Tuning the catalytic CO hydrogenation to straight- and long-chain aldehydes/alcohols and olefins/paraffins

Active learning streamlines development of high performance catalysts for higher alcohol synthesis

Developing efficient catalysts for syngas-based higher alcohol synthesis (HAS) remains a formidable research challenge. The chain growth and CO insertion requirements demand multicomponent materials, whose complex reaction dynamics and extensive chemical space defy catalyst design norms. We present an alternative strategy by integrating active learning into experimental workflows, exemplified via the FeCoCuZr catalyst family. Our data-aided framework streamlines navigation of the extensive composition and reaction condition space in 86 experiments, offering >90% reduction in environmental footprint and costs over traditional programs. It identifies the Fe65Co19Cu5Zr11 catalyst with optimized reaction conditions to attain higher alcohol productivities of 1.1 gHA h-1 gcat-1 under stable operation for 150 h on stream, a 5-fold improvement over typically reported yields. Characterization reveals catalytic properties linked to superior activities despite moderate higher alcohol selectivities. To better reflect catalyst demands, we devise multi-objective optimization to maximize higher alcohol productivity while minimizing undesired CO2 and CH4 selectivities. An intrinsic trade-off between these metrics is uncovered, identifying Pareto-optimal catalysts not readily discernible by human experts. Finally, based on feature-importance analysis, we formulate data-informed guidelines to develop performance-specific FeCoCuZr systems. This approach goes beyond existing HAS catalyst design strategies, is adaptable to broader catalytic transformations, and fosters laboratory sustainability.

Visualizing Phase Evolution of Co2C for Efficient Fischer-Tropsch to Olefins

Cobalt carbide (Co2C) possesses high catalytic efficiency Fischer-Tropsch synthesis (FTS), while the products selectivity appears sensitive to crystallography geometry. Since the Anderson-Schulz-Flory (ASF) distribution in FTS is broken through fabricating facetted Co2C nanocrystals, yet the underlying mechanism of Co2C crystallization remains unclarified suffering from sophisticated catalyst composition involving promoter agents. Herein, the synthesis of high-purity single-crystal nanoprisms (Co2C-p) for highly efficient FTS is reported to lower olefins. Through comprehensive microstructure analysis, e.g., high-resolution TEM, in situ TEM and electron diffraction, as well as finite element simulation of gas flow field, for the first time the full roadmap of forming catalytic active cobalt carbides is disclosed, starting from reduction of Co3O4 precursor to CoO intermediate, then carburization into Co2C-s and subsequent ripening growth into Co2C-p. This gas-induced engineering of crystal phase provides a new synthesis strategy, with many new possibilities for precise design of metal-based catalyst for diverse catalytic applications.

Ultrafast photoinduced C-H bond formation from two small inorganic molecules

The formation of carbon-hydrogen (C-H) bonds via the reaction of small inorganic molecules is of great significance for understanding the fundamental transition from inorganic to organic matter, and thus the origin of life. Yet, the detailed mechanism of the C-H bond formation, particularly the time scale and molecular-level control of the dynamics, remain elusive. Here, we investigate the light-induced bimolecular reaction starting from a van der Waals molecular dimer composed of two small inorganic molecules, H2 and CO. Employing reaction microscopy driven by a tailored two-color light field, we identify the pathways leading to C-H photobonding thereby producing HCO+ ions, and achieve coherent control over the reaction dynamics. Using a femtosecond pump-probe scheme, we capture the ultrafast formation time, i.e., 198 ± 16 femtoseconds. The real-time visualization and coherent control of the dynamics contribute to a deeper understanding of the most fundamental bimolecular reactions responsible for C-H bond formation, thus contributing to elucidate the emergence of organic components in the universe.

Intermetallic Ni3Ga1 Catalyst for Efficient Ammonia Reforming of Light Alkane

Ammonia reforming of light alkane is conventionally employed for HCN production where coproduct H2 is burned for heating owing to the high reaction temperature (1200 °C) of such a highly endothermic process. Here, we show that a Ni3Ga1 intermetallic compound (IMC) catalyst is highly efficient for such a reaction, realizing efficient conversion of C1-C3 alkanes at 575-750 °C. This makes it feasible for on-purpose COx-free H2 production assuming that ammonia, as an H2 carrier, is ubiquitously available from renewable energy. At 650 °C and an alkane/ammonia ratio of 1/2, ethane and propane conversion of ∼20% and methane conversion of 13% were obtained (with nearly 100% HCN selectivity for methane and ethane) over the unsupported Ni3Ga1 IMC, which also shows high stability due to the absence of coke deposition. This breakthrough is achieved by employing a stoichiometric Ni3Ga1 mixed oxalate solid solution as the precursor for the Ni3Ga1 IMC.

