Alkyl Imidazole Templated Synthesis Of Extra-large-pore Zeolites With High Si/Ge Ratio And Their Catalytic Performance Of Methanol To Hydrocarbons

Extra-large-pore zeolites have large-sized pore structures,which are beneficial to the adsorption and diffusion of bulky molecular,exhibiting unique application potential and attracting extensive attention.Germanosilicate is an important branch of extra-large-pore zeolites,but the use of germanium leads to high production cost and poor water resistance stability of the framework.In view of the above problems,this thesis is devoted to the direct synthesis of extra-large-pore zeolites with high Si/Ge ratio,and the influence of structure micro-variation of organic template agents on the framework,composition and catalytic performance of these materials was studied.The following research results are obtained:STW（10-membered ring）,ITT（18-membered ring）and NUD-1（18-membered ring）germanosilicate zeolites were synthesized using six di-and tri-substituted imidazole templates with different alkyl chain lengths.The increase of the alkyl chain length was beneficial to the formation of the extra-large-pore structure,and the change of the alkyl substitution number can lead to the the change of the extra-large-pore topology.The ITT zeolite synthesized from 1-hexyl-3-methylimidazole had the highest Si/Ge ratio（8.5）and zeolite yield（3.8 g zeolite/g Ge O₂）.Fluorescence spectra showed thatπ-πinteraction existed between imidazolium with the formation of the templates dimers,and the interaction increased with the carbon chain length.The molecular simulation results showed that the imidazole templates resided in paris on the cross section of the 18-membered ring channel,and the binding energy between the 1-hexyl-3-methylimidazole template and the ITT zeolite framework was the lowest（-41.04 KJ/mol·N）,which was beneficial to the crystallization of high Si/Ge ratio zeolites.Two extra-large-pore zeolites,Al-ITT and Al-IRR,were synthesized by Al incorporation,which affected the topology and framework composition of extra-large-pore zeolites.The incorporation of Al in the zeolite framework increased its acidity significantly,and the acid content gradually increased with the growth of the Si/Ge ratio.Compared with the literature,both of these two structures can be synthesized under the condition of higher Si/Ge ratio,with significantly improved yield.Appropriate increase of the Al content was beneficial for the improvement of the zeolites acidity.The high Si/Ge Al-ITT zeolite showed good catalytic activity and stability in the methanol-to-hydrocarbon catalytic reaction,the methanol conversion rate is higher than 95%.Compared with the traditional hexamethonium template-synthesized ITT,the resistance to deactivation was enhanced,and the catalytic performance remained basically unchanged after multiple regenerations.