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.     

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 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.     

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.     

Hydrogen and syngas production by methane dry reforming on SBA-15 supported nickel catalysts: On the effect of promotion by Ce0.75Zr0.25O2 mixed oxide

In this work, the effects of doping Ni-based SBA-15 catalysts with Ceria–Zirconia mixed oxide (CZ) on the activity and stability of these catalysts during syngas production by methane dry reforming (MDR) were investigated and compared with the activity and stability of unmodified Ni/SBA-15. The above catalysts were prepared by incipient wetness impregnation (IWI) with different impregnation strategy. The samples were characterized by nitrogen physisorption, X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), temperature programmed reduction (TPR) and H₂ chemisorption. The results indicated that the unmodified Ni/SBA-15 showed clear deactivation especially in the first period of the stability test and between 600 °C and 630 °C during the activity test whereas the CZ modified samples had better stability.     

Hydrogen production via CO2 reforming of CH4 over low-cost Ni/SBA-15 from silica-rich palm oil fuel ash (POFA) waste

H₂ was produced via CO₂ reforming of CH₄ (CRM) using low-cost Ni/SBA-15 synthesized from palm oil fuel ash (POFA) waste as silica precursor. A series of Ni/SBA-15 were synthesized by employing different Na₂SiO₃-POFA/P123 mass ratios (2.0, 2.9 and 4.0) and were compared with Ni/SBA-15 prepared from commercial Na₂SiO₃ (Ni/SBA-15(Comm.)). Na₂SiO₃-POFA/P123 = 2.9 was found to be the optimal synthesis ratio, which produces a well-defined hexagonal framework, smaller NiO particles, stronger Ni-support interaction, homogeneous metal distribution and higher amount of basic sites. The catalytic performance complied with the trend of Ni/SBA-15(R4.0) < Ni/SBA-15(R2.0) < Ni/SBA-15(R2.9) ≈ Ni/SBA-15(Comm.), indicating the excellent catalytic activity of Ni/SBA-15(R2.9) (H₂ selectivity = 87.6%). The favorable physicochemical properties of Ni/SBA-15(R2.9) ameliorated the active Ni metals stabilization over SBA-15 and boosted the catalyst's virtues towards an outstanding catalytic performance. Hence, it is affirmed that POFA with an optimal Na₂SiO₃-POFA/P123 ratio of 2.9 can be served as silica substitution of Ni/SBA-15 for efficient H₂ production via CRM.     

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.     

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.     

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.     

One-pot synthesis of NiO/SBA-15 monolith catalyst with a three-dimensional framework for CO2 methanation

The NiO/SBA-15 monolith with a three-dimensional (3D) network structure was synthesized by a facile one-pot hydrothermal method for CO₂ methanation. The results showed that the net-linked mesoporous framework of SBA-15 was well preserved after incorporation of 15 wt% NiO, and the one-pot prepared NiO/SBA-15-Op material exhibited higher surface area, larger pore volume than the NiO/SBA-15-Im synthesized by traditional impregnation method. In addition, NiO/SBA-15-Op showed higher catalytic activity and anti-sintering property of metallic Ni than NiO/SBA-15-Im for CO₂ methanation due to higher Ni dispersion and more Ni particles dispersed in the meso-channels.     

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.     

Ni/SBA-15 catalysts for hydrogen production by ethanol steam reforming: Effect of nickel precursor

The effect of nickel precursor on Ni/SBA-15 catalysts was studied in ethanol steam reforming (ESR) for hydrogen production. These catalysts were prepared via incipient-wetness impregnation method using nickel nitrate and nickel citrate precursors, respectively (denoted as Ni/SBA-15(N) and Ni/SBA-15(C), respectively), and characterized by various techniques including H₂-TPR, XRD, TEM and TG. It was found that the use of nickel citrate precursor, compared to nickel nitrate precursor, could greatly strengthen the NiO-support interaction and promote the homogeneous distribution of nickel species, to obtain the small nickel particles with high dispersion. After a 25 h time-on-stream test, much lower coke deposition was formed over Ni/SBA-15(C) than Ni/SBA-15(N). Moreover, NiC_x species had be found over the used Ni/SBA-15(C), in which the carbon could be removed easily at lower temperature to exposure the active Ni sites; While carbon nanofibers with regular graphite-structure were the primary coke species over the spent Ni/SBA-15(N), which was difficultly remove and thus covered the active Ni sites easily. Due to these, Ni/SBA-15(C) displayed the higher catalytic activities and better stabilities in ESR than Ni/SBA-15(N). In summary, nickel citrate is an excellent precursor for the preparation of Ni/SBA-15 catalysts with high dispersion and strong interaction.     

