Aerobic Oxidation of Veratryl Alcohol to Veratraldehyde with Heterogeneous Ruthenium Catalysts

Mayra Melián Rodriguez, Saravanamurugan Shunmugavel, Søren Kegnæs, Anders Riisager

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Abstract

Lignin is a complex polymeric molecule constituting various linkages between aromatic moieties. Typically, the β-O-4 linkage accounts for more than half of the linkage structures present in lignin. The current study focuses on the oxidative transformation of veratryl alcohol (VA)—a compound that can be formed by cleavage of β-O-4 linkages in lignin—to veratraldehyde (VAld) with air using ruthenium supported on γ-alumina or silica as catalyst with water or methanol as solvent in a batch reactor. Ru/Al2O3, prepared with ruthenium(IV)oxide hydrate showed superior catalytic activity, yielding 89 % VAld in water at 160 °C with 5 bar air pressure after 8 h of reaction. Prolonged reaction time led to significant formation of the decarbonylated product veratrol from VAld. When the reaction was completed under 20 bars of argon in methanol instead of water, the methyl ether of VA (i.e. 1,2-dimethoxy-4-(methoxymethyl)benzene) prevailed, indicating that methanol protected the hydroxyl group in VA from being oxidized to VAld. Catalysts containing alternative transition metals (Mn, Co, Cu and Ag) supported on Al2O3 gave significantly lower activities compared to Ru/Al2O3 under identical reaction conditions. The Ru/Al2O3 catalyst was reused in three consecutive reaction runs in water, but a decrease in VAld yield was obtained after the third cycle possibly due to leaching of Ru from the support.
Original languageEnglish
JournalTopics in catalysis
Volume58
Issue number14
Pages (from-to)1036-1042
Number of pages7
ISSN1022-5528
DOIs
Publication statusPublished - Oct 2015

Keywords

  • Heterogeneous catalysis
  • Ruthenium
  • Oxidation
  • Veratryl alcohol
  • Veratraldehyde

Cite this

Melián Rodriguez, Mayra ; Shunmugavel, Saravanamurugan ; Kegnæs, Søren ; Riisager, Anders. / Aerobic Oxidation of Veratryl Alcohol to Veratraldehyde with Heterogeneous Ruthenium Catalysts. In: Topics in catalysis. 2015 ; Vol. 58, No. 14. pp. 1036-1042.
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abstract = "Lignin is a complex polymeric molecule constituting various linkages between aromatic moieties. Typically, the β-O-4 linkage accounts for more than half of the linkage structures present in lignin. The current study focuses on the oxidative transformation of veratryl alcohol (VA)—a compound that can be formed by cleavage of β-O-4 linkages in lignin—to veratraldehyde (VAld) with air using ruthenium supported on γ-alumina or silica as catalyst with water or methanol as solvent in a batch reactor. Ru/Al2O3, prepared with ruthenium(IV)oxide hydrate showed superior catalytic activity, yielding 89 {\%} VAld in water at 160 °C with 5 bar air pressure after 8 h of reaction. Prolonged reaction time led to significant formation of the decarbonylated product veratrol from VAld. When the reaction was completed under 20 bars of argon in methanol instead of water, the methyl ether of VA (i.e. 1,2-dimethoxy-4-(methoxymethyl)benzene) prevailed, indicating that methanol protected the hydroxyl group in VA from being oxidized to VAld. Catalysts containing alternative transition metals (Mn, Co, Cu and Ag) supported on Al2O3 gave significantly lower activities compared to Ru/Al2O3 under identical reaction conditions. The Ru/Al2O3 catalyst was reused in three consecutive reaction runs in water, but a decrease in VAld yield was obtained after the third cycle possibly due to leaching of Ru from the support.",
keywords = "Heterogeneous catalysis, Ruthenium, Oxidation, Veratryl alcohol, Veratraldehyde",
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Aerobic Oxidation of Veratryl Alcohol to Veratraldehyde with Heterogeneous Ruthenium Catalysts. / Melián Rodriguez, Mayra; Shunmugavel, Saravanamurugan; Kegnæs, Søren; Riisager, Anders.

In: Topics in catalysis, Vol. 58, No. 14, 10.2015, p. 1036-1042.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Aerobic Oxidation of Veratryl Alcohol to Veratraldehyde with Heterogeneous Ruthenium Catalysts

AU - Melián Rodriguez, Mayra

AU - Shunmugavel, Saravanamurugan

AU - Kegnæs, Søren

AU - Riisager, Anders

PY - 2015/10

Y1 - 2015/10

N2 - Lignin is a complex polymeric molecule constituting various linkages between aromatic moieties. Typically, the β-O-4 linkage accounts for more than half of the linkage structures present in lignin. The current study focuses on the oxidative transformation of veratryl alcohol (VA)—a compound that can be formed by cleavage of β-O-4 linkages in lignin—to veratraldehyde (VAld) with air using ruthenium supported on γ-alumina or silica as catalyst with water or methanol as solvent in a batch reactor. Ru/Al2O3, prepared with ruthenium(IV)oxide hydrate showed superior catalytic activity, yielding 89 % VAld in water at 160 °C with 5 bar air pressure after 8 h of reaction. Prolonged reaction time led to significant formation of the decarbonylated product veratrol from VAld. When the reaction was completed under 20 bars of argon in methanol instead of water, the methyl ether of VA (i.e. 1,2-dimethoxy-4-(methoxymethyl)benzene) prevailed, indicating that methanol protected the hydroxyl group in VA from being oxidized to VAld. Catalysts containing alternative transition metals (Mn, Co, Cu and Ag) supported on Al2O3 gave significantly lower activities compared to Ru/Al2O3 under identical reaction conditions. The Ru/Al2O3 catalyst was reused in three consecutive reaction runs in water, but a decrease in VAld yield was obtained after the third cycle possibly due to leaching of Ru from the support.

AB - Lignin is a complex polymeric molecule constituting various linkages between aromatic moieties. Typically, the β-O-4 linkage accounts for more than half of the linkage structures present in lignin. The current study focuses on the oxidative transformation of veratryl alcohol (VA)—a compound that can be formed by cleavage of β-O-4 linkages in lignin—to veratraldehyde (VAld) with air using ruthenium supported on γ-alumina or silica as catalyst with water or methanol as solvent in a batch reactor. Ru/Al2O3, prepared with ruthenium(IV)oxide hydrate showed superior catalytic activity, yielding 89 % VAld in water at 160 °C with 5 bar air pressure after 8 h of reaction. Prolonged reaction time led to significant formation of the decarbonylated product veratrol from VAld. When the reaction was completed under 20 bars of argon in methanol instead of water, the methyl ether of VA (i.e. 1,2-dimethoxy-4-(methoxymethyl)benzene) prevailed, indicating that methanol protected the hydroxyl group in VA from being oxidized to VAld. Catalysts containing alternative transition metals (Mn, Co, Cu and Ag) supported on Al2O3 gave significantly lower activities compared to Ru/Al2O3 under identical reaction conditions. The Ru/Al2O3 catalyst was reused in three consecutive reaction runs in water, but a decrease in VAld yield was obtained after the third cycle possibly due to leaching of Ru from the support.

KW - Heterogeneous catalysis

KW - Ruthenium

KW - Oxidation

KW - Veratryl alcohol

KW - Veratraldehyde

U2 - 10.1007/s11244-015-0472-z

DO - 10.1007/s11244-015-0472-z

M3 - Journal article

VL - 58

SP - 1036

EP - 1042

JO - Topics in Catalysis

JF - Topics in Catalysis

SN - 1022-5528

IS - 14

ER -