Reforming Reaction Research Articles

Insights into reaction mechanisms: Water’s role in enhancing in-situ hydrogen production from methane conversion in sandstone

In-situ conversion of subsurface hydrocarbons via electromagnetic (EM) heating has emerged as a promising technology for producing carbon-zero, affordable hydrogen (H2) production directly from natural gas reservoirs. However, the reaction pathways and role of water as an additional hydrogen donor in EM-assisted methane-to-hydrogen (CH4-to-H2) conversion are poorly understood. Herein, we employ a combination of lab-scale EM-heating experiments and reaction modeling analyses to unravel the reaction pathways and elucidate water’s role in enhancing hydrogen production. The labelled hydrogen isotope of deuterium oxide (D2O) is used to trace the sources of hydrogen. The results show that water significantly boosts hydrogen yield via coke gasification at around 400 °C and steam methane reforming (SMR) reaction at over 600 °C in the presence of sandstone. Water-gas shift reaction exhibits a minor impact on this enhancement. Reaction mechanism analyses reveal that the involvement of water can initiate auto-catalytic loop reactions with methane, which not only generates additional hydrogen but also produces OH radicals that enhance the reactants’ reactivity. This work provides crucial insights into the reaction mechanisms involved in water-carbon-methane interactions and underscores water’s potential as a hydrogen donor for in-situ hydrogen production from natural gas reservoirs. It also addresses the challenges related to carbon deposition and in-situ catalyst regeneration during EM heating, thus derisking this technology and laying a foundation for future pilots.

Strong metal-support interaction induced excellent performance for photo-thermal catalysis methane dry reforming over Ru-cluster-ceria catalyst

The utilization of solar energy in driving methane dry reforming (MDR) reaction through photo-thermal synergetic catalysis could simultaneously realize the reduction of carbon footprint and the fixation of solar energy, which is an environmentally and economically beneficial route. However, the currently developed catalysts still require further optimization in catalytic performance and stability. Here, we prepared RuNC, a Ru nanoclusters catalyst anchored on CeO2 with strong metal-support interaction (SMSI) effect via a facile preparation method. The formation rates of H2 and CO over RuNC catalyst were 1.41 and 2.16 mol·gcat−1·h−1 respectively under photo-thermal catalysis (PTC) at 500 °C, which is up to one order of magnitude higher than existing PTC-MDR catalysts. Moreover, the prepared catalyst did not show significant deactivation under 100 hour test. The in-depth structure-function relationship between catalytic activity/stability and Ru nanocluster sites/induced SMSI effect were determined by systematic structural characterization. The advantages of RuNC catalyst structure under PTC catalytic conditions were demonstrated by optical characterization. Besides, the excitation-migration path of photo-electron under PTC conditions was determined by ISI-XPS experiments. Finally, the mechanism of PTC-MDR reaction and the specific reaction steps enhanced by light irradiation were determined by operando experiments. This work provided theoretical basis and excellent catalyst for the industrial application of PTC-MDR route.

A conical spiral methanol steam reforming reactor for spectral splitting-based concentrating photovoltaic-thermochemical hybrid production

The spectral beam splitting (SBS) photovoltaic-thermochemical hybrid system improves the solar thermal energy grade through photon energy cascade distribution and methanol steam reforming (MSR) reaction. Given the deficiency of MSR reactor development for dish-concentrating SBS systems, the conical spiral structure is introduced to the receiver/reactor in this work, thus facilitating efficient absorption of circular beams and ameliorating the adaptability of the production. Based on specially designed spectral beam splitter, the Monte Carlo ray tracing (MCRT) method is employed to simulate the non-imaging optical process and optimized reflective cone structure. Thermodynamics and kinetic models of the reactor are established and experimentally validated. The analysis results show that the reflective cone advances the optical efficiency of the reactor to 76.95%, and the conical spiral structure helps to enhance heat and mass transfer for utilization of the catalytic space. The mid/low-temperature reaction prefers a solution flow rate of less than 1.53 mL s−1 and a water-methanol ratio of 1.4–1.9, with the maximum solar thermochemical conversion rate of 54.5%. Moreover, the upgrading in photothermal and photovoltaic heat exceeds respectively 0.62 and 8.97 at less than 600 W m−2 of irradiation, demonstrating the adaptive potential of the reactor. In summary, the research results contribute to broadening the operating conditions of the hybrid production and the full-spectrum penetration of solar energy in distributed scenarios.

