Conventional Heating Method Research Articles

Facile Microwave Synthesis of Hierarchical Porous Copper Oxide and Its Catalytic Activity and Kinetics for Carbon Monoxide Oxidation.

The synthesis of copper oxide (CuO)-based nanomaterials has received a tremendous deal of interest in recent years. Particularly, the design and development of novel CuO structures with improved physical and chemical properties have attracted immense attention, especially for catalysis applications. We report on a rational, rapid, and surfactant-free microwave synthesis (MWS) of hierarchical porous copper oxide (HP-CuO) with a three-dimensional (3D) sponge-like topology using an MWS reactor. The activity of the microwave (MW)-synthesized HP-CuO catalysts for carbon monoxide (CO) oxidation was studied and compared to CuO prepared by the conventional heating method (CHM). Results showed that HP-CuO catalysts prepared by MWS for 10 and 30 min surpassed the CuO catalyst prepared by CHM, exhibiting T 80 of 98 and 115 °C, respectively, as compared to 185 °C of CuO prepared by CHM (T80 is the temperature corresponding to 80% CO conversion). In addition, the MW-synthesized HP-CuO catalysts outperformed the CHM-synthesized CuO, achieving a 100% CO conversion at 150 °C compared to 240 °C in the case of CuO prepared by CHM. Interestingly, the HP-CuO catalyst expressed workable CO conversion kinetics with a reaction rate of c.a.35 μmol s-1 g-1 at 150 °C and apparent activation energy (E a) of 82 kJ mol-1. The HP-CuO catalyst showed excellent cycling and long-term stabilities for CO oxidation up to 4 cycles and 72 h on the stream, respectively. The enhanced catalytic activity and stability of the HP-CuO catalyst appear to result from the unique topological and structural features of HP-CuO, which were revealed by SEM, XRD, Raman, BET, TGA, XPS, and TPR techniques.

An in situ study of the thermal decomposition of 2,2′-azobis(2-methylpropionitrile) radical chemistry using a dual-mode EPR resonator

A custom-built dual-mode EPR resonator was used to study the radical chemistry of AIBN thermal decomposition. This resonator enables both simultaneous in situ heating using microwaves and EPR measurements to be performed. The thermal decomposition of AIBN was compared following conventional heating methods and microwave-induced (or dielectric) heating methods. Under both heating conditions, the radicals formed and detected by EPR include the 2-cyano-2-propyl (CP●) and 2-cyano-2-propoxyl (CPO●) radicals. Under aerobic conditions, the observed relative distribution of these radicals as observed by EPR is similar following slow heating by conventional or dielectric methods. In both conditions, the kinetically favoured CPO● radicals and their adducts dominate the EPR spectra up to temperatures of approximately 80–90 °C. Under anaerobic conditions, the distribution can be altered as less CPO● is available. However, the observed results are notably different when rapid heating (primarily applied using a MW-induced T-jump) is applied. As the higher reaction temperatures are achieved on a faster timescale, none of the ST●-CPO adducts are actually visible in the EPR spectra. The more rapid and facile heating capabilities created by microwaves may therefore lead to the non-detection of radical intermediates compared to experiments performed using conventional heating methods.

The Effectiveness of Torrefied Agricultural Wastes using Conventional Heating

The production of wastes volume from agricultural wastes have led to the selection as a renewable energy feedstock, and it has the opportunity into energy market. A comparison is made between two mode of wastes that is treated (rinse and soaking in water for 12 hours) and raw of coconut husk (CH) tap under torrefaction were investigated. This work has utilized of conventional heating method with mild oxygen concentration for the properties and combustion characteristics feedstock output. As such the influenced parameters with size of 750μm, holding temperature at (200, 240, and 280 °C), and residence duration at (20, 40 and 60 minutes) were involved within this torrefaction setup. The combustion behaviour of tested coconut husks marked three discrete zone, whereby the severity setup resulted to increase the fixed carbon (FC) value, thus leading to higher ignition temperature. The changes in mass yield and the increased of honeycomb-like and spongy-like porous structure were recorded for treated coconut husk than of the raw. The functional group results from Fourier Transform Infrared (FTIR) test showed a valuable interest of treated mode also been discussed.

