CO2 Reforming Of Methane Reaction Research Articles

Study on the effect of promotors in CO2 utilization for syngas production via dry reforming of methane over Co-MOX/TiO2-Al2O3 (MOX = La, Ce, Mg, and K) catalysts

In this study, Co-based catalysts supported over Ti-Al oxide and promoted with La, Ce, Mg, and K metals were assessed for CO2 reforming of methane reaction to produce syngas. Titania-alumina mixed oxide supports were prepared using the template-assisted-solvothermal method, and then Co and promotors were co-impregnated over the as-prepared support. Different characterizations of catalysts showed that variation in promotor metal impacts these catalysts' physical and chemical properties. The Ti-Al oxide support possessed the perfect hexagonal morphology. Potassium-promoted catalysts possessed the highest number of basic sites, whereas the La-promoted catalyst possessed the highest number of acidic sites. La promotion improved the Co dispersion, while Mg promotion enhanced the metal support integration. La-promoted catalysts are deactivated because of active metal oxidation and the generation of hard carbon. The carbon was deposited in all catalysts; however, the activity of the Mg-promoted catalyst was unaffected. The intermediate surface basicity and strong metal support interaction improved the Mg-promoted catalyst's stability. The La and Mg-promoted catalysts possessed lower apparent activation energies.

Effect of modified surface of Co/Al2O3 on properties and catalytic performance for CO2 reforming of methane

This work objective is to reveal the advantages of the 10 wt%Co/Al2O3 catalyst that the Co surface was constructed through the impregnation associated with the 6 h of ammonia vapor diffusion (10Co(T)/Al2O3). The modified surface catalyst was characterized and tested for CO2 reforming of methane reaction (CRM) that converts two main greenhouse gases into H2 fuel and syngas. Compared with the 10 wt%Co/Al2O3 catalyst that the Co surface formed by traditional impregnation (10Co/Al2O3), the characterization outcome examined the creation of high-dispersive Co species on the modified surface catalyst. The dispersion of cobalt oxide derived by this method provided more Co2+/Co3+ on the surface, collaborated with the stronger metal-support interaction, which generates more oxygen vacancies. Consequently, this modified Co surface on 10 wt%Co/Al2O3 catalyst demonstrated higher activities and prevented the deposition of the hardest removable coke type during the CRM reaction time-on-stream. Overall, the Co surface of 10 wt%Co/Al2O3 catalyst prepared by impregnation associated with the 6 h of ammonia vapor diffusion had formed a high dispersion of small Co2+/Co3+ connecting with the support that developed abilities of Co/Al2O3 catalyst into a more practical CRM catalyst.

The bulk and supported perovskite-type catalysts for the CO2 reforming of methane: The effect of ceria and magnesia

BackgroundThe bulk or supported nickel catalysts are active in the dry reforming of methane to produce syngas. The nickel-based catalysts are deactivated quickly due to the metal sintering and coke deposition. Perovskite catalysts are stable, enhance the dispersion of the active sites, and resist metal sintering and coke deposition. The coke deposition is inhibited by increasing the CO2 adsorption and oxidation of the deposited coke. MethodsA series of ceria-doped perovskite catalysts La1-xCexNiO3, LaNi1-xCexO3 and magnesia-modified-alumina supported perovskite-type catalysts were prepared via the sol-gel method. The prepared catalysts were thoroughly characterized via state-of-the-art characterization techniques. Significant findingsThe incorporation of ceria assisted the supported catalysts in forming a dispersed phase at low loading and forming other NiO or NiO-MgO (solid solution) NiAl2O4 and MgAl2O4 (spinel phase). The catalytic activity for the CO2 reforming of methane reaction increased with the addition of magnesia and the substitution of La-ion with tetravalent metal cation (ceria). The doping of ceria increased the stability of the catalyst. The bulk catalyst La0.5Ce0.5NiO3 exhibited promising catalytic activity. The magnesia-modified-alumina-supported catalyst (50La0.5Ce0.5NiO3/8MgO-Al2O3) was more active than the alumina-supported or bulk-perovskite catalysts with low coke deposition and higher percent conversion of CH4 (97%) and CO2 (99%) at 1073 K.

