Thermal Heating Conditions Research Articles

Microwave-assisted synthesis of solketal from glycerol and acetone in the presence of SAPO-34 and SAPO-5

Solketal is one of the most promising additives improving the properties of motor fuels. Investigations related to process intensification of synthesis of solketal from glycerol and acetone is gaining importance. The present work illustrates the use of the microwave mode for intensification of this process in the presence of silicoaluminophosphates (SAPO) as catalysts. The main focus of the study was placed on tuning the textural, acidic, and catalytic properties of SAPO-34 and SAPO-5 via variation of the synthesis parameters, such as the nature of Al and Si sources and the structure-directing agent. The catalytic properties of SAPO materials were investigated in the synthesis of solketal from glycerol and acetone under microwave assistance at the acetone/glycerol molar ratio of 2.4 in a methanol solution (glycerol/methanol: 1 g/1 mL) and 56 °C. It was demonstrated that the selectivity towards solketal was 91.1–98.6 % in the presence of the studied materials. The activities of mesoporous SAPO-34 and SAPO-5 prepared in the presence of triethylamine were higher as compared with microporous SAPO-34 prepared in the presence of tetraethylammonium hydroxide due to the high mesoporosity and a larger content of acid sites. The 90.4 % conversion of glycerol and 98.6 % selectivity towards solketal were observed in the presence of mesoporous 7.6%SAPO-34 for 90 min. The advantage of using microwave technology is shown. The solketal yield in the reaction under microwave irradiation was 3 times higher than that in the process performed under thermal heating conditions.

Unraveling the Nano-Bio Interface Interactions of a Lipase Adsorbed on Gold Nanoparticles under Laser Excitation.

The complex nature and structure of biomolecules and nanoparticles and their interactions make it challenging to achieve a deeper understanding of the dynamics at the nano-bio interface of enzymes and plasmonic nanoparticles subjected to light excitation. In this study, circular dichroism (CD) and Raman spectroscopic experiments and molecular dynamics (MD) simulations were used to investigate the potential changes at the nano-bio interface upon plasmonic excitation. Our data showed that photothermal and thermal heating induced distinct changes in the secondary structure of a model nanobioconjugate composed of lipase fromCandida antarcticafraction B (CALB) and gold nanoparticles (AuNPs). The use of a green laser led to a substantial decrease in the α-helix content of the lipase from 66% to 13% and an increase in the β-sheet content from 5% to 31% compared to the initial conformation of the nanobioconjugate. In contrast, the differences under similar thermal heating conditions were only 55% and 11%, respectively. This study revealed important differences related to the enzyme secondary structure, enzyme-nanoparticle interactions, and the stability of the enzyme catalytic triad (Ser105-Asp187-His224), influenced by the instantaneous local temperature increase generated from photothermal heating compared to the slower rate of thermal heating of the bulk. These results provide valuable insights into the interactions between biomolecules and plasmonic nanoparticles induced by photothermal heating, advancing plasmonic biocatalysis and related fields.

Boundary value problems of the dynamics of thermoelastic rods and their solutions

We consider spatially one-dimensional boundary value problems of uncoupled thermoelasticity, which can be used to study various rod structures under thermal heating conditions. As is known, rod structures are connecting and transmission links of various parts of the machines and mechanisms. Here we propose a unified technique for solving various boundary value problems typical for practical applications. The problems of determining the thermally stressed state of a thermoelastic rod under various boundary conditions at its ends and acting power and heat sources along the entire length of the rod are considered. Based on the method of generalized functions, generalized solutions of non-stationary and stationary direct and semi-inverse boundary value problems under the action of power and heat sources of various types, including stationary sources of periodic oscillations, are constructed. Acting sources can also be specified by singular generalized functions, under various boundary conditions at the ends of the rod. Shock elastic waves that arise in such structures under the action of shock loads are considered. Regular integral representations of generalized solutions are obtained, which provide an analytical solution to the posed boundary value problems. The peculiarity of the constructed solutions makes them convenient for studying network thermoelastic systems that can be modeled by thermoelastic graphs.