Physical and chemical characteristics and activity of nickel-modified cobalt-iron-containing catalysts in the reaction of dry reforming of methane

In the process of dry reforming of methane (DRM), the activity of low-percentage catalysts based on cobalt and iron oxides and their modification with nickel oxide was studied. It has been established that the addition of nickel oxide into the Fe2O3/γ-Al2O3 catalyst increases the degree of methane conversion from 14 to 89%, and also increases the yield of target reaction products H2 to 43.0 vol.%, CO to 46.1 vol.% at 850 °C. On a Co3О4-NiО/γ-Al2O3 catalyst at 850 °C, methane conversion reaches to 88.1%, the yield of H2 and CO is 44.8%. TPR-H2 analyzes showed that the introduction of nickel oxide into Fe2O3/γ-Al2O3 composition, in contrast to the Co3O4/γ-Al2O3 catalyst, the temperature peaks of Fe2O3-NiО/γ-Al2O3, reduction shift towards lower temperatures and weaken the interaction of metals with the support - γ-Al2O3 and thereby the amount of active reduced particles of iron and nickel oxides increases, which ensures good catalytic activity of Fe2O3-NiО/γ-Al2O3. According to the XRD results, spinel-like form - NiFe2O4, NiAl2O4 and CoAl2O4, also phase as Fe2O3 were obtained on the Fe2O3-NiО/γ-Al2O3 catalyst. This indicates that the developed catalysts form new phases that are active at high temperatures to produce synthesis gas in reduction-oxidation processes during the DRM reaction.

Modeling and Numerical Investigations of Flowing N-Decane Partial Catalytic Steam Reforming at Supercritical Pressure

Steam reforming is an effective method for improving heat sinks of hypersonic aircraft at high flight Mach numbers. However, unlike the industrial process of producing hydrogen with a high water content, the catalytic steam reforming mechanism for the regeneration cooling process of hydrocarbon fuels with a water content below 30% is still unclear. Catalytic steam reforming (CSR) and catalytic thermal cracking (CTC) reactions occur at low temperatures, with the main products being hydrogen and carbon oxides. Thermal cracking (TC) reactions occur at high temperatures, with the main products being alkanes and alkenes. The above reaction exists simultaneously in the regeneration cooling channel, which is referred to as partial catalytic steam reforming (PCSR). Based on the experimental measurement results, an improved neural network correction method was used to establish a four-step global reaction model for the PCSR of n-decane under low water conditions. The reliability of the four-step model was verified by combining the model with a numerical simulation program and comparing it with the experimental results obtained by electric heating hydrocarbon fuels with a pressure of 3 MPa and a water content of 5/10/15%. The experimental and predicted results using the developed kinetic model are consistent with an error of less than 5% in the decane conversion rate. The average absolute error between the fuel outlet temperature and total heat sink is less than 10%. Using the PCSR model to predict the heat transfer characteristics of mixed fuels with different water contents, the convective heat transfer coefficient is basically the same, and the Nu number is affected by the thermal conductivity coefficient, showing different patterns with changes in the water content.

