共查询到20条相似文献,搜索用时 31 毫秒
1.
We investigate the effects of hydrogen addition on Fenimore NO formation in fuel-rich, low-pressure burner-stabilized CH4/O2/N2 flames. Towards this end, axial profiles of temperature and mole fractions of CH and NO are measured using laser-induced fluorescence (LIF). The experiments are performed at equivalent ratios of 1.3 and 1.5, using 0.25 mole fraction of hydrogen in the fuel, while varying the mass flux through the burner. The results are compared with those reported previously for burner-stabilized CH4/O2/N2 flames. The increased burning velocity caused by hydrogen addition is seen to result in a lower flame temperature as compared to methane flame stabilized at the same mass flux. This increase in burner stabilization upon hydrogen addition results in significantly lower CH mole fractions at φ = 1.3, but appears to have little effect on the CH profile at φ = 1.5. In addition, the results show that not only the maximum flame temperature is reduced upon hydrogen addition, but the local gas temperature in the region of the CH profile is lowered as well. The measured NO mole fractions are seen to decrease substantially for both equivalence ratios. Analysis of the factors responsible for Fenimore NO formation shows the reduction in temperature in the flame front to be the major factor in the decrease in NO mole fraction, with a significant contribution from the decrease in CH mole fraction at φ = 1.3. At φ = 1.5, the results suggest that the lower flame temperature upon hydrogen addition further retards the conversion of residual fixed-nitrogen species to NO under these rich conditions as compared to the equivalent methane flames. 相似文献
2.
P. Li F. Wang J. Mi B.B. Dally Z. Mei J. Zhang A. Parente 《International Journal of Hydrogen Energy》2014
The mechanisms of formation and destruction of NO in MILD combustion of CH4/H2 fuels blends are investigated both experimentally and numerically. Experiments are carried out at a lab-scale furnace with the mass fraction of hydrogen in fuel ranging from 0% to 15%; furnace temperature, extracted heat and exhaust NOx emissions are measured. Detailed chemical kinetics calculations utilizing computational fluid dynamics (CFD) and well-stirred reactor (WSR) are performed to better analyze and isolate the different mechanisms. 相似文献
3.
Role of CO2 in the CH4 oxidation and H2 formation during fuel-rich combustion in O2/CO2 environments
The effect of CO2 reactivity on CH4 oxidation and H2 formation in fuel-rich O2/CO2 combustion where the concentrations of reactants were high was studied by a CH4 flat flame experiment, detailed chemical analysis, and a pulverized coal combustion experiment. In the CH4 flat flame experiment, the residual CH4 and formed H2 in fuel-rich O2/CO2 combustion were significantly lower than those formed in air combustion, whereas the amount of CO formed in fuel-rich O2/CO2 combustion was noticeably higher than that in air. In addition to this experiment, calculations were performed using CHEMKIN-PRO. They generally agreed with the experimental results and showed that CO2 reactivity, mainly expressed by the reaction CO2 + H → CO + OH (R1), caused the differences between air and O2/CO2 combustion under fuel-rich condition. R1 was able to advance without oxygen. And, OH radicals were more active than H radicals in the hydrocarbon oxidation in the specific temperature range. It was shown that the role of CO2 was to advance CH4 oxidation during fuel-rich O2/CO2 combustion. Under fuel-rich combustion, H2 was mainly produced when the hydrocarbon reacted with H radicals. However, the hydrocarbon also reacted with the OH radicals, leading to H2O production. In fact, these hydrocarbon reactions were competitive. With increasing H/OH ratio, H2 formed more easily; however, CO2 reactivity reduced the H/OH ratio by converting H to OH. Moreover, the OH radicals reacted with H2, whereas the H radicals did not reduce H2. It was shown that OH radicals formed by CO2 reactivity were not suitable for H2 formation. As for pulverized coal combustion, the tendencies of CH4, CO, and H2 formation in pulverized coal combustion were almost the same as those in the CH4 flat flame. 相似文献
4.
