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61.
《International Journal of Hydrogen Energy》2019,44(20):9922-9929
Catalytic methane decomposition can become a green process for hydrogen production. In the present study, yttria doped nickel based catalysts were investigated for catalytic thermal decomposition of methane. All catalysts were prepared by sol-gel citrate method and structurally characterized with X-ray powder diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and Brunauer, Emmet and Teller (BET) surface analysis techniques. Activity tests of synthesized catalysts were performed in a tubular reactor at 500 ml/min total flow rate and in a temperature range between 390 °C and 845 °C. In the non-catalytic reaction, decomposition of methane did not start until 880 °C was reached. In the presence of the catalyst with higher nickel content, methane conversion of 14% was achieved at the temperature of 500 °C. Increasing the reaction temperature led to higher coke formation. Lower nickel content in the catalyst reduced the carbon formation. Consequently, with this type of catalyst methane conversion of 50% has been realized at the temperature of 800 °C. 相似文献
62.
《International Journal of Hydrogen Energy》2019,44(33):17460-17469
Methane decomposition into hydrogen and carbon is analyzed in a plasma reactor, with a rotating arc and different cross-sectional areas for the passing gas. This novel setup helps the arc discharge to sweep a larger fraction of the reactant which could cause a better interaction of methane molecules with plasma phase causing higher conversions. The effects of angular velocity of arc discharge, feed flow rate, and cross-sectional area for the passing gas were investigated on the reactor performance. Methane conversion increased significantly by changing the arc mode from stationary to rotating. Increasing the cross-sectional area for the passing gas causes conversion drop for stationary arc whereas a slight increase in conversion is observed for rotating arc mode. Hydrogen production rate of 100 ml/min with an energy yield of 26.8 g/kWh achieved at a methane flow rate of 150 ml/min. The residence time is estimated to be 0.2–3.9 s in the range of the present study, which is a much longer period compared to the plasma process time. Therefore, it is suggested that the mass transfer rate between the gas and plasma phase is the controlling factor for methane conversion. In this respect, an apparent reaction rate constant is derived by considering methane conversion as that fraction of gas, which is exposed to the active area of the plasma arc column. 相似文献
63.
《International Journal of Hydrogen Energy》2019,44(18):9210-9219
This paper presents an efficient framework for converting renewable energy to gas and reducing Carbon dioxide (CO2) footprint at the same time. The problem is presented in two levels. The first level is a minimization programming that minimizes operational cost and CO2 of generators. The CO2 is forwarded to the second level. In the second level, Carbon Capture and Storage (CCS) is designed to capture CO2. The CO2 is combined with Hydrogen and makes Methane (CH4). The required Hydrogen is obtained from water electrolyzer that is supplied by the solar system. The capacity and size of water electrolyzer, solar system, and CCS is designed by the planning in the second level while this programming maximizes profit from selling Methane. As a result, the first level presents minimization programming (i.e., minimizing cost and CO2) and the second level presents maximization programming (i.e., maximizing profit). The programming is developed taking into account solar uncertainty. The stochastic programming is implemented to cope with uncertainties. The problem is formulated as binary mixed integer linear programming and solved by GAMS software. The proposed power to gas (P2G) procedure efficiently designs proper solar system and deals with intermittency of solar energy, reduces CO2 footprint, maximizes profit, and minimizes operational cost of generators at the same time. 相似文献
64.
《International Journal of Hydrogen Energy》2019,44(43):23899-23911
Chlorella sp. biomass was used as the sole substrate for the production of hydrogen and methane through integrated dark fermentation (DF) and photo-fermentation (PF), and DF and anaerobic digestion (AD) processes. Prior to use in fermentations, the biomass was pretreated by acid-hydrothermal method, which yielded a maximum reducing sugar yield of 162.9 ± 4.2 mg g-biomass−1. The use of the microalgal hydrolysate to produce hydrogen by DF gave a hydrogen yield (HY) of 47.2 ± 1.1 mL g-volatile-solids−1 (VS). The subsequent use of the hydrogenic effluent in PF gave a HY of 125.0 ± 1.5 mL g-VS−1, while AD of the hydrogenic effluent gave a methane yield of 152.8 ± 1.3 mL g-VS−1. The total energy yield attained by the use of DF alone, the integrated DF-PF, and DF-AD processes were 0.51, 1.86 and 5.98 kJ g-VS−1, respectively. These results indicate that the integrated DF-AD process was effective in recovering energy from Chlorella sp. biomass. However, an energy balance analysis indicated that the process was not energetically feasible due to the high energy demand for the acid-hydrothermal pretreatment. 相似文献
65.
《International Journal of Hydrogen Energy》2019,44(32):17363-17380
Hydrogen (H2) and methane (CH4) are the potential alternative energy carriers with autonomous extensive and viable importance. These fuels could complement the advantages, and discard the disadvantages of each other, if produced simultaneously. Considering their complementary properties, co-production of a mixture of H2 and CH4 in the form of biohythane in two-stage anaerobic digestion (AD) process is gaining more interest than their individual production. Biohythane is a better transportation fuel than compressed natural gas (CNG) in terms of high range of flammability, reduced ignition temperature as well as time, without nitrous oxide (NOx) emissions, improved engine performance without specific modification, etc. Other than production of biohythane, performing two-stage AD is advantageous over one-stage AD due to short HRT, high energy recovery, high COD removal, higher H2 and CH4 yields, and reduced carbon dioxide (CO2) in biogas. For improved biohythane production, various aspects of two-stage AD need to be emphasized. Keeping the facts in mind, the process of two-stage AD along with microbial diversity in comparison to one-stage AD has been discussed in the previous sections of this review. For large scale commercial production, and utilization of biohythane in automobile sector, its execution needs evaluation of process parameters, and problems associated with two-stage AD. Hence, the later part of this review describes the production process of biohythane, concerned microbial diversity, operational process parameters, major challenges and their solutions, applications, and economic evaluation for enhanced production of biohythane. 相似文献
66.
