Reaction Rate Of CO Research Articles

Plasmon-Assisted Electrochemical CO2 Reduction on Copper Nanocubes

Optical excitation of plasmons on metal nanoparticles presents a promising opportunity to enable electrochemical CO2 conversion into hydrocarbons at low overpotentials on stable electrodes. Electrochemical CO2 conversion typically requires high overpotentials, resulting in low energy efficiency and catalyst reshaping. By using light to overcome reaction barriers, plasmon excitation has been shown to lower the required overpotential for electrochemical reactions. Plasmon excitation also facilitates C-C coupling on gold and silver, metals that usually produce no multicarbon products when used as electrocatalysts. While previous studies indicate clear potential that plasmon-based photo-electrocatalysts could enable new electrochemical pathways for CO2 reduction at low overpotentials and stable catalysts, yields and catalytic turnover remained low. To develop industrially viable photo-electrochemical CO2 reduction catalysts, the effect of plasmon excitation at high current density and high mass flux needs to be understood and optimized.Here we investigate the photo-electrochemical CO2 reduction on gold and copper nanoparticles on a gas diffusion electrode. We choose copper nanoparticles because they are the most promising electrocatalysts for C-C coupling and exhibit a strong plasmon resonance around 600 nm, yet have not been explored for plasmonic CO2 reduction. Gold nanoparticles are chosen due to their exceptional stability and because gold has been shown to perform C-C coupling under plasmon excitation, which does not happen electrochemically. Using a gas diffusion electrode allows efficient gas phase mass transport to and from the electrode. We synthesize 50 nm (100) faceted copper nanocubes using copper bromide and oleylamine, and gold nanorods using hexadecyltrimethylammonium bromide (CTAB) and sodium oleate (NaOL). In both cases, the nanoparticles have a plasmon resonance of 600 nm. We spray coat these nanoparticles onto a carbon paper gas diffusion membrane and incorporate them into our home-built gas reactor. First, we use real-time GC to investigate electrocatalysis in the dark and find high selectivity for CO on gold and high selectivity for ethylene and CH4 on copper. Then, we vary the optical illumination wavelength from 480 nm to 700 nm and the applied potential, investigating how these affect Faradaic efficiencies for the production of ethylene, CO, H2, and CH4 as well as photothermal contributions using an infrared camera. Finally, we use in-situ liquid cell transmission electron microscopy (TEM) to monitor nanoparticle stability and correlate morphological evolution with CO2 reaction rate. Our work provides the fundamental understanding necessary for building photo-electrocatalysts that can convert CO2 into value-added products under industrially relevant conditions.Figure caption: Schematic of our photo-electrochemical plasmonic gas diffusion electrode converting CO2 into hydrocarbons. Electrochemical CO2 conversion on gold typically leads to CO, under plasmon excitation gold can form hydrocarbons. Figure 1

Enhanced sintering resistance of NiFe‐based RWGS catalysts through Cu doping

AbstractThe reverse water‐gas shift (RWGS) reaction offers an effective method for mitigating CO2 emissions. Due to its affordability and physicochemical stability, iron has garnered significant attention as a potential catalyst for RWGS. The incorporation of nickel and copper promoters can enhance CO2 conversion and CO selectivity in Fe‐based catalysts. This study focuses on modifying the strength of the Strong Metal‐Support Interaction (SMSI) through particle size optimization. Doping Cu into NiFe‐based catalysts restricts particle size, which influences the curvature of the Ni0@FeOx interface. This curvature enhances the electron coupling between Ni0 and FeOx, promoting the formation of a denser and thicker Ni0 and FeOx layer. This results in a nearly 90% increase in the CO2 reaction rate during the sintering resistance test by anchoring Ni0 and facilitating electron transfer to active sites. Such morphological evolution improves high‐temperature resistance to sintering during RWGS. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Reaction Environment Regulation for Electrocatalytic CO2 Reduction in Acids.

