El-Nafaty, Usman Aliyu (1990) Methanol conversion to light olefins over commercial zeolites. Masters thesis, King Fahd University of Petroleum and Minerals.
The conversion of methanol to light olefins (MTO) over commercial narrow pore Silicoaluminophosphate SAPO-34, and petensil type ZSM-5 and Silicalite S-115, was studied in a fixed bed tubular reaction system. Nitrogen was used as carrier gas. Experiments were careied out at various temperatures, space velocities (WHSV) and methanol-to-nitrogen (wt) ratio to study their effects on catalyst activity, selectivity, product distribution and coke deposition. ZSM-5 and S-115 were modified by impregnation with various metal elements to investigate their effects on catalyst active life time and selectivity to lower olefins. At 400 C and 4 hr-1 WHSV SAPO-34 exhibited higher initial selectivity to lower olefins than both ZSM-5 and S-115 but also deactivated more rapidly ( 2hrs). This was attributed to the catalyst's narrow pore size which enhanced coke formation leading to poisoning of active sites and blockade of pore channel entrances. The optimum operating conditions for S-115 and ZSM-5 were found to be 375?C and 450?C respectively at 4 hr?¹ WHSV and 2.67 methanol-to-nitrogen (wt) ratio. S-115 showed higher overall selectivity to olefins than ZSM-5 at optimum conditions. Active life-on-stream was also longer for S-115 than ZSM-5 with 58.1 and 25.5 hr respectively. Since both zeolites have identical pore-sizes and structures, the better performance of S-115 was attributed to its higher silica/alumina ratio of 300 as compared to ZSM-5 which had a silica/alumina ratio of 40. Modification of the two zeolites with various elements showed the degree of selectivity to light olefins to vary according to the modifying element. With S-115, the selectivity was found to vary according to the order Ba > La > Ag > Cu > Ca > Sr > Ga > Cd. In, while for ZSN-5, the selectivity decreased in the order in Ag > Cu > Cd. Optimum Baloading on S-115 for high olefin yield was found to be 5.2% by impregnation and 0.03% by ion-exchange.
|Item Type:||Thesis (Masters)|
|Divisions:||College Of Engineering Sciences > Chemical Engineering Dept|
|Creators:||El-Nafaty, Usman Aliyu|
|Committee Advisor:||Al-Jarallah, Adnan M.|
|Committee Members:||Shalabi, Mazen A. and Sait, Mohammad Sadiq and Redwan, D. S.|
|Deposited By:||KFUPM ePrints Admin|
|Deposited On:||22 Jun 2008 16:59|
|Last Modified:||26 Apr 2011 08:00|
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