共查询到20条相似文献,搜索用时 46 毫秒
1.
Fumihiko Kosaka Toshiaki Yamaguchi Yuji Ando Takehisa Mochizuki Hideyuki Takagi Koichi Matsuoka Koji Kuramoto 《International Journal of Hydrogen Energy》2021,46(5):4116-4125
CO2 methanation has attracted considerable interests as a promising approach to productively utilizing CO2 and reducing emissions to realize a low-carbon society. One major difficulty with packed bed reactors for catalyzed CO2 methanation is maintaining an optimal reactor temperature distribution. Although a high temperature increases the catalytic activity, it also leads to the formation of an inlet hotspot, which causes thermal runaway, unfavorable equilibrium products, and catalyst degradation. To address this, in this study, we proposed an approach to manage the temperature profile in CO2 methanation reactors by increasing catalytic activity along the reactor length using different Ni composition catalysts (gradient-distributed Ni-YSZ catalyst). Ni-based tubular catalysts with different Ni compositions were prepared and stacked in order of ascending Ni content from the inlet to the outlet. The effect of gradient Ni compositions on the temperature profile was investigated based on both numerical simulations and experimental observations. The gradient-distributed Ni catalyst could successfully prevent hotspot formation at the inlet of the reactor compared to the highly active uniform catalysts. The use of the catalyst caused a small difference in the reactor temperature (of ~70 °C) and afforded a high CH4 yield (~90%). The proposed approach using gradient-distributed catalysts could be a potential method to manage CO2 methanation reactor temperature and to achieve high CO2 conversion in compact reactors. 相似文献
2.
Katarzyna Świrk Paulina Summa Dominik Wierzbicki Monika Motak Patrick Da Costa 《International Journal of Hydrogen Energy》2021,46(34):17776-17783
A series of V-promoted hydrotalcite-derived nickel catalysts (1.0, 2.0, and 4.0 wt%) were tested in CO2 methanation. Ni–I–V2.0 with 2.0 wt% vanadium loading showed the highest catalytic activity, achieving 74.7% of CO2 conversion and 100% of CH4 selectivity at 300 °C. XRD and XANES analyses showed that the smallest Ni0 particles in Ni–I–V2.0 were consistent with the improved textural features observed for this catalyst. Moreover, CO2-TPD revealed the highest sum of weak and medium basic sites in Ni–I–V2.0 that can positively influence catalytic behavior. For the studied catalysts, a clear correlation was demonstrated between the catalytic activity and specific surface area, as well as the basic properties. 相似文献
3.
Parisa Shafiee Seyed Mehdi Alavi Mehran Rezaei 《International Journal of Hydrogen Energy》2021,46(5):3933-3944
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
4.
Basem M. Al–Swai Noridah Binti Osman Anita Ramli Bawadi Abdullah Ahmad Salam Farooqi Bamidele Victor Ayodele David Onoja Patrick 《International Journal of Hydrogen Energy》2021,46(48):24768-24780
Running dry reforming of methane (DRM) reaction at low-temperature is highly regarded to increase thermal efficiency. However, the process requires a robust catalyst that has a strong ability to activate both CH4 and CO2 as well as strong resistance against deactivation at the reaction conditions. Thus, this paper examines the prospect of DRM reaction at low temperature (400–600 °C) over CeO2–MgO supported Nickel (Ni/CeO2–MgO) catalysts. The catalysts were synthesized and characterized by XRD, N2 adsorption/desorption, FE-SEM, H2-TPR, and TPD-CO2 methods. The results revealed that Ni/CeO2–MgO catalysts possess suitable BET specific surface, pore volume, reducibility and basic sites, typical of heterogeneous catalysts required for DRM reaction. Remarkably, the activity of the catalysts at lower temperature reaction indicates the workability of the catalysts to activate both CH4 and CO2 at 400 °C. Increasing Ni loading and reaction temperature has gradually increased CH4 conversion. 20 wt% Ni/CeO2–MgO catalyst, CH4 conversion reached 17% at 400 °C while at 900 °C it was 97.6% with considerable stability during the time on stream. Whereas, CO2 conversions were 18.4% and 98.9% at 400 °C and 900 °C, respectively. Additionally, a higher CO2 conversion was obtained over the catalysts with 15 wt% Ni content when the temperature was higher than 600 °C. This is because of the balance between a high number of Ni active sites and high basicity. The characterization of the used catalyst by TGA, FE-SEM and Raman Spectroscopy confirmed the presence of amorphous carbon at lower temperature reaction and carbon nanotubes at higher temperature. 相似文献
5.
