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A low olefins production process was developed with natural gas as the feedstock. The proposed process directly generates low olefins based on the Fischer–Tropsch synthesis reaction. The proposed p...

With a rapid developing global economy and population growth, demand for natural gas is expected to outpace supply. Current state of the art methanation catalysts like nickel-based (Ni) catalysts are susceptible to poisoning by sulfuric compounds present in the syngas. MoS2 is one of the few methanation catalysts not affected by sulfuric impurities, allowing the use of syngas feedstocks from coal gasification for direct methanation before extensive clean-up of the syngas. Increasing the number of Mo active sites is challenging since they are mostly located at the edges while the basal planes are mostly inert. In this study, we report a method of producing MoS2 with a significant amount of exposed edges (nano-flakes) which resulted in highly active MoS2 catalysts. Effects of support, Mo precursors and synthesis techniques on the formation of nano-MoS2 structure and methanation activity have been investigated. MoS2 nano-flakes can be produced from a solvothermal method or thermolysis of a thiomolydate precursor. The resulting MoS2 catalysts were tested for direct methanation of CO with H2 to CO ratio of 1:1 and 3000 ppm of H2S under 3 MPa. X-ray absorption spectroscopy was also utilized to gain more insight into the structure of the catalysts.

A thin hollow shell nanostructure can increase effectiveness of zeolites while allowing metal nanoparticles to be supported on both its inner and outer surfaces. Herein, nanoscale hollow spherical ZSM-5 (hsZSM5) shells were synthesized from sub-micron silica spheres through a dissolution–recrystallization mechanism with assistance of a positively charged polymer. The as-prepared hsZSM5 can function as a spacer: different metals (Mn) can be preferentially separated by the thin shell of hsZSM5, making the derived M1@hsZSM5@M2 suitable for tandem reactions. The dual-layer Co@hsZSM5@Pt shows higher resistance to metal sintering and alloying in tandem hydrogenation of CO2 (i.e.; reverse water gas shift reaction followed by Fischer–Tropsch reaction) to short-chain hydrocarbons, which can be used as an alternate clean feedstock to produce chemicals such as olefins, aromatics and polymers. Hydrocarbon selectivity of C2+ can be increased up to 46% in Co@hsZSM5@Pt, which was not observed in co-impregnated Pt–Co catalyst.

In the present work, in-depth characterization techniques combined with kinetic analyses were used to develop a deep understanding of the remarkable catalytic performance observed during propane dehydrogenation (PDH) over Ge-promoted Pt/SiO2. Following our previous work on Pt-Ge/Al2O3, we found Ge to significantly affect Pt catalytic performance, reaction mechanism and kinetics, regardless of the nature of the support. The synthesized catalysts were characterized using XAS, XPS, TPR, TGA, C3H6/C3H8-TPD, HRTEM, CO-chemisorption, BET, and CO-DRIFT. Upon Ge promotion to Pt nanoparticles supported on a large, neutral, SiO2 surface area, the bimetallic samples showed higher activation energy, lower desorption energy of C3H6, lower coke formation rates, and higher C3H6 selectivity as compared to the results from using the unpromoted catalyst. Ruling out the neutral SiO2’s support effect, the kinetic study indicates the C3H8 reaction order remains close to 1 for all the samples, while the H2 reaction order decreases from 0.04 to − 0.52 with increasing Ge loading from 0 wt% to 5 wt%. According to the kinetic analysis, the first C-H bond cleavage seems to be the rate-determining step. The addition of Ge enhances the adsorption of hydrogen, which explains the change of the hydrogen reaction order and the apparent activation energy exhibited by the bimetallic samples., The authors gratefully acknowledge the financial support by the Agency for Science, Technology and Research (A*STAR) of Singapore (AME-IRG Grant No. A1783c0016), and the National University of Singapore. Sajjad Rimaz is tankful to A*STAR for the Singapore International Graduate Award (SINGA) scholarship.

