In-depth Thermokinetic Investigation on Co-pyrolysis of Low-rank Coal and Algae Consortium Blends over CeO2 loaded Hydrotalcite (MgNiAl) Catalyst /

Abstract

This study investigates the co-pyrolysis behaviors 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. Whereas, copyrolysis of blends were performed in thermogravimetric analysis (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 TGA by employing the Coats-Redfern integral method through eighteen reaction mechanisms. The activation energy (Ea) for 100%BC was 85.04 kJ/mol through the F3 model, while for 100%AC showed 78.22 kJ/mol using the D3 model. Thermodynamic parameters such as Enthalpy (∆𝐻), and Gibbs free energy (∆𝐺) showed positive values, while Entropy (∆𝑆) was negative for each coal-biomass blend. The catalytic co-pyrolysis of the optimum blend (20BC-80AC) were studied using CeO2@MNA as a multifunctional catalyst. Catalytic co-pyrolysis of the optimum blend in an in-situ mixing with the catalyst CeO2@MNA was performed using TGA. The TG-DTG curve shows the decomposition rate of the optimum blend (20BC-80AC) being affected by the catalyst. The increased WL% shows a positive effect toward a higher yield of volatile matter. The kinetic triplets and thermodynamic parameters were calculated. The Ea of the optimum blend (20BC-80AC) in co-pyrolysis was further lowered through catalytic co-pyrolysis. The Ea of the optimum blend (20BC-80AC) in the first and second stages are (72.48 kJ/mol) and (13.76 kJ/mol), while 3wt.% further reduced its Ea in both stages as (67.82 kJ/mol) and (41.21 kJ/mol). The use of CeO2@MNA at 3wt.% 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.