V/AC催化剂NH_(3)-SCR低温脱硝机理的研究

Low temperature denitration mechanism of NH_(3)-SCR over V/AC catalyst

以硝酸活化后的椰壳活性炭(AC)为载体、VOSO_(4)为前驱物制备V/AC系列催化剂,利用SEM、BET、XRD、FT-IR、XPS对V/AC催化剂表面形貌、孔隙结构、晶体结构、官能团和活性组元价态的变化规律进行表征。改性机理研究结果表明,V/AC催化剂上块状钒物种均匀分散在AC表面且能高效构建出新结构,增大比表面积和孔体积;活性炭表面均可观察到V_(2)O_(5)和V_(2)O_(3)活性组元;随着钒氧化物负载量增加,—COOH和—OH官能团略微减少,负载量过多会破坏C—OH、C—O和C■O键。V/AC催化剂低温NH_(3)-SCR机理研究结果表明,通过V^(5+)和V^(4+)之间的氧化还原反应形成了活性氧空位,使表面吸附氧Oα的量增加,具有较高流动性,促进并吸附了更多的反应气体(NH_(3)、O_(2)、NO),致使标准SCR反应向快速SCR反应加速转化。

Coconut shell-based activated carbon (AC) activated by nitric acid is used as carrier,and VOSO_(4)is used as precursor,V/AC series catalysts are prepared.The surface morphology,pore structure,crystal structure,functional groups and valence states of active components of V/AC catalysts are characterized by means of SEM,BET,XRD,FT-IR and XPS.By exploring the modification mechanism,it is concluded that the massive vanadium species are evenly dispersed on the AC surface of V/AC catalyst,and can efficiently construct a new structure and increase the specific surface area and pore volume.Both V_(2)O_(5)and V_(2)O_(3)active components are observed on the surface of activated carbon.With the increase of loading amount of vanadium oxides,—COOH and—OH functional groups decrease slightly.Excessive loading amount will destroy C—OH,C—O and C■O bonds.The low temperature NH_(3)-SCR mechanism over V/AC catalyst is proposed as follows:reactive oxygen vacancies are formed through the redox reaction between V^(5+)and V^(4+),which increases the amount of oxygen adsorption Oα on the surface,and supplies higher fluidity,promotes and adsorbs more reaction gases (NH_(3),O_(2)and NO).Therefore,the transformation from standard SCR reaction to fast SCR reaction is accelerated.