Promoting nonsymmetric C-C coupling to valuable oxygenates without metal catalysts in alkali aqueous medium

Efficient conversion of C1 molecules into multicarbon oxygenates is a promising avenue for energy storage. Herein, we synthesize adjustable alkanoic acids/alcohols from formate C1 molecules via a hydrothermal reaction without any metal catalyst participation. This is achieved via HCO* and HCOO- nonsymmetric C-C coupling by alkali catalysis in aqueous medium.

The oscillating Fischer-Tropsch reaction

The mechanistic steps that underlie the formation of higher hydrocarbons in catalytic carbon monoxide (CO) hydrogenation at atmospheric pressure over cobalt-based catalysts (Fischer-Tropsch synthesis) have remained poorly understood. We reveal nonisothermal rate-and-selectivity oscillations that are self-sustained over extended periods of time (>24 hours) for a cobalt/cerium oxide catalyst with an atomic ratio of cobalt to cerium of 2:1 (Co2Ce1) at 220°C and equal partial pressures of the reactants. A microkinetic mechanism was used to generate rate-and-selectivity oscillations through forced temperature oscillations. Experimental and theoretical oscillations were in good agreement over an extended range of reactant pressure ratios. Additionally, phase portraits for hydrocarbon production were constructed that support the thermokinetic origin of our rate-and-selectivity oscillations.

ZrO2-Promoted Cu-Co, Cu-Fe and Co-Fe Catalysts for Higher Alcohol Synthesis

The development of efficient catalysts for the direct synthesis of higher alcohols (HA) via CO hydrogenation has remained a prominent research challenge. While modified Fischer-Tropsch synthesis (m-FTS) systems hold great potential, they often retain limited active site density under operating conditions for industrially relevant performance. Aimed at improving existing catalyst architectures, this study investigates the impact of highly dispersed metal oxides of Co-Cu, Cu-Fe, and Co-Fe m-FTS systems and demonstrates the viability of ZrO2 as a general promoter in the direct synthesis of HA from syngas. A volcano-like composition-performance relationship, in which 5-10 mol % ZrO2 resulted in maximal HA productivity, governs all catalyst families. The promotional effect resulted in a 2.5-fold increase in HA productivity for the optimized Cu1Co4@ZrO2-5 catalyst (Cu:Co = 1:4, 5 mol % ZrO2) compared to its ZrO2-free counterpart and placed Co1Fe4@ZrO2-10 among the most productive systems (345 mgHA h-1 gcat-1) reported in this category under comparable operating conditions, with stable performance for at least 300 h. ZrO2 assumes an amorphous and defective nature on the catalysts, leading to enhanced H2 and CO activation, facilitated formation of metallic and carbide phases, and structural stabilization.

A review of Co/Co2C-based catalysts in Fischer-Tropsch synthesis: from fundamental understanding to industrial applications

Fischer-Tropsch synthesis (FTS), which provides a green route to the production of clean fuels and fine chemicals, represents some significant applications of catalytic materials and processes in the chemical industry. FTS reactions show a diversity of mechanisms, involve various catalytic materials, and offer options for continuous investigation. Cobalt-based catalysts have been widely used for Fischer-Tropsch synthesis both in academia and in industry. This mini-review will focus on relevant research achievements in cobalt-based FTS catalysts by our group in the Dalian Institute of Chemical Physics (DICP). Specific contents will include the development of Co/Co₂C-based nano-catalysts (i) for the highly selective synthesis of clean fuels over Co-based catalysts supported by carbon materials and (ii) for the synthesis of linear α-alcohols and olefins over Co-Co₂C-based catalysts supported by carbon materials. The direct synthesis of linear α-alcohols from syngas using a Co-Co₂C/AC catalyst is highlighted. The innovative work of FTS using activated carbon (AC)-supported Co/Co₂C-based nano-catalysts could bring some insight into new FTS catalyst designs.

Recent advances in Co2C-based nanocatalysts for direct production of olefins from syngas conversion

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.

