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1.
《International Journal of Hydrogen Energy》2019,44(31):16516-16525
In this article mesoporous nanocrystalline 5 wt%M-95 wt%MgAl2O4 (M: CeO2, ZrO2, La2O3) powders were prepared by a novel on-step sol-gel process and employed as a support for the synthesis of 5 wt%Ni catalysts for synthesis gas production via dry reforming. The magnesium aluminate spinel prepared with this sol-gel method possessed a high BET area of 264 m2 g−1 with a high pore volume of 0.436 cm3 g−1. The results indicated that the addition of promoters (CeO2, ZrO2, La2O3) to magnesium aluminate improved the BET area and pore volume and also decreased the crystallite size. Among the prepared powders and catalysts, 5 wt%La2O3-95 wt%MgAl2O4 and 5 wt%Ni/5 wt%CeO2-95 wt%MgAl2O4 exhibited the highest BET area of 306 m2 g−1 and 263 m2 g−1, respectively. The catalytic results indicated that the 5 wt%Ni/5 wt%CeO2-95 wt%MgAl2O4 catalyst exhibited the highest activity and the lowest carbon formation among the prepared catalysts with the same content of the promoter. The influence of the CeO2 content on the textural and catalytic performance was also investigated and the results illustrated that the increment in CeO2 content improved the methane conversion and reduced the amount of deposited carbon, which could be related to the redox properties of the catalyst support. 相似文献
2.
Abdulkader Albarazi Patricia Beaunier Patrick Da Costa 《International Journal of Hydrogen Energy》2013
In this work, the effects of doping Ni-based SBA-15 catalysts with Ceria–Zirconia mixed oxide (CZ) on the activity and stability of these catalysts during syngas production by methane dry reforming (MDR) were investigated and compared with the activity and stability of unmodified Ni/SBA-15. The above catalysts were prepared by incipient wetness impregnation (IWI) with different impregnation strategy. The samples were characterized by nitrogen physisorption, X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), temperature programmed reduction (TPR) and H2 chemisorption. The results indicated that the unmodified Ni/SBA-15 showed clear deactivation especially in the first period of the stability test and between 600 °C and 630 °C during the activity test whereas the CZ modified samples had better stability. 相似文献
3.
《International Journal of Hydrogen Energy》2020,45(15):8418-8432
Three Ni/CeZrO2/MgAl2O4 catalysts synthesized using different Zr/Ce molar ratios (0.25, 1, and 4) were studied for methane tri-reforming. The catalysts were characterized using XRD, 27Al-NMR, H2-TPR, CO2-TPD, XPS, and in situ techniques (XPD and XANES). The addition of CeZrO2 at Zr/Ce = 0.25 on the MgAl2O4 spinel support considerably reduced the amount of carbon deposits, because the methane decomposition reaction was attenuated by the presence of less agglomerated Ni0 species produced after the reduction process. The highest CO2 adsorption capacity (basicity) was associated with the participation of medium-strength basic sites, which facilitated coke gasification and led to higher CO2 conversions. A syngas with quality (H2/CO ratio) of 1.8 was produced, suitable for use in Fischer-Tropsch reactions. 相似文献
4.
