W-doped ordered mesoporous Ni–Al2O3 catalyst for methanation of carbon monoxide

In order to simultaneously inhibit the Ni sintering and coke formation as well as investigate the effects of WO₃ promoter on catalytic performance, the ordered mesoporous Ni–WO₃/Al₂O₃ catalysts were synthesized by a facile one-pot evaporation-induced self-assembly method for CO methanation reaction to produce synthetic natural gas. Addition of WO₃ species could significantly promote the catalytic activity due to the enhancement of the Ni reducibility and the increase of active centers, and the optimal N10W5/OMA catalyst with NiO of 10 wt% and WO₃ of 5 wt% achieved the maximum CH₄ yield 80% at 425 °C, 0.1 MPa and a weight hourly space velocity of 60000 mL g⁻¹ h⁻¹. Besides, the reference catalyst N10W5/OMA-Im prepared by the conventional co-impregnation method was also evaluated. Compared with N10W5/OMA, N10W5/OMA-Im showed lower catalytic activity due to the partial block of channels by Ni and WO₃ nanoparticles, which reduced active centers and restrict the mass transfer during the reaction. In addition, the N10W5/OMA catalyst showed superior anti-sintering and anti-coking properties in a 425^oC-100 h-lifetime test, mainly because of confinement effect of ordered mesoporous structure to anchor the Ni particle in the alumina matrix.     

Three-dimensional porous Mn–Ni/Al2O3 microspheres for enhanced low temperature CO hydrogenation to produce methane

CO methanation has attracted much attention because it transforms CO in syngas and coke oven gas into CH₄. Here, porous Al₂O₃ microspheres were successfully used as catalyst supports meanwhile the Mn was used as a promoter of Ni/Al₂O₃ catalysts. The as-obtained Ni/Al₂O₃ and Mn–Ni/Al₂O₃ samples display a micro-spherical morphology with a center diameter near 10 μm. Versus the Ni/Al₂O₃ catalyst, the 10Mn–Ni/Al₂O₃ catalyst exhibits a high specific surface area of 92.5 m²/g with an average pore size of 7.0 nm. The 10Mn–Ni/Al₂O₃ catalyst has the best performance along with can achieve a CO conversion of 100% and a CH₄ selectivity of 90.7% at 300 °C. Even at 130 °C, the 10Mn–Ni/Al₂O₃ catalyst shows a CO conversion of 44.0% and a CH₄ selectivity of 84.1%. The higher low-temperature catalytic activity may be since the catalyst surface contains more CO adsorption sites and thus has a stronger adsorption performance for CO. Density functional theory (DFT) calculations confirm that the Mn additive enhances the adsorption of CO, especially for the 10Mn–Ni/Al₂O₃ catalyst with the strongest adsorption energy.     

Preparation and characterization of Ni based catalysts for the catalytic partial oxidation of methane: Effect of support basicity on H2/CO ratio and carbon deposition

The catalytic partial oxidation of methane (CPOM) was studied on Ni based catalysts. Catalysts were prepared by wet impregnation method and characterized by using AAS, BET, XRD, HRTEM, TPR, TPO, Raman Spectroscopy and TPSR techniques. The prepared catalysts showed nearly 95% CH₄ conversion and nearly 96% H₂ selectivity under the flow of 157,500 (L kg⁻¹ h⁻¹) with the ratio of CH₄/O₂ = 2 by using air as an oxidant at 1 atm and 800 °C. Support basicity greatly influenced the H₂/CO ratio and carbon deposition. It was found that the lowest carbon deposition occurred on Ni impregnated MgO catalyst. Considering the results, it was found that Ni/MgO catalyst with 10% Ni content would be the best catalyst amongst Ni/Al₂O₃, Ni/MgO/Al₂O₃, Ni/MgAl₂O₄ and Ni/Sorbacid for the CPOM only under more reductive conditions. Under optimum conditions, Ni/MgO showed poor performance and therefore Ni/Sorbacid would be the ideal catalyst because of its greater carbon resistance than the other catalysts.     

