共查询到20条相似文献,搜索用时 31 毫秒
1.
Won-Jun Jang Dae-Woon Jeong Jae-Oh Shim Hyun-Seog Roh In Hyuk Son Seung Jae Lee 《International Journal of Hydrogen Energy》2013
Ni–Ce0.8Zr0.2O2 and Ni–MgO–Ce0.8Zr0.2O2 catalysts were investigated for H2 production from CO2 reforming of CH4 reaction at a very high gas hourly space velocity of 480,000 h−1. Ni–MgO–Ce0.8Zr0.2O2 exhibited higher catalytic activity and stability (CH4 conversion >95% at 800 °C for 200 h). The outstanding catalytic performance is mainly due to the basic nature of MgO and an intimate interaction between Ni and MgO. 相似文献
2.
Jinhua Wang Zuohua Huang Hideaki Kobayashi Yasuhiro Ogami 《International Journal of Hydrogen Energy》2012
Laminar burning velocities of CO–H2–CO2–O2 flames were measured by using the outwardly spherical propagating flame method. The effect of large fraction of hydrogen and CO2 on flame radiation, chemical reaction, and intrinsic flame instability were investigated. Results show that the laminar burning velocities of CO–H2–CO2–O2 mixtures increase with the increase of hydrogen fraction and decrease with the increase of CO2 fraction. The effect of hydrogen fraction on laminar burning velocity is weakened with the increase of CO2 fraction. The Davis et al. syngas mechanism can be used to calculate the syngas oxyfuel combustion at low hydrogen and CO2 fraction but needs to be revised and validated by additional experimental data for the high hydrogen and CO2 fraction. The radiation of syngas oxyfuel flame is much stronger than that of syngas–air and hydrocarbons–air flame due to the existence of large amount of CO2 in the flame. The CO2 acts as an inhibitor in the reaction process of syngas oxyfuel combustion due to the competition of the reactions of H + O2 = O + OH, CO + OH = CO2 + H and H + O2(+M) = HO2(+M) on H radical. Flame cellular structure is promoted with the increase of hydrogen fraction and is suppressed with the increase of CO2 fraction due to the combination effect of hydrodynamic and thermal-diffusive instability. 相似文献
3.
Wei Tao Hongwei Cheng Weilin Yao Xionggang Lu Qiuhua Zhu Guangshi Li Zhongfu Zhou 《International Journal of Hydrogen Energy》2014
Syngas production by CO2 reforming of coke oven gas (COG) was studied in a fixed-bed reactor over Ni/La2O3–ZrO2 catalysts. The catalysts were prepared by sol–gel technique and tested by XRF, BET, XRD, H2-TPR, TEM and TG–DSC. The influence of nickel loadings and calcination temperature of the catalysts on reforming reaction was measured. The characterization results revealed that all of the catalysts present excellent resistance to coking. The catalyst with appropriate nickel content and calcination temperature has better dispersion of active metal and higher conversion. It is found that the Ni/La2O3–ZrO2 catalyst with 10 wt% nickel loading provides the best catalytic activity with the conversions of CH4 and CO2 both more than 95% at 800 °C under the atmospheric pressure. The Ni/La2O3–ZrO2 catalysts show excellent catalytic performance and anti-carbon property, which will be of great prospects for catalytic CO2 reforming of COG in the future. 相似文献
4.
Sufang He Hongmiao Wu Wanjin Yu Liuye Mo Hui Lou Xiaoming Zheng 《International Journal of Hydrogen Energy》2009
Ni/SiO2 and Ni–Al2O3/SiO2 catalysts were prepared by incipient wetness impregnation using citrate and nitrate precursors and tested with a reaction of combination of CO2 reforming and partial oxidation of methane to produce syngas (H2/CO). The catalytic activity of Ni/SiO2 and Ni–Al2O3/SiO2 greatly depended on interaction between NiO and support. NiO strongly interacted with support formed small nickel particles (about 4 nm for NiSC which is abbreviation of Ni/SiO2 prepared with Nickel citrate precursor) after reduction. The small nickel particles over NiSC catalysts exhibited a good catalytic performance. 相似文献
5.
