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Catalytic transformation of CO2 into chemicals in large demand such as ethanol has attracted much research attention under the background of establishing carbon-neutral societies. Supported Rh cata...

Cu–ZnO–Al2O3 catalysts are used as the industrial catalysts for water gas shift (WGS) and CO hydrogenation to methanol reactions. Herein, via a comprehensive experimental and theoretical calculation study of a series of ZnO/Cu nanocrystals inverse catalysts with well-defined Cu structures, we report that the ZnO–Cu catalysts undergo Cu structure-dependent and reaction-sensitive in situ restructuring during WGS and CO hydrogenation reactions under typical reaction conditions, forming the active sites of CuCu(100)-hydroxylated ZnO ensemble and CuCu(611)Zn alloy, respectively. These results provide insights into the active sites of Cu–ZnO catalysts for the WGS and CO hydrogenation reactions and reveal the Cu structural effects, and offer the feasible guideline for optimizing the structures of Cu–ZnO–Al2O3 catalysts., Identification of active sites of a catalyst is the Holy Grail in heterogeneous catalysis. Here, the authors successfully identify the CuCu(100)- hydroxylated ZnO ensemble and CuCu(611)Zn alloy as the active sites of Cu-ZnO catalysts for water gas shift and CO hydrogenation reactions, respectively.

Recent studies demonstrate that bifunctional catalysts composed of metal oxide and zeolite can effectively control the hydrocarbon distribution in syngas conversion. In this effort, a set of eight silicoaluminophosphate (SAPO) zeolites with different topology structures are synthesized and integrated with a binary ZnAlO oxide for syngas conversion. The effects of micropore window size and cage size of SAPO zeolites, and reaction conditions on the hydrocarbon distribution are preliminarily investigated. It was found that the hydrocarbon distribution is primarily determined by the window size of SAPO zeolites, and a volcano trend was observed between the chain length of hydrocarbon products and the window sizes. The cage size of zeolites and reaction conditions only modifies the hydrocarbon distribution in a narrow range of chain length. The effect of zeolite topology on the hydrocarbon distribution in syngas conversion is overall in line with that in methanol conversion. These findings provide an efficient strategy to increase the selectivity of an individual hydrocarbon product in syngas conversion, such as ethylene, propylene, butenes, iso-butane and C5–C11 iso-paraffins.

The hydrogenation of CO2 and CO to chemicals are highly attractive but very challenging. Here, we report that a Na- and Zn-promoted iron catalyst composed of Na+, ZnO and χ-Fe5C2 is efficient for the hydrogenation of CO2 and CO into C2+ olefins. The selectivity of C2−C12 olefins reached 78%, and the space–time yield of olefins attained as high as 3.4 g gcat−1h−1 in CO2 hydrogenation. The intrinsic formation rate of C2−C12 olefins in CO hydrogenation was about twice higher as compared to that in CO2 hydrogenation. The hydrogenation of CO2 to olefins proceeds via CO intermediate over our catalyst. We unravel that ZnO functions for the reverse water–gas shift reaction of CO2 to CO, while χ-Fe5C2 catalyzes CO hydrogenation to olefins and the presence of Na+ suppresses the hydrogenation of olefins. The close proximity between ZnO and χ-Fe5C2 plays a key role in conversion of CO2 to olefins.

Bifunctional process integrating methanol synthesis and methanol-to-olefins conversion provides a new synthetic strategy for lower olefins (C 2 C4=), whereas designing matchable zeolite components is still challenging due to the harsh reaction conditions. Here, a hierarchical SAPO-34 zeolite with a sandglass-like hollow structure is synthesized from an aluminum-rich precursor gel, which provides an abundance of crystal defects during zeolite crystallization. The bifunctional catalyst obtained by integrating the hierarchical SAPO-34 and ZnO ZrO2 oxide offers a C2 C4= selectivity of 80% at 25% CO conversion with excellent stability in syngas conversion. We demonstrate that in the presence of high-pressure hydrogen, a moderate density of acid sites is the prerequisite for obtaining high C2 C4= selectivity in syngas/methanol conversion, because the olefins are easily hydrogenated into alkanes by excessive Bronsted acid sites. The hierarchical architecture significantly prolongs the lifetime of bifunctional catalysts, by facilitating C2 C4= desorption and slowing down the coking rate.

