Hydrogen production by steam reforming of liquefied natural gas (LNG) over nickel catalysts supported on cationic surfactant-templated mesoporous aluminas

Two types of mesoporous γ-aluminas (denoted as A-A and A-S) are prepared by a hydrothermal method under different basic conditions using cationic surfactant (cetyltrimethylammonium bromide, CTAB) as a templating agent. A-A and A-S are synthesized in a medium of ammonia solution and sodium hydroxide solution, respectively. Ni/γ-Al₂O₃ catalysts (Ni/A-A and Ni/A-S) are then prepared by an impregnation method, and are applied to hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of a mesoporous γ-Al₂O₃ support on the catalytic performance of Ni/γ-Al₂O₃ is investigated. The identity of basic solution strongly affects the physical properties of the A-A and A-S supports. The high surface-area of the mesoporous γ-aluminas and the strong metal–support interaction of supported catalysts greatly enhance the dispersion of nickel species on the catalyst surface. The well-developed mesopores of the Ni/A-A and Ni/A-S catalysts prohibit the polymerization of carbon species on the catalyst surface during the reaction. In the steam reforming of LNG, both Ni/A-A and Ni/A-S catalysts give better catalytic performance than the nickel catalyst supported on commercial γ-Al₂O₃ (Ni/A-C). In addition, the Ni/A-A catalyst is superior to the Ni/A-S catalyst. The relatively strong metal–support interaction of Ni/A-A catalyst effectively suppresses the sintering of metallic nickel and the carbon deposition in the steam reforming of LNG. The large pores of the Ni/A-A catalyst also play an important role in enhancing internal mass transfer during the reaction.     

Hydrogen production by steam reforming of liquefied natural gas over a nickel catalyst supported on mesoporous alumina xerogel

Mesoporous alumina xerogel (A-SG) is prepared by a sol–gel method for use as a support for a nickel catalyst. The Ni/A-SG catalyst is then prepared by an impregnation method, and is applied to hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of the mesoporous alumina xerogel support on the catalytic performance of Ni/A-SG catalyst is investigated. For the purpose of comparison, a nickel catalyst supported on commercial alumina (A-C) is also prepared by an impregnation method (Ni/A-C). Both the hydroxyl-rich surface and the electron-deficient sites of the A-SG support enhance the dispersion of the nickel species on the support during the calcination step. The formation of the surface nickel aluminate phase in the Ni/A-SG catalyst remarkably increases the reducibility and stability of the catalyst. Furthermore, the high-surface area and the well-developed mesoporosity of the Ni/A-SG catalyst enhance the gasification of surface hydrocarbons that are adsorbed in the reaction. In the steam reforming of LNG, the Ni/A-SG catalyst exhibits a better catalytic performance than the Ni/A-C catalyst in terms of LNG conversion and hydrogen production. Moreover, the Ni/A-SG catalyst shows strong resistance toward catalyst deactivation.     

Effect of calcination temperature of mesoporous alumina xerogel (AX) supports on hydrogen production by steam reforming of liquefied natural gas (LNG) over Ni/AX catalysts

Mesoporous alumina xerogel (AX) supports prepared by a sol–gel method were calcined at various temperatures. Ni/mesoporous alumina xerogel (Ni/AX) catalysts were then prepared by an impregnation method, and were applied to the hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of calcination temperature of AX supports on the catalytic performance of Ni/AX catalysts in the steam reforming of LNG was investigated. Physical and chemical properties of AX supports and Ni/AX catalysts were strongly influenced by the calcination temperature of AX supports. Crystalline structure of AX supports was transformed in the sequence of γ-alumina → (γ + θ)-alumina → θ-alumina → (θ + α)-alumina with increasing calcination temperature from 700 to 1000 °C. Nickel species were strongly bonded to the divalent vacancy of γ-alumina, (γ + θ)-alumina, and θ-alumina through the formation of nickel aluminate phase. In the steam reforming of LNG, both LNG conversion and hydrogen composition in dry gas showed volcano-shaped curves with respect to calcination temperature of AX supports. Among the catalysts tested, Ni/AX-900 (nickel catalyst supported on AX that had been calcined at 900 °C) showed the best catalytic performance. The smallest nickel crystalline size and the strongest nickel–alumina interaction were responsible for high catalytic performance of Ni/AX-900 catalyst in the steam reforming of LNG.     

