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对于正构烷烃的脱氢环化反应,载铂的L沸石(PtKL)具有比传统的双功能重整催化剂高得多的活性及选择性。研究表明,KL沸石的结晶度、晶粒大小及状态随合成所用的原料组成及晶化条件而变化,并影响到PtKL催化剂的活性、选择性和稳定性。本文用低硅、低碱原料合成了高纯度、高结晶度、圆柱体状的L沸石,晶粒直径1.5μm以上,长径比1.0左右。以这种沸石为载体的PtKL催化剂对正构烷烃的脱氢环化具有非常高的活性和选择性。通过对沸石合成条件及催化性质的关联,发现KL沸石的结晶度越高,PtKL催化剂的活性及稳定性越好;当沸石的平均晶粒直径小于1μm或圆柱体的长径比大于2时,催化剂的氢解活性较高,脱氢环化的初始选择性下降。实验结果还表明。合成L沸石时伴生的部分W沸石杂晶对催化剂性能没有显著的影响。
For the dehydrocyclization of normal paraffins, the platinum loaded L zeolite (PtKL) has much higher activity and selectivity than the traditional bifunctional reforming catalysts. The results show that the crystallinity, crystal size and state of KL zeolite vary with the composition of raw materials and crystallization conditions used in the synthesis, and affect the activity, selectivity and stability of PtKL catalyst. In this paper, L zeolite with high purity, high crystallinity and cylinder shape was synthesized from low-silicon and low-alkali raw materials. The diameter of crystal was about 1.5μm and the aspect ratio was about 1.0. PtKL catalysts supported on this zeolite have very high activity and selectivity for dehydrocyclization of n-alkanes. It is found that the higher the crystallinity of KL zeolite, the better the activity and stability of PtKL catalyst. When the average crystallite diameter of zeolite is less than 1μm or the aspect ratio of the cylinder is greater than 2, The hydrogenolysis activity of the catalyst is high, and the initial selectivity for dehydrocyclization is decreased. The experimental results also show. Part of the zeolite W associated with the synthesis of L zeolite had no significant effect on the catalyst performance.