SCR脱硝反应活化能和指前因子分析

STUDY ON THE ACTIVATION ENERGY AND THE PRE-EXPONENTIAL FACTOR OF SCR DENITRIFICATION REACTION

为研究SCR脱硝反应活化能等动力学参数,制备了不同钒含量以及含钨(W)、铈(Ce)、FeSO_4的SCR脱硝催化剂。测定了催化剂的NO转化率,根据Eley-Rideal机理,推算反应化学反应速率常数k、活化能E_a和指前因子A,以及E_a和A的补偿效应。发现SCR脱硝反应活化能随着钒含量的增加而降低,催化剂表面钒氧物种的聚合程度越高,每个活性位参与SCR脱硝反应的活性越低。钨能降低SCR脱硝反应活化能,钨和钒参与脱硝反应时具有协同作用。同样质量百分含量条件下,脱硝反应活化能大小依次为:钒<铈<铁(FeSO_4)。钒质量分数在0.2%～0.6%时,商业SCR脱硝催化剂的活化能可取45.4 kJ/mol,只需要测定1个温度点的NO转化率,就可以预测该催化剂在一定温度范围内的NO转化率。

A series of catalysts with various V2O5 contents and catalysts containing W, Ce, FeSO4 were prepared to study the kinetics of selective catalytic reduction of NO with NH3. The NO conversion rate was tested on a fixed-bad reactor. Apparent activities, pre-exponential factor and their compensation effect were calculated in the light of Eley-Rideal mechanism. The results showed that the activation energies of SCR decreased with the increase of vanadium content. Tungsten could reduce the denitrification reaction activation energies of vanadium catalysts. The higher the polymerization state of vanadium species was, the lower the activity of each active site in the SCR denitrification reaction was, Tungsten and vanadium had synergistic effect in the process of denitrification. When the same element mass percentage was same, the apparent activation energies showed the following order： VCeFe. When vanadium mass content was in the range of 0.2%～0.6%, the activation energies of commercial SCR denitrification catalyst could be 45.4 kJ/mol. When we obtained NO conversion rate at a specified temperature, the NO conversion rate at any temperature could be fovecasted by using the formula devived in this paper.