•Ni/CeO2-ZrO2 particles were encapsulated in porous silica layer effectively.•A new Ni-O-Si configuration was formed at Ni-SiO2 interface in the coated catalyst.•Ni in atom Ni-O-Si configuration is more active than normal Ni atom•The TOF of Ni increased highest by 5.5 times after coating with SiO2 layer.Ni/CeO2-ZrO2 was encapsulated by SiO2 layer with expectation to obtain a high active catalyst for steam reforming of toluene. The coating structure was validated by X-ray diffraction experiments and electron microscope analysis. XPS data suggests the formation of a new Ni-O-Si configuration in core-shell catalysts. The presence of Ni-O-Si configuration shift electron from Ni to silica and thereby facilitates the intrinsic properties of catalysts. Compared to Ni/CeO2-ZrO2, turnover rate of Ni increased substantially in core-shell structures, Ni/CeO2-ZrO2@SiO2 with shell-to-core mass ratio as 1.0 showed about 5.5 times higher than the Ni/CeO2-ZrO2 catalyst.

•The intrinsic activity of Ni is greatly promoted by coating a SiO2 layer.•The TOF of Ni is increased by 8.3 times after coating with SiO2 layer.•Interaction of Ni and SiO2 plays a key role on enhancing of Ni intrinsic activity.•The interaction of Ni and SiO2 leads to partly oxidation of surface Ni atoms.•The partly oxidized Ni atom is more active than normal Ni atom.Porous silica coated Ni/CeO2ZrO2 catalysts were synthesized for steam reforming of acetic acid. The silica coated Ni/CeO2ZrO2 catalyst showed a significantly enhanced activity (95% acetic acid conversion) than the Ni/CeO2ZrO2 catalysts (62% acetic acid conversion) at a low temperature (550 °C). Interaction between Ni/CeO2ZrO2 and silica layer was proved to be a crucial role on enhancing of catalytic activities. Further characterization (XPS, H2-TPR) indicates this interaction facilitates the steam reforming reaction and raises the selectivity of CO by modifying the surface Ni electronic structure. In addition, the coated catalyst also exhibited a good stability and no obvious deactivation was detected at 550 °C and 600 °C within 30 h.

•Ni-CaO-La2O3 shows good performance for sorption enhanced steam reforming of acetic acid.•The H2 yield and H2 concentration through Ni-CaO-La2O3 with 20 wt% Ni reaches 86.02% and 92.24%, respectively.•Reforming reaction of acetic acid but the adsorption of CO2 is the rate limiting step.Sorption enhanced steam reforming of acetic acid over sorbent assisted catalyst of Ni-CaO-La2O3 were investigated for high-purity H2 production. Ni-CaO-La2O3 with 8, 16 and 20 wt% Ni were developed by sol-gel combustion synthesis and were characterized by TG, TPR, BET, SEM, XRD and XPS. The catalytic activities and stability of the catalysts were tested in a fixed reactor. H2 yield and H2 concentration through Ni-CaO-La2O3 with 20 wt% Ni reaches 86.02% and 92.24% during pre-breakthrough period, respectively, which is attributed to sufficient Ni active sites on the surface and good Ni dispersion. Catalytic activities of Ni-CaO-La2O3 with 20 wt% Ni maintain stable during sorption-enhanced steam reforming reaction, but CO2 sorption capacity slightly decreases due to blockage of pores and size increase of CaO particles within nine sorption/desorption cycles.Download high-res image (98KB)Download full-size image

Hydrogen production from steam reforming of acetic acid was investigated over Ni/La2O3-ZrO2 catalyst. A series of Ni/La2O3-ZrO2 catalysts were synthesized by sol-gel method coupled with wet impregnation, which was characterized by XRD, BET, TEM, EDS, TG, SEM and TPR. Catalytic activity of Ni/La2O3-ZrO2 was evaluated by steam reforming of acetic acid at the temperature range of 550-750 °C. The tetragonal phase La0.1Zr0.9O1.95 is formed through the doping of La2O3 into the ZrO2 lattice and nickel species are highly dispersed on the support with high specific surface area. H2 yield and CO2 yield of Ni/La2O3-ZrO2 catalyst with 15%wt Ni reaches 89.27% and 80.41% at 600 °C, respectively, which is attributed to high BET surface area and sufficient Ni active sites in strong interaction with the support. 15%wt Ni supported on La2O3-ZrO2 catalyst maintains relatively stable catalytic activities for a period of 20 h.