Based on the positive customer prospects and a market of EVs with immense development potential integrated with economic advantage and incentives from government policies in China, this paper aims to explore how Tesla utilizes its innovative operational strategy to improve brand competitiveness in the industrial competition, then its advantages and sustainability are analyzed through Porter competitive model. Particularly, the employed analysis could render more currently prevailed factors taken into account, then produce more comprehensive results with reflection on the market circumstance. According to the research, the positive market prospect and the effects of policy adjustments were investigated, and the factor of newly-entered competitors and the drawbacks like capacity shortage were concluded.

We have studied unsupported, silica gel- and amorphous silica–alumina-supported catalysts derived from K salts for the vapor-phase dehydration of lactic acid (LA) to acrylic acid (AA). A catalytic study shows that the supported catalysts improve the activity and selectivity for the production of AA and decrease the selectivity for the production of propionic acid (PA). The silica–alumina-supported catalysts remain fairly stable in the catalytic performance during 90 h of reaction. The IR spectroscopic characterization combined with the catalytic study demonstrates that potassium lactate (C3H5KO3) in situ generated from LA and a K salt is an important reaction intermediate for the production of AA and the catalytic stability is associated with the chemical stability of C3H5KO3 and the activity for the regeneration of C3H5KO3 in the catalytic cycle. On silica–alumina, C3H5KO3 is well stabilized and smoothly regenerated during the reaction, leading to the good catalytic stability. This work suggests for the first time that lactate salt acts as the true catalytic active species for the dehydration of LA to AA. We also propose a predominant reaction pathway for the vapor-phase dehydration of LA to AA with K salt catalyst systems.

The activity of zeolite-supported nanocatalysts is dependent on both the dispersion, size, and location of metal nanoparticles around the zeolite and the size and pore structure of the zeolite. In this study, a synthetic approach was developed to encapsulate metal catalysts within hollow interiors of single-crystal ZSM-5. Briefly, Stöber silica spheres were synthesized and then transformed to single-crystal nano-ZSM-5 (Si/Al = 60), followed by growth of embedded metal nanoparticles and subsequently creation of a nanosized (30-50 nm shell thickness) hollow hierarchical zeolite structure. Metal nanoparticles such as Co, Cu, Cu-Zn, Fe, and Ni can be supported on the inner wall of the hollow zeolite and the surrounding satellite mesopores, without any particles present on the external zeolite surface. When evaluated as a catalyst for the Fischer-Trøpsch reaction, the Fe@h-ZSM5 catalyst shows high activity, sintering and coking resistance (50% longer stability than Fe@ZSM5), and secondary cracking reactions in the acid sites in the ZSM-5 shell, which reduce C

Homogeneity emerges in the seat design. While, the innovation merely on exterior shape cannot satisfy the increasing multidimension need of users. Through the analysis of the contribution of subconscious behavior to design, this paper constructs a design process based on subconscious behavior and conducts the related design practice with this design process. Based on the observation and analysis of the subconscious behavior in the process of sitting, this paper builds the initial seat design model with the subconscious behavior, and approvals the completed design project with the integration of the consideration of dimensions, materials, processes. Then the design project is verified by the physical model test. This project targets to design a seat which breaks the homogeneity of the market as well as meets the subconscious needs of users.

