Characterization of clathrate hydrates with CO₂ + 1-propanol or 2-propanol: Implications for flow assurance, refrigeration, carbon capture, and skincare applications

There has been growing interest in the use of hydrate-based technology for energy and environmental applications; however, structural characterization of some hydrate phases relevant to these applications has not been dealt with sufficiently in previous studies. This paper reports crystallographic characterization of hydrates formed in [CO₂ + 1-propanol (propan-1-ol) + water] and [CO₂ + 2-propanol (propan-2-ol) + water] systems with powder X-ray diffraction (PXRD) and X-ray computed tomography (CT) measurements. It was revealed that structure I CO₂ hydrate and a non-crystalline phase involving 1-propanol are formed in CO₂ + 1-propanol system. As for CO₂ + 2-propanol system, crystalline structure of the formed hydrate differs depending on thermodynamic conditions; at 3.3 MPa, 274 K and at 2.2 MPa, 263 K, sI CO₂ hydrate was formed, whereas at lower pressure and temperature, i.e., 0.5 MPa and 255 K, a new tetragonal structure outside the canonical hydrates was identified. Implications of using 1-propanol as a thermodynamic inhibitor and kinetic promoter of hydrate formation are discussed, which opens some possibilities into petroleum exploration/production applications and the development of hydrate-based refrigeration systems. The structural identification of tetragonal (sII′) CO₂ + 2-propanol hydrate sheds new light on developing hydrate-based CCS process and novel skin care products.