Study On Catalysts And Decoupling Process Of NO_x Reduction By Pyrolysis Gas

NOx is one of the main air pollutants.It is the culprit in causing acid rain,photochemical smog and smog.NH3-SCR is the most effective NOx reduction technology in the past few decades,but there are problems such as ammonia leakage and secondary pollution that are difficult to solve.Pyrolysis gas is a mixture of carbon monoxide,methane and hydrogen,which is one of the by-products of coking in the factory.Since CO,CH4 and H2 have high reducing ability;pyrolysis gas is used as the reducing agent instead of anomina to research the catalytic reduction of NOx.In this paper,decoupling NO reduction technolodgy,which can divide the reaction into two processes of NOx adsorption and reduction,is used to take the research.Thus the influence of O2 on the selectivity of the reducing agent is elimitated.In this research,the NO reduction activities of zeolite catalysts and metal oxide catalysts were firstly tested,and then the adsorption-reduction decoupled NO reduction was also tested.For zeolite catalysts,BEA catalysts supported with Fe,Co,Ni,Cu were prepared,and then their catalytic activities of NO reduction by CO,CH4 and/or H2 were tested.The test results show that Cu-BEA is benefit to NO reduction by CO or H2(100%denitration efficiency at about 350 ? for NO reduction by CO,and 100%denitration eddiciency at 300 ? for NO reduction by H2).Co-BEA is benefit to NO reduction by CH4,and the efficiency rapidly increases from 20%to 80%in the temperature zone from 300 ? to 400 ?.Then H2-TPR,XRD,XPS and BET methods were used to characterize the BEA catalysts to explore their structural composition.Finally,in-situ Fourier transform infrared method was used to determine the infrared spectrum of the reducing process under variable temperature conditions,and the catalytic mechanism of BEA catalysts was analyzed.For metal oxide catalysts,Cu2M9CeOx catalysts(M= Fe,Co or Ni)were prepared,and then their catalytic activities of NO reduction by CO,CH4 and H2 were tested,respectively.The test results show that the activities of Cu2Fe9CeOx and Cu2Co9CeOx for NO reduction by CO and/or H2 are greatly improved compared with BEA catalysts(100%denitration efficiency at about 250? to 300?),but their activities for NO reduction by CH4 are greatly inhibited.Then the structure of Cu2M9CeOx was characterized by XRD,XPS and TEM method,and the catalytic mechanism of the catalyst was also studied by in-situ Fourier transform infrared method.Based on the performance of BEA and Cu2M9CeOx catalysts on NO reduction by pyrolysis gas,the NO adsorption-reduction ability of decoupled NO reduction by pyrolysis gas was then carried out.The experimental results show that Cu2M9CeOx and Cu-BEA have low adsorption abilities,while Co-BEA and Ni-BEA have high adsorption abilities(over 50%NO adsorption rate).However,the NO reduction rate is equal to zero for decoupling denitration by CO and/or H2,while the NO reduction rate id below 30%for decoupling denitration by CH4.Therefore,it is necessary to control some reaction conditions to improve the raction of decoupling denitration.In conclusion,BEA catalysts exhibit high activity in NO reduction by CO,CH4 and H2,and have nice NO adsorption ability.Cu2M9CeOx catalysts have higher catalytic activity for NO reduction by CO and H2 than BEA catalysts,but their catalytic activity for NO reduction by CH4 is low.Cu is an active metal element suitable for catalyzing NO reduction by CO and H2,and Co is an active metal element suitable for catalyzing NO reduction by CO and CH4.It is necessary to further study Cu-and Co-containing catalysts for their activity of NO reduction by pyrolysis gas.