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This density functional theory (DFT) study explores the efficacy of cooperative catalytic systems in enabling the ionic hydrogenation of N2 with H2, leading to NH3 formation. A set of N-heterocyclic carbene-based pincer tungsten/molybdenum metal complexes of the form [(PCP)M1(H)2] (M1 = W/Mo) were chosen to bind N2 at the respective metal centres. Simultaneously, cationic rhodium/iridium complexes of type [Cp*M2{2-(2-pyridyl)phenyl}(CH3CN)]+ (Cp* = C5(CH3)5 and M2 = Rh/Ir), are employed as cooperative coordination partners for heterolytic H2 splitting. The stepwise transfer of protons and hydrides to the bound N2 and intermediate NxHy units results in the formation of NH3. Interestingly, the calculated results reveal an encouraging low range of energy spans ranging from ∼30 to 42 kcal mol−1 depending on different combinations of ligands and metal complexes. The optimal combination of pincer ligand and metal center allowed for an energy span of unprecedented 29.7 kcal mol−1 demonstrating significant potential for molecular catalysts for the N2/H2 reaction system. While exploring obvious potential off-cycle reactions leading to catalyst deactivation, the computed results indicate that no increase in energy span would need to be expected. [ABSTRACT FROM AUTHOR]

The synthesis of a hierarchical SSZ-13 zeolite with mesopores and micropores is one of the most effective strategies to overcome the diffusion limitation imposed by the micropores of SSZ-13 in reactions involving bulky reactants or intermediates. A zeolite with nanosheet morphology possesses the advantages of large inter-sheet mesopore volume, more accessible acid sites and short diffusion path lengths. Nevertheless, only a few works focused on the synthesis of the nanosheet-assembled SSZ-13 zeolite. In this work, a nanosheet-assembled hierarchical SSZ-13-TP0.03 (thickness of 20 nm) zeolite was synthesized in a seed-assisted synthesis system by coupling a small amount of N, N, N-trimethyl-1-adamantylammonium hydroxide (TMAdaOH) with octadecyl-(3-trimethoxysilylpropyl)-ammonium chloride (TPOAC). In this strategy, the Si/Al ratio of the initial gel, seed, TPOAC and TMAdaOH amount in the synthesis system and the synergistic effects among them lead to the synthesis of SSZ-13 samples with various textural properties and morphologies. The distinct textural properties and morphologies of SSZ-13 result in the preparation of Pt/SSZ-13 catalysts with varied Pt dispersions. The catalyst, Pt supported on the nanosheet-assembled hierarchical SSZ-13 (Pt/SSZ-13-TP0.03), exhibits higher hydrogenation ability than its corresponding catalyst, Pt supported on microporous or hierarchical SSZ-13 in the hydrogenation of naphthalene. [ABSTRACT FROM AUTHOR]

Carbon-supported non-precious metal catalysts with highly exposed active sites have great potential for applications in the hydrogenation reduction of nitro compounds. Herein, a strategy for the preparation of carbon-supported Mo-based catalysts (Mo@C/MC) is proposed. Protein–Mo ion networks are first coated on the surface of microsphere carbons (MC). The coated MC employed as a precursor is then pyrolyzed to produce carbon-supported Mo-based catalysts. Notably, neither pore-forming agents nor post-treatment is required in the preparation of the catalyst. The active sites tend to disperse uniformly on the surface of the carbon matrix, facilitating the exposure of the active sites of the catalyst. The as-prepared catalyst Mo@C/MC shows high conversion (>99%) and selectivity (>98%) for the hydrogenation of nitro compounds under mild reaction conditions (100 °C, 5 bar H2). [ABSTRACT FROM AUTHOR]

Non-precious metal catalysts play a significant role in the field of hydrogenation. This study synthesized Co-BTC from cobalt nitrate hexahydrate and 1,3,5-tricarboxylic acid benzene. By changing the calcination temperature of Co-BTC in an inert atmosphere, a series of novel non-precious metal Co/C microsphere catalysts were successfully prepared. The composition and structure of the Co/C-n catalysts were characterised by FESEM, TEM, XRD, IR, XPS and BET. These results confirm that 1,3,5-benzenetricarboxylic acid provides a rich carbon matrix and metallic Co nanoparticles are generated by self-reduction on the carbon matrix. The graphite matrix formed during the calcination process has a rich pore structure and good dispersion of active components on the catalyst surface, which is very favourable for the catalytic reaction. In the hydrogenation of o-chloronitrobenzene (o-CNB) to o-chloroaniline (o-CAN), the Co/C-500 catalyst showed the best catalytic performance. At 80 °C and 2 MPa H2 for 60 minutes, the conversion rate of o-CNB reached 99% and the selectivity reached 99%. When the reaction takes 5 minutes, the conversion rate reaches 10.5%, and the TOF value reaches 36.3 h−1. The Co/C-500 catalyst can be easily recycled and reused after reaction with the help of a magnetic field. Moreover, this catalyst is also effective in the selective hydrogenation of other nitroaromatic hydrocarbons containing halogen or unsaturated groups to corresponding aniline. This simple and direct synthesis method may lead to the economic production of large-scale Co/C catalysts, which is an attractive prospect for the industrial trial production of corresponding aniline. [ABSTRACT FROM AUTHOR]

The hydrogenation of acetic acid-derived cyclohexyl acetate (CHA) is becoming a safe, efficient and promising route for the production of cyclohexanol (CHOL), an important chemical to produce e-caprolactam. In this work, Cu-Zr catalysts were prepared via different methods for the hydrogenation of CHA. The results showed that a Cu3Zr7-SG catalyst prepared by the sol-gel (SG) method was superior to Cu3Zr7-CP and Cu3Zr7-IM catalysts prepared by the coprecipitation (CP) and impregnation (IM) method, respectively. The Cu3Zr7-SG catalyst showed 97.4% CHA conversion and 95.5% selectivity to CHOL along with 96.3% selectivity to ethanol at 250 1C under 3 MPa of H2. Moreover, the Cu3Zr7-SG catalyst showed a mass specific activity of up to 29.8 gCHA gCu-1 h-1, higher than other Cu-based catalysts under similar conditions. Based on detailed characterization studies, it was found that the larger weak acid sites, more weak and moderate basic sites, higher Cu+/(Cu0 + Cu+) and oxygen vacancies on the surface of the Cu3Zr7-SG catalyst were beneficial for the hydrogenation of CHA. [ABSTRACT FROM AUTHOR]

The availability of catalytic sites for contact with reactants is a key issue to improve the performance of a catalyst, where constructing hollow structured nanomaterials has been considered as an effective strategy. Here, an N-doped carbon supported Ru catalyst with an interior cavity was synthesized by etching a MOF-derived core–shell precursor, in which metal Ru can be highly dispersed in the porous shell. This catalyst shows 98.7% conversion and >99% selectivity towards p-chloroaniline in the hydrogenation of p-chloronitrobenzene, which is better than the corresponding supported catalyst. Moreover, it also displays excellent stability with 5 cycle runs and good substrate universality for the hydrogenation of extensive substituted nitroarenes. Various characterization techniques and control experiments reveal the advantage of the unique structure to promote the mass transport and adsorption of reactant molecules on Ru sites. This work provides a novel strategy to design an efficient Ru-based catalyst for chemoselective hydrogenation. [ABSTRACT FROM AUTHOR]

