Kenaf-derived activated carbons (AKC) were prepared by H₃PO₄ activation for automobile canisters. The microstructural properties of AKC were observed using Raman spectra and X-ray diffraction. The textural properties were studied using N₂/77 K adsorption isotherms. Butane working capacity was determined according to the ASTM D5228. From the results, the specific surface area and total pore volume of the AKC was determined to be 1260–1810 m²/g and 0.68–2.77 cm³/g, respectively. As the activation time increased, the butane activity and retentivity of the AKC increased, and were observed to be from 32.34 to 58.81% and from 3.55 to 10.12%, respectively. The mesopore ratio of activated carbon increased with increasing activation time and was observed up to 78% at 973 K. This indicates that butane activity and retentivity could be a function not only of the specific surface area or total pore volume, but also of the mesopore volume fraction in the range of 2.8–3.8 nm and 5.5-6.5 nm of adsorbents, respectively. The AKC exhibit enhanced butane working capacity compared to commercial activated carbon with the high performance of butane working capacity due to its pore structure having a high mesopore ratio.

The unburned hydrocarbon (HC) emissions of automobiles are subject to strong regulations because they are known to be converted into fine dust, ozone, and photochemical smog. Pitch-based activated carbon fibers (ACF) prepared by steam activation can be a good solution for HC removal. The structural characteristics of ACF were observed using X-ray diffraction. The pore characteristics were investigated using N₂/77K adsorption isotherms. The butane working capacity (BWC) was determined according to ASTM D5228. From the results, the specific surface area and total pore volume of the ACF were determined to be 840–2630 m²/g and 0.33–1.34 cm³/g, respectively. The butane activity and butane retentivity of the ACF increased with increasing activation time and were observed to range between 15.78–57.33% and 4.19–11.47%, respectively. This indicates that n-butane adsorption capacity could be a function not only of the specific surface area or total pore volume but also of the sub-mesopore volume fraction in the range of 2.0–2.5 nm of adsorbents. The ACF exhibit enhanced BWC, and especially adsorption velocity, compared to commercial products (granules and pellets), with lower concentrations of n-butane due to a uniformly well-developed pore structure open directly to the outer surface.