Effect of Ni loading on SBA-15 synthesized from palm oil fuel ash waste for hydrogen production via CH4 dry reforming

The successful synthesis of SBA-15 using silica source extracted from palm oil fuel ash (POFA) was proven with the presence of mesostructure characteristics as evidenced by low angle XRD, N₂ adsorption-desorption isotherms and TEM. Different amounts of Ni were loaded on the synthesized SBA-15(POFA) using the impregnation method at 80 °C. The influence of Ni loading over the Ni/SBA-15(POFA) physiochemical properties and CO₂ reforming of CH₄ (CRM) were investigated in a stainless steel fixed-bed reactor at 800 °C and atmospheric pressure with 1:1 CO₂:CH₄ volumetric feed composition. An increment in Ni loading on SBA-15(POFA) from 1 to 5 wt% decreased the BET surface area and crystallinity of catalyst as proven by N₂ adsorption–desorption and XRD analysis. The catalytic performance of CRM followed the sequence of 3 wt% > 5 wt% > 2 wt% > 1 wt% -Ni/SBA-15(POFA). This result was owing to the even distribution of Ni and good Ni–O–Si interaction of 3 wt% Ni/SBA-15(POFA) as proved by TEM, FTIR and XPS. Lowest H₂/CO ratio and catalyst activity and stability of 1 wt% Ni/SBA-15(POFA) were due to the weaker Ni–O–Si interaction and small amount of basic sites that favor the reverse water gas shift (RWGS) reaction and carbon formation. The recent finding indicates that a quantity as small as 3 wt% Ni loaded onto SBA-15(POFA) could elicit outstanding catalytic performance in CRM, which was comparable with 10 wt% Ni loading catalysts reported in literature.     

Influence of impregnation assisted methods of Ni/SBA-15 for production of hydrogen via dry reforming of methane

SBA-15 support was successfully synthesized using extracted silica from palm oil fuel ash waste (POFA). Four types of Ni/SBA-15 catalysts were prepared via the ordinary impregnation technique (Ni/SBA-15(IM)) and assisted impregnation techniques including rotary evaporator (Ni/SBA-15(RE)), shaker (Ni/SBA-15(SH)) and ultrasonic (Ni/SBA-15(US)). The attributes of the Ni/SBA-15 were characterized using XRD, BET, FTIR, XPS, TEM, CO₂-TPD and TGA. The performance and stability of Ni/SBA-15 catalysts for up to 24 h were determined using a stainless steel fixed-bed reactor setup at 800 °C. The results in a descending order were ultrasonic (US) > ordinary impregnation (IM) > shaker (SH) > rotary evaporator (RE). The highest catalytic performance was achieved by Ni/SBA-15(US) owing to the location of Ni species inside the SBA-15 micelles, stronger Ni–O–Si interaction, and higher catalyst basicity. Lowest formation of graphite carbon on Ni/SBA-15(US) was correlated to the good dispersion of smaller Ni particles that were able to suppress the coke formation. The ultrasonic irradiation provided a cavitation effect which was able to destroy the soft agglomeration of Ni particles for better dispersion compared to IM, RE, and SH. This study provides an alternative in preparing better properties of catalyst to enhance the CO₂ reforming of CH₄ (CRM) in terms of activity and stability.     

Structural effect of Ni/SBA-15 by Zr promoter for H2 production via methane dry reforming

