Design of Ni/La2O3 catalysts for dry reforming of methane: Understanding the impact of synthesis methods

Fine-tuning of materials properties, particularly the catalytic properties, through innovative synthesis procedures has gained an increased research interest in the last decades. It is well known that synthesis procedures have considerable impact on the physio-chemical properties of the synthesized materials even if the chemical composition is maintained. Herein, we investigated the impact of selected synthesis methods on the catalytic performance of Ni/La₂O₃ for the dry reforming of methane (DRM), a challenging reaction known for severe coking. Although this catalyst has been frequently studied for DRM, however, tuning the structure-activity relationship by varying the synthesis routes has not been reported. Herein, the chosen synthesis techniques; for example the solution combustion synthesis (Ni/La-SC), sol-gel (Ni/La-SG), homogeneous precipitation (Ni/La-HP), solvothermal (Ni/La-ST), and modified oleylamine-assisted synthesis (Ni/La-ME); considerably affected the morphology, metal support interaction (MSI), and surface area of Ni/La₂O₃ catalysts leading to variation in their performance for DRM. The investigated catalysts were thoroughly characterized by using SEM-EDX, TEM, N₂-physisorption, XRD, XPS, and H₂-TPR to understand the structural properties. Their catalytic performance towards the DRM was evaluated by varying the temperature between 550 and 800 °C. DRM experiments demonstrated that among the studied catalysts, Ni/La-SC showed the best performance for DRM with a high catalytic activity and coking resistance. For instance, Ni/La-SC revealed the highest CO₂ and CH₄ conversions i.e. 97.9 ± 1.5% and 96.6 ± 1.8%, respectively at 800 °C. The same sample revealed the highest hydrogen yield i.e. 71.9% and the highest H₂/CO ratio i.e. 1.03 ± 0.013 at the same temperature. The results revealed that Ni/La-SC demonstrated the lowest increment (20.9%) in the Ni crystallite size after DRM reaction, highest durability, and the lowest rate of coke formation (42 ± 5.2 mg C/g_catalyst) over an operating period of 100 h at 800 °C. The outstanding performance of Ni/La-SC catalyst was credited to the small crystallite size of Ni, high Ni⁰/Ni²⁺ ratio, high BET area, and a good dispersion of nickel sites over the La₂O₃ support. The obtained results may open new frontiers for size and shape-controlled synthesis of nanostructured metals/metal oxides catalysts with controllable morphologies and dispersion that can lead to desirable catalytic properties.     

Effect of mineralizers for preparing ZrO2 support on the supported Ni catalyst for steam-CO2 bi-reforming of methane

Supported Ni catalysts on ZrO₂ towards steam-CO₂ bi-reforming (SCBR) of methane for the production of synthesis gas were synthesized by the hydrothermal process with different mineralizers followed by l-arginine ligand-assisted incipient wetness impregnation (HT-LA-IWI) method. The effect of type and amount of mineralizers for preparing ZrO₂ supports on the nature of supports and supported Ni catalysts, as well as on the catalytic properties and structure–performance relationship were investigated. Results show that the catalytic performance is strongly dependent on the morphology and textural of ZrO₂ support notably affected by the type and amount of mineralizer. The supported Ni catalyst on the ZrO₂ prepared by using sodium acetate (molar ratio of sodium acetate/zirconium, N_SAc/Zr = 0.5) as mineralizer (Ni/ZrO₂ (SAc0.5)) shows much higher catalytic activity than the one on ZrO₂ prepared by using sodium carbonate (molar ratio of sodium carbonate/zirconium, N_SC/Zr = 0.5) as a mineralizer (Ni/ZrO₂ (SC0.5)), ascribed to higher Ni dispersion and smaller average crystallite size of Ni. With respect to both activity and stability, the sodium acetate can be selected as a suitable mineralizer for the preparation of excellent ZrO₂ support. Furthermore, the increasing N_SAc/Zr from 0.5 to 2.0 leads to an increase in surface area but a decrease in pore diameter and pore volume, which endows the Ni/ZrO₂ (SAc2.0) catalyst with much larger average crystallite size of Ni but much worse Ni dispersion than Ni/ZrO₂ (SAc0.5). As a result, Ni/ZrO₂ (SAc2.0) shows much lower catalytic activity than Ni/ZrO₂ (SAc0.5). Moreover, the Ni/ZrO₂ (SAc2.0) catalyst shows worse Ni sintering resistance than Ni/ZrO₂ (SAc0.5) owing to its weaker NiZrO₂ interaction confirmed by H₂-TPR results, which endows it with lower catalytic stability although it has higher coke deposition resistance.     