Hydrogen production by steam reforming of liquefied natural gas (LNG) over mesoporous Ni-Al2O3 aerogel catalyst prepared by a single-step epoxide-driven sol-gel method

A mesoporous Ni-Al₂O₃ aerogel catalyst was prepared by a single-step epoxide-driven sol-gel method and a subsequent supercritical CO₂ drying method (NA-ES catalyst). For comparison, a mesoporous Ni-Al₂O₃ aerogel catalyst was also prepared by a single-step alkoxide-based sol-gel method and a subsequent supercritical CO₂ drying method (NA-AS catalyst). Differences in physicochemical properties and catalytic activities of mesoporous Ni-Al₂O₃ aerogel catalysts in the steam reforming of liquefied natural gas (LNG) were investigated. Textural properties of Ni-Al₂O₃ aerogel catalysts were affected by the preparation method. Nickel species were highly dispersed in alumina through the formation of nickel aluminate phase in both NA-ES and NA-AS catalysts. However, chemical states of Al atoms in both catalysts were quite different. In addition, nickel species in the NA-ES catalyst exhibited high reducibility and high dispersion compared to those in the NA-AS catalyst. In the steam reforming of LNG, NA-ES catalyst exhibited a better catalytic performance than NA-AS catalyst in terms of LNG conversion and hydrogen yield, although both catalysts showed a stable catalytic performance during the reaction without deactivation behavior. Furthermore, NA-ES catalyst with small average nickel diameter suppressed water-gas shift reaction. Reducibility and dispersion of nickel species served as important factors determining the catalytic performance of the catalysts.     

Hydrogen production by auto-thermal reforming of ethanol over nickel catalyst supported on mesoporous yttria-stabilized zirconia

Mesoporous yttria-stabilized zirconia (YSZ-X) supports with different Y/Zr molar ratio (X) were prepared by a sol–gel method. 20 wt% Ni catalysts supported on YSZ-X (X = 0, 0.1, 0.2, and 0.3) were then prepared by an incipient wetness impregnation method for use in hydrogen production by auto-thermal reforming of ethanol. The effect of Y/Zr molar ratio (X) on the catalytic performance of Ni/YSZ-X (X = 0, 0.1, 0.2, and 0.3) catalysts was investigated. Hydrogen selectivity and by-product distributions over the catalysts were different depending on the Y/Zr molar ratio (X). Hydrogen selectivity over Ni/YSZ-X (X = 0, 0.1, 0.2, and 0.3) catalysts showed a volcano-shaped curve with respect to Y/Zr molar ratio (X). Among the catalysts tested, Ni/YSZ-0.1 showed the best catalytic performance and the lowest carbon deposition in hydrogen production by auto-thermal reforming of ethanol. High reducibility and excellent structural stability of Ni/YSZ-0.1 catalyst were responsible for its superior catalytic performance.     

Hydrogen production by steam reforming of liquefied natural gas (LNG) over mesoporous Ni-La-Al2O3 aerogel catalysts: Effect of La content

Mesoporous Ni-La-Al₂O₃ aerogel catalysts (denoted as (40-x)NixLa) with different lanthanum content (x) were prepared by a single-step sol-gel method and a subsequent CO₂ supercritical drying method. The effect of lanthanum content on the physicochemical properties and catalytic performance of mesoporous (40-x)NixLa catalysts in the steam reforming of liquefied natural gas (LNG) was investigated. Physicochemical properties of (40-x)NixLa catalysts were strongly influenced by lanthanum content. Dispersion and reducibility of nickel aluminate phase in the (40-x)NixLa catalysts increased with increasing lanthanum content. Small amount of lanthanum addition was effective for dispersion of metallic nickel in the (40-x)NixLa catalysts, but large amount of lanthanum addition was not favorable for nickel dispersion due to the blocking of active sites. In the steam reforming of LNG, both LNG conversion and hydrogen yield showed volcano-shaped curves with respect to lanthanum content. Average nickel diameter of (40-x)NixLa catalysts was well correlated with LNG conversion and hydrogen yield over the catalysts. Among the catalysts tested, 36Ni4La (36 wt% Ni and 4 wt% La) catalyst with the smallest average nickel diameter exhibited the best catalytic performance and the strongest resistance toward carbon deposition in the steam reforming of LNG.     

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.     

