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1.
Supported Ni catalysts have been investigated for hydrogen production from steam reforming of glycerol. Ni loaded on Al2O3, La2O3, ZrO2, SiO2 and MgO were prepared by the wet-impregnation method. The catalysts were characterized by nitrogen adsorption–desorption, X-ray diffraction and scanning electron microscopy. The characterization results revealed that large surface area, high dispersion of active phase on support, and small crystalline sizes are attributes of active catalyst in steam reforming of glycerol to hydrogen. Also, higher basicity of catalyst can limit the carbon deposition and enhance the catalyst stability. Consequently, Ni/Al2O3 exhibited the highest H2 selectivity (71.8%) due to small Al2O3 crystallites and large surface area. Response Surface Methodology (RSM) could accurately predict the experimental results with R-square = 0.868 with only 4.5% error. The highest H2 selectivity of 86.0% was achieved at optimum conditions: temperature = 692 °C, feed flow rate = 1 ml/min, and water glycerol molar ratio (WGMR) 9.5:1. Also, the optimization results revealed WGMR imparted the greatest effect on H2 selectivity among the reaction parameters.  相似文献   

2.
Thermodynamic features of hydrogen production by glycerol steam reforming with in situ hydrogen extraction have been studied with the method of Gibbs free energy minimization. The effects of pressure (1–5 atm), temperature (600–1000 K), water to glycerol ratio (WGR, 3–12) and fraction of H2 removal (f, 0–1) on the reforming reactions and carbon formation were investigated. The results suggest separation of hydrogen in situ can substantially enhance hydrogen production from glycerol steam reforming, as 7 mol (stoichiometric value) of hydrogen can be obtained even at 600 K due to the hydrogen extraction. It is demonstrated that atmospheric pressure and a WGR of 9 are suitable for hydrogen production and the optimum temperature for glycerol steam reforming with in situ hydrogen removal is between 825 and 875 K, 100 K lower than that achieved typically without hydrogen separation. Furthermore, the detrimental influence of increasing pressure in terms of hydrogen production becomes marginal above 800 K with a high fraction of H2 removal (i.e., f = 0.99). High temperature and WGR are favorable to inhibit carbon production.  相似文献   

3.
This work studies 2 wt% Pt catalysts. The support is a SiO2-C composite whose main features are a high specific surface due to its mesoporosity, a higher thermal stability than the C support, and the absence of surface acid sites which could promote the dehydration reactions that produce coke precursors. The Pt/SiO2-C catalyst has very small metallic particles (dva = 1.37 nm) that favor the CC bond cleavage reactions which allow obtaining total gas conversion at 450 °C. With this catalyst, it is possible to obtain high yields to H2, between 4 and 5, which indicates that the active sites promote the WGS reaction, even with glycerol concentrations of 30 and 50%. Pt/SiO2-C is a very stable catalyst since it loses only 10% of its initial activity after 66 h on stream and is resistant to sintering and coke deposition.  相似文献   

4.
In the present work, a comparative study of Ni catalysts supported on commercially available alumina and lanthana-alumina carriers was undertaken for the glycerol steam reforming reaction (GSR). The supports and/or catalysts were characterized by PZC, BET, ICP, XRD, NH3-TPD, CO2-TPD, TPR and SEM. Carbon deposited on the catalytic surface was characterized by SEM, TPO and Raman. Concerning the Ni/LaAl sample it can be concluded that the presence of lanthana by: (a) facilitating the active species dispersion, (b) strengthening the interactions between nickel species and support, (c) increasing of the basic sites' population and redistributing the acid ones in terms of strength and density, provides a catalyst with improved performance for the GSR reaction, in terms of activity, H2 production and long term stability. TPO and Raman indicate that the carbon on the Ni/LaAl catalyst was mostly amorphous and was deposited mainly on the support surface. For the Ni/Al catalyst, graphitic carbon was prevalent and likely covered its active sites.  相似文献   

5.
The steam reforming of pyrolysis bio-oil is one proposed route to low carbon hydrogen production, which may be enhanced by combination with advanced steam reforming techniques. The advanced reforming of bio-oil is investigated via a thermodynamic analysis based on the minimisation of Gibbs Energy. Conventional steam reforming (C-SR) is assessed alongside sorption-enhanced steam reforming (SE-SR), chemical looping steam reforming (CLSR) and sorption-enhanced chemical looping steam reforming (SE-CLSR). The selected CO2 sorbent is CaO(s) and oxygen transfer material (OTM) is Ni/NiO. PEFB bio-oil is modelled as a surrogate mixture and two common model compounds, acetic acid and furfural, are also considered. A process comparison highlights the advantages of sorption-enhancement and chemical looping, including improved purity and yield, and reductions in carbon deposition and process net energy balance.The operating regime of SE-CLSR is evaluated in order to assess the impact of S/C ratio, NiO/C ratio, CaO/C ratio and temperature. Autothermal operation can be achieved for S/C ratios between 1 and 3. In autothermal operation at 30 bar, S/C ratio of 2 gives a yield of 11.8 wt%, and hydrogen purity of 96.9 mol%. Alternatively, if autothermal operation is not a priority, the yield can be improved by reducing the quantity of OTM. The thermodynamic analysis highlights the role of advanced reforming techniques in enhancing the potential of bio-oil as a source of hydrogen.  相似文献   

