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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]

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]

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]

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]

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]

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]

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]

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]

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]

Aiming at the preparation of metal catalysts with nanoscale structures, Ni–Cu/Al2O3 nanoparticle catalysts (i.e., Ni&Cu-NP/γ-Al2O3), containing a certain amount of Ni and Cu were prepared for the hydrogenation of acetylene. The highly dispersed and stable Ni&Cu-NP/γ-Al2O3 catalyst with a Ni : Cu atomic ratio of 1 : 1 was obtained from a NiCl2/CuCl2 precursor by a modified co-precipitation method, the average size of which was controlled at 10.0 ± 0.3 nm. Under optimal reaction conditions, approximately 100% conversion and 71% selectivity at 130 °C were achieved using the Ni&Cu-NP/γ-Al2O3 catalyst. The enhanced selectivity was attributed to the formation of nickel–copper alloys, which have been identified by both diffuse reflectance infrared Fourier transform spectroscopy and theoretical calculation results. [ABSTRACT FROM AUTHOR]

Developing a highly active, acid-resistant and low-cost catalyst which can perform well in aqueous solution has long been sought for practical and sustainable lignocellulosic biomass transformation. In this work, a series of Ce–P–Co heterogeneous catalysts were prepared by a convenient solvothermal method for catalytic hydrogenation of levulinic acid (LA) to gamma-valerolactone (GVL) in water. By comprehensive characterizations and catalytic measurements, the structure of the prepared Ce–P–Co samples was disclosed as (CePO4)m/Co2P composites with a modulated molar ratio (m) of 0.04–0.34. With the introduction of CePO4, the unique hydrogen activation on CePO4 markedly accelerated the reaction, with the GVL yield after 90 min on (CePO4)m/Co2P (45–97%) being much higher than on pure Co2P (26%), together with an attractive TOF of 0.27–0.61 s−1 on (CePO4)m/Co2P (comparable to precious metal catalysts). Further analysis of the kinetic and acidic features indicated a Langmuir–Hinshelwood mechanism, initiated by activation of H2 and LA on CePO4 and Co2P, respectively, followed by a surface reaction of the two activated species as the rate-determining step, as a plausible pathway for producing GVL from LA on (CePO4)m/Co2P. The consistent catalytic performance during recycling tests and the unchanged morphological, bulk and surface structure features of the used catalyst relative to the fresh catalyst confirmed that the (CePO4)m/Co2P structure was robust enough to endure the acidic aqueous environment for efficiently and sustainably converting LA to GVL. The advantages of high catalytic efficiency, stable, acid-resistant structure and low cost marked (CePO4)m/Co2P as a competitive and practical heterogeneous catalyst for sustainable, scaled-up lignocellulosic biomass transformation. [ABSTRACT FROM AUTHOR]

An understanding of the essential roles in adiponitrile hydrogenation is a significant factor in designing promising nickel catalysts. A series of Ni/Al2O3 catalysts have been synthesized by the deposition–precipitation method and used for the selective hydrogenation of adiponitrile. The formation of the Ni compositions and the chemical structures of the catalysts were modulated by the assisting precipitators. Characterization, including XRD, N2 adsorption–desorption, TEM, XPS, H2-TPD and NH3-TPD, were carried out. Smaller particles could be obtained via fast deposition of Ni2+ using NaOH in Ni/Al2O3–OH, or uniform crystal seeds using urea in Ni/Al2O3–U. The use of a strong alkali, and the formation of nickel hydroxide, facilitated the generation of Ni0 with a better H2 activation ability. Meanwhile, a huge number of nickel species in various oxidative states and strong acidity were simultaneously generated in Ni/Al2O3–U, leading easily to the cycloaddition by-products. A kinetics study revealed that adiponitrile hydrogenation is a second-order reaction with respect to adiponitrile. The number of Ni0 active sites and acid sites could be balanced via different precipitation and crystallization methods. The yield of 1,6-hexanediamine reached 75.0% at 90 °C with 20 wt% Ni/Al2O3–OH. [ABSTRACT FROM AUTHOR]