Huali Long Shuyong Shang Xumei Tao Yongxiang Yin Xiaoyan Dai 《International Journal of Hydrogen Energy》2008
CO2 reforming of CH4 to synthesis gas was investigated by cold plasma jet (CPJ) only and combination of cold plasma jet with Ni/γ-Al2O3 catalyst at atmospheric pressure. The higher selectivity of H2 and CO, and higher energy efficiency was obtained by this novel process. The optimum experimental conditions are: CH4 = 3.33 Nl/min, CO2 = 5.00 Nl/min, N2 = 8.33 Nl/min, and the input power at 770 W. The results showed that, for the plasma only, the conversions of CH4 and CO2 were 46% and 34%, the selectivities of CO and H2 were 85% and 78%, the energy efficiency was 2.9 mmol/kJ, respectively; for the combination of cold plasma jet with Ni/γ-Al2O3 catalyst, the conversions of CH4 and CO2 were increased by 14% and 6%, the yield of H2 and CO increased by 18% and 11%, the energy efficiency reached at 3.7 mmol/kJ, respectively. And the catalyst hasn't accessorial heating. The CPJ method has the advantage of simple processing and is easy to be industrialized. 相似文献
6.
Nawadee Srisiriwat Supaporn Therdthianwong Apichai Therdthianwong 《International Journal of Hydrogen Energy》2009
Oxidative steam reforming of ethanol at low oxygen to ethanol ratios was investigated over nickel catalysts on Al2O3 supports that were either unpromoted or promoted with CeO2, ZrO2 and CeO2–ZrO2. The promoted catalysts showed greater activity and a higher hydrogen yield than the unpromoted catalyst. The characterization of the Ni-based catalysts promoted with CeO2 and/or ZrO2 showed that the variations induced in the Al2O3 by the addition of CeO2 and/or ZrO2 alter the catalyst's properties by enhancing Ni dispersion and reducing Ni particle size. The promoters, especially CeO2–ZrO2, improved catalytic activity by increasing the H2 yield and the CO2/CO and the H2/CO values while decreasing coke formation. This results from the addition of ZrO2 into CeO2. This promoter highlights the advantages of oxygen storage capacity and of mobile oxygen vacancies that increase the number of surface oxygen species. The addition of oxygen facilitates the reaction by regenerating the surface oxygenation of the promoters and by oxidizing surface carbon species and carbon-containing products. 相似文献
7.
8.
Proper solution of vapor liquid equilibrium (VLE) is essential to the design and operation of CO2 capture and storage system (CCS). According to the requirements of engineering applications, cubic equations of state (EOS) are preferable to predict VLE properties. This paper evaluates the reliabilities of five cubic EOSs, including PR, PT, RK, SRK and 3P1T for predicting VLE of CO2 and binary CO2-mixtures containing CH4, H2S, SO2, Ar, N2 or O2, based on the comparisons with the collected experimental data. Results show that SRK is superior in the calculations about the saturated pressure of pure CO2; while for the VLE properties of binary CO2-mixtures, PR, PT and SRK are generally superior to RK and 3P1T. The impacts of binary interaction parameter kij were also analyzed. kij has very clear effects on the calculating accuracy of an EOS in the property calculations of CO2-mixtures. In order to improve the calculation accuracy, the binary interaction parameter was calibrated for all of the studied EOSs regarding every binary CO2-mixture. 相似文献
9.