Boosting CO2 reforming of methane via the metal-support interaction in mesostructured SBA-16-derived Ni nanoparticles

High surface area and porosity SBA-16 was synthesized and used as support for Ni nanoparticles using three methods including wet impregnation, citric acid-assisted impregnation, and ammonia evaporation. All the studied samples showed high activity in the CO2 reforming of methane reaction, however, the best catalytic behavior was found for the catalyst derived from ammonia evaporation. Based on characterization techniques, it was assumed that the improvement in Ni/SBA-16-AE performance was due to the strong metal-support interaction resulting from the formation of Ni-phyllosilicate. Additionally, a high Ni dispersion was observed which may be related to the confinement of cage-like pores of the SBA-16 matrix. The ammonia evaporation technique can well contribute to the limited sintering of Ni nanoparticles and reduced amount of deposited carbon.

Energy storage efficiency optimization of methane reforming with CO2 reactors for solar thermochemical energy storage☆

In CO2 reforming of methane solar thermochemical energy storage, much research has been conducted to enhance the thermochemical performance of the reactor. However, there has been little research conducted to investigate the effects of dimensions on the reactor thermochemical performance. Moreover, little innovation has occurred on optimizing reactor dimensions and operating conditions simultaneously. In this paper, a model has been developed to simulate CO2 reforming of methane reaction in a tubular packed reactor. By comparing with experimental and simulation data from another publication, the model is validated to be more accurate. A parametric study has been performed to investigate the effects of dimensions and operating conditions on the reactor thermochemical conversion and energy storage efficiency. The result shows that there is a trade-off between achieving a higher energy storage efficiency and decreasing the conversion by having smaller reactor with larger gas flow rate. An optimization study of all the design parameters, based on the reaction model coupled with a multistart optimization algorithm, is performed to find the maximum energy storage efficiency for a fixed required conversion. Without sacrificing the conversion, an energy storage efficiency of 0.77, which is 10% higher than the highest established experimental data, is obtained through optimization. The study provides a baseline for further thermodynamic analysis of the entire system.

Ceo2 promoted the performance of Ni/Al2O3 catalyst for CRM reaction

The promoted effect of CeO2 on the reaction of Ni/Al2O3 catalyst in the syngas of CO2 reforming of methane (CRM) was studied. The results showed that the catalyst prepared with CeO2 addition exhibited high activity and stability, and the conversions of CH4 and CO2 could reach 96% at 800 °C when the amount of Ce was 5 wt%. SEM, H2-TPR, CH4-TPSR and CO2/O2-TPO characterization indicated that addition CeO2 could enhance the interaction between support and Ni species in preparation process, enabling the capacity of catalyst to resist carbon deposition and metal sintering.

CO2 Reforming of Methane over Fe‐Modified Ni‐Based Catalyst for Syngas Production

Fe‐modified Ni‐based catalysts are synthesized using a microwave‐assisted synthesis method and are used for CO2 reforming of methane (CRM) with a small amount of oxygen to produce syngas. The effect of Fe loading, impregnation temperature, and microwave power on the structural feature and catalytic performance of prepared catalysts is examined. The results show that the addition of slight oxygen increases CH4 conversion and decreases coke deposit. The Fe loading has a remarkable influence on the structure and catalytic performance of the catalysts. The introduction of Fe into the Ni‐based catalyst improves the specific surface area and decreases the Ni particle size, which promotes the formation of the Fe–Ni alloy, resulting in the enhancement of catalytic activity, stability, and H2/CO ratio compared with an unmodified catalyst. However, higher Fe loading decreases the catalytic performance. The impregnation temperature and microwave power influence the catalytic activities remarkably. When Fe loading is 1 wt%, the impregnation temperature and microwave power are 60 °C and 600 W, respectively, the resultant catalyst shows the highest catalytic activity and maintains its activity for 80 h during CRM reaction. The research work provides a route to improve the catalytic performance of Ni‐based catalysts.

