Conventional Electric Furnace Research Articles

Activation of NO with microwave irradiation for low temperature direct decomposition

Direct decomposition of nitric oxide (NO) on metal oxides under microwave (MW) irradiation was investigated and it was found that the most metal oxides show higher NO decomposition activity than that in the conventional electric furnace heating at low temperature. Among the examined oxides, it was found that TiO2, CeO2, ZrO2, and Y2O3 show about 95 % or higher NO conversion at 573 K, and both N2 and O2 are formed with almost equimolar amount. In particular, ZrO2 exhibited high and stable NO decomposition activity more than 25 h. In this study, the influence of coexisting gases on NO decomposition activity on ZrO2 under microwave heating was further investigated and the direct decomposition of NO can be proceeded even in the presence of 5 % O2, 5 % CO2, or humidified condition. Mechanism of high NO decomposition activity under MW irradiation was also studied and it was found that removal of oxygen from the catalyst was much increased under MW irradiation because of direct activation of oxygen and also direct activation of NO which is also suggested by pulse reaction.

Production of Glass Foam in a Microwave Oven Using Agro-Industrial Waste as Raw Material

Climate change is characterized by shifts in temperature and climate patterns. Constructing new high-rise environments using materials that incorporate agro-industrial waste can help mitigate this impact without compromising technological properties. This study produced vitreous foams intended to replace natural aggregates in lightweight concrete partially. These foams were sintered in a microwave oven at temperatures of 750 °C, 800 °C, and 850 °C, utilizing glass powder and sugarcane bagasse ash as raw materials. The homogenization and preparation of these materials were conducted through a mechanical pelletization process, employing a constant rotation engine at approximately 40 rpm. The efficacy of microwave sintering was assessed by comparing the outcomes with those from sintering in a conventional electric muffle furnace under identical conditions. The results indicated that the microwave-sintered vitreous foams exhibited the following values for apparent density (≤0.30 g/cm3), porosity (86% to 94%), and compressive strength (0.48 MPa to 0.58 MPa), which align with the global standards for commercial vitreous foams. The microwave sintering route proved to be economically feasible by reducing sintering time and, consequently, energy costs, without sacrificing technological properties. The materials produced in this study offer a promising solution to minimize the environmental impact associated with constructing new buildings, particularly tall structures. Additionally, they support the circular economy by converting waste into valuable by-products.

In-situ observation of molten brazing filler metal permeating gap

Generally, brazing is completed when the brazing filler metal permeates the gap by uniform wetting. It is believed that the joining process is completed with the formation of joint defects ‘voids’ in the process of uniform wetting. However, previous studies have shown that what occurs when brazing is performed is non-uniform wetting. It is suggested that this non-uniform wetting is the cause of void generation. Wetting and spreading of brazing filler metal is tested on a metal plate, as described in JIS Z 3191. This is used to investigate the wetting of the brazing filler metal. However, this method does not cover the wetting of the molten brazing filler metal as it moves into the gap. Therefore, it is suggested that the JIS Z 3191 experiment is insufficient to evaluate the wetting of the molten brazing filler metal that penetrates into the gap. In this experiment, we created new specimen. It is called us ‘V-groove specimen’. Specimens were created with two base metals. They are pure copper and lead-free brass in which bismuth was used as an alternative element. In order to do in situ experiments, it was not possible to observe the inside of a conventional electric furnace. Therefore, we produced a furnace with a window for in-situ observation and experimented with it. As a result of experiments with V-groove specimens, it was found that there are two types of wetting of brazing filler metal. They are called ‘primary wetting’ and ‘secondary wetting’. The shape of the specimen was measured and evaluated for two types of wetting. The results showed that the primary wetting was measurable in shape and spread evenly. However, the shape of the secondary wetting could not be measured, and it was found to be non-uniformly spread.

