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Synthesis of mesoporous [Al]-[B]-ZSM-5, -SSZ-13 AND -SSZ-39 for methanol to olefins process

Karakaya Yalçın, Büşra
Light olefins such as ethylene and propylene are important building blocks for modern chemistry. Traditionally they are produced from steam cracking and fluid catalytic cracking (FCC), which are energy intensive and give low olefin yields. Increasing demand of light olefins and decreasing petroleum resources give rise to development of new methods to produce light olefins. Methanol to olefins (MTO) reaction, known as a non-oil route, has attracted huge attention in the last decades as an alternative for converting methanol to light olefins using solid acid catalysts; i.e., zeolites. In this thesis, boron containing mesoporous ZSM-5, SSZ-13 and boron containing SSZ-39 were synthesized using bottom-up approaches to increase the lifetime and olefin selectivity observed on the conventional zeolite catalysts. For ZSM-5, methods such as hard-templating, soft-templating and nanosized crystals were used. For SSZ-13, soft-templating using cetyltrimethylammonium bromide was used. Amongst the synthesized ZSM-5 zeolites, highest mesopore volume was obtained from nanosized crystals; i.e., NS-[Al]-[B]-ZSM-5 which was 0.185 cm3/g; whereas, NS-[Al]-[B]- SSZ-13 (3) showed the highest mesopore volume which is 0.417 cm3/g among SSZ- 13 zeolites. The increased mesopore volume in the NS-[Al]-[B]-ZSM-5 resulted in one-and-a-half-time increase in the lifetime of conventional ZSM-5 in the methanol to olefins (MTO) reaction. On the other hand, the highest propylene selectivity (41%) is observed on mes-[Al]-[B]-ZSM-5 due to selective incorporation of Al atoms and low defect-concentration of the synthesized zeolite.