Renewable hydrogen from glycerol steam reforming using Co–Ni–MgO based SBA-15 nanocatalysts

Steam reforming of glycerol was carried out using Si-based mesoporous SBA-15 catalysts. Different mesoporous catalysts- Co-SBA-15, Ni-SBA-15, Co–MgO-SBA-15, Ni–MgO-SBA-15, and Co–Ni-SBA-15 were prepared using a one-pot hydrothermal method. An incipient wetness impregnation method was used only for the bimetallic Co–Ni-SBA-15 catalyst (catalyst designated as Co–Ni-SBA-15-IMPG) to compare its activity to that prepared by the one-pot method. The catalysts were characterized using XRD, TPR, TEM, TGA-DSC, ICP-OES and N₂ adsorption-desorption analytical techniques. A high surface area in the range of 540–750 m²/g was observed depending on the catalyst composition. The glycerol steam reforming (GSR) activity of the catalysts was studied in the reaction temperature range of 450 °C–700 °C for hydrogen production. Results from the GSR studies for continuous 40 h showed that both Co–Ni-SBA-15-IMPG (impregnation) and Co–Ni-SBA-15 (one-pot) were resistant to deactivation, and both yielded 100% glycerol conversion for the entire 40 h. 10%Co–5%Ni-SBA-15 and 10%Co–5%Ni-SBA-15-IMPG produced (70–78) % and (60–78) % H₂ selectivity, respectively. Addition of MgO to Co-SBA-15 and Ni-SBA-15 increased the activity and stability of the catalysts. The catalyst stability performance followed the trend 10%Co–5%Ni > 10%Co–5%MgO >10%Co–5%Ni-IMPG. > 15%Co > 10%Ni–5%MgO >15%Ni-SBA-15. Thermal analyses of the spent catalyst showed a substantial amount of coke deposition which could be the major factor responsible for catalysts deactivation. Bimetallic catalysts prepared by one-pot method (10%Co–5%Ni-SBA-15) and incipient wetness impregnation (10%Co–5%Ni-SBA-15-IMPG) exhibited remarkable GSR activity compared to their monometallic counterparts. The GSR activity was observed in the order: 10%Co–5%Ni-IMPG ≥ 10%Co–5%Ni > 10%Co–5%MgO >15%Co > 15%Ni > 10%Ni–5%MgO.     

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.     

Tuning the metal-support interaction of methane tri-reforming catalysts for industrial flue gas utilization

This study investigates the role of metal-support interaction (MSI) in the performance of Ni/TiO₂, Ni/SBA-15, Ni/MgO, and Ni/Al₂O₃ catalysts for the tri-reforming of methane (TRM) reaction. To impart weak metal-support interaction (WMSI), the catalysts were calcined at 400 °C. While calcination at 850 °C or above temperature generated strong metal-support interaction (SMSI) in each catalyst. The experimental results reveal that Ni/TiO₂ and Ni/MgO catalysts having WMSI displayed high initial activity due to the higher extent of reduction and Ni dispersion. However, these catalysts deactivated during 10 h reaction run. On the other hand, the performances of Ni/TiO₂ and Ni/MgO catalysts having SMSI were unsatisfactory. For Ni/SBA-15 catalyst system, catalysts having weaker MSI were more active than the catalyst having stronger MSI. However, the stability of Ni/SBA-15 catalysts was governed by Ni confinement in the pores of SBA-15 rather than the strength of MSI. Ni/Al₂O₃ having SMSI had monodispersed Ni atoms in close association with Al₂O₃, which resulted in higher reforming activity compared to that of Ni/Al₂O₃ having WMSI. Overall, the present study asserts that the strength of MSI has a significant influence on the activity and stability of methane tri-reforming catalysts; however, the suitability of either strong or weak MSI is subject to catalyst composition.     

Catalytic steam reforming of glycerol over Ni–La2O3–CeO2/SBA-15 catalyst for stable hydrogen-rich gas production

Ni-based catalysts (Ni, Ni–La₂O₃, and Ni–La₂O₃–CeO₂) on mesoporous silica supports (SBA-15 and KIT-6) were prepared by an incipient wetness impregnation and tested in glycerol steam reforming (GSR) for hydrogen-rich gas production. The catalysts were characterized by the N₂-physisorption, TPD, X-ray diffraction (XRD), SEM-EDS, and TEM techniques. N₂-physisorption results of calcined catalysts highlight that adding of La₂O₃ increased surface area of the catalyst by preventing pore mouth plugging in SBA-15, which was frequently observed due to the growth of NiO crystals. A set of GSR experiments over the catalysts were performed in an up-flow continuous packed-bed reactor at 650 °C and atmospheric pressure. The highest hydrogen concentration of 62 mol% was observed with a 10%Ni–5%La₂O₃ –5%CeO₂/SBA-15 catalyst at a LHSV of 5.8 h⁻¹. Adding of CeO₂ to the catalyst appeared to increase catalytic stability by facilitating the oxidative gasification of carbon formed on/near nickel active sites of Ni–La₂O₃–CeO₂/SBA-15 and Ni–La₂O₃–CeO₂/KIT-6 catalyst during the glycerol steam reforming reaction.     

