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1.
This work reports the enhancing effect of a highly cost effective and efficient metal, Fe, incorporation to Co or Ni based Mo/Al_2O_3 catalysts in the oxidative desulfurization(ODS) of dibenzothiophene(DBT) using H_2O_2 and formic acid as oxidants. The influence of operating parameters i.e. reaction time, catalyst dose, reaction temperature and oxidant amount on oxidation process was investigated. Results revealed that 99% DBT conversion was achieved at 60 °C and 150 min reaction time over Fe–Ni–Mo/Al_2O_3. Fe tremendously enhanced the ODS activity of Co or Ni based Mo/Al_2O_3 catalysts following the activity order: Fe–Ni–Mo/Al_2O_3 NFe–Co–Mo/Al_2O_3 NNi–Mo/Al_2O_3 NCo–Mo/Al_2O_3, while H_2O_2 exhibited higher oxidation activity than formic acid over all catalyst systems. Insight about the surface morphology and textural properties of fresh and spent catalysts were achieved using scanning electron microscopy(SEM), X-ray diffraction(XRD), energy dispersive X-ray(EDX)analysis, Atomic Absorption Spectroscopy(AAS) and BET surface area analysis, which helped in the interpretation of experimental data. The present study can be deemed as an effective approach on industrial level for ODS of fuel oils crediting to its high efficiency, low process/catalyst cost, safety and mild operating condition.  相似文献   

2.
Low temperature growth process of carbon nanotubes (CNTs) over bi-metallic (Co–Fe) and tri-metallic (Ni–Co–Fe) catalysts on Si/Al/Al2O3 substrates is carried out from acetylene precursor using hydrogen, ammonia or nitrogen as a carrier in a low pressure chemical vapor deposition system. Using the tri-metallic Ni–Co–Fe catalyst template, vertically aligned CNTs of ~700 nm length could be grown already at 450 °C within 10 min using ammonia as a carrier. Within the same period of time, on bi-metallic Co–Fe catalyst templates, ~250 nm long aligned nanotubes emerged already at 400 °C in nitrogen carrier. At low temperatures most of the catalyst materials were elevated from the support by the grown nanotubes indicating tip growth mechanism. The structure of catalyst layers and nanotube films was studied using scanning and transmission electron microscopy and atomic force microscopy.  相似文献   

3.
Methane decomposition reaction has been studied at three different activation temperatures (500 °C, 800 °C and 950 °C) over mesoporous alumina supported Ni–Fe and Mn–Fe based bimetallic catalysts. On co-impregnation of Ni on Fe/Al2O3 the activity of the catalyst was retained even at the high activation temperature at 950 °C and up to 180 min. The Ni promotion enhanced the reducibility of Fe/Al2O3 oxides showing higher catalytic activity with a hydrogen yield of 69%. The reactivity of bimetallic Mn and Fe over Al2O3 catalyst decreased at 800 °C and 950 °C activation temperatures. Regeneration studies revealed that the catalyst could be effectively recycled up to 9 times. The addition of O2 (1 ml, 2 ml, 4 ml) in the feed enhanced substantially CH4 conversion, the yield of hydrogen and the stability of the catalyst.  相似文献   

4.
This paper reports on notable promotion of C2 + hydrocarbons formation from CO2 hydrogenation induced by combining Fe and a small amount of selected transition metals. Al2O3-supported bimetallic Fe–M (M = Co, Ni, Cu, Pd) catalysts as well as the corresponding monometallic catalysts were prepared, and examined for CO2 hydrogenation at 573 K and 1.1 MPa. Among the monometallic catalysts, C2 + hydrocarbons were obtained only with Fe catalyst, while Co and Ni catalysts yielded higher CH4 selectively than other catalysts. The combination of Fe and Cu or Pd led to significant bimetallic promotion of C2 + hydrocarbons formation from CO2 hydrogenation, in addition to Fe–Co formulation discovered in our previous work. CO2 conversion on Ni catalyst nearly reached equilibrium for CO2 methanation which makes this catalyst suitable for making synthetic natural gas. Fe–Ni bimetallic catalyst was also capable of catalyzing CO2 hydrogenation to C2 + hydrocarbons, but with much lower Ni/(Ni+Fe) atomic ratio compared to other bimetallic catalysts. The addition of a small amount of K to these bimetallic catalysts further enhanced CO2 hydrogenation activity to C2 + hydrocarbons. K-promoted Fe–Co and Fe–Cu catalysts showed better performance for synthesizing C2 + hydrocarbons than Fe/K/Al2O3 catalyst which has been known as a promising catalyst so far.  相似文献   

