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•CNF doped alumina was loaded with Mo and Co nanoparticles.•The prepared AlCNFMoCo catalyst was evaluated for HDS reactions.•The prepared catalyst showed higher catalytic efficiency ...than AlMoCo.
Developing more effective catalysts for the hydrodesulfurization (HDS) process has gained more importance in recent decades to produce ultraclean fuel. In the current study, a novel carbon nanofiber doped alumina (AlCNF) was prepared as a support for the MoCo catalyst for the HDS reaction of dibenzothiophene (DBT). The in-situ prepared composites were characterized by using Brunauer–Emmett–Teller (BET), temperature-programmed reduction (TPR) powder X-ray diffraction (XRD), scanning electron microscope (SEM), infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). The catalytic activity of the MoCo catalysts supported on nanofiber doped alumina (AlCNFMoCo) was tested and compared with the MoCo catalysts supported on alumina (AlMoCo). The AlCNFMoCo catalyst reduced the sulfur concentration in the liquid fuel down to below the allowed limit in a 6 h reaction time, showing a higher catalytic activity compared to AlMoCo. The improved catalytic activity of AlCNFMoCo can be explained by the high mesoporous surface area and the better dispersion of the MoCo metals on the AlCNF support compared to the alumina support. BET analysis indicated that the textural properties were improved by introducing CNF. The surface areas of AlMoCo and AlCNFMoCo were 166 and 200 m2/g. The SEM images indicated that the catalyst nanoparticles were well distributed on the surface of the CNF.
One dimensional pore zeolites such as ZSM-22 (TON) are potential catalysts for hydrocarbon conversion reactions, including methanol-to-propylene (MTP) reaction. Different crystal lengths of ZSM-22 ...zeolite were prepared and examined for the MTP reaction. Nanosized TON zeolites with crystal length of ∼100 nm were synthesized by dynamic hydrothermal synthesis. The zeolite crystal length was tuned by using ethylene glycol as crystal growth modifier. The crystal lengths of ZSM-22 zeolites (approximately 100 and 300 nm) were confirmed from FE-SEM and TEM micrographs. However, the textural properties such as BET surface area and crystallinity of crystals were fairly similar. The effect of ZSM-22 crystal length on catalytic activity and propylene yields in the methanol-to-propylene reaction was investigated. The TON nanocrystals resulted in a higher propylene yield and better catalytic stability compared to the submicrometer zeolite (∼300 nm). Deactivation was observed for all catalysts. However, longer lifetime was observed for the nanosized ZSM-22 with crystal length of ∼100 nm.
Series of nanosized iron- and cobalt-doped ceria–zirconia nanocomposites were prepared using a hydrothermal synthesis technique at 180 °C for 24 h, with the successful novel incorporation of both Co ...and Fe on ceria–zirconia, for n-hexane catalytic cracking. Effects of dopant ions on the improvement of intrinsic properties of ceria–zirconia nanocomposites were investigated using disparate characterization techniques. The synthesized ceria–zirconia nanocomposites exhibited similar X-ray diffraction (XRD) patterns, indicating full fusion of the metal ions into the ceria–zirconia lattice structure. The synthesized nanocomposite catalysts were tested for n-hexane cracking over 10 h time-on-stream, with no previous study or report for catalytic cracking of hexane via ceria–zirconia nanocomposites. Relatively high ethylene and propylene selectivity (both >62%) was obtained over CZ, FeCoCZa, and FeCoCZb over time-on-stream. Comparatively, the best catalytic activity and stability was exhibited by FeCoCZa with higher n-hexane conversion. Temperature and catalyst weight per feed flow rate (W/F) variations were investigated using the best catalyst (FeCoCZa). Higher conversions were obtained at higher temperature and lower W/F but with varied product selectivity and yield, over time-on-stream. In addition, the spent catalysts were successfully regenerated after catalytic testing via calcination at 600 °C for 4 h and reused for two additional cycles.