Preparation, characterization, and catalytic performance comparison of Ni/LaBO3 and Ru‐Ni/LaBO3 (B = Al, Fe) for methane steam reforming to hydrogen production

AbstractThe methane steam reforming (MSR) reaction is a significant process for hydrogen production, and developing catalysts with high activity and stability is crucial. In this work, the supported perovskite catalysts of Ni/LaBO3 and Ru‐Ni/LaBO3 (B = Al, Fe) were prepared by the sol–gel method using citric acid as a gelling agent for MSR to hydrogen production. The phase composition, pore structure, and surface morphology of the prepared catalysts were characterized by X‐ray diffractometer, Brunauer–Emett–Teller, scanning electron microscopy and energy dispersive spectroscopy, and X‐ray photoelectron spectroscopy. The reaction activity and stability of the prepared catalysts were tested in the fixed‐bed reactor with the temperature range of 500–800°C. The effect of Ru addition on the structure of perovskite and catalytic performance of MSR is explored. The results showed that 1wt%Ru–15wt%Ni/LaAlO3 catalyst exhibited the most excellent activity and stability during the reaction compared with the other three catalysts. The CH4 conversion, H2 selectivity, and H2 yield of the 1wt%Ru–15wt%Ni/LaAlO3 catalyst could reach 94.68%, 79.78%, and 48.65%, respectively, under the reaction temperature of 800°C and gas hourly space velocity of 36 000 mL/(gh), which were higher than those of a commercial catalyst. It was because that the relatively large surface area of perovskite support provides more active site and the addition of Ru enable Ni to have a smaller size and more dispersion. This study could provide a reference of perovskite catalysts for hydrogen production by MSR.

Numerical study on induction heating enhanced methanol steam reforming for hydrogen production

Electromagnetic induction heating technology, characterized by its non-contact thermal heat transfer, diminished thermal inertia, and facile temperature management, is applied in this study to enhance catalytic methanol steam reforming (MSR) reaction process. A two-dimensional reactor model was developed integrating electromagnetic field coupling with MSR reactions, fluid dynamics and heat transfer. In the reactor, heat is induced instantaneously on the magnetic material through an electromagnetic induction process, which generated by renewable electricity. Results showed that the Internal - Double Row Cylinder (IN-DRC, cylinder means that the shape of induction heating element is cylindrical.) highest heating efficiency is 38.3%, which is limited by the kinetics of MSR reaction. Here, thermal efficiency reaches its maximum with the reaction channel outlet temperature reaching about 580 K. Internal - Double Row Cylinder (IN-DRC) and Internal - Double Row Ball (IN-DRB, ball means that the shape of induction heating element is spherical) methanol conversions are virtually identical, with a maximum value close to 100%. Furthermore, the findings that the adoption of internal induced heating, in contrast to external heating, across the four reactor designs can effectively mitigate temperature gradient within the reactors. This reduction in thermal disparity significantly amplifies methanol conversion within the reactor, thereby markedly enhancing its overall performance in hydrogen production.Therefore, non-contact internal induction heating method has the potential for substantially hydrogen production processes.

Cu0·1In0·01/S-1 catalysts with high efficiency towards methanol steam reforming

Cu0·1/S-1, Cu0·1Zn0·01/S-1, Cu0.1Inx/S-1 (x = 0.01, 0.03, 0.05) and Cu0·1Ce0·01/S-1 were successfully prepared with S-1 as the carrier material and applied to methanol steam reforming (MSR) reaction. To further explore its chemical and physical properties, XRD, BET, SEM-EDS, ICP, FTIR, H2-TPR, NH3-TPD, CO2-TPD, and Raman were used to characterize the synthetic S-1 zeolite catalysts. The measured physicochemical properties revealed that utilizing S-1 zeolite as the carrier effectively altered the size of the metal particles, enhancing their dispersion and reduction characteristics. Compared with five different types of S-1 zeolite catalysts, the Cu0·1In0·01/S-1 catalyst has a large specific surface area and pore size. It exhibited superior active metal dispersion, with the lowest reduction temperature for the active metal CuO. The catalyst also showed a high Lewis acid content on its surface, forming the In-Lewis acid site. Consequently, the Cu0·1In0·01/S-1 catalyst exhibits exceptional performance in methanol steam reforming for hydrogen production reactions. It exhibited the best performance with a methanol conversion rate of 100%, H2 selectivity of 100% under the conditions of 1 MPa, 250 °C, the S/C molar ratio of 2.5, and the WHSV of 0.5 h−1, which outperforms most of the reported catalysts in methanol steam reforming.© 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Direct conversion of biogas to syngas over bimetallic nickel–cobalt supported on α-alumina catalysts

