Dry Reforming Of Methane Reaction Research Articles

Exceptional stability of spinel Ni–MgAl2O4 catalyst with ordered mesoporous structure for dry reforming of methane

The dry reforming of methane reaction holds significant importance for the comprehensive utilization of CO2 and CH4, contributing to carbon neutrality. However, due to the high reaction temperatures, catalyst deactivation due to carbon deposition and sintering remains a challenge. In this study, a one-pot method was employed to improve the solvent evaporation self-assembly process for the preparation of Ni–MgAl2O4 catalysts. The impact of calcination temperature (600 °C, 800 °C, and 1000 °C) on the ordered mesoporous structure of the catalyst was investigated. Catalysts without an ordered mesoporous structure, such as Ni–MgAl2O4-1000, suffered deactivation due to carbon deposition caused by the large size of Ni grains, while Ni–MgAl2O4-600 deactivated due to sintering caused by the lack of confinement effect of the support on Ni. Conversely, Ni–MgAl2O4 catalysts with an ordered mesoporous structure exhibited confinement effects on Ni metal, resulting in excellent resistance to carbon deposition and sintering. Further investigation into the effect of different loading methods of Ni on methane dry reforming was conducted. A comparison was made between Ni–MgAl2O4 (800 °C) prepared by the one-pot method and Ni/MgAl2O4 (800 °C) prepared by the impregnation method. It was observed that Ni–MgAl2O4 catalysts, with Ni incorporated into the support, exhibited strong interaction between Ni and the support. During a 500-h long-term reaction, both CO2 and CH4 conversion rates remained at 90% for Ni–MgAl2O4 catalysts, with less carbon deposition and slower grain growth rate, demonstrating excellent reaction activity and stability. In contrast, the performance of Ni/MgAl2O4 catalysts gradually declined after 260 h. Ni–MgAl2O4 catalysts with ordered mesopores and strong interaction between Ni and the support displayed superior resistance to carbon deposition and sintering.

Surface basic site effect on CoLa/m-Al2O3 catalysts for dry reforming of methane

Dry reforming of methane (DRM) is a novel technology that enables the direct utilization of greenhouse gases (CH4 and CO2) for the production of value-added products. In the DRM reaction, the acid-base characteristics of the catalyst support play a pivotal role in determining the performance of the catalyst. In this study, a series of Co-based catalysts with different alkali earth metal-modified Al2O3 composite supports, specifically m-Al2O3 (m=Ca, Mg, and Ba), were prepared using the impregnation method. Various characterization techniques were employed to investigate the impact of alkaline site modulation on the support surface with respect to anti-sintering and anti-coking properties. The results demonstrate that the m-Al2O3 composite support catalysts, prepared with Mg and Ca modulation, exhibit an abundance of basic sites and oxygen vacancies. This promotes the adsorption and activation of CO2, enhances the rate of carbon elimination, and effectively addresses carbon deposition and metal sintering issues. Notably, the CoLa/Mg-Al2O3 catalyst shows the highest performance under reaction conditions of 750 °C, with CH4 and CO2 conversions reaching 92.3 % and 97.5 %, respectively. On the other hand, the CoLa/Ba-Al2O3 catalysts display poor performance in dry reforming. Kinetic studies indicate that CoLa/Mg-Al2O3 catalyst significantly reduce the apparent activation energy required for CH4 and CO2 cracking. Furthermore, it is demonstrated that the introduction of alkali earth metals can promote the dissociation of CH4 and CO2.