High resolution planar laser-induced fluorescence (PLIF) was applied to investigate the local flame front structures of turbulent premixed methane/air jet flames in order to reveal details about turbulence and flame interaction. The targeted turbulent flames were generated on a specially designed coaxial jet burner, in which low speed stoichiometric gas mixture was fed through the outer large tube to provide a laminar pilot flame for stabilization of the high speed jet flame issued through the small inner tube. By varying the inner tube flow speed and keeping the mixture composition as that of the outer tube, different flames were obtained covering both the laminar and turbulent flame regimes with different turbulent intensities. Simultaneous CH/CH2O, and also OH PLIF images were recorded to characterize the influence of turbulence eddies on the reaction zone structure, with a spatial resolution of about 40 μm and temporal resolution of around 10 ns. Under all experimental conditions, the CH radicals were found to exist only in a thin layer; the CH2O were found in the inner flame whereas the OH radicals were seen in the outer flame with the thin CH layer separating the OH and CH2O layers. The outer OH layer is thick and it corresponds to the oxidation zone and post-flame zone; the CH2O layer is thin in laminar flows; it becomes broad at high speed turbulent flow conditions. This phenomenon was analyzed using chemical kinetic calculations and eddy/flame interaction theory. It appears that under high turbulence intensity conditions, the small eddies in the preheat zone can transport species such as CH2O from the reaction zones to the preheat zone. The CH2O species are not consumed in the preheat zone due to the absence of H, O, and OH radicals by which CH2O is to be oxidized. The CH radicals cannot exist in the preheat zone due to the rapid reactions of this species with O2 and CO2 in the inner-layer of the reaction zones. The local PLIF intensities were evaluated using an area integrated PLIF signal. Substantial increase of the CH2O signal and decrease of CH signal was observed as the jet velocity increases. These observations raise new challenges to the current flamelet type models. 相似文献
5.
The purpose of this study was to investigate the NOx formation and reduction mechanisms in staged O2/CO2 combustion and in air combustion. A flat CH4 flame doped with NH3 for fuel-N was formed over the honeycomb, and NOx formation characteristics were investigated. In addition, chemiluminescence of OH* distribution was measured, and CHEMKIN-PRO was used to investigate the detailed NOx reduction mechanism. In general, the NOx conversion ratio decreases with decreasing primary O2/CH4 ratio, whereas NH3 and HCN, which are easily converted to NOx in the presence of O2, increases rapidly. Therefore, a suitable primary O2/CH4 ratio exists in the staged combustion. Our experiments showed the primary O2/CH4 ratio, which gave the minimum fixed nitrogen compounds in O2/CO2 combustion, was lower than in air combustion. The NOx conversion ratio in O2/CO2 combustion was lower than in air combustion by 40% in suitable staged combustion. This could be explained by high CO2 concentrations in the O2/CO2 combustion. It was shown that abundant OH radicals were formed in O2/CO2 combustion through the CO2 + H → CO + OH, experimentally and numerically. OH radicals produced H and O radicals through H2 + OH → H + H2O and O2 + H → OH + O, because a mass of hydrogen source exists in the CH4 flame. O and OH radicals formed in the fuel-rich region enhanced the oxidation of NH3 and HCN. NOx formed by the oxidation of NH3 and HCN was converted to N2 because the oxidation occurred in the fuel-rich region where the NOx reduction effect was high. In fact, the oxidation of NH3 and HCN in the fuel-rich region was preferable to remaining NH3 and HCN before secondary O2 injection in the staged combustion. A significant reduction in NOx emission could be achieved by staged combustion in O2/CO2 combustion. 相似文献
6.