In this study, 13-Ni/ZrO2, 13-Ni3P/ZrO2, 13-Ni/SiO2, and 13-Ni3P/SiO2 catalysts were used in the hydrogenation of diethyl oxalate (DEO) to ethyl glycolate (Egly) to investigate the modulating effect of phosphorus. XRD, TEM, and FT-IR spectroscopy results indicated that phosphorus acts as a distributor of Ni metallic particles and thereby shows a segregation effect. The presence of P transformed the linkage of surface metals from an original Ni–Ni–Ni–Ni– to a P–Ni–P–Ni–P state, and FT-IR spectra showed that the former adsorbed CO in a combination of linear and bridging adsorption modes, whereas the latter predominantly in CO linear adsorption. Bridging adsorption occurs via dual sites and makes preliminary hydrogenation products less likely to detach from the catalyst surface, thus facilitating deep hydrogenation, while linear adsorption facilitates partial hydrogenation via rapid detachment of intermediate products such as Egly. Different loadings of Ni3P/SiO2 catalysts show incomplete phosphorylation with an increase in nickel loading, giving rise to a state of coexistence of Ni and Ni3P crystalline phases. This may lead to a coexistence of surface Ni–Ni–Ni–Ni and P–Ni–P–Ni–P and an increase in the corresponding bridging adsorption/linear adsorption ratios, making deep hydrogenation occur partially besides stepwise hydrogenation. [ABSTRACT FROM AUTHOR]

Excessive emission of CO2 into the atmosphere has severely impacted the global ecological environment. Converting CO2 into valuable chemicals and fuels is of great significance for sustainable development. However, low activity and undesirable selectivity often result from the inherent inertness of CO2. Herein, K- or/and Zn-modified Fe-based catalysts were prepared by an incipient-wetness impregnation method for CO2 hydrogenation via a cascade reaction. The results indicate that K species exist as K2O while Zn species exist as ZnFe2O4. In the CO2 hydrogenation pathway, K2O facilitates the adsorption of CO2 and restrains the adsorption of H2, accelerating the transformation of CO2 into C2–C4 olefins rather than paraffins while Zn species promote the dispersion of Fe species, leading to improved activity. Synergistically, a K- and Zn-modified Fe-based catalyst (2Zn–10K–Fe/Al) shows excellent catalytic CO2 hydrogenation activity, achieving a CO2 conversion of 77% which is 1.8 times that (42%) of the unmodified Fe-based catalyst (Fe/Al). Our catalyst also shows a significantly promoted selectivity to C2–C4 olefins of 17% in comparison with the Fe/Al catalyst (0%). It is envisioned that such a binary effect of elements might contribute to the low-cost and industrial production of Fe-based catalysts for selective CO2 conversion. [ABSTRACT FROM AUTHOR]

Pd25Cu75@SiO2 core–shell and PdCu@SiO2@Cu core–shell–satellite architectures were fabricated by silica-coating of Pd25Cu75 colloids in a reverse microemulsion. Hydrolysis of tetraethylorthosilicate in the reverse microemulsion containing hydrazine and ammonia yielded a core–shell structure, while the use of ammonia only, instead of a mixture of hydrazine and ammonia, formed a core–shell–satellite structure. The ammonia-leached copper species migrated onto the developing silica shell and formed smaller Cu clusters. Air-calcination at 673 K followed by H2-reduction at 773 K of the as-synthesized samples removed the organic surfactants and generated the permeable porous silica shells. The core–shell catalyst consisted of a metal core (8.5 nm) and a silica shell (7.8 nm), while the core–shell–satellite catalyst was composed by a metal core (7.0 nm), a silica shell (8.0 nm), and satellite Cu clusters (1.4 nm) on the silica shell. When used to catalyze the selective hydrogenation of acetylene to ethylene, the core–shell–satellite catalyst showed substantially enhanced activity and stability because of the synergetic catalysis between the metal core and the surrounding Cu clusters. [ABSTRACT FROM AUTHOR]

Herein, we report that Pd nanoparticles (NPs) anchored on graphitic nitride carbon (Pd/g-C3N4) catalysts with various Pd contents (1.55 wt%, 0.14 wt%, 0.04 wt%) are successfully prepared via a simple NaBH4 reduction method, exhibiting excellent catalytic activity and selectivity toward 4-aminophenol (4-AP) in 4-nitrophenol (4-NP) selective hydrogenation. 4-NP is completely converted to 4-AP (yield ∼ 100%) under quite moderate reaction conditions (40 °C, 2.0 MPa H2 and 5 min) over the 1.55 wt% Pd/g-C3N4 catalyst, with a high reaction rate r = 134.4 mol4-NP molPd−1 min−1. The excellent catalytic performance can be attributed to the following reasons: (1) a higher ratio of Pd(0)/Pdn+ provides much more exposed active sites for the potential adsorption and activation of the reactants, which is beneficial for increasing the reaction rate and catalytic activity; (2) Pd NPs are highly dispersed on g-C3N4 due to the strong interaction of Pd–N or Pd–C; (3) the interfacial synergism effect between Pd NPs and g-C3N4 enables the effective adsorption and activation of H2 (4-NP) at Pd (g-C3N4), promoting the catalytic hydrogenation of 4-NP and improving their catalytic properties. In addition, this catalyst has superior reusability. [ABSTRACT FROM AUTHOR]

We studied the Ni–Cu-acid multifunctional synergism in NiCu-phyllosilicate catalysts toward 1,4-butynediol hydrogenation to 1,4-butanediol by varying the reduction temperature, which can activate different bimetal and support interactions. Compared with a monometallic Ni phyllosilicate (phy), which only showed one type of metal species when reduced at ∼750 °C, there are three types of metal species for the bimetallic Ni–Cu-phyllosilicate derived catalysts, namely Cuphy, differentiated Ni, and Niphy. Thorough structure–activity/selectivity correlation investigations showed that, although the Ni9Cu1-P catalyst matrix can produce tiny amounts of differentiated Ni0 species under the induction of reduced Cu0 at R250 condition, it could not form Ni–Cu bimetallic interactions for the collaborative hydrogenation of 1,4-butynediol, and the product stays in the semi hydrogenated state. When the reduction temperature is raised to 500 °C, stable Ni–Cu alloy active sites exist, accompanied by the strong metal support interaction and metal acid effect derived from the intimate contact between the extracted metal sites and the surviving functional phyllosilicate support; these functionalities yield a supreme hydrogenation performance of the R500 sample with a 1,4-butanediol yield larger than 91.2%. [ABSTRACT FROM AUTHOR]

The selective depolymerization of PET plastics to p-xylene (xylene) is very challenging owing to the full deoxygenation of the terephthalic acid monomer and the retainment of the benzene ring through saturation. In this study, the modification of Co–Al catalysts by introducing a second metal (Fe, Cu, Ni, or Zn) was conducted to tailor the activity of the cobalt species for the conversion of PET to xylene. The results indicated that the CoFe alloy in the Co–Fe–Al catalyst weakened the adsorption/activation of H2, achieving xylene yields of >99.0% from PET. Co–Fe–Al suppressed the ring hydrogenation of the benzene ring, while Co–Al and Co–Ni–Al catalyzed the hydrogenation of the benzene ring and cleavage of the C–C bond in the intermediates. Benzene ring-containing intermediates showed a high affinity for Co–Ni–Al and Co–Al, facilitating their hydrogenation. Co–Fe–Al could preferably adsorb and activate the oxygen-containing functionalities of the intermediates for the deoxygenation reactions. The hydrogenolysis reaction of C–OH in intermediates, like 1,4-benzenedimethanol (Ea: 137.8 kJ mol−1), was the rate-determining step, while the hydrogenation of the carboxylic intermediates was much easier. [ABSTRACT FROM AUTHOR]

