Research progress in n(H₂)/n(CO) regulation technology of syngas for low-carbon chemical industry

Precise regulation of the hydrogen-to-carbon ratio （n（H₂）/n（CO）） in syngas is a key factor for the efficient preparation of high-value-added chemicals and represents one of the core technologies for the low-carbon transition of the coal chemical industry and related processes. It directly determines the production efficiency, energy consumption, and carbon emissions of downstream synthesis processes. Although the conventional Water–Gas Shift （WGS） reaction is the most commonly used method for n（H₂）/n（CO） adjustment, it is constrained by thermodynamic equilibrium and catalyst stability, and inevitably generates additional CO₂ during the reaction process. To break through the limitations of traditional n（H₂）/n（CO） regulation processes, this review elaborates on regulation strategies from a diversified perspective: the introduction of exogenous hydrogen enables rapid and precise n（H₂）/n（CO） adjustment, but its large-scale application is still limited by hydrogen production costs and infrastructure construction; emerging short-process catalytic technologies （such as CO₂ electrocatalysis and photocatalysis） can directly generate syngas with customized n（H₂）/n（CO） during the reaction, yet their current production yields do not match industrial-scale demand; process intensification and system coupling （including multi-reforming coupling, Sorption-Enhanced Water–Gas Shift, membrane reactor coupling, biomass gasification integrated with SEWGS and the reverse Boudouard reaction, and co-gasification） achieve synergy between syngas production, n（H₂）/n（CO） regulation, energy efficiency enhancement, and carbon emission reduction through multi-reaction synergy, in-situ product removal, reaction path integration, and feedstock complementarity. Overall analysis reveals that syngas n（H₂）/n（CO） regulation technology is shifting from “unit optimization” toward “systematic integrated coordination and optimization,” providing support for building a low-carbon, short-process, and highly flexible green syngas production and utilization platform, which is of great significance for achieving China’s carbon peaking and carbon neutrality goals.