Study of the Rod-Like and spherical nano-ZnO morphology on H2S removal from natural gas

The purpose of this work is to study the adsorption of H₂S from gas streams containing He and CH₄ with an emphasis on the influence of the sorbent morphology on the process of adsorption. As an example of the approach, a unique modified nano-ZnO sample with a Rod-like morphology was fabricated and comparatively studied together with a nano-spherical ZnO sample under various conditions. The objective was accomplished applying central composite design (CCD) in order to screen the effects of significant adsorption parameters obtained by Placket-Burman design. Morphology of the sorbent, temperature, space velocity and H₂S feed concentration were initially evaluated. Placket-Burman design experiments showed a wide deviation of adsorption capacity of 0.03-0.24 g H₂S/g ZnO. Results indicated that comparing other parameters Rod like morphology comparing spherical, had significant effect on all four independent H₂S adsorption parameters. Besides that, space velocity and H₂S feed concentration were found to be effective parameters on adsorption of hydrogen sulfide in the range of 4000-8000 h⁻¹ and 0.5-1 mol% respectively. Moreover, experiments revealed a negligible effect of adsorption temperature in range of 150-250 °C. The optimized condition obtained a dynamic capacity of 0.2401 g H₂S/g ZnO at space velocity 4000 h⁻¹ and H₂S feed concentration of 1 mol%. Proceeding our study by significant parameters, analysis of variance (ANOVA) displayed a high coefficient of determination (R²) value of 0.931-0.959, indicating the satisfactory adjustment of the quadratic model.