Direct Conversion of Syngas to Higher Alcohols via Tandem Integration of Fischer-Tropsch Synthesis and Reductive Hydroformylation

The selective conversion of syngas to higher alcohols is an attractive albeit elusive route in the quest for effective production of chemicals from alternative carbon resources. We report the tandem integration of solid cobalt Fischer–Tropsch and molecular hydroformylation catalysts in a one‐pot slurry‐phase process. Unprecedented selectivities (>50 wt %) to C₂₊ alcohols are achieved at CO conversion levels >70 %, alongside negligible CO₂ side‐production. The efficient overall transformation is enabled by catalyst engineering, bridging gaps in operation temperature and intrinsic selectivity which have classically precluded integration of these reactions in a single conversion step. Swift capture of 1‐olefin Fischer–Tropsch primary products by the molecular hydroformylation catalyst, presumably within the pores of the solid catalyst is key for high alcohol selectivity. The results underscore that controlled cooperation between solid aggregate and soluble molecular metal catalysts, which pertain to traditionally dichotomic realms of heterogeneous and homogeneous catalysis, is a promising blueprint toward selective conversion processes.

Aliphatic Aldehydes in the Earth's Crust-Remains of Prebiotic Chemistry?

The origin of life is a mystery that has not yet been solved in the natural sciences. Some promising interpretative approaches are related to hydrothermal activities. Hydrothermal environments contain all necessary elements for the development of precursor molecules. There are surfaces with possible catalytic activity, and wide ranges of pressure and temperature conditions. The chemical composition of hydrothermal fluids together with periodically fluctuating physical conditions should open up multiple pathways towards prebiotic molecules. In 2017, we detected potentially prebiotic organic substances, including a homologous series of aldehydes in Archean quartz crystals from Western Australia, more than 3 billion years old. In order to approach the question of whether the transformation of inorganic into organic substances is an ongoing process, we investigated a drill core from the geologically young Wehr caldera in Germany at a depth of 1000 m. Here, we show the existence of a similar homologous series of aldehydes (C₈ to C₁₆) in the fluid inclusions of the drill core calcites, a finding that supports the thesis that hydrothermal environments could possibly be the material source for the origin of life.

Tandem utilization of CO2 photoreduction products for the carbonylation of aryl iodides

Photocatalytic CO₂ reduction reaction has been developed as an effective strategy to convert CO₂ into reusable chemicals. However, the reduction products of this reaction are often of low utilization value. Herein, we effectively connect photocatalytic CO₂ reduction and amino carbonylation reactions in series to reconvert inexpensive photoreduction product CO into value-added and easily isolated fine chemicals. In this tandem transformation system, we synthesize an efficient photocatalyst, NNU-55-Ni, which is transformed into nanosheets (NNU-55-Ni-NS) in situ to improve the photocatalytic CO₂-to-CO activity significantly. After that, CO serving as reactant is further reconverted into organic molecules through the coupled carbonylation reactions. Especially in the carbonylation reaction of diethyltoluamide synthesis, CO conversion reaches up to 85%. Meanwhile, this tandem transformation also provides a simple and low-cost method for the ¹³C isotopically labeled organic molecules. This work represents an important and feasible pathway for the subsequent separation and application of CO₂ photoreduction product.

Direct synthesis of higher alcohols from syngas over modified Mo2C catalysts under mild reaction conditions

The RhK/Mo2C catalyst exhibited remarkable selectivity for higher alcohols synthesis from syngas under mild reaction conditions owing to the interface sites between Rh and Mo2C promoted by K, which greatly facilitated CO insertion.

Effect of potassium on carbon adsorption on the Co(0001) surface

The effect of potassium on carbon adsorption and deposition on the Co(0001) surface was studied on the basis of theoretical calculations. Thermodynamically, the surface C_n species is expected, and C₂ dimer may be a critical elementary unit. With the increase of carbon coverage, a fraction of the carbon atoms may diffuse into the subsurface. But kinetically, the formation of C_n species is more favorable, and there is no driving force for carbon to migrate into the subsurface. As the surface carbon concentration increases, the adsorbed carbon atoms turn into carbon chains and then into graphene sheets parallel to the surface. Potassium promoter has little effect on the most stable adsorption configurations of carbon atoms but increases the adsorption energy of carbon species, which can be explained by the decreasing of the surface work function resulting from the electron effect of potassium promoter. The potassium promotes carbon deposition and carbonization of the cobalt surface to a certain extent. These results could support some useful information for the carbon deposition and cobalt carbide formation.

