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

Pt-Loaded Nb─W Metal Composite Oxide for Selective Cleavage of Secondary C─O Bonds

Selective hydrogenolysis of glycerol to 1,3-propanediol (1,3-PDO) is recognized as one of the most promising reactions for the valorization of biomass. Precise activation of C─O bonds of glycerol molecule is the key step to realize the high yield of catalytic conversion. Here, a Pt-loaded Nb-W composite oxides with crystallographic shear phase for the precise activation and cleavage of secondary C─O (C(2)─O) bonds are first reported. The developed Nb14 W3 O44 with uniform structure possesses arrays of W-O-Nb active sites that totally distinct from individual WOx or NbOx species, which is superior to the adsorption and activation of C(2)─O bonds. The Nb14 W3 O44 support with rich reversible redox couples also promotes the electron feedback ability of Pt and enhances its interaction with Pt nanoparticles, resulting in high activity for H2 dissociation and hydrogenation. All these favorable factors confer the Pt/Nb14 W3 O44 excellent performance for selective hydrogenolysis of glycerol to 1,3-PDO with the yield of 75.2% exceeding the record of 66%, paying the way for the commercial development of biomass conversion. The reported catalysts or approach can also be adopted to create a family of Nb-W metal composite oxides for other catalytic reactions requiring selective C─O bond activation and cleavage.

Development of a chromium oxide loaded mesoporous silica as an efficient catalyst for carbon dioxide-free production of ethylene oxide

Ethylene oxide (EO) is a significant raw material used in many commodities for consumers, particularly ethoxylates, polymers, and certain other glycol derivatives. We synthesized a catalyst by incorporation of chromium oxide into a mesoporous silica material (Cr/MSM) via the hydrothermal method, an effective catalyst for partial ethylene oxidation for producing carbon dioxide (CO2) free EO. Subsequently, XRD, BET, XPS, and TEM were used to analyse the structural characteristics of the Cr/MSM catalyst. The catalytic performance of the synthesized catalyst was assessed in the liquid-phase epoxidation (LPE) of ethylene, utilizing peracetic acid (PAA) as an oxidant. This approach not only circumvented the generation of CO2 but also mitigated the risk of metal leaching. Confirmation of the successful production of EO was achieved through GC chromatography, where the presence of a peak with a retention time (RT) of 8.91 minutes served as conclusive evidence. We systematically explored a range of reaction parameters, including temperature, catalyst concentration, the molar ratio of ethylene to PAA, and solvent effect. This comprehensive investigation aimed to fine-tune the reaction conditions, ultimately improving ethylene conversion and enhancing the selectivity of the catalyst for EO production. This approach can effectively resolve the issues of greenhouse gas emissions and metal leaching that had been associated with previously reported catalysts.

Ru-MnOx Interaction for Efficient Hydrodeoxygenation of Levulinic Acid and Its Derivatives

Metal-oxide interaction was widely observed in supported metal catalysts, playing a significant role in tuning the catalytic performance. Here, we reported that the interaction of Ru and MnO_x was able to facilitate the hydrodeoxygenation of levulinic acid (LA) to 2-butanol with a high turnover frequency (1.99 × 10⁶ h^-1), turnover number (4411), and yield (98.8%). Moreover, this catalyst was capable of removing the hydroxymethyl group of lactones and diol with high yields of products. The high activity of the Ru-MnO_x catalyst was due to the strong Ru-MnO_x interaction, which facilitated reduction of Ru oxide to Ru⁰ and Mn oxide to Mn²⁺. The increased fractions of Ru⁰ and Mn²⁺ provided metal and Lewis acid sites, respectively, and therefore facilitated LA hydrodeoxygenation. A linear correlation between the hydrodeoxygenation activity of the Ru-MnO_x catalyst and [Mn²⁺]ln([Ru⁰]) was observed.

Selective Hydrodeoxygenation of Esters to Unsymmetrical Ethers over a Zirconium Oxide-Supported Pt-Mo Catalyst

The catalytic hydrodeoxygenation (HDO) of carbonyl oxygen in esters using H₂ is an attractive method for synthesizing unsymmetrical ethers because water is theoretically the sole coproduct. Herein, we report a heterogeneous catalytic system for the selective HDO of esters to unsymmetrical ethers over a zirconium oxide-supported platinum-molybdenum catalyst (Pt-Mo/ZrO₂). A wide range of esters were transformed into the corresponding unsymmetrical ethers under mild reaction conditions (0.5 MPa H₂ at 100 °C). The Pt-Mo/ZrO₂ catalyst was also successfully applied to the conversion of a biomass-derived triglyceride into the corresponding triether. Physicochemical characterization and control experiments revealed that cooperative catalysis between Pt nanoparticles and neighboring molybdenum oxide species on the ZrO₂ surface plays a key role in the highly selective HDO of esters. This Pt-Mo/ZrO₂ catalyst system offers a highly efficient strategy for synthesizing unsymmetrical ethers and broadens the scope of sustainable reaction processes.