Syngas is an essential feedstock for many valuable chemicals, produced primarily by steam reformation of methane. Recently, dry reformation (reaction between methane and carbon dioxide) has gained importance as both the reactants are greenhouse gases (GHGs). However, dry reformation (DRM) produces syngas with a low H2/CO (<1.0). The DRM requires catalyst such as nickel supported on alumina, which results in higher coke. In this study, 6Ni–6Co/α-Al2O3 and 12Ni/α-Al2O3 catalysts were prepared by wetness impregnation. The catalysts were characterized using FESEM, XRD, XPS, BET, H2-TPR, NH3-TPD and H2-Chemisorption. The catalyst performance under DRM conditions were carried out in a fixed bed reactor at 20,000 ml/gcat.hr GHSV, between 600 °C and 700 °C, at atmospheric pressure. The performance of the catalysts was compared based on conversion of methane and carbon dioxide, hydrogen to carbon monoxide and coke deposition. The rates of consumption of methane carbon dioxide were found to be equal, and higher rates were observed for 6Ni–6Co/α-Al2O3, which is attributed to NiAl2O4/CoAl2O4 phase of active metals, higher surface area, smaller crystallite size and higher dispersion. This active phase of catalyst also responsible for higher rate of CO2 adsorption and reduced coke deposition. Highest H2/CO was found to be 1.26 for 6Ni–6Co/α-Al2O3.

Nickel nanocatalyst on lanthanum aluminate: Optimizing preparation and evaluating performance in glycerol dry reforming for syngas production

In this study, mesoporous nanocrystalline Ni/La-Al catalysts with varying nickel (Ni) loadings (5, 10, 15, and 20 wt.%) were synthesized using a solid-state method for the glycerol dry reforming (GDR) reaction. The effects of different Ni loadings and the addition of steam on the structural and catalytic performance of the catalysts were investigated. Characterization techniques, including Brunauer-Emmett-Teller (BET) surface area analysis, temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), and X-ray diffraction (XRD) were employed to analyze the catalysts' properties. Results showed that increasing Ni loading to 10 wt.% improves the catalytic properties. However, by increasing the Ni loading, a decrease in catalytic properties due to increasing particle size, creating NiO bulk phase and surface pore blockage is obvious. A series of experiments were performed to investigate the effect of steam usage on catalytic properties. TPO analysis revealed that steam addition reduces the carbon deposition and shifts oxidation peaks to lower temperatures; consequently, the activity and stability of the catalyst will be enhanced. Although the 5 - 7.5 vol.% of steam in the feed composition significantly stabilizes the catalyst, it is possible to produce H2-rich synthesis gas, and conversely, increasing the temperature reduces the H2/CO ratio. Various examinations were conducted under different conditions, including varying gas hourly space velocity (GHSV), carbon-to-glycerol ratio (CGR), and temperature, to obtain more comprehensive data on the catalysts.

