Epoxidation of oleic acid under conventional heating and microwave radiation

2016 ◽  
Vol 102 ◽  
pp. 70-87 ◽  
Author(s):  
Adriana Freites Aguilera ◽  
Pasi Tolvanen ◽  
Kari Eränen ◽  
Sébastien Leveneur ◽  
Tapio Salmi
Keyword(s):  
Oleic Acid ◽  
Microwave Radiation ◽  
Conventional Heating

scholarly journals Microwaves and Heterogeneous Catalysis: A Review on Selected Catalytic Processes

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 246 ◽  
Author(s):  
Vincenzo Palma ◽  
Daniela Barba ◽  
Marta Cortese ◽  
Marco Martino ◽  
Simona Renda ◽  
...  
Keyword(s):  
Heterogeneous Catalysis ◽  
Energy Saving ◽  
Microwave Heating ◽  
Microwave Radiation ◽  
Heterogeneous Catalysts ◽  
Conventional Heating ◽  
Specific Effects ◽  
Natural Choice ◽  
Future Challenges ◽  
Catalyzed Reactions

Since the late 1980s, the scientific community has been attracted to microwave energy as an alternative method of heating, due to the advantages that this technology offers over conventional heating technologies. In fact, differently from these, the microwave heating mechanism is a volumetric process in which heat is generated within the material itself, and, consequently, it can be very rapid and selective. In this way, the microwave-susceptible material can absorb the energy embodied in the microwaves. Application of the microwave heating technique to a chemical process can lead to both a reduction in processing time as well as an increase in the production rate, which is obtained by enhancing the chemical reactions and results in energy saving. The synthesis and sintering of materials by means of microwave radiation has been used for more than 20 years, while, future challenges will be, among others, the development of processes that achieve lower greenhouse gas (e.g., CO2) emissions and discover novel energy-saving catalyzed reactions. A natural choice in such efforts would be the combination of catalysis and microwave radiation. The main aim of this review is to give an overview of microwave applications in the heterogeneous catalysis, including the preparation of catalysts, as well as explore some selected microwave assisted catalytic reactions. The review is divided into three principal topics: (i) introduction to microwave chemistry and microwave materials processing; (ii) description of the loss mechanisms and microwave-specific effects in heterogeneous catalysis; and (iii) applications of microwaves in some selected chemical processes, including the preparation of heterogeneous catalysts.

scholarly journals Application of microwave radiation in the grafting of acidic sites on SBA-15 type material

2021 ◽  
Author(s):  
Maciej Trejda ◽  
Magdalena Drobnik ◽  
Ardian Nurwita
Keyword(s):  
Microwave Radiation ◽  
Thermal Analyses ◽  
Conventional Heating ◽  
Material Surface ◽  
Test Reaction ◽  
Study Materials ◽  
Mesoporous Support ◽  
Acidic Sites ◽  
Post Synthesis ◽  
Adsorption Desorption

AbstractMesoporous silica of SBA-15 type was modified for the first time with 3-(trihydroxysiyl)-1-propanesulfonic acid (TPS) by post-synthesis modification involving microwave or conventional heating in order to generate the Brønsted acidic centers on the material surface. The samples structure and composition were examined by low temperature N2 adsorption/desorption, XRD, HRTEM, elemental and thermal analyses. The surface properties were evaluated by esterification of acetic acid with n-hexanol used as the test reaction. A much higher efficiency of TPS species incorporation was reached with the application of microwave radiation for 1 h than conventional modification for 24 h. It was found that the structure of mesoporous support was preserved after modification using both methods applied in this study. Materials obtained with the use of microwave radiation showed a superior catalytic activity and high stability.

