Application Of Sub-and Supercritical Water Technique In The Depolymerization Of Waste Nylon6

Recently, a mass of products of waste nylon6 not only do pollute environment but alsosquander the raw and processed materials. So the research of reclaiming waste nylon6 is aimportant problem that researchers are concerning and discussing.The paper represents the basic characteristics of the sub- and supercritical fluids, and theproperties, what chemical recycling of waste plastic comparers with traditional processes. Italso reviews the actuality of research in the depolymerization of waste nylon6 and others insub-and supercritical fluids. The depolymerization of waste nylon6 in sub- and supercriticalwater is investigated, in the higher temperature and pressure experimental apparatus that wedesign construct and install.It is the key to the investigations on reaction pathway and mechanism to analyze theliquid product. According to relevant literatures and the results of the experiments in thiswork, GC-MS, ultraviolet spectrometry are used to analyze the products in liquid qualitativelyand quantitatively. The influences of temperature, pressure, and reaction time on the yield ofthe products are studied by the fit graph bastes on the reaction results, and find out theoptimized conditions of the reaction.The results showed that the main products in liquid were aminocaproic acid andcaprolactam; the maximum yield is 6.6% and 96%, respectively. And both are the material ofpolymerization nylon6, which actualize environment protection, cycling utilize of wastenylon6. The reaction scheme of decomposition is represented. Nylon6 is decomposed intoaminocaproic acid by hydrolysis followed by cyclodehydration to caprolactam ordecomposition further to lower molecules, as cyclopentanone and so on.In sub- region, the higher is the reaction temperature, pressure, and time, the faster is thedepolymerization rate. In supercritical region, the prime yield of aminocaproic acid andcaprolactam come forth at 370℃, 25Mpa, which tally with the rule of the first-orderconsecutive reaction. At temperature above 370℃, pressure above and up to 30Mpa,secondary reaction is promoted in long reaction time.At each reaction conditions, the Ea and k are calculated according to Arrheniusrelationship and the kinetic analysis. These results suggest that hydrolysis is slower thancycylodehydration and apparent active energy Ea is less in the sub- and supercritical water. The experiments analysis that the depolymerization of waste nylon6 in sub- andsupercritical water and the influence of reaction condition on the yield of the products. Thesecan provide basic datas and technics condition for the industrilisation recycle of waste nylon6.