Advances in the Development of Novel Cobalt Fischer−Tropsch Catalysts for Synthesis of Long-Chain Hydrocarbons and Clean Fuels

Ni2 P Nanoalloy as an Air-Stable and Versatile Hydrogenation Catalyst in Water: P-Alloying Strategy for Designing Smart Catalysts

Non-noble metal-based hydrogenation catalysts have limited practical applications because they exhibit low activity, require harsh reaction conditions, and are unstable in air. To overcome these limitations, herein we propose the alloying of non-noble metal nanoparticles with phosphorus as a promising strategy for developing smart catalysts that exhibit both excellent activity and air stability. We synthesized a novel nickel phosphide nanoalloy (nano-Ni₂ P) with coordinatively unsaturated Ni active sites. Unlike conventional air-unstable non-noble metal catalysts, nano-Ni₂ P retained its metallic nature in air, and exhibited a high activity for the hydrogenation of various substrates with polar functional groups, such as aldehydes, ketones, nitriles, and nitroarenes to the desired products in excellent yields in water. Furthermore, the used nano-Ni₂ P catalyst was easy to handle in air and could be reused without pretreatment, providing a simple and clean catalyst system for general hydrogenation reactions.

High-Pressure Scanning Tunneling Microscopy

This is a Review of recent studies on surface structures of crystalline materials in the presence of gases in the mTorr to atmospheric pressure range, which brings surface science into a brand new direction. Surface structure is not only a property of the material but also depends on the environment surrounding it. This Review emphasizes that high/ambient pressure goes hand-in-hand with ambient temperature, because weakly interacting species can be densely covering surfaces at room temperature only when in equilibrium with a sufficiently high gas pressure. At the same time, ambient temperatures help overcome activation barriers that impede diffusion and reactions. Even species with weak binding energy can have residence lifetimes on the surface that allow them to trigger reconstructions of the atomic structure. The consequences of this are far from trivial because under ambient conditions the structure of the surface dynamically adapts to its environment and as a result completely new structures are often formed. This new era of surface science emerged and spread rapidly after the retooling of characterization techniques that happened in the last two decades. This Review is focused on the new surface structures enabled particularly by one of the new tools: high-pressure scanning tunneling microscopy. We will cover several important surfaces that have been intensely scrutinized, including transition metals, oxides, and alloys.

Oxygen-Blown Gasification of Pulp Mill Bark Residues for Synthetic Fuel Production

Synthetic fuel production via gasification of residual biomass streams from the pulp and paper industry can be an opportunity for the mills to enable improved resource utilization and at the same time reduce the production of excess heat. This paper summarizes initial oxygen-blown gasification experiments with two bark residues from a European pulp and paper mill, i.e., a softwood bark and a hardwood bark. The gasification process was characterized by measuring syngas yields and process efficiency to find optimum operating conditions. In addition, impurities in the syngas and ash behavior were characterized. Maximum yields of CO and H2 were obtained from softwood bark and amounted to approximately 29 and 15 mol/kg fuel, respectively. Optimum cold gas efficiency was achieved at an oxygen stoichiometric ratio of λ = 0.40 and was approximately 76% and 70% for softwood bark and hardwood bark, respectively. Increased λ had a reducing effect on pollutants in the syngas, e.g., higher hydrocarbons, NH3, HCl, and soot. The situation for sulfur species was more complex. Evaluation of the bark ashes indicated that slag formation could start already from 800 °C. Furthermore, a non-intrusive laser diagnostics technique gave rapid feedback on the millisecond scale. Measured syngas temperature and water content were in good agreement with the applied reference methods.

Reductive Hexamerization of CO Involving Cooperativity Between Magnesium(I) Reductants and [Mo(CO)6 ]: Synthesis of Well-Defined Magnesium Benzenehexolate Complexes*

