Catalysts For Dry Reforming Of Methane Research Articles

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.

Dry Reforming of Methane over Pyrochlore-Type La2Ce2O7-Supported Ni Catalyst: Effect of Particle Size of Support.

The properties of supports (such as oxygen vacancies, oxygen species properties, etc.) significantly impact the anti-carbon ability due to their promotional effect on the activation of CO2 in dry reforming of methane (DRM). Herein, pyrochlore-type La2Ce2O7 compounds prepared using co-precipitation (CP), glycine nitrate combustion (GNC) and sol-gel (S-G) methods, which have highly thermal stability and unique oxygen mobility, are applied as supports to prepare Ni-based catalysts for DRM. The effect of the calcining temperature (500, 600 and 700 °C) on La2Ce2O7(CP) has also been investigated. Based on multi-technique characterizations, it is found that the synthesis method and calcination temperature can influence the particle size of the La2Ce2O7 support. Changes in particle size strongly modulate the pore volume, specific surface area and numbers of surface oxygen vacancies of the La2Ce2O7 support. As a result, the distribution of supported Ni components is affected due to the different metal-support interaction, thereby altering the activity of the catalysts for cracking CH4. Moreover, the supports' abilities to adsorb and activate CO2 are also adjusted accordingly, accelerating the removal of the carbon deposited on the catalysts. Finally, La2Ce2O7(CP 600) with an appropriate particle size exhibits the best catalytic activity and stability in DRM.

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.

Synergistic effect of Ni and CeOx in NiCeOx/SSZ-13 catalyst for boosting activity and stability during dry reforming of methane

The stability of industrial catalysts for dry reforming of methane (DRM) reaction is still an urgent challenge. The multifunctional nanocatalyst of SSZ-13 supported Ni/CeOx bimetallic catalysts was successfully fabricated by the impregnation method. The Ni/CeOx species was dispersed highly in the microporous structure of SSZ-13, and the Ni active sites can activate the C-H bond dissociation of CH4, while the oxygen vacancy could promote the adsorption and activation of CO2. The NiCeOx/SSZ-13 catalyst showed excellent catalytic performance for dry reforming of methane, i.e., its conversion of CH4 and CO2 were 91 and 94%, and the ratio of H2/CO was about 0.88 at 750 °C after 50 h. Based on the results of CH4&CO2-TPSR and NH3-TPD, the synergy effect of NiCeOx species can promote the adsorption and activation of CH4 and CO2, and the coke on the surface during DRM is readily converted to CO by reacting with the surface oxygen from CeOx species, which effectively boost the elimination of carbon deposits. It highlights a new strategy for the fabrication of high-efficient zeolite catalysts for DRM to enhance the utilization of CH4 and CO2.

Highly Efficient and Selective Light-Driven Dry Reforming of Methane by a Carbon Exchange Mechanism.

Dry reforming of methane (DRM) is a promising technique for converting greenhouse gases (namely, CH4 and CO2) into syngas. However, traditional thermocatalytic processes require high temperatures and suffer from low selectivity and coke-induced instability. Here, we report high-entropy alloys loaded on SrTiO3 as highly efficient and coke-resistant catalysts for light-driven DRM without a secondary source of heating. This process involves carbon exchange between reactants (i.e., CO2 and CH4) and oxygen exchange between CO2 and the lattice oxygen of supports, during which CO and H2 are gradually produced and released. Such a mechanism deeply suppresses the undesired side reactions such as reverse water-gas shift reaction and methane deep dissociation. Impressively, the optimized CoNiRuRhPd/SrTiO3 catalyst achieves ultrahigh activity (15.6/16.0 mol gmetal-1 h-1 for H2/CO production), long-term stability (∼150 h), and remarkable selectivity (∼0.96). This work opens a new avenue for future energy-efficient industrial applications.

