System-level analysis for continuous BTX production from shale gas over Mo/HZSM-5 catalyst: Promotion effects of CO₂ co-feeding on process economics and environment

Benzene, toluene, and xylene (BTX) production from shale-derived CH₄, C₂H₆, and C₃H₈ is considered an energy-efficient technology substituting their naphtha-cracking counterparts. However, the economics of BTX production from shale gas remains questionable because of the rapid deactivation of the catalyst, originating from the coke generation. Herein, we present a BTX production strategy with CO₂ co-feeding for catalyst stability enhancement and additional H₂ production. Our process prevents coke deposition on the active sites of Mo and zeolite, and improves the operation time of reactors compared to that of shale gas without CO₂ co-feeding. Concurrently, H₂ and CO are produced with BTX owing to the dry reforming reaction of hydrocarbons over the Mo/HZSM-5 catalyst. Most importantly, the economics of BTX production with CO₂ co-feeding is evaluated using individual system components integrated with two different CH₄ conversion processes (steam-reforming-based H₂ and methanol production). The BTX production with CO₂ co-feeding lowers the methanol production cost by additionally producing methanol generated by CO from the BTX reactor, while the H₂ production cost increases. Moreover, the life cycle assessment proves that the CO₂ emission during the methanol production process is significantly reduced by recycling the CO₂ produced in the subsequent process.