Activity For Steam Reforming Research Articles

Comparative study on steam reforming of model aromatic compounds of biomass tar over Ni and Ni–Fe alloy nanoparticles

Steam reforming of tar model compounds (benzene, toluene and phenol) was carried out using Ni–Fe/Mg/Al catalysts prepared by calcination and reduction of hydrotalcite-like precursor. Ni–Fe/Mg/Al (Fe/Ni=0.25) catalyst showed higher activity (∼twice conversion rate based on catalyst weight) and better resistence to carbon deposition (∼one order smaller amount of deposited carbon) than Ni/Mg/Al. The difference in the weight-based rate and carbon deposition amount between catalysts with and without Fe was large when benzene or toluene was used as a substrate and high steam/carbon (S/C) ratio was applied. On the other hand, when phenol was used as a substrate, relatively large amount of carbon derived from decomposition of phenol was deposited on Ni–Fe/Mg/Al catalyst even with high (3.8) S/C ratio. The catalyst loses some activity for steam reforming of toluene when treated with phenol (untreated catalyst: ∼80% conversion of toluene (rate 51μmolg−1-cats−1); treated catalyst ∼60% (rate 38μmolg−1-cats−1)), probably because of the deposited carbon from phenol. Kinetic studies and O2- or H2O-TPO studies showed that phenol was strongly adsorbed on Fe site as well as Ni site, and the adsorbed phenol could be converted into carbonaceous species under the reaction conditions. On the other hand, the adsorbed phenol on Ni site underwent steam reforming, and the reaction was promoted by Fe.

Steam Reforming of Methane Over Catalyst Derived from Ordered Double Perovskite: Effect of Crystalline Phase Transformation

La2NiTiO6 double perovskite was synthesized by modified Pechini method. The catalyst activity for steam reforming of methane was investigated at temperatures from 450 to 950 °C, under different reduction conditions. By reducing La2NiTiO6 with 10 % H2/N2 at 1,000 °C, the crystalline phase changed to mainly Ni0 and La2TiO5, which decreases the onset temperature of methane conversion to 550 °C and provides a maximum methane conversion of 95 % at 950 °C. This activity is higher when compared to that achieved with La2NiTiO6 reduced with 1.8 % H2/Ar, which is composed of Ni0 supported on both non-stoichiometric La2NiTiO6 and La2O3, and also to those of unreduced La2NiTiO6 and Ni/La2O3 formed by reduction of LaNiO3. Activity improvement is related to the increased number of active sites and/or metal-support interaction.

Effects of Manganese Oxide Addition on Coking Behavior of Ni/YSZ Anodes for SOFCs

AbstractSolid oxide fuel cells with Ni‐MnO/yttria‐stabilized‐zirconia (YSZ) tricomposite anode supports were fabricated with different MnO concentrations, and the coking tolerances and catalytic activities were investigated in wet CH4 atmosphere. Ni0.9(MnO)0.1/YSZ (10MnO) anode support cell exhibited a maximum power density of 210, 354, 505, and 620 mWcm−2 at 700, 750, 800, and 850 °C, respectively, in H2. Moreover, a maximum power density in wet CH4 reaches 504 mWcm−2 at 800 °C; while the Ni/YSZ cell showed poorer performances. The coking tolerance improved with an increase in their MnO content, and the 10MnO anode showed the highest tolerance. 10MnO exhibited stable performance for more than 40 h in wet CH4 without undergoing deactivation. Furthermore, it showed negligible coke formation of 0.0045 g of coke per catalyst, during testing under steam reforming‐like conditions at a steam‐to‐carbon (S/C) ratio of 1. Outlet gas chromatography analysis indicated that MnO suppresses CH4 cracking, while only minimally lowering the catalytic activity of steam reforming. Thus, it can be inferred that MnO promotes the adsorption of steam and oxygen on the reaction sites, owing to its high basicity and oxygen storage capacity. The increase in the local S/C and oxygen‐to‐carbon ratios suppresses CH4 cracking and promotes coke gasification.