Synthesis of Biodiesel from Castor Oil Catalyzed by Cesium Phosphotungstate with the Assistance of Microwave

2013 ◽  
Vol 291-294 ◽  
pp. 300-306 ◽  
Author(s):  
Hong Yuan ◽  
Qing Shu
Keyword(s):  
Microwave Radiation ◽  
Castor Oil ◽  
Solid Acid ◽  
Maximum Yield ◽  
Conventional Heating ◽  
Molar Ratio ◽  
Mass Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Programmed

Two cesium phosphotungstate-derived solid acid catalysts (Cs2.5H0.5PW12 and Cs0.5H2.5PW12) were prepared. The resulting catalysts were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption and desorption isotherm and temperature programmed desorption of ammonia(NH3-TPD). The Cs2.5H0.5PW12 and Cs0.5H2.5PW12 were respectively used to catalyze the tranesterification of castor oil and methanol for the synthesis of biodiesel with the assistance of microwave. Results shown microwave radiation can greatly enhance the transesterification process when compared with conventional heating method. Cs2.5H0.5PW12 showed better catalyst performance than Cs0.5H2.5PW12. A maximum yield of 90% was obtained from the using of 30:1 molar ratio of methanol to castor oil and 15 wt % mass ratio of catalyst to castor oil at 343 K under microwave radiation after 4h.

Synthesis of Biodiesel Using Castor Oil under Microwave Radiation

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Hong Yuan ◽  
Bolun Yang ◽  
Hailiang Zhang ◽  
Xiaowei Zhou
Keyword(s):  
Microwave Heating ◽  
Microwave Radiation ◽  
Castor Oil ◽  
High Performance ◽  
Radiation Power ◽  
Acid Methyl Ester ◽  
Conventional Heating ◽  
Molar Ratio ◽  
Heterogeneous Base Catalyst ◽  
Heterogeneous Base

The castor oil was adopted to synthesize biodiesel (Fatty Acid Methyl Ester, FAME) under microwave radiation. Acid catalysts (NaHSO4•H2O and AlCl3) and heterogeneous base catalyst (Na2CO3) were evaluated in the present study. The amounts of FAME in the product were analyzed by high performance liquid chromatography (HPLC). Experimental results show that the microwave radiation was an efficient method to enhance the reaction process. When the transesterification was carried out at 338 K, with 18:1 molar ratio of methanol to castor oil, 7.5wt% mass ratio of catalyst to castor oil, 200w microwave radiation power and 120 minutes reaction time, yields of 74, 73, 90% were obtained respectively using catalysts of NaHSO4•H2O, AlCl3 and Na2CO3. The energy consumed by microwave heating and conventional heating in transesterification were measured, and the results showed that the microwave heating consumed less energy than the conventional heating to achieve the same amount of FAME.

scholarly journals Microwave Radiations for Heat-Setting of Polyester Fibers

2009 ◽  
Vol 4 (4) ◽  
pp. 155892500900400 ◽  
Author(s):  
Narendra Vinayak Bhat ◽  
Manik J. Kale ◽  
V. Gore Ajit
Keyword(s):  
Microwave Radiation ◽  
Structural Changes ◽  
Silicone Oil ◽  
Microwave Frequency ◽  
Industrial Applications ◽  
Heat Propagation ◽  
Conventional Heating ◽  
Maximum Effect ◽  
Radiation Process ◽  
Polyester Fibers

The use of radio and microwave frequency is gaining importance for industrial applications such as heating, drying, and other processing. The most important advantage of using microwave is that it is non-contact or localized heating and the heat is produced within the material. This can be much more effective than indirect heating where the heat propagation is by heat conduction through the material. We have been investigating the influence of microwave radiation on different fibers for the last few years. In the present investigation we used microwave frequency of 2450 MHz to investigate its effect on polyester fibers. The polyester fibers were heat set in air as well as a liquid, which acted as a lossy substances. The liquid was chosen on the basis of earlier experiments, which showed the maximum effect. A comparative study was also carried out using conventional heating in silicone oil. Using the method of X-ray Diffraction (XRD) we calculated the changes in % crystallinity and orientation. It was found that as the time of treatment under microwave radiation increased from 15 sec. to 120 sec. the order factor was found to increase from 0.32 to 0.71. The crystalline orientation as determined from the azimuthal scan was also found to increase. Such structural changes can be highly beneficial for the processing of fabric in industry. The microwave radiation process is fast, reliable and energy saving.

Does Thermal Annealing Affect the Mechanical Properties of Silkworm (Bombyx mori) Cocoon Silk?

