(85e) Na+-Gated Nanochannel Membrane for Renewable Fuel Synthesis

Sustainable energy, environment, water (H₂O), and food, in a large extent, depends on acquiring/capturing/utilizing small molecules, such as H₂O, ammonia (NH₃), carbon dioxide (CO₂), methane (CH₄), ethanol, and liquid hydrocarbons, etc. Precisely designing stable, molecular-scale pores for sieving these molecules, either from the final product or during their production processes, could be an effective way of separating these molecules or promoting their production using compact and well-engineered systems. Considering the very small sizes (0.26-1.0 nm) of these molecules and tiny size difference from their contaminants/byproducts, it is a grand challenge to design these molecular-scale pores. My research interest is focused on rationally designing and preparing nanoporous structures for precisely distinguishing molecules by size/shape differences, characterizing and understanding the nanostructures, and applying them for separation and catalysis. In this talk, I will first give an overview of my research work and then present our recent research work on Na⁺-gated nanochannel membrane and its application for boosting methanol and dimethyl ether (DME) synthesis.

By-product H₂O strongly inhibits the kinetics and thermodynamics of many important reactions for renewable fuel production, for example, CO₂ hydrogenation to methanol. NaA zeolitic nanochannels were found to be water-conductive and gas impeding. As a result, H₂O showed two to three orders of magnitude higher permeation rate than gases (as small as H₂) at elevated temperatures (200-250 ^oC) and pressures (21-35 bar). This is surprising because the literature in the past 20 years reported comparable water and gas permeation rates for NaA zeolite membranes prepared from all over the world. Our extensive comparative experiments suggest this is because of the drastic improvement of our NaA membrane quality, and thus the intrinsic behavior of the NaA nanochannels can be revealed. The profound impact of these nanochannels on boosting reactions, which are thermodynamically and kinetically inhibited by by-product H₂O, was demonstrated for methanol synthesis from CO₂ hydrogenation, due to the emergency of developing sustainable and renewable fuels as well as mitigating CO₂ related environmental issues. By generating a “dry” reaction environment using Na⁺-gated nanochannel membrane, greatly boosted DME synthesis from CO₂ and H₂ was also demonstrated. This important discovery of Na⁺-gated, water-conduction nanochannels may greatly improve energy efficiency of many important industrial processes and may also lead to novel applications utilizing special property of these water-conduction nanochannels.