Dynamic hydrogen production from ethanol steam-reforming reaction on NixMoy/SBA-15 catalytic system

This study examined the effects of advanced bimetallic catalytic species of Ni and Mo on hydrogen production from ethanol steam reforming. NixMoy/SBA-15 exhibited significantly higher ethanol steam-reforming activity at mild temperatures than monometallic Ni/SBA-15; the highest activity was achieved using the Ni0.95Mo0.05/SBA-15 catalyst. H2 production and ethanol conversion were maximized at 70–87% and 90–92%, respectively, over the temperature range of 500 to 800 °C with an EtOH : H2O ratio of 1:3 and a gas hourly space velocity of 3000 h−1. This highlights the synergy between the Ni and Mo loading on SBA-15 during ethanol steam reforming through the inhibition of Ni particle agglomeration and the consequent decrease in catalytic deactivation. In the proposed mechanism for ethanol steam reforming, Mo oxide promotes CH4-steam reforming at lower temperatures and depresses the CO-water gas shift reaction. Overall, hydrogen production is significantly higher over NixMoy/SBA-15 than over monometallic Ni/SBA-15 despite the evolution of CO gas. Copyright © 2014 John Wiley & Sons, Ltd.

Production of renewable hydrogen by steam reforming of tar from biomass pyrolysis over supported Co catalysts

Co catalyst supported on BaAl12O19 (BA) showed higher activity in the steam reforming of tar from the pyrolysis of biomass than those supported on Al2O3, ZrO2, SiO2, MgO, and TiO2. Characterization results indicate that the Co metal particles supported on BA had high dispersion, although the surface area of Co/BA was small. High dispersion of Co metal particles on BA can account for the high steam reforming activity, and this high dispersion is related to the strong basicity of the BA surface. Strong basicity of BA and high dispersion of Co metal particles on BA are connected to high H2O reactivity to form H2, probably at the interface between Co metal and BA. In addition, the Co/BA catalyst exhibited higher reusability through the coke combustion and the subsequent reduction treatment than the Co/Al2O3 catalyst. This is attributed to the suppression of the solid reaction between the oxidized Co and BA.

Effect of support composition and metal loading on Au catalyst activity in steam reforming of methanol

Gold (Au) supported on CeO2–Fe2O3 catalysts prepared by the deposition-coprecipitation technique were investigated for steam reforming of methanol (SRM). The 3 wt% Au/CeO2–Fe2O3 sample calcined at 400 °C achieved 100% methanol conversion and 74% hydrogen yield due to a strong Ce–Fe interaction in the active solid solution phase, CexFe1−xO2. The sintering of Au particles was observed when the highest metal content of 5 wt% was registered, which worsened the SRM activity. According to the TPR and TPO analysis, it was found that the transformation of the α-Fe2O3 structure in the mixed oxides and the coke deposition were the main factors for the rapid deactivation of the catalyst.

Catalytic properties of Ni-Zn alloy prepared by mechanical alloying for steam reforming from methanol

Amorphous Zn65Ni35 alloy, the composition of which lies between β1-NiZn and γ-NiZn phases, was prepared by mechanical alloying for 200 hours. The alloy was heat treated at various temperatures and leached in NaOH solution in an effort to enhance the catalytic properties for hydrogen production from methanol. X-ray diffraction study revealed that the amorphous phase crystallized during the heat treatment to the equilibrium β1-NiZn and γ-NiZn phases. It was found that Zn65Ni35 alloy leached after heat treatment at 928 K showed the highest catalytic activity for steam reforming of methanol. It is believed that the enhanced catalytic activity of the Zn65Ni35 alloy heat treated at 928 K is due to the dispersed Ni particles on β1-ZnNi matrix which was formed during leaching of the γ-Zn21Ni5 phase.

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 CO 2 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).