Features of CO₂ Hydrogenation on MoO₃/Al₂O₃ and γ-Al₂O₃

The physicochemical and catalytic (CO₂ hydrogenation) characteristics of Mo-containing catalysts have been studied. Catalysts with an oxide content of Mo 8 and 15 wt% were prepared by impregnation with ammonium paramolybdate γ-Al₂O₃ followed by drying and calcining at 500°C. The introduction of Mo oxide reduces the pore volume of the support and increases their average size, which indicates the distribution of the deposited molybdenum oxide in the pores of the support. According to X-ray diffraction data, the calcined catalyst contains practically no crystalline MoO₃ phase. According to the Raman spectra, oxygen-containing formations are present on the catalyst surface, in which Mo atoms are tetrahedrally and octahedrally coordinated with respect to oxygen atoms. The impregnated MoO₃ oxide is partially reduced by hydrogen during linear heating starting from 320°C. Hydrogenation of CO₂ (gas of composition, vol.%: 30.7 CO₂, 68 H₂, rest. N2, sample 0.5 g) was studied in the mode of linear heating up to 400°C. The main reaction is the reverse reaction of CO steam reforming. The contribution of the methanation reaction to CO₂ hydrogenation is small. An increase in temperature and pressure has a positive effect on CO₂ conversion. With an increase in pressure from 1 to 5 MPa, the CO content increases approximately twofold. In the hydrogenation of CO₂, γ-Al₂O₃, preheated in a flow of H₂ to 400°C, also exhibits noticeable activity, although significantly lower compared to Mo-containing catalysts. With increasing pressure, the activity of aluminium oxide and Mo-containing catalysts, increases.

Manganese-rhodium nanoparticles: Adsorption on titanium oxide surfaces and catalyst for syngas reactions.

Manganese-rhodium (Mn-Rh) nanoparticles have emerged as a promising candidate for catalytic applications in the production of syngas, a critical precursor for a wide range of industrial processes. This study employs a comprehensive, theoretical, and computational approach to investigate the structural and electronic properties of Mn-Rh nanoparticles, with a specific focus on their interaction with titanium oxide (TiO2) surfaces and their potential as catalysts for syngas reactions. The density functional theory calculations are employed to explore the adsorption behavior of Mn-Rh nanoparticles on TiO2 surfaces. By analyzing the adsorption energies, geometries, and electronic structure at the nanoscale interface, we provide valuable insights into the stability and reactivity of Mn-Rh nanoparticles when immobilized on TiO2 supports. Furthermore, the catalytic performance of Mn-Rh nanoparticles in syngas production is thoroughly examined. Through detailed reaction mechanism studies and kinetic analysis, we elucidate the role of Mn and Rh in promoting syngas generation via carbon dioxide reforming and partial oxidation reactions. The findings demonstrate the potential of Mn-Rh nanoparticles as efficient catalysts for these crucial syngas reactions. This research work not only enhances our understanding of the fundamental properties of Mn-Rh nanoparticles but also highlights their application as catalysts for sustainable and industrially significant syngas production.

Propane steam reforming over La0.8Sr0.2Ni1-yMyO3 (M = Cr, Mn, Fe, Co) perovskite-type oxides

Perovskite-type oxides have attracted significant attention in recent years as potential catalysts for hydrocarbon reforming reactions. Herein, a series of oxides with the formula La0.8Sr0.2Ni1-yMyO3 (LSNi1-yMy; M=Cr, Mn, Fe, Co) have been synthesized and tested for the propane steam reforming (PSR) reaction. Materials were characterized employing BET, XRD, H2-TPR, SEM/EDX, TEM/SAED and TPO techniques. Optimal results were obtained for LSNi0.5Cr0.5, which exhibited high propane conversion (78 %), H2-selectivity (98 %), and excellent stability with time-on-stream (40 hours) at 600 °C. This has been attributed to the exceptional ability of LSNi0.5Cr0.5 to maintain its perovskite structure under reaction conditions, the in situ formation of finely dispersed Ni-Cr alloy crystallites, and the suppression of reactions that lead to graphitic carbon deposition. This study provides deeper insight into the effects of structural properties and reducibility of perovskite-type oxides on their catalytic properties and can be used to design catalysts with improved performance.

