Synthesis, Structural Characterization And Properties Of Tetra-iso-amyl Ammonium Bromide Semiclathrate Hydrates Stable At Room Temperature

Hydrate based gas storage and carbon dioxide capture technologies have shown promising applications in many fields such as energy and environment.However,the promotion and application of these technologies also face many problems and challenges.One of the main reasons is that hydrates require high pressure and low temperature to form and maintain their thermodynamic stability.In recent years,researchers at home and abroad are using thermodynamic promoters to improve the thermodynamic stability of hydrates.Tetraisoamylammonium bromide?TiAAB?is one of the few semiclathrate promoters that can keep the hydrates stable at room temperature.However,there is less research on it at present.In view of this,many batches of TiAAB products were prepared in the laboratory,and the phase equilibrium properties,structure,and gas storage behavior of TiAAB semiclathrate hydrates were studied.The main contents are as follows:Synthesis section:The effect of factors such as reaction temperature,reaction time,and molar ratio of materials on the synthesis yield was investigated.Under the optimized conditions,132 g of TiAAB was synthesized in a single pass and the yield was about 79.4%.Further,a series of characterizations for the prepared TiAAB,such as nuclear magnetic resonance and elemental analysis,showed that the purity of the products is high.Phase diagrams section:Phase equilibrium conditions of TiAAB in ethyl acetate,water,and CH₄ and CO₂ were studied separately,and corresponding phase diagrams were made.It was found that the TiAAB aqueous solution exists in unique double liquid phase within a certain range of temperature and solubility;the addition of TiAAB greatly lowers the formation conditions of CH₄ and CO₂ hydrate,making them possible to form near room temperature and lower pressures.Crystal culture section:the effect of temperature,solubility and degree of under cooling on the TiAAB hydrate crystal growth was investigated.Under certain conditions,corresponding single crystal for three hydration indexes of TiAAB·26H₂O,TiAAB·32H₂O and TiAAB·38H₂O were obtained.Further,the structures of TiAAB single crystal and polycrystalline were characterized by X-ray diffraction and micro laser Raman.Gas storage behavior section:the formation kinetics of CH₄ and CO₂ hydrates were greatly increased by adding porous silica from rice husk as the support to the TiAAB aqueous solution.It was found that the gas hydrate under this system can not only be formed at about30°C,but also can reach 90%of the maximum capacity within 200 minutes.In addition,this system shows good regeneration performance.Further,raman characterization of the structures of TiAAB+CH₄?TiAAB+CO₂ systems proves that gas molecules exist in the vacant cages of TiAAB semiclathrate hydrates.