Urea-assisted synthesis towards a renewable rice husk silica-derived Ni-phyllosilicate catalyst for CO2 methanation

In this work, nickel phyllosilicate was prepared through the hydrothermal reaction of rice husk-derived silica (SR) and nickel nitrate. Owing to the loss of surface silanol group on SR during the calcination process, a small amount of Ni-phyllosilicate with Ni content of 10.2 wt% was obtained on N₂₂₀/SR, which was prepared under a very severe hydrothermal condition of 220 °C for 48 h. After the addition of urea, the dense flower-like nanosheets attributing to Ni-phyllosilicate were observed on the surface of N₁₈₀/SR-U-24 with high Ni content of 22.6 wt%, which was prepared under a much milder hydrothermal temperature of 180 °C and a shorter reaction time of 24 h. This was because urea could facilitate the formation of an important intermediate (Ni(OH)₂) and leaching of SiO₂, resulting in the quick formation of Ni-phyllosilicate. N₁₈₀/SR-U-24 exhibited both good catalytic activity and high long-term stability for CO₂ methanation due to the relatively high Ni content, fine Ni particles and the strong metal-support interaction derived from Ni-phyllosilicate.     

Green synthesis of MCM-41 derived from renewable biomass and construction of VOx-Modified nickel phyllosilicate catalyst for CO2 methanation

In order to achieve green synthesis of MCM-41 and address the sintering problem of Ni-based catalyst supported on silica material, MCM-41 with regular spherical morphology was prepared using sodium silicate extracted from renewable equisetum fluviatile as silicon source, and then a group of nickel phyllosilicates were synthesized via the reaction of MCM-41 sphere and nickel nitrate under hydrothermal condition. Much denser nanosheets corresponding to lamellar nickel phyllosilicate were formed on the surface of MCM-41 sphere with the raise of hydrothermal temperature in the range of 180–220 °C, resulting in the nickel content varying from 17.2 to 41.8 wt%. Fine Ni particles with size smaller than 6 nm could be obtained on the 750^oC-reduced catalyst owing to the strong nickel-silica interaction derived from Ni-phyllosilicate. After the addition of V₂O₅ promoter, Ni particle size was further reduced to around 4.5 nm at high Ni loading above 30 wt%. Vanadium species was in the mixed valence state of V(III), V(IV) and V(V) after reduction, which increased the electron cloud density of Ni⁰, resulting in high catalytic activity of the VO_x-modified Ni-phyllosilicate catalyst for CO₂ methanation. In a 100 h-400^oC-lifetime test and 600 °C-steam hydrothermal treatment, the VO_x-modified Ni-phyllosilicate catalyst also showed high long-term stability, excellent sintering resistance of metallic nickel particles and high hydrothermal stability due to the strong surface confinement effect of nickel phyllosilicate and promotion of VO_x species. In all, this work provided a green synthesis of MCM-41 as well as an efficient Ni/SiO₂ catalyst derived from nickel phyllosilicate for CO₂ methanation.     

Synthesis of Ni-phyllosilicate assisted by fluoroboric acid for CO2 methanation

How to efficiently prepare nickel phyllosilicate using the calcined biomass-based silica as the sacrificial template under the mild condition is a challenge. In this work, NH₄HF₂, H₂SiF₆ and HBF₄ were used as the assistor to facilitate the synthesis of Ni-phyllosilicate, which could be successfully synthesized under the mild condition of 120 °C for 12 h. Compared with NH₄HF₂ and H₂SiF₆, HBF₄ was the best fluorine-containing assistor. The HBF₄-assisted Ni phyllosilicate catalyst (Ni-Ps/B) exhibited the high CO₂ conversion of 80.0% and CH₄ selectivity of 98.3% at 450 °C due to its small particle size of 3.8 nm, high Ni content of 21.65 wt% as well as enhanced H₂ and CO₂ desorption capacity. The characterization results showed that HBF₄ converted to B₂O₃ after the hydrothermal reaction and thermal treatments, which could not only provide the physical barrier for Ni species during reduction process, but also be a promoter for Ni-Ps/B for CO₂ methanation. In all, HBF₄ was a competitive fluorine-containing assistor for the highly efficient synthesis of Ni-phyllosilicate catalysts.     

Which is the better catalyst for CO2 methanation – Nanotubular or supported Ni-phyllosilicate?