Traffic accidents have been closely concerned by the society, and the serious traffic accidents caused by vehicle and guardrail collisions are one of the main manifestations. However, the research in the field of vehicle and guardrail collisions is mainly limited to the waveform guardrail on the expressway, and there is little research on the urban road guardrail, especially in the secondary damage caused by guardrails field. Moreover, the collision between vehicle and the rectangular guardrail of city road is easy to form thin-walled long rod, and it penetrates the driver’s chest. To evaluate and analyze the injury results and mechanism of this phenomenon, a penetrating finite element model of chest bone characterized by Chinese human is established using the medical software (MIMICS) and engineering software (HYPERMESH). The model validation is mainly dependent on the corpse impact test. In addition, the software (LS-DYNA) is deployed to simulate the thin-walled long rod penetration. According to the analysis of the “PENETRATION,” it is found that the cavity effect produced by the thin-walled long rod through the chest, and the degree of chest damage is related to the speed, angle, weight, and stability of the thin-walled long rod. The difference between the peak value of collision corpse experiment and simulation peak value is less than 5%, which implies that the model is reasonable. Besides, the simulation results also confirm the accident and medical diagnosis cases. As a common form of secondary injury in traffic accidents and a typical case of medical penetrating injury, the thin-walled long rod penetrating injury has important reference value for studies in both directions.

Accidents involving collisions of heavy-duty trucks with highway bridge piers occurred occasionally, in which the bridge piers might be subjected to severe damage, and cause the collapse of the superstructure due to the loss of axial loading capacity. The existing researches are mostly concentrated on the light- or medium-duty trucks. This article mainly concerns about the collisions between the heavy-duty trucks (e.g. tractor-trailer) and bridge piers as well as the evaluation of the impact force. First, by modifying the finite element model of Ford F800 single-unit truck, which was developed by National Crash Analysis Center, the finite element model of a tractor-trailer is established. Then, the full-scale tractor-trailer crash test on concrete-filled steel pier jointly conducted by Texas Transportation Institute, Federal Highway Administration, and Texas Department of Transportation is numerically simulated. The impact process is well reproduced and the established model is validated by comparison of the impact force. It indicates that the tractor-trailer impact force time history consists of two or three peaks and the corresponding causes are revealed. Furthermore, the parametric influences on the impact force are discussed, including the diameter and cross section shape of the pier, cargo weight, impact velocity, relative impact position, and vehicle type. Finally, the finite element model of an actual reinforced concrete highway bridge pier is established, and the impact force and lateral displacement of the pier subjected to the impact of the tractor-trailer are numerically derived and discussed.

Substituted natural gas (SNG) production via methanation reaction from syngas generated through gasification of coal/biomass can increase the energy diversity and reduce the dependence of fossil oil especially for those areas where fossil oil resources are scarce. In this study, the preparation, characterization and catalytic performance of a Ni-based methanation catalyst, consisting of highly dispersed nano-Ni particles encapsulated in a mesoporous silica (mSiO2) matrix, named as Ni#mSiO2, is reported. Very small Ni particles (∼3 nm) were successfully synthesized via a two-step coprecipitation method with high Ni loading up to ∼40% in the mSiO2. The Ni#mSiO2 catalyst has shown improved Ni sintering, coking and sulfur resistance compared to a commercial Ni methanation catalyst. The superior performance of Ni#mSiO2 as compared to the supported Ni catalyst is attributed to the stabilization of Ni particles by the porous SiO2 matrix. This novel Ni#mSiO2 catalyst is robust and suitable to produce SNG from syngas derived from gasification process.

Molybdenum disulfide (MoS2) is a two-dimensional transition-metal dichalcogenide that can form layered nanosheets with catalytically active sites present at edge or defect sites. The density of such active sites can be further tuned by modifying the length, layer number, strain, and surface defects of the sheets. Herein, a synthetic approach has been developed to encapsulate nanoscale MoS2 nanosheets inside a mesoporous silica shell. Small molybdenum(IV) oxide (MoO2) cores were synthesized and coated with a mesoporous silica phase, followed by a conversion to MoS2@SiO2. The space constraint on the inner cores resulted in short, few-layered, highly curved MoS2 nanosheets with circular or flowerlike morphology. The MoS2@SiO2 was evaluated as a catalyst for decomposition of hydrogen sulfide (H2S), which shows high catalytic turnover frequency and superior thermal stability in comparison to unconstrained MoS2 catalysts.