Reactions of two magnesium(I) compounds, [{(^Ar Nacnac)Mg}₂ ] (^Ar Nacnac=[HC(MeCNAr)₂ ]^- ; Ar=mesityl (Mes) or o-xylyl (Xyl)), with CO in the presence of [Mo(CO)₆ ] lead to the reductive hexamerization of CO, and formation of magnesium benzenehexolate complexes, [{(^Ar Nacnac)Mg}₆ (C₆ O₆ )]. [Mo(CO)₆ ] is not consumed in these reactions, but is apparently required to initiate (or catalyze) the CO hexamerizations. A range of studies were used to probe the mechanism of formation of the benzenehexolate complexes. The magnesium(I) reductive hexamerizations of CO are closely related to Liebig's reduction of CO with molten potassium (to give K₆ C₆ O₆ , amongst other products), originally reported in 1834. As the mechanism of that reaction is still unknown, it seems reasonable that magnesium(I) reductions of CO could prove useful homogeneous models for its elucidation, and for the study of other C-C bond forming reactions that use CO as a C₁ feedstock (e.g. the Fischer-Tropsch process).

Ambient sunlight-driven photothermal methanol dehydrogenation for syngas production with 32.9 % solar-to-hydrogen conversion efficiency

Methanol dehydrogenation is an efficient way to produce syngas with high quality. The current efficiency of sunlight-driven methanol dehydrogenation is poor, which is limited by the lack of excellent catalysts and effective methods to convert sunlight into chemicals. Here, we show that atomically substitutional Pt-doped in CeO₂ nanosheets (Pt_s-CeO₂) exhibit excellent methanol dehydrogenation activity with 500-hr level catalytic stability, 11 times higher than that of Pt nanoparticles/CeO₂. Further, we introduce a photothermal conversion device to heat Pt_s-CeO₂ up to 299°C under 1 sun irradiation owning to efficient full sunlight absorption and low heat dissipation, thus achieving an extraordinarily high methanol dehydrogenation performance with a 481.1 mmol g⁻¹ h⁻¹ of H₂ production rate and a high solar-to-hydrogen (STH) efficiency of 32.9%. Our method represents another progress for ambient sunlight-driven stable and active methanol dehydrogenation technology.

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Atomically substitutional Pt-doped CeO₂ is active and robust for CH₃OH dehydrogenation

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The photothermal conversion device can heat Pt_s-CeO₂ to 299°C under 1 sun irradiation

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The joint system achieves a one sun irradiated H₂ production rate of 481.1 mmol g⁻¹ h⁻¹

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This system delivers a high solar-to-H₂ efficiency of 32.9% under one sun irradiation

Photocarrier-assisted photothermocatalysis of Fischer–Tropsch synthesis for the enhanced yield of C2–C4 hydrocarbons over a Co/SrTiO3 catalyst

Photocarrier-assisted photothermocatalysis enhanced the selectivity to C2−C4 hydrocarbons, which can be ascribed to the combined effect of photocatalysis and photothermal catalysis.

Highly dispersed Co nanoparticles embedded in a carbon matrix as a robust and efficient Fischer–Tropsch synthesis catalyst under harsh conditions

Series of catalysts with Co nanoparticles embedded in matrix of porous carbon is directly synthesized via a unique melting approach. No obvious deactivation is observed at high operating temperature and high CO conversion levels.

The relevance of Lewis acid sites on the gas phase reaction of levulinic acid into ethyl valerate using CoSBA-xAl bifunctional catalysts

CoSBA-xAl catalysts show a high yield in the levulinic acid conversion into ethyl valerate. This is due to the presence of weak Lewis acid sites associated with Co²⁺ species that have been stabilized by incorporation of Al into the support.

Efficient and steady production of 1 : 2 syngas (CO/H2) by simultaneous electrochemical reduction of CO2 and H2O

A guest–host pyrolysis strategy is used to synthesize a Co–C/N_x-based single-site catalyst, featuring excellent electrocatalytic performance for syngas production by electrochemical reduction of CO₂ and H₂O (FE nearly 100%, formation rate 1.08 mol g⁻¹ h⁻¹ at 1.0 V vs. RHE).

Isomorphic titanium-substituted mesoporous SBA-16 as support for cobalt Fischer–Tropsch synthesis catalysts: balance between dispersion and reduction

The delicate balance between dispersion and reduction of the Co-based Fischer–Tropsch synthesis catalyst is the golden key to enhancing catalytic performance, which highly depends on an optimized metal–support interaction.

Short-channel mesoporous SBA-15 silica modified by aluminum grafting as a support for CoRu Fischer–Tropsch synthesis catalysts

Highly ordered short-channel mesoporous silica SBA-15 with large pores (11.2 nm) was synthesized from tetramethyl orthosilicate, using the block copolymer Pluronic PE-10400 as structure-directing agent, and triisopropylbenzene as a swelling agent.