Improved structural stability and catalytic performance for CH4 reforming reaction of mesoporous MCM-41 analogs prepared by zeolitic subunits of MOR desilication

We demonstrated a new strategy for the preparation of highly stable mesoporous molecular sieves (TMM) by the desilication of MOR zeolite and self-assembling of the zeolite subunits in Na2O•(3.3–3.4) SiO2 aqueous solution. Na2O•(3.3–3.4) SiO2 in the aqueous solution plays two roles in the synthesis, one was providing a moderate alkaline medium with buffering effect for the desilication of MOR zeolite, other one was supplementing silica source. The desilication conduction of MOR zeolite was optimized by the adjustment of reaction temperature and time, pH in the solution. TMM were characterized by X-ray diffraction (XRD), N2 adsorption/desorption (BET), Fourier transformed infrared (FT-IR) and transmission electron microscopy (TEM). The characterization results showed that the characteristics of MOR zeolite, such as double six-membered or five-membered ring subunits, were still preserved in TMM, and TMM possessed well-ordered mesostructure of MOR zeolite crystals. Compared with the pure silica mesoporous molecular sieve (MCM-41, 4-day), the hydrothermal stability of TMM (17-day) was increased by 100% with refluxed water. The significantly improving of TMM hydrothermal stability was due to increase the surface hydrophobicity and the ratio of T12-ring, and decreased remarkably number of hydrophilic silanol groups. After hydrothermal treatment for 17-day, TMM also exhibited more efficient catalytic activation than MCM-41 treated for 4-day in CO2 reforming of methane reaction (700 °C). The 5 wt% Ni/TMM-17d-Glu (5 wt% Ni, loading) catalysts prepared by Glucose modified impregnation method exhibited excellent catalytic activity, which were providing 58% CO2 and 47% CH4 conversions at 700 °C.

Morphology-Dependent Catalytic Activity of Ru/CeO₂ in Dry Reforming of Methane.

Three morphology-controlled CeO2, namely nanorods (NRs), nanocubes (NCs), and nanopolyhedra (NPs), with different mainly exposed crystal facets of (110), (100), and (111), respectively, have been used as supports to prepare Ru (3 wt.%) nanoparticle-loaded catalysts. The catalysts were characterized by H2-temperature programmed reduction (H2-TPR), CO– temperature programmed desorption (CO-TPD), N2 adsorption–desorption, X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (XDS). The characterization results showed that CeO2-NRs, CeO2-NCs, and CeO2-NPs mainly expose (110), (100) and (111) facets, respectively. Moreover, CeO2-NRs and CeO2-NCs present higher oxygen vacancy concentration than CeO2-NPs. In the CO2 reforming of methane reaction, Ru/CeO2-NR and Ru/CeO2-NC catalysts showed better catalytic performance than Ru/CeO2-NPs, indicating that the catalysts with high oxygen vacancy concentration are beneficial for promoting catalytic activity.

CO2 reforming of methane to syngas at high pressure over bi-component Ni-Co catalyst: The anti-carbon deposition and stability of catalyst

