Mn-Ce/活性焦低温脱硝催化剂热再生机制

Thermal Regeneration Mechanisms of Mn-Ce/Activated Coke(AC) Catalysts for Low Temperature NO_x Reduction

采用等体积浸渍法制备Mn-Ce/活性焦催化剂,通过在固定床中分两阶段模拟移动床反应器脱硫脱硝过程,制得吸附SO2饱和的Mn-Ce/活性焦催化剂。采用氮气+水蒸汽的方法对催化剂进行再生,发现热再生后催化剂脱硝效率不理想,再生后脱硝效率低于50%。通过BET、XRD、XPS、TPD等表征手段研究发现,催化剂再生后比表面积、孔容都有所减小,Ce3+的含量和Lewis的量酸性位没有恢复,推测催化剂热再生时,吸附在孔道中的SO2与活性物质Ce O2发生反应生成Ce2(SO4)3或是Ce(SO4)2,减少了活性中心Ce的含量,阻塞了催化剂孔隙,使得催化剂再生后脱硝效率变差。

Mn-Ce/activated coke（AC） catalysts were synthesized via an impregnation method. A fixed bed was used to simulate a moving bed reactor under two stages with desulfurization and denitrification processes, and Mn-Ce/AC catalysts saturated with SO2 were prepared. Nitrogen and water vapor was used to thermally regenerate the catalyst. However, all of the NOx conversions rates were lower than 50%. Brunauer-Emmett-Teller method（BET）, X-ray photoelectron spectroscopy（XPS）, X-ray diffraction（XRD） and temperature programmed desorption（TPD） were used to characterize the catalyst and the results show that the surface area and pore volume of the regenerated catalyst decreased significantly, with no recovery of Ce^3＋ and Lewis acid sites. XPS results show that SO2 reacted with Ce O2 to form Ce2（SO4）3 or Ce（SO4）2, which reduced the active centers of Ce and blocked catalyst pores, and reduced NOx conversion rates of the regenerated catalysts.