The electrocatalytic CO2 reduction reaction (CO2RR) is a sustainable route for converting CO2 into value-added fuels and feedstocks, advancing a carbon-neutral economy. The electrolyte critically influences CO2 utilization, reaction rate and product selectivity. While typically conducted in neutral/alkaline aqueous electrolytes, the CO2RR faces challenges due to (bi)carbonate formation and its crossover to the anolyte, reducing efficiency and stability. Acidic media offer promise by suppressing these processes, but the low Faradaic efficiency, especially for multicarbon (C2+) products, and poor electrocatalyst stability persist. The effective regulation of the reaction environment at the cathode is essential to favor the CO2RR over the competitive hydrogen evolution reaction (HER) and improve long-term stability. This review examines progress in the acidic CO2RR, focusing on reaction environment regulation strategies such as electrocatalyst design, electrode modification and electrolyte engineering to promote the CO2RR. Insights into the reaction mechanisms via in situ/operando techniques and theoretical calculations are discussed, along with critical challenges and future directions in acidic CO2RR technology, offering guidance for developing practical systems for the carbon-neutral community.

Reaction Environment Regulation for Electrocatalytic CO2 Reduction in Acids

AbstractThe electrocatalytic CO2 reduction reaction (CO2RR) is a sustainable route for converting CO2 into value‐added fuels and feedstocks, advancing a carbon‐neutral economy. The electrolyte critically influences CO2 utilization, reaction rate and product selectivity. While typically conducted in neutral/alkaline aqueous electrolytes, the CO2RR faces challenges due to (bi)carbonate formation and its crossover to the anolyte, reducing efficiency and stability. Acidic media offer promise by suppressing these processes, but the low Faradaic efficiency, especially for multicarbon (C2+) products, and poor electrocatalyst stability persist. The effective regulation of the reaction environment at the cathode is essential to favor the CO2RR over the competitive hydrogen evolution reaction (HER) and improve long‐term stability. This review examines progress in the acidic CO2RR, focusing on reaction environment regulation strategies such as electrocatalyst design, electrode modification and electrolyte engineering to promote the CO2RR. Insights into the reaction mechanisms via in situ/operando techniques and theoretical calculations are discussed, along with critical challenges and future directions in acidic CO2RR technology, offering guidance for developing practical systems for the carbon‐neutral community.

Screening of organic lithium precursors for producing high-performance Li4SiO4-based thermochemical energy storage materials: Experimental and kinetic investigations

Thermochemical energy storage by using Li4SiO4 TCES materials has been considered a promising technology for efficient heat storage from high temperature sources (700–900 °C). It has been proven the utilization of organic lithium precursors could effectively improve the heat storage performance of derived Li4SiO4. Hence, in this work, 7 kinds of unreported organic lithium precursors were screened for producing high-performance Li4SiO4 TCES materials. The physicochemical properties, CO2 ad-desorption capacities and the heat storage/releasing performance of as-prepared Li4SiO4 were systematically evaluated by a series of experimental and kinetic investigations, and a dual modification effects of organic lithium precursor were revealed. As a consequence, 3 potential candidates including lithium benzoate, lithium oxalate and lithium citrate were screened out. Li4SiO4 adsorbents derived from these precursors show great heat storage amount promotions of over 50 % in comparison with the average capacity of traditional Li4SiO4 (~ 350 kJ/kg/cycle). Especially, the lithium citrate derived Li4SiO4 exhibits the greatest CO2 adsorption capacity, reaction rate and cyclic stability, leading to a cumulative storage amount of 5.9 MJ/kg within 10 cyclic heat storage/releasing processes. Above findings could provide guidance for the future development of high-performance Li4SiO4 materials and Li4SiO4-CO2 TCES systems.

Strong metal support interaction (SMSI) and MoO3 synergistic effect of Pt-based catalysts on the promotion of CO activity and sulfur resistance.