•Oxygen vacancies create Ce (III) to shorten the band gap and enhance the visible light absorption.•(111) plane is a superior position to enhance photocatalytic activity.•Oxygen vacancies and Ce (III) on the surface affects the band gap.•Cerium dioxide calcined under 400 °C shows superior photocatalytic activity.Experimental and computational (DFT) approaches were carried out to investigate oxygen vacancies on cerium dioxide. Computational result indicates oxygen vacancies can shorten the band gap of CeO2 and enhance the absorption for visible light because Ce (III) created by generation of oxygen vacancies is easier for excitation than Ce (IV) under same irradiation. The order of calculated band gap for Ce16O31, (111) < (113) < (133), and the absorption data suggests that (111) plane may be the most ideal position for oxygen vacancies to enhance photocatalytic activity. The result has been tested and verified by experimental study, including UV–Vis spectra, XPS, XRD and PL. The enhanced hydrogen productions of CeO2 samples, from 34.8 μmol to 63.0 μmol, are 2.0–3.5 times as high as that of commercial CeO2 (17.8 μmol).

•Ni/Ce–Zr–O catalyst was applied in reverse water gas shift reaction to realize the utilization of H2 and CO2.•The wt % of Ni in Ni/Ce–Zr–O was optimized during the catalytic process.•CO2 conversion reached 49.66% and maintained stable activity after reaction for 80 h at 750 °C.•CO selectivity of 99.65% was reached.A series of Ni-based catalysts supported on Ce–Zr–O were synthesized via impregnation and applied in the reverse water gas shift reaction (RWGS). BET, XRD, TPR, SEM, TEM and XPS were employed as the characterization of catalysts. Catalytic activities of Ni/Ce–Zr–O with different Ni contents were evaluated in RWGS under atmospheric pressure and at the temperature range of 550–750 °C in a fixed-bed quartz reactor. CO2 conversion reaches 49.66% and maintains stable after 80 h of reaction over 3 wt% Ni/Ce–Zr–O. CO selectivity can reach 99.65% for the catalyst with 10 wt% Ni at 750 °C. The Ni/Ce–Zr–O catalyst provides high activity, stability and selectivity in the conversion of CO2 to CO at high temperature. Ce–Zr–O solid solution is formed by co-precipitation and Ni is able to be incorporated into the Ce–Zr–O lattice via impregnation. The Ni species on catalyst surface can be considered as the active site for RWGS.

•New models were established to fit the process of dimethyl ether steam reforming.•The performances of the fixed bed reactor and the micro-reactor are compared.•The models are able to predict the best operating conditions.To enhance the heat and mass transfer during dimethyl ether (DME) steam reforming, a micro-reactor with catalyst coated on nickel foam support was designed and fabricated. A two-dimensional numerical model with SIMPLE algorithm and finite volume method was used to investigate 1) the fluid flow, 2) the heat transfer and 3) chemical reactions consist of DME hydrolysis, methanol steam reforming, methanol decomposition and water gas shift reactions. Both the numerical and the experimental results showed that the DME conversion in the micro-reactor is higher than that in the fixed bed reactor. The numerical study also showed that the velocity and the temperature distribution were more uniform in the micro-reactor. Wall temperature, porosity and steam/DME ratio have been investigated in order to optimize the process in the micro-reactor. The wall temperature of 270 °C and the steam/DME feed ratio of 5 were recommended. Meanwhile the results indicate that a larger porosity will give a higher DME conversion and CO concentration.