5 wt% of Ni/SBA-15 supported with numerous Zr loading (1–7 wt%) were produced using sol-gel technique at 60 °C. The influence of Zr promoter on the physiochemical properties of Ni/SBA-15 catalysts for methane dry reforming were examined in a fixed-bed reactor at 800 °C. Analytical characterizations including XRD, BET, FTIR, N₂ adsorption desorption, TEM and TGA were conducted to study the physiochemical properties of Zr/Ni/SBA-15 catalysts for the sake of identification of the amount of coke deposition formed on the spent catalyst. Increasing the amount of Zr loading from 1 to 7 wt% supported on Ni/SBA-15 reduced the catalyst's surface area as was proven from the physiochemical properties of Zr/Ni/SBA-15 catalyst. The catalytic activity test revealed that the optimum Zr loading was 1 wt% at which CH₄ and CO₂ conversions were 87.07% and 4.01%, meanwhile H₂:CO ratios was 0.42. This result was owing to the existence of the Zr species in promoting a good dispersion of Nickel (Ni) active sites on the catalyst surface as affirmed from XRD and FTIR results. The latest discovery indicates that promotion of 1 wt% Zr onto Ni/SBA-15 can prompt excellent catalytic performance in CRM.     

Promising hydrothermal technique for efficient CO2 methanation over Ni/SBA-15

The comparative study of different hydrothermal treatment techniques (Reflux (R) and Teflon (T)) and without hydrothermal technique (W) towards efficient CO₂ methanation over Ni/SBA-15 was discussed. X-ray diffraction (XRD), inductive coupling plasma-atomic emission spectroscopy (ICP-AES), N₂ adsorption-desorption isotherms (BET), Fourier transform infrared (FTIR) spectroscopy, UV-vis diffuse reflectance spectroscopy (UV-Vis DRS), scanning electron microscope – energy dispersion x-ray (SEM-EDX), and transmission electron microscope (TEM) analysis showed that Ni/SBA-15(R) possessed fascinating catalytic properties owing to the highest surface area (814 m²/g) and pore diameter (5.49 nm) of SBA-15(R), finest metal particles (17.92 nm), strongest metal-support interaction and highest concentration of basic sites. The efficacy of Ni/SBA-15 towards CO₂ methanation was descending as Ni/SBA-15(R) > Ni/SBA-15(T) > Ni/SBA-15(W), implying the outstanding performance of Ni/SBA-15(R) which in parallel with the characterization results. The lowest performance of Ni/SBA-15(W) was due to the poorest properties of support; lowest surface area and pore diameter, largest Ni sizes, weakest metal-support interaction and lowest concentration of basic sites. This study successfully developed fascinating Ni/SBA-15 through the reflux hydrothermal treatment technique for CO₂ methanation.     

Synthesis, characterization and catalytic performances of Ce-SBA-15 supported nickel catalysts for methane dry reforming to hydrogen and syngas

A series of Ce-incorporated SBA-15 mesoporous materials were synthesized through direct hydrothermal synthesis method and further impregnated with 12 wt.% Ni. The samples were characterized by ICP-AES, XRD, N₂ physisorption, XPS, TPR, H₂ chemisorption, TGA, temperature-programmed hydrogenation (TPH) and TEM measurements. The low-angle XRD and N₂ physisorption results showed the Ce successfully incorporated into the framework of SBA-15. The catalytic properties of these catalysts were investigated in methane reforming with CO₂. The Ce/Si molar ratio had a significant influence on the catalytic performance. The highest catalytic activity and long-term stability were obtained over the Ni/Ce-SBA-15 (Ce/Si = 0.04) sample. The improved catalytic behavior could be attributed to the cerium impact in the framework of SBA-15, where cerium promoted the dispersion of nano-sized Ni species and inhibited the carbon formation. In comparison with the effect of CeO₂ crystallites in SBA-15, cerium in the framework of SBA-15 promoted the formation of the nickel metallic particles with smaller size. The XRD and TGA results exhibited that carbon deposition was responsible for activity loss of Ni/SBA-15 and Ni/Ce-SBA-15 (Ce/Si = 0.06) catalysts. TEM results showed that the hexagonal mesopores of SBA-15 were still kept intact after reaction and the pore walls of SBA-15 prevented the aggregation of nickel.     

