Space-Confined Self-Regulation Mechanism from a Capsule Catalyst to Realize an Ethanol Direct Synthesis Strategy

A capsule catalyst, being composed of a catalytic zeolite membrane and a catalyst core, can accomplish multiple catalysis reactions or several organic synthesis reactions in a single step, enhancing energy efficiency, erasing unnecessary separation engineering, and creating many unexpected synergistic effects via tandem catalysis. This report discloses an ethanol synthesis strategy from syngas (CO + H-2) and syngas-derived dimethyl ether (DME) by a tailor-made catalyst with a macroscopic capsule structure. The macroscopically designed capsule catalyst consisted of a millimeter-sized Cu/ZnO core and a micrometer-sized H-Mordenite zeolite shell. The catalyst preparation process further successfully fabricated a zeolite shell, migrated a few Cu from the core, as the promoter of the shell, to significantly improve the catalyst performance. As the methanol byproduct can be easily recycled to DME as a reactant via a simple dehydration reaction, ethanol selectivity can reach 100% theoretically. It is demonstrated that a space-confined-self-regulation mechanism derived from a macroscopic capsule structure serves as a multifunctional switch to manipulate tandem reactions: arranging reaction steps in a favorable order and depressing side reactions simultaneously. These findings will inspire designing a heterogeneous catalyst with multiple functions, shortening the organic or catalytic synthesis route, and also open an avenue to ethanol synthesis from syngas, as DME is also simply produced from syngas.