In this work, a novel approach is used to synthesize an iron oxide doped carbon nanotube (CNT) membrane, with the goal of fully utilizing the unique properties of CNTs. No binder is used for the ...synthesis of the membrane; instead, iron oxide particles serve as a binding agent for holding the CNTs together after sintering at high temperature. The produced membrane exhibited a high water flux and strong fouling resistance. In the first step, CNTs were impregnated with various loadings of iron oxide (1, 10, 20, 30 and 50%) via wet chemistry techniques. Impregnated CNTs were then compacted at 200MPa and sintered at 1350°C for 5h to form a compact disc. The membranes were analysed by measuring their porosity, contact angle, diametrical compression test and water flux. The flux of pure water was observed to increase with an increase in iron oxide content. The permeate flux and rejection rate of sodium alginate (SA) were determined to predict the antifouling behaviour of the membrane. A maximum removal of 90 and 88% of SA was achieved for membranes with a 10 and 1% iron oxide content, respectively, after 3h. A minor decline in the permeate flux was observed for all membranes after 4h of operation.
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•Membranes comprising of iron oxide-impregnated carbon nanotube were synthesized.•The iron oxide nanoparticles serve as a binder to hold the nanotubes together in the matrix.•The novel CNT membrane exhibited high water flux and strong antifouling behaviour.•The membrane characteristics were influenced by the iron oxide content.
For the first time, a sequential fabrication step involving mechanochemistry, recrystallization, and dealumination was developed to convert low-cost natural zeolites to mordenite (MOR) nanoparticles. ...Natural zeolites are mostly found having poor textural properties and a high aluminum content, which are not suitable for most industrial catalytic reactions. The parent natural zeolites within the size of 1–10 μm were treated by ball milling to obtain nanosized particles with size in the range of 20–160 nm. The nitrogen physisorption study revealed that the external surface area and intercrystalline mesopore volume of the milled nanoparticles increased by 4- and 7-fold, respectively. Recrystallization by hydrothermal treatment in basic silicate solution was applied to recover the MOR crystallinity at 170 °C for 6 h. The recrystallized MOR samples were further subjected to acid dealumination treatment over different periods. The H-MOR samples were evaluated in a fixed-bed reactor for n-butane isomerization. The isobutane selectivity increased from 11 to 28% when the parent microparticle was substituted by the recrystallized nanoparticles. Moreover, the catalyst stability improved over the recrystallized nanoparticles. The dealuminated–recrystallized nanoparticle exhibited the highest selectivity of ca. 58% to isobutane and less deactivation rate as a result of low acid site density and small nanoparticle size.
•To utilize its high acidity, alumina-MoCo catalysts was doped with boron.•AlMoCoB5% showed enhanced hydrodesulphurization of dibenzothiophene.•The mechanism was proposed based on the ...characterization results and GC-SM.
The effect of boron content on hydrodesulphurization (HDS) activity was investigated under different optimized conditions. γ-Al2O3 was loaded with MoCo and then doped with boron. The obtained materials, i.e. AlMoCoB0%, AlMoCoB2%, and AlMoCoB5% were characterized by N2-physisorption, X-ray diffraction, temperature programmed analysis by reduction and desorption, Fourier-transform infrared spectroscopy, a scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis. The catalytic activity of the prepared catalysts was evaluated for the HDS of dibenzothiophene (DBT) using a Parr batch reactor at T = 300 °C and under 50 bar hydrogen partial pressure. The textural properties of the prepared catalysts were enhanced by introducing the boron. For example, the BET surface area of AlMoCoB5% was 206 m2/g which is higher than that of both AlMoCoB0% and AlMoCoB2%. The acidity and dispersion AlMoCoB5% were 0.77 and 2.46 (mmol/g), respectively, which increase its HDS activity. The boron enhanced the particle dispersion, leading to an improvement in the catalytic activity of the MoCo catalysts in the elimination of sulfur content. Experimental factors (such as temperature, pressure, the dosage of the catalysts and contact time) were investigated and optimized using a central composite design. The results revealed that the HDS was improved by increasing the temperature, pressure, and catalyst dosage. The optimum contact time was found to be 6 h with a dosage of 0.6 g. The experimental results indicated that AlMoCoB5% has the highest HDS activity, achieving more than 98% of sulfur removal, which is below the allowed sulfur level. The excellent catalytic activity of the AlMoCoB5% catalyst in the HDS of DBT is particularly useful for the ultradeep HDS of fuels.