Carbon dioxide reforming of methane over nickel catalysts supported on TiO2(001) nanosheets

As we all know, the critical problem of nickel catalysts for carbon dioxide reforming of methane is the deactivation of catalysts due to the carbon deposition and sintering of the active components under high temperature. It was reported that anatase TiO₂ nanosheets with high-energy (001) facets had strong interaction with nickel, which was probably beneficial to resist sintering of nickel nanoparticles and to eliminate deposited carbon via oxygen migration. In this study, Ni nanoparticles were supported on TiO2 nanosheets with exposed high-energy (001) facets. The Ni/TiO₂(001) catalysts were characterized by means of X-ray diffraction, transmission electron microscopy, physisorption of N₂, X-ray photoelectron spectroscopy and H₂ temperature-programmed reduction, and the spent catalysts were characterized by Roman and thermogravimetry analysis. The catalytic performance of Ni/TiO₂(001) catalysts were measured for carbon dioxide reforming of methane reaction. It was found that the prepared Ni/TiO₂(001) catalysts showed reasonably higher catalytic activity and stability compared with the nickel catalyst supported on commercial titanium oxide (P25). The high dispersion of nickel nanoparticles of Ni/TiO₂(001) catalysts was helpful to the resistance towards carbon deposition and the strong metal-support interaction was helpful to the resistance towards nickel sintering on account of the unusual surface properties of TiO₂(001).     

Diesel pre-reforming over highly dispersed nano-sized Ni catalysts supported on MgO–Al2O3 mixed oxides

A highly dispersed 50 wt% Ni/MgO–Al₂O₃ catalyst was prepared by deposition–precipitation (DP) method for the diesel pre-reforming reaction. The pH of the precursor solution was controlled from pH 9.5 to 12.0 to examine the effects on NiO crystallite size and metal dispersion. The increase of pH of the precursor solution causes an increase of specific surface area and metal dispersion, and reduces NiO crystallite size. The pre-reforming reaction was carried out using n-tetradecane as surrogate compound of diesel. The coke formation of used catalysts was examined by TGA, TEM, SEM, and Raman analysis. The 50 wt% Ni/MgO–Al₂O₃ catalyst prepared at pH 11.5 showed a high catalytic activity and excellent coke resistance due to high metal dispersion (8.71%), small NiO crystallite size (3.5 nm), and strong interaction between Ni and support. Furthermore, this catalyst showed a good stability in the pre-reforming reaction at S/C ratio of 3.5 and 450 °C for 88 h.     

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.     

Effects of magnesium and chromium addition on stability,activity and structure of copper-based methanol synthesis catalysts

Cu/ZnO/Al₂O₃-based catalysts for methanol synthesis are prepared through co-precipitation by addition of Mg and Cr. Precursors are characterized by XRD and Air-TGA. Catalysts, calcined at 450 °C, are examined by XRD and BET. Reduction characteristics of the catalysts are analyzed via H₂-TPR and H₂-TGA. Surface acidity of the catalysts is determined by TPAD-TGA. Addition of Mg and Cr causes formation of smaller CuO crystallite size, and increases surface area of catalysts by improving dispersion of CuO. Cr also improves stability of the catalysts against ambient conditions and prolongs their shelf life. The catalyst containing 6.4 mol % Cr has a methanol selectivity of 83.5% and a catalytic activity of 14.2 g methanol production which is the highest among other synthesized catalysts. High Cr loadings (32 mol %) reduce the catalytic activity. Cr containing catalysts continue to produce the highest amounts of methanol as compared with the catalysts without Cr where Cr prevents deactivation and sintering.     