A series of mesoporous nanocrystalline ceria–zirconia solid solutions with different Ce/Zr ratios were facilely synthesized via improved evaporation induced self-assembly strategy. The obtained materials with advantageous structural properties and excellent thermal stabilities were characterized by various techniques and investigated as the supports of the Ni based catalysts for CO2 reforming of CH4. The effects of Ce/Zr ratio and mesopore structure on promoting catalytic performances had been investigated. It was found that the catalyst supported on carrier with 50/50 Ce/Zr ratio behaved the highest catalytic activity. The reason for this might be that the mesoporous ceria–zirconia solid solution carrier contributed to the activation of CO2 by its own redox property. Compared with the catalyst without obvious mesostructure, the current mesoporous catalyst performed higher catalytic activity and better catalytic stability, demonstrating the advantages of the mesostructure. On the one hand, the predominant textural properties such as large surface area, big pore volume, and uniform channel helped to the high dispersion of the Ni particles among the mesoporous framework, finally leading to higher catalytic activity. On the other hand, the mesoporous matrix could stabilize the Ni nanoparticles under severe reduction and reaction conditions by the “confinement effect”, committed to better catalytic stability. Besides, the properties of the coke over the mesoporous catalyst were also carefully studied. Generally, these mesoporous nanocrystalline ceria–zirconia solid solutions were a series of promising catalytic carriers for CO2 reforming of CH4. 相似文献
10.
V. Ratna Kishore Ringkhang MuchaharyAnjan Ray M.R. Ravi 《International Journal of Hydrogen Energy》2009
Global warming due to CO2 emissions has led to the projection of hydrogen as an important fuel for future. A lot of research has been going on to design combustion appliances for hydrogen as fuel. This has necessitated fundamental research on combustion characteristics of hydrogen fuel. In this work, a combination of experiments and computational simulations was employed to study the effects of diluents (CO2, N2, and Ar) on the laminar burning velocity of premixed hydrogen/oxygen flames using the heat flux method. The experiments were conducted to measure laminar burning velocity for a range of equivalence ratios at atmospheric pressure and temperature (300 K) with reactant mixtures containing varying concentrations of CO2, N2, and Ar as diluents. Measured burning velocities were compared with computed results obtained from one-dimensional laminar premixed flame code PREMIX with detailed chemical kinetics and good agreement was obtained. The effectiveness of diluents in reduction of laminar burning velocity for a given diluent concentration is in the increasing order of argon, nitrogen, carbon dioxide. This may be due to increased capabilities either to quench the reaction zone by increased specific heat or due to reduced transport rates. The lean and stoichiometric H2/O2/CO2 flames with 65% CO2 dilution exhibited cellular flame structures. Detailed three-dimensional simulation was performed to understand lean H2/O2/CO2 cellular flame structure and cell count from computed flame matched well with the experimental cellular flame. 相似文献
11.
The permeance of a 50 μm thick PdAg (25 wt.% of silver) tubular membrane towards hydrogen was evaluated for hydrogen feed streams or binary mixtures of industrial relevance, namely of H2/CO or H2/CO2. 相似文献
12.
A series of ordered mesoporous MgO–Al2O3 composite oxides with various Mg containing were facilely synthesized via one-pot evaporation induced self-assembly strategy. These materials with advantageous structural properties and superior thermal stabilities were used as the supports of Ni based catalysts for CO2 reforming of CH4. These mesoporous catalysts behaved both high catalytic activities and long term stabilities toward this reaction. The effects of the mesopore structure and MgO basic modifier on catalytic performances were carefully studied. Specifically, their mesoporous frameworks could accommodate the gaseous reactants with more “accessible” Ni active centers; the “confinement effect” of the mesopores would effectively suppress the thermal sintering of the Ni nanoparticles; the modified MgO basic sites would enhance the chemisorption and activation of CO2. Consequently, the catalytic activities and stabilities of these catalysts were greatly promoted. Therefore, the present materials were considered as promising catalyst supports for CO2 reforming of CH4. 相似文献
13.
Jianqiang Zhu Xiaoxi PengLu Yao Xiaojiao DengHaiyang Dong Dongmei TongChangwei Hu 《International Journal of Hydrogen Energy》2013
Ni–Ce/SiO2 catalysts were prepared by calcination under Ar, CO2, O2 and H2 ambience, and applied in CO2 reforming of methane for synthesis gas production. BET, XRD, XPS, TPR, SEM, TEM and TPH techniques were employed to characterize the fresh and used catalysts. Highly dispersed nickel oxides bearing stronger interaction with SiO2 prevented the metal sintering. The formation of reactive carbon species on Ni–Ce/SiO2 catalyst calcined under Ar ambience effectively promoted the carbon elimination and kept the catalyst more stable. Nevertheless, the oxygen storage capacity of CeO2 might partly lose on Ni–Ce/SiO2 calcined under H2 ambience. As a result, the inhibition of carbon elimination and the deposition of inert carbon were responsible for its partial deactivation. 相似文献
14.