5.
Bulk Ni2P and Al2O3-supported Ni2P were prepared at low phosphidation temperature (300 °C) from Ni9S8 and NH4H2PO2, which were separated to avoid the formation of phosphate inside the support pores. The unsupported product phases were characterized by XRD and the Ni2P/Al2O3 catalysts by XRD, BET and TEM. A 10 wt.% Ni2P/Al2O3 catalyst, made by the Ni(NO3)2–NiO–Ni9S8–Ni2P path at a P/Ni ratio of 3, showed the highest activity in the hydrodesulfurization of dibenzothiophene. By separating the nickel and hypophosphite sources, Ni2P/Al2O3 catalysts could be obtained at low phosphidation temperature and with low degree of blockage of pores by surplus phosphorus.  相似文献   

6.
Carbon nanotubes (CNTs) were synthesized by the catalytic decomposition of acetylene over 40Fe:60Al2O3, 40Ni:60Al2O3 and 20Fe:20Ni:60Al2O3 catalysts. High density CNTs of 20 nm diameter were grown over the 20Fe:20Ni:60Al2O3 catalyst, whereas low growth density CNTs of 40 and 50 nm diameter were found over 40Fe:60Al2O3 and 40Ni:60Al2O3 catalysts. Smaller catalyst particles enabled the synthesis of highly dense, long and narrow-diameter CNTs. It was found that a homogeneous dispersion of the catalyst was an essential factor in achieving high growth density. The carbon yield and the quality of CNTs increased with increasing temperature. For the 20Fe:20Ni:60Al2O3 catalyst, the carbon yield reached 121% after 90 min at 700 °C. The CNTs were grown according to the tip growth mode. Based on reports regarding hydrocarbon adsorption and decomposition over different faces of Ni and Fe, the growth mechanism of CNTs over the 20Fe:20Ni:60Al2O3 catalyst are discussed.  相似文献   

7.
In a bio-refinery focused on fast pyrolysis, hydrogen (H2) producible from reforming of the aqueous fraction of bio-oil with steam can be utilized for upgrading pyrolytic lignin into fuels by hydrotreatment. In this work, propylene glycol (PG) was chosen as a typical compound symbolizing higher polyols in the bio-oil aqueous fraction. Catalytic processing of PG into H2 at low temperature (T = 500°C) was investigated using several commercial catalysts such as Ni/Al2O3, Ru/Al2O3, Ru/C, Pt/C, and Pd/C in a laboratory-scale fixed-bed reactor. The efficiencies of the catalysts were presented as selectivity to CO, CO2, CH4 and H2, and PG conversion into gaseous phase. Wide ranges of temperature (300–500°C), W/FO (18.6–92.9 g h/mol), and S/C ratio (5.6–12.7 mol/mol) were examined using Ni/Al2O3. At T = 500°C, H2 selectivity (73.7%) and PG conversion (66.2%) were maximized using ratios of catalyst mass to molar flow rate of PG (W/FO) = 18.6 g h/mol and steam to carbon (S/C) = 12.7 (10 wt% PG solution). It was found that Ni/Al2O3 demonstrates stable operation for at least 6 h of time-on-stream. Finally, a plausible reaction pathway for PG reforming was proposed.  相似文献   

8.
BACKGROUND: The effects of Co and Ce promoters on the performance of Ni (10 wt%)–Co (0.0, 2.75, 5.5 wt%)/Ce (0.0, 5.0, 10.0 wt%)–Al2O3 catalysts have been studied for steam reforming of C3H8 (SRP). In this work, Ni (NO3)2 and Co (NO3)2 are co-impregnated on the co-precipitated Al2O3–CeO2 supports. X-ray diffraction, N2 adsorption–desorption, H2-temperature-programmed reduction, high-resolution transmission electron microscopy, scanning electron microscopy and thermogravimetric/differential thermal analysis were accomplished to explain the SRP activity of the catalysts. The performance of the resulting catalysts was evaluated under the gas hourly space velocity (GHSV) = 45 000 mL h-1 gcat−1, T = 600 °C, steam/C3H8 ratio (S/C) = 3 and P = 1 atm. RESULTS: The experimental findings revealed that Ce and Co promoters markedly improved the catalyst activity, stability and H2 yield of Ni/Al2O3 catalyst. The sample with 2.75 wt% Co and 10.0 wt% Ce showed highest C3H8 conversion, while maximum yield of H2 was obtained for catalyst containing 5.5 wt% Co and 5.0 wt% Ce. CONCLUSION: Higher loadings of Co decreased C3H8 conversion and catalyst stability due to more coke formation on the catalyst surface, whereas Ce significantly improved catalyst resistance to coke deposition due to the enhanced Ni metal particles distribution over the support. © 2020 Society of Chemical Industry  相似文献   