Toluene steam reforming over nickel based catalysts

Steam reforming of toluene (SRT) has been studied initially in eight nickel-based catalysts where nickel (10 wt%) was incorporated in different supports (olivine, Al2O3, MgO, LDH, ZrO₂, CeO₂ and natural sepiolite) by the incipient wetness impregnation method. Among them, nickel catalyst based on sepiolite exhibited a promising catalytic performance, with a high conversion of toluene (16%), high selectivity to hydrogen (68.4%) and low production of undesired by-products (CO, CH₄, ethylene and benzene) at low temperature (500 °C). On the other hand, the incorporation of Ni in the sepiolitic material by precipitation (PP) has been considered as alternative method to the incipient wetness impregnation method (IWI). PP method allowed to prepare a Ni-based catalyst with a very high activity (conversion of toluene ~100%), high selectivity to hydrogen (73%) and lower production of undesirable by-products (5% CO, 2% CH₄ and 0% C₆H₆) at 575 °C. In addition, catalytic deactivation due to coke deposition and nickel sinterization was clearly lower for the catalyst synthesized by PP. Characterization by different physicochemical techniques (XRD, TEM, BET surface area, ICP-OES, TPR and EA) showed that PP method allowed to obtain a sepiolite-based catalyst containing Ni with larger external surface area and smaller, highly dispersed and easily reducible Ni metal particles. The results here discussed show that the Ni incorporation method has a clear influence in the preparation of nickel catalyst supported on sepiolite with improved catalytic performance in the steam reforming of toluene.     

Cu,Mg and Co effect on nickel-ceria supported catalysts for ethanol steam reforming reaction

Ethanol steam reforming is a promising reaction which produces hydrogen from bio and synthetic ethanol. In this study, the nano-structured Ni-based bimetallic supported catalysts containing Cu, Co and Mg were synthesized through impregnation method and characterized by XRD, BET, SEM, TPR and TPD analysis. The prepared catalysts were tested in steam reforming of ethanol in the S/C = 6, GHSV of 20,000 mL/(g_cat h) at the temperature range of 450–600 °C. Among the xNi/CeO₂ (x = 10, 13, 15 wt%) catalyst, the sample containing 13 wt% Ni with surface area of 64 m²/g showed the best performance with 89% ethanol conversion and 71% H₂ selectivity as well as low CO selectivity of 8% at 600 °C and The addition of Cu, Mg, and Co to catalyst structure were evaluated and it was found that the nature of second metal has a strong influence on the catalyst selectivity for H₂ production. Considering to results of TPR analysis, the 13Ni–4Cu/CeO₂ catalyst showed proper reduction which caused in better activity. On the other side based on TPD analysis, the more basic property of 13Ni–4Mg/CeO₂ bimetallic catalyst provided a better condition to methane steam reforming, leading to lower CH₄ selectivity and consequently more H₂ production. The 13Ni–4Cu/CeO₂ exhibited the highest activity and lowest selectivity towards ethanol conversion and CO production about 99% and 4%, while the 13Ni–4Mg/CeO₂ catalyst possessed the highest H₂ selectivity and lowest CH₄ selectivity about 74% and 1% respectively at 600 °C. The Ni–Cu and Ni–Mg bimetallic catalysts shows good stability with time on stream.     

Coal char supported Ni catalysts prepared for CO2 methanation by hydrogenation

Catalytic CO₂ methanation is a potential solution for conversion of CO₂ into valuable products, and the catalyst plays a crucial role on the CO₂ conversion and CH₄ selectivity. However, some details involved in the CO₂ methanation over the carbon supported Ni catalysts are not yet fully understood. In this work, commercial coal char (CC) supported Ni catalysts were designed and prepared by two different methods (impregnation-thermal treatment method and thermal treatment-impregnation method) for CO₂ methanation. Effects of the preparation conditions (including the thermal treatment temperature and time, the mass ratio of CC:Ni and the preparation method), as well as the reaction temperature of CO₂ methanation, were investigated on the catalyst morphology, reducibility, structure and catalytic performance. Fibrous Ni-CC catalyst is achieved and shows high CO₂ conversion (72.9%–100%) and CH₄ selectivity (>99.0%) during the 600-min methanation process. Adverse changes of the catalyst surface and textural properties, reducibility, particle size and morphology are the potential factors leading to the catalyst deactivation, and possible solutions resistant to the deactivation were analyzed and discussed. The CO₂ methanation mechanism with the CO route was proposed based on the oxidation-reduction cycle of Ni in this work.     

