OPTIMIZATION OF n-HEXANE REFORMING AND KINETICS OF CATALYST REGENERATION

• Main Author: MOHAMMED ISMAIL, REEM AHMED
• Format: Thesis
• Language: English
• Published: 2011
• Online Access: http://utpedia.utp.edu.my/2855/1/28-3-11.pdf; http://utpedia.utp.edu.my/2855/

Catalytic naphtha reforming is practiced extensively in the petroleum-refining industry to convert low research octane number (straight chain paraffin) naphtha feed into high RON component (aromatics and branch isomers) with minimum average molecular weight changes needed for the modern auto-industry. A valuable byproduct, hydrogen, from the process is added bonus needed for hydro processing operations in the refinery. Depending on the operating conditions, hydrogen may be consumed in unwanted hydrocracking reactions which directly contribute to deactivate the catalyst. The present study looks into the optimization of process variable (pressure, temperature and contact time) to maximize isomerization and aromatization (increasing RON value) reaction while minimizing the hydrocracking (catalyst deactivation and reducing RON) reactions in n-hexane reforming using commercially available Pt/Al2O3 catalyst. From the results it is found that high temperature (723 K) with low hydrogen partial pressure (300 KPa) and low contact time (1.78 to 2.4 minutes) favor the production of isomers and aromatics over coke precursors and cracked product species. Addition of CCl4 to the n-hexane reforming process which increases the catalyst acidity, promotes the formation of cracked products. Selective poisoning using dimethyl-disulfide on the other hand is found to decrease monofunctional metal-catalyzed reactions and increased the activity for the isomerization reactions.. To understand and enhance n-hexane reforming the kinetics and catalyst regeneration are also investigated using TGA and TPO analysis. From TPO analysis it was found that applying slow heating rate was the most efficient and convenient way to control the regeneration process. The TGA results indicate that there exist three types of coke categorize as soft, hard and laid coke which can be distinguished by a temperature profile. It was found that the hard coke followed by soft coke makes up the major constituent of the coked catalyst which can be removed successfully by proper regeneration process.