The catalytic performance of Ni-Co bi-component catalysts in CO2 reforming of methane (CRM) under high pressures was studied for obtaining highly stable Ni-based catalysts, which is important for the industrialization of high pressure CRM. A series of 5% (xNiyCo)/SBA-15 catalysts were prepared with a modified co-impregnation method by adding trace amount of β-cyclodextrin (CD) into Ni(NO3)2 impregnation solution. The effects of catalyst compositions (Ni/Co ratio) and the CRM reaction conditions (pressure, gas hourly space velocity, time on stream, etc) on the catalysts stabilities were investigated. The carbon deposition behaviors of the catalysts during the high pressure CRM reaction were disclosed through detailed characterizations of the spent catalysts. The type of coke, instead of the amount of deposited carbon, was proved to be responsible for the deactivation of 5% (xNiyCo)/SBA-15 catalysts during the high pressure reaction. The amount of carbon deposition depended strongly on the Co loading in the bimetallic catalysts. Long-term stability with 100 h TOS at 2.0 MPa and 800 °C was achieved for the optimized 5% (4.5Ni0.5Co)/SBA-15 catalyst and a slow deactivation (decrease in CH4 conversion) was observed. The reaction results with different reaction time over 5% (4.5Ni0.5Co)/SBA-15 at high pressures suggested that the accumulation of carbon deposition took place mainly at the initial stage of the CRM reaction. Moreover, the disorder degree of deposited carbon species and the sintering of metal particles were identified as the primary reasons for the deactivation of the catalysts. Trace Co enriched on Ni-Co surface of 5% (4.5Ni0.5Co)/SBA-15 suppressed Ni aggregation and facilitated the adsorption of co-reactant.

CO2 reforming of methane over NixMg6−xAl2 catalysts: Effect of lanthanum doping on catalytic activity and stability

NixMg6−xAl2 and NixMg6−xAl1.8La0.2 (x = 2, 4 or 6) catalysts were prepared via a co-precipitation method and calcined under an air flow at 800 °C. X-ray diffraction (XRD) results showed that the NixMg6−xAl1.8La0.2 catalysts contained different lanthanum oxide species after calcination. Fourier Transform Infrared Spectroscopy (FTIR) spectra demonstrated that the lanthanum doped catalysts adsorbed more CO2 compared to the lanthanum free solids. This improved basicity was verified in the CO2-TPD profiles. Temperature programmed reduction (TPR) analyses proved that the addition of lanthanum affected nickel species distribution in the catalysts and strengthened NiO-MgO interactions inside the solid matrix. The CO2 reforming of methane reaction (Ar/CO2/CH4:60/20/20; GHSV 60000 mL g−1 h−1) was carried out over the different catalysts in the temperature range of 600 °C–800 °C. Lanthanum addition improved the catalytic activity particularly by favoring the methane dry reforming reaction over all the other secondary reactions in addition to the creation of more basic sites that enhanced CO2 adsorption and contributed to the removal of carbon deposits. The most active lanthanum containing catalyst kept a constant catalytic performance for 14 h on stream despite the formation of carbon deposits. These carbon deposits can be removed under an oxidative atmosphere at moderate temperature due to the presence of lanthanum oxide species in the catalyst.

Characteristics of combined carbon dioxide reforming with partial oxidation of methane to produce hydrogen in the membrane reactor

Thermodynamic equilibrium constant method and mathematical model are used to analyze the investigating effects of temperature, α[oxygen-methane molar ratio] and β [carbon dioxide-methane molar ratio] on characteristics of oxidative CO2 reforming of methane reaction over Ni/Al2O3 catalysts to produce hydrogen in the membrane reactor. While keeping temperature at 1100 K, the membrane reactor is no longer useful to separate hydrogen when α > 0.6 for hydrogen in reaction side is no longer to permeate side. When increasing β, the methane conversion goes up firstly until the β is 1.3, which is higher than the inflection point at 1.1 in the model prediction. The hydrogen yield peaks at β = 0.5 in permeate side. Increasing the temperature or reducing the β will cause the molar ratio of H2/CO increase. However, changing α has no significant effect on adjusting the molar ratio of H2/CO. By establishing equilibrium reaction model, the system performance can be accurately predicted. Copyright © 2016 John Wiley & Sons, Ltd.