Local coordination environment triggers key Ni-O-Si copolymerization on silicalite-2 for dry reforming of methane

The development of dry reforming of methane (DRM) catalysts with good Ni loading, while retaining high metal dispersion is a critical issue, given the harsh industrial-relevant conditions. Here, we demonstrate the impact of the local coordination environment on the DRM activity of Ni-silicalite-2 (Ni-S2) catalysts. The grafted Ni(II) intermediates with high Ni-O-Si copolymerization (coordination number ratio Si: Ni=2.28) are discovered to redisperse Ni sites, even at 10 wt% Ni loading. Then, the partial S2 recrystallizes into new SiO2-nanowires to anchor Ni nanoparticles, via an ethylenediamine-assisted dissolution-recrystallization (enDR). Compared to the typical Ni-S2 catalyst with Ni phyllosilicate (CN ratio Si: Ni＜1), the Ni-S2-enDR shows high dispersion and stability at 800 °C and 450 L gcat−1 h−1, exhibiting negligible coke deposition and no growth of 4.25 nm Ni nanoparticles. The atomic level insights in nickel and silicon coordination reported in this work provide an instructive way of designing stable DRM catalysts.

Non-noble metal catalysts for dry reforming of methane: Challenges, opportunities, and future directions

The utilization of non-noble metal catalysts for the dry reforming of methane (DRM) has gained significant attention in recent years due to the increasing demand for clean and sustainable energy sources. DRM involves the conversion of methane (CH4) and carbon (IV) oxide (CO2) into synthesis gas (syngas), a valuable mixture of hydrogen (H2) and carbon monoxide (CO). Commercialization of non-noble metal catalysts for this reaction presents several challenges that must be addressed to achieve practical implementation. This short review discusses the challenges, opportunities, and future directions of non-noble metal catalysts for DRM. First, the limitations associated with the intrinsic activity and stability of non-noble metals, such as nickel, cobalt, and iron, are explored. Enhancing catalyst performance through compositional modifications, the incorporation of promoters and supports, are ways to overcome these challenges. Directions that hold promise for advancing non-noble metal catalysts in DRM, including the advanced exploration of bimetallic catalysts for synergistic effects, and the integration of non-noble metals into novel catalytic systems, were among the future proposals, while non-noble metal catalysts have the potential to revolutionize the production of syngas and contribute significantly to the transition towards sustainable energy solutions.

Assessing the effect of acid and alkali treatment on a halloysite-based catalyst for dry reforming of methane.

Dry reforming of methane (DRM) has recently received wide attention owing to its outstanding performance in the reduction and conversion of CH4 and CO2 to syngas (H2 and CO). From an industrial perspective, nickel (Ni)-supported catalysts have been deemed among the most suitable catalysts for DRM owing to their low cost and high activity compared to noble metals. However, a downside of nickel catalysts is their high susceptibility to deactivation due to coke formation and sintering at high temperatures. Using appropriate supports and preparation methods plays a major role in improving the activity and stability of Ni-supported catalysts. Halloysite nanotubes (HNTs) are largely utilized in catalysis as a support for Ni owing to their abundance, low cost, and ease of preparation. The treatment of HNTs (chemical or physical) prior to doping with Ni is considered a suitable method for increasing the overall performance of the catalyst. In this study, the surface of HNTs was activated with acids (HNO3 and H2SO4) and alkalis (NaOH and Na2CO3 + NaNO3) prior to Ni doping to assess the effects of support treatment on the stability, activity, and longevity of the catalyst. Nickel catalysts on raw HNT, acid-treated HNT, and alkali-treated HNT supports were prepared via wet impregnation. A detailed characterization of the catalysts was conducted using X-ray diffraction (XRD), BET surface area analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), solid-state nuclear magnetic resonance (ssNMR), H2-temperature programmed reduction, (H2-TPR), CO2-temperature programmed desorption (CO2-TPD), and Ni-dispersion via H2-pulse chemisorption. Our results reveal a clear alteration in the structure of HNTs after treatment, while elemental mapping shows a uniform distribution of Ni throughout all the different supports. Moreover, the supports treated with a molten salt method resulted in the overall highest CO2 and CH4 conversion among the studied catalysts and exhibited high stability over 24 hours testing.

