Catalytic Dry Reforming Of Methane Research Articles

Highly Dispersed Ni Nanoparticles on Anhydrous Calcium Silicate (ACS) Nanosheets for Catalytic Dry Reforming of Methane: Tuning the Activity by Different Ways of Ni Introduction

Three kinds of nickel-loaded anhydrous calcium silicate nanocatalysts (ACS), including Ni-ACS-Dop, Ni-ACS-Iex and Ni-ACS-Im, were prepared by introducing Ni species through doping in the synthesis of calcium silicate hydrate (CSH) nanosheets, ion-exchange with premade CSH nanosheets and deposition on calcined ACS nanosheets, respectively. Although Ni species were introduced in different ways, all the Ni-ACS catalysts showed similar chemical compositions and microstructures, where Ni nanoparticles were highly dispersed on the ultrathin ACS nanosheets with a large surface area and good thermal stability. However, the differences in the way of Ni introduction did produce Ni with different electronic states. The Ni-ACS-Iex catalyst with "surface Ni" as a dominant form had more electrons enriched on the surface of Ni, which led to the highest activity in the dry reforming of methane (DRM) reaction among the three catalysts, whereas the Ni-ACS-Dop catalyst with "lattice Ni" as a dominant form showed an electron-deficient property and lowest activity. Different from the introduction of a more favourable nanostructure or chemical component to the catalyst system, this work controlled the chemical environment of metal precursors and created metal catalysts with a preferred surface electronic state during synthesis, which could be a new strategy to improve the catalytic activity.

Ni-alumina dry reforming catalysts: Atomic layer deposition and the issue of Ni aluminate

Abstract A catalyst consisting of 2 wt% Ni supported on a commercially available transition alumina is modified using TMA-H2O ALD cycles to deposit thin alumina overcoats on the catalyst, and it is then investigated for the catalytic dry reforming of methane (DRM) at 700 °C. Highly dispersed Ni rapidly sinters to form bulk Ni particles on the uncoated catalyst. In contrast, deposition of an alumina overcoat by ALD significantly lowers the rate of Ni sintering, and also lowers the propensity towards carbon deposition during DRM. Additionally, it is experimentally demonstrated that the Ni aluminate (NiAl2O4) spinel phase is unstable under the present DRM conditions and slowly undergoes reduction to metallic Ni and Al2O3. Slow reduction of the Ni2+ from NiAl2O4 is proposed as the origin of the large increase in DRM activity observed for the alumina-overcoated Ni catalysts.

Role of Electric Field and Surface Protonics on Low-Temperature Catalytic Dry Reforming of Methane

The role of the electric field and surface protonics on low temperature catalytic dry reforming of methane was investigated over 1 wt %Ni/10 mol %La-ZrO2 catalyst, which shows very high catalytic a...

Lattice Strained Ni-Co alloy as a High-Performance Catalyst for Catalytic Dry Reforming of Methane

Dry reforming of methane (DRM) is an effective route to convert methane and carbon dioxide to syngas. Herein, we report an efficient nickel–cobalt bimetallic catalyst with an activity of 4.97 molCH4 molNi–1 s–1 at 800 °C. It is active at low temperature as well, and near-thermodynamic equilibrium conversion was achieved as low as 350 °C, with a high yield of H2 implying inhibition of side reactions: i.e., a reverse water-gas shift (RWGS) reaction. The formation of Ni-Co alloy during the reaction was observed, and its lattice contraction was revealed by HAADF-STEM and EXAFS experiments. The lattice-strained Ni-Co alloy has good CO2 dissociation ability, which is responsible for its superior catalytic performance. Its weak chemisorption with H2 results in inhibition of RWGS side reactions. This work is helpful in the design and development of other metal alloy materials with novel structures and/or electronic configurations for catalytic applications.