Hydrogenation of CO2 using renewable hydrogen to build block chemicals, such as lower olefins and aromatics, not only mitigates the CO2 emissions, but also realizes the utilization of CO2 as a carbon resource. However, it is difficult to activate the inert CO2 and precisely control the C–C coupling. As a result, the hydrogenation of CO2 mainly produces C1 product, and selective synthesis of hydrocarbon chemicals with C–C chains is challenging. In 2016, Chinese scientists first reported the relay catalysis, in which metal oxides and acidic zeolites were integrated together as bifunctional catalysts, for converting synthesis gas to lower olefins and aromatics. Inspired by this, a number of bifunctional catalysts have been recently reported for the hydrogenation of CO2 to lower olefins and aromatics, using the concept of replay catalysis. In this review, we summarize the recent advances in the transformation of CO2 to high-value chemicals and try to clarify how to connect two reactions with different characteristics. The key factors that affect the product distribution are also discussed.

Catalytic conversion of the syngas into higher alcohols (HAs) via Fischer–Tropsch (F–T) synthesis is essential due to the widespread applications of HAs. The interfaces of cobalt and cobalt carbide (Co2C) are found to efficiently promote the HAs formation. However, the study on the links between structural evolution of Co–Co2C interfaces and HAs production is still lacking. In this work, Co3O4 with different contents of sodium (Na) as promoters was synthesized and high-pressure F–T reaction (3 MPa) was carried out in the aim of accelerating the Co2C formation and tuning the interfaces of Co–Co2C. XRD, (HR)TEM, ICP, XPS and XAFS were conducted to study the relationship between the variations of Co–Co2C interfaces and HAs production. With the increasing Na contents, the ratios of Co to Co2C decreased as revealed by XAFS and the selectivity of HAs was decreasing. The fitting results from EXAFS revealed that the ratio of Co to Co2C is in direct proportion to the selectivity of HAs. This work provides a theoretical guidance to tune the interfaces of Co–Co2C and improve the HAs production in F–T reaction.

Identifying surface-active sites and reaction pathways is of great significance in heterogeneous catalysis. However, even for the simplest catalytic reaction, there could exist a myriad of possible...

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%.

Tandem catalysis via methanol intermediate is a promising route for the direct conversion of syngas into aromatics. However, the simultaneous formation of CO2 is a serious problem. Here, we demonstrate that CO2 was formed by the water-gas shift (WGS) reaction (CO + H2O → CO2 + H2) over a ZnO–ZrO2/H-ZSM-5 catalyst, and the net CO2 formation could be inhibited without affecting the formation of aromatics by co-feeding CO2.

Bifunctional catalysis coupling CO2 to methanol and methanol to hydrocarbons is a promising strategy for the direct hydrogenation of CO2 into high-value chemicals. However, bifunctional catalysts s...

Catalytic transformations of syngas (a mixture of H2 and CO), which is one of the most important C1-chemistry platforms, and CO2, a greenhouse gas released from human industrial activities but also a candidate of abundant carbon feedstock, into chemicals and fuels have attracted much attention in recent years. Fischer-Tropsch (FT) synthesis is a classic route of syngas chemistry, but the product selectivity of FT synthesis is limited by the Anderson-Schulz-Flory (ASF) distribution. The hydrogenation of CO2 into C2+ hydrocarbons involving C-C bond formation encounters similar selectivity limitation. The present article focuses on recent advances in breaking the selectivity limitation by using a reaction coupling strategy for hydrogenation of both CO and CO2 into C2+ hydrocarbons, which include key building-block chemicals, such as lower (C2-C4) olefins and aromatics, and liquid fuels, such as gasoline (C5-C11 hydrocarbons), jet fuel (C8-C16 hydrocarbons) and diesel fuel (C10-C20 hydrocarbons). The design and development of novel bifunctional or multifunctional catalysts, which are composed of metal, metal carbide or metal oxide nanoparticles and zeolites, for hydrogenation of CO and CO2 to C2+ hydrocarbons beyond FT synthesis will be reviewed. The key factors in controlling catalytic performances, such as the catalyst component, the acidity and mesoporosity of the zeolite and the proximity between the metal/metal carbide/metal oxide and zeolite, will be analysed to provide insights for designing efficient bifunctional or multifunctional catalysts. The reaction mechanism, in particular the activation of CO and CO2, the reaction pathway and the reaction intermediate, will be discussed to provide a deep understanding of the chemistry of the new C1 chemistry routes beyond FT synthesis.