Hydrogen-rich gas production from ethanol steam reforming over Ni/Ga/Mg/Zeolite Y catalysts at mild temperature

In order to reduce the coke formation over a conventional Ni/γ-Al₂O₄ catalyst and increase the activity at low temperature, we used the impregnation approach to synthesize MgO (30.0 wt.%)/Zeolite Y catalysts loaded with bimetallic Ni(10.0 wt.%)/Ga(10.0–30.0 wt.%) and study the steam-reforming reactions of ethanol. The Ga-loaded catalyst impregnated between the Ni and Mg components exhibits significantly higher reforming reactivity compared to the conventional Ni/Mg/Zeolite Y catalyst. The main products from steam reforming over the Ni/Ga/Mg/Zeolite Y catalyst are only H₂ and CH₄ at above 550 °C, and the catalytic performances differ according to the amount of Ga. The H₂ production and ethanol conversion are maximized at 87% and 100%, respectively, over Ni(10)/Ga(30)/Mg(30)/Zeolite Y at 700 °C for 1 h at CH₃CH₂OH:H₂O = 1:3 and a gas hourly space velocity (GHSV) of 6740 h⁻¹, and the high performance is maintained for up to 59 h.     

Ordered mesoporous MgO–Al2O3 composite oxides supported Ni based catalysts for CO2 reforming of CH4: Effects of basic modifier and mesopore structure

A series of ordered mesoporous MgO–Al₂O₃ composite oxides with various Mg containing were facilely synthesized via one-pot evaporation induced self-assembly strategy. These materials with advantageous structural properties and superior thermal stabilities were used as the supports of Ni based catalysts for CO₂ reforming of CH₄. These mesoporous catalysts behaved both high catalytic activities and long term stabilities toward this reaction. The effects of the mesopore structure and MgO basic modifier on catalytic performances were carefully studied. Specifically, their mesoporous frameworks could accommodate the gaseous reactants with more “accessible” Ni active centers; the “confinement effect” of the mesopores would effectively suppress the thermal sintering of the Ni nanoparticles; the modified MgO basic sites would enhance the chemisorption and activation of CO₂. Consequently, the catalytic activities and stabilities of these catalysts were greatly promoted. Therefore, the present materials were considered as promising catalyst supports for CO₂ reforming of CH₄.     

Ni–Fe/Mg(Al)O alloy catalyst for carbon dioxide reforming of methane: Influence of reduction temperature and Ni–Fe alloying on coking

Various Ni–Fe/Mg(Al)O alloy catalysts were obtained by calcination of Ni–Fe–Mg–Al hydrotalcite-like compounds, followed by reduction at different temperatures (973–1173 K). The characterizations of XRD and STEM-EDX suggest that the resulting Ni–Fe alloy particles are composition-uniform and size-controllable. The alloy composition is little affected by the reduction temperature, whereas the particle size (5.8–8.2 nm) increases with the increase of reduction temperature. This property is ascribed to the homogeneous distribution of nickel and iron species during the catalyst preparation. All of the Ni–Fe/Mg(Al)O alloy catalysts show relatively high and stable activity for CH₄–CO₂ reforming during 25 h of investigation at 773–1073 K. Particularly, the 973 K-reduced catalyst exhibits higher coke-resistance due to its smaller particle size. E_a-CH₄ and CH₄-TPSR measurements indicate that Ni–Fe alloying inhibits CH₄ dissociation. It is considered that during DRM CH₄ is dissociated at the Ni sites and CO₂ may be activated at the metal-support interface as well as the Fe sites. Ni–Fe alloying may inhibit CH₄ dissociation and/or promote CO₂ activation, thus contributing to the suppression of coke deposition.     

