Evaluating Light Olefin/Paraffin Separation Performance of MOF-808-based Adsorbents

Light olefins, such as ethylene and propylene, are highly demanded feedstocks in the chemical and petroleum industry, primarily for polymer production [1,2]. Presently, cryogenic distillation techniques are employed for the separation and purification of these olefins from their paraffin counterparts. These techniques are energy-intensive, due to the similarity of physical and chemical properties of the hydrocarbons. Hence, it is crucial to explore more efficient separation techniques, such as membranes, to mitigate the carbon emissions associated with these processes [2]. The class of mixed-matrix membranes (MMMs), containing a selective polymer and metal-organic framework (MOF) fillers, can enable the desired tuning of permeability and selectivity [3,4]. MOF-808 is a Zr-based MOF possesses a large surface area and pore volume. Its structure offers a stable and adaptable platform for incorporating various functionalities into its framework, facilitated by the coordination sites present on its Zr clusters [5]. The present research focuses on examining the adsorptive characteristics of both untreated and various types of functionalized MOF-808 materials. The primary objective is to assess the impact of functionalization on the adsorption properties and evaluate the potential of these materials as fillers in mixed matrix membranes (MMMs). We conducted pulse inverse gas chromatography (IGC) at a temperature range of 30-80 °C to determine adsorption thermodynamics, including Henry coefficients, thermodynamic selectivity, and isosteric heats of adsorption at infinite dilution. Figure 1 shows the elution chromatograms of single ethane, ethene, propane, and propene over MOF-808 at 80 °C. The pulse IGC results show that certain functionalities can improve MOF-808s selectivity for the unsaturated molecules. The heats of adsorption of C3s increased slightly after the functionalization of MOF-808. Isotherm measurements of single gas components at low-pressure range show the adsorption capacities of modified MOFs are higher compared to the pristine MOF. The results of this study offer perspectives for the design of MMMs with remarkable separation potential for light olefin/paraffin mixtures.