堀越 智

Recycling e-wastes using a VVF power cable through a rapid pyrolytic mechanism by microwave radiation is reported, and it is possible to produce copper wire and carbon resources without going through highly toxic intermediates.

Abstract Variable Frequency Microwave (VFM) radiation provides a solution to the inhomogeneity of the electric field in the cavity, which has long led to a decline in the reliability of microwave chemical data and its industrial utilization. Herein, we report in-situ three-dimensional experimental measurements of the electric field’s uniform distribution of VFMs within a multimode cavity under high power conditions, and their subsequent comparison to Fixed Frequency Microwaves (FFM) that could only be assessed earlier through theoretical analysis. We also examine the consequences of changes in VFM irradiation conditions and elucidate the threshold at which VFM irradiation might prove beneficial in syntheses. With an ultimate focus on the use of VFM microwave radiation toward industrial applications, we carried out an effective synthesis of 4-methylbyphenyl (4-MBP) in the presence of palladium (the catalyst) supported on activated carbon particulates (Pd/AC), and revisited two principal objectives: (a) the effective suppression of discharge phenomena (formation of hot spots), and (b) synthesis scale-up using a 5-fold increase in sample quantity and a 7.5-fold larger reactor size (diameter) than otherwise used in earlier studies.

Abstract The microwave vulcanization of tire rubber was investigated by monitoring the dielectric properties of the rubber polymer and other components of the formulation (including carbon filler, antioxidant, and vulcanization agents) as functions of frequency and temperature. The effect of the vulcanization reaction on the dielectric properties during heating was also assessed. The physical interaction between the crosslinked structure and the carbon black significantly favors the responsiveness to microwaves during the vulcanization reaction. Based on these basic data, microwave irradiation conditions were determined, and model tire samples were microwave vulcanized in a PTFE mold. It has achieved a shorter time of heating and 65% energy saving, but on the other hand, it has become clear that the vulcanization produces very poor physical quality compared to vulcanization by electric furnace heating. To solve this problem, we performed microwave irradiation using variable frequency microwave (VFM; 5.85 ~ 6.65 GHz) using glass fiber on polyetherketoneketone (PEEK/GF) mold. In VFM, compared to conventional fixed frequency microwave (FFM), successfully synthesized high‐quality tire rubber because it showed 4.2, 1.1, 2.0, 1.2, and 1.8 times higher values in terms of cross‐linking density value, hardness value, tensile strength, elongation at break, and 200% modulus, respectively.

<p>The discovery of a water-soluble polymer that cross-links to form a gel using a novel green gelation method: the microwave-induced in-liquid-plasma method that requires neither a cross-linking agent nor an initiator as are required in the conventional chemical method.</p>

This study used controlled microwaves to elucidate the response of adhesive components to microwaves and examined the advantages of microwave radiation in curing epoxy adhesives. Curing of adhesives with microwaves proceeded very rapidly, even though each component of the adhesive was not efficiently heated by the microwaves. The reason the adhesive cured rapidly is that microwave heating was enhanced by the electrically charged (ionic) intermediates produced by the curing reaction. In contrast, the cured adhesive displayed lower microwave absorption and lower heating efficiency, suggesting that the cured adhesive stopped heating even if it continued to be exposed to microwaves. This is a definite advantage in the curing of adhesives with microwaves, as, for example, adhesives dropped onto polystyrene could be cured using microwave heating without degrading the polystyrene base substrate.

The heptyl butanoate ester was synthesized from butanoic acid and heptanol in a heterogeneous medium in the presence of sulfonated activated carbon (AC-SO3H) catalyst particles subjected to microwave irradiation, which led to higher conversion yields (greater product yields) than conventional heating with an oil bath. The advantage of the microwaves appeared only when the moisture content in the butanoic acid batch(es) was high, suggesting that, unlike conventional heating, the reverse reaction caused by the moisture content and/or by the byproduct water was suppressed by the microwaves. This contrasted with the results that were found when carrying out the reaction in a homogeneous medium in the presence of the 2,4,6-trimethylpyridinium-p-toluene sulfonate (TMP-PTS) catalyst, as product yields were not improved by microwave heating relative to conventional heating. The removal of moisture/water content in the reaction solution was more pronounced when the reactor was cooled, as the reaction yields were enhanced via selective heating of the heterogeneous catalyst. A coupled electromagnetic field/heat transfer analysis gave credence to the selective heating of the AC-SO3H catalyst, which was further enhanced by cooling the reactor. It was deduced that unforeseen impurities and local high-temperature fields generated on the surface of small fine catalyst particles may have had an effect on the microwave chemistry such that the associated phenomena could be mistaken as originating from a nonthermal effect of the microwaves. Accordingly, it is highly recommended that impurities and selective heating be taken into consideration when examining and concluding the occurrence of a microwave nonthermal effect.