In industrial applications, Pt-based catalysts for CO oxidation have the dual challenges of CO self-poisoning and SO2 toxicity. This study used synthetic Keggin-type H3PMo12O40 (PMA) as the site of Pt, and the Pt-MoO3 produced by decomposition of PMA was anchored to TiO2 to construct the dual-interface structure of Pt-MoO3 and Pt-TiO2, abbreviated as Pt-P&M/TiO2. Pt-0.125P&M/TiO2 with a molar ratio of Pt to PMA of 8:1 showed both good CO oxidation activity and SO2 tolerance. In the CO activity test, the CO complete conversion temperature T100 of Pt-0.125P&M/TiO2 was 113 ℃ (compared with 135 ℃ for Pt/TiO2). In the SO2 resistance test, the conversion efficiency of Pt-0.125P&M/TiO2 at 170 ℃ remained at 60% after 72h, while that of Pt/TiO2 was only 13%. H2-TPR and XPS tests revealed that lattice oxygen provided by TiO2 and hydroxyl produced by MoO3 increased the CO reaction rate on Pt. According to the DFT theoretical calculation, the electronegative MoO3 attracted the d-orbital electrons of Pt, which reduced the adsorption energy of CO and SO2 from - 4.15eV and - 2.54eV to - 3.56eV and - 1.52eV, respectively, and further weakened the influence of strong CO adsorption and SO2 poisoning on the catalyst. This work explored the relationship between catalyst structure and catalyst performance and provided a feasible technical idea for the design of high-performance CO catalysts in industrial applications.

A multi-criteria optimization and decision-making framework of green DME reactor configurations with a focus on high productivity and low CO2 emission rate

The combination of a conventional Dimethyl Ether (DME) reactor with hydrogen perm-selective membrane and effluent recycling creates innovative membrane reactor (MR) configurations that can efficiently improve thermodynamic limits plus low kinetic rates. In the present article, two eco-friendly configurations were applied to the DME conventional reactor (CR) to boost the DME production rate, yield, and selectivity. These configurations comprise two concentric pipes in which in the 1st configuration the fresh synthesis gas is fed to the inner tube side, hydrogen permeates through the reaction zone, and finally the effluent is recycled back to the outer tube, while in the 2nd one, the effluent of outer tube recycled to the inner pipe. The comprehensive 1-D heterogeneous model has an excellent agreement with industrial data. Also, the simulation results reveal that the higher temperature profile in the 2nd configuration is the consequence of more intensification in the reaction zone by H2 injection and proper heat removal which leads to around 9.5 %, 8.22 %, and 10 % increases in the DME production rate, selectivity, and yield compared to CR, respectively. Enjoying reaction output recycling and H2 permeation, the reaction rate of CO and CO2 hydrogenation plus methanol dehydration enhances significantly in the 2nd scheme.According to Euclidean Distance, the optimization results show that the MODE algorithm has a better performance compared to NSGA-II to obtain optimal Pareto Front and also more rapid respect to lower computational time. The LINMAP approach provides a minimum deviation index among all three decision-making algorithms. Employing optimal operation conditions leads to an enhancement of 17 %, 47 %, and 36 % in DME production rate, selectivity, and yield compared to CR. This eco-friendly configuration prevents the emission of 22000 tons of per year CO2 to the atmosphere.

Experimental and kinetic study on the cyclic removal of low concentration CO2 by amine adsorbents in confined spaces

Amine-based adsorbents show great promise for removing low-concentration CO2 from environmental control and life support systems (ECLSSs) to ensure crew safety and task execution. In this work, granular silica gel (SG) support was prepared by the extrusion–spheronization (ES) method, and amine-based adsorbent pellets were synthesized by impregnating the SG support with tetraethylenepentamine (TEPA). Dynamic CO2 circulation removal tests were carried out under simulated confined space conditions in a 100 L chamber to evaluate the low concentration CO2 removal performance of the adsorbent pellets. The effect of operating parameters on CO2 removal performance was investigated by orthogonal experiments. CO2 adsorption capacity and removal efficiency were significantly affected by CO2 concentration and reaction temperature, while reaction rate was intimately depended on CO2 concentration and gas flow rate. The maximum CO2 adsorption capacity (0.55 mmol CO2/g), removal efficiency (83.25%) and reaction rate (0.93 mmol CO2/min) were achieved under the optimized conditions of 20 °C, 1.25%CO2 and 2 L/min. A kinetic equation well representing the correlation between reaction rate and CO2 concentration and gas flow rate was established. The TEPA-SG-ES adsorbent pellets exhibited satisfactory working stability, with CO2 removal efficiency and adsorption capacity slightly decreased from 83.25% and 0.55 mmol CO2/g to 75.45% and 0.53 mmol CO2/g in 10 cycles, respectively. The slight decay in CO2 adsorption performance was associated with the oxidative degradation of amine species in oxygenated atmosphere to form amide, nitrite and imine phases, and the change of amine distribution over the pellets in multiple cycles. Overall, the desired TEPA-SG-ES adsorbent pellets could be nice scavenger candidates for circulating purification of CO2 in confined spaces.

