无缓冲溶液条件下氟化铵对高温水热超稳Y型分子筛的改性研究

MODIFICATION OF ULTRASTABLE Y TYPE ZEOLITES BY NH_4F WITHOUT BUFFER SOLUTION

探索了用无缓冲溶液氯化铵处理超稳Y制备高硅铝比分子筛的可能性,系统地考察了反应时间、反应温度、氟化铵溶液加入量及溶液pH值对处理过程的影响。结果表明,在适宜的处理条件下能制备出硅铝比达20左右的超稳Y型分子筛;改性后超稳Y型分子筛的晶体结构热稳定性得到提高;脉冲微反的正己烷裂解活性下降而提高了烯烃的选择性。

The possibility of preparing high SiO_2/Al_2O_3 ratio USY zeolite by treating the USY prepared by high temperature steam treatment method with NH_4F without buffer solution was explored. The effect of treating conditions, such as reaction time, reaction temperature, amount of NH_4F solution and pH of the solution, on treatment process were investigated. The results showed that USY zeolites of SiO_2/Al_2O_3 ratio up to 20 can be prepared under proper treating conditions. The thermal stability of the crystal structure of modified USY zeolite is enhanced. Its n-hexane cracking activity after modification as determined by a pulse microreactor is reduced, while the olefin selectivity is increased.