Y2O3-promoted NiO/SBA-15 catalysts highly active for CO2/CH4 reforming

A series of Y₂O₃-promoted NiO/SBA-15 (9 wt% Ni) catalysts (Ni:Y weight ratio = 9:0, 3:1, 3:2, 1:1) were prepared using a sol–gel method. The fresh as well as the catalysts used in CO₂ reforming of methane were characterized using N₂-physisorption, XRD, FT-IR, XPS, UV, HRTEM, H₂-TPR, O₂-TPD and TG techniques. The results indicate that upon Y₂O₃ promotion, the Ni nanoparticles are highly dispersed on the mesoporous walls of SBA-15 via strong interaction between metal ions and the HO–Si-groups of SBA-15. The catalytic performance of the catalysts were evaluated at 700 °C during CH₄/CO₂ reforming at a gas hourly space velocity of 24 L g_cat⁻¹ h⁻¹(at 25 ^°C and 1 atm) and CH₄/CO₂molar ratio of 1. The presence of Y₂O₃ in NiO/SBA-15 results in enhancement of initial catalytic activity. It was observed that the 9 wt% Y–NiO/SBA-15 catalyst performs the best, exhibiting excellent catalytic activity, superior stability and low carbon deposition in a time on stream of 50 h.     

Mesocellular-foam-silica-supported Ni catalyst: Effect of pore size on H2 production from cellulose pyrolysis

Supported nickel metal can be used as a tar-cracking catalyst in the thermal processing of large organics to give H₂. Though porous supports offer the opportunity to disperse a relatively large amount of nickel, catalytic sites within small pores may be inaccessible to large tar molecules. To investigate this, we prepared nickel catalysts supported on γ-Al₂O₃ and on SBA-15- and mesocellular-foam-(MCF)-type silicas and studied their catalytic activities in the pyrolytic decomposition of cellulose (RT → 800 °C, ∂T/∂t = 40 °C/min). A thermogravimetric analyser-mass spectrometer (TG-MS) was used to study the influence of the Ni catalyst and support materials on the H₂ yield and selectivity. The silica-MCF-supported Ni catalyst decreased char residue and enhanced H₂ yield, producing 1.6 and 3.5× the H₂ yield obtained using SBA-15-supported Ni and γ-Al₂O₃-supported Ni, respectively. MCF, with ultra-large pores (d ∼ 15−50 nm), was thus identified as the most beneficial catalyst support for this application.     

Catalytic steam reforming of JP-10 over Ni/SBA-15

As the only H₂ resource on aircraft from the steam reforming of the jet fuels on board, catalytic steam reforming of JP-10 (one of Jet fuels) over nickel-based catalyst Ni/SBA-15 were first carried out in a fixed bed tube reactor to produce hydrogen on-site or on board. A series of Ni/SBA-15 catalysts with different Ni content (3, 5, 8 and 10.8 wt%) were prepared by a modified incipient wetness impregnation method with addition of sucrose as ligand. And the effect of operation conditions of temperature (630–700 °C), nickel loading, liquid hour space velocity (LHSV = 5, 10, 15 ml/g_cat·h), steam to carbon molar ratio (S/C = 3, 5) on the catalytic activity and selectivity was investigated. It was found that 8Ni/SBA-15 was the optimal catalyst for steam reforming of JP-10 even with a higher LHSV and fuel gas concentration, and approximately 100% conversion of JP-10 with over 80% selectivity to hydrogen under the recommended experimental conditions of 680 °C, S/C of 5, LHSV of 10 ml/g_cat·h. The catalytic activity of 8Ni/SBA-15 dropped slowly to 84% after 6.5 h in the stability test and the carbon deposited was less with just 6% mass loss from TGA measurement (coke deposition rate 0.01g_C/g_cath), which ascribed to possible reasons including confine effect of mesochannel of SBA-15, strengthened structure of mesochannels due to embeded Ni particles, and higher temperature to suppress the main carbon producing reaction.     

