共查询到20条相似文献,搜索用时 31 毫秒
1.
A. Caravaca V.J. Ferreira A. de Lucas-Consuegra J.L. Figueiredo J.L. Faria J.L. Valverde F. Dorado 《International Journal of Hydrogen Energy》2013
A novel combined single chamber solid electrolyte plus fixed bed reactor configuration was developed for the simultaneous production of H2 and C2 hydrocarbons from a humidified CH4 atmosphere. Hence, a Pt/YSZ/Ag solid electrolyte cell was placed on the top of an active oxidative coupling catalyst powder bed Ce–Na2WO4/SiO2. H2 was produced via steam electrolysis in a Pt cathode of the solid electrolyte cell (H2O + 2e− → H2 + O2−). Simultaneously, the produced O2− ions were electrochemically pumped to the Ag anode, leading to the C2s production, via oxidative coupling of CH4 (4CH4 + 3O2− → C2H4 + C2H6 + 3H2O + 6e−). Additionally, non-reacted O2− molecules desorbed to the gas phase (2O2− → O2+4e−) and reacted with CH4 in the catalyst bed leading to an increase of C2s yield. The influence of different reaction parameters was investigated together with long-term reaction experiments, confirming the stability of this configuration for its practical application. The obtained results demonstrated that the addition of an active catalyst bed strongly enhances both: the efficiency of the single chamber steam electrolysis and the oxidative coupling process. 相似文献
2.
Pawan Kumar Dubey Prashant Tripathi R.S. Tiwari A.S.K. Sinha O.N. Srivastava 《International Journal of Hydrogen Energy》2014
The utilization of solar energy for the conversion of water to hydrogen and oxygen has been considered to be an efficient strategy to solve crisis of energy and environment. Here, we report the synthesis of reduced graphene oxide–TiO2 nanoparticle composite system through the photocatalytic reduction of graphite oxide using TiO2 nanoparticles. Photoelectrochemical characterizations and hydrogen evolution measurements of these nanocomposites reveal that the presence of graphene enhances the photocurrent density and hydrogen generation rate. The optimum photocurrent density and hydrogen generation rate has been found to be 3.4 mA cm−2 and 127.5 μmole cm−2h−1 in 0.5 M Na2SO4 electrolyte solution under 1.5AM solar irradiance of white light with illumination intensity of 100 mW cm−2. In graphene–TiO2 nanocomposite, photogenerated electrons in TiO2 are scavenged by graphene sheets and percolate to counter electrode to reduce H+ to molecular hydrogen thus increasing the performance of water-splitting reaction. 相似文献
3.
Hydrogen discharge technique of high-strength low alloy steel for high-pressure gaseous hydrogen storage tank was developed by using an electrochemical technique. The electrochemical hydrogen discharge of high-strength low alloy steel were investigated in a deaerated borate buffer solution (0.3 M H3BO3 + 0.074 M N2B4O7, pH = 8.4). By applying a potential of +630 mVSCE which is higher than the hydrogen equilibrium potentials and lower than the pitting potential, the oxidation reaction of metal (Fe → Fe2+ + 2e−) is limited and oxidation reaction of the hydrogen (H2 + 2OH− → 2H2O + 2e−) was induced simultaneously. Thus, the pre-charged hydrogen inside the specimen was eliminated effectively without any damage to the specimen. The electrochemical hydrogen discharge method was performed at 25 °C, 50 °C and 75 °C. The efficiency of hydrogen discharge was accelerated with increasing temperature because the exchange current density of hydrogen is increased with temperature. 相似文献
4.
Raúl Sanz José Antonio CallesDavid Alique Laura Furones 《International Journal of Hydrogen Energy》2014
In this work, H2 production via catalytic water gas shift reaction in a composite Pd membrane reactor prepared by the ELP “pore-plating” method has been carried out. A completely dense membrane with a Pd thickness of about 10.2 μm over oxidized porous stainless steel support has been prepared. Firstly, permeation measurements with pure gases (H2 and N2) and mixtures (H2 with N2, CO or CO2) at four different temperatures (ranging from 350 to 450 °C) and trans-membrane pressure differences up to 2.5 bar have been carried out. The hydrogen permeance when feeding pure hydrogen is within the range 2.68–3.96·10−4 mol m−2 s−1 Pa−0.5, while it decreases until 0.66–1.35·10−4 mol m−2 s−1 Pa−0.5 for gas mixtures. Furthermore, the membrane has been also tested in a WGS membrane reactor packed with a commercial oxide Fe–Cr catalyst by using a typical methane reformer outlet (dry basis: 70%H2–18%CO–12%CO2) and a stoichiometric H2O/CO ratio. The performance of the reactor was evaluated in terms of CO conversion at different temperatures (ranging from 350 °C to 400 °C) and trans-membrane pressures (from 2.0 to 3.0 bar), at fixed gas hourly space velocity (GHSV) of 5000 h−1. At these conditions, the membrane maintained its integrity and the membrane reactor was able to achieve up to the 59% of CO conversion as compared with 32% of CO conversion reached with conventional packed-bed reactor at the same operating conditions. 相似文献
5.
