Boosting Renewable Methanol Production: A Study on Enriched Hydrogen Recovery Using Hollow Fiber Carbon Membranes in Syngas Stream Upgrades

Biomass gasification is a viable solution for generating H2; however, the syngas produced must be upgraded to make H2-containing streams suitable for other applications, such as renewable methanol production, by adjusting the H2/CO ratio. In this study, for the first time in literature, the separation properties of carbon hollow fiber membranes in binary and quaternary H2-containing mixtures with varying compositions were systematically explored. It was found that the developed carbon membranes exhibit relatively good selectivity for (H2+CO2) in mixtures with other gases such as N2 and CO, which are commonly present in syngas. A CO permeance of 0.8-1 GPU and an H2/CO selectivity of 30 were achieved for the first time through both single gas and mixed gas permeation testing. Furthermore, in the context of using these membranes for syngas upgrading, such as in an integrated biomass-to-biofuel (methanol) process for hydrogen enrichment or carbon capture and conversion, a technical feasibility analysis based on the separation performance of the carbon membrane system for syngas ratio adjustment and N2 removal was carried out. The results indicate that the prepared carbon membranes have the potential to adjust H2/CO ratio to 1-3 if a N2 removal ranging from 80 to 90 % is acceptable.