Introduction to Hydrates

Gas hydrates are solid ice-like materials that form at relatively high temperature. That is, they form at temperatures above the freezing point of water (0°C). 

In a gas hydrate, water forms a hydrogen-bonded cage and different molecules reside inside the cage. Water is called the host,  

In order for a hydrate to form, three conditions must be met  

Hydrate formation is favored by low temperature and high pressure, but the actual hydrate formation condition is a function of the gas under consideration. Different gases form hydrates at different conditions. 

It may seem obvious that some water must be present however, just having some water present is not enough. There must be enough water to form the hydrate phase. Ironically, if there is too much water present, a hydrate will not form either. If the hydrate former is present in too low a concentration, then it will merely dissolve in the water. Some acid gas disposal schemes take advantage of this property. 

---