Ethanol steam reforming over Ni/ZSM-5 nanosheet for hydrogen production

Compared to reforming reactions using hydrocarbons,ethanol steam reforming(ESR)is a sustainable alternative for hydrogen(H_(2))production since ethanol can be produced sustainably using biomass.This work explores the catalyst design strategies for preparing the Ni supported on ZSM-5 zeolite catalysts to promote ESR.Specifically,two-dimensional ZSM-5 nanosheet and conventional ZSM-5 crystal were used as the catalyst carriers and two synthesis strategies,i.e.,in situ encapsulation and wet impregnation method,were employed to prepare the catalysts.Based on the comparative characterization of the catalysts and comparative catalytic assessments,it was found that the combination of the in situ encapsulation synthesis and the ZSM-5 nanosheet carrier was the effective strategy to develop catalysts for promoting H_(2) production via ESR due to the improved mass transfer(through the 2-D structure of ZSM-5 nanosheet)and formation of confined small Ni nanoparticles(resulted via the in situ encapsulation synthesis).In addition,the resulting ZSM-5 nanosheet supported Ni catalyst also showed high Ni dispersion and high accessibility to Ni sites by the reactants,being able to improve the activity and stability of catalysts and suppress metal sintering and coking during ESR at high reaction temperatures.Thus,the Ni supported on ZSM-5 nanosheet catalyst prepared by encapsulation showed the stable performance with~88% ethanol conversion and~65% H_(2) yield achieved during a 48-h longevity test at 550-C.

Ethanol steam reforming over Ni-Cu/Al_2O_3-M_yO_z (M = Si, La, Mg,and Zn) catalysts

Ni-based catalysts doped with copper additives were studied on their role in ethanol steam reforming reaction. The effects of Cu content, support species involving Al2O3-SIO2, Al2O3-MgO, Al2O3-ZnO, and Al2O3-La2O3, on the catalytic performance were studied. Characterizations by TPR, XRD, NH3-TPD, XPS, and TGA indicated that catalysts 30Ni5Cu/Al2O3-MgO and 30Ni5Cu/Al2O3-ZnO have much higher H2 selectivity than 30Ni5Cu/Al2O3-SiO2, as well as good coke resistance. H2 selectivity for 30Ni5Cu/Al2O3-MgO catalyst was 73.3% at 450 ℃ and increased to 94.0% at 600℃, whereas for 30Ni5Cu/Al2O3-ZnO catalyst, the H2 selectivity was 63.6% at 450 ℃ and 95.2% at 600℃. TheseAl2O3-MgO and Al2O3-ZnO supported Ni-Cu bimetallic catalysts may have important applications in the production of hydrogen by ethanol steam reforming reactions.

Hydrogen production from steam reforming of ethanol over Ni/MgO-CeO_2 catalyst at low temperature

MgO,CeO2 and MgO-CeO2 with different mole ratio of Mg:Ce were prepared by solid-phase burning method.Catalysts Ni/MgO,Ni/CeO2 and Ni/MgO-CeO2 were prepared by impregnation method.The catalytic properties were evaluated in ethanol steam reforming(ESR) reaction.Specific surface areas of the supports were measured by nitrogen adsorption-desorption at 77 K,and the catalysts were characterized with X-ray diffraction(XRD),temperature programmed reduction(TPR) and thermogravimetric(TG).The results showed that well...

Boosting hydrogen and chemicals production through ethanol electro-reforming on Pt-transition metal anodes