Carbon materials show great potential in catalytic applications, due to their advantages of wide raw material sources, stable chemical properties, and large specific surface area. In this paper, N-doped biochar was prepared from Pennisetum giganteum for supporting PdLa bimetallic nanoparticles to achieve efficient conversion of acetylene. The results showed that the conversion and ethylene selectivity of the Pd0.25La0.25/N-pgBC bimetallic catalyst could reach 100% and 94.2%, respectively. From the characterization results, it could be inferred that the electron transfer from lanthanum to palladium can weaken the ethylene adsorption onto the negatively charged Pd sites and thus improve the selectivity of Pd0.25La0.25/N-pgBC. It is noted that the bimetallic PdLa/N-pgBC catalyst showed strong component dependence, which may be caused by the difference in electronic or geometric modification caused by different metal ratios. This work has shown that the active site separation effect formed by doping inert metals is of great significance to the whole catalytic field. [ABSTRACT FROM AUTHOR]

Indirect CO2 hydrogenation to methanol and ethylene glycol is a green, efficient, and economical technique for converting CO2 into high-value chemicals to address the intractable environmental crisis caused by CO2 emissions. However, traditional methods for screening and optimizing catalysts in this process mainly depend on experience and repeated 'trial-and-error' experiments, which are resource-, time- and cost-consuming tasks. Therefore, this study developed a machine learning framework for predicting the conversion ratio of ethylene carbonate and the yield of methanol and ethylene glycol from the indirect CO2 hydrogenation technology to accelerate the catalyst screening and optimization processes. The initial dataset was visualized by conducting principal component analysis and improved to ensure sufficient information variables for the machine learning model to distinguish between catalyst types. After comparing the optimized results of three algorithms, the neural network with two hidden layers is the core of the machine learning model of the indirect CO2 hydrogenation process. It was then further optimized by a feature engineering method coupled with feature importance analysis and the Pearson correlation matrix. It indicates that the optimized neural network model has higher performance, especially in predicting ethylene carbonate conversion and product yields. Compared with other input features, the space velocity and hydrogen/ester ratio are the two most important factors affecting the conversion ratio of ethylene carbonate and the yield of methanol and ethylene glycol. Based on the results of the feature importance analysis, a multi-objective optimization model with a genetic algorithm was employed to screen the most suitable catalyst. Compared with other catalysts, more efforts should be devoted to the optimized xMoOx–Cu/SiO2 catalyst for the industrialization of indirect CO2 hydrogenation technology after experimental verification. [ABSTRACT FROM AUTHOR]

The use of molecular oxygen is unquestionably the green path to the selective oxidation of alcohols to aldehyde and ketones. However, this reaction class poses safety problems associated with mixing oxygen with organic substrates. Continuous membrane reactors offer an attractive solution, owing to their ability to keep the oxygen phase separated from the liquid substrate, while controlling the dosing of oxygen during reaction. In this work, we demonstrate a slurry loop membrane reactor for continuous oxidations as well as hydrogenations. The catalyst slurry was circulated around a loop, to which a saturator containing a flat Teflon AF-2400 membrane was connected, along with a crossflow filter to keep the catalyst particles within the loop. Under a recycle flowrate 100 times higher than the inlet, the residence time distribution was found to be comparable to that of an ideal CSTR. A remarkably high kLa of 1.2 s−1 was achieved under a moderate specific power input of 2.4 kW m−3 during styrene hydrogenation. Continuous aerobic oxidations of various primary and secondary alcohols were carried out for 6–7 h at 90–120 °C and 2–6 bar, using a 1 wt% Au-Pd/TiO2 powder catalyst, leading to conversions between 17% and 75%. The reactor could also be operated in batch mode, achieving higher conversions, while scaled-up operations produced aldehyde yields of 0.4–19 g with only 88 mg of catalyst. Overall, the slurry loop membrane reactor provides significant advantages in terms of catalyst usage and process safety for aerobic oxidations. [ABSTRACT FROM AUTHOR]

Hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) is a key reaction in the conversion of biomass to renewable fuels and value-added chemicals. Developing low-cost, highly efficient and reusable non-noble metal-based heterogeneous catalysts is vital but challenging. Herein, non-noble Ni–Mn/SiO2 catalysts with a low Ni loading (2.0 wt%) were designed for the selective hydrogenation of LA to GVL. The results showed that the optimal Ni–Mn/SiO2 (Ni/Mn = 2) catalyst with well-dispersed and small-sized metal nanoparticles (2.21 nm) and moderate acid sites exhibited excellent activity and selectivity and achieved a 100% yield of GVL in a 1,4-dioxane solvent under mild reaction conditions (e.g., 0.8 mol% Ni, 140 °C and 2.0 MPa H2) for 5.5 h and a 100% GVL yield at 180 °C for 2 h with a turnover frequency (TOF) of 190.2 h−1, which is better than most non-noble metal catalysts reported. Furthermore, the catalyst exhibited excellent reusability and could be recycled at least five times with only slight activity loss. This work provides new insights for the rational design of highly efficient and stable non-noble metal catalysts for the conversion of LA to GVL. [ABSTRACT FROM AUTHOR]

The present work describes an unprecedented blueprint for the chiral (S)-1,1′-Bi-2-naphthol ligand (BINOL) immobilized on amine functionalized mesoporous silica nanoparticles (MSNs) via a linker, which is then converted into a ruthenium complex, i.e., Ru-BINOL-AP@MSNs (where AP = (3-aminopropyl)trimethoxysilane), without the use of deprotecting or protecting groups. Using a variety of techniques, such as FTIR, N2 adsorption–desorption isotherms, solid-state 13C CP MAS NMR, powder XRD, FESEM, HRTEM, XPS, and thermogravimetric analysis, the as-synthesized catalyst was persuasively verified. Asymmetric transformations of enantiomerically enriched chiral alcohols can be achieved with the aforesaid active catalytic precursors, making the proposed method even more appealing. During the asymmetric hydrogenation reaction, the Ru-BINOL-AP@MSNs catalyst proved to be catalytically competent, leading to an 84% conversion with an enantioselectivity >90% of the R-isomer. Furthermore, the synthesized catalyst was capable of being recycled five consecutive times with only a minute loss of its effectiveness, thereby reducing solvent waste and precious metal or ligand losses. [ABSTRACT FROM AUTHOR]