Deciphering the stability mechanism of Pt-Ni/Al2O3 catalysts in syngas production via DRM

Deactivation induced by coke deposition remains the foremost challenge in using Ni-based catalysts for the production of syngas via dry reforming of methane (DRM) reaction. Herein, highly dispersed Pt-Ni/Al2O3 bimetallic catalysts prepared by atomic layer deposition (ALD) displayed remarkable stability at 650 ℃ in the DRM reaction. The Pt-Ni catalysts underwent an activation process within the initial 10 h and maintained its activity without deactivation throughout the subsequent aging testing up to 48 h. In contrast, the Ni/Al2O3 rapidly deactivated over time. Despite its high CH4 conversion rates, the Pt-Ni bimetallic catalyst produced a substantial quantity of carbon nanotubes (CNTs) analogous to the Ni/Al2O3 catalyst. The discrepancy in stability performance between two catalysts derived from disparities in the carbon sites and structural defects evolving over reaction time. Regarding the catalysts with Pt decoration on the Ni surface, CNTs exhibited increasing structural defects and gradually deposited on the Al2O3 support without fully encapsulating the metal active sites, as evidenced by CH4-TPD experiments. In the case of Ni nanoparticles on Al2O3, crystalline CNTs with fewer defects accumulated, leading to rapid deactivation. These findings enhance our understanding of coke resistance in DRM catalysts and help the development of more robust bimetallic catalyst systems.

Tune and turn the pyrolysis of metal organic frameworks towards stable supported nickel catalysts for the dry reforming of methane

Dry reforming of methane (DRM) is an inimitable approach for eliminating both greenhouse gases, methane and CO2, while producing synthesis gas which further can be converted to added-value fuels. However, the industrialization of DRM has been limited due to sintering and coking to the catalysts under the harsh reaction conditions. Here, we propose a new methodology for producing tunable supported nickel-based catalysts for DRM using metal organic frameworks (MOFs) as precursors of the catalyst components. In particular, Ni- and La-MOFs were coalesced using sonication and then calcined at different temperatures to produce catalysts with tailored Ni metal size (5–20 nm) and tuned strong metal-support interactions (SMSI). Here, the synthesis of nickel and nickel oxide nanoparticles embedded on lanthanum-based supports by controlled calcination of the MOF structures is demonstrated; the Ni supported catalysts were then used for DRM reaction. Among the developed catalysts, the catalyst produced following calcination at 500 °C (Ni-La-500) has shown stable and high CH4 conversion rates under DRM conditions at 800 °C with negligible carbon formation at elevated gas hourly space velocities. Further, the catalytic performance of Ni-La-500 catalyst (sonicated) was compared to the physically mixed MOFs derived catalyst (Ni-La-500-PM), conventional wetness impregnated catalyst (Ni-La-500 WI), Ni-MOF derived unsupported catalyst (Ni-500), and lower Ni concentration catalyst (sonicated, 10Ni-La-500). The observed CH4 conversion rates at 50,000 mL·gcat–1·h−1 GHSV are 81.8, 67.9, 85.4, 34.7, and 57.9 % for Ni-La-500, Ni-La-500 PM, Ni-La-500 WI, Ni-500, and 10Ni-La-500 catalysts, respectively after 24 h of DRM reaction. With isotopic studies, it was found that the 18O exchange rate was higher in case of Ni-La-500-PM catalyst (8.1 mmol·g−1) as compared to Ni-La-500 catalyst (5.5 mmol·g−1). Prior interaction between MOFs, calcination temperatures, reaction conditions, and the carbon pathways during catalytic activity dictates the conversion rates and selectivity of the products. Overall, with the herein proposed approach of MOF-derived supported catalysts exceptional conversion rates and stability during the DRM reaction with nominal coking and sintering were demonstrated, solving the two major challenges faced by conventional and unsupported catalysts.

Rational design of silica nanoreactor encapsulated Ni for reinforcing coke-resistance in dry reforming of methane

Dry reforming of methane (DRM) provides a desired approach to produce valuable syngas in tackling greenhouse gases. Yet it faces a formidable challenge in the design and synthesis of high coke-resistant Ni-based catalysts. Herein, we report a nanoreactor strategy to construct a supported Ni catalyst (Ni@SiO2@SiO2) for reinforcing coke-resistance during DRM, by effectively encapsulating small Ni nanoparticles into dendritic fibrous silica (SiO2) nanospheres and coating SiO2 shell layers. Taking advantage of chemical characteristics of citric acid (CA), CA-chelated Ni impregnation enables the uniform immobilization of Ni species into the radial SiO2 framework, then following carbonization produces protective carbon layers on the Ni nanoparticle surface during SiO2 coating, which can be removed via oxidizing calcination. The resultant pomegranate-like nanoreactor catalyst possesses outstanding coke-resistance, without any detectable coke deposition after 200 h of DRM reaction at 700 ℃, benefiting from effectively restricting metal sintering and fully preventing formation of inert carbon species.