H2-rich syngas production from biogas reforming: Overcoming coking and sintering using bimetallic Ni-based catalysts

Dry reforming of methane is a very appealing catalytic route biogas (mainly composed by greenhouse gases: carbon dioxide and methane) conversion into added value syngas, which could be further upgraded to produce liquid fuels and added value chemicals. However, the major culprits of this reaction are coking and active phase sintering that result in catalysts deactivation. Herein we have developed a highly stable bimetallic Ni–Rh catalyst supported on mixed CeO₂–Al₂O₃ oxide using low-noble metal loadings. The addition of small amounts of rhodium to nickel catalysts prevents coke formation and improves sintering resistance, achieving high conversions over extended reaction times hence resulting in promising catalysts for biogas upgrading.     

Metal oxide (MgO,CaO, and La2O3) promoted Ni-Ce0.8Zr0.2O2 catalysts for H2 and CO production from two major greenhouse gases

The metal oxide (MgO, CaO, and La₂O₃) promoted Ni-Ce_0.8Zr_0.2O₂ catalysts have been applied for carbon dioxide reforming of methane (CDR) reaction and investigated the coke formation and sintering phenomenon in used catalysts. The Ni-MgO-Ce_0.8Zr_0.2O₂ catalyst exhibits high activity and stability at a very high gas hourly space velocity of 480,000 h⁻¹, resulting from high resistance to coke formation and Ni sintering. This is mainly due to small Ni crystallite size, strong basicity of MgO, and an intimate interaction between Ni and MgO.     

Glycerol steam reforming on supported Ru-based catalysts for hydrogen production for fuel cells

Glycerol steam reforming on Ru and Ru–Me (Me = Fe, Co, Ni, and Mo) catalysts supported on yttria, ceria–zirconia, and γ-alumina is studied at high temperatures for the production of hydrogen for fuel cell applications. The nature of the support notably affects the catalytic properties of these catalysts resulting in significant enhancements of the H₂ production turnover rate and product selectivity on the reducible yttria and ceria–zirconia supported Ru-based catalysts via facilitation of the water–gas shift reaction. The acidic γ-alumina supported Ru-based catalysts demonstrate a low H₂ production turnover rate with a high CO product selectivity and also favor the formation of C₁–C₂ hydrocarbons. Differently, the promotion effects due to Fe, Co, Ni, and Mo on the bimetallic Ru–Me catalysts are limited with only small increases in the glycerol conversion turnover rate for the Ru–Ni, Ru–Mo, and Ru–Co catalysts. The alumina supported Ru-based catalysts are deactivated by a significant extent with increasing on-stream time due to coking. The carbon deposition is insignificant on the yttria and ceria-zirconia supported catalysts, but moderate deactivation occurs due to sintering of the dispersed metal clusters. Influenced by the surface MoO_x species that hamper sintering of the surface metal clusters and by the Y₂O₃ support that prevents coking on the catalyst, the Ru–Mo/Y₂O₃ catalysts exhibit superior catalytic stability against deactivation.     

Hollow hierarchical Ni/MgO-SiO2 catalyst with high activity,thermal stability and coking resistance for catalytic dry reforming of methane

The methane dry reforming (DRM) simultaneously converts the two greenhouse gases and produces syngas (CO + H₂), which is being significant for both environmental and industrial consideration. Employing well-defined crystal oxides as precursors can produce Ni-based DRM catalysts with good sintering and coking resistance by enhancing the metal-support interactions. Adding basic promoters also is considered as an effective way to improve the coking resistance of DRM catalysts, although challenge remains in the control over the structure, morphology and interaction of the promoter in the catalyst. To well combine the two methods together for better catalytic performance, in this work a Ni/MgO-SiO₂ catalyst was synthesized through a facile one-pot hydrothermal process, during which Ni-phyllosilicate formed as the precursor of Ni particles and MgO promoter was generated in form of Mg-phyllosilicate. This Ni/MgO-SiO₂ had a hierarchical hollow sphere structure with large surface area (477.4 m²/g). Both the Ni particles (avg. 6.0 nm) and MgO promoter uniformly distributed. This hollow hierarchical catalyst performed high activity, thermal stability and coking resistance for catalytic dry reforming of methane.     

