In depth thermokinetic investigation on Co-pyrolysis of low-rank coal and algae consortium blends over CeO₂loaded hydrotalcite (MgNiAl) catalyst

This study investigates the co-pyrolysis behavior of bituminous coal (100%BC), algae consortium (100%AC), and their blends at various blending ratios. The pure and coal-biomass blends were characterized using CHN-S, GCV, and FTIR analysis. Whereas, the co-pyrolysis of blends were performed in a TGA. The deviation between the experimental and calculated values of weight loss (WL%), the residue left (RL%), and the maximum rate of weight loss (wt%/min) was used to calculate the synergistic effects. Kinetic parameters were investigated using the Coats-Redfern integral method through eighteen (18) reaction mechanistic models. The activation energy (Ea) for 100%BC was 85.04 kJ/mol through the F3 model, whilst for 100%AC showed 78.22 kJ/mol using the D3 model. Thermodynamic parameters such as Enthalpy (ΔH) and Gibbs free energy (ΔG) showed positive values, while Entropy (ΔS) was negative for each coal-biomass blend. The catalytic co-pyrolysis of the optimum blend (20BCE-80AC) was studied using CeO2 loaded MgNiAl (CeO2 @MNA) as a multifunctional catalyst. The increased WL% displayed a positive effect toward a higher yield of volatile matter. Ea of the optimum blend in co-pyrolysis was further reduced through catalytic co-pyrolysis and Ea in the first and second stages was 72.48 kJ/mol and 13.76 kJ/mol, while 3 wt% catalyst loading further reduced its Ea in both stages to 67.82 kJ/mol and 41.21 kJ/mol. The use of CeO2 @MNA at 3 wt% loading showed a reduction in the peak devolatilization temperature (Tp) of the optimum blend substantially increasing the reaction rate, and reducing the Ea required for the decomposition process.