沥青基球状活性炭担载尿素用于NO_2的低温选择性催化还原行为研究

Low-temperature selective catalytic reduction of NO_2 with urea supported on pitch-based spherical activated carbon

将作为还原剂的尿素担载于沥青基球状活性炭(PSAC)上研究了NO2的低温选择性催化还原(SCR)反应。结果表明,PSAC上尿素担载量的提高可以增大NO2与尿素的反应几率;当尿素担载量由8%提高到30%时,SCR反应脱硝活性显著提高,脱硝时间相应延长。在30～90℃,升高反应温度会减小NO2在PSAC表面的吸附量,从而导致NOx的脱除量减小。增加反应气氛中NO2和O2的浓度均有利于脱硝活性的提高,但当O2进料浓度大于9%时,继续增加O2进料浓度对脱硝活性的改善作用变得微弱。降低空速有利于提高脱硝活性和延长脱硝时间。当反应温度为30℃、空速为2 000 h-1、NO2和O2的进料浓度分别为0.05%和21%时,尿素担载量为8%的PSAC可在49 h内实现85%以上的NOx转化率。

Urea as reducing agent supported on pitch-based spherical activated carbon（PSAC） was studied for NO2 reduction at low temperatures（30~90 ℃）.The results showed that increasing urea loading from 8% to 30% raised the reaction probabilities of selective catalytic reduction（SCR） of NO2 by urea,which resulted in significant increase of the SCR activity;moreover,the NOx removal period was extended.In the temperature range of 30~90 ℃,high reaction temperature was unfavorable for NOx removal on account of the decreased NO2 adsorption on PSAC.It was found that the SCR activity was improved by increasing NO2 or O2 concentration in the feed gas.However,further increase in O2 concentration above 9% made a weak contribution to the improvement of the SCR activity.Decreasing space velocity not only increased the SCR activity but also prolonged the NOx removal period.More than 85% NOx conversion for 49 h could be achieved over PSAC with 8% urea loading at 30 ℃ under the condition of 0.05% NO2,21% O2 and a space velocity of 2 000 h-1.