Poly(methyl methacrylate) catalytic depolymerization to methacrylic acid

聚甲基丙烯酸甲酯（PMMA）具有优异的机械和物理性能，是表面涂层树脂、塑料、汽车背光源和电子产品，特别是led电视的原材料。这种聚合物的世界市场正在增长，但像其他热塑性塑料一样，回收技术还不完善。不合规格的铸板在熔融铅浴中解聚以回收单体，但它有环境问题，并且无法处理报废的成品。一次和二次（机械）回收方法产生的聚合物质量很差。在这里，我们考虑结合热化学和催化工艺将PMMA转化为单体甲基丙烯酸的三级回收方法。在第一个过程中，我们将PMMA颗粒直接注入300℃以上的催化流化床。聚合物熔化并与固体催化剂和过氧化氢接触，产生气态的甲基丙烯酸，我们在反应器的顶部回收。第二种技术依赖于将聚合物与自由基引发剂（如过氧化氢）一起送入高温下运行的挤出机。我们沿着挤出机的长度回收气态的甲基丙烯酸。这些技术也可以结合起来。除了了解反应动力学以设计商业反应器外，我们还必须确定如何传输嵌入在聚合物基体中的玻璃纤维和其他填料。我们将在610毫米的中试流化床上测试这些技术。

Polymethyl methacrylate (PMMA) has excellent mechanical and physical properties and is a raw material for surface coating resins, plastics, back lights of automobiles, and electronics, particularly LED-TVs. The world market for the polymer is growing but, like other thermoplastics, recycling technologies are inadequate. Off-spec cast sheets are depolymerized in molten lead baths to recover the monomer but it has environmental concerns and is incapable of treating end-of-life finished products. Primary and secondary (mechanical) recovery methods produce a poor quality polymer. Here we consider tertiary recovery methods combining thermochemical and catalytic processes to convert PMMA to the monomer methacrylic acid. In the first process, we inject PMMA particles directly into a catalytic fluidized bed operating above 300 oC. The polymer melts and contacts both a solid catalyst and hydrogen peroxide to produce gaseous methacrylic acid that we recover at the top of the reactor. The second technology relies on feeding polymer to an extruder operating at high temperature together with radical initiator (like hydrogen peroxide). We recover the gaseous methacrylic acid along the length of the extruder. These technologies may also be combined. Besides understanding the reaction kinetics to design a commercial reactor, we must also identify how to transport fibre glass and other fillers imbedded in the polymer matrix. We will test the technologies in a 610 mm pilot scale fluidized bed.