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121.
沉淀型Ni-La_2O_3/ZrO_2催化剂上CO_2甲烷化性能的研究 总被引:1,自引:0,他引:1
采用并流共沉淀法将不同量的稀土氧化物La2O3添加到Ni/ZrO2催化剂中,进行了XRD、TPR分析测试。结果表明,添加一定量的La2O3使催化剂的晶体结构发生变化,产生了新的物种,从而使催化剂表面改性,提高了NiO的分散度,有利于活性中心的形成,并且降低了催化剂的还原温度,当n(La)∶n(Ni)∶n(ZrO2)=0 4∶1∶1时效果最好;考察了反应温度和空速对CO2转化率的影响,在反应温度较低时,由于受到反应动力学的限制,CO2的转化率较低。 相似文献
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Kelly E. Sedor Mohammad M. Hossain Hugo I. de Lasa 《Chemical engineering science》2008,63(11):2994-3007
Chemical-looping combustion (CLC) is a technology that reduces the carbon dioxide emissions from fossil fuel power stations. A nickel supported on -alumina oxygen carrier is investigated in this study, for use in a CLC process. Oxygen carriers with various nickel loadings on alumina are prepared according to the incipient wetness technique. The reactivity and stability of the prepared oxygen carrier samples, during repeated reduction–oxidation cycles, is demonstrated using temperature programmed reduction and oxidation. Pulse chemisorption results show that the dispersion and active crystallite diameter of the nickel particles remain constant over multiple reduction–oxidation cycles, indicating that no agglomeration occurs up to a nickel loading of 20 wt% supported on alumina. The stability and reactivity of the oxygen carriers, under industrial relevant conditions, are also investigated using the CREC fluidized bed riser simulator. It is observed that a 20 wt% nickel supported on alumina oxygen carrier is stable under industrial relevant fluidized bed reaction conditions, converting 76% of methane to carbon dioxide and water vapor, the combustion products. The metal support interaction is assessed by H2 temperature programmed desorption, which shows that the metal-support interaction decreases as more nickel is loaded onto the alumina support. 相似文献
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《International Journal of Hydrogen Energy》2019,44(14):7205-7215
Thermocatalytic decomposition of methane is proposed to be an economical and green method to produce COx-free hydrogen and carbon nanomaterial. In present work, 60 wt% Ni/Al2O3 catalysts with different additives (Cu, Mn, Pd, Co, Zn, Fe, Mg) were prepared by co-impregnation method to investigate promotional effects of these metal additives on the activity and stability of 60 wt% Ni/Al2O3 and find out a really effective promoter for decomposition of methane. The catalyst was characterized by N2 adsorption/desorption, X-ray diffraction, scanning electron microscopy, inductively coupled plasma optical emission spectrometer and hydrogen temperature programmed reduction. While metal additives (5 wt%) were added into 60 wt% Ni/Al2O3, the activity stability of 60 wt% Ni/Al2O3 was improved and the CH4 conversion of 60 wt% Ni/Al2O3 was also improved except Zn addition. Mn addition was found to improve the catalytic activity of 60 wt% Ni/Al2O3 significantly and the CH4 conversion of 5 wt% Mn-60 wt% Ni/Al2O3 was ∼80%. Cu addition was found to remarkably improve the catalytic stability of 60 wt% Ni/Al2O3 and the CH4 conversion of 5 wt% Cu-60 wt% Ni/Al2O3 decreased from 61% to 45% after 250 min of reaction time. Carbon nanomaterials formed in the thermocatalytic decomposition process were characterized by X-ray diffraction, scanning electron microscopy, thermal gravimetric analyzer and Raman spectroscopy. Carbon deposits consist of amorphous carbon and carbon nanofibers. 相似文献
128.