Optimizing capacitance performance: Solar pyrolysis of lignocellulosic biomass for homogeneous porosity in carbon production

This work compares the effect of using a solar reactor against a conventional electrical furnace to obtain carbon materials by pyrolysis of a lignocellulosic precursor. The solar reactor is directly irradiated and includes modifications to improve the control of the process and the reproducibility of solar experiments. A bagasse of agave creole was selected as the lignocellulosic precursor or biomass to obtain carbon materials at temperatures of 700 °C. Comparing carbons produced by conventional and solar pyrolysis, higher crystallinity and lower hydrophilicity are evident in the former. Moreover, conventional pyrolysis tends to promote a more homogeneous porous structure in comparison to solar pyrolysis. However, within the spectrum of solar carbons produced, the morphology of biomass plays a crucial role in influencing the chemical composition and porosity properties. Specifically, the use of fibers instead of powders to produce carbons through solar pyrolysis results in a more homogeneous porosity, attributed to an enhanced volumetric absorption of solar radiation. This modification leads to a significant improvement in capacitance, increasing from 125 F/g to 175 F/g at 5 mV/s in aqueous electrolytes. The carbons from the solar furnace are reproducible, underlying the potential of the proposed process towards a sustainable alternative. To achieve a theoretical reference, the pyrolysis process was mimic trough Reactive Molecular Dynamics calculations modeling the initial structural conditions of agave biomass with its corresponding lignocellulosic components and considering analogous thermal conditions. The resulting carbon structures at the end of the simulations showed structural properties that are consistent with those observed in the pair distribution functions obtained from XRD and the pore size distribution from physisorption analyses. This combined experimental–theoretical approach offers the potential to elucidate porous carbon structures derived from pyrolysis processes powered by solar radiation . This method can help in the design and identification of lignocellulosic structures in biomass, with the resulting carbon materials suitable for energy storage applications.

Iron ore wires as consumable electrodes for the hydrogen plasma smelting reduction in future green steel production

In this work we investigate the feasibility and optimisation pathways for using oxide-filled consumable electrodes as both ore feeding system and reducing/melting arc carrier in the hydrogen plasma smelting reduction process. Similar in nature to Söderberg-type electrodes, but free of C-containing substances, this approach has the potential advantage of eliminating the carbon emissions stemming from conventional electric arc furnace electrodes while drastically simplifying the ore feeding into the process. Using a commercial welding setup with a 1.2 mm thick oxide-cored steel wire, area investigations indicate that approximately 50% of the introduced iron ore could be reduced to metallic iron at 100 A arc current under an Ar-10% H2 atmosphere independent from deposition time. The reduction efficiency was negatively affected by increasing arc current and it was increased by using the wire as the anode. Based on the performed variation of deposition parameters, microstructural characterisation results, high speed footage and first upscaling trials, the key scientific questions and engineering pathways for technological optmisiation towards future green steel production technology are outlined and discussed.

Efficient decarburization modification of coal gasification fine ash by microwave field activation

The presence of residual carbon in coal gasification fine ash (CGFA) significantly impacts its subsequent processing and utilization. This paper proposes and investigates the use of microwave field heating to decarburize CGFA, exploiting its favorable microwave absorbing characteristics attributed to its composite structure comprising carbon, iron, and water. The experimental results demonstrate an 81% reduction in the required time and a 74% decrease in energy consumption (based on preliminary calculations) to achieve a decarburization rate of 95% compared to conventional thermal electric furnace calcination methods. The treated CGFA exhibits optimized mineral species, reduced electron binding energy, enhanced solubility, and increased heat release intensity during hydration, leading to improved reactivity of mineral phases in alkaline environments. Furthermore, when used as supplementary cementitious material, the activity index of CGFA shows a remarkable 21% increase in macroscopic performance testing.

