浸渍液pH值对V-Mo/Ti脱硝催化剂性能的影响研究

Influence of impregnating pH valueon catalytic performance of V-Mo/Ti de-NO catalyst

为提升V-Mo/Ti催化剂的脱硝性能,在催化剂制备过程中调节浸渍工艺参数,制备了一系列不同浸渍液pH值的催化剂,采用XRD、N2-吸附脱附、拉曼光谱、UV-Vis、H2-TPR、NH3-TPD等手段对催化剂进行表征,考察了pH值的变化对催化剂物理化学性能的影响,采用固定床微型反应器对催化剂的脱硝性能进行评价。结果表明,降低浸渍液pH值,可以抑制催化剂上VOx物种的聚合,提升催化剂的还原性能,有利于提升催化剂的脱硝效率,降低脱硝反应过程中N2O生成量。同时,浸渍液pH值的变化,也会影响催化剂的酸性性能。当浸渍液pH值低于3.64时,催化剂酸性性能显著降低,造成催化剂脱硝性能降低;当浸渍液pH值控制在3.64时,催化剂的还原性能和酸性性能匹配较好,从而显示了较高的脱硝性能。

In order to improve the denitration performance of the V-Mo/Ti de-NOx catalyst,the impregnation process parameter(pH value) of the impregnation process during the catalyst production was modified.A series of V-Mo/Ti de-NOx catalysts were prepared by using different concentrations of citric acid as the impregnation solvent.XRD,N2-adsorption,Raman,UV-Vis,H2-TPR and NH3-TPD analyses were carried out to characterize the catalysts.The effect of different pH on catalyst properties was studied.Subsequently,the denitrification performance of the catalyst was tested via using a fix bed catalytic micro-reactor.It was found that the p H value of the impregnating solution may have an influence on the reducibility of the catalyst.With the decrease of the pH value of the impregnating solution,the polymerization of VOxspecies is inhibited.As a result,the reducibility of the catalyst is improved,and the catalytic performance of the catalyst is enhanced.Also,the generation of N2O during the de-NOx reaction is declined.At the same time,the pH value of the impregnating solution also has effect on the catalyst acidity.When the pH value of the impregnating solution is below 3.64,the acid property of the catalyst decreases obviously,which had negative impact on the catalytic activity of the catalysts.At pH 3.64,the matching of reducibility and the acidity of PR-2 catalyst is optimal,and the catalyst exhibited the highest NOx conversion among the catalysts investigated.When the reaction temperatures are 250℃,280℃,and 310℃,the NOx conversion of PR-2 catalyst are 69.9%,80.3%,and 89.3%,respectively.In addition,the PR-2 catalysts also show a wider catalytic activity temperature window and denitration efficiencythan that of the other catalysts.On the whole,PR-2 catalyst is a well kind of industrial catalyst for selectivity catalytic reduction of NO with NH3.