INCREASING ADSORPTION OF ACTIVATED CARBON FROM PALM OIL SHELL FOR ADSORB H₂S FROM BIOGAS PRODUCTION BY IMPREGNATION

Abstract

Biogas is the combustible gas produced through a biological process, known as anaerobic digestion which is the process operated at low-temperature and without air. Biogas consists of 55-80% CH₄, 20-45% CO₂ with trace amount of H₂S and other impurities. Common H₂S removal technologies from biogas fall into one of adsorption on a solid such as iron oxide based materials, activated carbon or impregnated activated carbon. Conventionally, activated carbon is produced from biomass residues and agricultural residues such as palm oil shell which promising approach for the production of cheap. It is so due to the palm oil shell carries a large amount of carbon content which it is the main composition of activated carbon. Therefore, it is usable as raw material for producing impregnated activated carbon and used as adsorbents. The aim of this study is a produce the activated carbon from palm oil shells by chemical activation using ZnCl₂ and optimal conditions after impregnated them with NaOH, KI and K₂CO₃ for H₂S absorption from biogas product. In this research, production of activated carbon involved three stages; (i) carbonization of raw material in an inert atmosphere which was carbonized in a muffle furnace at 600°C for 1 h; (ii) secondly activation of char product from the first stages at fixed bed reactor (stainless steel with 54.1 mm internal diameter and 320 mm length) which was studied to observe the effect of char product: Chemical agent ratio (ZnCl₂, 1:1 to 1:3), which there are activated at 700°C activation temperature for 2 h; and (iii) finally alkali impregnated activated carbon which were immersed 1:3 ratio in 500 mL of 1 N NaOH, KI and K₂CO₃ solutions and stirred for 30 min. The result showed that the surface area and the pore volume increased progressively with increasing the char product: Chemical agent ratio. The maximum surface area total pore volume of activated carbon product was 532.31 m²/g and 0.2973 cc g^-1 was obtained on ACZn13. While, the maximum surface area and the pore volume of modified impregnated activated carbon was 741.71 m²/g and 0.4210 cc g^-1 was obtained on K₂CO₃-AC. The results of the experiment demonstrated that with regard to adsorption of H₂S on K₂CO₃-AC which it had more than on KI-AC and NaOH was 3.26 and 8.8%, respectively. The conclusion showed that surface area, total pore volume and micropore volume were increasing with increased the char product: Chemical agent ratio (1:1 to 1:3). ACZn13 has good chemical and physical properties such as chemical content and surface area, which showed that the highest surface area (532.21 m²/g) and total pore volume (0.2973 cc g^-1). Therefore, K₂CO₃-AC impregnated activated carbon has a high surface area and showed be an efficient adsorbent for removal of H₂S from biogas product. Moreover, evaluating the content of H₂S adsorption was suggested.