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1.
The new multicomponent Co-based catalysts with additives of group 8 metal and rare earth elements and supported on alumina have been tested in the dry and steam conversion of a model biogas. The processes were carried out in a flow quartz reactor under the following conditions: atmospheric pressure, a gas hourly space velocity of 1000 h ?1 and temperatures of 300–800°C. The catalysts were characterised using electron microscopy, BET and X-ray analysis. The methane is almost completely converted in the dry reforming of biogas at T≤800°C. Synthesis gas with a ratio of H 2/CO>1.0 is a main product of biogas reforming over the multicomponent catalysts studied. Adding steam in a feed composition increases both the methane conversion and the hydrogen yield at lower temperatures. Almost complete methane conversion occurs at T<750°C in the steam reforming of biogas. The catalysts are highly effective and exhibit stable activity throughout 100 h of continuous testing. 相似文献
2.
Catalysts based on uranium oxides were systematically studied for the first time. Catalysts containing various amounts of uranium oxides (5 and 15%) supported on alumina and mixed Ni-U/Al 2O 3 catalysts were synthesized. The uranium oxide catalysts were characterized using the thermal desorption of argon, the low-temperature adsorption of nitrogen, X-ray diffraction analysis, and temperature-programmed reduction with hydrogen and CO. The effects of composition, preparation conditions, and thermal treatment on physicochemical properties and catalytic activity in the reactions of methane and butane oxidation, the steam and carbon dioxide reforming of methane, and the partial oxidation of methane were studied. It was found that a catalyst containing 5% U on alumina calcined at 1000°C was most active in the reaction of high-temperature methane oxidation. For the Ni-U/Al 2O 3 catalysts containing various uranium amounts (from 0 to 30%), the introduction of uranium as a catalyst constituent considerably increased the catalytic activity in methane steam reforming and partial oxidation. 相似文献
3.
Compressed liquid densities for propane—normal butane mixtures are reported at six temperatures between 10 and 60°C. For each isotherm, there are at least seven compositions ranging between 10 and 75 mol% propane at pressures from near saturation up to 9.65 MPa. The derived excess volumes are negative and represent a maximum of 0.5 percent of the mixture volume at 10°C. At 60°C, the excess volume can be up to 2.2% of the mixture volume. In addition to the binary data, limited density measurements were made on ternary mixtures containing up to 17 mol% ethane. 相似文献
4.
Jordan oil shale from El-Lajjun deposit was pyrolysed in a fixed-bed pyrolysis reactor and the influence of the pyrolysis
temperature between 400 to 620°C and the influence of the pyrolysis atmosphere using nitrogen and nitrogen/steam on the product
yield and gas composition were investigated. The gases analysed were H 2, CO, CO 2 and hydrocarbons from C 1 to C 4. The results showed for both nitrogen and nitrogen/steam that increase the pyrolysis bed temperature from 400 to 520°C resulted
in a significant increase in the oil yield, after which temperature the oil yield decreased. The alkene/alkane ratio including
ethene/ethane, propene/propane, and butene/butane ratios, can be used as an indication of pyrolysis temperature and the magnitude
of cracking reactions. Increasing alkene/alkane ratio occurring with increasing pyrolysis temperature. The alkene/alkane ratio
for nitrogen/steam pyrolysis atmosphere was lower than the one found under nitrogen atmosphere.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
The conversion of C 1–C 4 hydrocarbons into gaseous and liquid products in a dielectric barrier discharge plasma in the presence of water has been studied. The formation of a deposit on the electrode surface is prevented by introducing water in the liquid state into a gaseous hydrocarbon stream, a finding that has been confirmed by IR spectroscopic study of the electrode surface. Hydrogen and C 2+ hydrocarbons have been detected among the gaseous products of conversion, the liquid products being represented by C 6–C 10+ alkanes. The total liquid products have amounted to 13.4, 26.0, or 36.6% for the methane, propane, or n-butane conversion, respectively. A 10% propane or butane admixture to methane increases the yield of the liquid products to make 22.0 and 31.7% for the methane–propane and the methane–butane mixture, respectively. 相似文献
6.