The aqueous-phase reforming (APR) of n-butanol (n-BuOH) over Ni(20 wt%) loaded Al2O3 and CeO2 catalysts has been studied in this paper. Over 100 h of run time, the Ni/Al2O3 catalyst showed significant deactivation compared to the Ni/CeO2 catalyst, both in terms of production rates and the selectivity to H2 and CO2. The Ni/CeO2 catalyst demonstrated higher selectivity for H2 and CO2, lower selectivity to alkanes, and a lower amount of C in the liquid phase compared to the Ni/Al2O3 sample. For the Ni/Al2O3 catalyst, the selectivity to CO increased with temperature, while the Ni/CeO2 catalyst produced no CO. For the Ni/CeO2 catalyst, the activation energies for H2 and CO2 production were 146 and 169 kJ mol−1, while for the Ni/Al2O3 catalyst these activation energies were 158 and 175 kJ mol−1, respectively. The difference of the active metal dispersion on Al2O3 and CeO2 supports, as measured from H2-pulse chemisorption was not significant. This indicates deposition of carbon on the catalyst as a likely cause of lower activity of the Ni/Al2O3 catalyst. It is unlikely that carbon would build up on the Ni/CeO2 catalyst due to higher oxygen mobility in the Ni doped non-stoichiometric CeO2 lattice. Based on the products formed, the proposed primary reaction pathway is the dehydrogenation of n-BuOH to butaldehyde followed by decarbonylation to propane. The propane then partially breaks down to hydrogen and carbon monoxide through steam reforming, while CO converts to CO2 mostly through water gas shift. Ethane and methane are formed via Fischer-Tropsch reactions of CO/CO2 with H2. 相似文献
5.
《International Journal of Hydrogen Energy》2019,44(28):14303-14315
Syngas production via dry reforming of methane (DRM) was experimentally investigated using Ni-based catalyst. Ni/Al2O3 modification with CeO2 addition and O2 addition in the reactant were employed in this study to suppress carbon deposition and to enhance catalyst activity. It was found that DRM performance can be enhanced using CeO2 modified Ni/Al2O3 catalyst due to CeAlO3 formation. However, an optimum amount of CeO2 loading exists to obtain the best DRM performance due to the decrease in specific surface area as the CeO2 loading increases. Without O2 addition, the reverse water-gas shift reaction plays an important role in DRM. It was found that CH4 conversion and CO yield were enhanced while CO2 conversion and H2 yield are decreased as the CO2 amount in feedstock increased in DRM. With O2 addition in the fed reactant, it was found that the methane oxidation reaction plays an important role in DRM. CH4 conversion can be enhanced by O2 addition. However, decreases in CO2 conversion and H2 and CO yields occurred due to greater H2O and CO2 productions from the methane oxidation reaction. The thermogravimetric analysis (TGA) results showed that CeO2 modified Ni/Al2O3 catalyst would have the lowest amount of carbon deposition when O2 is introduced into the reaction. 相似文献
6.
Zahra Taherian Mardali Yousefpour Mohammad Tajally Behnam Khoshandam 《International Journal of Hydrogen Energy》2017,42(39):24811-24822
Methane reforming with CO2 over Samaria-promoted Ni and Co/SBA-15 was comparatively investigated. The Co, Ni (10%wt) and Sm (0.5, 1 and 1.5%wt) ions were introduced by two-solvent impregnation method. The Ni and Co catalysts with/without promoter, were examined by N2 adsorption-desorption, x-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), temperature programmed reduction (TPR) and thermogravimetric analysis (TGA) methods, and then evaluated in CO2 reforming of methane. The XRD and TEM results indicated that Ni and Co/SBA-15 promoted by 1%wt of Samaria, had the smallest NiO and Co3O4 particles size and the highest dispersion; as a result, they would rather studying dry reforming of methane test. Catalytic results indicated that Samaria promoted Ni/SBA-15 had the highest conversion (CH4 conversion~58% at 700 °C), while a remarkable decrease of catalytic activity was observed over Samaria-promoted Co/SBA-15 (CH4 conversion~25% at 700 °C). The positive effect of Samaria on Ni/SBA-15 catalyst activity is probably due to smaller NiO particles, higher NiO dispersion and lower trend to carbon deposition. On the contrary, the negative effect of Samaria on Co/SBA-15 catalyst activity is maybe due to Co oxidation to inactive phase and sintering of Co particles in high temperatures. 相似文献
7.