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.     

TiO2 and ZrO2 supported Ru catalysts for CO mitigation following the water-gas shift reaction

CO oxidation and methanation over Ru-TiO₂ and Ru-ZrO₂ catalysts were investigated for CO removal for applications in proton exchange membrane fuel cells. The catalysts were synthesised by the deposition precipitation method at a pH of 7–7.5 for better interactions between the support and the active Ru metal. Various characterization experiments such as TPR, XPS, FTIR-CO, CO chemisorption and HRTEM were conducted to better understand the physio-chemical properties of Ru on the supports. Both catalysts showed excellent activity for the total oxidation of CO, however, with the addition of H₂, the catalysts activity to CO oxidation decreased significantly. Higher temperatures for the preferential oxidation reaction indicated that the Ru catalysts not only oxidize CO, but hydrogenate it as well. Furthermore, H₂ oxidation was favoured over the catalysts. Hydrogenation of CO over these catalysts gave high CO conversion and selectivity towards CH₄. Both the catalysts showed similar activity across the temperature range screened and gave maximum CO conversions of 99.9% from 240 °C onwards, with 99.9% selectivity towards CH₄. The catalysts also showed good stability in the reaction and the similarities in the catalytic activity of these were attributed to the well-dispersed Ru metal over the supports. The Ru catalysts effectively reduced CO concentrations in the reformate gas to less than 10 ppm, as is required for practical applications.     

Catalytic performance of Ni catalysts for steam reforming of methane at high space velocity

Three Ni-based catalysts, namely Ni/ZrO₂/Al₂O₃, Ni/La-Ca/Al₂O₃ and Ni_0.5Mg_2.5AlO₉ catalysts were prepared, tested and characterized for steam reforming of methane (SRM), especially at high space velocities. Experimental results demonstrated that Ni_0.5Mg_2.5AlO₉ catalysts showed excellent catalytic activity, e.g., the high reaction performance (i.e., activity and stability) at a very short residence time of 20 ms. For the accompanied water gas shift (WGS) reaction with the SRM at the steam to methane ratio of 3:1, the overall hydrogen yield depended on both the CH₄ conversion and the CO₂ selectivity. The results showed that CO₂ selectivity had opposite trend compared with CH₄ conversion in such a short-contact process. Catalyst characterizations by XRD, SEM-EDS, TEM and TGA suggested that the good performance of nickel catalysts was closely related with the good dispersion of the active component. The nano-sized nickel particles in strong interaction with the supports would lead to the good dispersion, thereafter having a slight tendency to sintering, and then to coking.     

Boosting hydrogen production by ethanol steam reforming on cobalt-modified Ni–Al2O3 catalyst

Ethanol steam reforming (ESR) is one of the most promising reliable and recyclable technologies for hydrogen production. However, the development of robust, efficient Ni-based catalysts that minimize metal sintering and carbon deposition remains a key challenge. The influence of cobalt loading and ESR conditions on H₂ selectivity and catalytic stability is the focus of this study. Ni–Co/Al₂O₃ catalysts with various Co percentages were prepared by the co-impregnation method and complementary characterization tests were performed. Among the catalysts tested, Ni–Co/Al₂O₃ (5 wt% Co) exhibited the smallest metal crystallite size, the highest surface area, and the best catalytic performance. Thereafter, the effects of temperature, LHSV and S:C molar ratio were studied. 100% ethanol conversion and maximum H₂ selectivity (95.14%) were reached at 600 °C, 0.05 L/g_cat.h and S:C molar ratio of 12:1. Furthermore, ethanol turnover frequency (TOF) was computed for each catalyst. TOF results showed that the Ni–Co interaction had an impact on the catalytic activity. Finally, Ni2CoAl was subjected to 50-h stability test and only 6.12 mg_carbon/g_cat.h coke deposition was observed.     