Jeong Park Do Hyung Lee Sung Hwan Yoon Tran Manh Vu Jin Han Yun Sang In Keel 《International Journal of Hydrogen Energy》2009
Numerical study is conducted to grasp flame characteristics in H2/CO syngas counterflow diffusion flames diluted with He and Ar. An effective fuel Lewis number, applicable to premixed burning regime and even to moderately stretched diffusion flames, is suggested through the comparison among fuel Lewis number, effective Lewis number, and effective fuel Lewis number. Flame characteristics with and without the suppression of the diffusivities of H, H2, and He are compared in order to clarify the important role of preferential diffusion effects through them. It is found that the scarcity of H and He in reaction zone increases flame temperature whereas that of H2 deteriorates flame temperature. Impact of preferential diffusion of H, H2, and He in flame characteristics is also addressed to reaction pathways for the purpose of displaying chemical effects. 相似文献
7.
An experimental and kinetic modeling study of premixed NH3/CH4/O2/Ar flames at low pressure 总被引:1,自引:0,他引:1
An experimental and modeling study of 11 premixed NH3/CH4/O2/Ar flames at low pressure (4.0 kPa) with the same equivalence ratio of 1.0 is reported. Combustion intermediates and products are identified using tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry. Mole fraction profiles of the flame species including reactants, intermediates and products are determined by scanning burner position at some selected photon energies near ionization thresholds. Temperature profiles are measured by a Pt/Pt-13%Rh thermocouple. A comprehensive kinetic mechanism has been proposed. On the basis of the new observations, some intermediates are introduced. The flames with different mole ratios (R) of NH3/CH4 (R0.0, R0.1, R0.5, R0.9 and R1.0) are modeled using an updated detailed reaction mechanism for oxidation of CH4/NH3 mixtures. With R increasing, the reaction zone is widened, and the mole fractions of H2O, NO and N2 increase while those of H2, CO, CO2 and NO2 have reverse tendencies. The structural features by the modeling results are in good agreement with experimental measurements. Sensitivity and flow rate analyses have been performed to determine the main reaction pathways of CH4 and NH3 oxidation and their mutual interaction. 相似文献
8.
S. Liguori A. Iulianelli F. Dalena V. Piemonte Y. Huang A. Basile 《International Journal of Hydrogen Energy》2014
In this experimental study, a membrane reactor housing a composite membrane constituted by a thin Pd-layer supported onto Al2O3 is utilized to perform methanol steam reforming reaction to produce high-grade hydrogen for PEM fuel cell applications. The influence of various parameters such as temperature, from 280 to 330 °C, and pressure, from 1.5 to 2.5 bar, is analyzed. A commercial Cu/Zn-based catalyst is packed in the annulus of the membrane reactor and the experimental tests are performed at space velocity equal to 18,500 h−1 and H2O:CH3OH feed molar ratio equal to 2.5:1. Results in terms of methanol conversion, hydrogen recovery, hydrogen yield and products selectivities are given. As a best result of this work, 85% of methanol conversion and a highly pure hydrogen stream permeated through the membrane with a CO content lower than 10 ppm were reached at 330 °C and 2.5 bar. Furthermore, a comparison between the experimental results obtained in this work and literature data is proposed and discussed. 相似文献
9.
Extensive computations were made to determine the flammability limits of opposed-jet H2/CO syngas diffusion flames from high stretched blowoff to low stretched quenching. Results from the U-shape extinction boundaries indicate the minimum hydrogen concentrations for H2/CO syngas to be combustible are larger towards both ends of high strain and low strain rates. The most flammable strain rate is near one s−1 where syngas diffusion flames exist with minimum 0.002% hydrogen content. The critical oxygen percentage (or limiting oxygen index) below which no diffusion flames could exist for any strain rate was found to be 4.7% for the equal-molar syngas fuels (H2/CO = 1), and the critical oxygen percentage is lower for syngas mixture with higher hydrogen content. The flammability maps were also constructed with strain rates and pressures or dilution gases percentages as the coordinates. By adding dilution gases such as CO2, H2O, and N2 to make the syngas non-flammable, besides the inert effect from the diluents, the chemical effect of H2O contributes to higher flame temperature, while the radiation effect of H2O and CO2 plays an important role in the flame extinction at low strain rates. 相似文献
10.