Hydrogenation of carbon dioxide (CO2) to produce useful chemicals has been identified as a promising strategy for mitigation of greenhouse gas emission. Ruthenium (Ru) based catalysts have been reported to be the most active catalysts for the hydrogenation of CO2 to methane (CH4) which unfortunately is also a greenhouse gas and is difficult to activate. Controlling the hydrogenation selectivity to produce carbon monoxide (CO), a direct precursor for enormous important chemicals, thus becomes desirable. However, achieving high CO selectivity with supported Ru catalysts has remained a challenging task. In this work, we report the synthesis of highly selective and stable Ru@mSiO2 nanocatalysts via encapsulation of 1–3 nm Ru nanoparticles within mesoporous silica nanowires for hydrogenation of CO2 to CO. Calcination of the catalyst in nitrogen prevented sintering of the encapsulated Ru nanoparticles, making high CO selectivity of up to 100% possible, while larger (5–20 nm) Ru particles resulting from calcination in air favored formation of CH4. DRIFTS study of 1–3 nm Ru@mSiO2 and 5–20 nm Ru@mSiO2 catalysts after adsorption of reaction mixture of H2 and CO2 reveals that different reaction intermediates form on catalyst surface: CO-Run+ on 1–3 nm Ru@mSiO2 and formate species on 5–20 nm Ru@mSiO2, which are responsible for the distinctively different selectivity observed on 1–3 nm Ru@mSiO2 and 5–20 nm Ru@mSiO2 catalysts. Plausible reaction pathways have been proposed for selective hydrogenation of CO2 on the two types of catalysts, respectively. In addition, high CO selectivity of 1–3 nm Ru@mSiO2 catalyst has been demonstrated to be stable.

Germanium has emerged recently as a potential promoter for Pt-based catalysts for propane dehydrogenation (PDH) . However, its general practicality with other noble metals remains unexplored. Herein, the catalytic performance of Pd-Ge/SiO2 was investigated in propane dehydrogenation (PDH), wherein a significant improvement of the catalytic performance was obtained by Ge addition. Pd2/SiO2, the unpromoted sample, shows an initial conversion and selectivity of 21.0% and 53.6% at 550 °C, respectively. In addition, it deactivates rapidly with a deactivation constant (kd) of 1.7 × 10−2 min−1. Ge-promoted samples exhibit a slight decrease in activity, while catalyst selectivity and stability significantly increase. Upon adding 1 wt.% Ge (Pd2-Ge1/SiO2), the initial conversion decreases to 15.2%, whereas the initial selectivity increases to 91.9%. Further addition of Ge (2 wt.%, Pd2-Ge2/SiO2) leads to an initial conversion of 12.5% and an initial selectivity of 95.0%. Regarding catalyst stability, the deactivation constant is almost one order of magnitude lower for Ge-promoted catalysts (i.e., with 1 wt.% and 2 wt.% Ge); 2.9 × 10−3 min−1 and 2.0 × 10−3 min−1, respectively. The characterization results indicate that Ge imposes geometric and electronic modifications on Pd, decreasing catalytic activity for structure-sensitive side reactions and facilitating propylene desorption from surface. Hence, both the selectivity and stability of the catalysts have been significantly enhanced.

The gas-phase deoxydehydration of 2,3-butanediol to butene was investigated in a plug flow reactor over SiO2-supported vanadium oxide, γ-alumina, P/ZSM-5, and MgO catalysts with acid/base sites of varying strengths. 5 wt % vanadium on SiO2 (i.e., 5V/SiO2) showed the best performance with 100 % conversion and up to 45.2 % butene selectivity. The combination of weak acid sites and polymeric VOx surface species provided the 5V/SiO2 catalyst with bifunctional capabilities to achieve both dehydration and transfer hydrogenation, which allowed it to catalyze the deoxydehydration of 2,3-butanediol to butene even in the absence of H2. As 2,3-butanediol is a common yet underutilized biomass product, this reaction may provide a viable route for a biomass-to-chemicals application for 2,3-butanediol.

