Recycling Nylon 6 Carpet to Caprolactam

The recycling of nylon 6 carpet via depolymerization provides the potential for an environmentally benign new process to produce world-class caprolactam. This article describes the depolymerization of nylon 6 carpet in the presence of steam under medium pressure (800-1500 kPa, 100-200 psig). A small laboratory apparatus was set up to demonstrate the feasibility of the scheme. A total of eight runs were carried out using ～180 g of pellitized carpet and 2-6 g/min steam (at 101-1500 kPa, 0-200 psig, and 300-340°C). In our best run at 340°C, 6 g/min of steam, and 1500 kPa (200 psig) for 3 h, we obtained a 95% yield of crude caprolactam. The lactam purity was 94.4%, resulting in an overall 89.7% yield of caprolactam. The laboratory data were used to construct a computer model of the process for both batch and continuous-flow stirred reactors.