Preparation And Catalytic Performances Of Nitridated Zeolite For Prins Condensation Reaction

3-Methyl-3-butene-1-ol?MBO?is an important intermediate for fine chemicals,which has great potential applications in many fields such as architecture,medicine,perfume and material.In this thesis,MBO was synthesized via Prins condensation of isobutylene and paraformaldehyde using Y and Beta zeolites nitridated by NH₃.The preparation conditions of nitridated Y and Beta zeolites,the relationship between acidity,basicity and catalytic performances were systematically investigated.The main findings are summarized as follows:?1?A series of NY zeolites were prepared by high temperature nitridation.The results from XRD,²⁹Si MAS NMR and elemental analysis showed that nitridated zeolite had more Si-N species and nitrogen content under temperature of 850?,time of 12 h and NH₃ flow rate of 65ml/min.?2?The effects on structure,acid-base properties of Y zeolite nitridated under different atmosphere were studied.Their catalytic performances of Prins condensation and the coke content after the reaction were investigated in detail.Among them,Y zeolite nitridated with NH₃ containing 5%water shows high MBO selectivity and activity due to the decrease of the total acid quantity and increase of medium-strong basic sites with appropriate amount.The HCHO conversion is 92%,selectivity of MBO increases to 89%and its yield is up to 82%under the optimized reaction conditions.Most importantly,the coke content decreases from 27wt%to 4.3 wt%.?3?The catalytic performances of NBeta zeolite prepared under different nitridation conditions were investigated.It is found that NBeta zeolite prepared under the optimized conditions shows 83%selectivity and 80%yield of MBO with less than 10%selectivity of high carbon products.The acidity characterization of the fresh catalysts and TG analysis of the samples after the reaction indicate that the nitridation of Beta zeolites leads to a decrease of the total acid quantity,which inhibits the side reactions,enhances MBO selectivity and reduces the coke content to below 11 wt%.The regeneration capability of NBeta zeolite was also studied.It is found that NBeta zeolite has high stability and MBO yield decreases to 65%after 5 times of continuous regeneration.The reason may be that decomposition of Si-N in the regeneration process leads to the decrease of the base strength and amount.Meanwhile the disappearance of Si-N makes the covered acid site reappear or O replaces the N,which increases the acid amount.All lead to obvious decrease of MBO selectivity and yield.