Unveiling the promotion effect of Zr species on SBA-15 supported nickel catalysts for CO2 methanation

Introducing promoters on Ni-based catalysts for CO₂ methanation have been proved to be positive for enhancing their performance. And the correlation of the promotion mechanism and the reaction pathway is significant for designing efficient catalysts. In this contribution, series of Zr species promoted SBA-15 supported Ni catalysts were prepared by citric acid complexation method under a range of Zr/Ni atomic ratios from 0 to 2.5. In situ and ex situ characterizations were carried out. It was found that the addition of citric acid was conductive to improve CH₄ selectivity due to the higher concentrations of Ni⁰ confined in SBA-15, harvesting sufficient H atoms for CH₄ formation following formate pathway via a formyl intermediate. Furthermore, a coverage layer of Zr species was found on the support at Zr/Ni = 1.7, which interacted with the Ni particles, providing higher concentrations of medium basic sites for CO₂ activation. Accordingly, the optimum catalytic performance was obtained on ZrNi-1.7(CI), achieving CO₂ conversion as high as 78.1% and nearly 100% CH₄ selectivity at 400 °C, following the formate hydrogenation pathway. In addition, the ZrNi-1.7(CI) showed good stability owing to the confinement effect of SBA-15 and the Ni–Zr interaction, no carbon deposits were detected after 50 h test.     

CO2 reforming of methane over Ni/SBA-15 prepared with β-cyclodextrin – Role of β-cyclodextrin in Ni dispersion and performance

Ni/SBA-15-CD(1/X) catalysts were prepared by the impregnation of a certain amount of Ni(NO₃)₂ and various contents of β-cyclodextrin (CD), in which 1/X indicates the molar ratio of CD to Ni. The physicochemical properties of the catalysts were characterized by BET, XRD, TEM, TPR and TGA, and their catalytic performance in the CO₂ reforming of methane to syngas was evaluated using a fixed-bed quartz reactor. The characterization results revealed that Ni/SBA-15-CD(1/X) prepared with n(CD)/n(Ni) ratios in the range of 1/66–1/33 possessed smaller NiO particles and exhibited stronger interactions between NiO and SBA-15, whereas NiO particles were not well-dispersed on Ni/SBA-15-CD(1/X) catalysts prepared with further CD addition (1/X = 1/8 and 1/1). The reaction results indicated that the better-dispersed Ni/SBA-15-CD(1/X) catalysts, such as Ni/SBA-15-CD(1/66), Ni/SBA-15-CD(1/50) and Ni/SBA-15-CD(1/33), exhibited higher conversions and stronger abilities to resist carbon deposition. Regarding the role of CD in dispersing Ni particles, it could be speculated that complexes were formed between CD and Ni²⁺, as well as NO₃⁻, which would change the state of Ni species during the impregnation and heat treatment processes.     

Catalytic activity of SBA-15 supported Ni catalyst in CH4 dry reforming: Effect of Al,Zr, and Ti co-impregnation and Al incorporation to SBA-15

In this study, the catalytic activity of the mesoporous SBA-15 supported Ni–Al, Ni–Zr, and Ni–Ti catalysts prepared by an impregnation method were investigated in dry reforming of methane. In addition, Al incorporated SBA-15 (Al–SBA-15) materials used as catalyst support were synthesized following a one-pot hydrothermal route in three different conditions: synthesis in the presence of only HCl, only NaCl, and both HCl and NaCl (denoted as A, S, and B, respectively). All catalysts were characterized by XRD, N₂ adsorption-desorption isotherms, ICP-OES, DRIFTS, SEM, TEM-EDX and TGA techniques before and/or after reaction tests. Among Al, Zr, and Ti impregnated catalysts, Ni–Al impregnated catalyst showed the highest activity in dry reforming of methane. According to activity test results, Al–SBA-15 supported Ni catalyst prepared by the one-pot hydrothermal route in the presence of both HCl and NaCl showed the best catalytic activity with high methane (81%) and carbon dioxide conversion (88%) values at 750 °C. The highest H₂ and CO selectivity values were obtained with the same catalyst with an H₂/CO molar ratio of 0.80. Therefore, these results showed that partial Al (0.11%) incorporated into the structure of SBA-15 was sufficient to improve the catalytic activity of the catalyst in dry reforming of methane.     