A DFT study of elementary reaction steps of dry reforming of methane catalyzed by Ni: Explaining the difference between Ni particles supported on CeO2 and MnO[formula omitted]-doped CeO2

With the aid of DFT calculations, we investigate the elementary reaction steps of dry reforming of methane (DRM) on Ni(111) and NiO(100) as simple models of metallic and oxidized Ni catalysts. The reaction-path calculations reveal that DRM is feasible on metallic Ni at elevated temperatures. However, a notable problem with metallic Ni catalysts is the coke formation because the activation barrier for the C* formation is not considerably higher than those of the competing reactions that lead to the DRM products. In contrast, NiO does not encounter issues with coke formation, but it is not an effective catalyst due to too high activation energies and slow surface diffusion of H*. We also explain the experimentally observed difference between the DRM catalysts consisting of Ni particles supported on undoped and MnOx-doped CeO2 supports (designated as Ni/CeO2 and Ni/MnxCeO2, respectively). Specifically, we explain the absence of the 2020 cm−1 vibrational peak on the Ni/MnxCeO2 catalyst. Calculations univocally attribute the experimentally observed 2020 cm−1 peak to CO adsorbed on a top site of metallic Ni because all other sites and involved species display considerably different frequencies. The CO stretching frequency increases as Ni oxidizes, and on NiO(100), it is similar to the vibration of CO on the CeO2(111) support, about 2100 cm−1. Current results thus provide a sound explanation of why Ni/MnxCeO2 is a superior DRM catalyst to Ni/CeO2. In particular, the presence of the 2020 cm−1 peak on the Ni/CeO2 catalyst signals that Ni particles are sufficiently metallic and thus susceptible to carbon poisoning. In contrast, the absence of the 2020 cm−1 peak on the Ni/MnxCeO2 catalyst indicates that Ni particles are oxidized, i.e., the Ni oxidation is low enough to allow the DRM reaction but high enough to reduce the catalyst’s carbon poisoning.

Balancing elementary steps enables coke-free dry reforming of methane

Balancing kinetics, a crucial priority in catalysis, is frequently achieved by sacrificing activity of elementary steps to suppress side reactions and enhance catalyst stability. Dry reforming of methane (DRM), a process operated at high temperature, usually involves fast C-H activation but sluggish carbon removal, resulting in coke deposition and catalyst deactivation. Studies focused solely on catalyst innovation are insufficient in addressing coke formation efficiently. Herein, we develop coke-free catalysts that balance kinetics of elementary steps for overall thermodynamics optimization. Beginning from a highly active cobalt aluminum oxide (CoAl2O4) catalyst that is susceptible to severe coke formation, we substitute aluminum (Al) with gallium (Ga), reporting a CoAl0.5Ga1.5O4-R catalyst that performs DRM stably over 1000 hours without observable coke deposition. We find that Ga enhances DRM stability by suppressing C-H activation to balance carbon removal. A series of coke-free DRM catalysts are developed herein by partially substituting Al from CoAl2O4 with other metals.

Catalytic Performance of Bimetallic Cobalt–Nickel/Graphene Oxide for Carbon Dioxide Reforming of Methane

The design of economical and robust catalysts is a substantial challenge for the dry reforming of methane (DRM). Monometallic nickel-based catalysts used for DRM reactions had comparable activity to noble metals. However, they turned out to be less stable during the reactions. As a continuation of the interest in synthesizing catalysts for DRM, this paper evaluates the catalytic performance of bimetallic Co–Ni catalysts regarding their synergy effect, with graphene oxide (GO) as support for the first time. The synthesized bimetallic catalysts prepared via the wet-impregnation method were characterized using N2 physisorption analysis, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). The catalytic test was performed in a stainless-steel tubular reactor in atmospheric conditions with a reaction temperature of 800 °C, time-on-stream (TOS) of 300 min and CH4: CO2 being fed with a ratio of 1:1. The bimetallic 10 wt%Co–10 wt%Ni/GO and 20 wt%Co–10 wt%Ni/GO catalysts had a similar BET specific surface area in N2 physisorption analysis. The XRD pattern displayed a homogeneous distribution of the Co and Ni on the GO support, which was further validated through SEM–EDX. The conversion of CO2, CH4, and H2 yield decreased with reaction time due to the massive occurrence of side reactions. High conversions for CO2 and CH4 were 94.26% and 95.24%, respectively, attained by the bimetallic 20 wt%Co–10 wt%Ni/GO catalyst after 300 min TOS, meaning it displayed the best performance in terms of activity among all the tested catalysts.

