Performance Of Catalytic Oxidation Degradation Of Pbdd/Pbdfs By Carbon Nanotubes Supported Catalysts

With the growing application of bromine flame retardants (BFRs) in all fields, polybrominated dioxins and furans (PBDDs and PBDFs) pollution produced by processing waste of BFRs has become more severe. Characteristic of physical and chemical properties, toxicity, environmental distribution of PBDDs/PBDFs is similar to polychlorinated dioxins and furans (PCDDs and PCDFs). They have strong carcinogenic teratogenic effect as PCDDs and PCDFs, and even have a higher molecular weight, higher melting point, lower water solubility and lower saturated vapor pressure than PCDDs and PCDFs. It was showed that catalytic oxidation had high activity and stability on removal of PCDDs or PCDFs in many studies, but there were rarely research on catalytic oxidation of PBDDs or PBDFs.V2O5 shows good catalytic activity and stability in catalytic oxidation of PCDDs/PCDFs, while carbon nanotubes (CNTs) are a new kind of catalyst carrier with unique pipe cavity structure, hydrogen storage performance, electrical and mechanical properties. In this paper, V2O5/CNTs catalysts were prepared by impregnation method to examine the influence of different impregnation conditions and heat treatment process. Surface pattern and structure characteristics of catalysts was characterized by SEM, EDS spectrum TGA, TEM, XRD, XPS and ICP, etc. It was found that the mixture of ammonium metavanadate and carbon nanotubes after acid treatment that had been stirred for 25 hours at 60℃, then underwent calcination at 500℃ in nitrogen and 250℃ in air showed the best surface pattern and structure characteristic.Catalytic oxidation activity of V2O5/CNTs catalysts was investigated with o-bromine phenol (2-BrP) as simulated pollutants of PBDDs/PBDFs. Effects of temperature, O2 content, V loading and H2O content on 2-BrP removal were studied. The results showed that with a rise of temperature the removal for reaction off and on of 2-BrP by V2O5/CNTs catalysts increased and reached almost 100% at 300℃; The removal of 2-BrP by V2O5/CNTs catalysts increased in the order of 4%<10%<16%<0%<20% in different O2 content; The activity of V2O5/CNTs catalysts was enhanced first and then decreased with the increase of V loading and reached the best (89.6%) at 8.2% V loading; A small amount of H2O could promote the catalytic oxidation of 2-BrP. When it’s content was lower than 1.0%, H2O played a driving role, while when higher than 1.0%, it would inhibit the catalytic oxidation; Presence of SO2 would inhibit the activity of V2O5/CNTs catalysts to some extent; V2O5/CNTS catalysts could keep activity above 60% in off and on reaction for 120 min in 20% O2 at 280℃; It also researched influence of the addition of NiO and CeO2. It was found that both of them would inhibit the catalytic activity of V2O5/CNTs catalysts. In conclusion, the prepared V2O5/CNTS catalysts presented large V load and high dispersion and it showed high activity on degradation of 2-BrP in gas phase.