《International Journal of Hydrogen Energy》2019,44(37):20857-20871
The present work investigates the performance of Re-promoted Nickel-based catalyst supported on calcium oxide for glycerol dry reforming reaction. The catalysts were prepared using wet impregnation method and their catalytic performance was tested in a packed bed reactor with CO2 to glycerol ratio (CGR) of 1–5, reaction temperature of 600–900 °C and gas hourly specific velocity (GHSV) of 1.44 × 104–7.20 × 104 ml gcat−1 s−1. The optimum operating temperature for both Ni/CaO and ReNi/CaO is 800 °C, with the GHSV of 3.6 × 104 mL gcat−1s−1. The optimum CGR for Ni/CaO and ReNi/CaO is 1.0 and 3.0, respectively. At this condition, hydrogen gas is directly produced from glycerol decomposition and indirectly from water-gas-shift reaction. After 2 h at the optimum conditions, 5% ReNi/CaO gives optimal glycerol conversion and hydrogen yield of approximately 61% and 56%, respectively, while in comparison to 15% Ni/CaO, the conversion and yield are 35 and 30%, respectively. Characterization of the spent catalysts showed the existence of whisker carbon from the CO2 hydrogenation and methanation processes. By comparing to 15% Ni/CaO, the addition of Re increases the acidic sites of the catalyst and enhanced the surface adsorption of OH group of the glycerol. The adsorbed glycerol on the catalyst surface would further react with the adsorbed CO2 to yield gases products. Thus, the catalytic activity improved significantly. 相似文献
8.
《International Journal of Hydrogen Energy》2022,47(97):41294-41309
Fine-tuning of materials properties, particularly the catalytic properties, through innovative synthesis procedures has gained an increased research interest in the last decades. It is well known that synthesis procedures have considerable impact on the physio-chemical properties of the synthesized materials even if the chemical composition is maintained. Herein, we investigated the impact of selected synthesis methods on the catalytic performance of Ni/La2O3 for the dry reforming of methane (DRM), a challenging reaction known for severe coking. Although this catalyst has been frequently studied for DRM, however, tuning the structure-activity relationship by varying the synthesis routes has not been reported. Herein, the chosen synthesis techniques; for example the solution combustion synthesis (Ni/La-SC), sol-gel (Ni/La-SG), homogeneous precipitation (Ni/La-HP), solvothermal (Ni/La-ST), and modified oleylamine-assisted synthesis (Ni/La-ME); considerably affected the morphology, metal support interaction (MSI), and surface area of Ni/La2O3 catalysts leading to variation in their performance for DRM. The investigated catalysts were thoroughly characterized by using SEM-EDX, TEM, N2-physisorption, XRD, XPS, and H2-TPR to understand the structural properties. Their catalytic performance towards the DRM was evaluated by varying the temperature between 550 and 800 °C. DRM experiments demonstrated that among the studied catalysts, Ni/La-SC showed the best performance for DRM with a high catalytic activity and coking resistance. For instance, Ni/La-SC revealed the highest CO2 and CH4 conversions i.e. 97.9 ± 1.5% and 96.6 ± 1.8%, respectively at 800 °C. The same sample revealed the highest hydrogen yield i.e. 71.9% and the highest H2/CO ratio i.e. 1.03 ± 0.013 at the same temperature. The results revealed that Ni/La-SC demonstrated the lowest increment (20.9%) in the Ni crystallite size after DRM reaction, highest durability, and the lowest rate of coke formation (42 ± 5.2 mg C/gcatalyst) over an operating period of 100 h at 800 °C. The outstanding performance of Ni/La-SC catalyst was credited to the small crystallite size of Ni, high Ni0/Ni2+ ratio, high BET area, and a good dispersion of nickel sites over the La2O3 support. The obtained results may open new frontiers for size and shape-controlled synthesis of nanostructured metals/metal oxides catalysts with controllable morphologies and dispersion that can lead to desirable catalytic properties. 相似文献
9.
