Catalysts For Dry Reforming Research Articles

Effect of Ce promotion on catalytic activity of Ni-Al catalysts in dry reforming of methane

The Ni-Al, Ni-Ce and Ni-Ce-Al catalysts tested in the dry methane reforming (DRM) were studied. Catalysts were synthesized by solution combustion synthesis and characterized by BET, XRD and TEM. Catalytic activity was studied at 600–900 °C with a 33%CH4:33%CO2:34%Ar (vol.%) fed with total flow rate of 100 ml/ min (3000 h−1). The CH4 and CO2 conversion increased with the increasing of Ce up to 15 wt.%, however, with further increase in Ce content conversion of gases decreased. Carbon was formed as filaments when catalysts worked at high temperature. CeAlO3 species could prevent the formation of filamentous carbon during DRM. Solution combustion synthesis is attractive method of preparation of catalysts, due to high dispersion of Ni particles, thus, surface area is small, diminishing the coke deposition and enhancing the stability.

Understanding the role of Co segregation on the carbon deposition over Ni–Co bimetal catalyst in dry reforming of methane

Ni–Co bimetal catalysts showed the resistance to carbon deposition in DRM, and Co segregation on Ni surface plays very important role, but the underlying mechanism remains unclear. Hence, in current research, Ni and Ni–Co bimetal catalysts were prepared, and fixed-bed tests, characterizations and DFT calculations were carried out to uncover the effect of doped Co on the carbon formation and elimination process. DFT calculations suggested that Co segregation could promote the transfer of charge from the surface to CO2 and further affect CO2 activation. To some extent, the higher the Co concentrations on Ni surface, the more charge in adsorbed CO2, and the stronger ability for CO2 activation, which could produce more O and OH species to participate in CH consumption and C elimination. Furthermore, Co segregation could promote CH oxidation and C hydrogenation, which could inhibit the formation of carbon deposition and promote the C elimination. In addition, DFT calculations results were verified by experiments and characterizations, and found that Co segregation could reduce the amount of carbon deposition and lower the graphitization degree of carbon deposition, thus the resistance to carbon deposition in Ni–Co bimetal catalysts is improved.

Impact of chelating agents on precursor formation and efficiency of Ni/MgO-Al2O3 catalysts in dry reforming of methane

Using cheap and non-toxic chelating agents during catalyst preparation is considered as an effective tool to control the particle size and to strengthen the metal-support interactions (MSI), while keeping the simplicity of the selected preparation method. The previous properties are useful to improve the catalyst activity, stability, and selectivity in dry reforming of methane (DRM). Therefore, we prepared a series of low Ni loading (2.5 wt%) catalysts supported over MgO-Al2O3 (Mg/Al = 1.3) mixed oxide using the classic wet impregnation method modified with chelating agents (citric acid (CA), tartaric acid (TA) and diethylenetriaminepentaacetic acid (DTPA)) and subsequently evaluated these in DRM. Intensive catalyst characterization (ICP, BET, XRD, XPS, STEM, H2-TPR and O2-TPO) suggested the presence of different structure-activity relationships. Particularly, using chelating agents during catalyst preparation controlled the final particle size range, which in turn played a pivotal role in shaping the strength of the metal support interactions (MSI). These impacts were crucial to improve the activity, stability and to control the formation of coke deposits. Moreover, special focus was put on the catalytic testing of the outperforming sample (Ni(TA)/Mg1.3AlOx) prepared using tartaric acid as chelating agent under severe regimes prone to catalyst deactivation to demonstrate the benefits of the proposed preparation technique.