Energy and exergy evaluations of catalytic dry reforming of methane for syngas production in fixed-bed reactors

Energy and exergy evaluations of catalytic dry reforming of methane for syngas production in fixed-bed reactors

Energy and exergy evaluations of catalytic dry reforming of methane for syngas production in fixed-bed reactors

The energy and exergy characteristics of dry reforming of methane (DRM) were numerically studied in this study in a tubular fixed-bed reactor under heat supply from uniform temperature furnace or uniform wall heat flux. Variations in enthalpy, entropy and exergy were computed based on non-equilibrium thermodynamics for chemical reactions. The heat supply, heat of chemical reaction and entropy generation due to irreversibility were the sources that caused changes in enthalpy, entropy and exergy between the reactor inlet and outlet. Based on the simulated results it was found that the chemical reaction is the most dominant factor for entropy generation. It was also found that exergy at reactor outlet depends on the heat supply and a minimum value can be found due to contribution variations from the gas species involved in DRM.

LaNi1-xMnxO3 perovskite-type oxides as catalysts precursors for dry reforming of methane

A series of ternary perovskite-type oxides LaNi1-xMnxO3 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized by the sol–gel resin method in propionic acid, producing solids solutions of perovskite-type structures with crystallite sizes between 15–20 nm. The LaNi1-xMnxO3 catalysts were thoroughly characterized and tested in the catalytic dry reforming of methane (DRM) reaction. It was observed that the presence of Mn in the perovskite-type oxide increases the Ni3+ to Ni0 reduction temperature giving rise to formation of Ni0 nanoparticles on the MnOx-La2O3 matrix. The LaNi1-xMnxO3 with x ≤0.8 showed higher activities and selectivity’s towards syngas during the CH4–CO2 reforming, due to in situ formation of highly dispersed Ni0-metallic nanoparticles on the La2O2CO3-MnO-Mn2O3 solid matrix responsible for the high activity and high resistance to carbon buildup on the catalyst surface.

Microwave Heating-Assisted Catalytic Dry Reforming of Methane to Syngas

Natural gas is a robust and environmentally friendlier alternative to oil resources for energy and chemicals production. However, gas is distributed globally within shales and hydrates, which are generally remote and difficult reserves to produce. The accessibility, transportation, and distribution, therefore, bring major capital costs. With today’s low and foreseen low price of natural gas, conversion of natural gas to higher value-added chemicals is highly sought by industry. Dry reforming of methane (DRM) is a technology pathway to convert two critical greenhouse gas components, CH4 and CO2, to syngas, a commodity chemical feedstock. To date, the challenges of carbon deposition on the catalyst and evolution of secondary gas-phase products have prevented the commercial application of the DRM process. The recent exponential growth of renewable electricity resources, wind and solar power, provides a major opportunity to activate reactions by harnessing low-cost carbon-free energy via microwave-heating. This study takes advantage of differences in dielectric properties of materials to enable selective heating by microwave to create a large thermal gradient between a catalyst surface and the gas phase. Consequently, the reaction kinetics at the higher temperature catalyst surface are promoted while the reactions of lower temperature secondary gas-phase are reduced.

Hollow hierarchical Ni/MgO-SiO2 catalyst with high activity, thermal stability and coking resistance for catalytic dry reforming of methane

The methane dry reforming (DRM) simultaneously converts the two greenhouse gases and produces syngas (CO + H2), which is being significant for both environmental and industrial consideration. Employing well-defined crystal oxides as precursors can produce Ni-based DRM catalysts with good sintering and coking resistance by enhancing the metal-support interactions. Adding basic promoters also is considered as an effective way to improve the coking resistance of DRM catalysts, although challenge remains in the control over the structure, morphology and interaction of the promoter in the catalyst. To well combine the two methods together for better catalytic performance, in this work a Ni/MgO-SiO2 catalyst was synthesized through a facile one-pot hydrothermal process, during which Ni-phyllosilicate formed as the precursor of Ni particles and MgO promoter was generated in form of Mg-phyllosilicate. This Ni/MgO-SiO2 had a hierarchical hollow sphere structure with large surface area (477.4 m2/g). Both the Ni particles (avg. 6.0 nm) and MgO promoter uniformly distributed. This hollow hierarchical catalyst performed high activity, thermal stability and coking resistance for catalytic dry reforming of methane.