The aim of this work is to boost the combined hydrogen and added-values compounds generation(acetaldehyde, acetic acid and ethyl acetate) through ethanol electrochemical reforming using bimetallic anodes. In particular, the influence of the secondary metal on the electrochemical performance as well as on the product distribution was studied. For that purpose, Pt X/C electrocatalysts(where X corresponds to Cu, Co, Ni and Ru) were synthesized by the modified polyol method and tested in both half-cell and proton exchange membrane(PEM) cell configurations. Characterization results showed that incorporation of Ni and Co into the Pt matrix enhances the morphological properties of the material, providing smaller crystallite sizes, higher active surface areas and hence, better dispersion when comparing to Ru and Cu-based electrocatalysts. Ethanol oxidation reaction(EOR) was evaluated by cyclic, linear voltammetry and chronopotentiometry assays. Pt Co/C and Pt Ni/C exhibited the highest electrocatalytic activity at high polarization levels, which translate into an improvement of more than 30%(up to 1050 m A cm^(-2)) in the hydrogen production and chemical yields. On the other hand, Pt Ru/C results more advantageous for a lower potential interval(<0.85 V) promoting the acetic acid production despite sacrificing ethanol conversion. Pt Cu/C presented the lowest results in both electrochemical performance and product distribution. Such differences in the electrochemical performance can be rationalized in terms of the synergistic effect between both metals(particle size distribution, grade of dispersion and hydrophilic behavior), which demonstrate that the incorporation of a different secondary metal plays an essential role in the EOR development.

Kinetic behaviour of commercial catalysts for methane reforming in ethanol steam reforming process

Ethanol steam reforming has been studied in a fluidized bed （in order to ensure bed isothermicity） on commercial catalysts for methane reforming. The results allow analyzing the effect of temperature （in 300-700℃ range）, and both metal and support nature on the reaction indices （ethanol conversion, yields and selectivities to H2 and byproducts （CO2, CO, CH4 and C2H4O））. Special attention has been paid to catalysts＇ stability by comparing the evolution of the reaction indices with time on stream at 500°C （minimum CO formation） and 700℃ （minimum deactivation by coke deposition）. Although they provide a slightly lower H2 yield, the results evidence a good behaviour of Ni based catalysts, indicating that they are an interesting alternative of more expensive Rh based ones.

Silicon Nitride Supported Cobalt Catalyst for Enhanced Hydrogen Production from Ethanol Steam Reforming

Silicon nitride(Si_(3)N_(4))supported cobalt catalysts(Co/Si_(3)N_(4))were fabricated by using wetness impregnation procedure.The microscopic morphology,phase composition,and electronic states were characterized by XRD,TEM,SEM,and XPS,respectively.For comparison,cobalt catalyst supported on SiO_(2)(Co/SiO_(2))was also investigated.XPS studies and DFT calculations show that the cobalt species in Co/Si_(3)N_(4) have lower valence state than those in Co/SiO_(2).The catalytic ESR reactions demonstrate that Co/Si_(3)N_(4) exhibits distinctly higher catalytic activity and hydrogen selectivity than Si_(3)N_(4) support and Co/SiO_(2) catalyst with the identical cobalt loading,indicative of the favorable effect of Si_(3)N_(4) support on the catalytic performance of supported cobalt catalyst.Durability tests and TG-DSC studies show that Co/Si_(3)N_(4) catalyst exhibits better stability and resistance to coke during the same catalytic experiment period.

Hybrid structure of iron single atoms and metallic titanium for photothermal ethanol steam reforming

Photothermal ethanol steam reforming(ESR) is currently limited by low intrinsic activity and strong solar energy dissipation.Herein,we synthesized Fe single atoms supported on CeO_(2)(SA Fe-CeO_(2)) to exhibit excellent low-temperature ESR activity with a hydrogen production rate of 512 mmol g^(-1)h^(-1) at 350℃,becuase of the high oxidation state of Fe single atoms to weaken the reaction barrier of ethanol decomposition.Furthermore,a heterostructure of SA Fe-CeO_(2) and Ti foil could eliminate 66% of infrared radiation via the size effect,thus achieving a 3.5 sun-driven temperature of 347℃.Consequently,the heterostructure of SA Fe-CeO_(2) and Ti foil shows a hydrogen generation rate of 984 mmol g^(-1)h^(-1) of ESR and 11.31% of solar-to-hydrogen energy conversion efficiency,which outperforms other photothermal ethanol-hydrogen production systems.This study provides a new path for designing active catalytic sites and trapping light energy of photothermal catalysts.