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•Doping of ceria-zirconia with iron and cobalt was applied via hydrothermal synthesis.•Catalytic upgrading of oil sand bitumen via ceria-based catalysts in superheated steam ...environment.•Production of light oils and gaseous products via effective decomposition of heavy oil at 470 °C.•The spent catalysts exhibited stability and good potential for reusability.
Upgrading of oil sand bitumen by catalytic cracking of its heavy oil fraction via ceria-based catalysts was investigated in a fixed-bed flow-type reactor, in the presence of superheated steam and addition of water. The reaction was carried out over CeZr, FeCoCeZr1 and FeCoCeZr2 catalysts at 470 °C, Wcat/FFeed of 0.4 h and FH2O/Ffeed = 2. The oxygen species in the crystal lattice of the catalysts and the surface Lewis acid sites are responsible for the oxidative decomposition and catalytic cracking of the heavy oil, respectively. Higher light oil yield of approximately 60 mol%-C (gas oil and vacuum gas oil) and lowest coke yield (20.45 mol%-C) was obtained over CeZr catalyst. FeCoCeZr1 and FeCoCeZr2 gave lower residue and higher gas yield, with higher H2 and lower CO2 composition when compared to CeZr. The spent catalysts showed structural stability which is supported by the X-ray diffraction analysis, and thermal stability which agrees to the minimal weight loss from thermogravimetric analysis. The catalysts also exhibited good potential for reusability based on the analysis of the spent samples.
A novel approach was used to synthesize a silver doped-CNT membrane, with the aim of fully utilizing the anti-toxic properties of CNTs and silver. No binder was used for the synthesis of the ...membrane; instead, silver particles served as a binding material for the CNTs after sintering at high temperature. In the first step, CNTs were impregnated with different loadings of silver (1, 10 and 20wt.%) via a wet chemistry technique. Impregnated CNTs were then compacted at 200MPa and sintered at 800°C for 3h to form a compact disk (membrane). The powder materials were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and thermogravimetric analysis, while the membranes were characterized by measuring their porosity, contact angle, diametrical compression test, pure water permeate flux and antibacterial properties. The affinity of the membranes to biofouling was studied using Escherichia coli (E. coli). The produced membrane showed a high water permeate flux and exhibited strong antibacterial properties. All of the membranes with different silver loadings were able to remove/kill 100% of the bacteria tested; however, the CNT membrane with 10% silver showed a superior performance to the others. All bacteria were removed/killed by the membrane with 10% silver loading after the suspension had passed for only 60min. These membranes would be advantageous in a continuous filtration system for the removal of different contaminants from water via desalination, adsorption and sieving.
•Novel membranes comprising of CNT impregnated with silver have been synthesized.•The novel CNT membranes have potential of breakthrough in water desalination.•The affinity of membranes to biofouling was studied using Escherichia coli (E. coli) bacteria.•All the bacteria were removed/killed by membrane with 10% silver loadings in 60 min only.
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•Microwave-assisted alkaline post-treatment was applied to improve porosity of MTT zeolites.•The total pore volume was increased after the sequential treatment.•The hierarchical MTT ...zeolite prolong catalyst stability and deactivation rate became smaller.•Synthesis, alkaline–acid treatment and ion exchange were performed under microwave irradiation.•MTT zeolites were potential catalysts in n-hexane cracking with high selectivity to propylene.
Catalytic cracking of naphtha over one-dimensional (1D) pore zeolite was targeted by using n-hexane as a model compound. Novel hierarchical H-ZSM-23 (MTT), a 1D pore zeolite, was specially designed to maximize propylene yield from catalytic cracking. Very high propylene-to-ethylene ratio of 2.5 was achieved. The ZSM-23 with mesopores displayed an enhanced deactivation resistance compared to microporous parent crystals. Hierarchical ZSM-23 was synthesized rapidly by applying microwave-assisted hydrothermal synthesis (MAHyS) followed by microwave-assisted alkaline treatment and moderate acid treatment. Pore volume of hierarchical ZSM-23 was improved considerably compared with the ones of parent crystals. Physico-chemical properties of hierarchical ZSM-23 were studied by characterization techniques such as XRD, FE-SEM, N2 adsorption–desorption, 27Al and 29Si MAS NMR, NH3-TPD, and TEM.
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