Green C2-C4 hydrocarbon production through direct CO2 hydrogenation with renewable hydrogen: Process development and techno-economic analysis

Abstract

This study proposes a novel process for the light hydrocarbons production from captured CO2 and renewable hydrogen (H2). The process consists of two main stages: i) A reaction stage in which CO2 is converted into alkene-range hydrocarbons over a K-promoted Fe catalyst, and ii) a separation stage in which multiple technologies are integrated for the recycling of CO2, carbon monoxide (CO), and H2 and the purification of the main C2-C4 hydrocarbon products (e.g., light olefins) and byproduct (C5+). The methane (CH4) and CO rejected in the separation stage are fed into a combined heat and power (CHP) process to generate utilities on-site while C5+ considered as by-product. In the rigorous process models developed in this work, the required sub-processes are integrated at a plant-wide level and the optimal operation conditions are determined to ensure high energy efficiency and low environmental impact, as well as compliance with the product specifications. As a result, the proposed process could achieve 99.2% and 42.0% carbon and energy efficiencies, respectively. The unit production cost for the C2-C4 hydrocarbons was estimated to be 3.58 USD/kg, and the CO2 emission was estimated to be negative (−1.85 kg CO2 per kg C2-C4 hydrocarbon). In addition, an economic sensitivity analysis was performed to identify the major cost-drivers, such as low CO2 conversion or high prices for renewable H2, and to propose solutions to these bottlenecks to allow the development of economically viable applications.