Fig. 4

Comparisons of xylene isomers adsorptions over different zeolite catalysts. Pulse chromatography of xylene isomers (OX: o-xylene; MX: m-xylene; PX: p-xylene) passing through columns packed with coffin-shape HZSM-5_C1 (a) and b twinned HZSM-5_T, at 220 °C. Peak tailing and residence time difference between m-xylene and o-xylene was observed due to the existence of more straight channels openings and easier entry of m-xylene and o-xylene into the straight channels of coffin-shape HZSM-5 when compared to twinned HZSM-5. c Room temperature m-xylene adsorption rate over coffin-shape HZSM-5_C1 and twinned HZSM-5_T showing a lower m-xylene adsorption rate when less straight channels were involved in the adsorption process. Data were taken with m-xylene equilibrium pressure 1.3 mbar and fitted with a Lagergren adsorption equation⁵², where m_e and m were the quantity of m-xylene absorbed at equilibrium and at time t, respectively, and the slope of the fitted line was the adsorption rate