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Title: Bio-oil Stabilization by Hydrogenation over Reduced Metal Catalysts at Low Temperatures

Abstract

Biomass fast pyrolysis integrated with bio-oil upgrading represents a very attractive approach for converting biomass to hydrocarbon transportation fuels. However, the thermal and chemical instability of bio-oils presents significant problems when they are being upgraded, and development of effective approaches for stabilizing bio-oils is critical to the success of the technology. Catalytic hydrogenation to remove reactive species in bio-oil has been considered as one of the most efficient ways to stabilize bio-oil. This paper provides a fundamental understanding of hydrogenation of actual bio-oils over a Ru/TiO2 catalyst under conditions relevant to practical bio-oil hydrotreating processes. Bio-oil feed stocks, bio-oils hydrogenated to different extents, and catalysts have been characterized to provide insights into the chemical and physical properties of these samples and to understand the correlation of the properties with the composition of the bio-oil and catalysts. The results indicated hydrogenation of various components of the bio-oil, including sugars, aldehydes, ketones, alkenes, aromatics, and carboxylic acids, over the Ru/TiO2 catalyst and 120 to 160oC. Hydrogenation of these species significantly changed the chemical and physical properties of the bio-oil and overall improved its thermal stability, especially by reducing the carbonyl content, which represented the content of the most reactive species (i.e., sugar,more » aldehydes, and ketones). The change of content of each component in response to increasing hydrogen additions suggests the following bio-oil hydrogenation reaction sequence: sugar conversion to sugar alcohols, followed by ketone and aldehyde conversion to alcohols, followed by alkene and aromatic hydrogenation, and then followed by carboxylic acid hydrogenation to alcohols. Hydrogenation of bio-oil samples with different sulfur contents or inorganic material contents suggested that sulfur poisoning of the reduced Ru metal catalysts was significant during hydrogenation; however, the inorganics at low concentrations had minimal impact at short times on stream, indicating that sulfur poisoning was the primary deactivation mode for the bio-oil hydrogenation catalyst. Reducing the sulfur content in bio-oil could significantly increase the lifetime of the hydrogenation catalyst used. The knowledge gained during this work will allow rational design of more effective catalysts and processes for stabilizing and upgrading bio-oils.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1336009
Report Number(s):
PNNL-SA-118919
Journal ID: ISSN 2168-0485; BM0101010
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: ACS Sustainable Chemistry & Engineering; Journal Volume: 4; Journal Issue: 10
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 59 BASIC BIOLOGICAL SCIENCES