Microwave heating to form porous TiO2 layer on high-haze FTO film for dye-sensitized solar cell

A porous TiO2 layer was formed on a fluorine-doped tinoxide (FTO) film using a microwave heating technique, and applied to a dye-sensitized solar cell (DSSC). Under microwave irradiation, a self-heating process was induced in the FTO film to raise the substrate temperature up to 600 °C within a minute. After 12 min of microwave irradiation of the porous TiO2/FTO double layer, the internal resistances at the TiO2/FTO interface and the TiO2 interparticles were effectively reduced. By tuning the haze of the optical transmission through the FTO film, the photovoltaic performance was enhanced, and the conversion efficiency reached values as high as 7.2% at a haze of 31.5%, which was attributed to effective light harvesting within the cell. Unique ionic diffusion induced under microwave irradiation was detected at a lower substrate temperature, and the cell that formed at a substrate temperature of 350 °C exhibited a conversion efficiency of 6.5%, which is high for the sintering temperature. Although the photovoltaic performance was comparable to that of a general DSSC, a rapid sintering process that reduced the internal resistance within the cell was demonstrated using a microwave heating technique. Compared with a conventional electric furnace, the microwave heating technique can produce ceramics with high densities in a short time, and is an ideal tool for producing DSSCs.

Electric Arc Furnace Stirring: A Review

Thermodynamics and kinetics are affected by the stirring conditions. Higher‐stirring intensities promote conditions closer to equilibrium and increase the mass‐transfer coefficients. A major limitation of the conventional electric arc furnace (EAF) is the low velocities of liquid steel which result in very poor mixing conditions. The practical consequences are lower decarburization rates and lower melting rates. Herein, the forces that operate and promote the motion of liquid steel in a conventional EAF are reviewed in detail; buoyancy forces, momentum transfer by the oxygen jets, drag forces by CO bubbles are produced by decarburization and local electromagnetic forces at the electrode regions. It is shown in the short range and limited intensity of the previous forces. Bottom gas injection and electromagnetic stirring are the main methods that can induce forced convection in the EAF. The information available is summarized and analyzed to describe the results obtained at laboratory level and industrial scale using different stirring mechanisms. Finally, guidelines are provided in this review for further research on the basis of the limitations of the current results.

Microstructural and Mechanical Characterization of Al Nanocomposites Using GCNs as a Reinforcement Fabricated by Induction Sintering

High-energy ball milling is a process suitable for producing composite powders whose achieved microstructure can be controlled by the processing parameters. Through this technique, it is possible to obtain a homogeneous distribution of reinforced material into a ductile metal matrix. In this work, some Al/CGNs nanocomposites were fabricated through a high-energy ball mill to disperse nanostructured graphite reinforcements produced in situ in the Al matrix. To retain the dispersed CGNs in the Al matrix, avoiding the precipitation of the Al4C3 phase during sintering, the high-frequency induction sintering (HFIS) method was used, which allows rapid heating rates. For comparative purposes, samples in the green and sintered state processed in a conventional electric furnace (CFS) were used. Microhardness testing was used to evaluate the effectiveness of the reinforcement in samples under different processing conditions. Structural analyses were carried out through an X-ray diffractometer coupled with a convolutional multiple whole profile (CMWP) fitting program to determine the crystallite size and dislocation density; both strengthening contributions were calculated using the Langford-Cohen and Taylor equations. According to the results, the CGNs dispersed in the Al matrix played an important role in the reinforcement of the Al matrix, promoting the increase in the dislocation density during the milling process. The strengthening contribution of the dislocation density was ~50% of the total hardening value, while the contribution by dispersion of CGNs was ~22% in samples with 3 wt. % C and sintered by the HFIS method. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to analyze the morphology, size, and distribution of phases present in the Al matrix. From the analyses carried out in AFM (topography and phase images), the CGNs are located mainly around crystallites and present height profiles of 1.6 to 2 nm.