Performance of NiO doped on alkaline sludge from waste photovoltaic industries for catalytic dry reforming of methane.

Alkali sludge (AS) is waste abundantly generated from solar photovoltaic (PV) solar cell industries. Since this potential basic material is still underutilized, a combination with NiO catalyst might greatly influence coke resentence, especially in high-temperature thermochemical reactions (Arora and Prasad, RSC Adv. 6:108,668-108688, 2016). This paper investigated alkaline sludge containing 3CaO-2SiO2 doped with well-known NiO to enhance the dry reforming of methane (DRM) reaction. The wet-impregnation method was used to prepare the xNiO/AS (x = 5-15%) catalysts. Subsequently, all catalysts were tested by using X-ray diffraction (XRD), nitrogen adsorption/desorption (BET), temperature-programmed reduction of hydrogen (H2-TPR), temperature-programmed desorption of carbon dioxide (TPD-CO2), field emission scanning electron microscopy (FESEM-EDX), and X-ray photoelectron spectroscopy (XPS). The spent catalysts were analyzed by thermogravimetric analysis (TGA/DTG), transmission electron microscopy (TEM), and temperature-programmed oxidation (TPO). The catalytic performance of xNiO/AS catalysts was investigated in a fixed bed reactor connected with gas chromatography thermal conductivity detector (GC-TCD) at a CH4:CO2 flow rate of 30 mL-1 during a 10-h reaction by following (Shamsuddin et al., Int. J. Energy Res. 45:15,463-15,480, 2021d). For optimization parameters, the effects of NiO concentration (5, 10, and 15%), reaction temperature (700, 750, 800, 850, and 900 °C), catalyst loading (0.1, 0.2, 0.3, 0.4, and 0.5 g), and gas hourly space velocity (GHSV) range from 3000, 6000, 9000, 12,000, and 15,000 h-1 were evaluated. The results showed that physical characteristics such as BET surface area and porosity do not significantly impact NiO percentages of dispersion, whereas chemical characteristics like reducibility are crucial for the catalysts' efficient catalytic activity. Due to the active sites on the catalyst surface being more accessible, increased NiO dispersion resulted in higher reactant conversion. The catalytic performance on various parameters that showed 15%NiO/AS exhibited high reactant conversion up to 98% and 40-60% product selectivity in 700 °C, 0.2 g catalyst loading, and 12,000 h-1 GHSV. According to spent catalyst analyses, the catalyst was stable even after the DRM reaction. Meanwhile, increased reducibility resulted in more and better active site formation on the catalyst. Synergetic effect of efficient NiO as active metal and medium basic sites from AS enhanced DRM catalytic activity and stability with low coke formation.

Ni-Co alloy supported on CeO2 by SiO2 encapsulation for dry reforming of methane

Dry reforming of methane (DRM) is a highly endothermic reaction that needs harsh condition of high temperature for syngas production, which is challenged by developing catalysts with properties of anti-sintering and low carbon deposition. This work synthesized confined catalysts of (Co-Ni/CeO2)@SiO2 for DRM reaction. The catalysts possessed multifunction including size and alloy effects, metal-support interaction and confinement effect, which contributed to high rates of CH4 and CO2, marginal sintering of NiCo alloy and trace carbon deposition. The (3Ni-3Co/CeO2)@SiO2 catalyst reached rates as high as 4.74 mmol/(gNi·s) and 5.57 mmol/(gNi·s) for CH4 and CO2, respectively, at 1023 K. The rates were keeping stable for at least 36 h on stream. The characterizations of used samples revealed the limited size change of NiCo alloy and the low carbon deposition. The work provides valuable guidance for developing stable catalysts for DRM and other high temperature reactions.