Citation Formats

Wang, Huamin, Lee, Suh-Jane, Olarte, Mariefel V., and Zacher, Alan H. Bio-oil Stabilization by Hydrogenation over Reduced Metal Catalysts at Low Temperatures. United States: N. p., 2016. Web. doi:10.1021/acssuschemeng.6b01270.
Wang, Huamin, Lee, Suh-Jane, Olarte, Mariefel V., & Zacher, Alan H. Bio-oil Stabilization by Hydrogenation over Reduced Metal Catalysts at Low Temperatures. United States. doi:10.1021/acssuschemeng.6b01270.
Wang, Huamin, Lee, Suh-Jane, Olarte, Mariefel V., and Zacher, Alan H. Tue . "Bio-oil Stabilization by Hydrogenation over Reduced Metal Catalysts at Low Temperatures". United States. doi:10.1021/acssuschemeng.6b01270.
@article{osti_1336009,
title = {Bio-oil Stabilization by Hydrogenation over Reduced Metal Catalysts at Low Temperatures},
author = {Wang, Huamin and Lee, Suh-Jane and Olarte, Mariefel V. and Zacher, Alan H.},
abstractNote = {Biomass fast pyrolysis integrated with bio-oil upgrading represents a very attractive approach for converting biomass to hydrocarbon transportation fuels. However, the thermal and chemical instability of bio-oils presents significant problems when they are being upgraded, and development of effective approaches for stabilizing bio-oils is critical to the success of the technology. Catalytic hydrogenation to remove reactive species in bio-oil has been considered as one of the most efficient ways to stabilize bio-oil. This paper provides a fundamental understanding of hydrogenation of actual bio-oils over a Ru/TiO2 catalyst under conditions relevant to practical bio-oil hydrotreating processes. Bio-oil feed stocks, bio-oils hydrogenated to different extents, and catalysts have been characterized to provide insights into the chemical and physical properties of these samples and to understand the correlation of the properties with the composition of the bio-oil and catalysts. The results indicated hydrogenation of various components of the bio-oil, including sugars, aldehydes, ketones, alkenes, aromatics, and carboxylic acids, over the Ru/TiO2 catalyst and 120 to 160oC. Hydrogenation of these species significantly changed the chemical and physical properties of the bio-oil and overall improved its thermal stability, especially by reducing the carbonyl content, which represented the content of the most reactive species (i.e., sugar, aldehydes, and ketones). The change of content of each component in response to increasing hydrogen additions suggests the following bio-oil hydrogenation reaction sequence: sugar conversion to sugar alcohols, followed by ketone and aldehyde conversion to alcohols, followed by alkene and aromatic hydrogenation, and then followed by carboxylic acid hydrogenation to alcohols. Hydrogenation of bio-oil samples with different sulfur contents or inorganic material contents suggested that sulfur poisoning of the reduced Ru metal catalysts was significant during hydrogenation; however, the inorganics at low concentrations had minimal impact at short times on stream, indicating that sulfur poisoning was the primary deactivation mode for the bio-oil hydrogenation catalyst. Reducing the sulfur content in bio-oil could significantly increase the lifetime of the hydrogenation catalyst used. The knowledge gained during this work will allow rational design of more effective catalysts and processes for stabilizing and upgrading bio-oils.},
doi = {10.1021/acssuschemeng.6b01270},
journal = {ACS Sustainable Chemistry & Engineering},
number = 10,
volume = 4,
place = {United States},
year = {Tue Aug 30 00:00:00 EDT 2016},
month = {Tue Aug 30 00:00:00 EDT 2016}
}
  • Low-temperature hydrogenation of carbonyl fractions can greatly improve the thermal stability of fast pyrolysis bio-oil which is crucial to achieve long-term operation of high-temperature upgrading reactors. The current state of the art, precious metals such as ruthenium, although highly effective in carbonyl hydrogenation, rapidly loses performance due to sulfur sensitivity. The present work showed that molybdenum carbides were active and sulfur-tolerant in low-temperature conversion carbonyl compounds. Furthermore, due to surface bifunctionality (presence of both metallic and acid sites), carbides catalyzed both C=O bond hydrogenation and C-C coupling reactions retaining most of carbon atoms in liquid products as more stable andmore » higher molecular weight oligomeric compounds while consuming less hydrogen than ruthenium. The carbides proved to be resistant to other deactivation mechanisms including hydrothermal aging, oxidation, coking and leaching. These properties enabled carbides to achieve and maintain good catalytic performance in both aqueous-phase furfural conversion and real bio-oil stabilization with sulfur present. This finding strongly suggests that molybdenum carbides can provide a catalyst solution necessary for the development of commercially viable bio-oil stabilization technology.« less
  • Low-temperature hydrogenation of carbonyl fractions can greatly improve the thermal stability of fast pyrolysis bio-oil which is crucial to achieve long-term operation of high-temperature upgrading reactors. The current state of the art, precious metals such as ruthenium, although highly effective in carbonyl hydrogenation, rapidly loses performance due to sulfur sensitivity. The present work showed that molybdenum carbides were active and sulfur-tolerant in low-temperature conversion carbonyl compounds. Furthermore, due to surface bifunctionality (presence of both metallic and acid sites), carbides catalyzed both C=O bond hydrogenation and C-C coupling reactions retaining most of carbon atoms in liquid products as more stable andmore » higher molecular weight oligomeric compounds while consuming less hydrogen than ruthenium. The carbides proved to be resistant to other deactivation mechanisms including hydrothermal aging, oxidation, coking and leaching. These properties enabled carbides to achieve and maintain good catalytic performance in both aqueous-phase furfural conversion and real bio-oil stabilization with sulfur present. This finding strongly suggests that molybdenum carbides can provide a catalyst solution necessary for the development of commercially viable bio-oil stabilization technology.« less
  • Low-temperature hydrogenation of carbonyl compounds can greatly improve the thermal stability of fast pyrolysis bio-oil, thereby enabling long-term operation of upgrading reactors which generally require high temperatures to achieve deep deoxygenation. The state-of-the-art hydrogenation catalysts, precious metals such as ruthenium, although effective in carbonyl hydrogenation, deactivate due to high sulfur sensitivity. In the present work, we showed that molybdenum carbides were active and sulfur-tolerant in low-temperature conversion of carbonyl compounds. Furthermore, due to surface bifunctionality (i.e., both metallic and acid sites present), carbides catalyzed both C$=$O bond hydrogenation and C–C coupling reactions. Combined, these reactions transformed carbonyl compounds to moremore » stable and higher molecular weight oligomeric compounds while consuming less hydrogen than pure hydrogenation. The carbides proved to be resistant to other deactivation mechanisms including hydrothermal aging, oxidation, coking, and leaching. These properties enabled carbides to achieve and maintain good catalytic performance in both aqueous-phase furfural conversion and real bio-oil stabilization in the presence of sulfur. This finding strongly suggests that molybdenum carbides can provide a catalyst solution necessary for the development of practical bio-oil stabilization technology.« less