Dry Reforming Research Articles

Ni supported on desilicated HZSM-5 as catalyst for biogas reforming

In this study, Ni/HZSM-5 catalysts containing 3.0 and 5.0 wt% of Ni were used to produce hydrogen-rich streams through the dry reforming of methane, with biogas serving as the raw material. The effect of a desilication treatment on catalyst performance was evaluated. The removal of Si resulted in an increase in mesoporous volume. Moreover, in situ XANES and in situ XRD analyses revealed the formation of Ni2+ species with lower reducibility for desilicated samples. This was likely attributed to the presence of Ni2+ species confined within mesopores, promoting metal-support interaction, which leads to a higher metal dispersion, after reduction. The presence of small Ni particles resulted in a higher methane conversion and a low carbon formation during dry reforming of methane, regardless of nickel content.

Dynamic trap of Ni at elevated temperature for yielding high-efficiency methane dry reforming catalyst

Highly dispersed and stable metal catalysts with small nanoparticles have received extensive attention in elevated-temperature thermocatalytic process. However, the available strategies to stabilize metal sites, by constructing defective structures on catalyst supports and developing controllable preparation steps at room temperature, show limited effect, because these active metal sites can be mobile and sintering at elevated temperature. Herein, dealuminated Beta zeolite with abundant surface defects of silanol nests is applied as support, then dynamic trap strategy and subsequent reduction process at elevated temperature is devoted to transfer Ni-based precursors into the silanol nests, thus obtaining small nanoparticles Ni catalysts that are suitable for high-temperature methane dry reforming (DRM). Some in-situ characterization processes and the ingenious designed experiments are performed to identify the dynamic trapping process. The rational fabricated catalysts exhibit high catalytic reactivity for DRM reaction in long-term operation.

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

Efficient recycling and conversion of CO2 to methanol: Process design and environmental assessment

Carbon capture and carbon reuse in the chemical plants is one of the attractive prospective approaches to decrease the concerns about global warming and climate change. In the present study, is focused on the synthesis gas production from carbon dioxide in a methanol synthesis plant. In this regard, two methanol processes are proposed based on CO2 separation, recycling, and reforming. In the first scenario, CO2 is separated and recycled to the conventional reformer, while the process is equipped by a CO2 separation unit and dry methane reformer in the second scenario. The proposed processes are simulated and a sensitivity analysis is performed to investigated the effect of inputs on methanol productivity and carbon conversion. The operational parameters of proposed processes are optimized to enhance methanol productivity and CO2 conversion. Then, the processes are compared from energy efficiency, carbon efficiency, CO2 emission rate and methanol productivity viewpoints. The results showed that, in the second proposed scenario, methanol production rate approach to 5367 tons per day in comparison to 5030 tons per day for industrial unit. In addition, modification of conventional methanol process based on the second scenario could decrease CO2 emission rate about 56 tons per day.

A strategy of Co doping in MgO to significantly improve the performance of solar-driven thermocatalytic CO2 reduction on Ru/Co-MgO

Dry reforming of CH4 (DRM) driven solely by solar light provides an attractive strategy for solving energy shortages and global warming. The strategy faces two challenges: so far, high fuel productivity and solar-to-fuel efficiency (η) can only be realized at high solar intensities (usually more than 192 kW m−2). Furthermore, coking side reactions are more favorable in thermodynamically, which can lead to catalyst deactivation. Herein, a new nanocomposite of Ru nanoparticles (NPs) loaded on Co-doped MgO with reactive oxygen species and a strong optical absorption throughout the entire solar spectrum (Ru/Co-MgO) is prepared. At relatively low solar intensity (73.2 kw m−2), the solar-driven DRM on Ru/Co-MgO achieves high production rates of CO (rCO, 80.01 mmol g-1catalyst min−1) and H2 (rH2, 62.31 mmol g-1catalyst min−1) with larger η of 26.1 %, which shows an increase of 1.3-fold in rCO, rH2 and η, while a 65-fold decrease in coking rate (rC) compared to a reference catalyst of Ru and Co NPs loaded on MgO (RuCo/MgO). The significant improvement in the catalytic performance stems from the involvement of reactive oxygen (–Co–O–Mg–) in Co-MgO for the oxidation of C* species as a rate-determining step of DRM, which enhances the catalytic activity and significantly inhibits coking. Additionally, the light not only promotes the reactions both of DRM on Ru NPs and strongly adsorbed CO2 on Co-MgO with C* species at the Ru/Co-MgO interface, but also facilitates the dissociation of CO2 adsorbed on the oxygen vacancies of Ru/Co-MgO into CO, thus accelerating the synergistic effect between Ru NPs and Co-MgO.