《International Journal of Hydrogen Energy》2019,44(37):20738-20750
Dry reforming of methane to produce hydrogen-rich syngas is widely studied, where the productivity of the reaction is greatly dependent on the activity and stability of the catalyst. In this investigation, a binary catalyst support consisting of a SiO2CeO2 combination was developed to produce an efficient catalyst support with high resistance to carbon deposition during the reaction. Four different preparation methods (deposition-precipitation, DP; impregnation, IMP; sol-gel, SG; and ball milling, BM) were used to synthesize SiO2CeO2 supports, and 5 wt % nickel was added to the support via wet impregnation. The catalyst performance was recorded in the order: Ni/CS-DP ˃ Ni/CS-IMP ˃ Ni/CS-BM ˃ Ni/CS-SG at 800 °C for 10 h reaction with a CH4/CO2 feed-gas composition ratio of 1:1. Ni/CS-DP was seen to be the most promising catalyst, exhibiting H2 and CO selectivities of ∼95% and ∼73%, respectively, with a H2/CO ratio of >1:1, and maintaining 97% CH4 conversion up to 10 h of reaction with very low coke deposition. The superior catalytic performance of Ni/CS-DP was achieved as a result of the synergistic effects of high basicity and low reducibility, which was achieved via direct alteration during the preparation of the support. 相似文献
10.
《International Journal of Hydrogen Energy》2019,44(50):27429-27444
The Ni/pillared-bentonite catalysts with high BET area were synthesized and used in dry reforming reaction. The effects of different parameters such as calcination temperature, OH−/Al3+ ratio, temperature and time of pillaring process and the content of nickel on the textural and catalytic properties of the synthesized catalysts were studied. The results indicated that the 15 wt% Ni catalyst supported on pillared bentonite prepared under specified conditions (OH−/Al3+ = 2.2, pillaring temperature of 40 °C and pillaring time of 3 h) possessed the highest BET area (90.80 m2/g). Also, this catalyst possessed higher catalytic activity and stability with lower amount of deposited carbon in comparison to other prepared catalysts in methane reforming with CO2. 相似文献
11.
M.A. Goula N.D. Charisiou G. Siakavelas L. Tzounis I. Tsiaoussis P. Panagiotopoulou G. Goula I.V. Yentekakis 《International Journal of Hydrogen Energy》2017,42(19):13724-13740
The catalytic efficiency and bench scale time on steam stability of Ni dispersed on three commercially available catalytic supports (ZrO2, La2O3–ZrO2 and CeO2–ZrO2) has been studied for the dry reforming of methane (DRM) in the temperature range of 500–800 °C and a CH4/CO2 ratio equal to 1.5, simulating typical biogas quality. Ni supported on LaZr and CeZr carriers that obeyed enhanced basicity and oxygen ion lability values than Zr, exhibited superior catalytic efficiency and stability. A variety of techniques, namely N2 physisorption-desorption (BET method), powder X-ray diffraction (XRD), hydrogen temperature programmed reduction (H2-TPR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, potentiometric titration and inductively coupled plasma emission spectroscopy (ICP), were applied for the characterization of particles morphology, textural, structural and other physical properties of the materials, as well as the type of carbon deposited on the catalytic surface after exposure to DRM reaction conditions. Post-reaction analysis of the deposited carbon on the catalysts surfaces showed that the prominent trend of the carbon deposits on the Ni/Zr and Ni/LaZr samples was to have a filamentous tube like morphology (graphite-2H). In contrast, on the Ni/CeZr used catalyst, the formation of small amount of carbon tube-like architectures was detected. The enhanced basicity and Ni dispersion of the Ni/LaZr and Ni/CeZr samples as well as the high oxygen ion lability of the lattice oxygen in the latter, were considered to be the major factors involved in the superior efficiency and durability of these samples in comparison to Ni/Zr sample. 相似文献
12.