Evaluation of carbonation conversion of recycled concrete fines using high-temperature CO2: Reaction kinetics and statistical method for parameters optimization

Accelerated carbonation of recycled concrete fines (RCF) is an eco-friendly technology and has been considered as an effective way to achieve CO2 fixation and improve the cementitious activity of RCF. However, the slow gas-solid reaction under a standard (20 °C) environment is an issue affecting the carbonation performance. On the other hand, the surface water of alkaline solids plays a crucial role as an ionic transferring medium for high-temperature carbonation. This work, therefore, investigates the influences of operating parameters, i.e., temperature (60–180 °C), water content (W/S ratio; 0.1–0.5 ml/g) and carbonation duration (5–50 min) on the reaction of RCF. After that, multiple kinetics models, namely shrinking-core model and surface water coverage model, are presented to elucidate the carbonation kinetics of RCF under high-temperature environments. The maximum diffusivity of CO2 and carbonation rate of RCF are 1.33 × 10−6 cm2/min and 0.052 min−1, respectively at 100 °C, whereas the carbonated particles are surrounded by polyhedral calcite crystals. Kinetics study shows that the activity of calcium ions in water film decreases with higher temperature due to faster evaporation of water and the development of an electrical double layer in the interface particles. In addition, the non-evaporated surface water at high W/S ratios limits the CO2 penetration and reaction rate. Finally, the response surface methodology is employed for statistical prediction of the maximum conversion of RCF. Accordingly, the highest carbonation conversion of RCF is 56.69% for particles wetted with a W/S ratio of 0.3 ml/g and carbonated at 100 °C for 40 min.

Tuning the Surface Mn/Al Ratio and Crystal Crystallinity of Mn–Al Oxides by Calcination Temperature for Excellent Acetone Low-Temperature Mineralization

Here, Mn–Al oxides with the strengthened synergistic effect of Mn and Al species were fabricated by facilely adjusting the calcination temperature with the hydrolysis-driven redox-precipitation method. Results demonstrated that the surface Mn/Al ratio and KMn8O16 phase can be effectively tamed under different calcination temperatures, which obviously alter the CO2 selectivity, reaction rate, and stability of Mn–Al oxides for catalytic oxidation of acetone, among which the Mn5Al-350 catalyst exhibits the best catalytic performance (90% of acetone converted at 159 °C) with CO2 selectivity higher than 99.5%, mainly owing to its higher surface Mn/Al ratio and weaker Mn–O bond with more Mn3+ as compared to Mn5Al-250, Mn5Al-450, and Mn5Al-550. Although a decrease in the consumption rate of acetic acid in the presence of 3.0 vol % H2O leads to the slight reduction of acetone conversion and CO2 yield, Mn5Al-350 still exhibits a superior catalytic stability. The reaction intermediates including acetaldehyde, ethanol, acetic acid, and formic acid species before total mineralization are determined by proton transfer reaction–mass spectrometry, theoretical calculations, and in situ DRIFTS. Theoretical calculations also reveal that the p-orbital interaction of C with a certain anisotropy leads to a weak catalytic effect in the process of acetic acid decomposition as the rate-limiting step.

