New Routes for Refinery of Biogenic Platform Chemicals Catalyzed by Cerium Oxide-supported Ruthenium Nanoparticles in Water

Abstract

Highly selective hydrogenative carbon-carbon bond scission of biomass-derived platform oxygenates was achieved with a cerium oxide-supported ruthenium nanoparticle catalyst in water. The present catalyst enabled the selective cleavage of carbon-carbon σ bonds adjacent to carboxyl, ester, and hydroxymethyl groups, opening new eight synthetic routes to valuable chemicals from biomass derivatives. The high selectivity for such carbon-carbon bond scission over carbon-oxygen bonds was attributed to the multiple catalytic roles of the Ru nanoparticles assisted by the in situ formed Ce(OH) 3 .Current requirements to reduce carbon dioxide emissions have been the driving force for biorefinery utilizing renewable resources, such as plant biomass, as carbon-neutral feedstocks for commodity chemicals [1][2][3][4][5][6][7] . The development of highly efficient catalytic methods would greatly accelerate the utilization of biomass feedstocks in place of fossil resources. To date, much effort has been devoted to the direct carbon-oxygen (C-O) bond cleavage of high-oxygen containing biogenic polyols to produce valuable chemicals by hydrogenolysis and deoxydehydration 8,9 . For example, there are many attempts for the selective hydrogenolysis of glycerol, facilely obtained from fats and oils, to 1,2-propanediol and 1,3-propanediol as the valuable polyester monomers and solvents using the copperand platinum-based heterogeneous catalysts, respectively 10,11 . On the other hand, selective cleavage of carboncarbon (C-C) bonds has not yet been widely researched despite its great potential for extending the utility of biomass-derived oxygenates to obtain the desired carbon chain length [12][13][14] . The existing C-C bond cleavage methods include cracking, hydrocracking, decarbonylation, and decarboxylation 15 . However, these reactions often suffer from low selectivity toward the desired chemicals, limited substrate scope, and high reaction temperatures. Recently, decarboxylation reactions of fatty acids using Ni and Pd catalysts have been reported for the production of biofuels; however, these methods still require harsh reaction conditions [16][17][18] . Therefore, the development of selective and versatile C-C bond scission catalysts able to work under milder conditions is highly desired to open new routes for industrially important chemicals from a wide range of biomass derivatives 4 . In this work, we found that cerium oxide-supported ruthenium nanoparticles (Ru/CeO 2 ) efficiently promote the selective C-C bond scission of levulinic acid (LA) to 2-butanol (2-BuOH) in water. There are many reports on the catalytic transformation of LA to value-added C5 chemicals: e.g. γ-valerolactone (GVL) 19 ,1, 19 , and 2-methyltetrahydrofuran (MTHF) 20 . However, there are fewer examples of the refinery of LA into valuable C4 chemicals such as 2-butanol through C-C bond scission reactions 21 . The high generality of this method is demonstrated by its broad substrate scope for oxygenated compounds, where the cleavage of C-C bonds occurs chemosp...

Selective C−C Hydrogenolysis of Alkylbenzenes to Methylbenzenes with Suppression of Ring Hydrogenation

“…Too high H 2 pressure may lead to high selectivity to ring‐hydrogenated products. In fact, hydrogenation of aromatic ring over Ru/CeO 2 catalysts under high‐pressure H 2 (a few MPa) in batch reactor has been reported ,. At 533 K under H 2 /N 2 =3, 65 % yield of toluene (theoretical maximum=88 %) was obtained at W / F =0.4 g cat h −1 mol −1 .…”

Development of High Performance Heterogeneous Catalysts for Selective Cleavage of C−O and C−C Bonds of Biomass‐Derived Oxygenates

“…. We found that cerium‐oxide‐supported ruthenium nanoparticles (Ru/CeO 2 ) efficiently promote selective C−C bond scission of LA to 2‐butanol (2‐BuOH) in water . The high generality of this method is demonstrated by its broad substrate scope for oxygenated compounds, in which the cleavage of C−C bonds occurs chemospecifically at positions adjacent to the carboxyl, ester, and hydroxymethyl groups of oxygenated compounds (Figure ).…”

“… Time profiles of the hydrogenative decarboxylation of LA using Ru/CeO 2 . The reaction conditions were the same as those in Table , entry 1 …”

“… FE‐SEM images of (a) fresh Ru/CeO 2 and (b) used Ru/CeO 2 , and HR‐TEM images of (c, d) used Ru/CeO 2 . Yellow circles show the presence of Ru nanoparticles …”

“…Encouraged by these achievements, we applied our macroligand concept to the valorization of biogenic platform chemicals such as glycerol (C3), furfural (C5), and levulinic acid (C5) via selective cleavage of C−O bonds and C−C bonds. In this account, we describe our recent studies of the development of high‐performance macroligand catalysts aiming at a biomass refinery; i. e. transformation of glycerol, furfural, and levulinic acid to corresponding diols via selective cleavage of C−O and C−C bonds. Also, in addition to these cleavage reactions, the valorization of glycerol by acetylation and acetalization, and of levulinic acid by hydrogenation and one‐pot synthesis of 2‐methyltetrahydrofuran using our highly active heterogeneous catalysts were involved.…”