We report on the low-temperature steam reforming and water–gas shift processes to generate H₂ efficiently from water passed through MW-heated activated carbon (AC) particles, contrary to the inefficient conventional steam reforming at T ≈ 600 °C.

The application and advantages of variable frequency microwaves (VFM; range, 5.85–6.65 GHz) are reported for the first time in microwave chemistry, particularly when carrying out reactions catalyzed by metallic conductive catalysts so as to avoid the formation of arc discharges, and especially when using a strong microwave absorber such as activated carbon (AC) particulates as supports of metal-based catalysts. Two model reactions performed in low boiling point nonpolar solvents are described wherein arc discharges easily occur under the more conventional fixed frequency microwave (FFM) approach: (i) the synthesis of 4-methylbiphenyl (4MBP) by the Suzuki-Miyaura cross-coupling process catalyzed by Pd particles supported on AC particulates (Pd/AC), and (ii) the synthesis of toluene via the dehydrogenation of methylcyclohexane (MCH) catalyzed by Pt particles dispersed on AC particulates (Pt/AC). Contrary to the usage of fixed frequency microwaves (5.85 GHz and 6.65 GHz), the use of VFM microwaves increased the chemical yields of 4MBP {49% versus 5–8% after 60 min} and toluene {89% versus 24% after 10 min} by suppressing the formation of discharges that otherwise occur on the catalyst/AC surface with FFM microwaves. Consequently, relative to the latter approach, the VFM technology is significantly advantageous, especially in reactions with solid conductive catalysts, not least of which are the reduction in power consumption, thus energy savings, and the prevention of potential mishaps.

This journal is © The Royal Society of Chemistry. Carbon quantum dots (CQDs; luminescent carbon nanoparticles, size < 10 nm) have attracted much attention with respect to their eco-friendliness and multi-functionality. The solvent-dependent photoluminescence of CQDs has been well investigated to optimize the synthesis process and homogeneous dispersion. Although some alkan-1-ol solvents, such as ethanol, have been well utilized empirically as good solvents when synthesizing highly photoluminescent CQDs, the role of alkan-1-ol solvents, particularly long-chain alkan-1-ols (e.g., 1-nonanol, 1-decanol), has not yet been clarified. Herein, we demonstrate a method for the synthesis of strongly yellow emitting CQDs using solvothermal treatment and elucidate the role of alkan-1-ol solvents in the photoluminescence of CQDs. These CQDs have been characterized using theoretical calculations, ex situ morphological observations using transmission electron microscopy (TEM) and dynamic light scattering (DLS), and 500 MHz 1H nuclear magnetic resonance (NMR) and 13C NMR spectroscopy. A comparative study of alkan-1-ol solvents suggests a mechanism for the agglomeration and aggregation of carbon precursors, intermediates, and CQDs, which is expected to lead to further synthesis studies on highly luminescent CQDs.

The research of in-liquid plasma that uses microwave as an energy source can be generated without depending on the electric conductivity of the solution, so it has wide application. However, it is not practical because the microwave antenna (plasma electrode) is deteriorated immediately. We were noticed that the microwave is pulsed to solve this problem. In this study, its optimum conditions was investigated. The best parameters of pulse microwave power was investigated using the generator (peak power 380 W, pulse width 13.4 msec and pulse duty cycle 16.7 msec). Stable in-liquid plasma could be generated in this conditions. This optimised system of in-liquid plasma tried to use applications for wastewater treatment and gel synthesis. In first application (wastewater treatment), tetrabromobisphenol A (TBBPA) was ionized and minerated by using in-liquid plasma method for only 20 min, respectivily. In second one (gel synthesis), in-liquid plasma can synthesize gel-synthesis without crosslinking agent and initiator. This new method could synthesize gel of dimethyl polysiloxane (silicone) and polyvinilypirroridone (PVP) without both crosslinking agent and initiator, it suggested that in-liquid plasma method is effective as a green chemistry process.