Functionalized carbon materials are widely used in heterogeneous catalysis due to their unique properties such as adjustable surface properties, excellent thermal conductivity, high surface areas, tunable porosity, and moderate interactions with guest metals. The transformation of syngas into hydrocarbons (known as the Fischer-Tropsch synthesis) or oxygenates is an exothermic reaction and is typically catalyzed by transition metals dispersed on functionalized supports. Various carbon materials have been employed in syngas conversions not only for improving the performance or decreasing the dosage of expensive active metals but also for building model catalysts for fundamental research. This article provides a critical review on recent advances in the utilization of carbon materials, in particular the recently developed functionalized nanocarbon materials, for syngas conversions to either hydrocarbons or oxygenates. The unique features of carbon materials in dispersing metal nanoparticles, heteroatom doping, surface modification, and building special nanoarchitectures are highlighted. The key factors that control the reaction course and the reaction mechanism are discussed to gain insights for the rational design of efficient carbon-supported catalysts for syngas conversions. The challenges and future opportunities in developing functionalized carbon materials for syngas conversions are briefly analyzed.

Cu-ZnO-Al2O3 catalysts are used as the industrial catalysts for water gas shift (WGS) and CO hydrogenation to methanol reactions. Herein, via a comprehensive experimental and theoretical calculation study of a series of ZnO/Cu nanocrystals inverse catalysts with well-defined Cu structures, we report that the Cu-ZnO catalysts undergo Cu structure-dependent and reaction-sensitive in situ restructuring during WGS and CO hydrogenation reactions under typical reaction conditions, forming the active sites of CuCu(100)-hydroxylated ZnO ensemble and CuCu(611)Zn alloy, respectively. These results conclude the long-existing debates and provide the feasible guideline for optimizing the structures of Cu-ZnO-Al2O3 catalysts.

The selective hydrogenation of CO2 to value-added chemicals is attractive but still challenged by the high-performance catalyst. In this work, we report that gallium nitride (GaN) catalyzes the direct hydrogenation of CO2 to dimethyl ether (DME) with a CO-free selectivity of about 80%. The activity of GaN for the hydrogenation of CO2 is much higher than that for the hydrogenation of CO although the product distribution is very similar. The steady-state and transient experimental results, spectroscopic studies, and density functional theory calculations rigorously reveal that DME is produced as the primary product via the methyl and formate intermediates, which are formed over different planes of GaN with similar activation energies. This essentially differs from the traditional DME synthesis via the methanol intermediate over a hybrid catalyst. The present work offers a different catalyst capable of the direct hydrogenation of CO2 to DME and thus enriches the chemistry for CO2 transformations., The conversion of CO2 to valuable chemicals is still challenged by catalyst developments. Herein, the authors found that GaN is an efficient catalyst for selective CO2 hydrogenation to dimethyl ether as the primary product, in contrast to the traditional methanol-intermediate route over hybrid catalysts.

Tandem catalysis via methanol intermediate is a promising route for the direct conversion of syngas into aromatics. However, the simultaneous formation of CO2 is a serious problem. Here, we demonstrate that CO2 was formed by the water-gas shift (WGS) reaction (CO + H2O → CO2 + H2) over a ZnO-ZrO2/H-ZSM-5 catalyst, and the net CO2 formation could be inhibited without affecting the formation of aromatics by co-feeding CO2.