2012 ◽  
Vol 1465 ◽  
Author(s):  
Emily J. Reed ◽  
Christopher Viney
Keyword(s):  
Mechanical Properties ◽  
Bombyx Mori ◽  
Microwave Radiation ◽  
Constant Strain Rate ◽  
Annealing Treatment ◽  
Tensile Tests ◽  
Conventional Heating ◽  
Heating Rates ◽  
Microwave Exposure ◽  
Property Changes

ABSTRACTIt has been reported [1] that microwave radiation can enhance many of the mechanical properties of Bombyx mori silkworm cocoon silk, as measured in constant strain rate tensile tests to failure and in stress relaxation tests. The consequences of microwave radiation will affect decisions about the use of silk in settings subjected to significant microwave exposure – for example, as a reinforcing fiber in an epoxy matrix composite that may be microwave cured, or as a component in aircraft radomes.There are two possible mechanisms by which microwave radiation may affect a material [2]: (i) the radiation may enable chemical and/or microstructural changes – and therefore property changes – in the same way that conventional heating would, or (ii) the high heating rates that are achievable by microwaving may selectively favor changes that would be masked under conventional conditions, where heating rates are low enough to give preference to changes that have a lower activation energy. Here we explore the former possibility for silk.We characterized several mechanical properties of degummed and subsequently annealed B. mori silk, and compared them to the corresponding properties of degummed B. mori silk that was not annealed. The annealing treatment was carried out at 140 °C for 7 hours (conditions that optimally increased crystal size in an unrelated study of B. mori silk [3]), and then the fibers were allowed to cool gradually to room temperature over the course of an hour. Comparison of mechanical properties revealed no differences between the materials that we tested. Thus, for annealed silk, we do not observe the enhancements that can be achieved by microwaving. We conclude that in cases where microwaving affects the properties of silk, those changes are not a simple consequence of annealing by the microwaves.

Comparative study and simulation of tumor cell inactivation by microwave and conventional heating

2018 ◽  
Vol 37 (6) ◽  
pp. 1893-1904 ◽  
Author(s):  
Andreas Rosin ◽  
Michael Hader ◽  
Corinna Drescher ◽  
Magdalena Suntinger ◽  
Thorsten Gerdes ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Microwave Heating ◽  
Microwave Radiation ◽  
Thermal Inactivation ◽  
Inactivation Rate ◽  
Conventional Heating ◽  
Process Conditions ◽  
Sem Images ◽  
Content Type ◽  
Cell Inactivation

PurposeThis paper aims to investigate in a self-designed closed loop reactor process conditions for thermal inactivation of B16 melanoma cells by microwave and conventional heating.Design/methodology/approachBesides control experiments (37°C), inactivation rate was determined in the range from 42°C to 46°C. Heating was achieved either by microwave radiation at 2.45 GHz or by warm water. To distinguish viable from dead cells, AnnexinV staining method was used and supported by field effect scanning electron microscopy (FE-SEM) imaging. Furthermore, numerical simulations were done to get a closer look into both heating devices. To investigate the thermal influence on cell inactivation and the differences between heating methods, a reaction kinetics approach was added as well.FindingsControl experiments and heating at 42°C resulted in low inactivation rates. Inactivation rate at 44°C remained below 12% under conventional, whereas it increased to >70% under microwave heating. At 46°C, inactivation rate attained 68% under conventional heating; meanwhile, even 88% were determined under microwave heating. FE-SEM images showed a porous membrane structure under microwave heating in contrast to mostly intact conventional heated cells. Numerical simulations of both heating devices and a macroscopic Arrhenius approach could not sufficiently explain the observed differences in inactivation.Originality/valueA combination of thermal and electrical effects owing to microwave heating results in higher inactivation rates than conventional heating achieves. Nevertheless, it was not possible to determine the exact mechanisms of inactivation under microwave radiation.

scholarly journals Progress in the Production of Biogas from Maize Silage after Acid-Heat Pretreatment

Energies ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 8018
Author(s):  
Anna Nowicka ◽  
Marcin Zieliński ◽  
Marcin Dębowski ◽  
Magda Dudek
Keyword(s):  
Hydrochloric Acid ◽  
Microwave Heating ◽  
Microwave Radiation ◽  
Anaerobic Degradation ◽  
Fermentation Process ◽  
Plant Biomass ◽  
Biogas Production ◽  
Conventional Heating ◽  
Maize Silage ◽  
Methane Fermentation