Synthesis,characterization and catalytic performance of MgO-coated Ni/SBA-15 catalysts for methane dry reforming to syngas and hydrogen

A series of MgO-coated SBA-15 mesoporous silica with MgO contents ranging from 2 wt% to 15 wt% have been successfully synthesized by a simple one-pot synthesis method and further impregnated with 10 wt% Ni. Ni/SBA-15 modified with 8 wt% MgO was also prepared by conventional impregnation method. The materials were characterized by means of XRD, N₂ physisorption, TEM by applying high-angle annular dark field (HAADF), XPS, CO₂-TPD, TGA and temperature-programmed hydrogenation (TPH) techniques, and their catalytic performance was tested for methane reforming with CO₂. The results showed that MgO was successfully coated on the walls of mesoporous silica and the mesoporous structure of SBA-15 was well maintained after MgO modification. Compared to MgO-impregnated material, MgO-coated counterpart showed a better order in the mesostructure and more medium basic sites. The addition of MgO enhanced initial catalytic activity of Ni/SBA-15, and the catalyst with 8 wt% MgO coating showed the most excellent catalytic activity. The MgO coating induced an improved dispersion of Ni species and larger medium basic sites than that of MgO impregnation, which led to an enhanced long-term stability and resistance to carbon formation. The deposition of graphitic carbon species during the reaction was the main reason for the deactivation of Ni/SBA-15 catalyst.     

Optimal Ni loading towards efficient CH4 production from H2 and CO2 over Ni supported onto fibrous SBA-15

The transformation of SBA-15 into fibrous type SBA-15 (F-SBA-15) as well as the influence of Ni loadings (1, 3, 5, and 10 wt%) towards an efficient CH₄ production from H₂ and CO₂ were explored. The synthesized catalysts were characterized using XRD, BET, ICP-MS, FTIR, FESEM-EDX, TEM, and in-situ FTIR adsorbed pyrrole. Increasing Ni loadings onto F-SBA-15 support promoted excellent performance towards CO₂ methanation. The efficacy in CO₂ methanation over Ni/F-SBA-15 increased with a sequence of 1%Ni/F-SBA-15 < 3%Ni/F-SBA-15 < 5%Ni/F-SBA-15 ≈ 10%Ni/F-SBA-15, indicating the superior performance and stability of 5%Ni/F-SBA-15. The increasing trend was due to the fibrous morphology of support which enhanced the quantity of SiONi bond, triggered better Ni dispersion, strengthen metal-support interaction, and increased the basicity. However, higher Ni loadings (10 wt%) onto F-SBA-15 slightly declined the performance and stability of CO₂ methanation due to the limited spaces for substitution of Ni species with the silanol groups of F-SBA-15 upon the bulk Ni phase, poorer Ni dispersion, weaker metal-support interaction, and lower basicity. The new finding of combination between fibrous SBA-15 (F-SBA-15) with an optimum Ni loading contributed towards an outstanding performance and thus could be applied in various applications.     

Effect of La2O3 and CeO2 loadings on formation of nickel-phyllosilicate precursor during preparation of Ni/SBA-15 for hydrogen-rich gas production from ethanol steam reforming