Biogas reforming for hydrogen production over nickel and cobalt bimetallic catalysts

Ni/Co bimetallic catalysts supported by commercial γ-Al₂O₃ modified with La₂O₃ for biogas reforming were prepared by conventional incipient wetness impregnation. The catalysts were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), BET surface area and porosity analysis (BET), H₂ temperature-programmed reduction (H₂-TPR), transmission electron microscopy (TEM) and thermogravimetry coupled to differential scanning calorimetry (TG–DSC). XRD and XPS analysis revealed that a Ni/Co alloy was formed in the bimetallic catalysts. The Ni/Co ratio could be adjusted to improve pore textural properties, which enhanced the metal particle dispersion and resulted in smaller metal particle size, and thus increased the catalytic activity and resistance to carbon deposition. The activity and stability of the catalysts for biogas reforming was tested at 800 °C, ambient pressure, GHSV of 6000 ml g_cat⁻¹ h⁻¹ and a CH₄/CO₂ molar ratio of 1 without dilute gas. Experimental results showed that the catalytic activity could be closely related to the Ni/Co ratio. The bimetallic catalyst 7Ni3Co/LaAl exhibited better catalytic and anti-coking performance due to smaller metal particles, higher metal dispersion, uniform pore distribution, surface enrichment of Co, as well as the synergetic effect between Ni and Co. During a 290 h stability test over the catalyst 7Ni3Co/LaAl, the average conversion of CH₄ and CO₂, selectivity to H₂ and CO, and ratio of H₂/CO were 93.7%, 94.0%, 94.9%, 97.8%, and 0.97, respectively. The average coking rate was 0.0946 mg g_cat⁻¹ h⁻¹.     

Plasma-assisted CO2 reforming of methane over Ni-based catalysts: Promoting role of Ag and Sn secondary metals

Carbon dioxide (CO₂) and methane (CH₄) are the primary greenhouse gases (GHGs) that drive global climate change. CO₂ reforming of CH₄ or dry reforming of CH₄ (DRM) is used for the simultaneous conversion of CO₂ and CH₄ into syngas and higher hydrocarbons. In this study, DRM was investigated using Ag–Ni/Al₂O₃ packing and Sn–Ni/Al₂O₃ packing in a parallel plate dielectric barrier discharge (DBD) reactor. The performance of the DBD reactor was significantly enhanced when applying Ag–Ni/Al₂O₃ and Sn–Ni/Al₂O₃ due to the relatively high electrical conductivity of Ag and Sn as well as their anti-coke performances. Using Ag–Ni/Al₂O₃ consisting of 1.5 wt% Ag and 5 wt% Ni/Al₂O₃ as the catalyst in the DBD reactor, 19% CH₄ conversion, 21% CO₂ conversion, 60% H₂ selectivity, 81% CO selectivity, energy efficiency of 7.9% and 0.74% (by mole) coke formation were achieved. In addition, using Sn–Ni/Al₂O₃, consisting of 0.5 wt% Sn and 5 wt% Ni/Al₂O₃, 15% CH₄ conversion, 19% CO₂ conversion, 64% H₂ selectivity, 70% CO selectivity, energy efficiency of 6.0%, and 2.1% (by mole) coke formation were achieved. Sn enhanced the reactant conversions and energy efficiency, and resulted in a reduction in coke formation; these results are comparable to that achieved when using the noble metal Ag. The decrease in the formation of coke could be correlated to the increase in the CO selectivity of the catalyst. Good dispersion of the secondary metals on Ni was found to be an important factor for the observed increases in the catalyst surface area and catalytic activities. Furthermore, the stability of the catalytic reactions was investigated for 1800 min over the 0.5 wt% Ag-5 wt% Ni/Al₂O₃ and 0.5 wt% Sn-5 wt% Ni/Al₂O₃ catalysts. The results showed an increase in the reactant conversions with an increase in the reaction time.     

