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Syngas conversion provides an important platform for efficient utilization of various carbon-containing resources such as coal, natural gas, biomass, solid waste and even CO2. Various value-added fuels and chemicals including paraffins, olefins and alcohols can be directly obtained from syngas conversion via the Fischer–Tropsch Synthesis (FTS) route. However, the product selectivity control still remains a grand challenge for FTS due to the limitation of Anderson–Schulz–Flory (ASF) distribution. Our previous works showed that, under moderate reaction conditions, Co2C nanoprisms with exposed (101) and (020) facets can directly convert syngas to olefins with low methane and high olefin selectivity, breaking the limitation of ASF. The application of Co2C-based nanocatalysts unlocks the potential of the Fischer–Tropsch process for producing olefins. In this feature article, we summarized the recent advances in developing highly efficient Co2C-based nanocatalysts and reaction pathways for direct syngas conversion to olefins via the Fischer–Tropsch to olefin (FTO) reaction. We mainly focused on the following aspects: the formation mechanism of Co2C, nanoeffects of Co2C-based FTO catalysts, morphology control of Co2C nanostructures, and the effects of promoters, supports and reactors on the catalytic performance. From the viewpoint of carbon utilization efficiency, we presented the recent efforts in decreasing the CO2 selectivity for FTO reactions. In addition, the attempt to expand the target products to aromatics by coupling Co2C-based FTO catalysts and H-ZSM-5 zeolites was also made. In the end, future prospects for Co2C-based nanocatalysts for selective syngas conversion were proposed. [ABSTRACT FROM AUTHOR]

A Ru single-atom (Ru SA) catalyst supported on activated carbon was adopted to synthesize 3-pentanone with 83.3% selectivity via heterogeneous ethylene hydroformylation, while 52.1% ethane selectivity was obtained for Ru nanoparticles (Ru NPs). The atomically dispersed Ru species with oxidation state (Ruδ+) and Ru-C4O coordination structure were identified as the active sites for efficient C–C coupling to generate 3-pentanone, while metallic Ru nanoparticles exhibited high activity for ethylene hydrogenation to ethane. Density functional theory (DFT) calculation revealed that the energy barrier of the direct coupling of C2H5CO* with C2H5* to form 3-pentanone on Ru SA was much lower than that on Ru NPs. As a result, the formation of 3-pentanone over Ru SA was more favourable than propanal, which was admittedly generated via coupling of C2H5CO* and H*. This strategy may provide a potential green route for the one-pot synthesis of 3-pentanone with high atomic economy. [ABSTRACT FROM AUTHOR]

As is well known, CO2 is an attractive renewable C1 resource and H2 is a cheap and clean reductant. Combining CO2 and H2 to prepare building blocks for high-value-added products is an attractive yet challenging topic in green chemistry. A general and selective rhodium-catalyzed hydroformylation of alkenes using CO2/H2 as a syngas surrogate is described here. With this protocol, the desired aldehydes can be obtained in up to 97% yield with 93/7 regioselectivity under mild reaction conditions (25 bar and 80 °C). The key to success is the use of a bifunctional Rh/PTA catalyst (PTA: 1,3,5-triaza-7-phosphaadamantane), which facilitates both CO2 hydrogenation and hydroformylation. Notably, monodentate PTA exhibited better activity and regioselectivity than common bidentate ligands, which might be ascribed to its built-in basic site and tris-chelated mode. Mechanistic studies indicate that the transformation proceeds through cascade steps, involving free HCOOH production through CO2 hydrogenation, fast release of CO, and rhodium-catalyzed conventional hydroformylation. Moreover, the unconventional hydroformylation pathway, in which HCOOAc acts as a direct C1 source, has also been proved to be feasible with superior regioselectivity to that of the CO pathway. [ABSTRACT FROM AUTHOR]