Dry chitosan is an excellent candidate for facilitated transport membranes that can be utilized in industrial applications, such as fuel cell operations and other purification processes. This article is the first to report temperature effects on transport properties of CO 2, H 2, and N 2 in a gas mixture typical of such applications. At a feed pressure of 1.5 atm, CO 2 permeabilities increased (0.381–26.1 barrers) at temperatures of 20–150 °C with decreasing CO 2/N 2 (19.7–4.55) and CO 2/H 2 (3.14–1.71) separation factors. The pressure effect on solubilities and permeabilities were fitted to the extended dual mode model and its corresponding mixed gas permeation model. The dual mode and transport parameters, the sorption heats and the activation energies of Henry's and Langmuir's regimes and their pre‐exponential parameters were determined. The Langmuir's capacity constants were utilized to estimate chitosan's glass transition temperature (CO 2: 172 °C, N 2: 175 °C, and H 2: 171 °C). The activation energies of diffusion in the Henry's law and Langmuir regimes were dependent on the collision diameter of the gases. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2620–2631, 2007 相似文献
7.
New catalysts have been developed for the production of synthesis gas via a resource-saving and environmentally friendly process—dry reforming of methane. The catalysts are fabricated from NdCaCo 1–xNi x On precursors ( x = 0, 0.2, 0.4, 0.6, 0.8, 1) synthesized by a ceramic method. According to X-ray powder diffraction, when reacting with an equimolar CH 4/CO 2 mixture at 800–900°С, the precursors are converted into a mixture of neodymium and calcium oxides and cobalt and nickel metals. The catalyst based on NdCaNiO n at 850°С has ensured high conversions of methane (91%) and CO 2 (86%) at СО and hydrogen yields of 88 and 78%, respectively. At 940°С, the yield of CO is close to the quantitative one (97%). 相似文献
8.
Cloud-point data for the system poly(methyl methacrylate) (PMMA)–CO 2–methyl methacrylate (MMA) are measured in the temperature range of 26 to 170°C, to pressures as high as 2500 bar, and with cosolvent concentrations of 10.4, 28.9, and 48.4 wt.%. PMMA does not dissolve in pure CO 2 to 255°C and 2550 bar. The cloud-point curve for the PMMA–CO 2–10.4 wt.% MMA system exhibits a negative slope that reaches 2500 bar at 105°C. With 28.9 wt.% MMA the cloud-point curve remains relatively flat at ∼900 bar for temperatures between 25 and 170°C. With 48.4 wt.% MMA the cloud-point curve exhibits a positive slope that extends to 20°C and ∼100 bar. Pressure-composition isotherms are also reported for the CO 2–MMA system at 40.0, 80.0, 105.5°C. This system exhibits type-I phase behavior with a continuous mixture–critical curve. The Peng–Robinson (PR) and SAFT equations of state model the CO 2–MMA data reasonably well without any binary interaction parameters, although the PR equation provides a better representation of the mixture-critical region. It is not possible to obtain even a qualitative fit of the PMMA–MMA–CO 2 data with the SAFT equation of state. The SAFT model qualitatively shows that the cloud-point pressure decreases with increasing MMA concentration and that the cloud-point curve exhibits a positive slope for very high concentrations of MMA in solution. 相似文献
9.
We reported γ‐alumina supported molybdenum phosphide (MoP) catalysts as a novel catalyst for sulfur‐resistant methanation reaction. The precursors of the catalyst were prepared by impregnation method and the effect of reduction temperatures (550 °C, 600 °C, 650 °C) of the precursors for sulfur‐resistant methanation was examined. The results indicated catalyst obtained by lower reduction temperature delivered better sulfur‐resistant methanation performance. Meanwhile, the influence of H 2/CO ratios and H 2S content was also investigated. The results indicated that high H 2/CO ratio and low H 2S content was favorable for methanation of MoP catalysts. The catalysts were characterized by N 2 adsorption–desorption, XRD, XPS and TEM. The results confirmed that the MoP phase was formed on all the catalysts and the physicochemical properties of the samples influenced the performance for sulfur‐resistant methanation. 相似文献
10.