Metastable nickel–oxygen species modulate rate oscillations during dry reforming of methane

AbstractWhen a heterogeneous catalyst is active, it forms metastable structures that constantly transform into each other. These structures contribute differently to the catalytic function. Here we show the role of different metastable oxygen species on a Ni catalyst during dry reforming of methane by combining environmental scanning electron microscopy, near ambient pressure X-ray photoelectron spectroscopy, on-line product detection and computer vision. We highlight the critical role of dissociative CO2 adsorption in regulating the oxygen content of the catalyst and in CH4 activation. We also discover rate oscillations during dry reforming of methane resulting from the sequential transformation of metastable oxygen species that exhibit different catalytic properties: atomic surface oxygen, subsurface oxygen and bulk NiOx. The imaging approach allowed the localization of fluctuating surface regions that correlated directly with catalytic activity. The study highlights the importance of metastability and operando analytics in catalysis science and provides impetus towards the design of catalytic systems.

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.

Dry reforming of methane over Ni/Al2O3 catalysts: Support morphological effect on the coke resistance

Flower-like (Al2O3-F), wire-like (Al2O3-W) and sphere-like (Al2O3-S) alumina supported nickel catalysts (designated as Ni/Al2O3-F, Ni/Al2O3-W and Ni/Al2O3-S) were prepared for catalytic dry reforming of methane (DRM). The resultant catalysts exhibited variable catalytic activities and coke resistance performances in the reaction, which was closely dependent on their various physicochemical properties from the morphological effect of Al2O3 supports. To be precise, Ni/Al2O3-W presented adequately high catalytic activity and promising anti-coke behavior, which was attributed to its strong metal-support interaction, the surface dispersion of small-sized Ni nanoparticles and noticeable activation ability towards CO2. Ni/Al2O3-F possessed high anti-coke performance as well in terms of its significant CO2 activation ability. However, the encapsulation effect of Al2O3-F nanostructure resulted in insufficient abundance of metallic Ni active sites on the surface of Ni/Al2O3-F, thus giving rise to poor initial catalytic activity. The weak CO2 activation ability and the large particle size of metallic Ni on Ni/Al2O3-S induced the considerable formation of filamentous carbon after long-term DRM test. With regard to in situ DRIFTs analysis, the existence of OH* as the coke precursor scavenger and its reaction with the CHx* intermediate species from CH4 cracking were demonstrated to play crucial roles in dominating the overall anti-coke performances of Ni/Al2O3 catalysts. This work provides new insights into the development of high coke-resistance Ni-based catalysts from the perspective of support morphology modulation.

General Synthesis of High-Entropy Oxide Nanofibers.