Effects of microwave and conventional heating methods with various exposure times on the physical and chemical parameters, fatty acid composition, and sensory properties of extra virgin olive oil

Effects of microwave and conventional heating methods with various exposure times on the physical and chemical parameters, fatty acid composition, and sensory properties of extra virgin olive oil

Microwave Preparation of Porous Graphene from Wasted Tires and Its Pyrolysis Behavior

Nowadays, most waste tires are disposed of by direct combustion or via landfill, which inevitably creates a large volume of waste. However, the soft carbon found in tires can be an excellent precursor in the preparation of graphene. In this study, waste tires were mixed with potassium hydroxide and heated in a microwave environment to be converted rapidly into porous graphene, a process having no complicated pre-processing. Moreover, the processes, tools, and chemical reagents are distinct and inexpensive. This research innovatively uses the characteristics of microwave rapid and selective heating to study the pyrolysis behavior of waste tires after adding alkali, and realizes the conversion of soft carbon in tires to graphene. At the same time, the time required for the preparation process is greatly reduced which compared with conventional heating methods. Thermogravimetric analysis and dielectric property testing of the tires and mixtures were conducted to study their pyrolysis behavior and catalytic reactions. It was found that when the temperature reached more than 750 °C, potassium ions and carbon underwent a reduction reaction to generate potassium vapor, which catalyzed the carbon in the tires into porous graphene, and that microwave heating could shorten the heating time. Simultaneously, the carbon in the tire could be sheared smaller and thinner during the rapid pyrolysis and volatilization of the gas, benefitting the graphene production. The products of the mixed materials were then characterized and analyzed at different holding temperatures and times. As the holding time increased, the degree of graphitization of the products increased, the number of layers increased slightly, and the impurity elements were completely removed from the products.Graphical Abstract

Mathematical modeling of continuous induction heating of sour cherry juice

Induction heating is a noncontact heating method that enables heating of ferromagnetic materials. In this study, continuous induction heating system was custom set up and experimental and numerical results were compared. Sour cherry juice was heated to a target temperature value (75°C) at three different flow rates (200–250-300 ml/min) and three different set pipe wall temperatures (80–90–100°C) in experimental study. COMSOL Multiphysics 5.2 was used to solve mathematical models and visualize temperature distribution during heating and flowing. Magnetic field, heat transfer, and laminar flow physics paired each other in the model. It was concluded that the time-dependent variation of the sour cherry juice output temperature was successfully predicted by the model developed for induction process conditions. The developed models could be used to estimate process time, temperature history of materials, and effect of flow rate on heating rate any time during the continuous induction heating process. Practical applications Thermal processes applied in the food industry are aimed to inactivate the microorganisms in the food, to protect the nutrient content, and to have high energy efficiency. Conventional heating methods have a negative effect on the nutrient content of foods and the energy efficiency of the heating process due to long processing times. The advantages of induction heating are that it is a novel heating method, highly energy efficient, and performs heating process in a short time. In this study, a laboratory-scale continuous induction heating system to heat a liquid food product was established and numerical modeling of the heating process was performed. The obtained model will be an important data for installation of the continuous induction heating systems, scale-up in the continuous induction heating systems, and prediction to effects of the process parameters.

Design, Synthesis, SAR, Pharmacokinetic Prediction of New 4-Quinolones as Anti-Microbial Agents.

s of new 4-quinolone derivatives was synthesized by conventional heating method. For the synthesized compounds, we performed pharmacokinetic prediction, SAR and antimicrobial assay. The presence of halogen elements plays a key role in the biological activity that is clear by in vitro analysis. Target compounds exhibit moderate to significant activity near to standard marketed drugs like amoxycillin, chloramphenicol, ciprofloxacin, norfloxacin, griseofulvin, and nystatin.

