Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
Browse
2 results
Search Results
Article Citation - WoS: 11Citation - Scopus: 11Effect of Different Acidity Modifications on the Activity and Selectivity on H-Zsm5 Zeolites in N-Butene Isomerization(Springer Verlag, 2014) Kılıç, Emre; Yılmaz, SelahattinH-ZSM-5 was modified by silylation [tetraethylorthosilicate (TEOS) and triaminopropyltriethoxysilane], alkali (NaOH), acid (HCl) and ammoniumhexafluorosilicate (AHFS) treatments. The parent and modified zeolite forms were tested in n-butene isomerization. Modifications affected total acidities, the strength of the acid sites, pore sizes and surface areas of the H-ZSM-5 differently. The modifications decreased the conversion obtained by the parent catalyst. TEOS and alkali modifications did not promote formation of isobutene. Pre-alkali treatment before acid treatment increased selectivity to isobutene from 56.0 to 66.7 %, while conversion changed a little, it dropped from 52 to 50 %. AHFS modification provided the highest enhancement in selectivity to isobutene (87.5 %) for which n-butene conversion was dropped by about 10 % compared to H-ZSM-5. This was attributed to a slight modification of the pore size and to the reduction in strong and weak acid sites and generation of new Lewis acid sites.Article Citation - WoS: 41Citation - Scopus: 43Isomerisation of ?-Pinene Over Beta Zeolites Synthesised by Different Methods(Elsevier Ltd., 2005) Gündüz, Gönül; Dimitrova, Raina D.; Yılmaz, Selahattin; Dimitrov, Ljubomir; Spassova, MayaLiquid-phase α-pinene isomerisation at l00°C in a batch reactor is studied over Beta zeolites synthesised by different methods. It is confirmed that α-pinene forms a carbenium ion in an acidic environment, which rearranges without capture by nucleophiles, to form mainly hydrocarbons as camphene, terpinenes, terpinolenes and heavy products. The microporous Beta samples show low activity despite the high acidity most probably because of the hindered intermediate formation. The nature of the enhanced activity of Beta mesopores samples is suggested to be a result from the high accessibility of the acidic sites. The isomerisation of α-pinene was studied over Beta zeolites synthesised by different methods. The main products are camphene, terpinenes, terpinolenes and heavy products. Beta zeolites with micro-/mesopores reveal excellent activity because of the appropriate balance between acidity and bimodal pore system. The microporous Beta samples show low activity despite the good total acidity most probably because of the steric effect for the formation of the intermediate cations.