The effect of La2O3 and CeO2 modifiers on properties of Ni–Al catalysts for LNG prereforming

Ni/La–Al₂O₃ and Ni/Ce–Al₂O₃ catalysts with a small amount of promoters intended for prereforming of LNG were characterized by XRF, N₂ adsorption-desorption, XRD, H₂ chemisorption, HRTEM and XPS. The catalytic activity was evaluated in methane steam reforming both in the kinetic and diffusion regime, at temperatures characteristic of pre-reforming. Carbonaceous deposit was analysed by TPO-MS method. The nature and location of the coke were studied by HRTEM.La or Ce addition into Ni–Al system causes the increase of the active surface area of Ni by enhancing its dispersion. Studies at kinetic regime have shown that the promoted catalysts have almost twice the activity than reference Ni–Al catalyst. This effect was not confirmed by measurements in the diffusion regime on whole catalyst tablets. Almost identical textural properties of catalysts and diffusive limitations related to them but not the catalytic properties of the material itself appeared to be crucial factors. The presence of La (but not Ce) causes a significant increase in resistance to coking.     

Influence of the supports ZrO2 on selective methanation of CO over the nickel supported catalysts

It is attempted to optimize preparation of ZrO₂ as support of the nickel catalysts for selective methanation of CO in H₂-rich gas (CO-SMET). Therefore, the supports ZrO₂ were prepared at first by thermal decomposition method from zirconium oxynitrate and zirconium oxychloride at the calcination temperature of 400 °C and 800 °C, respectively. It is illustrated that the salt kind and calcination temperature affected phase state (tetragonal, monoclinic), crystallite size and specific surface area (SSA) of the supports. The difference in property of the supports influenced catalytic performance of the catalysts Ni/ZrO₂ for CO-SMET reaction. Especially, the chlorine ion residues in the support ZrO₂ prepared from zirconium oxychloride was beneficial for CO removal selectively. Furthermore, a precipitation method was adopted to prepare ZrO₂ for comparison with the thermal decomposition method with use of the zirconium oxychloride as starting material. It is found that the supports ZrO₂ prepared by the precipitation method induced a better dispersion of metallic Ni on its surface. The catalyst Ni/ZrO₂ with use of the support ZrO₂ prepared by the precipitation method and calcination at 400 °C exhibited a good performance at the reaction temperature of 220 °C in the 100 h durability test, where CO outlet concentration was kept below 10 ppm and the selectivity remained constant at 100%. Relation of Ni crystallite size and chlorine ion residues with the catalytic performance was discussed.     

Structure-dependent activity and stability of Al2O3 supported Rh catalysts for the steam reforming of n-dodecane

Steam reforming of liquid hydrocarbon fuels is an appealing way for the production of hydrogen. In this work, the Rh/Al₂O₃ catalysts with nanorod (NR), nanofiber (NF) and sponge-shaped (SP) alumina supports were successfully designed for the steam reforming of n-dodecane as a surrogate compound for diesel/jet fuels. The catalysts before and after reaction were well characterized by using ICP, XRD, N₂ adsorption, TEM, HAADF-STEM, H₂-TPR, CO chemisorption, NH₃-TPD, CO₂-TPD, XPS, Al²⁷ NMR and TG. The results confirmed that the dispersion and surface structure of Rh species is quite dependent on the enclosed various morphologies. Rh/Al₂O₃-NR possesses highly dispersed, uniform and accessible Rh particles with the highest percentage of surface electron deficient Rh⁰ active species, which due to the unique properties of Al₂O₃ nanorod including high crystallinity, relatively large alumina particle size, thermal stability, and large pore volume and size. As a consequent, Rh/Al₂O₃-NR catalyst exhibited superior catalytic activity towards steam reforming reactions and hydrogen production rate over other two catalysts. Especially, Rh/Al₂O₃-NR catalyst showed the highest hydrogen production rate of 87,600 mmol g_fuel^?1 g_Rh^?1min^?1 among any Rh-based catalysts and other noble metal-based catalysts to date. After long-term reaction, a significant deactivation occurred on Rh/Al₂O₃–NF and Rh/Al₂O₃-SP catalysts, due to aggregation and sintering of Rh metal particles, coke deposition and poor hydrothermal stability of nanofibrous structure. In contrast, the Rh/Al₂O₃-NR catalyst shows excellent reforming stability with negligible coke formation. No significantly sintering and aggregation of the Rh particles is observed after long-term reaction. Such great catalyst stability can be explained by the role of hydrothermal stable nanorod alumina support, which not only provides a unique environment for the stabilization of uniform and small-size Rh particles but also affords strong surface basic sites.     

