Title: Steam reforming of fast pyrolysis-derived aqueous phase oxygenates over Co, Ni, and Rh metals supported on MgAl₂O₄

Abstract

In this study we examine feasibility for steam reforming the mixed oxygenate aqueous fraction derived from mildly hydrotreated fast pyrolysis bio-oils. Catalysts selective towards hydrogen formation and resistant to carbon formation utilizing feeds with relatively low steam-to-carbon (S/C) ratios are desired. Rh (5 wt%), Pt (5 wt%), Ru (5 wt%), Ir (5 wt%), Ni (15 wt%), and Co (15 wt%) metals supported on MgAl₂O₄ were evaluated for catalytic performance at 500°C and 1 atm using a complex feed mixture comprising of acids, polyols, cycloalkanes, and phenolic compounds. The Rh catalyst was found to be the most active and resistant to carbon formation. The Ni and Co catalysts were found to be more active than the other noble metal catalysts investigated (Pt, Ru, and Ir). However, Ni was found to form significantly more carbon (coke) on the catalyst surface. Furthermore, Co was found to be the most selective towards H₂ formation. Evaluating the effect of temperature on stability for the Rh catalyst we found that catalyst stability was best when operated at 500°C as compared to the higher temperatures investigated (700, 800°C). When operating at 700°C significantly more graphitic formation was observed on the spent catalyst surface. Operating at 800°C resultedmore » in reactor plugging as a result of thermal decomposition of the reactants. Thus, a concept analogous to the petroleum industries’ use of a pre-reformer, operated at approximately 500°C for steam reforming of the heavier naphtha components, followed by a high temperature methane reforming operated in the 600-850°C temperature range, could be applied in the case of steam reforming biomass derived oxygenates. Moreover, stability evaluations were performed over the Rh, Ni, and Co catalysts at 500°C and 1 atm, under similar initial conversions, reveal the Co catalyst to be the most stable and selective towards H₂ production. Conversion and selectivity to CH₄ over Co remained relatively stable at approximately 80% and 1.2%, respectively. By contrast, the Rh and Ni catalysts CH₄ selectivity’s were approximately 7-8%. Thus suggesting that a Co type catalyst may be more suitable for the steam reforming of biomass derived oxygenates as compared to the more conventional Ni and Rh type steam reforming catalysts. However, deposition of carbon on the surface was observed. High resolution TEM on the spent catalysts revealed the formation of graphitic carbon on the Rh catalyst, and filamentous carbon formation was observed on both the Ni and Co catalysts, albeit less pronounced on Co. Thus there is certainly opportunity for improvement in Co catalyst design and/or with process optimization.« less

Authors:

Xing, Rong ^[1]; Dagle, Vanessa Lebarbier ^[1]; Flake, Matthew ^[1]; Kovarik, Libor ^[2]; Albrecht, Karl O. ^[1]; Deshmane, Chinmay ^[1]; Dagle, Robert A. ^[1]

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+ Show Author Affiliations

1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Inst. for Integrated Catalysis
2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)

Publication Date:

Fri Jul 01 00:00:00 EDT 2016

Research Org.:

Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1252849

Report Number(s):

PNNL-SA-111967
Journal ID: ISSN 0920-5861; 49140; 48163; BM0102060

DOE Contract Number:  

AC05-76RL01830

Resource Type:

Journal Article

Journal Name:

Catalysis Today

Additional Journal Information:

Journal Volume: 269; Journal Issue: C; Journal ID: ISSN 0920-5861

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

biomass; steam reforming; aqueous phase; oxygenates; rhodium; nickel; cobalt; Environmental Molecular Sciences Laboratory