Tailoring the shape of nanomaterials is a key factor to control their properties. In this presentation, individual porous NiO nanoflowers via α-Ni(OH)2 were fabricated through a simple solvothermal process without any surfactants or growth templates and their application in lithium battery was investigated. In the method, nickel acetate and urea were used as starting materials in ethanol media at 190 °C for 3 h followed by calcination at 400 °C. Electron microscopy studies revealed that initially fine nanoparticles precipitate during solvothermal treatment which then undergo aggregation and self-assembly resulting in nanoflowers. In prolonged time, each nanoflower gives rise to a solid well-faceted microparticle. The electrochemical performance of the NiO nanoflowers was investigated by cyclic voltammetry and conventional galvanostatic charge–discharge tests. The results showed an initial high discharge capacity of ∼1330 mAhg−1 after 10 cycles at 0.1 C rate and a stable capacity of 630 mAhg−1 after 40 cycles in the range of 0.01–3.0 V with the excellent columbic efficiency of ∼94%, suggesting that they have a very promising potential in the future application for lithium ion battery.

Alkali and alkaline-earth metal cation co-modified NaY zeolites were systematically synthesized and comprehensively investigated as catalysts for gas-phase dehydration of lactic acid (LA) to acrylic acid (AA). The long-term (time-on-stream >55 h) catalytic performance in four repeated reaction–regeneration cycles was studied. The best performing catalyst shows a consistently high AA selectivity of ∼84% at different weight hourly space velocity (WHSV) values ranging from 0.48 to 4.8 h−1. Most importantly, the catalyst can still deliver a high AA selectivity of ∼82% after four long-term reaction–regeneration cycles. The investigation shows that mild etching increases the defect density of the zeolite and thus leads to poor hydrothermal stability in the long-term reaction–regeneration cycles. The strong acidic adsorbate/catalyst surface interaction (base property) and the acidity of the catalyst are responsible for the catalyst deactivation. The role of the alkali and alkaline-earth metal cations and the transformation of these cations during the reaction and regeneration process are presented.

Rh–Fe catalysts supported on Ca–Al2O3, MgO and ZrO2 were evaluated in ethanol steam reforming at 623 K and compared to Rh catalysts on the same supports without iron promotion. The metal–support interaction among the three entities, i.e. Rh ↔ Fe2O3 ← support (ZrO2, MgO and Ca–Al2O3) was investigated using H2-chemisorption, TEM, XPS and in situ techniques such as DRIFTS, temperature-resolved XRD and XAS. As compared to the unpromoted Rh catalysts on the same supports, the CO selectivity is depressed in the presence of iron on Rh/MgO and Rh/Ca–Al2O3, the latter being significantly superior. The role of metal–support interaction for CO-free hydrogen generation was unravelled using a combination of techniques. It was found that the reducibility of iron oxide determines the extent of the strong metal support interaction between Rh and Fe2O3 and the reducibility of iron oxide was affected by the support. On Rh–Fe/Ca–Al2O3, a good balance of the interaction between Rh, Fe2O3 and Ca–Al2O3 prevents strong metal support interaction between Rh and Fe2O3 and thus promotes CO elimination via water–gas-shift reaction on Rh–FexOy sites.

In this work, non-precious metal catalysts (FeCoN) were loaded onto the surface of N-modified graphene (N-G), graphite and activated carbon during a simple yet effective chemical process. The oxygen reduction reaction (ORR) performance of the as-prepared catalysts with different pyrolysis temperatures were evaluated in 0.5 M H2SO4. The use of N-G at a pyrolysis temperature of 750 °C yielded the highest catalyst activity, while both the metal nitrides (MeN) and pyridinic N were demonstrated as the active center for the ORR. The pyridinic-N, which sits surrounding MeN works synergistically with metal nitrides to enhance the catalytic activity of the MeN/N-G composite. A maximum power density output of 130 mW cm−2 at 0.25 V was achieved in a membrane electrode assembly (MEA) using FeCoN-N-G as a cathode catalyst. The mechanism of the ORR at the catalyst and the nature of the active center are discussed.

