This paper presents the use of a commercial FlowSynth microwave reactor for the continuous production of biodiesel from palm oil. A high ester content of 99.4% can be obtained in only 1.75 min ...residence time at a methanol to oil molar ratio of 12, a microwave heating power of 400 W, reaction temperature of 70 °C and NaOH catalyst loading of 1%wt of oil. The process energy consumption has also been investigated in order to assess the potential advantages of using microwave irradiation for biodiesel production. The energy consumption of palm oil transesterification as low as 0.1167 kWh/L of biodiesel was required, proving that microwave reactors need less energy consumption as compared to conventional processes. Moreover, all main biodiesel properties are in accordance with EN/ASTM standards.
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•High ester content of 99.4% can be obtained in a short residence time of 1.75 min.•This process required an energy consumption of about a half of the conventional process.•All properties of obtained biodiesel were in the range of EN/ASTM standard limit.
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•Microwave assisted levulinic acid hydrogenation to 1,4-pentanediol over Au catalysts.•Complete selectivity to 1,4-pentanediol during solvent-free hydrogenation at 200 °C.•Cooperative ...role of Au nanoparticles and support as active sites.•Structural and morphological stability of the catalyst under hydrogenation conditions.•Au/TiO2 reused after reactivation by MW-assisted oxidation inside the reactor.
Microwave (MW) -assisted levulinic acid (LA) hydrogenation has been performed over two gold catalysts (commercial 1 wt% Au/TiO2 by AUROlite™ and 2.5 wt% Au/ZrO2, prepared using deposition-precipitation). MW-assisted LA hydrogenation was carried out in water and in solvent-free conditions via (i) H-transfer and (ii) molecular H2. Au/TiO2 promoted complete LA conversion and the further reduction of the produced GVL to 1,4-pentanediol (1,4-PDO) in the presence of 50 bar H2 at 150 °C (4-hour reaction). Interestingly, selectivity to 1,4-PDO was complete at 200 °C. Extended characterisation highlighted the cooperative role played by the gold nanoparticles and the support, onto which activated hydrogen atoms spillover to react with LA. This results in the remarkable activity of Au/TiO2. Both catalysts showed structural and morphological stability under reaction conditions. It was possible to reactivate the Au/TiO2 catalyst by MW-assisted oxidation, paving the way for catalyst recycling directly inside the MW reactor.
The impressive pharmacological properties shown by a number of coumarins have led to extraordinarily large emphasis being placed on the design of more efficient and greener synthetic procedures to ...produce them. The increasing use of enabling technologies, such as microwaves, ultrasound, new heterogeneous catalysts and greener solvents in recent years has made access to coumarin derivatives much simpler. This review will highlight the most recent synthetic advances that make use of non-conventional methods and energy sources and some perspectives for the future, in particular the synthesis of new hybrid molecules bearing a coumarin moiety with a dual mode of biological action.
The impressive pharmacological properties shown by a number of coumarins have led to extraordinarily large emphasis being placed on the design of more efficient and greener synthetic procedures to produce them.
•A combined mechanical stirred ultrasonic flow reactor (MS–US) has been designed for biodiesel production.•The MS–US reactor provided the highest reaction rate when compared with MS and US reactors ...used separately.•The transducer power plays a relevant role in the transesterification reaction.
This paper investigates the production of biodiesel from palm oil using a combined mechanical stirred and ultrasonic reactor (MS–US). The incorporation of mechanical stirring into the ultrasonic reactor explored the further improvement the transesterification of palm oil. Initial reaction rate values were 54.1, 142.9 and 164.2mmol/L min for the mechanical-stirred (MS), ultrasonic (US) and MS–US reactors, respectively. Suitable methanol to oil molar ratio and the catalyst loading values were found to be 6 and 1 of oil, respectively. The effect of ultrasonic operating parameters; i.e. frequency, location, and number of transducer, has been investigated. Based on the conversion yield at the reactor outlet after 1h, the number of transducers showed a relevant role in the reaction rate. Frequency and transducer location would appear to have no significant effect. The properties of the obtained biodiesel (density, viscosity, pour point, and flash point) satisfy the ASTM standard. The combined MS–US reactors improved the reaction rate affording the methyl esters in higher yield.
Bio-waste valorisation has been one of the hottest research topics worldwide over the last decade. Following the biorefinery concept, the main goals have been the search for inexpensive renewable ...resources for the production of chemicals, materials and energy, the transformation of bio-waste into useful by-products and the development of new technologies for process intensification to make all these conversions economically profitable. Bio-waste is generally a negative-cost feedstock for the potential production of high value-added chemicals and bioenergy. The present review has the aim of describing existing studies and applications of non-conventional energy sources such as microwaves, ultrasound and ball milling within this field. We have focused our attention on suitable protocols for the conversion of biomass into fine chemicals. Comparisons with classic procedures are a good means with which to highlight the huge advantages and potential scalability of these so-called "enabling technologies".
