Synthesis Of CHA Zeolite With Coal Gangue And Fly Ash

Coal gangue(CG)and fly ash(FA)are kinds of potential environmental pollutants.They are produced in the process of coal excavating,washing and combustion.So far,most of CG and FA are discharged in farmland and rivers,which may cause a serious threat to the environment and the human health.At present,the utilization of CG and FA is mainly focused on producing the civil construction material,such as,coal fly ash bricks,pozzolan cement,and so on.However,they are all low economic benefit utilization.CHA is a rhombohedral type zeolite with a unique 3-dimensional structure of 8-membered ring openings(diameter0.38nm*0.38nm)and intersecting channels.CHA structure contains cage formed from alternative 6-memberred ring and CHA cage.This unique structure not only enables CHA to efficiently separate different gases,but also make it applicable in reduction of NOx with NH3(NH3-SCR)and methanol-to-olefins.Currently,synthesis of zeolites from CG and FA as a high value-added product has attracted increasing attention.The main research work is listed as follows:1)The development of zeolties synthesis from CG and FA with vary methods was reviewed and the advantages and disadvantages of the synthetic methods were compared.Meanwhile,the present situation of the application of zeolite synthesized by CG and FA was introduced in this thesis.2)CG is rich in aluminium and silicon,previous recycling approaches cannot achieve the desired potential of CG but caused the waste of the aluminium and silicon resources.Because Zeolite is also rich in Al and Si,synthesis of zeolite with CG may achieve the desired potential of CG.Through XRD and SEM expertizing phase and ammonia nitrogen absorbing test,the results showed that synthesis of phase pure CHA zeolite from coal gangue was feasible.Through trial and error structural and EDS analysis,the optimal synthetic conditions of CHA zeolite were determined.3)The industrial solid waste coal fly ash was used as the raw material and then the high-silica CHA zeolite was synthesized by the method of a hydrothermal treatment.Adding potassium hydroxide can sufficiently resolve the inert crystal of the coal fly ash.The single phase of CHA zeolite was successfully synthesized after adding silicon source cabosil-M5 and aluminum source.Subsequently,the CHAzeolite synthesized on the optimal condition was analyzed by XRD and SEM.Test results showed that the chabazite obtained had the best ash alumina ratio and crystal structure.4)Through the characterization of XRD,SEM and nitrogen adsorption test,the results showed that synthesis of CHA zeolite from CG was feasible.Compared with the normal synthesis method,the synthesis CHA zeolite with gangue presented several advantages,e.g.the short crystallize time,simple reaction conditions,and the high pure.Furthermore,it can be easier to realize the industrial production and commercial application.