Photopolymerized Mixed Matrix Membranes for Liquid Organic Hydrogen Carrier Separation

TL;DR

A new membrane system is developed to efficiently separate hydrogen-rich and hydrogen-lean liquids for sustainable hydrogen transport.

Contribution

Photopolymerized mixed-matrix membranes with high MOF/Pd activated carbon loading enable selective LOHC separation under mild conditions.

Findings

Membranes achieved ideal aromatic/aliphatic selectivities of ≈12 and a toluene/methylcyclohexane separation factor of 1.8.

The fabrication method allows high filler loadings and creates stratified structures with multiple dense polymeric layers.

This system demonstrates the highest performance to date for LOHC separation using solvent nanofiltration.

Abstract

Liquid organic hydrogen carriers (LOHCs) are infrastructure‐compatible media for hydrogen storage and transport under ambient conditions, addressing hydrogen's volatility, low density, and high reactivity. Separating liquid hydrogen‐lean/hydrogen‐rich hydrocarbons without resorting to energy‐intensive phase changes is a key barrier to LOHC system implementation. Membrane operations that can separate hydrogen‐lean/hydrogen‐rich species can drive equilibria of dehydrogenation processes, enabling them to run at lower temperatures. Here, new photopolymerized mixed‐matrix membranes composed of a cyclic monomer and a metal organic framework (MOF)/palladium‐doped activated carbon mixture are presented. By leveraging an in situ photopolymerization strategy, high–filler‐loaded mixed‐matrix membranes exhibiting ideal aromatic/aliphatic selectivities of ≈12 and a toluene/methylcyclohexane (MCH) separation factor of 1.8 for membranes with filler loading of 20 wt.% are fabricated. This fabrication approach enables high filler loadings in the monomer and, for multi‐layer films, delivers a stratified structure where it induces the formation of multiple internal polymeric dense “skin” layers, which is ideal for the promotion of selective transport. It is compared that the early studies reported using only commonly reported metrics, rejection versus mixture permeance, with the present system, demonstrating the highest performance to date. This work highlights a high‐performance solvent nanofiltration platform for LOHC separation aligned with sustainable hydrogen production goals.

Photopolymerized membranes with high metal organic framework (MOF)/Pd activated carbon loading enable selective separation of hydrogen‐rich/lean liquid organic hydrogen carriers (LOHCs) under mild operational conditions. The employed fabrication approach yields stratified, multilayer structures with enhanced aromatic/aliphatic (toluene/methylcyclohexane) selectivity. This solvent nanofiltration platform advances energy‐efficient LOHC purification, which is aligned with sustainable hydrogen transportation.

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