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1.
The reverse water–gas shift chemical (RWGS) reaction is a promising technique of converting CO2 to CO at low operating temperatures, with high CO selectivity and negligible side products. In this study, we investigate the synthesis of Cu/CeO2 catalyst using Solution Combustion Synthesis (SCS) technique and its performance for the RWGS reaction using a tubular packed bed reactor. Results indicate that the catalytic activity and stability of CeO2 at low and moderate temperatures can be effectively improved by the addition of a small quantity of copper (1 wt%). The conversion of CO2 improves with an increase in temperature, with a maximum value of 70% at 600 °C, showing a steady time on stream (TOS) performance for 1200 min with negligible carbon deposition of <0.05 wt%. The high catalyst activity is due to the synergistic interaction between the active Cu0 species and Ce3+-oxygen vacancy. The Cu/CeO2 catalyst was also found to have 100% selectivity for CO, and no CH4 was detected in the outlet stream. Moreover, the morphological characteristics of the support and catalysts (fresh and post-reaction samples), as well as the impact of reaction on the catalysts surface were investigated using various methods such as x-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy with energy dispersive x-ray spectra (SEM/EDX). The results demonstrate that Cu/CeO2 offers a good potential for being a robust RWGS catalyst with exclusive selectivity for CO without the undesired methanation side-reaction.  相似文献   

2.
A series of La2O3–NiO–Al2O3 catalysts promoted by different loading of lanthanum were prepared via the hydrolysis-deposition method to improve the catalytic performance of nickel-based catalyst for CO2–CH4 reforming. The catalysts were characterized by N2 adsorption - desorption, XRD, H2-TPR, TG-DTG, TEM, Raman and TPH techniques. Results showed that the precursor of active component was mainly in the form of NiAl2O4 spinel, which almost disappeared after reduction process from XRD characterization, suggesting well reduction performance. The catalyst with La loading of 0.95 wt% (La–Ni-1) presented a small average Ni grain size of 7.71 nm and exhibited well catalytic performance at 800 °C, with CH4 conversion of 94.37%, CO2 conversion of 97.15%, H2 selectivity of 75.01% and H2/CO ratio of 0.92. The Ni grain size of La–Ni-1 increased only 5.84% to 8.16 nm after performance test, which was lower than that of others and indicated a well structure stability. Additionally, the strong carbon diffraction peak over La–Ni-0.5 and La–Ni-2 catalysts suggested the presence of crystalline carbon species accumulated on the catalysts, while there was no carbon peak over La–Ni-1 sample. A 150 h stability test for La–Ni-1 demonstrated that the conversion of CH4 was around 95%, higher than that of La–Ni-0 (without lanthanum addition) and La–Ni-4 (with La content of 3.82 wt%). The carbon deposition rate of La–Ni-1 was only 1.63 mg/(gcat·h), lower than that of La–Ni-4 (2.20 mg/(gcat·h)), showing both high activity and well stability. Therefore, the “confinement effect” of La2O3 to Ni crystalline grain would inhibit the sintering of active component, prevent the carbon deposition, and improve the catalytic reforming performance.  相似文献   

3.
The design and development of a high performance hydrogenation catalyst is an important challenge in the utilization of CO2 as resources. The catalytic performances of the supported catalyst can be effectively improved through the interaction between the active components and the support materials. The obtained results demonstrated that the oxygen vacancies and active Cu0 species as active sites can be formed in the Cu/CeO2-δ catalysts by the H2 reduction at 400 °C. The synergistic effect of the surface oxygen vacancies and active Cu0 species, and Cu0–CeO2-δ interface structure enhanced catalytic activity of the supported xCu/CeO2-δ catalysts. The electronic effect between Cu and Ce species boosted the adsorption and activation performances of the reactant CO2 and H2 molecules on the corresponding Cu/CeO2-δ catalyst. The Cu/CeO2-δ catalyst with the Cu loading of 8.0 wt% exhibited the highest CO2 conversion rate in the RWGS reaction, reaching 1.38 mmol·gcat−1 min−1 at 400 °C. Its excellent catalytic performance in the RWGS reaction was related to the complete synergistic interaction between the active species via Ce3+-□-Cu0 (□: oxygen vacancy). The Cu/CeO2-δ composite material is a superior catalyst for the RWGS reaction because of its high CO2 conversion and 100% CO selectivity.  相似文献   