The objective of this study is to investigate the impact of syngas composition by varying the H2/CO ratio (1:3, 1:1, and 3:1 by volume), the CO2 dilution (0%–40%), and methane addition (0%–40%) on laminar flame speed. Thus, laminar flame speeds of premixed syngas–air mixtures were measured for different equivalence ratios (0.8–2.2) and inlet temperatures (295–450 K) using the Bunsen-burner method. It was found that laminar flame speed increases with increasing H2/CO ratio, while CO2 dilution or CH4 addition decreased it. The location of the maximum flame speed shifts to richer mixtures with decreasing H2/CO ratio, while it shifts to leaner mixtures with the addition of CH4 due to its inherent slower flame speed. The location of the maximum flame speed is also shifted towards leaner mixtures with the addition of CO2 due to the preponderance of the reduction of the adiabatic flame temperature with increasing dilution. Comparison between experimental and numerical results shows a better agreement using a modified mechanism derived from GRI-Mech 3.0. A correlation, based on the experimental results, is proposed to calculate the laminar flame speed over a wide range of equivalence ratios, inlet temperatures, and fuel content. 相似文献
11.
T.S. Cheng Y.-C. ChangY.-C. Chao G.-B. ChenY.-H. Li C.-Y. Wu 《International Journal of Hydrogen Energy》2011,36(20):13207-13217
The effects of variations in the fuel composition on the characteristics of H2/CO/CH4/air flames of gasified biomass are investigated experimentally and numerically. Experimental measurements and numerical simulations of the flame front position and temperature are performed in the premixed stoichiometric H2/CO/CH4/air opposed-jet flames with various H2 and CO contents in the fuel. The adiabatic flame temperatures and laminar burning velocities are calculated using the EQUIL and PREMIX codes of Chemkin collection 3.5, respectively. Whereas the flame structures of the laminar premixed stoichiometric H2/CO/CH4/air opposed-jet flames are simulated using the OPPDIF package with the GRI-Mech 3.0 chemical kinetic mechanisms and detailed transport properties. The measured flame front position and temperature of the stoichiometric H2/CO/CH4/air opposed-jet flames are closely predicted by the numerical calculations. Detailed analysis of the calculated chemical kinetic structures reveals that the reaction rate of reactions (R38), (R46), and (R84) increase with increasing H2 content in the fuel mixture. It is also found that the increase in the laminar flame speed with H2 addition is most likely due to an increase in active radicals during combustion (chemical effect), rather than from changes in the adiabatic flame temperature (thermal effect). Chemical kinetic structure and sensitivity analyses indicate that for the stoichiometric H2/CO/CH4/air flames with fixed H2 concentration in the fuel mixture, the reactions (R99) and (R46) play a dominant role in affecting the laminar burning velocity as the CO content in the fuel is increased. 相似文献
12.
R.J.H. Klein-Douwel A.A. Konnov N.J. Dam J.J. ter Meulen 《Combustion and Flame》2011,158(11):2090-2104
Absorption spectra in the wavelength region around 329 nm have been recorded with the cavity ring-down technique in various low pressure (200 hPa) CH4/air flames, two of which with N2O (nitrous oxide) addition. NCN (cyanonitrene) absorption appears to be significant only in N2O-enriched flames, which also reveal spectrally nearby absorption by NH. In a φ = 1.14, N2O oxidizer volume fraction = 57.0% flame, an upper limit for the NCN mole fraction of 4.0 × 10−6 has been found. Absorption spectra have been recorded as a function of height and these clearly show the presence of CH2O (formaldehyde) and OH as well. In CH4/air flames, absorption by CH2O at and near the flame front is strong enough to mask any possible absorption signal due to NCN. OH absorption spectrally coincident with the maximum NCN absorption has been observed as well. CH2O absorption is present throughout the whole 327–331 nm range, which can severely affect the accuracy of NCN concentration measurements if both species are present in the measurement volume. This necessitates the acquisition of continuous spectra instead of absorption measurements at a few specific wavelengths. Absorption signals at wavelengths characteristic for NCN, CH2O, NH and OH are analysed as function of height in the flame. Probabilities that these signals may be assigned unambiguously to a single species are discussed. 相似文献
13.
