Preparation And Application Of Ag-Based Materials For Ethylene Removal

Fruit and vegetable production are abundant in China,while the preservation technology lags behind other countries,resulted in serious economic losses.Ethylene,as a gaseous plant growth hormone,is an important substance to promote the growth and ripening of fruits and vegetables.In generally,the freshness time of fruits and vegetables in storage and transportation prolonged by controlling the content of environmental ethylene.Therefore,it is a research hotspot for the removal of trace ethylene in the environment.A silver-based/molecular sieve?Ag/HZSM-5?removal material was prepared for the removal of trace ethylene in the environment at room temperature in this paper.The structure and surface chemical properties of the material were characterized by X-ray powder diffraction?XRD?,specific surface area?BET?,transmission electron microscopy?TEM?,surface acidity?NH₃-TPD,Py-IR?,etc.A self-made evaluation device was used to investigate the performance of material in the dynamic removal of ethylene at room temperature and explore the optimized application process parameters.The removal material is regenerated based on the reason of deactivation,and the reusability was investigated.Finally,the powder material is loaded on the base of honeycomb paper block to form monolithic material by coating method,and the practicability and convenience of the monolithic material were investigated.?1?Firstly,the influence of preparation conditions?Ag loading,calcination time and temperature?on the removal of ethylene from Ag/HZSM-5 at room-temperature was investigated,and then exploring the influence of dealuminated conditions?type of acid,acid concentration and treatment time?of HZSM-5 on the performance of material.The material was characterized by XRD,BET,TEM,NH₃-TPD and Py-IR.Results indicate that the performance of the material is mainly affected by the dispersion degree of Ag and pore structure of material.The catalyst obtained by roasting 2 h at 600?under 5%Ag loading support has high dispersion and best performance.After the modification of the support,the pore structure of the material was enlarged and the surface acidity changed,so that the Ag dispersion was promoted and the ethylene removal performance was improved.?2?The ability of material to convert ethylene into carbon dioxide at room temperature was investigated.And combined with TEM,XPS,BET,FTIR and other characterization methods.The results show that the chemical adsorption plays a major role,and the part of the catalysis exists on the catalyst(Y_CO2<10%).The reason for the deactivation of the catalyst is that the Ag site is occupied due to insufficient oxidation capacity,ethylene is only adsorbed on Ag⁺The second is by-product water molecules occupy pore channels and covering active components and Ag partial agglomeration.The performance after regeneration is 90%of that at initial use can be achieved by regenerated by roasting 120 min at 600?.After 4 times of regeneration,the performance of the catalyst can still reach more than 80%of the initial use.And in the actual preservation of fruits and vegetables showed a significant role in delaying decay.?3?The powder material was successfully formed on the base of honeycomb paper by coating method,and the powder firmly bonded on the base.The performance of ethylene removal was the highest when the concentrations of material and silica sol were 20 wt%and 10wt%,respectively.The time of ethylene removal efficiency was maintained above 98%is 261min,and after repeated regeneration for 4 times,the time of ethylene removal efficiency remained above 98% is 80%or more of initial use,that regeneration only through a simple microwave oven.More than 20 h can be maintained at low flow rate?10 m L/min?,and the maintenance time is obviously reduced under humidity?RH=52%? condition.