4.
This work introduces LaCo1-xNixO3 (x = 0, 0.1, 0.25, and 0.4) perovskite catalysts for enhancing the low temperature performance of reverse water-gas shift (RWGS) reaction. Incorporating Ni lowers the interaction between La-site and B-site, weakening the electron donation from La-site to B-site. The B-site elements with the weak interaction can be easily diffused from the bulk to form exsolved bimetallic Co–Ni alloy on the surface. This different interaction trends further control H2 dissociation activity and CO desorption that affect CO2 conversion and CO selectivity, respectively. While the Ni-incorporated catalyst shows a higher metal dispersion to enhance H2 dissociation activity and increases CO2 conversion, the La-sites with the weak electron donation further drive the strong adsorption of CO molecules to be additionally hydrogenated, eventually lower CO selectivity. However, incorporating 10 at% Ni into the B site of LaCoO3 (LaCo0.9Ni0.1O3) achieved a balanced effect between facile H2 dissociation and CO desorption to maximize RWGS activity. The LaCo0.9Ni0.1O3 catalyst displayed outstanding activity with an average CO2 conversion of 30.8%, which is close to the equilibrium conversion, and a CO selectivity of 98.8% at 475 °C over 50 h.  相似文献   

5.
Biogas, a mixture of CO2/CH4, is reasonable for conversion to syngas (H2/CO) by dry methane reforming (DMR) reaction. The modification of Ni/SBA-16 with a lanthanum promoter using the co-impregnation technique is investigated in this study. The temperature of reaction (600–750 °C), La loading (3.85–11.56 wt%), and Ni loading (10–30 wt%) are the parameters that are varied for maximizing reaction conversions. The synthesized catalysts and SBA-16 supporting material were characterized by several methods before and after reaction. According to the analysis, the existence of La2O3 particles on the catalyst's surface has decreased the particle sizes, as well as enhanced their dispersion. Therefore, the maximum CH4 conversion of 94.21%, CO2 conversion of 90.12%, H2 yield of 90.53%, and H2/CO molar ratio of 2.03 are achieved using 20Ni-5.78La/SBA16 at 700 °C. Besides, this catalyst showed lower deposited coke and higher stability compared with other synthesized catalysts.  相似文献   

6.
Hydrogen production via steam reforming of methanol is carried out over Cu/(Ce,Gd)O2−x catalysts at 210–600 °C. The CO content in reformate is about 1% at 210–270 °C, which are the typical temperature for hydrogen production via steam reforming of methanol. Largest H2 yield and CO2 selectivity and smallest CO content are obtained at 240 °C. The formation rate of CO increases with increasing temperature. The average formation rate of CO becomes larger than that of CO2 at about 450 °C. The H2 yield, the CO2 selectivity and the CO content become constant at about 550 °C. At 240 °C, the smallest CO content is obtained with a catalyst weight of 0.5 g and a Cu content of 3 wt%. The H2 yield, defined as H2/(CO + CO2) in formation rates, at 240 °C is always 3 and not affected by the variations of either the catalyst weight or the Cu content.  相似文献   

7.
For the first time, an innovative Cu-promoted metallurgical residue (xCu/UGSO, x = 5–20 wt% Cu) was developed for the valorization of CO2 into CO. The CO2 conversion follows a volcano shape as the Cu concentration increases, reaching the peak at an optimal value estimated at 15 wt% Cu. The formation of copper ferrite spinel helps improve the dispersion of Cu and promote the conversion of CO2 to CO. The strongest synergetic effect between Cu and Fe species leads to the highest reducibility and largest ratio of Cuα/(Cuα + Cu2+) in the 15Cu/UGSO catalyst, which could explain its highest CO2 conversion. As a result, CO2 conversion of 36.1% and CO selectivity of 99.3% are obtained at 400 °C and atmospheric pressure, which surpass the catalytic performance of some literature-reported Cu-based catalysts in the same reaction conditions.  相似文献   

