In the work presented here, a facile approach for the preparation of nitrogen-doped porous graphene was applied for the first time using ammonium acetate as a nitrogen rich precursor via pyrolysis at ...900 °C for 2 h.
The physicochemical properties of the prepared samples were determined using Field Emission Scanning Electron Microscopy (FE-SEM), Energy-dispersive X-ray spectroscopy (EDS) mapping, Raman spectroscopy and X–ray photoelectron spectroscopy (XPS). The prepared samples were further applied for the oxygen reduction reaction (ORR) in alkaline solution, and the electrochemical performance was investigated and compared with porous graphene and Pt/C 20 wt.%. The results revealed that introducing nitrogen to the graphene structure leads to improvement in catalytic activity, enhanced catalytic current as well as more positive potential. Furthermore, N-doped graphene prepared using ammonium acetate exhibited excellent methanol tolerance and long-term stability. Finally, it was shown that the optimal pyrolysis temperature was obtained at 900 °C. Therefore, it is concluded that ammonium acetate could be used as an effective precursor for the ORR.
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•Proposing a simple method for synthesizing nitrogen doped porous graphene.•First time use of Ammonium Acetate for preparing porous nitrogen doped graphene.•Preparing a nanocatalyst with superior ORR activity through simple method.
In this work, various methods (chemical vapor deposition (CVD), hydrothermal, and pyrolysis) have been applied for preparing sulfur–nitrogen co-doped porous graphene. Afterwards, the electrochemical ...behavior of the samples prepared through different techniques was investigated for oxygen reduction reaction (ORR). The prepared heteroatoms-doped electro-catalysts were thoroughly characterized by X-ray diffraction, Raman spectroscopy, N
2
adsorption-desorption, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy techniques. The results showed that co-doping of S and N into porous graphene significantly enhanced the ORR performance. The obtained results showed that the efficiency trend of preparation methods on the ORR performance followed as pyrolysis > CVD > hydrothermal. In addition, the electron transfer numbers in these methods at optimal conditions were 4.1, 3.4, and 2.6, respectively. Among different preparation techniques, pyrolysis as a post-synthesis doping technique has exhibited the most efficient ORR process, in which electron transfer follows the 4e pathway. Moreover, the catalyst prepared by the pyrolysis method has an onset potential of 0.93V which is very close to the conventional Pt/C 20 wt.% (0.99 V) electro-catalysts because of surface doping and better control over the final product. Finally, the microbial fuel cell test showed a high peak power density of 30.94 mW m
−2
for the optimal sample, which is close to the Pt/C 20 wt.% (38.63 mW m
−2
) cathodes, because of the synergistic effect of N and S co-doped carbon structure.
Graphical abstract
Synthesis and characterization of heteroatom co-doped graphenes using CVD, Pyrolysis and hydrothermal techniques are reported and their electrochemical behaviors evaluated. The results represent the high dependence of ORR activity of the prepared electrocatalysts to the synthesis method and the electrocatalyst via pyrolysis method shows high selectivity for the 4e
-
reduction.
Microstructure and adherence correlation of the enamel/steel interface in cobalt containing (CCE) and cobalt free (FCE) enamels was investigated. Results showed formation of small islands in the ...interfaces of the two samples. Consequently, the adherence mechanisms can be explained by the dendritic and chemical theories in both samples. Also cobalt and nickel oxides in enamels were reduced to the metallic state by base metal during firing. CCE showed stronger adherence than FCE due to higher amount of Co, in compare with Ni, migrated from the glass to steel. According to the electrolytic theory Co and Fe ions exchange in the interface leading to coarser roughening of the metal in the interface and hence, effectively increased the adhesion strength in CCE.
In the work presented here, the feasibility study of the methanol production from pure CO
2
and H
2
has been conducted. This study focused on investigation of the previous kinetic models used for ...methanol synthesis by hydrogenation process at different processing conditions such as: pressure, temperature, catalyst loading and molar ratio of H
2
to CO
2
to select the best one. The results showed that, the combined rate expression containing both CO and CO
2
hydrogenation terms would result in the better yield. Besides, it was found that the reactor containing recycle mood ensures a higher efficiency up to 65% methanol yield at the range of (200–250 °C) and 50 bar. The kinetic model based on CO and CO
2
hydrogenation along with the proposed configuration showed the reasonable methanol yield in a practical methanol plant as much as 41%.