Operando induced strong metal-support interaction of Rh/CeO2 catalyst in dry reforming of methane

Strong metal-support interaction (SMSI) is an important concept in heterogeneous catalysis that has a profound effect on the structure and activity of the supported metal catalyst. However, the catalyst with an uncontrolled SMSI state significantly prevents the accessibility of metal surface to reactants by encapsulation process which inevitably limits their practical application. Herein, we demonstrate that under the reaction condition of dry reforming of methane (DRM), the occurrence of SMSI (CO2-SMSI) can be operando induced between Rh and CeO2 which significantly improves the catalytic activity in DRM reaction. Detailed study has revealed that the formation of suitable Rhδ+/Rh0 species in CO2-SMSI is critical in improving CH4 activation, while the presence of permeable encapsulation layer is helpful to provide more active sites. This discovery provides a new approach to overcome the limitation of classical SMSI catalyst in DRM reaction.

Microwave-assisted hydrothermal synthesis of Ru/CeO2 catalyst for efficient and stable low-temperature dry reforming of methane

As the widely applied catalysts in dry reforming of methane (DRM), Ni-based catalysts typically suffer from severe coke formation on the catalyst leading to the deactivation of the catalyst. Meanwhile, with great trends of reducing the operating temperature for DRM reactions, the Ni-based catalysts can’t exhibit comparable reactivity in low-temperature DRM reactions. To reduce coke formation and achieve better reactivity at low temperatures, a novel Ru/CeO2 catalyst was synthesized through a microwave-assisted hydrothermal method and exploited in a low-temperature DRM reaction in a fixed bed reactor. It exhibited comparable activity of above 58 % CH4 and 71 % CO2 conversion with above 0.85 H2/CO ratio for over 120 h at 600 °C. Moreover, it remained stable without obvious coke deposition on the catalyst after the long-term experiment. The characterizations by XRD, XPS, HAADF-STEM, FTIR and some temperature-programmed experiments indicated that microwave irradiation and the introduction of glucose played important roles in achieving great thermal stability and better DRM reactivity of Ru/CeO2. Ru, as the active metal compared with Ni, exhibited moderate CH4 dissociation ability leading to excellent coke resistance. The novel Ru/CeO2 catalyst with high DRM reactivity, simple synthesis method and great coke resistance in this work offers a new opportunity for the commercialization of low-temperature DRM reaction.

Effect of Lanthanum Oxide on the Activity Ni-Co/Diatomite Catalysts in Dry Reforming of Methane

The effect of modifying additive (La2О3) on the activity of Ni-Co oxides was studied for the dry reforming of methane (DRM). The catalysts were prepared by impregnation of the granulated diatomite (D) and characterized by SEM, EDX, H2-TPR, XRD, and AES. It is shown that the addition of 1.5 wt.% La2O3 into the Ni-Co/D composition leads to an increase in the activity of the catalyst, providing a methane conversion that is close under thermodynamic equilibrium conditions in the temperature range of 700‒850 °С. The highest activity is achieved at T = 850 °C, the conversion of methane is 96%, and carbon dioxide is 92%. The addition of lanthanum oxide to the Ni-Co/D composition led to an increase in catalyst stability; after testing in the DRM reaction for 360 min, the deactivation coefficient for methane was 3.4%, and for carbon dioxide 2.5%. While significant deactivation is observed for Ni-Co/D, the deactivation coefficient for methane is 19%, and for carbon dioxide 36%. Many characterization results (SEM, H2-TPR, and XRD) confirm that Ni-Co-La/D has abundant surface oxygen and the presence of spinel structures that contribute to the reactivity of CH4 and CO2, which positively affect its activity.

Stability and Activity of Rhodium Promoted Nickel-Based Catalysts in Dry Reforming of Methane.

