Structure‐Reactivity Relations in Ruthenium Catalysed Furfural Hydrogenation

Nb-Based Catalysts for the Valorization of Furfural into Valuable Product through in One-Pot Reaction

Nb-based catalysts supported on porous silica with different textural properties have been synthesized, characterized, and tested in the one-pot reaction of furfural to obtain valuable chemicals. The catalytic results reveal that the presence of fluoride in the synthesis, which limits the growing of the porous silica, limits diffusional problems of the porous silica, obtaining higher conversion values at shorter reaction times. On the other hand, the incorporation of NbOx species in the porous silica provides Lewis acid sites and a small proportion of Brönsted acid sites, in such a way that the main products are alkyl furfuryl ethers, which can be used as fuel additives.

Converting waste tires into p-cymene through hydropyrolysis and selective gas-phase hydrogenation/dehydrogenation

The resource utilization and valorization of waste tires (WT) are of significant importance in reducing environmental pollution. To produce high-value p-cymene from WT, we propose a catalytic cascade process combining hydropyrolysis and catalytic gas-phase hydrotreating in a two-stage fixed-bed reactor. The effect of catalysts prepared with three different acidic supports on the hydrogenation/dehydrogenation of limonene, a compound derived from the hydropyrolysis of WT, was investigated. The p-cymene formation could be controlled by optimizing process parameters, including hydropyrolysis temperature, hydrogenation temperature, and catalyst-to-feedstock ratio (C/F). Experimental results indicated that, in the absence of a catalyst, limonene was the main product of WT depolymerization. Under optimized conditions (hydropyrolysis temperature of 425 ℃, hydrotreating temperature of 400 ℃, C/F of 10:1, and reaction pressure of 0.15 MPa), the highest relative content of p-cymene (79.1%) was obtained over the Pd/SBA-15 catalyst. This demonstrates that our proposed catalytic cascade process of hydropyrolysis and selective gas-phase hydrogenation/dehydrogenation can convert WT into p-cymene with high added value.

Rate Equations of Structure-Sensitive Catalytic Reactions with Arbitrary Kinetics

A general mathematical framework for the quantitative description of the cluster size dependence in heterogeneous catalytic reactions has been developed based on an analysis of the Gibbs energy of elementary reactions. The methodology was illustrated for a generic linear sequence of elementary reactions with three steps, a multi-step mechanism of ethanol oxidation comprising linear, nonlinear and quasi-equilibria steps and a network of parallel reactions in transformations of furfural.

Hydrogenation of furfural over Pd@ZIF-67 derived catalysts: direct hydrogenation and transfer hydrogenation

Pd particles coated with ZIF-67 (Pd@ZIF-67) was prepared from the self-reduction of palladium acetate.

Pathway to fully-renewable biobased polyesters derived from HMF and phenols

Building on previous work where 5-hydroxymethylfurfural (HMF) was selectively functionalized by etherification with phenols, we demonstrated that the oxidized versions of these HMF ethers can be converted to functionalized δ-hexalactones...

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.

Highly Dispersed CoNi Alloy Embedded in N-doped Graphitic Carbon for Catalytic Transfer Hydrogenation of Biomass-derived Furfural

The development of efficient, stable, and cost-effective heterogeneous catalysts for catalytic transfer hydrogenation (CTH) of biomass-derived furfural (FAL) is highly desired. Herein, series of N-doped graphitic carbon embedded CoNi bimetallic alloy nanoparticles were fabricated and used for the CTH of FAL to value-added furfuryl alcohol (FOL) with renewable isopropanol as hydrogen donor. Intrinsic catalytic activity examination indicated the catalytic performance of Ni_x Co_y @NGC (x:y=1 : 3, 1 : 1, 3 : 1) nanocatalysts were sensitive to their chemical compositions. The optimal Ni₁ Co₁ @NGC nanocatalyst with Ni/Co mole ratio of 1 : 1 afforded a largest FOL yield of 89.3% with nearly full conversion of FAL. The synergistic effect enabled by bimetallic alloys and the abundant N-based Lewis base sites and surface Co-N active species were revealed based on systematic structural characterization, responsible for the excellent catalytic efficiency of bimetallic Ni₁ Co₁ @NGC nanocatalyst for CTH of FAL.

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.

Metal-Catalyzed Hydrogenation of Biomass-Derived Furfural: Particle Size Effects and Regulation Strategies

The hydrogenation of furfural (FUR), a typical bio-based furan derivative, is a critical reaction within the roadmap for upgrading lignocellulosic biomass into high value-added chemicals and liquid fuels, the performance of which is strongly correlated with the catalysts' intrinsic peculiarities. Metal catalysts with tailorable sizes, uniform dispersions and robust sintering resistance are generally recognized as a prerequisite for obtaining better hydrogenation activity, selectivity and stability, which has prompted intensive research into metal particle size effects and their regulation strategies. The roles of metal particle sizes and corresponding dispersions of metal catalysts used for FUR hydrogenation have been clearly recognized to be crucial over the past decade. In this regard, this systematic Minireview aims to provide profound insights into particle size effects in the metal-catalyzed hydrogenation of FUR, as well as conditional and structural approaches to regulating these effects. In addition, from the aspect of catalyst stability, the impacts and improvements of the metal particle sintering issue are analyzed. Moreover, several suggestions are proposed in response to the challenges in regulating particle size effects. Furthermore, the viewpoints presented herein would potentially contribute to the rational development of metal hydrogenation catalysts and further help to boost a more sustainable biomass refining system.

