A method for quantitative evaluating the enhancement of the rate of Type Ⅱ photosensitized oxidation by D_2O was suggested. The effect of substrate concentration on this process was also discussed.
The chain reaction of 1,2-dichloroethane was initiated by photosensitization of SF_6 under the selective excitation using a cw CO_2 laser.Vinyl chloride with high purity was produced in the reaction process.The initia...The chain reaction of 1,2-dichloroethane was initiated by photosensitization of SF_6 under the selective excitation using a cw CO_2 laser.Vinyl chloride with high purity was produced in the reaction process.The initiation of the photosensitized chain reaction depends on the irradiated laser frequency.The mechanism of intermolecular resonant transfer of vibrational energy has been discussed.展开更多
The structures of 26 different congeners of polychlorinated biphenyls（PCBs, including monothrough deca-chlorinated） were optimized using density functional theory（DFT） calculations with the 6-31＋G（d,p） basis se...The structures of 26 different congeners of polychlorinated biphenyls（PCBs, including monothrough deca-chlorinated） were optimized using density functional theory（DFT） calculations with the 6-31＋G（d,p） basis set. The activation energies for the dechlorination of these systems were calculated for direct photodegradation and photosensitized degradation reaction pathways in the presence of natural organic matter（NOM）. The dechlorination mechanism of these PCBs and the ring-opening reaction mechanisms（using QST3 method） of the photosensitive degradation products were analyzed. The results showed that（i） the activation energy for the photosensitized degradation of PCBs was much lower than that of direct photodegradation;（ii） the degradation activities（i.e., C–Cl bond cleavage energies） were the same for both degradation pathways and followed the order ortho 〉 meta 〉 para;（iii） the degradation activities of asymmetric PCBs were higher than those of the corresponding symmetrical PCBs for the direct photodegradation and it was completely opposite in the photosensitive degradation;（iv） there was no correlation between the dissociation energy and the number of C–Cl bonds for the direct photodegradation and dechlorination products were all biphenyl;（v） the degradation activity of PCBs decreased as the number of C–Cl bonds increased in the presence of NOM; and（vi） even when the dechlorination reaction was incomplete, it produced chlorophenol. Furthermore, the free radicals of NOM led to the ring-opening reactions of PCBs via an initial addition step. The main site of these ring-opening reactions was the ortho position. Notably, the likelihood of ring-opening reactions occurring involving the degradation products increased as the degradation degree of PCBs increased.展开更多
文摘A method for quantitative evaluating the enhancement of the rate of Type Ⅱ photosensitized oxidation by D_2O was suggested. The effect of substrate concentration on this process was also discussed.
文摘The chain reaction of 1,2-dichloroethane was initiated by photosensitization of SF_6 under the selective excitation using a cw CO_2 laser.Vinyl chloride with high purity was produced in the reaction process.The initiation of the photosensitized chain reaction depends on the irradiated laser frequency.The mechanism of intermolecular resonant transfer of vibrational energy has been discussed.
基金supported by the Fundamental Research Funds for the Central Universities in 2013(JB2013146)the Key Projects in the National Science&Technology Pillar Program in the Eleventh Five-Year Plan Period(2008BAC43B01)
文摘The structures of 26 different congeners of polychlorinated biphenyls（PCBs, including monothrough deca-chlorinated） were optimized using density functional theory（DFT） calculations with the 6-31＋G（d,p） basis set. The activation energies for the dechlorination of these systems were calculated for direct photodegradation and photosensitized degradation reaction pathways in the presence of natural organic matter（NOM）. The dechlorination mechanism of these PCBs and the ring-opening reaction mechanisms（using QST3 method） of the photosensitive degradation products were analyzed. The results showed that（i） the activation energy for the photosensitized degradation of PCBs was much lower than that of direct photodegradation;（ii） the degradation activities（i.e., C–Cl bond cleavage energies） were the same for both degradation pathways and followed the order ortho 〉 meta 〉 para;（iii） the degradation activities of asymmetric PCBs were higher than those of the corresponding symmetrical PCBs for the direct photodegradation and it was completely opposite in the photosensitive degradation;（iv） there was no correlation between the dissociation energy and the number of C–Cl bonds for the direct photodegradation and dechlorination products were all biphenyl;（v） the degradation activity of PCBs decreased as the number of C–Cl bonds increased in the presence of NOM; and（vi） even when the dechlorination reaction was incomplete, it produced chlorophenol. Furthermore, the free radicals of NOM led to the ring-opening reactions of PCBs via an initial addition step. The main site of these ring-opening reactions was the ortho position. Notably, the likelihood of ring-opening reactions occurring involving the degradation products increased as the degradation degree of PCBs increased.