In order to investigate effects of morphology and crystalline phase of different Ni-phyllosilicate catalysts on the catalytic performance for CO₂ methanation, nanotubular Ni-phyllosilicate and MCM-41 supported Ni-phyllosilicate were synthesized through hydrothermal reaction of sodium silicate or MCM-41 with nickel nitrate. On one hand, nanosheets attributing to 2:1 type nickel phyllosilicate (Ni₃Si₄O₁₀(OH)₂·5H₂O) were uniformly grown on the surface of MCM-41 spheres to form the MCM-41 supported Ni-phyllosilicate (Ni/M). On the other hand, 1:1 type Ni-phyllosilicate with nanotubular morphology (Ni/N) was synthesized through the reaction of Na₂SiO₃ and nickel nitrate. After a series of tests and characterizations, it was found that Ni/N exhibited low thermal stability and poor anti-sintering property, leading to poor catalytic activity for CO₂ methanation. On the contrary, Ni/M was very stable, which obtained unchanged morphology and fine Ni particles after 750^oC-reduction, resulting in high catalytic activity and long-term stability for CO₂ methanation. In all, morphology and crystalline phase of Ni-phyllosilicate obviously affected catalytic performance, and the supported Ni-phyllosilicate catalyst was much better than the nanotubular Ni-phyllosilicate for CO₂ methanation in this work.     

Which intermediate is more efficient for Ni-phyllosilicate: Ni(OH)2 or H4SiO4?

Ni(OH)₂ and H₄SiO₄ are the two key intermediates for the synthesis of Ni-phyllosilicate, and the purpose of this work is to reveal which one is more efficient. The silica (D) was extracted from distillers’ grains, which was used as the sacrificial template for Ni-phyllosilicate. The formation of Ni(OH)₂ and H₄SiO₄ was enhanced by NaOH and NH₄F, respectively, and Ni/D-S (assisted by sodium hydroxide) and Ni/D-A (assisted by ammonium fluoride) were obtained. Although the amount of NaOH and NH₄F and hydrothermal synthesis procedures were identical, there was a significant difference of their Ni contents. The Ni content of Ni/D-S and Ni/D-A was 17.7 wt% and 2.5 wt%, respectively. As a result, Ni/D-S was more active for CO₂ methanation, whose CH₄ yield reached 61.6% at 450 °C, 0.1 MPa, 60 L g⁻¹·h⁻¹, while the maximum CH₄ yield of Ni/D-A was only 16.4% at 500 °C. However, the formation of Ni-phyllosilicate could also be improved after addition of more NH₄F, and the increased amount of H₄SiO₄ led to the high Ni content (33.4 wt%) of Ni/D-A-M (M refers to the addition of more ammonium fluoride) and enhanced catalytic performance for CO₂ methanation. It was concluded that Ni(OH)₂ and H₄SiO₄ were both important for the synthesis of Ni-phyllosilicate, while Ni(OH)₂ was the more efficient one.     

One-pot or two-pot synthesis? Using a more facile and efficient method to synthesize Ni-phyllosilicate catalyst derived from 3D-SBA-15

In order to compare the effect of preparation method on the catalytic performance over Ni/3D-SBA-15 catalyst for CO₂ methanation, one-pot and two-pot synthesis strategies were used in this work. 3D-SBA-15-derived Ni-phyllosilicate catalyst could be obtained via a two-pot hydrothermal synthesis using 3D-SBA-15 and nickel nitrate as precursors at 180 °C. This Ni-phyllosilicate catalyst with a monolithic macromorphology and a microcosmic appearance of 3D-networked framework covered by nanosheets, was also achieved via a one-pot hydrothermal method with elimination of the preparation and pretreatment of 3D-SBA-15. The one-pot-synthesized Ni/S–O catalyst not only showed high catalytic activity due to the small-sized Ni particles, but also exhibited excellent anti-sintering property owing to the strong metal-support interaction derived from Ni-phyllosilicate. Compared with the two-pot synthesis, many advantages were observed for one-pot synthesis including monolithic appearance, high convenience, large Ni-phyllosilicate amount and low cost.     

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.     