Evolution of microstructure induced by calcination in leached Al–Cu–Fe quasicrystal and its effects on catalytic activity

Effects of calcination on catalytic activity for steam reforming of methanol (SRM) over an Al–Cu–Fe quasicrystal (QC) leached with NaOH aq. have been investigated in terms of microstructure with X-ray diffraction and transmission electron microscope (TEM). Calcination at 600 °C in air drastically improved the catalytic activity of the leached QC. TEM observations on cross-section of the samples revealed that cubic Cu x Fe3-x-y Al y O4 spinel was formed at the outermost layer of the leached QC after calcinations. Prior to the catalytic reaction, the Cu x Fe3-x-y Al y O4 spinel decomposed to a composite where fine Cu nanoparticles dispersed in (Fe,Al)3O4 matrix under H2 treatment at 300 °C. Drastic increase in catalytic activity is responsible for the fine Cu nanoparticles in the composite. The Cu nanoparticles sit along the same orientation with (Fe,Al)3O4, e.g., Cu [013]//(Fe,Al)3O4 [013] and Cu [200]//(Fe,Al)3O4 [400]. This orientation relationship may stabilize the Cu nanoparticles through a bonding of Cu–O–Fe.

Effect of nickel nano-particle sintering on methane reforming activity of Ni-CGO cermet anodes for internal steam reforming SOFCs

In the present study, a single step synthesis of nano-sized NiO–Ce0.9Gd0.1O2 (NiO–CGO) composite powder was successfully accomplished by a glycine-nitrate-process (GNP) and its catalytic activity for steam reforming of methane (SRM) was investigated in the absence of electrochemical effects. From XRD, SEM and CHN analysis on the spent Ni-CGO cermet catalysts after the test with different flow rates and S/C ratios, we found that the main reason for the decrease in the reforming activity was not due to oxidation or sintering of bulk Ni catalyst and carbon formation on the catalyst surface. Time-on-stream analysis at 800°C for 80h showed a continuous decease in the reforming activity for steam rich conditions (S/C=1.5) whereas a constant and moderate reforming activity was observed for steam lean conditions (S/C=0.5). From TEM analysis it is clearly evidenced that the reason for continuous decrease in the reforming activity under steam rich conditions was due to nickel nano-particle sintering whereas no sintering occurred under steam lean conditions which indicated that the steam was primary cause for nickel nano-particle sintering. Furthermore, TEM/EDS analysis confirmed that the nickel nano-particles were mainly located on the surface of the CGO support which can suppress the carbon formation by maintaining good metal (Ni)–support (CGO) interaction even under steam lean conditions.

Effect of Ni/Al atomic ratio of mesoporous Ni–Al 2O 3 aerogel catalysts on their catalytic activity for hydrogen production by steam reforming of liquefied natural gas (LNG)

Mesoporous Ni–Al 2O 3 ( XNiAE) aerogel catalysts with different Ni/Al atomic ratio ( X) were prepared by a single-step sol-gel method and a subsequent CO 2 supercritical drying method. The effect of Ni/Al atomic ratio of mesoporous XNiAE aerogel catalysts on their physicochemical properties and catalytic activity for steam reforming of liquefied natural gas (LNG) was investigated. Textural properties and chemical properties of XNiAE catalysts were strongly influenced by Ni/Al atomic ratio. Nickel species were highly dispersed on the surface of XNiAE catalysts through the formation of surface nickel aluminate phase. In the steam reforming of LNG, both LNG conversion and hydrogen yield showed volcano-shaped curves with respect to Ni/Al atomic ratio. Average nickel diameter of XNiAl catalysts was well correlated with LNG conversion and hydrogen yield over the catalysts. Among the catalysts tested, 0.35NiAE (Ni/Al = 0.35) catalyst with the smallest average nickel diameter showed the best catalytic performance. The highest surface area, the largest pore volume, the largest average pore size, and the highest reducibility of 0.35NiAE catalyst were also partly responsible for its superior catalytic performance.

