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Volume 115
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Kinetic modeling of methyl methacrylate gas-phase decomposition and its impact on polymethyl methacrylate pyrolysis yields (Open Access)
Stefan Pielsticker *, Konstantinos Gfall, Wilko Rohlfs, Reinhold Kneer
Institute of Heat and Mass Transfer (WSA), RWTH Aachen University, Augustinerbach 6, 52056, Aachen, Germany
10.1016/j.partic.2026.05.011
Volume 115, August 2026, Pages 366-377
Received 12 January 2026, Revised 13 May 2026, Accepted 17 May 2026, Available online 28 May 2026, Version of Record 19 June 2026.
E-mail: pielsticker@wsa.rwth-aachen.de
Highlights

• Separate MMA kinetic modeling is undertaken to improve PMMA pyrolysis models.

• Low-energy decarboxylation dominates cracking reactions at low temperatures.

• Competitive reaction model (CRM) accurately predicts MMA product selectivity.

• Direct solid-to-gas pathways are key to predict low-temperature PMMA yields.

• Peak monomer recovery near 723 K shows excellent agreement with literature.


Abstract

Chemical recycling of polymethyl methacrylate (PMMA) to its monomer, methyl methacrylate (MMA), requires balancing primary depolymerization with the suppression of secondary gas-phase reactions. This study investigates non-oxidative MMA decomposition in a fluidized bed reactor across a temperature range of 623 to 1073 K using online FTIR spectroscopy. Experimental results reveal a significant shift in product selectivity: low temperatures favor a low-energy decarboxylation pathway (yielding CO2 and methanol), while high temperatures promote radical cracking (yielding CO and light hydrocarbons). To describe this, a two-competing-reactions model (CRM) is used, outperforming the traditional single first-order approaches. The CRM identifies two distinct activation energies: Ea,1 = 76.5 kJ mol−1 for decarboxylation and Ea,2 = 269.9 kJ mol−1 for cracking. The research further demonstrates that the classical sequential decomposition model (PMMA → MMA → light gases) overpredicts monomer yields at low temperatures. By integrating a direct solid-to-gas pathway to account for side-chain break-off and incorporating multi-volume reactor hydrodynamics, the model's predictive accuracy significantly improved. This integrated framework identifies an optimal recovery window near 723 K, achieving MMA yields over 95 %.

Graphical abstract
Keywords
MMA and PMMA pyrolysis; Fluidized bed reactor; FTIR gas analysis; Kinetic modelling; Primary and secondary reactions
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