Preparation of Ni/SiO2 using silicon-rich-biomass as source for acetic acid steam reforming

In this paper, four kinds of silicon-rich biomass (rice husk, rice straw, peanut shell, corncob) were used as raw materials for SiO₂ extraction by heat treatment method. And the extracted SiO₂ was applied to prepare Ni/SiO₂ catalyst for acetic acid (AcOH) steam reforming. Various characterization methods were used to analyze the purity, structure and specific surface area characteristics of SiO₂ extracted from different sources. It was found that the silica prepared by acid washing and calcination (AWC) had larger specific surface area, abundant pore channels and larger pore volume. By water washing and calcination (WWC), K₂O impurity would be remained in SiO₂, which might dissolve SiO₂ during the calcination process, generating an increase in the pore size and a decrease in the specific surface area. While the CaO impurity in SiO₂ promoted the dispersion of the active components and enhanced the interaction between the active component and the carrier. A series of reforming catalysts were prepared by using the obtained SiO₂ as carriers. It was found that the lifetime of catalyst from low to high was Ni/RS-SiO₂ <Ni/PS-SiO₂ <Ni/RH-SiO₂, which was in the opposite order of K₂O content. Acid washing was beneficial for the enhancement of Ni/RH-AC-SiO₂ activity, and the increase of Ni/RS-AC-SiO₂ stability. Among the four catalysts, the Ni/RH-AC-SiO₂ catalyst exhibited the highest carbon conversion (100%) and hydrogen yield at 600 °C, which may be because that the acid washing removed the metal oxide impurity K₂O. And its large specific surface area, the concentrated pore size distribution, and the suitable interactions between the support and carrier may also contribute to its high catalyst activity.     

Hydrogen and carbon allotrope production through methane cracking over Ni/bimodal porous silica catalyst: Effect of nickel precursor

Nickel-based catalyst is highly active for hydrogen production through methane cracking reaction at moderate reaction temperature. However, Ni catalyst is easily deactivated by carbon encapsulation. In order to solve this problem, this research studies the effect of nickel precursors—nickel acetate (NA), nickel carbonate (NC) and nickel nitrate (NN)—on the activity and stability of nickel/bimodal porous silica (Ni/BPS) catalyst in methane cracking reaction. It was found that these nickel precursor solutions had different pH values, resulting in different interactions between surface silanol groups of BPS supports and Ni. Among these catalysts, Ni(NC)/BPS catalyst exhibited high nickel dispersion and weak interaction between Ni and BPS support; it then gave the highest CH₄ conversion and better stability compared to the other catalysts. In addition, H₂ yield of Ni(NC)/BPS catalyst was 2.90 and 1.40 times higher than those of Ni(NA)/BPS and Ni(NN)/BPS catalysts, respectively. Moreover, carbon nanofibers were grown in Ni(NC)/BPS and Ni(NN)/BPS catalysts, whereas carbon nanotubes were formed on Ni(NA)/BPS catalyst, due to the different nickel particle sizes, dispersions, and Ni—BPS support interactions.     

Preparation and improvement of nickel catalyst supported ordered mesoporous spherical silica for thermocatalytic decomposition of methane

The thermocatalytic alteration of CH₄ into highly pure hydrogen and filaments of carbon was investigated on a series of Ni-catalysts with various contents (25, 40, 55, and 70 wt%) supported mesoporous spherical SiO₂. The silica with ordered structure and high specific surface area (1136 m²/g) was synthesized using the Stöber technique with TEOS as a silica precursor and CTAB as the template in a simple synthesis system of aqueous-phase. This technique led to the preparation of mesoporous spherical silica. The prepared samples were characterized using BET, TPR, XRD, TPO, and SEM analyses. The prepared catalysts with different nickel loading showed the BET surface area ranging from 225.0 to 725.7 m²/g. These results indicated that an increase in nickel content decreases the surface area and leads to a subsequent collapse of a pore structure. SEM analysis confirmed a spherical nanostructure of catalysts and revealed that with the increase in loading of Ni, the particle size enlarged, because of the agglomeration of the particles. The results implied that the high methane conversion of 54% obtained over the 55 wt% Ni/SiO₂ at 575 °C and this sample had higher stability at lower reaction temperature than the other prepared catalysts, slowly deactivation was observed for this catalyst at a period of 300 min of time on stream.     

