Biosurfactant as a Promoter of Methane Hydrate Formation: Thermodynamic and Kinetic Studies.

Amit Arora,Anil Kumar Singh,Rajnish Kumar,Chandrajit Balomajumder,Swaranjit Singh Cameotra,B Santhakumari,Sukumar Laik,Pushpendra Kumar

doi:10.1038/srep20893

Abstract

Natural gas hydrates (NGHs) are solid non-stoichiometric compounds often regarded as a next generation energy source. Successful commercialization of NGH is curtailed by lack of efficient and safe technology for generation, dissociation, storage and transportation. The present work studied the influence of environment compatible biosurfactant on gas hydrate formation. Biosurfactant was produced by Pseudomonas aeruginosa strain A11 and was characterized as rhamnolipids. Purified rhamnolipids reduced the surface tension of water from 72 mN/m to 36 mN/m with Critical Micelle Concentration (CMC) of 70 mg/l. Use of 1000 ppm rhamnolipids solution in C type silica gel bed system increased methane hydrate formation rate by 42.97% and reduced the induction time of hydrate formation by 22.63% as compared to water saturated C type silica gel. Presence of rhamnolipids also shifted methane hydrate formation temperature to higher values relative to the system without biosurfactant. Results from thermodynamic and kinetic studies suggest that rhamnolipids can be applied as environment friendly methane hydrate promoter.

Highlights

Natural gas hydrates (NGHs) are solid non-stoichiometric compounds often regarded as a generation energy source
The objective of this study is to explore the feasibility of using glycolipids type biosurfactant as methane hydrate generation promoter
Earlier strain A11 has been reported as plant-growth promoting (PGP) and multi-metal-resistant (MMR) bacterium capable of producing rhamnolipids while growing on glycerol supplemented minimal salt medium (MSM)[16]

Summary

Introduction

Natural gas hydrates (NGHs) are solid non-stoichiometric compounds often regarded as a generation energy source. Gas hydrate formation in a quiescent pure water-gas system involves clustering of water molecules by hydrogen bonding in liquid phase and subsequently occluding gas until a cluster of critical concentration and size is formed. This determines the critical nuclei for hydrate formation. Enhancing the rate of hydrate formation by surfactants can have tremendous influence on commercialization prospect as this can facilitate the conversion of natural gas into solid hydrates useful for storage www.nature.com/scientificreports/. Use of synthetic surfactant such as sodium dodeccyl sulfate (SDS), sodium tetradecyl sulfate (STS), sodium hexadecyl sulfate (SHS) in natural environment for enhancing NGHs generation could be a cause of concern as they have been reported to possess toxic effects for living organisms[11,12]

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Conclusion