Synthesis and biological activity of 5-acetyl- and 5-hydroxyalkyl1,3-dioxane derivatives

Objectives. To synthesize derivatives of 5-acetyl- and 5-hydroxyalkyl-1,3-dioxanes and evaluate their effect on platelet aggregation and plasma hemostasis.Methods. To determine the qualitative and quantitative composition of the reaction masses, gas chromatography-, chromate mass spectrometry-, and 1H and 13C nuclear magnetic resonance spectrometry methods were used.Results. Derivatives of 5-acetyl- and 5-hydroxyalkyl-1,3-dioxanes were obtained under thermal heating conditions in order to evaluate their effect on platelet aggregation and plasma hemostasis.Conclusions. Derivatives of 5-acetyl- and 5-hydroxyalkyl-1,3-dioxanes were synthesized in high yields. Their effect on platelet aggregation and plasma hemostasis was established.

In-situ formation of electron-deficient Pd sites on AuPd alloy nanoparticles under irradiation enabled efficient photocatalytic Heck reaction

Plasmonic metal nanoparticles have emerged as important candidates for photocatalysis. Numerous studies have shown that coupling of a plasmonic component (such as Au) as the light energy harvester with a catalytically active metal component (such as Pd) to form hybrid or alloy structures could achieve enhanced catalytic performance. However, the microscopic mechanism relative to the multicomponent plasmonic photocatalysis is still elusive. Here, we find that the electron-deficient Pd sites (Pdδ+) on AuPd alloy nanoparticle were formed under visible light irradiation, which play a decisive role in the AuPd alloy nanoparticle photocatalysis. The in-situ formed Pdδ+ under irradiation offers ideal platform for the catalytic reaction which is comparable to that under thermal heating conditions (>100 °C). The AuPd alloy nanoparticles show excellent conversion and selectivity for visible-light-driven Heck cross-coupling reaction under ambient conditions. The combination of experimental and density functional theory results suggest that the photocatalytic Heck reaction proceeds via a new radical-based single-electron transfer pathway on the AuPd alloy, and the in-situ formed Pdδ+ sites ideally provided efficient catalytic sites for the activation of reactant with much lower activation energy barrier under irradiation. The present work sheds light on the new mechanistic understandings of bimetallic plasmonic photocatalysis.

Analysis of Entropy Generation in Micropolar Magneto-Nanoliquid Material with Activation Energy and Nonlinear Radiation

This study investigates entropy production analysis in the flow of micropolar nanoliquid due to its application in thermal engineering systems for the identification of the factors which causes the destruction in the available energy and consequently affects overall performance of the thermal devices. The model is built on a two-dimensional porous stretching sheet with an incompressible fluid assumption and steady with the influence of variable thermal conductivity, nonlinear thermal radiation, haphazard motion and thermo-migration tiny particles. A prescribed surface temperature is adopted as the thermal heating condition while the impact of the reaction order and activation energy are incorporated into the concentration field. The model equations are restructured to ordinary derivative system, which is computationally solved by Fehlberg Runge-Kutta technique. The results agree well with previous outcomes for limiting situations while the effects of the embedded terms are presented graphs. The analysis reveals that a rise in variable thermal conductivity, the material term and viscous dissipation leads to a rise in the irreversibility process.