Gang Li Takuya NiimiMasakoto Kanezashi Tomohisa YoshiokaToshinori Tsuru 《International Journal of Hydrogen Energy》2013
A high-performance organosilica membrane was prepared via sol–gel processing for use in methylcyclohexane (MCH) dehydrogenation to produce high-purity hydrogen. The membrane showed a high H2 permeance of 1.29 × 10−6 mol m−2 s−1 Pa−1, with extremely high H2/C3H8 and H2/SF6 selectivities of 6680 and 48,900, respectively, at 200 °C. The extraction of hydrogen from the membrane reactor led to the MCH conversion higher than the thermodynamic equilibrium, with almost pure hydrogen obtained in the permeate stream without considering the effect of carrier gas and sweep gas in the membrane reactor, and the organosilica membrane reactor was very stable under the reaction conditions employed. 相似文献
6.
The present study focused on the mesophilic anaerobic bio-hydrogen production from PPS (pulp & paper sludge) and FW (food waste), and the subsequent anaerobic digestion of the effluent for the methane production under thermophilic conditions by a two-stage process. The maximum hydrogen yield of 64.48 mL g−1 VSfed and methane yield of 432.3 mL g−1 VSfed were obtained when PPS and FW were applied with 1: 1 VS ratio as the feedstock. No VFA were cumulated in the reactor during the period of hydrogen - methane fermentation, as well as no NH3–N and Na+ inhibition were found in the process. 71%–87% removal efficiencies of SCOD were attained for hydrogen and methane co-production. pH 4.8–6.4 and alkalinity 794–3316 mg CaCO3 L−1 for H2 fermentation, as well as pH 6.5–8.8 and alkalinity 4165–4679 mg CaCO3 L−1 for CH4 fermentation, were achieved without any adjustment. This work showed that anaerobic co-digestion of PPS and FW for hydrogen-methane co-production was a stable, reliable and effective way for energy recovery and bio-solid waste stabilization by the two-stage mesophilic–thermophilic process. 相似文献
7.
Wang Hui Feng XiaoqiongWang Xiaofang Cheng SanpingGao Shengli 《International Journal of Hydrogen Energy》2008
Pure hydrogen can be stored and supplied directly to polymer electrolyte fuel cell by the redox of iron oxide: Fe3O4 + 4H2 → 3Fe + 4H2O and 4H2O + 3Fe → Fe3O4 + 4H2. Four bimetal-modified samples were prepared by impregnation. The hydrogen storage properties of the samples were investigated. The result shows that the Fe2O3–Mo–Al sample presented the most excellent catalytic activity and cyclic stability. H2 forming temperature and H2 forming rate could be surprisingly decreased and enhanced, respectively. The average H2 forming temperature at the rate of 250 μmol min−1·Fe-g−1 for Fe2O3–Mo–Al in the first 4 cycles could be decreased from 469 °C before the addition of Mo–Al to 273 °C after the addition of Mo–Al. The reason for it may be that the Mo–Al additive in the sample can prevent from the sintering of the particles and accelerate the H2O decomposition due to Mo taking part in the redox reaction. The average storage capacity of Fe2O3–Mo–Al was up to 4.68 wt%. 相似文献
8.
A study was undertaken in order to investigate the potential of hydrogen (H2) generation by hydrolysis of solid sodium borohydride (NaBH4) with stoichiometric amount of distilled water (from molar ratios H2O/NaBH4 (mol/mol) of 2 to 18), in the presence of a powder nickel-ruthenium based catalyst, reused more than 300 times. The experiments, performed in batch reactors with different free volumes and bottom shapes (flat and conical) reveal – for the conical bottom shape with any excess of water – 8.1 H2 wt% and 92 kg H2/m3 (materials-only basis), and a H2 rate of 87.4 L(H2) min−1 g−1 catalyst, at the moderate pressure of ∼1.2 MPa. The results presented in this work give emphasis to the importance of considering the role of reactor bottom geometry on the solid NaBH4 hydrolysis studies performed with stoichiometric amounts of liquid water. 相似文献
9.