High-performing and durable MgO/Ni catalysts via atomic layer deposition for CO2 reforming of methane (CRM)

MgO-coated Ni catalysts with two different shell thicknesses were prepared using atomic layer deposition (ALD) and their catalytic activities for the CO2 reforming of CH4 (CRM) were compared with that of bare Ni catalyst. Conversion of CO2 and CH4 in the CRM reaction at 800°C was enhanced with increasing thickness of the ALD-deposited MgO shells. In particular, the catalytic activity of MgO/Ni catalyst prepared using 200 ALD MgO deposition cycles was fairly durable, with negligible deactivation during a 72h CRM reaction. We suggest that the MgO shell, which is highly basic and has high affinity to CO2, likely, accelerated the reverse CO disproportionation, thereby reducing the poisoning of Ni active sites during the CRM reaction. Furthermore, the 200-cycled MgO shell destroyed ensemble of Ni catalysts surface, allowing preservation of Ni active sites with preferential growth of filamentous carbon to layered graphitic ones. We suggest that the preparation of core–shell structures using ALD can be a promising strategy for fabricating highly active and durable catalysts that are operable at relatively high temperatures.

CO2 reforming of methane over Ni–Co/ZSM5 catalysts. Aging and carbon deposition study

The wet impregnation method was used to prepare ZSM5 supported nickel and/or cobalt monometallic and bimetallic catalysts with a 7 wt.% total metal loading. The CO2 reforming of methane reaction was carried out in the 600 °C–800 °C temperature range over the different catalysts (GHSV 60000 mL g−1 hr−1). The cobalt containing catalysts favored the reverse water gas shift reaction at high temperature and cobalt acted as a synergist to nickel, as overall, bimetallic catalysts showed better catalytic performance. Carbon deposition was less expressed over catalysts with high cobalt content. Following 12 h on stream at 700 °C, the bimetallic catalyst with cobalt to nickel ratio of 2, showed high CO2 and CH4 conversions (∼60%) accompanied with the lowest carbon deposition (5%). The thermal analysis of aged catalysts showed that among the deposited carbon species, it is the carbon present in the proximity of nickel and/or cobalt catalytic sites that is responsible of deactivation.

CO2 reforming of methane on Ni/γ-Al2O3 catalyst prepared by dielectric barrier discharge hydrogen plasma

Ni/γ-Al2O3 catalyst was prepared by direct treatment of Ni(NO3)2/γ-Al2O3 precursor with dielectric barrier discharge (DBD) hydrogen plasma at different input powers, characterized by XRD, H2-TPR, CO2-TPD, N2 adsorption and TEM, respectively, and used as the catalyst for CO2 reforming of methane (CRM). The results showed that the input power obviously affected the reduction degree and catalytic performances of catalysts. Low input power under 40 W mainly resulted in the decomposition of nickel nitrate into Ni oxides. The reduction degree, catalytic activity and stability increase with the input power. Similar catalytic performances in CRM reaction can be obtained when the power exceeds 80 W. Compared with the Ni/Al2O3 catalyst prepared by traditional method, Ni/γ-Al2O3 samples prepared by H2 DBD plasma exhibit better activities, stability and anti-carbon deposit performances. It is mainly ascribed to smaller Ni particle size, more basic sites and weaker basicity. The increase of Ni particle sizes due to the sintering at high temperature results in the decrease of catalytic activities and coke formation.

La0.6Sr0.4Co0.8Ni0.2O3−δ hollow fiber membrane reactor: Integrated oxygen separation – CO2 reforming of methane reaction for hydrogen production

An integrated reactor system which combines oxygen permeable La0.6Sr0.4Co0.8Ni0.2O3−δ (LSCN) perovskite ceramic hollow fiber membrane with Ni based catalyst has been successfully developed to produce hydrogen through oxy-CO2 reforming of methane (OCRM). Dense La0.6Sr0.4Co0.8Ni0.2O3−δ hollow fiber membrane was prepared using phase inversion-sintering method. OCRM reaction was tested from 650 °C to 800 °C with a quartz reactor packed with 0.5 g Ni/Al2O3 catalyst around the LSCN hollow fiber membrane. CH4 and CO2 were used as reactants and air as the oxygen source was fed through the bore side of the hollow fiber membrane. In order to gauge the effectiveness of this membrane reactor system, air flow was closed at 800 °C and dry reforming of methane (DRM) was tested for comparison. The results show that the oxygen fluxes of LSCN membrane swept by helium are nearly 3 times less than those swept by OCRM reactants. With increasing temperature and oxygen supply, methane conversion in the OCRM reactor reaches 100%, but CO2 conversion decreases from 87% to 72% due to the competition reaction with POM. CO selectivity is as high as nearly 100% at reaction temperatures of 700 °C–800 °C while H2 selectivity reaches a maximum of 88% at 700 °C. At 800 °C, when air supply was closed and DRM was conducted for comparison, CO selectivity decreased to 91%, resulting in carbon deposition which was around 4 times more than those obtained under OCRM reaction and H2/CO ratio decreased from 0.93 to 0.74, showing better carbon resistance and higher H2 selectivity of the Ni-based catalyst over the integrated oxygen separation-OCRM reaction across the LSCN hollow fiber membrane reactor.