Greenhouse gases abatement by catalytic dry reforming of methane to syngas over samarium oxide-supported cobalt catalyst

Anthropogenic activities often result in the emissions of methane (CH4) and carbon dioxide (CO2) which are the principal components of greenhouse gases. The mitigation of these gases to avert further occurrence of global warming has attracted a lot of research interest. In this study, the potential of greenhouse gases abatement via catalytic CO2 (dry) reforming of methane to syngas over samarium oxide-supported cobalt (20 wt% Co/80 wt% Sm2O3) catalyst was investigated. The 20 wt% Co/80 wt% Sm2O3 material was synthesized via wet impregnation method and characterized using different instrument techniques. The methane dry reforming reaction, as well as its kinetics over the catalyst, was studied in a stainless steel fixed-bed continuous flow reactor at feed (CH4:CO2) ratios range of 0.1–1.0, temperature range of 923–1023 K and gas hourly space velocity (GHSV) of 30,000 h−1. The 20 wt% Co/80 wt% Sm2O3 catalyst showed promising catalytic activity evident from the highest CH4 and CO2 conversion of ~71 and ~74% as well as the highest hydrogen (H2) and carbon monoxide (CO) yield of ~62 and ~73%, respectively. Moreover, the methane dry reforming over the 20 wt% Co/80 wt% Sm2O3 catalyst produces H2/CO ratio close to unity hence suitable for use as a chemical intermediate for synthesis of oxygenated fuels. The kinetic data obtained from the methane dry reforming were fitted to power law model. Apparent activation energies of 88.62, 80.12, 108.12 and 100.91 kJ mol−1 were obtained for CH4, CO2, H2 and CO, respectively. The characterization of the spent 20 wt% Co/80 wt% Sm2O3 catalyst after 4 h of time-on-stream has confirmed the presence of amorphous carbon which can easily be gasified.

Parametric study of catalytic dry reforming of methane for syngas production at elevated pressures

This study examined and elucidated the catalytic dry reforming of methane (DRM) for synthesis gas (syngas) production. The DRM performance was characterized using CH4 and CO2 conversions and product yields under various operating conditions and reactant compositions. A fixed-bed tubular reactor was used as the physical model and axisymmetric non-isothermal governing equations for the gas flow, energy transfer and species transport were solved numerically. The reactant inlet temperature was used as the primary parameter. Good agreement between the numerically predicted and experimentally measured data was obtained as the carbon formation reactions were included. A carbon-free reaction was obtained from the numerical model at high temperature which agreed with the thermodynamic equilibrium analysis. It was found that the DRM performance was degraded as the reaction pressure and reactant flow rate were increased. Under these conditions, carbon yield increases with the increase in pressure and reactant flow rate. It was also found that DRM performance can be enhanced by introducing excessive CO2 into the reaction system. Carbon formation was suppressed by the excessive CO2 supply. The numerical results also indicated that decreases in CO2 and CH4 partial pressures led to enhance the DRM performance. The addition of H2 as one of the reactants suppresses CH4 conversion and inhibited carbon formation while the addition of CO resulted in suppressing CO2 conversion and enhancing carbon formation.

Non-Thermal Plasma-Assisted Catalytic Dry Reforming of Methane and Carbon Dioxide Over G-C3N4-Based Catalyst

In the present study, pure plasma and plasma-assisted catalytic activation of reforming of methane and carbon dioxide into syngas production were performed in a coaxial dielectric barrier discharge (DBD) plasma reactor at low temperature. For pure plasma, higher input power was favorable for the conversions of CH4 and CO2 but led to lower selectivities of syngas, while selectivities of syngas increased under lower flow rate of feed gases. A high CH4/CO2 ratio was more selective for C2 hydrocarbon formation. Novel g-C3N4-based catalysts were prepared and filled in the discharge gap at low temperature. The cooperation effect of DBD plasma with g-C3N4 catalyst was achieved that contributed more to the activation of carbon dioxide than that of methane as well as the yield of CO for its low reduction potential. TiO2/g-C3N4 with heterogeneous structure as packing the catalyst bulks into the discharge zone was capable of further improving the reforming of methane and carbon dioxide. TiO2 mass ratio exhibited significant effect on dry reforming reactions and only TiO2/g-C3N4 with 1% TiO2 mass ratio presented enhanced hybrid effect than that of g-C3N4 catalyst.