8.
Carbon dioxide (CO2) and methane (CH4) are the primary greenhouse gases (GHGs) that drive global climate change. CO2 reforming of CH4 or dry reforming of CH4 (DRM) is used for the simultaneous conversion of CO2 and CH4 into syngas and higher hydrocarbons. In this study, DRM was investigated using Ag–Ni/Al2O3 packing and Sn–Ni/Al2O3 packing in a parallel plate dielectric barrier discharge (DBD) reactor. The performance of the DBD reactor was significantly enhanced when applying Ag–Ni/Al2O3 and Sn–Ni/Al2O3 due to the relatively high electrical conductivity of Ag and Sn as well as their anti-coke performances. Using Ag–Ni/Al2O3 consisting of 1.5 wt% Ag and 5 wt% Ni/Al2O3 as the catalyst in the DBD reactor, 19% CH4 conversion, 21% CO2 conversion, 60% H2 selectivity, 81% CO selectivity, energy efficiency of 7.9% and 0.74% (by mole) coke formation were achieved. In addition, using Sn–Ni/Al2O3, consisting of 0.5 wt% Sn and 5 wt% Ni/Al2O3, 15% CH4 conversion, 19% CO2 conversion, 64% H2 selectivity, 70% CO selectivity, energy efficiency of 6.0%, and 2.1% (by mole) coke formation were achieved. Sn enhanced the reactant conversions and energy efficiency, and resulted in a reduction in coke formation; these results are comparable to that achieved when using the noble metal Ag. The decrease in the formation of coke could be correlated to the increase in the CO selectivity of the catalyst. Good dispersion of the secondary metals on Ni was found to be an important factor for the observed increases in the catalyst surface area and catalytic activities. Furthermore, the stability of the catalytic reactions was investigated for 1800 min over the 0.5 wt% Ag-5 wt% Ni/Al2O3 and 0.5 wt% Sn-5 wt% Ni/Al2O3 catalysts. The results showed an increase in the reactant conversions with an increase in the reaction time.  相似文献   

9.
The catalytic effects of CO preferential oxidation and methanation catalysts for deep CO removal under different operating conditions (temperature, space velocity, water content, etc.) are systematically studied from the aspects of CO content, CO selectivity, and hydrogen loss index. Results indicate that the 3 wt% Ru/Al2O3 preferential oxidation catalysts reduce CO content to below 10 ppm with a high hydrogen consumption of 11.6–15.7%. And methanation catalysts with 0.7 wt% Ru/Al2O3 also exhibit excellent CO removal performance at 220–240 °C without hydrogen loss. Besides, NiClx/CeO2 methanation catalysts possess the characteristics of high space velocity, high activity, and high water-gas resistance, and can maintain the CO content at close to 20 ppm. Based on these experimental results, the coupling scheme of combining NiClx/CeO2 methanation catalysts (low cost and high reaction space velocity) with 0.7 wt% Ru/Al2O3 methanation catalysts (high activity) to reduce CO content to below10 ppm is proposed.  相似文献   

10.
A series of xMnCu/Ce catalysts with constant low Cu loading of 1 wt% were prepared by the simple impregnation method. The obtained catalysts were characterized by XRD, BET, H2-TPR and XPS, and the preferential oxidation of CO was evaluated in CO2/H2-rich atmospheres. It was shown that partial Mn and Cu could be incorporated into the Ceria lattice, forming surface ternary Cu–Mn–Ce oxide solid solutions. At Mn/Cu = 0.6, the catalyst presented strong interaction among Cu, Mn and Ce, had more Ce3+ and Mn4+ at the surface and showed the best catalytic performance, making CO conversion increase of 23.57% at 90 °C as compared with the Cu/Ce catalyst. For CO-Prox, the highest CO conversion was 94.7% with an oxidation selectivity of 78.9% at 125 °C. At this temperature, the catalyst revealed stable catalytic performance for a total TOS of 205 h. In addition, with CO/Ar as feed gas, CO conversion was 100%, confirming the negative effects of CO2/H2.  相似文献   