Supported Pt catalysts play an important role in selective hydrogenation reactions for upgrading bio-derived chemicals, and they are traditionally prepared by methods such as deposition–precipitation (DP), wet impregnation (WI) and chemical reduction (CR) using NaBH4 and H2 under thermal conditions. This study developed a new reduction method to produce supported Pt NPs on nanofibers, in which Ti3AlC2 (a typical MAX phase) and chloroplatinic acid (H2PtCl6) were employed as raw materials, using as-produced H2 as a reducing agent under hydrothermal synthetic conditions. In the selective hydrogenation of furfural to furfuryl alcohol, the newly-developed catalyst of Pt2.0/Ti3AlxC2Ty exhibited high furfural (FUR) conversion (86.3%) and excellent furfuryl alcohol (FA) selectivity (98.1%) under optimized reaction conditions of 600 rpm, 100 °C, 3 h, and 1 MPa H2 in aqueous media. Moreover, these fibrous catalysts exhibited strong reusability and recyclability for five runs without loss of activity and selectivity. [ABSTRACT FROM AUTHOR]

Pd particles coated with ZIF-67 (Pd@ZIF-67) was prepared from the self-reduction of palladium acetate. With isopropanol as the solvent, the furfural hydrogenation reaction performances of Pd@ZIF-67 and ZIF-67 heated at different temperatures were tested in H2 and N2 reaction atmosphere, respectively. The pyrolytic carbonization of Pd@ZIF-67 and ZIF-67 produced Pd–Co@C and Co@C in carbon coating structures, respectively. It was found that furfural hydrogenation reaction systems with different catalytic active sites included direct hydrogenation with H2 as the hydrogen source, and transfer hydrogenation with isopropanol as the hydrogen donor. The Pd–Co@C and Co@C with metal active sites both experienced direct hydrogenation and transfer hydrogenation simultaneously, and the direct hydrogenation activity was higher. The ZIF-67 with Lewis acidic sites experienced transfer hydrogenation, and the catalytic activity was higher than the transfer hydrogenation activity of Pd–Co@C and Co@C. Moreover, reaction routes in which furfural direct hydrogenation and transfer hydrogenation occurred in metal active sites and Lewis acidic sites were identified. [ABSTRACT FROM AUTHOR]

Although CO2 hydrogenation to formic acid has been widely investigated, the design of highly stable and effective heterogeneous catalysts is a long-standing challenge due to the instability of the active intermediate in water. Herein, both theoretical and experimental results revealed that the active Ir-H species appearing in the CO2 hydrogenation process can be easily hydrolyzed, resulting in the deactivation of the catalyst. Further research constructed a strategy to protect the active Ir-H species by utilizing a directlyknitted PNP-based catalyst (p-PNP-Ir) for CO2 hydrogenation to formic acid. An unpredictable conversion (TON = 1.11 × 106) can be achieved using p-PNP-Ir in water, being 3.15 times higher than that using the monomer PNP-Ir. Besides, the solid catalysts can be easily recycled for at least 15 runs without activity loss, highlighting their potential for practical applications in industry. [ABSTRACT FROM AUTHOR]

The effects of Zr single atom modification on the hydrogenation mechanism of CO2 to methanol on the Cu(111) surface were investigated by density functional theory (DFT). In the HCOO pathway, 11 elementary steps were involved, which were analyzed from the aspects of kinetics and thermodynamics of each elementary reaction. bi-HCOO*, HCOOH*, H2COO*, H2COOH*, H2CO* and H3CO* are the key intermediates that are most likely to be generated. The elementary reactions of H2COO*, H2CO* and H3CO* hydrogenation have relatively high activation barriers of about 1 eV, and they are the rate-limiting steps in this pathway. The desorption barriers of HCOOH* and H2CO* are much higher than the energy barriers required for continued hydrogenation; therefore, the formation of by-products is inhibited on the Zr1–Cu single atom catalyst surface. In the COOH pathway, the hydrogenation product trans-COOH* of CO2 can further hydrogenate to t,t-COHOH* through the formation of O-H bonds; then, it facilely dissociates into COH*, and COH* continues to hydrogenate into HCOH*, H2COH* and the final product of CH3OH. The last step is the rate-limiting step, with an activation energy of 1.48 eV. In the RWGS pathway, trans-COOH* transforms to cis-COOH*, and its continued hydrogenation is more favorable than dissociation in terms of kinetics and thermodynamics. The generated HCOOH is incorporated into the HCOO pathway. The results show that the HCOO pathway is more likely to occur and has higher selectivity on Zr-modified Cu-based catalysts. [ABSTRACT FROM AUTHOR]

We studied the hydrogenation at temperatures from 313–393 K of a biomass-derived platform molecule, 5-hydroxymethyl furfural (HMF)-acetone-HMF (HAH) over Pd, Ru, and Cu based catalysts. HAH was selectively hydrogenated to produce partially-hydrogenated monomers (PHAH) over Cu and Ru catalysts and to fully-hydrogenated HAH monomers (FHAH) over the Ru catalyst. Pd based catalysts yielded a mixture of partially and fully hydrogenated monomers. Lumped reaction kinetics models were employed to quantify the kinetic behavior for hydrogenation over Ru, Cu, and Pd catalysts. The 5-step pathway exhibited over Pd and Ru catalysts consists of both series and parallel reaction steps, where HAH is both converted to fully hydrogenated products sequentially via series reactions of partially hydrogenated intermediates, as well as converted directly in parallel reactions to form the fully hydrogenated products. In contrast, the 3-step pathway over the Cu catalyst consists only of the consecutive reaction steps, where the final product was formed via series reactions of intermediate products. Additionally, reaction over the Cu catalyst did not hydrogenate the furan rings of the HAH molecule and yielded a different final product than those hydrogenation over Pd and Ru catalysts. Batch conditions are determined for each hydrogenated product that give the highest yields in both batch and plug flow reactors. [ABSTRACT FROM AUTHOR]

Metal organic frameworks (MOFs) have been applied to stabilize metal nanoparticles due to their excellent properties, but there are many different viewpoints about the interaction between MOFs and nanoparticles, which is important for catalyst activity and selectivity. Herein, Pt nanoparticles supported on ZIF-8 and ZIF-67 with the same topological structure other than the metal joint were synthesized, and crotonaldehyde hydrogenation was chosen to investigate their catalytic performance. The results indicated that both the activity and crotyl alcohol selectivity over ZIF-67 were much higher than those over ZIF-8, in which the TOF was 188.3 h−1 for Pt@ZIF-67 and 7.5 h−1 for Pt@ZIF-8. More importantly, the selective hydrogenation product of the C＝O bond (crotyl alcohol) was not detected regardless of whether Pt nanoparticles were located in the interior or exterior of ZIF-8. A series of characterizations were carried out to explore the essential difference between the two supported ZIF catalysts, such as H2-spillover property tests, TEM, XPS, CO-DRIFTS, and operando-FTIR reaction. These results suggested that the H2-spillover of the ZIFs could play an important role in hydrogenation, besides the electron transfer between Pt and the metals in the ZIFs. [ABSTRACT FROM AUTHOR]