A numerical optimization study on the catalytic dry reforming of methane in a spatially resolved fixed-bed reactor

Fixed-bed reactors with a small tube-to-particle diameter ratio are typically used for highly exothermic or endothermic reactions. Flow, temperature and species distribution as well as the reaction rates are affected by the effect of the confining wall. In this study we have investigated numerically a spatially resolved fixed-bed including a detailed reaction mechanism for dry reforming of methane (DRM). Operating conditions in terms of feed composition, feed and heating temperature and feed mass flow could be identified, where the deactivation of the catalyst due to coking is prevented but still a reasonable conversion of methane and carbon dioxide as well as a high hydrogen selectivity can be achieved. Finally the need of a spatially resolved simulation is shown. While a pseudo-homogeneous 2D simulation needs significantly less computation time, it over predicts the conversion by approx. 20% due to an overestimated heat transfer.

Enhancing C–H Bond Activation of Methane via Temperature-Controlled, Catalyst–Plasma Interactions

Recent shale gas discoveries and advances in plasma chemistry provide the basis to exploit metal surface–plasma interactions to precisely control C–H bond activation on catalytic surfaces, leading to improved reaction efficiencies. Although the exact determination of plasma–catalyst interactions remains a topic of continuing research, this Letter provides evidence that plasma–catalyst interactions exist and can be used to significantly enhance the activation of C–H bonds at temperatures >630 K, probed by the catalytic dry reforming of methane with carbon dioxide using Ni/Al2O3. We systematically varied bulk temperature and plasma power to determine Ni–plasma interactions. In contrast to reactions at low temperatures ( 8 fold increase). Other competing contributors, such as gas-phase plasma reactions, charge confinement, and plasma-driven enhanced bulk gas temper...

Synthesis of ceria nanopowders by microwave-assisted hydrothermal method for dry reforming of methane

Cerium oxide powder catalyst was prepared by microwave-assisted hydrothermal synthesis, characterized by physicochemical techniques and tested in catalytic dry reforming of methane in view of a potential use as anode material of Solid Oxide Fuel Cells operated on biogas. The conventional hydrothermal method was also used for comparison to evaluate the benefits of the non conventional preparation route. Microstructure and reduction–reoxidation properties of samples prepared by both routes were studied by XRD, adsorption–desorption isotherms of N2 at −196 °C, Raman spectroscopy and temperature programmed reduction in H2. Repeated cycles consisting of temperature programmed reduction in CH4 (TPR-CH4) followed by temperature programmed oxidation in O2 (TPO) were also performed. The catalytic properties of CeO2 samples were investigated in dry reforming of methane between 750 and 900 °C under stoichiometric (0.5% CH4 and 0.5% CO2 in He carrier) and oxidizing (0.25% CH4–0.75% CO2 in He) conditions. The preparation under microwave irradiation allows: i) obtaining crystallites with smaller size, ii) enhancing the stability towards redox treatments, iii) improving the surface and bulk reducibility by H2 and CH4, iv) favoring the creation of defects. These improved properties correlate well with better catalytic performances in dry reforming of methane with respect to the conventionally prepared ceria sample.

Experimental and kinetic investigation of the plasma catalytic dry reforming of methane over perovskite LaNiO3 nanoparticles

Plasma-assisted catalytic conversion of CH4 and CO2 into synthesis gas was performed in a dielectric barrier discharge reactor coupled with perovskite La–Ni nanoparticles (LaNiO3 NPs). Compared to supported catalysts such as Ni/γ-Al2O3, La–Ni/γ-Al2O3 and Ni/La2O3, LaNiO3 NPs showed better catalytic performance. The results show that the low flow rate of feed gases and high input power were favorable for the conversions of CH4 and CO2 as well as the selectivities of desired products, but led to lower energy efficiency. A global kinetic model according to argon dilution in plasma-catalytic system was proposed and employed to foresee the CH4 and CO2 conversion assisted by plasma-catalysts hybrid effect. The kinetic model indicates that the reactant conversion rate was an exponential function of the discharge energy.

