Demethoxylation was kinetically and spectroscopically studied over three catalysts with different Ru^(0)/Ru^(δ+) ratios.In-situ spectroscopic tests demonstrated that the synergy between Ru^(0)and Ru^(δ+) was crucial...Demethoxylation was kinetically and spectroscopically studied over three catalysts with different Ru^(0)/Ru^(δ+) ratios.In-situ spectroscopic tests demonstrated that the synergy between Ru^(0)and Ru^(δ+) was crucial,and Ru^(0) was in charge of H_(2) activation and adsorption of aromatic ring while Ru^(δ+) adsorbed with O in methoxyl.A Langmuir-Hinshelwood kinetic model was proposed,and ratio of Ru^(0)/Ru^(δ+) was the key in deciding the rate-determining step(RDS):i)desorp-tion of toluene was RDS over catalyst with highRu^(0)ratio;ii)dissociation of H_(2) was RDS over Ru^(δ+) enriched catalyst;iii)demethoxylation was rate-determined by CO water-gas shift (WGS) when Ru^(0)/Ru^(δ+) approached~1.The best perfor-mance was obtained over Ru/NiAl_(2)O_(4)-200,which effectively enabled both C-O bond activation and rapid recovery of adsorption sites for aromatic rings.Finally,in-situ DRIFT studies on methoxy decomposition and CO-WGS unraveled that the electronic composition of Ru was more stable in Ru/NiAl_(2)O_(4)-200 which contributes to its excellence.展开更多
Transformation of lignin into high-value chemicals is hampered by the complexity of monomers obtained from lignin depolymerization. Here we report a strategy, composed of hy-dro-demethoxylation and de-alkylation react...Transformation of lignin into high-value chemicals is hampered by the complexity of monomers obtained from lignin depolymerization. Here we report a strategy, composed of hy-dro-demethoxylation and de-alkylation reactions, that is able to chemically converge various lig-nin-derived phenolic monomers into phenol in a single-step. Using 2-methoxy-4-propylphenol as a model compound, Pt/C exhibited the best performance in hydro-demethoxylation reaction afford-ing 80% 4-propylphenol from 2-methoxy-4-propylphenol, while H-ZSM-5 was identified as the most suitable catalyst for de-alkylation, achieving 83% yield of phenol from 4-propylphenol. Since the two catalysts operate under compatible conditions, combining the two catalysts to simultane-ously promote both hydro-demethoxylation and de-alkylation reactions was achieved. Configura-tion of how to organize the catalysts is a critical parameter, where the physical mixture of the two was most effective, providing over 60% phenol from 2-methoxy-4-propylphenol in a single-step.展开更多
基金supported financially by the National Key Research and Development Program of China(No.2022YFA1504900)the NSFC of China(No.22072041,21832002)the Science and Technology Commission of Shanghai Municipality(10dz2220500).
文摘Demethoxylation was kinetically and spectroscopically studied over three catalysts with different Ru^(0)/Ru^(δ+) ratios.In-situ spectroscopic tests demonstrated that the synergy between Ru^(0)and Ru^(δ+) was crucial,and Ru^(0) was in charge of H_(2) activation and adsorption of aromatic ring while Ru^(δ+) adsorbed with O in methoxyl.A Langmuir-Hinshelwood kinetic model was proposed,and ratio of Ru^(0)/Ru^(δ+) was the key in deciding the rate-determining step(RDS):i)desorp-tion of toluene was RDS over catalyst with highRu^(0)ratio;ii)dissociation of H_(2) was RDS over Ru^(δ+) enriched catalyst;iii)demethoxylation was rate-determined by CO water-gas shift (WGS) when Ru^(0)/Ru^(δ+) approached~1.The best perfor-mance was obtained over Ru/NiAl_(2)O_(4)-200,which effectively enabled both C-O bond activation and rapid recovery of adsorption sites for aromatic rings.Finally,in-situ DRIFT studies on methoxy decomposition and CO-WGS unraveled that the electronic composition of Ru was more stable in Ru/NiAl_(2)O_(4)-200 which contributes to its excellence.
文摘Transformation of lignin into high-value chemicals is hampered by the complexity of monomers obtained from lignin depolymerization. Here we report a strategy, composed of hy-dro-demethoxylation and de-alkylation reactions, that is able to chemically converge various lig-nin-derived phenolic monomers into phenol in a single-step. Using 2-methoxy-4-propylphenol as a model compound, Pt/C exhibited the best performance in hydro-demethoxylation reaction afford-ing 80% 4-propylphenol from 2-methoxy-4-propylphenol, while H-ZSM-5 was identified as the most suitable catalyst for de-alkylation, achieving 83% yield of phenol from 4-propylphenol. Since the two catalysts operate under compatible conditions, combining the two catalysts to simultane-ously promote both hydro-demethoxylation and de-alkylation reactions was achieved. Configura-tion of how to organize the catalysts is a critical parameter, where the physical mixture of the two was most effective, providing over 60% phenol from 2-methoxy-4-propylphenol in a single-step.