Ni, Co & Cu substituted CeO2: A catalyst that improves H2/CO ratio in the dry reforming of methane

This study focusses on developing a efficient heterogenous catalyst using a comparative approach of substituted and supported metal oxides. In this article two types of catalysts were prepared (I)Tri metal supported catalysts (NiCoCu/CeO2) and (II)-Trimetal substituted catalysts (Ce0.85Ni0.05Co0.05Cu0.05O2). The combination of transition-metal as Trimetal substituted catalyst is unique and novel and has not been explored earlier. The aim is to choose the right material which qualifies to be a potential DRM catalyst. The idea of comparing supported and substituted catalysts is to prove that substitution is indeed beneficial even though the surface may not have very high metal concentration. So, where the activity comes from? The activity comes from the activated oxygen which is generated on the surface as a result of the substitution. This activated oxygen is missing in the supported catalyst. In substitutional catalyst, the metals are substituted in the bulk while in the supported system the metals are confined to the surface. Both supported and substituted catalysts exhibit distinct differences in the dry reforming of methane (DRM) reaction. The NiCoCu substituted CeO2 exhibited high stability and activity under DRM reaction. Thermal gravimetric analysis (TGA) and transmission electron microscopy (TEM) explained that low amount of amorphous and graphitic carbon was deposited during the reaction in the substituted catalyst which is also removable easily. In comparison NiCoCu supported CeO2 catalyst is less reactive and less stable because carbon removal propensity is not good on the surface. Further investigation using the transient studies confirms the stability of the substituted catalyst is due to the ease of the reactions; C + OL → CO and CO2 + C → 2CO. The prevalence of methane decomposition step and the reactivity of the surface lattice oxygen (OL) is an essential tool to dictates the H2/CO ratio and the catalytic stability. Novelty of this work is in elucidating the exact role of surface oxygen in imparting the activity and stability to the DRM catalyst. This work also elucidates process mechanism for DRM in NiCoCu substituted CeO2 based on the transient reactivity of the catalyst. Our findings have significant implications in rationalizing the approach for the development of more efficient and effective DRM catalysts based on the principle of lattice oxygen.

Flower-like hollow Ni0.5/xMgO-Al2O3 catalysts with excellent stability for dry reforming of methane: The role of Mg addition

Dry reforming of methane (DRM) suffers catalysts deactivation due to severe coking. Ni/MgO-Al2O3 is a promising system for DRM catalysts with high coking resistance, as the addition of MgO in Ni/Al2O3 catalysts can improve the alkalinity of the support and enhance the metal-support interaction. However, so far the activity and stability of Ni/MgO-Al2O3 is still unsatisfactory while the role of Mg addition remains unclear. In this paper, a series Ni0.5/xMgO-Al2O3 catalysts with flower-like hollow sphere morphology and high surface area were synthesized via a facile hydrothermal method. Appropriate Mg addition promotes the formation of NiAl2O4 while more Mg addition leads to the formation of NixMgyO. Both cases can enhance the MSI of the catalysts without changing the morphology of the catalyst. More Mg addition also leads to stronger CO2 adsorption via improving the alkalinity. Nevertheless, overdose of Mg results in weaker MSI and the blockage of Ni active sites. Ni0.5/0.5MgO-Al2O3 with moderate Mg addition shows excellent activity (CH4 ∼ 75 %, CO2 ∼ 85 %) and stability (>100 h) at a high GHSV = 144000 ml/gcat·h−1 and 800 °C with nearly no coking formation (<0.8 wt%). This work helps reveal the role of MgO addition in Ni/Al2O3 systems and gives new insights into the design of DRM catalysts with high activity and stability.