Poly(ε‐caprolactone)/montmorillonite nanocomposites via Diels–Alder click reaction

AbstractSynthesis of nanocomposites by employing inorganic materials as nanofillers is one of the most effective ways to improve the mechanical and thermal properties of conventional polymers. To design and create new nanomaterials with unprecedented functional attributes, the fabrication techniques and chemistries employed often have utmost importance to attain a better structure–property relationship. In this respect, click chemistry‐based functional methodologies hold great promise in the fabrication of polymeric nanocomposites due to their excellent features. In this contribution, poly(ε‐caprolactone)/clay nanocomposites were prepared by Diels–Alder (DA) click reaction of maleimide end‐group containing poly(ε‐caprolactone) and furan functionalized montmorillonite (MMT). The methodology includes furan modification of MMT clay and ring‐opening polymerization of ε‐caprolactone that was initiated with a masked maleimide group containing alcohol and following retro DA reaction to obtain maleimide end group functional poly(ε‐caprolactone). Subsequently, polymer nanocomposites were efficiently fabricated via DA click reaction of functional poly(ε‐caprolactone) polymer and modified clay in thermal heating conditions at 80°C. The characterization of poly(ε‐caprolactone)/clay nanocomposites was carried out by thermogravimetric analysis, Fourier transform‐infrared spectroscopy, X‐ray diffraction spectroscopy, and transmission electron microscopy. Obtained results demonstrated that DA click reaction can be fruitfully employed in the fabrication of MMT‐based polymeric nanocomposites.

Microwave-assisted photooxidation of sulfoxides

We demonstrated microwave-assisted photooxidation of sulfoxides to the corresponding sulfones using ethynylbenzene as a photosensitizer. Efficiency of the photooxidation was higher under microwave irradiation than under conventional thermal heating conditions. Under the conditions, ethynylbenzene promoted the oxidation more efficiently than conventional photosensitizers benzophenone, anthracene, and rose bengal. Ethynylbenzene, whose T1 state is extremely resistant to intersystem crossing to the ground state, was suitable to this reaction because spectroscopic and related reported studies suggested that this non-thermal effect was caused by elongating lifetime of the T1 state by microwave. This is the first study in which ethynylbenzene is used as a photosensitizer in a microwave-assisted photoreaction.

Graphene oxide nanoflakes from various agrowastes

AbstractNowadays, the synthesis of graphene/ graphene oxide from graphite precursor using oxidizing agents is the most common procedure, but the direct synthesis of graphene or graphene oxide from a non‐graphitic carbonaceous material without using inert atmosphere is really a great challenge. Besides, the chemistry behind the development of graphitic structure from a non‐graphitic material during the thermal heating is still not clearly understood. In this research work, three agrowaste materials viz. rice husk, sugarcane bagasse and newspaper were selected and subjected to pyrolysis in presence of trace amount of air. The continued heating at the optimum temperature has resulted in aromatization and condensation along with the oxidation within the cellulosic structure of the agrowaste, which finally resulted in the formation of graphene oxide nanoflakes directly. The mechanism of formation of graphene oxide from these agrowaste materials was studied, which suggested that any carbonaceous waste materials can be converted to graphene oxide by optimizing the thermal heating conditions.

Influence of reagents mixture density on the radiation-thermal synthesis of lithium-zinc ferrites

Influence of Li2CO3-ZnO-Fe2O3 powder reagents mixture density on the synthesis efficiency of lithium-zinc ferrites in the conditions of thermal heating or pulsed electron beam heating was studied by X-Ray diffraction and magnetization analysis. The results showed that the including a compaction of powder reagents mixture in ferrite synthesis leads to an increase in concentration of the spinel phase and decrease in initial components content in lithium-substituted ferrites synthesized by thermal or radiation-thermal heating.

Radiation-Thermal Sintering of Zirconia Powder Compacts Under Conditions of Bilateral Heating Using Beams of Low-Energy Electrons

Comparative experiments on sintering zirconia ceramics are performed using colliding beams of low-energy electrons and under conditions of thermal heating. The density and microhardness of ceramic materials manufactured via different processes are determined. The use of a regime of bilateral heating by high-intensity,low-energy electron beams is shown to intensify the sintering process and yield material specimens with improved characteristics compared to those formed by thermal sintering.