CO2 and steam/CO2 electroreduction to CO and methane in solid oxide electrolytic cells (SOEC) has gained major attention in the past few years. This work evaluates, for the very first time, the performance of two different ZnO–Ag cathodes: one where ZnO nanopowder was mixed with Ag powder for preparing the cathode ink (ZnOmix–Ag cathode) and the other one where Ag cathode was infiltrated with a zinc nitrate solution (ZnOinf –Ag cathode). ZnOmix–Ag cathode had a better distribution of ZnO particles throughout the cathode, resulting in almost double CO generation while electrolysing both dry CO2 and H2/CO2 (4:1 v/v). A maximum overall CO2 conversion of 48% (in H2/CO2) at 1.7 V and 700 °C clearly indicated that as low as 5 wt% zinc loading is capable of CO2 electroreduction. It was further revealed that for ZnOinf –Ag cathode, most of CO generation took place through RWGS reaction, but for ZnOmix–Ag cathode, it was the synergistic effect of both RWGS reaction and CO2 electrolysis. Although ZnOinf –Ag cathode produced trace amount of methane at higher voltages, with ZnOmix–Ag cathode, there was absolutely no methane. This seems to be due to strong electronic interaction between Zn and Ag that might have suppressed the catalytic activity of the cathode towards methanation. 相似文献
11.
The present work aims to investigate several kinetic aspects of catalytic combustion of the stoichiometric propane–air mixture on a platinum wire in the presence of progressive CO 2 dilution, using a micro-calorimetric method. The method allowed the determination of the induction periods and of the reaction rates during transient and steady-state regimes at different initial pressures P 0 (10–101 kPa), wire temperatures T w (470–575 K) and gas-phase composition. The kinetic parameters were evaluated from regression analysis using empirical and mechanistic models. The dilution with CO 2 of the stoichiometric propane–air mixture (4.02% propane) was 10, 20, 30, 40, 50%. For additions equal to or greater than 23%, the gaseous system is outside the flammability limits reported in the literature. The kinetic characteristics of the catalytic combustion remain similar for the whole range, even for 50% CO 2 addition when the propane concentration in mixture diminishes to 2%, a concentration smaller than the lower explosion limit in air in normal conditions. 相似文献
12.
Ni 7.5/NaY catalysts were prepared using two different methods, the incipient wetness impregnation method and the “two-solvent” method. These catalysts were characterised by N 2 sorption, XRD, TEM and TPR. Their activity and stability in the dry reforming of methane were tested at atmospheric pressure under an equimolar mixture of methane and carbon dioxide. Three different Ni species, very small, spherical, and layers of nickel silicate were observed by TEM. The preparation by the two-solvent method led to a better dispersion of the active phase as well as to better activity and stability. These catalysts were promoted with small amounts (0.1 wt%) of rhodium. Rhodium facilitates the reducibility and greatly enhances catalytic activity. A complete conversion (100%) for CH 4 and CO 2 over the Rh promoted catalyst is achieved at 584 °C and 559 °C respectively, while for the non-promoted Ni7.5/NaY catalyst, only a 60% conversion rate for CH 4 and CO 2 is reached at the same temperatures. 相似文献
13.
The title compound reacts with molecular hydrogen at 60°C giving rise to the homometallic complexes Fe(CO) 5 and Co 2(CO) 8, and a very rich mixture of gaseous hydrocarbons (e.g. butenes from partial hydrogenation, butane from total hydrogenation and methane and propene from selective hydrogenolysis of the organic chain).The influence of concentration of the title complex, and partial pressure of hydrogen or carbon monoxide on the hydrogenation rate have been investigated. Although an unequivocal mechanism cannot be ascertained from the kinetic data owing to the complexity of the reaction, the pattern of products strongly indicates that the σ-interaction between the iron atom and the organic chain is preserved in the transition state. 相似文献
14.
The sorption enhanced reformer concept breaks the thermodynamic limits of steam methane reforming and water-gas shift reactions with selective CO 2 removal to produce more H 2. In this paper, we propose a dynamic kinetic model for sorption-enhanced steam reformers (SERs) integrated with biomass gasifiers. An analysis of operating conditions was conducted to examine high purity hydrogen production. The kinetic model was validated with published literature results at different reactor pressures (5-20 bar), steam/carbon ratios (2-5), and reactor temperatures (673K–1023K). This study shows that biomass gasifiers can be integrated with SER reactors to produce high purity H 2. 相似文献
15.
The ignition temperatures and effective activation energies of the ignition limits of mixtures (40–70% H 2 + 60–30% CH 4) stoich + air over Rh were experimentally determined at a pressure of 1 atm in the temperature range 20–300 °C. Over an ignition-treated Rh surface, the ignition temperature of a mixture of 70% H 2 + 30% methane + air is 62 °C. This indicates the potential of using Rh to markedly lower the ignition temperature of fuels based on hydrogen–methane mixtures. 相似文献
16.
