Decomposition Behavior Of EMT Hydrogen Hydrates By Molecular Dynamics Simulation

With the development of industrialization,the consumption of traditional energy sources has been greatly increased,but traditional energy sources such as oil are not renewable energy sources.Countries dominated by oil consumption are currently facing the threat of reduced energy.Hydrogen is a new energy source that is non-polluting and has a high calorific value,but due to the low density of hydrogen,the storage of hydrogen has become the primary factor restricting the utilization of hydrogen energy.Gas hydrate hydrogen storage technology has the advantages of low cost and high safety,and plays an important role in the field of hydrogen storage and transportation.At present,hydrogen hydrate has become one of the research hotspots in the field of energy environment.Hydrogen storage using gas hydrates is a practical,safe and simple way to store hydrogen.In addition,there are the following advantages:First,the material for storing hydrogen is water,which does not cause environmental pollution and can be recycled.Secondly,when the hydrate stores and releases hydrogen,the hydrogen does not undergo a chemical reaction,and the chemical properties do not change.Finally,the temperatures required for the decomposition of the hydrate to release the gas are within the normal temperature range.However,the use of hydrates to store hydrogen often requires low temperature and high pressure conditions.Therefore,most of the research mainly focuses on the following aspects:optimizing the formation conditions of gas hydrates;inhibiting or promoting reactions by adding suitable additives;and how to improve the hydrogen storage capacity of hydrates.However,solid hydrates can decompose under thermal stimulation or decompression conditions,producing gases and liquid water or ice,which is the inverse process of hydrate formation.The decomposition process of solid gas hydrates is an important and complex physical process,and the decomposition process of gas hydrates at home and abroad is relatively insufficient.In order to develop and store gas hydrate resources,it is essential to study the decomposition of gas hydrates.In addition,the use of hydrate storage and transportation gas technology,because of the high safety of hydrate gas storage,large reserves advantages,has been widely concerned by the industry.However,one of the key problems in solving this problem is to study the controlled decomposition of hydrates at low pressures.Therefore,the study of the decomposition kinetics of gas hydrates is of great significance for the development of hydrates and gas storage and transportation.This paper is mainly based on molecular dynamics simulation methods,and studies the decomposition process of EMT hydrogen gas hydrates at the molecular level（EMT structure is a new type of ultra-low density porous ice structure named after zeolite structure）.By simulating the decomposition process of EMT hydrogen hydrates with temperature change in three systems,the decomposition temperature at low pressure was found and the physical reasons behind the demise of EMT hydrogen hydrates were revealed.The microscopic mechanism of the decomposition process of EMT hydrogen hydrate can be summarized as follows:hydrogen molecules first diffuse in the skeleton of the hydrogen bond network of water molecules,resulting in holes,causing instability in the skeleton of the water cage,destroying the local skeleton,and then the hydrogen molecules escape,and finally the hydrate skeleton is completely destroyed.In addition,a comparative study method was used to compare whether or not C₂₀was added to the EMT hydrogen hydrate,and the decomposition process of EMT hydrogen hydrate was analyzed from the structural snapshot,radial distribution function,mean square displacement,and diffusion coefficient.The results show that the decomposition temperature of EMT hydrogen hydrate after the addition of C₂₀molecules rises from 250K to 260K,indicating that the addition of C₂₀can make the structure of EMT hydrogen hydrate more stable,and also play a key role in hydrogen transportation.All in all,the decomposition of hydrogen hydrates is a complex process.This paper only discusses hydrogen hydrates at the molecular level.However,molecular simulation is not only suitable for the above topics,but also for the formation kinetics of gas hydrates,hydrate structure determination and other fields.