Abstract
Reprocessing end-of-life polymethyl methacrylate (PMMA) in fluidized beds substitutes fossil fuels as a feedstock for methacrylic acid (MAA). Impurities and high operating and separation costs thwarted the commercialization of the simpler thermolysis PMMA to methyl methacrylate process. In a thermogravimetric analyzer, ≤ 6% of the PMMA decomposed at 230 ∘C, whereas it all reacted at 350∘C. In a 13 mm diameter micro-fluidized bed, all the PMMA reacted within 10 min at 350∘C while at 230 ∘C ≤ 30% reacted. Catalysts like γ-Al2O3, FCC, MoO3-ZrO2/SiO2, zeolite Y, and CsxH3-xPW12O40/SiO2 hydrolyze MMA to MAA. The maximum MAA yield was less than 8% for γ-Al2O3, FCC, MoO3-ZrO2/SiO2, while it reached 20% for the Cs heteropoly acid over SiO2 at 280 ∘C and exceeded 30% with zeolite Y. Coking on the catalyst and product decomposition along the reactor wall reduced MAA yield. A tandem reactor configuration-thermolysis followed by hydrolysis-will maximize MAA yield.
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