Effect of CeO_(2) on carbon deposition resistance of Ni/CeO_(2) catalyst supported on SiC porous ceramic for ethanol steam reforming

Ni/CeO_(2) catalysts(nCeO_(2):n_(Ni)=0,1,4,7,10)supported on SiC porous ce ramics for ethanol steam reforming(ESR)were investigated with respect to hydrogen production performance and growth of carbon deposition.The oxygen released from CeO_(2) enables the oxidation of CH_(x) species to serve as carbon precursors,thus providing Ni/CeO_(2) catalysts with stronger resistance to carbon deposition compared with Ni catalysts.The Ni/CeO_(2) catalysts prepared by inverse microemulsion and impregnation methods exhibit regular semicircular spherical shape on SiC porous ceramics.Under 500℃for 25 h of ESR reaction,the ethanol conversion rate over Ni/CeO_(2) catalysts(n_(CeO_(2)):n_(Ni)=7)is sustained up to 100%and H_(2) selectivity is essentially kept at 74%.The by-product selectivity declines stepwise with increasing content of CeO_(2),which is attributed to the adsorption and oxidation of CO and of CH_(x) species as CH_4 precursor from CeO_(2).The scanning electron microscopy(SEM)and transform electron microscopy(TEM)results reveal that further loading of CeO_(2) on the surface of Ni catalysts can alleviate both migration and sintering of Ni particles.Furthermore,carbon deposition on Ni/CeO_(2) catalysts preferentially outgrow filamentous rather than amorphous carbon,with a tendency for the latter to be more deactivated.

Hydrogen production by steam reforming of ethanol over copper doped Ni/CeO_2 catalysts

High surface area CeO2 was prepared by the surfactant-assisted route and was employed as catalyst support. The 0-3 at.% Cu doped Cu-Ni/CeO2 catalysts with 10 wt.% and 15 wt.% of total metal loading were prepared by an impregnation-coprecipitation method. The influence of Cu atomic content on the catalytic performance was investigated on the steam reforming of ethanol （SRE） for H2 production and the catalysts were characterized by N2 adsorption, inductively coupled plasma （ICP）, X-ray diffraction （XRD）, transmission electron microscopy （TEM）, temperature-programmed rerduction （TPR） and H2-pulse chemisorption techniques. The activity and products distribution behaviors of the catalysts were significantly affected by the doped Cu molar content based on the promotion effect on the dispersion of NiO particles and the interactions between Cu-Ni metal and CeO2 support. Significant increase in the ethanol conversion and hydrogen selectivity were obtained when moderate Cu metal was doped into the Ni/CeO2 catalyst. Over both of the 10Ni98.5Cu1.5/CeO2 and 15Ni98.5Cu1.5/CeO2 catalysts, more than 80% of ethanol conversion and 60% of H2 selectivity were obtained in the ethanol steam-reforming when the reaction temperature was above 450 ℃.

Holey platinum nanotubes for ethanol electrochemical reforming in aqueous solution

The catalytic/electrocatalytic performance of platinum(Pt)nanostructures highly relates to their morphology.Herein,we propose a facile self-template pyrolysis strategy at high temperature to synthesize one-dimensionally holey Pt nanotubes(Pt-hNTs)using Pt^(Ⅱ)-dimethylglyoxime complex(Pt^(Ⅱ)-DMG)nanorods as the reaction precursor.The coordination capability of DMG results in the generation of Pt^(Ⅱ)-DMG nanorods,whereas the reducibility of DMG at high temperature leads to the reduction of Pt^(Ⅱ)species in Pt^(Ⅱ)-DMG nanorods.During the reaction process,the inside-out Ostwald ripening phenomenon leads to the hollow morphology of Pt-hNTs.Benefiting from the physical characteristics of hollow and holey structure,Pt-hNTs with clean surface show superior electroactivity and durability for catalyzing ethanol electrooxidation as well as hydrogen evolution reaction in alkaline media.Under optimized experimental conditions,the constructed symmetric Pt-hNTs||Pt-hNTs ethanol electrolyzer only requires an electrolysis voltage of 0.40 V to achieve the electrochemical hydrogen production,demonstrating a highly energy saving strategy relative to traditional water electrolysis.