9.
This study used different metals to modify Rh/Al2O3 catalysts for NO reduction in a simulated waste incineration flue gas containing 6% O2. The characteristics of the modified catalysts were analyzed using BET, TEM and XRD. The results of the experiment reveal that Na addition can significantly affect the properties of Rh/Al2O3 catalysts on the BET surface area and Rh metal dispersion. Furthermore, Na addition was found to significantly enhance the NO conversion of Rh/Al2O3 at 250–350 °C. On the contrary, Cu, Ni, and Co addition was found to have slight suppression effects.  相似文献   

10.
CO2 methanation over supported ruthenium catalysts is considered to be a promising process for carbon capture and utilization and power-to-gas technologies. In this work 4% Ru/Al2O3 catalyst was synthesized by impregnation of the support with an aqueous solution of Ru(OH)Cl3, followed by liquid phase reduction using NaBH4 and gas phase activation using the stoichiometric mixture of CO2 and H2 (1:4). Kinetics of CO2 methanation reaction over the Ru/Al2O3 catalyst was studied in a perfectly mixed reactor at temperatures from 200 to 300 °C. The results showed that dependence of the specific activity of the catalyst on temperature followed the Arrhenius law. CO2 conversion to methane was shown to depend on temperature, water vapor pressure and CO2:H2 ratio in the gas mixture. The Ru/Al2O3 catalyst was later tested together with the K2CO3/Al2O3 composite sorbent in the novel direct air capture/methanation process, which combined in one reactor consecutive steps of CO2 adsorption from the air at room temperature and CO2 desorption/methanation in H2 flow at 300 or 350 °C. It was demonstrated that the amount of desorbed CO2 was practically the same for both temperatures used, while the total conversion of carbon dioxide to methane was 94.2–94.6% at 300 °C and 96.1–96.5% at 350 °C.  相似文献   

11.
NiMoS catalysts supported on MgO–Al2O3 oxides, with 95 and 80 mol% of MgO, were synthesized by sol–gel method. In order to study the Ni promoter effect, MgO–Al2O3 supports were impregnated with a pH = 9 solution of Mo and Ni–Mo, respectively; the catalysts were dried (D) and calcinated (C). Catalytic tests showed a Ni promoter effect of 4.5 on the NiMoMg95Al5-D catalyst and 8.5 on the calcinated one. The latter catalyst is more active than a commercial NiMo/Al2O3 catalyst. On the other side, the catalyst supported on Mg80Al20 solid did not show any Ni promoter effect. Raman and UV–vis diffuse reflectance spectroscopy showed that during the impregnation step, a strong support interaction with the ion MoO42? takes place on the Mo/MgO–Al2O3 solids. After calcination, MoO42? ion remained on the catalyst surface, but increased its interaction with the support. The presence of Ni2+Th, Ni2+Oh and MoO42? ions on dried NiMo/Mg95Al5 catalysts was confirmed, as well as the presence of Ni2+Th, Ni2+Oh, MoO42? and Mo7O246? ions on the calcinated catalyst. This suggests that Ni2+ ion allows polymerization of MoO42? to Mo7O246?, produced by Ni2+Oh–MoO42? and Ni2+Oh–Mo7O246? close interactions. The NiMo/Mg80Al20 solids also showed MoO3 species and a high Ni2+Th concentration. Thus, the Ni promoter effect and therefore, catalytic activity decreased, due to the formation of Ni2+Th–MgO and Ni2+Th–Al2O3 spinels.  相似文献   

12.
The performance of Co/Nb2O5 was compared to that of Co/γ-Al2O3 for the Fischer–Tropsch synthesis at 20 bar and over the temperature range of 220–260 °C. The C5+ selectivity of Nb2O5-supported cobalt catalysts was found to be very high, i.e. up to 90 wt% C5+ at 220 °C. The activity per unit weight cobalt was found to be similar for Nb2O5 and γ-Al2O3-supported catalysts at identical reaction temperature. However, due to the low porosity of crystalline Nb2O5, the cobalt loading was limited to 5 wt% and consequently the activity per unit weight of catalyst was lower than of Co/γ-Al2O3 catalysts with higher cobalt loadings. This low activity was largely compensated by increasing the reaction temperature, although the C5+ selectivity decreased upon increasing reaction temperature. Due to the high intrinsic C5+ selectivity, Nb2O5-supported catalysts could be operated up to ~250 °C at a target C5+ selectivity of 80 wt%, whereas γ-Al2O3-supported catalysts called for an operation temperature of ~210 °C. At this target C5+ selectivity, the activity per unit weight of catalyst was found to be identical for 5 wt% Co/Nb2O5 and 25 wt% Co/Al2O3, while the activity per unit weight of cobalt was a factor of four higher for the niobia-supported catalyst.  相似文献   