Catalysts of 0.54% (Pt, Rh, Pd or Ru)/Co(OH)2 and 1.23% Rh/Co(OH)2 were successfully synthesized via simple hydrothermal and precipitation methods for the selective hydrogenation of nitroarenes. It was found that 0.54% Rh/Co(OH)2 outperformed other catalysts, for example, 2-chloronitrobenzene hydrogenation (with a turnover frequency (TOF) of 575 h−1) under 3.0 MPa H2 at 100 °C for 1 h (much higher than that of 1.23% Rh/Co(OH)2; TOF, 398 h−1). Through characterization of the nanostructure (XRD, TEM, HRTEM, AC-STEM (spherical aberration-corrected scanning transmission electron microscopy), AC-STEM-EDX elemental mapping and line-scanning, H2-TPD, etc.), it was confirmed that Rh was dispersed in the form of single atoms and ultrasmall nanoclusters on Co(OH)2 for 0.54% Rh/Co(OH)2. Moreover, 0.54% Rh/Co(OH)2 also exhibited high selectivity for –NO2 hydrogenation for other selected nitroarene substrates hydrogenation reactions. This was mainly attributed to the presence of Rh as single atoms or super tiny nanoclusters in 0.54% Rh/Co(OH)2, leading to a significant increase in the number of active sites, beneficial adsorption of the –NO2-group at defect-rich Co(OH)2, and an interfacial synergy effect of Rh–Co(OH)2, thus improving the catalytic performance. [ABSTRACT FROM AUTHOR]

Biofuels have generated considerable interest as a direct substituent for fossil fuels due to the energy crisis and greenhouse effect. In this article, bifunctional Pt–Mo catalyst supported on activated carbon (AC) was fabricated for in situ hydrogenation of methyl stearate to alkanes using small amounts of formic acid (FA) as a hydrogen source. A total yield of 75.3% is obtained under 290 °C for 2 h with a small FA/methyl stearate mole ratio of 3.9. Prolonging the reaction time to 6 h results in a total yield of 100%. The experimental and characterization results indicate that the strong interaction of β-Mo2C and Pt over Pt–Mo/AC catalysts give rise to excellent catalytic performance and that Pt active sites are responsible for FA dehydrogenation and decarbonylation of methyl stearate to heptadecane and Pt-doped β-Mo2C active sites catalyzing hydrodeoxygenation of methyl stearate to octadenane. This catalyst is stable during three recycles and is versatile for various feedstocks. [ABSTRACT FROM AUTHOR]

Sodium lignosulfonate (LS) was valorized to low molecular weight (Mw) fractions by combining solvothermal (SF) and catalytic hydrogenolysis/hydrogenation fragmentation (SHF) in a continuous flow system. This was achieved in either alcohol/H2O (EtOH/H2O or MeOH/H2O) or H2O as a solvent and Ni on nitrogen-doped carbon as a catalyst. The tunability according to the temperature of both SF and catalytic SHF of LS has been separately investigated at 150 °C, 200 °C, and 250 °C. In SF, the minimal Mw was 2994 g mol−1 at 250 °C with a dispersity (Đ) of 5.3 using MeOH/H2O. In catalytic SHF using MeOH/H2O, extremely low Mw was found (433 mg gLS−1) with a Đ of 1.2 combined with 34 mg gLS−1. The monomer yield was improved to 42 mg gLS−1 using dual catalytic beds. These results provide direct evidence that lignin is an unstable polymer at elevated temperatures and could be efficiently deconstructed under hydrothermal conditions with and without a catalyst. [ABSTRACT FROM AUTHOR]

5-Hydroxymethylfurfural (HMF) is a versatile furanic compound used for producing various value-added chemicals, including 2,5-dihydromethylfuran (DHMF) and 2,5-dihydromethyltetrahydrofuran (DHMTHF), via selective hydrogenation of HMF. In order to reduce the cost of highly efficient noble metal catalysts, nickel (Ni) and copper (Cu) have been developed as cheaper catalysts for this reaction. These two catalysts show good efficiency but have different selectivity towards HMF hydrogenation products. This work applied plane-wave based density functional theory (DFT) to understand the different activity and selectivity of the Ni and Cu catalysts. The interaction of precursors/products on the Ni(111), Ni(100), Cu(111) and Cu(100) facets was investigated via the adsorption calculation in gas and aqueous phases. The temperature effect was also investigated. Our results revealed that not only the energetic properties but the structural and electronic charge properties are also important for describing the different catalytic behaviors in HMF hydrogenation. [ABSTRACT FROM AUTHOR]

Novel ionic materials derived from ruthenium cluster cation and tungstoaluminate anions have been developed and are proved to be robust, efficient and recyclable catalysts toward the selective hydrogenation of methyl levulinate (ML) to gamma-valerolactone (GVL) or methyl 4-hydroxypentanoate (4-HPTM) by tuning the acidity. The structure and properties of the catalysts were characterized using elemental analysis, 1H NMR, 27Al NMR, FT-IR, X-ray diffraction, and pyridine absorbed FT-IR, etc. The catalysts not only afforded excellent conversion and selectivity for GVL (99%) or 4-HPTM (88%) in the aqueous phase under very mild conditions (25 °C) but also showed good recyclability in five consecutive cycles without any significant loss in catalytic activity. In contrast to the direct intramolecular esterification of 4-HPTM in most previous reports, further characterization revealed that intramolecular cyclization proceeded via a metal and counterion (tungstoaluminate)-assisted mechanism on the anchored Ru cluster catalyst; moreover, the strong acidity on the catalysts can hamper the conversion of 4-HPTM into GVL. This rendered the Ru cation complex/tungstoaluminate ionic materials a potential candidate for the efficient production of either GVL or 4-HPTM from ML hydrogenation under very mild conditions. [ABSTRACT FROM AUTHOR]

Herein, Cu/ZrO2 catalysts containing different Cu contents with or without La-doping were used for the selective hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG). Effects of La addition and the optimal Cu content were thoroughly investigated. It was found that the Cu0/Cu+ pairs located at interfacial sites for CuO/ZrO2 catalysts with different Cu contents played an important role in the hydrogenation of DMO to EG. Interestingly, the La-doping could make the copper dispersion increase obviously. Besides, it greatly inhibited the crystal phase transformation from tetragonal to monoclinic zirconia regardless of being calcined at 750 °C. Meanwhile, the incorporation of La promoted the activation of hydrogen although resulting in a small increase in acidic/basic sites over the catalyst surface, which led to a higher conversion of DMO while the selectivity of EG decreased slightly. As a result, 97.2% selectivity of EG, which corresponds to 100% conversion of DMO, was achieved over the La-doped CuO/ZrO2 catalyst with 33 wt% Cu content, which was also stable for more than 168 h on stream. This results revealed that the strong interaction between La promoters and Cu species was another type of important active site with high catalytic efficiency in addition to the Cu0/Cu+ site of La-doped CuO/ZrO2 catalyst. [ABSTRACT FROM AUTHOR]

Mo/TiO2 catalysts with atomic dispersion of molybdenum appear active and stable in the gas-phase hydrogenation of CO2. A comparison between various titania materials shows a crucial effect of the support surface structure on the methanol yield. Molybdenum supported at low coverage on rutile titania nanorods is the most active and methanol-selective system. From catalyst characterization by aberration-corrected scanning transmission electron microscopy, near-ambient pressure X-ray photoelectron spectroscopy, diffuse reflectance UV-vis spectroscopy, and temperature-programmed techniques, we suggest that the most active catalysts for methanol production involve ultradispersed molybdate species with high reducibility and strong interaction with the rutile support. [ABSTRACT FROM AUTHOR]