6.
7.
In this work, thermodynamics was applied to investigate the glycerol autothermal reforming to generate hydrogen for fuel cell application. Equilibrium calculations employing the Gibbs free energy minimization were performed in a wide range of temperature (700–1000 K), steam to glycerol ratio (1–12) and oxygen to glycerol ratio (0.0–3.0). Results show that the most favorable conditions for hydrogen production are achieved with the temperatures, steam to glycerol ratios and oxygen to glycerol ratios of 900–1000 K, 9–12 and 0.0–0.4, respectively. Further, it is demonstrated that thermoneutral conditions (steam to glycerol ratio 9–12) can be obtained at oxygen to glycerol ratios of around 0.36 (at 900 K) and 0.38–0.39 (at 1000 K). Under these thermoneutral conditions, the maximum number of moles of hydrogen produced are 5.62 (900 K) and 5.43 (1000 K) with a steam to glycerol ratio of 12. Also, it should be noted that methane and carbon formation can be effectively eliminated.  相似文献   

8.
A thermodynamic analysis of hydrogen production via steam and autothermal reforming of beef tallow has been carried out via the Gibbs free energy minimization method. Equilibrium calculations are performed at atmospheric pressure with a wide range of temperatures (400–1200 °C), steam-to-beef tallow ratios (1–15) and oxygen-to-beef tallow ratios (0.0–2.0).  相似文献   

9.
Thermodynamic analyses of cracking, partial oxidation (POX), steam reforming (SR) and oxidative steam reforming (OSR) of butane and propane (for comparison) were performed using the Gibbs free energy minimization method under the reaction conditions of T = 250–1000 °C, steam-to-carbon ratio (S/C) of 0.5–5 and O2/HC (hydrocarbon) ratio of 0–2.4. The simulations for the cracking and POX processes showed that olefins and acetylene can be easily generated through the cracking reactions and can be removed by adding an appropriate amount of oxygen. For SR and OSR of propane and butane, predicted carbon formation only occurred at low S/C ratios (<2) with the maximum level of carbon formation at 550–650 °C. For the thermal-neutral conditions, the TN temperatures decrease with the increase of the S/C ratio (except for O/C = 0.6) and the decrease of the O/C ratio. The simulated results for SR or OSR of propane and butane are very close under the investigated conditions.  相似文献   

10.
A non-stoichiometric thermodynamic analysis is performed on the adsorption-enhanced steam reforming of glycerol for hydrogen production based on the principle of minimising the Gibbs free energy. The effects of temperature (600–1000 K), pressure (1–4 bar), water to glycerol feed ratio (3:1–12:1), percentage of CO2 adsorption (0–99%) and molar ratio of carrier gas to feed reactants (1:1–5:1) on the reforming reactions and carbon formation are examined. The results show that the use of a CO2 adsorbent enhances glycerol conversion to hydrogen and the maximum number of moles of hydrogen produced per mole of glycerol can be increased from 6 to 7 due to the CO2 adsorption. The analyses suggest that the most favourable temperature for steam–glycerol reforming is between 800 and 850 K in the presence of a CO2 adsorbent, which is about 100 K lower than that for reforming without CO2 adsorption. Although high pressures are favourable for CO2 adsorption, a lower operating pressure gives a higher overall hydrogen conversion. The most favourable water to glycerol feed ratio is found to be 9.0 above which the benefit becomes marginal. Carbon formation could occur at low water to glycerol feed ratios, and the use of a CO2 adsorbent can suppress the formation reaction and substantially reduce the lower limit of the water to glycerol feed ratio for carbon formation.  相似文献   

11.
In this paper the energetic optimization of a proton exchange membrane fuel cell integrated with a steam reforming system using ethanol as fuel is analysed. In order to obtain high hydrogen production, a thermodynamic analysis of the steam reforming process has been carried out and the optimal operating conditions has been defined. Moreover, the overall efficiency of the PEMFC-SR system has been investigated as a function of the fuel utilization factor and the effects of the anodic off-gas recirculation have been evaluated.  相似文献   

