Abstract:

The hydropyrolysis catalyst of waste plastics mostly uses precious metals such as Pt and Ru as catalytic sites, which is costly and difficult to be applied on a large scale, so it is urgent to develop a low-cost and efficient hydropyrolysis catalyst. In this study, FCC catalyst waste slag was modified by hydrogen ion exchange and used as catalyst for hydropyrolysis of low density polyethylene (LDPE). The FCC catalyst waste slag was characterized by XRF, XRD, N₂ adsorption-desorption, NH₃-TPD, and SEM. The effects of temperature, initial hydrogen pressure, time and catalyst dosage on the reaction performance were investigated. The results showed that after hydrogen ion exchange, the acidity of FCC catalyst waste slag was enhanced, and the acid content of weak acid was significantly increased, which was the key to improve the catalytic activity of FCC catalyst waste slag. At 330℃, 3MPa H₂ and 16h reaction time, FCC waste slag catalyst showed superior catalytic activity in converting LDPE into gas fuel with a yield of 89.4%, and the gas fuel was mainly composed of propane (volume selectivity of 53.6%) and butane (29.2%), which was similar to liquefied petroleum gas and could be used as gas fuel and chemical raw materials. Five recycle experiments under the optimal conditions showed that the catalytic activity was stable.

Key words: waste plastics, fluid catalytic cracking, catalyst waste slag, low density polyethylene, hydrogenation, pyrolysis, fuel

摘要：

废塑料的加氢热解大多使用Pt、Ru等贵金属作为催化位点，成本高昂且难以大规模应用，亟待开发一种成本低廉且高效的加氢热解催化剂。本文以流化催化裂化（FCC）催化剂废胶渣为催化剂，并采用氢离子交换对其改性，对FCC催化剂废胶渣进行了X射线荧光光谱仪（XRF）、X射线衍射（XRD）、N₂吸附-脱附、NH₃-程序升温脱附（NH₃-TPD）和扫描电子显微镜（SEM）表征。将氢离子交换后的FCC催化剂废胶渣催化剂用于低密度聚乙烯（LDPE）的加氢热解，考察了温度、初始氢气压力、时间和催化剂用量对反应的影响。结果显示，FCC催化剂废胶渣经过氢离子交换后酸度增强，弱酸酸量显著增加，这是提高FCC催化剂废胶渣催化活性的关键。FCC催化剂废胶渣催化剂在330℃、16h、3MPa H₂的条件下表现出了优异的催化活性，将LDPE高效转化为气体产物，产率达89.4%，且对气体产物的选择性以丙烷（53.6%，体积分数）和丁烷（29.2%，体积分数）为主，与液化石油气的组成类似，其可以作为气体燃料和化工原料使用。经最优条件下的5次循环实验发现，其催化活性的稳定性良好。

关键词: 废塑料, 流化催化裂化, 催化剂废胶渣, 低密度聚乙烯, 加氢, 热解, 燃料