不同分子筛对n-C_(12)催化裂化转化规律的影响

以正十二烷(n-C12)为模型化合物,在固定床微反装置上考察了USY,β,ZSM-5分子筛单独使用及其相互配合使用对链烷烃裂化产物的碳数分布和烃类组成的影响,尤其是对低碳烯烃(丙烯和丁烯)选择性及其收率的影响,并通过XRD,BET,XRF,NH3-TPD,Py-FTIR等分析手段对所采用的3种分子筛的基本性质进行了表征。实验结果表明,强酸比例较高的β分子筛对n-C12的裂化活性明显高于USY分子筛,且对丁烯尤其是异丁烯的选择性较高;当β分子筛与ZSM-5分子筛混合作为n-C12裂化的催化剂时,低碳烯烃的选择性却低于USY分子筛与ZSM-5分子筛混合的催化剂;但β分子筛较强的裂化性能使其与USY和ZSM-5分子筛中的一种或两种混合时,具有较高的n-C12转化率,所以在一定程度上也可以增产低碳烯烃。

Catalytic Cracking of n-Dodecane on Different Zeolites

Catalytic cracking of n-dodecane over USY,β,ZSM-5 zeolites and their composites with different formulae was investigated in a fixed-bed micro-reactor at 500 ℃.The effects of these catalysts on carbon number distribution,hydrocarbon composition,and low-carbon olefin selectivity and yield of the cracking products were discussed.The zeolite catalysts were characterized by means of XRD,BET,XRF,NH3-TPD and Py-FTIR.The results showed that the selectivity to low-carbon olefins on ZSM-5 and USY composite catalyst was significantly higher than that on β and ZSM-5 composite catalyst,although the selectivity to C4= and i-C4= on β zeolite was higher than that on USY.Because of high cracking activity of β zeolite,USY or ZSM-5 zeolite or both of them mixed with β zeolite could enhance the n-dodecane conversion significantly,so yield of low-carbon olefins could increase also.