Guan-Qiang Wang Ming-Song Chen Hong-Bin Li Y.C.Lin Wei-Dong Zeng Yan-Yong Ma 《材料科学技术学报》2021,77(18):47-57
The uniform refinement mechanisms and methods of deformed mixed and coarse grains inside a solution-treatment Ni-based superalloy during two-stage annealing treatment have been investigated.The two-stage heat treatment experiments include an aging annealing treatment(AT)and a subsequent recrystallization annealing treatment(RT).The object of AT is to precipitate some δ phases and consume part of storage energy to inhibit the grain growth during RT,while the RT is to refine mixed and coarse grains by recrystallization.It can be found that the recrystallization grains will quickly grow up to a large size when the AT time is too low or the RT temperature is too high,while the deformed coarse grains cannot be eliminated when the AT time is too long or the RT temperature is too low.In addition,the mixed microstructure composed of some abnormal coarse recrystallization grains(ACRGs)and a large number of fine grains can be observed in the annealed specimen when the AT time is 3 h and RT tem-perature is 980℃.The phenomenon attributes to the uneven distribution of δ phase resulted from the heterogeneous deformation energy when the AT time is too short.In the regions with a large number of δ phases,the recrystallization nucleation rate is promoted and the growth of grains is limited,which results in fine grains.However,in the regions with few δ phases,the recrystallization grains around grain boundaries can easily grow up,and the new recrystallization nucleus is difficult to form inside grain,which leads to ACRGs.Thus,in order to obtain uniform and fine annealed microstructure,it is a prereq-uisite to precipitate even-distributed δ phase by choosing a suitable AT time,such as 12 h.Moreover,a relative high RT temperature is also needed to promote the recrystallization nucleation around δ phase.The optimal annealing parameters range for uniformly refining mixed crystal can be summarized as:900℃×12 h+990℃×(40-60 min)and 900℃×12 h+1000℃×(10-15 min). 相似文献
129.
In this study, three kinds of WC-based cermet coatings including WC–CoCr coating, WC–Ni coating and WC–Cr3C2–Ni coating were prepared by the high-velocity oxygen-fuel (HVOF) spraying process. Scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and Vickers hardness tester were used to analyze the microstructure and mechanical properties of these coatings. The WC–CoCr coating presented the highest average microhardness of 1205 HV0.3, and then followed by the WC–Cr3C2–Ni coating (1188 HV0.3) and the WC–Ni coating (1105 HV0.3). The abrasive wear behavior of the WC-based coatings under the conditions of different applied loads and sediment concentrations were studied by a wet sand-rubber wheel tester. The results indicated that the abrasive wear loss rates of all the coatings increased with the increment of applied load or sediment concentration. In addition, the coatings with higher microhardness appeared to have higher abrasive wear resistance. The abrasive wear resistance of the WC-based coatings was 4–90 times higher than that of AISI 304 stainless steel under the same testing condition. The abrasive wear mechanism of the WC-based coatings was deduced to be the extrusion and removal of binder phases, as well as the fragmentation and peel-off of hard phases. 相似文献
130.
《International Journal of Hydrogen Energy》2020,45(51):27263-27278
Here, the Ni-based metallic nano-particles (Ni, NiMo and NiMoP) were electrodeposited on/in the surface of ERGO/CE substrate from a citrate-based electrolyte and their catalytic activities investigated towards methanol and ethanol electro-oxidation. The physicochemical characterizations of all prepared electrocatalysts were investigated by different electrochemical and non-electrochemical techniques. The electrocatalytic activities of the modified electrodes towards the electro-oxidation of methanol and ethanol were studied in 0.1 M NaOH solution by conventional electrochemical methods such as cyclic voltammetry and chronoamperometry. In the optimized electrodeposition conditions, the obtained electrochemical results indicate that the NiMoP/ERGO/CE displays dramatically improved electrocatalytic activity [Jpf (mA.cm−2) = 263.14 for methanol and Jpf (mA.cm−2) = 253.35 for ethanol], stability and poisoning tolerance towards the electro-oxidation of these fuels in alkaline solution. Finally, for comparison, the Ni (alone) and NiMo (binary) electrodeposited on/in the ERGO/CE (without P) and also studying the influence of the ERGO layers on the surface of CE, the NiMoP/CE (without ERGO) were prepared and applied as electrocatalysts. 相似文献