The discovery of high-entropy oxides (HEOs) in 2015 has provided a family of potential solid catalysts, due to their tunable components, abundant defects or lattice distorts, excellent thermal stability (ΔG↓ = ΔH - TΔS↑), and so on. When facing the heterogeneous catalysis by HEOs, the micrometer bulky morphology and low surface areas (e.g., <10 m2 g-1) by traditional synthesis methods obstructed their way. In this work, an electrospinning method to fabricate HEO nanofibers with diameters of 50-100 nm was demonstrated. The key point lay in the formation of one-dimensional filamentous precursors, during which the uniform dispersion of five metal species with disordered configuration would help to crystallize into single-phase HEOs at lower temperatures: inverse spinel (Cr0.2Mn0.2Co0.2Ni0.2Fe0.2)3O4 (400 °C), perovskite La(Mn0.2Cu0.2Co0.2Ni0.2Fe0.2)O3 (500 °C), spinel Ni0.2Mg0.2Cu0.2Mn0.2Co0.2)Al2O4 (550 °C), and cubic Ni0.2Mg0.2Cu0.2Zn0.2Co0.2O (750 °C). As a proof-of-concept, (Ni3MoCoZn)Al12O24 nanofiber exhibited good activity (CH4 Conv. > 96%, CO2 Conv. > 99%, H2/CO ≈ 0.98), long-time stability (>100 h) for the dry reforming of methane (DRM) at 700 °C without coke deposition, better than control samples (Ni3MoCoZn)Al12O24-Coprecipitation-700 (CH4 Conv. < 3%, CO2 Conv. < 7%). The reaction mechanism of DRM was studied by in situ infrared spectroscopy, CO2-TPD, and CO2/CH4-TPSR. This electrospinning method provides a synthetic route for HEO nanofibers for target applications.

Syngas production from photothermal synergistic dry reforming of CH4 over a core-shell structured Ni/CeO2–ZrO2@SiO2 catalyst

Photothermal synergistic catalysis (PTSC) offers promising potential for the dry reforming of methane (DRM) to produce syngas, but designing suitable catalysts suitable for photothermal processes poses significant challenges. In this study, we present a core-shell catalyst consisting of a SiO2 shell encapsulating Ni loaded on the CeO2–ZrO2 support, which proved to be well-suited for PTSC-DRM under milder conditions. Compared to traditional thermal catalysis (TC), PTSC at 600 °C exhibited superior CH4/CO2 conversions (63.5 %/55.9 %) and higher H2/CO yields (137.0 mmol·g-1·h-1/182.9 mmol·g-1·h-1). The TOFs under PTSC-DRM are 1.3–2.9 times higher than the corresponding TOFs in TC-DRM. The catalyst demonstrated strong stability during a 60-h aging test, which can be attributed to the restricted migration of Ni and the accelerated movement of oxygen induced by illumination via structure effect which also lead to the boosted activity benefited from a reduced bandgap of 2.2 eV and improved charge separation/migration efficiency during PTSC reaction.

Application of ZrO2-Based Hierarchical Nanofibers as a Promoter in Ni Catalyzed Methane Dry Re-Forming

Application of ZrO₂-Based Hierarchical Nanofibers as a Promoter in Ni Catalyzed Methane Dry Re-Forming

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.

Influence of Mn, Mg, Ce and P promoters on Ni-X/Al2O3 catalysts for dry reforming of methane

In this work, the performance of a series of nickel catalysts supported on alumina containing the promoters Mg, Mn, Ce and P was evaluated against the dry reforming of methane (DRM). Alumina support was obtained quickly and simply through the microwave-assisted combustion method using low levels of urea. The catalysts were characterized by XRD, TPR, FTIR and XRD in situ, proving that successive hydration and heat treatment steps during synthesis can generate modifications in the alumina phases, in addition to the formation of aluminate species that are reduced during the catalytic activation step and modify the level of interaction between active and support phases. The catalytic activity test was performed with GHSV = 100 L g−1 h−1 and the formed carbon was quantified by thermogravimetric analysis. The Mn promoter exhibited the highest methane conversion rate during the initial stages of the reaction, in which the presence of MnO2 favored parallel reactions of methane decomposition. The phosphorus and cerium produced smaller amounts of coke, reducing the carbon generated due to the interaction of promoters with carbon on the surface of the catalytic sites. The Mg increases the interaction of the active phase with the support.

Kinetics of thermal dry reforming of methane for syngas production and solid carbon capture

By combining numerical simulations and experiments, catalyst-free thermal dry reforming of biogas for sustainable syngas production and solid carbon capture is investigated under industrially viable conditions.

Integrating advanced fitting models with experimental catalysis to maximize H2 production in dry reforming using nickel on metalized-silica-alumina catalysts

This study explores the enhancement of hydrogen production via dry reforming of methane (DRM) using nickel catalysts supported on metalized silica-alumina.