Heating using microwave technique: An approach towards green chemistry

Green chemistry focuses on minimizing waste, minimizing use of chemicals/reagents, reducing pollution and preservation of human health and environment. Using conventional methods of synthesis are creating the said problems in present scenario. To solve these problems new alternate methods must be developed. Many alternatives have been already developed but many more have to do. Use of microwave radiations are one the alternative in which these radiations are used for heating purpose instead of conventional heating methods which uses solvents in large amount and requires much time. Lot of benefits are there in heating using microwave radiations over conventional methods of heating but have limitations too. Not for every reaction/synthesis, but microwaves can be only used for the reactant having specific properties. Single mode and multi-mode microwave ovens are usually used for achieving this purpose. Heating by microwave radiations not only saves time i.e. it converts hours to minutes because it accelerates the reaction, increases the yield, reduces the energy requirement and the most important thing is no or minimum pollution/waste. Health hazards are also been noticed in using these radiations both external and internal. This short communication was aimed to find out the necessity of alternative methods of synthesis that fulfils the concept of green chemistry which will fulfill the need of healthy life and environment.

Carbon and Carbon/Metal Hybrid Structures Enabled by Ultrafast Heating Methods

High‐temperature thermal treatment is a standard step in synthesis of many materials. Recently, ultrafast heating methods, such as Joule heating, laser, light, or microwave irradiations, have been used to create novel carbon materials and carbon/metal hybrid structures, demonstrating unique and often superior properties compared with those synthesized by conventional heating methods. They have shown promising application potentials in catalysis, batteries, supercapacitors, fuel cells, sensors, implants, actuators, lighting devices, and waste recycling. Herein, recent findings in creating novel carbon and carbon/metal hybrid structures by ultrafast heating methods are reviewed. The most frequently used ultrafast heating methods, their advantages, and their limitations are first described. Then, different carbon structures created by these methods, including graphene, reduced graphene oxide, hard carbon, carbon nanotube architectures, and other carbon hybrids, are summarized. Next, novel carbon/metal hybrid structures are reviewed, including carbon‐supported nanoparticles of monometals, metal alloys, metal composites, high‐entropy alloys, and single‐atom catalysts. Heating methods, critical precursors used, synthesis parameters affecting material structures, and mechanistic understanding of their unique synthesis processes are focused on. The essential properties of these novel structures and their applications are also summarized. Finally, knowledge gaps and technical challenges in using these methods for scalable material production are discussed.

Development and assessment of magnetic Fe2O3@MOF-74 composite sorbents for ethylene/ethane separation

Development of smart sorbents that can be regenerated when triggered by external stimuli such as magnetic field can overcome the poor energy utilization of the current sorbents investigated for light olefins/paraffins separation. In this work, we report the development of novel magnetic sorbents comprising of MOF-74 crystals and superparamagnetic Fe2O3 particles in a core–shell structure, and assessment of their C2H4/C2H6 separation performance. The electromagnetic properties of the materials were tuned by varying the Fe2O3 (Fex) loading (x = 1–20 wt%), and their effects on adsorption capacity, selectivity, and desorption rates were systematically investigated. The surface area, microporosity, and the C2H4/C2H6 selectivity of composites were reduced as the Fex content increased, while the specific heat absorption rate (SAR) was increased from 60 to 80 % upon varying the magnetic field intensity from 12.6 to 31.4 mT. On the basis of the SAR enhancement upon increasing the Fex loading, the C2H4 desorption rates were gradually increased with Fex up to 10 wt%, however beyond this composition a decline in the desorption rates was noted. Moreover, the cooling rate was found to be ∼76 % higher in induction heating compared to the conventional thermal heating method, which is expected to significantly shorten the cycle time, thereby reducing the column size and improving the throughput of the system. Our results highlight the importance of assessing the trade-offs between capture capacity and extent of responsiveness to magnetic field (i.e., temperature rise during regeneration) when developing smart sorbents. This work builds on previous studies that demonstrate the suitability of novel stimuli-responsive sorbents for next generation of olefin/paraffin separation systems.

