Study On Preparation Of In/H-Beta And Influence Factors Of Reduction Of NO_x By CH₄

Nitrogen oxides(NOx)in the exhaust are toxic to human's health and have introduced a lot of environmental problems.The activity of the reduction of NOx with methane(CH4)on In/H-Beta zeolite catalyst was studied in this paper.In addiation,the preparation conditions of In/H-Beta,the reaction mechanism on In/H-Beta,reaction conditions and poisoning resistances performance of catalyst were studied.The preparation method of series of In/H-Beta zeolite catalysts was ion exchange method.The effects of preparation conditions including carriers,exchange time,the concentrations of the solution and calcination temperature on the activity of the In/H-Beta catalysts were investigated.The physical and chemical properties of In/H-Beta catalysts prepared with different preparation conditions were analyzed through characterization techniques.The results of this research showed that the In/H-Beta catalyst with H-Beta as carrier,ion exchange time as 8 hours,exchange liquid concentration is 0.033 M,calcination temperature is 500 degrees Celsius showed the best activity.The maximum removal rate of NOx was about 93%when the temperature was 552?.The effects of the reaction conditions including reaction gas components,O2 concentrations,CH4:NO ratios,the space velocities and initial NO concentrations on the activity of reduction of NOx with CH4 on In/H-Beta were studied.The results in the paper showed that under O2 conditions,the change curves of NOx with NO and NO2 were basically the same,when O2 didn't present,the change curve of NOx when the reaction gas was NO2 was basically the same when the temperature was under 465? as the O2 existed.However,the removal rate of NOx when the reaction gas was NO without O2 was very low.And it indicated that the formation of NO2 was very important for the reaction.The removal rate of NOx was increased when the concentration of O2 was less than 10%,and the activity of the catalyst was the best when the concentration of O2 was10%then the removal rate of NOx decreased with the raise of the concentration of O2.The removal rate of NOx was increased when the ratio of CH4:NO increased.The highest removal rate of NOx was almost unchanged when the ratio of NOx was above 1.The In/H-Beta catalyst exhibited good activity in a wide range of space velocity.When the initial concentration of NO was among 300 and 700 ppm,the removal rate of NOx was high.The poisoning resistances of In/H-Beta zeolite catalyst were discussed.The impacts on the activity of reduction of NOx with CH4 under SO2 condition,H2O condition,and the presence of SO2 and H2O condition were investigated.And the poisoning reasons were studied through the analysis of the characterization technology.The results showed that the In/H-Beta zeolite catalyst had better resistance to sulfur.When the content of H2O was low,the In/H-Beta catalyst showed certain activity.While H2O and SO2 were exist at the same time,the catalyst was severely deactivated.The characterization showed that the introduction of SO2 led to the formation of sulfur species on the catalytic surface,and the presence of H2O destroyed the molecular sieve framework,and the oxidation-reduction quality and surface acidity weer also changed.The interaction of the two factors was significant to the structure of the catalyst,which might be the reason for the reduction of the catalyst activity.