Effect of calcination temperature of mesoporous nickel–alumina catalysts on their catalytic performance in hydrogen production by steam reforming of liquefied natural gas (LNG)

Mesoporous nickel–alumina (Ni–A-NS) catalysts prepared by a non-ionic surfactant-templating method were calcined at various temperatures for use in hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of calcination temperature of nickel–alumina catalysts on their physicochemical properties and catalytic activity for steam reforming of LNG was investigated. Nickel oxide species were finely dispersed on the surface of Ni–A-NS catalysts through the formation of nickel aluminate phase. Reducibility, nickel surface area, and nickel dispersion of Ni–A-NS catalysts decreased with increasing calcination temperature. In the steam reforming of LNG, both LNG conversion and hydrogen composition in dry gas decreased with increasing calcination temperature of Ni–A-NS catalysts. Nickel surface area and reducibility of Ni–A-NS catalysts were well correlated with catalytic performance of the catalysts. Among the catalysts tested, Ni–A-NS700 (nickel–alumina catalyst calcined at 700 °C) with the highest nickel surface area and the highest reducibility exhibited the best catalytic performance.

Promoting effect of small amount of Fe addition onto Co catalyst supported on α-Al 2O 3 for steam reforming of ethanol

We examined the promotion effect of loading small amounts of Fe onto various Co catalysts for steam reforming of ethanol. Among these catalysts, catalysts supported on SrTiO 3 and α-Al 2O 3 showed remarkable effects of iron loading onto cobalt catalyst. The Fe-loaded Co/α-Al 2O 3 showed higher yield of hydrogen, low coke deposition on the catalysts, and high activity for steam reforming of acetaldehyde, which was an intermediate of the steam reforming of ethanol. Characterization of the catalyst revealed that Fe and Co metal coexisted on the catalyst support. Synergetic effects of these two metals were observed.

Preparation of alkali-resistant, Sil-1 encapsulated nickel catalysts for direct internal reforming-molten carbonate fuel cell

Abstract A thin layer of silicalite-1 zeolite membrane was grown on the surface of Ni/SiO 2 and Ni/Al 2 O 3 catalyst beads after seeding and secondary regrowth to create core–shell catalysts that are resistant to alkali poisoning from direct internal reforming-molten carbonate fuel cell (DIR-MCFC). The zeolite shell thickness was optimized to prevent poisoning and minimize diffusion resistance. An out-of-cell test was designed to simulate the fuel cell operating conditions, which showed that the new core–shell catalysts maintained a high activity similar to the original fresh catalyst in spite of the exposure to alkali vapor at high temperature. The conventional Ni/SiO 2 and Ni/Al 2 O 3 catalysts suffered higher than 80% decrease in activity for steam reforming of methane reaction (SRM).

Effect of preparation method of mesoporous Ni–Al2O3 catalysts on their catalytic activity for hydrogen production by steam reforming of liquefied natural gas (LNG)

Abstract Mesoporous Ni–Al 2 O 3 catalysts were prepared by impregnation method (NiAl-IP), co-precipitation method (NiAl-CP), and sequential precipitation method (NiAl-SP) for use in hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of preparation method of mesoporous Ni–Al 2 O 3 catalysts on their catalytic activity for steam reforming of LNG was investigated. Physicochemical properties of Ni–Al 2 O 3 catalysts were strongly influenced by the preparation method of Ni–Al 2 O 3 catalysts. Surface area, pore volume, and average pore size of Ni–Al 2 O 3 catalysts decreased in the order of NiAl-SP > NiAl-CP > NiAl-IP. Nickel species strongly interacted with Al 2 O 3 supports through the formation of nickel aluminate phase. Surface nickel aluminate phase of Ni–Al 2 O 3 catalysts was readily reduced after the reduction process, while bulk nickel aluminate phase of NiAl-CP catalyst was hardly reducible. Nickel dispersion and nickel surface area of Ni–Al 2 O 3 catalysts decreased in the order of NiAl-SP > NiAl-CP > NiAl-IP. Among the catalysts tested, NiAl-SP catalyst with the highest nickel surface area showed the best catalytic performance in the steam reforming of LNG. Furthermore, finely dispersed nickel species in the NiAl-SP catalyst efficiently suppressed the carbon deposition during the reaction.

