09:30
Unconventional activation/energy supply methods 3
Chair: Nikolay Cherkasov
09:30
40 mins
#89
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KEYNOTE: Direct heating of heterogeneous catalysts by microwaves: Minimizing unwanted gas phase chemistry
Dr Jose Luis Hueso
(presenter: Jose L Hueso)
Abstract: Research in solid-gas heterogeneous catalytic processes is typically aimed towards optimization of catalyst composition to achieve a higher conversion and, especially, a higher selectivity. However, even with the most selective catalysts, an upper limit is found: above a certain temperature gas phase reactions become important and their effect cannot be neglected. Here, we apply a microwave field to a catalyst-support ensemble capable of direct microwave heating (MWH). We have taken extra precautions to ensure that i) the solid phase is free from significant hot spots and ii) an accurate estimation of both solid and gas temperatures is obtained. MWH allows operating with a catalyst that is significantly hotter than the surrounding gas, achieving a high conversion on the catalyst while reducing undesired homogeneous reactions. We demonstrate the concept with different catalysts, supports and reactions including the oxidative dehydrogenation of alkanes, the epoxidation of ethylene or the methane coupling.
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10:10
20 mins
#49
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DESIGN AND CHARACTERIZATION OF A MICROWAVED-ASSISTED MICROFIXED-BED FOR REACTIVE SEPARATIONS
Yung Wei Hsiao, Dionisios Vlachos
(presenter: Yung Wei Hsiao)
Abstract: Reactions for producing 5-hydroxymethyl-furfural (HMF) from sugar molecules are important in upgrading biomass to fuels and chemicals. Acid-catalysed fructose dehydration into HMF has been extensively studied, but the yield is limited by the subsequent HMF degradation into side products, such as rehydration to levulinic and formic acids. Adsorption of HMF in porous carbon materials can minimize the rehydration step and increase the overall yield without the high energy consumption of separating HMF from high boiling point solvents. Selective HMF adsorption on carbon BP2000 has been previously demonstrated in batch systems. In this work, we present a continuous flow micro-packed bed absorber that is capable of intensifying the reactive adsorption and desorption processes in a two-stage manner. The column adsorption performance is characterized as a function of flow velocity, solution concentration, and temperature. The breakthrough curves of single and multicomponent solutions are measured and used to derive adsorption kinetics using simple models. HMF recovery through desorption will also be discussed. Conventional and microwave-based heating are compared. These results enable further process intensification for development of future biorefineries.
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10:30
20 mins
#25
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HETEROGENEOUS CATALYTIC ISOMERIZATION OF GLUCOSE USING DIFFERENT ENERGY SUPPLY METHODS
Margarida Antunes, Diogo Falcão, Auguste Fernandes, Maria Ribeiro, Martyn Pillinger, João Rocha, Anabela Valente
(presenter: Anabela Valente)
Abstract: The isomerization of carbohydrate biomass-derived glucose gives fructose, which is important to end-use industries related to food and pharmaceutical segments. On the other hand, this reaction step is central to the valorization of cellulose and other glucose-based carbohydrates to furanic platform chemicals. Thus, efforts to develop improved glucose isomerization processes have been made, involving enzymatic or chemo-catalytic approaches [1]. In this work, the catalytic isomerization of glucose is studied under the influence of ultrasound (US) or microwave irradiation (MW); these methods are compared with conventional conduction/convection heat transfer modes (CC). The catalysts are zeotypes based on MFI and BEA frameworks, furnished with basicity associated with alkali and alkaline earth metals (Na, K, Ca, Mg) introduced via post-synthesis methods. The influence of the materials’ properties, and heating/stirring effects associated with the energy supply methods on the reaction kinetics, and aspects of catalyst stability are addressed. Very high fructose selectivity (> 90 %) at fair glucose conversions (20-25 %) were reached in the temperature range 75-100 ºC over Mg-containing zeotypes.
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10:50
20 mins
#38
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PROCESS INTENSIFICATION IN EPOXIDATION OF VEGETABLE OILS IN THE PRESENCE OF HETEROGENEOUS CATALYSIS IN A SUPERIOR RECYCLED REACTOR SYSTEM
Adriana Freites, Pasi Tolvanen, Sebastien Leveneur, Tapio Salmi
(presenter: Adriana Freites Aguilera)
Abstract: Epoxidized vegetable oils (EVO) are used for developing green intermediates for the synthesis of a variety of chemical compounds. Microwave (MW) and ultrasound (US) irradiation in chemistry are considered two of the best process intensification technologies1. Our goal was to develop a superior method for producing EVO with high yields, using less energy and shorter reaction times, applying MW and US technologies combined with Spinchem (RBR) Rotating Bed Reactor and a solid catalyst. Epoxidation of EVOs was executed in a semi-batch reactor system, using the Prileschajew oxidation (Fig. 1). The reactor system comprised a loop where the mixture was pumped through a cavity in which MW were irradiated and recirculated back to the reactor where the mixture was exposed to US. Mixing was improved by RBR, which allowed minimization of mass transfer limitations of the bi-phasic system as well as immobilization of the solid resin catalyst.
A clear enhancement of the epoxidation process was accomplished with MW heating in comparison to conventional heating: the product yield was doubled under comparable conditions at 40ºC. The mass transfer rate was improved by 30% by using the advanced Spinchem RBR. The results confirm that combination of several technologies is necessary to reach real process intensification in the very demanding epoxidation of vegetable oils.
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