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 H-2; however, the syngas produced must be upgraded to make H-2-containing streams suitable for other applications, such as renewable methanol production, by adjusting the H-2/CO ratio. In this study, for the first time in the literature, the separation properties of carbon hollow fiber membranes in binary and quaternary H-2-containing mixtures with varying compositions were systematically explored. It was found that the developed carbon membranes exhibit relatively good selectivity for (H-2+CO2) in mixtures with other gases such as N-2 and CO, which are commonly present in syngas. A CO permeance of 0.8-1 GPU and a H-2/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 N-2 removal was carried out. The results indicate that the prepared carbon membranes have the potential to adjust the H-2/CO ratio to 1-3 if a N-2 removal ranging from 80 to 90% is acceptable.