The importance of La₂O₃ or both La₂O₃ and CeO₂ promoters on the formation of nickel phyllosilicate (Ni₃Si₄O₁₂H₂) as a precursor of Ni/SBA-15 for ethanol steam reforming (ESR) was investigated. The catalyst was made by a one-step modified conventional triblock copolymer synthesis method (pH-Adjustment with ammonium hydroxide). The prepared catalysts were characterized by N₂ adsorption/desorption isotherms, XRD, H₂-TPR, SEM-EDS and TGA-DSC techniques. The N₂ adsorption/desorption isotherms identified the mesoporous nature of the catalysts and the XRD patterns of the calcined catalysts confirmed the formation of nickel-phyllosilicate structure. The H₂-TPR analysis revealed that the La₂O₃ loading considerably increased the interaction between nickel and silica frame work of SBA-15 support. The ability of these catalysts for hydrogen production from ethanol steam reforming (ESR) was evaluated in a packed bed reactor at 650 °C. In the case of Ni/SBA-15 catalysts without and with La₂O₃ promoter, the ESR experiments experienced metal sintering and coke formation. Meanwhile, the catalytic activity of both La₂O₃ and CeO₂ promoted Ni/SBA-15 catalyst (Ni-La₂O₃-CeO₂/SBA-15) remained stable with time on stream in terms of GPR and hydrogen selectivity. The stable performance of this catalyst was explained by the strong interaction of nickel with SBA-15 promoted by La₂O₃ and the suppression of coke formation by CeO₂.     

The reconstruction of Ni particles on SBA-15 by thermal activation for dry reforming of methane with excellent resistant to carbon deposition

The improved Ni/SBA-15 catalysts were prepared by thermal inducing method and applied to dry reforming of methane. The promoting effect exerted by thermal activated reconstruction was studied systematically by means of various characterization techniques. TEM results indicated that the thermal inducing process led to the reconstruction of Ni particles to form ultra-fine Ni nanoparticles (2–3 nm) uniformly distributed on SBA-15. The resulting Ni nanoparticles not only improved catalytic activity but also inhibited the formation of carbon deposition during the DRM reaction. The thermal treatment catalyst with tiny particles presented the superior catalytic performance in the DRM reaction, where H₂/CO ratio was close to 1 and no deactivation was discovered after continuous reaction at 750 °C for 50 h. Additionally, it was found that the metal-support interaction was strengthened observably after the thermal activated reconstruction. The strong interaction anchored Ni particles to prevent their high temperature sintering, thus forming stable catalytic centers. Therefore, the conversions of both CO₂ and CH₄ almost stabilized at 90% and 85%, respectively, for the thermal activated reconstruction samples during the long-term catalytic test.     

Supporting high-loading Ni on SBA-15 as highly active and durable catalyst for ammonia decomposition reaction

Although supported Ni is generally considered the most active non-noble metal catalyst for decomposing NH₃ to produce CO_x-free H₂, its activity is not sufficient. Herein, supporting high-loading Ni on SBA-15 is explored to alleviate the low intrinsic activity issue of Ni. SBA-15 supports with tunable textual properties are synthesized to support Ni catalyst for NH₃ decomposition. Characterization shows that Ni catalyst with a loading close to 40 wt% supported on SBA-15 with the largest specific surface area (Ni/SBA-15-80) exhibits a NH₃ decomposition performance much better than those reported on other Ni-based NH₃ decomposition catalysts, resulting from its favorable textural properties and high Ni loading. In addition, Ni/SBA-15-80 shows excellent catalytic stability, with no activity degradation over an 80-h NH₃ decomposition test. This work reveals the importance of textural properties of support and Ni loading to NH₃ decomposition performance and can provide a new idea for synthesizing high-performance NH₃ decomposition catalysts.     

CO2 reforming of methane on Ni/γ-Al2O3 catalyst prepared by dielectric barrier discharge hydrogen plasma

Ni/γ-Al₂O₃ catalyst was prepared by direct treatment of Ni(NO₃)₂/γ-Al₂O₃ precursor with dielectric barrier discharge (DBD) hydrogen plasma at different input powers, characterized by XRD, H₂-TPR, CO₂-TPD, N₂ adsorption and TEM, respectively, and used as the catalyst for CO₂ reforming of methane (CRM). The results showed that the input power obviously affected the reduction degree and catalytic performances of catalysts. Low input power under 40 W mainly resulted in the decomposition of nickel nitrate into Ni oxides. The reduction degree, catalytic activity and stability increase with the input power. Similar catalytic performances in CRM reaction can be obtained when the power exceeds 80 W. Compared with the Ni/Al₂O₃ catalyst prepared by traditional method, Ni/γ-Al₂O₃ samples prepared by H₂ DBD plasma exhibit better activities, stability and anti-carbon deposit performances. It is mainly ascribed to smaller Ni particle size, more basic sites and weaker basicity. The increase of Ni particle sizes due to the sintering at high temperature results in the decrease of catalytic activities and coke formation.     