Single-pass transformation of syngas into ethanol with high selectivity by triple tandem catalysis

Synthesis of ethanol from non-petroleum carbon resources via syngas (a mixture of H₂ and CO) is an important but challenging research target. The current conversion of syngas to ethanol suffers from low selectivity or multiple processes with high energy consumption. Here, we report a high-selective conversion of syngas into ethanol by a triple tandem catalysis. An efficient trifunctional tandem system composed of potassium-modified ZnO–ZrO₂, modified zeolite mordenite and Pt–Sn/SiC working compatibly in syngas stream in one reactor can afford ethanol with a selectivity of 90%. We demonstrate that the K⁺–ZnO–ZrO₂ catalyses syngas conversion to methanol and the mordenite with eight-membered ring channels functions for methanol carbonylation to acetic acid, which is then hydrogenated to ethanol over the Pt–Sn/SiC catalyst. The present work offers an effective methodology leading to high selective conversion by decoupling a single-catalyst-based complicated and uncontrollable reaction into well-controlled multi-steps in tandem in one reactor.

Direct synthesis of ethanol from non-petroleum carbon resources via syngas (CO/H₂) is a highly attractive but challenging target. Here, the authors report a triple tandem catalytic system for single-pass conversion of syngas into ethanol with selectivity as high as 90%.

Interfacial Fe5C2-Cu catalysts toward low-pressure syngas conversion to long-chain alcohols

Long-chain alcohols synthesis (LAS, C₅₊OH) from syngas provides a promising route for the conversion of coal/biomass/natural gas into high-value chemicals. Cu-Fe binary catalysts, with the merits of cost effectiveness and high CO conversion, have attracted considerable attention. Here we report a nano-construct of a Fe₅C₂-Cu interfacial catalyst derived from Cu₄Fe₁Mg₄-layered double hydroxide (Cu₄Fe₁Mg₄-LDH) precursor, i.e., Fe₅C₂ clusters (~2 nm) are immobilized onto the surface of Cu nanoparticles (~25 nm). The interfacial catalyst exhibits a CO conversion of 53.2%, a selectivity of 14.8 mol% and a space time yield of 0.101 g g_cat⁻¹ h⁻¹ for long-chain alcohols, with a surprisingly benign reaction pressure of 1 MPa. This catalytic performance, to the best of our knowledge, is comparable to the optimal level of Cu-Fe catalysts operated at much higher pressure (normally above 3 MPa).

Long-chain alcohols synthesis from syngas conversion is a promising route for the production of high-value chemicals. Here the authors show that a heterogeneous Fe₅C₂/Cu catalyst derived from layered double hydroxides precursor exhibits excellent performance with a space time yield of 0.101 g g_cat⁻¹ h⁻¹ at a low pressure of 1 MPa.

Effects of alkali metal promoters on the structure–performance relationship of CoMn catalysts for Fischer–Tropsch synthesis

Alkali metal promoters are beneficial for the formation and facet-stabilization of Co₂C nanoprisms for the FTO reaction.

Editorial: Cobalt and Iron Catalysis

Cobalt and iron have long history of importance in the field of catalysis that continues to this day [...]

Rate and selectivity hysteresis during the carbon monoxide hydrogenation over promoted Co/MnOx catalysts

While cobalt-based catalysts have been used in industrial Fischer-Tropsch synthesis for decades, little is known about how the dynamics of the Co-Co₂C phase transformation drive their performance. Here we report on the occurrence of hysteresis effects in the Fischer-Tropsch reaction over potassium promoted Co/MnO_x catalyst. Both the reaction rate and the selectivity to chain-lengthened paraffins and terminally functionalized products (aldehydes, alcohols, olefins) show bistability when varying the hydrogen/carbon monoxide partial pressures back and forth from overall reducing to carbidizing conditions. While the carbon monoxide conversion and the selectivity to functionalized products follow clockwise hysteresis, the selectivity to paraffins shows counter-clockwise behavior. In situ X-ray diffraction demonstrates the activity/selectivity bistability to be driven by a Co-Co₂C phase transformation. The conclusions are supported by High Resolution Transmission Electron Microscopy which identifies the Co-Co₂C transformation, Mn₅O₈ layered topologies at low H₂/CO partial pressure ratios, and MnO at high such ratios.

The question for the structure-reactivity relationship of cobalt-based catalysts for the carbon monoxide hydrogenation is as old as the reaction itself. Here the authors show kinetic hysteresis for a potassium-promoted cobalt-manganese oxide catalyst to be driven by the Co-Co₂C phase transition.