The direct conversion of CO2 into olefins has stimulated the enthusiasm because of its significant role in reducing CO2 emission and establishing carbon-neutrality society. Here, we report that Na and Zn promoted Fe (Na-Zn-Fe) catalysts show prominent catalytic performances, which provide C2-C12 olefin selectivity of 80% and high-valued C4+ linear α-olefin (LAO) selectivity of 46% at CO2 conversion of 39% in CO2 hydrogenation. The space-time yields (STYs) of C2-C12 olefins and LAOs could be achieved as high as 3.7 and 2.1 g gcat−1 h−1, respectively, which are significantly higher than those reported to date. The structure-performance of Na-Zn-Fe catalysts is well correlated. It is revealed that the addition of Zn into Fe catalysts remarkably reduces the particle size of Fe species, and enhances the H2 adsorption amount, which promote the activity of CO2 hydrogenation. The co-modification by Na promoter increases the CO2 adsorption, facilitates the formation of active Fe5C2 with higher proportion, and thus increases the CO2 conversion. Significantly, Na promoter is enriched on Fe surfaces and improves the olefin selectivity by inhibiting their hydrogenations. It is demonstrated that the reverse water–gas shift (RWGS) step in CO2 hydrogenation over Na-Zn-Fe catalyst is severely impeded by H2O, which formed during CO2 hydrogenation, and would make the CO2 conversion limited to an extent.

Selective conversion of syngas (CO/H2 ) into C2+ oxygenates is a highly attractive but challenging target. Herein, we report the direct conversion of syngas into methyl acetate (MA) by relay catalysis. MA can be formed at a lower temperature (ca. 473 K) using Cu-Zn-Al oxide/H-ZSM-5 and zeolite mordenite (H-MOR) catalysts separated by quartz wool (denoted as Cu-Zn-Al/H-ZSM-5|H-MOR) and also at higher temperatures (603-643 K) without significant deactivation using spinel-structured ZnAl2 O4 |H-MOR. The selectivity of MA and acetic acid (AA) reaches 87 % at a CO conversion of 11 % at 643 K. Dimethyl ether (DME) is the key intermediate and the carbonylation of DME results in MA with high selectivity. We found that the relay catalysis using ZnAl2 O4 |H-MOR|ZnAl2 O4 gives ethanol as the major product, while ethylene is formed with a layer-by-layer ZnAl2 O4 |H-MOR|ZnAl2 O4 |H-MOR combination. Close proximity between ZnAl2 O4 and H-MOR increases ethylene selectivity to 65 %.

The oxidative dehydrogenation of propane is an attractive reaction for propylene production, but the overoxidation leads to low propylene selectivity at considerable propane conversions. Here, we report the oxidative dehydrogenation of propane by oxygen in the presence of hydrogen chloride. CeO2 was found to be an efficient catalyst for the conversion of propane to propylene by (O2 + HCl). The reaction was structure-sensitive, and the catalytic behavior depended on the exposed facet of CeO2 nanocrystals. The nanorod exposing {110} and {100} facets showed the highest activity, whereas the nanocube enclosed by {100} facets was the most selective for propylene formation. The modification of CeO2 nanorods by NiO increased both propane conversion and propylene selectivity. A propylene selectivity of 80% was achieved at propane conversion of 69% over an 8 wt % NiO–CeO2 catalyst at 773 K, offering a single-pass propylene yield of 55%. No significant catalyst deactivation was observed in 100 h of reaction. HCl pl...

The direct conversion of syngas into lower olefins is a highly attractive route for the synthesis of lower olefins. The selectivity of lower olefins via the conventional Fischer–Tropsch (FT) synthesis is restricted to ∼60% with high CH4 selectivity due to the limitation by the Anderson–Schulz–Flory (ASF) distribution. Here, we report the design of bifunctional catalysts for the direct conversion of syngas into lower olefins with selectivity significantly breaking the ASF distribution. The selectivity of C2–C4 olefins reached 87% at a CO conversion of 10% and was sustained at 77% by increasing CO conversion to 29% over a bifunctional catalyst composed of Zn-doped ZrO2 nanoparticles and zeolite SSZ-13 nanocrystals. The selectivity of CH4 was lower than 3% at the same time. It is demonstrated that the molar ratio of Zn/Zr, the density of Bronsted acid sites of SSZ-13 and the proximity of the two components play crucial roles in determining CO conversion and lower-olefin selectivity. Our kinetic studies indicate that methanol and dimethyl ether (DME) are key reaction intermediates, and the conversion of syngas to methanol/DME is the rate-determining step over the bifunctional catalyst. Formate and methoxide species have been observed on Zn-doped ZrO2 surfaces during the activation of CO in H2, and the formed methanol/DME are transformed into lower olefins in SSZ-13.