Hydrogen production from ethanol steam reforming over Ni/SiO2 catalysts: A comparative study of traditional preparation and microwave modification methods

Four silica‐supported nickel catalysts with Ni content of 10 wt% were prepared by impregnation and coprecipitation methods with or without microwave‐assisted calcination. The prepared catalysts were characterized by some techniques (BET, XRD, TEM, XPS, H₂‐TPR, etc.) and evaluated with respect to steam reforming of ethanol (SRE) for hydrogen production. The results show that the prepared Ni/SiO₂ catalysts are all very active and selective for SRE. The high activity of the four catalysts may benefit from their high specific areas and the good dispersion of active components on the carrier. The rate of carbon deposition decreases with reaction temperature especially below 450 °C. The maximum hydrogen yield of 4.54 mol H₂/mol EtOH‐reacted can be obtained over the Ni/SiO₂ catalyst by the microwave‐assisted coprecipitation method at a reaction temperature of 600 °C, EtOH/H₂O molar ratio of 1:12, liquid hourly space velocity of 11.54 h^?1 and time on stream within 600 min. The Ni/SiO₂ catalysts with microwave modification exhibits better performances of hydrogen production, stability and resistance to carbon deposition than that without microwave modification preparation, which is mainly attributed to that the microwave‐assisted treatment can decrease the catalyst acidity and enhance the interaction between metal support. Copyright © 2013 John Wiley & Sons, Ltd.     

A study on optimization of acid sites concentration versus pore dimensions in modified solid acid catalysts for biodiesel production

The acid sites concentration of silica sulfuric acid was optimized against pore dimensions depending on the intensity of silanol groups as a key for binding modifier molecules. The texturally modified rice husk silica, of determined intensity of silanol groups, was functionalized with different loadings of SO₃H groups to produce solid acid catalysts with different concentrations of acid sites and different sizes of the pore systems. The catalysts were employed in trans-esterification of waste-cocking oil. The obtained optimum catalytic activity was attributed to the proper compensation between acid sites intensity and pore dimensions. The estimated TOF for methyl ester production was found to decrease with the increase of SO₃H loading on the catalyst surface. The role of compatibility of the reactants phase with the catalyst nature could be validated by the observed much higher activity of sulfonated lignin in the studied esterification reaction than the modified RHS-acid catalysts under study.     

Influence of Sn content on the electrocatalytic activity of NiSn alloy nanoparticles-incorporated carbon nanofibers toward methanol oxidation

Improvement of the electrocatalytic activity of nickel toward methanol oxidation can be conducted by exploiting the synergetic influence of a co-catalyst and/or utilizing a proper support. In this study, utilizing tin as a co-catalyst and supporting on carbon nanofibers are proposed to enhance methanol oxidation in the alkaline media. Typically, NiSn nanoparticles alloy-incorporated carbon nanofibers could be prepared by calcination of electrospun nanofibers composed of poly (vinyl alcohol), nickel acetate tetrahydrate and tin chloride under argon atmosphere at a high temperature. The influence of the co-catalyst content and the calcination temperature on the morphology, composition and electrocatalytic activity of the proposed nanofibers was investigated. Smooth electrospun nanofibers can be prepared regardless the tin chloride content up to 35 wt%, and the calcination process did not distinctly affect the nanofibrous morphology. Mostly, Ni₃Sn and Ni₃Sn₂ nanoparticles-incorporated amorphous carbon nanofibers were obtained at all the utilized calcination temperatures (700, 850 and 1000 °C) and examined SnCl₂ contents. However, at 10 wt% SnCl₂ content and 850 °C calcination temperature, single metallic compound (Ni₃Sn₂)-incorporated carbon nanofibers were synthesized. Electrochemical measurements indicated that the electrocatalytic activity depends strongly on the tin content as well as the calcination temperature. The nanofibers obtained from electrospun solution containing 10 wt% SnCl₂ and calcined at 850 °C showed very good performance compared to the other formulations. Typically, the corresponding onset potential of the methanol oxidation reaction using these nanofibers catalyst is 315 mV (vs. Ag/AgCl) while it was 405 mV for the nanofibers obtained from electrospun solution containing 0, 5, 15, 25 and 35 wt% SnCl₂. Moreover, the best nanofibers reveal the highest current density. Kinetic study indicated that the corresponding activation energy is 15.6 kJ/mol.     