Carburized cobalt catalyst for the Fischer–Tropsch synthesis

Catalysts with Co, Co3C, and Co2C phases are synthesized by controlling the carburization time. The catalyst with Co3C phase exhibits the highest activity in FTS reaction. DFT calculations reveal the high intrinsic activity of Co3C.

Performance of a NiFe2O4@Co Core-Shell Fischer-Tropsch Catalyst: Effect of Low Temperature Reduction

In situ TEM gas-cell imaging and spectroscopy with in situ XRD have been applied to reveal morphological changes in NiFe₂O₄@Co₃O₄ core-shell nanoparticles in hydrogen. The core-shell structure is retained upon reduction under mild conditions (180 °C for 1 h), resulting in a partially reduced shell. The core-shell structure was retained after exposing these reduced NiFe₂O₄@Co₃O₄ core-shell nanoparticles to Fischer-Tropsch conditions at 230 °C and 20 bar. Slightly harsher reduction (230 °C, 2 h) resulted in restructuring of the NiFe₂O₄@Co₃O₄ core-shell nanoparticles to form cobalt islands in addition to partially reduced NiFe₂O₄. NiFe₂O₄ underwent further transformation upon exposure to Fischer-Tropsch conditions, resulting in the formation of iron carbide and nickel/iron-nickel alloy. The turnover frequency in the Fischer-Tropsch synthesis over NiFe₂O₄@Co₃O₄ core-shell nanoparticles reduced in hydrogen at 180 °C for 1 h was estimated to be less than 0.02 s^-1 (cobalt-time yield of 8.40 μmol^.g^-1.s^-1) with a C₅₊ selectivity of 38 C-%. The low turnover frequency under these conditions in relation to the turnover frequency obtained with unsupported cobalt is attributed to the strain in the catalytically active cobalt.

The influence of hydrophobicity on Fischer-Tropsch synthesis catalysts

We review scientific works carried out on the influence of surface hydrophobicity on activity and product selectivity of supported cobalt and iron catalysts during Fischer-Tropsch synthesis (FTS). The characteristics of the surface of catalyst support may influence metal-support interactions, which leads to various degrees of metal dispersion and reducibility. Also, these support surface properties may influence the mass transfer of reactants and products at the catalyst active sites and subsequently affects the performance of the catalyst during FTS. Pre-silylated and post-silylated catalysts have been used to study the influence of surface hydrophobicity on the performance of FTS catalysts. The enhancement of FTS activity by hydrophobicity was mainly ascribed to the improved reducibility of metal oxide species. Furthermore, post-silylated supported iron catalysts favoured the suppression of water-gas shift (WGS) reaction, thereby hindering CO2 formation.

Improved H2 utilization by Pd doping in cobalt catalysts for reductive amination of polypropylene glycol

Cobalt based catalysts having enhanced H₂ dissociation and desorption were synthesized by inserting a trace amount of palladium. These catalysts were used for the reductive amination of polypropylene glycol (PPG) to polyetheramine (PEA). The catalytic activity toward PEA was significantly increased by incorporating an extremely low content of palladium (around 0.01 wt%) into cobalt based catalysts. The Pd inserted cobalt catalysts promoted reduction of cobalt oxide to cobalt metal and inhibited formation of cobalt nitride in the reductive amination. The Pd inserted cobalt catalysts not only enhanced hydrogen dissociation but also accelerated hydrogen desorption by increasing the electron density of cobalt through interaction between cobalt and palladium. These play a critical role in reducing cobalt oxide or cobalt nitride to cobalt metal as an active site for the reductive amination. Thus, the Pd inserted cobalt catalysts provide improved catalytic performance toward PEA production by maintaining the cobalt metal state.

Addition of Pd into Co helped remarkably to reduce cobalt oxide and nitride to cobalt metal by enhanced hydrogen dissociation and desorption.