Lei Zhang Liwei Pan Changjun Ni Tianjun Sun Shengsheng Zhao Shudong Wang Anjie Wang Yongkang Hu 《International Journal of Hydrogen Energy》2013
The Cu-based catalysts with different supports (CeO2, ZrO2 and CeO2–ZrO2) for methanol steam reforming (MSR) were prepared by a co-precipitation procedure, and the effect of different supports was investigated. The catalysts were characterized by means of N2 adsorption–desorption, X-ray diffraction, temperature-programmed reduction, oxygen storage capacity and N2O titration. The results showed that the Cu dispersion, reducibility of catalysts and oxygen storage capacity evidently influenced the catalytic activity and CO selectivity. The introduction of ZrO2 into the catalyst improved the Cu dispersion and catalyst reducibility, while the addition of CeO2 mainly increased oxygen storage capacity. It was noticed that the CeO2–ZrO2-containing catalyst showed the best performance with lower CO concentration, which was due to the high Cu dispersion and well oxygen storage capacity. Further investigation illuminated that the formation of CO on CuO/ZnO/CeO2–ZrO2 catalyst mainly due to the reverse water gas shift. In addition, the CuO/ZnO/CeO2–ZrO2 catalyst also had excellent reforming performance with no deactivation during 360 h run time and was used successfully in a mini reformer. The maximum hydrogen production rate in the mini reformer reached to 162.8 dm3/h, which can produce 160–270 W electric energy power by different kinds of fuel cells. 相似文献
15.
A type of Yb2O3 doped Ni–ZrO2 catalyst for ethanol steam reforming was developed, and displayed excellent catalyzing performance for the selective formation of H2 and CO2. Over a Ni1.25Zr1Yb0.8 catalyst, STY(H2) can maintain stable at the level of 0.396 mol h−1 g−1 (data taken 120 h after the reaction started) under the reaction conditions of 0.5 MPa and 723 K, which was 1.6 times that (0.247 mol h−1 g−1) of the Yb-free counterpart Ni1.25Zr1. Characterization of the catalyst revealed that dissolution of an appropriate amount of Yb3+ ions in the zirconia host resulted in the formation of the Zr–Yb composite oxide with cubic-ZrO2 structure, c-(Zr–Yb)Oz, which inhibited effectively the transformation of c-ZrO2 to thermodynamically more stable m-ZrO2, thus avoiding sintering of the (Zr–Yb)Oz composite. It was demonstrated that the doping of Yb2O3 to Ni–ZrO2 changed also the valence states or the micro-environments of the Ni-species at the quasi-active surface of the tested catalyst, which was conducive to inhibiting agglomeration of the Nix0–Nin+ species active catalytically, with resulting in maintaining the high metallic nickel dispersion and inhibiting coking. The aforementioned two factors both contributed to improving the activity and operating stability as well as heat-resistant quality of the catalyst. 相似文献
16.
Pristine Ni/γ–Al2O3 and CeO2–Ni/γ–Al2O3 catalysts were prepared by co-impregnation technique for dry reforming of propane. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were used to examine the structure and morphology of the catalysts before and after the reforming reactions. The excellent interaction between catalyst active phases was observed in both CeO2–Ni/γ–Al2O3 and Ni/γ–Al2O3 stabilized with polyethelene glycol (Ni/γ–Al2O3–PEG). Towards C3H8 and CO2 conversion, the CeO2–Ni/γ–Al2O3 and Ni/γ–Al2O3–PEG showed improved catalytic activity when compared to the pristine Ni/γ–Al2O3 catalyst. Interestingly, high H2 concentration was achieved with the CeO2–Ni/γ–Al2O3 and high CO concentration with the Ni/γ–Al2O3–PEG, which is due to the nanoconfinement of nickel particles within the support and favorable metal-support interaction as a result of plasma reduction. The CeO2–Ni/γ–Al2O3 catalyst exhibited better stability for anti-sintering and coke resistance, thus exhibiting high reactivity and durability in the dry reforming. 相似文献
17.
