Advancing the Hydrate-Based CO2 Separation Process by Implementing Spectroscopic Analysis and Process Simulation

The quest for environmentally sustainable solutions for CO2 recovery and purification has led to the development of innovative separation techniques, which are crucial for carbon capture, utilization, and storage (CCUS) applications. Moreover, refrigerant recovery techniques have been widely developed after the implementation of stringent global regulations on hydrofluorocarbon (HFC) emissions. This study explores the separation of R134a, a well-known HFC, from carbon dioxide (CO2), focusing on the feasibility of hydrate-based processes for the recovery of high-purity CO2. Phase equilibrium measurements, spectroscopic analysis, and process simulation studies were systematically performed to evaluate the operation conditions and energy requirements of the hydrate-based separation processes. Phase equilibrium measurements for R134a + CO2 mixtures at various concentrations were performed along with the structural analysis of mixed hydrates using low-temperature powder X-ray diffraction (PXRD). The experiments demonstrated the preferential occupation of R134a into hydrate cages, enriching CO2 in the vapor phase and achieving target purity levels of 99.0 mol % CO2. The PXRD patterns confirmed the formation of structure II hydrates with a lattice parameter of 17.2 & Aring; with inclusions of R134a in large cages, resulting in a higher exothermic heat of formation compared with that of structure I hydrates. Process simulations were performed to further extend these findings, highlighting the favorable operation conditions and the exothermic nature of hydrate formation, which suggested heat integration into other process units. This study represents a pioneering effort in modeling hydrate-based CO2 recovery processes, providing a significant contribution to the development of sustainable industrial practices and the advancement of CCUS technologies.