•Promoter Cr can reduce the average pore diameter and reduction temperature of catalyst.•The conversion of dimethyl ether and hydrogen yield reaches 99% and 95% respectively.•Catalyst is distributed on the metal foam back to maintain the porous structure.The CuZnAl/HZSM-5, CuZnAlCr/HZSM-5, CuZnAlZr/HZSM-5, CuZnAlCo/HZSM-5, and CuZnAlCe/HZSM-5 catalysts that were prepared by a co-precipitation method was used for hydrogen production from steam reforming of dimethyl ether (SRD) in a metal foam micro-reactor. These catalysts were characterized by means of XRD, TPR, SEM and BET surface areas. The results showed that promoter Cr can reduce the average pore diameter and reduction temperature of catalyst. The conversion of dimethyl ether and hydrogen yield reaches 99% and 95% respectively over CuZnAlCr/HZSM-5 catalyst under a relatively lower reaction temperature. The obtained hydrogen-riched gas is easy to purify and meet the need of polymer electrolyte membrane fuel cell. The effects of reaction temperature, space velocity and steam to DME ratio on SRD were investigated in a metal foam micro-reactor. At the conditions of T = 250 °C, the space velocity of 3884 ml/(g h), steam to DME = 5, DME conversion of >97% were obtained over the CuZnAlCr/HZSM-5 catalyst without obvious deactivation during 50 h.

•Co/CeO2 catalysts were synthesized by the glycine-nitrate combustion method.•Catalyst achieved almost 100% conversion at 150 °C without H2O and CO2.•The combustion method strengthen the Co–Ce interaction.Preferential oxidation of CO (CO-PrOx) is an important step to meet the need of the proton exchange membrane (PEM) fuel cell without the Pt anion poison. A glycine-nitrate approach was used for the synthesis of Co/CeO2 nanoparticle for preferential oxidation of CO, which a precursor solution was prepared by mixing glycine with an aqueous solution of blended nitrate in stoichiometric ratio. Then the glycine-mixed precursor solution was heated in a beaker for producing nanosized porous powders. Catalytic properties of the powders were investigated and results illustrate that the Co-loading of 30 wt.% catalysts exhibits excellent catalytic properties. Various characterization techniques like X-ray diffraction, SEM, BET, Raman and TPR were used to analyze the relationship between catalyst nature and catalytic performance. The X-ray diffraction patterns and SEM micrographs indicate that catalysts prepared by glycine-nitrate combustion own mesopore structure. The BET, Raman and TPR results showed that the high activity of the 30 wt.% Co-loading of Co/CeO2 catalysts is related to the high BET surface and the strongly interaction between fine-dispersed Co species and CeO2 support.

•Bi-functional CuZnAlCr/HZSM-5 catalysts have been used in dimethyl ether steam reforming.•A mass ratio of 1:1 between CuZnAlCr and HZSM-5 was optimized for the process.•The metal foam material and micro-reactor greatly enhanced the residence time of the reactant and catalyst.•Dimethyl ether conversion of 99% and hydrogen yield of >95% was reached.•CO concentration dropped to <10 ppm and hydrogen yield of ∼90% were achieved in the new-type system.A bi-function catalyst containing CuZnAlCr and HZSM-5 was used to generate hydrogen by stream reforming of dimethyl ether (SRD) in a metal foam micro-reactor and a fix-bed reactor. Dimethyl ether conversion of 99% and hydrogen yield of >95% was reached with HZSM-5/CuZnAlCr (mass ratio of 1:1) in the micro-reactor. A suitable balance between the dimethyl ether hydrolysis and methanol reforming steps requires the proper acidity and the metal sites. The CuZnAlCr/HZSM-5 properties, effect of CuZnAlCr to HZSM-5 mass ratio were investigated in the metal foam micro-reactor. Moreover, CO was removed from hydrogen-rich gas by preferential oxidation reaction (CO-PrOx) with PtFe/γ-Al2O3 catalyst in a similar metal foam micro-reactor follows the SRD stage. With the optimized O2/CO ratio and reaction temperature, the CO concentration dropped to <10 ppm and hydrogen yield of ∼90% were achieved in the new-type SRD-COPrOx system. The SRD-COPrOx system provide a constant hydrogen production with CO concentration lower than 10 ppm during 20 h. The results indicate that metal foam micro-reactor has the great potential in the DME steam reforming to supply hydrogen for low-temperature fuel cells.