Rong-rong Hu Chang-feng YanXiao-xiao Zheng Hong LiuZhou-yu Zhou 《International Journal of Hydrogen Energy》2013
Steam reforming of acetic acid, one model compounds of bio-oil, was studied on the Ni/ZrO2–CeO2 catalysts which were prepared by the impregnation method. The results showed that high acetic acid conversion and hydrogen yield were obtained in the temperature range of 650–750 °C when H2O/HAC ratio was 3. Nevertheless, the catalyst deactivation was caused by carbon deposition eventually with time-on-stream. In order to discuss the behavior of the carbon deposition on the Ni/ZrO2–CeO2 catalyst during steam reforming of bio-oil, the structure and morphology of carbon deposition were investigated by BET, XRD, TG/DTA, TPR, SEM and EDX techniques. All the experimental results showed acetone and CO were the important carbon precursors of acetic acid reforming and the graphitic-like carbon was the main type of carbon deposition on the surface of the deactivated 12%Ni/CeO2–ZrO2 catalyst. 相似文献
18.
Seung Ju Han Yongju Bang Jaekyeong Yoo Ki Hyuk Kang Ji Hwan Song Jeong Gil Seo In Kyu Song 《International Journal of Hydrogen Energy》2013
A mesoporous Ni–Al2O3–ZrO2 aerogel (Ni–AZ) catalyst was prepared by a single-step epoxide-driven sol–gel method and a subsequent supercritical CO2 drying method. For comparison, a mesoporous Al2O3–ZrO2 aerogel (AZ) support was prepared by a single-step epoxide-driven sol–gel method, and subsequently, a mesoporous Ni/Al2O3–ZrO2 aerogel (Ni/AZ) catalyst was prepared by an incipient wetness impregnation method. The effect of preparation method on the physicochemical properties and catalytic activities of Ni–AZ and Ni/AZ catalysts was investigated. Although both catalysts retained a mesoporous structure, Ni/AZ catalyst showed lower surface area than Ni–AZ catalyst. From TPR, XRD, and H2–TPD results, it was revealed that Ni–AZ catalyst retained higher reducibility and higher nickel dispersion than Ni/AZ catalyst. In the hydrogen production by steam reforming of ethanol, both catalysts showed a stable catalytic performance with complete conversion of ethanol. However, Ni–AZ catalyst showed higher hydrogen yield than Ni/AZ catalyst. Superior textural properties, high reducibility, and high nickel surface area of Ni–AZ catalyst were responsible for its enhanced catalytic performance in the steam reforming of ethanol. 相似文献
19.
Ni/γ-Al2O3 catalyst was prepared by direct treatment of Ni(NO3)2/γ-Al2O3 precursor with dielectric barrier discharge (DBD) hydrogen plasma at different input powers, characterized by XRD, H2-TPR, CO2-TPD, N2 adsorption and TEM, respectively, and used as the catalyst for CO2 reforming of methane (CRM). The results showed that the input power obviously affected the reduction degree and catalytic performances of catalysts. Low input power under 40 W mainly resulted in the decomposition of nickel nitrate into Ni oxides. The reduction degree, catalytic activity and stability increase with the input power. Similar catalytic performances in CRM reaction can be obtained when the power exceeds 80 W. Compared with the Ni/Al2O3 catalyst prepared by traditional method, Ni/γ-Al2O3 samples prepared by H2 DBD plasma exhibit better activities, stability and anti-carbon deposit performances. It is mainly ascribed to smaller Ni particle size, more basic sites and weaker basicity. The increase of Ni particle sizes due to the sintering at high temperature results in the decrease of catalytic activities and coke formation. 相似文献