One of the most effective technologies involving the use of lignocellulosic biomass is the production of biofuels, including methane-rich biogas. In order to increase the amount of gas produced, it is necessary to optimize the fermentation process, for example, by substrate pretreatment. The present study aimed to analyze the coupled effects of microwave radiation and the following acids: phosphoric(V) acid (H3PO4), hydrochloric acid (HCl), and sulfuric(VI) acid (H2SO4), on the destruction of a lignocellulosic complex of maize silage biomass and its susceptibility to anaerobic degradation in the methane fermentation process. The study compared the effects of plant biomass (maize silage) disintegration using microwave and conventional heating; the criterion differentiating experimental variants was the dose of acid used, i.e., 10% H3PO4, 10% HCl, and 10% H2SO4 in doses of 0.02, 0.05, 0.10, 0.20, and 0.40 g/gTS. Microwave heating caused a higher biogas production in the case of all acids tested (HCl, H2SO4, H3PO4). The highest biogas volume, exceeding 1800 L/kgVS, was produced in the variant with HCl used at a dose of 0.4 g/gTS.

scholarly journals TUNGSTEN CARBIDE NANOPOWDER SYNTHESIS UNDER THE EXPOSURE OF 24 GHZ GYROTRON RADIATION ON THE NANOCOMPOSITE OF THE W-C SYSTEM OBTAINED IN A THERMAL PLASMA

2019 ◽  
Author(s):  
Alexander Vodopyanov ◽  
Andrey Samokhin ◽  
Nikolay Aleksev ◽  
Mikhail Sinayskiy ◽  
Andrey Sorokin ◽  
...  
Keyword(s):  
Tungsten Carbide ◽  
Microwave Radiation ◽  
Electric Furnace ◽  
Conventional Heating ◽  
Average Particle ◽  
Hard Alloys ◽  
Target Product ◽  
Prolonged Heating ◽  
Nanocomposite System ◽  
24 Ghz

Nanoscale tungsten carbide WC powders are of practical interest for the creation of nanostructured hard alloys with enhanced physical and mechanical characteristics, wear-resistant nanostructured coatings, electrocatalysts in fuel cells, metal melt modifiers [1]. An efficient method for producing tungsten carbide nanopowder is a plasma-chemical synthesis of a multi-component powder nanocomposite system W-C in combination with its subsequent heat treatment [2]. Experimental studies have shown the possibility of producing tungsten carbide WC nanopowder by this method. But the transformation of the nanocomposite in the target product is accompanied by an increase in the size of nanoparticles. We assume that this growth is associated with prolonged heating (several hours) in an electric furnace at a temperature of about 1000 ° C. This time is necessary for the complete transformation of the nanocomposite into the target product. The aim of the work was an experimental study of the formation of tungsten carbide nanopowder WC when processing a multi-component powder nanocomposite system W-C in an electromagnetic field with a frequency of 24 GHz. A multipurpose gyrotron system with a nominal power of 7 kW with at a frequency of 24 GHz was used for the experiments. The microwave application system described in [3]. The powders were treated in an argon flow. The experiments were carried varying exposure time and microwave power. The samples of nanopowders obtained in the experiments were analyzed using the following methods: XRD, TEM, SEM, BET, LDA, CEA. It was established that microwave radiation with a frequency of 24 GHz allows heating samples of powders to a temperature of 1100-1200 C almost immediately (after 1-2 s) after switching on. The tungsten carbide WC is formed in a few minutes under the exposure to microwave radiation of the original W-C nanocomposite system. There is only a slight increase in the average particle size from 20 to 30 nm. The investigations showed that the synthesis of tungsten carbide WC under the microwave heating as compared to conventional heating in an electric furnace may be carried out for significantly less time while maintaining the particles in the nanometer range.The work was carried out within the framework of the Program #14 "Physical chemistry of adsorption phenomena and actinide nanoparticles" of the Presidium of the Russian Academy of Sciences.References Z. Zak Fang, Xu Wang, et al. Int. Journal of Refractory Metals & Hard Materials, 2009, 27, 288–299.Samokhin A., Alekseev N., et al. Plasma Chem. Plasma Proc., 2013, 33, 605–616.Samokhin A., Alekseev N., et al. J. Nanotechnol. Eng. Med., 2015, 6, 011008. 

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