The structures of freely propagating rich CH4/air and CH4/O2 flames were studied numerically using a relatively detailed reaction mechanism. Species diffusion was modeled using five different methods/assumptions to investigate the effects of species diffusion, in particular H2 and H, on superadiabatic flame temperature. With the preferential diffusion of H2 and H accounted for, significant amount of H2 and H produced in the flame front diffuse from the reaction zone to the preheat zone. The preferential diffusion of H2 from the reaction zone to the preheat zone has negligible effects on the phenomenon of superadiabatic flame temperature in both CH4/air and CH4/O2 flames. It is therefore demonstrated that the superadiabatic flame temperature phenomenon in rich hydrocarbon flames is not due to the preferential diffusion of H2 from the reaction zone to the preheat zone as recently suggested by Zamashchikov et al. [V.V. Zamashchikov, I.G. Namyatov, V.A. Bunev, V.S. Babkin, Combust. Explosion Shock Waves 40 (2004) 32]. The suppression of the preferential diffusion of H radicals from the reaction zone to the preheat zone drastically reduces the degree of superadiabaticity in rich CH4/O2 flames. The preferential diffusion of H radicals plays an important role in the occurrence of superadiabatic flame temperature. The assumption of unity Lewis number for all species leads to the suppression of H radical diffusion from the reaction zone to the preheat zone and significant diffusion of CO2 from the postflame zone to the reaction zone. Consequently, the degree of superadiabaticity of flame temperature is also significantly reduced. Through reaction flux analyses and numerical experiments, the chemical nature of the superadiabatic flame temperature phenomenon in rich CH4/air and CH4/O2 flames was identified to be the relative scarcity of H radical, which leads to overshoot of H2O and CH2CO in CH4/air flames and overshoot of H2O in CH4/O2 flames. 相似文献
14.
F.H.V. Coppens 《Combustion and Flame》2007,149(4):409-417
Experimental measurements of adiabatic burning velocity and NO formation in (CH4 + H2) + (O2 + N2) flames are presented. The hydrogen content in the fuel was varied from 0 to 35% and the oxygen content in the air from 20.9 to 16%. Nonstretched flames were stabilized on a perforated plate burner at 1 atm. The heat flux method was used to determine burning velocities under conditions when the net heat loss of the flame is zero. Adiabatic burning velocities of methane + hydrogen + nitrogen + oxygen mixtures were found in satisfactory agreement with the modeling. The NO concentrations in these flames were measured in the burnt gases at a fixed distance from the burner using probe sampling. In lean flames, enrichment by hydrogen has little effect on [NO], while in rich flames, the concentration of nitric oxide decreases significantly. Dilution by nitrogen decreases [NO] at any equivalence ratio. Numerical predictions and trends were found in good agreement with the experiments. Different responses of stretched and nonstretched flames to enrichment by hydrogen are demonstrated and discussed. 相似文献
15.