Effect of different catalyst on the co-cracking of Jatropha oil, vacuum residue and high density polyethylene

Co-processing of Jatropha oil (JO), vacuum residue (VR) and high density polyethylene (HDPE) were investigated to determine the behavior of the individual and blended mixture under atmospheric pressure and thermal heating conditions. A fixed bed tubular batch reactor was used for the experimental study under nitrogen atmosphere. The activity of the four catalysts CAT-A (Ni–Mo/SiAl), CAT-R (ZSM-5+SiAl), CAT-Z (ZSM-5) and FCC catalyst CAT-N on the co-cracking of binary and ternary mixture has been studied. CAT-R was the best catalyst used for JO+HDPE co-cracking as it leads to the formation of 45%, gasoline range hydrocarbons (C7–C11) and 49% diesel range hydrocarbons in the cracked liquid. CAT-Z was the best catalyst for VR+HDPE co-cracking as it lead to the formation of 33% olefins which were absent in the thermally cracked liquid. In case of JO+VR co-cracking CAT-Z was found to show increase in the liquid yield and it also lead to the formation of 37% gasoline range hydrocarbons and 35% diesel range hydrocarbons. It was also observed that the use of catalyst had a positive effect on the pH content of the catalytically cracked liquid products.

Microwave-Assisted Anomeric Deacetylation of Ribofuranoses with Fe(III) Reagents

Treatment of protected furanoses with FeCl3·6H2O in acetonitrile with microwave irradiation provides an efficient and mild protocol for regioselective removal of anomeric O-acetyl group. This method features cost efficient reagents, simple procedures, and high yields. The experimental results proved that microwave irradiation could notably shorten the reaction time and increase the product yield compared to the conventional thermal heating condition.

Ultrasonic-Assisted Deprotection of <i>tert</i>-Butyldimethylsilyl Ethers with Bromotrichloromethane in Methanol

Treatment of tert-butyldimethylsilyl (TBDMS) ethers of nucleosides with bromo-trichloromethane (CBrCl3) in methanol under ultrasonic conditions provides a mild and efficient method for desilylation. The experimental results showed that the employment of ultrasonic could notably improve the reaction efficiency compared with thermal heating condition.

Co-cracking of jatropha oil, vacuum residue and HDPE and characterization of liquid, gaseous and char products obtained

Co-processing of jatropha oil (JO), vacuum residue (VR) and high density polyethylene (HDPE) were investigated to determine the behavior of the individual and blended mixture under atmospheric pressure and thermal heating conditions. A fixed bed tubular batch reactor was used for the experimental study under nitrogen atmosphere with a nitrogen flow of 120ml/h. Higher conversion of the reactant mixture was observed with the formation of liquid, gases and residual char. The co-cracking/co-processing of the JO, VR and HDPE showed synergism in their co-cracking reaction. The liquid products obtained from the co-cracking of JO, VR and HDPE were mostly aliphatic in nature. The cracked liquid obtained from the co-cracking reactions showed the presence of mainly diesel range hydrocarbons, though cracked liquid of VR+HDPE and JO+VR+HDPE showed the presence of about 22% gasoline range hydrocarbons. The gaseous products obtained consisted of methane, n-pentane, n-butane, iso-butane, 2-methyl butane and certain uncondensed components. The chars obtained indicated the presence of metals such as Ni, Fe, V, Mg and K. The overall results indicate the existence of interactive reactions between the reactive moieties generated, when JO, VR and HDPE were co-cracked together.

Thermal Heating Effect on Structural and Mechanical Property of Diamond-Like Carbon Film Prepared by Filtered Cathodic Arc

Diamond-like carbon (DLC) films were deposited on magnetic recording head by Filtered Cathodic Arc (FCA) technique and a-Si base material was ion beam deposited as seed layer. To investigate the thermal stability of stack film, repeated cycle thermal heating at 200 °C was employed. Raman spectroscopy and nanoindenter (Hysitron) were performed to understand film structure and mechanical property as a function of thermal heating conditions. The roles of heating in material composition and wear behavior of DLC films are discussed. The Raman spectra revealed that G position, FWHM of G peak and Id/Ig change as with increasing heating cycle which agreed well with wear depth measured. With these results suggesting DLC film degraded with repeated heating at 200 °C.