Experimental Investigation on the Effect of Electrically Assisted Rapid Heating in Bulk Metal Forming

Many industries utilize hot metal forming to reduce forming forces and material flow issues. In this study, electrically assisted (EA) rapid heating is used in direct comparison to conventional heating methods. Three materials were investigated: AISI 4340, Al-7075-T6, and Ti-6Al-4V. Samples were heated at an approximate rate of 100 °C/s before applying compressive loads, simulating forging or other bulk deformation processes. Afterwards, samples were prepared for further microstructure evaluation. It was observed that high-rate temperature increase resulted in some developments in the microstructure and phases, as seen in AISI 4330, for example. Additionally, the effect of electricity was noticed to have a significant impact on flow stresses, as observed in many of the compression tests, immediately following the rapid heating process. Experiments and images from optical microscopy show that samples experienced drastic and immediate decrease in flow stress at all temperatures when using the EA rapid heating method versus the conventional method with seemingly no change to the material microstructure. This may be explained by the lack of phase changes at lower temperatures combined with the effect of electricity. Further investigation into the changes in micro-porosity, intermetallic phases, and changes in precipitates are suggested to supplement the current understanding of the drastic stress drop caused by passing electrical currents through metals.

Experimental investigation of the natural convection heat transfer characteristics of cylinder walls with a DBD actuator as the heat source

Conventional electric heating methods applied when evaluating the natural convection heat transfer parameters at the outer walls of cylinders produce uneven heat flows and large measurement errors. The present work addresses these issues by developing a new heating method using a dielectric barrier discharge (DBD) actuator as the heat source. An experimental system is constructed, where the thermal power output of the DBD actuator is first measured by calorimetry, and the natural convection heat transfer characteristics of a representative cylinder are analyzed with an explicit accounting of the temperature distribution at the outer wall of the cylinder. The results demonstrate that the DBD actuator can provide more uniform heat flow than conventional electric heaters. The temperature difference between the top and the bottom of the cylinder wall initially increases with increasing thermal power, decreases to a minimum at a thermal power of about 400 W, and subsequently increases with increasing thermal power. In addition, and the feasibility of the DBD actuator as a heat source is demonstrated according to the high degree of conformation between the calculated values and empirically established correlations between Nusselt number, which generally deviate by less than 10%.

Frequency-Variable Resonant Self-Heating Technique for Lithium-Ion Batteries at Low Temperature

This article presents a frequency-variable resonant self-heating technique for improving the heating speed of lithium-ion batteries at very low temperatures. In contrast to the conventional heating method with a fixed current and frequency, the proposed technique can increase the battery heating current by determining the minimum impedance of the lithium-ion batteries. Then, through a variable charging/discharging frequency operation, this technique can increase the heating speed without inducing a temperature plateau because of impedance reduction. A lithium-ion battery with improved self-heating performance at low temperatures was developed and used to verify the proposed self-heating technique. A simulation model and self-heating device (dc/dc converters) were also designed and tested at –30-°C ambient temperature. The proposed frequency-variable resonant self-heating technique achieved a heating speed four times faster (from 2784 s to 717 s) than the conventional self-heating technique. Thus, lithium-ion batteries can be used at cryogenic temperatures (–30 °C) by quickly raising the battery temperature with this technique.

Microwave assisted synthesis of substituted benzimidazoles using trimethylsilyl chloride as phase transfer catalyst, characterization, biological activities and molecular docking studies

A convenient method for the synthesis of imidazole derivatives using two phase system under microwave induced technique and phase transfer catalyst TMSCl (15%) is described. This technique has increased the rate of reaction drastically as well as the yield of the product when compared to conventional heating method. The synthesized compounds were screened for their in vitro antibacterial and antifungal activities against. The molecular docking studies were carried out using the software Arguslab 4.0.1. and minimum ligand pose energy of all the synthesized benzimidazoles, H-bond interactions and other electrostatic interactions in the active site of the target protein Thymidylate kinase (TMPK) was also investigated.

Research Progress on Magnetic Catalysts and Its Application in Hydrogen Production Area

The noncontact heating technology of IH targets heat directly where it is needed through the electromagnetic energy adsorption and conversion of magnetic materials. Unlike conventional heating methods, the heat generated by electromagnetic induction of magnetic materials can be applied directly into the reactor without heating the entire device; this new heating method is not only more energy efficient but also safer, cleaner and more sustainable if renewable electricity is adopted; moreover, magnetic catalysts can be recovered and reused by separating chemical reactants and products from the catalyst by the application of a magnetic field, and it can provide the required heat source for the reaction without altering its catalytic properties. Magnetic catalysts with an electric field have been applied to some industrial areas, such as the preparation of new materials, catalytic oxidation reactions, and high-temperature heat absorption reactions. It is a trend that is used in the hydrogen production process, especially the endothermic steam reforming process. Therefore, in this paper, the heat release mechanism, properties, preparation methods and the application of magnetic catalysts were presented. Highlights of the application and performance of magnetic catalysts in the hydrogen production area were also discussed.