Chemical effects of added CO2 on the extinction characteristics of H2/CO/CO2 syngas diffusion flames
Jeong Park Jeong Soo Kim Jin Oh Chung Jin Han Yun Sang In Keel 《International Journal of Hydrogen Energy》2009
Chemical effects of added CO2 on flame extinction characteristics are numerically studied in H2/CO syngas diffusion flames diluted with CO2. The two representative syngas flames of 80% H2 + 20% CO and 20% H2 + 80% CO are inspected according to the composition of fuel mixture diluted with CO2 and global strain rate. Particular concerns are focused on impact of chemical effects of added CO2 on flame extinction characteristics through the comparison of the flame characteristics between well-burning flames far from extinction limit and flames at extinction. It is seen that chemical effects of added CO2 reduce critical CO2 mole fraction at flame extinction and thus extinguish the flame at higher flame temperature irrespective of global strain rate. This is attributed by the suppression of the reaction rate of the principal chain branching reaction through the augmented consumption of H-atom from the reaction CO2 + H→CO + OH. As a result the overall reaction rate decreases. These chemical effects of added CO2 are similar in both well-burning flames far from extinction limit and flames at extinction. There is a mismatching in the behaviors between critical CO2 mole fraction and maximum flame temperature at extinction. This anomalous phenomenon is also discussed in detail. 相似文献
16.
The effects of CO addition on the characteristics of premixed CH4/air opposed-jet flames are investigated experimentally and numerically. Experimental measurements and numerical simulations of the flame front position, temperature, and velocity are performed in stoichiometric CH4/CO/air opposed-jet flames with various CO contents in the fuel. Thermocouple is used for the determination of flame temperature, velocity measurement is made using particle image velocimetry (PIV), and the flame front position is measured by direct photograph as well as with laser-induced predissociative fluorescence (LIPF) of OH imaging techniques. The laminar burning velocity is calculated using the PREMIX code of Chemkin collection 3.5. The flame structures of the premixed stoichiometric CH4/CO/air opposed-jet flames are simulated using the OPPDIF package with GRI-Mech 3.0 chemical kinetic mechanisms and detailed transport properties. The measured flame front position, temperature, and velocity of the stoichiometric CH4/CO/air flames are closely predicted by the numerical calculations. Detailed analysis of the calculated chemical kinetic structures reveals that as the CO content in the fuel is increased from 0% to 80%, CO oxidation (R99) increases significantly and contributes to a significant level of heat-release rate. It is also shown that the laminar burning velocity reaches a maximum value (57.5 cm/s) at the condition of 80% of CO in the fuel. Based on the results of sensitivity analysis, the chemistry of CO consumption shifts to the dry oxidation kinetics when CO content is further increased over 80%. Comparison between the results of computed laminar burning velocity, flame temperature, CO consumption rate, and sensitivity analysis reveals that the effect of CO addition on the laminar burning velocity of the stoichiometric CH4/CO/air flames is due mostly to the transition of the dominant chemical kinetic steps. 相似文献
17.
A process to produce hydrogen from polyethylene [–CH2–]n (PE) is developed by milling with Ca(OH)2 and Ni(OH)2 followed by heating the milled product. Characterizations by a set of analytical methods of X-ray diffraction (XRD), infrared spectroscopy (FT-IR), thermogravimetry–mass spectroscopy (TG/MS) and gas chromatography (GC) were performed on the milled and heated samples to monitor the process. It has been observed that addition of nickel hydroxide as well as increases in milling time and rotational speed of the mill is beneficial to the gas generation, mainly composed of H2 and CH4, CO, CO2. Gaseous compositions from the milled samples vary depending on the added molar ratio of calcium hydroxide. H2 emission occurs between 400 and 500 °C, and H2 concentration of 95% is obtained from the mixture of PE/Ca(OH)2/Ni(OH)2 (C:Ca:Ni = 6:14:1) sample, and the concentrations of CO and CO2 remain below 0.5%. The process offers a novel approach to treat waste plastic by transforming it into hydrogen. 相似文献
18.
Erjiang Hu Jin Fu Lun Pan Xue Jiang Zuohua Huang Yang Zhang 《International Journal of Hydrogen Energy》2012
Experimental and numerical study on laminar burning velocity of H2/CO/N2/CO2/air mixtures was conducted by using a constant volume bomb and Chemkin package. Good agreement between experimental measurements and numerical calculations by using USCII Mech is achieved. Diffusional-thermal instability is enhanced but hydrodynamic instability is insensitive to the increase of hydrogen fraction in fuel mixtures. For mixtures with different hydrogen fractions, the adiabatic flame temperature is not the dominant influencing factor while high thermal diffusivity of hydrogen obviously enhances the laminar burning velocity. Laminar burning velocities increase with increasing hydrogen fraction and equivalence ratio (0.4–1.0). This is mainly due to the high reactivity of H2 leading to high production rate of H and OH radicals. Reactions and play the dominant role in the production of H radical for mixtures with high hydrogen fraction, and reaction R31 plays the dominant role for mixtures with low hydrogen fraction. 相似文献
19.
