Crystal Structure and Guest Distribution of N2O Hydrate Determined by Powder X-ray Diffraction Measurements

Abstract

Research and development of control technology of N2O greenhouse gas are crucial for sustainable development. The crystallographic structural model of structure I (sI) for N2O hydrate, with a composition of N2O·6.1H2O and a density of 1.127 g/cm3 at 263 K, was obtained using powder X-ray diffraction data. In addition, the distributions of the disordered N2O molecules in 512 and 51262 host water cages of sI hydrate were explored. N2O in the large 51262 cage had an off-center distribution and it was out-of-plane to the long axis of the cage, and N2O in the small 512 cage had an isotropic distribution around its center. These crystallographic features of the N2O hydrate were identical to those of the CO2 hydrate, and an increase in cage occupancy depending on the formation pressure was observed. The hydrate composition and dissociation kinetics were discussed pertaining to the information required for the gas storage of N2O.