Syngas production by CO2 reforming of coke oven gas over Ni/La2O3–ZrO2 catalysts

Syngas production by CO₂ reforming of coke oven gas (COG) was studied in a fixed-bed reactor over Ni/La₂O₃–ZrO₂ catalysts. The catalysts were prepared by sol–gel technique and tested by XRF, BET, XRD, H₂-TPR, TEM and TG–DSC. The influence of nickel loadings and calcination temperature of the catalysts on reforming reaction was measured. The characterization results revealed that all of the catalysts present excellent resistance to coking. The catalyst with appropriate nickel content and calcination temperature has better dispersion of active metal and higher conversion. It is found that the Ni/La₂O₃–ZrO₂ catalyst with 10 wt% nickel loading provides the best catalytic activity with the conversions of CH₄ and CO₂ both more than 95% at 800 °C under the atmospheric pressure. The Ni/La₂O₃–ZrO₂ catalysts show excellent catalytic performance and anti-carbon property, which will be of great prospects for catalytic CO₂ reforming of COG in the future.     

Preparation and characterization of coke resistant Ni/SiO2 catalyst for carbon dioxide reforming of methane

Silica supported Ni catalyst is highly active for the CO₂ reforming of methane but it has poor stability due to coke formation. In this work, a glow discharge plasma was applied for the decomposition of nickel nitrate on the SiO₂ support, followed by thermal calcination in air. The plasma treatment enhances the interactions between the Ni particles and the silica and significantly improves the Ni dispersion. The plasma-treated Ni/SiO₂ catalyst exhibits comparable activity to the Ni/SiO₂ catalyst prepared by the thermal method without plasma treatment. The coke resistance of the Ni/SiO₂ catalyst is significantly enhanced by the plasma treatment.     

Modification of silica supported nickel catalysts with lanthanum for stability improvement in methane reforming with CO2

Dry reforming of methane (DRM) with excessive methane composition at CH₄/CO₂ = 1.2:1 was studied over lanthanum modified silica supported nickel catalysts (Ni-xLa-SiO₂, x: 1, 2, 4, and 6% in the target weight percent of La). The catalysts were prepared by ammonia evaporation method. Nickel phyllosilicate and La₂O₃ were the main phases in calcined catalysts. The modification of La enhanced the formation of 1:1 and Tran-2:1 nickel-phyllosilicate. There existed an optimum content of La loading at 1.50 wt% in Ni–2La–SiO₂ which resulted in its highest reduction degree (95.3%). The catalysts with appropriate amounts of La exhibited higher amount of CO₂ adsorption and created more medium and strong base centers. The sufficient number of exposed metallic nickel sites to catalyze the reforming reaction, as well as enough medium and strong basic sites in Ni–La–SiO₂ interface to accomplish the carbon removal were two important factors to attenuate catalyst deactivation. The catalyst stability evaluated at 750 °C for 10 h followed the order: Ni–2La–SiO₂ > Ni–4La–SiO₂ > Ni–1La–SiO₂ ≈ Ni–6La–SiO₂ > Ni–SiO₂. Ni–2La–SiO₂ catalyst possessed the lowest deactivation behavior, whose CH₄ conversion dropped from 60.2 to 55.9% after 30 h operation at 750 °C, indicating its high resistance against carbon deposition and sintering.     

Electro-oxidation of tri(ammonium) phosphate: New hydrogen source compatible with Ni-based electro-catalysts

Predominantly, the reported Ni-based electro-catalysts are not applicable anode materials for the alcohols-based proton exchange membrane fuel cells due to the high onset potentials. Alternatively, these non-precious materials can be exploited for hydrogen generation from alcohols with small biases. However, as the nickel oxy(hydroxide) active species is a reactant in the alcohols electro-oxidation reactions, so these materials are exhausted and have to be regenerated. Recently, hydrogen could be extracted from tri(ammonium) phosphate using Ni/C nanostructures as effective catalysts in a simple batch reactor. In this study, electro-oxidation of tri(ammonium) phosphate using Ni-decorated graphene is investigated. The utilized catalyst has been prepared by simple one-pot synthesis procedure; calcination of well mixed nickel acetate/commercial sugar composite. The results indicated that the prepared Ni-decorated graphene is an effective electro-catalyst for tri(ammonium) phosphate oxidation when the nickel content is optimized; 3 wt% metal is the best composition. Moreover, chronoamperometry analysis results indicated that the active layer is not being consumed during the electro-oxidation reaction of the tri(ammonium phosphate) which creates a distinct advantage for this fertilizer over alcohols. Stability of the active layer is attributed to performing Ni(OH)₂/Ni(OOH) redox reaction during tri(ammonium) phosphate electro-oxidation process. Overall, the study opens a new avenue for utilizing hydrogen-rich, cheap and available substances for hydrogen generation using continuously-active non-precious electrodes.     