A bifunctional catalyst composed of ZnGa2O4 with a spinel structure and molecular sieve SAPO-34 catalyses the direct conversion of CO2 to C2–C4 olefins with a selectivity of 86% and a CO2 conversion of 13% at 370 °C. The oxygen vacancies on ZnGa2O4 surfaces are responsible for CO2 activation, forming a methanol intermediate, which is then converted into C2–C4 olefins in SAPO-34.

Summary Syngas (CO/H 2 ) is a key platform for chemical utilization of non-petroleum carbon resources. Among syngas transformation routes, the direct synthesis of aromatics, which are among the most important bulk chemicals, is less successful because of the limited selectivity and poor catalyst stability. We report a successful design of bifunctional catalysts composed of Zn-doped ZrO 2 nanoparticles dispersed on zeolite H-ZSM-5 for one-step conversion of syngas to aromatics with high selectivity and stability. Aromatics with 80% selectivity at CO conversion of 20% were achieved, and there was no catalyst deactivation in 1,000 hr. Methanol and dimethyl ether were formed as major intermediates on Zn-doped ZrO 2 , which were subsequently converted into aromatics on H-ZSM-5 via olefins. We discovered a self-promotion mechanism of CO in the selective formation of aromatics. As well as being a reactant, CO facilitates the removal of hydrogen species formed on H-ZSM-5 in the dehydrogenative aromatization of olefins.

Uniform iron nanoparticles dispersed on polyaniline have been used as catalysts for the direct conversion of synthesis gas into lower olefins. As compared to active carbon and N-doped active carbon, polyaniline as a support of Fe catalysts showed higher selectivity of lower olefins (C2–4 ). The C2–4 selectivity reached ∼50% at a CO conversion of 79% over a 10 wt% Fe/polyaniline catalyst without any promoters. The XRD, H2-TPR, TEM and HRTEM studies revealed that the presence of nitrogen-containing groups in polyaniline structure could promote the dispersion and reduction of iron oxides, forming higher fraction of iron carbides with smaller mean sizes and narrower size distributions. The propylene-TPD result indicates that the use of polyaniline support facilitates the desorption of lower olefins, thus suppressing the consecutive hydrogenation to form undesirable lower paraffins.

ZnO-containing MFI zeolite catalysts with bimodal and trimodal hierarchical pore structures were prepared, characterized and studied for the conversion of methanol to aromatics. Treatments of H-ZSM-5 with NH4F and NaOH generated bigger micropores with a mean size of around 0.8 nm and mesopores with mean sizes of 5–20 nm, respectively. The combination of alkaline and fluoride treatments resulted in a trimodal pore structure. The method for H-ZSM-5 treatments affected the dispersion of ZnO. The fluoride treatment favoured the dispersion of ZnO, whereas the alkaline treatment led to large ZnO particles. We clarified that the hierarchical pore structure, acidity and dispersion of ZnO played crucial roles in the formation of aromatics. Benzene, toluene and xylenes (BTX) mainly constituted the aromatics over our catalysts, and the yield of BTX decreased with increasing reaction time. A larger density of Bronsted acidity favoured the yield of BTX at the initial stage but was unbeneficial to the stability for BTX formation. The increase in pore hierarchy suppressed the coke deposition inside the micropores and increased the coke tolerance, thus enhancing the catalyst stability for BTX formation. The catalyst with a larger pore hierarchy also showed higher selectivities for aromatics and BTX. Aromatics can be formed via lower olefin intermediates by hydrogen-transfer or dehydrogenation pathways. We propose that ZnO, in particular the highly dispersed ZnO clusters, enhances the selectivity for aromatics by catalysing the dehydrogenation pathway, whereas the hierarchical pore structure facilitates the transfer of reaction intermediates and thus accelerates the formation of aromatics.