Metal-Acid Synergy: Hydrodeoxygenation of Anisole over Pt/Al-SBA-15

Hydrodeoxygenation (HDO) is a promising technology to upgrade fast pyrolysis bio-oils but it requires active and selective catalysts. Here we explore the synergy between the metal and acid sites in the HDO of anisole, a model pyrolysis bio-oil compound, over mono- and bi-functional Pt/(Al)-SBA-15 catalysts. Ring hydrogenation of anisole to methoxycyclohexane occurs over metal sites and is structure sensitive; it is favored over small (4 nm) Pt nanoparticles, which confer a turnover frequency (TOF) of approximately 2000 h^-1 and a methoxycyclohexane selectivity of approximately 90 % at 200 °C and 20 bar H₂ ; in contrast, the formation of benzene and the desired cyclohexane product appears to be structure insensitive. The introduction of acidity to the SBA-15 support promotes the demethyoxylation of the methoxycyclohexane intermediate, which increases the selectivity to cyclohexane from 15 to 92 % and the cyclohexane productivity by two orders of magnitude (from 15 to 6500 mmol g_Pt ^-1  h^-1 ). Optimization of the metal-acid synergy confers an 865-fold increase in the cyclohexane production per gram of Pt and a 28-fold reduction in precious metal loading. These findings demonstrate that tuning the metal-acid synergy provides a strategy to direct complex catalytic reaction networks and minimize precious metal use in the production of bio-fuels.

Exploring the Reaction Mechanisms of Furfural Hydrodeoxygenation on a CuNiCu(111) Bimetallic Catalyst Surface from Computation

In this study, the selectively catalytic hydrodeoxygenation of furfural (F-CHO) to 2-methylfuran (F-CH₃) on the CuNiCu(111) bimetallic catalyst surface was systematically investigated based on the periodic density functional theory, including dispersion correction. The formation of furfuryl alcohol (F-CH₂OH) involved two steps: the preferred first step was the hydrogenation of the branched C atom, forming the alkoxyl intermediate (F-CHO + H = F-CH₂O), and the second step was H addition to the alkoxyl group, resulting in furfuryl alcohol (F-CH₂O + H = F-CH₂OH), which was the rate-controlling step. In contrast, in the formation of 2-methylfuran, the first step was the dehydroxylation of furfuryl alcohol, resulting in alkyl (F-CH₂) and OH (F-CH₂OH = F-CH₂ + OH) groups, the second step was the hydrogenation of F-CH₂ (F-CH₂ + OH + H = F-CH₃ + OH), and the rate-controlling step was the hydrogenation of OH to H₂O (OH + H = H₂O). Based on the comparison results of the NiCuCu(111), Cu(111), and CuNiCu(111) surfaces, it was concluded that the catalytic performance of the catalyst was closely related to the adsorption structure of furfural. These results provide a basis for studying the intrinsic activity of NiCu catalysts during the hydrodeoxygenation of refined oxygenated compounds involving biomass-derived oils.

Biomass valorisation over metal-based solid catalysts from nanoparticles to single atoms

Heterogeneous catalysts are vital to unlock superior efficiency, atom economy, and environmental friendliness in chemical conversions, with the size and speciation of the contained metals often playing a decisive role in the activity, selectivity and stability. This tutorial review analyses the impact of these catalyst parameters on the valorisation of biomass through hydrogenation and hydrodeoxygenation, oxidation, reforming and acid-catalysed reactions, spanning a broad spectrum of substrates including sugars and platform compounds obtained from (hemi)cellulose and lignin derivatives. It outlines multiple examples of classical structure sensitivity on nanoparticle-based materials with significant implications for the product distribution. It also shows how the recently emphasised application of metals in the form of ultrasmall nanoparticles (<2 nm), clusters and single atoms, while fulfilling superior metal utilisation and robustness, opens the door to unprecedented electronic and geometric properties. The latter can lead to facilitated activation of reactants as well as boosted selectivity control and synergy between distinct active sites in multifunctional catalysts. Based on the analysis conducted, guidelines for the selection of metals for diverse applications are put forward in terms of chemical identity and structure, and aspects that should be explored in greater depth for further improving the exploitation of metals in this research field and beyond are highlighted.

Influence of Structure Sensitivity on Apparent Activation Energy of Parallel Heterogeneous Catalytic Reactions

Abstract

Analysis of apparent activation energy is presented for different heterogeneous catalytic reactions with parallel reaction routes. In the case of kinetic coupling between catalytic cycles the activation energy in a particular route depends not only on the activation energies of the elementary steps comprising this route, but also on the frequency of the steps in a parallel route. Expressions were derived for coupling between routes through irreversible adsorption of the substrate, quasi-equilibrated binding as well as different substrate adsorption modes. Theoretical analysis of the apparent activation energy was extended for the reaction network with two routes possessing mechanistically different rate determining steps (i.e. monomolecular vs bimolecular). For structure sensitive reactions an expression for the apparent activation energy for parallel reactions was developed for cases with a continuous distribution of active centers and a cubo-octahedral representation of the metal clusters. A comparison between the theoretical analysis and experimental data on transformations of furfural to furfuryl alcohol and furan on ruthenium clusters shows applicability of the developed theoretical framework.

Graphic Abstract