Effects of Y2O3-modification to Ni/γ-Al2O3 catalysts on autothermal reforming of methane with CO2 to syngas

The effects of Y₂O₃-modification to Ni/γ-Al₂O₃ catalysts on autothermal reforming of methane to syngas were investigated. It was found that the introduction of Y₂O₃ (5%, 8%, 10%) lead to significant improvement in catalytic activity and stability, and the H₂/CO ratio could be adjusted via controlling the O₂/CO₂ ratio of the feed gas. According to the characterization results of catalysts before and after reaction, it was found that the Y₂O₃·γ-Al₂O₃ supported Ni catalysts had higher NiO reducibility, smaller Ni particle size, higher Ni dispersion and stronger basicity than those of the Ni/γ-Al₂O₃ catalysts. The analysis of catalysts after reaction showed that the addition of Y₂O₃ inhibited the Ni sintering, changed the type of coke and decreased the amount of coke on the catalysts. All the experimental results indicated that the introduction of Y₂O₃ to Ni/γ-Al₂O₃ resulted in excellent catalytic performances in autothermal reforming of methane, and Y₂O₃ played important roles in preventing metal sintering and coke deposition via controlling NiO reducibility, Ni particle size and dispersion, and basicity of catalysts.     

Hydrogen production from catalytic steam reforming of biomass pyrolysis oil or bio-oil derivatives: A review

Steam reforming of biomass pyrolysis oil or bio-oil derivatives is one of the attractive approaches for hydrogen production. The current research focused on the development of promising catalysts with favorable catalytic activity and high coke resistance. Noble metal such as Rh has been proven to achieve promising reforming reaction efficiencies. However, Ni has attracted considerable attention owing to its stability, cost effectiveness, and good activity in breaking C–C and C–H bonds. Nevertheless, Ni-based catalysts have serious carbon deposition problems arising from chemical poisoning, metal sintering, and poor metal dispersion. This paper attempted to review the current trends in catalyst development considering the aspects of supports, metals, and promoters as an effort to find possible solutions for the limitations of Ni-based catalysts. The present review also covered the current understanding on the reaction mechanisms as well as the future prospects in the field of steam reforming catalysts.     

The influence of preparation method of char supported metallic Ni catalysts on the catalytic performance for reforming of biomass tar

The char‐supported nickel catalysts prepared by wet impregnation and precipitation‐deposition methods under different nickel loadings and catalytic temperatures for catalytic reforming of rice husk tar were investigated. The influences of preparation methods on the physicochemical properties of catalysts and catalytic activity towards tar conversion and gas yield were studied. The results showed that char‐supported metallic Ni catalysts can be directly used without a reduction process because of carbon thermal reaction during calcination. The preparation method had a significant influence on the porosity and Ni dispersion of catalysts. The addition of Ni to char improved the specific surface area from 60 m² g^?1 to 346.8 m² g^?1 because of activation effect of nickel nitrate on char pore structure. The precipitation‐deposition method produced higher surface area, smaller Ni nanoparticulates with more corner and step sites, as well as more concentrated size distribution than those of wet impregnation method, leading to higher catalytic activity, in terms of high tar conversion efficiency (83%) and increasing syngas yield. The selectivity to phenols and naphthalene for precipitation‐deposited catalysts was strengthened, and the relative content of heavy tars was decreased remarkably. The increasing H₂ yield and concentration were indicative of efficient conversion of macromolecular organic matters into small molecules gases. In addition, the precipitation‐deposited catalyst exhibited weaker Ni sintering after reaction. The catalytic cracking temperature of 800° C and Ni loading of 10 wt% exhibited the best catalytic effects on gas distribution and tar conversion.