《International Journal of Hydrogen Energy》2020,45(36):18411-18425
The successful synthesis of SBA-15 using silica source extracted from palm oil fuel ash (POFA) was proven with the presence of mesostructure characteristics as evidenced by low angle XRD, N2 adsorption-desorption isotherms and TEM. Different amounts of Ni were loaded on the synthesized SBA-15(POFA) using the impregnation method at 80 °C. The influence of Ni loading over the Ni/SBA-15(POFA) physiochemical properties and CO2 reforming of CH4 (CRM) were investigated in a stainless steel fixed-bed reactor at 800 °C and atmospheric pressure with 1:1 CO2:CH4 volumetric feed composition. An increment in Ni loading on SBA-15(POFA) from 1 to 5 wt% decreased the BET surface area and crystallinity of catalyst as proven by N2 adsorption–desorption and XRD analysis. The catalytic performance of CRM followed the sequence of 3 wt% > 5 wt% > 2 wt% > 1 wt% -Ni/SBA-15(POFA). This result was owing to the even distribution of Ni and good Ni–O–Si interaction of 3 wt% Ni/SBA-15(POFA) as proved by TEM, FTIR and XPS. Lowest H2/CO ratio and catalyst activity and stability of 1 wt% Ni/SBA-15(POFA) were due to the weaker Ni–O–Si interaction and small amount of basic sites that favor the reverse water gas shift (RWGS) reaction and carbon formation. The recent finding indicates that a quantity as small as 3 wt% Ni loaded onto SBA-15(POFA) could elicit outstanding catalytic performance in CRM, which was comparable with 10 wt% Ni loading catalysts reported in literature. 相似文献
6.
《International Journal of Hydrogen Energy》2023,48(39):14608-14621
Catalytic CO2 methanation is a potential solution for conversion of CO2 into valuable products, and the catalyst plays a crucial role on the CO2 conversion and CH4 selectivity. However, some details involved in the CO2 methanation over the carbon supported Ni catalysts are not yet fully understood. In this work, commercial coal char (CC) supported Ni catalysts were designed and prepared by two different methods (impregnation-thermal treatment method and thermal treatment-impregnation method) for CO2 methanation. Effects of the preparation conditions (including the thermal treatment temperature and time, the mass ratio of CC:Ni and the preparation method), as well as the reaction temperature of CO2 methanation, were investigated on the catalyst morphology, reducibility, structure and catalytic performance. Fibrous Ni-CC catalyst is achieved and shows high CO2 conversion (72.9%–100%) and CH4 selectivity (>99.0%) during the 600-min methanation process. Adverse changes of the catalyst surface and textural properties, reducibility, particle size and morphology are the potential factors leading to the catalyst deactivation, and possible solutions resistant to the deactivation were analyzed and discussed. The CO2 methanation mechanism with the CO route was proposed based on the oxidation-reduction cycle of Ni in this work. 相似文献
7.
《International Journal of Hydrogen Energy》2023,48(64):24619-24627
Ni(OH)2 and H4SiO4 are the two key intermediates for the synthesis of Ni-phyllosilicate, and the purpose of this work is to reveal which one is more efficient. The silica (D) was extracted from distillers’ grains, which was used as the sacrificial template for Ni-phyllosilicate. The formation of Ni(OH)2 and H4SiO4 was enhanced by NaOH and NH4F, respectively, and Ni/D-S (assisted by sodium hydroxide) and Ni/D-A (assisted by ammonium fluoride) were obtained. Although the amount of NaOH and NH4F and hydrothermal synthesis procedures were identical, there was a significant difference of their Ni contents. The Ni content of Ni/D-S and Ni/D-A was 17.7 wt% and 2.5 wt%, respectively. As a result, Ni/D-S was more active for CO2 methanation, whose CH4 yield reached 61.6% at 450 °C, 0.1 MPa, 60 L g−1·h−1, while the maximum CH4 yield of Ni/D-A was only 16.4% at 500 °C. However, the formation of Ni-phyllosilicate could also be improved after addition of more NH4F, and the increased amount of H4SiO4 led to the high Ni content (33.4 wt%) of Ni/D-A-M (M refers to the addition of more ammonium fluoride) and enhanced catalytic performance for CO2 methanation. It was concluded that Ni(OH)2 and H4SiO4 were both important for the synthesis of Ni-phyllosilicate, while Ni(OH)2 was the more efficient one. 相似文献
8.
