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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. 2016. "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 = 2016,
month = 8
}
  • In earlier work it is shown that benzene could not be hydrogenated under 1 atm total pressure over the same reduced or sulfided molybdena-alumina catalyst which was hyperactive for olefin hydrogenation after similar pretreatment. Hydrogenation became detectable, however, after reduction at 800 C where the average oxidation number (O.N.) was 1.3 (e/Mo = 4.7) and the reaction became facile after reduction at 900 C where metallic molybdenum was evidently present (O.N. = 0.9); others have also reached this latter conclusion. Catalysts reduced below 600 C, as is the customary procedure, have O.N. {approx}4; they contain mainly Mo{sup 4+} together withmore » small amounts of Mo{sup 5+}, balanced by some lower valence states, but no evidence of Mo{sup 0} or metallic molybdenum has been expected or reported. It was suggested, therefore, that the hydrogenation of benzene carried out with P{sub H{sub 2}} {approximately} 1 atm might be used as a sensitive diagnostic test for the presence of this metal or conceivably some other low-valence state. In the present work these results have been extended to much higher hydrogen pressures. In spite of the fact that benzene could not be hydrogenated on conventionally prepared catalysts (reduced at T < 600 C), exchange between D{sub 2} and the benzene hydrogens occurred at 70 C. It was shown, however, that this process took place largely on the alumina portion of the surface although it was synergistically influenced by the dissociation of D{sub 2} on the molybdena sites. The exchange reaction could be effectively quenched by the chemisorption of CO{sub 2} prior to reaction. CO{sub 2} has been shown to chemisorb selectively on the alumina portion of the surface.« less
  • On the basis of the rate constant per active site determined by pulse surface reaction rate analysis (PSRA), the effect of the strong metal-support interaction (SMSI) on the hydrogenation of adsorbed CO was studied for titania-supported noble metal catalysts. Reduction at 773 K resulted in a drastic decrease in the amount of CO adsorbed on all noble metals examined. The observed suppression of CO chemisorption resulted mainly from SMSI, because the chemisorption ability was restored considerably by heating these catalysts in an O{sub 2} atmosphere and then reducing at 523 K. It was found that the effect of SMSI onmore » the hydrogenation of adsorbed CO was different from one noble metal to another, although its effect on CO chemisorption was common to all titania-supported noble metals. Pt and Pd exhibited a much higher hydrogenation activity in their SMSI state than in their normal state, whereas Rh, Ru, and Ir exhibited almost the same activity in both states. By heating titania-supported Pt and Pd in O{sub 2} and then reducing at 523 K, concomitant with destruction of the SMSI state, the high hydrogenation activity disappeared to near each original value. Subsequent reduction at 773 K again brought these catalysts to the SMSI state, accompanied by an increase in their activity. From these results, a possible cause is discussed for the high activity on Pt and Pd in the SMSI state and for its absence on Rh, Ru, and Ir in the SMSI state.« less
  • Ethane hydrogenolysis and carbon monoxide hydrogenation were studied over two niobia (Nb/sub 2/O/sub 5/)-supported nickel catalysts, containing 2 and 10 wt% nickel, which had been reduced in hydrogen at 573 or 773 K for 1 h. Compared to silica-supported nickel catalysts, these samples had lower ethane hydrogenolysis activity but higher CO hydrogenation activity. For some samples a different experimental rate law for ethane hydrogenolysis was observed. In CO hydrogenation, all samples showed a shift in product distribution to hydrocarbons higher than methane, and olefinic products were detected. These observations were attributed to strong metal-support interaction (SMSI). The use of thesemore » chemical probes identified different manifestation of SMSI that depend on crystallite size and reduction treatment. On the basis of these manifestations, a hierarchy consisting of five stages was developed to rank the extent of interaction in Ni/Nb/sub 2/O/sub 5/ catalysts. A mechanism of SMSI was proposed for a physical explanation of this hierarchy.« less
  • The formation of hydrocarbons in the reaction of CO + H/sub 2/ and CO/sub 2/ + H/sub 2/ was studied over rhodium catalysts supported on ZrO/sub 2/, Al/sub 2/O/sub 3/, SiO/sub 2/, and MgO. Among those catalysts, Rh on ZrO/sub 2/ was most active and Rh-MgO was least active for the above reactions. Over Rh-ZrO/sub 2/, the CO/sub 2/ + H/sub 2/ reaction took place even at 50/sup 0/C, whereas the CO + H/sub 2/ reaction occurred only at temperature higher than 130/sup 0/C. The reaction of CO/sub 2/ + H/sub 2/ produced only methane at temperatures up to 200/supmore » 0/C, but a small amount of CO formed along with methane in the reverse water gas shift reaction above 200/sup 0/C. In the case of the CO + H/sub 2/ reaction, the higher molecular weight hydrocarbons (C/sub 2/ approx. C/sub 4/) as well as CH/sub 4/ formed. The inverse kinetic isotope effect was observed in both reactions of CO + H/sub 2/(D/sub 2/) and CO/sub 2/ + H/sub 2/(D/sub 2/) over Rh-ZrO/sub 2/. However, the isotope effect was not observed in the CO/sub 2/ + H/sub 2/(D/sub 2/) reaction over Rh-Al/sub 2/O/sub 3/ whose effect in the CO + H/sub 2/ reaction was still inverse. The activity for the CO + H/sub 2/ reaction over the oxidized Rh-ZrO/sub 2/ and Rh-Al/sub 2/O/sub 3/ was almost 2 to 10 times higher than that on the reduced catalyst. The reaction mechanisms of the above reactions are discussed. 2 figures, 4 tables.« less