Direct Microwave Sintering of Poorly Coupled Ceramics in Electrochemical Devices

The use of microwaves as the energy source for synthesis and sintering of ceramics offers substantial advantages compared to conventional gas-fired and electric resistance furnaces. Benefits include much shorter processing times and reaching the sintering temperature more quickly, resulting in superior final product quality. Most oxide ceramics poorly interact with microwave irradiation at low temperatures; thus, a more complex setup including a susceptor is needed, which makes the whole process very complicated. This investigation pursued a new approach, which enabled us to use microwave irradiation directly in poorly coupled oxides. In many solid-state electrochemical devices, the support is either metal or can be reduced to metal. Metal powders in the support can act as an internal susceptor and heat the entire cell. Then sufficient interaction of microwave irradiation and ceramic material can occur as the sample temperature increases. This microwave heating and exothermic reaction of oxidation of the support can sinter the ceramic very efficiently without any external susceptor. In this study, yttria stabilized zirconia (YSZ) and a Ni-YSZ cermet support were used as an example. The cermet was used as the support, and a YSZ electrolyte was coated and sintered directly using microwave irradiation without the use of any susceptor. The results were compared to a similar cell prepared using a conventional electric furnace. The leakage test and full cell power measurement results revealed a fully leak-free electrolyte. Scanning electron microscopy and density measurements show that microwave sintered samples have lower open porosity in the electrode support than conventional heat treatment. This technique offers an efficient way to directly use microwave irradiation to sinter thin film ceramics without a susceptor.

Low-temperature microwave-driven thermochemical generation of hydrogen from steam reforming of alcohols over magnetite

In a previous study, we reported that hydrogen generation can be achieved quite efficiently from seawater and contaminated waters at low temperatures using a microwave-driven hydrogen production (MDHP) process and waste activated carbon as the microwave absorption heating element (MAHE). However, the problem with this method is that activated carbon (a heat source from the microwaves) is used in the decomposition of water in which the quantity of activated carbon continues to decrease in parallel with the evolution of hydrogen. This problem has been resolved in this study by using magnetite as a novel MAHE component at low temperatures; the energy-saving thermochemical steam reforming reaction was performed with a mixed water/ethanol solution, for which results showed a maximum hydrogen generation yield somewhat greater than 80%. No hydrogen evolved in the thermochemical steam reforming process upon heating the magnetite at 350 °C in a conventional electric furnace, in contrast to the case where hydrogen was generated in yields greater than 40% by heating at 350 °C with microwaves. The rate-determining energy required for hydrogen generation is evidently heat, as evidenced by the formation of microwave-generated microscopic high-temperature fields (hot spots) at an estimated temperature of ca. 760 °C at the magnetite surface, a result of microwave heterogeneous microscopic thermal effects (MHMEs), and this even if the average temperature of the magnetite bulk were 350 °C.

Sustainable glasses in the SiO2–P2O5–CaO–K2O system from waste and concentrated solar power

Sustainable glasses were prepared by green technology including the use of different wastes as raw materials and concentrated solar power (CSP) as renewable energy. The raw materials used to formulate the glasses were animal bone flour ash, which presents high contents of CaO, P2O5 and alkaline oxides; glassy sand from the waste of packaging glass submitted to a primary treatment, composed principally of SiO2; and potassium carbonate of reagent grade. Different exposure times to solar radiation were tested. For comparison, the same composition of glass was melted into a conventional electric furnace. The use of CSP to produce glasses reduces the melting time by approximately 90%, with consequent energy savings. The increased CSP processing time results in more amorphous and thermally stable glasses. The results showed the viability of producing ecofriendly glasses in the SiO2–P2O5–CaO–K2O system, which could be used as matrix-based fertilizers.

