Akademik Veri Yönetim Sistemi
Tez Türü: Doktora
Tezin Yürütüldüğü Kurum: Gazi Üniversitesi, Mühendislik Fakültesi, Kimya Mühendisliği, Türkiye
Tez Danışmanı: Hüseyin Arbağ
Tezin Onay Tarihi: 2024
Tezin Dili: İngilizce
Özet:
Olefins are unsaturated hydrocarbons with at least one C=C bond. Ethylene and propylene are considered light olefins. As petroleum resources deplete, alternative methods independent of petroleum, such as converting bio-waste-derived methanol to olefins (MTO) have become important for producing these key chemical building blocks. The aim of this thesis is to develop innovative catalysts that are stable under reaction conditions and exhibit high total light olefin selectivity for use in the MTO reaction. Within the scope of this study, the activities of mordenite (MOR), HZSM-5, and silica-based microsphere encapsulated HZSM-5 catalysts were investigated in the MTO reaction. MOR zeolite did not show any olefin selectivity in the MTO reaction. However, H3PO4 treatment and Ce addition increased the stability of the MOR catalysts and raised the light olefin selectivity up to 35%. Commercial HZSM-5 showed the highest methanol conversion (97%) and total light olefin selectivity (51%) at 450°C in the fixed-bed continuous flow reaction system in between 300-550°C. SEM-EDX, ICP-MS, and DRIFTS analysis showed that HCl, H3PO4, and H2SO4 treatment affected the Si/Al ratio and acidity of the HZSM -5 catalyst. BET analysis showed the increase in the surface area of bare HZSM-5 (316 m2 /g) up to 447 m2 /g due to dealumination. The highest total light olefin selectivity was obtained as 53% from the H3PO4-HZSM-5 catalyst. During the long-term activity tests, phosphoric acid treatment enhanced the stability and increased the amount of the total olefin selectivity of bare HZSM-5 by 33%. Different amounts of HZSM-5 (0.2, 0.5, and 1 g) were encapsulated with silica microspheres. Among silica-encapsulated HZSM-5 catalysts, the optimum amount of HZSM-5 to achieve high total olefin selectivity (49%) and the lowest side products except dimethyl ether was found as 0.5 g. TGA result showed that the coke deposition of spent HZSM-5 decreased from 9.5% to 4.7% (by wt.) after silica encapsulation. The silica-encapsulated catalysts are regenerable. H2O dilution of methanol feed increased the total light olefin selectivity of Si-HZSM-5MS (0.5g) catalyst from 59.3% up to 63.9%.