Preparation of high surface area Ni/MgAl2O4 nanocatalysts for CO selective methanation

Methanation of carbon monoxide in the H₂-rich gas stream was performed on a series of the Ni/MgAl₂O₄ catalysts in a fixed bed micro-reactor. The catalysts were synthesized using wetness impregnation method and the prepared samples were characterized by XRD, BET, SEM, TEM, H₂-TPR, CO chemisorption and CO-TPD techniques. The catalyst carrier was prepared by a novel sol-gel method using nitrate salts precursors and propylene oxide as a gelation agent. MgAl₂O₄ as catalyst carrier possessed a high BET area of 340 m² g^?1 with high pore volume (0.563 cc g^?1) and small pore size (6.56 nm). The catalysts also showed high BET area, which decreased with the increase in Ni content. These catalysts exhibited mesoporous structure with average nickel crystal size smaller than 20 nm. The catalyst with Ni content of 25 wt% exhibited the maximum CO conversion and CH₄ selectivity and can be considered as a catalyst with high catalytic potential for the selective methanation of carbon monoxide.     

Production of renewable hydrogen through aqueous-phase reforming of glycerol over Ni/Al2O3MgO nano-catalyst

In this study, a series of Ni nano-catalysts supported on Al₂O₃ and MgO were prepared through the co-precipitation technique. Effects of the Al/Mg ratio on physicochemical characteristics of Ni/Al₂O₃MgO catalysts were examined. Moreover, catalytic performance was investigated in order to determine the optimum catalyst for H₂ production in aqueous phase reforming (APR) of glycerol. It was revealed that, the APR activity of synthesized catalysts strongly depended on the aforementioned ratio. In addition, it was observed that, the catalytic activity of Ni/MgO and Ni/Al₂O₃ samples were both lower than that of the corresponding mixed oxide supports. Furthermore, it was shown that, amongst the compositionally different prepared mixed oxide materials, the respective catalytic activities increased through enhancing of the Al/Mg ratio. It was demonstrated that the Ni/Al₂Mg₁ catalyst possessed highest catalytic activity of 92% glycerol conversion and selectivity towards hydrogen production of 76%. Ultimately, it was concluded that, the APR activity lowered in the following order: Ni/Al₂Mg₁ > Ni/Al₁Mg₁ > Ni/Al₁Mg₂ > Ni/Al > Ni/Mg for the understudied synthesized materials.     

Hydrogen production from CH4 dry reforming over Sc promoted Ni / MCM-41

The activity of Ni supported on MCM-41 catalyst with/without scandium promoter was investigated for hydrogen production. The performance of the catalysts with different Sc loadings (0.00, 0.10, 0.25, 0.50, 0.75, 1.00 and 3.00 wt%) was examined. N₂ adsorption-desorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for the characterization of the catalytic materials. The prepared catalysts were tested in dry reforming of methane. The effect of Sc addition on activity, hydrogen yield, H₂/CO ratio and stability are discussed. CH₄ and CO₂ conversions were measured under atmospheric pressure at 800 °C. Low Sc loading (<0.75 wt%) showed a positive effect on H₂ yield, CH₄ and CO₂ conversions. Addition of Sc strengthened the interaction of Ni with support and also increased the basicity which in turn affected the amount of CO₂ adsorbed on the surface of the catalyst. Notably, promoting with Sc almost suppressed the carbon formation leading to outstanding catalytic stability; thus 17% carbon deposition reduction was attained. The effect of different reaction temperatures, GHSV and CH₄:CO₂ ratio was also investigated.     

Metal precursor impregnation sequence effect on the structure and performance of NiCo/MgO catalyst

The influence of metal precursor impregnation sequence has been analyzed in terms of catalytic activity and stability of NiCo/MgO catalysts for coke oven gas reforming of carbon dioxide. It is found that the metal precursor impregnation sequence overwhelmingly affected the interaction among Ni, Co and MgO and resulted in different CO₂ sorption capacity. Compared to the catalysts prepared by first Ni precursor impregnation (Co/Ni/MgO) or by simultaneous Ni and Co precursor impregnation (NiCo/MgO), the catalysts prepared by first Co precursor impregnation (Ni/Co/MgO) obtained a stronger interaction among Ni, Co and MgO, leading to strong CO₂ adsorption, smaller Ni particle size (9.6 nm), higher metal dispersion (10.6%), lower carbon deposition (1.5 wt%) and finally resulted in a superior catalytic activity and stability for coke oven gas reforming of carbon dioxide (CH₄ and CO₂ conversion were 55 ± 1% and 80 ± 2%, respectively). We also proposed a model for the effect of metal precursor impregnation sequence on the particle distribution of Ni and Co in NiCo/MgO catalyst.     