13.
The effect of Na addition on the performance of Rh/Al2O3 catalyst for NO reduction with CO in the presence of H2O and O2 was investigated. The reacted catalysts were analyzed by the FTIR technique to identify the products for further investigation on the possible catalytic reaction mechanisms and the reasons behind the H2O poisoning. Experimental results show that the removal efficiency of NO by Rh/Al2O3 catalyst was 63% at 250 °C but that decreased as the H2O content increased. Adding Na to modify the Rh/Al2O3 catalyst significantly enhanced the conversion of NO to 99% at 250–300 °C even as the H2O content was 1.6 vol%. The FTIR analyses results reveal that the abundant H2O in the flue gas can compete with NO to adsorb on the surfaces of Rh/Al2O3 and Rh-Na/Al2O3 catalysts and further enhance the formation of NO3 that reacts with H. The effects of H2O on Rh/Al2O3 and Rh-Na/Al2O3 catalysts can be eliminated by increasing the reaction temperature to higher than 300 °C. Rh-Na/Al2O3 is a feasible catalyst for NO reduction at such condition with relative high H2O and O2 contents.  相似文献   

14.
Multi-wall carbon nanotubes (MWNTs) were synthesized by catalytic decomposition of acetylene over Fe, Ni and Fe-Ni bimetallic catalysts supported on alumina under various controlled conditions. The growth density and diameter of CNTs were markedly dependent on the activation time of catalysts in H2 atmosphere, reaction time, reaction temperature, flow rate of acetylene, and catalyst composition. Bimetallic catalysts were apt to produce narrower diameter of CNTs than single metal catalysts. For the growth of CNTs at 600 ‡C under 10/100 seem flow of C2H2/H2 mixture, the narrowest diameter about 20 nm was observed at the reaction time of 1 h for 20Fe : 20Ni : 60Al2O3 catalyst, but at that of 1.5 h for 10Fe : 30Ni : 60Al2O3 catalyst. It was considered that the diameter and density of CNTs decreased with the increase of the growth time mainly due to hydrogen etching. The growth of CNTs followed the tip growth mode.  相似文献   

15.
A nickel (Ni) nanoparticle catalyst, supported on 4‐channel α‐Al2O3 hollow fibers, was synthesized by atomic layer deposition (ALD). Highly dispersed Ni nanoparticles were successfully deposited on the outside surfaces and the inside porous structures of hollow fibers. The catalyst was employed to catalyze the dry reforming of methane (DRM) reaction and showed a methane reforming rate of 2040 Lh?1gNi?1 at 800°C. NiAl2O4 spinel was formed when Ni nanoparticles were deposited on alpha‐alumina substrates by ALD, which enhanced the Ni‐support interaction. Different cycles (two, five, and ten) of Al2O3 ALD films were applied on the Ni/hollow fiber catalysts to further improve the interaction between the Ni nanoparticles and the hollow fiber support. Both the catalyst activity and stability were improved with the deposition of Al2O3 ALD films. Among the Al2O3 ALD coated catalysts, the catalyst with five cycles of Al2O3 ALD showed the best performance. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2625–2631, 2018  相似文献   

16.
To develop efficient steam reforming catalysts that are widely applicable to various volatile organic solvents under low temperatures, rare earth (La, Ce or Pr)-doped Ni/MgAl2O4 were prepared via a novel one-step sol–gel method. Through various characterizations and DFT calculations, it demonstrated that the rare earths not only improved the catalyst structure, but also promoted the dispersion, electron density and d-band center of Ni. Consequently, all the rare earth-doped Ni/MgAl2O4 catalysts exhibited higher catalytic activity in steam reforming of different volatile organic solvents than the Ni/MgAl2O4 in 500–550 °C. Thereinto, the 10Ni-2La/MgAl2O4 performed the best, achieving a conversion efficiency of 97.3% at 550 °C for the mixture of toluene, acetone, tetrahydrofuran, and n-hexane. The outstanding performance of Ni-La/MgAl2O4 catalyst arises from the structural compatibility between low-spin La atom and Ni cluster, which enables La to modify Ni dispersion and electronic structure more significantly than Ce or Pr.  相似文献   