Baolu Shi Bo Li Xiaoyao Zhao Run Chen Osamu Fujita Ningfei Wang 《International Journal of Hydrogen Energy》2018,43(31):14806-14815
In this study hydrogen flames have been attempted in a rapidly mixed tubular flame combustor for the first time, in which fuel and oxidizer are individually and tangentially injected into a cylindrical combustor to avoid flame flash back. Three different cases were designed to examine the effects of fuel and oxidizer feeding method, diluent property, oxygen content and equivalence ratio on the characteristics of hydrogen flame, including the flame structure, lean extinction limit, flame stability and temperature. The results show that by enhancing mixing rate through feeding system, the range of equivalence ratio for steady tubular flame can be much expanded for the N2 diluted mixture, however, at the oxygen content of 0.21 (hydrogen/air) the steady tubular flame is achieved only up to equivalence ratio of 0.5; by decreasing oxygen content, the lean extinction limit slightly increases, and the upper limit for steady tubular flame establishment increases significantly, resulting in an expanded tubular flame range. For CO2 diluted mixture, the stoichiometric combustion has been achieved within oxygen content of 0.1 and 0.25, for which the burned gas temperature is uniformly distributed inside the flame front; as oxygen content is below 0.21, a steady tubular flame can be obtained from the lean to rich limits; and the lean extinction limit increases from 0.17 to 0.4 as oxygen content decreases from 0.21 to 0.1, resulting in a shrunk tubular flame range. Laminar burning velocity, temperature and Damköhler number are calculated to examine the differences between N2 and CO2 diluted combustion as well as the requirement for hydrogen-fueled tubular flame establishment. 相似文献
20.
Jie Sun Jigang Li Cunni Xian Ligong Zhang Yulong Cheng Hong Li Liquan Chen 《International Journal of Hydrogen Energy》2010
Catalysts of nano-sized nickel oxide particles based on flowerlike lanthanum oxide microspheres with high disperse were prepared to achieve simultaneous dehydrogenation of ethanol and water molecules on multi-active sites. XRD, SEM, 77K N2 adsorption were used to analyze and observe the catalysts’ structure, morphology and porosity. Catalytic parameters with respect to yield of H2, activity, selectivity towards gaseous products and stability with time-on-stream and time-on-off-stream were all determined. This special morphology NiO/La2O3 catalyst represented more than 1000 h time-on-stream stability test and 500 h time-on-off-stream stability test for hydrogen fuel production from ethanol steam reforming at 300 °C without any deactivation. During the 1000 h time-on-stream stability test, ethanol–water mixtures could be converted into H2, CO, and CH4 with average selectivity values of 57.0, 20.1, 19.6 and little CO2 of 3.2 mol%, respectively, and average ethanol conversion values of 96.7 mol%, with H2 yield of 1.61 mol H2/mol C2H5OH. During the 500 h time-on-off-stream stability test, ethanol–water mixtures could be converted into H2, CO, CH4 and CO2 with average selectivity values of 65.1, 17.3, 15.1 and 2.5 mol%, respectively, and average ethanol conversion values of 80.0 mol%. For the ethanol-H2 and petrolic hybrid vehicle (EH–HV), the combustion value is the most important factor. So, it was very suitable for the EH–HV application that the low temperature ethanol steam reforming products’ distribution was with high H2, CO, CH4 and very low CO2 selectivity over the special NiO/La2O3 flowerlike microspheres. 相似文献