Selectivity control of nitrobenzene hydrogenation remains a great challenge, and it is desirable to develop a green and highly efficient catalytic route toward value-added metastable intermediate products. Herein, we reported that isolated Ru single atoms coordinated with oxygen atoms in CeO2 (Ru-SAs/CeO2) can achieve chemoselective hydrogenation of nitrobenzene to azoxybenzene with a selectivity of 88.2% in a continuous flow reactor using H2 without using any bases or expensive organic reducing agents, while 82.7% aniline selectivity was obtained by Ru nanoparticles. We demonstrated that the unique coordinated structure between Ru single atoms and O atoms preferentially controls the reaction route toward the coupling of nitrosobenzene and phenylhydroxylamine intermediates to form azoxybenzene while greatly suppressing over-hydrogenation. The present work provides an efficient strategy to regulate the reaction pathway of nitrobenzene hydrogenation with a green and industry-friendly process by designing highly dispersed Ru single atoms. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations were performed to investigate the catalytic cycle of methane conversion to methanol over both [Cu2(O2)]2+ and [Cu2(μ-O)]2+ active sites in the Cu-ZSM-5 catalyst. The [Cu2(O2)]2+ site is found to be active for the partial oxidation of methane to methanol, and although it has a higher energy barrier in the methane activation step, it involves a very low energy barrier in the methanol formation step (36.3 kJ mol−1) as well as a lower methanol desorption energy (52.5 kJ mol−1). As the [Cu2(O2)]2+ active site is also thermodynamically stable, it may play an important role during methane conversion to methanol. Furthermore, the methane activation step follows the homolytic route and the heterolytic route for the [Cu2(O2)]2+ and [Cu2(μ-O)]2+ active sites, respectively, whereas the methanol formation step follows the direct radical rebound mechanism and the indirect rebound mechanism, respectively. Our calculations further indicate that the electronic properties of the reactive O atoms in the active site influence their reactivity toward methane oxidation. More specifically, the higher the spin density and the more negative the charge of the reactive O atom at the active site are, the lower the energy barrier for methane activation will be; and the more negative the charge of the hydroxyl group in the reaction intermediate during the partial oxidation of methane to methanol is, the higher energy barrier of the methanol formation step will be in the triplet state. Furthermore, we used a larger cluster model to predict the mechanism of the methane activation step and the effect of atomic charge of the O atom at the [Cu2(μ-O)]2+ and [Cu2(O2)]2+ active sites on the energy barriers of partial oxidation of methane to methanol, and the conclusions drawn employing the larger cluster model are consistent with those drawn using the smaller double-5T-ring cluster model. In addition, different from the traditional mechanism for methane activation at [Cu2(O2)]2+, which consists of two transition states, we find that the partial oxidation of methane at [Cu2(O2)]2+ can also occur via a single step by direct insertion of one of the O atoms at the active site into the C–H bond of methane. [ABSTRACT FROM AUTHOR]

Cu single atoms embedded in the C3N4 (Cu-SAs/C3N4) matrix exhibited high activity with 95% oxygenate selectivity for the direct conversion of methane at ambient temperature. The presence of abundant anchoring sites in C3N4 led to highly dispersed Cu–N4 moieties, which were suggested to be the underlying active sites for methane conversion. [ABSTRACT FROM AUTHOR]

We develop an electric internal heating method based on a Ni-foam structured catalyst for CO2 methanation, in which the Joule heat generated by electric current passing through the catalyst drives the reaction. Compared with the conventional external heating method, EIH significantly enhances the catalytic activity and anti-poisoning ability of the catalyst. [ABSTRACT FROM AUTHOR]

Fischer–Tropsch (F–T) synthesis is an effective approach to convert the syngas of H2 and CO into lower olefin and other valuable products for the chemical industry. Cobalt carbide (Co2C), which was regarded as the sign of activity loss in the past, has recently been recognized as a highly-active phase for F–T synthesis. However, systematic study on the formation process of Co2C by F–T reaction is still lacking. Herein, for the first time, in situ XAFS (X-ray Absorption Fine Structure) experiments were conducted to elaborate the Co2C formation under operando conditions. F–T reaction processes starting from Co and CoO were analysed with the conclusion that Co2C could be formed under both conditions. For the CoO process, Co2C was transformed directly from CoO as a wavelet transform and EXAFS fitting results revealed that there was no sign of Co metal in the whole process. Thermodynamic analysis indicated that the ΔG value of the CoO process is much smaller than that of the Co process, which means that CoO is thermodynamically easier to transform to Co2C. Combining with the shorter reduction time from Co3O4 to CoO, it can be concluded that CoO is more favourable as the precursor to synthesize Co2C, which might be applied to the F–T industry. Besides, catalytic evaluation shows that the CO2 selectivity, CO conversion and the ratio of olefin/paraffin for the CoO process are different from those of the Co process. In addition, the reaction temperatures were also investigated wherein Co2C would be partially transformed to metallic Co when the temperature was increased up to 270 °C. This work provides fundamental and applicable guidance towards the synthesis of Co2C by F–T reaction. [ABSTRACT FROM AUTHOR]