Internal dry reforming of methane in solid oxide fuel cells

In the context of global efforts to reduce greenhouse gas emissions and combat extreme global warming, the direct dry reforming of methane reaction in solid oxide fuel cells presents a promising avenue for clean energy production. This study delves into the influence of temperature, gas composition, and current density on the kinetics of dry methane reforming in solid oxide fuel cells. Power Law and Langmuir-Hinshelwood kinetic models were proposed to highlight the impact of operating conditions on dry methane reforming reactions. Results revealed that the feed gas composition strongly affects methane conversion, with higher methane contents resulting in lower conversions. Increasing the CH4/CO2 ratio increases reaction rates, and the effect decreases at a ratio of 1.25. The changes in methane concentration on dry methane reforming reaction rate are more significant than those for carbon dioxide. However, increasing carbon dioxide concentration enhances methane conversion. The exothermic nature of CO2 adsorption suggests that the adsorption process is thermodynamically favourable in dry reforming, and the elevated temperatures generally improve reaction rates and methane conversion by removing carbon deposits and providing the energy needed to break down the chemical bonds in methane which facilitating its transformation. A higher current density significantly enhances the CO2 adsorption equilibrium constant and further increases methane conversion, highlighting the positive role of electrochemical reactions on dry methane reforming. This study aims to fill the knowledge gap regarding the influence of electrochemical reactions on dry methane reforming behaviours in solid oxide fuel cells, offering critical insights for advancing anode design, thus contributing to the development of solid oxide fuel cell technologies to address global warming and reduce greenhouse gas emissions.

Dry reforming of methane over Ni–Mg–Al and Ni–Ca–Al type hydrotalcite-like catalysts: effects of synthesis route and Ru incorporation

Abstract Ni-incorporated Mg–Al type hydrotalcite-like catalytic materials were synthesized following impregnation and co-precipitation routes, and their catalytic performances were compared in the dry-reforming reaction of methane. The effects of Ru impregnation on the catalytic performance of Ni-incorporated Mg–Al were also investigated. Results showed that the catalytic performance of the Ni-incorporated Mg–Al type catalyst (NiMgAlO), which was prepared by the co-precipitation route, was highly stable during dry-reforming reaction tests performed at 600 °C, extending up to 24 h. The fractional conversion of CO2 (0.42) was higher than the fractional conversion of CH4 (0.29) due to the contribution of the reverse water gas shift reaction. However, the contribution of the reverse water gas shift reaction to the product distribution was much less with the catalyst prepared following the impregnation route (Ni@MgAlO). This difference was shown to be mainly due to the state of the nickel in the catalyst structures. Ni-impregnated Ca–Al type hydrotalcite-like catalyst (Ni@CaAlO) was also synthesized and tested in dry reforming of methane. Results obtained with the Ni-impregnated Ca–Al type catalyst showed some changes in its structure and the formation of some CaCO3 during the dry reforming reaction. The comparison of the performances of Ni-impregnated Mg–Al and Ca–Al type catalysts showed a higher amount of coke on the surface of Ni@CaAlO than Ni@MgAlO. It was also concluded that significant coke minimization and highly stable catalytic performance could be achieved by the impregnation of 1 % Ru to the NiMgAlO catalyst. The amount of coke deposited on the catalyst decreased from about 30 % to less than 5 %, by Ru impregnation. The decrease of the surface area of the Ru-impregnated catalyst was also only about 3 % after 240 min of reaction time.

MOFs-derived Ni@ZrO2 catalyst for dry reforming of methane: Tunable metal-support interaction

Metal-support interaction (MSI) plays an important role in heterogeneous catalysis, that could be well regulated by many strategies. Here, Ni@ZrO2 catalysts were controllably synthesized by sacrificial Zr-MOFs template strategy, and were applied to the dry reforming of methane (DRM). Amongst, the Ni/ZrO2-B catalyst shows the best performance toward CH4 and CO2 conversion, H2/CO ratio, and stability, following by Ni/ZrO2-A and Ni/ZrO2C catalysts. The difference in catalytic performance should be ascribed to different synthetic strategy, resulting in different properties of Ni species and ZrO2 matrix, and interface interaction. It revealed that small Ni particles were benefit for CH4 activation, and strong MSI boosted CO2 activation, that could remain the Ni dispersion and thermal stability. This study is beneficial to the catalyst design in DRM reaction.

