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" Transient airflow in building drainage systems / "
John Swaffield.
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Latin Dissertation
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| Language of Document
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English
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| Record Number
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1112529
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| Doc. No
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TLpq303925344
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| Main Entry
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U. A. El-Nafaty
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| Title & Author
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Methanol conversion to light olefins over commercial zeolites\ U. A. El-Nafaty
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| College
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King Fahd University of Petroleum and Minerals (Saudi Arabia)
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| Date
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1990
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| student score
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1990
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| Degree
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M.Sc.
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| Page No
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183
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| Abstract
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The conversion of methanol to light olefins (MTO) over commercial narrow pore Silicoaluminophophate SAPO-34, and pentasil type ZSM-5 and Silicalite S-115, was studied in a fixed bed tubular reation system. Nitrogen was used as carrier gas. Experiments were caried 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 400C and 4 hr 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 formtion leading to poisoning of active sites an blockade of pore channel entrances. The optimum operting conditions for S-115 and ZSM-5 were found to be 375C and 450C respectively at 4hr 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 strucutres, 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 usd\rm Ba>La>Ag>Cu>Ca>Sr>Ga>Cd>In,usd while for ZSM-5, the selectivity decreased in the order usd\rm In>Ag>Cu>Cd.usd Optimum Ba-loading on S-115 for high olefin yield was found to be 5.2% by impregnation and 0.03% by ion-exchange.
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| Subject
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Applied sciences
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Chemical engineering
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