Hydrogen production from glycerin by steam reforming over nickel catalysts

Increasing biodiesel production has resulted in a glut of glycerin that has led to a precipitous drop in market prices. In this study, the use of glycerin as a biorenewable substrate for hydrogen production, using a steam reforming process, has been evaluated. Production of hydrogen from glycerin is environmentally friendly because it adds value to this byproduct generated from biodiesel plants. The study focuses on nickel-based catalysts with MgO, CeO₂, and TiO₂ supports. Catalysts were characterized with thermogravimetric analysis and X-ray diffraction techniques. Maximum hydrogen yield was obtained at 650 °C with MgO supported catalysts, which corresponds to 4 mol of H₂ out of 7 mol of stoichiometric maximum.     

Hydrogen production by steam reforming of simulated liquefied natural gas (LNG) over mesoporous nickel-M-alumina (M = Ni, Ce, La, Y, Cs, Fe, Co, and Mg) aerogel catalysts

Mesoporous nickel-M-alumina aerogel catalysts (denoted as NiMAE) with different second metal (M = Ni, Ce, La, Y, Cs, Fe, Co, and Mg) were prepared by a single-step sol-gel method and a subsequent CO₂ supercritical drying method. The effect of second metal of mesoporous nickel-M-alumina aerogel catalysts on their physicochemical properties and catalytic activity for steam reforming of simulated liquefied natural gas (LNG) was investigated. Textural and chemical properties of NiMAE catalysts were strongly influenced by the identity of second metal. Nickel species were highly dispersed on the surface of NiMAE catalysts through the formation of nickel aluminate phase. In the steam reforming of LNG, both LNG conversion and hydrogen yield decreased in the order of NiLaAE > NiCeAE > NiYAE > NiCsAE > NiNiAE > NiFeAE > NiCoAE > NiMgAE. Average nickel diameter of NiMAE catalysts was well correlated with LNG conversion and hydrogen yield over the catalysts. Among the catalysts tested, NiLaAE catalyst exhibited the best catalytic performance due to its smallest average nickel diameter. Furthermore, NiLaAE catalyst exhibited a strong capability of facilitating heat and mass transfer of reactant and product during the steam reforming of LNG. Water-gas shift reaction governed the steam reforming reaction over NiLaAE catalyst under the steam-rich reaction condition (steam/carbon > 2).     

Hydrogen production via the glycerol steam reforming reaction over nickel supported on alumina and lanthana-alumina catalysts

In the present work, a comparative study of Ni catalysts supported on commercially available alumina and lanthana-alumina carriers was undertaken for the glycerol steam reforming reaction (GSR). The supports and/or catalysts were characterized by PZC, BET, ICP, XRD, NH₃-TPD, CO₂-TPD, TPR and SEM. Carbon deposited on the catalytic surface was characterized by SEM, TPO and Raman. Concerning the Ni/LaAl sample it can be concluded that the presence of lanthana by: (a) facilitating the active species dispersion, (b) strengthening the interactions between nickel species and support, (c) increasing of the basic sites' population and redistributing the acid ones in terms of strength and density, provides a catalyst with improved performance for the GSR reaction, in terms of activity, H₂ production and long term stability. TPO and Raman indicate that the carbon on the Ni/LaAl catalyst was mostly amorphous and was deposited mainly on the support surface. For the Ni/Al catalyst, graphitic carbon was prevalent and likely covered its active sites.     

Hydrogen production by auto-thermal reforming of ethanol over nickel catalyst supported on metal oxide-stabilized zirconia

Metal oxide-stabilized mesoporous zirconia supports (M–ZrO₂) with different metal oxide stabilizer (M = Zr, Y, La, Ca, and Mg) were prepared by a templating sol–gel method. 20 wt% Ni catalysts supported on M–ZrO₂ (M = Zr, Y, La, Ca, and Mg) were then prepared by an incipient wetness impregnation method for use in hydrogen production by auto-thermal reforming of ethanol. The effect of metal oxide stabilizer (M = Zr, Y, La, Ca, and Mg) on the catalytic performance of supported nickel catalysts was investigated. Ni/M–ZrO₂ (M = Y, La, Ca, and Mg) catalysts exhibited a higher catalytic performance than Ni/Zr–ZrO₂, because surface oxygen vacancy of M–ZrO₂ (M = Y, La, Ca, and Mg) and reducibility of Ni/M–ZrO₂ (M = Y, La, Ca, and Mg) were enhanced by the addition of lower valent metal cation. Hydrogen yield over Ni/M–ZrO₂ (M = Zr, Y, La, Ca, and Mg) catalyst was monotonically increased with increasing both surface oxygen vacancy of M–ZrO₂ support and reducibility of Ni/M–ZrO₂ catalyst. Among the catalysts tested, Ni catalyst supported on yttria-stabilized mesoporous zirconia (Ni/Y–ZrO₂) showed the best catalytic performance.     