In Situ Ruthenium Catalyst Modification for the Conversion of Furfural to 1,2-Pentanediol

Exploiting biomass to synthesise compounds that may replace fossil-based ones is of high interest in order to reduce dependence on non-renewable resources. 1,2-pentanediol and 1,5-pentanediol can be produced from furfural, furfuryl alcohol or tetrahydrofurfuryl alcohol following a metal catalysed hydrogenation/C-O cleavage procedure. Colloidal ruthenium nanoparticles stabilized with polyvinylpyrrolidone in situ modified with different organic compounds are able to produce 1,2-pentanediol directly from furfural in a 36% of selectivity at 125 °C under 20 bar of H₂ pressure.

Taming the butterfly effect: modulating catalyst nanostructures for better selectivity control of the catalytic hydrogenation of biomass-derived furan platform chemicals

This minireview highlights versatile routes for catalyst nanostructure modulation for better hydrogenation selectivity control of typical biomass-derived furan platform chemicals to tame the butterfly effect on the catalytic selectivity.

Progress in Production of 1, 3-propanediol From Selective Hydrogenolysis of Glycerol

1,3-propanediol (1,3-PDO) is an important bulk chemical widely used in the polyester and polyurethane industry. The selective hydrogenolysis of glycerol to value-added 1,3-PDO is extremely attractive. However, the formation of 1,3-PDO is less thermodynamically stable than 1,2-PDO, and the steric hindrance effect in the reaction process makes the highly selective production of 1,3-PDO a great challenge. In this mini review, the recent research progress on the selective catalytic hydrogenolysis of glycerol to 1,3-PDO is overviewed and the catalytic mechanism of the reaction is summarized. We mainly focus on the different performances of each type of catalyst (Pt-W-based catalysts, Ir-Re based-catalysts, and other types) as well as the interactions between metals and supports. Finally, several personal perspectives on the opportunities and challenges within this promising field are discussed.

Recent Advances in Glycerol Catalytic Valorization: A Review

Once a biorefinery is ready to operate, the main processed materials need to be completely evaluated in terms of many different factors, including disposal regulations, technological limitations of installation, the market, and other societal considerations. In biorefinery, glycerol is the main by-product, representing around 10% of biodiesel production. In the last few decades, the large-scale production of biodiesel and glycerol has promoted research on a wide range of strategies in an attempt to valorize this by-product, with its transformation into added value chemicals being the strategy that exhibits the most promising route. Among them, C3 compounds obtained from routes such as hydrogenation, oxidation, esterification, etc. represent an alternative to petroleum-based routes for chemicals such as acrolein, propanediols, or carboxylic acids of interest for the polymer industry. Another widely studied and developed strategy includes processes such as reforming or pyrolysis for energy, clean fuels, and materials such as activated carbon. This review covers recent advances in catalysts used in the most promising strategies considering both chemicals and energy or fuel obtention. Due to the large variety in biorefinery industries, several potential emergent valorization routes are briefly summarized.

Recent Advances in Ruthenium-Catalyzed Hydrogenation Reactions of Renewable Biomass-Derived Levulinic Acid in Aqueous Media

Levulinic acid (LA) is classified as a key platform chemical for the development of future biorefineries, owing to its broad spectrum of potential applications and because it is simply available from lignocellulosic biomass through inexpensive and high-yield production routes. Catalytic hydrogenation reactions of LA into the pivotal intermediate compound γ-valerolactone (GVL), and beyond GVL to yield valeric acid (VA), 1,4-pentanediol (1,4-PDO), and 2-methyltetrahydrofuran (2-MTHF) have gained considerable attention in the last decade. Among the various transition metals used as catalysts in LA hydrogenation reactions, ruthenium-based catalytic systems have been the most extensively applied by far, due to the inherent ability of ruthenium under mild conditions to hydrogenate the keto functionality of LA selectively into an alcohol group to form 4-hydroxyvaleric acid intermediate, which yields GVL spontaneously after dehydration and cyclization. This review focuses on recent advances in the field of aqueous-phase ruthenium-catalyzed hydrogenation reactions of LA toward GVL, VA, 1,4-PDO, 2-MTHF, 2-pentanol, and 2-butanol. It employs heterogeneous catalysts on solid supports, and heterogeneous water-dispersible catalytic nanoparticles or homogeneous water-soluble catalytic complexes with biphasic catalyst separation, for the inter alia production of advanced biofuels such as valeric biofuels and other classes of liquid transportation biofuels, value-added fine chemicals, solvents, additives to gasoline, and to food as well. The significance of the aqueous solvent to carry out catalytic hydrogenations of LA has been highlighted because the presence of water combines several advantages: (i) it is highly polar and thus an ideal medium to convert polar and hydrophilic substrates such as LA; (ii) water is involved as a byproduct; (iii) the presence of the aqueous solvent has a beneficial effect and enormously boosts hydrogenation rates. In sharp contrast, the use of various organic solvents gives rise to a dramatic drop in catalytic activities. The promotional effect of water was proven by numerous experimental investigations and several theoretical studies employing various types of catalytic systems; (iv) the large heat capacity of water renders it an excellent medium to perform large scale exothermic hydrogenations more safely and selectively; and (v) water is a non-toxic, safe, non-inflammable, abundantly available, ubiquitous, inexpensive, and green/sustainable solvent.