Effects of the charge–dipole and charge–quadrupole interactions on the He+ + CO reaction rate coefficients at low collision energies

The reaction between He+ and CO forming He + C+ + O has been studied at collision energies in the range between 0 and k B ⋅ 25 K. These low collision energies are reached by measuring the reaction within the orbit of a Rydberg electron after merging a beam of He(n) Rydberg atoms and a supersonic beam of CO molecules with a rotational temperature of 6.5 K. The capture rate of the reaction drops by about 30% at collision energies below k B ⋅ 5 K. This behavior is analyzed in terms of the long-range charge–dipole and charge–quadrupole interactions using an adiabatic-channel capture model. Although the charge–dipole interaction has an effect on the magnitude of the rate coefficients, the effects of the charge–quadrupole interaction determine the main trend of the collision-energy dependence of the rate coefficients at low collision energies. The drop of the capture rate coefficient at low collision energies is attributed to the negative sign of the quadrupole moment of CO (Q zz = −2.839 D Å) and is caused by the |JM⟩ = |00⟩ and |1 ± 1⟩ rotational states of CO, which represent about 70% of the CO molecules at the rotational temperature of 6.5 K.

Nature and Dynamic Evolution of Rh Single Atoms Trapped by CeO2 in CO Hydrogenation

Metal single-atom catalysts (SACs) have attracted extensive interest because of their maximum atom efficiency and potentially good performances. However, the understanding of the catalytic behavior and the stability of SACs in high-temperature catalytic reactions remains a major challenge, especially under reducing conditions. In this work, we investigated the nature and stability of Rh/CeO2 SACs with different Rh loadings (0.2–4 wt % Rh) during syngas conversion (260 °C, 2 MPa). Using CO-DRIFTS, we found that atomically dispersed Rh was dispersed on Rh/CeO2 catalysts with an Rh loading up to 3 wt %. The Rh/CeO2 catalysts were stable in H2 up to 350 °C, while Rh nanoclusters were formed in CO at 200 °C. During syngas conversion at 260 °C, the Rh single atoms (Rhiso) on a 0.5 wt % Rh/CeO2 SAC slowly agglomerated to form Rh nanoclusters (RhNC) and a Rhiso/RhNC ratio of ∼1:2.5 was obtained after ∼10 h time-on-stream run. Furthermore, the Rhiso/RhNC ratio did not change with further reaction, indicating that the reaction reached steady state after a 10 h run. After the catalysts reached steady state (∼10 h), the Rhiso/RhNC ratio on the spent Rh/CeO2 catalysts decreased with the increase in Rh loadings, while the reactivity increased first and then decreased. We observed an optimal value of Rhiso/RhNC ≈ 1:3 on the 1 wt % Rh/CeO2 catalyst, showing the maximum reaction rates of CO (rCO) and ethanol selectivity (SEtOH) of 85.8 μmol/s/gRh and 26.2%, respectively. This indicated that the combination of Rh single atoms and Rh nanoclusters is beneficial to the ethanol selectivity and reaction rate, which was confirmed by DFT simulations. Moreover, the ratios of Rhiso/RhNC on the spent catalysts under the steady state have good relationships with the CO conversion rate and product selectivity in the reaction.

Numerical simulation of CO emission in a sintering pot under flue gas recirculation

A transient two-dimensional sintering model coupling porous medium flow, interphase heat mass transfer and reactions was established through computational fluid dynamics (CFD) method by Comsol Multiphysics 6.0 for a sintering pot under sintering flue gas recirculation (SFGR). The ignition was considered and CO was the carbon combustion intermediate and experienced catalytic oxidation in the ferric oxide bed. The model was verified by sintering pot experimental data of flue gas temperature and components fractions with maximum deviation less than 10 %. The bed temperature, CO emission and solid fuel consumption were focused under different SFGR parameters by the verified model. Ignition was important for the beginning flue gas component fractions, especially when the bed height was less than 700 mm. The effect of SFGR parameters on the maximum bed temperature (MBT) was sequenced: inlet gas velocity > inlet CO fraction > inlet O2 fraction > inlet gas temperature. MBT grew up when each of the four parameters increased. The impact on the CO emission was different: inlet CO fraction > inlet O2 fraction > inlet gas velocity > inlet gas temperature. CO emission declined when each of the parameters increased. The total reaction rate of CO was studied for explanation. The reduction of solid fuel consumption was studied by energy conservation to evaluate the influence of inlet CO, inlet gas temperature and flue gas recirculation fraction. The three factors had positive linear correlation with solid fuel consumption reduction. The reduction maximally reached 16.6 % at flue gas recirculation fraction of 50 %, inlet 2 % CO and 473.15 K temperature, providing theoretical support for SFGR application.

