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1.
The storage of excess electricity from renewable energy sources is nowadays a crucial topic. One promising technology is the methanol (CH3OH) synthesis from H2/CO2 mixtures. The achievable one‐pass conversion is limited within this exothermic equilibrium reaction. A possibility to overcome this limitation would be withdrawing CH3OH and H2O from the gas phase through in situ condensation under reaction conditions. In this work, the phase equilibrium for mixtures representative for different degrees of conversion was studied. A view cell was employed to determine systematically the single‐ and two‐phase regimes and obtain phase envelopes for mixtures of H2, CO2, CH3OH, and H2O from 66 to 305 °C and 61 to 233 bar. Furthermore, the densities in the single‐phase area were determined and quantified by an empirical model.  相似文献   

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Gas hydrates from a (40/60 mol %) CO2/H2 mixture, and from a (38.2/59.2/2.6 mol %) CO2/H2/C3H8 mixture, were synthesized using ice powder. The gas uptake curves were determined from pressure drop measurements and samples were analyzed using spectroscopic techniques to identify the structure and determine the cage occupancies. Powder X‐ray diffraction (PXRD) analysis at ?110°C was used to determine the crystal structure. From the PXRD measurement it was found that the CO2/H2 hydrate is structure I and shows a self‐preservation behavior similar to that of CO2 hydrate. The ternary gas mixture was found to form pure structure II hydrate at 3.8 MPa. We have applied attenuated total reflection infrared spectroscopic analysis to measure the CO2 distribution over the large and small cavities. 1H MAS NMR and Raman were used to follow H2 enclathration in the small cages of structure I, as well as structure II hydrate. © 2009 American Institute of Chemical Engineers AIChE J, 2009  相似文献   

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The extraction of C2H4 from C2H6/C2H4/C2H2 mixtures is of great significance in the chemical industry for C2H4 production but the process remains challenging due to the similarity of these C2 hydrocarbon species in their molecular size and physical properties. Here, we report the fluorination of a stable Zr-MOF, UiO-66, to fine-tune the pore dimensions and pore functionality. In particular, UiO-66-CF3 shows notably preferential adsorption of C2H6 and C2H2 over C2H4, with C2H2/C2H4 and C2H6/C2H4 selectivities of 1.4 and 1.9, respectively. Theoretical calculations provide insight into the binding sites of UiO-66-CF3 for C2 hydrocarbon adsorption. Breakthrough experiments further confirmed the capability of the material for purification of C2H4 from C2H2/C2H4/C2H6 ternary mixtures, evidenced by the high purity C2H4 (99.9%+) obtained directly from outlet gas.  相似文献   

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Activated hydrogen peroxide produces very reactive OH-radicals which destroy hazardous contaminants in water. The principles and different methods of activation are described. Results from laboratory studies show the numerous applications of this new technology. A successful scaleup of laboratory tests to an industrial level is discussed. Finally, a cost estimate for treating different types of water with hydrogen peroxide is presented.  相似文献   

7.
The influence of the preparation procedure of tungsten carbide on the mechanism of carburization is discussed. This work is focused on the reduction and the carburization of tungsten trioxide by a mixture of hydrocarbon and H2 to form WC. Temperature-programmed reaction spectra obtained with CH4, C2H6 and C2H4 have been measured. In presence of the CH4-H2 mixture, H2 is the reducing agent and the hydrocarbon is consumed for the carburization whereas C2H6 or C2H4 participates in the reduction of the tungsten oxide. The temperatures of reduction and carburization are lower by about 150 K using C2H6 or C2H4 instead of CH4. Such a decrease of the temperature of reduction of tungsten oxide is needed to avoid the formation of poorly reducible compounds that can occur during the preparation of supported tungsten carbide. Furthermore, the surface area of the resulting carbide is 25 m2/g with C2H6 and C2H4 and 10 m2/g with CH4. During the carburization, the deposit of excess carbon on the WC surface is larger with the C2 hydrocarbons than with CH4, but it protects the carbide and can be removed by hydrogen treatment. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

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Ni2P/MCM-41 with a stoichiometric Ni/P ratio prepared using a H2 plasma reduction method was passivated either by 10.0 vol.% H2S/H2 (Ni2P-S) or 1.0 vol.% O2/He (Ni2P-O). The XAS characterization demonstrated that the NiP bond of Ni2P was more sensitive to O2 than the NiNi bond while H2S mainly reacted with NiNi site. Moreover, Ni species in Ni2P-S was more electron-deficient. The different hydrodesulfurization performances of Ni2P-S and Ni2P-O were discussed by considering their different structure and electronic properties as well as the formation of a covalent nickel phosphosulfide phase.  相似文献   

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屈媛  高军  陈霖  靖金球 《弹性体》2006,16(5):23-26
首次以水合肼和双氧水的氧化还原反应对两嵌段共聚物SB进行选择性加氢,并着重考察了各种氢化条件对加氢反应的影响,加氢度达到95%。本方法既具有学术上的理论意义,又对光纤材料国产化有重要意义。  相似文献   

12.
Sintering of Cr2O3 was performed at 1530°C under low pO2 close to the Cr–Cr2O3 equilibrium generated by H2/H2O gas mixtures. Addition of 1 wt%ZrO2 and 0·1 wt%MgO increases the density of Cr2O3 from 97% TD to nearly full density. Rapid densification and the higher density are attributed to the appearance of a transient CrO liquid phase as a result of the presence of ZrO2 and MgO under the sintering conditions. A grain size reduction is also achieved owing to the presence of ZrO2 particles and the possible formation of a MgCr2O4 spinel at grain boundaries. There is no connection between densification and loss of material due to evaporation. ©  相似文献   

