氧化铜催化五氯苯生成二英的研究

研究在加热条件下，五氯苯在CuO表面催化生成二英（PCDD/Fs）的过程.结果表明，在200～350℃，PCDD/Fs的生成量随温度的升高而增加；在350～450℃，PCDD/Fs的生成量随温度的升高而减少.温度较低时（200～250℃），生成的PCDD/Fs以高氯取代同系物为主；温度较高时（400～450℃），则以低氯取代的同系物为主.但温度的改变并没有引起同一氯取代度PCDD/Fs中的异构体分布模式发生规律性变化.通过比较400℃条件下CuO催化五氯苯生成PCDD/Fs与CuO催化OCDD/F的脱氯降解情况，推测了五氯苯生成PCDD/Fs的途径.低氯取代的PCDDs可能主要来源于五氯苯生成的高氯取代PCDDs的进一步脱氯降解.而PCDFs则主要由五氯苯脱氯降解生成的低氯取代产物直接缩合生成.

PCDD/Fs Formation from Pentachlorobenzene Under the Catalysis of CuO

The formation processes of PCDD/Fs from pentachlorobenzene catalyzed by CuO under heating conditions were investigated. The results showed that, the amount of the formed PCDD/Fs increased with the temperature from 200 degrees C to 350 degrees C, and then decreased with futher increase of temperature from 350 degrees C to 450 degrees C. PCDD/Fs homologue pattern varied significantly according to the reaction temperature. At the lower temperature (200-250 degrees C), the major PCDD/Fs products were highly chlorinated ones; but at the higher temperature (400-450 degrees C), the low chlorinated PCDD/Fs predominated in the PCDD/Fs products. The change of temperature did not cause a systematical variation in the isomer distributions in each PCDD/Fs homologue. By comparing the formation of PCDD/Fs from pentachlorobenzene with the dechlorination of OCDD/F both under the catalysis of CuO at 400 degrees C, the precursor mechanism of PCDD/ Fs formation from pentachlorobenzene was speculated. Low chlorinated PCDDs mainly came from the dechlorination of highly chlorinated PCDDs which were formed from the pentachlorobenzene, whereas PCDFs could be mainly formed by the direct condensation of dechlorination products of pentachlorobenzene.