Hydrogen production via steam reforming of ethylene glycol over Attapulgite supported nickel catalysts

Steam reforming of ethylene glycol was investigated over Ni-based catalysts supported on Attapulgite (ATP; originating from Jiangsu (JS), Anhui, and Gansu (GS) provinces in China). N₂ adsorption–desorption, XRD, FTIR, H₂-TPR, NH₃-TPD, SEM, and TEM-EDS measurements were performed to analyze the catalyst properties. The results revealed that Ni/ATP_GS had the largest particle size (17.9 nm) and the highest reductive degree (98.0%). Consequently, Ni/ATP_GS showed the highest ethylene glycol conversion (97.2%) during the first 4 h of reaction. However, this catalyst showed the lowest H₂ yield (71.2%), possibly owing to large Ni particle sizes as well as ample surface acidic sites and acidity, leading to a high selectivity toward CH₄ (20.8%) and C₂H₄ (2.2%). In contrast, Ni/ATP_JS presented the highest H₂ yield (89.8%) owing to it having the smallest Ni particle sizes and lowest amount of surface acidic sites. Additionally, this catalyst showed the highest stability over 8 h of reaction. An examination of the spent catalysts revealed that Ni/ATP_JS possessed excellent antisintering and coking properties.     

Hydrogen production from acetic acid steam reforming over Ti-modified Ni/Attapulgite catalysts

Steam reforming of bio-oil derived oxygenates is a green and sustainable method for hydrogen production. In this work, hydrogen production from steam reforming of acetic acid (SRAA) was investigated over Ti-modified Ni/Attapulgite (ATP) catalysts that prepared via sequential precipitation technique. The effects of Ti additive, precipitation sequence and Ti-salt precursors (TiCl₄, TiOSO₄) on the structural and physicochemical properties of catalysts were characterized by N₂ adsorption-desorption, XRD, FT-IR, HRTEM, XPS, H₂-TPR and NH₃-TPD. These results indicated that the interaction among Ti species, Ni active metal and ATP enhanced the reduction performance as well as weakened surface acidity of the Ni/ATP catalyst, and also promoted the electron transfer to form Ni^δ? species. Obviously, compared with Ti precursor salts, the precipitation sequences played a key role in determining the surface properties of Ti-modified catalysts. Among them, the Ni–Ti_S/ATP catalyst synthesized by co-precipitation method exhibited better reducibility and lower surface acidity, as well as produced more Ni^δ? species and Ni^δ?-O_v-Ti³⁺ interface sites. Then the synergistic effects among the above-mentioned characters made the Ni–Ti_S/ATP catalyst present highest carbon conversion (93.4%) and H₂ yield (77.6%) during SRAA reactions. The analyses of XRD, HRTEM and TG were implemented on used catalysts and discovered Ni–Ti_S/ATP catalysts shown promising metal sintering and coke resistance, which mainly caused by the presence of flat Ni–Ti@ATP structures. The possible conversion mechanism of acetic acid in the flat Ni–Ti@ATP structure of co-precipitation Ti-modified catalyst was also elucidated.     

Glycerol steam reforming over Ni catalysts supported on ceria and ceria-promoted alumina

In this paper glycerol steam reforming over Ni catalysts supported on bare CeO₂ and Al₂O₃, and CeO₂-promoted Al₂O₃ to produce H₂ was studied. The catalytic activity results for the NiAl5Ce and NiAl10Ce catalysts showed that the incorporation of low ceria loadings enhances the activity of the NiAl catalyst prepared using a similar composition to the commercial Ni/Al₂O₃ catalysts. The catalyst surface characterization revealed that the good behaviour of the NiAl5Ce and the NiAl10Ce catalysts depends on the stabilization of Ni° particles which is promoted by the formation of nickel–ceria interactions. The increase of ceria content reduced the capacity of the NiAl20Ce catalyst to convert intermediate oxygenated hydrocarbons into H₂.     

