Effect of Zeolite Crystallite Size on Pt/KL Catalysts Used for the Aromatization of n-Octane SUPAK TRAKARNROEK, 1 SOMLAK ITTISANRONNACHAI, 1 SIRIPORN JONGPATIWUT, 1 THIRASAK RIRKSOMBOON, 1 SOMCHAI OSUWAN, 1 AND DANIEL E. RESASCO 2 1 The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok, Thailand 2 School of Chemical, Biological, and Materials Engineering, The University of Oklahoma, Norman, Oklahoma, USA The effects of varying zeolite crystallite size in n-octane aromatization over Pt=KL have been studied on a series of catalysts. Various KL zeolites were synthesized via microwave-hydrothermal treatment, which allows for good control of crystallite morphology. Zeolites with different crystallite sizes were prepared by varying aging time (17–24 h), amount of barium (0–445 ppm), and seeding (0–8 wt%). The results showed that higher aging time resulted in smaller zeolite crystallite size, whereas the addition of barium resulted in larger crystallite size. Moreover, the addition of seeding reduced the crystallite size from 1.47 to 0.94 lm. Pt supported on different zeolite catalysts (Pt=KL) was prepared by vapor phase impregnation (VPI). The fresh catalysts were characterized by DRIFTS of adsorbed CO and volumetric hydrogen chemisorption. The results indicated that Pt clusters are well dispersed inside the zeolite channel in all the catalysts prepared. The aromatization of n-octane was tested on the different catalysts at 500  C and atmospheric pressure. It was found that the catalytic activity of all catalysts dropped rapidly after about 200 min on stream due to coke plugging inside the pore of the KL zeolite. It was also observed that less ethylbenzene (EB) and o-xylene (OX) were obtained as the con- version increased because both EB and OX are converted to smaller molecules such as benzene, toluene, etc., by secondary hydrogenolysis. Furthermore, the EB=OX ratio increases with zeolite crystallite size due to an enhanced preferential conversion of the larger OX molecules compared to the narrower EB as their path through the pores is restricted. Keywords Microwave-hydrothermal treatment technique; n-Octane aromatiza- tion; Zeolite Introduction The aromatization of n-alkane is an important reaction used to obtain high–value- added products from a naphtha feedstock that is abundant in refinery operations. This reaction can be used in many industrial applications and can be carried out with Address correspondence to Siriporn Jongpatiwut, The Petroleum and Petrochemical College, Chulalongkorn University, Soi Chula12, Phyathai Rd., Pathumwan, Bangkok 10330, Thailand. E-mail: siriporn.j@chula.ac.th Chem. Eng. Comm., 194:946–961, 2007 Copyright # Taylor & Francis Group, LLC ISSN: 0098-6445 print/1563-5201 online DOI: 10.1080/00986440701232403 946