Non-thermal plasma (NTP) technology is gaining increasing interest for CO2 conversion due to its potential to convert inert and stable CO2 to value-added fuels and chemicals at ambient conditions. Combining catalysts with plasma can enhance conversion and energy efficiency simultaneously, overcoming the trade-off barrier commonly present in plasma processes. This work reports the influence of various ceria-promoted iron oxide catalysts on the decomposition of CO2 to carbon monoxide and oxygen in a packed bed, dielectric barrier discharge (DBD) reactor at low temperatures and ambient pressure. As ceria is an expensive rare earth metal, its combination with a cheap, abundant metal such as iron can make the process far more economical. The optimum CO2 conversion (24.5%) and energy efficiency (13.6%) were achieved using γ-Al2O3 supported 5Fe5Ce, almost twice the conversion attained using 10Fe (13.3%). Catalysts were characterized using N2 adsorption, X-ray diffraction (XRD), Raman spectroscopy, H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) analysis. A solid solution formed from the mixture of iron oxide and ceria. A critical concentration of iron oxide is required to increase the number of oxygen vacancy sites in the solid solution. The synergy between Fe and Ce, and thus the oxygen vacancy sites, can also be optimized via the synthesis method. A reaction mechanism has been proposed for CO2 conversion at the catalyst surfaces.

A variety of oxide-supported Rh catalysts prepared from frequently used oxides (γ-Al2O3, MgO, SiO2, CeO2, ZrO2, La2O3, Y2O3, TiO2 and ZnO) and Rh compounds (Rh(NO3)3·xH2O, RhCl3·xH2O, Rh(acac)3 and Rh4(CO)12) for H2 generation from ethanol steam reforming (ESR) at low temperatures (250–400 °C) have been studied. Catalytic screening shows that Rh/CeO2 is advantageous over other frequently used oxide-supported Rh catalysts. Rh/CeO2 behaves as the most effective catalyst for the water gas shift (WGS) pathway during ESR. A combination of CeO2 and Rh4(CO)12 with a 1% Rh loading results in an optimal-performance catalyst that brings about a CO-free H2 yield of 4 mol mol−1 C2H5OH at 350 °C with good catalytic stability. A comparison of the thermodynamic and catalytic data of ESR indicates that low-temperature ESR is strongly kinetically controlled over Rh/CeO2 in favour of H2 production via acetaldehyde steam reforming, acetone steam reforming, methane decomposition, steam reforming of adsorbed CHx (x = 1–3) and WGS pathways. Combined studies by catalytic stability, thermogravimetric analysis, X-ray photoelectron spectroscopy, transmission electron microscopy and X-ray diffraction suggest that the catalytic stability of Rh/CeO2 is markedly affected by coking which is the only cause of catalyst deactivation during low-temperature ESR and that both CeO2-supported Rh0 and Rh+ are the active sites for ESR to produce H2. The effects of support, Rh precursor, Rh loading and calcination of the precatalyst on the catalytic performance are discussed. In addition, catalytic roles played by typical oxides in reaction pathways during ESR are elucidated.