Estela Tapia-Venegas Juan Esteban Ramirez Andrés Donoso-Bravo Lorena Jorquera Jean-Phillipe Steyer Gonzalo Ruiz-Filippi 《International Journal of Hydrogen Energy》2013
The objective of this study was to evaluate the production of hydrogen in a two-stage CSTR system – both reactors having the same volume – and compare its performance with a conventional one-stage process. The lab-scale two-stage and one-stage systems were operated at five pHs and five hydraulic retention time (HRTs). The maximum volumetric hydrogen productivity and yield obtained with the two-stage system were 5.8 mmol L−1 h−1 and 2.7 mol H2 mol glucose−1, respectively, at an HRT of 12 h and pH 5.5. Overall, the two-stage system showed, at steady state, a better performance that the one-stage system for all the evaluated pHs. However, a comparison between the one-stage system, operating at 6 h of HRT, and the first reactor of the two-stage system at the same HRT did not show any significant difference, highlighting the positive impact of having a two-stage process. The determination of the ratio between the experimental measured H2 in the gas phase and the theoretical H2 generated in the liquid phase (discrepancy factor) indicated that an important part of the hydrogen produced in the first reactor was transferred into the second reactor instead of being desorbed in the headspace. Therefore, the improving of hydrogen production in the two-stage system is rather attributed to the increased transfer of hydrogen from liquid to gas than an actual total hydrogen production increase. 相似文献
10.
Wan-Ting Chen Vedran Jovic Dongxiao Sun-Waterhouse Hicham Idriss Geoffrey I.N. Waterhouse 《International Journal of Hydrogen Energy》2013
Low cost semiconductor photocatalysts that can efficiently harvest solar energy to generate H2 from water or biofuels will be critical to future hydrogen economies. In this study, low cost CuO/TiO2 photocatalysts (CuO loadings 0–15 wt.%) were prepared, characterized and evaluated for H2 production from ethanol–water mixtures (80 vol.% ethanol, 20 vol.% H2O) under UV excitation. TEM, XRF, EDAX, EPR, Raman, TGA, XPS and Cu L-edge NEXAFS data showed that at CuO loadings <5 wt.%, Cu(II) was highly dispersed over the TiO2 support, possibly as a sub-monolayer CuO species. At higher loadings, CuO crystallites of diameter 1–2 nm were identified. The photocatalytic activity of CuO/TiO2 photocatalysts was highly dependent on the CuO loading, with 1.25 wt.% CuO being optimal (H2 production rate = 20.3 mmol g−1 h−1). Results suggest that sub-monolayer coverages of Cu(II) or CuO on TiO2 are highly beneficial for H2 generation from ethanol–water mixtures and support the development of a sustainable H2 economy. 相似文献
11.
S. Suwarno J.K. Solberg J.P. Mæhlen R.V. Denys B. Krogh E. Ochoa-Fernández B.T. Børresen E. Rytter I.E. Gabis V.A. Yartys 《International Journal of Hydrogen Energy》2013
Phase transformations during dynamic dehydrogenation of Ti1−xVxH2 (x = 0.1; 0.2; 0.3) were studied using in situ Synchrotron X-Ray Diffraction (SR XRD) and non-isothermal kinetics experiments. The main dehydrogenation path for γ-Ti1−xVxH2 was found to be γ → δ → β → βalloy. Body-centred tetragonal δ-hydride was found to be an intermediate phase of the γ → β transformation in Ti0.8–0.9V0.1–0.2H2. TDS, in situ SR XRD and isoconversional kinetics studies showed that hydrogen desorption from Ti1−xVxH2 is composed of simultaneous reactions taking place between 300 and 600 °C. The effective activation energy of hydrogen desorption depends on the vanadium contents and the reaction pathway, increasing from 21 kJ/mol H2 (γ → δ) to 60–110 kJ/mol H2 (δ → β). 相似文献
12.
Peter G. LoutzenhiserAldo Steinfeld 《International Journal of Hydrogen Energy》2011,36(19):12141-12147
Solar syngas production from CO2 and H2O is considered in a two-step thermochemical cycle via Zn/ZnO redox reactions, encompassing: 1) the ZnO thermolysis to Zn and O2 using concentrated solar radiation as the source of process heat, and 2) Zn reacting with mixtures of H2O and CO2 yielding high-quality syngas (mainly H2 and CO) and ZnO; the ZnO is recycled to the first, solar step, resulting in net reaction βCO2 + (1 − β)H2O → βCO + (1 − β)H2. Syngas is further processed to liquid hydrocarbon fuels via Fischer-Tropsch or other catalytic processes. Second-law thermodynamic analysis is applied to determine the cycle efficiencies attainable with and without heat recuperation for varying molar fractions of CO2:H2O and solar reactor temperatures in the range 1900-2300 K. Considered is the energy penalty of using Ar dilution in the solar step below 2235 K for shifting the equilibrium to favor Zn production. 相似文献
13.
