic Contaminant Species, and CO2 Removal
EMSL Project ID
46194
Abstract
Syngas from biomass or coal has many applications in the area of catalytic fuels and chemicals synthesis, as well as hydrogen production for petroleum refineries, ammonia synthesis and for fuel cell applications [1]. In all cases, the gasifier-derived syngas must be treated to remove a number of impurities which would otherwise poison the processing catalysts [2]. Inorganic impurities include alkali salts, chloride, sulfur compounds, heavy metals, ammonia, and various P, As, Sb, and Se-containing compounds. Many of these must be removed to part per billion levels due to their strong interaction with water-gas-shift and synthesis catalysts. Product gas from a biomass gasifier also contains small quantities of hydrocarbon gases such as ethane, organic liquids broadly classified as tars, and inorganic impurities such as H2S, HCl, NH3, and alkali metals. These tars (e.g., aromatic hydrocarbons) are notorious for condensing and subsequently polymerizing on downstream equipment such as compressor and gas turbine surfaces if the gas is cooled sufficiently. Tars also potentially contribute to significant carbon deposition on catalyst surfaces for processes involved in adjusting the raw gas composition to a synthesis gas suitable for synthesis of higher alcohols or other products.
Although technical approaches currently exist for removal of the contaminant species, they are rather costly, employing solvents at ambient or lower temperature. The efficiency of hydrogen production would also be significantly improved if all the contaminants could be removed at temperatures higher than that employed in the low temperature water-gas-shift reaction (greater than 200oC). Additionally, after water-gas-shift, the hydrogen product contains a significant amount of CO2, which also needs to be removed. Conventionally, CO2 removal from H2 stream also requires low temperature solvent-based operation, or low-temperature pressure-swing absorption operations. The proposed absorption-enhanced reforming (AER) hydrogen production process, which combines hydrocarbon reforming, high temperature and low temperature water gas shift, and CO2 removal into one single unit, can significantly simplify current multi-step hydrogen production technologies [3,4]. Accordingly, by using a water-gas-shift catalyst mixed with a CO2 absorbent, it is also possible to produce high purity hydrogen directly from clean warm coal or biomass syngas. The high concentration CO2 stream removed from the syngas can be long-term stored or sequestered, which can mitigate the environmental problem of global warming.
The primary goals of this project are to develop catalyst and sorbent material suitable for a warm syngas cleanup process to include 1) catalytic tar and methane removal, and 2) inorganic contaminant and CO2 removal sorbents. Combined experimental, catalytic characterization, structural imaging, and computational investigations will offer better understanding of reaction mechanism and of the catalytic materials used for tar and hydrocarbon reforming. This will result in the design of catalysts less susceptible to carbon formation and sulfur poisoning. Additionally, characterization leading to better understanding of the H2S and CO2 sorbent material structure will lead to the development of improved cleanup materials. We propose to use the unique capabilities of EMSL (especially, TEM, XPS, NMR, EPR, and the Chinook super computer) to answer specific technical questions, answers to which will enable improved catalyst and material design. Materials with suitable performance are crucially necessary for the development of an advanced warm syngas cleanup process.
Project Details
Project type
Exploratory Research
Start Date
2011-10-01
End Date
2012-10-07
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Lebarbier VMC, RA Dagle, L Kovarik, KO Albrecht, XS Li, L Li, CE Taylor, X Bao, and Y Wang. 2014. "Sorption-Enhanced Synthetic Natural Gas (SNG) Production from Syngas: A Novel Process Combining CO Methanation, Water-Gas Shift, and CO2 Capture." Applied Catalysis. B, Environmental 144:223-232. doi:10.1016/j.apcatb.2013.06.034