The aim of this study is to investigate the promotional effect of Ce on Ni/ZSM-5 catalysts in the CO2 reforming of CH4 reaction. The evaluation of the catalytic performances of the composite catalysts was conducted in a fixed-bed reactor at atmospheric pressure. The influencing factors, including temperature, Ni and Ce loadings, molar feed ratio of CO2/CH4, and time-on-stream (TOS), were investigated. The characteristics of the catalysts were checked with Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The reduction and the basic properties of the composite catalysts were elucidated by temperature-programmed reduction by H2 (H2-TPR) and temperature-programmed desorption of CO2 (CO2-TPD), respectively. The reactivity of deposited carbon was studied by sequential temperature-programmed surface reaction of CH4 (CH4-TPSR) and temperature-programmed oxidation using CO2 and O2 (CO2-TPO and O2-TPO). Results indicate that higher CH4 conversion, H2 selectivity, and desired H2/CO ratio for 5 wt% Ni & 5 wt% Ce/ZSM-5 could be achieved with CO2/CH4 feed ratio close to unity over the temperature range of 500–900 °C. Moreover, the addition of Ce could not only promote CH4 decomposition for H2 production but also the gasification of deposited carbon with CO2. The dispersion of Ni particles could be improved with Ce presence as well. A partial reduction of CeO2 to CeAlO3 was observed from XPS spectra over 5 wt% Ni & 5 wt% Ce/ZSM-5 after H2 reduction and 24 h CO2–CH4 reforming reaction. Benefiting from the introduction of 5 wt% Ce, the calculated apparent activation energies of CH4 and CO2 over the temperature range of 700–900 °C could be reduced by 30% and 40%, respectively. 相似文献
9.
《International Journal of Hydrogen Energy》2020,45(32):16183-16192
CO2 methanation can effectively reduce the concentration of CO2 in the air and decrease environmental pollution. Therefore, it is essential to synthesize catalysts with high carbon deposition resistance and stability. Herein, the highly stabilized Ni-based catalysts derived from hydrotalcites are prepared by the self-sacrificial template method and used for CO2 methanation. The prepared Ni-based catalysts maintain the morphology of the hydrotalcites precursors and the Ni particles are embedded in the AlOx substrate. The catalyst show high performance at 350 °C, 0.1 MPa and a high space velocity of 30,000 mL g−1 h−1, with the conversion rate of CO2 and selectivity of CH4 reaching 87.5% and 100%, respectively. More importantly, the activity of catalyst does not decrease after continuous reaction for 200 h at 350 °C with different space velocities (30,000 and 60,000 mL g−1 h−1) owing to the confinement of the AlOx substrate, which suppress the undesirable agglomeration and sintering of the Ni particles. This unique mosaic structure has certain reference significance for studying materials with excellent stability at high temperatures. 相似文献
10.
《International Journal of Hydrogen Energy》2022,47(72):30830-30842
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
11.
