Abstract:

A catalyst for catalytic cracking of waste polypropylene plastics to produce light olefins based on ZSM-5 zeolites is developed, and the effect of process conditions is studied in a fixed bed reactor. The results show that using ZSM-5 zeolites catalyst to catalytically crack waste polypropylene plastics is an effective method to produce light olefins and by-product light aromatics. ZSM-5 zeolites catalyst with high Si/Al ratio has fewer strong acid centers and weak acid centers than that with low Si/Al ratio, which can inhibit the further reaction of light olefins to aromatics. In addition, adjusting the acidity of ZSM-5 zeolites catalyst by metal modification is also one of the methods to effectively improve the yield of light olefins. Under the optimized process conditions such as reaction temperature 500 ℃, nitrogen volume flow rate 8 L/h and volume space velocity 0.3 h^-1, the mass yields of light olefins and propylene by using ZSM-5 zeolites catalyst with high Si/Al ratio can reach 64.74% and 35.06% respectively.

Key words: polypropylene, waste plastics, catalytic cracking, catalyst, ZSM-5 zeolites, light olefins

摘要：

以ZSM-5分子筛为基础研制了聚丙烯废塑料催化裂解生产低碳烯烃的催化剂，并在固定床反应器上研究工艺条件对聚丙烯废塑料催化裂解生产低碳烯烃的影响。实验结果表明：利用ZSM-5分子筛催化剂催化裂解聚丙烯废塑料是生产低碳烯烃、副产轻质芳烃的有效办法；高硅铝比ZSM-5分子筛催化剂比低硅铝比ZSM-5分子筛催化剂具有较低的强酸中心和弱酸中心，能够抑制低碳烯烃进一步转化为芳烃等产物，并多产低碳烯烃，利用金属改性调变ZSM-5分子筛催化剂酸性也是有效提高低碳烯烃收率的方法之一；利用高硅铝比ZSM-5分子筛催化剂，在反应温度500℃、氮气体积流量8 L/h、体积空速0.3 h^-1等优化工艺条件下，聚丙烯催化裂解的低碳烯烃和丙烯质量收率分别高达64.74%和35.06%。

关键词: 聚丙烯, 废塑料, 催化裂解, 催化剂, ZSM-5分子筛, 低碳烯烃