Performance of An Energy Production System Consisting of Solar Collector, Biogas Dry Reforming Reactor and Solid Oxide Fuel Cell

Performance of An Energy Production System Consisting of Solar Collector, Biogas Dry Reforming Reactor and Solid Oxide Fuel Cell

Study on Cracking/Oxidation/Integrated Reforming Reaction for Efficient Conversion of Biomass to High‐Quality Syngas

AbstractThe advanced gasification technology of coal is mainly based on oxidation reaction and high temperature but is not suitable for biomass conversion. High tar and CO2 content are the two main issues that affect the efficiency of biomass gasification. In order to deeply convert hydrocarbons/tar and CO2 simultaneously, and enhance syngas yield, the cracking/partial oxidation/reforming reactions and their integrated reaction routes are investigated from an interrelated view. The effects of each reaction on the distribution of C/H elements in hydrocarbons/tar and syngas are illustrated. By cracking and oxidation reaction, the syngas yield can only reach 0.93 Nm3 kg−1, about 58 % of the theoretical maximum value; a large proportion of residual C/H atoms existing in stable hydrocarbons/tar/CO2/H2O are not converted. Based on the concept of lattice O oxidation combined with dry reforming, it realizes syngas yield (CO+H2) 1.56 Nm3 kg−1 with 91.6 % concentration, demonstrating that tar/hydrocarbons and CO2/H2O are converted to syngas efficiently. The effects of [O]/C ratio on gas yield represent a synergistic coordination between lattice Os oxidation and catalytic reforming reaction. Oxidation‐reforming is the optimum route for biomass conversion to high‐quality syngas.

Rigorous development and comparison of multi-dimensional reactor models encompassing the catalyst domains for steam methane reforming

Hydrogen is being considered as a possible large-scale carbon-free industrial combustion and transportation fuel. Steam methane reforming (SMR) reaction is the most dominant industrial hydrogen production method. This paper develops comprehensive models and delves into the influences of the multi-dimensional reactor and catalyst domains in SMR. Several single-scale or multi-scale SMR packed-bed reactor models are developed with the Aspen Custom Modeler and solved by the built-in finite difference method. These models are categorized into pseudo-homogeneous and heterogeneous models. This study thoroughly compares and discusses the effects of axial and/or radial mixing due to mass/heat dispersion as well as interfacial and intraparticle mass/heat transport phenomena across various types of reactor-catalyst configurations. Furthermore, insights into the prediction accuracy of each model under various operating conditions are provided. This research fills a gap in the existing literature by developing rigorous dynamic models for SMR reactors to investigate their profiles and performances, offering a clearer understanding of the relative importance of different modeling approaches in predicting the behavior of SMR reactors. The findings provide valuable guidelines for researchers and industry professionals in selecting the appropriate model for their design, analysis, optimization, and control tasks.

Construction of porous Cu/CeO2 catalyst with abundant interfacial sites for effective methanol steam reforming

Methanol is a promising hydrogen carrier for fuel cell vehicles (FCVs) via methanol steam reforming (MSR) reaction. Ceria supported copper catalyst has attracted extensive attentions due to the extraordinary oxygen storage capacity and abundant oxygen vacancies. Herein, we developed a colloidal solution combustion (CSC) method to synthesize a porous Cu/CeO2(CSC) catalyst. Compared with Cu/CeO2 catalysts prepared by other methods, the Cu/CeO2(CSC) catalyst possesses highly dispersed copper species and abundant Cu+-Ov-Ce3+ sites at the copper-ceria interface, contributing to methanol conversion of 66.3 %, CO2 selectivity of 99.2 %, and outstanding hydrogen production rate of 490 mmol gcat−1 h−1 under 250 °C. The linear correlation between TOF values and Cu+-Ov-Ce3+ sites amount indicates the vital role of Cu+-Ov-Ce3+ sites in MSR reaction, presenting efficient ability in activation of water. Subsequently, a deep understanding of CSC method is further presented. In addition to serving as a hard template, the colloidal silica also acts as disperser between nanoparticles, enhancing the copper-ceria interactions and facilitating the generation of Cu+-Ov-Ce3+ sites. This study offers an alternative approach to synthesize highly dispersed supported copper catalysts.