12.
Hydrogen production from steam reforming of glycerol in a fluidized bed reactor has been simulated using a CFD method by an additional transport equation with a kinetic term. The Eulerian–Eulerian two-fluid approach was adopted to simulate hydrodynamics of fluidization, and chemical reactions were modelled by laminar finite-rate model. The bed expansion and pressure drop were predicted for different inlet gas velocities. The results showed that the flow system exhibited a more heterogeneous structure, and the core-annulus structure of gas–solid flow led to back-mixing and internal circulation behaviour, and thus gave a poor velocity distribution. This suggests the bed should be agitated to maintain satisfactory fluidizing conditions. Glycerol conversion and H2 production were decreased with increasing inlet gas velocity. The increase in the value of steam to carbon molar ratio increases the conversion of glycerol and H2 selectivity. H2 concentrations in the bed were uneven and increased downstream and high concentrations of H2 production were also found on walls. The model demonstrated a relationship between hydrodynamics and hydrogen production, implying that the residence time and steam to carbon molar ratio are important parameters. The CFD simulation will provide helpful data to design and operate a bench scale catalytic fluidized bed reactor.  相似文献   

13.
Hydrogen production from glycerin by steam reforming over nickel catalysts   总被引:3,自引:0,他引:3  
Increasing biodiesel production has resulted in a glut of glycerin that has led to a precipitous drop in market prices. In this study, the use of glycerin as a biorenewable substrate for hydrogen production, using a steam reforming process, has been evaluated. Production of hydrogen from glycerin is environmentally friendly because it adds value to this byproduct generated from biodiesel plants. The study focuses on nickel-based catalysts with MgO, CeO2, and TiO2 supports. Catalysts were characterized with thermogravimetric analysis and X-ray diffraction techniques. Maximum hydrogen yield was obtained at 650 °C with MgO supported catalysts, which corresponds to 4 mol of H2 out of 7 mol of stoichiometric maximum.  相似文献   

14.
The aim of this study is to produce hydrogen through the glycerol steam reforming process. The reaction is carried out in a traditional reactor and an electrolessly plated Pd/Ag alloy membrane reactor, with varying reaction temperature, weight hourly specific velocity (WHSV) and water glycerol molar ratio (WGMR). The non-catalytic test was also employed for comparative purposes. The results show that the reaction is highly depending on temperature, and the maximum glycerol conversion achieved to 96.24% at 800 °C with a hydrogen yield of 5.82 mol-H2/mol-C3H8O3. It also found that the Pd/Ag membrane can effectively separate hydrogen from the reaction side and subsequently enhance the reaction rate in the membrane reactor. TGA measurements were employed to quantify the amounts of deposited carbon and the results also confirmed that the CeO2 modified catalyst can improve the carbon resistance as well as activity and stability.  相似文献   

15.
Thermodynamics was applied to investigate propane dry reforming (DR) and steam reforming (SR). Equilibrium calculations employing the Gibbs free energy minimization were performed upon a wide range of pressure (1–5 atm), temperature (700–1100 K), carbon dioxide to propane ratio (CPR, 1–12) and water to propane ratio (WPR, 1–18). From a thermodynamic perspective, it is demonstrated that DR is promising for production of synthesis gas with low hydrogen content, as opposite to SR which favours generation of synthesis gas with high hydrogen content. Complete conversion of propane was obtained for the range of pressure, temperature, CPR and WPR considered in this study. Atmospheric pressure is shown to be preferable for both DR and SR. Approximately 10 mol of synthesis gas can be produced per mole of propane at a temperature greater than 1000 K from DR when CPR is higher than 6. The optimum conditions for synthesis gas production from DR are found to be 975 K (CPR = 3) for a H2/CO ratio of 1 and 1100 K (CPR = 1) for a H2/CO ratio of 2. The greatest CO2 conversion (95%) can be obtained also at 1100 K and CPR = 1. Preferential conditions for hydrogen production from SR are achieved with the temperatures between 925 and 975 K and WPRs of 12–18. The maximum number of moles of hydrogen produced is 9.1 (925 K and WPR = 18). Under conditions that favour hydrogen production, methane and carbon formation can be eliminated to negligible level.  相似文献   