Production of hydrogen by ethanol steam reforming over catalysts from reverse microemulsion-derived nanocompounds

In the present work, hydrotalcite-like compound precursor for preparing mixed oxide catalyst was successfully synthesized by a novel method, which was a combination of the reverse microemulsion and coprecipitation methods. It was observed that the precursor obtained from the above method possessed superior characteristics for preparing mixed oxide catalyst used in ethanol steam reforming (ESR). Furthermore, for comparison, catalysts prepared from conventional coprecipitation and impregnation methods had been characterized together with the catalyst prepared from the new method. Besides ICP, BET, X-ray diffraction (XRD), temperature-programmed reduction (TPR), H₂-TPD, TG, and TEM analytic techniques, catalytic performance for ESR was also investigated. The results of XRD and TPR indicated that a solid solution phase existed in the catalysts obtained from reverse microemulsion and coprecipitation methods, while spinel phase together with solid solution were observed in the catalyst obtained from the impregnation method. The high BET surface area of the catalyst obtained from the reverse microemulsion method enhanced the dispersion and the surface area of nickel, which improved the catalyst performance. From TEM images, the aggregated Ni could be found in the catalyst obtained from the impregnation method, while the hydrotalcite-like compound precursors prepared from reverse microemulsion and coprecipitation methods produced homogeneously distributed active Ni metal species. The catalyst obtained from reverse microemulsion exhibited the best activity, stability, and least carbon deposition because of the formation of hydrotalcite-like compound precursor, uniform dispersion of active Ni metal species, and much more surface area supporting the active Ni metal sites.     

Effect of impregnation sequence of Mg on performance of mesoporous alumina supported Ni catalyst in dry reforming of methane

In this study, effect of Mg impregnation sequence on the activity of the mesoporous alumina supported Ni catalysts was investigated in dry reforming of methane. Characterization and activity test results showed that Mg incorporation sequence significantly influenced the physicochemical properties and the activity of the catalyst as well as coke deposition during reforming reaction. The synthesized catalysts were characterized by x-ray diffraction, N₂ adsorption, temperature programmed reduction, scanning electron microscopy, CO₂-temperature programmed desorption, inductively coupled plasma optical emission spectrometry, x-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy (FTIR) and pyridine adsorbed diffuse reflectance FTIR spectroscopy techniques. Mg incorporation altered the reduction profile of the monometallic catalyst and increased the reduction temperature of the nickel particles. XRD diffraction peaks corresponding to γ-A₂O₃ and α-Al₂O₃, as well as nickel-magnesium spinels and metallic Ni were observed depending on Mg incorporation sequence. The monometallic Ni catalyst showed higher activity than the bimetallic NiMg catalysts. However, coke formation was significantly influenced as a result of synthesis route. Total organic carbon, thermogravimetric analysis and SEM images exhibited that the highest coke formation was obtained over the catalyst which was prepared by sequential impregnation of Mg and then Ni. Almost no coke formation was observed on the spent catalyst, which was synthesized by simultaneously impregnation of Mg and Ni, due to the high interaction between Ni and Mg with the formation of a NiOMgO solid solution during the high calcination temperature.     

Pre-reforming of liquefied petroleum gas over nickel catalysts supported on magnesium aluminum mixed oxides

A series of Ni/Mg_xAl catalysts with different Mg/Al molar ratios were prepared by impregnating Mg-Al mixed oxides with nickel nitrate aqueous solution and used for the pre-reforming of LPG in the temperature range of 400-500 °C. XRD and H₂-TPR results showed that the Ni/Mg_xAl catalysts calcined at 800 °C mainly consisted of γ-Al₂O₃, Mg(Ni)Al₂O₄ and Mg(Ni)O phases varying with Mg/Al molar ratio without free NiO species observed. The effects of Mg/Al molar ratio, S/C molar ratio and reaction temperature on the catalytic behavior of the Ni/Mg_xAl catalysts were investigated in detail. The results revealed that the catalyst with Mg/Al molar ratio of 1.25 had the highest catalytic activity and stability. The increase in S/C molar ratio promoted both the steam reforming of LPG and the methanation of carbon oxides and hydrogen. The stability tests of 15%Ni/Mg_1.25Al catalyst showed that the catalyst was stable for the pre-reforming of LPG, and the stability decreased with elevating the reaction temperature due to more coke deposition.     