Cobalt nanoparticles were loaded onto mesoporous zeolite Na–Y (Na–meso-Y) by melt infiltration and impregnation methods. As compared to impregnation, melt infiltration resulted in Co nanoparticles with a narrower size distribution. The Co/Na–meso-Y catalyst prepared by the melt infiltration exhibited higher C10–C20 (diesel fuel) selectivity. The hydrogenolysis of heavier hydrocarbons was confirmed to occur under Fischer–Tropsch reaction conditions. Our studies for the hydrogenolysis of n-hexadecane revealed that the catalyst by the melt infiltration was more active and selective for the formation of C10–C15 hydrocarbons. We propose that the narrower Co size distribution favors the selective hydrogenolysis and thus the C10–C20 selectivity in Fischer–Tropsch synthesis. The addition of Mn with a proper content could further improve the diesel fuel selectivity to 65% by suppressing the formations of CH4 and lighter hydrocarbons. The Mn-modified Co/Na–meso-Y catalyst was very stable and no deactivation was obs...

Catalytic transformations of syngas (a mixture of H2 and CO), which is one of the most important C1-chemistry platforms, and CO2, a greenhouse gas released from human industrial activities but also a candidate of abundant carbon feedstock, into chemicals and fuels have attracted much attention in recent years. Fischer-Tropsch (FT) synthesis is a classic route of syngas chemistry, but the product selectivity of FT synthesis is limited by the Anderson-Schulz-Flory (ASF) distribution. The hydrogenation of CO2 into C2+ hydrocarbons involving C-C bond formation encounters similar selectivity limitation. The present article focuses on recent advances in breaking the selectivity limitation by using a reaction coupling strategy for hydrogenation of both CO and CO2 into C2+ hydrocarbons, which include key building-block chemicals, such as lower (C2-C4) olefins and aromatics, and liquid fuels, such as gasoline (C5-C11 hydrocarbons), jet fuel (C8-C16 hydrocarbons) and diesel fuel (C10-C20 hydrocarbons). The design and development of novel bifunctional or multifunctional catalysts, which are composed of metal, metal carbide or metal oxide nanoparticles and zeolites, for hydrogenation of CO and CO2 to C2+ hydrocarbons beyond FT synthesis will be reviewed. The key factors in controlling catalytic performances, such as the catalyst component, the acidity and mesoporosity of the zeolite and the proximity between the metal/metal carbide/metal oxide and zeolite, will be analysed to provide insights for designing efficient bifunctional or multifunctional catalysts. The reaction mechanism, in particular the activation of CO and CO2, the reaction pathway and the reaction intermediate, will be discussed to provide a deep understanding of the chemistry of the new C1 chemistry routes beyond FT synthesis.

The direct synthesis of lower (C2 to C4) olefins, key building-block chemicals, from syngas (H2/CO), which can be derived from various nonpetroleum carbon resources, is highly attractive, but the selectivity for lower olefins is low because of the limitation of the Anderson-Schulz-Flory distribution. We report that the coupling of methanol-synthesis and methanol-to-olefins reactions with a bifunctional catalyst can realize the direct conversion of syngas to lower olefins with exceptionally high selectivity. We demonstrate that the choice of two active components and the integration manner of the components are crucial to lower olefin selectivity. The combination of a Zr-Zn binary oxide, which alone shows higher selectivity for methanol and dimethyl ether even at 673 K, and SAPO-34 with decreased acidity offers around 70% selectivity for C2-C4 olefins at about 10% CO conversion. The micro- to nanoscale proximity of the components favors the lower olefin selectivity.