Synthesis of mesoporous silica (SBA-16) nanoparticles using silica extracted from stem cane ash and its application in electrocatalytic oxidation of methanol

In this work, a new catalyst based on modified mesoporous silica SBA-16 is proposed and used for electrochemical oxidation of methanol. Mesoporous silica SBA-16 nanoparticles are synthesized hydrothermally under the acidic medium using SiO₂/F127/BuOH/HCl/H₂O gel. Pure SiO₂ powder is prepared from inexpensive and environmentally friendly silica source of stem cane ash (SCA). The synthesized SBA-16 is characterized using X-ray diffraction, scanning electronic microscopy, transmission electron microscopy, Brumauer–Emmett–Teller (BET) and FT-IR techniques. The synthesized SBA-16 is modified with Ni(II) by dispersion in a 0.1 M nickel chloride solution. A modified carbon paste electrode (CPE) is prepared by mixing of NiSBA-16 to carbon paste (NiSBA-16CPE). The electrocatalytic oxidation of methanol was studied on modified electrode by cyclic voltammetry and chronoamperometry. From cyclic voltammetry, it is observed that the oxidation current is extremely increased by using NiSBA-16CPE compared to the nonmodified CPE. The incorporation of Ni²⁺ into SBA-16 channels provides the active sites for catalysis of methanol oxidation. Also, the rate constant for the catalytic reaction (k) of methanol is obtained.     

Methane bi-reforming over boron-doped Ni/SBA-15 catalyst: Longevity evaluation

A highly active and stable boron-promoted catalyst was successfully prepared by using the sequential incipient wetness impregnation technique and examined for methane bi-reforming reaction. The initial investigation found that the NiO and B₂O₃ particles were dispersed on the outer surface of the high surface area SBA-15 support. In addition, the catalytic activity was increased linearly with the tested reaction temperature due to the endothermic nature of the reaction. In fact, the catalyst achieved the CH₄ conversion and H₂/CO molar ratio of approximately 67.3% and 2.7, respectively at 1073 K. The resulting product ratio is highly suitable for downstream Fischer-Tropsch (FT) synthesis. The B-promoted catalyst showed the lowest degree of catalyst deactivation (4%) at 1023 K. Additionally, the XPS measurements unveiled that the boron facilitates the adsorption of CO₂ by donating electrons to the neighbouring Ni cluster and thus improved its catalytic performance. Furthermore, Raman and XRD analysis revealed that the boron promotion on 10%Ni/SBA-15 could prevent the reoxidation and deposition of carbonaceous species.     

Catalytic conversion of CH4 and CO2 to synthesis gas on Ni/SiO2 catalysts containing Gd2O3 promoter

A series of Ni/SiO₂ catalysts containing different amounts of Gd₂O₃ promoter was prepared, characterized by H₂-adsorption and XRD, and used for carbon dioxide reforming of methane (CRM) and methane autothermal reforming with CO₂ + O₂ (MATR) in a fluidized-bed reactor. The results of pulse surface reactions showed that Ni/SiO₂ catalysts containing Gd₂O₃ promoter could increase the activity for CH₄ decomposition, and Raman analysis confirmed that reactive carbon species mainly formed on the Ni/SiO₂ catalysts containing Gd₂O₃ promoter. In this work, it was found that methane activation and reforming reactions proceeded according to different mechanisms after Gd₂O₃ addition due to the formation of carbonate species. In addition, Ni/SiO₂ catalysts containing Gd₂O₃ promoter demonstrated higher activity and stability in both CRM and MATR reactions in a fluidized bed reactor than Ni/SiO₂ catalysts without Gd₂O₃ even at a higher space velocity.