A new method for separating HFC-134a from gas mixtures using clathrate hydrate formation

Area of Science:

• Chemical Engineering
• Separation Science
• Materials Science

Background:

• Hydrofluorocarbons (HFCs) like HFC-134a are widely used but require efficient separation methods.
• Gas mixtures containing N2 and HFC-134a pose separation challenges.
• Conventional separation techniques may be energy-intensive or require additives.

Purpose of the Study:

• To propose and investigate a new separation method for HFC-134a from N2 using gas hydrate formation.
• To determine the feasibility and efficiency of this hydrate-based separation process.
• To analyze the thermodynamic and kinetic aspects of mixed HFC-134a + N2 hydrate formation.

Main Methods:

• Experimental determination of three-phase (hydrate, liquid water, vapor) equilibria for HFC-134a + N2 + water mixtures.
• Analysis of hydrate and vapor phase compositions at equilibrium to assess separation efficiency.
• Kinetic experiments to monitor vapor phase composition changes and determine equilibrium times.
• X-ray diffraction to confirm the crystallographic structure of the formed hydrates.

Main Results:

• The mixed HFC-134a + N2 hydrates were confirmed to be of structure II.
• Separation experiments yielded HFC-134a with purity exceeding 99 mol % after hydrate formation and dissociation.
• The process operates effectively within mild temperature (275-285 K) and low-pressure (0.1-2.7 MPa) ranges.
• No additives were required to facilitate hydrate formation at reduced pressures.

Conclusions:

• Gas hydrate formation is a viable and efficient method for separating HFC-134a from N2-containing gas streams.
• The method offers high separation purity (>99 mol %) under mild operating conditions.
• This technique presents an environmentally friendly and cost-effective alternative to conventional separation processes.