Hydrogen production from the gasification of lignin with nickel catalysts in supercritical water

Hydrogen production from the gasification of lignin with Ni/MgO catalysts in supercritical water was conducted using stainless steel tube bomb reactor. Ni/MgO catalysts were prepared by impregnation method and were calcined at 773–1173 K in air for 8 h. The results of characterization for reduced Ni/MgO catalysts showed that Ni metal and NiO–MgO phase are formed after the reduction of calcined catalyst by _H2${\mathrm{H}}_2$. Furthermore, Ni metal surface area, which was calculated by CO chemical adsorption technique, decreased with increase in calcination temperatures. It was found that the carbon yield of gas products was increased with increase in Ni metal surface area except 10 wt% Ni/MgO (773 K) catalyst. Thus, it can be supposed that there is an optimal Ni particle size for the gasification of lignin in supercritical water. It should be noted that 10 wt% Ni/MgO (873 K) catalyst showed the best catalytic performance (carbon yield 30%) under reaction condition tested. It was concluded that Ni/MgO catalyst is a promising system for the gasification of lignin in supercritical water.     

Current advances in syngas (CO + H2) production through bi-reforming of methane using various catalysts: A review

Today, bi - reforming of methane is considered as an emerging replacement for the generation of high-grade synthesis gas (H₂:CO = 2.0), and also as an encouraging renewable energy substitute for fossil fuel resources. For achieving high conversion levels of CH₄, H₂O, and CO₂ in this process, appropriate operation variables such as pressure, temperature and molar feed constitution are prerequisites for the high yield of synthesis gas. One of the biggest stumbling blocks for the methane reforming reaction is the sudden deactivation of catalysts, which is attributed to the sintering and coke formation on active sites. Consequently, it is worthwhile to choose promising catalysts that demonstrate excellent stability, high activity and selectivity during the production of syngas. This review describes the characterisation and synthesis of various catalysts used in the bi-reforming process, such as Ni-based catalysts with MgO, MgO–Al₂O₃, ZrO_2, CeO₂, SiO₂ as catalytic supports. In summary, the addition of a Ni/SBA-15 catalyst showed greater catalytic reactivity than nickel celites; however, both samples deactivated strongly on stream. Ce-promoted catalysts were more found to more favourable than Ni/MgAl₂O₄ catalyst alone in the bi-reforming reaction due to their inherent capability of removing amorphous coke from the catalyst surface. Also, Lanthanum promoted catalysts exhibited greater nickel dispersion than Ni/MgAl₂O₄ catalyst due to enhanced interaction between the metal and support. Furthermore, La₂O₃ addition was found to improve the selectivity, activity, sintering and coking resistance of Ni implanted within SiO₂. Non-noble metal-based carbide catalysts were considered to be active and stable catalysts for bi-reforming reactions. Interestingly, a five-fold increase in the coking resistance of the nickel catalyst with Al₂O₃ support was observed with incorporation of Cr, La₂O₃ and Ba for a continuous reaction time of 140 h. Bi-reforming for 200 h with Ni-γAl₂O₃ catalyst promoted 98.3% conversion of CH₄ and CO₂ conversion of around 82.4%. Addition of MgO to the Ni catalyst formed stable MgAl₂O₄ spinel phase at high temperatures and was quite effective in preventing coke formation due to enhancement in the basicity on the surface of catalyst. Additionally, the distribution of perovskite oxides over 20 wt % silicon carbide-modified with aluminium oxide supports promoted catalytic activity. NdCOO₃ catalysts were found to be promising candidates for longer bi-reforming operations.     