Min Hye Youn Jeong Gil SeoSunyoung Park Ji Chul JungDong Ryul Park In Kyu Song 《International Journal of Hydrogen Energy》2008
Zirconia supports were prepared by a sol–gel method (S-ZrO2) and by a templating sol–gel method (M-ZrO2). Nickel catalysts supported on zirconia were then prepared by an incipient wetness impregnation method for use in hydrogen production by auto-thermal reforming of ethanol. For comparison, a commercial zirconia (C-ZrO2) was also employed as a support for nickel catalyst. The effect of preparation method of zirconia on the catalytic property and catalytic performance of supported nickel catalysts (Ni/C-ZrO2, Ni/S-ZrO2, and Ni/M-ZrO2) was investigated. The crystalline and physical property of zirconia supports and the catalytic performance of supported nickel catalysts were strongly affected by the preparation method of zirconia. BET surface area and pore volume were decreased in the order of M-ZrO2 > S-ZrO2 > C-ZrO2. Both M-ZrO2 and S-ZrO2 supports showed only tetragonal phase of ZrO2, while C-ZrO2 support exhibited tetragonal and monoclinic phases of ZrO2. Crystalline size of nickel species in the Ni/ZrO2 catalysts decreased with increasing surface area and pore volume of ZrO2 supports. All the Ni/ZrO2 catalysts exhibited 100% conversion of ethanol at 500 °C, while product distributions over the Ni/ZrO2 catalysts were different depending on the preparation method of zirconia. Among the catalysts tested, the Ni/M-ZrO2 catalyst showed the best catalytic performance in hydrogen production by auto-thermal reforming of ethanol. Well developed mesopore, high surface area, and pure tetragonal phase of ZrO2 were responsible for fine nickel dispersion and high catalytic performance of Ni/M-ZrO2. C–C bond cleavage reaction and methane steam reforming reaction were also accelerated over the Ni/M-ZrO2 catalyst. 相似文献
13.
P.K. Seelam M. Huuhtanen A. Sápi M. Szabó K. Kordás E. Turpeinen G. Tóth R.L. Keiski 《International Journal of Hydrogen Energy》2010
Hydrogen production by steam reforming of ethanol (SRE) was studied using steam-to-ethanol ratio of 3:1, between the temperature range of 150–450 °C over metal and metal oxide nanoparticle catalysts (Ni, Co, Pt and Rh) supported on carbon nanotubes (CNTs) and compared to a commercial catalyst (Ni/Al2O3). The aim was to find out the suitability of CNTs supports with metal nanoparticles for the SRE reactions at low temperatures. The idea to develop CNT-based catalysts that have high selectivity for H2 is one of the driving forces for this study. The catalytic performance was evaluated in terms of ethanol conversion, product gas composition, hydrogen yield and selectivity to hydrogen. The Co/CNT and Ni/CNT catalysts were found to have the highest activity and selectivity towards hydrogen formation among the catalysts studied. Almost complete ethanol conversion is achieved over the Ni/CNT catalyst at 400 °C. The highest hydrogen yield of 2.5 is, however, obtained over the Co/CNT catalyst at 450 °C. The formation of CO and CH4 was very low over the Co/CNT catalyst compared to all the other tested catalysts. The Pt and Rh CNT-based catalysts were found to have low activity and selectivity in the SRE reaction. Hydrogen production via steam reforming of ethanol at low temperatures using especially Co/CNT catalyst has thus potential in the future in e.g. the fuel cell applications. 相似文献
14.
Shima Valinejad Moghaddam Mehran Rezaei Fereshteh Meshkani Reihaneh Daroughegi 《International Journal of Hydrogen Energy》2018,43(34):16522-16533
In this paper, a series of mesoporous supported nickel based catalysts on nanocrystalline alumina carrier promoted with various metals (Fe, CO, Zr, La and Cu) were prepared and employed in carbon dioxide methanation reaction. The samples were characterized by XRD, BET, TPR and SEM techniques. The BET results showed that the incorporation of promoters into nickel based catalysts decreased the surface area. The results showed that among the prepared catalysts, 30 wt.%Ni-5 wt.%La/Al2O3 and 30 wt.%Ni-5 wt.%Fe/Al2O3 possessed the highest surface area and the largest pore volume, respectively. Likewise, there was a slight decrease in the pore volume and the average pore diameters of the promoted samples. The TPR results depicted that the incorporation of the promoters enhanced the reducibility of the catalysts and shifted the reduction of NiO species to a lower reduction temperature. The CO2 conversions of all promoted catalysts except Cu-promoted sample were higher peculiarly at low temperatures compared to those attained for the unpromoted catalyst. 30 wt.%Ni-5 wt.%Fe/Al2O3 catalyst exhibited the best catalytic performance (70.63% CO2 conversion and 98.87% CH4 selectivity at 350 °C), high stability and desirable resistance against sintering. 相似文献
15.