In this paper, the application of molecular catalysis for steam reforming of ethanol (SRE) is reviewed. Eight metals (Ni, Co, Cu, Pt, Rh, Pd, Ir and Ru) have shown high catalytic activity for SRE. Among them Ni and Rh are very promising because of high d character in the metal bond and low metal-oxygen bonding (vs. metal-carbon). They can effectively promote C-C bond cleavage in the rate-determining process during SRE. However, Rh is weak in water-gas-shift so that CH4 and CO become the main by-products at low reaction temperatures, while Ni catalysts suffer from rapid deactivation due to coking and sintering. Two low-temperature CO-free catalysts have been developed in our lab, namely Rh-Fe/Ca-Al2O3 and carbonyl-derived Rh-Co/CeO2, in which the presence of iron oxide or Co can promote water-gas-shift reaction and significantly improve the SRE performance. On the other hand, adding 3 wt% CaO to Ni/Al2O3 can greatly improve the catalyst stability because the Ca modification not only increases Ni concentration on the Ni/Ca-Al2O3 surface and 3d valence electron density, but also facilitates the water adsorption and coke gasification via water-gas-shift. The availability of abundant surface OH groups helps the formation and conversion of adsorbed formate intermediate. Hence, ethanol reaction on Ca-Al2O3-supported Ni, Pt, Pd and Rh catalysts are found to follow the formate-intermediated pathway, a new reaction pathway alternative to the traditional acetate-intermediated pathway.

The heteronuclear cobalt-platinum cluster [Co2Pt2(IPr)2(μ2-CO)4(CO)4] can be obtained from the [Pt(IPr)] fragment through an addition reaction with [Co2(CO)8], and with subsequent cluster fragmentation, with [Co4(CO)12] and [Co3(μ3-CH)(CO)9]; the latter reaction with the methylidyne cluster also afforded another cobalt-platinum cluster [Co4Pt2(μ6-C)(IPr)2(μ2-CO)5(CO)6]. These are the first examples of Co-Pt heteronuclear clusters containing NHC ligands.

This work reports a method that we have developed to successfully load Ag nanoparticles on the surfaces of MIL-53(Al) frameworks without inducing structural degradation. Compared to the free framework, the Ag-nanoparticle loaded MIL-53(Al) shows remarkable catalytic activity for CO oxidation and potential applications at reasonable temperature ranges.

An in situ DRIFTS study of ethanol adsorption and desorption was performed on Pt (Rh, Pd) supported on Al2O3 and Ca-Al2O3. Different from the well-known acetate-intermediate reaction mechanism observed on Al2O3-supported metal catalysts, formate species are exclusively observed on Pt (Rh, Pd) supported on Ca-Al2O3, offering a new mechanism denoted as the formate-intermediate mechanism. The key factor in determining the change in mechanism is the reduced availability of surface oxygen and the enhanced C–C breaking ability of the metal catalyst upon Ca modification. The formate-intermediate mechanism is favored in the presence of noble metals in the following order: Pt > Rh > Pd.

Through combined theoretical and experimental efforts, the reaction mechanism of ethanol steam reforming on Rh catalysts was studied. The results suggest that acetaldehyde (CH3CHO) is an important reaction intermediate in the reaction on nanosized Rh catalyst. Our theoretical work suggests that the H-bond effect significantly modifies the ethanol decomposition pathway. The possible reaction pathway on Rh (211) surface is suggested as CH3CH2OH → CH3CH2O → CH3CHO → CH3CO → CH3 + CO → CH2 + CO → CH + CO → C + CO, followed by the water gas shift reaction to yield H2 and CO2. In addition, we found that the water-gas shift reaction, not the ethanol decomposition, is the bottleneck for the overall ethanol steam reforming process. The CO + OH association is considered the key step, with a sizable energy barrier of 1.31 eV. The present work first discusses the mechanisms and the water effect in ethanol steam reforming reactions on Rh catalyst from both theoretical and experimental standpoints, which may shed light...

In this study, a Ge-promoted Pt catalyst with enhanced performance for propane dehydrogenation (PDH) has been developed. Pt0.5-Ge1.5/Al2O3 shows outstanding stability and performance (deactivation parameter: 0.10 1/h, propylene selectivity: 97.2%) in comparison with the monometallic Pt0.5/Al2O3 catalyst (deactivation parameter: 0.42 1/h, propylene selectivity: 56.9%). Effects of Ge loading (1.0%, 1.5%, 2.0%), reduction temperature and reaction temperature were investigated. Characterization techniques including XPS, BET, CO-DRIFTS, CO chemisorption, TG/DTA, RAMAN, XANES, and NH3-TPD were applied to study the fresh and spent catalysts. The modification of Pt structure and its electronic properties is ascribed to an alloy formation between Pt and Ge. Due to this alloy formation, Ge dilutes Pt surface, breaking the Pt ensembles and, at the same time, withdrawing electrons from Pt. As a result of these geometric and electronic modifications, superior performance of Pt0.5-Ge1.5/Al2O3 has been achieved.