Atom Probe Tomography for Catalysis Applications: A Review

Atom probe tomography is a well-established analytical instrument for imaging the 3D structure and composition of materials with high mass resolution, sub-nanometer spatial resolution and ppm elemental sensitivity. Thanks to recent hardware developments in Atom Probe Tomography (APT), combined with progress on site-specific focused ion beam (FIB)-based sample preparation methods and improved data treatment software, complex materials can now be routinely investigated. From model samples to complex, usable porous structures, there is currently a growing interest in the analysis of catalytic materials. APT is able to probe the end state of atomic-scale processes, providing information needed to improve the synthesis of catalysts and to unravel structure/composition/reactivity relationships. This review focuses on the study of catalytic materials with increasing complexity (tip-sample, unsupported and supported nanoparticles, powders, self-supported catalysts and zeolites), as well as sample preparation methods developed to obtain suitable specimens for APT experiments.

An Amorphous Nickel-Iron-Based Electrocatalyst with Unusual Local Structures for Ultrafast Oxygen Evolution Reaction

Rationally designing active and durable catalysts for the oxygen evolution reaction (OER) is of primary importance in water splitting. Perovskite oxides (ABO₃ ) with versatile structures and multiple physicochemical properties have triggered considerable interest in the OER. The leaching of A site cations can create nanostructures and amorphous motifs on the perovskite matrix, thus facilitating the OER process. However, selectively dissolving A site cations and simultaneously obtaining more active amorphous motifs derived from the B site cations remains a great challenge. Herein, a top-down strategy is proposed to transform bulk crystalline perovskite (LaNiO₃ ) into a nanostructured amorphous hydroxide by FeCl₃ post-treatment, resulting in an extremely low overpotential of 189 mV at 10 mA cm^-2 . The top-down-constructed amorphous catalyst with a large surface area has dual NiFe active sites, where high-valence Ni³⁺ -based edge-sharing octahedral frameworks are surrounded by interstitial distorted Fe octahedra and contribute to the superior OER performance. This top-down strategy provides a valid way to design novel perovskite-derived catalysts.

Facile efficient earth abundant NiO/C composite electrocatalyst for the oxygen evolution reaction

Due to the increasing energy consumption, designing efficient electrocatalysts for electrochemical water splitting is highly demanded. In this study, we provide a facile approach for the design and fabrication of efficient and stable electrocatalysts through wet chemical methods. The carbon material, obtained by the dehydration of sucrose sugar, provides high surface area for the deposition of NiO nanostructures and the resulting NiO/C catalysts show higher activity towards the OER in alkaline media. During the OER, a composite of NiO with 200 mg C can produce current densities of 10 and 20 mA cm-2 at a bias of 1.45 V and 1.47 V vs. RHE, respectively. Electrochemical impedance spectroscopy experiments showed the lowest charge transfer resistance and the highest double layer capacitance in the case of the NiO/C composite with 200 mg C. The presence of C for the deposition of NiO nanostructures increases the active centers and consequently a robust electrocatalytic activity is achieved. The obtained results in terms of the low overpotential and small Tafel slope of 55 mV dec-1 for non-precious catalysts are clear indications for the significant advancement in the field of electrocatalyst design for water splitting. This composite material based on NiO/C is simple and scalable for widespread use in various applications, especially in supercapacitors and lithium-ion batteries.

Promoted cobalt metal catalysts suitable for the production of lower olefins from natural gas

Due to the surge of natural gas production, feedstocks for chemicals shift towards lighter hydrocarbons, particularly methane. The success of a Gas-to-Chemicals process via synthesis gas (CO and H2) depends on the ability of catalysts to suppress methane and carbon dioxide formation. We designed a Co/Mn/Na/S catalyst, which gives rise to negligible Water-Gas-Shift activity and a hydrocarbon product spectrum deviating from the Anderson-Schulz-Flory distribution. At 240 °C and 1 bar, it shows a C2-C4 olefins selectivity of 54%. At 10 bar, it displays 30% and 59% selectivities towards lower olefins and fuels, respectively. The spent catalyst consists of 10 nm Co nanoparticles with hcp Co metal phase. We propose a synergistic effect of Na plus S, which act as electronic promoters on the Co surface, thus improving selectivities towards lower olefins and fuels while largely reducing methane and carbon dioxide formation.