Catalytic calcium-looping gasification of biochar with in situ CO2 utilization with improved energy efficiency

Abstract

Capture and conversion of CO2 from optimal-scenarios into fuels or chemicals provide a viable solution to combat climate change in reducing greenhouse gas emissions. Here, we propose and experimentally demonstrate that synergistic integration (Catalytic calcium-looping (CaL) gasification of biochar) can realize the capture and in situ conversion of CO2. Thermodynamic and kinetic estimations, catalytic conversion and cyclic tests and microstructure characterizations showed that by using a mixture of limestone and K2CO3-impregnated biochar, calcination fully coupled with the reverse Boudouard reaction can shift thermodynamic equilibrium and simultaneously induce the synergetic catalysis between CaCO3 and K2CO3, allowing for accelerating decarbonation kinetics, enhancing CO yield and maintaining stable cyclic CO2 conversion at lower temperatures (850 °C), as compared to the individual CaL and gasification processes. Theoretical calculations further revealed that the activation energy barriers for the monatomic C-assisted CO2 dissociation were lower than its desorption energy for CO2 on the K-doped CaO surface, demonstrating superior conversion reactivity. Importantly, the process is demonstrated in terms of practical scalability using a renewable and cost-effective reductant (biochar), a cheap catalyst (K2CO3) and inexpensive natural CO2 sorbents (limestone and dolomite) in an energy-efficient manner, therefore opening a unique direction for net-negative emission for large CO2 stationary sources eliminating the need for sequestration.