Hydrogen Production by Steam Reforming of Liquefied Natural Gas over Mesoporous Ni-Al2O3 Catalysts Prepared by a Co-Precipitation Method: Effect of Ni/Al Atomic Ratio

Mesoporous Ni-Al2O3 (XNiAl) catalysts with different Ni/Al atomic ratio (X) were prepared by a co-precipitation method for use in hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of Ni/Al atomic ratio of mesoporous XNiAl catalysts on their physicochemical properties and catalytic activity for steam reforming of LNG was investigated. Physical properties of XNiAl catalysts did not show a consistent trend with respect to Ni/Al atomic ratio, while chemical properties of XNiAl catalysts strongly influenced by Ni/Al atomic ratio. Nickel species were highly dispersed on the surface of XNiAl catalysts through the formation of nickel aluminate phase or solid solution of nickel oxide and 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 Ni/Al atomic ratio. Nickel surface area of XNiAl catalysts was well correlated with LNG conversion and hydrogen composition over the catalysts. Among the catalysts tested, 0.8NiAl (Ni/Al = 0.8) catalyst with the highest nickel surface area showed the best catalytic performance.

Effect of CexZr1-xO2 Promoter on Ni-Based SBA-15 Catalyst for Steam Reforming of Methane

Ni/CexZr1-xO2/SBA-15 catalysts were prepared and the catalytic activity for steam reforming of methane reaction was investigated. The addition of CexZr1-xO2 could obviously enhance catalytic activity of the Ni-based catalyst and Ni/CeO2/SBA-15 catalyst shows the excellent catalytic activity and stability at 800 °C over 792 h on steam. After reaction, the mesoporous structure of SBA-15 is still present and the pore walls of SBA-15 prevent the aggregation of nickel. The high catalytic activity and stability of Ni/CexZr1-xO2/SBA-15 catalyst is due to a CexZr1-xO2 layer precoated on SBA-15, which plays a role in forming high activity Ni species rather than bulk NiO and giving mobile oxygen species.

Hydrogen production via steam reforming of ethyl alcohol over nano-structured indium oxide catalysts

Mesoporous and worm-like In2O3 catalysts have been prepared using KIT-6 and MCM-41 silicas as templates, which show low crystallinities and high surface areas. Compared with commercial In2O3 catalyst with low surface area, these two nano-structured In2O3 catalysts exhibit higher catalytic activity for steam reforming of ethyl alcohol at low temperature to produce hydrogen containing no detectable CO impurity, presenting an advantage in comparison with the previous reported catalysts.

Ni catalysts for sorption enhanced steam methane reforming

Sorption enhanced steam methane reforming (SESMR) is a process for H2 production at low temperatures. The process requires an active and stable catalyst. For this purpose, a series of hydrotalcite-like catalysts (HT) with different Ni loadings have been prepared by a co-precipitation technique and compared with catalysts prepared by conventional incipient wetness impregnation. The co-precipitation route resulted in a stronger interaction between the support and nickel than the incipient wetness route. As a result, smaller Ni crystals with excellent stability and high activity for steam reforming of methane were obtained, even at high loadings. 40 wt% Ni/HT was found to be the most promising candidate for application in SESMR.

Reduction of Pd/ZnO Catalyst and Its Catalytic Activity for Steam Reforming of Methanol

The effect of reduction temperature of the coprecipitated 15.9%Pd/ZnO catalyst on the catalytic activity for steam reforming of methanol was investigated. The results showed that methanol conversion at 523 K reached a maximum of 41.6% with a CO2 selectivity of 94.6% and an outlet CO concentration of 1.26% over the catalyst reduced at 523–573 K. X-ray diffraction analysis revealed that a PdZn alloy began to form at a reduction temperature of 523 K. The improvement in activity at reduction temperature ranging from 523 to 573 K was attributed to the formation of the PdZn alloy with crystal size of 5–14 nm. The interaction between Pd and ZnO upon reduction was also explored by means of temperature-programmed reduction and X-ray diffraction. The results demonstrated that the reduction over Pd/ZnO might undergo a process PdO/ZnO → Pd/ZnO → PdZnO1–x/ZnO → PdZn alloy/ZnO. The PdZn alloy was partially oxidized to PdZnO1–x again during the reaction. The PdZn alloy and PdZnO1–x species might be the real active species.