《Advanced Powder Technology》2022,33(1):103377
Hierarchical structure and surface properties of selective support afford some special effects on the catalytic activity, which could be tuned to achieve improved performance. Herein, using a combination of hydrothermal coprecipitation and thermal processing, we integrated highly-distributed Co3O4 spinel nanospecies on laminated hierarchically structured Al2O3 which could be used as a highly efficient VOCs treatment catalyst. Impressively, compared to Co-free Al2O3 counterpart (SBET = 188.2 m2·g?1), these obtained Co3O4 spinel functionalized catalysts are endowed with adjustable Co loading, optimized Co activity state, and obviously improved hierarchically structural properties (SBET = 274.7 m2·g?1). The microporous and mesoporous structures both existed in the obtained Al2O3, which is beneficial to the heterogeneous catalytic reaction process. The results reveal that the proper Co loading in the hierarchically structured Al2O3 could enable the rational modulation of catalytic activity in the combustion of toluene and exceeds the commercial 5 wt% Pd/C catalyst in the light of total catalytic oxidation ability. This developed heterogeneous Co3O4 compositing hierarchically structured Al2O3 provides a significant potential value for practical VOCs treatment. 相似文献
67.
《International Journal of Hydrogen Energy》2022,47(79):33664-33676
Strontium ferrite (SrFeO3-δ) is a very attractive oxygen transfer agent for chemical looping reactions and hydrogen-rich syngas generation. Dispersing SrFeO3 in a medium such as Ca0.5Mn0.5O could enhance the activity and cyclability. In this study, SrFeO3-δ-Ca0.5Mn0.5O (30 wt% SrFeO3-δ) nanocomposite with a reticulated foam structure was explored as the oxygen carrier for chemical looping reforming of methane in a solar tubular reactor. The foam nanocomposite was prepared by a hard-templating method. The performance was investigated at temperatures of 850–1000 °C and methane flowrates of 25–250 STP mL/min, and the oxidative gas was either CO2 or H2O in the oxidation step. In the reduction step of 27 successive redox cycles, the production rate of CO changed marginally and CO yield maintained at about 1.9 mmol/g, even though sintering occurred. The productivity of H2 decreased first and then tended to be stable at 3.8 mmol/g (i.e., twice the CO yield) as the cycling number increased (the average oxygen storage capacity of the material was ~1.95 mmol/g). Microscopic and X-ray diffraction investigations suggested that the element distribution pattern and crystalline phase of the foam nanocomposite remained almost unchanged after 27 redox cycles, confirming material stability. The maximum solar-to-fuel efficiency for the foam nanocomposite was 5.68%, which was 21.4% higher than that for the powder nanocomposite. To increase syngas productivity and solar-to-fuel efficiency, it is required to conduct the reforming reaction at high temperatures and methane flowrates. However, the energy upgrade factor will decrease as methane flowrate increases. 相似文献
68.
Nanoceria was synthesized by treating cerium carbonate hydrate in a molten KOH-NaOH mixture at 200 °C. The nanoceria thus synthesized under a hydrogen atmosphere had a crystal size of 21.6 nm measured by XRD, consistent with the particle size of 23 nm measured by TEM. Raman spectra results indicated that the nanoceria produced under hydrogen had a downshift of 0.9 cm?1 from the sample synthesized in air. XPS spectra showed that the Ce3+ fraction of the nanoceria synthesized in hydrogen was greater than that produced in air. The oxygen vacancies were formed by partial oxidization of the precursor in molten KOH-NaOH mixture. The UV–visible absorption properties of ceria synthesized under hydrogen showed a 34 nm red-shift compared with that synthesized in air. The nanoceria prepared in this work had a better catalytic property for CO oxidization than the commercial nanoceria. Results indicated that the increased Ce3+ fraction or oxygen vacancies formed by this partial oxidization process extended the absorption edge of ceria resulting in a narrower band gap, and enhanced the catalytic activity of nanoceria. This method has proven to provide a simple and scalable method for the synthesis of high quality nanoceria. 相似文献
69.
70.
Serdar Akbayrak Yalçın Tonbul Saim Özkar 《International Journal of Hydrogen Energy》2021,46(27):14259-14269
Herein, we report the use of tungsten(VI) oxide (WO3) as support for Rh0 nanoparticles. The resulting Rh0/WO3 nanoparticles are highly active and stable catalysts in H2 generation from the hydrolysis of ammonia borane (AB). We present the results of our investigation on the particle size distribution, catalytic activity and stability of Rh0/WO3 catalysts with 0.5%, 1.0%, 2.0% wt. Rh loadings in the hydrolysis reaction. The results reveal that Rh0/WO3 (0.5% wt. Rh) is very promising catalyst providing a turnover frequency of 749 min?1 in releasing 3.0 equivalent H2 per mole of AB from the hydrolysis at 25.0 °C. The high catalytic activity of Rh0/WO3 catalyst is attributed to the reducible nature of support. The report covers the results of kinetics study as well as comparative investigation of activity, recyclability, and reusability of colloidal(0) nanoparticles and Rh0/WO3 (0.5 % wt. Rh) catalyst in the hydrolysis reaction. 相似文献