Ni Catalysts For Dry Reforming Research Articles

Effect of Ga-Promoted on Ni/Zr + Al2O3 Catalysts for Enhanced CO2 Reforming and Process Optimization

AbstractIn this study, zirconia-modified alumina support (S) was used to investigate Ga-promoted Ni catalysts for dry reforming of methane (DRM). The catalysts (Ni + (0–3) wt% Ga/S) were prepared using the wet impregnation method and calcined at 700 °C for 3 h. The inclusion of Ga enhanced the surface area, basicity, and metal-support interaction of the Ni-Ga/S catalysts. Smaller Ni particles containing Ga were seen in the TEM. The most active and stable catalyst was Ni + 2.0 Ga/S, having a conversion of 35% CO2 and 28% CH4 at 600 °C and displaying less (17%) carbon deposition. Furthermore, the DRM process was optimized by a mathematical model. The model determined the optimal conditions as follows: temperature (800 °C), gas flow rate (GHSV—30,000 ml h−1gcat−1), and methane to carbon dioxide ratio (1:1). The model predicts CH4 and CO2 conversions of 76.76% and 82.0%, respectively, and an H2/CO ratio of 1.02, compared to experimental results showing CH4 conversion at 74.56%, CO2 conversion at 83.25%, and an H2/CO ratio of 1.01. The model demonstrates excellent agreement with the experimental observations, exhibiting less than 3% error. Graphical Abstract

Different supported Ni catalysts for dry reforming of methane: Effect of calcination temperature

Due to the increased environmental consciousness about reducing greenhouse gas emissions of CH4 and CO2, an intriguing study issue is the dry reformation of CH4 (DRM) over a catalyst made of Ni.). Herein in this work, 5.0 wt% NiO was loaded on various supports (S = TiO2-P25, Al2O3, MgO, and ZrO2) through the process of dry impregnation. At 600 °C or 800 °C, the catalysts were then calcined to investigate the impact of calcination temperature on the catalytic performance. The catalysts were characterized by N2 physisorption, Raman spectroscopy, thermalgravimetric analysis, XRD, and TEM. The best catalyst was obtained when the MgO-supported Ni catalyst was operated at 700 °C and was calcined at 600 °C. This catalyst gave average conversions of CH4 and CO2 of 70.04 % and 77.2 %, respectively. However, when the calcination temperature of the same catalyst was increased to 800 °C, the average conversions of CH4 and CO2 dropped to 37.9 % and 48.07 %, respectively. Thus, the calcination pretreatment strongly influenced the catalyst performance, where rising the calcination temperature lowered the activity. The Al2O3-supported sample had the highest surface area, metal-support interaction, and activity. It produced a large amount of carbon nanotubes, whereas the MgO-supported sample presented the least carbon formation, the lowest deactivation factor, and no morphology change due to the reaction in the TEM.

Unravelling the Anomalous Coking Resistance over Boron Nitride-Supported Ni Catalysts for Dry Reforming of Methane

Unravelling the Anomalous Coking Resistance over Boron Nitride-Supported Ni Catalysts for Dry Reforming of Methane

Stabilizing Supported Ni Catalysts for Dry Reforming of Methane by Combined La Doping and Al Overcoating Using Atomic Layer Deposition

Stabilizing Supported Ni Catalysts for Dry Reforming of Methane by Combined La Doping and Al Overcoating Using Atomic Layer Deposition

Synergistic effect of Promoter addition and Nickel Loading for Catalysed Dry Reforming of Methane

This paper investigates the synergistic influence of both catalyst active sites Lanthanum promoter and Nickel loading on supported Ni catalysts for Dry Reforming of Methane (DRM) reaction. Alumina-supported nanosized Ni-based catalysts were synthesized using the impregnation method with varying percentages of Lanthanum promoter. Structural analysis via XRD, SEM and PSD show Nickel and lanthanum were homogeneously dispersed on Al2O3 supported catalyst with a range of 40-90 nm were obtained. Lanthanum addition favours equilibrated reaction equivalent to DRM mechanism. Increasing the La percentage and temperature however shifts the equilibrium to a higher conversion of CH4 (72%) hence higher H2 selectivity (70%).

High performance and stable mesoporous MgO–ZrO2 supported Ni catalysts for dry reforming of methane

Catalysts for dry reforming of methane (DRM) based on Ni are used widely. However, due to carbon deposition or active metal sintering, deactivation is inevitably attached to these catalysts. Ni catalysts supported on mesoporous MgO–ZrO2 have been synthesized by surfactant-assisted route and impregnation method, and their catalytic performance for DRM reaction has been investigated in this study. The specific surface area of the mesoporous support is approximately 64.7 ​m2 ​g−1 after calcination at 700° for 2 ​h. Catalyst with 10 ​wt% Ni content shows the best catalytic performance. The conversion rates of CH4 and CO2 are higher than 80%, while the selectivity values of CO and H2 are higher than 90%. After a long-term DRM test, according to the weight loss by TG, the catalysts carbon deposition with 7.5 ​wt% and 10 ​wt% content are 46.2% and 19.9%, respectively.