The rhodium oxide (Rh2O3) doping effect on the activity and stability of nickel catalysts supported over yttria-stabilized zirconia was examined in dry reforming of methane (DRM) by using a tubular reactor, operated at 800 °C. The catalysts were characterized by using several techniques including nitrogen physisorption, X-ray diffraction, transmission electron microscopy, H2-temperature programmed reduction, CO2-temperature programmed Desorption, and temperature gravimetric analysis (TGA). The morphology of Ni-YZr was not affected by the addition of Rh2O3. However, it facilitated the activation of the catalysts and reduced the catalyst's surface basicity. The addition of 4.0 wt.% Rh2O3 gave the optimum conversions of CH4 and CO2 of ~89% and ~92%, respectively. Furthermore, the incorporation of Rh2O3, in the range of 0.0-4.0 wt.% loading, enhanced DRM and decreased the impact of reverse water gas shift, as inferred by the thermodynamics analysis. TGA revealed that the addition of Rh2O3 diminished the carbon formation on the spent catalysts, and hence, boosted the stability, owing to the potential of rhodium for carbon oxidation through gasification reactions. The 4.0 wt.% Rh2O3 loading gave a 12.5% weight loss of carbon. The TEM images displayed filamentous carbon, confirming the TGA results.

Efficient Calcium Looping-Integrated Methane Dry Reforming by Dual Functional Aerosol Ca–Ni–Ce Nanoparticle Clusters

Calcium looping (CaL) integrated with methane dry reforming (DRM) shows promise for carbon capture and utilization. To enhance the CaL–DRM tandem processes, a raspberry-structured aerosol dual-functional material composed of CaO (CO2 adsorbent), Ni (DRM catalyst), and CeO2 (promoter) was fabricated via gas-phase evaporation-induced self-assembly. The utilization of Ca–Ni–Ce is highly beneficial by the creation of metal–support–promoter interaction for promoting an effective carbon capture followed by interfacial catalysis, providing an alternative pathway with enhanced redox ability and reduction of activation energy. The Ca–Ni–Ce composite materials with clustered particle characteristics showed great improvement in the performance of cyclic CaL–DRM in comparison to the reported values: low required carbonation/decarbonation temperatures (400/600 °C), high CO2 uptake efficiency (12.1 mmolCO2/gCaO), ultrahigh CO2 conversion (97.2%) under relatively low-temperature operation (600 °C), and sufficiently high operational stability. Overall, the proposed Ca–Ni–Ce hybrid material fabricated via the aerosol synthetic method demonstrates significant advances in the low-temperature CaL–DRM processes, showing promise as a sustainable chemical engineering route for industrial applications.

Morphology effect of ceria support with hierarchical structure on the catalytic performance for nickel-based catalysts in dry reforming of methane

CeO2 is widely used as Ni-based catalyst support in methane dry reforming (DRM), and the hierarchical structure of the ceria behaves a favorable effect on the performance of the catalyst. Ceria with different morphologies, including dumbbell (CeO2-D), bouquet (CeO2-B) and shuttle (CeO2-S) shapes, are hydrothermally prepared, and the effect of ceria shape on the catalytic performance of Ni/CeO2 in DRM is investigated by a fixed-bed tubular reactor. The results indicate that Ni/CeO2-D demonstrates the best reaction conversions & TOF value, whose conversions of CH4 & CO2 can reach 92% & 87%, respectively. Furthermore, a series of characterization results (XPS, H2-TPR and Raman) confirm that the Ni/CeO2-D own the abundant oxygen vacancies and strong metal-support interaction, which promote the reactivity of CH4 and CO2, resulting in its most prominent catalytic performance. Additionally, Ni/CeO2-D possesses other distinct advantages due to its hierarchical dumbbell-like structure confirmed by high Ni dispersion (H2-TPD), abundant surface oxygen (H2-TPR) and sufficient basic sites (CO2-TPD).