Sustainable H2 production from ethanol steam reforming over a macro-mesoporous Ni/Mg-Al-O catalytic monolith

A macro-meso-porous monolithic Ni-based catalyst was prepared via an impregnation route using polystyrene foam as the template and then used in the steam reforming of ethanol to produce a H2-rich gas. The Ni/Mg-A1 catalyst has a hierarchically macro-meso-porous structure as indicated by photographs and scanning electron microscopy （SEM）. The surface area of the catalyst was 230 m2＂ g 1 and the Ni dispersion was 5.62%. Compared to the pelletized sample that was prepared without a template, the macro-meso-porous Ni/Mg-A1 monolith exhibited superior reactivity in terms of H2 production and also had lower CH4 yields at 700~C and 800℃. Furthermore, the monolithic catalyst maintained excellent activity and H2 selectivity after 100-h on-stream at 700℃, as well as good resistance to coking and metal sintering.

La_2O_2CO_3 supported Ni-Fe catalysts for hydrogen production from steam reforming of ethanol

La2O2CO3 was prepared by calcination of La2 （CO3）3 in the air. Catalysts Ni-Fe/La2O2CO3 with different mole ratios of Ni to Fe, Ni/La2O2CO3 and Fe/La2O2CO3 were prepared by impregnation method. The catalytic properties were evaluated on steam reforming of ethanol （SRE） from 300 to 700 ℃ under atmospheric pressure and the samples were characterized by Brunauer-Emmett-Teller method （BET）, X-ray diffraction （XRD） and temperature programmed reduction （TPR）. The results showed that Ni-Fe bimetallic catalysts exhibited higher activities than single metallic catalysts, which was attributed to the co-existence of well dispersed Ni, Fe and LaFeyNi1-yO3. It was found that the catalyst Ni-Fe/La2O2CO3 containing 10 wt.% Ni and 3 wt.%-5 wt.% Fe showed the best performance, the conversion of ethanol was 100%, the selectivity of H2 was higher than 90%, and the selectivity of CO was lower than 1.5% at 400 ℃.

Ethanol dry reforming for syngas production over Ir/CeO_2 catalyst

Syngas production from CO2 reforming of ethanol over an Ir/Ce O2 catalyst was investigated. Catalysts characterization was conducted by X-ray diffraction（XRD）, temperature programmed reduction（TPR）, transmission electron microscopy（TEM） and temperature programmed oxidation（TPO）. The Ir/Ce O2 catalyst was more active and stable toward syngas formation（molar ratio ~1）. The superior catalytic performance was interpreted in terms of the strong interaction between Ir particles and ceria support which was crucial for efficient ethanol/CO2 activation and coke removal on the catalyst surface.

Role of Sn in Ni-Sn/CeO2 Catalysts for Ethanol Steam Reforming

Reducible oxides （e.g.,CeO2 and ZrO2） supported 3d transition metals （e.g.,Ni,Co,Pt） exhibit remarkable catalytic activity in reactions that involve water activation,such as steam reforming and water gas shift.This paper describes the influence of Sn addition on the performance of Ni/CeO2 catalysts in ethanol steam reforming.0.25 wt% Sn addition improved the stability of Ni/CeO2 by forming Ni-Sn bimetallic nanoparticles with Sn enriched surfaces to suppress the carbon deposition.Ni0.25Sn/CeO2 kept over 90% ethanol conversion in a 20 h stability test at 600 ℃ with over 60% hydrogen selectivity under a gas hourly space velocity of 57000 mL/（g·h）.However,the presence of Sn decreased the overall oxygen storage capacity and oxygen mobility of NiSn/CeO2,which hampered water activation process and coke elimination occurring at the interface between Ni and CeO2.Additionally,ethanol decomposition was also suppressed due to the coverage of Sn atoms on Ni surfaces.

