Removal of Siloxanes from Model Biogas by Means of Deep Eutectic Solvents in Absorption Process.

Edyta Słupek,Patrycja Makoś-Chełstowska,Jacek Gębicki

doi:10.3390/ma14020241

Edyta Słupek, Patrycja Makoś-Chełstowska + Show 1 more

Open Access

https://doi.org/10.3390/ma14020241

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Abstract

The paper presents the screening of 20 deep eutectic solvents (DESs) composed of tetrapropylammonium bromide (TPABr) and glycols in various molar ratios, and 6 conventional solvents as absorbents for removal of siloxanes from model biogas stream. The screening was achieved using the conductor-like screening model for real solvents (COSMO-RS) based on the comparison of siloxane solubility in DESs. For the DES which was characterized by the highest solubility of siloxanes, studies of physicochemical properties, i.e., viscosity, density, and melting point, were performed. DES composed of tetrapropylammonium bromide (TPABr) and tetraethylene glycol (TEG) in a 1:3 molar ratio was used as an absorbent in experimental studies in which several parameters were optimized, i.e., the temperature, absorbent volume, and model biogas flow rate. The mechanism of siloxanes removal was evaluated by means of an experimental FT-IR analysis as well as by theoretical studies based on σ-profile and σ-potential. On the basis of the obtained results, it can be concluded that TPABr:TEG (1:3) is a very effective absorption solvent for the removal of siloxanes from model biogas, and the main driving force of the absorption process is the formation of the hydrogen bonds between DES and siloxanes.

Highlights

The production of energy from renewable sources is a choice resulting from the policy of environmental protection or care of the environment but is an obligation imposed by the European Union in the form of numerous ordinances and international agreements [1]
The results indicate that the flow rate has only a minor effect on siloxane uptake compared to deep eutectic solvents (DESs) volume
The siloxane solubility was predicted by means of the COSMO-RS model where the highest solubility of both linear and cyclic siloxanes was present in the DES

Summary

Introduction

The production of energy from renewable sources is a choice resulting from the policy of environmental protection or care of the environment but is an obligation imposed by the European Union in the form of numerous ordinances and international agreements [1]. More and more EU countries are focusing their attention on managing waste materials from various industries for the production of biogas [2,3,4,5]. This approach is consistent with the theory of sustainable development. During the combustion of such types of biogas, silicone may be released and combined with oxygen This can lead to the formation of silica deposits. The oldest and most widely used process for the treatment of gaseous streams is the application of water or amine scrubbers [11,12]. In recent years, more and more scientific research has been devoted to the search for new “green solvents” that will have higher purification efficiency of biogas streams with a simultaneous lower energy demand during regeneration [19]

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