Pongtanawat Khemthong Pairat Photai Nurak Grisdanurak 《International Journal of Hydrogen Energy》2013
CuO was introduced into porous TiO2 nanorod through impregnation method. Before the impregnation step, TiO2 nanorod was hydrothermally synthesized from TiO2 powder in aqueous NaOH solution and followed by thermal treatment at 450 °C. The structures and properties of impregnated samples were characterized using various techniques, including XRD, BET, XAS, TEM, and UV-DRS. Their photocatalytic performance on simultaneous hydrogen production from pure water and aqueous methanol solution was also investigated under solar light. It was found that CuO/TiO2 nanorod possessed a high surface area, good photocatalytic property and excellent hydrogen generation activity. Incorporation of Cu ions into the lattice framework of anatase TiO2 nanorod enhanced the efficiency in visible region at 438–730 nm. Moreover, the XAS results showed that some Cu ions formed solid solution in the TiO2 nanorod (CuxT1−xO2). However, the excessive incorporation of Cu ions did not improve any ability of anatase TiO2 nanorod for production of hydrogen from pure water splitting. This could be due to the excessive CuO agglomeration at outside-pores which blocked the sensitization of TiO2 nanorod. Only 1% Cu/TiO2 nanorod was found to be a remarkable and an efficient photocatalyst for hydrogen production under solar light from both pure water and sacrificial methanol splitting. The highest rate of hydrogen production of 139.03 μmol h−1 gcatalyst−1 was found in sacrificial methanol which was 3.24% higher than in pure water. 相似文献
14.
This study investigated the effect of gases such as CO2, N2, H2O on hydrogen permeation through a Pd-based membrane −0.012 m2 – in a bench-scale reactor. Different mixtures were chosen of H2/CO2, H2/N2/CO2 and H2/H2O/CO2 at temperatures of 593–723 K and a hydrogen partial pressure of 150 kPa. Operating conditions were determined to minimize H2 loss due to the reverse water gas shift (RWGS) reaction. It was found that the feed flow rate had an important effect on hydrogen recovery (HR). Furthermore, an identification of the inhibition factors to permeability was determined. Additionally, under the selected conditions, the maximum hydrogen permeation was determined in pure H2 and the H2/CO2 mixtures. The best operating conditions to separate hydrogen from the mixtures were identified. 相似文献
15.
Shiping ZhangFangming Jin Xu ZengJiajun Hu Zhibao HuoYuanqing Wang Noriaki WatanabeNobuo Hirano Noriyoshi Tsuchiya 《International Journal of Hydrogen Energy》2011,36(15):8878-8884
Hydrogen production from water with S2− as a reductant under hydrothermal conditions is an effective new method, in which S2− is oxidized into S2O32−, SO32− and SO42−. However, the reactor wall had great effect on hydrogen production as large amount hydrogen is produced with Hastelloy C-22 reactor while almost no hydrogen generated in SUS 316 reactor. Therefore, the influence of main components of Hastelloy C-22 reactor (Co/W/Ni) and SUS 316 reactor (Fe) on hydrogen production with H2S as the reductant was investigated. The results showed that Fe had negative effect, whereas W, Co and Ni had significant positive effect on improving hydrogen production. These results provided a possible explanation for no hydrogen generated with SUS 316 reactor,and some suggestions for improving hydrogen production. The highest hydrogen production of 199 mL (2 times than the control) was obtained with 4.00 mmol Co, 4.00 mmol W, and 1.00 mmol Ni. 相似文献
16.
Nitrogen/titanium dioxide (N/TiO2) visible light photocatalysts were prepared using the sol–gel method. The catalysts were characterized using transmission electron microscopy, reflective UV–visible spectroscopy, specific surface area measurements, and X-ray diffraction. The prepared catalysts were used to generate hydrogen gas through the water-splitting reaction under visible light (wavelengths greater than 400 nm). Various N/Ti addition ratios were tested, and the hydrogen generation rates were compared to determine the optimal ratio. The maximal hydrogen production rate (approximately 55 μmol h−1 g−1) was attained when the N/Ti ratio of N–TiO2 was 10. When PdO and Pt were loaded onto the N–TiO2 catalyst, the hydrogen generation rates increased to 544 and 772 μmol h−1 g−1, respectively. The highest hydrogen production rate (2460 μmol h−1 g−1) was obtained when bimetallic 0.05 wt% PdO-0.10 wt% Pt/N–TiO2 was used. After three times use the hydrogen yield of the catalyst was maintained as 83%. A possible mechanism of water splitting catalyzed by this visible light photocatalyst is proposed. 相似文献
17.