Synthesis and uranium adsorption studies of UiO-66 (Ce) based metal organic frameworks from aqueous solutions

Ce based Metal Organic Framework (MOF) UiO-66 (Ce) and a MOF-composite CeO2@UiO-66 (Ce) were prepared by conventional heating and hydrothermal method respectively. Both the MOFs were characterized using X-ray Diffraction (XRD) technique, Fourier Transform Infra Red (FT-IR) spectroscopy, Field Emission-Secondary Electron Microscopy (FE–SEM), Small Angle X-ray Scattering (SAXS), Thermogravimetric Analysis (TGA), Differential Thermal Analysis (DTA) and Transmission Electron Microscopy (TEM). N2 adsorption-desorption isotherms of UiO-66 (Ce) showed large specific surface area of ∼981 m2/g and a reasonably large pore volume compared to the composite sample. Their uranium adsorption capacity in aqueous solutions was investigated in the pH range 2–6. Uranium adsorption experiments indicated reasonably higher uranium adsorption capacity of 239 mg/g for CeO2@UiO-66 (Ce) compared to UiO-66 (Ce) (190 mg/g). Kinetic studies revealed rapid uranium adsorption in pure MOF compared to the composite material which was attributed to the blocking of pores by CeO2 nanoparticles in the composite material. These frameworks showed good thermal stability as revealed by the thermogravimetric studies. The synthesized MOFs exhibit moderate recyclability using dilute acid and can be utilized in successive cycles. The selectivity studies showed that these MOFs are highly selective to U (VI) compared to Fe (III), Co (II), Ni (II) and Sr (II). This study could pave a way for more advanced material synthesis involving MOFs which could prove very beneficial for the wastewater remediation thus creating a safer environment to live in.

Microwave-Induced Deep Catalytic Oxidation of NO Using Molecular-Sieve-Supported Oxygen-Vacancy-Enriched Fe-Mn Bimetal Oxides.

A novel microwave (MW) catalytic oxidation denitrification method was developed, which can deeply oxidize NO into nitrate/nitrite with little NO2 yield. A molecular-sieve-supported oxygen-vacancy-enriched Fe2O3-MnO2 catalyst (Ov-Fe-Mn@MOS) was fabricated. Physicochemical properties of the catalyst were revealed by various characterization methods. MW irradiation was superior to the conventional heating method in NO oxidation (90.5 vs 70.6%), and MW empowered the catalyst with excellent low-temperature activity (100-200 °C) and good resistance to H2O and SO2. Ion chromatography analysis demonstrated that the amount of nitrate/nitrite accounted for over 90.0% of the N products, but the main product gradually varied from nitrate to nitrite as the reaction proceeded because of the switching of the main reaction path of NO removal. Mechanism analyses clarified that NO oxidation was a non-radical catalytic reaction: (i) the chemisorbed NO on ≡Mn(IV) reacted with O2* to produce nitrate and (ii) the excited NO* due to MW irradiation reacted with the active O* generated from Ov···O2 to form nitrite. Density functional theory calculations combined with electron paramagnetic resonance tests revealed the promotional effects of Fe2O3 in (i) boosting the Ov's quantity; (ii) facilitating O2 adsorption; (iii) increasing the nitrite formation; and (iv) alleviating the suppression of SO2.

Amine-Modified Chitosan Flocculant Synthesized via Single-Mode Microwave Method for Laundry Wastewater Treatment.

