Waste artificial marble powder (AMP), a composite material of poly(methyl methacrylate) (PMMA) and aluminum tri hydroxide (ATH; Al(OH)₃), was recycled using supercritical fluids, in which the depolymerization and thermal decomposition of organic materials and the dehydration of inorganic substances occur simultaneously. For PMMA depolymerization in AMP, higher temperatures are required than for PMMA alone, because of the ATH in AMP. Moreover, as Al(OH)₃ transforms to alumina (Al₂O₃), the generated water influences the methyl methacrylate (MMA) yield. In supercritical methanol, MMA is a major product, whereas in sub- and supercritical water, methacrylic acid (MAA) is the main product. The highest yield of MMA was obtained at 573 K in supercritical methanol. The excess methanol in supercritical methanol suppresses the hydrolysis of MMA to MAA, a reaction that reduces the yield of MMA in sub- and supercritical water. MMA was depolymerized in supercritical methanol, but when the reaction proceeded further, the yield of MMA decreased due to thermal decomposition and/or other chemical reactions. While ATH was converted to boehmite (AlOOH) in sub- and supercritical water, the transformation of ATH was minimized in supercritical methanol.

废人造大理石粉末（AMP）是聚甲基丙烯酸甲酯（PMMA）和三氢氧化铝（ATH; Al（OH）₃）的复合材料，使用超临界流体进行再循环，其中有机材料解聚和热分解同时发生无机物的脱水。对于AMP中的PMMA解聚，由于AMP中的ATH，因此比单独的PMMA需要更高的温度。此外，随着Al（OH）₃转变成氧化铝（Al ₂ O ₃），生成的水会影响甲基丙烯酸甲酯（MMA）的产量。在超临界甲醇中，MMA是主要产品，而在亚临界和超临界水中，甲基丙烯酸（MAA）是主要产品。在超临界甲醇中，在573 K下可获得最高的MMA收率。超临界甲醇中过量的甲醇会抑制MMA水解为MAA，这会降低亚临界和超临界水中MMA的收率。MMA在超临界甲醇中解聚，但是当反应进一步进行时，由于热分解和/或其他化学反应，MMA的收率下降。当ATH在亚临界和超临界水中转化为勃姆石（AlOOH）时，在超临界甲醇中ATH的转化最小。