基于XRD和FITR的Ce-V-Ti催化剂减排烧结烟气二噁英的活性分析

doi:10.3964/j.issn.1000-0593(2021)01-0327-06

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Abstract Dioxins are a group of chlorinated volatile organic pollutants (VOCs) with environmental persistence, biological accumulation and long-term residual properties. It can cause teratogenic, carcinogenic and mutagenic hazards. During the iron ore sintering process, dioxins can be catalytically synthesized from chlorine-containing precursors by Ullman reaction in the alkaline environment or by some catalytic components on the surface of fly ash. Besides, dioxins can be synthesized by de novo through elementary reaction. Iron ore sintering process is one of the most emission sources of dioxins. Physical adsorption technology can only remove pollutants from gas phase to the solid phase and increase the aftertreatment problem of fly ash. Besides, there is a risk of dioxins regeneration under 250～350 ℃. Catalytic combustion can be completely degradation dioxins into CO₂，H₂O and HCl/Cl₂ over catalysts. It is an efficient, energy conservation and low-cost method to avoid secondary pollution. However, the working temperature of traditional catalysts is too high to the end temperature of the sintering flue gas. It is important to improve the catalytic activity at low temperature to achieve high efficiency catalytic combustion of VOCs from iron ore sintering flue gas. As Ce has the 4f orbital coordination effect and Lewis acid site, which plays a crucial role in the activation of C—H and C—Cl bonds in organic pollutants, the anti-chlorine toxicity and combustion activity of the catalystcan be improved by doping transition metal or adjusting the proportion of active components of catalysts. Hence, the effect of different Ce/V weight ratio of Ce-V-Ti catalysts prepared by sol-gel method were studied in this paper. Chlorobenzene was used as the model molecule of dioxins. The phase, specific area, molecular structure and functional groups of Ce-V-Ti catalysts were characterized by XRD, BET,XPS and FTIR. The results show that the catalytic activity of chlorobenzene over Ce-V-Ti catalysts with 15 Wt% Ce and 2.5 Wt% V can achieve CB conversion of 60% at 150 ℃ and 95% at 300 ℃ under the reaction conditions of GHSV=30 000 h^-1, 20% O₂ and 100 ppm CB. The chemical interaction between the barrier and the active component affected the catalytic activity of catalysts. According to the spectroscopic analysis, the XRD pattern of Ce-V-Ti catalysts was mainly anatase TiO₂. The specific surface area was 95.53 m²·g^-1, the volume of the pore was 0.29 cm³·g^-1，and D_BJH was 6.5 nm. Most of the functional groups on the Ce-V-Ti catalysts were C—H groups and O—H, which was expedited the adsorption and desorption of CB. The introduction of V as co-catalytic compositioninto Ce-Ti catalyst promoted the solid solution reaction of Ce element and increased the oxygen vacancy on the surface of the catalyst, which was conducive to improving the catalytic activity of the catalyst. Meanwhile, the oxidation reaction of V in low-price promotes the reduction reaction of Ce.

Key words：Catalytic combustion; Dioxins; Ce-V-Ti catalysts; Spectral analysis; Iron ore sintering flue gas

Received: 2019-11-23 Accepted: 2020-04-11

Corresponding Authors: LONG Hong-ming E-mail: yaflhm@126.com

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2021)01-0327-06 OR https://www.gpxygpfx.com/EN/Y2021/V41/I01/327