Hydrogen-rich gas production from waste plastics by pyrolysis and low-temperature steam reforming over a ruthenium catalyst

Operating conditions for low-temperature pyrolysis and steam reforming of plastics over a ruthenium catalyst were investigated. In the range studied, the highest gas and lowest coke fractions for polystyrene (PS) with a 60 g h⁻¹ scale, continuous-feed, two-stage gasifier were obtained with a pyrolyzer temperature of 673 K, steam reforming temperature of 903 K, and weight hourly space velocity (WHSV) of 0.10 g-sample g-catalyst⁻¹ h⁻¹. These operating conditions are consistent with optimum conditions reported previously for polypropylene. Our results indicate that at around 903 K, the activity of the ruthenium catalyst was high enough to minimize the difference between the rates of the steam reforming reactions of the pyrolysates from polystyrene and polypropylene. The proposed system thus has the flexibility to compensate for differences in chemical structures of municipal waste plastics. In addition, the steam reforming temperature was about 200 K lower than the temperature used in a conventional Ni-catalyzed process for the production of hydrogen. Low-temperature steam reforming allows for lower thermal input to the steam reformer, which results in an increase in thermal efficiency in the proposed process employing a Ru catalyst. Because low-temperature steam reforming can be also expected to reduce thermal degradation rates of the catalyst, the pyrolysis-steam reforming process with a Ru catalyst has the potential for use in small-scale production of hydrogen-rich gas from waste plastics that can be used for power generation.     

Hydrogen production by steam reforming of acetic acid: Comparison of conventional supported metal catalysts and metal-incorporated mesoporous smectite-like catalysts

The activities of various metal catalysts were tested in steam reforming of acetic acid for the production of H₂, using conventional metal oxides and transition metal-incorporated mesoporous smectite-like materials as supports. It has been found that Pt is superior to Ni, Co, and Fe among Al₂O₃ supported catalysts, Al₂O₃ is more effective than ZrO₂ and SiO₂ as support for Pt, Ni incorporated smectite (SM(Ni)) support is more effective than Fe and Co incorporated ones for Pt, and SM(Ni) is also active in the absence of Pt. The total activity for the conversion of acetic acid is in the order of Pt/Al₂O₃ > Pt/SM(Ni) > SM(Ni) but the ability of H₂ production is comparable among these catalysts. These catalysts (and the other ones) were observed to lose their activities during the reforming reactions. The activity of Pt/Al₂O₃ decreased during the whole course of reaction up to 10 h. In contrast, the activity of SM(Ni) also decreased within 2 h but it showed a stable activity in the following stage of reaction. The initial activity of the used Pt/SM(Ni) and SM(Ni) was able to be almost completely restored by thermal treatment with H₂ but less effectively for the used Pt/Al₂O₃. The catalyst deactivation was shown to occur by the formation and deposition of carbon materials on the catalysts (XRD, TEM, thermal analysis). The properties of carbon deposits formed on Pt/Al₂O₃ and SM(Ni) catalysts should be different and this may be responsible for the differences in the extent of deactivation and in the regeneration behavior between the two catalysts.     

Hydrogen production from acetic acid steam reforming over nickel-based catalyst synthesized via MOF process

In our earlier work, we have reported that Ni supported on γ-Al₂O₃–La₂O₃–CeO₂ (ALC) catalyst prepared via metal organic framework (MOF) was more active for acetic acid steam reforming (AASR) [1]. Here we report detailed study on the performance of this catalyst for AASR. Effects of operating conditions such as temperatures (400–650 °C), steam to carbon molar ratio (S/C) and feed flow rate (1.5–5.5 mL/h) were evaluated and optimized. Results showed an excellent activity for AASR at the molar ratio S/C = 6.5, feed flow rate = 2.5 mL/h and, at 600 °C with almost total conversion and more than 90% of H₂ yield. The ordered porous structure of embedded nickel supported catalyst promotes excellent steam reforming activity and water gas shift reaction even at low temperatures, which leads to the good stable behaviour up to 36 h of TOS. The coke formation was also significantly suppressed by ALC support. Catalyst regenerated by passing oxygen at 500 °C and followed by reduction in hydrogen also show a good activity. Catalysts were characterized by DT-TGA, XRD, TEM, H₂-TPR and N₂-adsorption-desorption to understand the micro structure and coke deposition behaviour.