Novel nanopromoters achieve the improvement of formation kinetics and apparent density of methane hydrates simultaneously
Natural gas, is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, but commonly including varying amounts of other higher alkanes, and sometimes a small percentage of carbon dioxide, nitrogen, hydrogen sulfide, or helium. In recent times, it has been going through a continuous increase in the global consumption during the past decades, due to the advantage such as clean energy. As such, efficient technologies for natural gas storage and transportation are critical to utilize this energy resource, especially for the areas lack of natural gas resource. One of the most feasible storage approaches has been through methane hydrates. Under suitable pressure, methane hydrated can achieve storage capacity of about 170 vol/vol (volume methane per volume hydrates) and be stored stably under relatively milder conditions compared to high pressure compressed natural gas. However, given that methane hydrate formation usually goes through a stochastic induction period and a slow growth period, achieving the rapid hydrate formation is essential for the utilization of this technology. Noteworthy literature has shown that loosely formed hydrates can cause low storage efficiency. Reported attempts to resolve this include the installation of a vertically moved impactor in the reactor and achieved the reciprocating intensification of the hydrates during the formation process, while applying porous materials.
In essence, research has that it is of great value to develop novel nano-promoters that can not only enhance the hydrate formation rate, but also enable the formed hydrates to agglomerate compactly in the reactor. In particular, a previous study by the same authors here grafted SO3− covalently on the surface of polymer nanospheres and used the SO3−-coated nanospheres to promote methane hydrate formation; high promotion efficiency was obtained. To improve on this, Qingdao University of Science and Technology researchers: Dr. Yan Lin, Dr. Li Liu, Dr. Meng-Ting Sun, Dr. Chen Chen, Dr. Guo-Dong Zhang, Dr. Yan He Professor Fei Wang, proposed to use the polymer nanospheres as the carriers and prepared novel nanopromoters by grafting different hydrophilic groups on the carriers, including SO3−, COO− and N(CH3)3+. Their work is currently published in the research journal, AlChE Journal.
In their approach, they proposed that by regulating the hydrophilic groups on the nanopromoter surface, one could not only analyze the different promotion efficiency of different hydrophilic groups, but also achieve the rapid formation of methane hydrates together with compact agglomeration in the reactor. Specifically, the researchers prepared novel nanopromoters by grafting hydrophilic groups covalently on polystyrene nanospheres ([email protected]), and for the first time achieved rapid formation of methane hydrates together compact agglomeration by regulating the hydrophilic groups on the surface of nanopromoters.
The authors reported that when -SO3−@PSNS was used, methane hydrates formed rapidly but loosely in the reactor; while for COO−@PSNS and N(CH3)3+@PSNS, even the hydrate formation rate was seriously reduced, the formed hydrates agglomerated compactly in the reactor bottom. Interestingly, when both SO3− and COO− were fixed on the nanospheres, both the hydrate growth rate and agglomeration compactness were controlled.
In summary, novel nanopromoters for methane hydrate formation were prepared by grafting hydrophilic groups on polymer nanospheres; and it was confirmed that the hydrophilic groups dominated the promotion efficiency. In a statement to Advances in Engineering, Professor Fei Wang mentioned that their work not only revealed that the dominant role of the hydrophilic groups of the promoters in promoting methane hydrate formation, but also provided a way to achieve both the rapid hydrate formation and high agglomeration compactness by using nanopromoters, which, therefore is of great significance to the industrial application of the hydrate-based natural gas storage & transportation
Yan Lin, Li Liu, Meng-Ting Sun, Chen Chen, Guo-Dong Zhang, Yan He, Fei Wang. Rapid formation of methane hydrates with compact agglomeration via regulating the hydrophilic groups of nanopromoters. American Institute of Chemical Engineers Journal 2020; volume 66: page 16296.