Molecular catalysis for the steam reforming of ethanol

In this paper, the application of molecular catalysis for steam reforming of ethanol （SRE） is reviewed. Eight metals （Ni, Co, Cu Pt, Rh, Pd, Ir and Ru） have shown high catalytic activity for SRE. Among them Ni and Rh are very promising because of high d character in the metal bond and low metal-oxygen bonding （vs. metal-carbon）. They can effectively promote C-C bond cleavage in the rate-determining process during SRE. However, Rh is weak in water-gas-shift so that CH4 and CO become the main by-products at low reaction temperatures, while Ni catalysts suffer from rapid deactivation due to coking and sintering. Two low-temperature CO-free catalysts have been developed in our lab, namely Rh-Fe/Ca-Al2O3 and carbonyl-derived Rh-Co/CeO2, in which the presence of iron oxide or Co can promote water-gas-shift reaction and significantly improve the SRE performance. On the other hand, adding 3 wt% CaO to Ni/Al2O3 can greatly improve the catalyst stability because the Ca modification not only increases Ni concentration on the Ni/Ca-Al2O3 surface and 3d valence electron density, but also facilitates the water adsorption and coke gasification via water-gas-shift. The availability of abundant surface OH groups helps the formation and conversion of adsorbed formate intermediate. Hence, ethanol reaction on Ca-Al2O3-supported Ni, Pt, Pd and Rh catalysts are found to follow the formate-intermediated pathway, a new reaction pathway alternative to the traditional acetate-interrnediated pathway.

Regulation of Oxygen Activity by Lattice Confinement over Ni_(x)Mg_(1-x)O Catalysts for Renewable Hydrogen Production

The chemical looping steam reforming(CLSR)of bioethanol is an energy-efficient and carbon-neutral approach of hydrogen production.This paper describes the use of a Ni_(x)Mg_(1-x)O solid solution as the oxy-gen carrier(OC)in the CLSR of bioethanol.Due to the regulation effect of Mg^(2+)in Ni_(x)Mg_(1-x)O,a three-stage reaction mechanism of the CLSR process is proposed.The surface oxygen of Ni_(x)Mg_(1-x)O initially causes complete oxidation of the ethanol.Subsequently,H_(2)O and bulk oxygen confined by Mg^(2+)react with etha-nol to form CH_(3)COO^(*)followed by H_(2) over partially reduced Ni_(x)Mg_(1-x)O.Once the bulk oxygen is con-sumed,the ethanol steam reforming process is promoted by the metallic nickel in the stage Ⅲ.As a result,Ni_(0.4)Mg_(0.6)O exhibits a high H_(2) selectivity(4.72 mol H_(2) per mole ethanol)with a low steam-to-carbon molar ratio of 1,and remains stable over 30 CLSR cycles.The design of this solid-solution OC pro-vides a versatile strategy for manipulating the chemical looping process.

Ni/Y_2O_3-Al_2O_3 catalysts for hydrogen production from steam reforming of ethanol at low temperature

Y2O3-Al2O3 with different mole ratios of Y：Al were prepared by co-precipitation method. Catalysts Ni/Y2O3, Ni/Al2O3 and Ni/ Y2O3-Al2O3 were prepared by impregnation method. The result of BET showed that Al2O3 with relative high surface area was in favor of Ni distribution, whilst the TPR test demonstrated that composite support had appropriate synergistic effect between active constituent and sup-port, and NiO could be reduced more easily than loaded on the single support. H2-TPD test indicated that the catalyst NYA11 had lots of ac-tivity sites where H could be desorbed easily, which led to hydrogen-rich production over the catalyst. Composite support catalysts exhibited high activity for ethanol steam reforming （SRE）, and the supported catalyst with composite of 1：1 mole ratio of Y：Al exhibited the optimum catalytic properties for SRE. Ethanol could be completely converted over catalyst NYA11 even at 450 °C, and there had no inactivation after 60 h continuous reaction, hydrogen yield appeared maximum 35.9% at 400 ℃, and tended to increase with increasing H2O/EtOH molar ratio and feed flow rate.