《International Journal of Hydrogen Energy》2020,45(11):6604-6620
In this research, the propane steam reforming (PSR) as a promising alternative route over a mesoporous NiO–MgO–SiO2 catalyst to produce syngas (SG) was undertaken. This catalyst was prepared using a co-precipitation method followed by hydrothermal treatment. The influence of such catalyst preparation factors as the hydrothermal time and temperature, pH and calcination temperature on the physicochemical characteristics of the prepared samples were examined. Next, these materials were characterized through the BET-BJH, XRD, TPR, and FTIR analyses. The thermal stability of this catalyst was tested through the TGA and DTA techniques. Furthermore, the deactivation of the calcined catalysts at different temperatures was investigated via the TPO analysis. The utilized synthesis method led to preparation of a species with a mesoporous structure possessing a rather high surface area of 741 m2g-1. The catalyst performance at a reaction temperature of 550 °C revealed that, the increment in calcination temperature from 500 to 800 °C led to lowering of the propane conversion as well as the hydrogen yield from 65 to 37.4% and 39.4 to 22.6%, respectively. Meanwhile, the extent of the deposited coke upon the catalyst surface was reduced when implementing the higher calcination temperature. This was attributed to high amounts of the NiO, which was included in the solid solution containing the MgO–SiO2 support. In other words, the isolation of Ni2+ with Mg2+ species and strong interaction between NiO and MgO decreased the NiO particle size hence, its reducibility. These in turn led to the formation of smaller active sites possessing higher deactivation resistance against sintering and coke deposition. Thus, a highly active and stable catalyst was developed. 相似文献
16.
Zahra Taherian Mardali Yousefpour Mohammad Tajally Behnam Khoshandam 《International Journal of Hydrogen Energy》2017,42(26):16408-16420
Ni-based/SBA-15 catalysts, were promoted by 3wt % of samaria (Sm2O3), Yttria (Y2O3) and Zirconia (ZrO2), by two-solvent impregnation method. The catalysts characterization was performed by N2 adsorption–desorption, X-ray Diffraction (XRD), X-ray Fluorescence (XRF), High Resolution Transmission Electron Microscopy (HRTEM), Field Emission Electron Scanning Microscopy (FESEM), Temperature Programmed Oxidation/Reduction (TPO/TPR) and NH3-Temperature Programmed Desorption (NH3-TPD) techniques. Then, evaluated by CO2/methane reforming.The CO2/methane reforming outcomes revealed that samaria-promoted catalyst showed excellent activity, stability and cock resistance, while yttria-promoted catalyst just illustrated good activity at high temperature and zirconia-promoted catalyst didn't show any modification in catalytic performance in comparison to Ni-based catalyst with no promoter. Samaria-promoted TEM and TPR analysis, indicated adding samaria improved the NiO particles interaction with SBA-15 support pores wall and NiO dispersion. The TPO analysis displayed that coke deposition in samaria-promoted sample after 12 h reaction is less than yttria-promoted during stream of 5 h. Also, it is suggested that for samaria containing catalyst, cock deposition occurred on the support. Therefore, nickel active sites were preserved for time on stream of 12 h, which is the main reason for samaria-promoted catalyst superior stability than other's. 相似文献
17.