Vinegar fermentation wastewater with different initial COD contents (9.66–48.6 g L−1) were used for hydrogen gas production with simultaneous COD removal by electro-hydrolysis. The applied DC voltage was constant at 4 V. The highest cumulative hydrogen production (3197 ml), hydrogen yield (2766 ml H2 g−1 COD), hydrogen formation rate (799 ml d−1), and percent hydrogen (99.5%) in the gas phase were obtained with the highest initial COD of 48.6 g COD L−1. The highest energy efficiency (48%) was obtained with the lowest COD content of 9.66 g L−1. Hydrogen gas production by water electrolysis was less than 250 ml and wastewater control resulted in less than 25 ml H2 in 96 h. The highest (12%) percent COD removal was obtained with the lowest COD content. Hydrogen gas was produced by reaction of (H+) ions present in raw WW ( pH = 3.0) and protons released from acetic acid with electrons provided by electrical current. Electro-hydrolysis of vinegar wastewater was proven to be an effective method of H2 gas production with some COD removal. 相似文献
18.
Guilherme PeixotoNora Katia Saavedra Maria Bernadete A. VarescheMarcelo Zaiat 《International Journal of Hydrogen Energy》2011,36(15):8953-8966
The production of hydrogen from soft-drink wastewater in two upflow anaerobic packed-bed reactors was evaluated. The results show that soft-drink wastewater is a good source for hydrogen generation. Data from both reactors indicate that the reactor without medium containing macro- and micronutrients (R2) provided a higher hydrogen yield (3.5 mol H2 mol−1 of sucrose) as compared to the reactor (R1) with a nutrient-containing medium (3.3 mol H2 mol−1 of sucrose). Reactor R2 continuously produced hydrogen, whereas reactor R1 exhibited a short period of production and produced lower amounts of hydrogen. Better hydrogen production rates and percentages of biogas were also observed for reactor R2, which produced 0.4 L h−1 L−1 and 15.8% of H2, compared to reactor R1, which produced 0.2 L h−1 L−1 and 2.6% of H2. The difference in performance between the reactors was likely due to changes in the metabolic pathway for hydrogen production and decreases in bed porosity as a result of excessive biomass growth in reactor R1. Molecular biological analyses of samples from reactors R1 and R2 indicated the presence of several microorganisms, including Clostridium (91% similarity), Enterobacter (93% similarity) and Klebsiella (97% similarity). 相似文献
19.
Jun Xing Yu Hang Li Hai Bo Jiang Yun Wang Hua Gui Yang 《International Journal of Hydrogen Energy》2014
Photocatalytic hydrogen production from water or organic compounds is a promising way to resolve our energy crisis and environmental problems in the near future. Over the past decades, many photocatalysts have been developed for solar water splitting. However, most of these photocatalysts require cocatalyst to facilitate H2 evolution reaction and noble metals as key cocatalysts are widely used. Consequently, the condition of noble metal cocatalyst including the size and valence state etc plays the key role in such photocatalytic system. Here, the size and valence state effect of Pt on photocatalytic H2 evolution over platinized TiO2 photocatalyst were studied for the first time. Surprisingly, it was found that Pt particle size does not affect the photoreaction rate with the size range of several nanometers in this work, while it is mainly depended on the valence state of Pt particles. Typically, TOFs of TiO2 photodeposited with 0.1–0.2 wt% Pt can exceed 3000 h−1. 相似文献
20.
Mengkui Tian Wenjie Peng Baiwei Shang Wenliang Tao Ya Xiao 《International Journal of Hydrogen Energy》2012
Photoelectrochemical water splitting is a promise way to transfer solar energy to hydrogen as chemical energy carrier. In this paper, visible light driven tin oxide based photoelectrodes were obtained through dipping SnCl2·2H2O EtOH solution on FTO or metal Ti substrate and with further heat treatment process. Photoelectrochemical measurements with three electrodes configuration revealed that this obtained photoelectrode showed n-type responsive properties and the photocurrent density reached mA/cm2 level without any modification under visible light irradiation (λ > 420 nm). XRD, UV–Vis spectrum and control experimental results proposed that the visible light driven mechanism for the tin oxide based photoanode maybe ascribed to Sn4+/Sn2+ transformation and surface oxygen deficiency, and the tin oxide can be denoted as SnO2−x. 相似文献