A green strategy was developed for the synthesis of various value-added chemicals using methanol, acetonitrile, acetic acid, acetone and ethyl acetate as the hydrogen source by coupling them with olefins over heterogeneous photocatalysts. A radical coupling mechanism was proposed for the hydrofunctionalization of olefins with methanol to higher aliphatic alcohols over the Pt/TiO2 catalyst as the model reaction. C–H bond cleavage and C–C bond formation between photogenerated radicals and terminal olefins were accomplished in a single reaction at high efficiency. Our approach is atomically economical with high anti-Markovnikov regioselectivity and promising application potential under mild reaction conditions. [ABSTRACT FROM AUTHOR]

Highly dispersed FeMn nanoparticles were encapsulated with a carbon layer to form a core–shell structure. This catalyst (FeMn@C) exhibited distinguished catalytic activity, high light-olefin selectivity (40.6%) and superior stability in the Fischer–Tropsch synthesis. Furthermore, it was revealed that the carbon layer facilitated the formation of χ-Fe5C2 with suitable particle size, which is responsible for the enhanced catalytic activity. In particular, the core–shell structure of FeMn@C could also influence the distribution of hydrocarbons and the catalyst stability due to the confinement effect. [ABSTRACT FROM AUTHOR]

Syngas conversion provides an important platform for efficient utilization of various carbon-containing resources such as coal, natural gas, biomass, solid waste and even CO 2 . Various value-added fuels and chemicals including paraffins, olefins and alcohols can be directly obtained from syngas conversion via the Fischer-Tropsch Synthesis (FTS) route. However, the product selectivity control still remains a grand challenge for FTS due to the limitation of Anderson-Schulz-Flory (ASF) distribution. Our previous works showed that, under moderate reaction conditions, Co 2 C nanoprisms with exposed (101) and (020) facets can directly convert syngas to olefins with low methane and high olefin selectivity, breaking the limitation of ASF. The application of Co 2 C-based nanocatalysts unlocks the potential of the Fischer-Tropsch process for producing olefins. In this feature article, we summarized the recent advances in developing highly efficient Co 2 C-based nanocatalysts and reaction pathways for direct syngas conversion to olefins via the Fischer-Tropsch to olefin (FTO) reaction. We mainly focused on the following aspects: the formation mechanism of Co 2 C, nanoeffects of Co 2 C-based FTO catalysts, morphology control of Co 2 C nanostructures, and the effects of promoters, supports and reactors on the catalytic performance. From the viewpoint of carbon utilization efficiency, we presented the recent efforts in decreasing the CO 2 selectivity for FTO reactions. In addition, the attempt to expand the target products to aromatics by coupling Co 2 C-based FTO catalysts and H-ZSM-5 zeolites was also made. In the end, future prospects for Co 2 C-based nanocatalysts for selective syngas conversion were proposed.

We develop an electric internal heating method based on a Ni-foam structured catalyst for CO2 methanation, in which the Joule heat generated by electric current passing through the catalyst drives the reaction. Compared with the conventional external heating method, EIH significantly enhances the catalytic activity and anti-poisoning ability of the catalyst.

Direct production of olefins via syngas conversion over a Co 2 C-based catalyst was investigated in a slurry bed reactor (SBR). It was found that the total selectivities to olefins and oxygenates reached 88.8C% at a CO conversion of 29.5% at 250 °C, 5 bar and H 2 /CO = 0.5. The hydrocarbon distribution greatly deviated from the classical Anderson-Schulz-Flory (ASF) distribution, with only 2.6C% methane selectivity was obtained. XRD and TEM characterization verified that the Co 2 C nanoprisms with special exposed facts of (101) and (020) constitutes the Fischer-Tropsch to olefins (FTO) active site. The catalytic activity increased gradually with rising the reaction temperature, while the product distribution almost kept unchanged under various reaction condition in SBR. Compared to the reaction in FBR, the Co 2 C-based catalyst exhibited relative better catalytic performance during FTO process in SBR. Specifically, a higher CO conversion, a lower methane selectivity and a higher total selectivities to olefins and oxygenates were achieved in SBR. In addition, the catalyst can be in situ reduced in slurry bed reactor at mild temperature (300 °C) and no obvious deactivation was found within nearly 100 h time-on-stream, which suggested a promising route for the direct production of olefins via syngas in industrial application., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)