A novel cyclic thermal treatment for enhanced globularisation kinetics in Ti-6Al-4V alloy: Experimental, constitutive and FE based analyses

Secondary hot-working on dual phase titanium alloys are essential for microstructural modification to tailor mechanical properties, which is typically challenging due to a narrow available processing window, especially during industrial scale manufacturing. Poor workability, strain induced porosity and adiabatic temperature rise in α + β phase region (i.e., sub-transus) are some of the main challenges faced. Cyclic thermal treatment (CTT) is an emerging technology showing potentials for microstructure modification (i.e., globularisation) in Ti‐6Al‐4V with significantly reduced mechanical work in the α + β region. This study summarises the results of CTT investigations conducted on a wrought Ti‐6Al‐4V alloy subjected to various thermo-mechanical conditions to develop different initial microstructures. Samples with uniform strain distributions were extracted from pre-forged samples and subsequently subjected to CTT using both conventional electric furnace (i.e., for slow heating and cooling rates), and induction heating (i.e., for faster heating and cooling rates). CTT of the samples forged at sub-transus temperature in conventional furnace led to maximum (i.e. ~100%) globularisation and significant coarsening of α grains, resulting in an equiaxed bimodal microstructure. On the other hand, CTT with induction heating method has resulted in a maximum of 80% globularisation fraction in samples forged to 60% reduction, and ~35% globularisation fraction in those forged to 20% reduction. The globularisation mechanisms during CTT of the sub-transus forged samples was dominated by the boundary splitting and thermal grooving. A Johnson-Mehl-Avarmi-Kolmogorov (JMAK) based model has been developed to predict the evolution of globularisation and grain growth during CTT. The developed JMAK model was then successfully incorporated into DEFORM® software as post-processing user subroutines. The predicted microstructure evolution by Finite Element (FE) simulations shown a good convergence towards the experimentally measured data following CTT.

Catalyst Ni-Mo/Al2O3 promoted with infrared heating calcination for hydrodesulfurization of shale oil

Ni-Mo/Al2O3 catalyst calcinated using infrared radiation heating was applied for the first time to hydrodesulfurization (HDS) of shale oil in a fixed bed reactor. Its catalytic performance was measured under varied operating conditions and compared to that obtained by using a catalyst with the same Ni-Mo composition but calcinated in a conventional electric furnace. The operation parameters of HDS were varied among temperature (320–400 °C), pressure (1.0–4.0 Mpa), H2/oil (v/v) (200:1–600:1) and LHSV (1–4 h−1). Under all tested conditions, the catalyst using the infrared heating method always yielded a product oil having the lower sulfur content than the catalyst heated by the conventional furnace did. At the optimal condition of T = 380 °C, P = 4 MPa, H2/oil (v/v) = 600:1 and LHSV = 4 h−1, the infrared-heating catalyst enabled the oil to decrease its sulfur content to 2600 ppm, which thus met the national Marine fuel oil standard (S < 0.5 wt%, GB1711-2015, China). Characterization of the fresh, sulfided and spent catalysts shown that the catalyst calcinated with the infrared heating had the higher BET surface area, smaller and narrower size distribution of metal particles, higher binding energy between Mo and S, and more oxygen-deficient sites in comparison with the catalyst calcined using conventional electric heating.

Synthesis of Non-Cubic Nitride Phases of Va-Group Metals (V, Nb, and Ta) from Metal Powders in Stream of NH3 Gas under Concentrated Solar Radiation

Using a high-flux solar furnace, loosely compacted powders of Va-group transition metal (V, Nb, and Ta) were reacted with stream of NH3 gas (uncracked NH3 gas) being heated by concentrated solar beam to a temperature (T) range between 600 and 1000 °C. From V, sub-nitride V2N (γ phase) and hypo-stoichiometric mono-nitride VN possessing fcc (face-centered cubic) crystal lattice structure (δ phase) were synthesized. On the other hand, in the reaction product from Nb and Ta, hexagonal mono-nitride phase with N/M atom ratio close to 1 (ε phase) was detected. The reaction duration was normalized to be 60 min. In a conventional industrial or laboratory electric furnace, the synthesis of mono-nitride phase with high degree of crystallinity that yield sharp XRD peaks for Va-group metal might take a quite long duration even at T exceeding 1000 °C. In contrast, mono–nitride phase MN of Va-group metal was synthesized for a relatively short duration of 60 min at T lower than 1000 °C being co-existed with lower nitride phases.

