It was proposed that incorporation of nitrogen groups on mesoporous silica pores would enhance its surface polarity and improve adsorption of gaseous BTX (benzene, toluene, and m-xylene). Among the popular list of mesoporous silica adsorbents, KIT-6 and SBA-15 were selected as a result of their superior textural properties, as well as because they are being widely reported in literature. After preliminary screening using toluene test, KIT-6 was chosen to have better affinity and therefore selected for Aptes (3-aminopropyl triethoxysilane) surface modification. Aptes modification was performed through the grafting method utilizing factorial design of experimental techniques to identify the effective process variable covering the parameters: Aptes concentration, reaction temperature, and reaction duration. The results of a statistical design of experiments using Minitab-15 showed that Aptes concentration was the only significant factor which affects the silica adsorbent BET surface area. Benzene adsorption was found to be highest on KIT-6 adsorbent, while m-xylene and toluene had their highest values on 0.006% Aptes adsorbent (KIT-6 modified with 0.006% v/v Aptes) relative to other adsorbents. m-Xylene had the highest adsorption relative to toluene and benzene on all modified silica adsorbents (0.006% Aptes, 0.33% Aptes, and 0.66% Aptes) except for 8% Aptes adsorbent. 0.006% Aptes adsorbent was selected as the best adsorbent for BTX adsorption.