(550d) Preparation and Characterization of Novel Clinoptilolites: Treatment of Natural Gas Type Mixtures Using Inorganic Membranes

A significant quantity of natural gas reserves in the United States do not meet the pipeline specification of having less than 4% N₂ content and thus require further refinement. This proves to be tough for smaller producers due to the economies of scale necessary for conventional separation techniques such as cryogenic distillation. The integration of adsorption technology within these upgrading processes may achieve a more economically efficient separation. To that end, the characterization of adsorbents is important to optimise adsorption selectivity for this separation.

Clinoptilolite is a natural zeolite that may be modified through cation exchange to induce favourable adsorption characteristics such as high CH₄/N₂ separation properties. This adsorbent material is a promising candidate for the application of natural gas upgrading.

In this work, experimental equilibrium adsorption isotherms and uptake measurements of CO₂, CH₄ and N₂ gases are presented for various clinoptilolites. Additionally, the effects of competitive adsorption of binary CH₄-N₂ mixtures on the studied adsorbents is shown. The applicability of this material in novel inorganic membranes is discussed, and a novel membrane preparation technique is explored using clinoptilolite particles sintered within a glass binder. The prepared membrane surface was characterized using SEM and XRD analyses and the membranes were tested for the permeation properties of several constituent gases present in natural gas type mixtures.