Hydrate-based gas separation is used for carbon dioxide (CO2) sequestration. However, the requirement for high-performance additives to combat its low gas storage capacity makes this method expensive and environmentally unfriendly.
Study: Magnetically recyclable -SO3– coated nanoparticles promote gas storage through hydrate formation. Image credit: VectorMine/Shutterstock.com
A paper recently published in ACS Applied Materials and Interfaces discussed the synthesis of a new hydrate promoter, iron oxide (Fe3O4) nanoparticles coated with copolystyrene-styrene sulfonate sodium (Fe3O4) that have an integrated shell structure and synthesized by emulsion polymerization.
During the formation of methane hydrate, [email protected]3O4 nanoparticles served as an efficient promoter and reduced the induction time by one-third compared to the commonly used promoter sodium dodecyl sulfate (SDS). In addition, the gas storage capacity has increased to 155 volume per volume (v/v).
Furthermore, SDS and other surfactant-based promoters induced foam formation during hydrate decomposition. This problem of foam formation was solved by replacing the promoters mentioned above with [email protected]Nanoparticles of 3O4. In addition, these [email protected]3O4 nanoparticles as promoters improved the CO2 storage capacity by more than 30% due to the formation of a marine environment mimicking fine sediments.
In addition, the integration of magnetically recoverable nanoparticles improved the gas storage efficiency due to the formation of gas hydrates. This excellent recycling performance provided a new way to solve the environmental and economic problems commonly encountered in the use of additives.
Gas storage with gas hydrates
Due to the demand for greenhouse gas treatment and clean energy requirements, there has been a growing need for industrial-scale gas storage and transportation. In addition, laying pipelines for long-distance gas transportation is an expensive and risky process, as natural geological hazards that affect pipelines cause corrosion and blockage.
To this end, an easy and inexpensive gas storage method for convenient gas transportation is needed to achieve environmentally friendly and low-carbon energy use. One way to realize this is to compress the storage volume as much as possible for easy gas transport. However, natural gas compression requires special facilities and extreme storage environments, limiting its practical application for commercialization.
Due to their adsorption capacity, molecular organic frameworks (MOFs), activated carbon, and other porous materials were previously explored for gas storage. Structurally, gas hydrates are solid gel-like components with cage-structured host water molecules and guest molecules. The formation of these gas hydrates takes place at low temperature and moderately high pressure. In addition, these gas hydrates have a large gas storage capacity (216 v/v for methane).
The introduction of surfactants can improve the gas storage capacity and the formation kinetics of gas hydrates along with a greater number of nucleation sites. Although MOFs can promote the formation of methane hydrates using promoters such as sodium polystyrene sulfonate and SDS they produce foam formation during hydrate decomposition.
In the present work, magnetically recoverable core-shell nanoparticles were prepared and used as hydrate promoters to reduce the hydrate induction time. The process was free of additive losses. These core-shell nanoparticles were characterized for their surface properties and the reduction of foam formation during hydrate decomposition, essential for easy gas storage, was discussed.
Furthermore, the effect of surfactant concentration on the induction time (during hydrate formation) and its gas storage capacity was investigated. Finally, the correlation between the magnetic property of prepared nanoparticles and marine sediments during CO2 gas storage and its underlying mechanism were discussed.
The experimental results revealed that, compared to the SDS samples with a concentration of 500 milligrams per liter, the induction time of gas hydrate formation in the PNS-0.4 sample was reduced from 243, 7 ± 27.8 minutes to 151 ± 14.4 minutes. Here, 0.4 represents the mass ratio of sodium p-styrene sulfonate. Therefore, PNS-0.4 showed good gas storage capacity.
In addition, the induction time of PNS-0.3 (802.1 ± 27.8 minutes) was higher than samples PNS-0.4 and PNS-0.5, suggesting the role of concentration in the dispersion of nanoparticles. Moreover, this induction time of PNS-0.3 was much higher than that of pure SDS and PNS samples. Thus, PNS nanoparticles accelerated the hydrate nucleation process and reduced the induction time.
conclusion
To summarize, gas hydrate promoters based on integrated core-shell structured nanoparticles were synthesized by emulsion polymerization. These nanoparticles promoted hydrate growth efficiently and showed good recycling properties. The encapsulation of the polymer in magnetic cores facilitated the surface functionalization of the prepared nanoparticles.
The isothermal hydrate formation test revealed that PNS-0.4 showed a 30% reduced induction time compared to the traditional SDS solution. In addition, the methane gas storage capacity was increased by 20%. Furthermore, PNS mimicked marine sediment in terms of CO2 gas storage.
The introduction of the PNS nanoparticles into the solution resulted in rapid nucleation and slight growth of gas hydrate, overcoming the mass transfer limitation. In addition, the surface functional groups of the nanoparticles helped to prevent foam formation during hydrate decomposition. In addition, the new nanoparticles showed good reuse performance with recyclability up to five times.
reference
Zhao, Y., Yang, M., Li, M., Dong, H., Ge, Y., Li, Q., Zhang, L. et al. (2022) Magnetically recyclable -SO3– coated nanoparticles promote gas storage through hydrate formation. ACS Applied Materials and Interfaces https://pubs.acs.org/doi/10.1021/acsami.2c06230
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