A facile approach to direct preparation of Pt nanocatalysts from oxidative dechloridation of supported H2PtCl6 by oxygen plasma

Effective dechlorination, as well as high dispersion, is necessary in the Pt nanocatalyst preparation from cheap chlorine-containing precursors like H2PtCl6. We herein report a facile approach to direct preparation of Pt nanocatalysts from oxidative dechloridation of the TiO2 (P25) supported H2PtCl6 by O2 plasma. Oxygen plasma can completely dechlorinate, enhance the dispersion of Pt nanoparticles, and create large number of low-coordinated sites, thus leading to the highest activity in WGS reaction. At 200 oC, the O2 plasma treated Pt nanocatalyst achieves CO reaction rate of 1.07 mmol·mg−1·h−1 in WGS reaction, which is significantly higher than that of H2 and N2 plasmas treated samples. The oxidative dechloridation mechanism of O2 plasma and structure–activity relationship of the supported Pt nanocatalysts were demonstrated.

Some new insights into the effect of CO2 partial pressure on the non-isothermal gasification

Lignite and coffee char-CO2 gasification had been studied via thermogravimetry analysis (TGA) at the heating rate of 15–25 K/min and the CO2 partial pressure range of 0.02–0.08 MPa. The relationship between gas partial pressure and reaction rate was explored in non-isothermal gasification. The results showed that there was a certain reaction order relationship between different CO2 partial pressures and reaction rate at a constant heating rate in non-isothermal gasification. When the heating rate was 15–25 K/min, the reaction order of coffee grounds char (CGC) was 0.14–0.36 in the char conversion range of 0.3–0.8. The reaction order of the lignite char (LC) was basically the same in the range of char conversion of 0.3–0.8, about 0.15±0.01.

Kinetic insights into the effect of promoters on Co/Al2O3 for Fischer-Tropsch synthesis

The fundamentals of promoter effects in the Fischer − Tropsch synthesis over Co-based catalysts were systematically investigated by employing the Rh, Ir, Sb and Ga as promoters of Co/Al2O3. Various characterizations showed the higher dispersion and reducibility over Rh- and Ir- promoted catalysts would cause a promoted adsorption property, while the Sb- and Ga- promoted catalysts showed a contrary result because the formation of alloy suppressed the accessibility of Co species. Based on the experimental results and kinetic calculations, a linear relationship for the activation energies of these catalysts as a function of activation entropies was proposed. Besides, steady state isotopic transient kinetic analysis (SSITKA) revealed that promoters mainly affected the surface CHx concentration to alter the CO reaction rate, and the chain growth rate constants would affect the product distribution. Since CoRhA and CoIrA greatly enhanced the CHx concentration and inhibited the chain growth ability, they owned a higher CO reaction rate and CH4 selectivity. While the CoSbA and CoGaA suppressed the CHx concentration and intrinsic activity, but enhanced the chain growth ability, thereby revealing a lower CO reaction rate and CH4 selectivity. Furthermore, the reactivity and selectivity difference were attributed to the modification of adsorption strength dictated by the enthalpy of activation on cobalt catalysts with different promoters. These findings provide kinetic insights into the promoter effects and pave the way for optimizing catalysts.