In this study, an effective and environmentally friendly polyaminated cross-linked chitosan (M-PACTS) flocculant was successfully synthesized via circular focus single-mode microwave synthesizer irradiation. Epichlorohydrin and tetraethylenepentamine were used as the cross-linking agent and active cationic reagent, respectively. The same formation was used to prepare cationic lightly cross-linked chitosan (C-PACTS) via the conventional heating method. The flocculant was characterized using Fourier transform infrared spectroscopy, X-ray diffraction analysis, and scanning electron microscopy. The flocculation capability of C-PACTS and M-PACTS was compared using laundry wastewater as a model pollutant. The pH, PACTS dosage, temperature, stirring rate, stirring time, and setting time were systematically investigated. The experimental results showed that circular focus single-mode microwave synthesizer irradiation was a more efficient method to modify chitosan. M-PACTS exhibited a higher capacity for turbidity and chemical oxygen demand (CODCr) removal. Under optimal conditions, the removal rate values of M-PACTS were up to 96% (turbidity) and 78% (CODCr). The proposed PACTS is suitable for treatment of polluted wastewater in an eco-friendly manner without causing secondary pollution.

Numerical analysis of zero-carbon HCCI engine fuelled with steam diluted H[formula omitted]/H[formula omitted]O[formula omitted] blends

The addition of hydrogen peroxide and steam to a hydrogen-fuelled HCCI engine was investigated at various fuel lean conditions (ϕeff = 0.2–0.6) and compression ratios (15–20) using a 0-dimensional numerical model. The use of hydrogen peroxide as an ignition promoter demonstrated increased IMEP (16%–39%), thermal efficiency (up to 2%), and reduced NOx (50%–76%) when compared to the conventional method of intake charge heating. When hydrogen peroxide was used as an ignition promoter, a 15% addition of steam was sufficient to reduce NOx by 93%–97%, though this reduced IMEP and thermal efficiency slightly. When heat transfer was considered and steam addition was increased from 0%–10%, no increase in intake air heating was able to match the IMEP of 5% hydrogen peroxide addition without an increase in the equivalence ratio (up to 40%). The parametric space of hydrogen peroxide (0%–25%) and steam (0%–40%) addition was explored in view of engine performance metrics, showing the complete range of conditions possible through control of both inputs. A three-order reduction in NOx was possible through steam addition. An optimal balance of performance and emissions occurred at 5%–10% hydrogen peroxide and 10%–15% steam addition. In a study of compression ratio, very little hydrogen peroxide addition (<5%) was required to achieve 98% of the maximum efficiency at higher compression ratios (19–20), though at lower compression ratios (<17) impractical quantities of hydrogen peroxide were required. The 10% steam addition present at these conditions led to extremely low NOx levels for ϕeff of 0.3 and 0.4, though at ϕeff of 0.5 NOx levels would require some after-treatment. Maintaining constant a high or low load across steam additions was possible through reasonable adjustment of hydrogen peroxide addition.

Microwave-Assisted Solvothermal Synthesis of Mo-Doped TiO2 with Exceptional Textural Properties and Superior Adsorption Kinetics.

Assigned to their outstanding physicochemical properties, TiO2-based materials have been studied in various applications. Herein, TiO2 doped with different Mo contents (Mo-TiO2) was synthesized via a microwave-assisted solvothermal approach. This was achieved using titanium (IV) butoxide and molybdenum (III) chloride as a precursor and dodecylamine as a surface directing agent. The uniform effective heating delivered by microwave heating reduced the reaction time to less than 30 min, representing several orders of magnitude lower than conventional heating methods. The average particle size ranged between 9.7 and 27.5 nm and it decreased with increasing the Mo content. Furthermore, Mo-TiO2 revealed mesoporous architectures with a high surface area ranging between 170 and 260 m2 g−1, which is superior compared to previously reported Mo-doped TiO2. The performance of Mo-TiO2 was evaluated towards the adsorption of Rhodamine B (RhB). In contrast to TiO2, which revealed negligible adsorption for RhB, Mo-doped samples depicted rapid adsorption for RhB, with a rate that increased with the increase in Mo content. Additionally, Mo-TiO2 expressed enhanced adsorption kinetics for RhB compared to state-of-the-art adsorbents. The introduced synthesis procedure holds a grand promise for the versatile synthesis of metal-doped TiO2 nanostructures with outstanding physicochemical properties.