Hydrogen production from low-temperature methanol steam reforming over silver-promoted CuO/ZnO/Ag/Al2O3 Catalyst

Cu-based catalysts featured with high activity at low temperatures and suppressed CO generation are expected to attract significant attention in the methanol steam reforming (MSR) reaction for on-board hydrogen production for proton exchange membrane fuel cells. Herein, we demonstrate that Ag incorporation into a CuO/ZnO/Al2O3 catalyst leads to enhanced hydrogen production activity and suppressed CO selectivity in MSR reactions at low temperatures (200–220 °C). The characterization results revealed that incorporation of a small amount of Ag in the catalyst not only improves the dispersion of the polymetallic components and diversifies the Cu species, but also lowers Cu reduction temperature and brings more oxygen vacancies, thereby leading to improved catalytic performance. The preparation conditions, structure-activity relationship, and stability of the Ag-promoted catalyst were investigated in detail based on time-on-steam tests and characterizations. This finding paves a new possible way for the optimization of the Cu-based catalysts for MSR.

Synergetic Cu0 and Cu+ on the surface of Al2O3 support enhancing methanol steam reforming reaction

The methanol steam reforming (MSR) reaction was a crucial pathway for hydrogen production, with Cu-based catalysts widely applied. It was established that the isolated Cu0-site path and Cu+-site path were responsible for methanol conversion. However, a “Seesaw Effect” existed between the activation of *CH3O and the formation of CO2. Specifically, Cu0 site favored *CH3O activation but facilitated the reverse water gas shift (RWGS) process. Conversely, Cu+ site suppressed CO and promoted CO2 formation but had a reduced ability for *CH3O dehydrogenation. In this work, a Cu0-Cu+ synergy path was proposed, Cu0 sites activate CH3OH into *CH2O, and the subsequent conversion of *CH2O is catalyzed over the Cu+ site. Characterization and calculation results demonstrated that this synergy path subtly avoids two rate-determining steps (*CH3O → *CH2O on Cu+ sites and bi-*CHOO → *CO2 on Cu0 site). The migration of *CH2O from the Cu0 site to Cu+ sites was a critical step in constructing a synergy path. Moreover, MSR performance was governed by the quantity of synergy sites (Cu0/Cu+) and the amount of matched Cu0-Cu+ sites, both of which could be adjusted by varying the Cu loading (1–20%). An optimal 9% Cu enhanced the synergy interaction, with a Cu0/Cu+ ratio of 1.2 and the highest amount of Cu0-Cu+ sites (609.4 μmol/g), giving rise to high methanol conversion and low CO concentration. The discovery in this work provided theoretical guidance for constructing high-performance Cu-based catalysts.

Formation of a Porous Crystalline Mg1‒ x Al2O y Overlayer on Metal Catalysts via Controlled Solid-State Reactions for High-temperature Stable Catalysis.

Catalyst deactivation by sintering and coking is a long-standing issue in metal-catalyzed harsh high-temperature hydrocarbon reactions. Ultrathin oxide coatings of metal nanocatalysts have recently appeared attractive to address this issue, while the porosity of the overlayer is difficult to control to preserve the accessibility of embedded metal nanoparticles, thus often leading to a large decrease in activity. Here, we report that a nanometer-thick alumina coating of MgAl2O4-supported metal catalysts followed by high-temperature reduction can transform a nonporous amorphous alumina overlayer into a porous Mg1‒xAl2Oy crystalline spinel structure with a pore size of 2‒3 nm and weakened acidity. The high porosity stems from the restrained Mg migration from the MgAl2O4 support to the alumina overlayer through solid-state reactions at high temperatures. The resulting Ni/MgAl2O4 and Pt/MgAl2O4 catalysts with a porous crystalline Mg1‒xAl2Oy overlayer achieved remarkably high stability while preserving much higher activity than the corresponding alumina-coated Ni and Pt catalysts on MgO and Al2O3 supports in the reactions of dry reforming of methane and propane dehydrogenation, respectively.