Simulative optimization of catalyst configuration for biogas dry reforming

Biogas dry reforming is a promising technology for converting biomass into high-value products and reducing greenhouse gas emissions. Recent improvements to biogas reforming have mainly focused on the preparation of functional catalysts; however, little attention has been paid to the effects of catalyst configuration in plug flow reactors. In this study, a Ni/MgO catalyst for biogas reforming was synthesized via the wet impregnation method. Parameters were optimized using an experimental rig and then simulations were performed using an Aspen HYSYS reaction simulator. We simulated loading the same amount of catalyst into 1, 2, 3, or 10 zones inside the reactor and compared performance parameters, including H₂ yield, CO yield, CH₄ conversion, and CO₂ conversion. The results of simulations showed that a 2-zone configuration with a catalyst ratio of 1:4 was optimal, with 88.2% H₂ yield, 83.5% CO yield, 96.4% CH₄ conversion, and 91.7% CO₂ conversion. Catalyst zone number, catalyst distribution, and catalyst zone position all had significant effects on catalytic behavior. The findings of this study provide new insights into the processes of biogas reforming and other heterogeneous catalysis reactions.     

Dynamic hydrogen production from ethanol steam‐reforming reaction on NixMoy/SBA‐15 catalytic system

This study examined the effects of advanced bimetallic catalytic species of Ni and Mo on hydrogen production from ethanol steam reforming. Ni_xMo_y/SBA‐15 exhibited significantly higher ethanol steam‐reforming activity at mild temperatures than monometallic Ni/SBA‐15; the highest activity was achieved using the Ni_0.95Mo_0.05/SBA‐15 catalyst. H₂ production and ethanol conversion were maximized at 70–87% and 90–92%, respectively, over the temperature range of 500 to 800 °C with an EtOH : H₂O ratio of 1:3 and a gas hourly space velocity of 3000 h^?1. This highlights the synergy between the Ni and Mo loading on SBA‐15 during ethanol steam reforming through the inhibition of Ni particle agglomeration and the consequent decrease in catalytic deactivation. In the proposed mechanism for ethanol steam reforming, Mo oxide promotes CH₄‐steam reforming at lower temperatures and depresses the CO‐water gas shift reaction. Overall, hydrogen production is significantly higher over Ni_xMo_y/SBA‐15 than over monometallic Ni/SBA‐15 despite the evolution of CO gas. Copyright © 2014 John Wiley & Sons, Ltd.     

Reforming of bioethanol over Ni/Al2O3 and Ni/CeZrO2/Al2O3 catalysts in supercritical water for hydrogen production

Bioethanol was reformed in supercritical water (SCW) at 500 °C and 25 MPa on Ni/Al₂O₃ and Ni/CeZrO₂/Al₂O₃ catalysts to produce high-pressure hydrogen. The results were compared with non-catalytic reactions. Under supercritical water and in a non-catalytic environment, ethanol was reformed to H₂, CO₂ and CH₄ with small amounts of CO and C2 gas and liquid products. The presence of either Ni/Al₂O₃ or Ni/CeZrO₂/Al₂O₃ promoted reactions of ethanol reforming, dehydrogenation and decomposition. Acetaldehyde produced from the decomposition of ethanol was completely decomposed into CH₄ and CO, which underwent a further water-gas shift reaction in SCW. This led to great increases in ethanol conversion and H₂ yield on the catalysts of more than 3-4 times than that of the non-catalytic condition. For the catalytic operation, adding small amounts of oxygen at oxygen to ethanol molar ratio of 0.06 into the feed improved ethanol conversion, at the expense of some H₂ oxidized to water, resulting in a slightly lower H₂ yield. The ceria-zirconia promoted catalyst was more active than the unpromoted catalyst. On the promoted catalyst, complete ethanol conversion was achieved and no coke formation was found. The ceria-zirconia promoter has important roles in improving the decomposition of acetaldehyde, the enhancement of the water-gas shift as well as the methanation reactions to give an extremely low CO yield and a tremendously high H₂/CO ratio. The SCW environment for ethanol reforming caused the transformation of gamma-alumina towards the corundum phase of the alumina support in the Ni/Al₂O₃ catalyst, but this transformation was slowed down by the presence of the ceria-zirconia promoter.