Calcium looping of CO2 capture coupled to syngas production using Ni-CaO-based dual functional material

Calcium looping (CaL), which involves carbonation of CaO by CO2 and regeneration of CaO through the conversion of the captured CO2 into useful products, shows promise for carbon capture and utilization. By integrating CaL with methane dry reforming (DRM), the captured CO2 can be converted into syngas, a valuable chemical feedstock and fuel. Herein, a dual functional material (DFM) composed of CaO (CO2 adsorbent), Ni (DRM catalyst) and CeO2 (promoter for DRM) had been developed to drive the CaL-DRM tandem processes. The CaO-Ni-CeO2 DFM possessed high performance of cyclic CaL-DRM: high CO2 uptake efficiency (10.3 mmolCO2/gCaO), high H2 and CO yields (754.4 mmolH2/gNi and 454.6 mmolCO/gNi), moderate required temperature for carbonation (450 °C) and subsequent methane dry reforming (680 °C), and sufficiently high stability. The carbonation of CaO was strongly influenced by the basicity of the material, and the conversion of CH4 with the captured CO2 was affected by the Ni dispersion in the material. Overall, our work demonstrates a prototype study of using a temperature-programmed reaction platform for a quantitative, real-time analysis on CaL-DRM kinetics. The mechanistic understanding of CaL-DRM by the CaO-Ni-CeO2 DFM were elucidated, showing promise for the catalyst optimizations.

Ni-Al Self-Propagating High-Temperature Synthesis Catalysts in Dry Reforming of Methane to Hydrogen-Enriched Fuel Mixtures

The worldwide increase in demand for environmentally friendly energy has led to the intensification of work on the synthesis of H2-containing fuel. The dry reforming of methane has become one of the most important avenues of research since the consumption of two greenhouse gases reduces the rate of global warming. A study of NiAl composite materials as catalysts for methane reforming has been carried out. Self-propagating high-temperature synthesis (SHS) has been used to produce NiAl catalysts. Comparative studies were carried out regarding the dry reforming and partial oxidation of methane, as well as catalysts prepared using the impregnation (IM) and SHS methods. A catalyst with 29% Ni and 51% Al after SHS contains the phases of NiAl and NiAl2O4, which are active phases in the dry reforming of methane. The optimal crystal lattice parameter (for the maximum possible conversion of CO2 and CH4) is 3.48–3.485 Å for Al2O3, which plays the role of a catalyst carrier, and 1.42 Å, for NiAl2O4, which plays the role of a catalyst. The aim of the work is to develop a new and efficient catalyst for the dry reforming of methane into a synthesis gas, which will further promote the organization of a new era of environmentally friendly energy-saving production methods.

Enhanced carbon tolerance of hydrotalcite-derived Ni-Ir/Mg(Al)O catalysts in dry reforming of methane under elevated pressures

Pressurized dry reforming of methane (DRM) is highly desirable in terms of economy and efficiency, but imposes increased risk of catalyst carbon deposition. Here, hydrotalcite-derived Ni-Ir/MgAl(O) catalysts with various Ir/Ni molar fractions (0, 5, 10, 15, 20, 25 and 30%) have been successfully prepared by one-step co-precipitation method. The promoting effect of Ir on the catalytic performance of catalysts in pressurized DRM was focused. After adding Ir, the catalyst stabilities (reflected by the deactivation degree) were significantly improved and were comparable when the amount of Ir was high (≥15%). Long-term stability for 180 h at 1.0 MPa and 850 °C under 60,000 mL·gcat−1·h−1 was achieved on catalyst 100Ni20Ir, and the final CH4 conversion was still above 68.5%. Detailed characterizations disclosed that the addition of Ir favored the formation of smaller Ni particles and enhanced the carbon tolerance properties of catalysts. The effective inhibition of the formation of encapsulated graphitic carbon and better carbon nanotubes removal characteristics were responsible for the enhanced carbon tolerance behaviors. The carbon deposition, especially the encapsulated graphitic carbon, was proved to be the major cause of catalyst deactivation. Our findings bring us one step closer to developing durable and coke-resistant catalysts suitable for high pressure DRM.

