Tandem fluidized bed/milli-second fixed bed reactor produces methacrylic acid from poly(methyl methacrylate)

Abstract

Producing monomers from end-of-life plastics is a sustainable alternative to petroleum as a feedstock. Fluidized beds are more effective than molten metal baths and agitated vessels to deconstruct poly(methyl methacrylate) (PMMA) to MMA because of their higher heat transfer rates. Here, we developed a tandem reactor to produce methacrylic acid (MAA). PMMA depolymerized to MMA in a fluidized bed of sand above 300 ∘C in the first step and then MMA hydrolyzed to MAA over zeolite Y suspended in glass wool at a contact time of 200 ms. MAA yield approached 48% while MMA conversion was about 50%. At high temperatures, cyclic hydrocarbons produced during the reaction condensed in the fixed bed hydrolysis section and reactor lines. Reacting PMMA to MAA in a tandem reactor is of industrial interest for end-of-life PMMA containing fillers and additives because of the higher MAA yield compared to reprocessing MAA in a single vessel.