NiGa nano-alloy for the dry reforming of methane: Influences of Ga alloying with Ni on the catalytic activity and stability

The massive emission of CO2 and CH4 has caused serious environmental and ecological problems, and dry reforming of methane reaction has received widespread attentions due to the fact that it can eliminate the two gas simultaneously. Herein, Ni60Ga40/Al2O3 (molar ratio of Ni:Ga was 60:40) catalyst was synthesized by mechanochemical synthesis method, offering 75 % CH4 conversion, 85 % CO2 conversion, and H2/CO ratio of 0.93 at 750 °C during 120 h test. Ni in Ni60Ga40/Al2O3 combines with Ga to form Ni3Ga intermetallic compound, which inhibits the sintering of Ni and rapid cracking of CH4. Moreover, the extra Ga species, existing in the form of Ga2O3-Al2O3 with abundant oxygen vacancy, boosts CO2 activation and prevents carbon development on catalyst surface. In contrast, for the pure Ni/Al2O3 and Ga/Al2O3 catalysts, the stability and catalytic activity couldn’t be obtained synchronously. This work particularly investigated the CH4 dissociation and CO2 activation for the NiGa/Al2O3 catalysts, establishing the foundation for rational design of low-cost performance catalysts for the dry reforming of methane reactions.

Surface control of Ni-Al2O3 dry reforming of methane catalyst by composition segregation

Catalyst surface control is of great importance considering that a catalytic reaction initially starts with surface atoms’ interaction with reactant molecules. In the present study, we synthesized the Ni-Al2O3 dry reforming of methane (DRM) catalyst via the spray-pyrolysis-assisted evaporation-induced self-assembly (EISA) method in order to systematically investigate catalyst surface change as controlled by composition segregation. The present results showed that segregation in the Ni-Al2O3 catalyst had successfully occurred by the post-annealing process and that the segregated Ni nanoparticles were located on the catalyst surface with simultaneous reduction to metal. The size of the surface Ni nanoparticles was highly dependent on the post-annealing temperature, whereas the electronic properties did not consistently align with the trend of particle-size growth, indicating that the particle-growth mechanism underwent alterations from segregation to sintering as the temperature was increased. In other words, when the reduction temperature for metal segregation is excessively high, particle-growth on the external catalyst surface, as induced by post-annealing, is primarily attributable to particle sintering rather than to metal segregation. This phenomenon directly results in decreased Ni surface density. The catalytic DRM reaction revealed that due to sintering, the catalytic performance did not align with the trend of Ni particle-size growth, and the conversion of CH4/CO2 was closely associated with Ni surface density. This information will offer valuable insight to future research focused on development of Ni-based catalysts for DRM reactions.

Methane dry reforming: influence of the SiO2 and Al2O3 supports on the catalytic properties of Ni catalysts

The effect of the support nature (SiO2, Al2O3, SiO2–Al2O3) on the catalytic performance of Ni-based catalysts prepared by the incipient wetness method was explored in the dry reforming of methane reaction, and the catalysts were characterized by TG-DTA, SEM-EDX, XRD and UV-VIS methods. The results demonstrate that NiO supported on SiO2-modified Al2O3 exhibits superior catalytic performance in methane dry reforming in the temperature range of 650–700 °C.

Immobilization of Ni on MOF-derived CeO2 for promoting low-temperature dry reforming of methane

