Supercritical diethylamine facilitated loading of ultrafine Ru particles on few-layer graphene for solvent-free hydrogenation of levulinic acid to γ-valerolactone

Synergistic RuCo atomic pair with enhanced activity toward levulinic acid hydrogenation

Development of efficient metal-based catalysts is of great importance for levulinic acid (LA) hydrogenation to γ-valerolactone (GVL). The widely employed Ru-based catalysts are advantageous for H2 dissociation, however, the steric hindrance of large Ru particles hampers their coordination to CO moiety in LA, and thereby decreasing the activity. Herein, we report a Ru1Co1NC double single-atom catalyst (DSAC) with synergistic Ru and Co atomic pairs for LA hydrogenation into GVL. The Ru and Co doped zeolitic imidazole frameworks (RuCo-doped ZIF-8) precursor was rationally designed ((Ru + Co)/(Zn + Ru + Co) = 2 at.%), where the Zn node spatially isolates Ru and Co species, expanding the adjacent RuCo distance and facilitating the formation of the RuCo atomic pair upon pyrolysis, with each atom coordinated with three nitrogen atoms (N3Ru1Co1N3). The Ru1Co1NC catalyst exhibits outstanding catalytic activity, with a turnover frequency (TOF) of 1980 h-1, surpassing previously reported Ru-based catalysts. Experimental investigation and density functional theory (DFT) calculations reveal that the electron-rich Ru induced by less electronegative Co facilitates H2 dissociation, while atomic Ru in dual-atomic pairs promotes CO activation, Ru and Co atomic pairs synergistically enhancing LA conversion to GVL. This research will shed light on the precise control of active sites at atomic scale, and also provides a new concept for designing high-performance Ru-based catalysts towards LA hydrogenation to GVL.

Hydrogenation of Carboxylic Acids, Esters, and Related Compounds over Heterogeneous Catalysts: A Step toward Sustainable and Carbon-Neutral Processes

The catalytic hydrogenation of esters and carboxylic acids represents a fundamental and important class of organic transformations, which is widely applied in energy, environmental, agricultural, and pharmaceutical industries. Due to the low reactivity of the carbonyl group in carboxylic acids and esters, this type of reaction is, however, rather challenging. Hence, specifically active catalysts are required to achieve a satisfactory yield. Nevertheless, in recent years, remarkable progress has been made on the development of catalysts for this type of reaction, especially heterogeneous catalysts, which are generally dominating in industry. Here in this review, we discuss the recent breakthroughs as well as milestone achievements for the hydrogenation of industrially important carboxylic acids and esters utilizing heterogeneous catalysts. In addition, related catalytic hydrogenations that are considered of importance for the development of cleaner energy technologies and a circular chemical industry will be discussed in detail. Special attention is paid to the insights into the structure-activity relationship, which will help the readers to develop rational design strategies for the synthesis of more efficient heterogeneous catalysts.

Highly efficient and selective aqueous phase hydrogenation of aryl ketones, aldehydes, furfural and levulinic acid and its ethyl ester catalyzed by phosphine oxide-decorated polymer immobilized ionic liquid-stabilized ruthenium nanoparticles

Phosphine oxide-decorated polymer immobilized ionic liquid stabilized RuNPs catalyse the hydrogenation of aryl ketones with remarkable selectivity for the CO bond, complete hydrogenation to the cyclohexylalcohol and hydrogenation of levulinic acid to γ-valerolactone.