Tuning of Ionic Second Coordination Sphere in Evolved Rhenium Catalyst for Efficient Visible-Light-Driven CO2 Reduction

Developing an efficient and easy-to-handle strategy in designing catalysts for CO₂ reduction into CO by harnessing sunlight is a promising project. Here, a facile strategy was developed to design a Re catalyst modified with an ionic secondary coordination sphere for photoreduction of CO₂ to CO by visible light. By adding ionic liquids or tuning a different ionic secondary coordination sphere, it was discovered that an outstanding optical property, other than CO₂ absorption ability or the ability to dissociation of chloride anion, is the prerequisite for catalyst design. Accordingly, a novel Re catalyst, {Re[BpyMe(tris(2-hydroxyethyl)amine)](CO)₃ Cl}Br (Re-THEA), was designed, screened, and resulted in a relative high quantum yield (up to 34 %) for visible-light-induced CO₂ reduction with a single-molecule system. DFT calculations, combined with experimental outcomes, suggested the pendant ionic tris(2-hydroxyethyl)amino (THEA) group on Re-THEA can enhance visible-light absorption, stabilize reaction intermediates, and suppress the Re-Re dimer formation.

Stabilization of ε-iron carbide as high-temperature catalyst under realistic Fischer-Tropsch synthesis conditions

The development of efficient catalysts for Fischer–Tropsch (FT) synthesis, a core reaction in the utilization of non-petroleum carbon resources to supply energy and chemicals, has attracted much recent attention. ε-Iron carbide (ε-Fe₂C) was proposed as the most active iron phase for FT synthesis, but this phase is generally unstable under realistic FT reaction conditions (> 523 K). Here, we succeed in stabilizing pure-phase ε-Fe₂C nanocrystals by confining them into graphene layers and obtain an iron-time yield of 1258 μmol_CO g_Fe⁻¹s⁻¹ under realistic FT synthesis conditions, one order of magnitude higher than that of the conventional carbon-supported Fe catalyst. The ε-Fe₂C@graphene catalyst is stable at least for 400 h under high-temperature conditions. Density functional theory (DFT) calculations reveal the feasible formation of ε-Fe₂C by carburization of α-Fe precursor through interfacial interactions of ε-Fe₂C@graphene. This work provides a promising strategy to design highly active and stable Fe-based FT catalysts.

ε-Fe₂C has been identified as the highly active phase for Fischer-Tropsch synthesis (FTS), but is stable only at low-temperature. Here, the authors show that ε-Fe₂C phase can be stabilized even at ~ 573 K by being encapsulated inside graphene layers, and retains high activity in FTS.

Synergistic effect of hierarchical nanopores in Co-doped cobalt oxide 3D flowers for electrochemical energy storage

Hybridizing hierarchical porous transition oxides composed of nanoscale building blocks is highly desirable for improving the electrochemical performance of energy storage. Herein, we contribute a fabrication of novel hierarchically nanoporous flower-shaped metal/transition oxide (Co/Co₃O₄–CoO) with controllable three-dimensional structure. The designed Co/Co₃O₄–CoO 3D flowers (3DFs) are made of petal-shaped nanoporous Co₃O₄–CoO nanosheets with tunable pore sizes, in which metallic Co nanoparticles tend to attach to the edge of larger ones. The hierarchically nanoporous 3DFs with bimodal pore size distribution and higher fraction of small nanopores exhibit a higher specific capacitance (902.3 F g⁻¹ at current density of 2 A g⁻¹) and better cyclability than the uniformly nanoporous 3DFs with unimodal pore size distribution and larger BET surface area. The enhanced capacitance is mainly derived from the synergistic effect of hierarchical nanopores, in which large nanopores disproportionately facilitate osmotic solution flux and diffusive solute transport, whilst small nanopores supply faster channels for electron transportation and ion diffusion. Our work should provide a strategy to fabricate a smart functional hierarchical nanoporous architecture with 3DF structures for the development of electrochemical energy storage materials.

Hybridizing hierarchical porous transition oxides composed of nanoscale building blocks is highly desirable for improving the electrochemical performance of energy storage.