Syngas production from dry methane reforming over yttrium-promoted nickel-KIT-6 catalysts

Dry reforming of methane was studied over Ni,Y-promoted KIT-6 ordered mesoporous silicas, prepared by incipient impregnation (nickel content 12 wt%, yttrium content of 4 wt%, 8 wt% or 12 wt%). The catalysts were characterized by XRF, FT-IR, TGA/DSC-MS, N₂-adsorption, TEM, HRTEM, XRD and TPR-H₂. The promotion with 8 wt% Y (Y/Si = 0.05) resulted in the highest activity and H₂/CO molar ratio closer to the stoichiometric value at temperatures from 600 to 750 °C. The characterization results of the yttrium promoted materials showed higher reducibility of the bulk NiO, bigger Ni crystallite size after reduction and DRM test, and better dispersion of nickel in the channels of the KIT-6 support. Additionally, larger Ni particles were observed on the external surface of the support, which may be related to catalytic selectivity towards carbon forming reactions. Upon dry methane reforming the segregated phases of Niº, Y₂O₃, and possibly Y₂Si₂O₇ were registered. No presence of a Ni,Y alloy was observed.     

Preparation and characterization of Ni catalysts supported on pillared nanoporous bentonite powders for dry reforming reaction

The Ni/pillared-bentonite catalysts with high BET area were synthesized and used in dry reforming reaction. The effects of different parameters such as calcination temperature, OH⁻/Al³⁺ ratio, temperature and time of pillaring process and the content of nickel on the textural and catalytic properties of the synthesized catalysts were studied. The results indicated that the 15 wt% Ni catalyst supported on pillared bentonite prepared under specified conditions (OH⁻/Al³⁺ = 2.2, pillaring temperature of 40 °C and pillaring time of 3 h) possessed the highest BET area (90.80 m²/g). Also, this catalyst possessed higher catalytic activity and stability with lower amount of deposited carbon in comparison to other prepared catalysts in methane reforming with CO₂.     

Effect of SiO2-ZrO2 supports prepared by a grafting method on hydrogen production by steam reforming of liquefied natural gas over Ni/SiO2-ZrO2 catalysts

SiO₂-ZrO₂ supports with various zirconium contents are prepared by grafting a zirconium precursor onto the surface of commercial Carbosil silica. Ni(20 wt.%)/SiO₂-ZrO₂ catalysts are then prepared by an impregnation method, and are applied to hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of SiO₂-ZrO₂ supports on the performance of the Ni(20 wt.%)/SiO₂-ZrO₂ catalysts is investigated. SiO₂-ZrO₂ prepared by a grafting method serves as an efficient support for the nickel catalyst in the steam reforming of LNG. Zirconia enhances the resistance of silica to steam significantly and increases the interaction between nickel and the support, and furthermore, prevents the growth of nickel oxide species during the calcination process through the formation of a ZrO₂-SiO₂ composite structure. The crystalline structures and catalytic activities of the Ni(20 wt.%)/SiO₂-ZrO₂ catalysts are strongly influenced by the amount of zirconium grafted. The conversion of LNG and the yield of hydrogen show volcano-shaped curves with respect to zirconium content. Among the catalysts tested, the Ni(20 wt.%)/SiO₂-ZrO₂ (Zr/Si = 0.54) sample shows the best catalytic performance in terms of both LNG conversion and hydrogen yield. The well-developed and pure tetragonal phase of ZrO₂-SiO₂ (Zr/Si = 0.54) appears to play an important role in the adsorption of steam and subsequent spillover of steam from the support to the active nickel. The small particle size of the metallic nickel in the Ni(20 wt.%)/SiO₂-ZrO₂ (Zr/Si = 0.54) catalyst is also responsible for its high performance.