The development of highly active catalysts for low-temperature dry reforming of methane (DRM) is of great importance for the utilization of CO2 and CH4. Herein, the MOF-derived CeO2-supported Ni (Ni/CeO2-M) catalyst was facilely and mildly prepared, and its catalytic performance for DRM reactions at 400–600 °C was explored and compared with commercial CeO2-supported Ni (Ni/CeO2-C). At 550 °C, the CO2 and CH4 conversions of Ni/CeO2-M are 40.1 % and 30.8 %, respectively, which are significantly higher than those of Ni/CeO2-C (27.3 % and 15.5 %, respectively). The analysis of covariance also shows that the conversions of CO2 and CH4 of Ni/CeO2-M are 8.90 % and 11.65 % higher than those of Ni/CeO2-C after eliminating the effect of temperature, respectively. After 10 h of DRM reaction, Ni/CeO2-M exhibits better resistance to carbon deposition and sintering than Ni/CeO2-C, and carbon deposition is related to the reaction temperature rather than the catalyst. Morphological analysis suggests that, unlike the serious Ni accumulation on Ni/CeO2-C, metallic Ni is uniformly immobilized on Ni/CeO2-M. The highly dispersed metallic Ni0 on Ni/CeO2-M facilitates the dissociation of CH4, and more oxygen vacancies facilitate the dissociation of CO2 into CO and active O. Therefore, Ni/CeO2-M exhibits better catalytic performance and is very promising for low-temperature DRM reactions.

Enhancing catalytic performance, coke resistance, and stability with strontium-promoted Ni/WO3-ZrO2 catalysts for methane dry reforming

The first step of the DRM reaction is just the decomposition of CH4 into CH4−x (x = 1–4). The next step comprises two steps, namely the oxidation of CH4−x into syngas (by CO2) and the self-polymerization of CH4−x species. The earlier one is known as dry reforming of methane (DRM), and the latter one generates carbon deposits over the catalyst surface. In this study, we investigated the impact of 1–3 wt% Sr over Ni-based catalysts on a ZrO2-WO3 support on the catalytic activity and coke deposit. Various characterization techniques such as thermogravimetric analysis, X-ray diffraction, Raman spectroscopy, temperature-programed oxidation, temperature-programed reduction, and temperature-programed desorption were used to assess the physicochemical properties of the fresh and spent catalysts. The addition of 2wt% Sr promoter significantly improves the catalyst’s basicity in strong basic sites region through Sr2+ mediated interaction of CO2 species as well as inhibits the deposition of carbyne type carbon. Enhanced CO2 interaction results into the potential oxidation of carbon deposit and the highest CH4 conversion, reaching 60% up to 470 min TOS at a reaction temperature of 700 ℃.Graphical abstract

Dry reforming of methane by La2NiO4 perovskite oxide: B-site substitution improving reactivity and stability

The development of highly active and stable catalyst materials is the focus of dry reforming of methane (DRM) technology. The effect of substituting transition metals (Mn, Fe, Co, and Cu) on the B-site of La2NiO4 perovskite on the DRM catalytic performance was investigated. Compared to the unsubstituted sample, the Co-substituted sample exhibited reduced reactivity but increased carbon deposition; the Mn-substituted and Fe-substituted samples demonstrated decreased reactivity and carbon deposition; the Cu-substituted sample displayed a slight decrease in CH4 conversion but a substantial increase in carbon resistance. The effect of the substitution ratios of Cu elements was further investigated. The results showed that Cu substitution could maintain the perovskite phase in the samples. In the 5-h DRM reaction, the reactivity of the samples exhibited a decreasing trend as Cu substitution ratios increased. All Cu-containing samples displayed carbon deposition rates lower than 0.4 mg/(g*h), resulting in an over 90-fold improvement in carbon resistance compared to the La2NiO4 sample. Further investigations revealed that the La2Ni0.6Cu0.4O4 sample exhibited stable activity during the 50-h DRM reaction with only a small amount of amorphous carbon in the reacted sample (no obvious carbon nanotubes were observed). Characterization results indicated that the enhanced carbon resistance in Cu-substituted samples was attributed to the Ni-Cu alloy formation, which inhibited CH4 decomposition reactions and reduced solid carbon generation rates. Density functional theory (DFT) calculations showed that the partial substitution of Cu could increase the energy barrier of the CH* dehydrogenation step, which in turn reduced the rate of solid carbon generation.