Impact of Coordination Features of Co(II)-Glycine Complex on the Surface Sites of Co/SiO2 for Fischer–Tropsch Synthesis

To investigate the effect of coordination features of Co(II)-glycine complex on the performance of Co/SiO2 for Fischer–Tropsch (FT) synthesis, Co(II)-glycine complex precursors were prepared by the conventional method, i.e., simply adding glycine to the solution of Co nitrate and novel route, i.e., reaction of glycine with cobalt hydroxide. The SiO2-supported Co catalysts were prepared by using the different Co(II)-glycine complexes. It is found that glycine is an effective chelating agent for improving the dispersion of Co and the mass-specific activity in FT synthesis when the molar ratio of glycine/Co2+ = 3, which is independent to the preparation method in this study. Significantly, the surface Co properties were significantly influenced by the coordination features of the Co2+ and the molar ratio of glycine to Co2+ in the Co(II)-glycine complex. Specifically, the Co(3gly)/SiO2 catalyst prepared by the novel route exhibits smaller and homogenous Co nanoparticles, which result in improved stability compared to Co-3gly/SiO2 prepared by the conventional method. Thus, the newly developed method is more controllable and promising for the synthesis of Co-based catalysts for FT synthesis.

Novel Heterogeneous Catalysts for CO2 Hydrogenation to Liquid Fuels

Carbon dioxide (CO₂) hydrogenation to liquid fuels including gasoline, jet fuel, diesel, methanol, ethanol, and other higher alcohols via heterogeneous catalysis, using renewable energy, not only effectively alleviates environmental problems caused by massive CO₂ emissions, but also reduces our excessive dependence on fossil fuels. In this Outlook, we review the latest development in the design of novel and very promising heterogeneous catalysts for direct CO₂ hydrogenation to methanol, liquid hydrocarbons, and higher alcohols. Compared with methanol production, the synthesis of products with two or more carbons (C₂₊) faces greater challenges. Highly efficient synthesis of C₂₊ products from CO₂ hydrogenation can be achieved by a reaction coupling strategy that first converts CO₂ to carbon monoxide or methanol and then conducts a C-C coupling reaction over a bifunctional/multifunctional catalyst. Apart from the catalytic performance, unique catalyst design ideas, and structure-performance relationship, we also discuss current challenges in catalyst development and perspectives for industrial applications.

Enhanced CO evolution for photocatalytic conversion of CO2 by H2O over Ca modified Ga2O3

Artificial photosynthesis is a desirable critical technology for the conversion of CO₂ and H₂O, which are abundant raw materials, into fuels and chemical feedstocks. Similar to plant photosynthesis, artificial photosynthesis can produce CO, CH₃OH, CH₄, and preferably higher hydrocarbons from CO₂ using H₂O as an electron donor and solar light. At present, only insufficient amounts of CO₂-reduction products such as CO, CH₃OH, and CH₄ have been obtained using such a photocatalytic and photoelectrochemical conversion process. Here, we demonstrate that photocatalytic CO₂ conversion with a Ag@Cr-decorated mixture of CaGa₄O₇-loaded Ga₂O₃ and the CaO photocatalyst leads to a satisfactory CO formation rate (>835 µmol h^-1) and excellent selectivity toward CO evolution (95%), with O₂ as the stoichiometric oxidation product of H₂O. Our photocatalytic system can convert CO₂ gas into CO at >1% CO₂ conversion (>11531 ppm CO) at ambient temperatures and pressures.

Quantitative carbon distribution analysis of hydrocarbons, alcohols and carboxylic acids in a Fischer-Tropsch product from a Co/TiO2 catalyst during gas phase pilot plant operation

Comprehensive two-dimensional gas chromatography (GCxGC) analysis for 1-alcohols and gas chromatography–mass spectrometry (GC-MS) analysis for carboxylic acids, derivatised as their methyl esters, have been applied to liquid and wax Fischer-Tropsch (FT) hydrocarbon products. These methods in combination with conventional one-dimensional gas chromatography (GC) analysis of the aqueous, gaseous, liquid hydrocarbon and wax products plus conventional high-performance liquid chromatography (HPLC) analysis of the aqueous phase has allowed a quantitative distribution analysis of FT hydrocarbon and oxygenated products to be demonstrated for a Co/TiO2 catalyst operating in a fixed bed gas phase pilot plant utilising CANSTM catalyst carrier devices. The GC-MS method used is, to the best of our knowledge, the first application of this derivatisation route for the quantification of individual carboxylic acids in FT hydrocarbon product streams.