Comparative analysis for pyrolysis of sewage sludge in tube reactor heated by electromagnetic induction and electrical resistance furnace

A comparative study was conducted on the pyrolysis of sewage sludge in tube reactors heated by electromagnetic induction (EMI) and conventional electrical resistance furnace (ERF). A minimal effect of pyrolysis temperature and initial moisture content on the distribution of pyrolytic products was obtained. Compared with the counterpart from ERF pyrolysis, the bio-char from EMI pyrolysis exhibited less ash content (46.38 wt%) and higher organic matter content (53.62 wt%). SEM and FTIR test showed similar microstructure characterizations in the two bio-chars. The specific area of bio-char from EMI pyrolysis was 8.6 m2/g. EMI pyrolysis increased the total content of aliphatic/aromatics in the bio-oil from 10.8 wt% to 15.6 wt% and the hydrogen/carbon monoxide in the bio-gas from 33.8 vol% to 41.1 vol% because of possible cracking and reforming reactions. Increased sulfur content in the bio-oil and decreased hazard gas content (such as hydrogen sulfide and sulfur dioxide) in the bio-gas were obtained during EMI pyrolysis. The actual energy consumption for EMI and ERF pyrolysis were 4.62 MJ/kg and 6.65 MJ/kg. Increasing the feedstock content would reduce the energy consumption unit energy consumption. Less system energy loss during EMI pyrolysis might explain the higher energy recovery from EMI pyrolysis than that from ERF. Despite some disadvantages, EMI pyrolysis shows potential in real-plant applications.

Improved properties of Pb(Zr0.52Ti0.48)O3 films by hot plate annealing on LaNiO3 bottom electrode

Pb(Zr0.52Ti0.48)O3 (PZT) perovskite ferroelectric thin films were fabricated on LaNiO3 buffer silicon substrate by sol–gel spin coating technique. The thickness of PZT films was about 150 nm, and the thickness of LNO films as electrodes was about 120 nm. The prepared PZT thin films were annealed by hot plate annealing and conventional electric furnace annealing at various temperatures for 30 min. The microstructure of annealed films was analyzed by different techniques. The obtained results demonstrated that the perovskite phase can be achieved in films by both methods of annealing. Structural and morphological characterizations substantiated that hot plate annealing method can facilitate the formation of perovskite phase of PZT films than the electric furnace annealing. Consequently, the films annealed using hot plate exhibited more excellent electrical properties. The higher dielectric permittivity, remnant polarization, and the lower dielectric dissipation were observed for the thin films annealed at 550 °C by the hot plate. The values of remnant polarization and coercive field of PZT annealed on the hot plate were 36.4 μC/cm2 and 168 kV/cm, respectively. These results demonstrated that the crystallization of ferroelectric PZT films was improved by hot plate annealing.

An experimental study and WinXCom calculations on X-ray photon characteristics of Bi2O3- and Sb2O3-added waste soda-lime-silica glass

Radiation is used in a variety of different fields, and thus protection from its hazardous effects become a popular subject for researchers. For this purpose, in the present study, waste soda-lime-silica glasses as SiO2–Na2O–CaO–Bi2O3 and SiO2–Na2O–CaO–Sb2O3 were investigated for X-rays photon characteristics in the energies of 0.01–0.1 MeV via WinXCom program, and the results were compared with the experimental findings obtained at 0.04 MeV. Waste packaging glass was evaluated by adding varying amounts (0.005, 0.05, and 0.5 percentages) of Bi2O3 and Sb2O3. Seven different glass batches were prepared by following the procedures of precisely weighing the relevant amounts to obtain 10 g specimen in total, homogeneously mixing the respective contents, and thoroughly melting in an Au–Pt crucible via conventional electrical furnace at 1250 °C for 4 h. The linear attenuation coefficient (LAC) for glass specimens were experienced at 0.04 MeV, and it was found out that increasing contents of both oxides increased the LAC implying that a decrease in X-ray transmission occurred. From the point of WinXCom calculations, the LAC and mass attenuation coefficient (MAC) increased while half value layer (HVL) and mean free path (MFP) thicknesses decreased as the oxide substances increased in the glass specimens. That is, Sb2O3 addition provided higher X-rays attenuation characteristics in comparison to Bi2O3 additive. Further, the experimental data at 0.04 MeV were compared with WinXCom calculations, and it was figured out that the data were parallel for each other, but the correlation coefficient (R2) was found as 0.15 which means that the values were in loose agreement.