Steam reforming of acetic acid, one model compounds of bio-oil, was studied on the Ni/ZrO2–CeO2 catalysts which were prepared by the impregnation method. The results showed that high acetic acid conversion and hydrogen yield were obtained in the temperature range of 650–750 °C when H2O/HAC ratio was 3. Nevertheless, the catalyst deactivation was caused by carbon deposition eventually with time-on-stream. In order to discuss the behavior of the carbon deposition on the Ni/ZrO2–CeO2 catalyst during steam reforming of bio-oil, the structure and morphology of carbon deposition were investigated by BET, XRD, TG/DTA, TPR, SEM and EDX techniques. All the experimental results showed acetone and CO were the important carbon precursors of acetic acid reforming and the graphitic-like carbon was the main type of carbon deposition on the surface of the deactivated 12%Ni/CeO2–ZrO2 catalyst.Highlights► The Ni/ZrO2–CeO2 catalysts were used in the steam reforming reaction of acetic acid. ► The results showed that it could give high acetic acid conversion and hydrogen yield. ► The stability tests showed acetone and CO was the important carbon precursors. ► The graphitic-like carbon is the main type of carbon deposition in the deactivation.

The calcination process may influence subsequent fragmentation, sintering and swelling when CaO derived from limestone acts as a CO2 or SO2-sorbent in combustion, gasification and reforming. Sorbent properties are affected by CO2 partial pressure, total pressure, temperature, heating rate, impurities and sample size. In this study, the effect of calcination heating rate was investigated based on an electrically heated platinum foil. The effects of heating rate (up to 800 °C/s), calcination temperature (700–950 °C), particle size (90–180 μm) and sweep gas velocity were investigated. Higher initial heating rates led to lower extents of limestone calcination, but the extents of carbonation of the resulting CaO were similar to each other. Calcium utilization declined markedly during carbonation or sulphation of CaO after calcination by rapid heating. Experimental results show that carbonation and calcium utilization were most effective for carbonation temperatures between 503 and 607 °C. Increasing the extent of calcination is not the best way to improve overall calcium utilization due to the vast increase in energy consumption.

This paper presents the results of the investigation on steam reforming bio-oil aqueous fraction coupled with in situ carbon dioxide capture for hydrogen production. Experiments were carried out in a bench-scale fixed-bed reactor with calcined dolomite as the sorbent. The effects of temperature and water to bio-oil ratio on hydrogen production are reported. In the presence of calcined dolomite, maximum hydrogen yield of 75% was obtained among without sorbent, with CaO and with calcined dolomite at 600 °C, whereas hydrogen content was 83%, a little lower than that of 85% when CaO was used. Hydrogen content varies little at different water to bio-oil ratios and hydrogen yield was the greatest at the water to bio-oil ratio of 1:1. After regeneration of the sorbent, hydrogen content was back to the initial level but the hydrogen yield dropped.