Whilst the hydrocarbons and oxygenates that were identified are known compounds formed during the low temperature, Co catalysed, FT process the combination of the multiple analysis techniques used has allowed a level of detail to be gained on the product composition that is seldom reported.

Additionally, 1H nuclear magnetic resonance spectroscopy (NMR) and 13C NMR analyses were used to quantify the average concentration of 1-olefin, cis- and trans-2-olefins, 1-alcohol and aldehyde as appropriate for the technique used. Comparison of GCxGC versus 1H NMR and GC-MS versus a KOH titration confirmed the applicability of the chromatographic methods for the quantitative analysis of FT oxygenated compounds. Long-chain 1-alcohols and carboxylic acids, ≥ C3, were found to be present at levels of 1/10th and 1/1000th that of hydrocarbons of equivalent carbon chain length respectively. The 1-olefin:n-paraffin ratio in the hydrocarbon liquid and wax products was found to decrease significantly with increasing carbon chain length and much more so than those of the 2-olefin or 1-alcohol.

Nickel-assisted complete cleavage of CO by a silylene/siliconoid hybrid under formation of an Si[double bond, length as m-dash]C enol ether bridge

Reaction of a silylene-functionalized Si6 siliconoid with CO in the presence of catalytic quantities of a nickel(0) complex results in the complete cleavage of the CO triple bond, but preserves the Si6 scaffold with an exohedrally incorporated Si[double bond, length as m-dash]C enol ether bridge. The uncompromised cluster core emphasizes the role of the so-called benzpolarene motif as the energetic silicon pendants of benzene in carbon chemistry.

Chemical Batteries with CO2

Efforts to obtain raw materials from CO₂ by catalytic reduction as a means of combating greenhouse gas emissions are pushing the boundaries of the chemical industry. The dimensions of modern energy regimes, on the one hand, and the necessary transport and trade of globally produced renewable energy, on the other, will require the use of chemical batteries in conjunction with the local production of renewable electricity. The synthesis of methanol is an important option for chemical batteries and will, for that reason, be described here in detail. It is also shown that the necessary, robust, and fundamental understanding of processes and the material science of catalysts for the hydrogenation of CO₂ does not yet exist.

Metal 3D printing technology for functional integration of catalytic system

Mechanical properties and geometries of printed products have been extensively studied in metal 3D printing. However, chemical properties and catalytic functions, introduced by metal 3D printing itself, are rarely mentioned. Here we show that metal 3D printing products themselves can simultaneously serve as chemical reactors and catalysts (denoted as self-catalytic reactor or SCR) for direct conversion of C1 molecules (including CO, CO₂ and CH₄) into high value-added chemicals. The Fe-SCR and Co-SCR successfully catalyze synthesis of liquid fuel from Fischer-Tropsch synthesis and CO₂ hydrogenation; the Ni-SCR efficiently produces syngas (CO/H₂) by CO₂ reforming of CH₄. Further, the Co-SCR geometrical studies indicate that metal 3D printing itself can establish multiple control functions to tune the catalytic product distribution. The present work provides a simple and low-cost manufacturing method to realize functional integration of catalyst and reactor, and will facilitate the developments of chemical synthesis and 3D printing technology.

Metal 3D printing is a very promising technology to revolutionize catalytic systems. Here the authors show that metal 3D printing products themselves can simultaneously serve as chemical reactors and catalysts for conversion of C1 molecules into high value-added chemicals.

Heavy-Metal-Free Fischer-Tropsch Type Reaction: Sequential Homologation of Alkylborane Using a Combination of CO and Hydrides as Methylene Source

Carbon homologation reactions occur within the well-known Fischer-Tropsch process, usually mediated by transition metal catalysts at high temperature. Here we report the low-temperature, heavy-metal-free homologation of a carbon chain using CO as a C₁-source showing for the first time that transition-metal catalysts are not required for Fischer-Tropsch-type reactivity. Reaction of an alkylborane in the presence of either LiHBEt₃ or LiAlH₄ resulted in multiple CO insertion/reduction events to afford elongated chains by more than two methylene (-CH₂-) units, affording aldehyde products upon oxidative aqueous workup. Theoretical and experimental mechanistic studies indicate that the boron terminus is responsible for CO incorporation as well as sequential hydride delivery leading to reduction of acylborane intermediates to alkylboranes.