《International Journal of Hydrogen Energy》2022,47(89):37792-37810
Dry reforming of methane (DRM) with excessive methane composition at CH4/CO2 = 1.2:1 was studied over lanthanum modified silica supported nickel catalysts (Ni-xLa-SiO2, x: 1, 2, 4, and 6% in the target weight percent of La). The catalysts were prepared by ammonia evaporation method. Nickel phyllosilicate and La2O3 were the main phases in calcined catalysts. The modification of La enhanced the formation of 1:1 and Tran-2:1 nickel-phyllosilicate. There existed an optimum content of La loading at 1.50 wt% in Ni–2La–SiO2 which resulted in its highest reduction degree (95.3%). The catalysts with appropriate amounts of La exhibited higher amount of CO2 adsorption and created more medium and strong base centers. The sufficient number of exposed metallic nickel sites to catalyze the reforming reaction, as well as enough medium and strong basic sites in Ni–La–SiO2 interface to accomplish the carbon removal were two important factors to attenuate catalyst deactivation. The catalyst stability evaluated at 750 °C for 10 h followed the order: Ni–2La–SiO2 > Ni–4La–SiO2 > Ni–1La–SiO2 ≈ Ni–6La–SiO2 > Ni–SiO2. Ni–2La–SiO2 catalyst possessed the lowest deactivation behavior, whose CH4 conversion dropped from 60.2 to 55.9% after 30 h operation at 750 °C, indicating its high resistance against carbon deposition and sintering. 相似文献
12.
Yan Xu Yingquan Wu Jing Li Shuai Wei Xinhua Gao Peng Wang 《International Journal of Hydrogen Energy》2021,46(40):20919-20929
Exploiting Ni-based catalysts with excellent low-temperature activity is significant for CO2 methanation, which is a promising route to CO2 utilization. In this work, a facile combustion-impregnation method was developed to prepare the SiO2 supported Ni catalysts. Small Ni particles (around 6 nm) and massive Ni–SiO2 interface could be obtained due to the “combustion” process. The H2-temperature programmed desorption (H2-TPD) revealed the existence of Ni–SiO2 interface and confirmed the high Ni dispersion obtained by this method, which were vital for the activation of reactant. Moreover, more medium basic sites which were beneficial for the CO2 activation could also be created. In comparison with the reference Ni/SiO2 catalyst prepared by the conventional impregnation method, much higher CO2 conversion (66.9%) and more superior selectivity to CH4 (94.1%) were achieved with the Ni/SiO2-Gly catalyst at 350 °C. Additionally, it was also found that glucose, citric acid and glycine were all effective fuels for this combustion-impregnation method, and the as-prepared catalysts all exhibited greatly improved low-temperature activity. Therefore, this work represents an important step toward developing Ni-based catalysts for CO2 methanation by a promising wide-used method. 相似文献
13.
N. Abdullah N. Ainirazali H. Ellapan 《International Journal of Hydrogen Energy》2021,46(48):24806-24813
5 wt% of Ni/SBA-15 supported with numerous Zr loading (1–7 wt%) were produced using sol-gel technique at 60 °C. The influence of Zr promoter on the physiochemical properties of Ni/SBA-15 catalysts for methane dry reforming were examined in a fixed-bed reactor at 800 °C. Analytical characterizations including XRD, BET, FTIR, N2 adsorption desorption, TEM and TGA were conducted to study the physiochemical properties of Zr/Ni/SBA-15 catalysts for the sake of identification of the amount of coke deposition formed on the spent catalyst. Increasing the amount of Zr loading from 1 to 7 wt% supported on Ni/SBA-15 reduced the catalyst's surface area as was proven from the physiochemical properties of Zr/Ni/SBA-15 catalyst. The catalytic activity test revealed that the optimum Zr loading was 1 wt% at which CH4 and CO2 conversions were 87.07% and 4.01%, meanwhile H2:CO ratios was 0.42. This result was owing to the existence of the Zr species in promoting a good dispersion of Nickel (Ni) active sites on the catalyst surface as affirmed from XRD and FTIR results. The latest discovery indicates that promotion of 1 wt% Zr onto Ni/SBA-15 can prompt excellent catalytic performance in CRM. 相似文献
14.