Particle size effect in the low temperature reforming of methane by carbon dioxide on silica-supported Ni nanoparticles

The influence of nickel particle size in the range of 1.6–7.3nm on catalyst performance in low temperature CO2 reforming of methane reaction has been investigated using well-defined catalysts based on a neutral silica support. XAS and XPS studies indicated a reduction degree greater than 90%. The intrinsic Ni/SiO2 performances were found to be independent of nickel particle size in dry reforming at 773K using a CH4/CO2 ratio of 1.3 at 1atm, both at an early stage and in steady state conditions. The H2/CO ratio was also found to be structure in sensitive but is controlled by thermodynamics through the faster reverse water gas shift reaction.

Catalyst Deactivation Simulation Through Carbon Deposition in Carbon Dioxide Reforming over Ni/CaO-Al2O3 Catalyst

Major problem in CO2 reforming of methane (CORM) process is coke formation which is a carbonaceous residue that can physically cover active sites of a catalyst surface and leads to catalyst deactivation. A key to develop a more coke-resistant catalyst lies in a better understanding of the methane reforming mechanism at a molecular level. Therefore, this paper is aimed to simulate a micro-kinetic approach in order to calculate coking rate in CORM reaction. Rates of encapsulating and filamentous carbon formation are also included. The simulation results show that the studied catalyst has a high activity, and the rate of carbon formation is relatively low. This micro-kinetic modeling approach can be used as a tool to better understand the catalyst deactivation phenomena in reaction via carbon deposition. © 2011 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

TiO2/Ni Inverse-Catalysts Prepared by Atomic Layer Deposition (ALD)

Atomic layer deposition (ALD) was used to deposit TiO2 on Ni particles, and the catalytic activity of Ni for CO2 reforming of methane (CRM) was evaluated. In the presence of TiO2 islands on Ni surfaces, the onset temperature of the CRM reaction was lower than that of bare Ni. During the CRM reaction, carbon was deposited on the surface of bare Ni, which reduced the catalytic activity of the surface with time, and TiO2 islands were able to remove carbon deposits from the surface. When the Ni surface was completely covered with TiO2, the catalytic activity disappeared, demonstrating that tuning of the TiO2 coverage on Ni is important to maximize the activity of the CRM reaction.

High-Stable Mesoporous Ni-Ce/Clay Catalysts for Syngas Production

A mesoporous-type catalytic support was synthesized through the modification of a smectite with polyvinyl alcohol (PVA) and microwaves. Texture and micro-morphology of the support was determined. Several techniques were employed in order to describe the chemical environment of active species on the surface. Ni0 particle sizes were dependent on the structural site of reducible species. High stable Ni-Ce catalysts (calcined at 800 °C) were evaluated in the CO2 reforming of methane reaction at 700 °C (WHSV = 96 L g−1 h−1, without dilution gas and pre-reduction). The catalysts have presented CH4 conversions between 40 and 65%, CO2 conversion between 35 and 65% and H2/CO ratios between 0.2 and 0.4. Delaminated-clay was synthesized from a natural smectite using polyvinyl alcohol and microwaves. Ni-Ce catalysts supported on delaminated clay achieved high stability in dry reforming of methane for syngas production.