(173j) Application of Fluidized Bed Reactors for CO2 Hydrogenation for the Production of Hydrocarbons

The major sources of CO2 emissions in the oil refining process include atmospheric and vacuum distillation processes, reforming processes, fluid catalytic cracking (FCC) processes, and hydrogen production processes. Particularly, the off-gas generated after the hydrogen production process contains about 24 vol% of low-purity CO2 along with H2 and CO, and it is the largest source of CO2 emissions in the refining process. Technologies for directly converting low-purity CO2 into hydrocarbons are being researched and developed. The reaction mechanism involves converting CO2 to CO via the reverse water-gas shift (rWGS) reaction, and then converting CO and H2 into hydrocarbons via the Fischer-Tropsch (FT) synthesis. Iron-based catalysts are most reported for satisfying both reactions simultaneously, and there are ongoing studies on improving conversion rates by adding alkali metal-based co-catalysts. However, most studies have been conducted in fixed-bed reactors, and there are problems such as catalyst degradation due to the exothermic nature of the FT reaction, which leads to a decrease in catalyst activity. Thus, research is needed to control the heat and solve the problem of local thermal runaway. In this study, a lab-scale bubbling fluidized bed reactor (BFB) was utilized for its good response to exothermic reactions and ability to maintain a constant operating temperature. Basic experiments were conducted to understand the heat transfer and CO2 conversion reaction characteristics. Heat transfer coefficients were derived through the cooling tubes installed in the reactor, and the optimal heat transfer coefficients were determined based on various fluidization velocities (0.725bar), and temperatures (200~400℃). Based on this, foundational research on CO2 conversion was conducted.