Mesocellular silica foam-based Ni catalysts for dry reforming of CH4 (by CO2)

Nickel-containing mesocellular silica foam (MCF) catalysts were prepared for dry reforming of methane (DRM). Different methods were used for the synthesis of the MCFs supports in order to enhance their surface areas and pore volumes. The incorporation of nickel was done by three different methods: incipient wetness impregnation, two-solvents post-synthesis method and direct one-pot synthesis introduction. All prepared materials were calcined then characterized by N2 sorption, X-Ray Diffraction (XRD), Transmission Electronic Microscopy (TEM), Temperature Programmed Reduction (TPR) and X-Ray Fluorescence (XRF). Their catalytic performances were tested in DRM between 200 and 770 °C, then for 4 h (stability test) at 650 °C, using a Gas Hourly Space Velocity (GHSV) of 36 L g−1 h−1 and an equimolar ratio of reactants. Promising results were obtained by using direct synthesis method (DS) in which small Ni particles in strong interaction with the support were formed.

The effect of La on the hydrotalcite derived Ni catalysts for dry reforming of methane

A series of 20Ni-Mg-Al hydrotalcite-like (HT) precursors were prepared to study the influence of lanthanum (La) on the catalytic activity of the catalysts in the dry reforming of methane (DRM). The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD) and temperature-programmed reduction (TPR). All catalysts presented ordered mesoporous structures with a large specific surface area. XRD confirmed the presence of HT structure for all of the precursors while the La promotion resulted in an additional phase of Lanthanum carbonate hydroxide. TPR study showed larger reduction degree for the catalysts but also reduction peaks that are shifted to higher temperatures. DRM reactions at 600 and 750 °C revealed that the DRM activity was increased by the addition of La, while the stability of the catalysts was reduced at 600 °C.

Morphology effect of zirconia support on the catalytic performance of supported Ni catalysts for dry reforming of methane

An immature pinecone shaped hierarchically structured zirconia (ZrO2-ipch) and a cobblestone-like zirconia nanoparticulate (ZrO2-cs), both with the monoclinic phase (m-phase), were synthesized by the facile hydrothermal method and used as the support for a Ni catalyst for the dry reforming of methane (DRM) with CO2. ZrO2-ipch is a much better support than ZrO2-cs and the traditional ZrO2 irregular particles made by a simple precipitation method (ZrO2-ip). The supported Ni catalyst on ZrO2-ipch (Ni/ZrO2-ipch) exhibited outstanding catalytic activity and coke-resistant stability compared to the ones on ZrO2-cs (Ni/ZrO2-cs) and ZrO2-ip (Ni/ZrO2-ip). Ni/ZrO2-ip exhibited the worst catalytic performance. The origin of the significantly enhanced catalytic performance was revealed by characterization including XRD, N2 adsorption measurement (BET), TEM, H2-TPR, CO chemisorption, CO2-TPD, XPS and TGA. The superior catalytic activity of Ni/ZrO2-ipch to Ni/ZrO2-cs or Ni/ZrO2-ip was ascribed to a higher Ni dispersion, increased reducibility, enhanced oxygen mobility, and more basic sites with a higher strength, which were due to the unique hierarchically structural morphology of the ZrO2-ipch support. Ni/ZrO2-ipch exhibited better stability for the DRM reaction than Ni/ZrO2-ip, which was ascribed to its higher resistance to Ni sintering due to a strengthened metal-support interaction and the confinement effect of the mesopores and coke deposition resistance. The higher coking resistance of Ni/ZrO2-ipch for the DRM reaction in comparison with Ni/ZrO2-ip orignated from the coke-removalability of the higher amount of lattice oxygen and more basic sites, confirmed by XPS and CO2-TPD analysis, and the stabilized Ni on the Ni/ZrO2-ipch catalyst by the confinement effect of the mesopores of the hierarchical ZrO2-ipch support. The superior catalytic performance and coking resistance of the Ni/ZrO2-ipch catalyst makes it a promising candidate for synthesis gas production from the DRM reaction.

Uncoupling the size and support effects of Ni catalysts for dry reforming of methane

The dry reforming of methane (DRM; CH4+CO2↔2H2+2CO) can be a good way to utilize greenhouse gases for the production of valuable syn-gas. Ni-based catalysts have been used for this reaction; however, the Ni size effect and support effect were highly coupled and therefore could not be observed separately. Here, a unique catalyst in which the Ni nanoparticle size and support can be varied independently was devised. Highly uniform Ni nanoparticles with sizes of 2.6, 5.2, 9.0, and 17.3nm were tested for DRM at 800°C without a significant change in the Ni size, and overlayers of various metal oxides, including SiO2, Al2O3, MgO, ZrO2, TiO2, were tested with the 5.2nm of Ni nanoparticles. The dependence of the CH4 or CO2 turnover frequency on the Ni size and support was evaluated separately. The 2.6nm Ni nanoparticles showed 4.1 times higher methane turnover frequency than those with a size of 17.3nm. When various metal oxide overlayers were tested with the same 5.2nm Ni, Al2O3 exhibited 4.3 times higher methane turnover frequency than SiO2. The independent observation of the effects of the Ni nanoparticle size and support will provide valuable guidelines for designing effective methane dry reforming catalysts.