Review and Outlook of Confined Ni Catalysts for the Dry Reforming of Methane Reaction

Review and Outlook of Confined Ni Catalysts for the Dry Reforming of Methane Reaction

Hydrothermally synthesized tremella-like monometallic Ni/SiO2 for effective and stable dry reforming of methane (DRM) to syngas

Despite its activity, monometallic Ni-catalyst is highly susceptible to coke deposition and sintering in catalyzing dry reforming of methane (DRM). To counter these, a novel tremella-like monometallic Ni/SiO2 catalyst was hydrothermally synthesized herein, realizing excellent activity, outstanding coke inhibition and robust structural stability for a durable DRM reaction. Functionality-speaking, the tapered ends of Ni-petals, sized at 8–15 nm, permit high DRM activity with suppressed coke formation while its thicker base spatially prevents Ni-sintering during high temperature reaction. Meanwhile, the open structure of catalyst resulting from such tremella-like structure also enhances the diffusion of reactants/products gas to/from catalytic surface, thus augmenting its activity for DRM. With merely 5 wt% Ni incorporated, CO2 and CH4 conversions of ∼90% could be attained with only ∼15% activity drop after 75 h of DRM. Full-restoration of activity could facilely be attained using 90 min in-situ oxidative regeneration. Mechanistic study coupling sorptive investigation, ex-situ XRD, and SEM reveals the pronounced adsorption tendency of CH4 over those of CO2, H2 and CO, confirming the adherence of DRM to Eley-Rideal reaction model in current study. Significantly, this study provides a new morphological-controlled strategy to conveniently impart excellent coke-inhibiting and sintering-resisting capability to monometallic Ni-catalyst.

Role of promoter on the catalytic activity of novel hollow bimetallic Ni–Co/Al2O3 catalyst in the dry reforming of methane process: Optimization using response surface methodology

In this research, the effect of promoter addition and its type on the catalytic performance and morphology properties of bimetallic Ni–Co catalysts on the novel hollow Al2O3 support was investigated in the dry reforming of methane (DRM) process. The response surface method (RSM) based on the optimal custom model was employed for maximizing CH4 and CO2 conversions, as well as H2 and CO yield. Four independent variables including Co to Ni mass ratio (0, 0.5, 1), DRM temperature (600, 650, 700 °C), CH4/CO2 molar ratio (1, 1.5, 2), and catalyst type (without promoter, with Mg or Y promoter) were selected for this purpose. Among three suggested optimized catalysts by the design expert, the yttrium-promoted one with 1 Co/Ni mass ratio (1Ni–Co–Y/Al) depicted the highest CH4 conversion of 86.50 %, CO2 conversion of 92.00 %, H2 yield of 85.11 %, and CO yield of 93.54 % at lower temperature of 679 °C and equal CH4/CO2 mole ratio of 1. The structural characterizations confirmed that the high activity of 1Ni–Co–Y/Al could be due to the better dispersed active sites and higher surface area of this catalyst compared with un-promoted and Mg-promoted samples. The time-on-stream performance of optimized catalysts at their optimized conditions was also compared experimentally, results of which showed more stability and activity of the Y-promoted sample during 12 h DRM reaction. The TGA, EDX, XRD, FESEM, and N2 physisorption techniques demonstrated the lower structural change and deposited carbon on the 1Ni–Co–Y/Al surface after reaction, which may be because of higher oxygen storage capacity (OSC) of this catalyst.

Active Ni-Titanate Nanostructures for Dry Reforming of Methane

One of the main causes of climate change is the increased concentration of greenhouse gases from anthropogenic sources. Therefore, the search for processes that provide mitigation of these gases is imperative and very important. Dry reforming of methane (DRM) is a process that converts CO2 and CH4 in pure syngas. Thus, this study aims to evaluate the influence of the calcination temperature (500 and 700 °C) in the titanate nanotubes (TNT) structure. The calcination at 700 °C led to a new morphology in the form of titanate nanorods (TNR). TNT and TNR nanostructures were modified with Ni and used as catalysts in the DRM reaction. The CO2 and CH4 conversions were around 60 and 48%, respectively, when using Ni-TNT500 at 700 ºC, while values around 85 and 70%, respectively, were obtained using TNR in the same reactional condition. Both catalysts presented values of H2/CO ratio near 1.