Enhanced coke resistance of boron-promoted Co/P/Al2O3 catalysts in dry reforming of methane

Enhanced coke resistance of boron-promoted Co/P/Al2O3 catalysts in dry reforming of methane

Developing silicalite-1 encapsulated Ni nanoparticles as sintering-/coking-resistant catalysts for dry reforming of methane

The stability of catalysts in dry reforming of methane (DRM) is a known issue. In this paper an encapsulation strategy has been employed to improve the stability compared with conventional impregnation methods. Herein, nickel nanoparticles encapsulated in silicalite-1 were prepared using a range of methods including post treatment, direct hydrothermal and seed-directed methods to investigate the effect of synthesis protocol on the properties of catalysts, such as degree of encapsulation and Ni dispersion, and anti-coking/-sintering performance in DRM. The Ni@SiO2-S1 catalysts obtained by the seed-directed synthesis presented the full encapsulation of Ni NPs by the zeolite framework with small particle sizes (∼2.9 nm) and strong metal-support interaction, which could sterically hinder the migration/aggregation of Ni NPs and carbon deposition. Therefore, Ni@SiO2-S1 showed stable CO2/CH4 conversions of 80% and 73%, respectively, with negligible metal sintering and coking deposition (∼0.5 wt%) over 28 h, which outperformed the other catalysts prepared. In contrast, the catalysts developed by the post-treatment and ethylenediamine-protected hydrothermal methods showed the co-existence of Ni phase on the internal and external surfaces, i.e. incomplete encapsulation, with large Ni particles, contributing to Ni sintering and coking. The correlation of the synthesis-structure-performance in this study sheds light on the design of coking-/sintering-resistant encapsulated catalysts for DRM.

The tailored role of “defect” sites on γ-alumina: A key to yield an efficient methane dry reforming catalyst with superior nickel utilization

Strong metal support interaction between Ni and γ-Al2O3, resulted from the excessive hydroxyl groups on the Al2O3 support, has restricted Ni utilization in the traditional Ni/Al2O3 catalyst, which hampered its commercial application. Meanwhile, the concept of surface defects in activating single-carbon chemicals of CH4 and CO2 has attracted much attention in heterogeneous catalysis. Thus, designing better Ni/Al2O3 system in generating surface defects without losing active Ni into Al2O3 support remains challenging. Herein, the development of tailored defect sites on Al2O3 through hydroxyl-exposed strategy shows dual role of stabilizing the active Ni sites and holding responsible for catalyzing CH4 dry reforming (DRM) reaction via a more efficient route, which emphasizes the superior behavior of the traditional Ni/Al2O3 catalyst. It is considered that it can be appropriately used for reactions using not only excellent DRM catalysts but also other Ni catalysts.

Evaluating the effect of torrefaction on the pyrolysis of biomass and the biochar catalytic performance on dry reforming of methane

The torrefaction and pyrolysis experiments on hawthorn seed (HS) were carried out, and biochar obtained was utilized as a catalyst in dry reforming of methane (DRM) under microwave field. The product was characterized and analyzed to explore the influence of torrefaction on HS, subsequent pyrolysis process and catalytic performance of biochar. Results reveal that increasing torrefaction temperature enhanced deoxygenation and dehydration of solid product, thus increase gas and liquid product. And the yield of tar increases significantly with pyrolysis temperature. The carbon content of biochar with potential as carbon-based catalyst can exceed 80%. As torrefaction was implement before pyrolysis, not only was smokey flavor of tar improved, but also carbonization of biochar was further enhanced. As torrefaction temperature and pyrolysis temperature was respectively set at 300 °C and 600 °C, the biochar acquired could make the conversion rate of CH4 and CO2 reach 75% and 85% in the DRM reaction, respectively.

Effect of B site substitution in Gd2B2-xNiyO7-δ (B= Ti, Zr) ternary metal oxide catalysts in dry reforming of methane

Structured catalysts are emerging as active and durable catalysts in dry reforming of methane due to their inherent characteristics like lattice insertion of active metals and consequent stability imparted. Here we report Ti and Zr substituted Gd2B2-xNiyO7-δ (B = Ti, Zr) catalysts synthesized by citrate gel method, which are characterized and tested for dry reforming of methane. Structure and Ni substitution has been confirmed by Rietveld refinement of powder XRD patterns and Raman analysis. TPR and CO2-TPD were performed to analyze the reducibility and effect of basic sites of catalysts in DRM activity. Ni doped Ti analogue shows stable and superior activity towards dry reforming of methane for 100 h. The in situ IR studies and XPS analysis confirmed the presence of surface hydroxyl species in this catalyst, which triggers the activation of CO2 and provides higher and durable activity in dry reforming reaction. Absence of any C formation in this catalyst after durability test indicates the mechanism of C gasification by the surface hydroxyl species enhancing stable activity for long durations.