Employing a Nickel‐Containing Supramolecular Framework as Ni Precursor for Synthesizing Robust Supported Ni Catalysts for Dry Reforming of Methane

AbstractThis work presents a facile and efficient approach for preparing well dispersed supported Ni catalyst (HMA@Ni/SBA‐15) for dry reforming of methane (DRM) through the modified impregnation method by using a hexamethylenetetramine (HMA) Ni(II) complex, a three‐dimensional hydrogen‐bonded supramolecular framework, as Ni precursor. By employing this method, the NiII cation was discretely impregnated into the mesoporous channels of SBA‐15 support by the “obstacle effect” of the HMA coordination shell of the Ni complex; and then the Ni nanoparticles were stabilized inside the mesoporous channels of SBA‐15 by the confinement effect. The developed HMA@Ni/SBA‐15 catalyst demonstrated much higher catalytic activity and much better catalytic stability than the traditional Ni/SBA‐15 towards this reaction. The superior catalytic activity was suggested to be associated with the enhanced Ni dispersion and the improved reduction degree of NiO. In addition, the confinement effect of mesopore channels and strengthened interaction between Ni and support by improved Ni dispersion contributed to stabilizing Ni particles during the reduction and reaction process at high temperature. The strengthened Ni–support interaction of HMA@Ni/SBA‐15 favored the formation of whisker‐like carbon, which did not depress the accessibility of Ni active sites. However, owing to the weaker Ni–support interaction, the clearly observed shell‐like carbon closely encapsulated on Ni nanoparticles of spent Ni/SBA‐15 would significantly depress the accessibility of Ni active sites to reactants. The combination of stabilized Ni nanoparticles and well‐kept Ni accessibility of HMA@Ni/SBA‐15 catalyst allows it to show outstanding catalytic stability for DRM reaction. The much superior catalytic activity and stability of the developed HMA@Ni/SBA‐15 catalyst to the traditional Ni/SBA‐15 make it a promising candidate for producing synthesis gas through DRM reaction.

Structural response of Ni/ZrO2 to feed modulations during CH4 reforming reactions

Time resolved oxidation and reduction cycles of ZrO2-supported Ni catalysts for dry reforming of CH4 (CO2 + CH4 ↔ 2 CO + 2 H2) during feed modulations have been studied. Under reaction conditions (1073 K) Ni remains fully reduced, whereas switching the feed gas to pure CO2 results in a slow (25 sec) formation of a stable NiO phase. When switching back to reaction conditions the NiO phase is rapidly reduced (∼ 1 sec) to metallic Ni. In the context of this study, a novel capillary cell has been built, allowing the parallel treatment of 5 catalyst samples with different gas compositions and different pressures. A comparison of the capillary cell to conventional systems regarding the spectral quality and the kinetic data shows that the capillary cell can be used to obtain identical kinetic data and high quality X-ray absorption spectra.

High performance of Mg–La mixed oxides supported Ni catalysts for dry reforming of methane: The effect of crystal structure

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.

Stabilities of zeolite-supported Ni catalysts for dry reforming of methane

Ni/γ-Al 2 O 3 , Ni/Y-zeolite, and Ni/H-ZSM-5 catalysts were prepared using the incipient wetness impregnation method. Their catalytic performance in dry reforming of methane was studied. The fresh and used catalysts and deposited carbon were characterized using H 2 temperature-programmed reduction, temperature-programmed oxidation, N 2 adsorption-desorption, X-ray diffraction, and thermogravimetric analysis. The H-ZSM-5-supported Ni catalyst proved to be more stable than the other two catalysts, as it had the lowest carbon deposition. In dry reforming of methane, the Ni catalyst supported on H-ZSM-5 zeolite was found to be more stable than those supported on alumina or Y-zeolite.

Carbon deposition on borated alumina supported nano-sized Ni catalysts for dry reforming of CH4

Borated alumina supported 5wt% Ni catalysts with B2O3 loading varying from 0wt%, 1wt%, 5wt% to 10wt% were prepared and characterized by XRD, H2-TPR, CO2-TPD, NH3-TPD, in situ DRIFTS study, and evaluated for dry reforming of methane. The addition of B2O3 influences the activity and stability of the catalysts significantly. Ni particle size increases from 5.8 to 9.1nm with increasing the B2O3 loading from 0 to 10wt%. In the kinetic control temperature region (700°C) there is no linear relationship between the Ni particle size and the catalyst activity/stability. The formation of strong Lewis acid sites causes severe carbon deposition on 1wt% and 10wt% B2O3 loaded Ni catalysts, hence decreasing catalytic activity and stability. The formation of weak Lewis acid sites and O–H groups on 5wt% B2O3 promoted Ni catalyst is found to significantly facilitate carbon removal and improve the stability of the catalysts. The reaction mechanism of dry reforming of methane over borated-alumina supported Ni catalysts is proposed, especially the promotional effect of OH groups on the suppression of carbon formation being emphasized.