A Mini-Review on Lanthanum–Nickel-Based Perovskite-Derived Catalysts for Hydrogen Production via the Dry Reforming of Methane (DRM)

Given that the attempts to head toward a hydrogen economy are gathering pace, the dry reforming of methane (DRM) to produce hydrogen-rich syngas is a reaction that is worthy of investigation. Nickel-based catalysts have been extensively examined as a cost-effective solution for DRM, though they suffer from fast deactivation caused by coke accumulation. However, a number of published studies report high catalytic performance in terms of both activity and stability for La–Ni-based perovskite-derived catalysts used in DRM in comparison to other corresponding materials. In the work presented herein, a thorough analysis regarding the application of La–Ni-based perovskite catalysts for DRM is carried out. LaNiO3 is known for its anti-coking ability owing to the strong interaction between CO2 and La2O3. A further modification to improve the catalytic performance can be achieved by the partial or complete substitution of A or/and B sites of the perovskite catalysts. The latest developments with respect to this topic are also discussed in this manuscript. Even though the low surface area of perovskite catalysts has always been an obstacle for their commercialization, new supported and porous perovskite materials have recently emerged to address, at least partly, the challenge. Finally, conclusions and future outlooks for developing novel perovskite catalysts that may potentially pioneer new technology are included.

Mo promoting Ni-based catalysts confined by halloysite nanotubes for dry reforming of methane: Insight of coking and H2S poisoning resistance

Dry reforming of methane (DRM) shows promise for converting greenhouse gases into syngas but developing stable Ni-based catalysts resistant to sintering, coking, and H2S poisoning is challenging. We developed a highly effective catalyst by confining Mo-promoted Ni-based catalysts within halloysite nanotubes. Mo alloying with Ni inhibits Ni particles' migration out of the nanotubes, preventing the sintering of metals while decreasing the graphitic degree of carbon, which can balance the formation and removal of coke. Mo slows down H2S poisoning on Ni by adsorbing it competitively, maintaining a balance between carbon formation and removal even when H2S adsorbed on Mo hinders its role. With the inclusion of Mo, the rate of deactivation in the presence of H2S was reduced by half. Our research highlights the numerous advantages of Mo species and draws a correlation between carbon deposition and H2S poisoning, which offer new insights for designing efficient DRM catalysts.

Ni-Fe/La2O3 bimetallic catalysts for methane dry reforming: Elucidating the role of Fe for improving coke resistance

Dry reforming of methane (DRM) offers an effective approach for converting two cheap undesired greenhouse gases into valuable chemical feedstock of syngas. In this work, with the objective to obtain high efficiency Ni-based catalyst with superior coke resistance, a series of 6Ni-xFe/La2O3 catalysts were prepared by co-impregnation method, and were applied to DRM reaction. Effects of Fe doping, support contents, Ni dispersion on DRM performance of 6Ni-xFe/La2O3 catalysts were investigated. X-ray diffraction analysis and STEM-EDS mapping revealed that Ni-Fe alloy particles were well formed in the fresh reduced 6Ni-xFe/La2O3 catalysts. H2-TPR results showed that the addition of Fe can enhance the interaction between and Ni active sites and La2O3 support. In-situ Raman and TGA-DSC results demonstrated that the amount of La2O2CO3 species increased rapidly during DRM stability test on the spent Ni/La2O3 catalyst, leading to an obvious accumulation of carbon deposits. With the promotion by Fe, the reaction between the La2O2CO3 species and carbonaceous deposits can be accelerated, which results in more active and stable catalysts with significantly improved coking resistance. In addition, more oxygen vacancies could be obtained on Ni/La2O3 catalyst by Fe doping, as evidenced by the XPS results. It was concluded that these were the major reasons accounting for the significantly improved coke resistance for the 6Ni-xFe/La2O3 catalysts.

