Reactive extrusion recycling of polymethyl methacrylate to methyl methacrylate and methacrylic acid
Bibliographic record
Abstract
The global production of polymethyl methacrylate (PMMA) reached 4 million tonnes annually, yet only 10% of PMMA, primarily post-industrial scraps, is recycled. Recycling end-of-life PMMA, which often contains additives or composite components, poses challenges in achieving crude methyl methacrylate (MMA) monomer with comparable purity to post-industrial scraps. Hydrolyzing end-of-life PMMA presents a viable alternative to produce methacrylic acid (MAA) and simplifies the purification process of crude MMA. However, current PMMA hydrolysis is limited to lab-scale and batch operations in fluidized/fixed beds and stirred tank reactors. In this study, we demonstrate a pilot-scale, two-stage reactive hydrolysis extrusion system for the continuous conversion of injection- and extrusion-grade PMMA scraps into MMA and/or MAA at 330 °C to 370 °C. Residence time distribution (RTD) tests characterized the hydrodynamics of the screw configuration for PMMA extrusion, revealing that lower screw speed and feeding rate increase reaction time. A Plackett-Burman design identified temperature and catalyst type as significant factors for MMA hydrolysis. Under optimized conditions, hydrolysis extrusion without any catalysts achieved the highest MMA yield of 89% and 96% PMMA conversion. Hydrolysis extrusion with 10% H-type zeolite Y with an SiO 2 /Al 2 O 3 ratio of 80 at 370 °C resulted in a 5.3% MAA yield, a 67% MMA yield, and near-complete PMMA conversion. Liquid acid catalysts directly hydrolyzed PMMA to poly(MMA-co-MAA) copolymer and/or PMAA, followed by dehydration of two adjacent acid groups to form six-member glutaric anhydride. KOH solution hydrolyzed PMMA to poly(MMA-co-MAA) and/or PMAA potassium salt. • A two-stage reactive hydrolysis extrusion system recycles PMMA continuously. • Non-catalytic reactive hydrolysis extrusion converts 96% PMMA at a 89% MMA yield. • Acid and alkali solutions hydrolyze PMMA to poly(MMA-co-MAA) and its salt. • Hydrolysis extrusion with 10% HY(80) yields 5.3% MAA and 100% PMMA conversion. • Switching from vacuum to atmospheric degassing boosts MMA yield by 4.8 times.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".