Combining glucose dehydration and the subsequent hydrogenation in one pot is a preferable approach for process development as such a method allows in situ generation of the reactive intermediate to undergo further reaction without extra energy-intensive separation. Herein, phosphotungstic acid and various types of titania (anatase, rutile, P25) supported Ru-based catalysts were considered as the dehydration and hydrogenation catalysts, respectively. Modulating the different reactant media (N2, H2), various products were obtained with GBL–H2O as the solvent. A considerable yield (42%) of levulinic acid (LA) and γ-valerolactone (GVL) (40%) were obtained in nitrogen and subsequent hydrogen. Ru/TiO2 (rutile) was the favorable hydrogenation catalyst among the three types of Ru/TiO2. Meanwhile, a certain amount of sorbitol (36%) was obtained in pure hydrogen. The hydrogenation of glucose is more likely to occur than the glucose dehydration. The physicochemical properties of the catalysts were characterized by XRD, BET, TPR, STEM and in situ CO/FT-IR, and the results show that well-dispersed Ru particles are located on the rutile crystallites, which facilitated the hydrogenation of LA. A strong metal support interaction (SMSI) was responsible for the various microstructure properties and the different hydrogenation reactivity. This work allows a better understanding of the reaction paths of glucose conversion. [ABSTRACT FROM AUTHOR]

Photocatalytic CO2 reduction is a highly vital process for converting CO2 into valuable chemicals. However, the reaction always proceeds less efficaciously at low temperature. A combination of optical and thermal conditions is one of the feasible approaches to achieve the reaction with high efficiency and has gained much attention recently. In the present work, we prepared several Co–Cu–Mn trimetallic catalysts via a simple co-precipitation method, which were used in catalyzing photothermal CO2 reduction to hydrocarbons. The metal composition and reduction temperature of the catalysts had important effects on their structural and photoelectrical characteristics and adsorption behaviors, further resulting in diverse catalytic performances. Among the prepared trimetallic catalysts, Co7Cu1Mn1Ox(200), with a Co/Cu/Mn molar ratio of 7/1/1 and reduced at 200 °C in H2 for 2 h, could produce CH4 with an activity of 14.5 mmol gcat−1 h−1 in 10% CO2/30% H2/60% N2, and CH4 and C2+ hydrocarbons with the activities of 15.9 and 7.5 mmol gcat−1 h−1 in 25% CO2/75% H2, respectively. The present strategy for constructing trimetallic oxide catalysts for the photothermal reaction not only provides a highly active catalyst for CO2 utilization, but also offers a potential possibility for reducing the high temperature of conventional thermal reactions. [ABSTRACT FROM AUTHOR]

The hydrogenative conversions of the biobased platform molecules 4-hydroxycyclopent-2-enone and cyclopentane-1,3-dione to their corresponding 1,3-diols are established using a pre-activated Knölker-type iron catalyst. The catalyst exhibits a high selectivity for ketone reduction, and does not induce dehydration. Moreover, by using different substituents of the ligand, the cis–trans ratio of the products can be affected substantially. A decent compatibility of this catalytic system with various structurally related substrates is demonstrated. [ABSTRACT FROM AUTHOR]

The development of active and selective non-noble metal-based catalysts for the chemoselective reduction of nitro compounds in aquo media under mild conditions is an attractive research area. Herein, the synthesis of subnanometric and stable cobalt nanoclusters, covered by N-doped carbon layers as core–shell (Co@NC-800), for the chemoselective reduction of nitroarenes is reported. The Co@NC-800 catalyst was prepared by the pyrolysis of the Co(tpy)2 complex impregnated on Vulcan carbon. In fact, the use of a molecular complex based on six N–Co bonds drives the formation of a well-defined and distributed cobalt core–shell nanocluster covered by N-doped carbon layers. In order to elucidate its nature, it has been fully characterized by using several advanced techniques. In addition, this as-prepared catalyst showed high activity, chemoselectivity and stability toward the reduction of nitro compounds with H2 and under mild reaction conditions; water was used as a green solvent, improving the previous results based on cobalt catalysts. Moreover, the Co@NC-800 catalyst is also active and selective for the one-pot synthesis of secondary aryl amines and isoindolinones through the reductive amination of nitroarenes. Finally, based on diffraction and spectroscopic studies, metallic cobalt nanoclusters with surface CoNx patches have been proposed as the active phase in the Co@NC-800 material. [ABSTRACT FROM AUTHOR]

The effect of supports (SiO2, ZnO, ZrO2 and Al2O3) on the hydrogenation and water-tolerance of copper catalysts were studied at reaction condition containing water. The copper catalysts with different supports showed different hydrogenation and water-tolerance performances. The result of XRD, BET, Raman, TPR, XPS, N2O titration and TEM confirmed the interactions between copper and supports, and the formation of Cu–MxOy (M = Zn, Zr, and Al) interfaces had great effects on the catalytic activity and water-tolerance performance. In particular, too strong interactions suppressed the reduction of copper oxides, resulting in a low catalytic activity. Nevertheless, the formation of Cu–MxOy could provide more active sites, which provided more chances for the reactants to touch the active sites. By this method, the loss of active sites due to competitive adsorption between water and ethyl acetate could be made up, so that the water-tolerance of copper catalysts was improved. [ABSTRACT FROM AUTHOR]

Selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde is captivating due to its industrial relevance. Herein, a two-step synthesis method was adopted to develop oxygen vacancies in Pd@ZrO2 catalysts. The oxygen vacancies were developed in Pd@ZrO2 catalysts during impregnation of Pd which was confirmed by XPS and HR-TEM analyses. The characterization results revealed that there was a synergistic role of oxygen vacancies and nano-sized active Pd metals in Pd@ZrO2 catalysts that assisted in achieving selectivity for hydrocinnamaldehyde which has been discussed in this study. We also studied the effects of different reaction parameters which revealed that 4 wt% Pd loading in a Pd@ZrO2 catalyst provided enough active sites for complete conversion of CAL. Additionally, 100 °C temperature and 10 bar H2 pressure provided enough energy for effective collisions and activation of reactants and catalysts to form the desired product in a reaction time of 9 h. Therefore, a defect-rich 4-Pd@ZrO2 catalyst demonstrated complete CAL conversion with 86% yield towards HCAL which is the best result amongst various Pd@ZrO2 catalysts with different Pd loading investigated for the hydrogenation of cinnamaldehyde. Moreover, a plausible mechanism was proposed to support the chemoselective hydrogenation of cinnamaldehyde over a 4-Pd@ZrO2 catalyst. Along with high catalytic performance, the 4-Pd@ZrO2 catalyst also showed impressive recyclability performance for up to six recycles. Thus, the oxygen-vacancy-rich Pd@ZrO2 can be considered as an efficient catalyst for the chemoselective hydrogenation of cinnamaldehyde. [ABSTRACT FROM AUTHOR]