Highly dispersed mesoporous Cu/γ-Al2O3 catalyst for RWGS reaction

The extensive use of fossil energy leads to the wanton emission of CO2 and serious environmental problems. The resource utilization of CO2 is an effective way to solve this problem. The key of CO2 resource utilization is the design and preparation of high active CO2 hydrogenation catalyst. In this paper, supported Cu/γ-Al2O3 catalysts were prepared by wet impregnation and grinding methods, respectively. The physicochemical properties of the prepared Cu/γ-Al2O3 catalysts were characterized by XRD, BET, CO2-TPD and Quasi in-situ XPS, and the reducibility of the precursors was studied by H2-TPR. The results show that Cu content directly affects the Cu0 species crystallinity and even affects the adsorption and activation of CO2 molecules for the Cu/γ-Al2O3 catalyst. The dispersion of Cu0 species in the prepared Cu/γ-Al2O3 catalysts can be further improved by grinding method. The CO2 reaction rate on the Cu/γ-Al2O3 catalyst prepared by grinding method can be significantly increased to 2.12 × 10−5 mol/gcat/s at 400 °C.

Ceria-supported Pd catalysts with different size regimes ranging from single atoms to nanoparticles for the oxidation of CO

Supported metal catalysts are the most widely used in industrial processes and the metal particle size plays a crucial factor in determining the catalytic performance. Herein, CeO2-supported Pd catalysts with different Pd size regimes ranging from single atoms, to nanoclusters (1–2 nm), and to nanoparticles (>2 nm) were used for both CO oxidation and preferential oxidation of CO in H2 (CO-PROX). Compared to Pd nanoclusters and nanoparticles, CeO2-supported single Pd atoms (PdSA/CeO2) are the most intrinsically active in CO oxidation, with an apparent activation energy of ca. 40 kJ mol−1. Results of kinetic investigations and in situ diffuse reflectance infrared Fourier transformed spectroscopy demonstrate the CO oxidation proceeding through a Langmuir-Hinshelwood mechanism with the decomposition of formate species acting dominantly as the rate-determining step. The CO reaction rate is exclusively promoted on PdSA/CeO2 catalysts for the CO-PROX reaction, which could be ascribed to a stronger H-spillover effect on isolated Pd sites to produce bridged-OH on CeO2 surface, simultaneously facilitating the consumptions of bicarbonate and formate species. There results greatly deepen the fundamental understanding of the Pd size regimes over Pd/CeO2 catalysts for the oxidation of CO.

Co‐Feeding of Ethene, Propene, and 1‐Butene to Co‐Mn‐Catalyzed Fischer‐Tropsch Synthesis

AbstractIn Fischer‐Tropsch synthesis (FTS), a variety of hydrocarbons with different chain lengths are formed. The selectivities depend on the catalyst and the reaction conditions. Co‐feeding olefins allows changing the selectivity even outside the rules of the Anderson‐Schulz‐Flory distribution. In this work, ethene, propene, and 1‐butene were co‐fed to Co‐Mn‐catalyzed FTS to increase the olefin selectivity in the C3‐ to C8‐fraction. An increase of the CO reaction rate and oxygenate selectivity indicates that besides FTS also hydroformylation takes place. While the predominant reaction is the unwanted hydrogenation of the co‐fed olefins, this could in case of ethene be reduced by lowering the H2 pressure.

Unraveling catalytic properties by yttrium promotion on mesoporous SBA-16 supported nickel catalysts towards CO2 methanation

The ordered mesoporous silica SBA-16 with high specific surface area and pore volume was synthesized and used to prepare Ni/SBA-16 catalysts promoted with yttrium. These promoted catalysts were tested in CO2 methanation reaction and characterized by N2 sorption, small-angle/wide-angle XRD, TEM, XPS, H2-TPR, CO2-TPD, and TGA/DSC-MS. The results revealed that Ni/Y/SBA-16 catalysts performed better catalytic performance in CO2 methanation compared to the non-promoted Ni/SBA-16 catalyst. The best catalytic activity was found for the catalyst promoted with 10 wt% Y. The improved performance of such catalysts was attributed to the increase of reducibility of nickel species, the increase in surface oxygen species, and the abundance of moderate basic sites caused by Y promotion. Furthermore, the CO2 reaction rate and turnover frequency of CO2 were well correlated with the number of moderate basic sites. Finally, all the tested catalysts are highly stable during the 8 h time-on-stream catalytic test.