In this research, we ameliorated the problems of carbon quantum dots synthesis and luminescence (quantum yields) by the novel synthesis protocol using microwave chemistry. Specifically, we synthesized high quantum yields carbon quantum dots (61%) by utilizing a microwave chemical synthesis, synthesizing at low pressure condition (lower than 5 atom) and short reaction time (3 hrs). The achievement of this high quantum yields made it clear that the contribution of polyethylene glycol (PEG) shell to carbon quantum dots is large. It was confirmed from the DLS and TEM image that the particle size of the synthesized particles was 8 to 13 nm. On the other hand, the relationship between the polymerization degree of added PEG and the quantum yields to the addition amount is summarized. The quantum yields of carbon quantum dots without addition of PEG was 16.7 %, while it was improved at 61.1 % when 0.6 g of PEG 6000 (Molecular weight: 6000) was added. Furthermore, we compared microwave with conventional method, and it was revealed that higher luminescent and narrower sized carbon quantum dots were synthesized in microwave heating than conventional method. This result presumably comes from the nature of microwave selective heating of carbon precursor.

Wettability patterns were fabricated on a surface based on titanium dioxide (TiO2) by etching of a Ti substrate with sulfuric acid and coating with TiO2 nanoparticles. Images obtained using a field emission scanning electron microscope and three-dimensional laser microscope reveal that the etched surface was covered with TiO2 nanoparticles and the surface roughness of TiO2-coated sample was lower value (2.51 µm) that of sample coated without TiO2 (3.19 µm), indicating that the surface roughness was decreased by coating with TiO2 nanoparticles. It was also confirmed that the crystal structure of TiO2-coated sample was rutile and anatase. The TiO2-coated sample modified with self-assembled monolayers (SAMs) showed a superhydrophobic property. The surface of the TiO2-coated sample gradually transformed into a superhydrophilic surface under UV irradiation because of the photocatalytic decomposition of the SAMs, and the decrease in the contact angle on the TiO2-coated sample was faster than that on the sample without TiO2 coating. In addition, the TiO2-coated sample produced renewable wettability patterns for blood, which demonstrate the great potential of this material in biomedical applications.

People typically discard pharmaceutical products into the trash, or garbage or sewage systems to ultimately ending up in municipal wastewater treatment plants, which traditionally use non-photochemical ozonation to decompose contaminants, but often failing to completely eliminate them. Accordingly, photochemical advanced oxidation processes (AOPs) have been developed to remedy such situations. Unfortunately, these remain at the developmental stages and have yet to be implemented in practical applications. This review describes UV/ozonation, UV/peroxidation, UV/ozonation/peroxidation, photo-Fenton processes, and photocatalytic oxidation processes (e.g. UV/TiO2) all of which depend on generating highly reactive oxygen species (e.g., [rad]OH radicals, hydroperoxy radicals, superoxide anion radicals) to dispose of emerging aquatic contaminants. Albeit non-exhaustive, the review explores the progress made in the last 2–3 years by focusing on light-driven degradation processes to eliminate such pharmaceutical contaminants as non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics and hormones, many of which have been detected in aqueous ecosystems.

Selective heating of microwave-absorbing solid catalysts in a heterogeneous medium may affect a chemical reaction; such selectivity cannot be achieved by conventional oil-bath or steam heating methods. Moreover, microwave methods are often misunderstood with respect to equipment and temperature measurements, so that additional experimentation is necessary. In this regard, the present study intended to clarify the effect of microwave selective heating on acid hydrolytic processes using a sulfonated activated carbon catalyst (AC-SO3H). The model reaction chosen was the acid hydrolysis of cellulose carried out in a Pyrex glass microwave reactor, with the process being monitored by examining the quantity of total sugar, reducing sugar, and glucose produced. Heat transfer from the catalyst to the aqueous solution through absorption of microwaves by the catalyst occurred as predicted from a simulation of heat transfer processes. The resulting experimental consequences are compared with those from the more uniform microwave conduction heating method by also performing the reaction in a SiC microwave reactor wherein microwaves are absorbed by SiC. Some inferences of the influence of microwave selective heating of carbon-based catalyst particles are reported. Under selective heating conditions (Pyrex glass reactor), the yield of glucose from the acid hydrolysis of cellulose was 56% upon microwave heating at 200 degrees C, nearly identical with the yield (55%) when the hydrolytic process was performed under mainly conventional heating conditions in the SiC reactor. Although the beneficial effect of catalyst selective heating was not reflected in the reaction efficiency, there were substantial changes in the state of adsorption of cellulose on the catalyst surface.