Catalytic performance of Samaria-promoted Ni and Co/SBA-15 catalysts for dry reforming of methane

Methane reforming with CO₂ over Samaria-promoted Ni and Co/SBA-15 was comparatively investigated. The Co, Ni (10%wt) and Sm (0.5, 1 and 1.5%wt) ions were introduced by two-solvent impregnation method. The Ni and Co catalysts with/without promoter, were examined by N2 adsorption-desorption, x-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), temperature programmed reduction (TPR) and thermogravimetric analysis (TGA) methods, and then evaluated in CO₂ reforming of methane. The XRD and TEM results indicated that Ni and Co/SBA-15 promoted by 1%wt of Samaria, had the smallest NiO and Co₃O₄ particles size and the highest dispersion; as a result, they would rather studying dry reforming of methane test. Catalytic results indicated that Samaria promoted Ni/SBA-15 had the highest conversion (CH₄ conversion～58% at 700 °C), while a remarkable decrease of catalytic activity was observed over Samaria-promoted Co/SBA-15 (CH₄ conversion～25% at 700 °C). The positive effect of Samaria on Ni/SBA-15 catalyst activity is probably due to smaller NiO particles, higher NiO dispersion and lower trend to carbon deposition. On the contrary, the negative effect of Samaria on Co/SBA-15 catalyst activity is maybe due to Co oxidation to inactive phase and sintering of Co particles in high temperatures.     

Esterification of lauric acid with butanol over mesoporous materials

Mesoporous silica (e.g. SBA-15) was evaluated in the esterification of lauric acid with butanol. ZnO/SBA-15 and MgO/SBA-15 were synthesized and characterized using N₂ adsorption/desorption isotherms at 77 K, ²⁹Si magic angle spinning solid state nuclear magnetic resonance (²⁹Si MAS NMR), X-ray diffraction (XRD) and Small-Angle X-ray scattering (SAXS). The nanostructural parameters obtained from SAXS analysis were very similar for all samples revealing that the impregnation method for incorporation of Zn and Mg in mesoporous silica did not affect its structure. Both catalysts ZnO/SBA-15 and MgO/SBA-15 were able to promote the esterification reaction of lauric acid with 1-butanol at mild reactions conditions.     

Highly dispersed NiCu nanoparticles on SBA-15 for selective hydrogenation of methyl levulinate to γ-valerolactone

Copper and nickel nanoparticles highly dispersed on an ordered mesoporous silica support (SBA-15) were prepared by a glycol-assisted impregnation method and tested for the catalytic transfer hydrogenation reaction of methyl levulinate to γ-valerolactone (GVL). Characterizations by high resolution transmission electron microscopy, X-ray diffraction, N₂ sorption, H₂ temperature-programmed reduction and X-ray absorption spectroscopy confirm that the highly dispersed nanoparticles were well-anchored to the mesopores of SBA-15 with the strong interaction. Comparing to a catalyst synthesized by a conventional aqueous impregnation method, our catalyst shows a higher conversion and greater selectivity towards GVL of reaction at 140–170 °C using 2-propanol as a solvent and a hydrogen donor. Results showed that NiCu/SBA-15 (EG) had much better activity, providing 91.3% conversion of ML with 89.7% selectivity towards GVL in 3 h at 140 °C. The high compositional homogeneity, uniform distribution of the nanoparticles in the mesoporous channels and the strong interaction between the metal nanoparticles and SBA-15 contribute to the superior catalytic performance. This catalyst also demonstrates superb stability over the course of 5 reaction cycles without significant loss in catalytic activity and selectivity towards GVL formation.     

Hydrogen production from oxidative steam reforming of methanol: Effect of the Cu and Ni impregnation on ZrO2 and their molecular simulation studies

Cu and Ni were supported on ZrO₂ by co-impregnation and sequential impregnation methods, and tested in the oxidative steam reforming of methanol (OSRM) reaction for H₂ production as a function of temperature. Surface area of the catalysts showed differences as a function of the order in which the metals were added to zirconia. Among them, the Cu/ZrO₂ catalyst had the lowest surface area. XRD patterns of the bimetallic catalysts did not show diffraction peaks of the Cu, Ni or bimetallic Cu–Ni alloys. In addition, TPR profiles of the bimetallic catalysts had the lowest reduction temperature compared with the monometallic samples. The reactivity of the catalysts in the range of 250–350 °C showed that the bimetallic samples prepared by successive impregnation had highest catalytic activity among all the catalysts studied. These results were also confirmed by theoretical calculations. The reactivity of the monometallic and bimetallic structures obtained by molecular simulation followed the next order: Ni_shellCu_core/ZrO₂ ≅ Cu_shellNi_core/ZrO₂ > Ni/Cu/ZrO₂ > Cu/Ni/ZrO₂ > Cu–Ni/ZrO₂ > Cu/ZrO₂ > Ni/ZrO₂. These findings agree with the experimental results, indicating that the bimetallic catalysts prepared by successive impregnation show a higher reactivity than the Cu–Ni system obtained by co-impregnation. In addition, the selectivity for H₂ production was higher on these catalysts. This result could be associated also to the presence of the bimetallic Cu–Ni and core–shell Ni/Cu nanoparticles on the catalysts, as was evidenced by TEM–EDX analysis, suggesting that the OSRM reaction may be a structure–sensitive reaction.