Removal of sulfurous gases during microwave pyrolysis of biomass using Cu-Y adsorption

With the widespread utilization of biomass resources, the released sulfurous gases during its pyrolysis will cause environmental pollution. The Cu-Y adsorbent offers an effective solution to this issue due to its superior sulfur adsorption capacity. In this study, the effects on the performance of biochar and the sulfur adsorption capacity of the adsorbent were investigated by adjusting the Cu loading and the co-pyrolysis temperature. The results indicated that increasing both these parameters will facilitate the decomposition of organic sulfur in biochar, leading to the formation of sulfurous gases. The 15 wt% Cu-Y adsorbent exhibited the best synergistic catalytic-adsorption performance at 300 °C, achieving a maximum sulfur adsorption capacity of 9.88 mg S/g. And the biochar desulfurization efficiency reached 83.7 %. Characterization analysis revealed that excessive Cu loading (>15 wt%) reduced the specific surface area and mesopore volume of the Cu-Y adsorbent. Furthermore, Cu species tend to aggregate into metal clusters ranging from 130 to 300 nm, which can mask active sites and consequently reduce the adsorption capacity. Additionally, high temperature (350 °C) caused the structural collapse of the Cu-Y adsorbent, leading to a significant decline in sulfur adsorption capacity. This study further clarified the adsorption mechanism of various sulfurous gases, including dimethyl disulfide (C 2 H 6 S 2 ), dimethyl sulfide (C 2 H 6 S), carbonyl sulfide (COS), carbon disulfide (CS 2 ), thiophene (C 4 H 4 S), methanethiol (CH 3 SH), and hydrogen sulfide (H 2 S). These results confirmed the dual functionality of Cu-Y adsorbent in enhancing biochar quality and adsorbing sulfur emissions, providing a sustainable strategy for cleaner biomass conversion.