11.
Hydrogen (H2) production in a clean and green manner via renewable sources is at present of great interest. Ethylene glycol, a bio-based feedstock, offers a sustainable route for high purity H2 production. In the current investigation, MgO based mixed metal oxides containing CeO2, La2O3 and ZrO2 were synthesized and used to support 20 wt% Ni–Cu (1:1). The impacts of altering support characteristics on catalytic behavior have been studied and compared in H2 synthesis via ethylene glycol steam reforming (SR), employing various characterization techniques such as XRD, SEM, EDX, TEM, H2-TPR, H2-TPD, TG-DSC and BET. Further, high resolution XPS studies were performed to explore the valence states and effectiveness of surface engineering of the catalysts. Assessment of the efficacy of catalysts was done via several parameters such as reactant conversion, H2 concentration and long-term stability. All the synthesized materials produced encouraging results with high H2 yield and conversion under the said operating conditions [T- 623 to 773 K; GHSV - 3120 to 6240 h?1; P - 0.1 MPa; S/C - 3 to 7.5 mol/mol]. Amongst the three catalysts, Ni–Cu/La2O3–MgO and Ni–Cu/CeO2–MgO exhibited superior behavior for high H2 production. Ni–Cu/La2O3–MgO was better in comparison to Ni–Cu/CeO2–MgO in terms of reactant conversion whereas Ni–Cu/CeO2–MgO showed highest H2 concentration (98 mol %) and improved stability along with absence of carbon deposition owing to its high mobile oxygen vacancies in its lattice. The highly active cubic CeO2 species and its long-term durability (up to 8 cycles) owing to its exceptional redox property further justified its efficacy. The optimized process showed that at T = 773 K, GHSV = 3120 h?1, S/C = 4.5 mol/mol for Ni–Cu/La2O3–MgO and Ni–Cu/CeO2–MgO and at T = 773 K, GHSV = 3120 h?1, S/C = 6 mol/mol and for Ni–Cu/ZrO2–MgO, maximum H2 concentration was obtained. At the end, reaction pathway followed by the catalysts was proposed.  相似文献   

12.
This review aims to provide an overview of the main catalytic studies of H2 production by ethanol steam reforming (ESR). The reaction is endothermic and produces H2, CO2, CH4, CO and coke. The conversion and H2 selectivity of these products depended greatly of the physicochemical properties of the catalysts, active metal, promoters, temperature, long-term reaction, water/ethanol ratio, space velocity, contact time, and presence of O2. Initial total conversion has been reported in all catalysts evaluated between 300 and 850 °C. The noble catalysts with high selectivity to H2 (more than 80%) were: Rh, Ru, Pd and Ir and non-noble metal catalysts were: Ni, Co and Cu. The support materials include CeO2, ZnO, MgO, Al2O3, zeolites-Y, TiO2, SiO2, La2O2CO3, CeO2–ZrO2 and hydrotalcites. The impregnation method produced the best noble metal catalysts in terms of selectivity and conversion. The decrease of coke was related with the presence of basic sites on the support.  相似文献   

13.
In this study, a simple solid-state synthesis method was employed for the preparation of the Ni–Co–Al2O3 catalysts with various Co loadings, and the prepared catalysts were used in CO2 methanation reaction. The results demonstrated that the incorporation of cobalt in nickel-based catalysts enhanced the activity of the catalyst. The results showed that the 15 wt%Ni-12.5 wt%Co–Al2O3 sample with a specific surface area of 129.96 m2/g possessed the highest catalytic performance in CO2 methanation (76.2% CO2 conversion and 96.39% CH4 selectivity at 400 °C) and this catalyst presented high stability over 10 h time-on-stream. Also, CO methanation was investigated and the results showed a complete CO conversion at 300 °C.  相似文献   

14.
The selective oxidation of CO in the presence of H2 was investigated on Au catalysts promoted with different amounts of Cu. Au catalysts were prepared by the deposition–precipitation method and exhibited a satisfactory activity at low temperature with adequate selectivity. A considerable improvement in CO conversion was achieved when the O2/CO ratio was increased from the value of 0.5–1.0. The addition of Cu to Au/Al2O3 catalysts caused an increase in the selectivity to CO oxidation due to an interaction between Au and Cu on the surface of the catalysts. However, this beneficial effect was limited to an optimal content of Cu. The catalysts were characterized by temperature programmed reduction and DRS UV–vis spectroscopy, indicating the formation of small bimetallic Au–Cu particles. The presence of water vapor in the feed stream played a positive effect in the CO conversion and selectivity while the CO2 presence diminished the CO conversion and selectivity. In the case of a realistic reformate, when both H2O and CO2 are present, the positive effect of H2O was able to compensate the negative effect of CO2 depending on the temperature of reaction.  相似文献   