《International Journal of Hydrogen Energy》2019,44(21):10427-10442
In this paper, the combination of dry reforming and partial oxidation of methane on nickel catalysts supported on mesoporous MgAl2O4 was investigated. The support was prepared by a facile sol-gel route using propylene oxide as a gelation agent. The characterizations of the catalysts were performed by BET, XRD, TPR, TPO, TPH, UV–vis, CO-dispersion, SEM and TEM techniques. In addition, the effects of nickel content, reaction and reduction temperatures, feed ratio and the GHSV value on the physicochemical and catalytic properties were studied. The results revealed that the nickel content had an optimum value of 7.5 wt% and the catalyst with this content of nickel exhibited the highest activity. Furthermore, the results demonstrated that the increase in reaction temperature enhanced the rate of the dry reforming reaction and led to obtain a H2/CO ratio around unity. The 7.5 wt% nickel catalyst showed a 5% decline in activity within 15 h in combined reforming. The TPO analysis showed that there was no deposited carbon on the catalyst surface in combined reforming and the SEM analysis confirmed the results of TPO analysis. 相似文献
18.
Kah Weng Siew Hua Chyn Lee Jolius Gimbun Chin Kui Cheng 《International Journal of Hydrogen Energy》2014
Dry reforming of glycerol has been carried out over alumina-supported Ni catalyst promoted with lanthanum. The catalysts were characterized using EDX, liquid N2 adsorption, XRD technique as well as temperature-programmed reduction. Significantly, catalytic glycerol dry reforming under atmospheric pressure and at reaction temperature of 1023 K employing 3 wt%La–Ni/Al2O3 catalyst yielded H2, CO and CH4 as main gaseous products with H2:CO < 2.0. Post-reaction, XRD analysis of used catalysts showed carbon deposition during glycerol dry reforming. Consequently, BET surface area measurement for used catalysts yielded 10–21% area reduction. Temperature-programmed gasification studies with O2 as a gasification agent has revealed that La promotion managed to reduce carbon laydown (up to 20% improvement). In comparison, the unpromoted Ni/Al2O3 catalyst exhibited the highest carbon deposition (circa 33.0 wt%). 相似文献
19.
A 3 wt% La-promoted Ni/Al2O3 catalyst was prepared via wet co-impregnation technique and physicochemically-characterized. Lanthanum was responsible for better metal dispersion; hence higher BET specific surface area (96.0 m2 g−1) as compared to the unpromoted Ni/Al2O3 catalyst (85.0 m2 g−1). In addition, the La-promoted catalyst possessed finer crystallite size (9.1 nm) whilst the unpromoted catalyst measured 12.8 nm. Subsequently, glycerol dry reforming was performed at atmospheric pressure and temperatures ranging from 923 to 1123 K employing CO2-to-glycerol ratio from zero to five. Significantly, the reaction results have yielded syngas as main gaseous products with H2:CO ratios always below than 2.0 with concomitant maximum 96% glycerol conversion obtained at the CO2-to-glycerol ratio of 1.67. In addition, the glycerol consumption rate can be adequately captured using power law modelling with the order of reactions equal 0.72 and 0.14 with respect to glycerol and CO2 whilst the activation energy was 35.0 kJ mol−1. A 72 h longevity run moreover revealed that the catalyst gave a stable catalytic performance. 相似文献
20.
Ming-Pin Lai Rong-Fang Horng Wei-Hsiang Lai Chiou-Hwang Lee 《International Journal of Hydrogen Energy》2013
A porous medium-catalyst hybrid reformer for CO2 conversion by dry auto-thermal reforming (DATR) was investigated in this study, and its operating range was discovered. The hybrid design was used to enhance the oxidative heat release by internal heat recirculation during exothermic reaction conditions, thereby increasing the CO2 conversion efficiency. The experimental results show that the CO2 conversion could be enhanced with higher catalyst inlet temperatures. The examination of the operating range of DATR showed that the CO2 conversion efficiency increased at higher reaction temperatures and CO2/CH4 ratios (≧1). Moreover, DATR in high temperature conditions must be carried out with high O2/CH4 ratios. Under these conditions of high oxygen content, CO2 generation and reduction reactions occur simultaneously. Overall, optimal CO2 conversion can be obtained with an O2/CO2 ratio of approximately 0.5. At these conditions, CO2 conversion efficiency can reach approximately 13% without external heat addition. 相似文献