17.
Steam reforming of commercially available LPG using Ru/Al2O3 and Ni/Al2O3 catalysts has been studied at temperatures between 573 and 773 K. Ru/Al2O3 catalyst showed higher rates of reaction and lower activation energies of the three main components of LPG, compared with Ni/Al2O3. However, Ni/Al2O3 catalyst showed a better H2:CH4 selectivity. The activation energy of n-butane was the lowest over Ru/Al2O3, whereas over Ni/Al2O3, propane had the lowest activation energy. The activation energy of i-butane was always the highest over both catalysts, which suggests that both catalysts performed better with unbranched molecules. A slight increase in activation energy was observed, when each component of the LPG mixture was studied separately as a pure gas, compared with being mixed in LPG. At a constant temperature of 773 K, hydrogen production yield and H2:CH4 selectivity were determined using Ru/Al2O3 at different steam:carbon (S:C) ratios and LPG flow rates. It was found that the yield and selectivity increased with the increase in S:C ratio and the decrease in the flow rate. The highest yield of 0.64 was achieved using S:C ratio of 6.5 and a LPG flow rate of 50 mL min?1. The work provides valuable information on steam reforming of pure components of LPG, compared with when they are in the mixture. The comparison is done using conventional steam reforming catalyst, Ni/Al2O3, and compared with Ru/Al2O3. The observed trends and variations in reaction rates, in pure and mixed gases, indicated that the mechanism of steam reforming of a hydrocarbon mixture depends on its composition.  相似文献   

18.
The synthesis of carbon nanotubes (CNTs) from ethylene decomposition by Fe/Al2O3 and Fe/Ni/Al2O3 catalysts (Fe:Ni=10:1) is studied. A small amount of nickel introduced into the catalyst can significantly increase the yield of CNTs, but the nanotubes change from straight tubes with concentric parallel carbon sheets to helical tubes of the fish-bone type. Raman characterization of CNTs prepared at 823 and 1023 K and CNTs annealed at 2473 K shows that CNTs deposited on the Fe/Ni/Al2O3 catalyst have poor crystallinity, as compared with that on the Fe/Al2O3 catalyst. These differences are explained by a mechanism of formation of helical tubes of the fish bone type that takes into consideration the differences in the chemical nature of the catalyst with and without nickel.  相似文献   

19.
Novel CuxNiy/γ-Al2O3 alloy catalysts were prepared and studied for methanol synthesis from CO/CO2 hydrogenation. The structure of the catalysts was characterized using N2 adsorption–desorption, X-ray diffraction, transmission electron microscopy, scanning transmission electron microscopy, X-ray photoelectron spectroscopy and temperature-programmed reduction. The characterization results demonstrated the formation of CuNi alloy. The strong interaction between Cu and Ni had a promotion effect for methanol synthesis. Cu3Ni7/γ-Al2O3 catalyst exhibited the highest formation rate of CH3OH, which is 5.86 mmol/g h, much higher than the commercial Cu/ZnO/Al2O3 catalyst at the same reaction conditions.  相似文献   

20.
On-site ammonia (NH3) decomposition is considered as a potential path to supply CO x-free hydrogen for fuel cell vehicles. In this article, monometallic catalysts (Fe, Co, Ni, and Mo) and bimetallic catalysts (Fe–Co, Mo–Co, Fe–Ni, and Mo–Ni) were prepared and tested in plasma-catalytic NH3 decomposition, where 6Fe–4Ni catalyst exhibited the highest activity and synergistic capability with plasma. At 500°C, NH3 were completely decomposed (>99.9% NH3 conversion); the rate of H2 production and the energy consumption of H2 production reached 0.96 mol g−1 h−1 and 0.050 kW h (mol g−1)−1, respectively. The 200 h continuous operation results indicate an excellent durability of 6Fe–4Ni catalyst. The catalysts characterization and plasma diagnosis results indicate that NH3 was pre-activated by plasma into excited-state species (NH3, ˙NH2, and ˙NH), and the 6Fe–4Ni catalyst exhibited the highest capability to adsorb excited NH3, ˙NH2, and ˙NH species, which could be the main reason why 6Fe–4Ni catalyst exhibited the highest activity. © 2018 American Institute of Chemical Engineers AIChE J, 65: 691–701, 2019  相似文献   

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