Bio-waste valorisation has been one of the hottest research topics worldwide over the last decade.
Glycerol has the potential to be both an excellent renewable solvent in modern chemical processes and a versatile building block in biorefineries. Both of these potential applications may be made ...easier and more convenient by microwave and/or ultrasound irradiation. As glycerol is a nontoxic, biodegradable compound, it will provide important environmental benefits to new platform products. Furthermore, significant markets in polymers, polyethers, fuel additives, nanoparticles and other valuable compounds may well be opened up by cutting down the high purification cost of glycerol. The aim of this review is to highlight the best literature examples of glycerol being used, either as a solvent or as a reagent, to give interesting results under microwave or ultrasound irradiation.
Glycerol has the potential to be both an excellent renewable solvent in modern chemical processes and a versatile building block in biorefineries.
A new simple flow system which is made up of a multi-rotor high-shear mixer connected to a multimode microwave reactor has been assembled. This simple loop reactor has been successfully used in the ...NaOH-catalyzed transesterification of refined palm oil in methanol. Thanks to optimal mass/heat transfer, full conversion was achieved within 5 min (biodiesel yield of 99.80%). High-quality biodiesel was obtained that is in accordance with international specifications and analytical ASTM standards. The procedure's high efficiency and low energy consumption should pave the way for process scale up.
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•The combination of HSM-MW flow system for biodiesel production has been proposed.•Highly efficient mass and heat transfer in transesterification reaction.•The hybrid reactor enables a complete conversion in 5 min reaction time.•The new system halved the energy consumption of conventional processes.
We describe herein an unprecedented mechanochemical "parallel synthesis" of 3,4-dihydro-2H-benzoe1,3oxazine derivatives via a one pot three component reaction. The new milling system uses a ...multiposition jar (variable sizes are possible), allowing for the processing of up to 12 samples simultaneously, leading to the formation of a fungicide and a building block for polymer preparation with higher throughput compared to standard milling devices.
Summary
Objective: The aim of this review is to evaluate and summarize the available scientific information on the commonest plant extracts marketed in Western countries. In view of the intense, ...ongoing search for new plant extracts with powerful anti‐inflammatory activity, we paid particular attention to this topic. The aim is to provide broad coverage of as many potentially useful plants as possible and then to focus on those with the greatest therapeutic potential.
Methods: Our bibliographic sources were the SciFinder databases: CAPLUS, MEDLINE, REGISTRY, CASREACT, CHEMLIST, CHEMCATS (update to October 2007). In order to assess the value of clinical trials, we focused a specific search on clinical investigations concerning nine plants with the most trial data, viz., Althaea officinalis, Calendula officinalis, Centella asiatica, Echinacea purpurea, Passiflora incarnata, Punica granatum, Vaccinium macrocarpon, Vaccinium myrtillus, Valeriana officinalis. This was carried out in several databases (update to June 2008): ISI Web of KnowledgeSM (ISI WoK), SciFinder (CAPLUS, MEDLINE, REGISTRY, CASREACT, CHEMLIST, CHEMCATS) and PubMed (indexed for MEDLINE).
Results: Our survey covers roughly a 1000 plants, although clinical trials have been published only for 156 plants supporting specific pharmacological activities and therapeutic applications. However, for about half of the plants, in vitro and in vivo studies provide some support for therapeutic use. For one‐fifth of the plants included in our search, only phytochemical studies were found. Their properties and indications were often attributed to the presence of certain compounds, but no evidence concerning the activities of the whole extracts was presented. We found that for about 12% of the plants, currently available on the Western market, no substantial studies on their properties had been published, while there was strong evidence that 1 in 200 were toxic or allergenic, so that their use ought to be discouraged or forbidden. Nine plants had considerable evidence of therapeutic effect, viz., A. officinalis, Calendula officinalis, Centella asiatica, E. purpurea, Passiflora incarnata, Punica granatum, Vaccinium macrocarpon, Vaccinium myrtillus, Valeriana officinalis.
Conclusion: The present review provides a baseline on the level of evidence available on many herbal preparations and should be of help to those intending to research further on these topics.
Preventing recurrences and metastasis of prostate cancer after prostatectomy by administering adjuvant therapies is quite a controversial issue. In addition to effectiveness, absence of side effects ...and long term toxicity are mandatory. Curcuminoids (Curc) extracted with innovative techniques and effectively loaded by polymeric nanobubbles (Curc-NBs) satisfy such requirements. Curc-NBs showed stable over 30 d, were effectively internalized by tumor cells and were able to slowly release Curc in a sustained way. Significant biological effects were detected in PC-3 and DU-145 cell lines where Curc-NBs were able to inhibit adhesion and migration, to promote cell apoptosis and to affect cell viability and colony-forming capacity in a dose-dependent manner. Since the favourable effects are already detectable at very low doses, which can be reached at a clinical level, the actual drug concentration can be visualized and monitored by US or MRI, Curc-NBs can be proposed as an effective adjuvant theranostic tool.
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