High‐Temperature Hydrogen Adsorption Properties of Precursor‐Derived Nickel Nanoparticle‐Dispersed Amorphous Silica

Ikuhara, Y.; Mori, Hiroshi; Saito, Tomohiro; Iwamoto, Yuji

doi:10.1111/j.1551-2916.2006.01434.x

Cited by 55 publications

(44 citation statements)

References 35 publications

(40 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The reduction kinetics also needs high temperature preferentially ≥ 500 ºC as reported elsewhere for metal oxide silica membranes [1,15].…”

Section: Fig 1 the Volumetric Adsorption Systemmentioning

confidence: 99%

“…It is important to understand that the reduction of metal oxides in silica membranes is not a new concept, and it had been tried over a decade ago, though the redox effect on gas permeation is a recent finding. For instance, in 2005 Kanezashi et al [14] reported strong NiO peaks detected by XRD analysis for nickel oxide doped silica membranes upon calcination at 500°C, though NiO silica was reduced to pure Ni upon exposure to a H 2 atmosphere [15]. There are examples in the literature showing that metal oxides embedded into silica underwent reduction [16,17] as H 2 was able to diffuse through the silica network and reduce metal oxides particles in xerogels.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Improved pore connectivity by the reduction of cobalt oxide silica membranes

Ji¹,

Smart²,

Bhatia³

et al. 2015

Separation and Purification Technology

View full text Add to dashboard Cite

This work investigated the permeation of binary gas mixtures in non-reducing (He/CO 2 ) and reducing (H 2 /Ar) conditions at temperatures ranging from 200 to 500 ºC. A common performance aspect under both non-reducing and reducing conditions was that the He and H 2 purity in the permeate stream was independent of temperature for the tested binary gas mixtures, except at very high He/CO 2 or H 2 /Ar concentrations (≥90/10) in the retentate stream. Under non-reducing conditions, the transport of gases was consistent with molecular sieving properties of silica derived membranes, and He permeance was constant irrespective of the He/CO 2 binary concentration tested.An anomalous H 2 transport was observed under reduced conditions, as unexpectedly the H 2 permeance was higher for gas mixtures instead of single gas. Further tests showed that H 2 permeance increased 170% as the gas mixture changed from single H 2 gas to H 2 /Ar gas mixtures.This was attributed to the experimental procedure, as the membranes were partially reduced each day and tested for gas permeation from pure H 2 to lower H 2 concentration in gas mixtures. Under these partial reducing conditions, H 2 slowly reacts with the surface of the dense Co 3 O 4 particle, thus 2 forming a porous CoO region. The increase in H 2 permeance was therefore attributed to improved pore connectivity between the silica structure and the porous CoO region.

show abstract

“…The reduction kinetics also needs high temperature preferentially ≥ 500 ºC as reported elsewhere for metal oxide silica membranes [1,15].…”

Section: Fig 1 the Volumetric Adsorption Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Improved pore connectivity by the reduction of cobalt oxide silica membranes

Ji¹,

Smart²,

Bhatia³

et al. 2015

Separation and Purification Technology

View full text Add to dashboard Cite

show abstract

“…This result may be caused by the affinity of nickel for hydrogen. 6 Moreover, all membranes have a high hydrogen permeance at 100°C, with values over Published on the web September 28, 2011…”

Section: ¹1mentioning

confidence: 99%

Synthesis and Characterization of Ni-doped Silica Membranes Prepared Using a Hybrid Sol–Gel/CVD Method

Araki

Yano²,

Tanaka

et al. 2011

Chemistry Letters

View full text Add to dashboard Cite

Improving the hydrogen permeation flux, while maintaining high hydrogen selectivity, is important for reducing membrane areas and enhancing membrane reactor (MR) performance. We have attempted to enhance the hydrogen permeation through the addition of nickel, which will improve both hydrogen adsorption and pore size control. The silica layer was deposited with high selectivity, using an extended counter-diffusion CVD method.Hydrogen is widely used in chemical and petroleum industries and has been predicted to be a clean fuel for polymer electrolyte fuel cells (PEFCs) in the future. More than the half the hydrogen worldwide is produced from the steam reforming (SR) of natural gas, whose main feedstock is methane.1 In this reaction, by-product gases, such as carbon dioxide, carbon monoxide, and methane, in addition to hydrogen, make up the reforming gas. Therefore, much research has been focused on separation technologies, such as membrane separation. Of the primary membrane materials, silica has attracted much attention, owing to its high heat stability and low production cost.Recently silica-based membranes, which have high hydrogen permeance and high selectivity, have been prepared using a hybrid processing method that combines the solgel and CVD methods.2 In this study, a Ni-doped silica membrane is prepared using a hybrid method involving the solgel and high-pressure CVD methods. Ni-doped silica layers were prepared on ¡-alumina support with a £-alumina interlayer, using the sol gel method. We have attempted to enhance hydrogen permeation through the addition of nickel, which is expected to improve the hydrogen adsorption and pore size control. Silica membranes with a high selectivity were subsequently prepared using counter-diffusion CVD, under high-pressure conditions at the membrane side, where tetramethylorthosilicate (TMOS) is supplied.An ¡-alumina tube (10 mm o.d., 6 mm i.d., 35 mm length, Noritake Co., Ltd.) with a £-alumina layer was used as the membrane substrate. The porous ¡-alumina tube (35 mm length) was joined to a dense ¡-alumina tube (10 mm o.d., 6 mm i.d., 250 mm length) and an ¡-alumina disk (12 mm diameter, 2 mm thickness) with a glass sealant. The £-alumina interlayers were prepared by dipping ¡-alumina tubes into a 0.6 mol L ¹1 boehmite (£-AlOOH) sol, containing 1.5 wt % poly(vinyl alcohol). The tube was dried at room temperature for 3 h and then calcined at 600°C for 3 h, at a heating and cooling rate of 1°C min ¹1. Tetraethoxysilane (20 g, Wako) was added after all the nickel(II) nitrate hexahydrate (Ni/Si mol ratio = 0.5, 0.25, and 0) had dissolved in ethanol. 1 M HNO 3 (7.5 mL) was added dropwise to the mixture with gentle stirring at room temperature over a period of 15 min.3,4 The temperature was then increased to 70°C and the mixture was heated at reflux for 150 min. The resulting solution was diluted to 0.1 mol L ¹1 in ethanol. The membrane substrate was dipped into the nickelsilica solution for 10 s. Finally, the membrane was dried at room temperature for 3 h and calcined at 873 ...

