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The mysterious structure of ice: Why are hydrates called the 'brothers of ice'?
Hydrates, or gas hydrates, are crystalline, water-based solids that resemble ice in appearance. In these structures, small nonpolar molecules (usually gases) or polar molecules with large hydrophobic groups are trapped in a "cage" of ice-water molecules held together by hydrogen bonds. These hydrates are natural resources with important economic value, but their complex structures and formation mechanisms remain mysterious.
The structure formation of hydrates relies on trapped molecules; without the support of these molecules, the hydrate's lattice structure will collapse and transform into a regular ice crystal structure or liquid water.
Formation and types of hydrates
Hydrates are usually formed under appropriate temperature and pressure conditions and mainly include low molecular weight gases, such as oxygen (O2), hydrogen (H2), nitrogen (N2), carbon dioxide (CO2), methane (CH4), etc. The structure of hydrates is mainly divided into two types: type I (hydrate sI) and type II (hydrate sII) cubic lattice structures.
The unit cell of Type I hydrate contains 46 water molecules, forming two types of cages: small cages and large cages. Type II contains 136 water molecules and has more small and large cages.
History of hydrates
The first record of hydrates dates back to 1810, when chemist Humphrey Davy discovered their existence. Over time, research on hydrates gradually increased, especially in 1934, when Hammerschmidt discovered that hydrates could form blockages in gas pipelines, which triggered subsequent research.
The interest in hydrates is not limited to their physical and chemical properties but also includes their potential energy resources.
Application potential of hydrates
Because hydrates can be used as a carrier for gas storage and transportation, countries have regarded them as potential energy resources. It is estimated that the inventory of methane hydrate at the bottom of the deep sea reaches 6.4 megatons. This data has undoubtedly attracted the attention of many countries and triggered a series of explorations on energy development.
Problems that develop in pipelines
The formation of hydrates in pipelines is a major industrial challenge, because when hydrates form, crystals will aggregate, causing pipeline blockage, thereby affecting the flow of gas.
Preventing hydrate formation is an important industrial task, usually achieved by changing operating conditions or adding inhibitors.
Hydrate and climate change
In addition, in terms of climate change, the study of hydrates is also of great significance. Scientists have suggested that the deposition of carbon dioxide hydrates could become a new way to reduce greenhouse gases, potentially helping to combat climate change by converting CO2 into a safe solid form.
Extraterrestrial Hydrate
Hydrates do not only exist on Earth. Scientists have also discovered similar structures on outer planets and satellites. They may form under extreme environmental conditions, which further proves the universality and importance of hydrates.
Future research directions
Although current research on hydrates has achieved some results, its formation mechanism and behavioral characteristics still require further exploration. Since commercial production will take some time, countries still face many technical challenges in exploring this resource.
How will hydrates affect future energy policy and environmental governance?