Maximizing the use of palladium without compromises in catalytic activity and stability in the combustion of methane is extremely challenging due to the harsh operation conditions. To achieve this goal, a series of core-shell-structured catalysts with different amounts of palladium nanoparticles confined in hydrophobic silicalite-1 (Pd@S-1) was designed. Unexpectedly, a volcanic trend between catalytic activity and palladium loading was found as the loading increased from 0.3 wt% to 1.6 wt%, among which the 0.6 wt%Pd@S-1 exhibited the highest catalytic activity with a complete combustion temperature of 380 °C. Besides, the 0.6 wt%Pd@S-1 showed an ultrahigh stability in the high temperature applications due to the spatial confinement of palladium inside the rigid zeolite matrix. Moreover, owing to the hydrophobicity of the pure silica zeolite, the Pd@S-1 could selectively hinder the diffusion of water vapor into the palladium sites, leading to the outstanding water-resistance ability.

Zn–ZrO2/SSZ-13 catalyzed direct conversion of syngas into lower olefins via methanol/DME intermediates with 77% selectivity at 29% CO conversion., The direct conversion of syngas into lower olefins is a highly attractive route for the synthesis of lower olefins. The selectivity of lower olefins via the conventional Fischer–Tropsch (FT) synthesis is restricted to ∼60% with high CH4 selectivity due to the limitation by the Anderson–Schulz–Flory (ASF) distribution. Here, we report the design of bifunctional catalysts for the direct conversion of syngas into lower olefins with selectivity significantly breaking the ASF distribution. The selectivity of C2–C4 olefins reached 87% at a CO conversion of 10% and was sustained at 77% by increasing CO conversion to 29% over a bifunctional catalyst composed of Zn-doped ZrO2 nanoparticles and zeolite SSZ-13 nanocrystals. The selectivity of CH4 was lower than 3% at the same time. It is demonstrated that the molar ratio of Zn/Zr, the density of Brønsted acid sites of SSZ-13 and the proximity of the two components play crucial roles in determining CO conversion and lower-olefin selectivity. Our kinetic studies indicate that methanol and dimethyl ether (DME) are key reaction intermediates, and the conversion of syngas to methanol/DME is the rate-determining step over the bifunctional catalyst. Formate and methoxide species have been observed on Zn-doped ZrO2 surfaces during the activation of CO in H2, and the formed methanol/DME are transformed into lower olefins in SSZ-13.

Selectivity control is a challenging goal in Fischer-Tropsch (FT) synthesis. Hydrogenolysis is known to occur during FT synthesis, but its impact on product selectivity has been overlooked. Demonstrated herein is that effective control of hydrogenolysis by using mesoporous zeolite Y-supported cobalt nanoparticles can enhance the diesel fuel selectivity while keeping methane selectivity low. The sizes of the cobalt particles and mesopores are key factors which determine the selectivity both in FT synthesis and in hydrogenolysis of n-hexadecane, a model compound of heavier hydrocarbons. The diesel fuel selectivity in FT synthesis can reach 60 % with a CH4 selectivity of 5 % over a Na-type mesoporous Y-supported cobalt catalyst with medium mean sizes of 8.4 nm (Co particles) and 15 nm (mesopores). These findings offer a new strategy to tune the product selectivity and possible interpretations of the effect of cobalt particle size and the effect of support pore size in FT synthesis.

Syngas, a mixture of CO and H2 (CO/H2), is a key platform for the utilization of nonpetroleum carbon resources such as natural gas or shale gas and coal. Syngas can also be produced from renewable carbon feedstocks such as biomass and even CO2. A variety of products including hydrocarbons and oxygenates, which can be fuels and chemicals, may be produced from syngas. The catalytic transformation of syngas into value-added products is the core of C1 chemistry. This review highlights advances in the past decade in catalytic conversions of syngas into hydrocarbons with an emphasis on selective formations of C5 + hydrocarbons, which are mainly used as liquid fuels, and lower (C2–C4) olefins, key building-block chemicals. Since CO2 is also contained in syngas from some resources, the catalytic hydrogenation of CO2 to hydrocarbons will also be briefly described. Fischer–Tropsch synthesis is a well-established process for syngas to hydrocarbons, but many fundamental aspects remain unclear because of the complexity of the reaction. The products of Fischer–Tropsch synthesis usually follow the Anderson–Schulz–Flory distribution, which is very wide and is nonselective for a target product such as liquid fuels or lower olefins. This article highlights recent advances in understanding the active phase of Fischer–Tropsch catalysts and in designing efficient catalysts using new materials. Furthermore, this article pays particular attention to the breakthrough in the selectivity control, which is the most important challenge for scientific research in syngas chemistry. Besides insights into various factors determining product selectivity as well as activity, we will also discuss emerging methodologies and strategies for the selective conversion of syngas into a specific range of hydrocarbons.