13.
The effects of adding mixtures of titania and zirconia on the methanol synthesis activity and selectivity of Cu/SiO2 were investigated. The synthesis of methanol from both CO/H2 and CO2/H2 mixtures was examined at 0.65 MPa and temperatures between 448 and 573 K. For CO hydrogenation, the addition of ZrO2 alone increased the methanol synthesis activity of Cu/SiO2 by up to three-fold. Substitution of a portion of the ZrO2 by TiO2 decreased the methanol synthesis activity of the catalyst relative to that observed when only ZrO2 is added. ZrO2 addition also enhanced the methane synthesis activity by as much as seven fold. In the case of CO2 hydrogenation, the maximum methanol synthesis activity is achieved when a 50/50 wt% mixture of ZrO2 and TiO2 is added to Cu/SiO2. Neither the presence of the oxide additive nor its composition had any effect on the activity of the reverse water–gas-shift reaction, which suggests that this reaction proceeds only on Cu. The observed effects of ZrO2 and TiO2 on the catalytic activity of methanol synthesis from CO and CO2, and methane synthesis from CO, are interpreted in terms of the strength and concentration of acidic and basic groups on the surface of the dispersed oxide.  相似文献   

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介绍了合成氨厂在液氮洗精制气未合格之前的状况,采取了提前用氮气开启氢氮气压缩机打内循环、待液氮洗精制气合格后完成无间隔接气的措施,结果表明:缩短了约2h的开车时间,减少了约16万m3的精制气放空,大大降低了开车成本。  相似文献   

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《Journal of aerosol science》1999,30(8):1095-1113
A physical box model simulating the aerosol particle evolution along air mass trajectories is developed to provide a tool for interpreting the local observations of stratospheric aerosols (i.e., polar stratospheric clouds). The model calculates the composition and the size distributions of H2SO4/H2O and HNO3/H2SO4/H2O liquid droplets. The parameterization of the physical processes affecting the dynamics of HNO3 and H2SO4 solid hydrates and ice particle size distributions is also included, but not used. This work is restricted to some speculations about the liquid to solid transition, according to existing theories. The evolution of liquid particles is simulated taking into account nucleation, diffusive condensation/evaporation and coagulation. This paper reports the physical and numerical details of the model, which are discussed within the framework of the current understanding of the stratospheric aerosol physics. Performance and limitations of the model are discussed on the basis of the evolution of particle size, and composition along synthetic air mass thermal histories. Size distributions and size-dependent acid weight fractions of the liquid stratospheric aerosols consisting of HNO3/H2SO4/H2O are calculated in the cases of air mass thermal histories with different cooling rates and with rapid temperature fluctuations.  相似文献   

18.
The effect of zirconia promotion on Cu/SiO2 for the hydrogenation of CO and CO2 at 0.65 MPa has been investigated at temperatures between 473 and 573 K. With increasing zirconia loading, the rate of methanol synthesis is greatly enhanced for both CO and CO2 hydrogenation, but more significantly for CO hydrogenation. For example, at 533 K the methanol synthesis activity of 30.5 wt% zirconia-promoted Cu/SiO2 is 84 and 25 times that of unpromoted Cu/SiO2 for CO and CO2 hydrogenation, respectively. For all catalysts, the rate of methanol synthesis from CO2/H2 is higher than that from CO/H2. The apparent activation energy for methanol synthesis from CO decreases from 22.5 to 17.5 kcal/mol with zirconia addition, suggesting that zirconia alters the reaction pathway. For CO2 hydrogenation, the apparent activation energies (~12 kcal/mol) for methanol synthesis and the reverse water-gas shift (RWGS) reaction are not significantly affected by zirconia addition. While zirconia addition greatly increases the methanol synthesis rate for CO2 hydrogenation, the effect on the RWGS reaction activity is comparatively small. The observed effects of zirconia are interpreted in terms of a mechanism which zirconia serves to adsorb either CO or CO2, whereas Cu serves to adsorb H2. It is proposed that methanol is formed by the hydrogenation of the species adsorbed on zirconia.  相似文献   

19.
The oxidation reaction of CO with O2 on the FeOx/Pt/TiO2 catalyst is markedly enhanced by H2 and/or H2O, but no such enhancement occurs on the Pt/TiO2 catalyst. Isotope effects were studied by H2/D2 and H2O/D2O on the FeOx/Pt/TiO2 catalyst, and almost the same magnitude of isotope effect of ca. 1.4 was observed for the enhancement of the CO conversion by H2/D2 as well as by H2O/D2O at 60 °C. This result suggests that the oxidation of CO with O2 via such intermediates as formate or bicarbonate in the presence of H2O, in which H2O or D2O acts as a molecular catalyst to promote the oxidation of CO as described below.   相似文献   

20.
Methyl mercaptan and by-product thiophene can be obtained from the reaction of CO/H2/H2S mixtures over α-Al2O3 at 340 °C, and selectivities of methyl mercaptan of ≥98% can be readily obtained in a sustained reaction. γ-Al2O3 and Cr2O3 were also found to be active catalysts and gave high selectivities to methyl mercaptan, although these catalysts gave (CH3)2S as by-product rather than thiophene. In the absence of H2S, all the catalysts displayed virtually no catalytic activity.  相似文献   

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