《International Journal of Hydrogen Energy》2020,45(17):10423-10432
A series of bi-metallic layered double hydroxide derived materials, containing a fixed amount of Ni promoted with various amounts of Fe were obtained by co-precipitation. The synthesized materials were characterized by X-ray diffraction (XRD), temperature-programmed reduction (H2-TPR), temperature-programmed desorption of CO2 (CO2-TPD), elemental analysis and low temperature N2 sorption and tested as catalysts in CO2 methanation at atmospheric pressure. The obtained results confirmed the formation of mixed nano-oxides after thermal decomposition of the precursor and suggest successful introduction of both nickel and iron into the layers of Layered Double Hydroxides (LDHs). The introduction of Fe into the layered double hydroxides changed the interaction between Ni and supports matrix as proven by temperature programmed reduction (H2-TPR). The introduction of low amount of iron influenced positively the catalytic activity in CO2 methanation at 250 °C, with CO2 conversion increasing from 21% to 72% with CH4 selectivity ranging from 97 to 99% at 250 °C. No other products, except CH4 and CO were registered during the experiments. In order to enhance the catalytic activity a non-thermal plasma created by dielectric barrier discharge was applied. The obtained results prove that plasma could replace the need of heating the reactor in a dynamic system working temporarily when excess energy is available. 相似文献
15.
Joon Yeob LeeDae-Won Lee Yoon-Ki HongKwan-Young Lee 《International Journal of Hydrogen Energy》2011,36(14):8173-8180
The goal of this study was to investigate Cr-free, Fe/Ni, metal oxide catalysts for the high temperature shift (HTS) reaction of a fuel processor using liquefied natural gas (LNG). As hexavalent chromium (Cr6+) in commercial HTS catalyst is a hazardous material, we selected Ni as a substitute for chromium in the Fe-based HTS catalyst and investigated the HTS activities of these Cr-free, metal oxide catalysts under the LNG reformate condition. Cr-free, Fe/Ni-based catalysts containing Ni instead of Cr were prepared by coprecipitation and their performance was evaluated under a gas mixture condition (56.7% H2, 10% CO, 26.7% H2O, and 6.7% CO2) that simulated the gas composition from a steam methane reformer (SMR, at H2O/CH4 ratio = 3 with 100% CH4 conversion). Under this condition, the Fe/Ni catalysts showed higher CO removal activities than Fe-only and Cr-containing catalysts, but the methanation was promoted when the Ni content in the catalyst exceeded 50 wt%. Brunner-Emmett-Teller (BET), X-ray diffraction (XRD), inductively coupled plasma (ICP) and X-ray photoelectron spectroscopy (XPS) analyses were performed to explain the HTS activity of the Fe/Ni catalysts based on the catalyst structure. 相似文献
16.
《International Journal of Hydrogen Energy》2023,48(12):4694-4707
Introducing promoters on Ni-based catalysts for CO2 methanation have been proved to be positive for enhancing their performance. And the correlation of the promotion mechanism and the reaction pathway is significant for designing efficient catalysts. In this contribution, series of Zr species promoted SBA-15 supported Ni catalysts were prepared by citric acid complexation method under a range of Zr/Ni atomic ratios from 0 to 2.5. In situ and ex situ characterizations were carried out. It was found that the addition of citric acid was conductive to improve CH4 selectivity due to the higher concentrations of Ni0 confined in SBA-15, harvesting sufficient H atoms for CH4 formation following formate pathway via a formyl intermediate. Furthermore, a coverage layer of Zr species was found on the support at Zr/Ni = 1.7, which interacted with the Ni particles, providing higher concentrations of medium basic sites for CO2 activation. Accordingly, the optimum catalytic performance was obtained on ZrNi-1.7(CI), achieving CO2 conversion as high as 78.1% and nearly 100% CH4 selectivity at 400 °C, following the formate hydrogenation pathway. In addition, the ZrNi-1.7(CI) showed good stability owing to the confinement effect of SBA-15 and the Ni–Zr interaction, no carbon deposits were detected after 50 h test. 相似文献
17.
Pd–Rh/metal foam catalyst was studied for steam methane reforming and application to SOFC fuel processing. Performance of 0.068 wt% Pd–Rh/metal foam catalyst was compared with 13 wt% Ni/Al2O3 and 8 wt% Ru/Al2O3 catalysts in a tubular reactor. At 1023 K with GHSV 2000 h−1 and S/C ratio 2.5, CH4 conversion and H2 yield were 96.7% and 3.16 mol per mole of CH4 input for Pd–Rh/metal foam, better than the alumina-supported catalysts. In 200 h stability test, Pd–Rh/metal foam catalyst exhibited steady activity. Pd–Rh/metal foam catalyst performed efficiently in a heat exchanger platform reactor to be used as prototype SOFC fuel processor: at 983 K with GHSV 1200 h−1 and S/C ratio 2.5, CH4 conversion was nearly the same as that in the tubular reactor, except for more H2 and CO2 yields. Used Pd–Rh/metal foam catalyst was characterized by SEM, TEM, BET and CO chemisorption measurements, which provided evidence for thermal stability of the catalyst. 相似文献
18.