Perovskites as oxygen storage materials for chemical looping partial oxidation and reforming of methane.

The traditional partial oxidation, dry reforming and steam reforming of methane technologies are separated into two reactors for execution by chemical looping technology, which can avoid the defects exposed in the traditional process (avoiding carbon accumulation, reducing costs, etc.). The key to chemical looping technology is to find suitable oxygen carriers (OCs), which can store and release oxygen to form a closed loop in the chemical looping. The purpose of this review is to summarize the current status of perovskite oxides for partial oxidation and reforming of methane in chemical looping, describe the structure, oxygen capacity, oxygen migration rate and common synthesis methods of perovskites in chemical looping. In addition, the effects of impregnation loading, ion doping, and structural morphology on the catalytic conversion of CH4 by perovskite OCs and the reaction mechanism on the OCs are also discussed.

Carbon Dioxide Reforming of Methane in a Microchannel Reactor

In this work, an experimental study of CO2 reforming of methane in a microchannel reactor was carried out. Two types of microchannel reactors were used in the experiments: a slot ring channel with a catalyst applied to the outer surface of the inner cylinder, a pack of corrugated plates, on the surface of which the catalyst was applied.

Highly stable 3D-printed monolithic Al2O3-supported Ni-based structured catalysts for dry reforming of methane

Nickel (Ni)-based powder catalysts with poor stability used in dry reforming of methane (DRM) suffer from severe coking and high bed pressure drop. We successfully prepared a monolithic NiAl2O4/Al2O3 structured catalyst using 3D printed α-Al2O3 topological carrier followed by Ni impregnation and calcination at 1400 oC to improve the stability and decrease the pressure drop. The monolithic Ni/NiAl2O4/Al2O3 structured catalyst reduced from NiAl2O4/Al2O3 could inhibit coke accumulation effectively and exhibit excellent catalytic performance. During the 750-h stability test, monolithic Ni/NiAl2O4/Al2O3 catalyst exhibited 3% CH4 conversion degradation and 0.37 mgC h-1 gcat-1 coke accumulation rate. The formation mechanisms of two different types of cokes were proposed to explain the performance. Monolithic Ni/NiAl2O4/Al2O3 structured catalyst also exhibited a lower pressure drop and superior stability than the powder catalyst. This work serves as a guide for preparing the monolithic Ni-based structured catalyst with outstanding stability and low pressure drop for practical application in DRM.

Unraveling the effect of particle size of active metals in Ni/MgO on methane activation and carbon growth mechanism.

For dry reforming of methane, the active metal particle size of the catalyst has a significant effect on both the reaction activity and the resistance to carbon deposition. In this study, nickel particles of different sizes (Ni13, Ni25, and Ni37) supported on the MgO(100) slab are used to study the mechanism of CH4 activation and carbon growth based on DFT theoretical calculations. According to the results, the energy of adsorption for reaction intermediates changes depending on the size of the active metal. The adsorption process of CH3, CH2, CH and C on Ni25/MgO has a maximum exothermic value. Furthermore, the energy barriers of CH4 four-step dehydrogenation are lowest on Ni25/MgO during the CH4 activation process. The growth process of carbon deposition on the catalysts is also investigated in this work. The results indicate that the growth of carbon from C5 to C6 is difficult to proceed on Ni13/MgO due to size and active site limitation. Additionally, with an increase in particle size of the active metal, the absolute value of growth energy and average carbon binding energy of Cn increase on both Ni25/MgO and Ni37/MgO. It is proved that smaller particle size presents better resistance to carbon deposition. In the studied size range, Ni25/MgO is demonstrated to have greater catalytic activity and better resistance to carbon deposition.

Recent advances in promoting dry reforming of methane using nickel-based catalysts

The achievements of dry reforming of methane over Ni-based catalysts are presented with focus on the modification factors to enhance sintering and coking resistance, elaborated in the context of support, promoter, and preparation.