Effect of in situ SiC and MoSi2 phases on the oxidation behavior of HfB2-based composites

Monolithic HfB2 and HfB2-15vol%SiC-15vol%MoSi2 composite samples were oxidized by a conventional electric furnace at 1700 °C for 5 h. Microstructural and phase analysis of the oxidized samples were performed by X-ray diffraction (XRD) analysis and field emission scanning electron microscope (FESEM) equipped with energy-dispersive spectroscopy (EDS). Besides, for analyzing the oxidation mechanism of the samples, thermodynamic calculations were also accomplished by HSC software. The changes in weight and thickness of the oxide scale were measured and the oxide growth rate of the oxidized samples was subsequently calculated. The results showed that HfB2-15vol%SiC-15vol%MoSi2 composite was much more resisted than that monolithic HfB2 due to the formation of a thin Si-rich glass layer on the surface of the composite sample. By acting to fill the porosities between HfO2 grains, Si-based glass phase enhanced the oxidation resistance of HfB2-15vol%SiC-15vol%MoSi2 composite. Conversely, the oxidized monolithic HfB2 had only a thick porous oxide layer (HfO2) which led to considerably lower oxidation resistance. On the other side, three layers containing HfO2 and Si-based glass phases were formed on the oxidized HfB2-15vol%SiC-15vol%MoSi2 composite. Moreover, no porosities and no porous layers were also detected on the oxidized composite sample. Consequently, HfB2-15vol%SiC-15vol%MoSi2 composite had a parabolic behavior owing to its diffusion-controlled oxidation under the isothermal oxidation process.

Influence of the Calcination Technique of Silica on the Properties and Performance of Ni/SiO2 Catalysts for Synthesis of Hydrogen via Methane Cracking Reaction.

Deactivation of catalysts due to rapid blocking of active surfaces and pores is a major problem for methane cracking. The removal of the template using different calcination methods contributes to the different characteristics of catalyst support. Therefore, silica supports were prepared with the sol–gel method, where sodium silicate and chitosan are a silica source and a template, respectively. Calcination using a microwave muffle furnace (MWF) was preferred over the conventional electric muffle furnace at the heating rates of 2 and 17 °C/min (CEF2 and CEF17, respectively) in order to remove the chitosan template. A nickel nitrate precursor was loaded onto the obtained silica supports by the incipient wetness impregnation method. The properties of the silica support and the Ni/SiO2 catalysts were characterized by means of N2-sorption, X-ray diffraction, scanning electron microscopy–energy-dispersive X-ray, field emission transmission electron microscopy, and H2 temperature-programmed reduction. The catalytic activity was evaluated using a fixed-bed reactor at 550 °C with a CH4/N2 ratio of 1:4 in the feed. The amount and the allotropes of carbon deposited on the spent catalysts were investigated using thermogravimetric/differential thermal analysis. The results showed that the SiO2-MWF support had a higher surface area and a larger pore volume of a mesoporous structure with larger interparticle channels than that of the SiO2-CEF supports. This leads to the higher dispersion of Ni metal particles over and inside the interparticle channels of the SiO2-MWF support. This provided a higher metal–support interaction, resulting in lower rates of methane conversion and carbon deposition on the catalyst surface than those of Ni/SiO2-CEF catalysts. However, it displayed a lower bed pressure. It was found that the carbon fibers deposited on all the catalysts were multiwalled carbon nanotubes (MWCNTs). Additionally, the base-growth mechanism of MWCNTs was only exhibited by the Ni/SiO2-MWF catalyst.