Solvent- and catalyst-free synthesis of bis-adducts of 3-formylchromone as potential antimicrobial agents

A facile and ecofriendly synthesis of new (chromon-3-yl)bis(heteroaryl)methanes 5a–d, from 3-formylchromone 1 and active methylene compounds 2–4 is reported under solvent-free, catalyst-free thermal heating condition in good yields. The synthesized compounds were characterized on the basis of elemental and spectral (IR, 1H NMR, and mass spectrometry) analysis. All the target compounds were evaluated for their in vitro antimicrobial activity against Streptococcus pyogenes, Methicillin resistant Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli bacterial strains, and fungal cultures of Candida albicans, Aspergillus fumigatus, Trichophyton mentagrophytes, and Penicillium marneffei by disk diffusion assay with slight modifications. The minimum inhibitory concentration was determined for the test compounds as well as for reference standards. Among the tested compounds, 5b has shown the most potent antibacterial as well as antifungal activities.

Thermal characterization of novel p-nitrobenzylacrylate–diisopropyl fumarate copolymer synthesized under microwave energy

Copolymers of p-nitrobenzyl acrylate and diisopropyl fumarate with different feed ratios were synthesized under microwave and thermal heating conditions, and then characterized by IR, 1H-, and 13C-NMR spectroscopy. Average molecular weights were analyzed by size exclusion chromatography (SEC). Monomer reactivity ratios were obtained from an extended Kelen–Tudos method. Differential scanning calorimetry and thermogravimetry were used to evaluate the thermal behavior of all copolymers synthesized under microwave energy. Based on the products analyzed by SEC and gas chromatography–mass spectrometry, a possible mechanism of degradation is postulated.

Syntheses of CdTe Quantum Dots and Nanoparticles through Simple Sonochemical Method under Multibubble Sonoluminescence Conditions

Colloidal cadmium telluride (CdTe) quantum dots (QDs) and their nanoparticles have been synthesized by one pot sonochemical reactions under multibubble sonoluminescence (MBSL) conditions, which are quite mild and facile compared to other typical high temperature solution-based methods. For a typical reaction, and tellurium powder with hexadecylamine and trioctylphosphine/trioctylphosphineoxide (TOP/TOPO) as a dispersant were sonicated in toluene solvent at 20 KHz and a power of 220W for 5-40 min at 60 . The sizes of CdTe particles, in a very wide size range from 2 nm-30 , were controllable by varying the sonicating and thermal heating conditions. The prepared CdTe QDs show different colors from pale yellow to dark brown and corresponding photoluminescence properties due mainly to the quantum confinement effect. The CdTe nanoparticles of about 20 nm in average were found to have band gap of 1.53 eV, which is the most optimally matched band gap to solar spectrum.

Thermodynamic Analysis of Mn-depleted Zone Near Ti Oxide Inclusions for Intragranular Nucleation of Ferrite in Steel

A series of thermodynamic analyses have been performed to elucidate possible mechanism of Mn-depleted zone (MDZ) development near Ti oxide inclusions as nucleation sites of Intragranular Acicular Ferrite (IGF) transformation in steels, using a computational thermodynamic approach (CALPHAD). It is demonstrated that thermodynamic calculations are able to reproduce experimentally known inclusions evolution in the steels. The MDZ development near the Ti2O3 inclusions is shown to be a result of Mn absorption into the Ti2O3. Moreover, from thermodynamic analysis of phase equilibria in the Mn–Ti complex oxide system, it is proposed that a phase change of inclusion from (Ti3O5) s.s. (pseudobrookite structure solid solution dissolving Mn) to (Ti2O3) s.s. (ilmenite structure solid solution dissolving Mn) accelerate the Mn absorption into the Ti2O3 inclusion in steel. From a series of thermodynamic calculations, optimum thermal heating condition to enhance Mn absorption into Ti2O3 inclusions as well as IGF formation is discussed.