show abstract

“…Figure 2.4. Structure evolution of (a) acid and (b) base catalysed sol-gel during calcination [48] In terms of silica membranes, the silica sol-gel method has been further improved by incorporating extra species/reactants, such as transitional metal alkoxides [53][54][55][56], surfactants [57,58] or metal salts [59][60][61][62][63] to functionalise the resultant materials. These reactants play various roles during the sol-gel method.…”

Section: Sol-gel Methodsmentioning

confidence: 99%

“…Then several research groups reported silica membranes based on different metal/ metal oxides, such as Al [83], Ti [89], Zr [90][91][92] Other than improved hydrothermal stability, these dopants can also confer extra properties to membrane materials. For examples, a nickel doped silica membrane showed a unique gas permeation property wherein the hydrogen permeance increased with increasing nickel content up to a molar ratio of 0.3 for (Ni/Ni+Si) and it was five times higher than the permeance of He [59]. Boffa et al [103] observed a very low permeance of CO2 which did not follow molecular sieving transport phenomena for a sol-gel derived Nb-Si membrane.…”

Section: Hydrothermal Stability Of Silica Based Membranesmentioning

confidence: 99%

Development of microporous cobalt oxide silica membrane for CO2/H2 separation

Liu¹

View full text Add to dashboard Cite

Hydrogen as a clean energy carrier is proposed as a long term solution to address issues related to global warming, energy security and air pollution. H2 production is currently fossil fuel based and this is expected to remain the case during the transition to cleaner sources. Hence, high performance H2 separation from CO2 is required to meet purity production targets, whilst the CO2 can be transported and stored in safe geological sites. Microporous silica membranes are a promising technology for processing syngas streams because of the simplicity of the sol-gel synthesis coupled with great pore size tailorability at molecular sieving dimensions. However, poor hydrothermal stability of silica membranes remains a contributing factor to the delay of the commercial deployment of this technology, particularly for processing wet syngas streams at high temperature (500-600 °C).Recent improvements have been attained by doping metal oxides in the silica matrix. Cobalt oxide silica membranes show excellent separation performance and improved hydrothermal stability.However, there are significant knowledge gaps associated with the fundamental understanding of the influence of cobalt dopant on the hydrothermal stability of silica matrices. To address these gaps, this thesis systematically investigated the physicochemical properties and hydrothermal stability of cobalt oxide silica materials and the performance of resultant membranes.The first key contribution of this thesis is the finding that the hydrothermal stability of cobalt doped silica materials is highly dependent on the cobalt phase, particularly Co 3+ as cobalt tetroxide (Co3O4).The Co3O4 silica materials resulted in less than 25% surface area loss whilst maintaining microporous structures when exposed to harsh hydrothermal conditions of 75 mol% H2O(v) at 550 °C for 40 h.Contrary to this, silica samples without Co3O4 completely densified under the same testing conditions. It is postulated that Co3O4 nanoparticles 'shielded' the silica matrix and inhibited to a certain degree the hydrolysis and condensation of the silica in the pores walls, thus conferring improved hydrothermal stability.A second key contribution is evidenced by sol-gel conditioning, thus aiding the formation of the Co3O4 in the silica network. By increasing the water ratio and decreasing the ethanol ratio, Co3O4 was formed at a much lower loading (Co/Si=0.1) than previously reported. The cobalt silica materials synthesised from the new sol-gel conditions showed a lower surface area loss after hydrothermal treatment (HT). The local structures around cobalt atoms were probed by X-ray absorption spectroscopy (XAS). For the low cobalt loading sample (Co/Si=0.05), the XAS results showed that the cobalt was highly dispersed in the silica network in a tetrahedral coordination (Co 2+ ) with oxygen and a small proportion of Co-Co interactions in the second shell. Co3O4 long range order was ii observed for higher cobalt loading samples (Co/Si=0.10, 0.25), which suggests that Co3O4 acts as a ph...

show abstract

High‐Temperature Hydrogen Adsorption Properties of Precursor‐Derived Nickel Nanoparticle‐Dispersed Amorphous Silica

Cited by 55 publications

References 35 publications

Improved pore connectivity by the reduction of cobalt oxide silica membranes

Improved pore connectivity by the reduction of cobalt oxide silica membranes

Synthesis and Characterization of Ni-doped Silica Membranes Prepared Using a Hybrid Sol–Gel/CVD Method

Development of microporous cobalt oxide silica membrane for CO2/H2 separation

Contact Info

Product

Resources

About