15.
A comparative study of 10 wt% Co-based catalysts supported on La2O3, AlZnOx and AlLaOx was performed for glycerol steam reforming (GSR). The catalysts physicochemical characterization was done through several techniques. All catalysts were screened in terms of catalytic activity and time-on-stream stability for GSR. The catalytic activity experiments aimed to assess the effect of temperature (400–700 °C) on the glycerol conversion and yield of gaseous products (H2, CO2, CO and CH4). Additionally, catalytic stability experiments were conducted at 625 °C to investigate deactivation of the catalysts, in which a drop in the activity was observed, especially for Co/La2O3. The glycerol conversion into gaseous products as a function of the time-on-stream was more affected for all catalysts in comparison to total glycerol conversion, being this effect assigned to the increase in the formation of liquid products and to the formation of coke. CoAlLaOx was observed to be more carbon-resistant, followed by CoAlZnOx, through the measurement of the quantity of carbonaceous species formed during the GSR experiments. A NiAlLaOx catalyst was also prepared and assessed in terms of catalytic stability for GSR; a stable behavior was observed throughout all experiment in relation to glycerol conversion into gaseous products and H2 yield.  相似文献   

16.
Ethanol steam reforming is a promising reaction which produces hydrogen from bio and synthetic ethanol. In this study, the nano-structured Ni-based bimetallic supported catalysts containing Cu, Co and Mg were synthesized through impregnation method and characterized by XRD, BET, SEM, TPR and TPD analysis. The prepared catalysts were tested in steam reforming of ethanol in the S/C = 6, GHSV of 20,000 mL/(gcat h) at the temperature range of 450–600 °C. Among the xNi/CeO2 (x = 10, 13, 15 wt%) catalyst, the sample containing 13 wt% Ni with surface area of 64 m2/g showed the best performance with 89% ethanol conversion and 71% H2 selectivity as well as low CO selectivity of 8% at 600 °C and The addition of Cu, Mg, and Co to catalyst structure were evaluated and it was found that the nature of second metal has a strong influence on the catalyst selectivity for H2 production. Considering to results of TPR analysis, the 13Ni–4Cu/CeO2 catalyst showed proper reduction which caused in better activity. On the other side based on TPD analysis, the more basic property of 13Ni–4Mg/CeO2 bimetallic catalyst provided a better condition to methane steam reforming, leading to lower CH4 selectivity and consequently more H2 production. The 13Ni–4Cu/CeO2 exhibited the highest activity and lowest selectivity towards ethanol conversion and CO production about 99% and 4%, while the 13Ni–4Mg/CeO2 catalyst possessed the highest H2 selectivity and lowest CH4 selectivity about 74% and 1% respectively at 600 °C. The Ni–Cu and Ni–Mg bimetallic catalysts shows good stability with time on stream.  相似文献   

17.
Copper–ceria catalysts with three different Cu loadings (1, 7 and 15 wt%) were prepared by incipient wet impregnation, dried at 120 °C and calcined in air at 500 °C. The as-prepared catalysts were characterized by XRD, BET, Diffuse Reflectance Spectroscopy (DRS–UV–visible), Raman spectroscopy, CO and H2-TPR, CO-TPR, CO-TPD and Oxygen Storage Capacity (OSC) measurements (with CO and O2 concentration step-changes). The results indicated a good dispersion of copper for catalysts with 1 and 7 wt% Cu; however, bulk CuO was present for catalyst with 15 wt% Cu loading. Catalyst with 7 wt% Cu was observed to have very high capacity to release lattice oxygen to oxidize CO at low temperature. Activity results for CO oxidation in the absence and in the presence of 60% H2, demonstrated a very similar performance for catalysts with 7 and 15 wt% Cu (both with T100 = 112 °C), and much better than that of catalyst loaded with 1 wt% Cu. Catalyst with 7 wt% of copper shows very high activity (100% in a wide temperature window) and selectivity (higher than 85%), which makes an attractive for its use in purification of hydrogen for fuel cell applications. The presence of a mixture of CO2 and H2O inhibited catalyst activity, with CuO/CeO2 catalyst with 7 wt% Cu exhibiting the best performance in the overall reaction temperature range. This could be attributed to the presence of highly disperse copper, only part of it in deep interaction with ceria. The effect of O2/CO ratio (λ) and the potential reversibility of the inhibitory effect of CO2 and H2O were also investigated.  相似文献   

