A New Pressure‐induced Mechanism of Polyvinyl Chloride Pyrolysis with Formation of Nanodiamonds

Abstract

AbstractApplication of high pressure to molecular compounds with high compressibility can initiate chemical reactions, unexpected under normal conditions. Here we present the evidence of pressure‐induced change in the mechanism of dehydrochlorination at polyvinyl chloride (PVC) pyrolysis. PVC pyrolysis was investigated at pressures from 2 to 9 GPa and temperatures up to 1600 °C. At critical pressures of 8–9 GPa, decomposition of PVC starts at 500 °C and results in formation of ultrasmall nanodiamonds. Based on density functional theory calculations, we show that intermolecular linking by single C−C bonds during dehydrochlorination is responsible for the scenario of carbonization, leading to nanodiamonds formation. At decreased pressure, carbonized product consists mainly of graphite‐like carbon, implying that high‐pressure intermolecular dehydrochlorination of PVC becomes inferior to “normal”, intramolecular one. Our study suggests that at low pressures, random intermolecular linking of PVC with formation of single HCl molecules may trigger “normal”, HCl‐catalyzed dehydrochlorination.