A series of composite catalysts Ni/CeO2–ZrO2 were prepared via impregnation method with Ni as the active metal. A laboratory-scale fixed-bed reactor was employed to investigate the catalyst performance during hydrogen production by steam reforming bio-oil aqueous fraction. Effects of water-to-bio-oil ratio (W/B), reaction temperature, and the loaded weight of Ni and Ce on the hydrogen production performance of Ni/CeO2–ZrO2 catalysts were examined. The obtained results were compared with commercial nickel-based catalysts (Z417). The best performance of Ni/CeO2–ZrO2 catalyst was observed when the Ni and Ce loaded weight were 12% and 7.5% respectively. At W/B = 4.9, T = 800 °C, H2 yield reaches the highest of 69.7% and H2 content of 61.8% were obtained. Under the same condition, H2 yield and H2 content were higher than commercial nickel-based catalysts (Z417).

•Calcining in H2 is conducted to improve the conductivity of TiO2 nanotube arrays.•H-TNTA is used as support of IrO2 to form OER catalyst.•IrO2/H-TNTA shows higher OER activity and lower onset potential than IrO2/air-TNTA.•Increasing the loading of IrO2 effectively improves the stability of IrO2/H-TNTA.IrO2 was electro-deposited on hydrogenated TiO2 nanotube arrays (TNTA) to form IrO2/H-TNTA for oxygen evolution reaction (OER). Hydrogenation by calcining in H2 atmosphere was conducted to improve the electric conductivity, which was owing to partially reduce of Ti4+ in TNTA. It was found that hydrogenated TiO2 can facilitate the electro-deposition of IrO2, and elevate the OER activity compared to that of non-calcined and air-calcined TNTA, which would be due to the improved conductivity of H-TNTA. IrO2/H-TNTA shows a five-fold higher activity than IrO2/air-TNTA with the same loading amount. The coverage of IrO2 on the surface of hydrogenated TNTA is crucial to the stability of catalyst and with the increased loading amount of IrO2, IrO2/H-TNTA shows much higher stability.

•A new one-step method for synthesize cuprous oxide nanospheres was carried out.•The Cu2O nanospheres formed the core–shell structure with 5 wt.% GO.•Size and dispersity of Cu2O nanospheres can be controlled through GO addition.•GO was partly reduced for better charge separation and transfer during catalysis.A new one-step method for synthesize cuprous oxide nanosphere without any additive surfactant in room temperature and atmospheric pressure was carried. The nanospheres with the diameters less than 100 nm were well-dispersed and formed the core–shell structure with the GO. The partial reduction of GO increases the atomic percentage of sp2 carbon (graphene sheets). It was found that sp2 carbon with better conductivity plays an important role in mitigating electron–hole recombination and enhancing electron transfer between Cu2O and GO and thus enhance the photocatalytic activity. The highest hydrogen yields for GO-modified samples (118.3 μmol) were more than twice as large as that of bare Cu2O nanosphere (44.6 μmol).

•Evolution from first phase-separation to secondary phase-separation.•Combination of self-assembling processes in solution and in bulk.•Production of hybrid material with pseudo-hexagonal nanostructures.This work contributes to a new protocol of patterning gold nanoparticles (NPs) via secondary phase-separation of micelle template of PS-b-P2VP-b-PEO block copolymer. The immiscibility between hydrophobic PS and hydrophilic P2VP and PEO leads to a bulk phase-separation in large compound micelles (LCMs) when heated at the temperature of 130 °C. The bulk-separated template then constitutes an ideal precursor for Au NPs loading by an immersion in an aqueous solution bath of chloroauric acid such that the primed P2VP domains would coordinate to the charged [AuCl4]− through electrostatic interactions. With the following treatment of air plasma, pseudo-hexagonal nanopatterns are created with Au NPs on P2VP matrix.A secondary phase-separated nanostructure was designed on heating large-sized compound micelles (LCMs) above the glassy transition temperature (Tg) of the block copolymer. The resultant pseudo-hexagonal structure was then used as a template for metal loading by a immersion bath in an aqueous solution of chloroauric acid such that the primed P2VP domains would coordinate to the charged [AuCl4]− through electrostatic interactions. With following treatment of air plasma ion etching to reduce the metal ions and to remove the PS template, hybrid materials were created with Au NPs on the pseudo-hexagonal P2VP matrix.