16.
Thermodynamic equilibrium for glycerol steam reforming to hydrogen with carbon dioxide capture was investigated using Gibbs free energy minimization method. Potential advantage of using CaO as CO2 adsorbent is to generate hydrogen-rich gas without a water gas shift (WGS) reactor for proton exchange membrane fuel cell (PEMFC) application. The optimal operation conditions are at 900 K, the water-to-glycerol molar ratio of 4, the CaO-to-glycerol molar ratio of 10 and atmospheric pressure. Under the optimal conditions, complete glycerol conversion and 96.80% H2 and 0.73% CO concentration could be achieved with no coke. In addition, reaction conditions for coke-free and coke-formed regions are also discussed in glycerol steam reforming with or without CO2 separation. Glycerol steam reforming with CO2 adsorption has the higher energy efficiency than that without adsorption under the same reaction conditions.  相似文献   

17.
Thermodynamic investigation of glycerol reforming has been performed to study hydrogen production, carbon dioxide evolution and coke formation. Gibb's free energy direct minimization procedure was used to calculate the concentration of different components at equilibrium. The analysis was performed at temperatures from 300K to 1000K under unit atmospheric pressure. A comparative study on steam reforming of glycerol (SRG) and glycerol reforming reaction with hydrazine has been conducted in the presence of hydrazine that act as a suitable reducing agent. Incorporation of hydrazine into glycerol reforming system helped in minimizing coke formation, maximizing hydrogen and syn-gas production. A complete conversion of glycerol with coke free products, along with reduced level of carbon dioxide and maximum hydrogen generation was obtained when glycerol steam reforming process (S/G = 1) was combined with higher moles of hydrazine. Reformation at higher temperatures could enhance the hydrogen production and decrease carbon generation due to methanation reaction and hence optimum results were accomplished at 1000K and atmospheric pressure.  相似文献   

18.
In the past few years there has been a growing interest in environmentally clean renewable sources for hydrogen production. In this context new technologies have been developed for ethanol and glycerine reforming. Hydrogen production varies significantly according to the operating conditions such as pressure, temperature and feed reactants ratio. The thermodynamic analysis provides important knowledge about the effects of those variables on the process of ethanol and glycerine reforming. The present work was aimed at analyzing the thermodynamic steam reforming of ethanol and glycerine, using Gibbs free energy minimization using actual temperature and pressure data found in the literature. The nonlinear programming model was implemented in GAMS® and the CONOPT2 solver was used to solve the equations. The ideality in gaseous phase and the formation of solid carbon was considered. The methodology used reproduced the most relevant papers involving experimental studies and thermodynamic analysis.  相似文献   

19.
In this work, a methanol steam reforming (MSR) reactor was operated using an indirect heating method. A thermal circuit was constructed between the MSR reactor and the electrical heater to supply the heat required for the endothermic reaction, and deionized water was used as the heat transfer medium (HTM). The MSR reactors featured a shell-and-tube type design to operate at high pressures. A Cu/Zn catalyst was installed on the tube side, and HTM was supplied to the shell side. To improve the heat transfer performance, the heat transfer area between the shell and tube was increased from 598 to 1117 cm2. Because the MSR reactor had a sufficient heat exchange area corresponding to the catalytic reaction rate, the heat exchange area had little effect on methanol conversion. However, the heat exchange area had a greater effect on the performance because the operating temperature of reactor was lower. Under the same operating temperature conditions, the MSR reactor operated under the indirect heating method showed relatively higher methanol conversion than the MSR reactor operated in an electric furnace because of the effective heat transfer by the latent heat of saturated steam. The MSR reactor based on the indirect heating method was continuously operated at 250 °C for 72 h to verify characteristic start-up and operation. The results showed that the MSR reactor could be operated at a constant temperature; however, low methanol conversion at low operating temperatures led to slow catalyst degradation. In addition, the MSR reactor required more than 2 h for initial start-up and for restart after emergency shutdown because the HTM needed to be evaporated and pressurized to the target pressure.  相似文献   

20.
Glycerol reforming under catalytic supercritical water at temperatures in the range of 723–848 K using Co catalyst deposited on various supports including ZrO2, yttria-stabilized zirconia (YSZ), La2O3, γ-Al2O3, and α-Al2O3 was investigated. An increase in operating temperature promoted the continued increase in glycerol conversion; however, carbon formation causing system operation failure was observed for γ-Al2O3 and α-Al2O3 at high operating temperatures (i.e. 748–798 K). Co supported on YSZ provided the most efficient performance for hydrogen production. 10 wt.% Co loading on YSZ support was an optimum amount to enhance the reaction. The increase in glycerol conversion and reduction of the amount of liquid products were observed for lower weight hourly space velocity (WHSV), higher operating temperature or higher cobalt loading. On Co/YSZ catalyst, glycerol conversion of 0.94 and hydrogen yield of 3.72 was obtained with WHSV of 6.45 h−1at 773 K.  相似文献   

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