18.
Hydrogen is an ideal energy carrier and can play a very important role in the energy system. The present study investigated the enhancement of hydrogen production from catalytic dry reforming process. Two catalysts namely Ni/γ-Al2O3 and Co/γ-Al2O3 promoted with different amounts of strontium were used to explore selectivity and yield of hydrogen production. Spent and fresh catalysts were characterized using techniques such as BET, XRD, H2-TPR, CO2-TPD, TGA and O2-TPO. The catalyst activity and characterization results displayed stability improvement due to addition of Sr promoter. The least coke formations i.e. 3.8 wt% and 5.1 wt% were obtained using 0.75 wt% Sr doped in Ni/γ-Al2O3 and 0.5 wt% Sr doped in Co/γ-Al2O3 catalysts respectively. Time on stream tests of promoted catalysts for about six hours at 700 °C showed stable hydrogen selectivity. Moreover, the hydrogen selectivity was significantly improved by the addition of Sr in Ni and Co based catalysts. For instance the hydrogen selectivity increased from 45.9% to 47.8% for Ni/γ-Al2O3 and from 48% to 50.9% for Co/γ-Al2O3 catalyst by the addition of 0.75 wt% Sr in Ni/γ-Al2O3 and 0.5 wt% Sr in Co/γ-Al2O3 catalyst respectively.  相似文献   

19.
《能源学会志》2020,93(6):2544-2549
Hydrogen-rich syngas was successfully produced from catalytic steam gasification of petroleum coke. This work studied the steam gasification of petroleum coke over KOH, K2CO3, KNO3, CaO, Fe2O3, K2CO3–CaO and K2CO3–Fe2O3 in a pressurized fixed bed. KOH and K2CO3 demonstrated good catalytic activity compared with other catalysts. The carbon conversion efficiency (CCE) increased from 14.7 wt% to 61.4 wt% and 87.9 wt% after adding 10 wt% K2CO3 and 10 wt% KOH, respectively, and H2 content increased from 60.9 vol% to 66.7 vol% and 64.2 vol%. The increase of gasification temperature and pressure resulted in the increase of CCE. However, raising temperature was beneficial to the increase of H2 and CO contents, while the elevated pressure was in favor of the formation of CH4. In addition, the K-catalytic steam gasification of petroleum coke accorded with the oxygen transfer and intermediate hybrid mechanism.  相似文献   

20.
In this study, methane and methanol steam reforming reactions over commercial Ni/Al2O3, commercial Cu/ZnO/Al2O3 and prepared Ni–Cu/Al2O3 catalysts were investigated. Methane and methanol steam reforming reactions catalysts were characterized using various techniques. The results of characterization showed that Cu particles increase the active particle size of Ni (19.3 nm) in Ni–Cu/Al2O3 catalyst with respect to the commercial Ni/Al2O3 (17.9). On the other hand, Ni improves Cu dispersion in the same catalyst (1.74%) in comparison with commercial Cu/ZnO/Al2O3 (0.21%). A comprehensive comparison between these two fuels is established in terms of reaction conditions, fuel conversion, H2 selectivity, CO2 and CO selectivity. The prepared catalyst showed low selectivity for CO in both fuels and it was more selective to H2, with H2 selectivities of 99% in methane and 89% in methanol reforming reactions. A significant objective is to develop catalysts which can operate at lower temperatures and resist deactivation. Methanol steam reforming is carried out at a much lower temperature than methane steam reforming in prepared and commercial catalyst (275–325 °C). However, methane steam reforming can be carried out at a relatively low temperature on Ni–Cu catalyst (600–650 °C) and at higher temperature in commercial methane reforming catalyst (700–800 °C). Commercial Ni/Al2O3 catalyst resulted in high coke formation (28.3% loss in mass) compared to prepared Ni–Cu/Al2O3 (8.9%) and commercial Cu/ZnO/Al2O3 catalysts (3.5%).  相似文献   

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