Investigation Of Supercritical Water Oxidation Of 1,2-dichlorobenzene And 3-chlorotoluene In A Fused Silica Capillary Reactor By Raman Spectroscopy

Chlorinated organic pollutants have always been a hotspot and problem because of its wide pollution area,high toxicity and difficult to be removed.Supercritical Water oxidation?SCWO?is an advanced oxidation technology,what make it a good candidate for many applications in the decomposition of chlorinated organic pollutants.In this study a fused silica capillary reactor?FSCR?combined with heating/cooling stage and Raman spectroscopy has been used to investigate the decomposition of 1,2-dichlorobenzene or 3-chlorotoluene during the SCWO.The results are showed as follows:?1?The phase behavior of 1,2-dichlorobenzene or 3-chlorotoluene in H₂O/H₂O₂was observed continuously under a microscope and recorded with a digital-camera/recording system,There were obvious phase changes for1,2-dichlorobenzene or 3-chlorotoluene in H₂O system during heating and cooling process,but the volume of the two almost have no changes after heating and cooling,which shows that in H₂O system 1,2-dichlorobenzene or 3-chlorotoluene could not be decomposed,observing 1,2-dichlorobenzene and 3-chlorotoluene gradually dissolved completely to form a homogeneous liquid solution in H₂O₂ system above332.2?and 304.2?,respectively.After heating and cooling process the volumes of two organic have obviously decreased,which suggested that two material in system of H₂O₂ can be oxidized.?2?The effects of oxidant multiples,reaction temperature and reaction time on the decomposition of 1,2-dichlorobenzene and 3-chlorotoluene in SCWO process were investigated.The optimal oxidant multiples of 1,2-dichlorobenzene and3-chlorotoluene are 2.0 and 1.5,repectively;The increase of reaction temperature or the extension of reaction time could promoted the removal rate of organic matter.When the reaction temperature was 440?and residence time was 4 min,the removal rate of 1,2-dichlorobenzene reached 100%.While the removal rate of 3-chlorotoluene reached 100%when reaction temperature was 340?and reaction time was 8 min.?3?Raman spectroscopy was used to determine the gas phase composition?CO₂and O₂?of two organic matter in SCWO process.The productivity of CO₂ increased with the increasing of reaction temperature and/or the extending of reaction time.Under the same experimental conditions,the yield of CO₂ was inferior to the removal rate of the corresponding organic matter.This proved that the degradation oxidation reaction of two kinds organic matter are multistep reactions.When the reaction temperature was 440?and the reaction time was 8 min,CO₂ productivity which produced by 1,2-dichlorobenzene was 100%,while CO₂ productivity of3-chlorotoluene was 100%when the reaction temperature was 460?and the residence time was 8 min.1,2-dichlorobenzene,3-chlorotoluene and their oxidation intermediate products were completely degraded under such condition.?4?The reaction kinetics showed that the formation of CO₂ in the SCWO of1,2-dichlorobenzene and 3-chlorotoluene was a first-order reaction.The intermediate products produced in the process of oxidative degradation were detected qualitatively by GC-MS.The reaction mechanism for 1,2-dichlorobenzene and 3-chlorotoluene in SCWO were proposed based on the experimental results.