Low temperature ethanol steam reforming (ESR) was studied over a series of 1 wt% Rh–x % Fe catalysts with various Fe loading (x = 0–10 wt%) and on different supports (Ca–Al2O3, SiO2 and ZrO2). The results show that close interaction between Rh and Fe is required to reduce the CO selectivity to almost negligible values. In addition, Rh–Fe supported on Ca–Al2O3 exhibits the best performance in terms of CO selectivity and hydrogen yield as compared to other supports. Characterization by XPS and XANES indicates the presence of FexOy species upon reduction, resulting in the formation of coordinatively unsaturated ferrous (CUF) active sites along the Rh–FexOy interface. These CUF sites promote water–gas shift reaction during low temperature ESR. Temperature programmed oxidation and Raman spectroscopy of spent catalysts also indicate that the addition of iron oxide reduces coke deposition and forms more reactive coke. Hence, the catalyst lifespan is significantly extended.

Hydrogen is a clean energy carrier for the future. More efficient, economic and small-scale syngas production has therefore important implications not only on the future sustainable hydrogen-based economy but also on the distributed energy generation technologies such as fuel cells. In this paper, a new concept for syngas production is presented with the use of redox stable lanthanum chromite and lanthanum ferrite perovskites with A-site doping of Ba, Ca, Mg and Sr as the pure atomic oxygen source for the catalytic partial oxidation of methane. In this process, catalytic partial oxidation reaction of methane occurs with the lattice oxygen of perovskites, forming H2 and CO syngas. The oxygen vacancies due to the release of lattice oxygen ions are regenerated by passing air over the reduced nonstoichiometric perovskites. Studies by XRD, temperature-programmed reduction (TPR) and activity measurements showed the enhanced effects of alkaline element A-site dopants on reaction activity of both LaCrO3 and LaFeO3 oxides. In both series, Sr and Ca doping promotes significantly the activity towards the syngas production most likely due to the significantly increased mobility of the lattice oxygen in perovskite oxide structures. The active oxygen species and performance of the LaACrO3 and LaAFeO3 perovskite oxides with respect to the catalytic partial oxidation of methane are discussed.

A series of mixed Mg–La oxide supports with various Mg2+/La3+ mole ratios were prepared via co-precipitation of Mg and La nitrates, and then impregnated to form 5 wt.% Ni catalysts. The as-prepared catalysts were evaluated in DRM reaction for 200 h and characterized by means of in situ DRIFTS, XRD, TEM, CO2-TPD, XPS, and TGA. It was found that the interaction of suitable amount of MgO with La2O3 stabilized cubic La2O3 species in catalysts, which has high basicity to adsorb CO2 forming monoclinic La2O2CO3 (Ia) species in DRM reaction. The introduction of MgO also created surface oxygen ions (i.e. O–). Both monoclinic La2O2CO3 (Ia) and surface oxygen species are able to oxidize and remove deposited carbon, keeping the Ni catalyst at high activity and stability. Low Mg2+/La3+ ratios generated hexagonal La2O3 and La2O2CO3 (II) in DRM reaction. The hexagonal La2O2CO3 (II) did not play significant role in carbon removal so that the catalysts deactivated fast.

We report a synthesis method that made use of a dual-glycol system, allowing discrete and size-tunable Cu nanoparticles to be deposited onto ZnO nanorods. Successful reduction of Cu was demonstrate...