The hydrogenation of carbohydrates to polyols is an industrially important process, but it requires air-unstable, non-noble metal catalysts with low activity and harsh reaction conditions. Herein, we report a hydrotalcite (HT)-supported nickel phosphide nanoparticle (nano-Ni2P/HT) that exhibits both air stability and high activity for the selective hydrogenation of D -glucose to D -sorbitol in water. The nano-Ni2P/HT catalyst provides D -sorbitol in excellent yield with >99% selectivity under mild reaction conditions, and is the first non-noble metal catalyst that can operate under just 1 bar of H2 or at ambient temperature. This high-performance nano-Ni2P/HT catalyst is significantly different from conventional Ni(0) and NiO nanoparticles and Raney catalysts, which result in almost no production of D -sorbitol, demonstrating the unique catalysis of nano-Ni2P/HT. Furthermore, nano-Ni2P/HT shows the highest activity among those reported for non-noble metal catalysts. The nano-Ni2P/HT catalyst can also be reused without sacrificing its high activity and selectivity. Additionally, the successful transformation of a concentrated D -glucose solution (50 wt%) to D -sorbitol has been achieved. This is the first example of an air-stable, highly active, and reusable non-noble metal catalyst that can replace conventional catalysts used for D -sorbitol production, thus providing a cheap, green, and sustainable route for this process. [ABSTRACT FROM AUTHOR]

Synthesis of an easily separable and efficient catalyst is of great significance for selective hydrogenation of unsaturated functional groups. In this work, novel magnetic flower-like carbonaceous Pd catalysts are constructed for the selective reduction of the C＝C bond. According to the characterization results, a flower-like architecture is observed in the catalysts containing both Fe3O4 and Pd NPs, which is constructed by the secondary self-assembly in the preparation process due to the interaction between Pd and magnetic nitrogen-doped graphene (Fe3O4-NG). More flower-like structures are formed by increasing the Pd loading amount, further enhancing the specific surface area of the catalyst. The specific surface area of Pd-FONG-3 is the highest (521.17 m2 g−1). Combining the results of characterization and experiments, it is found that the catalytic activity is positively related to the flower-like architecture and the interaction between Pd NPs (6.0 nm) and Fe3O4 NPs (6.7 nm). Fe3O4 is not only beneficial to the magnetic recovery of the catalyst, but also acts as a cocatalyst, which can significantly improve the reactant conversion. Moreover, N species play an important role in protecting the C＝O bond, resulting in the selective hydrogenation of the C＝C group. Herein, Pd-FONG-3 exhibits excellent activity in the selective hydrogenation of cinnamaldehyde (CAL) with 99.5% conversion and 96.5% hydrocinnamaldehyde (HCAL) selectivity, and its catalytic performance is much better than that of the commercial 5% Pd/C catalyst (100% conversion and 69.1% HCAL selectivity). This work provides a new strategy to construct highly active catalysts with magnetic recovery properties for selective hydrogenation of C＝C bonds, and Pd-FONG-3 shows tremendous application foreground. [ABSTRACT FROM AUTHOR]

Converting CO2 to liquid (C5+) hydrocarbons remains a significant hurdle. Our study shows that CoFe/HZSM-5 boosts C5+ selectivity to 73.4%, up from 59% for Fe/HZSM-5. This study highlights the pivotal roles of zeolite acidity and catalyst proximity in this improvement. These insights pave the way for more effective CO2 utilization. [ABSTRACT FROM AUTHOR]

Exploration of highly selective catalysts for CO2 hydrogenation remains a great challenge since the reduction of CO2 over the supported metal catalysts may give rise to various products in response to the modulation of the chemical state of active sites. Herein, by varying the pretreatment temperature of iridium/titanium oxide (Ir/TiO2) catalysts, the selectivity of CO2 hydrogenation from CH4 to sole production of CO can be finely tuned. The change of product selectivity is achieved in such a way that the selectivity greatly depend on the formation of a reduced TiOx overlayer around Ir nanoparticles (NPs) as originated from the strong metal–support interaction (SMSI). With only a weak reduction treatment, the exposed Ir NPs without a TiOx coating promote CH4 production exclusively. After the catalyst undergoes a high temperature reduction, the evolution of the TiOx coating over Ir NPs shows a preference for CO production with an inhibition of further methanation. This study not only provides insights into the regulation of CO2 hydrogenation by SMSI, but also serves as an effective approach to tuning other catalytic processes. [ABSTRACT FROM AUTHOR]

Bio-based primary diamines are important building blocks for sustainable bio-polymers, but their synthesis remains challenging due to the high susceptibility to polymerization. Herein, we have developed a new strategy to suppress the polymerization by employing a more nucleophilic alkylamine to scavenge the dialdehyde and a Co/ZrO2 catalyst to regulate the trans-imination and hydrogenation activity. With this strategy, 2,5-bis(aminomethyl)furan (BAMF), a promising monomer for the production of new polyamides and polyureas, is successfully synthesized via the reductive amination of biomass-derived 2,5-diformylfuran (DFF) under a H2 and NH3 atmosphere with an unprecedentedly high selectivity up to 95%. This strategy is applicable to the reductive amination of other biomass-derived dialdehydes, thus paving a new way to bio-based diamine monomers. [ABSTRACT FROM AUTHOR]

Cellulose-derived levulinic acid (LA) can be converted into gamma-valerolactone (GVL), a sustainable platform chemical for the production of bio-based chemicals. However, LA as an organic acid causes severe metal leaching during the heterogeneous hydrogenation of LA to GVL, especially in the presence of water. Various endeavors for preventing metal leaching have focused more on the process and less on the intrinsic nature of catalysts. The aim of this work is to derive a novel metal-leaching-resistant catalyst for the aqueous-phase hydrogenation of LA into GVL by using a nanocomposite containing three components, Ag, ZrO2, and graphene oxide (GO). The AgZrO2GO catalyst without pre-reduction treatment resulted in complete conversion of LA and approximately 100 mol% selectivity to GVL in the aqueous reaction, and metal leaching from the catalyst was completely eliminated. The relationship between the catalytic performance and the distinct physicochemical properties of the catalyst was extensively discussed. [ABSTRACT FROM AUTHOR]

As a novel alkane isomerization catalyst, namely CoH/Hβ, was prepared by the reduction of CoH(P(OPh)3)4, which was pre-impregnated on Hβ as support. The as-prepared CoH/Hβ catalyst was structurally compared with CoH(P(OPh)3)4, CoH(P(OPh)3)4/Hβ via FT-IR, TPR, SEM, XRD and other techniques. The results show that the new organometallic hydride catalyst was synthesized successfully and exhibited excellent catalytic performance for the isomerization of n-hexane. For the best performance of the CoH/Hβ catalyst, the optimal catalytic reaction temperature, pressure, space velocity, and hydrogen/oil molar ratio were 300 °C, 2.0 MPa, 1.0 h−1, and 4.0, respectively, in the isomerization process of n-hexane. Under the optimal reaction conditions, the conversion of n-hexane, the yield of isomerization, and the selectivity towards iso-paraffins were 80.2%, 63.0%, and 78.6%, respectively. This performance is mainly attributed to the new structure of Co–H hydride in the CoH/Hβ catalyst, which has strong hydrogenation/dehydrogenation activity in the isomerization of n-hexane. [ABSTRACT FROM AUTHOR]

Ru–carbon catalysts with different physical morphologies and chemical states of Ru were prepared by different methods and used to catalyze the hydrolytic hydrogenation of cellulose at high temperatures. The physical morphology of Ru particles and the chemical state of Ru significantly influenced the catalytic performance. The Ru nanoparticles in Ru@MC prepared by the in situ carbothermal reduction method exhibited a special chemical state due to the strong interaction with carbon. The special structure could not only prevent the growth of Ru particles but also enhance the hydrogen spillover effect and improve the hydrogenation efficiency. Among the Ru–carbon catalysts, Ru@MC showed the best catalytic performance with a 72.4% yield of sorbitol. Furthermore, the embedded structure of Ru@MC stabilized the Ru nanoparticles, and the catalyst could be reused at least 6 times. [ABSTRACT FROM AUTHOR]

