H2 and CO are the most critical components within the product gas obtained from the gasification of biomass. The composition of H2 and CO is of significant importance as their ratio defines the utilization of the syngas. Application of syngas can include power generation, chemical products such as methanol, NH3, and FT diesel. The objective of this study to optimize the parametric conditions for H2/CO ratio in the gasification of PKS in TGA-MS set up using coal bottom ash as a catalyst and CaO as adsorbent. The experiments were designed using RSM and the effect of parameters such as temperature from (650-750 °C), particle size (0.5-1.0 mm), CaO/biomass ratio (0.5-2.0), and CBA wt (0.02-0.10). The study demonstrates that the H2/CO ratio is mostly influenced factor followed by the temperature and particle size, whereas the CaO/biomass ratio and CBA wt are third and fourth influencing factors on H2/CO ratio. The maximum H2/CO ratio of 1.47 at optimum temperature of 715 °C, Particle size of 0.65 mm, CaO/biomass ratio of 1.45, and CBA wt of 0.09. H2/CO ratio is important for its conversion into many products, such as methane, methanol, and FT diesel. © 2020 Elsevier B.V.