Plasma-assisted catalytic dry reforming of methane: Highly catalytic performance of nickel ferrite nanoparticles embedded in silica

Spinel nickel ferrite nanoparticles (NiFe2O4 NPs) embedded in silica (NiFe2O4#SiO2) was prepared to enhance the reaction performance of the dry reforming of methane in a coaxial dielectric barrier discharge reactor. NiFe2O4 NPs of around 10 nm were effectively embedded in porous SiO2 NPs (∼100 nm in diameter). Compared to the supported Ni-based catalysts (Ni/γ-Al2O3, Ni–Fe/γ-Al2O3, Ni–Fe/SiO2, and NiFe2O4), the NiFe2O4#SiO2 catalyst placed at the discharge zone exhibited excellent catalytic performance and high resistance to carbon formation during dry reforming under ambient conditions without the involvement of extra heat. The synergetic effect between the non-thermal plasma and the NiFe2O4#SiO2 catalyst favored the conversion of CH4 and CO2 into syngas. The results indicated that the special structure of the as-synthesized NiFe2O4#SiO2 catalyst was capable of restraining the aggregation of Ni–Fe alloy and suppressing the carbon formation in the reforming process.

Detailed numerical simulations of catalytic fixed-bed reactors: Heterogeneous dry reforming of methane

Highly endothermic (or exothermic) heterogeneous catalytic reactions are performed commonly in fixed-bed reactors with small tube-to-particle-diameter ratios N both in industrial and lab-scale applications. For these reactor configurations conventional plug flow models and pseudo-homogeneous kinetic models fail. An adequate modeling can be carried out with full computational fluid dynamics (CFD) in combination with detailed reaction mechanisms. In this study, a full three-dimensional fixed-bed reactor for the catalytic dry reforming of methane (DRM) over rhodium was simulated with a detailed reaction mechanism. The bed consists of 113 spherical solid particles in which thermal conductivity was considered. Two different Reynolds numbers were investigated, i.e., 35 and 700. The simulated DRM fixed-bed reactor demonstrates the strong interaction between chemical kinetics and transport of momentum, heat and mass. The observed velocity, temperature and species fields are characterized by their three-dimensional behavior and interactions highlighting their complexity and discrepancy from lumped model predictions. In addition, the reaction mechanism determines regions with catalyst deactivation by carbon deposition. This study demonstrates the advantages of modeling heterogeneous catalytic fixed-bed reactors with small N fully in three-dimensional in combination with detailed reaction mechanisms. Finally, this modeling approach reduces dependencies on empiricism for the calculation of multiscale reaction devices.

Catalytic Dry Reforming of Methane on Ruthenium-Doped Ceria and Ruthenium Supported on Ceria

Two types of Ru–ceria catalysts were investigated, one prepared by combustion to create an atomically doped metal oxide, and the other, prepared by impregnation, as supported Ru oxide. They have different physical properties (as measured by X-ray photoelectron spectroscopy, X-ray diffraction, and Infrared spectra of adsorbed CO) but identical catalytic activity for dry reforming of methane. We show that the catalyst for dry reforming is partially reduced using XPS and IR spectroscopy. Furthermore, transient oxidation reaction spectroscopy with oxygen pulses confirms partial reduction of the catalyst is necessary for dry reforming activity.

CeO2–SiO2 supported nickel catalysts for dry reforming of methane toward syngas production

Supported nickel catalysts (5wt.% Ni) on binary CeO2–SiO2 (CS) with different ceria loading were prepared by wet impregnation and evaluated under catalytic dry reforming of methane (DRM) reaction to produce syngas. Analytical methods of characterization i.e. EDX, BET surface area, XRD, H2-TPR, CO2-TPD, TEM, SEM and TGA were conducted to analyze the physico-chemical properties of the prepared samples as well as to identify the carbon formation of the spent catalysts. The results showed that the properties of CeO2–SiO2 (Ni/xCS) catalysts were superior to the Ni/SiO2 and Ni/CeO2 catalysts, in terms of particle sizes, Ni dispersion, reducibility and basicity. The catalyst evaluation showed that ceria addition on the Ni-supported catalysts influenced the catalytic performances and hindered the carbon formation significantly. In this study, Ni/CS catalyst with 9wt.% ceria exhibited good properties, high catalytic performance, elevated stability and low carbon deposition, thus considered to be the best catalyst with the optimal amount of ceria.