Enhanced catalytic activity for methane dry reforming of Ce-doped Ba0.9Zr0.7Y0.2Ni0.1O3-δ perovskite catalyst

Dry reforming of methane (DRM) holds great economic value and environmental protection significance. In our previous study, an in-situ reduced Ni-doped BaZrO3-δ-based catalyst was used as the DRM reforming layer, which exhibited remarkable coking-resistance. To further enhance its DRM catalytic activity and durability, Ce was doped at the B-site of Ba0.9Zr0.7Y0.2Ni0.1O3-δ, and the positive effects of Ce doping on DRM catalytic activity was investigated. Among the various Ce-doped catalysts, the perovskite catalyst with a Ce doping amount of 20 mol. % (i.e., Ba0.9Zr0.5Ce0.2Y0.2Ni0.1O3-δ) demonstrated the highest catalytic activity. At 750 °C, the CH4 and CO2 conversions reached as high as 80.1 % and 85.3 % respectively. Additionally, this catalyst exhibited excellent DRM catalytic durability, and no coking was detected after a 60 h durability test at 700 °C. The enhanced DRM catalytic activity and high coking-resistance can be attributed to the increased concentration of oxygen vacancies, improved hydration capacity, and enhanced CO2 adsorption capacity. The Ce doping in perovskite catalysts provides valuable insights for the construction of DRM catalysts with superior catalytic activity and durability.

Theoretical study of the mechanism of dry reforming of methane over Pd-doped CeO2 supported-Ru catalyst: The importance of oxygen self-spillover behavior

Carbon deposition negatively affects the dry reforming of methane (DRM). Thus, here, palladium (Pd) was doped to Ru/CeO2 to enhance the oxygen self-spillover behavior on the interface, and the obtained effects were studied using the density functional theory (DFT) and microkinetic modeling. After doping Pd, the lattice oxygen was active. To simulate conditions closer to those of an experiment, a dynamic model under realistic conditions and a static model were considered. For the dynamic model, lattice oxygen atoms spilled over from the surface to the Ru spontaneously. DFT calculations demonstrated that interfacial oxygen self-spillover plays a pivotal role in increasing C-O formation and enhancing the DRM reaction rate while inhibiting the rapid decomposition of CHx, which hinders C* formation. Coke formation analysis indicated that oxygen spillover inhibits the coupling of C*-C* (C*+C*→C2*), leading to strong resistance to coke deposition and preventing the deactivation of catalysts. Microkinetic simulations showed that the dynamic model has a higher turnover frequency (TOF) rate and a higher selectivity for the DRM reaction. The high catalytic activity of the dynamic model is mainly due to the low coverage by CH*/C* on the catalyst’s surface. We expect that our results will provide a strategy for the design of DRM catalysts by enhancing interfacial oxygen self-spillover, using doped atoms.

A strategy of constructing the Ni@silicalite-1 catalyst structure with high activity and resistance to sintering and carbon deposition for dry reforming of methane

Dry reforming of methane (DRM) as a promising reaction has both benefits reducing greenhouse gasses’ emissions and producing syngas for Fischer-Tropsch synthesis, whereas the Ni based DRM catalysts significantly suffer from deactivation due to the problems of metal sintering and carbon deposition. This paper reports a strategy for preparing the Ni@silicalite-1 catalyst, with which the nickel metal was encapsulated into the silicalite-1 zeolite crystals as Ni nano-particles (Ni NPs) with much high dispersion. Being benefited from this special structure, the catalyst displayed much high activity and durability under ultra-high space velocity (GHSV = 900,000 mL⋅gcat−1⋅h−1) reaction conditions. The high durability of the catalyst is originated from the strong interaction of Ni with the support and the encapsulation of the composite in the zeolite framework, which made the catalyst highly resistant to sintering and coke deposition. The much high activity of the catalyst should be the result of that Ni was highly dispersed in the catalyst and channels of the zeolite provide pathway for the reactant molecules contacting the Ni NPs and for the product molecules releasing there.