The effects of the ZnO/SiO2 ratio on the water tolerance of Cu/SiO2 and Cu/ZnO catalysts were studied by ethyl acetate with 5 wt% water hydrogenation. Notably, the addition of an appropriate amount of ZnO endows Cu/SiO2 catalysts with satisfactory water-tolerant hydrogenation performance by a decrease in the reaction temperature without sacrificing conversion. At the same time, agglomeration can be alleviated for Cu/ZnO catalysts due to the optimal addition of SiO2, which is considered as a partition material that effectively hinders the agglomeration of the Cu/ZnO catalyst. However, the addition of ZnO was not favourable for the copper dispersion of Cu/SiO2. The stability of Cu/SiO2 catalyst quickly degraded due to excessive ZnO being introduced by sintering. The copper dispersion of Cu/ZnO catalysts initially increased with increasing SiO2 content, but then decreased. The addition of excess SiO2 also led to decreased activity and rapid deactivation of the Cu/ZnO catalyst. In our study, the appropriate addition of ZnO (5 wt%) and SiO2 (5 wt%) had a positive effect on the Cu/SiO2 and Cu/ZnO catalysts, respectively. [ABSTRACT FROM AUTHOR]

The catalytic hydrogenation of aromatic nitro compounds containing multiple functional groups into amino compounds with high conversion rates, selectivity, and stability under mild conditions is a great challenge. Herein, a well defined catalyst (Co@NC) is prepared through the pyrolysis of the Co-centered metal–organic framework (MOF) at the optimized temperature. The as-synthesized catalyst exhibits a high conversion rate and selectivity for the hydrogenation of 12 aromatic nitro compounds with different competing groups into desired amino compounds with hydrazine hydrate under mild conditions (80 °C, 30 min, and 1 atm). The catalyst also shows excellent stability and can be reused over 20 times without considerably losing its activity. It is found that the Co–Nx site is the main active site for catalytic hydrogenation, and the Mott–Schottky effect between the surface Co NPs and N-doped carbon can further promote the hydrogenation reaction. EXAFS, TEM, XPS, and Raman analyses confirm that cobalt nanoparticles (NPs) are properly encapsulated by the N-doped carbon matrix at the optimized temperature, and the Co species maintain a high spin state after the catalysis, which may be responsible for the high performance of Co@NC. This work demonstrates not only a highly efficient catalyst for hydrogenation under mild conditions, but also provides insight into the active sites in Co-based catalysts for hydrogenation. [ABSTRACT FROM AUTHOR]

In this study, a facile method for the synthesis of leach proof and earth-abundant non-noble Ni nanoparticles on N-doped carbon nanotubes is reported. The catalyst was synthesized by an impregnation–carbonization method, wherein a Ni-chitosan complex upon carbonization in a 5% H2/N2 atmosphere at 800 °C yielded Ni-containing N-doped CNTs. Chitosan served as a single source of carbon and nitrogen, and the nanotube growth was facilitated by the in situ formed Ni nanoparticles. The nanocatalyst was thoroughly characterized by several techniques; elemental mapping by SEM and TEM analysis confirmed the uniform distribution of Ni nanoparticles on the surface of N-doped CNTs with an average size in the range of 10–15 nm. The catalyst efficiently reduced a variety of nitroarenes (>99%) into their corresponding amines at a moderate pressure (5 bar) and a comparatively lower temperature (80 °C). Furthermore, the easy recovery of the catalyst using an external magnetic field along with high activity and easy recyclability makes the protocol eco-friendly. [ABSTRACT FROM AUTHOR]

The hydrogenation of nitroarenes is one of the most important strategies for the preparation of anilines. However, it is still a great challenge to develop mild and efficient synthetic routes toward aniline synthesis, particularly those employing both non-precious metal catalysts and low-pressure H2. Herein, we report a highly efficient protocol for the selective hydrogenation of nitroarenes in neutral H2O using H2 (1 atm) over a heterogeneous Zn(0) catalyst under mild conditions. The nitro groups of an array of nitroarenes can be converted into –NH2 with up to 99% conversions and a selectivity of >99%, even when functionalized with easily reducible substituents, or in the presence of aromatic ketones or styrene. This study might open an avenue for the selective hydrogenation of nitroarenes over a zinc catalyst using 1 atm H2. [ABSTRACT FROM AUTHOR]

We report the design of a new iron catalyst for the asymmetric transfer hydrogenation of ketones. This type of iron catalyst combines the structural characteristics of the Noyori hydrogenation catalyst (an axially chiral 2,2′-bis(phosphino)-1,1′-binaphthyl fragment and the metal–ligand bifunctional motif) and an ene(amido) group that can activate the iron center. After activation by 8 equivalents of potassium tert-butoxide, (SA,RP,SS)-7a and (SA,RP,SS)-7b are active but nonenantioselective catalysts for the transfer hydrogenation of acetophenone and α,β-unsaturated aldehydes at room temperature in isopropanol. A maximum turnover number of 14480 was observed for (SA,RP,SS)-7a in the reduction of acetophenone. The right combination of the stereochemistry of the axially chiral 2,2′-bis(phosphino)-1,1′-binaphthyl group and the carbon-centered chiral amine-imine moiety in (SA,RP,RR)-7b′ afforded an enantioselective catalyst for the preparation of chiral alcohols with moderate to good yields and a broad functional group tolerance. [ABSTRACT FROM AUTHOR]

The utilization of CO2 to synthesize environmentally benign liquid fuels offers a solution to replacing depleting petroleum resources. Herein, a ternary CuZnZr (CZZ) metal oxide catalyst and a SAPO-34 zeolite were synthesized by co-precipitation and hydrothermal synthesis, respectively. Different metals were impregnated into the latter to obtain MeSAPO-34 (Me = Mn, Zn and Zr). A granule mixture of CZZ and MeSAPO-34 components (CZZ/MeSAPO-34 catalyst) was then effectively utilized in a tandem catalytic process for one-step CO2 hydrogenation to liquefied petroleum gas (LPG). The CZZ/MeSAPO-34 catalysts were characterized by using XRD, H2-TPR, BET, SEM-EDS and NH3-TPD techniques. SEM-EDS and XRD results indicated that an appropriate amount of Zr metal loading induced minimum zeolite framework collapse compared to a similar amount of Mn and Zn, which was more favorable for higher activity. In addition, NH3-TPD results revealed that the acidity of SAPO-34 could be altered after impregnation with different metals in different quantities. Tuning the acid density and strength, together with adjusting the CZZ to MeSAPO-34 weight ratio, had a collectively critical effect on LPG selectivity. An effective hydrogenation microenvironment which favors lower alkane formation (C3–C4) was enhanced after the acidity of the molecular sieve was tuned. LPG selectivity could reach 86% over the CZZ/5% ZrSAPO-34 catalyst at 2 MPa, 350 °C, a W/F ratio of 6, a H2/CO2 ratio of 3 and a weight ratio of 1. [ABSTRACT FROM AUTHOR]