Fischer-Tropsch synthesis is a key reaction in the utilization of non-petroleum carbon resources, such as methane (natural gas, shale gas, and biogas), coal, and biomass, for the sustainable production of clean liquid fuels from synthesis gas. Selectivity control is one of the biggest challenges in Fischer-Tropsch synthesis. This Minireview focuses on the development of new catalysts with controllable product selectivities. Recent attempts to increase the selectivity to C5+ hydrocarbons by preparing catalysts with well-defined active phases or with new supports or by optimizing the interaction between the promoter and the active phase are briefly highlighted. Advances in developing bifunctional catalysts capable of catalyzing both CO hydrogenation to heavier hydrocarbons and hydrocracking/isomerization of heavier hydrocarbons are critically reviewed. It is demonstrated that the control of the secondary hydrocracking reactions by using core-shell nanostructures or solid-acid materials, such as mesoporous zeolites and carbon nanotubes with acid functional groups, is an effective strategy to tune the product selectivity of Fischer-Tropsch synthesis. Very promising selectivities to gasoline- and diesel-range hydrocarbons have been attained over some bifunctional catalysts.

Functionalised carbon nanotube (CNT)-supported Au-Pd alloy nanoparticles were highly efficient catalysts for the aerobic oxidation of amines. We achieved the highest turnover frequencies (>1000 h(-1)) for the oxidative homocoupling of benzylamine and the oxidative dehydrogenation of dibenzylamine. We discovered a cooperative effect between Au-Pd nanoparticles and ketone/quinone groups on CNTs.

Bifunctional Fischer-Tropsch (FT) catalysts that couple uniform-sized Co nanoparticles for CO hydrogenation and mesoporous zeolites for hydrocracking/isomerization reactions were found to be promising for the direct production of gasoline-range (C5-11 ) hydrocarbons from syngas. The Brønsted acidity results in hydrocracking/isomerization of the heavier hydrocarbons formed on Co nanoparticles, while the mesoporosity contributes to suppressing the formation of lighter (C1-4 ) hydrocarbons. The selectivity for C5-11 hydrocarbons could reach about 70 % with a ratio of isoparaffins to n-paraffins of approximately 2.3 over this catalyst, and the former is markedly higher than the maximum value (ca. 45 %) expected from the Anderson-Schulz-Flory distribution. By using n-hexadecane as a model compound, it was clarified that both the acidity and mesoporosity play key roles in controlling the hydrocracking reactions and thus contribute to the improved product selectivity in FT synthesis.

Fischer-Tropsch synthesis is a key reaction in the utilization of non-petroleum carbon resources, such as methane (natural gas, shale gas, and biogas), coal, and biomass, for the sustainable production of clean liquid fuels from synthesis gas. Selectivity control is one of the biggest challenges in Fischer-Tropsch synthesis. This Minireview focuses on the development of new catalysts with controllable product selectivities. Recent attempts to increase the selectivity to C5+ hydrocarbons by preparing catalysts with well-defined active phases or with new supports or by optimizing the interaction between the promoter and the active phase are briefly highlighted. Advances in developing bifunctional catalysts capable of catalyzing both CO hydrogenation to heavier hydrocarbons and hydrocracking/isomerization of heavier hydrocarbons are critically reviewed. It is demonstrated that the control of the secondary hydrocracking reactions by using core-shell nanostructures or solid-acid materials, such as mesoporous zeolites and carbon nanotubes with acid functional groups, is an effective strategy to tune the product selectivity of Fischer-Tropsch synthesis. Very promising selectivities to gasoline- and diesel-range hydrocarbons have been attained over some bifunctional catalysts.

NSF of China [20625310, 20923004, 21033006]; National Basic Program of China [2010CB732303]; Key Scientific Project of Fujian Province [2009HZ0002-1]; Doctoral Program of Higher Education [20090121110007]