Nickel–aluminium and magnesium–aluminium hydrotalcites were prepared by co-precipitation and subsequently submitted to calcination. The mixed oxides obtained from the thermal decomposition of the synthesized materials were characterized by XRD, H 2-TPR, N 2 sorption and elemental analysis and subsequently tested in the reaction of methane dry reforming (DRM) in the presence of excess of methane (CH 4/CO 2/Ar = 2/1/7). DMR in the presence of the nickel-containing hydrotalcite-derived material showed CH 4 and CO 2 conversions of ca. 50% at 550 °C. The high values of the H 2/CO molar ratio indicate that at 550 °C methane decomposition was strongly influencing the DRM process. The sample reduced at 900 °C showed better catalytic performance than the sample activated at 550 °C. The catalytic performance in isothermal conditions from 550 °C to 750 °C was also determined. 相似文献
17.
A sol–gel route to synthesize nanocrystalline praseodymium-, samarium- and gadolinium-doped ceria powders for solid oxides fuel Cells SOFCs is presented. The method involves metal nitrates with propionic acid (both as chelating ligand and solvent), gel formation, liquid nitrogen quenching, drying at 150 °C/24 h, and finally decomposition at 450 °C in nitrogen followed by calcination at 650 °C in air. TG–DTA, BET, XRD, FTIR, UV–vis and catalytic tests were used to characterize the samples. Ce 0.8Pr 0.2O 2?δ sample exhibited the best catalytic performance in methane steam reforming under water deficient conditions, closely followed by Ce 0.9Gd 0.1O 2?δ, Ce 0.8Sm 0.2O 2?δ and Ce 0.8Gd 0.2O 2?δ catalysts. The superior catalytic performance of Ce 0.8Pr 0.2O 2?δ sample was attributed to the existence of praseodymium species (Pr 4+/Pr 3+) strongly interacting with ceria. The two systems act synergistically in the catalytic steam reforming of methane. 相似文献
18.
Process in which sulfur is produced from a gas containing 25–55% SO 2 was studied in order to evaluate the real efficiency of the catalytic post-reduction of sulfur dioxide in a pilot unit with gas flow rate of up to 1.2 nm 3 h –1 at the following temperatures (°C): thermal stage 850–1100, catalytic conversion 350–570, and Claus reactor 219–279. It was found that the conversion at 400–550°C and space velocity of 1600 h –1 on AOK-78-57 promoted aluminum oxide catalyst provides full processing of organosulfur compounds (CS 2 and COS). The temperature dependence of the conversion/generation of hydrogen sulfide on AOK-78-57 catalyst corresponds to the equilibrium model. It was experimentally confirmed that the homogeneous reduction of sulfur dioxide gas with methane at T ≈ 1100°C, with catalytic post-reduction at 400–550°C and subsequent Claus-conversion of the reduced gas at 230–260°C, provide a sufficiently deep (by 92–95%) general processing of sulfur dioxide gas to sulfur. 相似文献
19.
Methane pyrolysis and steam reforming were studied over a series of nickel catalysts (Ni-Al 2O 3, Ni/MgO, and Ni/LiAlO 2) under the same conditions (650-750°C, P CH4 = 0.001-0.03 MPa). Unlike heterogeneous reaction of pyrolysis, some of the steps of steam reforming of methane occur in the
gas phase. When gasphase reactions were suppressed, the rate and activation energy of steam reforming are close to the corresponding
kinetic characteristics for pyrolysis. Hypothetically, the rate-limiting step of the process is the dissociative adsorption
of methane on nickel in this case. 相似文献
20.
CO methanation on Ni/CeO 2 has recently received increasing attention. However, the low-temperature activity and carbon resistance of Ni/CeO 2 still need to be improved. In this study, plasma decomposition of nickel nitrate was performed at ca. 150°C and atmospheric pressure. This was followed by hydrogen reduction at 500 °C in the absence of plasma, and a highly dispersed Ni/CeO 2 catalyst was obtained with improved CO adsorption and enhanced metal-support interaction. The plasma-decomposed catalyst showed significantly improved low-temperature activity with high methane selectivity (up to 100%) and enhanced carbon resistance for CO methanation. For example, at 250°C, the plasma-decomposed catalyst showed a CO conversion of 96.8% with high methane selectivity (almost 100%), whereas the CO conversion was only 14.7% for a thermally decomposed catalyst. 相似文献
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