《International Journal of Hydrogen Energy》2023,48(64):24884-24893
How to efficiently prepare nickel phyllosilicate using the calcined biomass-based silica as the sacrificial template under the mild condition is a challenge. In this work, NH4HF2, H2SiF6 and HBF4 were used as the assistor to facilitate the synthesis of Ni-phyllosilicate, which could be successfully synthesized under the mild condition of 120 °C for 12 h. Compared with NH4HF2 and H2SiF6, HBF4 was the best fluorine-containing assistor. The HBF4-assisted Ni phyllosilicate catalyst (Ni-Ps/B) exhibited the high CO2 conversion of 80.0% and CH4 selectivity of 98.3% at 450 °C due to its small particle size of 3.8 nm, high Ni content of 21.65 wt% as well as enhanced H2 and CO2 desorption capacity. The characterization results showed that HBF4 converted to B2O3 after the hydrothermal reaction and thermal treatments, which could not only provide the physical barrier for Ni species during reduction process, but also be a promoter for Ni-Ps/B for CO2 methanation. In all, HBF4 was a competitive fluorine-containing assistor for the highly efficient synthesis of Ni-phyllosilicate catalysts. 相似文献
19.
《International Journal of Hydrogen Energy》2022,47(53):22442-22453
A series of supported Ni catalysts have been prepared from NixMg3?xAl hydrotalcite-like compounds (HTlcs) and the influence of Ni:Mg molar ratio on the structural property and catalytic activity for CO2 methanation is investigated. The catalysts were characterized by N2 physical adsorption, X-ray powder diffraction (XRD), temperature-programmed reduction (H2-TPR), temperature-programmed desorption (CO2-TPD), H2 chemisorption, scanning electronic microscopy (SEM), scanning transmission electronic microscopy (STEM), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). By reducing HTlcs at 800 °C, well dispersed Ni particles with average size of 5–10 nm are formed. The Ni crystal size decreases with the decrease of Ni:Mg ratio, attributable to the strong interaction between nickel and magnesium oxides. Among the catalysts, Ni2Mg1Al-HT shows the highest activity, giving ~93% CO2 conversion and >99% CH4 selectivity at 275 °C and SV = 5000 mL g?1 h?1. Meanwhile, this catalyst exhibits good stability without obvious sintering and coking. The high activity is related to the large amount of surface Ni0 species and medium basic sites. From CO2-TPD and DRIFTS, it is inferred that CO2 adsorbs on the medium basic sites, i.e., Ni–Mg(Al)O interface, forming monodentate carbonate. In situ DRIFTS reveals that monodentate carbonate, monodentate formate, and adsorbed CO are the main intermediate species, suggesting that the reaction may proceed via the formate formation route. 相似文献
20.
《International Journal of Hydrogen Energy》2019,44(33):17750-17766
Biogas can be highlighted as a renewable raw material for the production of hydrogen. In this study, Ni-M-Al catalysts were evaluated to obtain hydrogen from the biogas reforming. The catalysts were synthesized by coprecipitation with Ni and Al with a molar percentage of 55 and 33%, respectively, varying the third component M = Mg, Li, Ca, La, Cu, Co, Zn, with a molar percentage of 11%. The reactions were carried out in a fixed bed tubular reactor using a synthetic biogas (70% of CH4 and 30% of CO2). The results showed that the CH4 conversion increased with the temperature up to 700 °C for La11, Cu11, and Zn11 catalysts. CO2 conversion increased for all catalysts in the range of 500–700 °C. The H2/CO molar ratios observed in the reactions were higher than 1 due to the contribution of the CH4 decomposition reaction. The catalyst containing La presented better stability in the reactions due to the stronger acid sites and high resistance to sintering. Carbon filaments were produced by all catalysts at 600 and 700 °C. Sintering was the main cause of deactivation of the catalysts, except for La11. 相似文献