Conversion-Indexed Reactive Conditioning Tunes the Metal-Oxide Balance for Mixed Alcohol Synthesis from Syngas

Abstract

Lower-alcohol synthesis requires dissociative CO activation and oxygen-retaining CO insertion at neighboring sites, yet pretreatment shifts their balance without leaving a measurable state coordinate. Here, a Fe–Co–Ni/Ca12Al14O33 catalyst built from coarse commercial non-noble-metal powders reaches a selected working state under CH4/CO2 reactive conditioning indexed to CH4-conversion recovery rather than elapsed time. Methane-derived carbon removes lattice oxygen as CO rather than water, reducing accessible Ni/Co oxides to fcc Ni–Co without further H2 consumption, while framework-bound Fe remains oxidic. The accompanying contraction opens intergranular voids and exposes metal-oxide boundaries, while CO2 carbonates part of the basic surface. At the 20% endpoint, Ni–Co supplies surface carbon and CHx, adjacent Fe–O retains CO for insertion, and carbonate coverage restricts the water-gas shift. This state affords 64.12% CO conversion and 59.88% alcohol selectivity at 260 °C, 2.5 MPa, H2/CO = 1.5, and holds both over 50 h. Composition and conditioning set which function the converted carbon meets, whereas H2/CO governs chain termination, so the intermediate optimum reflects a matched interfacial state rather than the greatest extent of reduction. Reaction-derived carbon thus reconstructs the catalyst while reporting on that reconstruction, establishing catalyst state as a design variable selected after synthesis. The principle should extend to any catalyst whose activation is itself a measurable reaction, offering state-selective design for reconstruction-driven systems and, on renewable syngas, circular-carbon conversion.