In this paper, the optimization of the methanol production process is investigated. For this purpose, the parameters affecting methanol production including catalyst type (4 cases), temperature, ...pressure, and GHSV have been investigated and then by selecting the appropriate catalyst and process conditions, possible process changes such as hydrogen injection as make up, applying two reactors and inert gases, the use of dry hydrogen, and adding recycle stream on methanol yield have been studied.
Then, by selecting the appropriate process, simulating, and validating the simulation results, the selected catalyst is used for the process. The process is simulated in 8 cases with changes in the studied parameters and the amount of recycle flow. Then, the key parameters of the optimized process were compared with the baseline. The results showed that, the investment costs (smaller dimensions of process equipment such as compressors, reactors, and distillation columns, etc. due to recycling flow reduction) and current costs (including electricity and steam consumption), significantly improved.
In general, the use of CuZnOAl2O3 catalyst in the methanol production process reduced the reactor temperature, decreased the recycle flow by about 38% and reduced the electrical energy consumption and steam consumption relative to the baseline by about 5% and 67%, respectively. Finally by the process optimization conducted in this work, in addition to reducing the recycle flow and reducing energy consumption, it is possible to annually reduce the GHG emissions of 7526.35 ton CO2eq and 19.43 tons of air pollutants (per 100 kton/y of methanol production).
•The process parameters affecting methanol production were optimized.•The recycle flow and energy consumption were reduced by 38% and 17%, respectively.•The GHG and air pollutants were decreased by about 16.9% relative to the baseline.
Palladium (Pd) membranes on porous stainless steel (PSS) were prepared by electroless plating. An intermediate layer of NaX nanozeolite was employed to modify the pore size of the PSS support and ...improve the hydrogen permeability. NaX nanozeolites were synthesized using convectional hydrothermal method. The NaX intermediate layer was coated by vacuum-assisted method on the PSS surface. The structure and morphology of the prepared membranes were characterized using SEM, XPS and XRD analysis. Permeation measurements were conducted using H2, N2 and mixture of H2/N2 at different temperatures (350–450 °C), and trans-membrane pressures (4–8 bar). The results indicated that the permeability and hydrogen selectivity were increased by enhancement in temperature and pressure. The hydrogen fluxes in H2/N2 mixtures were lower than those corresponding to pure hydrogen at the same partial pressures and temperatures. The obtained results suggests that the use of NaX nanozolite is an effective intermediate layer in Pd/PSS membranes for hydrogen separation.
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•Intermediate layer of NaX nanozeolite was employed for hydrogen separation.•NaX nanozeolites were synthesized using convectional hydrothermal method.•Permeability was increased by enhancement in temperature and pressure.•Hydrogen selectivity was increased by enhancement in temperature and pressure.•The maximum H2/N2 ideal selectivity of Pd/NaX/PSS was found to be 685.8.
TiO2 photocatalyst was used to degrade Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) from petrochemical wastewater. The photocatalytic performance of the TiO2 was studied with ...variations of treatment parameters such as temperature, pH, contact time, and catalyst dosage. Design of Experiment (DOE) utilizing the Taguchi method was used to find and optimize the process model. Results for photocatalytic degradation of COD and BOD indicated the proper performance of TiO2 as the photocatalyst. The best result was achieved at pH 5 after 90 min with 73% COD conversion. COD degradation of petrochemical waste was optimized according to the experimental results, while process optimization indicated best process conditions are pH ≈ 5.2, temperature ≈ 42.8 °C, catalyst dosage = 0.75, and contact time of 88 min.
In this work, two solutions for waste management of organochlorine waste in one industrial polyvinyl chloride (PVC) plant, (a) combustion by a high-performance incinerator and (b) separation by a ...distillation column sequence, were compared according to environmental and economic parameters. In the case of using high-performance (HP) incinerator and maintaining the existing incinerator, approximately 65% of the produced organochlorine waste must be disposed of in the new incinerator, whereas in the distillation column sequence for recovery of the organochlorine waste, 60 kg/h chloroform and 60 kg/h chloroform plus 60 kg/h nanocarbon can be produced in scenario 1 and 2, respectively. All the scenarios showed a fairly good internal rate of return (IRR) and positive net present value (NPV). Moreover, in terms of emission reduction, distillation techniques including chloroform and chloroform plus nanocarbon can significantly reduce greenhouse gas emissions by 2062 and 4724 tons/year, respectively. Also, disposal by HP incinerator can lessen green house gas (GHG)s by 6948 tons/year. Also, the life cycle assessment (LCA) evaluation revealed that in view of the global warming impact category, the distillation scenarios have the better result in comparison to the existing condition, whereas in other impact categories, the existing condition is in a better situation.