Highly dispersed Ni/Al2O3 catalysts for dry reforming of methane prepared by alkaline-induced adsorption process

Ni–Al catalysts were widely developed for methane dry reforming (DRM) and other valuable reactions, but the low utilization of Ni species on the Al2O3 support has limited its further application. In this paper, Ni species were induced to anchor on the mesoporous Al2O3 under alkaline conditions. Notably, alkaline treatment caused the corrosion and restructure of the mesoporous Al2O3, and this reorganization process of Al2O3 and the presence of defects from ligand-unsaturated Al3+ (Alpenta3+) promoted Ni species to remain uniform dispersion on the surface. In combination with TEM, HRTEM, UV–vis and H2 chemisorption, it is observed that Al2O3 formed a special layered stacking structure under alkaline conditions, which contributed to the homogeneous distribution of Ni species on the catalyst surface. Surprisingly, the catalyst showed good low-temperature DRM reactivity, which was superior to the conventional Ni–Al catalysts prepared by impregnation method and the most Ni–Al catalysts reported in the literatures. The CH4 reforming rate of RCH4-mNi = 80.16 (L/h/g) at 550 °C was obtained on the conventional impregnation catalyst, while the Ni–Al catalysts by adsorption showed a significant increase in the CH4 reforming rate of RCH4-mNiRCH4−mNi = 160.87 (L/h/g). Consequently, the present work provides some ideas for the synthesis of efficient Ni–Al catalysts for DRM as well as other meaningful reactions.

Influence of Supports on the Catalytic Activity and Coke Resistance of Ni Catalyst in Dry Reforming of Methane

The dependence of the catalytic activity and coke resistance of Ni-based catalysts on the support type was investigated in the dry reforming of methane (DRM). Catalysts were prepared using incipient wetness impregnation and analyzed using ICP-OES, BET-BJH, XRD, H2-chemisorption, H2-TPR, and CO2-TPD. DRM was performed at 600–750 °C at 144,000 mL/gcat∙h of GHSV (CH4/CO2/N2 = 1/1/1). Ni/Al2O3 and Ni/MgO catalysts formed NiAl2O4 and NiO-MgO solid solutions, respectively, owing to strong binding between the metal and support. In contrast, MgO-Al2O3 and MgAl2O4 supports suppressed NiAl2O4 and NiO-MgO solid solution formation, due to Mg addition, with high metal dispersions of 4.6 and 6.6%, respectively. In the DRM reaction, the Ni/MgO-Al2O3 and Ni/MgAl2O4 catalysts showed high CH4 conversions of 78.1 and 76.8%, respectively, compared with Ni/Al2O3 and Ni/MgO at 750 °C. A stability test was performed at 600 °C for 20 h. A coke study of the spent catalysts was performed using SEM and TGA. Alkaline-earth metal-containing catalysts Ni/MgO-Al2O3 and Ni/MgAl2O4 with strong CO2 adsorption properties showed 20 wt% reduction in carbon deposition compared to commercial catalysts. Therefore, the support and basic properties of the catalyst significantly influenced the catalyst performance and coke resistance in the DRM.

Developing Silicalite-1 Encapsulated Ni Nanoparticles as Sintering-/Coking-Resistant Catalysts for Dry Reforming of Methane

Developing Silicalite-1 Encapsulated Ni Nanoparticles as Sintering-/Coking-Resistant Catalysts for Dry Reforming of Methane